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evolutionary_advantage_of_red-green_color_blindness/Evolution.txt	Evolution is the change in the heritable characteristics of biological populations over successive generations. Evolution occurs when evolutionary processes such as natural selection and genetic drift act on genetic variation, resulting in certain characteristics becoming more or less common within a population over successive generations. The process of evolution has given rise to biodiversity at every level of biological organisation. The theory of evolution by natural selection was conceived independently by Charles Darwin and Alfred Russel Wallace in the mid-19th century as an explanation for why organisms are adapted to their physical and biological environments. The theory was first set out in detail in Darwin's book On the Origin of Species. Evolution by natural selection is established by observable facts about living organisms: (1) more offspring are often produced than can possibly survive; (2) traits vary among individuals with respect to their morphology, physiology, and behaviour; (3) different traits confer different rates of survival and reproduction (differential fitness); and (4) traits can be passed from generation to generation (heritability of fitness). In successive generations, members of a population are therefore more likely to be replaced by the offspring of parents with favourable characteristics for that environment. In the early 20th century, competing ideas of evolution were refuted and evolution was combined with Mendelian inheritance and population genetics to give rise to modern evolutionary theory. In this synthesis the basis for heredity is in DNA molecules that pass information from generation to generation. The processes that change DNA in a population include natural selection, genetic drift, mutation, and gene flow. All life on Earth—including humanity—shares a last universal common ancestor (LUCA), which lived approximately 3.5–3.8 billion years ago. The fossil record includes a progression from early biogenic graphite to microbial mat fossils to fossilised multicellular organisms. Existing patterns of biodiversity have been shaped by repeated formations of new species (speciation), changes within species (anagenesis), and loss of species (extinction) throughout the evolutionary history of life on Earth. Morphological and biochemical traits tend to be more similar among species that share a more recent common ancestor, which historically was used to reconstruct phylogenetic trees, although direct comparison of genetic sequences is a more common method today. Evolutionary biologists have continued to study various aspects of evolution by forming and testing hypotheses as well as constructing theories based on evidence from the field or laboratory and on data generated by the methods of mathematical and theoretical biology. Their discoveries have influenced not just the development of biology but also other fields including agriculture, medicine, and computer science. Evolution in organisms occurs through changes in heritable characteristics—the inherited characteristics of an organism. In humans, for example, eye colour is an inherited characteristic and an individual might inherit the "brown-eye trait" from one of their parents. Inherited traits are controlled by genes and the complete set of genes within an organism's genome (genetic material) is called its genotype. The complete set of observable traits that make up the structure and behaviour of an organism is called its phenotype. Some of these traits come from the interaction of its genotype with the environment while others are neutral. Some observable characteristics are not inherited. For example, suntanned skin comes from the interaction between a person's genotype and sunlight; thus, suntans are not passed on to people's children. The phenotype is the ability of the skin to tan when exposed to sunlight. However, some people tan more easily than others, due to differences in genotypic variation; a striking example are people with the inherited trait of albinism, who do not tan at all and are very sensitive to sunburn. Heritable characteristics are passed from one generation to the next via DNA, a molecule that encodes genetic information. DNA is a long biopolymer composed of four types of bases. The sequence of bases along a particular DNA molecule specifies the genetic information, in a manner similar to a sequence of letters spelling out a sentence. Before a cell divides, the DNA is copied, so that each of the resulting two cells will inherit the DNA sequence. Portions of a DNA molecule that specify a single functional unit are called genes; different genes have different sequences of bases. Within cells, each long strand of DNA is called a chromosome. The specific location of a DNA sequence within a chromosome is known as a locus. If the DNA sequence at a locus varies between individuals, the different forms of this sequence are called alleles. DNA sequences can change through mutations, producing new alleles. If a mutation occurs within a gene, the new allele may affect the trait that the gene controls, altering the phenotype of the organism. However, while this simple correspondence between an allele and a trait works in some cases, most traits are influenced by multiple genes in a quantitative or epistatic manner. Evolution can occur if there is genetic variation within a population. Variation comes from mutations in the genome, reshuffling of genes through sexual reproduction and migration between populations (gene flow). Despite the constant introduction of new variation through mutation and gene flow, most of the genome of a species is very similar among all individuals of that species. However, discoveries in the field of evolutionary developmental biology have demonstrated that even relatively small differences in genotype can lead to dramatic differences in phenotype both within and between species. An individual organism's phenotype results from both its genotype and the influence of the environment it has lived in. The modern evolutionary synthesis defines evolution as the change over time in this genetic variation. The frequency of one particular allele will become more or less prevalent relative to other forms of that gene. Variation disappears when a new allele reaches the point of fixation—when it either disappears from the population or replaces the ancestral allele entirely. Mutations are changes in the DNA sequence of a cell's genome and are the ultimate source of genetic variation in all organisms. When mutations occur, they may alter the product of a gene, or prevent the gene from functioning, or have no effect. About half of the mutations in the coding regions of protein-coding genes are deleterious — the other half are neutral. A small percentage of the total mutations in this region confer a fitness benefit. Some of the mutations in other parts of the genome are deleterious but the vast majority are neutral. A few are beneficial. Mutations can involve large sections of a chromosome becoming duplicated (usually by genetic recombination), which can introduce extra copies of a gene into a genome. Extra copies of genes are a major source of the raw material needed for new genes to evolve. This is important because most new genes evolve within gene families from pre-existing genes that share common ancestors. For example, the human eye uses four genes to make structures that sense light: three for colour vision and one for night vision; all four are descended from a single ancestral gene. New genes can be generated from an ancestral gene when a duplicate copy mutates and acquires a new function. This process is easier once a gene has been duplicated because it increases the redundancy of the system; one gene in the pair can acquire a new function while the other copy continues to perform its original function. Other types of mutations can even generate entirely new genes from previously noncoding DNA, a phenomenon termed de novo gene birth. The generation of new genes can also involve small parts of several genes being duplicated, with these fragments then recombining to form new combinations with new functions (exon shuffling). When new genes are assembled from shuffling pre-existing parts, domains act as modules with simple independent functions, which can be mixed together to produce new combinations with new and complex functions. For example, polyketide synthases are large enzymes that make antibiotics; they contain up to 100 independent domains that each catalyse one step in the overall process, like a step in an assembly line. One example of mutation is wild boar piglets. They are camouflage coloured and show a characteristic pattern of dark and light longitudinal stripes. However, mutations in the melanocortin 1 receptor (MC1R) disrupt the pattern. The majority of pig breeds carry MC1R mutations disrupting wild-type colour and different mutations causing dominant black colouring. In asexual organisms, genes are inherited together, or linked, as they cannot mix with genes of other organisms during reproduction. In contrast, the offspring of sexual organisms contain random mixtures of their parents' chromosomes that are produced through independent assortment. In a related process called homologous recombination, sexual organisms exchange DNA between two matching chromosomes. Recombination and reassortment do not alter allele frequencies, but instead change which alleles are associated with each other, producing offspring with new combinations of alleles. Sex usually increases genetic variation and may increase the rate of evolution. The two-fold cost of sex was first described by John Maynard Smith. The first cost is that in sexually dimorphic species only one of the two sexes can bear young. This cost does not apply to hermaphroditic species, like most plants and many invertebrates. The second cost is that any individual who reproduces sexually can only pass on 50% of its genes to any individual offspring, with even less passed on as each new generation passes. Yet sexual reproduction is the more common means of reproduction among eukaryotes and multicellular organisms. The Red Queen hypothesis has been used to explain the significance of sexual reproduction as a means to enable continual evolution and adaptation in response to coevolution with other species in an ever-changing environment. Another hypothesis is that sexual reproduction is primarily an adaptation for promoting accurate recombinational repair of damage in germline DNA, and that increased diversity is a byproduct of this process that may sometimes be adaptively beneficial. Gene flow is the exchange of genes between populations and between species. It can therefore be a source of variation that is new to a population or to a species. Gene flow can be caused by the movement of individuals between separate populations of organisms, as might be caused by the movement of mice between inland and coastal populations, or the movement of pollen between heavy-metal-tolerant and heavy-metal-sensitive populations of grasses. Gene transfer between species includes the formation of hybrid organisms and horizontal gene transfer. Horizontal gene transfer is the transfer of genetic material from one organism to another organism that is not its offspring; this is most common among bacteria. In medicine, this contributes to the spread of antibiotic resistance, as when one bacteria acquires resistance genes it can rapidly transfer them to other species. Horizontal transfer of genes from bacteria to eukaryotes such as the yeast Saccharomyces cerevisiae and the adzuki bean weevil Callosobruchus chinensis has occurred. An example of larger-scale transfers are the eukaryotic bdelloid rotifers, which have received a range of genes from bacteria, fungi and plants. Viruses can also carry DNA between organisms, allowing transfer of genes even across biological domains. Large-scale gene transfer has also occurred between the ancestors of eukaryotic cells and bacteria, during the acquisition of chloroplasts and mitochondria. It is possible that eukaryotes themselves originated from horizontal gene transfers between bacteria and archaea. Some heritable changes cannot be explained by changes to the sequence of nucleotides in the DNA. These phenomena are classed as epigenetic inheritance systems. DNA methylation marking chromatin, self-sustaining metabolic loops, gene silencing by RNA interference and the three-dimensional conformation of proteins (such as prions) are areas where epigenetic inheritance systems have been discovered at the organismic level. Developmental biologists suggest that complex interactions in genetic networks and communication among cells can lead to heritable variations that may underlay some of the mechanics in developmental plasticity and canalisation. Heritability may also occur at even larger scales. For example, ecological inheritance through the process of niche construction is defined by the regular and repeated activities of organisms in their environment. This generates a legacy of effects that modify and feed back into the selection regime of subsequent generations. Other examples of heritability in evolution that are not under the direct control of genes include the inheritance of cultural traits and symbiogenesis. From a neo-Darwinian perspective, evolution occurs when there are changes in the frequencies of alleles within a population of interbreeding organisms, for example, the allele for black colour in a population of moths becoming more common. Mechanisms that can lead to changes in allele frequencies include natural selection, genetic drift, and mutation bias. Evolution by natural selection is the process by which traits that enhance survival and reproduction become more common in successive generations of a population. It embodies three principles: More offspring are produced than can possibly survive, and these conditions produce competition between organisms for survival and reproduction. Consequently, organisms with traits that give them an advantage over their competitors are more likely to pass on their traits to the next generation than those with traits that do not confer an advantage. This teleonomy is the quality whereby the process of natural selection creates and preserves traits that are seemingly fitted for the functional roles they perform. Consequences of selection include nonrandom mating and genetic hitchhiking. The central concept of natural selection is the evolutionary fitness of an organism. Fitness is measured by an organism's ability to survive and reproduce, which determines the size of its genetic contribution to the next generation. However, fitness is not the same as the total number of offspring: instead fitness is indicated by the proportion of subsequent generations that carry an organism's genes. For example, if an organism could survive well and reproduce rapidly, but its offspring were all too small and weak to survive, this organism would make little genetic contribution to future generations and would thus have low fitness. If an allele increases fitness more than the other alleles of that gene, then with each generation this allele has a higher probability of becoming common within the population. These traits are said to be "selected for." Examples of traits that can increase fitness are enhanced survival and increased fecundity. Conversely, the lower fitness caused by having a less beneficial or deleterious allele results in this allele likely becoming rarer—they are "selected against." Importantly, the fitness of an allele is not a fixed characteristic; if the environment changes, previously neutral or harmful traits may become beneficial and previously beneficial traits become harmful. However, even if the direction of selection does reverse in this way, traits that were lost in the past may not re-evolve in an identical form. However, a re-activation of dormant genes, as long as they have not been eliminated from the genome and were only suppressed perhaps for hundreds of generations, can lead to the re-occurrence of traits thought to be lost like hindlegs in dolphins, teeth in chickens, wings in wingless stick insects, tails and additional nipples in humans etc. "Throwbacks" such as these are known as atavisms. Natural selection within a population for a trait that can vary across a range of values, such as height, can be categorised into three different types. The first is directional selection, which is a shift in the average value of a trait over time—for example, organisms slowly getting taller. Secondly, disruptive selection is selection for extreme trait values and often results in two different values becoming most common, with selection against the average value. This would be when either short or tall organisms had an advantage, but not those of medium height. Finally, in stabilising selection there is selection against extreme trait values on both ends, which causes a decrease in variance around the average value and less diversity. This would, for example, cause organisms to eventually have a similar height. Natural selection most generally makes nature the measure against which individuals and individual traits, are more or less likely to survive. "Nature" in this sense refers to an ecosystem, that is, a system in which organisms interact with every other element, physical as well as biological, in their local environment. Eugene Odum, a founder of ecology, defined an ecosystem as: "Any unit that includes all of the organisms...in a given area interacting with the physical environment so that a flow of energy leads to clearly defined trophic structure, biotic diversity, and material cycles (i.e., exchange of materials between living and nonliving parts) within the system...." Each population within an ecosystem occupies a distinct niche, or position, with distinct relationships to other parts of the system. These relationships involve the life history of the organism, its position in the food chain and its geographic range. This broad understanding of nature enables scientists to delineate specific forces which, together, comprise natural selection. Natural selection can act at different levels of organisation, such as genes, cells, individual organisms, groups of organisms and species. Selection can act at multiple levels simultaneously. An example of selection occurring below the level of the individual organism are genes called transposons, which can replicate and spread throughout a genome. Selection at a level above the individual, such as group selection, may allow the evolution of cooperation. Genetic drift is the random fluctuation of allele frequencies within a population from one generation to the next. When selective forces are absent or relatively weak, allele frequencies are equally likely to drift upward or downward in each successive generation because the alleles are subject to sampling error. This drift halts when an allele eventually becomes fixed, either by disappearing from the population or by replacing the other alleles entirely. Genetic drift may therefore eliminate some alleles from a population due to chance alone. Even in the absence of selective forces, genetic drift can cause two separate populations that begin with the same genetic structure to drift apart into two divergent populations with different sets of alleles. According to the neutral theory of molecular evolution most evolutionary changes are the result of the fixation of neutral mutations by genetic drift. In this model, most genetic changes in a population are thus the result of constant mutation pressure and genetic drift. This form of the neutral theory has been debated since it does not seem to fit some genetic variation seen in nature. A better-supported version of this model is the nearly neutral theory, according to which a mutation that would be effectively neutral in a small population is not necessarily neutral in a large population. Other theories propose that genetic drift is dwarfed by other stochastic forces in evolution, such as genetic hitchhiking, also known as genetic draft. Another concept is constructive neutral evolution (CNE), which explains that complex systems can emerge and spread into a population through neutral transitions due to the principles of excess capacity, presuppression, and ratcheting, and it has been applied in areas ranging from the origins of the spliceosome to the complex interdependence of microbial communities. The time it takes a neutral allele to become fixed by genetic drift depends on population size; fixation is more rapid in smaller populations. The number of individuals in a population is not critical, but instead a measure known as the effective population size. The effective population is usually smaller than the total population since it takes into account factors such as the level of inbreeding and the stage of the lifecycle in which the population is the smallest. The effective population size may not be the same for every gene in the same population. It is usually difficult to measure the relative importance of selection and neutral processes, including drift. The comparative importance of adaptive and non-adaptive forces in driving evolutionary change is an area of current research. Mutation bias is usually conceived as a difference in expected rates for two different kinds of mutation, e.g., transition-transversion bias, GC-AT bias, deletion-insertion bias. This is related to the idea of developmental bias. Haldane and Fisher argued that, because mutation is a weak pressure easily overcome by selection, tendencies of mutation would be ineffectual except under conditions of neutral evolution or extraordinarily high mutation rates. This opposing-pressures argument was long used to dismiss the possibility of internal tendencies in evolution, until the molecular era prompted renewed interest in neutral evolution. Noboru Sueoka and Ernst Freese proposed that systematic biases in mutation might be responsible for systematic differences in genomic GC composition between species. The identification of a GC-biased E. coli mutator strain in 1967, along with the proposal of the neutral theory, established the plausibility of mutational explanations for molecular patterns, which are now common in the molecular evolution literature. For instance, mutation biases are frequently invoked in models of codon usage. Such models also include effects of selection, following the mutation-selection-drift model, which allows both for mutation biases and differential selection based on effects on translation. Hypotheses of mutation bias have played an important role in the development of thinking about the evolution of genome composition, including isochores. Different insertion vs. deletion biases in different taxa can lead to the evolution of different genome sizes. The hypothesis of Lynch regarding genome size relies on mutational biases toward increase or decrease in genome size. However, mutational hypotheses for the evolution of composition suffered a reduction in scope when it was discovered that (1) GC-biased gene conversion makes an important contribution to composition in diploid organisms such as mammals and (2) bacterial genomes frequently have AT-biased mutation. Contemporary thinking about the role of mutation biases reflects a different theory from that of Haldane and Fisher. More recent work showed that the original "pressures" theory assumes that evolution is based on standing variation: when evolution depends on events of mutation that introduce new alleles, mutational and developmental biases in the introduction of variation (arrival biases) can impose biases on evolution without requiring neutral evolution or high mutation rates. Several studies report that the mutations implicated in adaptation reflect common mutation biases though others dispute this interpretation. Recombination allows alleles on the same strand of DNA to become separated. However, the rate of recombination is low (approximately two events per chromosome per generation). As a result, genes close together on a chromosome may not always be shuffled away from each other and genes that are close together tend to be inherited together, a phenomenon known as linkage. This tendency is measured by finding how often two alleles occur together on a single chromosome compared to expectations, which is called their linkage disequilibrium. A set of alleles that is usually inherited in a group is called a haplotype. This can be important when one allele in a particular haplotype is strongly beneficial: natural selection can drive a selective sweep that will also cause the other alleles in the haplotype to become more common in the population; this effect is called genetic hitchhiking or genetic draft. Genetic draft caused by the fact that some neutral genes are genetically linked to others that are under selection can be partially captured by an appropriate effective population size. A special case of natural selection is sexual selection, which is selection for any trait that increases mating success by increasing the attractiveness of an organism to potential mates. Traits that evolved through sexual selection are particularly prominent among males of several animal species. Although sexually favoured, traits such as cumbersome antlers, mating calls, large body size and bright colours often attract predation, which compromises the survival of individual males. This survival disadvantage is balanced by higher reproductive success in males that show these hard-to-fake, sexually selected traits. Evolution influences every aspect of the form and behaviour of organisms. Most prominent are the specific behavioural and physical adaptations that are the outcome of natural selection. These adaptations increase fitness by aiding activities such as finding food, avoiding predators or attracting mates. Organisms can also respond to selection by cooperating with each other, usually by aiding their relatives or engaging in mutually beneficial symbiosis. In the longer term, evolution produces new species through splitting ancestral populations of organisms into new groups that cannot or will not interbreed. These outcomes of evolution are distinguished based on time scale as macroevolution versus microevolution. Macroevolution refers to evolution that occurs at or above the level of species, in particular speciation and extinction; whereas microevolution refers to smaller evolutionary changes within a species or population, in particular shifts in allele frequency and adaptation. Macroevolution the outcome of long periods of microevolution. Thus, the distinction between micro- and macroevolution is not a fundamental one—the difference is simply the time involved. However, in macroevolution, the traits of the entire species may be important. For instance, a large amount of variation among individuals allows a species to rapidly adapt to new habitats, lessening the chance of it going extinct, while a wide geographic range increases the chance of speciation, by making it more likely that part of the population will become isolated. In this sense, microevolution and macroevolution might involve selection at different levels—with microevolution acting on genes and organisms, versus macroevolutionary processes such as species selection acting on entire species and affecting their rates of speciation and extinction. A common misconception is that evolution has goals, long-term plans, or an innate tendency for "progress", as expressed in beliefs such as orthogenesis and evolutionism; realistically however, evolution has no long-term goal and does not necessarily produce greater complexity. Although complex species have evolved, they occur as a side effect of the overall number of organisms increasing and simple forms of life still remain more common in the biosphere. For example, the overwhelming majority of species are microscopic prokaryotes, which form about half the world's biomass despite their small size, and constitute the vast majority of Earth's biodiversity. Simple organisms have therefore been the dominant form of life on Earth throughout its history and continue to be the main form of life up to the present day, with complex life only appearing more diverse because it is more noticeable. Indeed, the evolution of microorganisms is particularly important to evolutionary research, since their rapid reproduction allows the study of experimental evolution and the observation of evolution and adaptation in real time. Adaptation is the process that makes organisms better suited to their habitat. Also, the term adaptation may refer to a trait that is important for an organism's survival. For example, the adaptation of horses' teeth to the grinding of grass. By using the term adaptation for the evolutionary process and adaptive trait for the product (the bodily part or function), the two senses of the word may be distinguished. Adaptations are produced by natural selection. The following definitions are due to Theodosius Dobzhansky: Adaptation may cause either the gain of a new feature, or the loss of an ancestral feature. An example that shows both types of change is bacterial adaptation to antibiotic selection, with genetic changes causing antibiotic resistance by both modifying the target of the drug, or increasing the activity of transporters that pump the drug out of the cell. Other striking examples are the bacteria Escherichia coli evolving the ability to use citric acid as a nutrient in a long-term laboratory experiment, Flavobacterium evolving a novel enzyme that allows these bacteria to grow on the by-products of nylon manufacturing, and the soil bacterium Sphingobium evolving an entirely new metabolic pathway that degrades the synthetic pesticide pentachlorophenol. An interesting but still controversial idea is that some adaptations might increase the ability of organisms to generate genetic diversity and adapt by natural selection (increasing organisms' evolvability). Adaptation occurs through the gradual modification of existing structures. Consequently, structures with similar internal organisation may have different functions in related organisms. This is the result of a single ancestral structure being adapted to function in different ways. The bones within bat wings, for example, are very similar to those in mice feet and primate hands, due to the descent of all these structures from a common mammalian ancestor. However, since all living organisms are related to some extent, even organs that appear to have little or no structural similarity, such as arthropod, squid and vertebrate eyes, or the limbs and wings of arthropods and vertebrates, can depend on a common set of homologous genes that control their assembly and function; this is called deep homology. During evolution, some structures may lose their original function and become vestigial structures. Such structures may have little or no function in a current species, yet have a clear function in ancestral species, or other closely related species. Examples include pseudogenes, the non-functional remains of eyes in blind cave-dwelling fish, wings in flightless birds, the presence of hip bones in whales and snakes, and sexual traits in organisms that reproduce via asexual reproduction. Examples of vestigial structures in humans include wisdom teeth, the coccyx, the vermiform appendix, and other behavioural vestiges such as goose bumps and primitive reflexes. However, many traits that appear to be simple adaptations are in fact exaptations: structures originally adapted for one function, but which coincidentally became somewhat useful for some other function in the process. One example is the African lizard Holaspis guentheri, which developed an extremely flat head for hiding in crevices, as can be seen by looking at its near relatives. However, in this species, the head has become so flattened that it assists in gliding from tree to tree—an exaptation. Within cells, molecular machines such as the bacterial flagella and protein sorting machinery evolved by the recruitment of several pre-existing proteins that previously had different functions. Another example is the recruitment of enzymes from glycolysis and xenobiotic metabolism to serve as structural proteins called crystallins within the lenses of organisms' eyes. An area of current investigation in evolutionary developmental biology is the developmental basis of adaptations and exaptations. This research addresses the origin and evolution of embryonic development and how modifications of development and developmental processes produce novel features. These studies have shown that evolution can alter development to produce new structures, such as embryonic bone structures that develop into the jaw in other animals instead forming part of the middle ear in mammals. It is also possible for structures that have been lost in evolution to reappear due to changes in developmental genes, such as a mutation in chickens causing embryos to grow teeth similar to those of crocodiles. It is now becoming clear that most alterations in the form of organisms are due to changes in a small set of conserved genes. Interactions between organisms can produce both conflict and cooperation. When the interaction is between pairs of species, such as a pathogen and a host, or a predator and its prey, these species can develop matched sets of adaptations. Here, the evolution of one species causes adaptations in a second species. These changes in the second species then, in turn, cause new adaptations in the first species. This cycle of selection and response is called coevolution. An example is the production of tetrodotoxin in the rough-skinned newt and the evolution of tetrodotoxin resistance in its predator, the common garter snake. In this predator-prey pair, an evolutionary arms race has produced high levels of toxin in the newt and correspondingly high levels of toxin resistance in the snake. Not all co-evolved interactions between species involve conflict. Many cases of mutually beneficial interactions have evolved. For instance, an extreme cooperation exists between plants and the mycorrhizal fungi that grow on their roots and aid the plant in absorbing nutrients from the soil. This is a reciprocal relationship as the plants provide the fungi with sugars from photosynthesis. Here, the fungi actually grow inside plant cells, allowing them to exchange nutrients with their hosts, while sending signals that suppress the plant immune system. Coalitions between organisms of the same species have also evolved. An extreme case is the eusociality found in social insects, such as bees, termites and ants, where sterile insects feed and guard the small number of organisms in a colony that are able to reproduce. On an even smaller scale, the somatic cells that make up the body of an animal limit their reproduction so they can maintain a stable organism, which then supports a small number of the animal's germ cells to produce offspring. Here, somatic cells respond to specific signals that instruct them whether to grow, remain as they are, or die. If cells ignore these signals and multiply inappropriately, their uncontrolled growth causes cancer. Such cooperation within species may have evolved through the process of kin selection, which is where one organism acts to help raise a relative's offspring. This activity is selected for because if the helping individual contains alleles which promote the helping activity, it is likely that its kin will also contain these alleles and thus those alleles will be passed on. Other processes that may promote cooperation include group selection, where cooperation provides benefits to a group of organisms. Speciation is the process where a species diverges into two or more descendant species. There are multiple ways to define the concept of "species." The choice of definition is dependent on the particularities of the species concerned. For example, some species concepts apply more readily toward sexually reproducing organisms while others lend themselves better toward asexual organisms. Despite the diversity of various species concepts, these various concepts can be placed into one of three broad philosophical approaches: interbreeding, ecological and phylogenetic. The Biological Species Concept (BSC) is a classic example of the interbreeding approach. Defined by evolutionary biologist Ernst Mayr in 1942, the BSC states that "species are groups of actually or potentially interbreeding natural populations, which are reproductively isolated from other such groups." Despite its wide and long-term use, the BSC like other species concepts is not without controversy, for example, because genetic recombination among prokaryotes is not an intrinsic aspect of reproduction; this is called the species problem. Some researchers have attempted a unifying monistic definition of species, while others adopt a pluralistic approach and suggest that there may be different ways to logically interpret the definition of a species. Barriers to reproduction between two diverging sexual populations are required for the populations to become new species. Gene flow may slow this process by spreading the new genetic variants also to the other populations. Depending on how far two species have diverged since their most recent common ancestor, it may still be possible for them to produce offspring, as with horses and donkeys mating to produce mules. Such hybrids are generally infertile. In this case, closely related species may regularly interbreed, but hybrids will be selected against and the species will remain distinct. However, viable hybrids are occasionally formed and these new species can either have properties intermediate between their parent species, or possess a totally new phenotype. The importance of hybridisation in producing new species of animals is unclear, although cases have been seen in many types of animals, with the gray tree frog being a particularly well-studied example. Speciation has been observed multiple times under both controlled laboratory conditions and in nature. In sexually reproducing organisms, speciation results from reproductive isolation followed by genealogical divergence. There are four primary geographic modes of speciation. The most common in animals is allopatric speciation, which occurs in populations initially isolated geographically, such as by habitat fragmentation or migration. Selection under these conditions can produce very rapid changes in the appearance and behaviour of organisms. As selection and drift act independently on populations isolated from the rest of their species, separation may eventually produce organisms that cannot interbreed. The second mode of speciation is peripatric speciation, which occurs when small populations of organisms become isolated in a new environment. This differs from allopatric speciation in that the isolated populations are numerically much smaller than the parental population. Here, the founder effect causes rapid speciation after an increase in inbreeding increases selection on homozygotes, leading to rapid genetic change. The third mode is parapatric speciation. This is similar to peripatric speciation in that a small population enters a new habitat, but differs in that there is no physical separation between these two populations. Instead, speciation results from the evolution of mechanisms that reduce gene flow between the two populations. Generally this occurs when there has been a drastic change in the environment within the parental species' habitat. One example is the grass Anthoxanthum odoratum, which can undergo parapatric speciation in response to localised metal pollution from mines. Here, plants evolve that have resistance to high levels of metals in the soil. Selection against interbreeding with the metal-sensitive parental population produced a gradual change in the flowering time of the metal-resistant plants, which eventually produced complete reproductive isolation. Selection against hybrids between the two populations may cause reinforcement, which is the evolution of traits that promote mating within a species, as well as character displacement, which is when two species become more distinct in appearance. Finally, in sympatric speciation species diverge without geographic isolation or changes in habitat. This form is rare since even a small amount of gene flow may remove genetic differences between parts of a population. Generally, sympatric speciation in animals requires the evolution of both genetic differences and nonrandom mating, to allow reproductive isolation to evolve. One type of sympatric speciation involves crossbreeding of two related species to produce a new hybrid species. This is not common in animals as animal hybrids are usually sterile. This is because during meiosis the homologous chromosomes from each parent are from different species and cannot successfully pair. However, it is more common in plants because plants often double their number of chromosomes, to form polyploids. This allows the chromosomes from each parental species to form matching pairs during meiosis, since each parent's chromosomes are represented by a pair already. An example of such a speciation event is when the plant species Arabidopsis thaliana and Arabidopsis arenosa crossbred to give the new species Arabidopsis suecica. This happened about 20,000 years ago, and the speciation process has been repeated in the laboratory, which allows the study of the genetic mechanisms involved in this process. Indeed, chromosome doubling within a species may be a common cause of reproductive isolation, as half the doubled chromosomes will be unmatched when breeding with undoubled organisms. Speciation events are important in the theory of punctuated equilibrium, which accounts for the pattern in the fossil record of short "bursts" of evolution interspersed with relatively long periods of stasis, where species remain relatively unchanged. In this theory, speciation and rapid evolution are linked, with natural selection and genetic drift acting most strongly on organisms undergoing speciation in novel habitats or small populations. As a result, the periods of stasis in the fossil record correspond to the parental population and the organisms undergoing speciation and rapid evolution are found in small populations or geographically restricted habitats and therefore rarely being preserved as fossils. Extinction is the disappearance of an entire species. Extinction is not an unusual event, as species regularly appear through speciation and disappear through extinction. Nearly all animal and plant species that have lived on Earth are now extinct, and extinction appears to be the ultimate fate of all species. These extinctions have happened continuously throughout the history of life, although the rate of extinction spikes in occasional mass extinction events. The Cretaceous–Paleogene extinction event, during which the non-avian dinosaurs became extinct, is the most well-known, but the earlier Permian–Triassic extinction event was even more severe, with approximately 96% of all marine species driven to extinction. The Holocene extinction event is an ongoing mass extinction associated with humanity's expansion across the globe over the past few thousand years. Present-day extinction rates are 100–1000 times greater than the background rate and up to 30% of current species may be extinct by the mid 21st century. Human activities are now the primary cause of the ongoing extinction event; global warming may further accelerate it in the future. Despite the estimated extinction of more than 99% of all species that ever lived on Earth, about 1 trillion species are estimated to be on Earth currently with only one-thousandth of 1% described. The role of extinction in evolution is not very well understood and may depend on which type of extinction is considered. The causes of the continuous "low-level" extinction events, which form the majority of extinctions, may be the result of competition between species for limited resources (the competitive exclusion principle). If one species can out-compete another, this could produce species selection, with the fitter species surviving and the other species being driven to extinction. The intermittent mass extinctions are also important, but instead of acting as a selective force, they drastically reduce diversity in a nonspecific manner and promote bursts of rapid evolution and speciation in survivors. Concepts and models used in evolutionary biology, such as natural selection, have many applications. Artificial selection is the intentional selection of traits in a population of organisms. This has been used for thousands of years in the domestication of plants and animals. More recently, such selection has become a vital part of genetic engineering, with selectable markers such as antibiotic resistance genes being used to manipulate DNA. Proteins with valuable properties have evolved by repeated rounds of mutation and selection (for example modified enzymes and new antibodies) in a process called directed evolution. Understanding the changes that have occurred during an organism's evolution can reveal the genes needed to construct parts of the body, genes which may be involved in human genetic disorders. For example, the Mexican tetra is an albino cavefish that lost its eyesight during evolution. Breeding together different populations of this blind fish produced some offspring with functional eyes, since different mutations had occurred in the isolated populations that had evolved in different caves. This helped identify genes required for vision and pigmentation. Evolutionary theory has many applications in medicine. Many human diseases are not static phenomena, but capable of evolution. Viruses, bacteria, fungi and cancers evolve to be resistant to host immune defences, as well as to pharmaceutical drugs. These same problems occur in agriculture with pesticide and herbicide resistance. It is possible that we are facing the end of the effective life of most of available antibiotics and predicting the evolution and evolvability of our pathogens and devising strategies to slow or circumvent it is requiring deeper knowledge of the complex forces driving evolution at the molecular level. In computer science, simulations of evolution using evolutionary algorithms and artificial life started in the 1960s and were extended with simulation of artificial selection. Artificial evolution became a widely recognised optimisation method as a result of the work of Ingo Rechenberg in the 1960s. He used evolution strategies to solve complex engineering problems. Genetic algorithms in particular became popular through the writing of John Henry Holland. Practical applications also include automatic evolution of computer programmes. Evolutionary algorithms are now used to solve multi-dimensional problems more efficiently than software produced by human designers and also to optimise the design of systems. The Earth is about 4.54 billion years old. The earliest undisputed evidence of life on Earth dates from at least 3.5 billion years ago, during the Eoarchean Era after a geological crust started to solidify following the earlier molten Hadean Eon. Microbial mat fossils have been found in 3.48 billion-year-old sandstone in Western Australia. Other early physical evidence of a biogenic substance is graphite in 3.7 billion-year-old metasedimentary rocks discovered in Western Greenland as well as "remains of biotic life" found in 4.1 billion-year-old rocks in Western Australia. Commenting on the Australian findings, Stephen Blair Hedges wrote: "If life arose relatively quickly on Earth, then it could be common in the universe." In July 2016, scientists reported identifying a set of 355 genes from the last universal common ancestor (LUCA) of all organisms living on Earth. More than 99% of all species, amounting to over five billion species, that ever lived on Earth are estimated to be extinct. Estimates on the number of Earth's current species range from 10 million to 14 million, of which about 1.9 million are estimated to have been named and 1.6 million documented in a central database to date, leaving at least 80% not yet described. Highly energetic chemistry is thought to have produced a self-replicating molecule around 4 billion years ago, and half a billion years later the last common ancestor of all life existed. The current scientific consensus is that the complex biochemistry that makes up life came from simpler chemical reactions. The beginning of life may have included self-replicating molecules such as RNA and the assembly of simple cells. All organisms on Earth are descended from a common ancestor or ancestral gene pool. Current species are a stage in the process of evolution, with their diversity the product of a long series of speciation and extinction events. The common descent of organisms was first deduced from four simple facts about organisms: First, they have geographic distributions that cannot be explained by local adaptation. Second, the diversity of life is not a set of completely unique organisms, but organisms that share morphological similarities. Third, vestigial traits with no clear purpose resemble functional ancestral traits. Fourth, organisms can be classified using these similarities into a hierarchy of nested groups, similar to a family tree. Due to horizontal gene transfer, this "tree of life" may be more complicated than a simple branching tree, since some genes have spread independently between distantly related species. To solve this problem and others, some authors prefer to use the "Coral of life" as a metaphor or a mathematical model to illustrate the evolution of life. This view dates back to an idea briefly mentioned by Darwin but later abandoned. Past species have also left records of their evolutionary history. Fossils, along with the comparative anatomy of present-day organisms, constitute the morphological, or anatomical, record. By comparing the anatomies of both modern and extinct species, palaeontologists can infer the lineages of those species. However, this approach is most successful for organisms that had hard body parts, such as shells, bones or teeth. Further, as prokaryotes such as bacteria and archaea share a limited set of common morphologies, their fossils do not provide information on their ancestry. More recently, evidence for common descent has come from the study of biochemical similarities between organisms. For example, all living cells use the same basic set of nucleotides and amino acids. The development of molecular genetics has revealed the record of evolution left in organisms' genomes: dating when species diverged through the molecular clock produced by mutations. For example, these DNA sequence comparisons have revealed that humans and chimpanzees share 98% of their genomes and analysing the few areas where they differ helps shed light on when the common ancestor of these species existed. Prokaryotes inhabited the Earth from approximately 3–4 billion years ago. No obvious changes in morphology or cellular organisation occurred in these organisms over the next few billion years. The eukaryotic cells emerged between 1.6 and 2.7 billion years ago. The next major change in cell structure came when bacteria were engulfed by eukaryotic cells, in a cooperative association called endosymbiosis. The engulfed bacteria and the host cell then underwent coevolution, with the bacteria evolving into either mitochondria or hydrogenosomes. Another engulfment of cyanobacterial-like organisms led to the formation of chloroplasts in algae and plants. The history of life was that of the unicellular eukaryotes, prokaryotes and archaea until about 610 million years ago when multicellular organisms began to appear in the oceans in the Ediacaran period. The evolution of multicellularity occurred in multiple independent events, in organisms as diverse as sponges, brown algae, cyanobacteria, slime moulds and myxobacteria. In January 2016, scientists reported that, about 800 million years ago, a minor genetic change in a single molecule called GK-PID may have allowed organisms to go from a single cell organism to one of many cells. Soon after the emergence of these first multicellular organisms, a remarkable amount of biological diversity appeared over approximately 10 million years, in an event called the Cambrian explosion. Here, the majority of types of modern animals appeared in the fossil record, as well as unique lineages that subsequently became extinct. Various triggers for the Cambrian explosion have been proposed, including the accumulation of oxygen in the atmosphere from photosynthesis. About 500 million years ago, plants and fungi colonised the land and were soon followed by arthropods and other animals. Insects were particularly successful and even today make up the majority of animal species. Amphibians first appeared around 364 million years ago, followed by early amniotes and birds around 155 million years ago (both from "reptile"-like lineages), mammals around 129 million years ago, Homininae around 10 million years ago and modern humans around 250,000 years ago. However, despite the evolution of these large animals, smaller organisms similar to the types that evolved early in this process continue to be highly successful and dominate the Earth, with the majority of both biomass and species being prokaryotes. The proposal that one type of organism could descend from another type goes back to some of the first pre-Socratic Greek philosophers, such as Anaximander and Empedocles. Such proposals survived into Roman times. The poet and philosopher Lucretius followed Empedocles in his masterwork De rerum natura (lit. 'On the Nature of Things'). In contrast to these materialistic views, Aristotelianism had considered all natural things as actualisations of fixed natural possibilities, known as forms. This became part of a medieval teleological understanding of nature in which all things have an intended role to play in a divine cosmic order. Variations of this idea became the standard understanding of the Middle Ages and were integrated into Christian learning, but Aristotle did not demand that real types of organisms always correspond one-for-one with exact metaphysical forms and specifically gave examples of how new types of living things could come to be. A number of Arab Muslim scholars wrote about evolution, most notably Ibn Khaldun, who wrote the book Muqaddimah in 1377 AD, in which he asserted that humans developed from "the world of the monkeys", in a process by which "species become more numerous". The "New Science" of the 17th century rejected the Aristotelian approach. It sought to explain natural phenomena in terms of physical laws that were the same for all visible things and that did not require the existence of any fixed natural categories or divine cosmic order. However, this new approach was slow to take root in the biological sciences: the last bastion of the concept of fixed natural types. John Ray applied one of the previously more general terms for fixed natural types, "species", to plant and animal types, but he strictly identified each type of living thing as a species and proposed that each species could be defined by the features that perpetuated themselves generation after generation. The biological classification introduced by Carl Linnaeus in 1735 explicitly recognised the hierarchical nature of species relationships, but still viewed species as fixed according to a divine plan. Other naturalists of this time speculated on the evolutionary change of species over time according to natural laws. In 1751, Pierre Louis Maupertuis wrote of natural modifications occurring during reproduction and accumulating over many generations to produce new species. Georges-Louis Leclerc, Comte de Buffon, suggested that species could degenerate into different organisms, and Erasmus Darwin proposed that all warm-blooded animals could have descended from a single microorganism (or "filament"). The first full-fledged evolutionary scheme was Jean-Baptiste Lamarck's "transmutation" theory of 1809, which envisaged spontaneous generation continually producing simple forms of life that developed greater complexity in parallel lineages with an inherent progressive tendency, and postulated that on a local level, these lineages adapted to the environment by inheriting changes caused by their use or disuse in parents. (The latter process was later called Lamarckism.) These ideas were condemned by established naturalists as speculation lacking empirical support. In particular, Georges Cuvier insisted that species were unrelated and fixed, their similarities reflecting divine design for functional needs. In the meantime, Ray's ideas of benevolent design had been developed by William Paley into the Natural Theology or Evidences of the Existence and Attributes of the Deity (1802), which proposed complex adaptations as evidence of divine design and which was admired by Charles Darwin. The crucial break from the concept of constant typological classes or types in biology came with the theory of evolution through natural selection, which was formulated by Charles Darwin and Alfred Wallace in terms of variable populations. Darwin used the expression "descent with modification" rather than "evolution". Partly influenced by An Essay on the Principle of Population (1798) by Thomas Robert Malthus, Darwin noted that population growth would lead to a "struggle for existence" in which favourable variations prevailed as others perished. In each generation, many offspring fail to survive to an age of reproduction because of limited resources. This could explain the diversity of plants and animals from a common ancestry through the working of natural laws in the same way for all types of organism. Darwin developed his theory of "natural selection" from 1838 onwards and was writing up his "big book" on the subject when Alfred Russel Wallace sent him a version of virtually the same theory in 1858. Their separate papers were presented together at an 1858 meeting of the Linnean Society of London. At the end of 1859, Darwin's publication of his "abstract" as On the Origin of Species explained natural selection in detail and in a way that led to an increasingly wide acceptance of Darwin's concepts of evolution at the expense of alternative theories. Thomas Henry Huxley applied Darwin's ideas to humans, using paleontology and comparative anatomy to provide strong evidence that humans and apes shared a common ancestry. Some were disturbed by this since it implied that humans did not have a special place in the universe. The mechanisms of reproductive heritability and the origin of new traits remained a mystery. Towards this end, Darwin developed his provisional theory of pangenesis. In 1865, Gregor Mendel reported that traits were inherited in a predictable manner through the independent assortment and segregation of elements (later known as genes). Mendel's laws of inheritance eventually supplanted most of Darwin's pangenesis theory. August Weismann made the important distinction between germ cells that give rise to gametes (such as sperm and egg cells) and the somatic cells of the body, demonstrating that heredity passes through the germ line only. Hugo de Vries connected Darwin's pangenesis theory to Weismann's germ/soma cell distinction and proposed that Darwin's pangenes were concentrated in the cell nucleus and when expressed they could move into the cytoplasm to change the cell's structure. De Vries was also one of the researchers who made Mendel's work well known, believing that Mendelian traits corresponded to the transfer of heritable variations along the germline. To explain how new variants originate, de Vries developed a mutation theory that led to a temporary rift between those who accepted Darwinian evolution and biometricians who allied with de Vries. In the 1930s, pioneers in the field of population genetics, such as Ronald Fisher, Sewall Wright and J. B. S. Haldane set the foundations of evolution onto a robust statistical philosophy. The false contradiction between Darwin's theory, genetic mutations, and Mendelian inheritance was thus reconciled. In the 1920s and 1930s, the modern synthesis connected natural selection and population genetics, based on Mendelian inheritance, into a unified theory that included random genetic drift, mutation, and gene flow. This new version of evolutionary theory focused on changes in allele frequencies in population. It explained patterns observed across species in populations, through fossil transitions in palaeontology. Since then, further syntheses have extended evolution's explanatory power in the light of numerous discoveries, to cover biological phenomena across the whole of the biological hierarchy from genes to populations. The publication of the structure of DNA by James Watson and Francis Crick with contribution of Rosalind Franklin in 1953 demonstrated a physical mechanism for inheritance. Molecular biology improved understanding of the relationship between genotype and phenotype. Advances were also made in phylogenetic systematics, mapping the transition of traits into a comparative and testable framework through the publication and use of evolutionary trees. In 1973, evolutionary biologist Theodosius Dobzhansky penned that "nothing in biology makes sense except in the light of evolution", because it has brought to light the relations of what first seemed disjointed facts in natural history into a coherent explanatory body of knowledge that describes and predicts many observable facts about life on this planet. One extension, known as evolutionary developmental biology and informally called "evo-devo," emphasises how changes between generations (evolution) act on patterns of change within individual organisms (development). Since the beginning of the 21st century, some biologists have argued for an extended evolutionary synthesis, which would account for the effects of non-genetic inheritance modes, such as epigenetics, parental effects, ecological inheritance and cultural inheritance, and evolvability. In the 19th century, particularly after the publication of On the Origin of Species in 1859, the idea that life had evolved was an active source of academic debate centred on the philosophical, social and religious implications of evolution. Today, the modern evolutionary synthesis is accepted by a vast majority of scientists. However, evolution remains a contentious concept for some theists. While various religions and denominations have reconciled their beliefs with evolution through concepts such as theistic evolution, there are creationists who believe that evolution is contradicted by the creation myths found in their religions and who raise various objections to evolution. As had been demonstrated by responses to the publication of Vestiges of the Natural History of Creation in 1844, the most controversial aspect of evolutionary biology is the implication of human evolution that humans share common ancestry with apes and that the mental and moral faculties of humanity have the same types of natural causes as other inherited traits in animals. In some countries, notably the United States, these tensions between science and religion have fuelled the current creation–evolution controversy, a religious conflict focusing on politics and public education. While other scientific fields such as cosmology and Earth science also conflict with literal interpretations of many religious texts, evolutionary biology experiences significantly more opposition from religious literalists. The teaching of evolution in American secondary school biology classes was uncommon in most of the first half of the 20th century. The Scopes Trial decision of 1925 caused the subject to become very rare in American secondary biology textbooks for a generation, but it was gradually re-introduced later and became legally protected with the 1968 Epperson v. Arkansas decision. Since then, the competing religious belief of creationism was legally disallowed in secondary school curricula in various decisions in the 1970s and 1980s, but it returned in pseudoscientific form as intelligent design (ID), to be excluded once again in the 2005 Kitzmiller v. Dover Area School District case. The debate over Darwin's ideas did not generate significant controversy in China. Heredity Further information: Introduction to genetics, Genetics, and Heredity DNA structure. Bases are in the centre, surrounded by phosphate–sugar chains in a double helix. Evolution in organisms occurs through changes in heritable characteristics—the inherited characteristics of an organism. In humans, for example, eye colour is an inherited characteristic and an individual might inherit the "brown-eye trait" from one of their parents. Inherited traits are controlled by genes and the complete set of genes within an organism's genome (genetic material) is called its genotype. The complete set of observable traits that make up the structure and behaviour of an organism is called its phenotype. Some of these traits come from the interaction of its genotype with the environment while others are neutral. Some observable characteristics are not inherited. For example, suntanned skin comes from the interaction between a person's genotype and sunlight; thus, suntans are not passed on to people's children. The phenotype is the ability of the skin to tan when exposed to sunlight. However, some people tan more easily than others, due to differences in genotypic variation; a striking example are people with the inherited trait of albinism, who do not tan at all and are very sensitive to sunburn. Heritable characteristics are passed from one generation to the next via DNA, a molecule that encodes genetic information. DNA is a long biopolymer composed of four types of bases. The sequence of bases along a particular DNA molecule specifies the genetic information, in a manner similar to a sequence of letters spelling out a sentence. Before a cell divides, the DNA is copied, so that each of the resulting two cells will inherit the DNA sequence. Portions of a DNA molecule that specify a single functional unit are called genes; different genes have different sequences of bases. Within cells, each long strand of DNA is called a chromosome. The specific location of a DNA sequence within a chromosome is known as a locus. If the DNA sequence at a locus varies between individuals, the different forms of this sequence are called alleles. DNA sequences can change through mutations, producing new alleles. If a mutation occurs within a gene, the new allele may affect the trait that the gene controls, altering the phenotype of the organism. However, while this simple correspondence between an allele and a trait works in some cases, most traits are influenced by multiple genes in a quantitative or epistatic manner. Sources of variation Main article: Genetic variation Further information: Genetic diversity and Population genetics White peppered mothBlack morph in peppered moth evolution Evolution can occur if there is genetic variation within a population. Variation comes from mutations in the genome, reshuffling of genes through sexual reproduction and migration between populations (gene flow). Despite the constant introduction of new variation through mutation and gene flow, most of the genome of a species is very similar among all individuals of that species. However, discoveries in the field of evolutionary developmental biology have demonstrated that even relatively small differences in genotype can lead to dramatic differences in phenotype both within and between species. An individual organism's phenotype results from both its genotype and the influence of the environment it has lived in. The modern evolutionary synthesis defines evolution as the change over time in this genetic variation. The frequency of one particular allele will become more or less prevalent relative to other forms of that gene. Variation disappears when a new allele reaches the point of fixation—when it either disappears from the population or replaces the ancestral allele entirely. Mutation Main article: Mutation Duplication of part of a chromosome Mutations are changes in the DNA sequence of a cell's genome and are the ultimate source of genetic variation in all organisms. When mutations occur, they may alter the product of a gene, or prevent the gene from functioning, or have no effect. About half of the mutations in the coding regions of protein-coding genes are deleterious — the other half are neutral. A small percentage of the total mutations in this region confer a fitness benefit. Some of the mutations in other parts of the genome are deleterious but the vast majority are neutral. A few are beneficial. Mutations can involve large sections of a chromosome becoming duplicated (usually by genetic recombination), which can introduce extra copies of a gene into a genome. Extra copies of genes are a major source of the raw material needed for new genes to evolve. This is important because most new genes evolve within gene families from pre-existing genes that share common ancestors. For example, the human eye uses four genes to make structures that sense light: three for colour vision and one for night vision; all four are descended from a single ancestral gene. New genes can be generated from an ancestral gene when a duplicate copy mutates and acquires a new function. This process is easier once a gene has been duplicated because it increases the redundancy of the system; one gene in the pair can acquire a new function while the other copy continues to perform its original function. Other types of mutations can even generate entirely new genes from previously noncoding DNA, a phenomenon termed de novo gene birth. The generation of new genes can also involve small parts of several genes being duplicated, with these fragments then recombining to form new combinations with new functions (exon shuffling). When new genes are assembled from shuffling pre-existing parts, domains act as modules with simple independent functions, which can be mixed together to produce new combinations with new and complex functions. For example, polyketide synthases are large enzymes that make antibiotics; they contain up to 100 independent domains that each catalyse one step in the overall process, like a step in an assembly line. One example of mutation is wild boar piglets. They are camouflage coloured and show a characteristic pattern of dark and light longitudinal stripes. However, mutations in the melanocortin 1 receptor (MC1R) disrupt the pattern. The majority of pig breeds carry MC1R mutations disrupting wild-type colour and different mutations causing dominant black colouring. Sex and recombination Further information: Sexual reproduction, Genetic recombination, and Evolution of sexual reproduction In asexual organisms, genes are inherited together, or linked, as they cannot mix with genes of other organisms during reproduction. In contrast, the offspring of sexual organisms contain random mixtures of their parents' chromosomes that are produced through independent assortment. In a related process called homologous recombination, sexual organisms exchange DNA between two matching chromosomes. Recombination and reassortment do not alter allele frequencies, but instead change which alleles are associated with each other, producing offspring with new combinations of alleles. Sex usually increases genetic variation and may increase the rate of evolution. This diagram illustrates the twofold cost of sex. If each individual were to contribute to the same number of offspring (two), (a) the sexual population remains the same size each generation, where the (b) Asexual reproduction population doubles in size each generation. The two-fold cost of sex was first described by John Maynard Smith. The first cost is that in sexually dimorphic species only one of the two sexes can bear young. This cost does not apply to hermaphroditic species, like most plants and many invertebrates. The second cost is that any individual who reproduces sexually can only pass on 50% of its genes to any individual offspring, with even less passed on as each new generation passes. Yet sexual reproduction is the more common means of reproduction among eukaryotes and multicellular organisms. The Red Queen hypothesis has been used to explain the significance of sexual reproduction as a means to enable continual evolution and adaptation in response to coevolution with other species in an ever-changing environment. Another hypothesis is that sexual reproduction is primarily an adaptation for promoting accurate recombinational repair of damage in germline DNA, and that increased diversity is a byproduct of this process that may sometimes be adaptively beneficial. Gene flow Further information: Gene flow Gene flow is the exchange of genes between populations and between species. It can therefore be a source of variation that is new to a population or to a species. Gene flow can be caused by the movement of individuals between separate populations of organisms, as might be caused by the movement of mice between inland and coastal populations, or the movement of pollen between heavy-metal-tolerant and heavy-metal-sensitive populations of grasses. Gene transfer between species includes the formation of hybrid organisms and horizontal gene transfer. Horizontal gene transfer is the transfer of genetic material from one organism to another organism that is not its offspring; this is most common among bacteria. In medicine, this contributes to the spread of antibiotic resistance, as when one bacteria acquires resistance genes it can rapidly transfer them to other species. Horizontal transfer of genes from bacteria to eukaryotes such as the yeast Saccharomyces cerevisiae and the adzuki bean weevil Callosobruchus chinensis has occurred. An example of larger-scale transfers are the eukaryotic bdelloid rotifers, which have received a range of genes from bacteria, fungi and plants. Viruses can also carry DNA between organisms, allowing transfer of genes even across biological domains. Large-scale gene transfer has also occurred between the ancestors of eukaryotic cells and bacteria, during the acquisition of chloroplasts and mitochondria. It is possible that eukaryotes themselves originated from horizontal gene transfers between bacteria and archaea. Epigenetics Further information: Epigenetics Some heritable changes cannot be explained by changes to the sequence of nucleotides in the DNA. These phenomena are classed as epigenetic inheritance systems. DNA methylation marking chromatin, self-sustaining metabolic loops, gene silencing by RNA interference and the three-dimensional conformation of proteins (such as prions) are areas where epigenetic inheritance systems have been discovered at the organismic level. Developmental biologists suggest that complex interactions in genetic networks and communication among cells can lead to heritable variations that may underlay some of the mechanics in developmental plasticity and canalisation. Heritability may also occur at even larger scales. For example, ecological inheritance through the process of niche construction is defined by the regular and repeated activities of organisms in their environment. This generates a legacy of effects that modify and feed back into the selection regime of subsequent generations. Other examples of heritability in evolution that are not under the direct control of genes include the inheritance of cultural traits and symbiogenesis. Evolutionary forces Mutation followed by natural selection results in a population with darker colouration. From a neo-Darwinian perspective, evolution occurs when there are changes in the frequencies of alleles within a population of interbreeding organisms, for example, the allele for black colour in a population of moths becoming more common. Mechanisms that can lead to changes in allele frequencies include natural selection, genetic drift, and mutation bias. Natural selection Main article: Natural selection See also: Dollo's law of irreversibility Evolution by natural selection is the process by which traits that enhance survival and reproduction become more common in successive generations of a population. It embodies three principles: Variation exists within populations of organisms with respect to morphology, physiology and behaviour (phenotypic variation). Different traits confer different rates of survival and reproduction (differential fitness). These traits can be passed from generation to generation (heritability of fitness). More offspring are produced than can possibly survive, and these conditions produce competition between organisms for survival and reproduction. Consequently, organisms with traits that give them an advantage over their competitors are more likely to pass on their traits to the next generation than those with traits that do not confer an advantage. This teleonomy is the quality whereby the process of natural selection creates and preserves traits that are seemingly fitted for the functional roles they perform. Consequences of selection include nonrandom mating and genetic hitchhiking. The central concept of natural selection is the evolutionary fitness of an organism. Fitness is measured by an organism's ability to survive and reproduce, which determines the size of its genetic contribution to the next generation. However, fitness is not the same as the total number of offspring: instead fitness is indicated by the proportion of subsequent generations that carry an organism's genes. For example, if an organism could survive well and reproduce rapidly, but its offspring were all too small and weak to survive, this organism would make little genetic contribution to future generations and would thus have low fitness. If an allele increases fitness more than the other alleles of that gene, then with each generation this allele has a higher probability of becoming common within the population. These traits are said to be "selected for." Examples of traits that can increase fitness are enhanced survival and increased fecundity. Conversely, the lower fitness caused by having a less beneficial or deleterious allele results in this allele likely becoming rarer—they are "selected against." Importantly, the fitness of an allele is not a fixed characteristic; if the environment changes, previously neutral or harmful traits may become beneficial and previously beneficial traits become harmful. However, even if the direction of selection does reverse in this way, traits that were lost in the past may not re-evolve in an identical form. However, a re-activation of dormant genes, as long as they have not been eliminated from the genome and were only suppressed perhaps for hundreds of generations, can lead to the re-occurrence of traits thought to be lost like hindlegs in dolphins, teeth in chickens, wings in wingless stick insects, tails and additional nipples in humans etc. "Throwbacks" such as these are known as atavisms. These charts depict the different types of genetic selection. On each graph, the x-axis variable is the type of phenotypic trait and the y-axis variable is the number of organisms. Group A is the original population and Group B is the population after selection. · Graph 1 shows directional selection, in which a single extreme phenotype is favoured. · Graph 2 depicts stabilizing selection, where the intermediate phenotype is favoured over the extreme traits. · Graph 3 shows disruptive selection, in which the extreme phenotypes are favoured over the intermediate. Natural selection within a population for a trait that can vary across a range of values, such as height, can be categorised into three different types. The first is directional selection, which is a shift in the average value of a trait over time—for example, organisms slowly getting taller. Secondly, disruptive selection is selection for extreme trait values and often results in two different values becoming most common, with selection against the average value. This would be when either short or tall organisms had an advantage, but not those of medium height. Finally, in stabilising selection there is selection against extreme trait values on both ends, which causes a decrease in variance around the average value and less diversity. This would, for example, cause organisms to eventually have a similar height. Natural selection most generally makes nature the measure against which individuals and individual traits, are more or less likely to survive. "Nature" in this sense refers to an ecosystem, that is, a system in which organisms interact with every other element, physical as well as biological, in their local environment. Eugene Odum, a founder of ecology, defined an ecosystem as: "Any unit that includes all of the organisms...in a given area interacting with the physical environment so that a flow of energy leads to clearly defined trophic structure, biotic diversity, and material cycles (i.e., exchange of materials between living and nonliving parts) within the system...." Each population within an ecosystem occupies a distinct niche, or position, with distinct relationships to other parts of the system. These relationships involve the life history of the organism, its position in the food chain and its geographic range. This broad understanding of nature enables scientists to delineate specific forces which, together, comprise natural selection. Natural selection can act at different levels of organisation, such as genes, cells, individual organisms, groups of organisms and species. Selection can act at multiple levels simultaneously. An example of selection occurring below the level of the individual organism are genes called transposons, which can replicate and spread throughout a genome. Selection at a level above the individual, such as group selection, may allow the evolution of cooperation. Genetic drift Further information: Genetic drift and Effective population size Simulation of genetic drift of 20 unlinked alleles in populations of 10 (top) and 100 (bottom). Drift to fixation is more rapid in the smaller population. Genetic drift is the random fluctuation of allele frequencies within a population from one generation to the next. When selective forces are absent or relatively weak, allele frequencies are equally likely to drift upward or downward in each successive generation because the alleles are subject to sampling error. This drift halts when an allele eventually becomes fixed, either by disappearing from the population or by replacing the other alleles entirely. Genetic drift may therefore eliminate some alleles from a population due to chance alone. Even in the absence of selective forces, genetic drift can cause two separate populations that begin with the same genetic structure to drift apart into two divergent populations with different sets of alleles. According to the neutral theory of molecular evolution most evolutionary changes are the result of the fixation of neutral mutations by genetic drift. In this model, most genetic changes in a population are thus the result of constant mutation pressure and genetic drift. This form of the neutral theory has been debated since it does not seem to fit some genetic variation seen in nature. A better-supported version of this model is the nearly neutral theory, according to which a mutation that would be effectively neutral in a small population is not necessarily neutral in a large population. Other theories propose that genetic drift is dwarfed by other stochastic forces in evolution, such as genetic hitchhiking, also known as genetic draft. Another concept is constructive neutral evolution (CNE), which explains that complex systems can emerge and spread into a population through neutral transitions due to the principles of excess capacity, presuppression, and ratcheting, and it has been applied in areas ranging from the origins of the spliceosome to the complex interdependence of microbial communities. The time it takes a neutral allele to become fixed by genetic drift depends on population size; fixation is more rapid in smaller populations. The number of individuals in a population is not critical, but instead a measure known as the effective population size. The effective population is usually smaller than the total population since it takes into account factors such as the level of inbreeding and the stage of the lifecycle in which the population is the smallest. The effective population size may not be the same for every gene in the same population. It is usually difficult to measure the relative importance of selection and neutral processes, including drift. The comparative importance of adaptive and non-adaptive forces in driving evolutionary change is an area of current research. Mutation bias Mutation bias is usually conceived as a difference in expected rates for two different kinds of mutation, e.g., transition-transversion bias, GC-AT bias, deletion-insertion bias. This is related to the idea of developmental bias. Haldane and Fisher argued that, because mutation is a weak pressure easily overcome by selection, tendencies of mutation would be ineffectual except under conditions of neutral evolution or extraordinarily high mutation rates. This opposing-pressures argument was long used to dismiss the possibility of internal tendencies in evolution, until the molecular era prompted renewed interest in neutral evolution. Noboru Sueoka and Ernst Freese proposed that systematic biases in mutation might be responsible for systematic differences in genomic GC composition between species. The identification of a GC-biased E. coli mutator strain in 1967, along with the proposal of the neutral theory, established the plausibility of mutational explanations for molecular patterns, which are now common in the molecular evolution literature. For instance, mutation biases are frequently invoked in models of codon usage. Such models also include effects of selection, following the mutation-selection-drift model, which allows both for mutation biases and differential selection based on effects on translation. Hypotheses of mutation bias have played an important role in the development of thinking about the evolution of genome composition, including isochores. Different insertion vs. deletion biases in different taxa can lead to the evolution of different genome sizes. The hypothesis of Lynch regarding genome size relies on mutational biases toward increase or decrease in genome size. However, mutational hypotheses for the evolution of composition suffered a reduction in scope when it was discovered that (1) GC-biased gene conversion makes an important contribution to composition in diploid organisms such as mammals and (2) bacterial genomes frequently have AT-biased mutation. Contemporary thinking about the role of mutation biases reflects a different theory from that of Haldane and Fisher. More recent work showed that the original "pressures" theory assumes that evolution is based on standing variation: when evolution depends on events of mutation that introduce new alleles, mutational and developmental biases in the introduction of variation (arrival biases) can impose biases on evolution without requiring neutral evolution or high mutation rates. Several studies report that the mutations implicated in adaptation reflect common mutation biases though others dispute this interpretation. Genetic hitchhiking Further information: Genetic hitchhiking, Hill–Robertson effect, and Selective sweep Recombination allows alleles on the same strand of DNA to become separated. However, the rate of recombination is low (approximately two events per chromosome per generation). As a result, genes close together on a chromosome may not always be shuffled away from each other and genes that are close together tend to be inherited together, a phenomenon known as linkage. This tendency is measured by finding how often two alleles occur together on a single chromosome compared to expectations, which is called their linkage disequilibrium. A set of alleles that is usually inherited in a group is called a haplotype. This can be important when one allele in a particular haplotype is strongly beneficial: natural selection can drive a selective sweep that will also cause the other alleles in the haplotype to become more common in the population; this effect is called genetic hitchhiking or genetic draft. Genetic draft caused by the fact that some neutral genes are genetically linked to others that are under selection can be partially captured by an appropriate effective population size. Sexual selection Further information: Sexual selection Male moor frogs become blue during the height of mating season. Blue reflectance may be a form of intersexual communication. It is hypothesised that males with brighter blue coloration may signal greater sexual and genetic fitness. A special case of natural selection is sexual selection, which is selection for any trait that increases mating success by increasing the attractiveness of an organism to potential mates. Traits that evolved through sexual selection are particularly prominent among males of several animal species. Although sexually favoured, traits such as cumbersome antlers, mating calls, large body size and bright colours often attract predation, which compromises the survival of individual males. This survival disadvantage is balanced by higher reproductive success in males that show these hard-to-fake, sexually selected traits. Natural outcomes A visual demonstration of rapid antibiotic resistance evolution by E. coli growing across a plate with increasing concentrations of trimethoprim Evolution influences every aspect of the form and behaviour of organisms. Most prominent are the specific behavioural and physical adaptations that are the outcome of natural selection. These adaptations increase fitness by aiding activities such as finding food, avoiding predators or attracting mates. Organisms can also respond to selection by cooperating with each other, usually by aiding their relatives or engaging in mutually beneficial symbiosis. In the longer term, evolution produces new species through splitting ancestral populations of organisms into new groups that cannot or will not interbreed. These outcomes of evolution are distinguished based on time scale as macroevolution versus microevolution. Macroevolution refers to evolution that occurs at or above the level of species, in particular speciation and extinction; whereas microevolution refers to smaller evolutionary changes within a species or population, in particular shifts in allele frequency and adaptation. Macroevolution the outcome of long periods of microevolution. Thus, the distinction between micro- and macroevolution is not a fundamental one—the difference is simply the time involved. However, in macroevolution, the traits of the entire species may be important. For instance, a large amount of variation among individuals allows a species to rapidly adapt to new habitats, lessening the chance of it going extinct, while a wide geographic range increases the chance of speciation, by making it more likely that part of the population will become isolated. In this sense, microevolution and macroevolution might involve selection at different levels—with microevolution acting on genes and organisms, versus macroevolutionary processes such as species selection acting on entire species and affecting their rates of speciation and extinction. A common misconception is that evolution has goals, long-term plans, or an innate tendency for "progress", as expressed in beliefs such as orthogenesis and evolutionism; realistically however, evolution has no long-term goal and does not necessarily produce greater complexity. Although complex species have evolved, they occur as a side effect of the overall number of organisms increasing and simple forms of life still remain more common in the biosphere. For example, the overwhelming majority of species are microscopic prokaryotes, which form about half the world's biomass despite their small size, and constitute the vast majority of Earth's biodiversity. Simple organisms have therefore been the dominant form of life on Earth throughout its history and continue to be the main form of life up to the present day, with complex life only appearing more diverse because it is more noticeable. Indeed, the evolution of microorganisms is particularly important to evolutionary research, since their rapid reproduction allows the study of experimental evolution and the observation of evolution and adaptation in real time. Adaptation Further information: Adaptation Homologous bones in the limbs of tetrapods. The bones of these animals have the same basic structure, but have been adapted for specific uses. Adaptation is the process that makes organisms better suited to their habitat. Also, the term adaptation may refer to a trait that is important for an organism's survival. For example, the adaptation of horses' teeth to the grinding of grass. By using the term adaptation for the evolutionary process and adaptive trait for the product (the bodily part or function), the two senses of the word may be distinguished. Adaptations are produced by natural selection. The following definitions are due to Theodosius Dobzhansky: Adaptation is the evolutionary process whereby an organism becomes better able to live in its habitat or habitats. Adaptedness is the state of being adapted: the degree to which an organism is able to live and reproduce in a given set of habitats. An adaptive trait is an aspect of the developmental pattern of the organism which enables or enhances the probability of that organism surviving and reproducing. Adaptation may cause either the gain of a new feature, or the loss of an ancestral feature. An example that shows both types of change is bacterial adaptation to antibiotic selection, with genetic changes causing antibiotic resistance by both modifying the target of the drug, or increasing the activity of transporters that pump the drug out of the cell. Other striking examples are the bacteria Escherichia coli evolving the ability to use citric acid as a nutrient in a long-term laboratory experiment, Flavobacterium evolving a novel enzyme that allows these bacteria to grow on the by-products of nylon manufacturing, and the soil bacterium Sphingobium evolving an entirely new metabolic pathway that degrades the synthetic pesticide pentachlorophenol. An interesting but still controversial idea is that some adaptations might increase the ability of organisms to generate genetic diversity and adapt by natural selection (increasing organisms' evolvability). A baleen whale skeleton. Letters a and b label flipper bones, which were adapted from front leg bones, while c indicates vestigial leg bones, both suggesting an adaptation from land to sea. Adaptation occurs through the gradual modification of existing structures. Consequently, structures with similar internal organisation may have different functions in related organisms. This is the result of a single ancestral structure being adapted to function in different ways. The bones within bat wings, for example, are very similar to those in mice feet and primate hands, due to the descent of all these structures from a common mammalian ancestor. However, since all living organisms are related to some extent, even organs that appear to have little or no structural similarity, such as arthropod, squid and vertebrate eyes, or the limbs and wings of arthropods and vertebrates, can depend on a common set of homologous genes that control their assembly and function; this is called deep homology. During evolution, some structures may lose their original function and become vestigial structures. Such structures may have little or no function in a current species, yet have a clear function in ancestral species, or other closely related species. Examples include pseudogenes, the non-functional remains of eyes in blind cave-dwelling fish, wings in flightless birds, the presence of hip bones in whales and snakes, and sexual traits in organisms that reproduce via asexual reproduction. Examples of vestigial structures in humans include wisdom teeth, the coccyx, the vermiform appendix, and other behavioural vestiges such as goose bumps and primitive reflexes. However, many traits that appear to be simple adaptations are in fact exaptations: structures originally adapted for one function, but which coincidentally became somewhat useful for some other function in the process. One example is the African lizard Holaspis guentheri, which developed an extremely flat head for hiding in crevices, as can be seen by looking at its near relatives. However, in this species, the head has become so flattened that it assists in gliding from tree to tree—an exaptation. Within cells, molecular machines such as the bacterial flagella and protein sorting machinery evolved by the recruitment of several pre-existing proteins that previously had different functions. Another example is the recruitment of enzymes from glycolysis and xenobiotic metabolism to serve as structural proteins called crystallins within the lenses of organisms' eyes. An area of current investigation in evolutionary developmental biology is the developmental basis of adaptations and exaptations. This research addresses the origin and evolution of embryonic development and how modifications of development and developmental processes produce novel features. These studies have shown that evolution can alter development to produce new structures, such as embryonic bone structures that develop into the jaw in other animals instead forming part of the middle ear in mammals. It is also possible for structures that have been lost in evolution to reappear due to changes in developmental genes, such as a mutation in chickens causing embryos to grow teeth similar to those of crocodiles. It is now becoming clear that most alterations in the form of organisms are due to changes in a small set of conserved genes. Coevolution Further information: Coevolution The common garter snake has evolved resistance to the defensive substance tetrodotoxin in its amphibian prey. Interactions between organisms can produce both conflict and cooperation. When the interaction is between pairs of species, such as a pathogen and a host, or a predator and its prey, these species can develop matched sets of adaptations. Here, the evolution of one species causes adaptations in a second species. These changes in the second species then, in turn, cause new adaptations in the first species. This cycle of selection and response is called coevolution. An example is the production of tetrodotoxin in the rough-skinned newt and the evolution of tetrodotoxin resistance in its predator, the common garter snake. In this predator-prey pair, an evolutionary arms race has produced high levels of toxin in the newt and correspondingly high levels of toxin resistance in the snake. Cooperation Further information: Co-operation (evolution) Not all co-evolved interactions between species involve conflict. Many cases of mutually beneficial interactions have evolved. For instance, an extreme cooperation exists between plants and the mycorrhizal fungi that grow on their roots and aid the plant in absorbing nutrients from the soil. This is a reciprocal relationship as the plants provide the fungi with sugars from photosynthesis. Here, the fungi actually grow inside plant cells, allowing them to exchange nutrients with their hosts, while sending signals that suppress the plant immune system. Coalitions between organisms of the same species have also evolved. An extreme case is the eusociality found in social insects, such as bees, termites and ants, where sterile insects feed and guard the small number of organisms in a colony that are able to reproduce. On an even smaller scale, the somatic cells that make up the body of an animal limit their reproduction so they can maintain a stable organism, which then supports a small number of the animal's germ cells to produce offspring. Here, somatic cells respond to specific signals that instruct them whether to grow, remain as they are, or die. If cells ignore these signals and multiply inappropriately, their uncontrolled growth causes cancer. Such cooperation within species may have evolved through the process of kin selection, which is where one organism acts to help raise a relative's offspring. This activity is selected for because if the helping individual contains alleles which promote the helping activity, it is likely that its kin will also contain these alleles and thus those alleles will be passed on. Other processes that may promote cooperation include group selection, where cooperation provides benefits to a group of organisms. Speciation Main article: Speciation Further information: Assortative mating and Panmixia The four geographic modes of speciation Speciation is the process where a species diverges into two or more descendant species. There are multiple ways to define the concept of "species." The choice of definition is dependent on the particularities of the species concerned. For example, some species concepts apply more readily toward sexually reproducing organisms while others lend themselves better toward asexual organisms. Despite the diversity of various species concepts, these various concepts can be placed into one of three broad philosophical approaches: interbreeding, ecological and phylogenetic. The Biological Species Concept (BSC) is a classic example of the interbreeding approach. Defined by evolutionary biologist Ernst Mayr in 1942, the BSC states that "species are groups of actually or potentially interbreeding natural populations, which are reproductively isolated from other such groups." Despite its wide and long-term use, the BSC like other species concepts is not without controversy, for example, because genetic recombination among prokaryotes is not an intrinsic aspect of reproduction; this is called the species problem. Some researchers have attempted a unifying monistic definition of species, while others adopt a pluralistic approach and suggest that there may be different ways to logically interpret the definition of a species. Barriers to reproduction between two diverging sexual populations are required for the populations to become new species. Gene flow may slow this process by spreading the new genetic variants also to the other populations. Depending on how far two species have diverged since their most recent common ancestor, it may still be possible for them to produce offspring, as with horses and donkeys mating to produce mules. Such hybrids are generally infertile. In this case, closely related species may regularly interbreed, but hybrids will be selected against and the species will remain distinct. However, viable hybrids are occasionally formed and these new species can either have properties intermediate between their parent species, or possess a totally new phenotype. The importance of hybridisation in producing new species of animals is unclear, although cases have been seen in many types of animals, with the gray tree frog being a particularly well-studied example. Speciation has been observed multiple times under both controlled laboratory conditions and in nature. In sexually reproducing organisms, speciation results from reproductive isolation followed by genealogical divergence. There are four primary geographic modes of speciation. The most common in animals is allopatric speciation, which occurs in populations initially isolated geographically, such as by habitat fragmentation or migration. Selection under these conditions can produce very rapid changes in the appearance and behaviour of organisms. As selection and drift act independently on populations isolated from the rest of their species, separation may eventually produce organisms that cannot interbreed. The second mode of speciation is peripatric speciation, which occurs when small populations of organisms become isolated in a new environment. This differs from allopatric speciation in that the isolated populations are numerically much smaller than the parental population. Here, the founder effect causes rapid speciation after an increase in inbreeding increases selection on homozygotes, leading to rapid genetic change. The third mode is parapatric speciation. This is similar to peripatric speciation in that a small population enters a new habitat, but differs in that there is no physical separation between these two populations. Instead, speciation results from the evolution of mechanisms that reduce gene flow between the two populations. Generally this occurs when there has been a drastic change in the environment within the parental species' habitat. One example is the grass Anthoxanthum odoratum, which can undergo parapatric speciation in response to localised metal pollution from mines. Here, plants evolve that have resistance to high levels of metals in the soil. Selection against interbreeding with the metal-sensitive parental population produced a gradual change in the flowering time of the metal-resistant plants, which eventually produced complete reproductive isolation. Selection against hybrids between the two populations may cause reinforcement, which is the evolution of traits that promote mating within a species, as well as character displacement, which is when two species become more distinct in appearance. Geographical isolation of finches on the Galápagos Islands produced over a dozen new species. Finally, in sympatric speciation species diverge without geographic isolation or changes in habitat. This form is rare since even a small amount of gene flow may remove genetic differences between parts of a population. Generally, sympatric speciation in animals requires the evolution of both genetic differences and nonrandom mating, to allow reproductive isolation to evolve. One type of sympatric speciation involves crossbreeding of two related species to produce a new hybrid species. This is not common in animals as animal hybrids are usually sterile. This is because during meiosis the homologous chromosomes from each parent are from different species and cannot successfully pair. However, it is more common in plants because plants often double their number of chromosomes, to form polyploids. This allows the chromosomes from each parental species to form matching pairs during meiosis, since each parent's chromosomes are represented by a pair already. An example of such a speciation event is when the plant species Arabidopsis thaliana and Arabidopsis arenosa crossbred to give the new species Arabidopsis suecica. This happened about 20,000 years ago, and the speciation process has been repeated in the laboratory, which allows the study of the genetic mechanisms involved in this process. Indeed, chromosome doubling within a species may be a common cause of reproductive isolation, as half the doubled chromosomes will be unmatched when breeding with undoubled organisms. Speciation events are important in the theory of punctuated equilibrium, which accounts for the pattern in the fossil record of short "bursts" of evolution interspersed with relatively long periods of stasis, where species remain relatively unchanged. In this theory, speciation and rapid evolution are linked, with natural selection and genetic drift acting most strongly on organisms undergoing speciation in novel habitats or small populations. As a result, the periods of stasis in the fossil record correspond to the parental population and the organisms undergoing speciation and rapid evolution are found in small populations or geographically restricted habitats and therefore rarely being preserved as fossils. Extinction Further information: Extinction Tyrannosaurus rex. Non-avian dinosaurs died out in the Cretaceous–Paleogene extinction event at the end of the Cretaceous period. Extinction is the disappearance of an entire species. Extinction is not an unusual event, as species regularly appear through speciation and disappear through extinction. Nearly all animal and plant species that have lived on Earth are now extinct, and extinction appears to be the ultimate fate of all species. These extinctions have happened continuously throughout the history of life, although the rate of extinction spikes in occasional mass extinction events. The Cretaceous–Paleogene extinction event, during which the non-avian dinosaurs became extinct, is the most well-known, but the earlier Permian–Triassic extinction event was even more severe, with approximately 96% of all marine species driven to extinction. The Holocene extinction event is an ongoing mass extinction associated with humanity's expansion across the globe over the past few thousand years. Present-day extinction rates are 100–1000 times greater than the background rate and up to 30% of current species may be extinct by the mid 21st century. Human activities are now the primary cause of the ongoing extinction event; global warming may further accelerate it in the future. Despite the estimated extinction of more than 99% of all species that ever lived on Earth, about 1 trillion species are estimated to be on Earth currently with only one-thousandth of 1% described. The role of extinction in evolution is not very well understood and may depend on which type of extinction is considered. The causes of the continuous "low-level" extinction events, which form the majority of extinctions, may be the result of competition between species for limited resources (the competitive exclusion principle). If one species can out-compete another, this could produce species selection, with the fitter species surviving and the other species being driven to extinction. The intermittent mass extinctions are also important, but instead of acting as a selective force, they drastically reduce diversity in a nonspecific manner and promote bursts of rapid evolution and speciation in survivors. Applications Main articles: Applications of evolution, Selective breeding, and Evolutionary computation Concepts and models used in evolutionary biology, such as natural selection, have many applications. Artificial selection is the intentional selection of traits in a population of organisms. This has been used for thousands of years in the domestication of plants and animals. More recently, such selection has become a vital part of genetic engineering, with selectable markers such as antibiotic resistance genes being used to manipulate DNA. Proteins with valuable properties have evolved by repeated rounds of mutation and selection (for example modified enzymes and new antibodies) in a process called directed evolution. Understanding the changes that have occurred during an organism's evolution can reveal the genes needed to construct parts of the body, genes which may be involved in human genetic disorders. For example, the Mexican tetra is an albino cavefish that lost its eyesight during evolution. Breeding together different populations of this blind fish produced some offspring with functional eyes, since different mutations had occurred in the isolated populations that had evolved in different caves. This helped identify genes required for vision and pigmentation. Evolutionary theory has many applications in medicine. Many human diseases are not static phenomena, but capable of evolution. Viruses, bacteria, fungi and cancers evolve to be resistant to host immune defences, as well as to pharmaceutical drugs. These same problems occur in agriculture with pesticide and herbicide resistance. It is possible that we are facing the end of the effective life of most of available antibiotics and predicting the evolution and evolvability of our pathogens and devising strategies to slow or circumvent it is requiring deeper knowledge of the complex forces driving evolution at the molecular level. In computer science, simulations of evolution using evolutionary algorithms and artificial life started in the 1960s and were extended with simulation of artificial selection. Artificial evolution became a widely recognised optimisation method as a result of the work of Ingo Rechenberg in the 1960s. He used evolution strategies to solve complex engineering problems. Genetic algorithms in particular became popular through the writing of John Henry Holland. Practical applications also include automatic evolution of computer programmes. Evolutionary algorithms are now used to solve multi-dimensional problems more efficiently than software produced by human designers and also to optimise the design of systems. Evolutionary history of life Life timelineThis box: viewtalkedit−4500 —–—–−4000 —–—–−3500 —–—–−3000 —–—–−2500 —–—–−2000 —–—–−1500 —–—–−1000 —–—–−500 —–—–0 — Water Single-celled life Photosynthesis Eukaryotes Multicellular life Plants Arthropods MolluscsFlowersDinosaurs MammalsBirdsPrimatesHadeanArcheanProterozoicPhanerozoic ←Earth formed←Earliest water←LUCA←Earliest fossils←LHB meteorites←Earliest oxygen←Pongola glaciation←Atmospheric oxygen←Huronian glaciation←Sexual reproduction←Earliest multicellular life←Earliest fungi←Earliest plants←Earliest animals←Cryogenian ice age←Ediacaran biota←Cambrian explosion←Andean glaciation←Earliest tetrapods←Karoo ice age←Earliest apes / humans←Quaternary ice age(million years ago)*Ice Ages Main article: Evolutionary history of life See also: Timeline of the evolutionary history of life Origin of life Further information: Abiogenesis, Earliest known life forms, Panspermia, and RNA world hypothesis The Earth is about 4.54 billion years old. The earliest undisputed evidence of life on Earth dates from at least 3.5 billion years ago, during the Eoarchean Era after a geological crust started to solidify following the earlier molten Hadean Eon. Microbial mat fossils have been found in 3.48 billion-year-old sandstone in Western Australia. Other early physical evidence of a biogenic substance is graphite in 3.7 billion-year-old metasedimentary rocks discovered in Western Greenland as well as "remains of biotic life" found in 4.1 billion-year-old rocks in Western Australia. Commenting on the Australian findings, Stephen Blair Hedges wrote: "If life arose relatively quickly on Earth, then it could be common in the universe." In July 2016, scientists reported identifying a set of 355 genes from the last universal common ancestor (LUCA) of all organisms living on Earth. More than 99% of all species, amounting to over five billion species, that ever lived on Earth are estimated to be extinct. Estimates on the number of Earth's current species range from 10 million to 14 million, of which about 1.9 million are estimated to have been named and 1.6 million documented in a central database to date, leaving at least 80% not yet described. Highly energetic chemistry is thought to have produced a self-replicating molecule around 4 billion years ago, and half a billion years later the last common ancestor of all life existed. The current scientific consensus is that the complex biochemistry that makes up life came from simpler chemical reactions. The beginning of life may have included self-replicating molecules such as RNA and the assembly of simple cells. Common descent Further information: Common descent and Evidence of common descent All organisms on Earth are descended from a common ancestor or ancestral gene pool. Current species are a stage in the process of evolution, with their diversity the product of a long series of speciation and extinction events. The common descent of organisms was first deduced from four simple facts about organisms: First, they have geographic distributions that cannot be explained by local adaptation. Second, the diversity of life is not a set of completely unique organisms, but organisms that share morphological similarities. Third, vestigial traits with no clear purpose resemble functional ancestral traits. Fourth, organisms can be classified using these similarities into a hierarchy of nested groups, similar to a family tree. The hominoids are descendants of a common ancestor. Due to horizontal gene transfer, this "tree of life" may be more complicated than a simple branching tree, since some genes have spread independently between distantly related species. To solve this problem and others, some authors prefer to use the "Coral of life" as a metaphor or a mathematical model to illustrate the evolution of life. This view dates back to an idea briefly mentioned by Darwin but later abandoned. Past species have also left records of their evolutionary history. Fossils, along with the comparative anatomy of present-day organisms, constitute the morphological, or anatomical, record. By comparing the anatomies of both modern and extinct species, palaeontologists can infer the lineages of those species. However, this approach is most successful for organisms that had hard body parts, such as shells, bones or teeth. Further, as prokaryotes such as bacteria and archaea share a limited set of common morphologies, their fossils do not provide information on their ancestry. More recently, evidence for common descent has come from the study of biochemical similarities between organisms. For example, all living cells use the same basic set of nucleotides and amino acids. The development of molecular genetics has revealed the record of evolution left in organisms' genomes: dating when species diverged through the molecular clock produced by mutations. For example, these DNA sequence comparisons have revealed that humans and chimpanzees share 98% of their genomes and analysing the few areas where they differ helps shed light on when the common ancestor of these species existed. Evolution of life Main articles: Evolutionary history of life and Timeline of evolutionary history of life Evolutionary tree showing the divergence of modern species from their common ancestor in the centre. The three domains are coloured, with bacteria blue, archaea green and eukaryotes red. Prokaryotes inhabited the Earth from approximately 3–4 billion years ago. No obvious changes in morphology or cellular organisation occurred in these organisms over the next few billion years. The eukaryotic cells emerged between 1.6 and 2.7 billion years ago. The next major change in cell structure came when bacteria were engulfed by eukaryotic cells, in a cooperative association called endosymbiosis. The engulfed bacteria and the host cell then underwent coevolution, with the bacteria evolving into either mitochondria or hydrogenosomes. Another engulfment of cyanobacterial-like organisms led to the formation of chloroplasts in algae and plants. The history of life was that of the unicellular eukaryotes, prokaryotes and archaea until about 610 million years ago when multicellular organisms began to appear in the oceans in the Ediacaran period. The evolution of multicellularity occurred in multiple independent events, in organisms as diverse as sponges, brown algae, cyanobacteria, slime moulds and myxobacteria. In January 2016, scientists reported that, about 800 million years ago, a minor genetic change in a single molecule called GK-PID may have allowed organisms to go from a single cell organism to one of many cells. Soon after the emergence of these first multicellular organisms, a remarkable amount of biological diversity appeared over approximately 10 million years, in an event called the Cambrian explosion. Here, the majority of types of modern animals appeared in the fossil record, as well as unique lineages that subsequently became extinct. Various triggers for the Cambrian explosion have been proposed, including the accumulation of oxygen in the atmosphere from photosynthesis. About 500 million years ago, plants and fungi colonised the land and were soon followed by arthropods and other animals. Insects were particularly successful and even today make up the majority of animal species. Amphibians first appeared around 364 million years ago, followed by early amniotes and birds around 155 million years ago (both from "reptile"-like lineages), mammals around 129 million years ago, Homininae around 10 million years ago and modern humans around 250,000 years ago. However, despite the evolution of these large animals, smaller organisms similar to the types that evolved early in this process continue to be highly successful and dominate the Earth, with the majority of both biomass and species being prokaryotes. History of evolutionary thought Main article: History of evolutionary thought Further information: History of speciation Lucretius Alfred Russel Wallace Thomas Robert Malthus In 1842, Charles Darwin penned his first sketch of On the Origin of Species. Classical antiquity The proposal that one type of organism could descend from another type goes back to some of the first pre-Socratic Greek philosophers, such as Anaximander and Empedocles. Such proposals survived into Roman times. The poet and philosopher Lucretius followed Empedocles in his masterwork De rerum natura (lit. 'On the Nature of Things'). Middle Ages In contrast to these materialistic views, Aristotelianism had considered all natural things as actualisations of fixed natural possibilities, known as forms. This became part of a medieval teleological understanding of nature in which all things have an intended role to play in a divine cosmic order. Variations of this idea became the standard understanding of the Middle Ages and were integrated into Christian learning, but Aristotle did not demand that real types of organisms always correspond one-for-one with exact metaphysical forms and specifically gave examples of how new types of living things could come to be. A number of Arab Muslim scholars wrote about evolution, most notably Ibn Khaldun, who wrote the book Muqaddimah in 1377 AD, in which he asserted that humans developed from "the world of the monkeys", in a process by which "species become more numerous". Pre-Darwinian The "New Science" of the 17th century rejected the Aristotelian approach. It sought to explain natural phenomena in terms of physical laws that were the same for all visible things and that did not require the existence of any fixed natural categories or divine cosmic order. However, this new approach was slow to take root in the biological sciences: the last bastion of the concept of fixed natural types. John Ray applied one of the previously more general terms for fixed natural types, "species", to plant and animal types, but he strictly identified each type of living thing as a species and proposed that each species could be defined by the features that perpetuated themselves generation after generation. The biological classification introduced by Carl Linnaeus in 1735 explicitly recognised the hierarchical nature of species relationships, but still viewed species as fixed according to a divine plan. Other naturalists of this time speculated on the evolutionary change of species over time according to natural laws. In 1751, Pierre Louis Maupertuis wrote of natural modifications occurring during reproduction and accumulating over many generations to produce new species. Georges-Louis Leclerc, Comte de Buffon, suggested that species could degenerate into different organisms, and Erasmus Darwin proposed that all warm-blooded animals could have descended from a single microorganism (or "filament"). The first full-fledged evolutionary scheme was Jean-Baptiste Lamarck's "transmutation" theory of 1809, which envisaged spontaneous generation continually producing simple forms of life that developed greater complexity in parallel lineages with an inherent progressive tendency, and postulated that on a local level, these lineages adapted to the environment by inheriting changes caused by their use or disuse in parents. (The latter process was later called Lamarckism.) These ideas were condemned by established naturalists as speculation lacking empirical support. In particular, Georges Cuvier insisted that species were unrelated and fixed, their similarities reflecting divine design for functional needs. In the meantime, Ray's ideas of benevolent design had been developed by William Paley into the Natural Theology or Evidences of the Existence and Attributes of the Deity (1802), which proposed complex adaptations as evidence of divine design and which was admired by Charles Darwin. Darwinian revolution The crucial break from the concept of constant typological classes or types in biology came with the theory of evolution through natural selection, which was formulated by Charles Darwin and Alfred Wallace in terms of variable populations. Darwin used the expression "descent with modification" rather than "evolution". Partly influenced by An Essay on the Principle of Population (1798) by Thomas Robert Malthus, Darwin noted that population growth would lead to a "struggle for existence" in which favourable variations prevailed as others perished. In each generation, many offspring fail to survive to an age of reproduction because of limited resources. This could explain the diversity of plants and animals from a common ancestry through the working of natural laws in the same way for all types of organism. Darwin developed his theory of "natural selection" from 1838 onwards and was writing up his "big book" on the subject when Alfred Russel Wallace sent him a version of virtually the same theory in 1858. Their separate papers were presented together at an 1858 meeting of the Linnean Society of London. At the end of 1859, Darwin's publication of his "abstract" as On the Origin of Species explained natural selection in detail and in a way that led to an increasingly wide acceptance of Darwin's concepts of evolution at the expense of alternative theories. Thomas Henry Huxley applied Darwin's ideas to humans, using paleontology and comparative anatomy to provide strong evidence that humans and apes shared a common ancestry. Some were disturbed by this since it implied that humans did not have a special place in the universe. Pangenesis and heredity The mechanisms of reproductive heritability and the origin of new traits remained a mystery. Towards this end, Darwin developed his provisional theory of pangenesis. In 1865, Gregor Mendel reported that traits were inherited in a predictable manner through the independent assortment and segregation of elements (later known as genes). Mendel's laws of inheritance eventually supplanted most of Darwin's pangenesis theory. August Weismann made the important distinction between germ cells that give rise to gametes (such as sperm and egg cells) and the somatic cells of the body, demonstrating that heredity passes through the germ line only. Hugo de Vries connected Darwin's pangenesis theory to Weismann's germ/soma cell distinction and proposed that Darwin's pangenes were concentrated in the cell nucleus and when expressed they could move into the cytoplasm to change the cell's structure. De Vries was also one of the researchers who made Mendel's work well known, believing that Mendelian traits corresponded to the transfer of heritable variations along the germline. To explain how new variants originate, de Vries developed a mutation theory that led to a temporary rift between those who accepted Darwinian evolution and biometricians who allied with de Vries. In the 1930s, pioneers in the field of population genetics, such as Ronald Fisher, Sewall Wright and J. B. S. Haldane set the foundations of evolution onto a robust statistical philosophy. The false contradiction between Darwin's theory, genetic mutations, and Mendelian inheritance was thus reconciled. The 'modern synthesis' Main article: Modern synthesis (20th century) In the 1920s and 1930s, the modern synthesis connected natural selection and population genetics, based on Mendelian inheritance, into a unified theory that included random genetic drift, mutation, and gene flow. This new version of evolutionary theory focused on changes in allele frequencies in population. It explained patterns observed across species in populations, through fossil transitions in palaeontology. Further syntheses Since then, further syntheses have extended evolution's explanatory power in the light of numerous discoveries, to cover biological phenomena across the whole of the biological hierarchy from genes to populations. The publication of the structure of DNA by James Watson and Francis Crick with contribution of Rosalind Franklin in 1953 demonstrated a physical mechanism for inheritance. Molecular biology improved understanding of the relationship between genotype and phenotype. Advances were also made in phylogenetic systematics, mapping the transition of traits into a comparative and testable framework through the publication and use of evolutionary trees. In 1973, evolutionary biologist Theodosius Dobzhansky penned that "nothing in biology makes sense except in the light of evolution", because it has brought to light the relations of what first seemed disjointed facts in natural history into a coherent explanatory body of knowledge that describes and predicts many observable facts about life on this planet. One extension, known as evolutionary developmental biology and informally called "evo-devo," emphasises how changes between generations (evolution) act on patterns of change within individual organisms (development). Since the beginning of the 21st century, some biologists have argued for an extended evolutionary synthesis, which would account for the effects of non-genetic inheritance modes, such as epigenetics, parental effects, ecological inheritance and cultural inheritance, and evolvability. Social and cultural responses Further information: Social effects of evolutionary theory, 1860 Oxford evolution debate, Rejection of evolution by religious groups, Objections to evolution, and Evolution in fiction As evolution became widely accepted in the 1870s, caricatures of Charles Darwin with an ape or monkey body symbolised evolution. In the 19th century, particularly after the publication of On the Origin of Species in 1859, the idea that life had evolved was an active source of academic debate centred on the philosophical, social and religious implications of evolution. Today, the modern evolutionary synthesis is accepted by a vast majority of scientists. However, evolution remains a contentious concept for some theists. While various religions and denominations have reconciled their beliefs with evolution through concepts such as theistic evolution, there are creationists who believe that evolution is contradicted by the creation myths found in their religions and who raise various objections to evolution. As had been demonstrated by responses to the publication of Vestiges of the Natural History of Creation in 1844, the most controversial aspect of evolutionary biology is the implication of human evolution that humans share common ancestry with apes and that the mental and moral faculties of humanity have the same types of natural causes as other inherited traits in animals. In some countries, notably the United States, these tensions between science and religion have fuelled the current creation–evolution controversy, a religious conflict focusing on politics and public education. While other scientific fields such as cosmology and Earth science also conflict with literal interpretations of many religious texts, evolutionary biology experiences significantly more opposition from religious literalists. The teaching of evolution in American secondary school biology classes was uncommon in most of the first half of the 20th century. The Scopes Trial decision of 1925 caused the subject to become very rare in American secondary biology textbooks for a generation, but it was gradually re-introduced later and became legally protected with the 1968 Epperson v. Arkansas decision. Since then, the competing religious belief of creationism was legally disallowed in secondary school curricula in various decisions in the 1970s and 1980s, but it returned in pseudoscientific form as intelligent design (ID), to be excluded once again in the 2005 Kitzmiller v. Dover Area School District case. The debate over Darwin's ideas did not generate significant controversy in China. See also Devolution (biology) – Notion that species can revert to primitive forms	biology	998	https://da.wikipedia.org/wiki/Art	Art	Arten (species, forkortet sp., flertal: spp.) er den grundlæggende systematiske enhed inden for biologien. Arten defineres ofte som en naturlig gruppe af populationer, hvor udveksling af gener finder sted (eller kan finde sted) og som i forhold til forplantning er isoleret fra andre grupper. Det vil sige at kun individer inden for samme art kan parre sig og få forplantningsdygtigt afkom. Dette kaldes det biologiske artsbegreb. For organismer, der formerer sig ukønnet eller ved selvbestøvning, må arter afgrænses ud fra ligheder og forskelle mellem forskellige individer. Nogle dyrearter kan i fangenskab hybridisere og få fertilt afkom, men da dette ikke vil ske i naturen, selv om de mødes her, betragtes de som forskellige arter. Eksempel To heste kan parre sig og få et føl, der igen kan få føl med andre heste – hestene tilhører derfor samme art. En hest og et æsel kan også parre sig og deres unger kaldes enten muldyr eller mulæsel, afhængig af hvem der er moren, men muldyret eller mulæselet kan (normalt) ikke få unger, da de oftest er sterile. Af den grund regnes hest og æsel som to forskellige arter. Det samme princip gælder også for planterne. Denne naturskabte afgrænsning mellem to arter kaldes en artsbarriere. Den kan af og til gennembrydes, når ellers sterile krydsninger spontant eller kunstigt får gennemført en kromosomfordobling. Se f.eks. Vadegræs (Spartina pectinata). Arter over for hybrider Man kan dog godt komme ud for, at arter kan krydses og får blandet afkom, men hybriden vil kun kunne bestå på steder, hvor ingen af forældrearterne kan klare sig. Dette er et særligt udpræget problem med Rododendron (Rhododendron) og Tjørn (Crataegus), fordi disse slægter breder sig voldsomt efter skovbrand eller stormfald. Da hybriderne bliver frugtbare i en yngre alder end arterne, kan de dominere i en periode, men når skoven lukker sig, så fortrænges hybriderne og kun de specialiserede arter kan overleve i skovens dybe skygge eller ude i lyset i sumpe, på ur og i kalksten, m.m. Flere artsbegreber Fordi det biologiske artsbegreb kan være besværligt at anvende i praksis, er der efterhånden skabt en række andre artsbegreber: Morfologisk artsbegreb Arterne adskiller sig fra hinanden ved deres bygning. Dette begreb er blevet meget anvendt gennem tiden. Økologisk artsbegreb Definerer en art som en gruppe af organismer, der udfylder samme niche. Krydsninger mellem to nærtstående arter vil ikke være optimalt tilpasset til forældrearternes nicher og vil ikke klare sig i konkurrencen. Evolutionære artsbegreb Også kaldet det kladistiske eller fylogenetiske artsbegreb. Naturen er dynamisk, ikke statisk - alle arter ændrer sig med tiden og bliver, hvis de ikke uddør som følge af konkurrence, naturkatastrofer m.v., til én eller flere nye arter. Det evolutionære artsbegreb minder om det biologiske, men inddrager tidsdimensionen, det vil sige at en art udvikler sig over tid og at nye arter opstår ved artsdannelse. Individer der fylogenetisk har samme stamfader tilhører samme art. Pluralistisk artsbegreb En art er et samfund af populationer, der formerer sig og lever inden for en bestemt niche i naturen. Se også Systematik Evolutionsteori Kilder Lars Skipper: Hvad er en art? Citat: "...Arten er den eneste [klassifikations-kategori] der eksisterer i virkeligheden, alle andre (slægter, familier, ordener m.v.) er indført for overskuelighedens skyld..." Eksterne henvisninger 2003-12-31, ScienceDaily: Working On The 'Porsche Of Its Time': New Model For Species Determination Offered Citat: "...two species of dinosaur that are members of the same genera varied from each other by just 2.2 percent. Translation of the percentage into an actual number results in an average of just three skeletal differences out of the total 338 bones in the body. Amazingly, 58 percent of these differences occurred in the skull alone. "This is a lot less variation than I'd expected," said Novak..." 2003-08-08, ScienceDaily: Cross-species Mating May Be Evolutionarily Important And Lead To Rapid Change, Say Indiana University Researchers Citat: "...the sudden mixing of closely related species may occasionally provide the energy to impel rapid evolutionary change..." 2004-01-09 ScienceDaily: Mayo Researchers Observe Genetic Fusion Of Human, Animal Cells; May Help Explain Origin Of AIDS Citat: "...The researchers have discovered conditions in which pig cells and human cells can fuse together in the body to yield hybrid cells that contain genetic material from both species..."What we found was completely unexpected," says Jeffrey Platt, M.D..." 2000-09-18, ScienceDaily: Scientists Unravel Ancient Evolutionary History Of Photosynthesis Citat: "...gene-swapping was common among ancient bacteria early in evolution..." 2004-06-07, Sciencedaily: Parting Genomes: University Of Arizona Biologists Discover Seeds Of Speciation Citat: "...There's a huge amount of biodiversity out there, and we don't know where it comes from. Evolutionary biologists are excited to figure out what causes what we see out there--the relative forces of selection and drift--whether things are adapting to their environment or variation is random..." 2005-07-05, Sciencedaily: Trees, Vines And Nets -- Microbial Evolution Changes Its Face Citat: "... EBI researchers have changed our view of 4 billion years of microbial evolution...In all, more than 600,000 vertical transfers are observed, coupled with 90,000 gene loss events and approximately 40,000 horizontal gene transfers...A few species, including beneficial nitrogen-fixing soil bacteria, appear to be 'champions'of horizontal gene transfer; "it's entirely possible that apparently harmless organisms are quietly spreading antibiotic resistance under our feet," concludes Christos Ouzounis..." 2005-11-11, Sciencedaily: Lateral Thinking Produces First Map Of Gene Transmission Citat: "...Their results clearly show genetic modification of organisms by lateral transfer is a widespread natural phenomenon, and it can occur even between distantly related organisms... it was assumed that transfer of genes could only be vertical, i.e. from parents to offspring..." Økologi Biologi	danish	0.791178
neurons_form_connections/whatisbrainplasticit.txt	Edition:Available editions United States Donate Get newsletter Become an author Sign up as a reader Sign in The Conversation Search analysis, research, academics… Academic rigor, journalistic flair Arts + CultureEconomyEducationEnvironment + EnergyEthics + ReligionHealthPolitics + SocietyScience + TechPodcasts What is brain plasticity and why is it so important? Published: April 4, 2016 11:24am EDT Author Duncan Banks Lecturer in Biomedical Sciences, The Open University Disclosure statement Dr Duncan Banks is currently in receipt of grants totalling £355,000 from Regenero Ltd., Milton Keynes Council and Sir Halley Stewart Trust. In the past he has been awarded grants from the MRC, Wellcome Trust, Glaxo SmithKline and ReGen Therapeutics. He is waiting to hear about grant applications to the Economic and Social Research Council and European Food Safety Authority. Partners The Open University The Open University provides funding as a founding partner of The Conversation UK. View all partners CC BY ND We believe in the free flow of information Republish our articles for free, online or in print, under a Creative Commons license. The malleable brain. www.shutterstock.com Email X (Twitter)323 Facebook2.5k LinkedIn Print Neuroplasticity – or brain plasticity – is the ability of the brain to modify its connections or re-wire itself. Without this ability, any brain, not just the human brain, would be unable to develop from infancy through to adulthood or recover from brain injury. What makes the brain special is that, unlike a computer, it processes sensory and motor signals in parallel. It has many neural pathways that can replicate another’s function so that small errors in development or temporary loss of function through damage can be easily corrected by rerouting signals along a different pathway. The problem becomes severe when errors in development are large, such as the effects of the Zika virus on brain development in the womb, or as a result of damage from a blow to the head or following a stroke. Yet, even in these examples, given the right conditions the brain can overcome adversity so that some function is recovered. The brain’s anatomy ensures that certain areas of the brain have certain functions. This is something that is predetermined by your genes. For example, there is an area of the brain that is devoted to movement of the right arm. Damage to this part of the brain will impair movement of the right arm. But since a different part of the brain processes sensation from the arm, you can feel the arm but can’t move it. This “modular” arrangement means that a region of the brain unrelated to sensation or motor function is not able to take on a new role. In other words, neuroplasticity is not synonymous with the brain being infinitely malleable. Don’t let yourself be misled. Understand issues with help from experts Part of the body’s ability to recover following damage to the brain can be explained by the damaged area of the brain getting better, but most is the result of neuroplasticity – forming new neural connections. In a study of Caenorhabditis elegans, a type of nematode used as a model organism in research, it was found that losing the sense of touch enhanced the sense of smell. This suggests that losing one sense rewires others. It is well known that, in humans, losing one’s sight early in life can heighten other senses, especially hearing. As in the developing infant, the key to developing new connections is environmental enrichment that relies on sensory (visual, auditory, tactile, smell) and motor stimuli. The more sensory and motor stimulation a person receives, the more likely they will be to recover from brain trauma. For example, some of the types of sensory stimulation used to treat stroke patients includes training in virtual environments, music therapy and mentally practising physical movements. The basic structure of the brain is established before birth by your genes. But its continued development relies heavily on a process called developmental plasticity, where developmental processes change neurons and synaptic connections. In the immature brain this includes making or losing synapses, the migration of neurons through the developing brain or by the rerouting and sprouting of neurons. There are very few places in the mature brain where new neurons are formed. The exceptions are the dentate gyrus of the hippocampus (an area involved in memory and emotions) and the sub-ventricular zone of the lateral ventricle, where new neurons are generated and then migrate through to the olfactory bulb (an area involved in processing the sense of smell). Although the formation of new neurons in this way is not considered to be an example of neuroplasticity it might contribute to the way the brain recovers from damage. Growing then pruning As the brain grows, individual neurons mature, first by sending out multiple branches (axons, which transmit information from the neuron, and dendrites, which receive information) and then by increasing the number of synaptic contacts with specific connections. Why doesn’t everyone make a full recovery after a stroke? www.shutterstock.com At birth, each infant neuron in the cerebral cortex has about 2,500 synapses. By two or three-years-old, the number of synapses per neuron increases to about 15,000 as the infant explores its world and learns new skills – a process called synaptogenesis. But by adulthood the number of synapses halves, so-called synaptic pruning. Whether the brain retains the ability to increase synaptogenesis is debatable, but it could explain why aggressive treatment after a stroke can appear to reverse the damage caused by the lack of blood supply to an area of the brain by reinforcing the function of undamaged connections. Forging new paths We continue to have the ability to learn new activities, skills or languages even into old age. This retained ability requires the brain to have a mechanism available to remember so that knowledge is retained over time for future recall. This is another example of neuroplasticity and is most likely to involve structural and biochemical changes at the level of the synapse. Reinforcement or repetitive activities will eventually lead the adult brain to remember the new activity. By the same mechanism, the enriched and stimulating environment offered to the damaged brain will eventually lead to recovery. So if the brain is so plastic, why doesn’t everyone who has a stroke recover full function? The answer is that it depends on your age (younger brains have a better chance of recovery), the size of the area damaged and, more importantly, the treatments offered during rehabilitation. Neuroscience Neurobiology Neuroplasticity Neurogenesis Rehabilitation Want to write? Write an article and join a growing community of more than 182,600 academics and researchers from 4,946 institutions. Register now Editorial Policies Community standards Republishing guidelines Friends of The Conversation Analytics Our feeds Donate Get newsletter Who we are Our charter Our team Partners and funders Resource for media Contact us En Español Privacy policy Terms and conditions Corrections Copyright © 2010–2024, The Conversation US, Inc.	biology	227625	https://sv.wikipedia.org/wiki/Neuropsykologi	Neuropsykologi	Neuropsykologi är läran om de relationer som finns mellan beteende och hjärnans funktion. Neuropsykologiska studier intresserar sig för hur olika delar av hjärnan påverkar beteendet och vilka delar som kontrollerar olika områden som stress, minne och depression. Sambandet mellan beteendet och hjärnan studeras ur olika synvinklar och under olika tillstånd, exempelvis när personen löser olika typer av praktiska eller känslomässiga uppgifter, är vakna eller sover. Neuropsykologin fördjupar sig också inom hur hormoner och olika kemiska processer påverkar människans psyke. Man är även intresserad av att studera nervsystemets funktion. Neuropsykologin drar nytta av information från många olika områden, exempelvis anatomi, biologi, biofysik, filosofi och fysiologi. Den centrala fokusen inom disciplinen är att utveckla kunskap om mänskligt beteende baserat på hjärnans funktion och den neuropsykologisk forskningen kan utnyttjas för att förstå hjärnskadors inverkan på beteendet. Utveckling Neuropsykologin är en relativt ung disciplin. Kärnan i forskningen var – och har förblivit – strävan att genom god diagnostik och behandling hjälpa hjärnskadade. Därför har ambitionerna att förstå mänskliga neuropsykologiska system utvecklats parallellt med viktigt sjukvårdsarbete. Forskning inom angränsade områden har lett till att neuropsykologin idag är en uttalad vetenskaplig disciplin. Historia Redan på mitten av 1800-talet fick neuropsykologin ett uppsving. På 1860-talet beskrev nämligen Paul Broca ett samband mellan psykisk störning och en skada inom en avgränsad del av hjärnan. Broca fann att en skada i vänster pannlob orsakade en språkstörning som innebar att patienten hade svårigheter att uttala ord. Patienten kunde förstå vad som sades men förmådde inte uttrycka sig begripligt. I och med detta upptäckte man möjligheterna att systematiskt studera hur människor drabbas psykologiskt av spontana hjärnskador. Under de kommande årtiondena kom många forskare att ägna sig åt att studera relationen mellan intellektuella störningar och hjärnskador. Undersökningar av hjärnskadade patienters intellektuella och beteendemässiga störningar gav en inblick i människans mest komplexa neuropsykologiska system. Patientstudier slog fast att de psykiska och beteendemässiga rubbningarnas karaktär berodde på skadornas utbredning i hjärnan. Kring år 1900 började man intressera sig för hur språket kan påverkas av hjärnskador, så kallad afasilära. De kliniska studierna visade att språkliga färdigheter organiseras av den vänstra hjärnhalvan. Efterhand kunde man kartlägga afasivarianterna och språkets olika delkomponenter neuronalt så pass bra att afasiläran som utvecklades på 1900-talet idag utgör kärnan för diagnostiken vid språkrubbningar orsakade av hjärnskador. 1900-talet blev en gyllene epok inom neuropsykologin och allt fler psykologiska funktioner kopplades till speciella områden i hjärnan. Studier av traumatiska hjärnskador gjordes under första och andra världskriget av bland andra Alexander Luria som erbjöd ytterligare kunskap. Utan hjärnskador som spontant drabbar människor är det troligt att den neuropsykologiska kunskapsutvecklingen troligen haft en djurexperimentell karaktär från början. Däremot skiljer sig människans intellektuella kapacitet betydligt från djurets. Trots utvecklingen av nya metoder inom neuropsykologin har spontana hjärnskador förblivit neuropsykologins främsta kunskapskälla. Under 1980-talet växte en ny gren av neuropsykologi fram, kognitiv neuropsykologi. Inom kognitiv neuropsykologi använder man metoder och teorier som är utvecklade inom den kognitiva psykologin när man studerar hjärnskador. Nutid Moderna neuropsykologiska teorier, till exempel den ovan nämnde Alexander Lurias dynamiska lokalisationsteori, innebär en kompromiss av två tidigare teorier om hur hjärnans funktion utvecklas. Den ena av dessa tidigare teorier menade att mentala förmågor var lokaliserade till avgränsade delar av hjärnan, medan den andra teorin såg hjärnan som en funktionell helhet. Moderna teorier anser alltså att mentala funktioner, som språk, minne eller planeringsförmåga, är produkter av samverkan mellan olika hjärnområden, där varje hjärnområde har en delfunktion. På senare år har man med hjälp av avancerade metoder kunnat visa att hjärnans sätt att arbeta är mer komplext än innan. Exempelvis har man kunnat se att hjärnan kan bearbeta information parallellt i olika delar av hjärnan samtidigt. Metoder Sedan 1970-talet har de neuropsykologiska metoderna genomgått en snabb utveckling. Sedan 1930-talet har man kunnat registrera hjärnans elektriska aktivitet med hjälp av EEG. När man tidigare studerade effekterna av olika hjärnskador eller hjärnsjukdomar kunde skadans lokalisation dock vanligtvis inte fastställas förrän vid en obduktion. Idag finns en hel del metoder för att fastställa en hjärnskadas lokalisation på levande människor och utan att patienten tar skada av undersökningen. Med hjälp av datortomografi och magnetkamera kan hjärnskadans lokalisation och natur fastställas med stor precision. Även avancerade tekniker som mäter hjärnans blodflöde och ämnesomsättning har tillkommit. Tack vare dessa tekniker kan man analysera hjärnan i detalj för att ta reda på vilka delar av hjärnan som förändrar sin aktivitet vid olika former av psykisk aktivitet. Detta ger oss kunskap om vilka hjärnområden som ligger bakom våra mentala förmågor. Utvecklingen av neuropsykologiska metoder och test är också viktigt för att kunna se på vilket sätt en hjärnskada eller sjukdom stör aktiviteten i andra delar av hjärnan, då individuella funktionsnedsättningar inte alltid kan avgöras genom var en skada är lokaliserad. Neuropsykolog Neuropsykologer är specialiserade psykologer som arbetar med behandling och med neuropsykologisk utredning, det vill säga diagnosticering och kartläggning av kognitiva funktioner. En neuropsykolog är specialister på att analysera störningar av intellektuella, känslomässiga och personlighetsmässiga funktioner. Med hjälp av neuropsykologiska metoder kan man fastställa vilka funktionella system och vilka delfunktioner som har påverkats av en eventuell hjärnskada. Utifrån resultaten av en neuropsykologisk utredning kan neuropsykologen tala om vilka förmågor som är intakta. Denna information är viktig vid patientens rehabilitering. Neuropsykologisk behandling Den mänskliga hjärnan är mycket komplex och innefattar komplexa neuropsykologiska system. Det förekommer också stora individuella variationer såväl vad gäller hjärnans uppbyggnad och arbetssätt som hur den kommer till användning under individens liv. Det är därför viktigt att neuropsykologisk behandling baseras på omsorgsfulla undersökningar av patientens neuropsykologiska svårigheter och kartläggningar av återstående resurser. Detta innebär att man alltså måste veta vilka områden hjärnskadan eller sjukdomen har påverkat och på så sätt veta vilka system som påverkats samt vilka förmågor som är intakta. Därför krävs förståelse för de neuropsykologiska systemen samt den stora variationen av reaktioner som en hjärnskada kan leda till. Den kliniska neuropsykologin bygger på kunskaper inom psykologi och neurologi, som man endast kan få genom omfattande och väl förvaltad klinisk erfarenhet. Den handlar även om mänskliga tragedier, och tolkningar av dessa kräver inlevelse och personlig mognad. Dessutom är det värt att tillägga att merparten av alla hjärnskadade patienter, främst de äldsta, är så svårt drabbade och har så begränsade psykiska resurser att egentliga rehabiliteringsinsatser inte är aktuella. Många av dem lider av hjärnsjukdomar som orsakar förvärrade sjukdomstillstånd. Det är därför viktigt att insatserna bygger på professionellt bemötande, medmänsklig rådgivning och omvårdnad. Framförallt kräver all neuropsykologisk rådgivning och omvårdnadsinsatser goda kunskaper om patienternas sjukdomstillstånd. Viktigt att komma ihåg är också att behandling av hjärnskadade är en ständigt pågående process. Se även Neuropsykiatri Neurovetenskap Källor Noter Psykologi Neurologi Psykofysiologi	swedish	0.463747
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[ review ](/cddis/articles?type=review) 4. article Neuronal survival in the brain: neuron type-specific mechanisms [ Download PDF ](/articles/cddis201764.pdf) [ Download PDF ](/articles/cddis201764.pdf) * Review * [ Open access ](https://www.springernature.com/gp/open-research/about/the-fundamentals-of-open-access-and-open-research) * Published: 02 March 2017 # Neuronal survival in the brain: neuron type-specific mechanisms * Ulrich Pfisterer 1 & * Konstantin Khodosevich 1 [ _Cell Death & Disease _ ](/cddis) volume 8 , page e2643 ( 2017 ) Cite this article * 16k Accesses * 82 Citations * 25 Altmetric * [ Metrics details ](/articles/cddis201764/metrics) ### Subjects * [ Cell death ](/subjects/cell-death) * [ Cell signalling ](/subjects/cell-signalling) * [ Development of the nervous system ](/subjects/development-of-the-nervous-system) * [ Neurogenesis ](/subjects/neurogenesis) ## Abstract Neurogenic regions of mammalian brain produce many more neurons that will eventually survive and reach a mature stage. Developmental cell death affects both embryonically produced immature neurons and those immature neurons that are generated in regions of adult neurogenesis. Removal of substantial numbers of neurons that are not yet completely integrated into the local circuits helps to ensure that maturation and homeostatic function of neuronal networks in the brain proceed correctly. External signals from brain microenvironment together with intrinsic signaling pathways determine whether a particular neuron will die. To accommodate this signaling, immature neurons in the brain express a number of transmembrane factors as well as intracellular signaling molecules that will regulate the cell survival/death decision, and many of these factors cease being expressed upon neuronal maturation. Furthermore, pro-survival factors and intracellular responses depend on the type of neuron and region of the brain. Thus, in addition to some common neuronal pro- survival signaling, different types of neurons possess a variety of 'neuron type-specific' pro-survival constituents that might help them to adapt for survival in a certain brain region. This review focuses on how immature neurons survive during normal and impaired brain development, both in the embryonic/neonatal brain and in brain regions associated with adult neurogenesis, and emphasizes neuron type-specific mechanisms that help to survive for various types of immature neurons. Importantly, we mainly focus on _in vivo_ data to describe neuronal survival specifically in the brain, without extrapolating data obtained in the PNS or spinal cord, and thus emphasize the influence of the complex brain environment on neuronal survival during development. ### Similar content being viewed by others ![](https://media.springernature.com/w215h120/springer- static/image/art%3A10.1038%2Fs41583-021-00433-z/MediaObjects/41583_2021_433_Fig1_HTML.png) ### [ Formation and integration of new neurons in the adult hippocampus ](https://www.nature.com/articles/s41583-021-00433-z?fromPaywallRec=false) Article 25 February 2021 ![](https://media.springernature.com/w215h120/springer- static/image/art%3A10.1038%2Fs41583-023-00760-3/MediaObjects/41583_2023_760_Fig1_HTML.png) ### [ Human neuronal maturation comes of age: cellular mechanisms and species differences ](https://www.nature.com/articles/s41583-023-00760-3?fromPaywallRec=false) Article 23 November 2023 ![](https://media.springernature.com/w215h120/springer- static/image/art%3A10.1038%2Fs41419-022-05340-4/MediaObjects/41419_2022_5340_Fig1_HTML.png) ### [ Diverse maturity-dependent and complementary anti-apoptotic brakes safeguard human iPSC-derived neurons from cell death ](https://www.nature.com/articles/s41419-022-05340-4?fromPaywallRec=false) Article Open access 21 October 2022 ## Facts * During development neurons express a set of pro-survival/death molecules that are not present in adult brain. * Neuronal survival in the brain often relies on different external factors in comparison with the spinal cord and PNS. * Different types of neurons in the brain possess some common, but also distinct components of pro-survival signaling. * Immature neurons are more vulnerable to stress factors that trigger neuronal death than mature neurons. ## Open questions * How abundant are distinct components of pro-survival signaling in different types of neurons that might adapt neuronal survival to the region of the brain, that is, neuron type-specific survival? * How do survival mechanisms of embryonically and adult-born neurons differ, that is, survival in immature _versus_ mature brain? * During what period of brain development do the various types of neurons die? * What mechanisms account for higher vulnerability of immature neurons to stress factors? During brain development, an excessive number of neurons is generated and, depending on the region and neuronal type, a varying number of neurons die before they mature. [ 1 ](/articles/cddis201764#ref-CR1 "Southwell DG, Paredes MF, Galvao RP, Jones DL, Froemke RC, Sebe JY et al. Intrinsically determined cell death of developing cortical interneurons. Nature 2012; 491: 109–113.") , [ 2 ](/articles/cddis201764#ref-CR2 "Oo TF, Burke RE . The time course of developmental cell death in phenotypically defined dopaminergic neurons of the substantia nigra. Brain Res Dev Brain Res 1997; 98: 191–196.") , [ 3 ](/articles/cddis201764#ref-CR3 "Burek MJ, Oppenheim RW . Programmed cell death in the developing nervous system. Brain Pathol 1996; 6: 427–446.") , [ 4 ](/articles/cddis201764#ref-CR4 "White FA, Keller-Peck CR, Knudson CM, Korsmeyer SJ, Snider WD . Widespread elimination of naturally occurring neuronal death in Bax-deficient mice. J Neurosci 1998; 18: 1428–1439.") , [ 5 ](/articles/cddis201764#ref-CR5 "Lossi L, Merighi A . In vivo cellular and molecular mechanisms of neuronal apoptosis in the mammalian CNS. Prog Neurobiol 2003; 69: 287–312.") A high rate of neuronal death also occurs in the regions of adult neurogenesis. [ 6 ](/articles/cddis201764#ref-CR6 "Sun W, Winseck A, Vinsant S, Park OH, Kim H, Oppenheim RW . Programmed cell death of adult-generated hippocampal neurons is mediated by the proapoptotic gene Bax. J Neurosci 2004; 24: 11205–11213.") , [ 7 ](/articles/cddis201764#ref-CR7 "Kim WR, Kim Y, Eun B, Park OH, Kim H, Kim K et al. Impaired migration in the rostral migratory stream but spared olfactory function after the elimination of programmed cell death in Bax knock-out mice. J Neurosci 2007; 27: 14392–14403.") , [ 8 ](/articles/cddis201764#ref-CR8 "Mouret A, Gheusi G, Gabellec MM, de Chaumont F, Olivo-Marin JC, Lledo PM . Learning and survival of newly generated neurons: when time matters. J Neurosci 2008; 28: 11511–11516.") , [ 9 ](/articles/cddis201764#ref-CR9 "Khodosevich K, Lazarini F, von Engelhardt J, Kaneko H, Lledo PM, Monyer H . Connective tissue growth factor regulates interneuron survival and information processing in the olfactory bulb. Neuron 2013; 79: 1136–1151.") The process of neuronal overproduction and elimination is necessary to optimize brain connectivity. Disturbances in regulating developmental neuronal death not only change cell composition and connectivity within local neuronal networks, but also alter global brain activity and, thus, cognition. Several types of brain disorders enhance the death of immature neurons (i.e., postmitotic neurons, but before complete maturation) during brain development that could lead to decline in cognitive abilities. After maturation, neurons become resistant to the signaling that was involved in the life/death decision at immature stages since, once neurogenesis is halted, it is advantageous to protect mature neurons that cannot be produced again (protection of immature and mature neurons is compared in Benn and Woolf [ 10 ](/articles/cddis201764#ref-CR10 "Benn SC, Woolf CJ . Adult neuron survival strategies—slamming on the brakes. Nat Rev Neurosci 2004; 5: 686–700.") and Kole _et_ _al._ [ 11 ](/articles/cddis201764#ref-CR11 "Kole AJ, Annis RP, Deshmukh M . Mature neurons: equipped for survival. Cell Death Dis 2013; 4: e689.") ). There are two distinct modes of neurogenesis – although the majority of neurons are generated during the embryonic period and their production is discontinued either in the embryonic brain or early postnatally (later referred to as embryonic neurogenesis), [ 12 ](/articles/cddis201764#ref-CR12 "Buss RR, Sun W, Oppenheim RW . Adaptive roles of programmed cell death during nervous system development. Annu Rev Neurosci 2006; 29: 1–35.") some populations of neurons are continuously generated throughout the life of an animal (later referred to as adult neurogenesis) [ 13 ](/articles/cddis201764#ref-CR13 "Aimone JB, Li Y, Lee SW, Clemenson GD, Deng W, Gage FH . Regulation and function of adult neurogenesis: from genes to cognition. Physiol Rev 2014; 94: 991–1026.") , [ 14 ](/articles/cddis201764#ref-CR14 "Khodosevich K, Alfonso J, Monyer H . Dynamic changes in the transcriptional profile of subventricular zone-derived postnatally born neuroblasts. Mech Dev 2013; 130: 424–432.") (see [ Figures 1a and b ](/articles/cddis201764#Fig1) , respectively). The death of neurons that are born embryonically reaches a peak in the neonatal brain and affects neurons that are still immature, [ 15 ](/articles/cddis201764#ref-CR15 "Ferrer I, Bernet E, Soriano E, del Rio T, Fonseca M . Naturally occurring cell death in the cerebral cortex of the rat and removal of dead cells by transitory phagocytes. Neuroscience 1990; 39: 451–458.") , [ 16 ](/articles/cddis201764#ref-CR16 "Ferrer I, Soriano E, del Rio JA, Alcantara S, Auladell C . Cell death and removal in the cerebral cortex during development. Prog Neurobiol 1992; 39: 1–43.") , [ 17 ](/articles/cddis201764#ref-CR17 "Finlay BL, Slattery M . Local differences in the amount of early cell death in neocortex predict adult local specializations. Science 1983; 219: 1349–1351.") and the critical period for survival of adult-generated neurons is within 4 weeks after their birth; following this period of maturation, they become resistant to cell death. [ 8 ](/articles/cddis201764#ref-CR8 "Mouret A, Gheusi G, Gabellec MM, de Chaumont F, Olivo-Marin JC, Lledo PM . Learning and survival of newly generated neurons: when time matters. J Neurosci 2008; 28: 11511–11516.") , [ 9 ](/articles/cddis201764#ref-CR9 "Khodosevich K, Lazarini F, von Engelhardt J, Kaneko H, Lledo PM, Monyer H . Connective tissue growth factor regulates interneuron survival and information processing in the olfactory bulb. Neuron 2013; 79: 1136–1151.") , [ 18 ](/articles/cddis201764#ref-CR18 "van Praag H, Kempermann G, Gage FH . Running increases cell proliferation and neurogenesis in the adult mouse dentate gyrus. Nat Neurosci 1999; 2: 266–270.") Figure 1 [ ![figure 1](//media.springernature.com/lw685/springer- static/image/art%3A10.1038%2Fcddis.2017.64/MediaObjects/41419_2017_Article_BFcddis201764_Fig1_HTML.jpg) ](/articles/cddis201764/figures/1) Neuronal death during embryonic and adult neurogenesis. ( a ) During embryonic brain development, neurons are born around the ventricles and migrate toward various brain regions. Cortical principal neurons and interneurons are born in the dorsal and ventral telencephalon, respectively. The majority of interneurons are born in the medial and caudal (data not shown) ganglionic eminences (MGE and CGE, respectively), whereas striatal medium spiny neurons are born in the lateral ganglionic eminence (LGE). Dopaminergic and cerebellar neurons are born in the ventricular zones of the mesencephalon and cerebellum, respectively. Red cells in each region depict dying immature neurons. Peak period of developmental cell death is given for each type of neurons. ( b ) The SGZ of the dentate gyrus in the hippocampus and the SVZ of the lateral ventricles continue to generate neurons throughout life. The SGZ generates neuroblasts that translocate within the SGZ and mature into excitatory granule cells. Neuroblasts that are generated in the SVZ migrate a long distance through the rostral migratory stream toward the olfactory bulb and mature into two major populations of inhibitory interneurons – granule and periglomerular cells. More than half of adult- generated neurons die by apoptosis. Red cells in each region depict dying immature neurons. Peak period of developmental cell death is given for each type of neurons. CB, cerebellum; CP, cortical plate; CX, cortex; DG, dentate gyrus; GE, ganglionic eminence; HP, hippocampus; LGE, lateral GE; LV, lateral ventricle; MB, midbrain; MGE, medial GE; RMS, rostral migratory stream; OB, olfactory bulb [ Full size image ](/articles/cddis201764/figures/1) Principles of neuronal survival are often generalized and data from different areas of the CNS are extrapolated to the CNS as a whole. Indeed, pro-survival signaling does converge on some common core components ( [ Figure 2 ](/articles/cddis201764#Fig2) ). However, data accumulated over the recent years show that different types of neurons in the brain might use different pro-survival mechanisms as there are a variety of routes by which core pro- survival components could be activated. Thus, we propose 'neuron type- specific' pro-survival mechanisms that will heavily rely upon (1) composition of extracellular pro-survival factors that are available in a certain brain area at a certain time period, (2) composition of transmembrane molecules (e.g. receptors or ion channels) that are expressed on distinct types of neurons and (3) composition of cytosolic molecules that could propagate pro- survival signaling from the cell membrane toward common core components ( [ Figure 2 ](/articles/cddis201764#Fig2) ). Figure 2 [ ![figure 2](//media.springernature.com/lw685/springer- static/image/art%3A10.1038%2Fcddis.2017.64/MediaObjects/41419_2017_Article_BFcddis201764_Fig2_HTML.jpg) ](/articles/cddis201764/figures/2) Components of survival/death signaling in immature neurons. Extracellular pro- survival factors that are available in a certain brain area stimulate a variety of receptors and ion channels on neurons located in the area. Transcription factors involved in neuronal differentiation determine what combination of receptors and ion channels will be expressed on a particular neuron. Such neuron type-specific combination of receptors and channels propagates pro-survival signaling to intermediate components, some of which express broadly, whereas others have restricted expression only in one or few types of neurons. Finally, all pro-survival signaling converges on core components that inhibit neuronal death [ Full size image ](/articles/cddis201764/figures/2) It should be noted that not only pro-survival, but also pro-death pathways could be neuron type specific. In general terms, it is pro-survival signaling that blocks intrinsic pro-death signaling, and when there is a lack of pro- survival signaling, pro-death pathways are triggered. However, in a recent paper [ 19 ](/articles/cddis201764#ref-CR19 "Nikoletopoulou V, Lickert H, Frade JM, Rencurel C, Giallonardo P, Zhang L et al. Neurotrophin receptors TrkA and TrkC cause neuronal death whereas TrkB does not. Nature 2010; 467: 59–63.") it was shown that survival of CNS neurons during development is regulated by 'dependence receptors' that activate pro-death signaling when not bound to their ligands (reviewed in Dekkers _et al._ [ 20 ](/articles/cddis201764#ref-CR20 "Dekkers MP, Nikoletopoulou V, Barde YA . Cell biology in neuroscience: death of developing neurons: new insights and implications for connectivity. J Cell Biol 2013; 203: 385–393.") ). Although the extent of expression and the number of dependence receptors still remain to be determined in the developing brain, the presence of such a mechanism indicates that neuron type-specific pro-death pathways do exist. ## Neuron type-specific pro-survival mechanisms As different types of neurons survive in different brain areas and at different periods of brain development, the transcriptome of the surviving neuron should 'prepare' the neuron to survive in a certain environment. The preparation is coordinated by distinct sets of transcription factors that are involved in differentiation of specific types of neurons. These transcription factors drive expression of transmembrane and intracellular molecules that are necessary to recognize and respond to the local environment. Neurons failing to differentiate properly are less likely to respond to signals from local brain environment and could be eliminated during maturation. Interestingly, the period of developmental cell death differs across types of neurons/brain areas. For instance, GABAergic interneurons of the cortex and medium spiny neurons exhibit one peak of cell death at P7-P11 [ 1 ](/articles/cddis201764#ref-CR1 "Southwell DG, Paredes MF, Galvao RP, Jones DL, Froemke RC, Sebe JY et al. Intrinsically determined cell death of developing cortical interneurons. Nature 2012; 491: 109–113.") and P2-P7, [ 21 ](/articles/cddis201764#ref-CR21 "Fishell G, van der Kooy D . Pattern formation in the striatum: neurons with early projections to the substantia nigra survive the cell death period. J Comp Neurol 1991; 312: 33–42.") respectively, whereas two distinct peaks of developmental cell death have been observed for dopaminergic neurons, at P0-P6 and ~P14, [ 2 ](/articles/cddis201764#ref-CR2 "Oo TF, Burke RE . The time course of developmental cell death in phenotypically defined dopaminergic neurons of the substantia nigra. Brain Res Dev Brain Res 1997; 98: 191–196.") and for Purkinje cells, at ~E15 and ~P3. [ 22 ](/articles/cddis201764#ref-CR22 "Dusart I, Guenet JL, Sotelo C . Purkinje cell death: differences between developmental cell death and neurodegenerative death in mutant mice. Cerebellum 2006; 5: 163–173.") The difference in survival mechanisms between embryonically and adult-born neurons illustrates the importance of time period of neuronal survival with regard to brain maturation, since embryonically born _immature_ neurons must survive in _immature_ brain, whereas adult-born _immature_ neurons must survive in _mature_ brain. Thus, there is high pressure for adult-born neurons to integrate into the pre-existing mature circuits, which is absent for embryonically born neurons. This is supported, for instance, by a higher vulnerability of adult-born neurons to impairment in NMDA receptor (NMDAR) expression, since ablation of NR1 or NR2B subunit markedly augments death of adult-born neurons during maturation, [ 23 ](/articles/cddis201764#ref-CR23 "Lin CW, Sim S, Ainsworth A, Okada M, Kelsch W, Lois C . Genetically increased cell-intrinsic excitability enhances neuronal integration into adult brain circuits. Neuron 2010; 65: 32–39.") , [ 24 ](/articles/cddis201764#ref-CR24 "Tashiro A, Sandler VM, Toni N, Zhao C, Gage FH . NMDA-receptor-mediated, cell-specific integration of new neurons in adult dentate gyrus. Nature 2006; 442: 929–933.") , [ 25 ](/articles/cddis201764#ref-CR25 "Kelsch W, Li Z, Eliava M, Goengrich C, Monyer H . GluN2B-containing NMDA receptors promote wiring of adult-born neurons into olfactory bulb circuits. J Neurosci 2012; 32: 12603–12611.") whereas studies of global or early postnatal knockout of these subunits do not report increase in apoptosis of embryonically produced neurons. [ 26 ](/articles/cddis201764#ref-CR26 "Forrest D, Yuzaki M, Soares HD, Ng L, Luk DC, Sheng M et al. Targeted disruption of NMDA receptor 1 gene abolishes NMDA response and results in neonatal death. Neuron 1994; 13: 325–338.") , [ 27 ](/articles/cddis201764#ref-CR27 "Kutsuwada T, Sakimura K, Manabe T, Takayama C, Katakura N, Kushiya E et al. Impairment of suckling response, trigeminal neuronal pattern formation, and hippocampal LTD in NMDA receptor epsilon 2 subunit mutant mice. Neuron 1996; 16: 333–344.") , [ 28 ](/articles/cddis201764#ref-CR28 "von Engelhardt J, Doganci B, Jensen V, Hvalby O, Gongrich C, Taylor A et al. Contribution of hippocampal and extra- hippocampal NR2B-containing NMDA receptors to performance on spatial learning tasks. Neuron 2008; 60: 846–860.") The effect of brain maturation on neuronal survival might also be illustrated by a decrease in survival of small axonless neurons – a type of neurons that is generated both during embryonic and adult neurogenesis. [ 29 ](/articles/cddis201764#ref-CR29 "Le Magueresse C, Alfonso J, Khodosevich K, Arroyo Martin AA, Bark C, Monyer H . "Small axonless neurons": postnatally generated neocortical interneurons with delayed functional maturation. J Neurosci 2011; 31: 16731–16747.") The majority of these neurons survive in the deep cortical layers when circuits are still immature, and gradual maturation of the brain correlates with a decreased number of newly added neurons, [ 29 ](/articles/cddis201764#ref-CR29 "Le Magueresse C, Alfonso J, Khodosevich K, Arroyo Martin AA, Bark C, Monyer H . "Small axonless neurons": postnatally generated neocortical interneurons with delayed functional maturation. J Neurosci 2011; 31: 16731–16747.") although the number of these neurons could be increased by pathological conditions such as stroke. [ 30 ](/articles/cddis201764#ref-CR30 "Kreuzberg M, Kanov E, Timofeev O, Schwaninger M, Monyer H, Khodosevich K . Increased subventricular zone-derived cortical neurogenesis after ischemic lesion. Exp Neurol 2010; 226: 90–99.") Support of neuronal survival by the local environment depends on whether a specific factor itself and its receptor are expressed in the region. Availability of pro-survival factors varies within the brain and even cortical layers, [ 31 ](/articles/cddis201764#ref-CR31 "Huang ZJ, Kirkwood A, Pizzorusso T, Porciatti V, Morales B, Bear MF et al. BDNF regulates the maturation of inhibition and the critical period of plasticity in mouse visual cortex. Cell 1999; 98: 739–755.") , [ 32 ](/articles/cddis201764#ref-CR32 "Katoh-Semba R, Takeuchi IK, Semba R, Kato K . Distribution of brain-derived neurotrophic factor in rats and its changes with development in the brain. J Neurochem 1997; 69: 34–42.") , [ 33 ](/articles/cddis201764#ref-CR33 "Patz S, Wahle P . Developmental changes of neurotrophin mRNA expression in the layers of rat visual cortex. Eur J Neurosci 2006; 24: 2453–2460.") and response to different pro-survival factors markedly changes over a course of neuronal maturation. [ 34 ](/articles/cddis201764#ref-CR34 "Catapano LA, Arnold MW, Perez FA, Macklis JD . Specific neurotrophic factors support the survival of cortical projection neurons at distinct stages of development. J Neurosci 2001; 21: 8863–8872.") Moreover, certain intracellular pro-survival molecules are present only in some types of neurons, but not in others. For instance, BDNF promotes survival of dopaminergic neurons, medium spiny neurons and cerebellar granule cells, [ 35 ](/articles/cddis201764#ref-CR35 "Baydyuk M, Xie Y, Tessarollo L, Xu B . Midbrain-derived neurotrophins support survival of immature striatal projection neurons. J Neurosci 2013; 33: 3363–3369.") , [ 36 ](/articles/cddis201764#ref-CR36 "Baquet ZC, Bickford PC, Jones KR . Brain- derived neurotrophic factor is required for the establishment of the proper number of dopaminergic neurons in the substantia nigra pars compacta. J Neurosci 2005; 25: 6251–6259.") , [ 37 ](/articles/cddis201764#ref-CR37 "Kokubo M, Nishio M, Ribar TJ, Anderson KA, West AE, Means AR . BDNF-mediated cerebellar granule cell development is impaired in mice null for CaMKK2 or CaMKIV. J Neurosci 2009; 29: 8901–8913.") but it is dispensable for survival of GABAergic neurons in the cortex [ 1 ](/articles/cddis201764#ref-CR1 "Southwell DG, Paredes MF, Galvao RP, Jones DL, Froemke RC, Sebe JY et al. Intrinsically determined cell death of developing cortical interneurons. Nature 2012; 491: 109–113.") although the latter express TrkB receptor and BDNF is available in the surrounding environment. [ 31 ](/articles/cddis201764#ref-CR31 "Huang ZJ, Kirkwood A, Pizzorusso T, Porciatti V, Morales B, Bear MF et al. BDNF regulates the maturation of inhibition and the critical period of plasticity in mouse visual cortex. Cell 1999; 98: 739–755.") , [ 38 ](/articles/cddis201764#ref-CR38 "Polleux F, Whitford KL, Dijkhuizen PA, Vitalis T, Ghosh A . Control of cortical interneuron migration by neurotrophins and PI3-kinase signaling. Development 2002; 129: 3147–3160.") In the following, we summarize the evidence for neuron type-specific pro- survival mechanisms during embryonic and adult neurogenesis (see overview in [ Table 1 ](/articles/cddis201764#Tab1) ). Table 1 Examples of neuron type-specific pro-survival genes [ Full size table ](/articles/cddis201764/tables/1) ### Embryonic neurogenesis: glutamatergic neurons The most information regarding survival of glutamatergic neurons in the brain was obtained by studying cerebellar granule cells and principal neurons of the hippocampus and cortex ( [ Figure 3a ](/articles/cddis201764#Fig3) ). The peak of cortical principal neuron cell death is at P4–P8, [ 39 ](/articles/cddis201764#ref-CR39 "Verney C, Takahashi T, Bhide PG, Nowakowski RS, Caviness VS Jr. . Independent controls for neocortical neuron production and histogenetic cell death. Dev Neurosci 2000; 22: 125–138.") whereas the majority of immature cerebellar granule cells die at P5–P9. [ 40 ](/articles/cddis201764#ref-CR40 "Wood KA, Dipasquale B, Youle RJ . In situ labeling of granule cells for apoptosis-associated DNA fragmentation reveals different mechanisms of cell loss in developing cerebellum. Neuron 1993; 11: 621–632.") Although knockout of a single neurotrophic factor or its receptor does not have large effects on neuronal survival during brain development, [ 41 ](/articles/cddis201764#ref-CR41 "Henderson CE . Role of neurotrophic factors in neuronal development. Curr Opin Neurobiol 1996; 6: 64–70.") double knockout of _Ntrk2_ and _Ntrk3_ (genes coding for TrkB and TrkC, respectively) results in the massive death of immature granule cells in the cerebellum and dentate gyrus. [ 42 ](/articles/cddis201764#ref-CR42 "Minichiello L, Klein R . TrkB and TrkC neurotrophin receptors cooperate in promoting survival of hippocampal and cerebellar granule neurons. Genes Dev 1996; 10: 2849–2858.") This could be explained either by redundancy of intracellular pro-survival pathways that are triggered by each of the receptors or by compensatory effects in knockout mice. Furthermore, often data obtained _in vivo_ differs from _in vitro_ experiments, highlighting importance of brain environment for action of a particular pro-survival factor. For instance, BDNF was shown to promote neuronal survival in the culture, [ 43 ](/articles/cddis201764#ref- CR43 "Murase S, Owens DF, McKay RD . In the newborn hippocampus, neurotrophin- dependent survival requires spontaneous activity and integrin signaling. J Neurosci 2011; 31: 7791–7800.") but deletion of _Bdnf_ in all postmitotic neurons in the brain did not have a large effect on their survival. [ 44 ](/articles/cddis201764#ref-CR44 "Rauskolb S, Zagrebelsky M, Dreznjak A, Deogracias R, Matsumoto T, Wiese S et al. Global deprivation of brain-derived neurotrophic factor in the CNS reveals an area-specific requirement for dendritic growth. J Neurosci 2010; 30: 1739–1749.") Figure 3 [ ![figure 3](//media.springernature.com/lw685/springer- static/image/art%3A10.1038%2Fcddis.2017.64/MediaObjects/41419_2017_Article_BFcddis201764_Fig3_HTML.jpg) ](/articles/cddis201764/figures/3) Neuron type-specific pro-survival signaling in embryonically born neurons. ( a ) Signaling involved in survival and cell death of glutamatergic neurons exemplified by cerebellar granule cells and cortical projection neurons. ( b ) Pro-survival and apoptotic signaling in GABAergic neurons illustrated by Purkinje cells, medium spiny neurons and cortical interneurons. ( c ) Signaling regulating survival or cell death in dopaminergic neurons. Green arrows: activation of signaling; dashed green arrow: proposed activation of signaling; red blunt arrows: inhibition of signaling; black arrows: activation of receptors on immature neurons from the extracellular space; dashed black arrows: protein secretion to the extracellular space; red cross: lack of signaling; Pi: phosphorylation [ Full size image ](/articles/cddis201764/figures/3) Granule cells of the cerebellum represent a population of glutamatergic neurons that could be a target of pro-survival action of BDNF. Deleting _Camk4_ and _Camkk2_ genes in mice enhances apoptosis in immature granule cells in the cerebellum, which is associated with a decrease in levels of CREB1 and BDNF expression. [ 37 ](/articles/cddis201764#ref-CR37 "Kokubo M, Nishio M, Ribar TJ, Anderson KA, West AE, Means AR . BDNF-mediated cerebellar granule cell development is impaired in mice null for CaMKK2 or CaMKIV. J Neurosci 2009; 29: 8901–8913.") It was proposed that Ca 2+ entering immature granule cells triggers activation of the calmodulin/CaMKK2/CaMKIV cascade, which, in turn, activates CREB1 and transcription of _Bdnf_ gene. [ 37 ](/articles/cddis201764#ref-CR37 "Kokubo M, Nishio M, Ribar TJ, Anderson KA, West AE, Means AR . BDNF-mediated cerebellar granule cell development is impaired in mice null for CaMKK2 or CaMKIV. J Neurosci 2009; 29: 8901–8913.") Survival of granule cells is also promoted by IGF1 that enhances expression of Bcl-2 and Bcl-x L thus inhibiting caspase-3 activity. [ 45 ](/articles/cddis201764#ref-CR45 "Chrysis D, Calikoglu AS, Ye P, D'Ercole AJ . Insulin-like growth factor-I overexpression attenuates cerebellar apoptosis by altering the expression of Bcl family proteins in a developmentally specific manner. J Neurosci 2001; 21: 1481–1489.") The existence of neuron type-specific pro-survival mechanisms in glutamatergic neurons was recently highlighted by the identification of a pro-survival pathway that was largely restricted to cortical principal neurons of layer V, which require trophic support from microglia to survive during early postnatal development. [ 46 ](/articles/cddis201764#ref-CR46 "Ueno M, Fujita Y, Tanaka T, Nakamura Y, Kikuta J, Ishii M et al. Layer V cortical neurons require microglial support for survival during postnatal development. Nat Neurosci 2013; 16: 543–551.") Microglia secrete IGF1, which binds to IGF1R on immature layer V neurons and activates the IRS1/PI3K/Akt1 cascade inhibiting caspase-3-dependent apoptosis. [ 46 ](/articles/cddis201764#ref-CR46 "Ueno M, Fujita Y, Tanaka T, Nakamura Y, Kikuta J, Ishii M et al. Layer V cortical neurons require microglial support for survival during postnatal development. Nat Neurosci 2013; 16: 543–551.") Microglia are activated via CX3CL1, which is released from layer V neurons and interacts with CX3CR1 on microglia. Interestingly, caspase-3-dependent apoptosis of cortical excitatory, but not inhibitory, neurons was shown to be activated by Rho GTPase RhoA. [ 47 ](/articles/cddis201764#ref-CR47 "Sanno H, Shen X, Kuru N, Bormuth I, Bobsin K, Gardner HA et al. Control of postnatal apoptosis in the neocortex by RhoA- subfamily GTPases determines neuronal density. J Neurosci 2010; 30: 4221–4231.") Inhibiting RhoA signaling in the developing brain rescues up to 25% of cortical neurons from apoptosis. ### Embryonic neurogenesis: GABAergic neurons Only few studies have investigated developmental death of GABAergic neurons, and these were mainly focused on Purkinje cells of the cerebellum and medium spiny neurons of the striatum that exhibit a peak of cell death at ~E15 and ~P3, [ 22 ](/articles/cddis201764#ref-CR22 "Dusart I, Guenet JL, Sotelo C . Purkinje cell death: differences between developmental cell death and neurodegenerative death in mutant mice. Cerebellum 2006; 5: 163–173.") and at P2–P7, [ 21 ](/articles/cddis201764#ref-CR21 "Fishell G, van der Kooy D . Pattern formation in the striatum: neurons with early projections to the substantia nigra survive the cell death period. J Comp Neurol 1991; 312: 33–42.") respectively ( [ Figure 3b ](/articles/cddis201764#Fig3) ). Lhx1/Lhx5 transcription factors together with their co-activator Ldb1 promote survival of postmitotic Purkinje cells at E13.5–E15.5. [ 48 ](/articles/cddis201764#ref-CR48 "Zhao Y, Kwan KM, Mailloux CM, Lee WK, Grinberg A, Wurst W et al. LIM-homeodomain proteins Lhx1 and Lhx5, and their cofactor Ldb1, control Purkinje cell differentiation in the developing cerebellum. Proc Natl Acad Sci USA 2007; 104: 13182–13186.") Interestingly, two members of the EBF (early B-cell factor) family of transcription factors – EBF1 and EBF2 – are involved in survival of medium spiny [ 49 ](/articles/cddis201764#ref-CR49 "Garel S, Marin F, Grosschedl R, Charnay P . Ebf1 controls early cell differentiation in the embryonic striatum. Development 1999; 126: 5285–5294.") and Purkinje neurons, [ 50 ](/articles/cddis201764#ref-CR50 "Croci L, Chung SH, Masserdotti G, Gianola S, Bizzoca A, Gennarini G et al. A key role for the HLH transcription factor EBF2COE2,O/E-3 in Purkinje neuron migration and cerebellar cortical topography. Development 2006; 133: 2719–2729.") respectively, during perinatal development. In Purkinje cells, EBF2 binds to _Igf1_ promoter and activates _Igf1_ expression that results in local IGF1 secretion and potentiation of Akt1-dependent pro-survival signaling. [ 51 ](/articles/cddis201764#ref-CR51 "Croci L, Barili V, Chia D, Massimino L, van Vugt R, Masserdotti G et al. Local insulin-like growth factor I expression is essential for Purkinje neuron survival at birth. Cell Death Differ 2011; 18: 48–59.") All the aforementioned transcription factors were also shown to be involved in differentiation and/or migration of medium spiny and Purkinje neurons, and thus immature neurons might die because they are not able to complete their differentiation programs. Although, overall, neurotrophins do not have a large role in survival of immature GABAergic neurons, BDNF and NT-3 were shown to enhance survival of immature medium spiny neurons, as they are secreted by midbrain dopaminergic neurons during a critical period of striatal neuron survival and activate pro- survival signaling via TrkB and TrkC receptors. [ 35 ](/articles/cddis201764#ref-CR35 "Baydyuk M, Xie Y, Tessarollo L, Xu B . Midbrain-derived neurotrophins support survival of immature striatal projection neurons. J Neurosci 2013; 33: 3363–3369.") Recently, it was shown that around 40% of immature cortical GABAergic interneurons die during the first two postnatal weeks (with the peak at P7–P11). [ 1 ](/articles/cddis201764#ref-CR1 "Southwell DG, Paredes MF, Galvao RP, Jones DL, Froemke RC, Sebe JY et al. Intrinsically determined cell death of developing cortical interneurons. Nature 2012; 491: 109–113.") Their survival did not depend on TrkB expression, but was regulated by either cell- autonomous or population-autonomous mechanisms that activated pro-apoptotic Bax signaling. ### Embryonic neurogenesis: dopaminergic neurons Apoptosis of immature dopaminergic neurons occurs at two developmental stages – at P0–P6 and ~P14. [ 2 ](/articles/cddis201764#ref-CR2 "Oo TF, Burke RE . The time course of developmental cell death in phenotypically defined dopaminergic neurons of the substantia nigra. Brain Res Dev Brain Res 1997; 98: 191–196.") Three main transcription factors involved in specification dopaminergic neurons – _Nurr1_ , _Pitx3_ and _En1_ – also regulate their survival. [ 52 ](/articles/cddis201764#ref-CR52 "Arenas E, Denham M, Villaescusa JC . How to make a midbrain dopaminergic neuron. Development 2015; 142: 1918–1936.") , [ 53 ](/articles/cddis201764#ref-CR53 "Kadkhodaei B, Ito T, Joodmardi E, Mattsson B, Rouillard C, Carta M et al. Nurr1 is required for maintenance of maturing and adult midbrain dopamine neurons. J Neurosci 2009; 29: 15923–15932.") , [ 54 ](/articles/cddis201764#ref-CR54 "Sonnier L, Le Pen G, Hartmann A, Bizot JC, Trovero F, Krebs MO et al. Progressive loss of dopaminergic neurons in the ventral midbrain of adult mice heterozygote for Engrailed1. J Neurosci 2007; 27: 1063–1071.") , [ 55 ](/articles/cddis201764#ref-CR55 "van den Munckhof P, Luk KC, Ste-Marie L, Montgomery J, Blanchet PJ, Sadikot AF et al. Pitx3 is required for motor activity and for survival of a subset of midbrain dopaminergic neurons. Development 2003; 130: 2535–2542.") Both Nurr1 and Pitx3 were shown to activate expression of BDNF, [ 56 ](/articles/cddis201764#ref-CR56 "Peng C, Aron L, Klein R, Li M, Wurst W, Prakash N et al. Pitx3 is a critical mediator of GDNF-induced BDNF expression in nigrostriatal dopaminergic neurons. J Neurosci 2011; 31: 12802–12815.") , [ 57 ](/articles/cddis201764#ref-CR57 "Volpicelli F, Caiazzo M, Greco D, Consales C, Leone L, Perrone-Capano C et al. Bdnf gene is a downstream target of Nurr1 transcription factor in rat midbrain neurons in vitro. J Neurochem 2007; 102: 441–453.") which promotes survival of a subpopulation of dopaminergic neurons from E16 onward [ 36 ](/articles/cddis201764#ref-CR36 "Baquet ZC, Bickford PC, Jones KR . Brain- derived neurotrophic factor is required for the establishment of the proper number of dopaminergic neurons in the substantia nigra pars compacta. J Neurosci 2005; 25: 6251–6259.") via TrkB receptors [ 58 ](/articles/cddis201764#ref-CR58 "Checa N, Canals JM, Gratacos E, Alberch J . TrkB and TrkC are differentially regulated by excitotoxicity during development of the basal ganglia. Exp Neurol 2001; 172: 282–292.") , [ 59 ](/articles/cddis201764#ref-CR59 "Zaman V, Nelson ME, Gerhardt GA, Rohrer B . Neurodegenerative alterations in the nigrostriatal system of trkB hypomorphic mice. Exp Neurol 2004; 190: 337–346.") ( [ Figure 3c ](/articles/cddis201764#Fig3) ). Another BDNF receptor, low-affinity neurotrophin receptor p75 NTR , promotes cell death of immature dopaminergic neurons. [ 60 ](/articles/cddis201764#ref-CR60 "Alavian KN, Sgado P, Alberi L, Subramaniam S, Simon HH . Elevated P75NTR expression causes death of engrailed-deficient midbrain dopaminergic neurons by Erk1/2 suppression. Neural Dev 2009; 4: 11.") Expression of p75 NTR is repressed by En1/2, [ 60 ](/articles/cddis201764#ref-CR60 "Alavian KN, Sgado P, Alberi L, Subramaniam S, Simon HH . Elevated P75NTR expression causes death of engrailed-deficient midbrain dopaminergic neurons by Erk1/2 suppression. Neural Dev 2009; 4: 11.") and as En1 was also proposed to co-activate expression of Nurr1-dependent genes, [ 61 ](/articles/cddis201764#ref-CR61 "Veenvliet JV, Dos Santos MT, Kouwenhoven WM, von Oerthel L, Lim JL, van der Linden AJ et al. Specification of dopaminergic subsets involves interplay of En1 and Pitx3. Development 2013; 140: 3373–3384.") En1 could enhance survival of immature dopaminergic neurons via two pathways – enhancing BDNF expression (via Nurr1) and repressing p75 NTR expression. Pro-death signaling from p75 NTR suppresses ERK1/2 activity and likely inhibits anti-apoptotic activity of Bcl-2 family members, [ 60 ](/articles/cddis201764#ref-CR60 "Alavian KN, Sgado P, Alberi L, Subramaniam S, Simon HH . Elevated P75NTR expression causes death of engrailed-deficient midbrain dopaminergic neurons by Erk1/2 suppression. Neural Dev 2009; 4: 11.") thus activating a classical apoptosis pathway via Bax, caspase-3 and caspase-9. [ 62 ](/articles/cddis201764#ref-CR62 "Yamaguchi Y, Miura M . Programmed cell death in neurodevelopment. Dev Cell 2015; 32: 478–490.") Caspase-3/-9 activation is inhibited by dual-specificity tyrosine- phosphorylation regulated kinase 1A (Dyrk1a), a Down syndrome-associated gene. [ 63 ](/articles/cddis201764#ref-CR63 "Barallobre MJ, Perier C, Bove J, Laguna A, Delabar JM, Vila M et al. DYRK1A promotes dopaminergic neuron survival in the developing brain and in a mouse model of Parkinson's disease. Cell Death Dis 2014; 5: e1289.") Involvement of neuron type-specific signaling in survival of dopaminergic neurons is highlighted by inhibition of developmental apoptosis by TGF _β_ -Smad-Hipk2 pathway. [ 64 ](/articles/cddis201764#ref-CR64 "Zhang J, Pho V, Bonasera SJ, Holtzman J, Tang AT, Hellmuth J et al. Essential function of HIPK2 in TGFbeta-dependent survival of midbrain dopamine neurons. Nat Neurosci 2007; 10: 77–86.") Interestingly, although transforming growth factor (TGF) _β_ 1 and _β_ 2 had little effect on modulation of survival of immature dopaminergic neurons, stimulation by TGF _β_ 3 led to activation of Smad2/3 that directly interacted with Hipk2 and inhibited caspase-3-dependent apoptosis. ### Adult neurogenesis: subventricular zone (SVZ) Survival of postnatally born neurons in the olfactory bulb is regulated by neuronal activity ( [ Figure 4a ](/articles/cddis201764#Fig4) ). Ablation or enhancement of olfactory activity onto maturing granule cells decreases or increases their survival, respectively. [ 65 ](/articles/cddis201764#ref-CR65 "Petreanu L, Alvarez-Buylla A . Maturation and death of adult-born olfactory bulb granule neurons: role of olfaction. J Neurosci 2002; 22: 6106–6113.") , [ 66 ](/articles/cddis201764#ref-CR66 "Rey NL, Sacquet J, Veyrac A, Jourdan F, Didier A . Behavioral and cellular markers of olfactory aging and their response to enrichment. Neurobiol Aging 2012; 33: 626 e629–626 e623.") However, similar enhancement does not affect periglomerular neurons, [ 9 ](/articles/cddis201764#ref-CR9 "Khodosevich K, Lazarini F, von Engelhardt J, Kaneko H, Lledo PM, Monyer H . Connective tissue growth factor regulates interneuron survival and information processing in the olfactory bulb. Neuron 2013; 79: 1136–1151.") , [ 66 ](/articles/cddis201764#ref-CR66 "Rey NL, Sacquet J, Veyrac A, Jourdan F, Didier A . Behavioral and cellular markers of olfactory aging and their response to enrichment. Neurobiol Aging 2012; 33: 626 e629–626 e623.") which could be explained by neuron type-specific pro- survival mechanisms. Furthermore, stimulation of periglomerular neurons by a single odorant decreases their survival in the region that is activated by the odorant. [ 9 ](/articles/cddis201764#ref-CR9 "Khodosevich K, Lazarini F, von Engelhardt J, Kaneko H, Lledo PM, Monyer H . Connective tissue growth factor regulates interneuron survival and information processing in the olfactory bulb. Neuron 2013; 79: 1136–1151.") Apoptosis is stimulated by connective tissue growth factor (CTGF) that, in combination with TGF _β_ 2, activate TGF _β_ Rs and Smads in immature periglomerular neurons. [ 9 ](/articles/cddis201764#ref-CR9 "Khodosevich K, Lazarini F, von Engelhardt J, Kaneko H, Lledo PM, Monyer H . Connective tissue growth factor regulates interneuron survival and information processing in the olfactory bulb. Neuron 2013; 79: 1136–1151.") Figure 4 [ ![figure 4](//media.springernature.com/lw685/springer- static/image/art%3A10.1038%2Fcddis.2017.64/MediaObjects/41419_2017_Article_BFcddis201764_Fig4_HTML.jpg) ](/articles/cddis201764/figures/4) Neuron type-specific pro-survival signaling in adult-born neurons. ( a ) Signaling involved in survival and cell death of immature neurons that are born during adult neurogenesis in the SVZ. ( b ) Signaling involved in survival and cell death of immature neurons that are born during adult neurogenesis in the SGZ. Green arrows: activation of signaling; red blunt arrows: inhibition of signaling; black arrows: activation of receptors on immature neurons from the extracellular space; Pi: phosphorylation [ Full size image ](/articles/cddis201764/figures/4) Few neurotransmitter receptors on newborn SVZ neurons mediate pro-survival effects of neuronal activation. Glutamate NMDAR activity is required for survival of neuroblasts during their migration from the SVZ through the RMS and when maturing in the olfactory bulb. [ 23 ](/articles/cddis201764#ref- CR23 "Lin CW, Sim S, Ainsworth A, Okada M, Kelsch W, Lois C . Genetically increased cell-intrinsic excitability enhances neuronal integration into adult brain circuits. Neuron 2010; 65: 32–39.") , [ 67 ](/articles/cddis201764#ref- CR67 "Platel JC, Dave KA, Gordon V, Lacar B, Rubio ME, Bordey A . NMDA receptors activated by subventricular zone astrocytic glutamate are critical for neuroblast survival prior to entering a synaptic network. Neuron 2010; 65: 859–872.") This pro-survival effect likely depends on Ca 2+ that enters into neuroblasts via NMDAR. When already in the olfactory bulb, expression of nicotinic acetylcholine receptor (nAChR) subunit _β_ 2 regulates apoptosis in newborn granule cells. [ 68 ](/articles/cddis201764#ref-CR68 "Mechawar N, Saghatelyan A, Grailhe R, Scoriels L, Gheusi G, Gabellec MM et al. Nicotinic receptors regulate the survival of newborn neurons in the adult olfactory bulb. Proc Natl Acad Sci USA 2004; 101: 9822–9826.") Knockout of the subunit results in 50% increase in survival of immature neurons, and stimulation of nAChR could be considered as another 'negative' regulator of immature neuronal survival in postnatal neurogenesis, similar to CTGF. Phosphorylation of CREB1 was shown to promote survival of SVZ-derived neuroblasts, [ 69 ](/articles/cddis201764#ref-CR69 "Giachino C, De Marchis S, Giampietro C, Parlato R, Perroteau I, Schutz G et al. cAMP response element- binding protein regulates differentiation and survival of newborn neurons in the olfactory bulb. J Neurosci 2005; 25: 10105–10118.") , [ 70 ](/articles/cddis201764#ref-CR70 "Herold S, Jagasia R, Merz K, Wassmer K, Lie DC . CREB signalling regulates early survival, neuronal gene expression and morphological development in adult subventricular zone neurogenesis. Mol Cell Neurosci 2011; 46: 79–88.") where CREB1 might be activated by Ca 2+ signaling via calmodulin and CaMKIV. [ 71 ](/articles/cddis201764#ref-CR71 "Khodosevich K, Monyer H . Signaling in migrating neurons: from molecules to networks. Front Neurosci 2011; 5: 28.") , [ 72 ](/articles/cddis201764#ref- CR72 "Khodosevich K, Seeburg PH, Monyer H . Major signaling pathways in migrating neuroblasts. Front Mol Neurosci 2009; 2: 7.") As NMDAR are involved in survival of SVZ neuroblasts, [ 23 ](/articles/cddis201764#ref-CR23 "Lin CW, Sim S, Ainsworth A, Okada M, Kelsch W, Lois C . Genetically increased cell-intrinsic excitability enhances neuronal integration into adult brain circuits. Neuron 2010; 65: 32–39.") , [ 67 ](/articles/cddis201764#ref-CR67 "Platel JC, Dave KA, Gordon V, Lacar B, Rubio ME, Bordey A . NMDA receptors activated by subventricular zone astrocytic glutamate are critical for neuroblast survival prior to entering a synaptic network. Neuron 2010; 65: 859–872.") and upon opening they allow Ca 2+ entry into neuroblasts, [ 67 ](/articles/cddis201764#ref-CR67 "Platel JC, Dave KA, Gordon V, Lacar B, Rubio ME, Bordey A . NMDA receptors activated by subventricular zone astrocytic glutamate are critical for neuroblast survival prior to entering a synaptic network. Neuron 2010; 65: 859–872.") it is likely that Ca 2+ entry via NMDAR triggers CREB1-dependent pro-survival cascade (although other receptors on neuroblasts could also mediate Ca 2+ entry). [ 72 ](/articles/cddis201764#ref-CR72 "Khodosevich K, Seeburg PH, Monyer H . Major signaling pathways in migrating neuroblasts. Front Mol Neurosci 2009; 2: 7.") , [ 73 ](/articles/cddis201764#ref-CR73 "Khodosevich K, Zuccotti A, Kreuzberg MM, Le Magueresse C, Frank M, Willecke K et al. Connexin45 modulates the proliferation of transit-amplifying precursor cells in the mouse subventricular zone. Proc Natl Acad Sci USA 2012; 109: 20107–20112.") Knockout of _Creb1_ was shown to decrease expression of the polysialylated isoform of the neural cell adhesion molecule (PSA-NCAM), [ 70 ](/articles/cddis201764#ref-CR70 "Herold S, Jagasia R, Merz K, Wassmer K, Lie DC . CREB signalling regulates early survival, neuronal gene expression and morphological development in adult subventricular zone neurogenesis. Mol Cell Neurosci 2011; 46: 79–88.") which, in turn, could promote survival of immature olfactory bulb neurons by inhibiting p75 NTR expression. [ 74 ](/articles/cddis201764#ref-CR74 "Gascon E, Vutskits L, Jenny B, Durbec P, Kiss JZ . PSA-NCAM in postnatally generated immature neurons of the olfactory bulb: a crucial role in regulating p75 expression and cell survival. Development 2007; 134: 1181–1190.") Among p75 NTR activating neurotrophins only the role of BDNF in postnatal SVZ neurogenesis has been studied, and _Ntrk2_ knockout decreases the survival of dopaminergic periglomerular neurons, but not any other cells. [ 75 ](/articles/cddis201764#ref-CR75 "Bergami M, Vignoli B, Motori E, Pifferi S, Zuccaro E, Menini A et al. TrkB signaling directs the incorporation of newly generated periglomerular cells in the adult olfactory bulb. J Neurosci 2013; 33: 11464–11478.") , [ 76 ](/articles/cddis201764#ref-CR76 "Galvao RP, Garcia-Verdugo JM, Alvarez-Buylla A . Brain-derived neurotrophic factor signaling does not stimulate subventricular zone neurogenesis in adult mice and rats. J Neurosci 2008; 28: 13368–13383.") Mammalian target of rapamycin (mTOR) pathway promotes the survival of SVZ neuroblasts via hypoxia-inducible factor 1a (HIF1A). [ 77 ](/articles/cddis201764#ref-CR77 "Feliciano DM, Zhang S, Quon JL, Bordey A . Hypoxia-inducible factor 1a is a Tsc1-regulated survival factor in newborn neurons in tuberous sclerosis complex. Hum Mol Genet 2013; 22: 1725–1734.") Tuberous sclerosis proteins 1 and 2 (TSC1/2) inhibit mTOR, and HIF1A is strongly upregulated in _Tsc1−/−_ neuroblasts, thereby increasing their survival. [ 77 ](/articles/cddis201764#ref-CR77 "Feliciano DM, Zhang S, Quon JL, Bordey A . Hypoxia-inducible factor 1a is a Tsc1-regulated survival factor in newborn neurons in tuberous sclerosis complex. Hum Mol Genet 2013; 22: 1725–1734.") mTOR is most likely activated by PI3K/Akt1 signaling as many components of this pathway were shown to be present in SVZ neuroblasts. [ 72 ](/articles/cddis201764#ref-CR72 "Khodosevich K, Seeburg PH, Monyer H . Major signaling pathways in migrating neuroblasts. Front Mol Neurosci 2009; 2: 7.") , [ 78 ](/articles/cddis201764#ref-CR78 "Khodosevich K, Monyer H . Signaling involved in neurite outgrowth of postnatally born subventricular zone neurons in vitro. BMC Neurosci 2010; 11: 18.") Finally, pro-survival signaling in newborn SVZ neurons converges on Bcl-2 family members and caspase−3/−9. [ 7 ](/articles/cddis201764#ref-CR7 "Kim WR, Kim Y, Eun B, Park OH, Kim H, Kim K et al. Impaired migration in the rostral migratory stream but spared olfactory function after the elimination of programmed cell death in Bax knock-out mice. J Neurosci 2007; 27: 14392–14403.") , [ 79 ](/articles/cddis201764#ref-CR79 "Miwa N, Storm DR . Odorant-induced activation of extracellular signal-regulated kinase/mitogen- activated protein kinase in the olfactory bulb promotes survival of newly formed granule cells. J Neurosci 2005; 25: 5404–5412.") ### Adult neurogenesis: subgranular zone (SGZ) Less is known regarding neuronal survival in the SGZ in comparison with the SVZ. Activation of NMDAR on newborn SGZ neurons enhances their survival, [ 24 ](/articles/cddis201764#ref-CR24 "Tashiro A, Sandler VM, Toni N, Zhao C, Gage FH . NMDA-receptor-mediated, cell-specific integration of new neurons in adult dentate gyrus. Nature 2006; 442: 929–933.") and it is likely that the pro- survival effect depends on Bcl-2 stimulation ( [ Figure 4b ](/articles/cddis201764#Fig4) ). [ 80 ](/articles/cddis201764#ref-CR80 "Mu Y, Zhao C, Toni N, Yao J, Gage FH . Distinct roles of NMDA receptors at different stages of granule cell development in the adult brain. Elife 2015; 4: e07871.") Protection of newborn dentate gyrus neurons by Bcl-2 signaling was also shown in transgenic mice that overexpress Bcl-2. [ 81 ](/articles/cddis201764#ref-CR81 "Kuhn HG, Biebl M, Wilhelm D, Li M, Friedlander RM, Winkler J . Increased generation of granule cells in adult Bcl-2-overexpressing mice: a role for cell death during continued hippocampal neurogenesis. Eur J Neurosci 2005; 22: 1907–1915.") Bcl-2 activity might be stimulated by Akt1 signaling, which was shown to enhance neuronal survival in the SGZ. [ 82 ](/articles/cddis201764#ref-CR82 "Fuchs C, Trazzi S, Torricella R, Viggiano R, De Franceschi M, Amendola E et al. Loss of CDKL5 impairs survival and dendritic growth of newborn neurons by altering AKT/GSK-3beta signaling. Neurobiol Dis 2014; 70: 53–68.") Cyclin-dependent kinase-like 5 (CDKL5) activates Akt1 and also inhibits Gsk-3 _β_ thus activating CREB1-dependent gene expression. Similar to the SVZ, apoptosis in newborn SGZ neurons converges on Bcl-2/Bax activity. [ 6 ](/articles/cddis201764#ref-CR6 "Sun W, Winseck A, Vinsant S, Park OH, Kim H, Oppenheim RW . Programmed cell death of adult-generated hippocampal neurons is mediated by the proapoptotic gene Bax. J Neurosci 2004; 24: 11205–11213.") Two growth factors promote survival of granule cells in the SGZ – TGF _β_ 1 and IGF1. [ 83 ](/articles/cddis201764#ref-CR83 "Kandasamy M, Lehner B, Kraus S, Sander PR, Marschallinger J, Rivera FJ et al. TGF-beta signalling in the adult neurogenic niche promotes stem cell quiescence as well as generation of new neurons. J Cell Mol Med 2014; 18: 1444–1459.") , [ 84 ](/articles/cddis201764#ref-CR84 "Lichtenwalner RJ, Forbes ME, Sonntag WE, Riddle DR . Adult-onset deficiency in growth hormone and insulin-like growth factor-I decreases survival of dentate granule neurons: insights into the regulation of adult hippocampal neurogenesis. J Neurosci Res 2006; 83: 199–210.") Importantly, both factors have little (if any) contribution to survival of adult-born neurons in the olfactory bulb, [ 9 ](/articles/cddis201764#ref-CR9 "Khodosevich K, Lazarini F, von Engelhardt J, Kaneko H, Lledo PM, Monyer H . Connective tissue growth factor regulates interneuron survival and information processing in the olfactory bulb. Neuron 2013; 79: 1136–1151.") , [ 85 ](/articles/cddis201764#ref-CR85 "Hurtado-Chong A, Yusta-Boyo MJ, Vergano-Vera E, Bulfone A, de Pablo F, Vicario-Abejon C . IGF-I promotes neuronal migration and positioning in the olfactory bulb and the exit of neuroblasts from the subventricular zone. Eur J Neurosci 2009; 30: 742–755.") indicating neuron type-specific role of TGF _β_ 1 and IGF1 in survival of adult-born neurons. ## Common signaling that regulates neuronal survival in the brain Many neuron type-specific pro-survival pathways eventually converge on pro- apoptotic and pro-survival members of Bcl-2 family and caspase-3/caspase-9 ( [ Figure 2 ](/articles/cddis201764#Fig2) ). Neuronal apoptosis in the brain is inhibited by Bcl-2 and Bcl-x L pro-survival proteins, [ 86 ](/articles/cddis201764#ref-CR86 "Motoyama N, Wang F, Roth KA, Sawa H, Nakayama K, Nakayama K et al. Massive cell death of immature hematopoietic cells and neurons in Bcl-x-deficient mice. Science 1995; 267: 1506–1510.") , [ 87 ](/articles/cddis201764#ref-CR87 "Shindler KS, Latham CB, Roth KA . Bax deficiency prevents the increased cell death of immature neurons in bcl-x- deficient mice. J Neurosci 1997; 17: 3112–3119.") , [ 88 ](/articles/cddis201764#ref-CR88 "Nakamura A, Swahari V, Plestant C, Smith I, McCoy E, Smith S et al. Bcl-xL is essential for the survival and function of differentiated neurons in the cortex that control complex behaviors. J Neurosci 2016; 36: 5448–5461.") , [ 89 ](/articles/cddis201764#ref-CR89 "Savitt JM, Jang SS, Mu W, Dawson VL, Dawson TM . Bcl-x is required for proper development of the mouse substantia nigra. J Neurosci 2005; 25: 6721–6728.") whereas pro-apoptotic proteins, mainly Bax and Bak, promote neuronal death. [ 87 ](/articles/cddis201764#ref-CR87 "Shindler KS, Latham CB, Roth KA . Bax deficiency prevents the increased cell death of immature neurons in bcl-x- deficient mice. J Neurosci 1997; 17: 3112–3119.") , [ 88 ](/articles/cddis201764#ref-CR88 "Nakamura A, Swahari V, Plestant C, Smith I, McCoy E, Smith S et al. Bcl-xL is essential for the survival and function of differentiated neurons in the cortex that control complex behaviors. J Neurosci 2016; 36: 5448–5461.") Massive death of immature neurons in the brain of _Bcl2l1−/−_ (gene name for Bcl-x L ) mice suggests that Bcl-x L is the major neuronal pro-survival protein of Bcl-2 family, [ 86 ](/articles/cddis201764#ref-CR86 "Motoyama N, Wang F, Roth KA, Sawa H, Nakayama K, Nakayama K et al. Massive cell death of immature hematopoietic cells and neurons in Bcl-x-deficient mice. Science 1995; 267: 1506–1510.") , [ 87 ](/articles/cddis201764#ref-CR87 "Shindler KS, Latham CB, Roth KA . Bax deficiency prevents the increased cell death of immature neurons in bcl-x- deficient mice. J Neurosci 1997; 17: 3112–3119.") and it becomes important for survival only at the stage of postmitotic neurons, but not before. [ 88 ](/articles/cddis201764#ref-CR88 "Nakamura A, Swahari V, Plestant C, Smith I, McCoy E, Smith S et al. Bcl-xL is essential for the survival and function of differentiated neurons in the cortex that control complex behaviors. J Neurosci 2016; 36: 5448–5461.") Another anti-apoptotic member of the Bcl-2 family, myeloid cell leukemia 1 (Mcl-1), was also shown to be critical for survival of immature neurons during embryonic development. [ 90 ](/articles/cddis201764#ref-CR90 "Arbour N, Vanderluit JL, Le Grand JN, Jahani-Asl A, Ruzhynsky VA, Cheung EC et al. Mcl-1 is a key regulator of apoptosis during CNS development and after DNA damage. J Neurosci 2008; 28: 6068–6078.") Several transcription factors promote neuronal survival, most likely by activating transcription of pro-survival genes and/or inhibiting pro-apoptotic genes. A family of myocyte enhancer factor 2 (MEF2) transcription factors, MEF2A, 2C and 2D, are expressed in the mouse brain during development and are critical for the survival of immature neurons. [ 91 ](/articles/cddis201764#ref-CR91 "Akhtar MW, Kim MS, Adachi M, Morris MJ, Qi X, Richardson JA et al. In vivo analysis of MEF2 transcription factors in synapse regulation and neuronal survival. PLoS ONE 2012; 7: e34863.") Widespread loss of neurons was also reported for knockout of another transcription factor – p73 (a member of p53 family proteins). [ 92 ](/articles/cddis201764#ref-CR92 "Pozniak CD, Barnabe-Heider F, Rymar VV, Lee AF, Sadikot AF, Miller FD . p73 is required for survival and maintenance of CNS neurons. J Neurosci 2002; 22: 9800–9809.") The loss of neurons started to be visible during second postnatal week, and was attributed to the anti- apoptotic role of the truncated form of p73, ΔNp73, which antagonizes p53 function and inhibits Bax and caspase-3/-9-dependent apoptosis. [ 93 ](/articles/cddis201764#ref-CR93 "Jacobs WB, Walsh GS, Miller FD . Neuronal survival and p73/p63/p53: a family affair. Neuroscientist 2004; 10: 443–455.") Finally, members of the CREB family of transcription factors, CREB1 and CREM, activate pro-survival signaling in postmitotic neurons around the time of perinatal development (E16.5-P0). [ 94 ](/articles/cddis201764#ref-CR94 "Mantamadiotis T, Lemberger T, Bleckmann SC, Kern H, Kretz O, Martin Villalba A et al. Disruption of CREB function in brain leads to neurodegeneration. Nat Genet 2002; 31: 47–54.") Activity-dependent survival of immature neurons via action of GABA and/or glutamate neurotransmitters was proposed for many neuronal subtypes. [ 95 ](/articles/cddis201764#ref-CR95 "Luhmann HJ, Sinning A, Yang JW, Reyes-Puerta V, Stuttgen MC, Kirischuk S et al. Spontaneous neuronal activity in developing neocortical networks: from single cells to large-scale interactions. Front Neural Circuits 2016; 10: 40.") For instance, deletion of syntaxin-binding protein 1 ( _Stxbp1_ ) that is required for synaptogenesis and neurotransmission results in widespread neuronal death during brain development. [ 96 ](/articles/cddis201764#ref-CR96 "Verhage M, Maia AS, Plomp JJ, Brussaard AB, Heeroma JH, Vermeer H et al. Synaptic assembly of the brain in the absence of neurotransmitter secretion. Science 2000; 287: 864–869.") Furthermore, pharmacological inhibition of NMDAR leads to a pronounced decrease in survival of neurons during postnatal brain development. [ 97 ](/articles/cddis201764#ref-CR97 "Ikonomidou C, Bosch F, Miksa M, Bittigau P, Vockler J, Dikranian K et al. Blockade of NMDA receptors and apoptotic neurodegeneration in the developing brain. Science 1999; 283: 70–74.") , [ 98 ](/articles/cddis201764#ref-CR98 "Heck N, Golbs A, Riedemann T, Sun JJ, Lessmann V, Luhmann HJ . Activity-dependent regulation of neuronal apoptosis in neonatal mouse cerebral cortex. Cereb Cortex 2008; 18: 1335–1349.") , [ 99 ](/articles/cddis201764#ref-CR99 "Wagner-Golbs A, Luhmann HJ . Activity- dependent survival of developing neocortical neurons depends on PI3K signalling. J Neurochem 2012; 120: 495–501.") However, as discussed above, knockouts of genes coding for NMDAR subunits show marked increase in neuronal death only during adult neurogenesis. [ 26 ](/articles/cddis201764#ref-CR26 "Forrest D, Yuzaki M, Soares HD, Ng L, Luk DC, Sheng M et al. Targeted disruption of NMDA receptor 1 gene abolishes NMDA response and results in neonatal death. Neuron 1994; 13: 325–338.") , [ 27 ](/articles/cddis201764#ref-CR27 "Kutsuwada T, Sakimura K, Manabe T, Takayama C, Katakura N, Kushiya E et al. Impairment of suckling response, trigeminal neuronal pattern formation, and hippocampal LTD in NMDA receptor epsilon 2 subunit mutant mice. Neuron 1996; 16: 333–344.") , [ 28 ](/articles/cddis201764#ref-CR28 "von Engelhardt J, Doganci B, Jensen V, Hvalby O, Gongrich C, Taylor A et al. Contribution of hippocampal and extra- hippocampal NR2B-containing NMDA receptors to performance on spatial learning tasks. Neuron 2008; 60: 846–860.") , [ 100 ](/articles/cddis201764#ref-CR100 "Maskos U, McKay RD . Neural cells without functional N-Methyl-D-Aspartate $NMDA$ receptors contribute extensively to normal postnatal brain development in efficiently generated chimaeric NMDA R1 -/- <—> +/+ mice. Dev Biol 2003; 262: 119–136.") Neuronal activity also generates reactive oxygen species (ROS) that could damage maturing neurons and trigger apoptosis. Protection from ROS is particularly important for immature neurons since they are often easier to excite than mature ones. [ 101 ](/articles/cddis201764#ref-CR101 "Schmidt- Hieber C, Jonas P, Bischofberger J . Enhanced synaptic plasticity in newly generated granule cells of the adult hippocampus. Nature 2004; 429: 184–187.") , [ 102 ](/articles/cddis201764#ref-CR102 "Wang XQ, Deriy LV, Foss S, Huang P, Lamb FS, Kaetzel MA et al. CLC-3 channels modulate excitatory synaptic transmission in hippocampal neurons. Neuron 2006; 52: 321–333.") It was recently shown that knockout of the gene coding for the antioxidant protein lanthionine synthetase C-like protein 1 (LanCL1) causes massive neuronal death in the brain due to reduced glutathione-mediated antioxidant defense and via Bax activation. [ 103 ](/articles/cddis201764#ref-CR103 "Huang C, Chen M, Pang D, Bi D, Zou Y, Xia X et al. Developmental and activity-dependent expression of LanCL1 confers antioxidant activity required for neuronal survival. Dev Cell 2014; 30: 479–487.") ## Survival of neurons in injured brain Immature neurons are more vulnerable to stress factors than mature neurons, as it is easier for external stimuli to trigger neuronal death during development than in adult brain. [ 11 ](/articles/cddis201764#ref-CR11 "Kole AJ, Annis RP, Deshmukh M . Mature neurons: equipped for survival. Cell Death Dis 2013; 4: e689.") Although the exact mechanisms of such vulnerability are unknown, it is likely that neurons over maturation devise a highly protective strategy against any external stress. Furthermore, expression of some pro-death molecules, for example, dependence receptors, [ 19 ](/articles/cddis201764#ref-CR19 "Nikoletopoulou V, Lickert H, Frade JM, Rencurel C, Giallonardo P, Zhang L et al. Neurotrophin receptors TrkA and TrkC cause neuronal death whereas TrkB does not. Nature 2010; 467: 59–63.") , [ 20 ](/articles/cddis201764#ref-CR20 "Dekkers MP, Nikoletopoulou V, Barde YA . Cell biology in neuroscience: death of developing neurons: new insights and implications for connectivity. J Cell Biol 2013; 203: 385–393.") could be limited to immature neurons. Therefore, similar stress factors might be more potent enhancers of neuronal death during development than in adult brain. In addition to common stress factors that stimulate neuronal death both during development and in adult, few factors are specific for the developing brain – for instance, misplacement of neurons could trigger their death due to impairment in neuronal connectivity. Certain types of immature neurons are more strongly affected by the stress than the others highlighting neuron type- specific mechanisms of survival. Below we discuss factors that affect survival of neurons during abnormal brain development. ### Oxidative stress Oxidative stress contributes to severe neurodevelopmental deficits in the developing mammalian brain caused by chronic exposure to either reduced (hypoxia–ischemia) or elevated (hyperoxia) levels of oxygen ( [ Figure 5 ](/articles/cddis201764#Fig5) ). Figure 5 [ ![figure 5](//media.springernature.com/lw685/springer- static/image/art%3A10.1038%2Fcddis.2017.64/MediaObjects/41419_2017_Article_BFcddis201764_Fig5_HTML.jpg) ](/articles/cddis201764/figures/5) Cell signaling under hypoxic (purple arrows) and hyperoxic (blue arrows) conditions in immature neurons _in vivo_ . Arrows: activation of signaling; blunt arrows: inhibition of signaling; vertical small arrow: elevated expression level [ Full size image ](/articles/cddis201764/figures/5) Perinatal hypoxia–ischemia or neonatal stroke is the main cause of neurodevelopmental deficits in newborns. It is accompanied by an overall decrease in cortical and hippocampal volumes due to neuronal death and atrophy. One of the major causes of neuronal death is excitotoxicity due to overactivation of NMDAR on immature neurons by the release of glutamate. [ 104 ](/articles/cddis201764#ref-CR104 "Gucuyener K, Atalay Y, Aral YZ, Hasanoglu A, Turkyilmaz C, Biberoglu G . Excitatory amino acids and taurine levels in cerebrospinal fluid of hypoxic ischemic encephalopathy in newborn. Clin Neurol Neurosurg 1999; 101: 171–174.") , [ 105 ](/articles/cddis201764#ref-CR105 "Pu Y, Li QF, Zeng CM, Gao J, Qi J, Luo DX et al. Increased detectability of alpha brain glutamate/glutamine in neonatal hypoxic-ischemic encephalopathy. AJNR Am J Neuroradiol 2000; 21: 203–212.") Pathological influx of Ca 2+ via NMDAR is followed by aberrant production of free radicals and mitochondrial dysfunction, which leads to the release of cytochrome C and, consequently, neuronal death. [ 106 ](/articles/cddis201764#ref-CR106 "Fiskum G, Murphy AN, Beal MF . Mitochondria in neurodegeneration: acute ischemia and chronic neurodegenerative diseases. J Cereb Blood Flow Metab 1999; 19: 351–369.") , [ 107 ](/articles/cddis201764#ref-CR107 "Kumar A, Mittal R, Khanna HD, Basu S . Free radical injury and blood-brain barrier permeability in hypoxic-ischemic encephalopathy. Pediatrics 2008; 122: e722–e727.") Importantly, interneurons were shown to be less susceptible to hypoxic cell death – although neonatal hypoxia slows maturation of interneurons, it does not affect their survival. [ 108 ](/articles/cddis201764#ref-CR108 "Komitova M, Xenos D, Salmaso N, Tran KM, Brand T, Schwartz ML et al. Hypoxia-induced developmental delays of inhibitory interneurons are reversed by environmental enrichment in the postnatal mouse forebrain. J Neurosci 2013; 33: 13375–13387.") A glutamate-independent mechanism contributing to hypoxia–ischemia-induced neuronal death reveals transient receptor potential melastatin 7 (TRPM7) as a key factor. [ 109 ](/articles/cddis201764#ref-CR109 "Chen W, Xu B, Xiao A, Liu L, Fang X, Liu R et al. TRPM7 inhibitor carvacrol protects brain from neonatal hypoxic-ischemic injury. Mol Brain 2015; 8: 11.") As early as 24 h after neonatal ischemic insult, TRPM7 protein levels were upregulated, which might lead to increase in caspase-3-dependent apoptosis by inhibiting Akt1 and promoting Bax _versus_ Bcl-2 expression. Overexposure to oxygen could cause hyperoxia in the brain, which was shown to affect preterm born neonates receiving oxygen supplementation. [ 110 ](/articles/cddis201764#ref-CR110 "Deuber C, Terhaar M . Hyperoxia in very preterm infants a systematic review of the literature. J Perinat Neonat Nur 2011; 25: 268–274.") Hyperoxia mainly affects cortical areas and in mice the effect on neuronal survival is most pronounced between P3 and P7. [ 111 ](/articles/cddis201764#ref-CR111 "Ikonomidou C, Kaindl AM . Neuronal death and oxidative stress in the developing brain. Antioxid Redox Signal 2011; 14: 1535–1550.") Apoptosis is caspase-3 dependent and could be enhanced because of decreased pro-survival signaling from Akt1 and Erk1/2. [ 112 ](/articles/cddis201764#ref-CR112 "Kaindl AM, Sifringer M, Zabel C, Nebrich G, Wacker MA, Felderhoff-Mueser U et al. Acute and long-term proteome changes induced by oxidative stress in the developing brain. Cell Death Differ 2006; 13: 1097–1109.") Importantly, the effect is limited to immature neurons, as hyperoxia at later ages does not affect neuronal survival. Hyperoxia also triggers an inflammatory response that could further promote neuronal death via increased levels of several interleukins - IL-1 _β_ , IL-18 and IL-18 receptor _α_ (IL-18R _α_ ). [ 113 ](/articles/cddis201764#ref-CR113 "Felderhoff-Mueser U, Sifringer M, Polley O, Dzietko M, Leineweber B, Mahler L et al. Caspase-1-processed interleukins in hyperoxia-induced cell death in the developing brain. Ann Neurol 2005; 57: 50–59.") ### Fetal alcohol spectrum disorders (FASDs) FASDs are triggered by gestational alcohol exposure and lead to impaired brain development accompanied by deficits in cognitive functions. [ 114 ](/articles/cddis201764#ref-CR114 "Riley EP, Infante MA, Warren KR . Fetal alcohol spectrum disorders: an overview. Neuropsychol Rev 2011; 21: 73–80.") Data from animal models of prenatal alcohol exposure suggest that neuronal cell death is one of the major effects contributing to the disease phenotype ( [ Figure 6 ](/articles/cddis201764#Fig6) ). [ 115 ](/articles/cddis201764#ref-CR115 "Goodlett CR, Horn KH, Zhou FC . Alcohol teratogenesis: mechanisms of damage and strategies for intervention. Exp Biol Med $Maywood$ 2005; 230: 394–406.") Figure 6 [ ![figure 6](//media.springernature.com/lw685/springer- static/image/art%3A10.1038%2Fcddis.2017.64/MediaObjects/41419_2017_Article_BFcddis201764_Fig6_HTML.jpg) ](/articles/cddis201764/figures/6) Cell signaling upon alcohol exposure of immature neurons _in vivo_ . Green arrows: activation of signaling; red blunt arrows: inhibition of signaling; vertical small arrow: elevated expression level [ Full size image ](/articles/cddis201764/figures/6) Early postnatal (P7) exposure of rats to EtOH induces widespread apoptosis, indicated by increased activation of caspase-3 as early as 8 h and neurodegeneration within less than 24 h after EtOH treatment. [ 116 ](/articles/cddis201764#ref-CR116 "Wilson DA, Peterson J, Basavaraj BS, Saito M . Local and regional network function in behaviorally relevant cortical circuits of adult mice following postnatal alcohol exposure. Alcohol Clin Exp Res 2011; 35: 1974–1984.") Differential susceptibility of immature neurons to alcohol-induced stress is underlined by variability of the extent of neuronal death in different brain regions. Thus, the retrosplenial cortex and hippocampus were most affected, whereas the olfactory bulb and piriform cortex exhibited much less apoptosis. [ 116 ](/articles/cddis201764#ref-CR116 "Wilson DA, Peterson J, Basavaraj BS, Saito M . Local and regional network function in behaviorally relevant cortical circuits of adult mice following postnatal alcohol exposure. Alcohol Clin Exp Res 2011; 35: 1974–1984.") In another study, the overall architecture of mouse brains exposed to alcohol at P7 appeared to be unaltered, but the number of calretinin-positive and parvalbumin-positive GABAergic neurons was strongly reduced, indicating that they are more prone to alcohol-induced cell death when immature. [ 117 ](/articles/cddis201764#ref-CR117 "Smiley JF, Saito M, Bleiwas C, Masiello K, Ardekani B, Guilfoyle DN et al. Selective reduction of cerebral cortex GABA neurons in a late gestation model of fetal alcohol spectrum disorder. Alcohol 2015; 49: 571–580.") Misplacing GABAergic neurons could contribute to their death since low doses of prenatal alcohol increase ambient GABA levels in the extracellular space and upregulate GABA A receptors on neuroblasts that lead to aberrant neuroblast migration. [ 118 ](/articles/cddis201764#ref-CR118 "Cuzon VC, Yeh PW, Yanagawa Y, Obata K, Yeh HH . Ethanol consumption during early pregnancy alters the disposition of tangentially migrating GABAergic interneurons in the fetal cortex. J Neurosci 2008; 28: 1854–1864.") Ethanol possesses NMDA antagonist and GABA A agonist activities and both activities could induce apoptosis during brain development. [ 97 ](/articles/cddis201764#ref-CR97 "Ikonomidou C, Bosch F, Miksa M, Bittigau P, Vockler J, Dikranian K et al. Blockade of NMDA receptors and apoptotic neurodegeneration in the developing brain. Science 1999; 283: 70–74.") , [ 119 ](/articles/cddis201764#ref-CR119 "Ikonomidou C, Bittigau P, Ishimaru MJ, Wozniak DF, Koch C, Genz K et al. Ethanol-induced apoptotic neurodegeneration and fetal alcohol syndrome. Science 2000; 287: 1056–1060.") Thus, apoptotic effects of ethanol exposure are closely related to those observed with either disrupted NMDA or elevated GABA signaling. The former has been extensively studied in immature neurons using NMDAR inhibitors causing rapid neuronal death of both excitatory and inhibitory neurons associated with decreased Bcl-2, Erk1/2 and CREB1 and increased activated caspase-3 levels. [ 120 ](/articles/cddis201764#ref-CR120 "Coleman LG Jr, Jarskog LF, Moy SS, Crews FT . Deficits in adult prefrontal cortex neurons and behavior following early post-natal NMDA antagonist treatment. Pharmacol Biochem Behav 2009; 93: 322–330.") , [ 121 ](/articles/cddis201764#ref-CR121 "Hansen HH, Briem T, Dzietko M, Sifringer M, Voss A, Rzeski W et al. Mechanisms leading to disseminated apoptosis following NMDA receptor blockade in the developing rat brain. Neurobiol Dis 2004; 16: 440–453.") , [ 122 ](/articles/cddis201764#ref- CR122 "Lema Tome CM, Nottingham CU, Smith CM, Beauchamp AS, Leung PW, Turner CP . Neonatal exposure to MK801 induces structural reorganization of the central nervous system. Neuroreport 2006; 17: 779–783.") Embryonically administered EtOH was also shown to decrease activation of pro- survival PI3K/Akt1 signaling and increase activation of glycogen synthase kinase-3 _β_ (GSK-3 _β_ ). [ 123 ](/articles/cddis201764#ref-CR123 "de la Monte SM, Wands JR . Chronic gestational exposure to ethanol impairs insulin- stimulated survival and mitochondrial function in cerebellar neurons. Cell Mol Life Sci 2002; 59: 882–893.") The latter could stimulate neuronal death by activating Bax and, thus, caspase-3-dependent apoptosis. [ 124 ](/articles/cddis201764#ref-CR124 "Liu Y, Chen G, Ma C, Bower KA, Xu M, Fan Z et al. Overexpression of glycogen synthase kinase 3beta sensitizes neuronal cells to ethanol toxicity. J Neurosci Res 2009; 87: 2793–2802.") Neuronal cell loss as a consequence of alcohol exposure in models of FASD can be attributed in part to oxidative stress. Analysis of the cerebella of P1 rats chronically exposed to ethanol from E6 shows a decrease in mRNA levels of mitochondrial respiration complex genes in granule cells, combined with increased expression of pro-apoptotic p53 and oxidative stress markers. [ 125 ](/articles/cddis201764#ref-CR125 "Chu J, Tong M, de la Monte SM . Chronic ethanol exposure causes mitochondrial dysfunction and oxidative stress in immature central nervous system neurons. Acta Neuropathol 2007; 113: 659–673.") EtOH also inhibits nuclear translocation of nuclear factor erythroid 2-related factor 2 (Nrf2), a transcription factor that is responsible for expression of those genes that protect against oxidative stress and reduce production of ROS. [ 126 ](/articles/cddis201764#ref-CR126 "Kumar A, Singh CK, Lavoie HA, Dipette DJ, Singh US . Resveratrol restores Nrf2 level and prevents ethanol-induced toxic effects in the cerebellum of a rodent model of fetal alcohol spectrum disorders. Mol Pharmacol 2011; 80: 446–457.") In the cerebellum, ROS can activate c-jun N-terminal kinase (JNK) at P4, but not at P7 rats, highlighting a time window in immature granule cells when they are most vulnerable to the oxidative stress. [ 127 ](/articles/cddis201764#ref-CR127 "Heaton MB, Paiva M, Kubovec S . Differential effects of ethanol on bid, tBid, and Bax:tBid interactions in postnatal day 4 and postnatal day 7 rat cerebellum. Alcohol Clin Exp Res 2015; 39: 55–63.") , [ 128 ](/articles/cddis201764#ref-CR128 "Heaton MB, Paiva M, Kubovic S, Kotler A, Rogozinski J, Swanson E et al. Differential effects of ethanol on c-jun N-terminal kinase, 14-3-3 proteins, and Bax in postnatal day 4 and postnatal day 7 rat cerebellum. Brain Res 2012; 1432: 15–27.") JNK, in turn, removes pro-survival 14-3-3 protein from its dimer with Bax, thus making it possible for cytosolic Bax to translocate into the mitochondria leading to mitochondrial dysfunction and neuronal apoptosis via release of cytochrome C. ### Traumatic brain injury (TBI) Although brain injury due to physical trauma is common in both developing and adult brains, the effect of such injury on the immature brain is much more devastating. [ 129 ](/articles/cddis201764#ref-CR129 "Giza CC, Prins ML . Is being plastic fantastic? Mechanisms of altered plasticity after developmental traumatic brain injury. Dev Neurosci-Basel 2006; 28: 364–379.") Strikingly, in a rat model of the disorder, the extent of neuronal apoptosis is age-related, with the P3–P7 brains being most vulnerable. [ 130 ](/articles/cddis201764#ref-CR130 "Bittigau P, Sifringer M, Pohl D, Stadthaus D, Ishimaru M, Shimizu H et al. Apoptotic neurodegeneration following trauma is markedly enhanced in the immature brain. Ann Neurol 1999; 45: 724–735.") Apoptosis of immature neurons was associated with enhanced expression of c-Jun and reduced expression of Bcl-2 and Bcl-x L leading to the release of cytochrome C and neuronal cell death. [ 130 ](/articles/cddis201764#ref-CR130 "Bittigau P, Sifringer M, Pohl D, Stadthaus D, Ishimaru M, Shimizu H et al. Apoptotic neurodegeneration following trauma is markedly enhanced in the immature brain. Ann Neurol 1999; 45: 724–735.") , [ 131 ](/articles/cddis201764#ref-CR131 "Felderhoff-Mueser U, Sifringer M, Pesditschek S, Kuckuck H, Moysich A, Bittigau P et al. Pathways leading to apoptotic neurodegeneration following trauma to the developing rat brain. Neurobiol Dis 2002; 11: 231–245.") Caspase-1 was shown to promote neuronal death by activating two proinflammatory cytokines, IL-1 _β_ and IL-18, acting via IL-18 R on neurons. [ 113 ](/articles/cddis201764#ref-CR113 "Felderhoff- Mueser U, Sifringer M, Polley O, Dzietko M, Leineweber B, Mahler L et al. Caspase-1-processed interleukins in hyperoxia-induced cell death in the developing brain. Ann Neurol 2005; 57: 50–59.") , [ 132 ](/articles/cddis201764#ref-CR132 "Sifringer M, Stefovska V, Endesfelder S, Stahel PF, Genz K, Dzietko M et al. Activation of caspase-1 dependent interleukins in developmental brain trauma. Neurobiol Dis 2007; 25: 614–622.") Interestingly, immature neurons are also the most affected by TBI population in the regions of adult neurogenesis in mice. [ 133 ](/articles/cddis201764#ref-CR133 "Kim DH, Ko IG, Kim BK, Kim TW, Kim SE, Shin MS et al. Treadmill exercise inhibits traumatic brain injury-induced hippocampal apoptosis. Physiol Behav 2010; 101: 660–665.") , [ 134 ](/articles/cddis201764#ref-CR134 "Zhou H, Chen L, Gao X, Luo B, Chen J . Moderate traumatic brain injury triggers rapid necrotic death of immature neurons in the hippocampus. J Neuropathol Exp Neurol 2012; 71: 348–359.") ### Other diseases Neuronal death contributes to phenotypic effects observed in several other neurodevelopmental disorders. Defects in microtubules because of mutations in tubulin alpha or beta genes are often associated with cortical malformations (e.g., lissencephaly or polymicrogyria) because of neuronal misplacement and subsequent death of misplaced neurons. [ 135 ](/articles/cddis201764#ref- CR135 "Jaglin XH, Poirier K, Saillour Y, Buhler E, Tian G, Bahi-Buisson N et al. Mutations in the beta-tubulin gene TUBB2B result in asymmetrical polymicrogyria. Nat Genet 2009; 41: 746–752.") For instance, deletion of _Tubb2_ gene during brain development causes aberrant neuronal migration and arrest of cells near the ventricles that eventually leads to enhanced neuronal apoptosis. [ 135 ](/articles/cddis201764#ref-CR135 "Jaglin XH, Poirier K, Saillour Y, Buhler E, Tian G, Bahi-Buisson N et al. Mutations in the beta- tubulin gene TUBB2B result in asymmetrical polymicrogyria. Nat Genet 2009; 41: 746–752.") , [ 136 ](/articles/cddis201764#ref-CR136 "Stottmann RW, Donlin M, Hafner A, Bernard A, Sinclair DA, Beier DR . A mutation in Tubb2b, a human polymicrogyria gene, leads to lethality and abnormal cortical development in the mouse. Hum Mol Genet 2013; 22: 4053–4063.") Although apoptosis was proposed to be augmented in a variety of psychiatric disorders, including schizophrenia and autism spectrum disorders (ASDs), the data were often obtained by analyzing adult brains. Experimental evidence in younger brains is rather limited to gene expression measurements using western blot or PCR. [ 137 ](/articles/cddis201764#ref-CR137 "Wei H, Alberts I, Li X . The apoptotic perspective of autism. Int J Dev Neurosci 2014; 36: 13–18.") Furthermore, it remains to be investigated whether a reduction in the number of GABAergic neurons that was reported in postmortem brains of patients with schizophrenia, bipolar disorder and ASDs [ 138 ](/articles/cddis201764#ref- CR138 "Pantazopoulos H, Wiseman JT, Markota M, Ehrenfeld L, Berretta S . Decreased numbers of somatostatin-expressing neurons in the amygdala of subjects with bipolar disorder or schizophrenia: relationship to circadian rhythms. Biol Psychiatry 2016; 81: 536–547.") , [ 139 ](/articles/cddis201764#ref-CR139 "Hashemi E, Ariza J, Rogers H, Noctor SC, Martinez-Cerdeno V . The number of parvalbumin-expressing interneurons is decreased in the medial prefrontal cortex in autism. Cereb Cortex 2016 $doi:10.1093/cercor/bhw021$.") occurs before neuronal maturation is finished. In addition, it might be that the strength of marker expression rather than the number of neurons is affected. [ 140 ](/articles/cddis201764#ref-CR140 "Chung DW, Fish KN, Lewis DA . 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Biotech Research and Innovation Centre (BRIC), University of Copenhagen, Copenhagen, Denmark Ulrich Pfisterer & Konstantin Khodosevich Authors 1. Ulrich Pfisterer [ View author publications ](/search?author=Ulrich%20Pfisterer) You can also search for this author in [ PubMed ](http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=search&term=Ulrich%20Pfisterer) [ Google Scholar ](http://scholar.google.co.uk/scholar?as_q=&num=10&btnG=Search+Scholar&as_epq=&as_oq=&as_eq=&as_occt=any&as_sauthors=%22Ulrich%20Pfisterer%22&as_publication=&as_ylo=&as_yhi=&as_allsubj=all&hl=en) 2. Konstantin Khodosevich [ View author publications ](/search?author=Konstantin%20Khodosevich) You can also search for this author in [ PubMed ](http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=search&term=Konstantin%20Khodosevich) [ Google Scholar ](http://scholar.google.co.uk/scholar?as_q=&num=10&btnG=Search+Scholar&as_epq=&as_oq=&as_eq=&as_occt=any&as_sauthors=%22Konstantin%20Khodosevich%22&as_publication=&as_ylo=&as_yhi=&as_allsubj=all&hl=en) ### Corresponding author Correspondence to [ Konstantin Khodosevich ](mailto:[email protected]) . ## Ethics declarations ### Competing interests The authors declare no conflict of interest. ## Additional information Edited by A Verkhratsky ## Rights and permissions _Cell Death and Disease_ is an open-access journal published by _Nature Publishing Group_ . This work is licensed under a Creative Commons Attribution 4.0 International License. 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0-.92-.08-1.33-.25-.41-.16-.77-.4-1.08-.7-.3-.31-.54-.69-.72-1.13-.17-.44-.26-.95-.26-1.52zm4.61-.62c0-.55-.11-.98-.34-1.28-.23-.31-.58-.47-1.06-.47-.41 0-.77.15-1.08.45-.31.29-.5.73-.57 1.3zm3.01 2.23c.31.24.61.43.92.57.3.13.63.2.98.2.38 0 .65-.08.83-.23s.27-.35.27-.6c0-.14-.05-.26-.13-.37-.08-.1-.2-.2-.34-.28-.14-.09-.29-.16-.47-.23l-.53-.22c-.23-.09-.46-.18-.69-.3-.23-.11-.44-.24-.62-.4s-.33-.35-.45-.55c-.12-.21-.18-.46-.18-.75 0-.61.23-1.1.68-1.49.44-.38 1.06-.57 1.83-.57.48 0 .91.08 1.29.25s.71.36.99.57l-.74.98c-.24-.17-.49-.32-.73-.42-.25-.11-.51-.16-.78-.16-.35 0-.6.07-.76.21-.17.15-.25.33-.25.54 0 .14.04.26.12.36s.18.18.31.26c.14.07.29.14.46.21l.54.19c.23.09.47.18.7.29s.44.24.64.4c.19.16.34.35.46.58.11.23.17.5.17.82 0 .3-.06.58-.17.83-.12.26-.29.48-.51.68-.23.19-.51.34-.84.45-.34.11-.72.17-1.15.17-.48 0-.95-.09-1.41-.27-.46-.19-.86-.41-1.2-.68z" fill="#535353"/></g></svg>) ](https://crossmark.crossref.org/dialog/?doi=10.1038/cddis.2017.64) ### Cite this article Pfisterer, U., Khodosevich, K. Neuronal survival in the brain: neuron type- specific mechanisms. _Cell Death Dis_ 8 , e2643 (2017). https://doi.org/10.1038/cddis.2017.64 [ Download citation ](https://citation- needed.springer.com/v2/references/10.1038/cddis.2017.64?format=refman&flavour=citation) * Received : 17 October 2016 * Revised : 24 January 2017 * Accepted : 31 January 2017 * Published : 02 March 2017 * Issue Date : March 2017 * DOI : https://doi.org/10.1038/cddis.2017.64 ### Share this article Anyone you share the following link with will be able to read this content: Get shareable link Sorry, a shareable link is not currently available for this article. Copy to clipboard Provided by the Springer Nature SharedIt content-sharing initiative ## This article is cited by * ### [ Neurodevelopmental disorders—high-resolution rethinking of disease modeling ](https://doi.org/10.1038/s41380-022-01876-1) * Konstantin Khodosevich * Carl M. 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Katalogen består huvudsakligen av stjärnhopar, nebulosor och galaxer. Övriga objekt i katalogen går att hitta på de andra undersidorna till New General Catalogue. Informationen om stjärnbilderna i listan kommer ur The Complete New General Catalogue and Index Catalogue of Nebulae and Star Clusters by J. L. E. Dreyer, som nåddes genom VizieR Service (webbsida: http://vizier.u-strasbg.fr/viz-bin/VizieR). Galaxernas morfologiska typer och objekt som tillhör Lilla magellanska molnet är identifierade genom att använda NASA/IPAC Extragalactic Database (webbsida: http://nedwww.ipac.caltech.edu/). Övrigt data i tabellen kommer från SIMBAD Astronomical Database (webbsida: http://simbad.u-strasbg.fr/simbad/) om inget annat nämns. 1–100 101–200 201–300 301–400 401–500 501–600 601–700 701–800 801–900 901–1000 Referenser Noter 1 NGC-objekt 0001-0999	swedish	0.887774
neurons_form_connections/explainernaturenurtu.txt	Edition:Available editions United States Donate Get newsletter Become an author Sign up as a reader Sign in The Conversation Search analysis, research, academics… Academic rigor, journalistic flair Arts + CultureEconomyEducationEnvironment + EnergyEthics + ReligionHealthPolitics + SocietyScience + TechPodcasts Explainer: nature, nurture and neuroplasticity Published: February 26, 2013 1:55pm EST Author Anthony Hannan Head of Neural Plasticity and ARC Future Fellow, Florey Institute of Neuroscience and Mental Health Disclosure statement Anthony Hannan receives funding from ARC and NHMRC. Partners View all partners CC BY ND We believe in the free flow of information Republish our articles for free, online or in print, under a Creative Commons license. Neuroplasticity refers to the way in which the cells in the brain change in response to experience. Hey Paul Studios Email X (Twitter)23 Facebook302 LinkedIn Print The human brain is the most complex and extraordinary structure in the known universe. And while there are many awe-inspiring facets of the brain, I will focus here on “neuroplasticity”, a term that has been bandied about a lot in the last couple of years. Neuroplasticity refers to the way in which the cells in the brain (and other parts of the nervous system), change in response to experience. This is not simply a curious by-product of complex evolution but serves important functions such as learning, memory and response to brain damage. Neuroplasticity is constantly occurring in both the developing and adult brain, but this article will focus on the adult brain and how some of the types of neuroplasticity affect the healthy and diseased brains. Marvellous neuroplasticity The human brain is thought to contain over 100 billion neurons interconnected by over a trillion synapses (the points of contact between neurons which transfer and store information). Over recent decades, it’s been shown that a key mechanism whereby we lay down new memories is via “synaptic plasticity”. Get facts about the coronavirus pandemic and the latest research Changes occur in brain wiring, modifying the strength of connections between neurons. This form of neuroplasticity can involve adding or removing new synapses. If you remember anything you’ve read in this article, then you may have stored that new information in your brain via the formation of new connections between specific subsets of neurons. Another form of neuroplasticity now known to occur in the brains of humans, and other mammals, is known as “adult neurogenesis”. It was thought for most of the 20th century that new neurons could not be born in the adult brain of mammals, such as humans. But part of the scientific revolution of brain research in recent decades has been the realisation that there are specific regions within the brain where neurons can be born throughout life. Adult neurogenesis in a part of the brain called the hippocampus is thought to contribute to memory formation. In another part of the brain, the birth of new neurons is thought to contribute to our sense of smell. This neuroplasticity gives the brain another of its many unique features, the fact that it never really ceases to develop. Indeed, the formation of new neurons and synapses in the adult brain constitutes a process of “microdevelopment”, which forms a continuum with the “macrodevelopment” of the embryonic and postnatal periods. Neuroplasticity’s limitations All of this neuroplasticity occurs in the healthy brain, so why can’t the brain repair itself following the onslaught of devastating brain diseases such as Alzheimer’s, Huntington’s, Parkinson’s and dementia? The implication is that the toxicity of these disease processes, due to both genetic and environmental factors, may overcome the brain’s capacity for self-repair and functional compensation. But other brain disorders, such as stroke and traumatic brain injury, have revealed that neuroplasticity can occur in response to brain insults. Researchers have shown that substantial remodelling occurs to allow some recovery of function following a stroke, and can happen within hours of the event if the patient is encouraged to begin rehabilitation as soon as possible. Research I’m involved in has shown that environmental enrichment, with increased levels of cognitive stimulation and physical activity, can delay disease onset and slow progression in a genetic model of the fatal inherited disorder, Huntington’s disease. Prior to this work, Huntington’s had been considered the “epitome of genetic determinism”. But this discovery suggests there’s no such thing as a purely genetic brain disorder and that “exercising the brain” can influence or even delay the progress of a disease. Therapeutic neuroplasticity Our recent work is influencing the design of new clinical trials, with the demonstration that dementia and depression in Huntington’s can also be delayed by increased cognitive activity and physical exercise. Environmental enrichment has been found to be beneficial in models of schizophrenia and autism spectrum disorders, which involve abnormalities of brain development. The findings show that neuroplasticity may be harnessed to delay onset, slow progression and possibly even reverse symptoms of various brain disorders. One idea which has emerged from these experimental findings is that of “enviromimetics”. We are exploring the possibility of enviromimetics as a class of new drugs that mimic or enhance the beneficial effects of enhanced cognitive stimulation and physical exercise. No, not a drug that means you don’t have to exercise! The idea is that these putative drugs would complement the beneficial effects of exercise and environmental stimulation. Enviromimetics could possibly achieve therapeutic effects via enhancement of neuroplasticity, thus providing a “brain boost” to help this extraordinary organ protect and repair itself. These new discoveries in the field of neuroplasticity have implications for how each of us may protect our brain from the relentless weathering of ageing and disease. It’s known that lifestyle factors that are good for the body, such as regular physical exercise and a healthy diet, are also beneficial for the brain. And those who keep their brains stimulated with regular complex mental activities (such as reading The Conversation and conversing) may also help delay onset of common brain diseases, such as Alzheimer’s and dementia. The harsh reality of life is that we are each dealt a genetic deck of cards at conception, which we can do nothing about. However, our growing knowledge of neuroplasticity demonstrates that we can all engage in healthy lifestyles to help protect our brains. Neuroscientists are now attempting to develop new therapies to enhance neuroplasticity, to combat the enormous and expanding burden of brain and mind disorders. Neurodegenerative disease Neuroplasticity Alzheimer's disease Huntington's disease Want to write? Write an article and join a growing community of more than 182,600 academics and researchers from 4,946 institutions. Register now Editorial Policies Community standards Republishing guidelines Friends of The Conversation Analytics Our feeds Donate Get newsletter Who we are Our charter Our team Partners and funders Resource for media Contact us En Español Privacy policy Terms and conditions Corrections Copyright © 2010–2024, The Conversation US, Inc.	biology	227625	https://sv.wikipedia.org/wiki/Neuropsykologi	Neuropsykologi	Neuropsykologi är läran om de relationer som finns mellan beteende och hjärnans funktion. Neuropsykologiska studier intresserar sig för hur olika delar av hjärnan påverkar beteendet och vilka delar som kontrollerar olika områden som stress, minne och depression. Sambandet mellan beteendet och hjärnan studeras ur olika synvinklar och under olika tillstånd, exempelvis när personen löser olika typer av praktiska eller känslomässiga uppgifter, är vakna eller sover. Neuropsykologin fördjupar sig också inom hur hormoner och olika kemiska processer påverkar människans psyke. Man är även intresserad av att studera nervsystemets funktion. Neuropsykologin drar nytta av information från många olika områden, exempelvis anatomi, biologi, biofysik, filosofi och fysiologi. Den centrala fokusen inom disciplinen är att utveckla kunskap om mänskligt beteende baserat på hjärnans funktion och den neuropsykologisk forskningen kan utnyttjas för att förstå hjärnskadors inverkan på beteendet. Utveckling Neuropsykologin är en relativt ung disciplin. Kärnan i forskningen var – och har förblivit – strävan att genom god diagnostik och behandling hjälpa hjärnskadade. Därför har ambitionerna att förstå mänskliga neuropsykologiska system utvecklats parallellt med viktigt sjukvårdsarbete. Forskning inom angränsade områden har lett till att neuropsykologin idag är en uttalad vetenskaplig disciplin. Historia Redan på mitten av 1800-talet fick neuropsykologin ett uppsving. På 1860-talet beskrev nämligen Paul Broca ett samband mellan psykisk störning och en skada inom en avgränsad del av hjärnan. Broca fann att en skada i vänster pannlob orsakade en språkstörning som innebar att patienten hade svårigheter att uttala ord. Patienten kunde förstå vad som sades men förmådde inte uttrycka sig begripligt. I och med detta upptäckte man möjligheterna att systematiskt studera hur människor drabbas psykologiskt av spontana hjärnskador. Under de kommande årtiondena kom många forskare att ägna sig åt att studera relationen mellan intellektuella störningar och hjärnskador. Undersökningar av hjärnskadade patienters intellektuella och beteendemässiga störningar gav en inblick i människans mest komplexa neuropsykologiska system. Patientstudier slog fast att de psykiska och beteendemässiga rubbningarnas karaktär berodde på skadornas utbredning i hjärnan. Kring år 1900 började man intressera sig för hur språket kan påverkas av hjärnskador, så kallad afasilära. De kliniska studierna visade att språkliga färdigheter organiseras av den vänstra hjärnhalvan. Efterhand kunde man kartlägga afasivarianterna och språkets olika delkomponenter neuronalt så pass bra att afasiläran som utvecklades på 1900-talet idag utgör kärnan för diagnostiken vid språkrubbningar orsakade av hjärnskador. 1900-talet blev en gyllene epok inom neuropsykologin och allt fler psykologiska funktioner kopplades till speciella områden i hjärnan. Studier av traumatiska hjärnskador gjordes under första och andra världskriget av bland andra Alexander Luria som erbjöd ytterligare kunskap. Utan hjärnskador som spontant drabbar människor är det troligt att den neuropsykologiska kunskapsutvecklingen troligen haft en djurexperimentell karaktär från början. Däremot skiljer sig människans intellektuella kapacitet betydligt från djurets. Trots utvecklingen av nya metoder inom neuropsykologin har spontana hjärnskador förblivit neuropsykologins främsta kunskapskälla. Under 1980-talet växte en ny gren av neuropsykologi fram, kognitiv neuropsykologi. Inom kognitiv neuropsykologi använder man metoder och teorier som är utvecklade inom den kognitiva psykologin när man studerar hjärnskador. Nutid Moderna neuropsykologiska teorier, till exempel den ovan nämnde Alexander Lurias dynamiska lokalisationsteori, innebär en kompromiss av två tidigare teorier om hur hjärnans funktion utvecklas. Den ena av dessa tidigare teorier menade att mentala förmågor var lokaliserade till avgränsade delar av hjärnan, medan den andra teorin såg hjärnan som en funktionell helhet. Moderna teorier anser alltså att mentala funktioner, som språk, minne eller planeringsförmåga, är produkter av samverkan mellan olika hjärnområden, där varje hjärnområde har en delfunktion. På senare år har man med hjälp av avancerade metoder kunnat visa att hjärnans sätt att arbeta är mer komplext än innan. Exempelvis har man kunnat se att hjärnan kan bearbeta information parallellt i olika delar av hjärnan samtidigt. Metoder Sedan 1970-talet har de neuropsykologiska metoderna genomgått en snabb utveckling. Sedan 1930-talet har man kunnat registrera hjärnans elektriska aktivitet med hjälp av EEG. När man tidigare studerade effekterna av olika hjärnskador eller hjärnsjukdomar kunde skadans lokalisation dock vanligtvis inte fastställas förrän vid en obduktion. Idag finns en hel del metoder för att fastställa en hjärnskadas lokalisation på levande människor och utan att patienten tar skada av undersökningen. Med hjälp av datortomografi och magnetkamera kan hjärnskadans lokalisation och natur fastställas med stor precision. Även avancerade tekniker som mäter hjärnans blodflöde och ämnesomsättning har tillkommit. Tack vare dessa tekniker kan man analysera hjärnan i detalj för att ta reda på vilka delar av hjärnan som förändrar sin aktivitet vid olika former av psykisk aktivitet. Detta ger oss kunskap om vilka hjärnområden som ligger bakom våra mentala förmågor. Utvecklingen av neuropsykologiska metoder och test är också viktigt för att kunna se på vilket sätt en hjärnskada eller sjukdom stör aktiviteten i andra delar av hjärnan, då individuella funktionsnedsättningar inte alltid kan avgöras genom var en skada är lokaliserad. Neuropsykolog Neuropsykologer är specialiserade psykologer som arbetar med behandling och med neuropsykologisk utredning, det vill säga diagnosticering och kartläggning av kognitiva funktioner. En neuropsykolog är specialister på att analysera störningar av intellektuella, känslomässiga och personlighetsmässiga funktioner. Med hjälp av neuropsykologiska metoder kan man fastställa vilka funktionella system och vilka delfunktioner som har påverkats av en eventuell hjärnskada. Utifrån resultaten av en neuropsykologisk utredning kan neuropsykologen tala om vilka förmågor som är intakta. Denna information är viktig vid patientens rehabilitering. Neuropsykologisk behandling Den mänskliga hjärnan är mycket komplex och innefattar komplexa neuropsykologiska system. Det förekommer också stora individuella variationer såväl vad gäller hjärnans uppbyggnad och arbetssätt som hur den kommer till användning under individens liv. Det är därför viktigt att neuropsykologisk behandling baseras på omsorgsfulla undersökningar av patientens neuropsykologiska svårigheter och kartläggningar av återstående resurser. Detta innebär att man alltså måste veta vilka områden hjärnskadan eller sjukdomen har påverkat och på så sätt veta vilka system som påverkats samt vilka förmågor som är intakta. Därför krävs förståelse för de neuropsykologiska systemen samt den stora variationen av reaktioner som en hjärnskada kan leda till. Den kliniska neuropsykologin bygger på kunskaper inom psykologi och neurologi, som man endast kan få genom omfattande och väl förvaltad klinisk erfarenhet. Den handlar även om mänskliga tragedier, och tolkningar av dessa kräver inlevelse och personlig mognad. Dessutom är det värt att tillägga att merparten av alla hjärnskadade patienter, främst de äldsta, är så svårt drabbade och har så begränsade psykiska resurser att egentliga rehabiliteringsinsatser inte är aktuella. Många av dem lider av hjärnsjukdomar som orsakar förvärrade sjukdomstillstånd. Det är därför viktigt att insatserna bygger på professionellt bemötande, medmänsklig rådgivning och omvårdnad. Framförallt kräver all neuropsykologisk rådgivning och omvårdnadsinsatser goda kunskaper om patienternas sjukdomstillstånd. Viktigt att komma ihåg är också att behandling av hjärnskadade är en ständigt pågående process. Se även Neuropsykiatri Neurovetenskap Källor Noter Psykologi Neurologi Psykofysiologi	swedish	0.463747
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Laplagne Federal University of Rio Grande do Norte, Brazil ](https://loop.frontiersin.org/people/34474/overview) Reviewed by [ ![Sebastien Couillard- Despres](https://loop.frontiersin.org/images/profile/26248/32) Sebastien Couillard-Despres Institute of Experimental Neuroregeneration, Paracelsus Medical University, Austria ](https://loop.frontiersin.org/people/26248/overview) [ ![Jose Manuel Garcia- Verdugo](https://loop.frontiersin.org/images/profile/51701/32) Jose Manuel Garcia-Verdugo University of Valencia, Spain ](https://loop.frontiersin.org/people/51701/overview) Table of contents * Abstract * Brief Historical Perspective: Revisiting A Never-Ending Story * Neurogenic Processes: Well-Defined Origin, Ill-Defined Markers, Uneven Outcome * Current State of the Art: Adult Neurogenesis or Immature Neurons for the Human Brain? * Current Research Gaps and Future Directions * Key Concepts * Author Contributions * Conflict of Interest * Acknowledgments * References Export citation * [ EndNote ](/journals/neuroscience/articles/10.3389/fnins.2020.00075/endNote) * [ Reference Manager ](/journals/neuroscience/articles/10.3389/fnins.2020.00075/reference) * [ Simple Text file ](/journals/neuroscience/articles/10.3389/fnins.2020.00075/text) * [ BibTex ](/journals/neuroscience/articles/10.3389/fnins.2020.00075/bibTex) ![Crossmark icon](/article-pages/_nuxt/img/crossmark.5c8ec60.svg) Check for updates Download article Download * [ Download PDF ](/journals/neuroscience/articles/10.3389/fnins.2020.00075/pdf?isPublishedV2=false) * [ ReadCube ](http://www.readcube.com/articles/10.3389/fnins.2020.00075) * [ EPUB ](/journals/neuroscience/articles/10.3389/fnins.2020.00075/epub?isPublishedV2=false) * [ XML (NLM) ](/journals/neuroscience/articles/10.3389/fnins.2020.00075/xml/nlm?isPublishedV2=false) ## MINI REVIEW article Front. Neurosci. , 04 February 2020 Sec. Neurogenesis Volume 14 - 2020 \| [ https://doi.org/10.3389/fnins.2020.00075 ](https://doi.org/10.3389/fnins.2020.00075) This article is part of the Research Topic Fundamentals of 21st Century Neuroscience [ View all 32 articles ](https://www.frontiersin.org/research- topics/8552/fundamentals-of-21st-century-neuroscience/articles) # Brain Structural Plasticity: From Adult Neurogenesis to Immature Neurons [ ![\\r\\nChiara La Rosa,](https://loop.frontiersin.org/images/profile/615948/74) Chiara La Rosa ](https://loop.frontiersin.org/people/615948) 1,2 [ ![Roberta Parolisi](https://loop.frontiersin.org/images/profile/260598/74) Roberta Parolisi ](https://loop.frontiersin.org/people/260598) 1 [ ![Luca Bonfanti,](https://loop.frontiersin.org/images/profile/3519/74) Luca Bonfanti ](https://loop.frontiersin.org/people/3519) 1,2 * 1 Neuroscience Institute Cavalieri Ottolenghi, Orbassano, Italy * 2 Department of Veterinary Sciences, University of Turin, Turin, Italy Brain structural plasticity is an extraordinary tool that allows the mature brain to adapt to environmental changes, to learn, to repair itself after lesions or disease, and to slow aging. A long history of neuroscience research led to fascinating discoveries of different types of plasticity, involving changes in the genetically determined structure of nervous tissue, up to the ultimate dream of neuronal replacement: a stem cell-driven “adult neurogenesis” (AN). Yet, this road does not seem a straight one, since mutable dogmas, conflicting results and conflicting interpretations continue to warm the field. As a result, after more than 10,000 papers published on AN, we still do not know its time course, rate or features with respect to other kinds of structural plasticity in our brain. The solution does not appear to be behind the next curve, as differences among mammals reveal a very complex landscape that cannot be easily understood from rodents models alone. By considering evolutionary aspects, some pitfalls in the interpretation of cell markers, and a novel population of undifferentiated cells that are not newly generated [immature neurons (INs)], we address some conflicting results and controversies in order to find the right road forward. We suggest that considering plasticity in a comparative framework might help assemble the evolutionary, anatomical and functional pieces of a very complex biological process with extraordinary translational potential. GRAPHICAL ABSTRACT [ ![www.frontiersin.org](https://www.frontiersin.org/files/Articles/512123/fnins-14-00075-HTML/image_m/fnins-14-00075-a001.jpg) ](https://www.frontiersin.org/files/Articles/512123/fnins-14-00075-HTML/image_m/fnins-14-00075-a001.jpg) Graphical Abstract. Neurogenesis (present both in the embryonic and adult brain) is a multistep biological process spanning from the division of stem/progenitor cells to the functional integration of new neurons in neural circuits. “Immaturity” is a phase in this process, also occurring in cells that are generated before birth but retain molecular features of “youth” during adulthood. These immature neurons (INs) share markers with newly born neurons. All these cells express doublecortin (DCX), which therefore cannot be considered a unique marker for neurogenic processes. Present knowledge suggests that, despite the common cellular/molecular features shared among mammals, more complex processes, such as some forms of brain plasticity, may differ remarkably, with a general trend of reduced adult neurogenesis (AN) from rodents to large-brained species, and possible inverse tendency for INs. ## Brief Historical Perspective: Revisiting A Never-Ending Story Most neuronal plasticity in mammals relies on changes of synaptic contacts between pre-existing cells (synaptic strengthening, formation, elimination; Forrest et al., 2018 ). By considering the number of synapses in the brain (estimated in the trillions: 10 15 /mm 3 in humans; Chklovskii et al., 2004 ), this can be considered the main potential for structural modification in the mammalian central nervous system (CNS). Nevertheless, this kind of plasticity does not add or replace neurons. Unlike non-mammalian vertebrates, which show remarkable neuronal cell renewal in their CNS ( Ganz and Brand, 2016 ), the mammalian brain is far less capable of forming new neurons ( Rakic, 1985 ; Weil et al., 2008 ; Bonfanti, 2011 ). The exception is a process called “adult neurogenesis” (AN), conferred by active stem cell niches that produce new neurons throughout life in restricted regions of the paleocortex (olfactory bulb) and archicortex (hippocampus) ( Kempermann et al., 2015 ; Lim and Alvarez-Buylla, 2016 ). Yet, after 60 years of intense research and more than 10,000 peer-reviewed publications, we still do not know if our brain maintains such capability ( Duque and Spector, 2019 ; Petrik and Encinas, 2019 ; Snyder, 2019 ). Although we have learned a lot about neural stem cell (NSC) biology and the molecular/cellular mechanisms that sustain neurogenesis in rodents ( Bond et al., 2015 ; Kempermann et al., 2015 ; Lim and Alvarez-Buylla, 2016 ), direct analysis of human brain has produced many conflicting results (discussed in Arellano et al., 2018 ; Kempermann et al., 2018 ; Paredes et al., 2018 ; Parolisi et al., 2018 ; Petrik and Encinas, 2019 ). Here, we try to address such controversy by highlighting some biases and questionable interpretations, recurrent in the field, and by introducing the new concept of “immature neurons” (INs). The intense research following the “re-discovery” of AN in mammals (starting from the seminal work of Lois and Alvarez-Buylla (1994) , but adding to the pioneering studies of Joseph Altman and Fernando Nottebohm) were carried out almost exclusively using mice and rats. These studies were aimed to exploit endogenous and exogenous sources of stem/progenitor cells for therapeutic purposes ( Bao and Song, 2018 ); however, the reparative capacity of mammalian AN was not sufficient, even in rodents ( Bonfanti and Peretto, 2011 ; Lois and Kelsch, 2014 ). Further studies began to reveal that the main significance of the newborn neurons is linked to physiological roles, related to learning and adaptation to a changing environment ( Kempermann, 2019 ). What appeared interesting is the discovery that AN is highly modulated by the internal/external environment and, ultimately, by lifestyle ( Vivar and van Praag, 2017 ; Kempermann, 2019 ), which opened the road to prevention of age-related problems. These results also began to highlight the importance of evolutionary aspects (and constraints) revealed by the remarkable differences that exist among mammals ( Barker et al., 2011 ; Amrein, 2015 ; Feliciano et al., 2015 ). As stated by Faykoo-Martinez et al. (2017) : “Species- specific adaptations in brain and behavior are paramount to survival and reproduction in diverse ecological niches and it is naive to think AN escaped these evolutionary pressures” (see also Amrein, 2015 ; Lipp and Bonfanti, 2016 ). Subsequently, several studies addressed the issue of AN in a wider range of species, including wild-living and large-brained mammals that displayed a varied repertoire of anatomical and behavioral features, quite different from those of mice (reviewed in Barker et al., 2011 ; Amrein, 2015 ; Lipp and Bonfanti, 2016 ; Paredes et al., 2016 ; Parolisi et al., 2018 ). Though still too fragmentary to support exhaustive conclusions about phylogeny (much less function), this landscape of heterogeneity directs us to re-evaluate, discuss and better contextualize the observations obtained in rodents, especially in the perspective of translation to humans (analyzed in Lipp and Bonfanti, 2016 ; Paredes et al., 2016 ; Parolisi et al., 2018 ; Duque and Spector, 2019 ; Snyder, 2019 ). Comparative approaches strongly indicate that there is a decrease in the remarkable plastic events that lead to whole cell changes (i.e., AN) with increasing brain size. In an evolutionary framework, the absence/reduction of neurogenesis should not be viewed as a limit, rather as a requirement linked to increased computational capabilities. Unfortunately, this same fact turns into a “necessary evil” when brain repair is needed: a requirement for stability and a high rate of cell renewal, apparently, cannot coexist ( Rakic, 1985 ; Arellano et al., 2018 ). Why then do some reports claim the existence of AN in humans? Several scientists in the field warn of high profile papers published on human AN that were technically flawed, their interpretations going well beyond what the data could support; some have never been reproduced (these aspects are thoroughly reviewed in Oppenheim, 2018 ; Duque and Spector, 2019 ). Apart from the soundness of data, a strong species bias exists in the neurogenesis literature, due to an overestimation of the universality of laboratory rodents as animal models ( Amrein, 2015 ; Lipp and Bonfanti, 2016 ; Bolker, 2017 ; Faykoo-Martinez et al., 2017 ; Oppenheim, 2019 ). There is also a common misunderstanding that the putative existence of AN in primates suggests or provides evolutionary proof that the same process exists in humans. In fact, the few existing reports are on non-human primates (common marmosets and macaca), endowed with smaller, less gyrencephalic brains and lower computational capacity, compared to apes ( Roth and Dicke, 2005 ). Systematic, quantitative studies in apes (family _Hominidae_ ) are still lacking and most studies carried out in monkeys suggest that very low levels of hippocampal neurogenesis persist during adulthood. In _Callithrix jacchus_ , proliferating doublecortin (DCX)+ neuroblasts were virtually absent in adults and markers of cell proliferation and immaturity declined with age ( Amrein et al., 2015 ). In another study involving _Macaca mulatta_ and _Macaca fascicularis_ , the estimated rate of hippocampal neurogenesis was approximately 10 times lower than in adult rodents ( Kornack and Rakic, 1999 ). These data, along with evidence that AN is virtually absent in cetaceans ( Patzke et al., 2015 ; Parolisi et al., 2017 ), do provide strong support for declining rates of AN in large-brained mammals ( Paredes et al., 2016 ). The reasons for some of these misunderstandings are analyzed in the next paragraph. ## Neurogenic Processes: Well-Defined Origin, Ill-Defined Markers, Uneven Outcome ### Origin The birth of neurons from NSC/radial glia cells has been well demonstrated both in embryonic and AN ( Lim and Alvarez-Buylla, 2014 ; Berg et al., 2019 ). The germinal layers in the embryo and the neurogenic sites in the adult brain (subventricular zone, V-SVZ; subgranular zone, SGZ; hypothalamus) are microenvironments in which the NSCs are regulated so that new neurons can be formed. Hence, an adult neurogenic process, as we now understand it, must be sustained by an active NSC niche ( Figure 1A ). If we accept this definition, then the biological limits of mammalian AN are clear: it is highly restricted to small neurogenic zones, most cells proliferating outside these regions are glial cells, it is related to physiological needs and species- specific adaptations/behaviors, and it is strictly linked to the different animal species, developmental stages and ages ( Bonfanti, 2016 ; Paredes et al., 2016 ). FIGURE 1 [ ![www.frontiersin.org](https://www.frontiersin.org/files/Articles/512123/fnins-14-00075-HTML/image_m/fnins-14-00075-g001.jpg) ](https://www.frontiersin.org/files/Articles/512123/fnins-14-00075-HTML/image_m/fnins-14-00075-g001.jpg) Figure 1. Shared aspects and differences in neurogenic and non-neurogenic processes. (A) Neurogenic events (both in embryo and adult) are multistep processes starting from stem cell division and coming out with the functional integration of mature neurons into the neural circuits. Immature neurons (INs; detectable with molecular markers of “immaturity” transiently expressed during the maturation process) represent only a phase in such a process. Gray rectangles on the right: different situations/developmental stages sharing a phase of neuronal immaturity. Color code: _green_ , stem/progenitor cells, proliferative events and newly generated neurons; _red_ , state of immaturity (shared by newly generated and non-newly generated neurons); _dark gray_ , maturity (black dots, synaptic contacts); _brown_ , doublecortin- immunoreactive (DCX+) cells. (B,C) The occurrence of DCX in the adult mammalian brain is no more an unequivocal proof that cells are newly generated since DCX is also expressed by populations of (non-newly generated) INs located in different brain regions (cerebral cortex, amygdala, claustrum and white matter, B ). (C) At least two categories of DCX+ cells have been identified: newly generated (continuously produced within active neural stem cell niches) and non-newly generated INs. (D) Non-newly generated INs prevail in some large-brained, gyrencephalic mammals, which tend to show lower rates of adult neurogenesis and longer times of maturation for the newly generated neurons, what might explain the finding of many INs associated with a few proliferative events in the human hippocampus ( _pink area:_ current gap of knowledge). AM, amygdala; CL, claustrum; NC, neocortex; PC, paleocortex; OB, olfactory bulb. Also, in the case of well-established NSC niches (V-SVZ and SGZ), the mainstream view that considers AN at the same level of other stem cell-derived regenerative processes is misleading. Even in mice, the rate of neurogenesis drops exponentially during life due to stem cell depletion ( Ben Abdallah et al., 2010 ; Encinas et al., 2011 ; Smith et al., 2019 ), a condition that is very different from adult cell renewal processes in the body, which proceed at a steady rate throughout life ( Semënov, 2019 ). The cells produced by hippocampal AN are not destined to fully and continuously replace old granular cells (as in blood or epidermis), but rather to provide a supply of new elements to complete the functional development of the dentate gyrus ( Semënov, 2019 ). Whether quiescent progenitors can provide slow genesis of new neurons outside the neurogenic sites and in the absence of a niche remains to be demonstrated ( Feliciano et al., 2015 ). ### Markers The issue of detecting (and interpreting) structural plasticity in different mammalian brains is complicated by a substantial lack of highly specific markers. Biological events involving developmental stages (i.e., embryonic and AN) are dynamic, multistep processes characterized by transient gradients of molecular expression ( Figures 1A,B ). Most cellular markers available for this kind of research are necessarily ill-defined, since they are associated with developmental/maturational stages of the cells (dynamic changes of molecular gradients) that are not exactly the same in different cell populations, brain regions and/or animal species. For instance, markers of stem cells (Sox2, nestin) or newborn neurons (DCX, PSA-NCAM) are abundant in these cell categories but not exclusively associated with them, being detectable also in other contexts. The cytoskeletal protein DCX is also abundant in cells that are born prenatally, and then remain undifferentiated for long times by continuing to express immaturity molecules (INs, Gómez- Climent et al., 2008 ; Bonfanti and Nacher, 2012 ; König et al., 2016 ; Piumatti et al., 2018 ; Rotheneichner et al., 2018 ; Figures 1B–D ). Considering DCX as a proxy for AN (as nestin was in the past for NSCs) or PSA- NCAM and DCX as markers for cell migration, are among the most common biases. A population of these cells, called cortical immature neurons (cINs), is resident in layer II of the adult cerebral cortex: the cINs are neither newborn nor migrating cells, though they heavily express DCX and co-express PSA-NCAM ( Bonfanti and Nacher, 2012 ). Before 2008, these features of “retained immaturity” where not known and we ignored that INs can also be found in extra-cortical regions ( Luzzati et al., 2009 ; Bonfanti and Nacher, 2012 ; König et al., 2016 ; Piumatti et al., 2018 ). At that time, it was common to read statements like “DCX could be developed into a suitable marker for AN and may provide an alternative to BrdU labeling” ( Brown et al., 2003 ), which is now questionable. The picture has changed and “time” has emerged as an important variable: the duration of “transient” marker expression in the cells, making more difficult to interpret cell maturation. The highly variable periods necessary for cell maturation/integration of neurons in different contexts (see below), along with their different origins (pre- or postnatal), introduce new nuances and further difficulties in determining which kind of plasticity is actually involved in different species, ages, and brain regions. ### Outcome The final outcome of neurogenic processes (not intended as the phenotypic fate of the cells, but their survival over time) can be heterogeneous concerning both the single cells and the whole process. Apart from V-SVZ and SGZ, in which the ultimate functional integration into the olfactory bulb and hippocampus is well established, for other potential sources of new neurons the destiny of the progeny is far from clear. A third neurogenic site in the hypothalamus hosts an NSC-like niche that produces neurons with unclear fate, in terms of their final integration ( Bonfanti and Peretto, 2011 ). Similarly, in ectopic examples of “parenchymal” neurogenesis (e.g., rabbit striatum and cerebellum; reviewed in Feliciano et al., 2015 ) the genesis of new neurons seems to be followed by their disappearance, suggesting a transient existence ( Gould et al., 2001 ; Luzzati et al., 2014 ). By considering the whole neurogenic process across time, its rate is progressively reduced with age, and the reduction is greater and faster in large-brained mammals ( Paredes et al., 2016 ; Parolisi et al., 2018 ). Hence, a different outcome of AN can depend on the animal species. More generally, structural plasticity could be viewed as a progressive postnatal maturation of single brain regions/cell populations differing by location and time course, aimed at providing dynamic modulation based on life experiences. According to this view, AN in large-brained mammals would fall in the general rule of critical periods: temporal windows in which it is allowed, followed by the complete development of neural circuits ( Semënov, 2019 ). It has been shown recently that mouse cINs can mature and be integrated into circuits at different ages ( Benedetti et al., 2019 ), likely achieving a sort of “delayed neurogenesis.” A recent report showing an abundance of INs in the sheep brain ( Piumatti et al., 2018 ) supports the hypothesis that these cells might represent an evolutionary choice in large-brained mammals, as an alternative/parallel form of plasticity ( Palazzo et al., 2018 ). By putting together origin, markers and timing of the maturation of different types of young neurons existing in the adult brain, the differences/similarities between AN and INs come into light: some markers are shared (DCX, PSA-NCAM), whereas the time of their expression and the origin of the cells (prenatal or postnatal) can be quite different ( Figures 1A,B ). ## Current State of the Art: Adult Neurogenesis or Immature Neurons for the Human Brain? After some reports described a dramatic postnatal drop of neurogenesis in the human brain, occurring in the V-SVZ around the second year of life ( Sanai et al., 2011 ) and in the hippocampal SGZ between age 5 and 13 years ( Cipriani et al., 2018 ; Sorrells et al., 2018 ), other studies reported that neurogenesis was maintained in the human hippocampus ( Boldrini et al., 2018 ; Moreno-Jimenéz et al., 2019 ; Tobin et al., 2019 ). However, in these latter studies, expression of molecular markers associated with stages of neuronal maturation (nestin, Sox2, DCX, and PSA-NCAM), was found mainly in large, ramified cells resembling INs, rather than the small, bipolar morphology typical of recently generated neuroblasts. Virtually all the studies (supporting or refuting existence of AN) failed to identify substantial rates of cell proliferation or a recognizable niche-like histological structure. Tissue quality in non-perfused specimens (postmortem interval and fixation) is certainly important in detecting some markers: more DCX+ neurons were detected in human brain hippocampus by Moreno-Jimenéz et al. (2019) with respect to Sorrells et al. (2018) . Yet, in non-perfused tissues, an internal positive control is required ( Figures 2A,B ). Sorrells et al. (2018) performed a complete histologic analysis using whole sections of hippocampus examined through pre-, postnatal and adult ages, thus providing an internal control for cell marker expression and its progressive drop over time ( Figure 2B ). In contexts providing the above mentioned internal controls, Ki-67 antigen staining for cell proliferation did work well in brain tissues extracted 18–40 h prior fixation, and then left in formalin for years ( Parolisi et al., 2017 ; Figures 2A,A ’). Aside from the number of cells detected, the DCX+ elements described in this way, without substantial proliferative activity, typical neuroblast morphology, or histological demonstration of a stem cell niche, cannot be considered an indication of “AN,” but rather of putative INs. FIGURE 2 [ ![www.frontiersin.org](https://www.frontiersin.org/files/Articles/512123/fnins-14-00075-HTML/image_m/fnins-14-00075-g002.jpg) ](https://www.frontiersin.org/files/Articles/512123/fnins-14-00075-HTML/image_m/fnins-14-00075-g002.jpg) Figure 2. (A,B) Internal controls are needed for confirming the occurrence/absence of low/absent neurogenesis. Since most neurogenic processes substantially decrease with age, the detection of their markers at different time points (especially those related with cell proliferation), from early pre-postnatal stages to adulthood/aging, provides proof for their detectability in a given tissue. (A) Detection of very low rates of cell division (Ki-67 antigen) in the SVZ-like region of the neonatal dolphin, indicating that the periventricular germinal layer is already vestigial at birth. By contrast, a still highly proliferative external granule layer (EGL) is detectable in the cerebellum of the same animals (A’) . (B) Dramatic reduction of cell proliferation (green) in the dentate gyrus of the human hippocampus at different pre-, post-natal, and adult ages. Modified from Parolisi et al. (2017) (A , A’) and Sorrells et al. (2018) (B) ; reproduced with permission from Springer Nature. (C) Beside common features shared at the cellular and molecular level, some complex biological processes, such as brain plasticity, can remarkably differ as a consequence of evolutionary differences among mammalian species. Left, mammals consist of around 30 orders of animals including more than 5.000 species highly differing for anatomy, physiology, behavior, habitat; right, the heterogeneity affects distinct neuroanatomy, brain size and computational capacities. Color code: red and green coherent with Figure 1 ; red and green square sizes indicate the importance of different types of plasticity in different species on the basis of the current literature (approximate estimation in the absence of systematic, comparable studies); _pink area_ , current gap of knowledge concerning primates. The origin and identity of the DCX+ cells in the human hippocampus remains to be determined: they look like young neurons in the absence of a proliferative niche, though located within a previously active neurogenic site. Something similar has been described in the human amygdala, wherein robust neurogenesis in the perinatal period is followed by an early drop of cell proliferation and persistence of DCX+ cells ( Sorrells et al., 2019 ). This discrepancy is the current gap of knowledge: no sharp limits seem have been discovered between AN and INs in the human brain. On the basis of the currently available technical tools it is quite difficult to establish if some quiescent/slowly proliferating progenitors can be the source of these DCX+ neurons (also because similar processes are lacking in rodents). Reports in mammals living longer than mice indicate that the cells generated in their hippocampi mature across longer time courses (3 months in sheep, 6 months in monkeys, with respect to 3–4 weeks in rodents; Kornack and Rakic, 1999 ; Kohler et al., 2011 ; Brus et al., 2013 ; Figure 1D ), thus suggesting that a slow, delayed maturation of neurons might replace neurogenic processes at certain ages. This hypothesis is coherent with the “preference” of INs in the relatively large sheep brain ( Piumatti et al., 2018 ) and points to the possibility of a “reservoir of young neurons” in the mature brain of large- brained species ( Palazzo et al., 2018 ; Rotheneichner et al., 2018 ; La Rosa et al., 2019 ). ## Current Research Gaps and Future Directions Despite a huge amount of data on brain structural plasticity, many gaps of knowledge still remain unresolved, mainly concerning differences between rodents and humans, and the identity of the “young” neurons. We lack highly specific markers and the experience to interpret them in some contexts (e.g., the capability to discriminate among different types of plasticity involving different degrees of immaturity). We lack systematic and comparable studies encompassing very different animal species or different developmental stages/brain regions within a single species, carried out with standard protocols for fixation, tissue processing and cell counting methods. Particularly in humans, there is an urgent need to reproduce and confirm results. To fill these gaps, experimental approaches/tools are needed to study cell proliferation/survival processes that are slow and scattered (in space and time) in large brains. ## Key Concepts Clarifying which types of plasticity can persist in the adult human brain is important for obvious translational purposes. Mice and humans share striking biological similarities, mainly regarding basic molecular mechanisms, yet important differences also emerge when complex biological processes are concerned ( Figure 2C ). There are substantial differences in the rate of AN and existence of INs among mammals: we are starting to learn that evolution might have sculpted multifaceted nuances instead of sharply defined processes. Since working directly on the human brain implies obvious ethical and technical limits, large-brained animal models are required. Dominant models may bias research directions or omit important context ( Bolker, 2017 ); on the other hand, large animals are not easy to handle, and working on them is ethically disputable, time consuming and costly. The solution might consist of a mix of purposes, including: (i) rigorous adherence to the definition of AN to distinguish it from INs; (ii) development of new markers for better assessment of different phases of neuronal maturation; (iii) understanding of phylogenetic/evolutionary aspects of structural plasticity and their ramifications/adaptations in mammals; (iv) awareness that AN “function” remains substantially unsolved and that AN may not be a function, but rather a “tool” that the brains uses to perform/improve different functions based on different adaptations. Hence, the functions revealed in rodents can be specific to their ecological niche/behavior/needs ( Amrein, 2015 ), and not fully transferable to humans. We must remember that there are no ends in science but only new, unexpected twists in the road driven by new technologies. ## Author Contributions LB wrote the manuscript. CL and RP contributed to write the manuscript and performed the experiments allowing this mini-review to be written. ## Conflict of Interest The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest. ## Acknowledgments We thank Richard Vernell for thorough revision of the English language. ## References Amrein, I. (2015). Adult hippocampal neurogenesis in natural populations of mammals. _Cold Spring Harb. Perspect. 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Neurobiol._ 86, 48–59. doi: 10.1016/j.pneurobio.2008.06.001 [ PubMed Abstract ](http://www.ncbi.nlm.nih.gov/sites/entrez?Db=pubmed&Cmd=ShowDetailView&TermToSearch=18602443) \| [ CrossRef Full Text ](https://doi.org/10.1016/j.pneurobio.2008.06.001) \| [ Google Scholar ](http://scholar.google.com/scholar_lookup?&title=The+injured+nervous+system%3A+a+Darwinian+perspective%2E&journal=Prog%2E+Neurobiol%2E&author=Weil+Z.+M.&author=Norman+G.+J.&author=De+Vries+A.+C.&author=Nelson+R.+J.&publication_year=2008&volume=86&pages=48–59) Keywords : neurogenesis, immature neurons, doublecortin, postnatal brain development, cerebral cortex Citation: La Rosa C, Parolisi R and Bonfanti L (2020) Brain Structural Plasticity: From Adult Neurogenesis to Immature Neurons. _Front. Neurosci._ 14:75. doi: 10.3389/fnins.2020.00075 Received: 14 November 2019; Accepted: 20 January 2020; Published: 04 February 2020. Edited by: [ Diego Andrés Laplagne ](https://loop.frontiersin.org/people/34474/overview) , Federal University of Rio Grande do Norte, Brazil Reviewed by: [ Sebastien Couillard-Despres ](https://loop.frontiersin.org/people/26248/overview) , Paracelsus Medical University, Austria [ Jose Manuel Garcia-Verdugo ](https://loop.frontiersin.org/people/51701/overview) , University of Valencia, Spain Copyright © 2020 La Rosa, Parolisi and Bonfanti. This is an open-access article distributed under the terms of the [ Creative Commons Attribution License (CC BY) ](http://creativecommons.org/licenses/by/4.0/) . The use, distribution or reproduction in other forums is permitted, provided the original author(s) and the copyright owner(s) are credited and that the original publication in this journal is cited, in accordance with accepted academic practice. No use, distribution or reproduction is permitted which does not comply with these terms. Correspondence: Luca Bonfanti, [ [email protected] ](mailto:[email protected]) Disclaimer: All claims expressed in this article are solely those of the authors and do not necessarily represent those of their affiliated organizations, or those of the publisher, the editors and the reviewers. 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All rights reserved [ Privacy policy ](https://www.frontiersin.org/legal/privacy-policy) \| [ Terms and conditions ](https://www.frontiersin.org/legal/terms-and-conditions)	biology	1043622	https://no.wikipedia.org/wiki/Johan%20Frederik%20Storm	Johan Frederik Storm	Johan Frederik Storm (født 8. januar 1951) er en norsk lege og professor i nevrofysiologi ved Universitetet i Oslo (UiO). Storm studerte medisin (og emner i matematikk, kjemi, logikk og filosofi) ved Universitetet i Oslo og ble cand.med. i 1978. Han var vitenskapelig assistent, stipendiat og postdoktor i Per Andersens gruppe og Fulbright-stipendiat ved State University of New York (1984–1987). Han ble dr.med. ved Universitetet i Oslo i 1989, og har gjesteforsker hos Bert Sakmann og Jörg Geiger ved Max-Planck-Gesellschaft i Heidelberg og Frankfurt. Han er professor ved Institutt for medisinsk basalfag ved UiO fra 1996. Forskning og undervisning Han har publisert mer enn 120 vitenskapelige publikasjoner, blant annet i større, internasjonalt anerkjente tidsskrift som Nature, Neuron, Nature Neuroscience og PNAS. Han er blitt sitert mer enn 9400 ganger og har en H-indeks på 45 (i10 index 62). Han forsker på elektriske signaler og koder i hjernebarkens celler og nettverk. Han har oppdaget nye mekanismer for regulering av ionekanaler og nerveimpulsers varighet og frekvens, synapsers effektivitet, integrasjon, elektrisk resonans og regulering av bevissthetstilstand (søvn, våkenhet, oppmerksomhet) som også bidrar til til å forklare epilepsi, autisme og hjerneskade. Siden 2015 har Storm og hans forskergruppe fokusert på bevissthetsforskning, dvs. hvordan fysisk aktivitet i hjernen gir opphav til subjektive opplevelser. Gruppen studerer sammenhenger mellom signaler i celler og høyere hjernefunksjoner (med patch clamp i isolerte hjerneskiver fra dyr og mennesker, og til søvn- og anestesi-forskning på mennesker). De har funnet og testet nye metoder for objektive målinger av hjernens bevissthetstilstander, og hvordan signalene endres under søvn, drømming, generell anestesi (narkose) og psykedeliske tilstander (ketamin). Nylig har Storm og kolleger fremsatt nye hypoteser om hvordan drømmer dannes og hvordan narkose virker. Han innførte i 2006 forelesninger om bevissthet og bevissthetsforstyrrelser for legestudenter, og tok initiativet til et tverrfakultært masterkurs i nevrobiologi ved UiO (MBV9340 - Advanced neurobiology). Storm underviser i nevrobiologi, biofysikk, høyere hjernefunksjoner og evolusjonsbiologi. Verv, samarbeid Storm leder forskergruppen Hjernens signaler («Brain Signalling») ved UiO og har blant annet vært gruppeleder ved Senter for fremragende forskning (SFF), Centre for Molecular Biology and Neuroscience (CMBN, 2002-2012), ledet et Storforsk-prosjekt (NFR), ledet og deltatt i flere andre NFR- og EU-finansierte-prosjekter, ledet den norske noden av International Neuroinformatics Coordination Facility (INCF), medlem av Scientific Advisory Board, Neuroscience Center, Helsinki, leder fra 2013 SERTA: The Changing Brain (Medisinsk fakultet, UiO)., og leder fra 2019 UiO:Life Science Convergence environment Conscious Brain Concepts, et tverrfaglig samarbeid mellom medisinsk hjerneforskere, filosofer, of psykologer ved UiO. Storm er styremedlem i Norwegian Neuroscience Society (NNS), og stiftet i 2013 det tverrfaglige Forum for bevissthetsforskning (FBF). Han er leder i Akademisk forum (tidligere Professorforeningen), og er engasjert i forskningsformidling og offentlig debatt om forskning og universitetspolitiske spørsmål, ytringsfrihet og habilitet. I 2015 fikk et konsortium ledet av Storm tildelt et stort forskningsprosjekt for å forske på bevissthet, innenfor «The Human Brain Project», som er et av EUs flaggskip-prosjekter. Det var første gang bevissthetsforskning fikk en plass i «The Human Brain Project». Storm ledet "the Human Brain Project's first large international conference devoted to the understanding of consciousness" i Barcelona i juni 2018 (http://hbp-ic.com/scientific-information/programme/ ), symposier om bevissthetsforskning i Paris (European Institute for Theoretical Neuroscience, 2017) og i Washington DC, USA (Society for Neuroscience, 2017). Forskningen akter å finne ut mer om det fysiske grunnlaget for bevissthet. Blant samarbeidspartnerne er Mathew Larkum og Jaan Aru (Berlin), William Phillips (Stirling, Skottland), Marcello Massimini (Milano), Giulio Tononi (Wisconsin), Lars Muckli (Glasgow), Francesca Siclari (Lausanne), Steven Laureys (Liege), og forskere ved Spesialsykehuset for epilepsi (SSE) og ved nevrokirurgisk avdeling ved Oslo universitetssykehus.. Storm er medlem av Det Norske Videnskaps-Akademi og Det Kongelige Norske Videnskabers Selskab. Referanser Eksterne lenker Norsk hjemmeside og engelsk hjemmeside ved UiO Forum for bevissthetsforskning (FBF) Norwegian Neuroscience Society (NNS) http://bevissthetsforum.no/symposium-on-consciousness-in-washington-dc-18-nov-2017/ (http://hbp-ic.com/scientific-information/programme/) https://www.uio.no/english/research/strategic-research-areas/life-science/research/convergence-environments/consciousbrainconcepts/ https://eitnconf-090317.sciencesconf.org/ https://forskning.no/hjernen-sovn/forskere-kan-ha-funnet-ut-hvor-drommer-kommer-fra/1779982 Norske medisinprofessorer Professorer ved Universitetet i Oslo Medlemmer av Det Norske Videnskaps-Akademi Medlemmer av Det Kongelige Norske Videnskabers Selskab	norwegian_bokmål	0.801179
neurons_form_connections/Synaptogenesis.txt	Synaptogenesis is the formation of synapses between neurons in the nervous system. Although it occurs throughout a healthy person's lifespan, an explosion of synapse formation occurs during early brain development, known as exuberant synaptogenesis. Synaptogenesis is particularly important during an individual's critical period, during which there is a certain degree of synaptic pruning due to competition for neural growth factors by neurons and synapses. Processes that are not used, or inhibited during their critical period will fail to develop normally later on in life. Formation of the neuromuscular junction[edit] Function[edit] The neuromuscular junction (NMJ) is the most well-characterized synapse in that it provides a simple and accessible structure that allows for easy manipulation and observation. The synapse itself is composed of three cells: the motor neuron, the myofiber, and the Schwann cell. In a normally functioning synapse, a signal will cause the motor neuron to depolarize, by releasing the neurotransmitter acetylcholine (ACh). Acetylcholine travels across the synaptic cleft where it reaches acetylcholine receptors (AChR) on the plasma membrane of the myofiber, the sarcolemma. As the AChRs open ion channels, the membrane depolarizes, causing muscle contraction. The entire synapse is covered in a myelin sheath provided by the Schwann cell to insulate and encapsulate the junction. Another important part of the neuromuscular system and central nervous system are the astrocytes. While originally they were thought to have only functioned as support for the neurons, they play an important role in functional plasticity of synapses. Origin and movement of cells[edit] During development, each of the three germ layer cell types arises from different regions of the growing embryo. The individual myoblasts originate in the mesoderm and fuse to form a multi-nucleated myotube. During or shortly after myotube formation, motoneurons from the neural tube form preliminary contacts with the myotube. The Schwann cells arise from the neural crest and are led by the axons to their destination. Upon reaching it, they form a loose, unmyelinated covering over the innervating axons. The movement of the axons (and subsequently the Schwann cells) is guided by the growth cone, a filamentous projection of the axon that actively searches for neurotrophins released by the myotube. The specific patterning of synapse development at the neuromuscular junction shows that the majority of muscles are innervated at their midpoints. Although it may seem that the axons specifically target the midpoint of the myotube, several factors reveal that this is not a valid claim. It appears that after the initial axonal contact, the newly formed myotube proceeds to grow symmetrically from that point of innervation. Coupled with the fact that AChR density is the result of axonal contact instead of the cause, the structural patterns of muscle fibers can be attributed to both myotatic growth as well as axonal innervation. The preliminary contact formed between the motoneuron and the myotube generates synaptic transmission almost immediately, but the signal produced is very weak. There is evidence that Schwann cells may facilitate these preliminary signals by increasing the amount of spontaneous neurotransmitter release through small molecule signals. After about a week, a fully functional synapse is formed following several types of differentiation in both the post-synaptic muscle cell and the pre-synaptic motoneuron. This pioneer axon is of crucial importance because the new axons that follow have a high propensity for forming contacts with well-established synapses. Post-synaptic differentiation[edit] The most noticeable difference in the myotube following contact with the motoneuron is the increased concentration of AChR in the plasma membrane of the myotube in the synapse. This increased amount of AChR allows for more effective transmission of synaptic signals, which in turn leads to a more-developed synapse. The density of AChR is > 10,000/μm and approximately 10/μm around the edge. This high concentration of AChR in the synapse is achieved through clustering of AChR, up-regulation of the AChR gene transcription in the post-synaptic nuclei, and down-regulation of the AChR gene in the non-synaptic nuclei. The signals that initiate post-synaptic differentiation may be neurotransmitters released directly from the axon to the myotube, or they may arise from changes activated in the extracellular matrix of the synaptic cleft. Clustering[edit] AChR experiences multimerization within the post-synaptic membrane largely due to the signaling molecule Agrin. The axon of the motoneuron releases agrin, a proteoglycan that initiates a cascade that eventually leads to AChR association. Agrin binds to a muscle-specific kinase (MuSK) receptor in the post-synaptic membrane, and this in turn leads to downstream activation of the cytoplasmic protein Rapsyn. Rapsyn contains domains that allow for AChR association and multimerization, and it is directly responsible for AChR clustering in the post-synaptic membrane: rapsyn-deficient mutant mice fail to form AChR clusters. Synapse-specific transcription[edit] The increased concentration of AChR is not simply due to a rearrangement of pre-existing synaptic components. The axon also provides signals that regulate gene expression within the myonuclei directly beneath the synapse. This signaling provides for localized up-regulation of transcription of AChR genes and consequent increase in local AChR concentration. The two signaling molecules released by the axon are calcitonin gene-related peptide (CGRP) and neuregulin, which trigger a series of kinases that eventually lead to transcriptional activation of the AChR genes. Extrasynaptic repression[edit] Repression of the AChR gene in the non-synaptic nuclei is an activity-dependent process involving the electrical signal generated by the newly formed synapse. Reduced concentration of AChR in the extrasynaptic membrane in addition to increased concentration in the post-synaptic membrane helps ensure the fidelity of signals sent by the axon by localizing AChR to the synapse. Because the synapse begins receiving inputs almost immediately after the motoneuron comes into contact with the myotube, the axon quickly generates an action potential and releases ACh. The depolarization caused by AChR induces muscle contraction and simultaneously initiates repression of AChR gene transcription across the entire muscle membrane. Note that this affects gene transcription at a distance: the receptors that are embedded within the post-synaptic membrane are not susceptible to repression. Pre-synaptic differentiation[edit] Although the mechanisms regulating pre-synaptic differentiation are unknown, the changes exhibited at the developing axon terminal are well characterized. The pre-synaptic axon shows an increase in synaptic volume and area, an increase of synaptic vesicles, clustering of vesicles at the active zone, and polarization of the pre-synaptic membrane. These changes are thought to be mediated by neurotrophin and cell adhesion molecule release from muscle cells, thereby emphasizing the importance of communication between the motoneuron and the myotube during synaptogenesis. Like post-synaptic differentiation, pre-synaptic differentiation is thought to be due to a combination of changes in gene expression and a redistribution of pre-existing synaptic components. Evidence for this can be seen in the up-regulation of genes expressing vesicle proteins shortly after synapse formation as well as their localization at the synaptic terminal. Synaptic maturation[edit] Immature synapses are multiply innervated at birth, due to the high propensity for new axons to innervate at a pre-existing synapse. As the synapse matures, the synapses segregate and eventually all axonal inputs except for one retract in a process called synapse elimination. Furthermore, the post-synaptic end plate grows deeper and creates folds through invagination to increase the surface area available for neurotransmitter reception. At birth, Schwann cells form loose, unmyelinated covers over groups of synapses, but as the synapse matures, Schwann cells become dedicated to a single synapse and form a myelinated cap over the entire neuromuscular junction. Synapse elimination[edit] The process of synaptic pruning known as synapse elimination is a presumably activity-dependent process that involves competition between axons. Hypothetically, a synapse strong enough to produce an action potential will trigger the myonuclei directly across from the axon to release synaptotrophins that will strengthen and maintain well-established synapses. This synaptic strengthening is not conferred upon the weaker synapses, thereby starving them out. It has also been suggested that in addition to the synaptotrophins released to the synapse exhibiting strong activity, the depolarization of the post-synaptic membrane causes release of synaptotoxins that ward off weaker axons. Synapse formation specificity[edit] A remarkable aspect of synaptogenesis is the fact that motoneurons are able to distinguish between fast and slow-twitch muscle fibers; fast-twitch muscle fibers are innervated by "fast" motoneurons, and slow-twitch muscle fibers are innervated by "slow" motoneurons. There are two hypothesized paths by which the axons of motoneurons achieve this specificity, one in which the axons actively recognize the muscles that they innervate and make selective decisions based on inputs, and another that calls for more indeterminate innervation of muscle fibers. In the selective paths, the axons recognize the fiber type, either by factors or signals released specifically by the fast or slow-twitch muscle fibers. In addition, selectivity can be traced to the lateral position that the axons are predeterminately arranged in order to link them to the muscle fiber that they will eventually innervate. The hypothesized non-selective pathways indicate that the axons are guided to their destinations by the matrix through which they travel. Essentially, a path is laid out for the axon and the axon itself is not involved in the decision-making process. Finally, the axons may non-specifically innervate muscle fibers and cause the muscles to acquire the characteristics of the axon that innervates them. In this path, a "fast" motoneuron can convert any muscle fiber into a fast-twitch muscle fiber. There is evidence for both selective and non-selective paths in synapse formation specificity, leading to the conclusion that the process is a combination of several factors. Central nervous system synapse formation[edit] Although the study of synaptogenesis within the central nervous system (CNS) is much more recent than that of the NMJ, there is promise of relating the information learned at the NMJ to synapses within the CNS. Many similar structures and basic functions exist between the two types of neuronal connections. At the most basic level, the CNS synapse and the NMJ both have a nerve terminal that is separated from the postsynaptic membrane by a cleft containing specialized extracellular material. Both structures exhibit localized vesicles at the active sites, clustered receptors at the post-synaptic membrane, and glial cells that encapsulate the entire synaptic cleft. In terms of synaptogenesis, both synapses exhibit differentiation of the pre- and post-synaptic membranes following initial contact between the two cells. This includes the clustering of receptors, localized up-regulation of protein synthesis at the active sites, and neuronal pruning through synapse elimination. Despite these similarities in structure, there is a fundamental difference between the two connections. The CNS synapse is strictly neuronal and does not involve muscle fibers: for this reason the CNS uses different neurotransmitter molecules and receptors. More importantly, neurons within the CNS often receive multiple inputs that must be processed and integrated for successful transfer of information. Muscle fibers are innervated by a single input and operate in an all or none fashion. Coupled with the plasticity that is characteristic of the CNS neuronal connections, it is easy to see how increasingly complex CNS circuits can become. Factors regulating synaptogenesis in the CNS[edit] Signaling[edit] The main method of synaptic signaling in the NMJ is through use of the neurotransmitter acetylcholine and its receptor. The CNS homolog is glutamate and its receptors, and one of special significance is the N-methyl-D-aspartate (NMDA) receptor. It has been shown that activation of NMDA receptors initiates synaptogenesis through activation of downstream products. The heightened level of NMDA receptor activity during development allows for increased influx of calcium, which acts as a secondary signal. Eventually, immediate early genes (IEG) are activated by transcription factors and the proteins required for neuronal differentiation are translated. The NMDA receptor function is associated with the estrogen receptor in hippocampal neurons. Experiments conducted with estradiol show that exposure to the estrogen significantly increases synaptic density and protein concentration. Synaptic signaling during synaptogenesis is not only activity-dependent, but is also dependent on the environment in which the neurons are located. For instance, brain-derived neurotrophic factor (BDNF) is produced by the brain and regulates several functions within the developing synapse, including enhancement of transmitter release, increased concentration of vesicles, and cholesterol biosynthesis. Cholesterol is essential to synaptogenesis because the lipid rafts that it forms provide a scaffold upon which numerous signaling interactions can occur. BDNF-null mutants show significant defects in neuronal growth and synapse formation. Aside from neurotrophins, cell-adhesion molecules are also essential to synaptogenesis. Often the binding of pre-synaptic cell-adhesion molecules with their post-synaptic partners triggers specializations that facilitate synaptogenesis. Indeed, a defect in genes encoding neuroligin, a cell-adhesion molecule found in the post-synaptic membrane, has been linked to cases of autism and mental retardation. Finally, many of these signaling processes can be regulated by matrix metalloproteinases (MMPs) as the targets of many MMPs are these specific cell-adhesion molecules. Morphology[edit] The special structure found in the CNS that allows for multiple inputs is the dendritic spine, the highly dynamic site of excitatory synapses. This morphological dynamism is due to the specific regulation of the actin cytoskeleton, which in turn allows for regulation of synapse formation. Dendritic spines exhibit three main morphologies: filopodia, thin spines, and mushroom spines. The filopodia play a role in synaptogenesis through initiation of contact with axons of other neurons. Filopodia of new neurons tend to associate with multiply synapsed axons, while the filopodia of mature neurons tend to sites devoid of other partners. The dynamism of spines allows for the conversion of filopodia into the mushroom spines that are the primary sites of glutamate receptors and synaptic transmission. Environmental enrichment[edit] Rats raised with environmental enrichment have 25% more synapses than controls. This effect occurs whether a more stimulating environment is experienced immediately following birth, after weaning, or during maturity. Stimulation effects not only synaptogenesis upon pyramidal neurons but also stellate ones. Contributions of the Wnt protein family[edit] The (Wnt) family, includes several embryonic morphogens that contribute to early pattern formation in the developing embryo. Recently data have emerged showing that the Wnt protein family has roles in the later development of synapse formation and plasticity. Wnt contribution to synaptogenesis has been verified in both the central nervous system and the neuromuscular junction. Central nervous system[edit] Wnt family members contribute to synapse formation in the cerebellum by inducing presynaptic and postsynaptic terminal formation. This brain region contains three main neuronal cell types- Purkinje cells, granule cells and mossy fiber cells. Wnt-3 expression contributes to Purkinje cell neurite outgrowth and synapse formation. Granule cells express Wnt-7a to promote axon spreading and branching in their synaptic partner, mossy fiber cells. Retrograde secretion of Wnt-7a to mossy fiber cells causes growth cone enlargement by spreading microtubules. Furthermore, Wnt-7a retrograde signaling recruits synaptic vesicles and presynaptic proteins to the synaptic active zone. Wnt-5a performs a similar function on postsynaptic granule cells; this Wnt stimulates receptor assembly and clustering of the scaffolding protein PSD-95. In the hippocampus Wnts in conjunction with cell electrical activity promote synapse formation. Wnt7b is expressed in maturing dendrites, and the expression of the Wnt receptor Frizzled (Fz), increases highly with synapse formation in the hippocampus. NMDA glutamate receptor activation increases Wnt2 expression. Long term potentiation (LTP) due to NMDA activation and subsequent Wnt expression leads to Fz-5 localization at the postsynaptic active zone. Furthermore, Wnt7a and Wnt2 signaling after NMDA receptor mediated LTP leads to increased dendritic arborization and regulates activity induced synaptic plasticity. Blocking Wnt expression in the hippocampus mitigates these activity dependent effects by reducing dendritic arborization and subsequently, synaptic complexity. Neuromuscular junction[edit] Similar mechanisms of action by Wnts in the central nervous system are observed in the neuromuscular junction (NMJ) as well. In the Drosophila NMJ mutations in the Wnt5 receptor Derailed (drl) reduce the number of and density of synaptic active zones. The major neurotransmitter in this system is glutamate. Wnt is needed to localize glutamatergic receptors on postsynaptic muscle cells. As a result, Wnt mutations diminish evoked currents on the postsynaptic muscle. In the vertebrate NMJ, motor neuron expression of Wnt-11r contributes to acetylcholine receptor (AChR) clustering in the postsynaptic density of muscle cells. Wnt-3 is expressed by muscle fibers and is secreted retrogradely onto motor neurons. In motor neurons, Wnt-3 works with Agrin to promote growth cone enlargement, axon branching and synaptic vesicle clustering.	biology	31340	https://sv.wikipedia.org/wiki/Synaps	Synaps	Synaps är en koppling mellan två neuroner eller mellan en neuron och en målcell. Den vedertagna bilden av en synaps består av en presynaptisk del i axonens ände (presynaptisk terminal), det synaptiska gapet (synapsspringan, synapsspalten, synapsklyftan eller synapsgapet) och en postsynaptisk del i den andra nervcellen. Information från en sådan synaps överförs genom att så kallade signalsubstanser frisläpps från den presynaptiska terminalen och som sedan genom diffusion når den postsynaptiska nervcellen. När en neurotransmittor binder till en receptor på den postsynaptiska cellen förändras membranpotentialen, vilket kan alstra en aktionspotential. Det är aktionspotentialer som överför signalen genom nervcellen. Det som bestämmer om en neurotransmittor kommer att alstra en aktionspotential är dels vilken typ av neurotransmittor som frisläpps, och dels mängden. Vissa neurotransmittorer (till exempel GABA) hämmar den postsynaptiska nervcellen från att alstra en aktionspotential genom att öppna kloridkanaler. Därmed blir den postsynaptiska membranpotentialen mer negativ, och kommer således längre bort från det tröskelvärde som krävs för en aktionspotential. Andra neurotransmittorer såsom acetylkolin och glutamat exciterar det postsynaptiska membranet. Slutligen är det nödvändigt att neurotransmittorn försvinner från det synaptiska gapet för att möjliggöra att en ny signal kan vidarebefordras. Olika mekanismer existerar för att återställa den synaptiska mikromiljön, till exempel genom att neurotransmittorer tas upp i axonen igen via membranbundna pumpar, eller att enzymer bryter ner neurotransmittorerna. Typer av synapskopplingar Det finns ett antal olika typer av synapser, nämligen: Dendrodendritisk: Koppling mellan två dendriter. Axodendritisk: Koppling mellan ett axon och en dendrit. Axoextracellulär: Ett axon som kan frigöra signalsubstanser i den extracellulära vätskan. Axosomatisk: Koppling mellan ett axon och en nervcells soma (cellkropp). Axosynaptisk: Ett axon som kopplar till ett annat axons terminal. Axoaxonisk: En koppling mellan ett axon och ett annat axon. Axosekretisk: Ett axon som kan frigöra signalsubstanser i ett blodkärl. Axolagostik: En lago som kopplas mellan ett axon och en cellkärna. Nervceller Cellbiologi	swedish	0.529386
see_when_eyes_closed/Phosphene.txt	A phosphene is the phenomenon of seeing light without light entering the eye. The word phosphene comes from the Greek words phos (light) and phainein (to show). Phosphenes that are induced by movement or sound may be associated with optic neuritis. Phosphenes can be induced by mechanical, electrical, or magnetic stimulation of the retina or visual cortex, or by random firing of cells in the visual system. Phosphenes have also been reported by meditators (called nimitta), people who endure long periods without visual stimulation (the prisoner's cinema), or those who ingest psychedelic drugs. Causes[edit] Mechanical stimulation[edit] The most common phosphenes are pressure phosphenes, caused by rubbing or applying pressure on or near the closed eyes. They have been known since antiquity, and described by the Greeks. The pressure mechanically stimulates the cells of the retina. Experiences include a darkening of the visual field that moves against the rubbing, a diffuse colored patch that also moves against the rubbing, well defined shapes such as bright circles that exist near or opposite to where pressure is being applied, a scintillating and ever-changing and deforming light grid with occasional dark spots (like a crumpling fly-spotted flyscreen), and a sparse field of intense blue points of light. Pressure phosphenes can persist briefly after the rubbing stops and the eyes are opened, allowing the phosphenes to be seen on the visual scene. Hermann von Helmholtz and others have published drawings of their pressure phosphenes. One example of a pressure phosphene is demonstrated by gently pressing the side of one's eye and observing a colored ring of light on the opposite side, as detailed by Isaac Newton. Another common phosphene is "seeing stars" from a sneeze, laughter, a heavy and deep cough, blowing of the nose, a blow on the head or low blood pressure (such as on standing up too quickly or prior to fainting). It is possible these involve some mechanical stimulation of the retina, but they may also involve mechanical and metabolic (such as from low oxygenation or lack of glucose) stimulation of neurons of the visual cortex or of other parts of the visual system. Less commonly, phosphenes can also be caused by some diseases of the retina and nerves, such as multiple sclerosis. The British National Formulary lists phosphenes as an occasional side effect of at least one anti-anginal medication. The name "phosphene" was coined by J. B. H. Savigny, better known as the ship's surgeon of the wrecked French frigate Méduse. It was first employed by Serre d'Uzes to test retinal function prior to cataract surgery. Electrical stimulation[edit] Phosphenes have been created by electrical stimulation of the brain, reported by neurologist Otfrid Foerster as early as 1929. Brindley and Lewin (1968) inserted a matrix of stimulating electrodes directly into the visual cortex of a 52-year-old blind female, using small pulses of electricity to create phosphenes. These phosphenes were points, spots, and bars of colorless or colored light. Brindley and Rushton (1974) used the phosphenes to create a visual prosthesis, in this case by using the phosphenes to depict Braille spots. In recent years, researchers have successfully developed experimental brain–computer interfaces or neuroprostheses that stimulate phosphenes to restore vision to people blinded through accidents. Notable successes include the human experiments by William H. Dobelle and Mark Humayun and animal research by Dick Normann. A noninvasive technique that uses electrodes on the scalp, transcranial magnetic stimulation, has also been shown to produce phosphenes. Experiments with humans have shown that when the visual cortex is stimulated above the calcarine fissure, phosphenes are produced in the lower part of the visual field, and vice versa. Others[edit] Phosphenes have been produced by intense, changing magnetic fields, such as with transcranial magnetic stimulation (TMS). These fields can be positioned on different parts of the head to stimulate cells in different parts of the visual system. They also can be induced by alternating currents that entrain neural oscillation as with transcranial alternating current stimulation. In this case they appear in the peripheral visual field. This claim has been disputed. The alternative hypothesis is that current spread from the occipital electrode evokes phosphenes in the retina. Phosphenes created by magnetic fields are known as magnetophosphenes. Astronauts exposed to radiation in space have reported seeing phosphenes. Patients undergoing radiotherapy have reported seeing blue flashes of light during treatment; the underlying phenomenon has been shown to resemble Cherenkov radiation. Phosphenes can be caused by some medications, such as Ivabradine. Mechanism[edit] Most vision researchers believe that phosphenes result from the normal activity of the visual system after stimulation of one of its parts from some stimulus other than light. For example, Grüsser et al. showed that pressure on the eye results in activation of retinal ganglion cells in a similar way to activation by light. An ancient, discredited theory is that light is generated in the eye. A version of this theory has been revived, except, according to its author, that "phosphene lights are [supposed to be] due to the intrinsic perception of induced or spontaneous increased biophoton emission of cells in various parts of the visual system (from retina to cortex)" Anthropological research[edit] In 1988, David Lewis-Williams and T. A. Dowson published an article about phosphenes and other entoptic phenomena. They argued that non-figurative art of the Upper Paleolithic depicts visions of phosphenes and neurological "form constants", probably enhanced by hallucinogenic drugs. Research[edit] Research has looked into visual prosthesis for the blind, which involves use of arrays of electrodes implanted in the skull over the occipital lobe to produce phosphenes. There have been long term implants of this type. Risks, such as infections and seizures, have been an impediment to their development. A possible use of phosphenes as part of a brain to brain communication system has been reported. The system called BrainNet, produces phosphenes using transcranial magnetic stimulation (TMS). The goal of the research is to connect thoughts brain to brain using a system where signals are detected using electroencephalography (EEG) and delivered using transcranial magnetic stimulation (TMS). An experiment was conducted with 5 different groups, each contained three people. The subjects were split into two groups. Two subjects functioned as the senders, and were connected to EEG electrodes, and a third person functioned as the receiver, who wore the TMS helmet. Each person was stationed in front of a television screen with a Tetris-style game. The senders had to determine if there was a need to rotate the falling blocks, but without the ability to rotate them – only the receiver was able to perform this operation. At the edges of each screen, were two icons with two flashing lights in two different frequencies, (one at 15 Hz and the other at 17 Hz). The sender focused on one icon, or the other to signal that the block should be rotated to the right or the left. The EEG produced a unique signal, which was transmitted to the TMS helmet of the receiver, who perceived phosphenes which differed for the 15 Hz and 17 Hz signal, and rotated the block in the relevant direction. The experiment achieved 81% success. See also[edit] Closed-eye hallucination – Class of hallucination Dark retreat – Tibetan Buddhism advanced practice Isolation tank – Pitch-black, light-proof, soundproof environment heated to the same temperature as the skin Prisoner's cinema – Visual phenomenon involving seeing animated lights in the darkness Scintillating scotoma – Visual aura associated with migraine Photopsia – Presence of perceived flashes of light in one's field of vision Visual snow – Class of hallucinationPages displaying short descriptions of redirect targets HPPD – Medical condition	biology	24270	https://da.wikipedia.org/wiki/Fotonisk%20krystal	Fotonisk krystal	Fotoniske krystaller er metamaterialer, der udgøres af periodiske dielektriske eller metal-dielektriske (nano)strukturer som er designet til at påvirke elektromagnetiske bølgers (EM) udbredelse på den samme måde som det periodiske potential i et halvledende krystal påvirker elektronernes bevægelse ved at definere tilladte og forbudte elektriske energibånd. Fraværet af tilladte udbredelsesenergibånd indeni strukturen for et interval af bølgelængder kaldes et fotonisk båndgab, som forårsager bemærkelsesværdige optiske fænomener, som bl.a. resulterer i; spontan udsendelse, generering af alle regnbuens farver ud fra infrarødt-lys, højreflekterende spejle som virker i alle retninger og lysleder med lavt tab, og materialer med negativt brydningsindeks. Fotonisk krystal er grundlæggende set baseret på det fysiske fænomen diffraktion. Kilder/referencer Se også Kvantemekanik Optik Nanoteknologi Kvanteø Opal Eksterne henvisninger Webarchive backup: Ingeniøren nr. -3/1999: Dansk gennembrud i fiberoptik Danske og engelske forskere har sammen bevist, at optisk fiber med huller i kan transportere lys over lange afstande. Vejviser: Photonic Crystal and Photonic Band Gap Links Cnet, August 31, 2000, Why photonics? Citat: "...Demand for photonic equipment is skyrocketing. Internet traffic on the backbone networks has been doubling every three months and shows no sign of abating. Companies are laying fiber in just about every cross-country right-of-way they can find. First it was along the railways, and now it's the gas pipelines, sewers and just about any conduit you can think of... " November 3, 2000, Sandia LabNews: Cheesecloth-like photonics device bends light with little loss Citat: "...the cheesecloth-like structure can be considered essentially a wire for light...Because of the very small light loss, the technique offers the potential of ultimately replacing electronic chips with faster, cooler photonic chips...two-dimensional crystals are cheaper and far easier to build..." Number 646 #1, July 16, 2003, AIP: Photonic Crystal Shifts Energy Citat: "...Shawn Lin and his Sandia colleagues, in the course of their studies of photonic crystals, have seemed to challenge the venerable formulation, made by Max Planck a hundred years ago, of what kind of emission spectrum a body should have..." CERN Courier: Photonic crystal makes flat lens Citat: "...The key to creating the flat lens lies with the recent advent of materials – photonic crystals – that effectively have a negative index of refraction...the principle could herald a revolution in optics..." BBC News: 3 January, 2001, Sea mouse promises bright future Citat: "...The sea mouse, or Aphrodita, has spines that normally appear deep red in colour. But when light falls on a spine perpendicular to its axis, stripes of different colours appear – strong blues and greens..."The simple structure responsible for this effect is a remarkable example of photonic engineering by a living organism."..."These structures may have application in photonic communications, where there is much interest in fabricating photonic crystal fibres with similar morphology."..." Metamaterialer Fotonik	danish	0.653631
see_when_eyes_closed/Brain.txt	The brain is an organ that serves as the center of the nervous system in all vertebrate and most invertebrate animals. In vertebrates, a small part of the brain called the hypothalamus is the neural control center for all endocrine systems. The brain is the largest cluster of neurons in the body and is typically located in the head, usually near organs for special senses such as vision, hearing and olfaction. It is the most energy-consuming organ of the body, and the most specialized, responsible for endocrine regulation, sensory perception, motor control, and the development of intelligence. While invertebrate brains arise from paired segmental ganglia (each of which is only responsible for the respective body segment) of the ventral nerve cord, vertebrate brains develop axially from the midline dorsal nerve cord as a vesicular enlargement at the rostral end of the neural tube, with centralized control over all body segments. All vertebrate brains can be embryonically divided into three parts: the forebrain (prosencephalon, subdivided into telencephalon and diencephalon), midbrain (mesencephalon) and hindbrain (rhombencephalon, subdivided into metencephalon and myelencephalon). The spinal cord, which directly interacts with somatic functions below the head, can be considered a caudal extension of the myelencephalon enclosed inside the vertebral column. Together, the brain and spinal cord constitute the central nervous system in all vertebrates. In humans, the cerebral cortex contains approximately 14–16 billion neurons, and the estimated number of neurons in the cerebellum is 55–70 billion. Each neuron is connected by synapses to several thousand other neurons, typically communicating with one another via root-like protrusions called dendrites and long fiber-like extensions called axons, which are usually myelinated and carry trains of rapid micro-electric signal pulses called action potentials to target specific recipient cells in other areas of the brain or distant parts of the body. The prefrontal cortex, which controls executive functions, is particularly well developed in humans. Physiologically, brains exert centralized control over a body's other organs. They act on the rest of the body both by generating patterns of muscle activity and by driving the secretion of chemicals called hormones. This centralized control allows rapid and coordinated responses to changes in the environment. Some basic types of responsiveness such as reflexes can be mediated by the spinal cord or peripheral ganglia, but sophisticated purposeful control of behavior based on complex sensory input requires the information integrating capabilities of a centralized brain. The operations of individual brain cells are now understood in considerable detail but the way they cooperate in ensembles of millions is yet to be solved. Recent models in modern neuroscience treat the brain as a biological computer, very different in mechanism from a digital computer, but similar in the sense that it acquires information from the surrounding world, stores it, and processes it in a variety of ways. This article compares the properties of brains across the entire range of animal species, with the greatest attention to vertebrates. It deals with the human brain insofar as it shares the properties of other brains. The ways in which the human brain differs from other brains are covered in the human brain article. Several topics that might be covered here are instead covered there because much more can be said about them in a human context. The most important that are covered in the human brain article are brain disease and the effects of brain damage. The shape and size of the brain varies greatly between species, and identifying common features is often difficult. Nevertheless, there are a number of principles of brain architecture that apply across a wide range of species. Some aspects of brain structure are common to almost the entire range of animal species; others distinguish "advanced" brains from more primitive ones, or distinguish vertebrates from invertebrates. The simplest way to gain information about brain anatomy is by visual inspection, but many more sophisticated techniques have been developed. Brain tissue in its natural state is too soft to work with, but it can be hardened by immersion in alcohol or other fixatives, and then sliced apart for examination of the interior. Visually, the interior of the brain consists of areas of so-called grey matter, with a dark color, separated by areas of white matter, with a lighter color. Further information can be gained by staining slices of brain tissue with a variety of chemicals that bring out areas where specific types of molecules are present in high concentrations. It is also possible to examine the microstructure of brain tissue using a microscope, and to trace the pattern of connections from one brain area to another. The brains of all species are composed primarily of two broad classes of cells: neurons and glial cells. Glial cells (also known as glia or neuroglia) come in several types, and perform a number of critical functions, including structural support, metabolic support, insulation, and guidance of development. Neurons, however, are usually considered the most important cells in the brain. The property that makes neurons unique is their ability to send signals to specific target cells over long distances. They send these signals by means of an axon, which is a thin protoplasmic fiber that extends from the cell body and projects, usually with numerous branches, to other areas, sometimes nearby, sometimes in distant parts of the brain or body. The length of an axon can be extraordinary: for example, if a pyramidal cell (an excitatory neuron) of the cerebral cortex were magnified so that its cell body became the size of a human body, its axon, equally magnified, would become a cable a few centimeters in diameter, extending more than a kilometer. These axons transmit signals in the form of electrochemical pulses called action potentials, which last less than a thousandth of a second and travel along the axon at speeds of 1–100 meters per second. Some neurons emit action potentials constantly, at rates of 10–100 per second, usually in irregular patterns; other neurons are quiet most of the time, but occasionally emit a burst of action potentials. Axons transmit signals to other neurons by means of specialized junctions called synapses. A single axon may make as many as several thousand synaptic connections with other cells. When an action potential, traveling along an axon, arrives at a synapse, it causes a chemical called a neurotransmitter to be released. The neurotransmitter binds to receptor molecules in the membrane of the target cell. Synapses are the key functional elements of the brain. The essential function of the brain is cell-to-cell communication, and synapses are the points at which communication occurs. The human brain has been estimated to contain approximately 100 trillion synapses; even the brain of a fruit fly contains several million. The functions of these synapses are very diverse: some are excitatory (exciting the target cell); others are inhibitory; others work by activating second messenger systems that change the internal chemistry of their target cells in complex ways. A large number of synapses are dynamically modifiable; that is, they are capable of changing strength in a way that is controlled by the patterns of signals that pass through them. It is widely believed that activity-dependent modification of synapses is the brain's primary mechanism for learning and memory. Most of the space in the brain is taken up by axons, which are often bundled together in what are called nerve fiber tracts. A myelinated axon is wrapped in a fatty insulating sheath of myelin, which serves to greatly increase the speed of signal propagation. (There are also unmyelinated axons). Myelin is white, making parts of the brain filled exclusively with nerve fibers appear as light-colored white matter, in contrast to the darker-colored grey matter that marks areas with high densities of neuron cell bodies. Except for a few primitive organisms such as sponges (which have no nervous system) and cnidarians (which have a diffuse nervous system consisting of a nerve net), all living multicellular animals are bilaterians, meaning animals with a bilaterally symmetric body plan (that is, left and right sides that are approximate mirror images of each other). All bilaterians are thought to have descended from a common ancestor that appeared late in the Cryogenian period, 700–650 million years ago, and it has been hypothesized that this common ancestor had the shape of a simple tubeworm with a segmented body. At a schematic level, that basic worm-shape continues to be reflected in the body and nervous system architecture of all modern bilaterians, including vertebrates. The fundamental bilateral body form is a tube with a hollow gut cavity running from the mouth to the anus, and a nerve cord with an enlargement (a ganglion) for each body segment, with an especially large ganglion at the front, called the brain. The brain is small and simple in some species, such as nematode worms; in other species, such as vertebrates, it is a large and very complex organ. Some types of worms, such as leeches, also have an enlarged ganglion at the back end of the nerve cord, known as a "tail brain". There are a few types of existing bilaterians that lack a recognizable brain, including echinoderms and tunicates. It has not been definitively established whether the existence of these brainless species indicates that the earliest bilaterians lacked a brain, or whether their ancestors evolved in a way that led to the disappearance of a previously existing brain structure. This category includes tardigrades, arthropods, molluscs, and numerous types of worms. The diversity of invertebrate body plans is matched by an equal diversity in brain structures. Two groups of invertebrates have notably complex brains: arthropods (insects, crustaceans, arachnids, and others), and cephalopods (octopuses, squids, and similar molluscs). The brains of arthropods and cephalopods arise from twin parallel nerve cords that extend through the body of the animal. Arthropods have a central brain, the supraesophageal ganglion, with three divisions and large optical lobes behind each eye for visual processing. Cephalopods such as the octopus and squid have the largest brains of any invertebrates. There are several invertebrate species whose brains have been studied intensively because they have properties that make them convenient for experimental work: The first vertebrates appeared over 500 million years ago (Mya), during the Cambrian period, and may have resembled the modern hagfish in form. Jawed fish appeared by 445 Mya, amphibians by 350 Mya, reptiles by 310 Mya and mammals by 200 Mya (approximately). Each species has an equally long evolutionary history, but the brains of modern hagfishes, lampreys, sharks, amphibians, reptiles, and mammals show a gradient of size and complexity that roughly follows the evolutionary sequence. All of these brains contain the same set of basic anatomical components, but many are rudimentary in the hagfish, whereas in mammals the foremost part (the telencephalon) is greatly elaborated and expanded. Brains are most commonly compared in terms of their size. The relationship between brain size, body size and other variables has been studied across a wide range of vertebrate species. As a rule, brain size increases with body size, but not in a simple linear proportion. In general, smaller animals tend to have larger brains, measured as a fraction of body size. For mammals, the relationship between brain volume and body mass essentially follows a power law with an exponent of about 0.75. This formula describes the central tendency, but every family of mammals departs from it to some degree, in a way that reflects in part the complexity of their behavior. For example, primates have brains 5 to 10 times larger than the formula predicts. Predators tend to have larger brains than their prey, relative to body size. All vertebrate brains share a common underlying form, which appears most clearly during early stages of embryonic development. In its earliest form, the brain appears as three swellings at the front end of the neural tube; these swellings eventually become the forebrain, midbrain, and hindbrain (the prosencephalon, mesencephalon, and rhombencephalon, respectively). At the earliest stages of brain development, the three areas are roughly equal in size. In many classes of vertebrates, such as fish and amphibians, the three parts remain similar in size in the adult, but in mammals the forebrain becomes much larger than the other parts, and the midbrain becomes very small. The brains of vertebrates are made of very soft tissue. Living brain tissue is pinkish on the outside and mostly white on the inside, with subtle variations in color. Vertebrate brains are surrounded by a system of connective tissue membranes called meninges that separate the skull from the brain. Blood vessels enter the central nervous system through holes in the meningeal layers. The cells in the blood vessel walls are joined tightly to one another, forming the blood–brain barrier, which blocks the passage of many toxins and pathogens (though at the same time blocking antibodies and some drugs, thereby presenting special challenges in treatment of diseases of the brain). Neuroanatomists usually divide the vertebrate brain into six main regions: the telencephalon (cerebral hemispheres), diencephalon (thalamus and hypothalamus), mesencephalon (midbrain), cerebellum, pons, and medulla oblongata. Each of these areas has a complex internal structure. Some parts, such as the cerebral cortex and the cerebellar cortex, consist of layers that are folded or convoluted to fit within the available space. Other parts, such as the thalamus and hypothalamus, consist of clusters of many small nuclei. Thousands of distinguishable areas can be identified within the vertebrate brain based on fine distinctions of neural structure, chemistry, and connectivity. Although the same basic components are present in all vertebrate brains, some branches of vertebrate evolution have led to substantial distortions of brain geometry, especially in the forebrain area. The brain of a shark shows the basic components in a straightforward way, but in teleost fishes (the great majority of existing fish species), the forebrain has become "everted", like a sock turned inside out. In birds, there are also major changes in forebrain structure. These distortions can make it difficult to match brain components from one species with those of another species. Here is a list of some of the most important vertebrate brain components, along with a brief description of their functions as currently understood: The most obvious difference between the brains of mammals and other vertebrates is in terms of size. On average, a mammal has a brain roughly twice as large as that of a bird of the same body size, and ten times as large as that of a reptile of the same body size. Size, however, is not the only difference: there are also substantial differences in shape. The hindbrain and midbrain of mammals are generally similar to those of other vertebrates, but dramatic differences appear in the forebrain, which is greatly enlarged and also altered in structure. The cerebral cortex is the part of the brain that most strongly distinguishes mammals. In non-mammalian vertebrates, the surface of the cerebrum is lined with a comparatively simple three-layered structure called the pallium. In mammals, the pallium evolves into a complex six-layered structure called neocortex or isocortex. Several areas at the edge of the neocortex, including the hippocampus and amygdala, are also much more extensively developed in mammals than in other vertebrates. The elaboration of the cerebral cortex carries with it changes to other brain areas. The superior colliculus, which plays a major role in visual control of behavior in most vertebrates, shrinks to a small size in mammals, and many of its functions are taken over by visual areas of the cerebral cortex. The cerebellum of mammals contains a large portion (the neocerebellum) dedicated to supporting the cerebral cortex, which has no counterpart in other vertebrates. The brains of humans and other primates contain the same structures as the brains of other mammals, but are generally larger in proportion to body size. The encephalization quotient (EQ) is used to compare brain sizes across species. It takes into account the nonlinearity of the brain-to-body relationship. Humans have an average EQ in the 7-to-8 range, while most other primates have an EQ in the 2-to-3 range. Dolphins have values higher than those of primates other than humans, but nearly all other mammals have EQ values that are substantially lower. Most of the enlargement of the primate brain comes from a massive expansion of the cerebral cortex, especially the prefrontal cortex and the parts of the cortex involved in vision. The visual processing network of primates includes at least 30 distinguishable brain areas, with a complex web of interconnections. It has been estimated that visual processing areas occupy more than half of the total surface of the primate neocortex. The prefrontal cortex carries out functions that include planning, working memory, motivation, attention, and executive control. It takes up a much larger proportion of the brain for primates than for other species, and an especially large fraction of the human brain. The brain develops in an intricately orchestrated sequence of stages. It changes in shape from a simple swelling at the front of the nerve cord in the earliest embryonic stages, to a complex array of areas and connections. Neurons are created in special zones that contain stem cells, and then migrate through the tissue to reach their ultimate locations. Once neurons have positioned themselves, their axons sprout and navigate through the brain, branching and extending as they go, until the tips reach their targets and form synaptic connections. In a number of parts of the nervous system, neurons and synapses are produced in excessive numbers during the early stages, and then the unneeded ones are pruned away. For vertebrates, the early stages of neural development are similar across all species. As the embryo transforms from a round blob of cells into a wormlike structure, a narrow strip of ectoderm running along the midline of the back is induced to become the neural plate, the precursor of the nervous system. The neural plate folds inward to form the neural groove, and then the lips that line the groove merge to enclose the neural tube, a hollow cord of cells with a fluid-filled ventricle at the center. At the front end, the ventricles and cord swell to form three vesicles that are the precursors of the prosencephalon (forebrain), mesencephalon (midbrain), and rhombencephalon (hindbrain). At the next stage, the forebrain splits into two vesicles called the telencephalon (which will contain the cerebral cortex, basal ganglia, and related structures) and the diencephalon (which will contain the thalamus and hypothalamus). At about the same time, the hindbrain splits into the metencephalon (which will contain the cerebellum and pons) and the myelencephalon (which will contain the medulla oblongata). Each of these areas contains proliferative zones where neurons and glial cells are generated; the resulting cells then migrate, sometimes for long distances, to their final positions. Once a neuron is in place, it extends dendrites and an axon into the area around it. Axons, because they commonly extend a great distance from the cell body and need to reach specific targets, grow in a particularly complex way. The tip of a growing axon consists of a blob of protoplasm called a growth cone, studded with chemical receptors. These receptors sense the local environment, causing the growth cone to be attracted or repelled by various cellular elements, and thus to be pulled in a particular direction at each point along its path. The result of this pathfinding process is that the growth cone navigates through the brain until it reaches its destination area, where other chemical cues cause it to begin generating synapses. Considering the entire brain, thousands of genes create products that influence axonal pathfinding. The synaptic network that finally emerges is only partly determined by genes, though. In many parts of the brain, axons initially "overgrow", and then are "pruned" by mechanisms that depend on neural activity. In the projection from the eye to the midbrain, for example, the structure in the adult contains a very precise mapping, connecting each point on the surface of the retina to a corresponding point in a midbrain layer. In the first stages of development, each axon from the retina is guided to the right general vicinity in the midbrain by chemical cues, but then branches very profusely and makes initial contact with a wide swath of midbrain neurons. The retina, before birth, contains special mechanisms that cause it to generate waves of activity that originate spontaneously at a random point and then propagate slowly across the retinal layer. These waves are useful because they cause neighboring neurons to be active at the same time; that is, they produce a neural activity pattern that contains information about the spatial arrangement of the neurons. This information is exploited in the midbrain by a mechanism that causes synapses to weaken, and eventually vanish, if activity in an axon is not followed by activity of the target cell. The result of this sophisticated process is a gradual tuning and tightening of the map, leaving it finally in its precise adult form. Similar things happen in other brain areas: an initial synaptic matrix is generated as a result of genetically determined chemical guidance, but then gradually refined by activity-dependent mechanisms, partly driven by internal dynamics, partly by external sensory inputs. In some cases, as with the retina-midbrain system, activity patterns depend on mechanisms that operate only in the developing brain, and apparently exist solely to guide development. In humans and many other mammals, new neurons are created mainly before birth, and the infant brain contains substantially more neurons than the adult brain. There are, however, a few areas where new neurons continue to be generated throughout life. The two areas for which adult neurogenesis is well established are the olfactory bulb, which is involved in the sense of smell, and the dentate gyrus of the hippocampus, where there is evidence that the new neurons play a role in storing newly acquired memories. With these exceptions, however, the set of neurons that is present in early childhood is the set that is present for life. Glial cells are different: as with most types of cells in the body, they are generated throughout the lifespan. There has long been debate about whether the qualities of mind, personality, and intelligence can be attributed to heredity or to upbringing. Although many details remain to be settled, neuroscience shows that both factors are important. Genes determine both the general form of the brain and how it reacts to experience, but experience is required to refine the matrix of synaptic connections, resulting in greatly increased complexity. The presence or absence of experience is critical at key periods of development. Additionally, the quantity and quality of experience are important. For example, animals raised in enriched environments demonstrate thick cerebral cortices, indicating a high density of synaptic connections, compared to animals with restricted levels of stimulation. The functions of the brain depend on the ability of neurons to transmit electrochemical signals to other cells, and their ability to respond appropriately to electrochemical signals received from other cells. The electrical properties of neurons are controlled by a wide variety of biochemical and metabolic processes, most notably the interactions between neurotransmitters and receptors that take place at synapses. Neurotransmitters are chemicals that are released at synapses when the local membrane is depolarised and Ca enters into the cell, typically when an action potential arrives at the synapse – neurotransmitters attach themselves to receptor molecules on the membrane of the synapse's target cell (or cells), and thereby alter the electrical or chemical properties of the receptor molecules. With few exceptions, each neuron in the brain releases the same chemical neurotransmitter, or combination of neurotransmitters, at all the synaptic connections it makes with other neurons; this rule is known as Dale's principle. Thus, a neuron can be characterized by the neurotransmitters that it releases. The great majority of psychoactive drugs exert their effects by altering specific neurotransmitter systems. This applies to drugs such as cannabinoids, nicotine, heroin, cocaine, alcohol, fluoxetine, chlorpromazine, and many others. The two neurotransmitters that are most widely found in the vertebrate brain are glutamate, which almost always exerts excitatory effects on target neurons, and gamma-aminobutyric acid (GABA), which is almost always inhibitory. Neurons using these transmitters can be found in nearly every part of the brain. Because of their ubiquity, drugs that act on glutamate or GABA tend to have broad and powerful effects. Some general anesthetics act by reducing the effects of glutamate; most tranquilizers exert their sedative effects by enhancing the effects of GABA. There are dozens of other chemical neurotransmitters that are used in more limited areas of the brain, often areas dedicated to a particular function. Serotonin, for example—the primary target of many antidepressant drugs and many dietary aids—comes exclusively from a small brainstem area called the raphe nuclei. Norepinephrine, which is involved in arousal, comes exclusively from a nearby small area called the locus coeruleus. Other neurotransmitters such as acetylcholine and dopamine have multiple sources in the brain but are not as ubiquitously distributed as glutamate and GABA. As a side effect of the electrochemical processes used by neurons for signaling, brain tissue generates electric fields when it is active. When large numbers of neurons show synchronized activity, the electric fields that they generate can be large enough to detect outside the skull, using electroencephalography (EEG) or magnetoencephalography (MEG). EEG recordings, along with recordings made from electrodes implanted inside the brains of animals such as rats, show that the brain of a living animal is constantly active, even during sleep. Each part of the brain shows a mixture of rhythmic and nonrhythmic activity, which may vary according to behavioral state. In mammals, the cerebral cortex tends to show large slow delta waves during sleep, faster alpha waves when the animal is awake but inattentive, and chaotic-looking irregular activity when the animal is actively engaged in a task, called beta and gamma waves. During an epileptic seizure, the brain's inhibitory control mechanisms fail to function and electrical activity rises to pathological levels, producing EEG traces that show large wave and spike patterns not seen in a healthy brain. Relating these population-level patterns to the computational functions of individual neurons is a major focus of current research in neurophysiology. All vertebrates have a blood–brain barrier that allows metabolism inside the brain to operate differently from metabolism in other parts of the body. The neurovascular unit regulates cerebral blood flow so that activated neurons can be supplied with energy. Glial cells play a major role in brain metabolism by controlling the chemical composition of the fluid that surrounds neurons, including levels of ions and nutrients. Brain tissue consumes a large amount of energy in proportion to its volume, so large brains place severe metabolic demands on animals. The need to limit body weight in order, for example, to fly, has apparently led to selection for a reduction of brain size in some species, such as bats. Most of the brain's energy consumption goes into sustaining the electric charge (membrane potential) of neurons. Most vertebrate species devote between 2% and 8% of basal metabolism to the brain. In primates, however, the percentage is much higher—in humans it rises to 20–25%. The energy consumption of the brain does not vary greatly over time, but active regions of the cerebral cortex consume somewhat more energy than inactive regions; this forms the basis for the functional brain imaging methods of PET, fMRI, and NIRS. The brain typically gets most of its energy from oxygen-dependent metabolism of glucose (i.e., blood sugar), but ketones provide a major alternative source, together with contributions from medium chain fatty acids (caprylic and heptanoic acids), lactate, acetate, and possibly amino acids. Information from the sense organs is collected in the brain. There it is used to determine what actions the organism is to take. The brain processes the raw data to extract information about the structure of the environment. Next it combines the processed information with information about the current needs of the animal and with memory of past circumstances. Finally, on the basis of the results, it generates motor response patterns. These signal-processing tasks require intricate interplay between a variety of functional subsystems. The function of the brain is to provide coherent control over the actions of an animal. A centralized brain allows groups of muscles to be co-activated in complex patterns; it also allows stimuli impinging on one part of the body to evoke responses in other parts, and it can prevent different parts of the body from acting at cross-purposes to each other. The human brain is provided with information about light, sound, the chemical composition of the atmosphere, temperature, the position of the body in space (proprioception), the chemical composition of the bloodstream, and more. In other animals additional senses are present, such as the infrared heat-sense of snakes, the magnetic field sense of some birds, or the electric field sense mainly seen in aquatic animals. Each sensory system begins with specialized receptor cells, such as photoreceptor cells in the retina of the eye, or vibration-sensitive hair cells in the cochlea of the ear. The axons of sensory receptor cells travel into the spinal cord or brain, where they transmit their signals to a first-order sensory nucleus dedicated to one specific sensory modality. This primary sensory nucleus sends information to higher-order sensory areas that are dedicated to the same modality. Eventually, via a way-station in the thalamus, the signals are sent to the cerebral cortex, where they are processed to extract the relevant features, and integrated with signals coming from other sensory systems. Motor systems are areas of the brain that are involved in initiating body movements, that is, in activating muscles. Except for the muscles that control the eye, which are driven by nuclei in the midbrain, all the voluntary muscles in the body are directly innervated by motor neurons in the spinal cord and hindbrain. Spinal motor neurons are controlled both by neural circuits intrinsic to the spinal cord, and by inputs that descend from the brain. The intrinsic spinal circuits implement many reflex responses, and contain pattern generators for rhythmic movements such as walking or swimming. The descending connections from the brain allow for more sophisticated control. The brain contains several motor areas that project directly to the spinal cord. At the lowest level are motor areas in the medulla and pons, which control stereotyped movements such as walking, breathing, or swallowing. At a higher level are areas in the midbrain, such as the red nucleus, which is responsible for coordinating movements of the arms and legs. At a higher level yet is the primary motor cortex, a strip of tissue located at the posterior edge of the frontal lobe. The primary motor cortex sends projections to the subcortical motor areas, but also sends a massive projection directly to the spinal cord, through the pyramidal tract. This direct corticospinal projection allows for precise voluntary control of the fine details of movements. Other motor-related brain areas exert secondary effects by projecting to the primary motor areas. Among the most important secondary areas are the premotor cortex, supplementary motor area, basal ganglia, and cerebellum. In addition to all of the above, the brain and spinal cord contain extensive circuitry to control the autonomic nervous system which controls the movement of the smooth muscle of the body. Many animals alternate between sleeping and waking in a daily cycle. Arousal and alertness are also modulated on a finer time scale by a network of brain areas. A key component of the sleep system is the suprachiasmatic nucleus (SCN), a tiny part of the hypothalamus located directly above the point at which the optic nerves from the two eyes cross. The SCN contains the body's central biological clock. Neurons there show activity levels that rise and fall with a period of about 24 hours, circadian rhythms: these activity fluctuations are driven by rhythmic changes in expression of a set of "clock genes". The SCN continues to keep time even if it is excised from the brain and placed in a dish of warm nutrient solution, but it ordinarily receives input from the optic nerves, through the retinohypothalamic tract (RHT), that allows daily light-dark cycles to calibrate the clock. The SCN projects to a set of areas in the hypothalamus, brainstem, and midbrain that are involved in implementing sleep-wake cycles. An important component of the system is the reticular formation, a group of neuron-clusters scattered diffusely through the core of the lower brain. Reticular neurons send signals to the thalamus, which in turn sends activity-level-controlling signals to every part of the cortex. Damage to the reticular formation can produce a permanent state of coma. Sleep involves great changes in brain activity. Until the 1950s it was generally believed that the brain essentially shuts off during sleep, but this is now known to be far from true; activity continues, but patterns become very different. There are two types of sleep: REM sleep (with dreaming) and NREM (non-REM, usually without dreaming) sleep, which repeat in slightly varying patterns throughout a sleep episode. Three broad types of distinct brain activity patterns can be measured: REM, light NREM and deep NREM. During deep NREM sleep, also called slow wave sleep, activity in the cortex takes the form of large synchronized waves, whereas in the waking state it is noisy and desynchronized. Levels of the neurotransmitters norepinephrine and serotonin drop during slow wave sleep, and fall almost to zero during REM sleep; levels of acetylcholine show the reverse pattern. For any animal, survival requires maintaining a variety of parameters of bodily state within a limited range of variation: these include temperature, water content, salt concentration in the bloodstream, blood glucose levels, blood oxygen level, and others. The ability of an animal to regulate the internal environment of its body—the milieu intérieur, as the pioneering physiologist Claude Bernard called it—is known as homeostasis (Greek for "standing still"). Maintaining homeostasis is a crucial function of the brain. The basic principle that underlies homeostasis is negative feedback: any time a parameter diverges from its set-point, sensors generate an error signal that evokes a response that causes the parameter to shift back toward its optimum value. (This principle is widely used in engineering, for example in the control of temperature using a thermostat.) In vertebrates, the part of the brain that plays the greatest role is the hypothalamus, a small region at the base of the forebrain whose size does not reflect its complexity or the importance of its function. The hypothalamus is a collection of small nuclei, most of which are involved in basic biological functions. Some of these functions relate to arousal or to social interactions such as sexuality, aggression, or maternal behaviors; but many of them relate to homeostasis. Several hypothalamic nuclei receive input from sensors located in the lining of blood vessels, conveying information about temperature, sodium level, glucose level, blood oxygen level, and other parameters. These hypothalamic nuclei send output signals to motor areas that can generate actions to rectify deficiencies. Some of the outputs also go to the pituitary gland, a tiny gland attached to the brain directly underneath the hypothalamus. The pituitary gland secretes hormones into the bloodstream, where they circulate throughout the body and induce changes in cellular activity. The individual animals need to express survival-promoting behaviors, such as seeking food, water, shelter, and a mate. The motivational system in the brain monitors the current state of satisfaction of these goals, and activates behaviors to meet any needs that arise. The motivational system works largely by a reward–punishment mechanism. When a particular behavior is followed by favorable consequences, the reward mechanism in the brain is activated, which induces structural changes inside the brain that cause the same behavior to be repeated later, whenever a similar situation arises. Conversely, when a behavior is followed by unfavorable consequences, the brain's punishment mechanism is activated, inducing structural changes that cause the behavior to be suppressed when similar situations arise in the future. Most organisms studied to date use a reward–punishment mechanism: for instance, worms and insects can alter their behavior to seek food sources or to avoid dangers. In vertebrates, the reward-punishment system is implemented by a specific set of brain structures, at the heart of which lie the basal ganglia, a set of interconnected areas at the base of the forebrain. The basal ganglia are the central site at which decisions are made: the basal ganglia exert a sustained inhibitory control over most of the motor systems in the brain; when this inhibition is released, a motor system is permitted to execute the action it is programmed to carry out. Rewards and punishments function by altering the relationship between the inputs that the basal ganglia receive and the decision-signals that are emitted. The reward mechanism is better understood than the punishment mechanism, because its role in drug abuse has caused it to be studied very intensively. Research has shown that the neurotransmitter dopamine plays a central role: addictive drugs such as cocaine, amphetamine, and nicotine either cause dopamine levels to rise or cause the effects of dopamine inside the brain to be enhanced. Almost all animals are capable of modifying their behavior as a result of experience—even the most primitive types of worms. Because behavior is driven by brain activity, changes in behavior must somehow correspond to changes inside the brain. Already in the late 19th century theorists like Santiago Ramón y Cajal argued that the most plausible explanation is that learning and memory are expressed as changes in the synaptic connections between neurons. Until 1970, however, experimental evidence to support the synaptic plasticity hypothesis was lacking. In 1971 Tim Bliss and Terje Lømo published a paper on a phenomenon now called long-term potentiation: the paper showed clear evidence of activity-induced synaptic changes that lasted for at least several days. Since then technical advances have made these sorts of experiments much easier to carry out, and thousands of studies have been made that have clarified the mechanism of synaptic change, and uncovered other types of activity-driven synaptic change in a variety of brain areas, including the cerebral cortex, hippocampus, basal ganglia, and cerebellum. Brain-derived neurotrophic factor (BDNF) and physical activity appear to play a beneficial role in the process. Neuroscientists currently distinguish several types of learning and memory that are implemented by the brain in distinct ways: The field of neuroscience encompasses all approaches that seek to understand the brain and the rest of the nervous system. Psychology seeks to understand mind and behavior, and neurology is the medical discipline that diagnoses and treats diseases of the nervous system. The brain is also the most important organ studied in psychiatry, the branch of medicine that works to study, prevent, and treat mental disorders. Cognitive science seeks to unify neuroscience and psychology with other fields that concern themselves with the brain, such as computer science (artificial intelligence and similar fields) and philosophy. The oldest method of studying the brain is anatomical, and until the middle of the 20th century, much of the progress in neuroscience came from the development of better cell stains and better microscopes. Neuroanatomists study the large-scale structure of the brain as well as the microscopic structure of neurons and their components, especially synapses. Among other tools, they employ a plethora of stains that reveal neural structure, chemistry, and connectivity. In recent years, the development of immunostaining techniques has allowed investigation of neurons that express specific sets of genes. Also, functional neuroanatomy uses medical imaging techniques to correlate variations in human brain structure with differences in cognition or behavior. Neurophysiologists study the chemical, pharmacological, and electrical properties of the brain: their primary tools are drugs and recording devices. Thousands of experimentally developed drugs affect the nervous system, some in highly specific ways. Recordings of brain activity can be made using electrodes, either glued to the scalp as in EEG studies, or implanted inside the brains of animals for extracellular recordings, which can detect action potentials generated by individual neurons. Because the brain does not contain pain receptors, it is possible using these techniques to record brain activity from animals that are awake and behaving without causing distress. The same techniques have occasionally been used to study brain activity in human patients with intractable epilepsy, in cases where there was a medical necessity to implant electrodes to localize the brain area responsible for epileptic seizures. Functional imaging techniques such as fMRI are also used to study brain activity; these techniques have mainly been used with human subjects, because they require a conscious subject to remain motionless for long periods of time, but they have the great advantage of being noninvasive. Another approach to brain function is to examine the consequences of damage to specific brain areas. Even though it is protected by the skull and meninges, surrounded by cerebrospinal fluid, and isolated from the bloodstream by the blood–brain barrier, the delicate nature of the brain makes it vulnerable to numerous diseases and several types of damage. In humans, the effects of strokes and other types of brain damage have been a key source of information about brain function. Because there is no ability to experimentally control the nature of the damage, however, this information is often difficult to interpret. In animal studies, most commonly involving rats, it is possible to use electrodes or locally injected chemicals to produce precise patterns of damage and then examine the consequences for behavior. Computational neuroscience encompasses two approaches: first, the use of computers to study the brain; second, the study of how brains perform computation. On one hand, it is possible to write a computer program to simulate the operation of a group of neurons by making use of systems of equations that describe their electrochemical activity; such simulations are known as biologically realistic neural networks. On the other hand, it is possible to study algorithms for neural computation by simulating, or mathematically analyzing, the operations of simplified "units" that have some of the properties of neurons but abstract out much of their biological complexity. The computational functions of the brain are studied both by computer scientists and neuroscientists. Computational neurogenetic modeling is concerned with the study and development of dynamic neuronal models for modeling brain functions with respect to genes and dynamic interactions between genes. Recent years have seen increasing applications of genetic and genomic techniques to the study of the brain and a focus on the roles of neurotrophic factors and physical activity in neuroplasticity. The most common subjects are mice, because of the availability of technical tools. It is now possible with relative ease to "knock out" or mutate a wide variety of genes, and then examine the effects on brain function. More sophisticated approaches are also being used: for example, using Cre-Lox recombination it is possible to activate or deactivate genes in specific parts of the brain, at specific times. The oldest brain to have been discovered was in Armenia in the Areni-1 cave complex. The brain, estimated to be over 5,000 years old, was found in the skull of a 12 to 14-year-old girl. Although the brains were shriveled, they were well preserved due to the climate found inside the cave. Early philosophers were divided as to whether the seat of the soul lies in the brain or heart. Aristotle favored the heart, and thought that the function of the brain was merely to cool the blood. Democritus, the inventor of the atomic theory of matter, argued for a three-part soul, with intellect in the head, emotion in the heart, and lust near the liver. The unknown author of On the Sacred Disease, a medical treatise in the Hippocratic Corpus, came down unequivocally in favor of the brain, writing: The Roman physician Galen also argued for the importance of the brain, and theorized in some depth about how it might work. Galen traced out the anatomical relationships among brain, nerves, and muscles, demonstrating that all muscles in the body are connected to the brain through a branching network of nerves. He postulated that nerves activate muscles mechanically by carrying a mysterious substance he called pneumata psychikon, usually translated as "animal spirits". Galen's ideas were widely known during the Middle Ages, but not much further progress came until the Renaissance, when detailed anatomical study resumed, combined with the theoretical speculations of René Descartes and those who followed him. Descartes, like Galen, thought of the nervous system in hydraulic terms. He believed that the highest cognitive functions are carried out by a non-physical res cogitans, but that the majority of behaviors of humans, and all behaviors of animals, could be explained mechanistically. The first real progress toward a modern understanding of nervous function, though, came from the investigations of Luigi Galvani (1737–1798), who discovered that a shock of static electricity applied to an exposed nerve of a dead frog could cause its leg to contract. Since that time, each major advance in understanding has followed more or less directly from the development of a new technique of investigation. Until the early years of the 20th century, the most important advances were derived from new methods for staining cells. Particularly critical was the invention of the Golgi stain, which (when correctly used) stains only a small fraction of neurons, but stains them in their entirety, including cell body, dendrites, and axon. Without such a stain, brain tissue under a microscope appears as an impenetrable tangle of protoplasmic fibers, in which it is impossible to determine any structure. In the hands of Camillo Golgi, and especially of the Spanish neuroanatomist Santiago Ramón y Cajal, the new stain revealed hundreds of distinct types of neurons, each with its own unique dendritic structure and pattern of connectivity. In the first half of the 20th century, advances in electronics enabled investigation of the electrical properties of nerve cells, culminating in work by Alan Hodgkin, Andrew Huxley, and others on the biophysics of the action potential, and the work of Bernard Katz and others on the electrochemistry of the synapse. These studies complemented the anatomical picture with a conception of the brain as a dynamic entity. Reflecting the new understanding, in 1942 Charles Sherrington visualized the workings of the brain waking from sleep: The invention of electronic computers in the 1940s, along with the development of mathematical information theory, led to a realization that brains can potentially be understood as information processing systems. This concept formed the basis of the field of cybernetics, and eventually gave rise to the field now known as computational neuroscience. The earliest attempts at cybernetics were somewhat crude in that they treated the brain as essentially a digital computer in disguise, as for example in John von Neumann's 1958 book, The Computer and the Brain. Over the years, though, accumulating information about the electrical responses of brain cells recorded from behaving animals has steadily moved theoretical concepts in the direction of increasing realism. One of the most influential early contributions was a 1959 paper titled What the frog's eye tells the frog's brain: the paper examined the visual responses of neurons in the retina and optic tectum of frogs, and came to the conclusion that some neurons in the tectum of the frog are wired to combine elementary responses in a way that makes them function as "bug perceivers". A few years later David Hubel and Torsten Wiesel discovered cells in the primary visual cortex of monkeys that become active when sharp edges move across specific points in the field of view—a discovery for which they won a Nobel Prize. Follow-up studies in higher-order visual areas found cells that detect binocular disparity, color, movement, and aspects of shape, with areas located at increasing distances from the primary visual cortex showing increasingly complex responses. Other investigations of brain areas unrelated to vision have revealed cells with a wide variety of response correlates, some related to memory, some to abstract types of cognition such as space. Theorists have worked to understand these response patterns by constructing mathematical models of neurons and neural networks, which can be simulated using computers. Some useful models are abstract, focusing on the conceptual structure of neural algorithms rather than the details of how they are implemented in the brain; other models attempt to incorporate data about the biophysical properties of real neurons. No model on any level is yet considered to be a fully valid description of brain function, though. The essential difficulty is that sophisticated computation by neural networks requires distributed processing in which hundreds or thousands of neurons work cooperatively—current methods of brain activity recording are only capable of isolating action potentials from a few dozen neurons at a time. Furthermore, even single neurons appear to be complex and capable of performing computations. So, brain models that do not reflect this are too abstract to be representative of brain operation; models that do try to capture this are very computationally expensive and arguably intractable with present computational resources. However, the Human Brain Project is trying to build a realistic, detailed computational model of the entire human brain. The wisdom of this approach has been publicly contested, with high-profile scientists on both sides of the argument. In the second half of the 20th century, developments in chemistry, electron microscopy, genetics, computer science, functional brain imaging, and other fields progressively opened new windows into brain structure and function. In the United States, the 1990s were officially designated as the "Decade of the Brain" to commemorate advances made in brain research, and to promote funding for such research. In the 21st century, these trends have continued, and several new approaches have come into prominence, including multielectrode recording, which allows the activity of many brain cells to be recorded all at the same time; genetic engineering, which allows molecular components of the brain to be altered experimentally; genomics, which allows variations in brain structure to be correlated with variations in DNA properties and neuroimaging. Animal brains are used as food in numerous cuisines. Some archaeological evidence suggests that the mourning rituals of European Neanderthals also involved the consumption of the brain. The Fore people of Papua New Guinea are known to eat human brains. In funerary rituals, those close to the dead would eat the brain of the deceased to create a sense of immortality. A prion disease called kuru has been traced to this. Anatomy Cross section of the olfactory bulb of a rat, stained in two different ways at the same time: one stain shows neuron cell bodies, the other shows receptors for the neurotransmitter GABA. The shape and size of the brain varies greatly between species, and identifying common features is often difficult. Nevertheless, there are a number of principles of brain architecture that apply across a wide range of species. Some aspects of brain structure are common to almost the entire range of animal species; others distinguish "advanced" brains from more primitive ones, or distinguish vertebrates from invertebrates. The simplest way to gain information about brain anatomy is by visual inspection, but many more sophisticated techniques have been developed. Brain tissue in its natural state is too soft to work with, but it can be hardened by immersion in alcohol or other fixatives, and then sliced apart for examination of the interior. Visually, the interior of the brain consists of areas of so-called grey matter, with a dark color, separated by areas of white matter, with a lighter color. Further information can be gained by staining slices of brain tissue with a variety of chemicals that bring out areas where specific types of molecules are present in high concentrations. It is also possible to examine the microstructure of brain tissue using a microscope, and to trace the pattern of connections from one brain area to another. Cellular structure Neurons generate electrical signals that travel along their axons. When a pulse of electricity reaches a junction called a synapse, it causes a neurotransmitter chemical to be released, which binds to receptors on other cells and thereby alters their electrical activity. The brains of all species are composed primarily of two broad classes of cells: neurons and glial cells. Glial cells (also known as glia or neuroglia) come in several types, and perform a number of critical functions, including structural support, metabolic support, insulation, and guidance of development. Neurons, however, are usually considered the most important cells in the brain. The property that makes neurons unique is their ability to send signals to specific target cells over long distances. They send these signals by means of an axon, which is a thin protoplasmic fiber that extends from the cell body and projects, usually with numerous branches, to other areas, sometimes nearby, sometimes in distant parts of the brain or body. The length of an axon can be extraordinary: for example, if a pyramidal cell (an excitatory neuron) of the cerebral cortex were magnified so that its cell body became the size of a human body, its axon, equally magnified, would become a cable a few centimeters in diameter, extending more than a kilometer. These axons transmit signals in the form of electrochemical pulses called action potentials, which last less than a thousandth of a second and travel along the axon at speeds of 1–100 meters per second. Some neurons emit action potentials constantly, at rates of 10–100 per second, usually in irregular patterns; other neurons are quiet most of the time, but occasionally emit a burst of action potentials. Axons transmit signals to other neurons by means of specialized junctions called synapses. A single axon may make as many as several thousand synaptic connections with other cells. When an action potential, traveling along an axon, arrives at a synapse, it causes a chemical called a neurotransmitter to be released. The neurotransmitter binds to receptor molecules in the membrane of the target cell. Synapses are the key functional elements of the brain. The essential function of the brain is cell-to-cell communication, and synapses are the points at which communication occurs. The human brain has been estimated to contain approximately 100 trillion synapses; even the brain of a fruit fly contains several million. The functions of these synapses are very diverse: some are excitatory (exciting the target cell); others are inhibitory; others work by activating second messenger systems that change the internal chemistry of their target cells in complex ways. A large number of synapses are dynamically modifiable; that is, they are capable of changing strength in a way that is controlled by the patterns of signals that pass through them. It is widely believed that activity-dependent modification of synapses is the brain's primary mechanism for learning and memory. Most of the space in the brain is taken up by axons, which are often bundled together in what are called nerve fiber tracts. A myelinated axon is wrapped in a fatty insulating sheath of myelin, which serves to greatly increase the speed of signal propagation. (There are also unmyelinated axons). Myelin is white, making parts of the brain filled exclusively with nerve fibers appear as light-colored white matter, in contrast to the darker-colored grey matter that marks areas with high densities of neuron cell bodies. Evolution Main article: Evolution of the brain Generic bilaterian nervous system Nervous system of a generic bilaterian animal, in the form of a nerve cord with segmental enlargements, and a "brain" at the front Except for a few primitive organisms such as sponges (which have no nervous system) and cnidarians (which have a diffuse nervous system consisting of a nerve net), all living multicellular animals are bilaterians, meaning animals with a bilaterally symmetric body plan (that is, left and right sides that are approximate mirror images of each other). All bilaterians are thought to have descended from a common ancestor that appeared late in the Cryogenian period, 700–650 million years ago, and it has been hypothesized that this common ancestor had the shape of a simple tubeworm with a segmented body. At a schematic level, that basic worm-shape continues to be reflected in the body and nervous system architecture of all modern bilaterians, including vertebrates. The fundamental bilateral body form is a tube with a hollow gut cavity running from the mouth to the anus, and a nerve cord with an enlargement (a ganglion) for each body segment, with an especially large ganglion at the front, called the brain. The brain is small and simple in some species, such as nematode worms; in other species, such as vertebrates, it is a large and very complex organ. Some types of worms, such as leeches, also have an enlarged ganglion at the back end of the nerve cord, known as a "tail brain". There are a few types of existing bilaterians that lack a recognizable brain, including echinoderms and tunicates. It has not been definitively established whether the existence of these brainless species indicates that the earliest bilaterians lacked a brain, or whether their ancestors evolved in a way that led to the disappearance of a previously existing brain structure. Invertebrates Fruit flies (Drosophila) have been extensively studied to gain insight into the role of genes in brain development. This category includes tardigrades, arthropods, molluscs, and numerous types of worms. The diversity of invertebrate body plans is matched by an equal diversity in brain structures. Two groups of invertebrates have notably complex brains: arthropods (insects, crustaceans, arachnids, and others), and cephalopods (octopuses, squids, and similar molluscs). The brains of arthropods and cephalopods arise from twin parallel nerve cords that extend through the body of the animal. Arthropods have a central brain, the supraesophageal ganglion, with three divisions and large optical lobes behind each eye for visual processing. Cephalopods such as the octopus and squid have the largest brains of any invertebrates. There are several invertebrate species whose brains have been studied intensively because they have properties that make them convenient for experimental work: Fruit flies (Drosophila), because of the large array of techniques available for studying their genetics, have been a natural subject for studying the role of genes in brain development. In spite of the large evolutionary distance between insects and mammals, many aspects of Drosophila neurogenetics have been shown to be relevant to humans. The first biological clock genes, for example, were identified by examining Drosophila mutants that showed disrupted daily activity cycles. A search in the genomes of vertebrates revealed a set of analogous genes, which were found to play similar roles in the mouse biological clock—and therefore almost certainly in the human biological clock as well. Studies done on Drosophila, also show that most neuropil regions of the brain are continuously reorganized throughout life in response to specific living conditions. The nematode worm Caenorhabditis elegans, like Drosophila, has been studied largely because of its importance in genetics. In the early 1970s, Sydney Brenner chose it as a model organism for studying the way that genes control development. One of the advantages of working with this worm is that the body plan is very stereotyped: the nervous system of the hermaphrodite contains exactly 302 neurons, always in the same places, making identical synaptic connections in every worm. Brenner's team sliced worms into thousands of ultrathin sections and photographed each one under an electron microscope, then visually matched fibers from section to section, to map out every neuron and synapse in the entire body. The complete neuronal wiring diagram of C.elegans – its connectome was achieved. Nothing approaching this level of detail is available for any other organism, and the information gained has enabled a multitude of studies that would otherwise have not been possible. The sea slug Aplysia californica was chosen by Nobel Prize-winning neurophysiologist Eric Kandel as a model for studying the cellular basis of learning and memory, because of the simplicity and accessibility of its nervous system, and it has been examined in hundreds of experiments. Vertebrates The brain of a shark The first vertebrates appeared over 500 million years ago (Mya), during the Cambrian period, and may have resembled the modern hagfish in form. Jawed fish appeared by 445 Mya, amphibians by 350 Mya, reptiles by 310 Mya and mammals by 200 Mya (approximately). Each species has an equally long evolutionary history, but the brains of modern hagfishes, lampreys, sharks, amphibians, reptiles, and mammals show a gradient of size and complexity that roughly follows the evolutionary sequence. All of these brains contain the same set of basic anatomical components, but many are rudimentary in the hagfish, whereas in mammals the foremost part (the telencephalon) is greatly elaborated and expanded. Brains are most commonly compared in terms of their size. The relationship between brain size, body size and other variables has been studied across a wide range of vertebrate species. As a rule, brain size increases with body size, but not in a simple linear proportion. In general, smaller animals tend to have larger brains, measured as a fraction of body size. For mammals, the relationship between brain volume and body mass essentially follows a power law with an exponent of about 0.75. This formula describes the central tendency, but every family of mammals departs from it to some degree, in a way that reflects in part the complexity of their behavior. For example, primates have brains 5 to 10 times larger than the formula predicts. Predators tend to have larger brains than their prey, relative to body size. The main subdivisions of the embryonic vertebrate brain (left), which later differentiate into structures of the adult brain (right) All vertebrate brains share a common underlying form, which appears most clearly during early stages of embryonic development. In its earliest form, the brain appears as three swellings at the front end of the neural tube; these swellings eventually become the forebrain, midbrain, and hindbrain (the prosencephalon, mesencephalon, and rhombencephalon, respectively). At the earliest stages of brain development, the three areas are roughly equal in size. In many classes of vertebrates, such as fish and amphibians, the three parts remain similar in size in the adult, but in mammals the forebrain becomes much larger than the other parts, and the midbrain becomes very small. The brains of vertebrates are made of very soft tissue. Living brain tissue is pinkish on the outside and mostly white on the inside, with subtle variations in color. Vertebrate brains are surrounded by a system of connective tissue membranes called meninges that separate the skull from the brain. Blood vessels enter the central nervous system through holes in the meningeal layers. The cells in the blood vessel walls are joined tightly to one another, forming the blood–brain barrier, which blocks the passage of many toxins and pathogens (though at the same time blocking antibodies and some drugs, thereby presenting special challenges in treatment of diseases of the brain). Neuroanatomists usually divide the vertebrate brain into six main regions: the telencephalon (cerebral hemispheres), diencephalon (thalamus and hypothalamus), mesencephalon (midbrain), cerebellum, pons, and medulla oblongata. Each of these areas has a complex internal structure. Some parts, such as the cerebral cortex and the cerebellar cortex, consist of layers that are folded or convoluted to fit within the available space. Other parts, such as the thalamus and hypothalamus, consist of clusters of many small nuclei. Thousands of distinguishable areas can be identified within the vertebrate brain based on fine distinctions of neural structure, chemistry, and connectivity. The main anatomical regions of the vertebrate brain, shown for shark and human. The same parts are present, but they differ greatly in size and shape. Although the same basic components are present in all vertebrate brains, some branches of vertebrate evolution have led to substantial distortions of brain geometry, especially in the forebrain area. The brain of a shark shows the basic components in a straightforward way, but in teleost fishes (the great majority of existing fish species), the forebrain has become "everted", like a sock turned inside out. In birds, there are also major changes in forebrain structure. These distortions can make it difficult to match brain components from one species with those of another species. Here is a list of some of the most important vertebrate brain components, along with a brief description of their functions as currently understood: See also: List of regions in the human brain The medulla, along with the spinal cord, contains many small nuclei involved in a wide variety of sensory and involuntary motor functions such as vomiting, heart rate and digestive processes. The pons lies in the brainstem directly above the medulla. Among other things, it contains nuclei that control often voluntary but simple acts such as sleep, respiration, swallowing, bladder function, equilibrium, eye movement, facial expressions, and posture. The hypothalamus is a small region at the base of the forebrain, whose complexity and importance belies its size. It is composed of numerous small nuclei, each with distinct connections and neurochemistry. The hypothalamus is engaged in additional involuntary or partially voluntary acts such as sleep and wake cycles, eating and drinking, and the release of some hormones. The thalamus is a collection of nuclei with diverse functions: some are involved in relaying information to and from the cerebral hemispheres, while others are involved in motivation. The subthalamic area (zona incerta) seems to contain action-generating systems for several types of "consummatory" behaviors such as eating, drinking, defecation, and copulation. The cerebellum modulates the outputs of other brain systems, whether motor-related or thought related, to make them certain and precise. Removal of the cerebellum does not prevent an animal from doing anything in particular, but it makes actions hesitant and clumsy. This precision is not built-in but learned by trial and error. The muscle coordination learned while riding a bicycle is an example of a type of neural plasticity that may take place largely within the cerebellum. 10% of the brain's total volume consists of the cerebellum and 50% of all neurons are held within its structure. The optic tectum allows actions to be directed toward points in space, most commonly in response to visual input. In mammals, it is usually referred to as the superior colliculus, and its best-studied function is to direct eye movements. It also directs reaching movements and other object-directed actions. It receives strong visual inputs, but also inputs from other senses that are useful in directing actions, such as auditory input in owls and input from the thermosensitive pit organs in snakes. In some primitive fishes, such as lampreys, this region is the largest part of the brain. The superior colliculus is part of the midbrain. The pallium is a layer of grey matter that lies on the surface of the forebrain and is the most complex and most recent evolutionary development of the brain as an organ. In reptiles and mammals, it is called the cerebral cortex. Multiple functions involve the pallium, including smell and spatial memory. In mammals, where it becomes so large as to dominate the brain, it takes over functions from many other brain areas. In many mammals, the cerebral cortex consists of folded bulges called gyri that create deep furrows or fissures called sulci. The folds increase the surface area of the cortex and therefore increase the amount of gray matter and the amount of information that can be stored and processed. The hippocampus, strictly speaking, is found only in mammals. However, the area it derives from, the medial pallium, has counterparts in all vertebrates. There is evidence that this part of the brain is involved in complex events such as spatial memory and navigation in fishes, birds, reptiles, and mammals. The basal ganglia are a group of interconnected structures in the forebrain. The primary function of the basal ganglia appears to be action selection: they send inhibitory signals to all parts of the brain that can generate motor behaviors, and in the right circumstances can release the inhibition, so that the action-generating systems are able to execute their actions. Reward and punishment exert their most important neural effects by altering connections within the basal ganglia. The olfactory bulb is a special structure that processes olfactory sensory signals and sends its output to the olfactory part of the pallium. It is a major brain component in many vertebrates, but is greatly reduced in humans and other primates (whose senses are dominated by information acquired by sight rather than smell). Birds Main article: Avian brain This section is an excerpt from Avian brain.[edit] Brains of an emu, a kiwi, a barn owl, and a pigeon, with visual processing areas labelled The avian brain is the central organ of the nervous system in birds. Birds possess large, complex brains, which process, integrate, and coordinate information received from the environment and make decisions on how to respond with the rest of the body. Like in all chordates, the avian brain is contained within the skull bones of the head. The bird brain is divided into a number of sections, each with a different function. The cerebrum or telencephalon is divided into two hemispheres, and controls higher functions. The telencephalon is dominated by a large pallium, which corresponds to the mammalian cerebral cortex and is responsible for the cognitive functions of birds. The pallium is made up of several major structures: the hyperpallium, a dorsal bulge of the pallium found only in birds, as well as the nidopallium, mesopallium, and archipallium. The bird telencephalon nuclear structure, wherein neurons are distributed in three-dimensionally arranged clusters, with no large-scale separation of white matter and grey matter, though there exist layer-like and column-like connections. Structures in the pallium are associated with perception, learning, and cognition. Beneath the pallium are the two components of the subpallium, the striatum and pallidum. The subpallium connects different parts of the telencephalon and plays major roles in a number of critical behaviours. To the rear of the telencephalon are the thalamus, midbrain, and cerebellum. The hindbrain connects the rest of the brain to the spinal cord. The size and structure of the avian brain enables prominent behaviours of birds such as flight and vocalization. Dedicated structures and pathways integrate the auditory and visual senses, strong in most species of birds, as well as the typically weaker olfactory and tactile senses. Social behaviour, widespread among birds, depends on the organisation and functions of the brain. Some birds exhibit strong abilities of cognition, enabled by the unique structure and physiology of the avian brain. Mammals The most obvious difference between the brains of mammals and other vertebrates is in terms of size. On average, a mammal has a brain roughly twice as large as that of a bird of the same body size, and ten times as large as that of a reptile of the same body size. Size, however, is not the only difference: there are also substantial differences in shape. The hindbrain and midbrain of mammals are generally similar to those of other vertebrates, but dramatic differences appear in the forebrain, which is greatly enlarged and also altered in structure. The cerebral cortex is the part of the brain that most strongly distinguishes mammals. In non-mammalian vertebrates, the surface of the cerebrum is lined with a comparatively simple three-layered structure called the pallium. In mammals, the pallium evolves into a complex six-layered structure called neocortex or isocortex. Several areas at the edge of the neocortex, including the hippocampus and amygdala, are also much more extensively developed in mammals than in other vertebrates. The elaboration of the cerebral cortex carries with it changes to other brain areas. The superior colliculus, which plays a major role in visual control of behavior in most vertebrates, shrinks to a small size in mammals, and many of its functions are taken over by visual areas of the cerebral cortex. The cerebellum of mammals contains a large portion (the neocerebellum) dedicated to supporting the cerebral cortex, which has no counterpart in other vertebrates. Primates See also: Human brain Encephalization Quotient Species EQ Human 7.4–7.8 Common chimpanzee 2.2–2.5 Rhesus monkey 2.1 Bottlenose dolphin 4.14 Elephant 1.13–2.36 Dog 1.2 Horse 0.9 Rat 0.4 The brains of humans and other primates contain the same structures as the brains of other mammals, but are generally larger in proportion to body size. The encephalization quotient (EQ) is used to compare brain sizes across species. It takes into account the nonlinearity of the brain-to-body relationship. Humans have an average EQ in the 7-to-8 range, while most other primates have an EQ in the 2-to-3 range. Dolphins have values higher than those of primates other than humans, but nearly all other mammals have EQ values that are substantially lower. Most of the enlargement of the primate brain comes from a massive expansion of the cerebral cortex, especially the prefrontal cortex and the parts of the cortex involved in vision. The visual processing network of primates includes at least 30 distinguishable brain areas, with a complex web of interconnections. It has been estimated that visual processing areas occupy more than half of the total surface of the primate neocortex. The prefrontal cortex carries out functions that include planning, working memory, motivation, attention, and executive control. It takes up a much larger proportion of the brain for primates than for other species, and an especially large fraction of the human brain. Development Main article: Neural development Brain of a human embryo in the sixth week of development The brain develops in an intricately orchestrated sequence of stages. It changes in shape from a simple swelling at the front of the nerve cord in the earliest embryonic stages, to a complex array of areas and connections. Neurons are created in special zones that contain stem cells, and then migrate through the tissue to reach their ultimate locations. Once neurons have positioned themselves, their axons sprout and navigate through the brain, branching and extending as they go, until the tips reach their targets and form synaptic connections. In a number of parts of the nervous system, neurons and synapses are produced in excessive numbers during the early stages, and then the unneeded ones are pruned away. For vertebrates, the early stages of neural development are similar across all species. As the embryo transforms from a round blob of cells into a wormlike structure, a narrow strip of ectoderm running along the midline of the back is induced to become the neural plate, the precursor of the nervous system. The neural plate folds inward to form the neural groove, and then the lips that line the groove merge to enclose the neural tube, a hollow cord of cells with a fluid-filled ventricle at the center. At the front end, the ventricles and cord swell to form three vesicles that are the precursors of the prosencephalon (forebrain), mesencephalon (midbrain), and rhombencephalon (hindbrain). At the next stage, the forebrain splits into two vesicles called the telencephalon (which will contain the cerebral cortex, basal ganglia, and related structures) and the diencephalon (which will contain the thalamus and hypothalamus). At about the same time, the hindbrain splits into the metencephalon (which will contain the cerebellum and pons) and the myelencephalon (which will contain the medulla oblongata). Each of these areas contains proliferative zones where neurons and glial cells are generated; the resulting cells then migrate, sometimes for long distances, to their final positions. Once a neuron is in place, it extends dendrites and an axon into the area around it. Axons, because they commonly extend a great distance from the cell body and need to reach specific targets, grow in a particularly complex way. The tip of a growing axon consists of a blob of protoplasm called a growth cone, studded with chemical receptors. These receptors sense the local environment, causing the growth cone to be attracted or repelled by various cellular elements, and thus to be pulled in a particular direction at each point along its path. The result of this pathfinding process is that the growth cone navigates through the brain until it reaches its destination area, where other chemical cues cause it to begin generating synapses. Considering the entire brain, thousands of genes create products that influence axonal pathfinding. The synaptic network that finally emerges is only partly determined by genes, though. In many parts of the brain, axons initially "overgrow", and then are "pruned" by mechanisms that depend on neural activity. In the projection from the eye to the midbrain, for example, the structure in the adult contains a very precise mapping, connecting each point on the surface of the retina to a corresponding point in a midbrain layer. In the first stages of development, each axon from the retina is guided to the right general vicinity in the midbrain by chemical cues, but then branches very profusely and makes initial contact with a wide swath of midbrain neurons. The retina, before birth, contains special mechanisms that cause it to generate waves of activity that originate spontaneously at a random point and then propagate slowly across the retinal layer. These waves are useful because they cause neighboring neurons to be active at the same time; that is, they produce a neural activity pattern that contains information about the spatial arrangement of the neurons. This information is exploited in the midbrain by a mechanism that causes synapses to weaken, and eventually vanish, if activity in an axon is not followed by activity of the target cell. The result of this sophisticated process is a gradual tuning and tightening of the map, leaving it finally in its precise adult form. Similar things happen in other brain areas: an initial synaptic matrix is generated as a result of genetically determined chemical guidance, but then gradually refined by activity-dependent mechanisms, partly driven by internal dynamics, partly by external sensory inputs. In some cases, as with the retina-midbrain system, activity patterns depend on mechanisms that operate only in the developing brain, and apparently exist solely to guide development. In humans and many other mammals, new neurons are created mainly before birth, and the infant brain contains substantially more neurons than the adult brain. There are, however, a few areas where new neurons continue to be generated throughout life. The two areas for which adult neurogenesis is well established are the olfactory bulb, which is involved in the sense of smell, and the dentate gyrus of the hippocampus, where there is evidence that the new neurons play a role in storing newly acquired memories. With these exceptions, however, the set of neurons that is present in early childhood is the set that is present for life. Glial cells are different: as with most types of cells in the body, they are generated throughout the lifespan. There has long been debate about whether the qualities of mind, personality, and intelligence can be attributed to heredity or to upbringing. Although many details remain to be settled, neuroscience shows that both factors are important. Genes determine both the general form of the brain and how it reacts to experience, but experience is required to refine the matrix of synaptic connections, resulting in greatly increased complexity. The presence or absence of experience is critical at key periods of development. Additionally, the quantity and quality of experience are important. For example, animals raised in enriched environments demonstrate thick cerebral cortices, indicating a high density of synaptic connections, compared to animals with restricted levels of stimulation. Physiology The functions of the brain depend on the ability of neurons to transmit electrochemical signals to other cells, and their ability to respond appropriately to electrochemical signals received from other cells. The electrical properties of neurons are controlled by a wide variety of biochemical and metabolic processes, most notably the interactions between neurotransmitters and receptors that take place at synapses. Neurotransmitters and receptors Neurotransmitters are chemicals that are released at synapses when the local membrane is depolarised and Ca enters into the cell, typically when an action potential arrives at the synapse – neurotransmitters attach themselves to receptor molecules on the membrane of the synapse's target cell (or cells), and thereby alter the electrical or chemical properties of the receptor molecules. With few exceptions, each neuron in the brain releases the same chemical neurotransmitter, or combination of neurotransmitters, at all the synaptic connections it makes with other neurons; this rule is known as Dale's principle. Thus, a neuron can be characterized by the neurotransmitters that it releases. The great majority of psychoactive drugs exert their effects by altering specific neurotransmitter systems. This applies to drugs such as cannabinoids, nicotine, heroin, cocaine, alcohol, fluoxetine, chlorpromazine, and many others. The two neurotransmitters that are most widely found in the vertebrate brain are glutamate, which almost always exerts excitatory effects on target neurons, and gamma-aminobutyric acid (GABA), which is almost always inhibitory. Neurons using these transmitters can be found in nearly every part of the brain. Because of their ubiquity, drugs that act on glutamate or GABA tend to have broad and powerful effects. Some general anesthetics act by reducing the effects of glutamate; most tranquilizers exert their sedative effects by enhancing the effects of GABA. There are dozens of other chemical neurotransmitters that are used in more limited areas of the brain, often areas dedicated to a particular function. Serotonin, for example—the primary target of many antidepressant drugs and many dietary aids—comes exclusively from a small brainstem area called the raphe nuclei. Norepinephrine, which is involved in arousal, comes exclusively from a nearby small area called the locus coeruleus. Other neurotransmitters such as acetylcholine and dopamine have multiple sources in the brain but are not as ubiquitously distributed as glutamate and GABA. Electrical activity Brain electrical activity recorded from a human patient during an epileptic seizure As a side effect of the electrochemical processes used by neurons for signaling, brain tissue generates electric fields when it is active. When large numbers of neurons show synchronized activity, the electric fields that they generate can be large enough to detect outside the skull, using electroencephalography (EEG) or magnetoencephalography (MEG). EEG recordings, along with recordings made from electrodes implanted inside the brains of animals such as rats, show that the brain of a living animal is constantly active, even during sleep. Each part of the brain shows a mixture of rhythmic and nonrhythmic activity, which may vary according to behavioral state. In mammals, the cerebral cortex tends to show large slow delta waves during sleep, faster alpha waves when the animal is awake but inattentive, and chaotic-looking irregular activity when the animal is actively engaged in a task, called beta and gamma waves. During an epileptic seizure, the brain's inhibitory control mechanisms fail to function and electrical activity rises to pathological levels, producing EEG traces that show large wave and spike patterns not seen in a healthy brain. Relating these population-level patterns to the computational functions of individual neurons is a major focus of current research in neurophysiology. Metabolism All vertebrates have a blood–brain barrier that allows metabolism inside the brain to operate differently from metabolism in other parts of the body. The neurovascular unit regulates cerebral blood flow so that activated neurons can be supplied with energy. Glial cells play a major role in brain metabolism by controlling the chemical composition of the fluid that surrounds neurons, including levels of ions and nutrients. Brain tissue consumes a large amount of energy in proportion to its volume, so large brains place severe metabolic demands on animals. The need to limit body weight in order, for example, to fly, has apparently led to selection for a reduction of brain size in some species, such as bats. Most of the brain's energy consumption goes into sustaining the electric charge (membrane potential) of neurons. Most vertebrate species devote between 2% and 8% of basal metabolism to the brain. In primates, however, the percentage is much higher—in humans it rises to 20–25%. The energy consumption of the brain does not vary greatly over time, but active regions of the cerebral cortex consume somewhat more energy than inactive regions; this forms the basis for the functional brain imaging methods of PET, fMRI, and NIRS. The brain typically gets most of its energy from oxygen-dependent metabolism of glucose (i.e., blood sugar), but ketones provide a major alternative source, together with contributions from medium chain fatty acids (caprylic and heptanoic acids), lactate, acetate, and possibly amino acids. Function Model of a neural circuit in the cerebellum, as proposed by James S. Albus Information from the sense organs is collected in the brain. There it is used to determine what actions the organism is to take. The brain processes the raw data to extract information about the structure of the environment. Next it combines the processed information with information about the current needs of the animal and with memory of past circumstances. Finally, on the basis of the results, it generates motor response patterns. These signal-processing tasks require intricate interplay between a variety of functional subsystems. The function of the brain is to provide coherent control over the actions of an animal. A centralized brain allows groups of muscles to be co-activated in complex patterns; it also allows stimuli impinging on one part of the body to evoke responses in other parts, and it can prevent different parts of the body from acting at cross-purposes to each other. Perception Diagram of signal processing in the auditory system The human brain is provided with information about light, sound, the chemical composition of the atmosphere, temperature, the position of the body in space (proprioception), the chemical composition of the bloodstream, and more. In other animals additional senses are present, such as the infrared heat-sense of snakes, the magnetic field sense of some birds, or the electric field sense mainly seen in aquatic animals. Each sensory system begins with specialized receptor cells, such as photoreceptor cells in the retina of the eye, or vibration-sensitive hair cells in the cochlea of the ear. The axons of sensory receptor cells travel into the spinal cord or brain, where they transmit their signals to a first-order sensory nucleus dedicated to one specific sensory modality. This primary sensory nucleus sends information to higher-order sensory areas that are dedicated to the same modality. Eventually, via a way-station in the thalamus, the signals are sent to the cerebral cortex, where they are processed to extract the relevant features, and integrated with signals coming from other sensory systems. Motor control Motor systems are areas of the brain that are involved in initiating body movements, that is, in activating muscles. Except for the muscles that control the eye, which are driven by nuclei in the midbrain, all the voluntary muscles in the body are directly innervated by motor neurons in the spinal cord and hindbrain. Spinal motor neurons are controlled both by neural circuits intrinsic to the spinal cord, and by inputs that descend from the brain. The intrinsic spinal circuits implement many reflex responses, and contain pattern generators for rhythmic movements such as walking or swimming. The descending connections from the brain allow for more sophisticated control. The brain contains several motor areas that project directly to the spinal cord. At the lowest level are motor areas in the medulla and pons, which control stereotyped movements such as walking, breathing, or swallowing. At a higher level are areas in the midbrain, such as the red nucleus, which is responsible for coordinating movements of the arms and legs. At a higher level yet is the primary motor cortex, a strip of tissue located at the posterior edge of the frontal lobe. The primary motor cortex sends projections to the subcortical motor areas, but also sends a massive projection directly to the spinal cord, through the pyramidal tract. This direct corticospinal projection allows for precise voluntary control of the fine details of movements. Other motor-related brain areas exert secondary effects by projecting to the primary motor areas. Among the most important secondary areas are the premotor cortex, supplementary motor area, basal ganglia, and cerebellum. In addition to all of the above, the brain and spinal cord contain extensive circuitry to control the autonomic nervous system which controls the movement of the smooth muscle of the body. Major areas involved in controlling movement Area Location Function Ventral horn Spinal cord Contains motor neurons that directly activate muscles Oculomotor nuclei Midbrain Contains motor neurons that directly activate the eye muscles Cerebellum Hindbrain Calibrates precision and timing of movements Basal ganglia Forebrain Action selection on the basis of motivation Motor cortex Frontal lobe Direct cortical activation of spinal motor circuits Premotor cortex Frontal lobe Groups elementary movements into coordinated patterns Supplementary motor area Frontal lobe Sequences movements into temporal patterns Prefrontal cortex Frontal lobe Planning and other executive functions Sleep Main article: Sleep See also: Arousal Many animals alternate between sleeping and waking in a daily cycle. Arousal and alertness are also modulated on a finer time scale by a network of brain areas. A key component of the sleep system is the suprachiasmatic nucleus (SCN), a tiny part of the hypothalamus located directly above the point at which the optic nerves from the two eyes cross. The SCN contains the body's central biological clock. Neurons there show activity levels that rise and fall with a period of about 24 hours, circadian rhythms: these activity fluctuations are driven by rhythmic changes in expression of a set of "clock genes". The SCN continues to keep time even if it is excised from the brain and placed in a dish of warm nutrient solution, but it ordinarily receives input from the optic nerves, through the retinohypothalamic tract (RHT), that allows daily light-dark cycles to calibrate the clock. The SCN projects to a set of areas in the hypothalamus, brainstem, and midbrain that are involved in implementing sleep-wake cycles. An important component of the system is the reticular formation, a group of neuron-clusters scattered diffusely through the core of the lower brain. Reticular neurons send signals to the thalamus, which in turn sends activity-level-controlling signals to every part of the cortex. Damage to the reticular formation can produce a permanent state of coma. Sleep involves great changes in brain activity. Until the 1950s it was generally believed that the brain essentially shuts off during sleep, but this is now known to be far from true; activity continues, but patterns become very different. There are two types of sleep: REM sleep (with dreaming) and NREM (non-REM, usually without dreaming) sleep, which repeat in slightly varying patterns throughout a sleep episode. Three broad types of distinct brain activity patterns can be measured: REM, light NREM and deep NREM. During deep NREM sleep, also called slow wave sleep, activity in the cortex takes the form of large synchronized waves, whereas in the waking state it is noisy and desynchronized. Levels of the neurotransmitters norepinephrine and serotonin drop during slow wave sleep, and fall almost to zero during REM sleep; levels of acetylcholine show the reverse pattern. Homeostasis Cross-section of a human head, showing location of the hypothalamus For any animal, survival requires maintaining a variety of parameters of bodily state within a limited range of variation: these include temperature, water content, salt concentration in the bloodstream, blood glucose levels, blood oxygen level, and others. The ability of an animal to regulate the internal environment of its body—the milieu intérieur, as the pioneering physiologist Claude Bernard called it—is known as homeostasis (Greek for "standing still"). Maintaining homeostasis is a crucial function of the brain. The basic principle that underlies homeostasis is negative feedback: any time a parameter diverges from its set-point, sensors generate an error signal that evokes a response that causes the parameter to shift back toward its optimum value. (This principle is widely used in engineering, for example in the control of temperature using a thermostat.) In vertebrates, the part of the brain that plays the greatest role is the hypothalamus, a small region at the base of the forebrain whose size does not reflect its complexity or the importance of its function. The hypothalamus is a collection of small nuclei, most of which are involved in basic biological functions. Some of these functions relate to arousal or to social interactions such as sexuality, aggression, or maternal behaviors; but many of them relate to homeostasis. Several hypothalamic nuclei receive input from sensors located in the lining of blood vessels, conveying information about temperature, sodium level, glucose level, blood oxygen level, and other parameters. These hypothalamic nuclei send output signals to motor areas that can generate actions to rectify deficiencies. Some of the outputs also go to the pituitary gland, a tiny gland attached to the brain directly underneath the hypothalamus. The pituitary gland secretes hormones into the bloodstream, where they circulate throughout the body and induce changes in cellular activity. Motivation Components of the basal ganglia, shown in two cross-sections of the human brain. Blue: caudate nucleus and putamen. Green: globus pallidus. Red: subthalamic nucleus. Black: substantia nigra. The individual animals need to express survival-promoting behaviors, such as seeking food, water, shelter, and a mate. The motivational system in the brain monitors the current state of satisfaction of these goals, and activates behaviors to meet any needs that arise. The motivational system works largely by a reward–punishment mechanism. When a particular behavior is followed by favorable consequences, the reward mechanism in the brain is activated, which induces structural changes inside the brain that cause the same behavior to be repeated later, whenever a similar situation arises. Conversely, when a behavior is followed by unfavorable consequences, the brain's punishment mechanism is activated, inducing structural changes that cause the behavior to be suppressed when similar situations arise in the future. Most organisms studied to date use a reward–punishment mechanism: for instance, worms and insects can alter their behavior to seek food sources or to avoid dangers. In vertebrates, the reward-punishment system is implemented by a specific set of brain structures, at the heart of which lie the basal ganglia, a set of interconnected areas at the base of the forebrain. The basal ganglia are the central site at which decisions are made: the basal ganglia exert a sustained inhibitory control over most of the motor systems in the brain; when this inhibition is released, a motor system is permitted to execute the action it is programmed to carry out. Rewards and punishments function by altering the relationship between the inputs that the basal ganglia receive and the decision-signals that are emitted. The reward mechanism is better understood than the punishment mechanism, because its role in drug abuse has caused it to be studied very intensively. Research has shown that the neurotransmitter dopamine plays a central role: addictive drugs such as cocaine, amphetamine, and nicotine either cause dopamine levels to rise or cause the effects of dopamine inside the brain to be enhanced. Learning and memory Almost all animals are capable of modifying their behavior as a result of experience—even the most primitive types of worms. Because behavior is driven by brain activity, changes in behavior must somehow correspond to changes inside the brain. Already in the late 19th century theorists like Santiago Ramón y Cajal argued that the most plausible explanation is that learning and memory are expressed as changes in the synaptic connections between neurons. Until 1970, however, experimental evidence to support the synaptic plasticity hypothesis was lacking. In 1971 Tim Bliss and Terje Lømo published a paper on a phenomenon now called long-term potentiation: the paper showed clear evidence of activity-induced synaptic changes that lasted for at least several days. Since then technical advances have made these sorts of experiments much easier to carry out, and thousands of studies have been made that have clarified the mechanism of synaptic change, and uncovered other types of activity-driven synaptic change in a variety of brain areas, including the cerebral cortex, hippocampus, basal ganglia, and cerebellum. Brain-derived neurotrophic factor (BDNF) and physical activity appear to play a beneficial role in the process. Neuroscientists currently distinguish several types of learning and memory that are implemented by the brain in distinct ways: Working memory is the ability of the brain to maintain a temporary representation of information about the task that an animal is currently engaged in. This sort of dynamic memory is thought to be mediated by the formation of cell assemblies—groups of activated neurons that maintain their activity by constantly stimulating one another. Episodic memory is the ability to remember the details of specific events. This sort of memory can last for a lifetime. Much evidence implicates the hippocampus in playing a crucial role: people with severe damage to the hippocampus sometimes show amnesia, that is, inability to form new long-lasting episodic memories. Semantic memory is the ability to learn facts and relationships. This sort of memory is probably stored largely in the cerebral cortex, mediated by changes in connections between cells that represent specific types of information. Instrumental learning is the ability for rewards and punishments to modify behavior. It is implemented by a network of brain areas centered on the basal ganglia. Motor learning is the ability to refine patterns of body movement by practicing, or more generally by repetition. A number of brain areas are involved, including the premotor cortex, basal ganglia, and especially the cerebellum, which functions as a large memory bank for microadjustments of the parameters of movement. Research Main article: Neuroscience "Brain research" redirects here. For the scientific journal, see Brain Research. The Human Brain Project is a large scientific research project, starting in 2013, which aims to simulate the complete human brain. The field of neuroscience encompasses all approaches that seek to understand the brain and the rest of the nervous system. Psychology seeks to understand mind and behavior, and neurology is the medical discipline that diagnoses and treats diseases of the nervous system. The brain is also the most important organ studied in psychiatry, the branch of medicine that works to study, prevent, and treat mental disorders. Cognitive science seeks to unify neuroscience and psychology with other fields that concern themselves with the brain, such as computer science (artificial intelligence and similar fields) and philosophy. The oldest method of studying the brain is anatomical, and until the middle of the 20th century, much of the progress in neuroscience came from the development of better cell stains and better microscopes. Neuroanatomists study the large-scale structure of the brain as well as the microscopic structure of neurons and their components, especially synapses. Among other tools, they employ a plethora of stains that reveal neural structure, chemistry, and connectivity. In recent years, the development of immunostaining techniques has allowed investigation of neurons that express specific sets of genes. Also, functional neuroanatomy uses medical imaging techniques to correlate variations in human brain structure with differences in cognition or behavior. Neurophysiologists study the chemical, pharmacological, and electrical properties of the brain: their primary tools are drugs and recording devices. Thousands of experimentally developed drugs affect the nervous system, some in highly specific ways. Recordings of brain activity can be made using electrodes, either glued to the scalp as in EEG studies, or implanted inside the brains of animals for extracellular recordings, which can detect action potentials generated by individual neurons. Because the brain does not contain pain receptors, it is possible using these techniques to record brain activity from animals that are awake and behaving without causing distress. The same techniques have occasionally been used to study brain activity in human patients with intractable epilepsy, in cases where there was a medical necessity to implant electrodes to localize the brain area responsible for epileptic seizures. Functional imaging techniques such as fMRI are also used to study brain activity; these techniques have mainly been used with human subjects, because they require a conscious subject to remain motionless for long periods of time, but they have the great advantage of being noninvasive. Design of an experiment in which brain activity from a monkey was used to control a robotic arm Another approach to brain function is to examine the consequences of damage to specific brain areas. Even though it is protected by the skull and meninges, surrounded by cerebrospinal fluid, and isolated from the bloodstream by the blood–brain barrier, the delicate nature of the brain makes it vulnerable to numerous diseases and several types of damage. In humans, the effects of strokes and other types of brain damage have been a key source of information about brain function. Because there is no ability to experimentally control the nature of the damage, however, this information is often difficult to interpret. In animal studies, most commonly involving rats, it is possible to use electrodes or locally injected chemicals to produce precise patterns of damage and then examine the consequences for behavior. Computational neuroscience encompasses two approaches: first, the use of computers to study the brain; second, the study of how brains perform computation. On one hand, it is possible to write a computer program to simulate the operation of a group of neurons by making use of systems of equations that describe their electrochemical activity; such simulations are known as biologically realistic neural networks. On the other hand, it is possible to study algorithms for neural computation by simulating, or mathematically analyzing, the operations of simplified "units" that have some of the properties of neurons but abstract out much of their biological complexity. The computational functions of the brain are studied both by computer scientists and neuroscientists. Computational neurogenetic modeling is concerned with the study and development of dynamic neuronal models for modeling brain functions with respect to genes and dynamic interactions between genes. Recent years have seen increasing applications of genetic and genomic techniques to the study of the brain and a focus on the roles of neurotrophic factors and physical activity in neuroplasticity. The most common subjects are mice, because of the availability of technical tools. It is now possible with relative ease to "knock out" or mutate a wide variety of genes, and then examine the effects on brain function. More sophisticated approaches are also being used: for example, using Cre-Lox recombination it is possible to activate or deactivate genes in specific parts of the brain, at specific times. History See also: History of neuroscience Illustration by René Descartes of how the brain implements a reflex response The oldest brain to have been discovered was in Armenia in the Areni-1 cave complex. The brain, estimated to be over 5,000 years old, was found in the skull of a 12 to 14-year-old girl. Although the brains were shriveled, they were well preserved due to the climate found inside the cave. Early philosophers were divided as to whether the seat of the soul lies in the brain or heart. Aristotle favored the heart, and thought that the function of the brain was merely to cool the blood. Democritus, the inventor of the atomic theory of matter, argued for a three-part soul, with intellect in the head, emotion in the heart, and lust near the liver. The unknown author of On the Sacred Disease, a medical treatise in the Hippocratic Corpus, came down unequivocally in favor of the brain, writing: Men ought to know that from nothing else but the brain come joys, delights, laughter and sports, and sorrows, griefs, despondency, and lamentations. ... And by the same organ we become mad and delirious, and fears and terrors assail us, some by night, and some by day, and dreams and untimely wanderings, and cares that are not suitable, and ignorance of present circumstances, desuetude, and unskillfulness. All these things we endure from the brain, when it is not healthy...— On the Sacred Disease, attributed to Hippocrates Andreas Vesalius' Fabrica, published in 1543, showing the base of the human brain, including optic chiasma, cerebellum, olfactory bulbs, etc. The Roman physician Galen also argued for the importance of the brain, and theorized in some depth about how it might work. Galen traced out the anatomical relationships among brain, nerves, and muscles, demonstrating that all muscles in the body are connected to the brain through a branching network of nerves. He postulated that nerves activate muscles mechanically by carrying a mysterious substance he called pneumata psychikon, usually translated as "animal spirits". Galen's ideas were widely known during the Middle Ages, but not much further progress came until the Renaissance, when detailed anatomical study resumed, combined with the theoretical speculations of René Descartes and those who followed him. Descartes, like Galen, thought of the nervous system in hydraulic terms. He believed that the highest cognitive functions are carried out by a non-physical res cogitans, but that the majority of behaviors of humans, and all behaviors of animals, could be explained mechanistically. The first real progress toward a modern understanding of nervous function, though, came from the investigations of Luigi Galvani (1737–1798), who discovered that a shock of static electricity applied to an exposed nerve of a dead frog could cause its leg to contract. Since that time, each major advance in understanding has followed more or less directly from the development of a new technique of investigation. Until the early years of the 20th century, the most important advances were derived from new methods for staining cells. Particularly critical was the invention of the Golgi stain, which (when correctly used) stains only a small fraction of neurons, but stains them in their entirety, including cell body, dendrites, and axon. Without such a stain, brain tissue under a microscope appears as an impenetrable tangle of protoplasmic fibers, in which it is impossible to determine any structure. In the hands of Camillo Golgi, and especially of the Spanish neuroanatomist Santiago Ramón y Cajal, the new stain revealed hundreds of distinct types of neurons, each with its own unique dendritic structure and pattern of connectivity. Drawing by Santiago Ramón y Cajal of two types of Golgi-stained neurons from the cerebellum of a pigeon In the first half of the 20th century, advances in electronics enabled investigation of the electrical properties of nerve cells, culminating in work by Alan Hodgkin, Andrew Huxley, and others on the biophysics of the action potential, and the work of Bernard Katz and others on the electrochemistry of the synapse. These studies complemented the anatomical picture with a conception of the brain as a dynamic entity. Reflecting the new understanding, in 1942 Charles Sherrington visualized the workings of the brain waking from sleep: The great topmost sheet of the mass, that where hardly a light had twinkled or moved, becomes now a sparkling field of rhythmic flashing points with trains of traveling sparks hurrying hither and thither. The brain is waking and with it the mind is returning. It is as if the Milky Way entered upon some cosmic dance. Swiftly the head mass becomes an enchanted loom where millions of flashing shuttles weave a dissolving pattern, always a meaningful pattern though never an abiding one; a shifting harmony of subpatterns.— Sherrington, 1942, Man on his Nature The invention of electronic computers in the 1940s, along with the development of mathematical information theory, led to a realization that brains can potentially be understood as information processing systems. This concept formed the basis of the field of cybernetics, and eventually gave rise to the field now known as computational neuroscience. The earliest attempts at cybernetics were somewhat crude in that they treated the brain as essentially a digital computer in disguise, as for example in John von Neumann's 1958 book, The Computer and the Brain. Over the years, though, accumulating information about the electrical responses of brain cells recorded from behaving animals has steadily moved theoretical concepts in the direction of increasing realism. One of the most influential early contributions was a 1959 paper titled What the frog's eye tells the frog's brain: the paper examined the visual responses of neurons in the retina and optic tectum of frogs, and came to the conclusion that some neurons in the tectum of the frog are wired to combine elementary responses in a way that makes them function as "bug perceivers". A few years later David Hubel and Torsten Wiesel discovered cells in the primary visual cortex of monkeys that become active when sharp edges move across specific points in the field of view—a discovery for which they won a Nobel Prize. Follow-up studies in higher-order visual areas found cells that detect binocular disparity, color, movement, and aspects of shape, with areas located at increasing distances from the primary visual cortex showing increasingly complex responses. Other investigations of brain areas unrelated to vision have revealed cells with a wide variety of response correlates, some related to memory, some to abstract types of cognition such as space. Theorists have worked to understand these response patterns by constructing mathematical models of neurons and neural networks, which can be simulated using computers. Some useful models are abstract, focusing on the conceptual structure of neural algorithms rather than the details of how they are implemented in the brain; other models attempt to incorporate data about the biophysical properties of real neurons. No model on any level is yet considered to be a fully valid description of brain function, though. The essential difficulty is that sophisticated computation by neural networks requires distributed processing in which hundreds or thousands of neurons work cooperatively—current methods of brain activity recording are only capable of isolating action potentials from a few dozen neurons at a time. Furthermore, even single neurons appear to be complex and capable of performing computations. So, brain models that do not reflect this are too abstract to be representative of brain operation; models that do try to capture this are very computationally expensive and arguably intractable with present computational resources. However, the Human Brain Project is trying to build a realistic, detailed computational model of the entire human brain. The wisdom of this approach has been publicly contested, with high-profile scientists on both sides of the argument. In the second half of the 20th century, developments in chemistry, electron microscopy, genetics, computer science, functional brain imaging, and other fields progressively opened new windows into brain structure and function. In the United States, the 1990s were officially designated as the "Decade of the Brain" to commemorate advances made in brain research, and to promote funding for such research. In the 21st century, these trends have continued, and several new approaches have come into prominence, including multielectrode recording, which allows the activity of many brain cells to be recorded all at the same time; genetic engineering, which allows molecular components of the brain to be altered experimentally; genomics, which allows variations in brain structure to be correlated with variations in DNA properties and neuroimaging. Society and culture As food Main article: Brain as food Gulai otak, beef brain curry from Indonesia Animal brains are used as food in numerous cuisines. In rituals Some archaeological evidence suggests that the mourning rituals of European Neanderthals also involved the consumption of the brain. The Fore people of Papua New Guinea are known to eat human brains. In funerary rituals, those close to the dead would eat the brain of the deceased to create a sense of immortality. A prion disease called kuru has been traced to this. See also Philosophy portal Brain–computer interface Central nervous system disease List of neuroscience databases Neurological disorder Optogenetics Outline of neuroscience Aging brain	biology	322049	https://da.wikipedia.org/wiki/Neuron	Neuron	Et neuron (fra græsk: sene, nerve), også kaldet en nervecelle, er en celletype i nervesystemet. De adskiller sig fra andre celler ved deres mange udløbere, kaldet dendritter og aksoner, og ved at være specialiseret i transmittering af signaler, dels elektrisk intraneuronalt og dels ved hjælp af transmitterstoffer interneuronalt, der virker på andre neuroners eller effektorvævenes receptorer (se for eksempel G-protein-koblede receptorer, GPCR og den motoriske endeplade). Af neurotransmittere kan nævnes serotonin, acetylkolin, dopamin, adrenalin og noradrenalin. Formålet med hjernens netværk af neuroner er kommunikation og informationsbehandling. Opbygning Neuroner er de centrale komponenter i hjernen og rygmarven i centralnervesystemet (CNS) samt ganglier i det perifere nervesystem (PNS). En typisk neuron består af et cellelegeme (soma), dendritter og et axon. Dendritter er tynde strukturer, der udspringer fra cellekroppen og ofte strækker sig flere hundrede mikrometer og forgrener sig flere gange. En Axon, også kaldet en nervefiber når de er myelinerede, udspringer fra cellen ved et sted kaldet axon højen og rejser op til en en meter i mennesker og endnu længere i andre arter. En neurons cellekroppe har ofte flere dendritter, men aldrig til mere end ét Axon. Neuronets lange aksoner kan være omgivet af en isolerende fedtskede kaldet myelinskeden, som har til funktion at øge signaleringshastigheden. Myelinskeden produceres og vedligeholdes i centralnervesystemet af oligodendrocytter og af Schwannske celler i det perifere nervesystem. I de fleste tilfælde er neuroner genereret af særlige typer af stamceller. Det menes generelt, at neuroner ikke undergår celledeling, men nyere forskning hos hunde viser, at det i nogle tilfælde sker i nethinden. Astrocytter er stjerneformede gliaceller, der er også blevet observeret at blive til neuroner. Hos mennesker ophører neurogenese stort set i voksenalderen, men i to områder i hjernen, hippocampus og den olfaktoriske pære, er der beviser for generering af nye neuroner. Kommunikation mellem neuroner En neuron behandler og sender oplysninger gennem elektriske og kemiske signaler. Nervecellernes signaler bygger på en spændingsforskel mellem nervecellens indre og ydre, kaldet membranpotentialet. Er neuronet i hvile, kaldes spændingsforskellen for hvilemembranpotentialet. Er ændringen i membranpotentialet tilstrækkelig stor, genereres en (alt-eller-intet) elektrokemisk puls kaldet et aktionspotentiale, som bevæger sig hurtigt langs cellens axon og aktiverer synaptiske forbindelser til andre celler. Neurontyper Neuroner kan overordnet inddeles i projektionsneuroner Golgi type 1 med et enkelt langt akson, der kan kommunikere med andre regioner af nervesystemet, og interneuroner Golgi type 2 som kun befinder sig i en hjerneregion. Der er dog ikke skarp adskillelse mellem disse to typer. Specialiserede neuroner omfatter: 1) sensoriske neuroner, der reagerer på berøring, lyd, lys og alle andre stimuli, der påvirker cellerne via vores sanser, som derefter sender signaler til rygmarven og hjernen; 2) motoriske neuroner, der modtager signaler fra hjernen og rygmarven, som bevirker muskelsammentrækninger og påvirker glandulare udgange; 3) interneuroner, der forbinder neuroner i den samme region i hjernen eller rygmarven. Se også Dendrit, akson, soma, gliacelle Kranienerver Neuropeptid Eksterne henvisninger	danish	0.434241
see_when_eyes_closed/Closed-eye_hallucination.txt	Closed-eye hallucinations and closed-eye visualizations (CEV) are hallucinations that occur when one's eyes are closed or when one is in a darkened room. They should not be confused with phosphenes, perceived light and shapes when pressure is applied to the eye's retina, or some other non-visual external cause stimulates the eye. Some people report CEV under the influence of psychedelics; these are reportedly of a different nature than the "open-eye" hallucinations of the same compounds. Similar hallucinations that occur due to loss of vision are called "visual release hallucinations". Levels of CEV perception[edit] See also: Creative visualization There are five known levels of CEV perception which can be achieved either through chemical stimuli or through meditative relaxation techniques. Level 1 and 2 are very common and often happen every day. It is still normal to experience level 3, and even level 4, but only a small percentage of the population does this without psychedelic drugs, meditation or extensive visualization training. Level 1: Visual noise[edit] CEV noise simulation The most basic form of CEV perception that can be immediately experienced in normal waking consciousness involves a seemingly random noise of pointillistic light or dark regions with no apparent shape or order. This can be seen when the eyes are closed and looking at the back of the eyelids. In a bright room, a dark red can be seen, owing to a small amount of light penetrating the eyelids and taking on the color of the blood it has passed through. In a dark room, blackness can be seen or the object can be more colourful. But in either case it is not a flat unchanging redness/blackness. Instead, if actively observed for a few minutes, one becomes aware of an apparent disorganized motion, a random field of lightness or darkness that overlays the redness or blackness of closed eyelids. For a person who tries to actively observe this closed-eye perception on a regular basis, there comes a point where if they look at a flat-shaded object with their eyes wide open, and try to actively look for this visual noise, they will become aware of it and see the random pointillistic disorganized motion as if it were a translucent overlay on top of what is actually being seen by their open eyes. CEV noise simulation with multiple colors (Purple, Green, Yellow) When seen overlaid onto the physical world, this CEV noise does not obscure physical vision at all, and in fact is hard to notice if the visual field is highly patterned, complex, or in motion. When active observation is stopped, it is not obvious or noticeable, and seemingly disappears from normal physical perception. Individuals suffering from visual snow syndrome see similar noise but experience difficulty blocking it from conscious perception. Level 2: Light or dark flashes[edit] CEV noise simulation with multiple colors and flashing dot Some mental control can be exerted over these closed-eye visualizations, but it usually requires a bit of relaxation and concentration to achieve. When properly relaxed it is possible to cause regions of intense black, bright white or even colors such as yellow, green, or pink to appear in the noise. These regions can span the entire visual field, but seem to be fleeting in nature. Level 3: Patterns, motion, and color[edit] Level 3 CEV simulation without noise This level is relatively easily accessible to people who use psychedelic drugs such as LSD. However, it is also accessible to people involved in deep concentration for long periods of time. When lying down at night and closing the eyes, right before sleep or just before waking up, the complex motion of these patterns can become directly visible without any great effort thanks to hypnagogic hallucination. The patterns themselves might resemble fractals. Level 4: Objects and things[edit] This is a fairly deep state. At this level, thoughts visually manifest as objects or environments. When this level is reached, the CEV noise seems to calm down and fade away, leaving behind an intense flat ordered blackness. The visual field becomes a sort of active space. A side component of this is the ability to feel motion when the eyes are closed. CEV noise simulation with disappearing flashing image Opening the eyes returns one to the normal physical world, but still with the CEV object field overlaid onto it and present. In this state it is possible to see things that appear to be physical objects in the open-eye physical world, but that aren't really there. If we remember that the essential difference between what we call the real world and the world of imagination and hallucination, is not the elements of which we build them up but the sequence in which these elements appear... then it follows that the sequences directed from without represent a limitation of the otherwise unlimited combinations of the selective forms released at random from within.— Jurij Moskvitin, Essay on the origin of thought. Level 5: Overriding physical perception[edit] Level 5 CEV simulation This level can be entered from complete sensory deprivation, as experienced in an isolation tank or deep trance of hypnosis, but even there it requires great relaxation. According to lucid dreaming researcher Stephen LaBerge, perceptions can come from either the senses or imagination. An inhibitory system involving the thalamus, likely involving serotonergic neurons, inhibits imaginary perceptions from becoming too activated so they turn into hallucinations. This system is inhibited during REM sleep, and the imagination can freely run into the perceptual systems. What happens at level 5 is likely that this system is inhibited, just like in REM sleep, by different causes like sensory deprivation, psychedelic drugs or meditative relaxation techniques. What is not a CEV[edit] This section does not cite any sources. Please help improve this section by adding citations to reliable sources. Unsourced material may be challenged and removed. (February 2013) (Learn how and when to remove this template message) Afterimage (palinopsia)[edit] Image burn-in occurs when very bright objects lie in one's field of vision, and should not be confused with closed-eye hallucinations. Visual burn-in from bright lights is visible for a few minutes after closing the eyes, or by blinking repeatedly, but the burn-in effect slowly fades away as the retina recovers, whereas the waking-consciousness CEV noise will not disappear if observed continuously over a period of time. Entoptic phenomena[edit] CEV does not include entoptic phenomena such as "floaters", which are instead caused by opacities in the vitreous humour and often appear as cells or strands in the field of vision. Full-closing and reopening the eyelids creates a very definite wiper-ridge in the tear film that is readily visible. Fully closing and reopening the eyelids also often stirs up the vitreous which settles down after a brief moment due to gravity. The motion of waking-consciousness CEV noise is not so directly and physically controllable and repeatable. Blue-sky sprites[edit] CEV does not seem to be related to the "sprites" (blue field entoptic phenomenon) that can be seen as dots darting around when staring up into a bright blue sky on a sunny day (not looking at the sun). These dots superimposed over a flat blue background are white blood cells moving through the blood vessels of the retina. The motion of waking-consciousness CEV noise is uniformly random compared to the waking-consciousness blue-sky sprite motion. Physical retinal stimulation[edit] CEV is unrelated to the visual noise seen when the retina is physically stimulated. The retina can be made to produce light patterns of visual noise simply by one rubbing their eyes somewhat forcefully in a manner that increases intraocular pressure. Additionally, retinal noise can be produced by touching near the rear of the eyeball producing pressure phosphenes (for example, if one closes one's eyes, looks all the way left, and lightly touches the rightmost part of the eye socket, this produces visual noise in the shape of a circle that appears at the left side of the visual field – a practice that is neither painful nor dangerous). None of these are closed-eye hallucinations, but rather the experience of mechanical stimuli distorted into visual stimuli. Thus, pressure phosphenes are sensory distortions, and not hallucinations, as the latter is an unreal perception in the absence of stimuli. See also[edit] Dark retreat – Tibetan Buddhism advanced practice Eigengrau – Illusionary dark gray color Eidetic memory – Ability to recall an image from memory after one viewing Entoptic phenomenon – Visual effect whose source is within the eye itself Form constant – Recurringly observed geometric pattern Ganzfeld effect – Psychological phenomenon Hallucinogen – General group of pharmacological agents Hallucinogen persisting perception disorder – Medical condition Haidinger's brush – Visible effect of polarised light Prisoner's cinema – Visual phenomenon involving seeing animated lights in the darkness Sleep paralysis – Sleeping disorder	biology	122445	https://sv.wikipedia.org/wiki/Optisk%20illusion	Optisk illusion	Optisk illusion (eller synvilla) är en illusion som ger ett synintryck som ger en vinklad bild av verkligheten. Det som ögat ser tolkas av det centrala nervsystemet och utgör den visuella perceptionsförmågan, vilket kan ge en illusionistisk bild som är motsägelsefull eller omöjlig. Det finns tre olika huvudtyper av optiska illusioner: literala optiska illusioner, som skapar illusioner som skiljer sig från objektet som skapar dem, psykologiska illusioner: som är en perceptionseffekt av en riktad stimulans av exempelvis ljus, skärpa, färg eller rörelse och slutligen kognitiva illusioner: där ögats tolkade bild ger omedvetna slutsatser. Psykologiska illusioner Psykologiska illusioner kan exempelvis vara den efterbild som kan följa efter ett skarpt ljusintag eller en längre tids fokusering av ett objekt eller mönster av något slag - ljus, skärpa, lutning, färg, rörelse mm. Teorin är att den individuellt reflexmässiga tolkningen, påverkas av repetitiva eller enskilt förstärkta perceptionskanaler, vilket skapar en psykologisk obalans som förändrar perceptionen (den uppfattade bilden). Hermanns nätillusion (bilden) och Machs band är två illusioner som förklarar det väl. När det gäller de breda svartgråa banden i Machs band uppträder en lateral inhibering i receptionsfältet, där de ljusa och mörka receptorerna tävlar med varandra med att vara aktiva, som förklarar varför vi ser band med förhöjda tonvärden vid kulörkanterna i illusionen. När väl en receptor är påkopplad, kopplas de angränsande receptorerna av och resultatet blir skarpare skiljelinjer. I nätillusionen uppträder grå punkter i rutnätets skärningspunkter på grund av inhiberade receptorer som ett resultat av den mörka bakgrundens starka tonvärde. Lateral inhibering har också använts för att förklara nät-illusionen, men har sedan tillbakavisats. Kognitiva illusioner De kognitiva illusionerna uppträder genom samverkande antaganden som bildar omedvetna slutsatser, en idé som fysiologen och fysikern Hermann von Helmholtz lade fram på 1800-talet. De kognitiva illusionerna delas vanligen upp i tvetydiga illusioner, förvrängande illusioner, paradoxala illusioner och fictionillusioner. Tvetydiga illusioner är bilder eller objekt som framkallar en perceptionsväxling mellan alternativa tolkningar. Neckers kub är ett tidigt känt exempel liksom den på senare tid skapade siluettdansaren. Förvrängande illusioner karaktäriseras genom att de förvränger storlek, längd, eller krökning. Ett slående exempel är Café wall illusion, se bild. Ett annat exempel är den berömda Müller-Lyer-illusionen. Paradoxala illusioner genereras av objekt som är paradoxala eller omöjliga, som exempelvis Den omöjliga triangeln i Vattenfallet av M.C. Escher eller omöjliga trappor som Penrose trappa i Eschers litografi Trappa upp och trappa ned. Triangeln, liksom trappan, är illusioner som är kognitiva missuppfattningar då de angränsande ytorna inte kan mötas. Fictionillusioner definieras genom perceptionen av objekt som faktiskt inte existerar för någon annan än den enskilde betraktaren. De är helt enkelt hallucinationer, som exempelvis kan vara skapade under inflytande av droger eller psykiska sjukdomar. Förklaring av kognitiva illusioner Perceptionens struktur För att världen ska vara begriplig är det nödvändigt att organisera olika intryck till något meningsfullt. Gestaltpsykologin menar att en väg till detta är genom den individuella perceptionsstimuleringen. Gestaltpsykologi kan användas för att förklara flera illusioner inkluderat anka-hare-illusionen på bilden till höger. Bilden kan både ses som huvudet på en anka som är vänd åt vänster eller som huvudet på en hare som spejar åt höger, beroende på vilket perspektiv som fångas. Samma gestaltpsykologi kan användas för att förklara de skenbara konturerna i illusionen Kanizsas triangel, som här beskriver en icke existerande svävande vit triangel. Hjärnan har behovet att känna igen föremål och former och har en tendens att skapa en trolig form, trots att den egentligen bara är antagen. En annan förklaring på Kanizsa-triangeln är dock baserad på evolutionspsykologi och det faktum att vi för att överleva måste vara effektiva vid tolkandet av ofullständiga eller tvetydiga former, även om det ibland kan bli fel. Perceptionens struktur som medger och uppmuntrar skapandet av meningsfulla former är också den princip som de flesta välkända illusionerna bygger på, inklusive så kallade omöjliga objekt. Vår hjärna försöker skapa något användbart av de pusselbitar som finns tillgängliga, som vrids och vänds tills något användbart eller trovärdigt har byggts upp i tanken. Djup- och rörelseperception Illusioner kan baseras på en individuell förmåga att se i tre dimensioner, även om den använda bilden bara är i två dimensioner. Ponzo-illusionen är ett exempel som använder en tvådimensionell miljö för att skapa en 'skenbar' tredimensionell bild. Bildens parallella linjer säger oss att objekten högre i synfältet är längre bort och därför uppfattar vi att de gula balkarna har olika bredd, trots att de när de träffar näthinnan är lika långa. De optiska illusionerna som ses i ett falskt perspektiv (diorama) använder också olika djupseende effekter. Den holländske målaren M.C. Eschers målning vattenfallet använder djup och närhet samt vår uppfattningsförmåga till att skapa en illusion. Vårt sinne för djup och rörelse används för flera sensoriska illusioner. Filmens animation är baserad på illusionen att hjärnan uppfattar en serie av något olika bilder som visas i en snabb följd, som en rörlig bild. Även när vi själva rör oss till exempel i ett fordon, så kan vi uppfatta stationära omgivande objekt såsom rörliga. Vi uppfattar också att stora objekt, som ett flygplan, rör sig långsammare än mindre objekt, som en bil, trots att flygplanet i de flesta fall är betydligt snabbare. Phi-fenomenet är ännu ett exempel på hur vår perception uppfattar rörelse, vilket här mestadels består i blinkande lampor i tät följd. Färg- och ljusstyrkans konstanter Illusioner kan skapas av olika perceptionskonstanter. Färgen och ljusstyrkans konstanter är ansvariga för det faktum att ett känt objekt kommer att uppträda i samma färg oavsett mängden av ljus som reflekteras från det. En illusion som baseras på färg eller kontrastskillnad kan skapas när ljusstyrkan eller färgtonen i dess omgivning förändras i ett okänt objekt. Kontrasten i objektet kommer att framstå som mörkare mot ett svart fält, som reflekterar en mindre mängd ljus än ett vitt fält, även om objektet själv har samma färgton. Med samma metodik kommer vår perception att kompensera för skillnader i kontrast beroende på färgtonen i den omgivande miljön. Objektets konstant Precis som med färgigenkänning har hjärnan kapacitet och vilja att förstå kända föremåls form eller storlek. Ett exempel kan vara att en dörr uppfattas att vara en rektangel, oavsett hur bildvinkeln ändras när den öppnas eller stängs. Okända föremål däremot, följer inte alltid regeln om formkonstant och kan lättare ändra aktuellt perspektiv. Shepards formillusion är ett känt exempel på en illusion som är baserad på förvrängning av formens konstant. Framtida perception Forskaren Mark Changizi från Rensselaer Polytechnic Institute i New York säger att optiska illusioner är en erfarenhet de flesta genomgår under uppvaknandet genom nervbanornas reaktionstid. När ljuset träffar en receptor åtgår det cirka en tiondels sekund innan hjärnan översätter signalen till en visuell bild av miljön. Forskarna känner till eftersläpningen och diskussioner har rört sig runt olika teorier hur vi kompenserar för detta och någon teori är inriktad på hur vårt motoriksystem hanterar eftersläpningen genom att modifiera rörelseschemat i motsvarande grad. Changizi hävdar att det mänskliga visuella systemet har utvecklat en kompensering för den ingående reaktionstiden, genom att generera bilder som visar vad som kommer att ske en tiondels sekund in i framtiden. Denna framförhållning möjliggör att reagera i realtid, när det gäller reflexmässiga handlingar som till exempel att fånga en flygande boll eller att manövrera smidigt genom en folkmassa. Illusioner uppkommer när vårt centrala nervsystem försöker att förutspå framtiden och när bilden inte matchar verkligheten. Ett exempel är illusionen som kallas Hering-illusionen som liknar ett cykelhjuls ekrar runt en centrumpunkt, med vertikala linjer på var sida om detta centrum. Illusionen får oss att tänka att vi rör oss framåt och därför slår vi på vårt prognossinne. Eftersom vi faktiskt inte rör oss framåt och figuren är statisk, missbedömer vi de raka linjerna till att vara bågformade. Chnagizi säger: "Evolutionen har sett till att geometriska figurer som denna framkallar en nära framtida förutsägelse. De konvergerande linjerna mot centrumpunkten (ekrarna) framkallar föreställningen att vi rör oss framåt - som vi skulle göra i verkligheten, där en dörrkarm (ett par vertikala linjer) ser ut att bågna utåt när vi passerar genom den - och vi försöker att föreställa oss hur världen kommer att se ut i nästa ögonblick." Illusioner Ames rum Autostereogram Beta movement Blivet (eller Impossible trident illusion) Café wall illusion Cornsweets illusion Den dansande siluetten Den omöjliga triangeln (eller Penrose triangel) Ebbinghaus illusion Nät-illusionen Herings illusion Kanizsas triangel Lutande torn-illusionen Lilac chaser Machs band Magnetisk kulle McColloughs effekt Månillusionen Müller-Lyer-illusionen Neckers kub Penrose trappa Phi-fenomenet Poggendorffs illusion Ponzos illusion Pulfrich effekt (eller Pulfrich pendulum illusion) Pusselparadoxen (eller Missing square puzzle) Rubins vas Samma färg-illusionen Shepards formillusion Spiral-illusion Vagnshjuls-effekten Wundts illusion Zöllners illusion Många konstnärer har arbetat med optiska illusioner exempelvis: M. C. Escher, Bridget Riley, Salvador Dalí, Giuseppe Arcimboldo, Marcel Duchamp, Oscar Reutersvärd och Charles Allan Gilbert. Också många samtida konstnärer experimenterar med illusioner som exempelvis: Octavio Ocampo, Dick Termes, Shigeo Fukuda, Patrick Hughes, István Orosz, Rob Gonsalves och Akiyoshi Kitaoka. Optiska illusioner används också i filmteknik i form av forced perspective. Kognitiva processers hypotes Hypotesen runt optiska illusioner hävdar att dessa visuella fenomen uppkommer på grund av nervsystemets självlärande och effektiviserande kunskapsbank (cacheminne), som hjälper oss att förstå 3D-scener i det fall att det kanske är nödvändigt för att snabbt fatta ett tryggt beslut i ovanliga situationer. I denna mening kan kognitiva processer sägas vara ett ramverk för att förstå och utveckla optiska illusioner, som varande en empirisk och statistisk grund för att lösa motsvarande problem. Forskningen indikerar att 3D-visioner stödjer och förstärker ett lärande vid planering av rörelser. Under läroprocessen uppdateras vårt beteende runt nära objekt, av de perceptiva data vi uppfattar. Representationen av mer fjärran objekt är dock mindre adekvat, då det inte bara är månen som ser större ut då vi betraktar den nära horisonten. I ett fotografi med ett avlägset motiv upplever vi alla objekt som mindre än de skulle vara i en egen synlig upplevelse. Näthinnans bild är vår huvudsakligt drivande parameter, men det vi ser är en virtuell 3D-bild av scenen framför oss. Vi ser inte en fysisk bild av världen, utan vi ser objekt som den fysiska världen själv inte är uppbyggd av. Vi ser det på det sätt som vårt centrala nervsystem strukturerar upp för oss. Namn, färger, vanliga former och annan information runt tingen vi kommer i kontakt med bearbetas ständigt, vilka sedan kompletterar vår upplevelse av den aktuella scenen. Vi ser den mest relevanta information som vårt sinne kan uttolka, från den bästa 3D-bilden som vi kan producera. Illusionerna är ett sätt att omedvetet bedöma och tolka verkligheten, i konflikt med mer resonerande ställningstaganden. Galleri Referenser Noter Tryckta källor Eagleman, D.M. (2001) Visual Illusions and Neurobiology. Nature Reviews Neuroscience. 2(12): 920-6. (pdf) Gregory Richard (1997) Knowledge in perception and illusion. Phil. Trans. R. Soc. Lond. B 352:1121-1128. (pdf) Purves D, Lotto B (2002) Why We See What We Do: An Empirical Theory of Vision. Sunderland, MA: Sinauer Associates. Purves D, Lotto RB, Nundy S (2002) Why We See What We Do. American Scientist 90 (3): 236-242. Purves D, Williams MS, Nundy S, Lotto RB (2004) Perceiving the intensity of light. Psychological Rev. Vol. 111: 142-158. Renier, L., Laloyaux, C., Collignon, O., Tranduy, D., Vanlierde, A., Bruyer, R., De Volder, A.G. (2005). The Ponzo illusion using auditory substitution of vision in sighted and early blind subjects. Perception, 34, 857–867. Renier, L., Bruyer, R., & De Volder, A. G. (2006). Vertical-horizontal illusion present for sighted but not early blind humans using auditory substitution of vision. Perception & Psychophysics, 68, 535–542. Yang Z, Purves D (2003) A statistical explanation of visual space. Nature Neurosci 6: 632-640. Se även Forcerat perspektiv Hägring Kamouflage Ljusadaption Opkonst Trompe l'œil Externa länkar Opt Illusions Optical Illusions & Visual Phenomena, från Michael Bach. Nya illusioner, från conflusions.com Skolprojekt om illusioner, från GH-School Hausen, Tyskland Visuella perceptionsillusioner, från Archimedes Laboratory Project LITE: Atlas of visual phenomena, från Boston University, USA Se svartvit illusion i färg Det omöjliga görs möjligt? från youtube.com	swedish	0.625224
see_when_eyes_closed/Darkness.txt	Darkness is defined as a lack of illumination, an absence of visible light, or a surface that absorbs light, such as a black one. Human vision is unable to distinguish colors in conditions of very low luminance because the hue-sensitive photoreceptor cells on the retina are inactive when light levels are insufficient, in the range of visual perception referred to as scotopic vision. The emotional response to darkness has generated metaphorical usages of the term in many cultures, often used to describe an unhappy or foreboding feeling. "Darkness" may also refer to night, which occurs when the Sun is more than 18° below the horizon. Scientific[edit] Perception[edit] The perception of darkness differs from the mere absence of light due to the effects of after images on perception. In perceiving, the eye is active, and the part of the retina that is unstimulated produces a complementary afterimage. Physics[edit] See also: Light and Heat death of the universe In terms of physics, an object is said to be dark when it absorbs photons, causing it to appear dim compared to other objects. For example, matte black paint does not reflect much visible light and appears dark, whereas white paint reflects much light and appears bright. For more information, see color. An object may appear dark, but it may be bright at a frequency that humans cannot perceive. A dark area has limited light sources, making things hard to see. Exposure to alternating light and darkness (night and day) has caused several evolutionary adaptations to darkness. When a vertebrate, like a human, enters a dark area, its pupils dilate, allowing more light to enter the eye and improving night vision. Also, the light detecting cells in the human eye (rods and cones) will regenerate more unbleached rhodopsin when adapting to darkness. One scientific measure of darkness is the Bortle scale, which indicates the night sky's and stars' brightness at a particular location, and the observability of celestial objects at that location. The material known as Vantablack is one of the darkest substances known, absorbing up to 99.965% of visible light (at 663 nm if the light is perpendicular to the material), and was developed by Surrey NanoSystems in the United Kingdom. The name is a compound of the acronym VANTA (vertically aligned nanotube arrays) and the color black. Technical[edit] The color of a point, on a standard 24-bit computer display, is defined by three RGB (red, green, blue) values, each ranging from 0–255. When the red, green, and blue components of a pixel are fully illuminated (255,255,255), the pixel appears white; when all three components are unilluminated (0,0,0), the pixel appears black. Cultural[edit] Artistic[edit] Caravaggio's The Calling of St Matthew uses darkness for its chiaroscuro effects. Main article: Tints and shades This section has multiple issues. Please help improve it or discuss these issues on the talk page. (Learn how and when to remove these template messages) This section does not cite any sources. Please help improve this section by adding citations to reliable sources. Unsourced material may be challenged and removed. (January 2010) (Learn how and when to remove this template message) This section possibly contains original research. Please improve it by verifying the claims made and adding inline citations. Statements consisting only of original research should be removed. (November 2014) (Learn how and when to remove this template message) (Learn how and when to remove this template message) Artists use darkness to emphasize and contrast the presence of light. Darkness can be used as a counterpoint to areas of lightness to create leading lines and voids. Such shapes draw the eye around areas of the painting. Shadows add depth and perspective to a painting. See chiaroscuro for a discussion of the uses of such contrasts in visual media. Color paints are mixed together to create darkness, because each color absorbs certain frequencies of light. Theoretically, mixing together the three primary colors, or the three secondary colors, will absorb all visible light and create black. In practice, it is difficult to prevent the mixture from taking on a brown tint. Literature[edit] Separation of light and darkness on the first day of creation, from the Sistine Chapel ceiling by Michelangelo Further information: Light and darkness As a poetic term in the Western world, darkness is used to connote the presence of shadows, evil, and foreboding, or in modern parlance, to connote that a story is grim, heavy, and/or depressing. Religion[edit] The first creation narrative in Judaism and Christianity begins with darkness, into which is introduced the creation of light, and the separation of this light from the darkness (as distinct from the creation of the Sun and Moon on the fourth day of creation). Thus, although both light and darkness are included in the comprehensive works of God, darkness was considered "the second to last plague" (Exodus 10:21), and the location of "weeping and gnashing of teeth" (Matthew 8:12). Erebus was a primordial deity in Greek mythology, representing the personification of darkness. Philosophy[edit] In Chinese philosophy, yin is the complementary feminine part of the taijitu and is represented by a dark lobe. Poetry[edit] The use of darkness as a rhetorical device has a long-standing tradition. William Shakespeare, working in the 16th and 17th centuries, made a character called the "prince of darkness" (King Lear: III, iv) and gave darkness jaws with which to devour love. (A Midsummer Night's Dream: I, i) Geoffrey Chaucer, a 14th-century Middle English writer of The Canterbury Tales, wrote that knights must cast away the "workes of darkness". In Divine Comedy, Dante described hell as "solid darkness stain'd". Language[edit] In Old English there were three words that could mean darkness: heolstor, genip, and sceadu. Heolstor also meant "hiding-place" and became holster. Genip meant "mist" and fell out of use like many strong verbs. It is however still used in the Dutch saying "in het geniep" which means secretly. Sceadu meant "shadow" and remained in use. The word dark eventually evolved from the word deorc. See also[edit] Lightness Shadow Theory of colours Nyctophobia	biology	282808	https://da.wikipedia.org/wiki/Skygge	Skygge	En skygge er et område som er mindre belyst end omgivelserne på grund af at et lysbrydende objekt er placeret i mellem området og en lyskilde. Man siger at objektet kaster skygge. Lyskilden kan f.eks. være solen, et stearinlys eller en lampe. Skygger tager form efter det lysbrydende objekt, dog kan skyggen være deformeret eller forvredet afhængig af strukturen af underlaget den falder på, og afhængig af vinklen hvormed lyset rammer objektet. Jo mindre vinklen er mellem lysets retning og den overflade som skyggen falder på, desto længere er skyggen. Dette ses f.eks. sidst på eftermiddagen og om aftenen, når solen er ved at gå ned bag horisonten. Hvis lyskilden befinder sig meget tæt på objektet bliver skyggen meget stor. Kanten på en skygge vil være mere veldefineret i skarpt lys end i svagt. Dette skyldes at lyset spredes. Hvis lyset falder tæt ind på kanten af et objekt som befinder sig tæt ved den overflade den kaster skygge på, vil skyggens kant være meget skarp. Ved en måneformørkelse er jorden det lysbrydende objekt og kaster skygge på månen. Brug af skygge i kunsten Billedkunstnere har altid været inspireret af lys/skygge-virkninger. Dette ses tydelig ved relieffer og tredimensionale fremstillinger som statuer og skulpturer, hvis placering i forhold til lyskilderne bidrager til den endelige virkning. I malerkunsten bruger kunstnerne ofte gråtoner til at skabe en tredimenional effekt ved at efterligne skyggevirkningerne. For malerkunsten som efterligner naturen, er det vigtig at lægge mærke til farvetonerne på skyggepartierne (der er ofte et blåtonerr fra himmellyset, men også farvereflekser fra omgivelserne som er belyst). Andre typer af skygger I overført betydning anvendes ordet som en form for stråling, f.eks. radioskygge, der er radiosignaler der f.eks. bliver standset af et bjerg og derfor ikke kan modtages. Udtrykket regnskygge beskriver situationen i et område, som ligger i ly af en bjergkæde og derfor får mindre nedbør, end det er normalt for regionen. Se også Optik	danish	0.663174
see_when_eyes_closed/Visual_system.txt	The visual system is the physiological basis of visual perception (the ability to detect and process light). The system detects, transduces and interprets information concerning light within the visible range to construct an image and build a mental model of the surrounding environment. The visual system is associated with the eye and functionally divided into the optical system (including cornea and lens) and the neural system (including the retina and visual cortex). The visual system performs a number of complex tasks based on the image forming functionality of the eye, including the formation of monocular images, the neural mechanisms underlying stereopsis and assessment of distances to (depth perception) and between objects, motion perception, pattern recognition, accurate motor coordination under visual guidance, and colour vision. Together, these facilitate higher order tasks, such as object identification. The neuropsychological side of visual information processing is known as visual perception, an abnormality of which is called visual impairment, and a complete absence of which is called blindness. The visual system also has several non-image forming visual functions, independent of visual perception, including the pupillary light reflex and circadian photoentrainment. This article describes the human visual system, which is representative of mammalian vision, and to a lesser extent the vertebrate visual system. System overview[edit] This diagram linearly (unless otherwise mentioned) tracks the projections of all known structures that allow for vision to their relevant endpoints in the human brain. Click to enlarge the image. Representation of optic pathways from each of the 4 quadrants of view for both eyes simultaneously Optical[edit] Together, the cornea and lens refract light into a small image and shine it on the retina. The retina transduces this image into electrical pulses using rods and cones. The optic nerve then carries these pulses through the optic canal. Upon reaching the optic chiasm the nerve fibers decussate (left becomes right). The fibers then branch and terminate in three places. Neural[edit] Most of the optic nerve fibers end in the lateral geniculate nucleus (LGN). Before the LGN forwards the pulses to V1 of the visual cortex (primary) it gauges the range of objects and tags every major object with a velocity tag. These tags predict object movement. The LGN also sends some fibers to V2 and V3. V1 performs edge-detection to understand spatial organization (initially, 40 milliseconds in, focusing on even small spatial and color changes. Then, 100 milliseconds in, upon receiving the translated LGN, V2, and V3 info, also begins focusing on global organization). V1 also creates a bottom-up saliency map to guide attention or gaze shift. V2 both forwards (direct and via pulvinar) pulses to V1 and receives them. Pulvinar is responsible for saccade and visual attention. V2 serves much the same function as V1, however, it also handles illusory contours, determining depth by comparing left and right pulses (2D images), and foreground distinguishment. V2 connects to V1 - V5. V3 helps process 'global motion' (direction and speed) of objects. V3 connects to V1 (weak), V2, and the inferior temporal cortex. V4 recognizes simple shapes, and gets input from V1 (strong), V2, V3, LGN, and pulvinar. V5's outputs include V4 and its surrounding area, and eye-movement motor cortices (frontal eye-field and lateral intraparietal area). V5's functionality is similar to that of the other V's, however, it integrates local object motion into global motion on a complex level. V6 works in conjunction with V5 on motion analysis. V5 analyzes self-motion, whereas V6 analyzes motion of objects relative to the background. V6's primary input is V1, with V5 additions. V6 houses the topographical map for vision. V6 outputs to the region directly around it (V6A). V6A has direct connections to arm-moving cortices, including the premotor cortex. The inferior temporal gyrus recognizes complex shapes, objects, and faces or, in conjunction with the hippocampus, creates new memories. The pretectal area is seven unique nuclei. Anterior, posterior and medial pretectal nuclei inhibit pain (indirectly), aid in REM, and aid the accommodation reflex, respectively. The Edinger-Westphal nucleus moderates pupil dilation and aids (since it provides parasympathetic fibers) in convergence of the eyes and lens adjustment. Nuclei of the optic tract are involved in smooth pursuit eye movement and the accommodation reflex, as well as REM. The suprachiasmatic nucleus is the region of the hypothalamus that halts production of melatonin (indirectly) at first light. Structure[edit] The human eye (horizontal section)The image projected onto the retina is inverted due to the optics of the eye. The eye, especially the retina The optic nerve The optic chiasma The optic tract The lateral geniculate body The optic radiation The visual cortex The visual association cortex. These are components of the visual pathway also called the optic pathway that can be divided into anterior and posterior visual pathways. The anterior visual pathway refers to structures involved in vision before the lateral geniculate nucleus. The posterior visual pathway refers to structures after this point. Eye[edit] Main articles: Eye and Anterior segment of eyeball Light entering the eye is refracted as it passes through the cornea. It then passes through the pupil (controlled by the iris) and is further refracted by the lens. The cornea and lens act together as a compound lens to project an inverted image onto the retina. S. Ramón y Cajal, Structure of the Mammalian Retina, 1900 Retina[edit] Main article: Retina The retina consists of many photoreceptor cells which contain particular protein molecules called opsins. In humans, two types of opsins are involved in conscious vision: rod opsins and cone opsins. (A third type, melanopsin in some retinal ganglion cells (RGC), part of the body clock mechanism, is probably not involved in conscious vision, as these RGC do not project to the lateral geniculate nucleus but to the pretectal olivary nucleus.) An opsin absorbs a photon (a particle of light) and transmits a signal to the cell through a signal transduction pathway, resulting in hyper-polarization of the photoreceptor. Rods and cones differ in function. Rods are found primarily in the periphery of the retina and are used to see at low levels of light. Each human eye contains 120 million rods. Cones are found primarily in the center (or fovea) of the retina. There are three types of cones that differ in the wavelengths of light they absorb; they are usually called short or blue, middle or green, and long or red. Cones mediate day vision and can distinguish color and other features of the visual world at medium and high light levels. Cones are larger and much less numerous than rods (there are 6-7 million of them in each human eye). In the retina, the photoreceptors synapse directly onto bipolar cells, which in turn synapse onto ganglion cells of the outermost layer, which then conduct action potentials to the brain. A significant amount of visual processing arises from the patterns of communication between neurons in the retina. About 130 million photo-receptors absorb light, yet roughly 1.2 million axons of ganglion cells transmit information from the retina to the brain. The processing in the retina includes the formation of center-surround receptive fields of bipolar and ganglion cells in the retina, as well as convergence and divergence from photoreceptor to bipolar cell. In addition, other neurons in the retina, particularly horizontal and amacrine cells, transmit information laterally (from a neuron in one layer to an adjacent neuron in the same layer), resulting in more complex receptive fields that can be either indifferent to color and sensitive to motion or sensitive to color and indifferent to motion. Mechanism of generating visual signals[edit] The retina adapts to change in light through the use of the rods. In the dark, the chromophore retinal has a bent shape called cis-retinal (referring to a cis conformation in one of the double bonds). When light interacts with the retinal, it changes conformation to a straight form called trans-retinal and breaks away from the opsin. This is called bleaching because the purified rhodopsin changes from violet to colorless in the light. At baseline in the dark, the rhodopsin absorbs no light and releases glutamate, which inhibits the bipolar cell. This inhibits the release of neurotransmitters from the bipolar cells to the ganglion cell. When there is light present, glutamate secretion ceases, thus no longer inhibiting the bipolar cell from releasing neurotransmitters to the ganglion cell and therefore an image can be detected. The final result of all this processing is five different populations of ganglion cells that send visual (image-forming and non-image-forming) information to the brain: M cells, with large center-surround receptive fields that are sensitive to depth, indifferent to color, and rapidly adapt to a stimulus; P cells, with smaller center-surround receptive fields that are sensitive to color and shape; K cells, with very large center-only receptive fields that are sensitive to color and indifferent to shape or depth; another population that is intrinsically photosensitive; and a final population that is used for eye movements. A 2006 University of Pennsylvania study calculated the approximate bandwidth of human retinas to be about 8960 kilobits per second, whereas guinea pig retinas transfer at about 875 kilobits. In 2007 Zaidi and co-researchers on both sides of the Atlantic studying patients without rods and cones, discovered that the novel photoreceptive ganglion cell in humans also has a role in conscious and unconscious visual perception. The peak spectral sensitivity was 481 nm. This shows that there are two pathways for vision in the retina – one based on classic photoreceptors (rods and cones) and the other, newly discovered, based on photo-receptive ganglion cells which act as rudimentary visual brightness detectors. Photochemistry[edit] Main article: Visual cycle The functioning of a camera is often compared with the workings of the eye, mostly since both focus light from external objects in the field of view onto a light-sensitive medium. In the case of the camera, this medium is film or an electronic sensor; in the case of the eye, it is an array of visual receptors. With this simple geometrical similarity, based on the laws of optics, the eye functions as a transducer, as does a CCD camera. In the visual system, retinal, technically called retinene1 or "retinaldehyde", is a light-sensitive molecule found in the rods and cones of the retina. Retinal is the fundamental structure involved in the transduction of light into visual signals, i.e. nerve impulses in the ocular system of the central nervous system. In the presence of light, the retinal molecule changes configuration and as a result, a nerve impulse is generated. Optic nerve[edit] Main article: Optic nerve Information flow from the eyes (top), crossing at the optic chiasma, joining left and right eye information in the optic tract, and layering left and right visual stimuli in the lateral geniculate nucleus. V1 in red at bottom of image. (1543 image from Andreas Vesalius' Fabrica) The information about the image via the eye is transmitted to the brain along the optic nerve. Different populations of ganglion cells in the retina send information to the brain through the optic nerve. About 90% of the axons in the optic nerve go to the lateral geniculate nucleus in the thalamus. These axons originate from the M, P, and K ganglion cells in the retina, see above. This parallel processing is important for reconstructing the visual world; each type of information will go through a different route to perception. Another population sends information to the superior colliculus in the midbrain, which assists in controlling eye movements (saccades) as well as other motor responses. A final population of photosensitive ganglion cells, containing melanopsin for photosensitivity, sends information via the retinohypothalamic tract to the pretectum (pupillary reflex), to several structures involved in the control of circadian rhythms and sleep such as the suprachiasmatic nucleus (the biological clock), and to the ventrolateral preoptic nucleus (a region involved in sleep regulation). A recently discovered role for photoreceptive ganglion cells is that they mediate conscious and unconscious vision – acting as rudimentary visual brightness detectors as shown in rodless coneless eyes. Optic chiasm[edit] Main article: Optic chiasm The optic nerves from both eyes meet and cross at the optic chiasm, at the base of the hypothalamus of the brain. At this point, the information coming from both eyes is combined and then splits according to the visual field. The corresponding halves of the field of view (right and left) are sent to the left and right halves of the brain, respectively, to be processed. That is, the right side of primary visual cortex deals with the left half of the field of view from both eyes, and similarly for the left brain. A small region in the center of the field of view is processed redundantly by both halves of the brain. Optic tract[edit] Main article: Optic tract Information from the right visual field (now on the left side of the brain) travels in the left optic tract. Information from the left visual field travels in the right optic tract. Each optic tract terminates in the lateral geniculate nucleus (LGN) in the thalamus. Six layers in the LGN Lateral geniculate nucleus[edit] Main article: Lateral geniculate nucleus The lateral geniculate nucleus (LGN) is a sensory relay nucleus in the thalamus of the brain. The LGN consists of six layers in humans and other primates starting from catarrhines, including cercopithecidae and apes. Layers 1, 4, and 6 correspond to information from the contralateral (crossed) fibers of the nasal retina (temporal visual field); layers 2, 3, and 5 correspond to information from the ipsilateral (uncrossed) fibers of the temporal retina (nasal visual field). Layer one contains M cells, which correspond to the M (magnocellular) cells of the optic nerve of the opposite eye and are concerned with depth or motion. Layers four and six of the LGN also connect to the opposite eye, but to the P cells (color and edges) of the optic nerve. By contrast, layers two, three and five of the LGN connect to the M cells and P (parvocellular) cells of the optic nerve for the same side of the brain as its respective LGN. Spread out, the six layers of the LGN are the area of a credit card and about three times its thickness. The LGN is rolled up into two ellipsoids about the size and shape of two small birds' eggs. In between the six layers are smaller cells that receive information from the K cells (color) in the retina. The neurons of the LGN then relay the visual image to the primary visual cortex (V1) which is located at the back of the brain (posterior end) in the occipital lobe in and close to the calcarine sulcus. The LGN is not just a simple relay station, but it is also a center for processing; it receives reciprocal input from the cortical and subcortical layers and reciprocal innervation from the visual cortex. Scheme of the optic tract with image being decomposed on the way, up to simple cortical cells (simplified) Optic radiation[edit] Main article: Optic radiation The optic radiations, one on each side of the brain, carry information from the thalamic lateral geniculate nucleus to layer 4 of the visual cortex. The P layer neurons of the LGN relay to V1 layer 4C β. The M layer neurons relay to V1 layer 4C α. The K layer neurons in the LGN relay to large neurons called blobs in layers 2 and 3 of V1. There is a direct correspondence from an angular position in the visual field of the eye, all the way through the optic tract to a nerve position in V1 (up to V4, i.e. the primary visual areas. After that, the visual pathway is roughly separated into a ventral and dorsal pathway). Visual cortex[edit] Main article: Visual cortex Visual cortex: V1; V2; V3; V4; V5 (also called MT) The visual cortex is the largest system in the human brain and is responsible for processing the visual image. It lies at the rear of the brain (highlighted in the image), above the cerebellum. The region that receives information directly from the LGN is called the primary visual cortex, (also called V1 and striate cortex). It creates a bottom-up saliency map of the visual field to guide attention or eye gaze to salient visual locations, hence selection of visual input information by attention starts at V1 along the visual pathway. Visual information then flows through a cortical hierarchy. These areas include V2, V3, V4 and area V5/MT (the exact connectivity depends on the species of the animal). These secondary visual areas (collectively termed the extrastriate visual cortex) process a wide variety of visual primitives. Neurons in V1 and V2 respond selectively to bars of specific orientations, or combinations of bars. These are believed to support edge and corner detection. Similarly, basic information about color and motion is processed here. Heider, et al. (2002) have found that neurons involving V1, V2, and V3 can detect stereoscopic illusory contours; they found that stereoscopic stimuli subtending up to 8° can activate these neurons. Visual cortex is active even during resting state fMRI. Visual association cortex[edit] Main article: Two-streams hypothesis As visual information passes forward through the visual hierarchy, the complexity of the neural representations increases. Whereas a V1 neuron may respond selectively to a line segment of a particular orientation in a particular retinotopic location, neurons in the lateral occipital complex respond selectively to complete object (e.g., a figure drawing), and neurons in visual association cortex may respond selectively to human faces, or to a particular object. Along with this increasing complexity of neural representation may come a level of specialization of processing into two distinct pathways: the dorsal stream and the ventral stream (the Two Streams hypothesis, first proposed by Ungerleider and Mishkin in 1982). The dorsal stream, commonly referred to as the "where" stream, is involved in spatial attention (covert and overt), and communicates with regions that control eye movements and hand movements. More recently, this area has been called the "how" stream to emphasize its role in guiding behaviors to spatial locations. The ventral stream, commonly referred to as the "what" stream, is involved in the recognition, identification and categorization of visual stimuli. Intraparietal sulcus (red) However, there is still much debate about the degree of specialization within these two pathways, since they are in fact heavily interconnected. Horace Barlow proposed the efficient coding hypothesis in 1961 as a theoretical model of sensory coding in the brain. Limitations in the applicability of this theory in the primary visual cortex (V1) motivated the V1 Saliency Hypothesis that V1 creates a bottom-up saliency map to guide attention exogenously. With attentional selection as a center stage, vision is seen as composed of encoding, selection, and decoding stages. The default mode network is a network of brain regions that are active when an individual is awake and at rest. The visual system's default mode can be monitored during resting state fMRI: Fox, et al. (2005) have found that "The human brain is intrinsically organized into dynamic, anticorrelated functional networks'", in which the visual system switches from resting state to attention. In the parietal lobe, the lateral and ventral intraparietal cortex are involved in visual attention and saccadic eye movements. These regions are in the Intraparietal sulcus (marked in red in the adjacent image). Development[edit] Infancy[edit] See also: Infant vision Newborn infants have limited color perception. One study found that 74% of newborns can distinguish red, 36% green, 25% yellow, and 14% blue. After one month, performance "improved somewhat." Infant's eyes do not have the ability to accommodate. The pediatricians are able to perform non-verbal testing to assess visual acuity of a newborn, detect nearsightedness and astigmatism, and evaluate the eye teaming and alignment. Visual acuity improves from about 20/400 at birth to approximately 20/25 at 6 months of age. All this is happening because the nerve cells in their retina and brain that control vision are not fully developed. Childhood and adolescence[edit] Depth perception, focus, tracking and other aspects of vision continue to develop throughout early and middle childhood. From recent studies in the United States and Australia there is some evidence that the amount of time school aged children spend outdoors, in natural light, may have some impact on whether they develop myopia. The condition tends to get somewhat worse through childhood and adolescence, but stabilizes in adulthood. More prominent myopia (nearsightedness) and astigmatism are thought to be inherited. Children with this condition may need to wear glasses. Adulthood[edit] Vision is often one of the first senses affected by aging. A number of changes occur with aging: Over time, the lens become yellowed and may eventually become brown, a condition known as brunescence or brunescent cataract. Although many factors contribute to yellowing, lifetime exposure to ultraviolet light and aging are two main causes. The lens becomes less flexible, diminishing the ability to accommodate (presbyopia). While a healthy adult pupil typically has a size range of 2–8 mm, with age the range gets smaller, trending towards a moderately small diameter. On average tear production declines with age. However, there are a number of age-related conditions that can cause excessive tearing. Other functions[edit] Balance[edit] Along with proprioception and vestibular function, the visual system plays an important role in the ability of an individual to control balance and maintain an upright posture. When these three conditions are isolated and balance is tested, it has been found that vision is the most significant contributor to balance, playing a bigger role than either of the two other intrinsic mechanisms. The clarity with which an individual can see his environment, as well as the size of the visual field, the susceptibility of the individual to light and glare, and poor depth perception play important roles in providing a feedback loop to the brain on the body's movement through the environment. Anything that affects any of these variables can have a negative effect on balance and maintaining posture. This effect has been seen in research involving elderly subjects when compared to young controls, in glaucoma patients compared to age matched controls, cataract patients pre and post surgery, and even something as simple as wearing safety goggles. Monocular vision (one eyed vision) has also been shown to negatively impact balance, which was seen in the previously referenced cataract and glaucoma studies, as well as in healthy children and adults. According to Pollock et al. (2010) stroke is the main cause of specific visual impairment, most frequently visual field loss (homonymous hemianopia, a visual field defect). Nevertheless, evidence for the efficacy of cost-effective interventions aimed at these visual field defects is still inconsistent. Clinical significance[edit] Visual pathway lesions From top to bottom: 1. Complete loss of vision, right eye 2. Bitemporal hemianopia 3. Homonymous hemianopsia 4. Quadrantanopia 5&6. Quadrantanopia with macular sparing Proper function of the visual system is required for sensing, processing, and understanding the surrounding environment. Difficulty in sensing, processing and understanding light input has the potential to adversely impact an individual's ability to communicate, learn and effectively complete routine tasks on a daily basis. In children, early diagnosis and treatment of impaired visual system function is an important factor in ensuring that key social, academic and speech/language developmental milestones are met. Cataract is clouding of the lens, which in turn affects vision. Although it may be accompanied by yellowing, clouding and yellowing can occur separately. This is typically a result of ageing, disease, or drug use. Presbyopia is a visual condition that causes farsightedness. The eye's lens becomes too inflexible to accommodate to normal reading distance, focus tending to remain fixed at long distance. Glaucoma is a type of blindness that begins at the edge of the visual field and progresses inward. It may result in tunnel vision. This typically involves the outer layers of the optic nerve, sometimes as a result of buildup of fluid and excessive pressure in the eye. Scotoma is a type of blindness that produces a small blind spot in the visual field typically caused by injury in the primary visual cortex. Homonymous hemianopia is a type of blindness that destroys one entire side of the visual field typically caused by injury in the primary visual cortex. Quadrantanopia is a type of blindness that destroys only a part of the visual field typically caused by partial injury in the primary visual cortex. This is very similar to homonymous hemianopia, but to a lesser degree. Prosopagnosia, or face blindness, is a brain disorder that produces an inability to recognize faces. This disorder often arises after damage to the fusiform face area. Visual agnosia, or visual-form agnosia, is a brain disorder that produces an inability to recognize objects. This disorder often arises after damage to the ventral stream. Other animals[edit] See also: Eye, Vision in birds, Parietal eye, Vision in fish, Arthropod visual system, and Cephalopod eye Different species are able to see different parts of the light spectrum; for example, bees can see into the ultraviolet, while pit vipers can accurately target prey with their pit organs, which are sensitive to infrared radiation. The mantis shrimp possesses arguably the most complex visual system of any species. The eye of the mantis shrimp holds 16 color receptive cones, whereas humans only have three. The variety of cones enables them to perceive an enhanced array of colors as a mechanism for mate selection, avoidance of predators, and detection of prey. Swordfish also possess an impressive visual system. The eye of a swordfish can generate heat to better cope with detecting their prey at depths of 2000 feet. Certain one-celled microorganisms, the warnowiid dinoflagellates have eye-like ocelloids, with analogous structures for the lens and retina of the multi-cellular eye. The armored shell of the chiton Acanthopleura granulata is also covered with hundreds of aragonite crystalline eyes, named ocelli, which can form images. Many fan worms, such as Acromegalomma interruptum which live in tubes on the sea floor of the Great Barrier Reef, have evolved compound eyes on their tentacles, which they use to detect encroaching movement. If movement is detected, the fan worms will rapidly withdraw their tentacles. Bok, et al., have discovered opsins and G proteins in the fan worm's eyes, which were previously only seen in simple ciliary photoreceptors in the brains of some invertebrates, as opposed to the rhabdomeric receptors in the eyes of most invertebrates. Only higher primate Old World (African) monkeys and apes (macaques, apes, orangutans) have the same kind of three-cone photoreceptor color vision humans have, while lower primate New World (South American) monkeys (spider monkeys, squirrel monkeys, cebus monkeys) have a two-cone photoreceptor kind of color vision. Biologists have determined that humans have extremely good vision compared to the overwhelming majority of animals, particularly in daylight, though a few species have better. Other animals such as dogs are thought to rely more on senses other than vision, which in turn may be better developed than in humans. History[edit] In the second half of the 19th century, many motifs of the nervous system were identified such as the neuron doctrine and brain localization, which related to the neuron being the basic unit of the nervous system and functional localisation in the brain, respectively. These would become tenets of the fledgling neuroscience and would support further understanding of the visual system. The notion that the cerebral cortex is divided into functionally distinct cortices now known to be responsible for capacities such as touch (somatosensory cortex), movement (motor cortex), and vision (visual cortex), was first proposed by Franz Joseph Gall in 1810. Evidence for functionally distinct areas of the brain (and, specifically, of the cerebral cortex) mounted throughout the 19th century with discoveries by Paul Broca of the language center (1861), and Gustav Fritsch and Eduard Hitzig of the motor cortex (1871). Based on selective damage to parts of the brain and the functional effects of the resulting lesions, David Ferrier proposed that visual function was localized to the parietal lobe of the brain in 1876. In 1881, Hermann Munk more accurately located vision in the occipital lobe, where the primary visual cortex is now known to be. In 2014, a textbook "Understanding vision: theory, models, and data" illustrates how to link neurobiological data and visual behavior/psychological data through theoretical principles and computational models. See also[edit] Achromatopsia Akinetopsia Apperceptive agnosia Associative visual agnosia Asthenopia Astigmatism Color blindness Echolocation Computer vision Helmholtz–Kohlrausch effect – how color balance affects vision Magnocellular cell Memory-prediction framework Prosopagnosia Scotopic sensitivity syndrome Recovery from blindness Visual agnosia Visual modularity Visual perception Visual processing	biology	84004	https://sv.wikipedia.org/wiki/Syn	Syn	Syn är den del av nervsystemet som gör det möjligt för en organism att se. Den räknas även till människans sinnen. Olika djur har olika synsystem och kan uppfatta ljus av olika våglängder. Människan kan uppfatta ljus mellan 380 och 750 nm vilket brukar kallas synligt ljus. Synen bygger på samverkan mellan en rad organ i kroppen. För att ett skarpt seende skall komma till stånd fordras förutom bildens inträffande på näthinnan, ett klart medium, näthinnans, synnervens och hjärnans integritet, tillräcklig belysning, samt att avståndet till föremålet är tillräckligt stort. Det finns ca 130 miljoner synsinnesceller i ögonen. Historia 1802 postulerade Thomas Young existensen av tre typer av fotoreceptorer i ögat som var känsliga för var och speciella våglängde i det synliga ljusspektrat. Hermann von Helmholtz utvecklade teorin ytterligare 1850 och menade att de tre typerna kunde klassificeras efter de tre färgerna RGB och att ljusstyrkan tolkades av hjärnan som synliga kulörer. Teorin bevisades över ett århundrade senare år 1964 när mätningar på en enda tappcell kunde göras med hjälp av mikrospektrofotopi. Fysikern John Strutt, 3:e baron Rayleigh ställde upp kriterier för vilken vinkel som behövs för optisk upplösning vilken är beroende på ljusets våglängd. Ögat Ögat registrerar elektromagnetisk strålning som bryts av hornhinna och lins och som projiceras på näthinnan (retina) längst bak i ögat. Cellerna där är specialiserade fotoreceptorer och brukar delas in i stavar som registrerar ljusstyrka och tre typer av tappar som registrerar färgerna rött, blått och grönt. Att man inte ser färg i mörker beror på att de färgkänsliga tapparna kräver mycket ljus för att aktiveras. I mörker är det endast stavarna som skickar information till hjärnan och de kan inte "se" färg. Nerver som är fästa på de celler som är sammankopplade med fotoreceptorerna kommer samman till synnerven vid blinda fläcken som är den punkt i ögat där nerverna passerar ut till hjärnan och här finns inga sinnesceller. Den gula fläcken på näthinnan består av enbart tappar och det är på detta område som ljuset ska brytas för att man ska se skarpt med det direkta seendet, fovea. Resten av näthinnan står för det indirekta seendet, och har inte lika stark skärpa då det består av mestadels stavar. Stavarna är kopplade med flera celler vilket gör att upplösningen försämras, tapparna däremot kopplar endast med en cell och kan därför skicka högupplöst information till hjärnan. Ögat kontrolleras av en rad viljestyrda och icke viljestyrda muskler vilket gör att man kan vrida på ögonen och av en ringmuskel som drar ut linsen vilket justerar skärpan. Att man har två ögon ger ett djupseende som består i att hjärnan kan tolka de skillnader som finns i bilderna de olika ögonen förmedlar och gör att man lättare kan bedöma avstånd, speciellt till närliggande föremål. Nervsystemet Synnerven transporterar signaler från ögat till synnervskorsningen (chiasm), som är en korsning där synnerverna korsas. De passerar sedan genom optiska gångar till laterala knäkroppen (lateral geniculate nucleus), en mellanstation på väg mot syncentrum i bakre delen av hjärnbarken. Väl där tolkas synsignalerna. Synfel Brytningsfel Närsynthet Översynthet Astigmatism Ögonsjukdomar Presbyopi (nedsatt ackommodationsförmåga). Grå starr Grön starr Färgblindhet beror ofta på att någon av de tre olika typerna av tappar saknas och är ofta medfött. Blindhet Referenser Noter Externa länkar På engelska Wikipedia finns två artiklar visual system (synsystemet) och visual perception(synuppfattningen) som behandlar synen från olika perspektiv. Sinnesorgan	swedish	0.545248
tree_grow_cut/how-to-manage-tree-suckers.txt	Home About PLANT LIBRARY Blog Employment Contact Back What We Do Planting Instructions Plant Warranty Mulch Calculator Team Home About What We Do Planting Instructions Plant Warranty Mulch Calculator Team PLANT LIBRARY Blog Employment Contact # HOW TO MANAGE TREE SUCKERS * * * During the summer, your trees will bloom with beautiful leaves in the heat. However, hotter weather usually encourages some tree suckers. To maintain your tree's aesthetic, you'll want to stop these tree suckers from growing. Unfortunately, any tree can suffer from developing the growth of tree suckers, which is likely to happen if the tree is injured or under stress! Not to worry if you've never dealt with these suckers, as stopping tree suckers is simple and effective with the right tools and steps! ## What are Tree Suckers? Tree suckers are miniature tree-looking shoots at the bottom of your tree's trunk; they can sprout if your tree is stressed from a type of illness and is exerting energy to grow more branches. Suckers can also happen in grafted trees, where the stem of one plant is fused with the rootstalk of another. When you first see tree suckers developing, it's important to remove suckers and sprouts, especially from fruit trees. If you leave tree suckers to continue to grow on the tree, it can stunt the growth of healthy roots and prolong the growth time of flowers or fruits! ## Suckers on Grafted Trees Suckers can also happen in grafted trees, where the stem of one plant is fused with the rootstalk of another. Suckers can sprout if the base of the stem fails, and the rootstock begins to send out its suckers. Grafts typically fail on smaller ornamental trees , such as crabapples or redbuds , so it's important to keep an eye on your trees and take action as soon as possible to stop tree suckers. ## How to Prune Suckers Pruning is a great solution to maintain your tree's appearance and temporarily stop sucker growth. If you want to stop tree suckers' growth for longer, you need to trim them and then pull tree suckers out of the roots with leather gloves. You can also use a hatchet to get a firmer grip around the sucker to pull them off. Suckers that are difficult to remove may require a saw; simply cut as close to the trunk at the base of the tree as you can. Digging around the sucker is another effective solution if you're having trouble accessing the base, as exposing it will help you prune it at the base easier. Once exposed, you can use pruning shears to cut at the bottom as close as possible to the trunk. Use pruners or a billhook saw to clean up any stubs that remain to ensure your tree's base is nice and tidy. It's vital to remember that pruning a plant while it's actively growing and establishing its root system can stress it out. Try to remove suckers while they're young so that it doesn't impact the tree too much, or save it for early spring while it is still dormant and not actively growing. ### More Pruning Tips * Avoid pruning too much, as over-pruning can encourage the growth of tree suckers, especially when it's a few years old. * To aid wound healing, cut the plant sucker as near the tree as possible, but leave the collar at the point where the tree sucker and the tree connect. * For young sprouts, you don't need to create a clean cut since the wound will heal quickly. You can even rub the sprouts off with your thumb if you catch them early enough. * You can use herbicide to kill the suckers and prevent regrowth, if you have a challenging case on your hands! Just make sure it includes glyphosate and follow the instructions carefully. If you need assistance with stopping tree suckers, please don't hesitate to contact us at Dammann's Garden Company or speak with us in person at our greenhouse. We're happy to help ensure your trees are healthy and thriving this summer! Mattew Dammann June 27, 2022 Dammann's Garden Company Dammann's Garden Company , Indianapolis , gardening tips , gardening , garden center Facebook 0 Twitter LinkedIn 0 Pinterest 0 0 Likes Previous #### THE BEST WAYS TO PREVENT COMMON VEGGIE DISEASES Mattew Dammann July 4, 2022 Dammann's Garden Company Dammann's Garden Company, Indianapolis, gardening tips, gardening, garden center Next #### CREATING A POLLINATOR-FRIENDLY GARDEN Mattew Dammann June 20, 2022 Dammann's Garden Company Dammann's Garden Company, Indianapolis, gardening tips, gardening, garden center ### PRODUCTS & SERVICES Annuals • Trees • Shrubs • Perennials • Houseplants • Delivery & Planting • Mulches & Soils • Fertilizers • Horticulturists • Edibles • Wild Bird • Garden Workshops • Disease & Pest Control • Organics ### HOURS Monday–Saturday: 9am–6pm Sunday: 10am-5pm ### LOCATION 5129 S Emerson Ave. Indianapolis, IN 46237 ### CONTACT [email protected] (317) 786-0799 ### FOLLOW US ON INSTAGRAM Dammann's Garden Company 5129 S Emerson Ave., Indianapolis, IN 46237, United States (317) 786-0799 [email protected] Hours Mon 9am to 6pm Tue 9am to 6pm Wed 9am to 6pm Thu 9am to 6pm Fri 9am to 6pm Sat 9am to 6pm Sun 10am to 5pm Ⓒ Dammann’s Garden Company 2023	biology	873454	https://sv.wikipedia.org/wiki/Tr%C3%A4dv%C3%A5rd	Trädvård	Trädvård eller trädvårdsarbete kallas det arbete som omfattar plantering, kontroll och underhåll av träd, för att de ska hålla sig friska och vara säkra för omgivningen. Det inkluderar även studier om hur träd växer och reaktioner på till exempel miljö och odlingsmetoder. Det läggs mest energi på träd i trädgårdar, parker eller i urbana områden, där träd planteras för behaglighet. En person som har som yrke att arbeta med trädvård kallas arborist och denne arbetar även med att avlägsna träd och stubbar. En arborist använder sig av olika redskap och tekniker för att beskära och fälla träd. Däribland utrustning för att klättra vid beskäring såsom sele och olika sågar. Andra förekommande hjälpmedel är stubbfräs för att avlägsna stubbarna efter fällning och flishugg för bearbetning av träd, kvistar och stockar. Redskapsbärare / kompaktlastare är också ett komplement för trädvårdsentreprenörer då de ska bära stockar, grenar, mata flishuggen eller vid plantering av häckar och träd. Se även Trädbeskärning Naturbruk	swedish	0.758308
tree_grow_cut/Meristem.txt	The meristem is a type of tissue found in plants. It consists of undifferentiated cells (meristematic cells) capable of cell division. Cells in the meristem can develop into all the other tissues and organs that occur in plants. These cells continue to divide until they become differentiated and lose the ability to divide. Differentiated plant cells generally cannot divide or produce cells of a different type. Meristematic cells are undifferentiated or incompletely differentiated. They are totipotent and capable of continued cell division. Division of meristematic cells provides new cells for expansion and differentiation of tissues and the initiation of new organs, providing the basic structure of the plant body. The cells are small, with small vacuoles or none, and protoplasm filling the cell completely. The plastids (chloroplasts or chromoplasts), are undifferentiated, but are present in rudimentary form (proplastids). Meristematic cells are packed closely together without intercellular spaces. The cell wall is a very thin primary cell wall. The term meristem was first used in 1858 by Carl Wilhelm von Nägeli (1817–1891) in his book Beiträge zur Wissenschaftlichen Botanik ("Contributions to Scientific Botany"). It is derived from the Greek word merizein (μερίζειν), meaning to divide, in recognition of its inherent function. There are three types of meristematic tissues: apical (at the tips), intercalary or basal (in the middle), and lateral (at the sides also known as cambium). At the meristem summit, there is a small group of slowly dividing cells, which is commonly called the central zone. Cells of this zone have a stem cell function and are essential for meristem maintenance. The proliferation and growth rates at the meristem summit usually differ considerably from those at the periphery. Primary meristems[edit] Apical meristems give rise to the primary plant body and are responsible for primary growth, or an increase in length or height. Apical meristems may differentiate into three kinds of primary meristem: Protoderm: lies around the outside of the stem and develops into the epidermis. Procambium: lies just inside of the protoderm and develops into primary xylem and primary phloem. It also produces the vascular cambium, and cork cambium, secondary meristems. The cork cambium further differentiates into the phelloderm (to the inside) and the phellem, or cork (to the outside). All three of these layers (cork cambium, phellem, and phelloderm) constitute the periderm. In roots, the procambium can also give rise to the pericycle, which produces lateral roots in eudicots. Ground meristem: Composed of parenchyma, collenchyma and sclerenchyma cells that develop into the cortex and the pith. Secondary meristems[edit] After the primary growth, lateral meristems develop as secondary plant growth. This growth adds to the plant in diameter from the established stem but not all plants exhibit secondary growth. There are two types of secondary meristems: the vascular cambium and the cork cambium. Vascular cambium, which produces secondary xylem and secondary phloem. This is a process that may continue throughout the life of the plant. This is what gives rise to wood in plants. Such plants are called arboraceous. This does not occur in plants that do not go through secondary growth (known as herbaceous plants). Cork cambium, which gives rise to the periderm, which replaces the epidermis. Apical meristems Apical Meristems are the completely undifferentiated (indeterminate) meristems in a plant. These differentiate into three kinds of primary meristems. The primary meristems in turn produce the two secondary meristem types. These secondary meristems are also known as lateral meristems as they are involved in lateral growth. Organisation of an apical meristem (growing tip)Central zonePeripheral zoneMedullary (i.e. central) meristemMedullary tissue There are two types of apical meristem tissue: shoot apical meristem (SAM), which gives rise to organs like the leaves and flowers, and root apical meristem (RAM), which provides the meristematic cells for future root growth. SAM and RAM cells divide rapidly and are considered indeterminate, in that they do not possess any defined end status. In that sense, the meristematic cells are frequently compared to the stem cells in animals, which have an analogous behavior and function. The apical meristems are layered where the number of layers varies according to plant type. In general the outermost layer is called the tunica while the innermost layers are the corpus. In monocots, the tunica determines the physical characteristics of the leaf edge and margin. In dicots, layer two of the corpus determines the characteristics of the edge of the leaf. The corpus and tunica play a critical part of the plant physical appearance as all plant cells are formed from the meristems. Apical meristems are found in two locations: the root and the stem. Some arctic plants have an apical meristem in the lower/middle parts of the plant. It is thought that this kind of meristem evolved because it is advantageous in arctic conditions. Shoot Apical Meristems[edit] Shoot apical meristems of Crassula ovata (left). Fourteen days later, leaves have developed (right). Shoot apical meristems are the source of all above-ground organs, such as leaves and flowers. Cells at the shoot apical meristem summit serve as stem cells to the surrounding peripheral region, where they proliferate rapidly and are incorporated into differentiating leaf or flower primordia. The shoot apical meristem is the site of most of the embryogenesis in flowering plants. Primordia of leaves, sepals, petals, stamens, and ovaries are initiated here at the rate of one every time interval, called a plastochron. It is where the first indications that flower development has been evoked are manifested. One of these indications might be the loss of apical dominance and the release of otherwise dormant cells to develop as auxiliary shoot meristems, in some species in axils of primordia as close as two or three away from the apical dome. The shoot apical meristem consists of four distinct cell groups: Stem cells The immediate daughter cells of the stem cells A subjacent organizing center Founder cells for organ initiation in surrounding regions These four distinct zones are maintained by a complex signalling pathway. In Arabidopsis thaliana, 3 interacting CLAVATA genes are required to regulate the size of the stem cell reservoir in the shoot apical meristem by controlling the rate of cell division. CLV1 and CLV2 are predicted to form a receptor complex (of the LRR receptor-like kinase family) to which CLV3 is a ligand. CLV3 shares some homology with the ESR proteins of maize, with a short 14 amino acid region being conserved between the proteins. Proteins that contain these conserved regions have been grouped into the CLE family of proteins. CLV1 has been shown to interact with several cytoplasmic proteins that are most likely involved in downstream signalling. For example, the CLV complex has been found to be associated with Rho/Rac small GTPase-related proteins. These proteins may act as an intermediate between the CLV complex and a mitogen-activated protein kinase (MAPK), which is often involved in signalling cascades. KAPP is a kinase-associated protein phosphatase that has been shown to interact with CLV1. KAPP is thought to act as a negative regulator of CLV1 by dephosphorylating it. Another important gene in plant meristem maintenance is WUSCHEL (shortened to WUS), which is a target of CLV signaling in addition to positively regulating CLV, thus forming a feedback loop. WUS is expressed in the cells below the stem cells of the meristem and its presence prevents the differentiation of the stem cells. CLV1 acts to promote cellular differentiation by repressing WUS activity outside of the central zone containing the stem cells. The function of WUS in the shoot apical meristem is linked to the phytohormone cytokinin. Cytokinin activates histidine kinases which then phosphorylate histidine phosphotransfer proteins. Subsequently, the phosphate groups are transferred onto two types of Arabidopsis response regulators (ARRs): Type-B ARRS and Type-A ARRs. Type-B ARRs work as transcription factors to activate genes downstream of cytokinin, including A-ARRs. A-ARRs are similar to B-ARRs in structure; however, A-ARRs do not contain the DNA binding domains that B-ARRs have, and which are required to function as transcription factors. Therefore, A-ARRs do not contribute to the activation of transcription, and by competing for phosphates from phosphotransfer proteins, inhibit B-ARRs function. In the SAM, B-ARRs induce the expression of WUS which induces stem cell identity. WUS then suppresses A-ARRs. As a result, B-ARRs are no longer inhibited, causing sustained cytokinin signaling in the center of the shoot apical meristem. Altogether with CLAVATA signaling, this system works as a negative feedback loop. Cytokinin signaling is positively reinforced by WUS to prevent the inhibition of cytokinin signaling, while WUS promotes its own inhibitor in the form of CLV3, which ultimately keeps WUS and cytokinin signaling in check. Root apical meristem[edit] 10x microscope image of root tip with meristemquiescent centercalyptrogen (live rootcap cells)rootcapsloughed off dead rootcap cellsprocambium Unlike the shoot apical meristem, the root apical meristem produces cells in two dimensions. It harbors two pools of stem cells around an organizing center called the quiescent center (QC) cells and together produces most of the cells in an adult root. At its apex, the root meristem is covered by the root cap, which protects and guides its growth trajectory. Cells are continuously sloughed off the outer surface of the root cap. The QC cells are characterized by their low mitotic activity. Evidence suggests that the QC maintains the surrounding stem cells by preventing their differentiation, via signal(s) that are yet to be discovered. This allows a constant supply of new cells in the meristem required for continuous root growth. Recent findings indicate that QC can also act as a reservoir of stem cells to replenish whatever is lost or damaged. Root apical meristem and tissue patterns become established in the embryo in the case of the primary root, and in the new lateral root primordium in the case of secondary roots. Intercalary meristem[edit] In angiosperms, intercalary (sometimes called basal) meristems occur in monocot (in particular, grass) stems at the base of nodes and leaf blades. Horsetails and Welwitschia also exhibit intercalary growth. Intercalary meristems are capable of cell division, and they allow for rapid growth and regrowth of many monocots. Intercalary meristems at the nodes of bamboo allow for rapid stem elongation, while those at the base of most grass leaf blades allow damaged leaves to rapidly regrow. This leaf regrowth in grasses evolved in response to damage by grazing herbivores. Floral meristem[edit] Further information: ABC model of flower development When plants begin flowering, the shoot apical meristem is transformed into an inflorescence meristem, which goes on to produce the floral meristem, which produces the sepals, petals, stamens, and carpels of the flower. In contrast to vegetative apical meristems and some efflorescence meristems, floral meristems cannot continue to grow indefinitely. Their growth is limited to the flower with a particular size and form. The transition from shoot meristem to floral meristem requires floral meristem identity genes, that both specify the floral organs and cause the termination of the production of stem cells. AGAMOUS (AG) is a floral homeotic gene required for floral meristem termination and necessary for proper development of the stamens and carpels. AG is necessary to prevent the conversion of floral meristems to inflorescence shoot meristems, but is identity gene LEAFY (LFY) and WUS and is restricted to the centre of the floral meristem or the inner two whorls. This way floral identity and region specificity is achieved. WUS activates AG by binding to a consensus sequence in the AG's second intron and LFY binds to adjacent recognition sites. Once AG is activated it represses expression of WUS leading to the termination of the meristem. Through the years, scientists have manipulated floral meristems for economic reasons. An example is the mutant tobacco plant "Maryland Mammoth". In 1936, the department of agriculture of Switzerland performed several scientific tests with this plant. "Maryland Mammoth" is peculiar in that it grows much faster than other tobacco plants. Apical dominance[edit] Apical dominance is where one meristem prevents or inhibits the growth of other meristems. As a result, the plant will have one clearly defined main trunk. For example, in trees, the tip of the main trunk bears the dominant shoot meristem. Therefore, the tip of the trunk grows rapidly and is not shadowed by branches. If the dominant meristem is cut off, one or more branch tips will assume dominance. The branch will start growing faster and the new growth will be vertical. Over the years, the branch may begin to look more and more like an extension of the main trunk. Often several branches will exhibit this behavior after the removal of apical meristem, leading to a bushy growth. The mechanism of apical dominance is based on auxins, types of plant growth regulators. These are produced in the apical meristem and transported towards the roots in the cambium. If apical dominance is complete, they prevent any branches from forming as long as the apical meristem is active. If the dominance is incomplete, side branches will develop. Recent investigations into apical dominance and the control of branching have revealed a new plant hormone family termed strigolactones. These compounds were previously known to be involved in seed germination and communication with mycorrhizal fungi and are now shown to be involved in inhibition of branching. Diversity in meristem architectures[edit] The SAM contains a population of stem cells that also produce the lateral meristems while the stem elongates. It turns out that the mechanism of regulation of the stem cell number might be evolutionarily conserved. The CLAVATA gene CLV2 responsible for maintaining the stem cell population in Arabidopsis thaliana is very closely related to the maize gene FASCIATED EAR 2(FEA2) also involved in the same function. Similarly, in rice, the FON1-FON2 system seems to bear a close relationship with the CLV signaling system in Arabidopsis thaliana. These studies suggest that the regulation of stem cell number, identity and differentiation might be an evolutionarily conserved mechanism in monocots, if not in angiosperms. Rice also contains another genetic system distinct from FON1-FON2, that is involved in regulating stem cell number. This example underlines the innovation that goes about in the living world all the time. Role of the KNOX-family genes[edit] Note the long spur of the above flower. Spurs attract pollinators and confer pollinator specificity. (Flower: Linaria dalmatica) Complex leaves of Cardamine hirsuta result from KNOX gene expression Genetic screens have identified genes belonging to the KNOX family in this function. These genes essentially maintain the stem cells in an undifferentiated state. The KNOX family has undergone quite a bit of evolutionary diversification while keeping the overall mechanism more or less similar. Members of the KNOX family have been found in plants as diverse as Arabidopsis thaliana, rice, barley and tomato. KNOX-like genes are also present in some algae, mosses, ferns and gymnosperms. Misexpression of these genes leads to the formation of interesting morphological features. For example, among members of Antirrhineae, only the species of the genus Antirrhinum lack a structure called spur in the floral region. A spur is considered an evolutionary innovation because it defines pollinator specificity and attraction. Researchers carried out transposon mutagenesis in Antirrhinum majus, and saw that some insertions led to formation of spurs that were very similar to the other members of Antirrhineae, indicating that the loss of spur in wild Antirrhinum majus populations could probably be an evolutionary innovation. The KNOX family has also been implicated in leaf shape evolution (See below for a more detailed discussion). One study looked at the pattern of KNOX gene expression in A. thaliana, that has simple leaves and Cardamine hirsuta, a plant having complex leaves. In A. thaliana, the KNOX genes are completely turned off in leaves, but in C.hirsuta, the expression continued, generating complex leaves. Also, it has been proposed that the mechanism of KNOX gene action is conserved across all vascular plants, because there is a tight correlation between KNOX expression and a complex leaf morphology. Indeterminate growth of meristems[edit] Further information: Root nodule Though each plant grows according to a certain set of rules, each new root and shoot meristem can go on growing for as long as it is alive. In many plants, meristematic growth is potentially indeterminate, making the overall shape of the plant not determinate in advance. This is the primary growth. Primary growth leads to lengthening of the plant body and organ formation. All plant organs arise ultimately from cell divisions in the apical meristems, followed by cell expansion and differentiation. Primary growth gives rise to the apical part of many plants. The growth of nitrogen-fixing root nodules on legume plants such as soybean and pea is either determinate or indeterminate. Thus, soybean (or bean and Lotus japonicus) produce determinate nodules (spherical), with a branched vascular system surrounding the central infected zone. Often, Rhizobium-infected cells have only small vacuoles. In contrast, nodules on pea, clovers, and Medicago truncatula are indeterminate, to maintain (at least for some time) an active meristem that yields new cells for Rhizobium infection. Thus zones of maturity exist in the nodule. Infected cells usually possess a large vacuole. The plant vascular system is branched and peripheral. Cloning[edit] Under appropriate conditions, each shoot meristem can develop into a complete, new plant or clone. Such new plants can be grown from shoot cuttings that contain an apical meristem. Root apical meristems are not readily cloned, however. This cloning is called asexual reproduction or vegetative reproduction and is widely practiced in horticulture to mass-produce plants of a desirable genotype. This process known as mericloning, has been shown to reduce or eliminate viruses present in the parent plant in multiple species of plants. Propagating through cuttings is another form of vegetative propagation that initiates root or shoot production from secondary meristematic cambial cells. This explains why basal 'wounding' of shoot-borne cuttings often aids root formation. Induced meristems[edit] Meristems may also be induced in the roots of legumes such as soybean, Lotus japonicus, pea, and Medicago truncatula after infection with soil bacteria commonly called Rhizobia. Cells of the inner or outer cortex in the so-called "window of nodulation" just behind the developing root tip are induced to divide. The critical signal substance is the lipo-oligosaccharide Nod factor, decorated with side groups to allow specificity of interaction. The Nod factor receptor proteins NFR1 and NFR5 were cloned from several legumes including Lotus japonicus, Medicago truncatula and soybean (Glycine max). Regulation of nodule meristems utilizes long-distance regulation known as the autoregulation of nodulation (AON). This process involves a leaf-vascular tissue located LRR receptor kinases (LjHAR1, GmNARK and MtSUNN), CLE peptide signalling, and KAPP interaction, similar to that seen in the CLV1,2,3 system. LjKLAVIER also exhibits a nodule regulation phenotype though it is not yet known how this relates to the other AON receptor kinases. Lateral Meristems[edit] Lateral meristems, the form of secondary plant growth, add growth to the plants in their diameter. This is primarily observed in perennial dicots that survive from year to year. There are two types of lateral meristems: vascular cambium and cork cambium. In vascular cambium, the primary phloem and xylem are produced by the apical meristem. After this initial development, secondary phloem and xylem are produced by the lateral meristem. The two are connected through a thin layer of parenchymal cells which are differentiated into the fascicular cambium. The fascicular cambium divides to create the new secondary phloem and xylem. Following this the cortical parenchyma between vascular cylinders differentiates interfascicular cambium. This process repeats for indeterminate growth. Cork cambium creates a protective covering around the outside of a plant. This occurs after the secondary xylem and phloem has expanded already. Cortical parenchymal cells differentiate into cork cambium near the epidermis which lays down new cells called phelloderm and cork cells. These cork cells are impermeable to water and gases because of a substance called suberin that coats them. See also[edit] Primary growth Secondary growth Stem cell Thallus Tissues	biology	4114105	https://sv.wikipedia.org/wiki/Rhammatophyllum%20flexuosum	Rhammatophyllum flexuosum	Rhammatophyllum flexuosum är en korsblommig växtart som först beskrevs av Karl Heinz Rechinger, och fick sitt nu gällande namn av Al-shehbaz och Oliver Appel. Rhammatophyllum flexuosum ingår i släktet Rhammatophyllum och familjen korsblommiga växter. Inga underarter finns listade i Catalogue of Life. Källor Korsblommiga växter flexuosum	swedish	0.883715
tree_grow_cut/anatomy.cfm.txt	pinterest-circle facebook-circle twitter-circle instagram-circle ss- standard-direct-right ss-standard-cart ss-standard-close ss-standard-exit ss-standard-notebook ss-standard-redirect ss-standard-rows ss-standard- search ss-standard-user delivery-truck arrow-right-line * Our Work ###### Trees In Communities * Community Forests * Community Tree Recovery * Alliance for Community Trees * Energy-Saving Trees * Tree Campus Higher Education * Tree Campus K–12 * Tree Campus Healthcare * Tree City USA * Tree Line USA * Tree Cities of the World ###### Trees In Forests * Reforestation * Arbor Day Carbon * Rain Forest Rescue ###### Conferences * Partners in Community Forestry * Trees & Utilities View all of our work * Get Involved * Corporate Partnerships * Membership * Gift Planning * Celebrate Arbor Day * About Us * Our Impact * Annual Report * Board & Executive Team * Our Commitment to DEI * Careers * Contact Us * Trees * Shop for Trees * Tree Identification * Planting & Care * The Power of Trees * Choosing a Tree * Stories * Shop * Tree Nursery * Trees for Others * Arbor Day Coffee * Give-A-Tree Cards * Apparel * More Products * Arbor Day Farm * Join * Donate track order log in search ###### Trees In Communities * Community Forests * Community Tree Recovery * Alliance for Community Trees * Energy-Saving Trees * Tree Campus Higher Education * Tree Campus K–12 * Tree Campus Healthcare * Tree City USA * Tree Line USA * Tree Cities of the World ###### Trees In Forests * Reforestation * Arbor Day Carbon * Rain Forest Rescue ###### Conferences * Partners in Community Forestry * Trees & Utilities View all of our work Join Donate * Home * Trees * Tree Guide * Anatomy of a Tree #### Tree Guide * Browse Tree Database * Anatomy of a Tree * Tree Classification * Glossary of Tree Terms * Tree Benefit Calculator * References * Tree Health Guide * Get 10 Free Trees * Shop for Trees More in the Tree Guide # Anatomy of a Tree ## Leaves Leaves carry out photosynthesis, making food for the tree and releasing oxygen into the air. And this tells us much about their shapes. For example, the narrow needles of a Douglasfir can expose as much as three acres of chlorophyll surface to the sun. The lobes, leaflets and jagged edges of many broad leaves have their uses, too. They help evaporate the water used in food-building, reduce wind resistance and even provide “drip tips” to shed rain that, left standing, could decay the leaf. ## Branches and Twigs Branches and twigs grow out of the tree trunk and serve as support structures for leaves, flowers and fruit. They also transport materials between the trunk and the leaves. ## Trunk The trunk of a tree is made up of five different layers. 1. The outer bark is the tree's protection from the outside world. Continually renewed from within, it helps keep out moisture in the rain and prevents the tree from losing moisture when the air is dry. It insulates against cold and heat and wards off insect enemies. 2. The inner bark , or “phloem,” is the pipeline through which food is passed to the rest of the tree. It lives for only a short time then dies and turns to cork to become part of the protective outer bark. 3. The cambium cell layer is the growing part of the trunk. It annually produces new bark and new wood in response to hormones that pass down through the phloem with food from the leaves. These hormones, called “auxins,” stimulate growth in cells. Auxins are produced by leaf buds at the ends of branches as soon as they start growing in the spring. 4. Sapwood is the tree's pipeline for water moving up to the leaves. Sapwood is new wood. As newer rings of sapwood are laid down, inner cells lose their vitality and turn to heartwood. 5. Heartwood is the central, supporting pillar of the tree. Although dead, it will not decay or lose strength while the outer layers are intact. A composite of hollow, needlelike cellulose fibers bound together by a chemical glue called lignin, it is in many ways as strong as steel. Set vertically, a 1" x 2" cross section that is 12" long can support twenty tons! ## Roots Contrary to popular belief, tree roots are typically found in the top three feet of the soil. They also expand well beyond the dripline, often occupying an area two to four times the size of the tree crown. A tree’s root system works to absorb water and minerals from the soil, anchor the tree to the ground, and store food reserves for the winter. It is made up of two kinds of roots: large perennial roots and smaller, short-lived feeder roots. ### Get the Latest News and Info Right in Your Inbox By subscribing, you will receive stories illustrating the power of trees, the latest news and updates, and how we can make a positive impact together. Email Address Are you human? Privacy Policy ###### We inspire people to plant, nurture, and celebrate trees. 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Det läggs mest energi på träd i trädgårdar, parker eller i urbana områden, där träd planteras för behaglighet. En person som har som yrke att arbeta med trädvård kallas arborist och denne arbetar även med att avlägsna träd och stubbar. En arborist använder sig av olika redskap och tekniker för att beskära och fälla träd. Däribland utrustning för att klättra vid beskäring såsom sele och olika sågar. Andra förekommande hjälpmedel är stubbfräs för att avlägsna stubbarna efter fällning och flishugg för bearbetning av träd, kvistar och stockar. Redskapsbärare / kompaktlastare är också ett komplement för trädvårdsentreprenörer då de ska bära stockar, grenar, mata flishuggen eller vid plantering av häckar och träd. Se även Trädbeskärning Naturbruk	swedish	0.758308
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How Tree Trunks Are Cut to Produce Wood With Different Appearances and Uses # How Tree Trunks Are Cut to Produce Wood With Different Appearances and Uses * * * * * Save Save this picture! © José Tomás Franco * Written by José Tomás Franco * Published on August 08, 2019 Share Share * Facebook * Twitter * Mail * Pinterest * Whatsapp Or https://www.archdaily.com/894449/how-tree-trunks-are-cut-to-produce-wood-with- different-appearances-and-uses Clipboard "COPY" Copy As wood is one of the most widely-used materials in the world, architects are accustomed to being able to easily obtain sawn wood at a nearby store. However, many of us know little about its manufacturing process and all the operations that determine its appearance, dimensions, and other important aspects of its performance. The lumber we use to build is extracted from the trunks of more than 2000 tree species worldwide, each with different densities and humidity levels . In addition to these factors, the way in which the trunk is cut establishes the functionality and final characteristics of each wood section. Let's review the most-used cuts. ## Parts of a Trunk A trunk is composed mainly of cellulose fibers joined by lignin. From the outside to the inside, we can identify the following parts: * Bark : irregular layer composed of dead cells that protect the inner layers. * Cambium : the layer next to the bark, where new cells are generated that increase trunk diameter each year. * Sapwood : young, clearer and growing wood, with high water content and little lignin. * Heartwood : adult, dark wood, more rigid and hard because of its high lignin content. * Pith : central part of the trunk, very rigid and cohesive, without humidity. Save this picture! © José Tomás Franco When classifying woods for building according to their hardness—for both soft or hardwoods—it's fundamental to define the proportion of Sapwood to Heartwood inside the trunk. Softwoods (from fast-growing trees) are usually cheaper and easier to handle but are less resistant, while hardwoods (extracted from slow- growing trees) typically have greater strength but are more expensive and delicate. The growth rings, which tell us the age of the tree, and the medullary rays, which move the sap along the tree vertically, will also make a difference in the aesthetics and characteristics of the resulting wooden board. ## The Many Ways to Saw a Trunk and Their Results Although these techniques and their denominations may differ depending on the country and the use required, there are three main ways to cut a log into boards: Rift, Quarter and Flat Sawn– and a series of variations that arise from them: ### Rift Sawn This cut is made perpendicular to the growth rings. It keeps the wood grain visible and avoids warping (deformations in the shape of the board) or fissures (longitudinal cracks), but wastes more material than other cut types. Save this picture! © José Tomás Franco ### Quarter Sawn The trunk is cut into quarters, obtaining pieces that are not too prone to warping with a large number of visible rings. Save this picture! © José Tomás Franco ### Flat Sawn/Live Sawn This is a widely used method, although the resulting pieces are not of the best quality since most include a certain percentage of the Sapwood and the Heartwood. The centerpiece that coincides with the core can tend to break, while the remaining pieces are prone to warp and curl. Save this picture! © José Tomás Franco ### Parallel Boards This is similar to the Flat Sawn system, but in this case, pieces of a smaller section are obtained, leaving fewer problems with warping. Save this picture! © José Tomás Franco ### Cantibay Method This method allows for wide boards without major waste, while also eliminating the core of the trunk. Save this picture! © José Tomás Franco ### Quarter Sawn (Alternative Method) The trunk is cut into four quarters to extract pieces of good quality in terms of strength and appearance. Save this picture! © José Tomás Franco ### Whole Piece In this case, the trunk is used to its maximum potential, eliminating the bark to obtain a single square log. Save this picture! © José Tomás Franco ### Cross Cut This cut focuses on obtaining very resistant pieces, using the heartwood of the trunk to the full. From the remaining sapwood, smaller pieces are cut. Save this picture! © José Tomás Franco ### Interlocked Cut The boards intersecting the core of the trunk are cut first. The remaining wood provides boards that are thinner but quite resistant to deformation. Save this picture! © José Tomás Franco ## Deformations When wood—which has a high moisture content as it grows—dries, different contractions occur depending on the cut made and the resulting arrangement of the growth rings. Although this varies in different species, the deformation is always greater in the direction tangential to the rings than in the radial direction. Save this picture! © José Tomás Franco Check all the wood projects published on our site here. This article was originally published on May 21, 2018. Share Share * Facebook * Twitter * Mail * Pinterest * Whatsapp Or https://www.archdaily.com/894449/how-tree-trunks-are-cut-to-produce-wood-with- different-appearances-and-uses Clipboard "COPY" Copy About this author José Tomás Franco Author ••• ## #Tags News Articles Sustainability Lumber Wood Materials Cite: Franco, José Tomás. "How Tree Trunks Are Cut to Produce Wood With Different Appearances and Uses" 08 Aug 2019. ArchDaily . Accessed . <https://www.archdaily.com/894449/how-tree-trunks-are-cut-to-produce-wood- with-different-appearances-and-uses> ISSN 0719-8884 * * * * * * * * * * * * ## Top #Tags * Sustainability * Technology * Materials * Metaverse * * * * * * * * * * * * Save ## 想阅读文章的中文版本吗? ### 如何切割树干，产生不同外观和用途的木材？是否翻译成中文现有为你所在地区特制的网站？想浏览ArchDaily中国吗? Take me there » ✖ ### You've started following your first account! ### Did you know? You'll now receive updates based on what you follow! Personalize your stream and start following your favorite authors, offices and users. Go to my stream * * * * * * * * * * * * * * * ## Top #Tags * Sustainability * Technology * Materials * Metaverse * * * * * * * * * * * *	biology	861250	https://da.wikipedia.org/wiki/Stillads	Stillads	Et stillads er en midlertidig arbejdsplatform eller ophængskonstruktion. Moderne stilladser er baseret på modulsystemer som kan bygges i flere etager og sektioner ved siden af hinanden. Ofte bliver stilladser forankret til objektet som stilladset er opstillet ved for styrket stabilitet. Stilladser bruges både ved opførsel af nye bygninger og ved renovering som eksempelvis facade, vindueer eller tag. I dag består stilladser typisk af rammer i aluminiumsrør eller stålrør i standardiserede længder og med gribeordninger og låseanordninger i hver ende for sammenføjning, stabilisering og udvidelse. Gulvene er gerne standardiserede moduler i aluminiumsprofiler og/eller vandfaste træplader med anordninger til at sikre forankring til stilladsets ramme. Alt efter nationen er der forskellige krav til stilladser. I Danmark skal de fastgøres, og der skal være knæ og fodlister, der både sikrer arbejderne fra at falde ud, og forbipasserende mod værktøj der bliver sparket ned. I andre lande er kravene løsere og i Asien bruges stilladser af bambus i stor udstrækning. Galleri Eksterne henvisninger Illustrated Formwork and Temporary Work Glossary New York City Scaffolding Regulations PDF (shows nine types of scaffolding) OSHA Publication 3150, A Guide to Scaffold Use in the Construction Industry OSHA scaffold types illustrated Illustrations of many kinds of scaffolding Byggeteknik Stiger	danish	0.896252
butterflies_stage/Holometabolism.txt	Holometabolism, also called complete metamorphosis, is a form of insect development which includes four life stages: egg, larva, pupa, and imago (or adult). Holometabolism is a synapomorphic trait of all insects in the superorder Holometabola. Immature stages of holometabolous insects are very different from the mature stage. In some species the holometabolous life cycle prevents larvae from competing with adults because they inhabit different ecological niches. The morphology and behavior of each stage are adapted for different activities. For example, larval traits maximize feeding, growth, and development, while adult traits enable dispersal, mating, and egg laying. Some species of holometabolous insects protect and feed their offspring. Other insect developmental strategies include ametabolism and hemimetabolism. Developmental stages[edit] There are four general developmental stages, each with its own morphology and function. Various insect eggs. Egg[edit] The first stage of the insect life cycle is the egg, or embryo, for all developmental strategies. The egg begins as a single cell which divides and develops into the larval form before hatching. Some insects reproduce by parthenogenesis or may be haplodiploid, and produce viable eggs without fertilization. The egg stage in most insects is very short, only a few days. However, insects may hibernate, or undergo diapause in the egg stage to avoid extreme conditions, in which case this stage can last several months. The eggs of some types of insects, such as tsetse flies, or aphids (which are hemimetabolous), hatch before they are laid. Scarabaeiform larva and exarate pupae of a rhinoceros beetle. Larva[edit] The second stage of the holometabolous life cycle is the larva (plural: larvae). Many adult insects lay their eggs directly onto a food source so the larvae may begin eating as soon as they hatch. Larvae never possess wings or wing buds, and have simple rather than compound eyes. In most species, the larval stage is mobile and worm-like in form. Larvae can be classified by their body type: Elateriform: wireworm-like, as in the beetle family Elateridae. Eruciform: caterpillar-like, as in the Lepidoptera and Symphyta. Some that lack legs, such as the larvae of Nematoceran flies such as mosquitoes, are called apodous eruciform. Scarabaeiform: grub-like, with a head-capsule, as in the beetle family Scarabaeidae. Vermiform: maggot-like, as in most species of Brachyceran flies. Campodeiform: similar to members of the genus Campodea, elongated, more or less straight, flattened, and active, with functional legs. The larval stage is variously adapted to gaining and accumulating the materials and energy necessary for growth and metamorphosis. Most holometabolous insects pass through several larval stages, or instars, as they grow and develop. The larva must moult to pass from each larval stage. These stages may look very similar and differ mostly in size, or may differ in many characteristics including, behavior, color, hairs, and spines, and even number of legs. Differences between larval stages are especially pronounced in insects with hypermetamorphosis. It is not uncommon that larval tissue that is broken down during metamorphosis increase in size by cell enlargement, while cells and tissues that will turn into imago grows by an increase in numbers. Prepupa[edit] Main article: Prepupa Some insects, including species of Coleoptera, Diptera and Hymenoptera, have a prepupa stage after the larva stage and before the pupa stage. This is similar in shape to the larva and can still move around, but it does not feed. The flies of superfamily Hippoboscoidea are unusual in that a larva develops inside its mother and is born in the prepupa stage, whereupon it immediately progresses to the pupa stage. If looking at only the time spent outside the mother, then the first stage of the life cycle in Hippoboscoidea would be the prepupa. Rhopalomyia solidaginis, pupa and emerging adult. Pupa[edit] Main article: Pupa To enter the third stage of homometabolous development, the larva undergoes metamorphosis into a pupa. The pupa is a quiescent, non-feeding developmental stage. Most pupae move very little, although the pupae of some species, such as mosquitoes, are mobile. In preparation for pupation, the larvae of many species seek protected sites or construct a protective cocoon of silk or other material, such as its own accumulated feces. Some insects undergo diapause as pupa. In this stage, the insect's physiology and functional structure, both internal and external, change drastically. Pupae can be classified into three types: obtect, exarate, and coarctate. Obtect pupae are compact, with the legs and other appendages enclosed, such as a butterfly chrysalis. Exarate pupae have their legs and other appendages free and extended. Coarctate pupae develop inside the larval skin. Imago[edit] The final stage of holometabolous insect development is the adult, or imago. Most adult insects have wings (excepting where secondarily lost) and functioning reproductive organs. Most adult insects grow very little after eclosion from the pupa. Some adult insects do not feed at all, and focus entirely on mating and reproduction. Some adult insects are postmitotic at adult emergence, with dividing cells restricted to specific organs. Cyrtodiopsis dalmanni is one such species, that does feed in the adult stage but does not grow in size. Nutrition is utilized in adults for growth of the internal reproductive structures. Evolutionary context of holometabolan development[edit] Around 45% to 60% of all known living species are holometabolan insects. Juveniles and adult forms of holometabolan insects often occupy different ecological niches, exploiting different resources. This fact is considered a key driver in the unusual evolutionary diversification of form and physiology within this group. According to the latest phylogenetic reconstructions, holometabolan insects are monophyletic, which suggests that the evolutionary innovation of complete metamorphosis occurred only once. Paleontological evidence shows that the first winged insects appeared in the Paleozoic. Carboniferous fossil samples (approximately 350 Ma) already display a remarkable diversity of species with functional wings. These fossil remains show that the primitive Apterygota, and the ancient winged insects were ametabolous (completely lacking metamorphosis). By the end of the Carboniferous, and into the Permian (approximately 300 Ma), most pterygotes had post-embryonic development which included separated nymphal and adult stages, which shows that hemimetaboly had already evolved. The earliest known fossil insects that can be considered holometabolan appear in the Permian strata (approximately 280 Ma). Phylogenetic studies also show that the sister group of Holometabola is Paraneoptera, which includes hemimetabolan species and a number of neometabolan groups. The most parsimonious evolutionary hypothesis is that holometabolans originated from hemimetabolan ancestors. Theories on the origin of holometabolan metamorphosis[edit] The origin of complete metamorphosis in insects has been the subject of a long lasting, and, at times, fierce debate. One of the first theories proposed was one by William Harvey in 1651. Harvey suggested that the nutrients contained within the insect egg are so scarce that there was selection for the embryo to be forced to hatch before the completion of development. During the post-hatch larval life, the "desembryonized" animal would accumulate resources from the external environment and reach the pupal stage, which Harvey viewed as the perfect egg form. However, Jan Swammerdam conducted a dissection study and showed that pupal forms are not egg-like, but instead more of a transitional stage between larvae and adult. In 1883, John Lubbock revitalized Harvey's hypothesis and argued that the origin and evolution of holometabolan development can be explained by the precocious eclosion of the embryo. Hemimetabolan species, whose larvae look like the adult, have an embryo that completes all developmental stages (namely: "protopod", "polipod", and "oligopod" stages) inside the eggshell. Holometabolan species instead have vermiform larvae and a pupal stage after incomplete development and hatching. The debate continued through the twentieth century, with some authors (like Charles Pérez in 1902) claiming the precocious eclosion theory outlandish, Antonio Berlese reestablishing it as the leading theory in 1913, and Augustus Daniel Imms disseminating it widely among Anglo-Saxon readers from 1925 (see Wigglesworth 1954 for review). One of the most contentious aspects of the precocious eclosion theory that fueled further debate in the field of evolution and development was the proposal that the hemimetabolan nymphal stages are equivalent to the holometabolan pupal stage. Critics of this theory (most notably H. E. Hinton) argue that post-embryonic development in hemimetabolans and holometabolans are equivalent, and rather the last nymphal instar stage of hemimetabolans would be homologous to the holometabolan pupae. More modern opinions still oscillate between these two conceptions of the hemi- to holometabolan evolutionary trend. J.W. Truman and L.M. Riddiford, in 1999, revitalized the precocious eclosion theory with a focus on endocrine control of metamorphosis. They postulated that hemimetabolan species hatch after three embryonic "moults" into a nymphal form similar to the adult, whereas holometabolan species hatch after only two embryonic 'moults' into vermiform larvae that are very different from the adult. In 2005, however, B. Konopová and J. Zrzavý reported ultrastructural studies across a wide range of hemimetabolan and holometabolan species and showed that the embryo of all species in both groups produce three cuticular depositions. The only exception was the Diptera Cyclorrhapha (unranked taxon of "high" Dipterans, within the infraorder Muscomorpha, which includes the highly studied Drosophila melanogaster) which has two embryonic cuticles, most likely due to secondary loss of the third. Critics of the precocious eclosion theory also argue that the larval forms of holometabolans are very often more specialized than those of hemimetabolans. X. Belles illustrates that the maggot of a fruitfly "cannot be envisaged as a vermiform and apodous (legless) creature that hatched in an early embryonic stage." It is in fact extremely specialized: for example, the cardiostipes and dististipes of the mouth are fused, as in some mosquitoes, and these parts are also fused to the mandibles and thus form the typical mouth hooks of fly larvae. Maggots are also secondarily, and not primitively, apodous. They are more derived and specialized than the cockroach nymph, a comparable and characteristic hemimetabolan example. More recently, an increased focus on the hormonal control of insect metamorphosis has helped resolve some of the evolutionary links between hemi- and holometabolan groups. In particular, the orchestration of the juvenile hormone (JH) and ecdysteroids in molting and metamorphosis processes has received much attention. The molecular pathway for metamorphosis is now well described: periodic pulses of ecdysteroids induce molting to another immature instar (nymphal in hemimetabolan and larval in holometabolan species) in the presence of JH, but the programmed cessation of JH synthesis in instars of a threshold size leads to ecdysteroid secretion inducing metamorphosis. Experimental studies show that, with the exception of higher Diptera, treatment of the final instar stage with JH causes an additional immature molt and repetition of that stage. The increased understanding of the hormonal pathway involved in metamorphosis enabled direct comparison between hemimetabolan and holometabolan development. Most notably, the transcription factor Krüppel homolog 1 (Kr-h1) which is another important antimetamorphic transducer of the JH pathway (initially demonstrated in D. melanogaster and in the beetle Tribolium castaneum) has been used to compare hemimetabolan and holometabolan metamorphosis. Namely, the Krüppel homolog 1 discovered in the cockroach Blattella germanica (a representative hemimatabolan species), "BgKr-h1", was shown to be extremely similar to orthologues in other insects from holometabolan orders. Compared to many other sequences, the level of conservation is high, even between B. germanica and D. melanogaster, a highly derived holometabolan species. The conservation is especially high in the C2H2 Zn finger domain of the homologous transducer, which is the most complex binding site. This high degree of conservation of the C2H2 Zn finger domain in all studied species suggests that the Kr-h1 transducer function, an important part of the metamorphic process, might have been generally conserved across the entire class Insecta. In 2009, a retired British planktologist, Donald I. Williamson, published a controversial paper in the journal Proceedings of the National Academy of Sciences (via Academy member Lynn Margulis through a unique submission route in PNAS that allowed members to peer review manuscripts submitted by colleagues), wherein Williamson claimed that the caterpillar larval form originated from velvet worms through hybridogenesis with other organisms, giving rising to holometabolan species. This paper was met with severe criticism, and spurred a heated debate in the literature. Orders[edit] The holometabolous insect orders are: Coleoptera – Beetles Diptera – Flies Hymenoptera – Ants, bees, sawflies, and wasps Lepidoptera – Butterflies and moths Mecoptera – Scorpionflies Megaloptera – Alderflies, dobsonflies, and fishflies Miomoptera (extinct) Neuroptera – Lacewings, antlions, etc. Protodiptera (extinct) Raphidioptera – Snakeflies Siphonaptera – Fleas Strepsiptera – Twisted-winged parasites Trichoptera – Caddisflies See also[edit] Hypermetamorphosis Metamorphosis	biology	998	https://da.wikipedia.org/wiki/Art	Art	Arten (species, forkortet sp., flertal: spp.) er den grundlæggende systematiske enhed inden for biologien. Arten defineres ofte som en naturlig gruppe af populationer, hvor udveksling af gener finder sted (eller kan finde sted) og som i forhold til forplantning er isoleret fra andre grupper. Det vil sige at kun individer inden for samme art kan parre sig og få forplantningsdygtigt afkom. Dette kaldes det biologiske artsbegreb. For organismer, der formerer sig ukønnet eller ved selvbestøvning, må arter afgrænses ud fra ligheder og forskelle mellem forskellige individer. Nogle dyrearter kan i fangenskab hybridisere og få fertilt afkom, men da dette ikke vil ske i naturen, selv om de mødes her, betragtes de som forskellige arter. Eksempel To heste kan parre sig og få et føl, der igen kan få føl med andre heste – hestene tilhører derfor samme art. En hest og et æsel kan også parre sig og deres unger kaldes enten muldyr eller mulæsel, afhængig af hvem der er moren, men muldyret eller mulæselet kan (normalt) ikke få unger, da de oftest er sterile. Af den grund regnes hest og æsel som to forskellige arter. Det samme princip gælder også for planterne. Denne naturskabte afgrænsning mellem to arter kaldes en artsbarriere. Den kan af og til gennembrydes, når ellers sterile krydsninger spontant eller kunstigt får gennemført en kromosomfordobling. Se f.eks. Vadegræs (Spartina pectinata). Arter over for hybrider Man kan dog godt komme ud for, at arter kan krydses og får blandet afkom, men hybriden vil kun kunne bestå på steder, hvor ingen af forældrearterne kan klare sig. Dette er et særligt udpræget problem med Rododendron (Rhododendron) og Tjørn (Crataegus), fordi disse slægter breder sig voldsomt efter skovbrand eller stormfald. Da hybriderne bliver frugtbare i en yngre alder end arterne, kan de dominere i en periode, men når skoven lukker sig, så fortrænges hybriderne og kun de specialiserede arter kan overleve i skovens dybe skygge eller ude i lyset i sumpe, på ur og i kalksten, m.m. Flere artsbegreber Fordi det biologiske artsbegreb kan være besværligt at anvende i praksis, er der efterhånden skabt en række andre artsbegreber: Morfologisk artsbegreb Arterne adskiller sig fra hinanden ved deres bygning. Dette begreb er blevet meget anvendt gennem tiden. Økologisk artsbegreb Definerer en art som en gruppe af organismer, der udfylder samme niche. Krydsninger mellem to nærtstående arter vil ikke være optimalt tilpasset til forældrearternes nicher og vil ikke klare sig i konkurrencen. Evolutionære artsbegreb Også kaldet det kladistiske eller fylogenetiske artsbegreb. Naturen er dynamisk, ikke statisk - alle arter ændrer sig med tiden og bliver, hvis de ikke uddør som følge af konkurrence, naturkatastrofer m.v., til én eller flere nye arter. Det evolutionære artsbegreb minder om det biologiske, men inddrager tidsdimensionen, det vil sige at en art udvikler sig over tid og at nye arter opstår ved artsdannelse. Individer der fylogenetisk har samme stamfader tilhører samme art. Pluralistisk artsbegreb En art er et samfund af populationer, der formerer sig og lever inden for en bestemt niche i naturen. Se også Systematik Evolutionsteori Kilder Lars Skipper: Hvad er en art? Citat: "...Arten er den eneste [klassifikations-kategori] der eksisterer i virkeligheden, alle andre (slægter, familier, ordener m.v.) er indført for overskuelighedens skyld..." Eksterne henvisninger 2003-12-31, ScienceDaily: Working On The 'Porsche Of Its Time': New Model For Species Determination Offered Citat: "...two species of dinosaur that are members of the same genera varied from each other by just 2.2 percent. Translation of the percentage into an actual number results in an average of just three skeletal differences out of the total 338 bones in the body. Amazingly, 58 percent of these differences occurred in the skull alone. "This is a lot less variation than I'd expected," said Novak..." 2003-08-08, ScienceDaily: Cross-species Mating May Be Evolutionarily Important And Lead To Rapid Change, Say Indiana University Researchers Citat: "...the sudden mixing of closely related species may occasionally provide the energy to impel rapid evolutionary change..." 2004-01-09 ScienceDaily: Mayo Researchers Observe Genetic Fusion Of Human, Animal Cells; May Help Explain Origin Of AIDS Citat: "...The researchers have discovered conditions in which pig cells and human cells can fuse together in the body to yield hybrid cells that contain genetic material from both species..."What we found was completely unexpected," says Jeffrey Platt, M.D..." 2000-09-18, ScienceDaily: Scientists Unravel Ancient Evolutionary History Of Photosynthesis Citat: "...gene-swapping was common among ancient bacteria early in evolution..." 2004-06-07, Sciencedaily: Parting Genomes: University Of Arizona Biologists Discover Seeds Of Speciation Citat: "...There's a huge amount of biodiversity out there, and we don't know where it comes from. Evolutionary biologists are excited to figure out what causes what we see out there--the relative forces of selection and drift--whether things are adapting to their environment or variation is random..." 2005-07-05, Sciencedaily: Trees, Vines And Nets -- Microbial Evolution Changes Its Face Citat: "... EBI researchers have changed our view of 4 billion years of microbial evolution...In all, more than 600,000 vertical transfers are observed, coupled with 90,000 gene loss events and approximately 40,000 horizontal gene transfers...A few species, including beneficial nitrogen-fixing soil bacteria, appear to be 'champions'of horizontal gene transfer; "it's entirely possible that apparently harmless organisms are quietly spreading antibiotic resistance under our feet," concludes Christos Ouzounis..." 2005-11-11, Sciencedaily: Lateral Thinking Produces First Map Of Gene Transmission Citat: "...Their results clearly show genetic modification of organisms by lateral transfer is a widespread natural phenomenon, and it can occur even between distantly related organisms... it was assumed that transfer of genes could only be vertical, i.e. from parents to offspring..." Økologi Biologi	danish	0.791178
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(Photo via Videoblocks) The transformation of a caterpillar into a butterfly or moth is one of the more wondrous processes to witness in the natural world, as one creature becomes what is seemingly another creature entirely. We know, though, that caterpillars become butterflies or moths as a normal part of their life cycle. There's nothing mysterious or magical about it; it's simply science in motion. A key part of that transformation is a chrysalis or cocoon, but these two things are not one and the same. Instead, each is a part of the life cycle for either a butterfly or a moth, but not both. To better understand, let's start with a quick look at the life cycle of butterflies and moths. These insects start life as eggs, which are laid by adults. The egg hatches and the insect moves into the larva stage, which for both butterflies and moths takes the form of a caterpillar, according to the [ Academy of Natural Sciences ](https://ansp.org/exhibits/online- exhibits/butterflies/lifecycle/) . The larva then becomes a pupa, which is the transitional stage. After the transition, the adult butterfly or moth emerges. [ WHAT'S THE DIFFERENCE: BUTTERFLY VS. MOTH ](https://www.reconnectwithnature.org/News-Events/The-Buzz/What-s-The- Difference-Butterfly-Vs-Moth) It's this transitional pupal stage where both chrysalises and cocoons are essential for the change into a butterfly or a moth, but only butterflies use a chrysalis and only moths use a cocoon. In the pupal stage, a caterpillar transforms into a butterfly in a chrysalis, while a moth uses a cocoon for its pupal transformation, according to the [ Florida Museum ](https://www.floridamuseum.ufl.edu/discover-butterflies/faq/) . This transformation, called metamorphosis, happens inside a chrysalis for butterflies and inside a cocoon for moths, but chrysalises and cocoons are actually quite different. A chrysalis is an exoskeleton, a hard, smooth covering enveloping the insect inside as it transforms from a caterpillar to a butterfly, according to [ Monarch Joint Venture ](https://monarchjointventure.org/faq/whats-the-difference-between-a- chrysalis-and-a-cocoon) . Moths, on the other hand, spin cocoons from silk, encasing themselves in the silky layer. How long it takes for adult moths and butterflies to emerge from their cocoons and chrysalises respectively varies among species, but it typically takes between five and 21 days. Both chrysalises and cocoons offer protection for the insects as they undergo metamorphosis, and moths' cocoons also provide warmth, the Joint Venture reports. Where we may find them differs, though. Chrysalises are usually found hanging from a structure, while cocoons are typically buried in the ground or in leaf litter or attached to the side of a structure. One thing that butterflies and moths have in common is that both are holometabolous, which means that the insects undergo complete metamorphosis in their four life stages, according to the [ Library of Congress ](https://www.loc.gov/everyday-mysteries/zoology/item/how-can-you-tell-the- difference-between-a-butterfly-and-a-moth/) . Some insects do not undergo complete metamorphosis and instead go through gradual changes in size and form. 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[ Donate to the Friends of the Forest Preserve Foundation ](http://www.willcountynature.org/)	biology	2129580	https://sv.wikipedia.org/wiki/Carpilius%20corallinus	Carpilius corallinus	Carpilius corallinus är en kräftdjursart som först beskrevs av J. F. W. Herbst 1783. Carpilius corallinus ingår i släktet Carpilius och familjen Carpiliidae. Inga underarter finns listade i Catalogue of Life. Bildgalleri Källor Tiofotade kräftdjur corallinus	swedish	1.346544
butterflies_stage/butterflymomentcocoo.txt	Skip to main content * [ Visit ](/visit-info/) * [ Learn ](/learn-discover/) * [ Collections + Research ](/collections-research/) * [ News + Blogs ](/news-blogs/) * [ About + Support ](/about-support/) # [ Florida Museum ](/) * Search Submit Search * [ Visit ](/visit-info/) * [ Learn ](/learn-discover/) * [ Collections + Research ](/collections-research/) * [ News + Blogs ](/news-blogs/) * [ About + Support ](/about-support/) * [ Visit ](/visit/) * [ Events ](/calendar/) * [ Exhibits ](/exhibits/) * * [ Plan Your Visit ](/visit/plan/) * [ Adult Groups ](/groups/) * [ Youth Field Trips ](/field-trips/) * [ Shops + Plant Sale ](/shops/) * * [ Calendar ](/calendar/) * [ Kids + Family Events ](/kids/) * [ Travel Program ](/events/travel-program/) * * [ Limited Time Only ](/exhibits/featured/) * [ Always on Display ](/exhibits/permanent/) * [ Online Exhibits ](/exhibits/online/) Exhibits # Butterfly Rainforest Moment, Cocoon vs. Chrysalis by Ryan Fessenden and Radha Krueger Jul 3, 2020 * [ Exhibits ](/exhibits/) * [ Limited Time Only ](https://www.floridamuseum.ufl.edu/exhibits/featured/) * [ Colorful Dancing Spiders ](https://www.floridamuseum.ufl.edu/exhibits/colorful-dancing-spiders/) * [ Black in Natural History Museums Scavenger Hunt ](https://www.floridamuseum.ufl.edu/exhibits/black-in-nhms/) * [ Always on Display ](https://www.floridamuseum.ufl.edu/exhibits/permanent/) * [ Butterfly Rainforest ](https://www.floridamuseum.ufl.edu/exhibits/butterfly-rainforest/) * [ Canopy Cam ](https://www.floridamuseum.ufl.edu/exhibits/butterfly-rainforest/canopy-cam/) * [ Chrysalis Cam ](https://www.floridamuseum.ufl.edu/exhibits/butterfly-rainforest/chrysalis-cam/) * [ Butterflies of the Rainforest ID Guide ](https://www.floridamuseum.ufl.edu/exhibits/butterfly-rainforest/searchable-id-gallery/) * [ Indoor Butterfly Exhibits ](https://www.floridamuseum.ufl.edu/exhibits/butterfly-exhibits/) * [ Discovery Zone ](https://www.floridamuseum.ufl.edu/exhibits/discovery-zone/) * [ Exploring Our World ](https://www.floridamuseum.ufl.edu/exhibits/exploring-our-world/) * [ Florida Fossils: Evolution of Life and Land ](https://www.floridamuseum.ufl.edu/exhibits/florida-fossils/) * [ South Florida People & Environments ](https://www.floridamuseum.ufl.edu/exhibits/south-florida/) * [ Water Shapes Florida ](https://www.floridamuseum.ufl.edu/exhibits/water-shapes-florida/) * [ Explore Outside ](https://www.floridamuseum.ufl.edu/exhibits/outside/) * [ Florida Wildflower Garden Path ](https://www.floridamuseum.ufl.edu/exhibits/wildflower-garden/) * [ Fossil Plant Garden ](https://www.floridamuseum.ufl.edu/exhibits/fossil-plant-garden/) * [ Coming Soon ](https://www.floridamuseum.ufl.edu/exhibits/coming-soon/) * [ Online Exhibits ](https://www.floridamuseum.ufl.edu/exhibits/online/) * [ Exhibits Blog ](https://www.floridamuseum.ufl.edu/exhibits/experience-exhibits/) * [ Traveling Exhibits Program ](https://www.floridamuseum.ufl.edu/exhibits/lease/) * [ Megalodon: Largest Shark that Ever Lived ](https://www.floridamuseum.ufl.edu/rentmegalodon/) * [ Our Changing Climate: Past and Present ](https://www.floridamuseum.ufl.edu/exhibits/lease/climate-past-present/) * [ Our Changing Climate: Sea Level Rise ](https://www.floridamuseum.ufl.edu/exhibits/lease/climate-sea-level-rise/) * [ Earth’s Forecast: Hurricanes and Climate Change ](https://www.floridamuseum.ufl.edu/exhibits/lease/earths-forecast/) * [ Edible Insects: It’s What’s For Dinner ](https://www.floridamuseum.ufl.edu/exhibits/lease/edible-insects/) * [ Mosquitoes: Friend or Foe? ](https://www.floridamuseum.ufl.edu/exhibits/lease/mosquitoes-friend-or-foe/) Spend a moment in our _[ Butterfly Rainforest ](https://www.floridamuseum.ufl.edu/exhibits/butterfly-rainforest/) _ with Ryan talking about pupa—the stage where caterpillars transform into butterflies and months. Did you know that only moths make cocoons? And some moths don’t even do that! A butterfly caterpillar will become a chrysalis, which is just the insect with a hard exterior. They do not build cocoons of silk and plant matter. Instead they take on colors and shapes that camouflage them in their surroundings. You can see chrysalis and cocoons in our Rearing Lab when you visit. ### Transcript Hello, welcome to the _Butterfly Rainforest_ at the Florida Museum of Natural History. My name is Ryan and today we’ll actually be talking a little bit more about moths then just butterflies. Specifically I want to talk about the misconception of the butterfly cocoon. There is no such thing as a butterfly cocoon. A cocoon is an extra layer of silk and that leaves that a moth will weave around itself before it pupate. This is a moth pupa, the Atlas moth, and it will rest inside of the cocoon. Kind of like a sleeping bag. Just like that. Butterfly pupa by contrast, also called a chrysalis, does not have a cocoon. It does not sit inside a cocoon which is made up of silk and leaves. The butterfly pupae is basically naked as it were, which is why a lot of butterfly pupae tend to look like things blending into their environment like this pipevine swollowtail pupa. Some of them will be green like leaves, some will have a shiny metallic exterior or just have little dots of gold on them like a monarch pupa. There is no such thing as a butterfly cocoon, just a butterfly pupa or a chrysalis. Just to complicate matters a little bit more, there are many moth pupa that do not make cocoons either. This moth pupa is found in the dirt. Many many species of moths will as Kepler’s, burrow into the dirt and pupa instead of taking the time never to make a moth cocoon. We will keep them all hanging for you to see at the _Butterfly Rainforest_ , so we hope you come on out and take a look and enjoy them. Have a great rest of the day. Thank you very much. * * * About the [ _Butterfly Rainforest_ exhibit ](https://www.floridamuseum.ufl.edu/exhibits/butterfly-rainforest/) [ Support the exhibit ](https://www.floridamuseum.ufl.edu/support/inspired- giving/cbs-butterfly-rainforest-endowment/) Video by Ryan Fessenden; Produced by Radha Krueger Posted In: * [ Butterfly Rainforest Moment ](https://www.floridamuseum.ufl.edu/exhibits/blog/topic/butterfly-rainforest-moment/) Tagged: * [ Ryan Fessenden ](https://www.floridamuseum.ufl.edu/exhibits/blog/tag/ryan-fessenden/) ### Recent Posts * [ Behind the Scenes: Florida Museum’s Water Shapes Florida Exhibit Comes to Life ](https://www.floridamuseum.ufl.edu/exhibits/blog/behind-the-scenes-water-shapes-florida/) * [ Winter 2023 in the Butterfly Rainforest ](https://www.floridamuseum.ufl.edu/exhibits/blog/winter-2023-in-the-butterfly-rainforest/) * [ Fall 2023 in the Butterfly Rainforest ](https://www.floridamuseum.ufl.edu/exhibits/blog/fall-2023-in-the-butterfly-rainforest/) * [ Spiders Alive! ](https://www.floridamuseum.ufl.edu/exhibits/blog/past-special-exhibit-spiders-alive-2023/) * [ Florida Oligocene painting by David Miller ](https://www.floridamuseum.ufl.edu/exhibits/blog/florida-oligocene-painting-by-david-miller/) ### Archives Archives Select Month March 2024 January 2024 September 2023 August 2023 July 2023 June 2023 April 2023 March 2023 February 2023 January 2023 December 2022 September 2022 July 2022 June 2022 May 2022 April 2022 March 2022 February 2022 December 2021 September 2021 March 2021 January 2021 October 2020 September 2020 August 2020 July 2020 June 2020 May 2020 April 2020 March 2020 February 2020 January 2020 December 2019 August 2019 May 2019 October 2018 September 2018 May 2018 March 2018 January 2018 October 2017 September 2017 August 2017 July 2017 June 2017 May 2017 April 2017 March 2017 February 2017 January 2017 December 2016 November 2016 October 2016 September 2016 August 2016 July 2016 June 2016 May 2016 April 2016 March 2016 February 2016 September 2015 January 2015 September 2014 January 2014 August 2013 ### Categories * [ Butterfly Rainforest Exhibit ](https://www.floridamuseum.ufl.edu/exhibits/blog/topic/butterfly-rainforest-exhibit/) * [ Butterfly Rainforest Moment ](https://www.floridamuseum.ufl.edu/exhibits/blog/topic/butterfly-rainforest-moment/) * [ Discovery Zone ](https://www.floridamuseum.ufl.edu/exhibits/blog/topic/discovery-zone/) * [ Exhibits News ](https://www.floridamuseum.ufl.edu/exhibits/blog/topic/exhibits-news/) * [ Florida Fossils ](https://www.floridamuseum.ufl.edu/exhibits/blog/topic/florida-fossils/) * [ Indoor Butterfly Exhibit ](https://www.floridamuseum.ufl.edu/exhibits/blog/topic/indoor-butterfly/) * [ South Florida Exhibit ](https://www.floridamuseum.ufl.edu/exhibits/blog/topic/south-florida-exhibit/) * [ Special Exhibit ](https://www.floridamuseum.ufl.edu/exhibits/blog/topic/special-exhibit/) * [ Water Shapes Florida ](https://www.floridamuseum.ufl.edu/exhibits/blog/topic/water-shapes-florida/) #### Exhibits contact info Florida Museum of Natural History Gainesville, FL 32611 352-846-2000 (Exhibits) #### Florida Museum Newsletters [ Subscribe Now ](/subscribe/) #### Museum Info * [ Hours, Tickets + Directions ](/visit/plan/) * [ Staff Directory ](/directory/) #### Legal * [ © Copyright 2024 ](/about/copyright/) * [ Contact the Web Manager ](/contact/) * This page uses [ Google Analytics ](https://analytics.google.com) * [ Google Privacy Policy ](https://www.google.com/policies/privacy/) * [ UF Privacy Policy ](http://privacy.ufl.edu/privacy-policies-and-procedures/onlineinternet-privacy-statement/) * [ Log In ](https://www.floridamuseum.ufl.edu/exhibits/wp-login.php?action=shibboleth) Page Last Updated: 02/01/2023 [ ![Florida Museum of Natural History logo](https://www.floridamuseum.ufl.edu/wp-content/themes/wp-floridamuseum- theme/dist/assets/fm-logo-BvbW_WxB.svg) ](https://www.floridamuseum.ufl.edu/) [ ![University of Florida logo](https://www.floridamuseum.ufl.edu/wp- content/themes/wp-floridamuseum-theme/dist/assets/uf-logo-r4pS3ARA.svg) ](http://www.ufl.edu/) [ ![Facebook logo](https://www.floridamuseum.ufl.edu/wp-content/themes/wp- floridamuseum-theme/dist/assets/facebook-icon-5b7G_cnt.svg) ](http://facebook.com/floridamuseum) [ ![Twitter logo](https://www.floridamuseum.ufl.edu/wp-content/themes/wp-floridamuseum- theme/dist/assets/twitter-icon-HRo0n78r.svg) ](http://twitter.com/floridamuseum) [ ![Instagram logo](https://www.floridamuseum.ufl.edu/wp-content/themes/wp-floridamuseum- theme/dist/assets/instagram-icon-HMGbGoWr.svg) ](http://instagram.com/floridamuseum) [ ![YouTube logo](https://www.floridamuseum.ufl.edu/wp-content/themes/wp-floridamuseum- theme/dist/assets/youtube-icon-OX2RbHuz.svg) ](http://www.youtube.com/user/floridamuseum) [ ![Pinterest logo](https://www.floridamuseum.ufl.edu/wp-content/themes/wp-floridamuseum- theme/dist/assets/pinterest-icon-evrUUZYP.svg) ](http://pinterest.com/floridamuseum) [ ![LinkedIn logo](https://www.floridamuseum.ufl.edu/wp-content/themes/wp-floridamuseum- theme/dist/assets/linkedin-icon-c3R0OZYY.svg) ](https://www.linkedin.com/company/florida-museum-of-natural-history) [ ![Tripadvisor logo](https://www.floridamuseum.ufl.edu/wp-content/themes/wp- floridamuseum-theme/dist/assets/tripadvisor-icon-mMLDjc9i.svg) ](https://www.tripadvisor.com/Attraction_Review-g34242-d126929-Reviews- Florida_Museum_of_Natural_History-Gainesville_Florida.html)	biology	3377576	https://sv.wikipedia.org/wiki/Euceromasia%20floridensis	Euceromasia floridensis	Euceromasia floridensis är en tvåvingeart som beskrevs av Henry J. Reinhard 1957. Euceromasia floridensis ingår i släktet Euceromasia och familjen parasitflugor. Inga underarter finns listade i Catalogue of Life. Källor Parasitflugor floridensis	swedish	1.212027
butterflies_stage/butterflycocoonsmade.txt	Skip to main content Skip to navigation [ ](/) Open main menu Close main menu * [ About ](https://askdruniverse.wsu.edu/about/) * [ Explore ](https://askdruniverse.wsu.edu/explore/) * [ Videos ](https://askdruniverse.wsu.edu/type/video/) * [ Activities ](https://askdruniverse.wsu.edu/activities/) * [ Podcasts ](https://askdruniverse.wsu.edu/podcasts/) Open Search Search for: Close Search [ Washington State University ](https://wsu.edu/) * Search * Contact * Share * [ About ](https://askdruniverse.wsu.edu/about/) * [ Explore ](https://askdruniverse.wsu.edu/explore/) * [ Videos ](https://askdruniverse.wsu.edu/type/video/) * [ Activities ](https://askdruniverse.wsu.edu/activities/) * [ Podcasts ](https://askdruniverse.wsu.edu/podcasts/) * [ facebook ](https://www.facebook.com/WSUPullman) * [ twitter ](https://twitter.com/wsupullman) * [ youtube ](https://www.youtube.com/washingtonstateuniv) * [ Social media at WSU ](https://socialmedia.wsu.edu/) * [ myWSU ](https://portal.wsu.edu/) * [ Access ](https://access.wsu.edu/) * [ Policies ](https://policies.wsu.edu/) * [ © ](https://copyright.wsu.edu) [ Ask Dr. Universe ](https://askdruniverse.wsu.edu/) Posts [ University Communications Network ](https://ucomm.wp.wsu.edu "Go to University Communications Network.") > [ Ask Dr. Universe ](https://askdruniverse.wsu.edu "Go to Ask Dr. Universe.") > [ Plants, Animals, Microbes ](https://askdruniverse.wsu.edu/category/plantsanimalsbugs/ "Go to the Plants, Animals, Microbes category archives.") > What are butterfly cocoons made of? # What are butterfly cocoons made of? — Anabelle, 8, Massachusetts August 24, 2023 [ melissamayer ](https://askdruniverse.wsu.edu/author/melissamayer/ "Posts by melissamayer") Dear Anabelle, When I was a kit, I looked a lot like the adult cat I would become—even though I was smaller and fluffier. But wiggly [ caterpillars ](https://www.youtube.com/watch?v=el_lPd2oFV4) don’t look like butterflies at all. I talked about this with my friend [ Allan Felsot ](https://environment.wsu.edu/allan-felsot/) . He’s an insect scientist at Washington State University. He told me cocoons are mostly silk. But they’re usually made by moths. A butterfly “cocoon” isn’t really a cocoon at all. It’s called a chrysalis. ![A brown silk cocoon on a green leaf](https://s3.wp.wsu.edu/uploads/sites/2332/2023/08/Opisthograptis_luteolata_- _pupating_A_-_03_-_cocoon_done-396x261.jpg) A moth’s cocoon, credit: entomart Both butterflies and moths belong to a big group of insects that go through [ complete metamorphosis ](https://www.youtube.com/watch?v=HpC7zkQlLw4) . They have four life stages: egg, larva, pupa and adult. They go through a massive change to become an adult. That big change happens when the insect is a pupa. That’s like their teenager stage. A moth pupa usually changes inside a silk cocoon. Sometimes people harvest that silk to make fabric. A butterfly pupa might look like a cocoon, but it’s different. “Many butterflies have what we call a naked pupa or chrysalis,” Felsot said. “The wings, mouthparts and antennae are glued to the body, and it’s compressed. But if you poke it, you’ll see it wiggles around.” A butterfly pupa is covered with the same tough skin that you see on any insect. It’s just a temporary, baggy version of that skin called a [ chrysalis ](https://www.youtube.com/watch?v=G8hQU-Zj99g) . The chrysalis is often tethered with silk, so it stays put. ![A mostly green chrysalis hangs from a silk thread. The chrysalis is partly transparent, and the butterfly's wing is visible inside.](https://s3.wp.wsu.edu/uploads/sites/2332/2023/08/caterpillar-5339044_1280-396x264.jpg) A butterfly’s chrysalis Insect silk generally comes from the same organs that make saliva. “There are lots of things that salivary glands do,” Felsot said. “One thing is produce silk proteins. These are in the form of a gel. So, it’s very viscous, and it’s forced out as a drop. But then the insect pulls away from it—maybe they wiggle their head or move their body a little bit—and that spins it into a fiber.” As the gel hits the air and the insect pulls away from it, the silk [ crystallizes ](https://www.youtube.com/watch?v=PgSRAsgrKmg) . The particles in the silk line up in an orderly way. That makes the silk strong. The silks made by different kinds of insects are all a little bit different. Insects use silk for all kinds of things. Some insects like moths wrap silk around their bodies to make a silk cocoon. Some insects use silk like glue to make cases out of stuff they find. ![A caddisfly and its case made of bits of sand and gravel](https://s3.wp.wsu.edu/uploads/sites/2332/2023/08/caddisfly-396x360.jpeg) A caddisfly’s case, credit: NSF One of my favorites is the [ caddisfly ](https://www.youtube.com/watch?v=Z3BHrzDHoYo) . They’re related to butterflies and moths, but their larvae live underwater. Some caddisflies use silk to glue together tiny bits of sand and debris. It forms a little house a larva can live in and carry around. When it’s time to change into an adult, the insect usually seals up the entrance to the case with more silk. Caddisfly silk is so special—sticky, stretchy and waterproof—that scientists want to copy it so they can make better bandages and stitches. Scientists study insect and spider silks to learn how to make all kinds of things. It’s just one more way insects make our lives smooth as silk. Sincerely, Dr. Universe Categorized [ Plants, Animals, Microbes ](https://askdruniverse.wsu.edu/category/plantsanimalsbugs/) Categorized [ Entomology ](https://askdruniverse.wsu.edu/?wsuwp_university_category=entomology) Tagged [ butterflies ](https://askdruniverse.wsu.edu/tag/butterflies/) [ caddisflies ](https://askdruniverse.wsu.edu/tag/caddisflies/) [ chrysalis ](https://askdruniverse.wsu.edu/tag/chrysalis/) [ cocoon ](https://askdruniverse.wsu.edu/tag/cocoon/) [ moths ](https://askdruniverse.wsu.edu/tag/moths/) [ silk ](https://askdruniverse.wsu.edu/tag/silk/) Location [ WSU Tri-Cities ](https://askdruniverse.wsu.edu/?wsuwp_university_location=wsu-tri-cities) « [ Why do owls stay up at night? ](https://askdruniverse.wsu.edu/2023/08/18/owls-stay-night/) [ What makes fireflies light up at night? ](https://askdruniverse.wsu.edu/2023/08/31/makes-fireflies-light-night/) » * [ About ](https://askdruniverse.wsu.edu/about/) * [ Explore ](https://askdruniverse.wsu.edu/explore/) * [ Videos ](https://askdruniverse.wsu.edu/type/video/) * [ Activities ](https://askdruniverse.wsu.edu/activities/) * [ Podcasts ](https://askdruniverse.wsu.edu/podcasts/) [ ![](https://s3.wp.wsu.edu/uploads/sites/2332/2021/10/5296516_tweet_twitter_twitter- logo_icon.png) ](http://twitter.com/askdruniverse) [ ![](https://s3.wp.wsu.edu/uploads/sites/2332/2021/10/5365678_fb_facebook_facebook- logo_icon-792x792.png) ](http://fb.com/askdruniverse) Ask Dr. Universe is a science-education project based out of University Marketing & Communications at Washington State University. © 2022 Washington State University \| [ Copyright ](https://printing.wsu.edu/copyright/) ![](https://s3.wp.wsu.edu/uploads/sites/2332/2021/09/WSU-lockup-horz- rev-396x78.png)	biology	2600227	https://sv.wikipedia.org/wiki/Duolandrevus%20rufus	Duolandrevus rufus	Duolandrevus rufus är en insektsart som beskrevs av Lucien Chopard 1931. Duolandrevus rufus ingår i släktet Duolandrevus och familjen syrsor. Underarter Arten delas in i följande underarter: D. r. rufus D. r. obscurus D. r. pahangensis Källor Syrsor rufus	swedish	1.114973
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There is a range of species available as livestock. Schools can see [ Recommended School Species ](index.php?route=product/category&path=70) . Butterflies and moths are supplied for historic, scientific and identification collections, medical research, for photography and conservation, and even just for their incredible beauty and natural history interest. Read about the History of Worldwide Butterflies [ HERE ](https://www.wwb.co.uk/index.php?route=information/information&information_id=4) [ . ](https://www.wwb.co.uk/index.php?route=information/information&information_id=4) To send a GIFT CERTIFICATE Click [ here ](https://www.wwb.co.uk/index.php?route=checkout/voucher) ====================== --- Welcome to the WWB Website ENQUIRING ABOUT AN ORDER? Before you email, please check the Availability showing for the species. Check your Order History for a note on your account. Click on View Item . This should answer your query. If you do enquire, please quote the ORDER NUMBER and SPECIES If you wish to edit your order, click on Shopping Cart where you can change the quantities or remove an item. It is essential to click the blue circular arrow ikon after making a change on an item, which updates the calculations. Then proceed to Checkout. If your order is not going through at checkout, you are then with PayPal, not on the WWB website, it sometimes helps to try an alternative valid card, otherwise, you can select to pay by PayPal instead of a card. When paying, y ou are on the payment handler's site, not WWB. if you see a message Authentication required it means that your card is not being accepted. You can try another card. Login to My Account to follow availability of booked items. You can see your order history, Store Credits and check on dispatch. Booked species may have an update note. If none please check the species text on the website to see the current availability. Have you received the latest WWB NEWS? To receive WWB NEWS by email in future, please go to your Account and click NEWS Subscribe. It's free. You will be notified about current and coming species, special offers and more. Click [ here ](https://www.wwb.co.uk/index.php?route=ne/show&uid=cm9iZXJ0QGdvb2RkZW4uY29tfDcyNzkzMg==) to see an example of the WWB NEWS. Most items on the website pages have multiple pictures which show when you click the main picure. If you hover the cursor over a picture, arrows appear left or right so you can scroll through the pictures enlarged. You can click any picture to see it enlarged. LIVING BUTTERFLIES and MOTHS. For film shoots, weddings and other events we are sometimes asked for butterflies to release. Foreign species cannot be used for this and we don't supply living adults. You can buy pupae but not to a specific date, so you need to organise the synchronisation of emergence for the particular requirement. Send a GIFT CERTIFICATE To make sure that the recipient gets the greatest benefit, let them choose from the whole WWB website the things they MOST want. This is a wonderful way to mark an event, birthday, anniversary or show appreciation to friends or family, or to encourage a budding interest, even to start a new one. Click [ here ](https://www.wwb.co.uk/index.php?route=checkout/voucher) to select one of the pictures to accompany your Gift. \| Availability: The availability of each species is shown. Orders are booked, and the availability can change. Anything that is immediately available is shown as NOW . If a month or period is shown, and we are at that time, unless the availability is NOW, we must wait until the species is ready to be sent out. As soon as it is, the availability changes to NOW, and dispatch commences. Orders sent internationally are at the risk of the purchaser: When placing an order to be sent internationally, you agree to accept non-arrival, delay or hatching or death of livestock - all risks. We do everything possible to get your order to you safely, by post. Dormant livestock can normally be sent by post, but in hot seasons all livestock is at risk. For European destinations orders can be sent by courier, and arrive in only a few days after dispatch. If this is not shown as the means of sending and you wish to order Express courier, please select Express European courier (XXP) from the main menu. Click on XXP and add this to your order. We cannot send by courier to USA, AUS,NZ, S. Africa and most other countries outside Europe. Even though Express courier costs considerably more: it does not guarantee safe arrival, but usually ensures prompt delivery in fresh condition and perfect health. Time in the Post: Ordered items may come from several different sources, breeders, publishers, manufacturers in different places, even from another country. Most orders are sent by post and arrive with your letters. ** There is no tracking. Please remember that each species has its season, and allow for this, also for the possibility of your order being posted internationally, which can take a week or two to arrive. Orders for European destinations may be sent by Express courier, once the species is available, if it is obligatory because the species develops quickly, or because it is specifically requested. Generally Express courier takes 1-3 days and is the best way to send livestock that requires special handling, however this is not guaranteed and both mail and courier service is sometimes extended, outside anybody's control, due to Covid 19. Orders can be seen on your account Order History. Enquiries about how long delivery will take will not be replied to because the delivery time in the post is inconsistent, and not in anyone's control. Most orders are arriving in good time and good condition. PLEASE BE PATIENT! _Thank you._ \| ![](image/data/ACPcover.jpg) \| \| BEGINNER? If you have not reared butterflies and moths before, please take note of the foodplants your larvae will need. To know how to keep caterpillars, hatch out pupae and care for your livestock we recommend the handbook The All Colour Paperback BUTTERFLIES which is on the Schools Page and in the Book Section. It is packed with information and will help you a great deal. LIVESTOCK If you are a beginner and need information on rearing from small caterpillars, or hatching out pupae, please order the book shown above. INSTRUCTIONS ARE NOT SENT WITH EACH SPECIES, you need to acquire basic skills and this book is a simple way to learn them. Newly hatched or small larvae are too small to be put into a cage or aquarium. If you can put them on growing foodplant, protected with a sleeve, that is ideal. Alternatively keep in a plastic box, lined with absorbent paper, in close confinement with fresh foodplant, and changed daily. Fuller hints on the page for Plastic Rearing Containers. For illustrated instructios see the All Colour Paperback BUTTERFLIES. \| LIVESTOCK ON THE WWB WEBSITE is very wide-ranging. Please scroll down the different sections. There are some very interesting species for the connoisseur and for the beginner. AWAY DATES ON YOUR ACCOUNT please enter dates when you cannot receive livestock. Letting us know by any other means will not apply the dates to the system and will not prevent dispatch of orders when you cannot receive them. NEWS and UPDATES Just go to My Account and click to receive these. RECOMMENDATIONS Breeding stock of 5 or 10 pupae: If the species breeds easily, or you are experienced and if both sexes emerge at about the same time, 5 pupae may well be enough to give you a pairing and fertile eggs. With TEN pupae, the chances of breeding success are considerably improved. Classic species. The WWB website has a very wide range of species from all over the world, including Deathshead Hawkmoth, Swallowtails, wonderful Exotic Butterfly Pupae , tropical giants such as the Atlas Moths and a variety of amazing Moon Moths . The anticipated season for availability is shown for each one. PLEASE SEE FEATURED SPECIES AND CURRENT LIVESTOCK SEE FEATURED SPECIES There are some very unusual species and offers. THERE ARE STAR CLASSIC and RARE SPECIES that are particularly rare and desirable. These include the Purple Emperors and Swallowtails. SEE MARKET STALL Section for a list of SPECIA L OFFERS whilst stocks last! Announcing the new Goodden GemLight SUPER! ![](https://cdn.wwb.co.uk/image/data/0 NEWS HEADERS/GemLight Super Header.jpg) The Goodden GEMLIGHT SUPER is a leap forward in technology, greatly advanced on its predecessor the Goodden GemLight. The new light is more powerful, and has three different emitters, Blue, Green and Ultraviolet, all the most attractive to insects. The combination is a greater attractant than UV alone. No batteries to charge and replace: simply plug into a powerbank. The GemLight Super enables serious moth trapping in remote areas without weighty batteries, cables, a generator or mains supply. Click[ HERE ](https://www.wwb.co.uk/index.php?route=product/product&keyword=SUPER&product_id=6953) to see more. ================ CURRENT LIVESTOCK to see all that is available, and keep checking back. Please visit the WWB website regularly, to see all the other species new to our lists, as they appear CURRENT PUPAE include a number of rarer Hawkmoth species of interest to the Sphingid connoisseur. SEEDS of two rare foodplants are available right now. Milk Parsley _Peucedanum palustre_ is the preferred foodplant of the Swallowtail Butterfly _Papilio machaon._ Sow the seed immediately and it germinates with vigour. The seed does not store for long. Also available now is seed of Great Water Dock _Rumex hydropathalum,_ the preferred foodplant of the Large Copper Butterfly _Lycaena dispar._ ============= For GIFT SUGGESTIONS please click on that section in the menu top left of the Home Page, or click[ here. ](https://www.wwb.co.uk/index.php?route=product/category&path=112) For some years two favourite Silkmoths that were once always available, have become very scarce in captivity. The Indian Moon Moth _Actias selene_ has almost completely disappeared in captive breeding, but eggs will again be available in the coming season. The Chinese Oak Silkmoth _Antheraea pernyi_ has become week and inbred in captivity, but now we have wild silk cocoons direct from China. Cocoons are available immediately, and eggs can be booked for supply from May onwards. SEE CURRENT LIVESTOCK for other eggs and larvae that are available NOW. Worldwide Butterflies NEWS keeps you informed of current livestock changes and availability, and often includes special offers and promotions. PUPAE NEST: At this time, with the new season ahead, it is a good opportunity to set up a practical emerging cage. WWB has devised the PUPAE NEST , which is the most successful way of keeping pupae moist, safe and able to be examined whenever required. The Pupae Nest is suitable for all pupae, but is particularly ideal for pupae that live on or under the ground. Pupae are arranged in depressions in specially formed foam sheets, which keeps the pupae separate, moist, and in hygienic conditions. Please see the Pupae Nest in the section for Plastic Rearing Containers. For the Field Naturalist there is the new Spring Frame Pocket Net. Please see this in the Equipment section of this website. The design is practical, construction rugged, and the net fits nicely in the pocket, but can be deployed in seconds when required. This keeps both hands free for examination and photography, when the net is not in current use. Osier Willow _S. viminalis._ Years ago we planted a stick that was floating down a river in Wiltshire. That was in 1954! It grew - rapidly - producing a wealth of leaves. We tried it as a foodplant and discovered that not only did British species do well on it, but exotic silkmoth larvae as well. An amazing foodplant that grows prodigeously, looks most attractive grown formally in a garden, or in a wild setting. Moonlander Moth Trap and Goodden GemLight. No other trap is so compact and lightweight for travel. The only ultra compact trap and light for travel and sampling insects in remote habitats. Rearing Cages There are cages for travel, small ones for starters, Giant for larger breeding programmes and the range of Pyjama Cages in three sizes. Pyjama Cages are practical in use and one of the most important features is that, a used cage can be renovated to almost new state in only a few minutes. No need to replace netting that is worn or dirty, simply by removing the entire netting cover and replacing with a new or freshly washed one. Sleeves. Sleeving is the most natural method for rearing larvae, proving constantly fresh food, with protection from parasites and predators, and preventing escape. The WWB sleeves uniquely have zip access which is a great convenience and time-saver. Five sizes from small to giant. This RECOMMENDED section is constantly evolving. Please keep visiting the WWB website to see more, and all the other changes and additions. # Worldwide Butterflies - over 50 years of supplying butterflies, moths, livestock, and entomological equipment Featured [ Clouded Yellow Crocea 10 Larvae ](https://www.wwb.co.uk/clouded-yellow- crocea-larvae) [ ![Clouded Yellow Crocea 10 Larvae](https://cdn.wwb.co.uk/image/cache/data/Pieridae/Crocea f open-150x150.jpg) ](https://www.wwb.co.uk/clouded-yellow-crocea-larvae) Larvae are ready for dispatch immediately. Availability: NOW £12.95 [ View Info ](https://www.wwb.co.uk/clouded-yellow-crocea-larvae) Add to Cart [ Emperor Moth pavonia 15 eggs ](https://www.wwb.co.uk/index.php?route=product/product&product_id=6773) [ ![Emperor Moth pavonia 15 eggs ](https://cdn.wwb.co.uk/image/cache/data/Saturniidae/Pavonia large larvae 1970 Sm Adj-150x150.jpg) ](https://www.wwb.co.uk/index.php?route=product/product&product_id=6773) Eggs are now being laid and orders are being sent out. Availability: NOW £12.95 [ View Info ](https://www.wwb.co.uk/index.php?route=product/product&product_id=6773) Add to Cart [ Giant Atlas Moth Attacus atlas 15 eggs ](https://www.wwb.co.uk/giant-atlas- moth-attacus-atlas-15-eggs) [ ![Giant Atlas Moth Attacus atlas 15 eggs](https://cdn.wwb.co.uk/image/cache/data/Saturniidae/Atlas on Nerium 7980 Sm 1-150x150.jpg) ](https://www.wwb.co.uk/giant-atlas-moth-attacus- atlas-15-eggs) Eggs are being laid now and eggs are being shipped immediately. Availability: NOW £15.95 [ View Info ](https://www.wwb.co.uk/giant-atlas-moth-attacus-atlas-15-eggs) Add to Cart [ Chinese Oak Silkmoth Antheraea pernyi Large cocoons fresh from CHINA ](https://www.wwb.co.uk/chinese-oak-silkmoth-a-pernyi-5-cocoons) [ ![Chinese Oak Silkmoth Antheraea pernyi Large cocoons fresh from CHINA](https://cdn.wwb.co.uk/image/cache/data/Saturniidae/Pernyi larva and moth-150x150.jpg) ](https://www.wwb.co.uk/chinese-oak-silkmoth-a- pernyi-5-cocoons) With great difficulty and expense we have fresh cocoons again from China Availability: NOW [ View Info ](https://www.wwb.co.uk/chinese-oak-silkmoth-a-pernyi-5-cocoons) Add to Cart [ Brahmaea tancrei Asian Owl Moth 15 eggs or 10 larvae according to availability ](https://www.wwb.co.uk/index.php?route=product/product&product_id=6472) [ ![Brahmaea tancrei Asian Owl Moth 15 eggs or 10 larvae according to availability](https://cdn.wwb.co.uk/image/cache/data/Saturniidae/Tancrei larva + moth -150x150.jpg) ](https://www.wwb.co.uk/index.php?route=product/product&product_id=6472) Eggs available immediately. Most spectacular larvae and extraordinary moth. Availability: NOW £17.95 [ View Info ](https://www.wwb.co.uk/index.php?route=product/product&product_id=6472) Add to Cart [ FREEDOM CAGE Multipurpose cage for larger breeding projects ](https://www.wwb.co.uk/index.php?route=product/product&product_id=6969) [ ![FREEDOM CAGE Multipurpose cage for larger breeding projects](https://cdn.wwb.co.uk/image/cache/data/Cages/Freedom Cage composite Sm-150x150.jpg) ](https://www.wwb.co.uk/index.php?route=product/product&product_id=6969) A completely new range of cages, including a GIANT that makes a portable flight cage. Availability: NOW [ View Info ](https://www.wwb.co.uk/index.php?route=product/product&product_id=6969) Add to Cart [ Scarlet Tiger Moth dominula 20 eggs ](https://www.wwb.co.uk/index.php?route=product/product&product_id=6839) [ ![Scarlet Tiger Moth dominula 20 eggs](https://cdn.wwb.co.uk/image/cache/data/Moths/Dominula drying 7420 Sm-150x150.jpg) ](https://www.wwb.co.uk/index.php?route=product/product&product_id=6839) Larvae are already pupating. We are taking orders now for eggs next month. Availability: June/July £12.95 [ View Info ](https://www.wwb.co.uk/index.php?route=product/product&product_id=6839) Add to Cart [ Lime Hawk tiliae 15 eggs or 10 larvae according to availability ](https://www.wwb.co.uk/index.php?route=product/product&product_id=6894) [ ![Lime Hawk tiliae 15 eggs or 10 larvae according to availability](https://cdn.wwb.co.uk/image/cache/data/Sphingidae/Tiliae large larva 7673 Sm-150x150.jpg) ](https://www.wwb.co.uk/index.php?route=product/product&product_id=6894) Early eggs immediately available. Availability: NOW £12.50 [ View Info ](https://www.wwb.co.uk/index.php?route=product/product&product_id=6894) Add to Cart [ Marsh Fritillary aurinia 5 pupae ](https://www.wwb.co.uk/index.php?route=product/product&product_id=6361) [ ![Marsh Fritillary aurinia 5 pupae](https://cdn.wwb.co.uk/image/cache/data/Nymphalidae/Aurinia on Dandelion Sm -150x150.jpg) ](https://www.wwb.co.uk/index.php?route=product/product&product_id=6361) Pupae available now. Easy to pair and breed. Availability: NOW £19.00 £14.95 [ View Info ](https://www.wwb.co.uk/index.php?route=product/product&product_id=6361) Add to Cart [ OSIGIAN Mulberry cuttings TEN cuttings ready to propagate immediately. ](https://www.wwb.co.uk/index.php?route=product/product&product_id=6974) [ ![OSIGIAN Mulberry cuttings TEN cuttings ready to propagate immediately.](https://cdn.wwb.co.uk/image/cache/data/Plants/Osigian cuttings A-150x150.jpeg) ](https://www.wwb.co.uk/index.php?route=product/product&product_id=6974) A unique cultivar of Mulberry, not grown anywhere else. Can you help maintain this exceptional tree? Availability: NOW £12.95 [ View Info ](https://www.wwb.co.uk/index.php?route=product/product&product_id=6974) Add to Cart [ Orange Tip Anthocharis cardamines pupae ](https://www.wwb.co.uk/orange-tip- anthocharis-cardamines-pupae) [ ![Orange Tip Anthocharis cardamines pupae](https://cdn.wwb.co.uk/image/cache/data/Pieridae2/Cardamines M on Hesperis Sm-150x150.jpg) ](https://www.wwb.co.uk/orange-tip-anthocharis- cardamines-pupae) Orange Tips are on the wing and this is the time to get them to lay on growing flowerheads. Pupae are ready NOW! Availability: NOW [ View Info ](https://www.wwb.co.uk/orange-tip-anthocharis-cardamines-pupae) Add to Cart [ Brimstone rhamni 10 larvae ](https://www.wwb.co.uk/index.php?route=product/product&product_id=6353) [ ![Brimstone rhamni 10 larvae ](https://cdn.wwb.co.uk/image/cache/data/Pieridae2/Rhamni larva and adult-150x150.jpg) ](https://www.wwb.co.uk/index.php?route=product/product&product_id=6353) Brimstones are already laying, so larvae should be early this season. Availability: Spring 2024 £13.95 [ View Info ](https://www.wwb.co.uk/index.php?route=product/product&product_id=6353) Add to Cart [ Actias dubernardi China 15 eggs or 10 larvae, according to availability. ](https://www.wwb.co.uk/actias-dubernardi-china-15-eggs) [ ![Actias dubernardi China 15 eggs or 10 larvae, according to availability.](https://cdn.wwb.co.uk/image/cache/data/Saturniidae/Dubernardi pair-150x150.jpg) ](https://www.wwb.co.uk/actias-dubernardi-china-15-eggs) Eggs are being sent direct to customers by our European breeder. Magnificent larvae and the most delicate and elegant moths. Availability: May £19.50 [ View Info ](https://www.wwb.co.uk/actias-dubernardi-china-15-eggs) Add to Cart [ Large Copper dispar batavus 10 larvae ](https://www.wwb.co.uk/large-copper- dispar-batavus-10-larvae) [ ![Large Copper dispar batavus 10 larvae](https://cdn.wwb.co.uk/image/cache/data/CopperGroup3_thumb-150x150.jpg) ](https://www.wwb.co.uk/large-copper-dispar-batavus-10-larvae) There is a danger of this species being no longer available. Few captive colonies exist. Can you help nurture a colony? Availability: Spring £25.95 [ View Info ](https://www.wwb.co.uk/large-copper-dispar-batavus-10-larvae) Add to Cart [ Tiger Swallowtail glaucus pupae ](https://www.wwb.co.uk/tiger-swallowtail- glaucus-pupa) [ ![Tiger Swallowtail glaucus pupae ](https://cdn.wwb.co.uk/image/cache/data/Glaucus_thumb-150x150.jpg) ](https://www.wwb.co.uk/tiger-swallowtail-glaucus-pupa) In stock again in good numbers. Breeds well, larvae thrive on Ash and other foodplants. Availability: NOW [ View Info ](https://www.wwb.co.uk/tiger-swallowtail-glaucus-pupa) Add to Cart [ Garden Tiger caja Woolly Bears. 10 Larvae ](https://www.wwb.co.uk/garden- tiger-caja-10-larvae) [ ![Garden Tiger caja Woolly Bears. 10 Larvae](https://cdn.wwb.co.uk/image/cache/data/Moths/Caja curled larvae 6044 Adj-150x150.jpg) ](https://www.wwb.co.uk/garden-tiger-caja-10-larvae) Everybody's favourite Woolly Bear larvae, out of hibernation and growing fast! Offered in 10's and 50's Availability: NOW £12.95 [ View Info ](https://www.wwb.co.uk/garden-tiger-caja-10-larvae) Add to Cart [ Clifden Nonpareil (Blue Underwing) Catocala fraxini SPECIAL PRICE! 30 Eggs for the price of 15 ](https://www.wwb.co.uk/index.php?route=product/product&product_id=6923) [ ![Clifden Nonpareil $Blue Underwing$ Catocala fraxini SPECIAL PRICE! 30 Eggs for the price of 15](https://cdn.wwb.co.uk/image/cache/data/Moths/Fraxini L Sm-150x150.jpg) ](https://www.wwb.co.uk/index.php?route=product/product&product_id=6923) Amazing breeding success has produced so many eggs that there are now huge reductions in price for 30 or even 100! Availability: NOW £14.95 [ View Info ](https://www.wwb.co.uk/index.php?route=product/product&product_id=6923) Add to Cart [ EARLY Peacock Butterfly Inachis io 10 larvae ](https://www.wwb.co.uk/early- peacock-butterfly-inachis-io-10-larvae) [ ![EARLY Peacock Butterfly Inachis io 10 larvae ](https://cdn.wwb.co.uk/image/cache/data/Nymphalidae/Peacock 0743 cropped Adj Sm-150x150.jpg) ](https://www.wwb.co.uk/early-peacock-butterfly-inachis- io-10-larvae) Larvae from May. Prepare potted nettle in advance. Fast growing. Fabulous butterflies! Availability: From May £21.95 [ View Info ](https://www.wwb.co.uk/early-peacock-butterfly-inachis- io-10-larvae) Add to Cart [ EARLY Small Tortoiseshell Aglais urticae 10 larvae SPECIAL PRICE ](https://www.wwb.co.uk/early-small-tortoiseshell-aglais-urticae-larvae) [ ![EARLY Small Tortoiseshell Aglais urticae 10 larvae SPECIAL PRICE](https://cdn.wwb.co.uk/image/cache/data/UrticaeOnBuddleia_thumb-150x150.jpg) ](https://www.wwb.co.uk/early-small-tortoiseshell-aglais-urticae-larvae) Early larvae in April. Prepare potted nettle in advance. Availability: From May £22.95 [ View Info ](https://www.wwb.co.uk/early-small-tortoiseshell-aglais-urticae- larvae) Add to Cart [ Small Eggar Moth Eriogaster lanestris An egg batch 200 - 300 eggs ](https://www.wwb.co.uk/index.php?route=product/product&product_id=6918) [ ![Small Eggar Moth Eriogaster lanestris An egg batch 200 - 300 eggs](https://cdn.wwb.co.uk/image/cache/data/Moths/Lanestris SS + EGGS-150x150.jpg) ](https://www.wwb.co.uk/index.php?route=product/product&product_id=6918) Furry strings of 200 -300 eggs laid on twigs. An opportunity to introduce this species into wild hedgerows and combat their loss through modern hedge manicure! Availability: NOW £29.95 [ View Info ](https://www.wwb.co.uk/index.php?route=product/product&product_id=6918) Add to Cart [ Painted Lady cardui 5 larvae in Pot on Diet ](https://www.wwb.co.uk/painted- lady-cardui--5-larvae-in-pot-on-diet) [ ![Painted Lady cardui 5 larvae in Pot on Diet](https://cdn.wwb.co.uk/image/cache/data/Nymphalidae/Cardui on pot of young larvae-150x150.jpg) ](https://www.wwb.co.uk/painted-lady-cardui-- 5-larvae-in-pot-on-diet) Ideal as a starter for young people. No foodplant to change. Observe development from caterpillar to butterfly without having to clean or feed! Availability: New Orders April 2024 [ View Info ](https://www.wwb.co.uk/painted-lady-cardui--5-larvae-in-pot-on- diet) Add to Cart [ Glanville Fritillary cinxia 10 larvae ](https://www.wwb.co.uk/glanville- fritillary-cinxia-larvae) [ ![Glanville Fritillary cinxia 10 larvae](https://cdn.wwb.co.uk/image/cache/data/Nymphalidae/Cinxia Three larvae on moss 5412 Sm-150x150.jpg) ](https://www.wwb.co.uk/glanville-fritillary- cinxia-larvae) Post hibernation larvae ready now. Feed on Narrow Leaved Plantain. Availability: April 2025 £12.95 [ View Info ](https://www.wwb.co.uk/glanville-fritillary-cinxia-larvae) Add to Cart [ Cinnabar Moth Hipocrita jacobaeae 50 pupae SPECIAL OFFER! ](https://www.wwb.co.uk/index.php?route=product/product&product_id=6966) [ ![Cinnabar Moth Hipocrita jacobaeae 50 pupae SPECIAL OFFER!](https://cdn.wwb.co.uk/image/cache/data/Moths/Cinnabar wings spread 0009 Sm-150x150.jpg) ](https://www.wwb.co.uk/index.php?route=product/product&product_id=6966) This species is much less common than it was. We can help boost populations by releasing where Ragwort grows. Availability: NOW £92.50 £62.95 [ View Info ](https://www.wwb.co.uk/index.php?route=product/product&product_id=6966) Add to Cart [ Oleander Hawk nerii 15 eggs or 10 larvae, according to availability ](https://www.wwb.co.uk/oleander-hawk-nerii-eggs) [ ![Oleander Hawk nerii 15 eggs or 10 larvae, according to availability](https://cdn.wwb.co.uk/image/cache/data/Sphingidae/Nerii 0054 Adj Sm-150x150.jpg) ](https://www.wwb.co.uk/oleander-hawk-nerii-eggs) Breeding has started. Eggs first half of March. Availability: Early 2024 £17.95 [ View Info ](https://www.wwb.co.uk/oleander-hawk-nerii-eggs) Add to Cart [ Deathshead Hawk Atropos 15 Eggs or 10 larvae according to availability ](https://www.wwb.co.uk/index.php?route=product/product&product_id=6379) [ ![Deathshead Hawk Atropos 15 Eggs or 10 larvae according to availability](https://cdn.wwb.co.uk/image/cache/data/Sphingidae/Atropos 2006 + larva Sm-150x150.jpg) ](https://www.wwb.co.uk/index.php?route=product/product&product_id=6379) Breeding for the new season has started! Eggs are being sent out now. Availability: Spring £19.95 [ View Info ](https://www.wwb.co.uk/index.php?route=product/product&product_id=6379) Add to Cart [ Giant Atlas Moth Attacus atlas dormant WINTER cocoons from Thailand ](https://www.wwb.co.uk/giant-atlas-moth-attacus-atlas-cocoons) [ ![Giant Atlas Moth Attacus atlas dormant WINTER cocoons from Thailand](https://cdn.wwb.co.uk/image/cache/data/Saturniidae/Atlas Frankie Sm 9007-150x150.jpg) ](https://www.wwb.co.uk/giant-atlas-moth-attacus-atlas- cocoons) Dormant atlas cocoons have been difficult to obtain but they are available again right now. Keep cold until incubation in spring. Availability: NOW [ View Info ](https://www.wwb.co.uk/giant-atlas-moth-attacus-atlas-cocoons) Add to Cart [ Setting Strips - GLASSINE PAPER on a roll ](https://www.wwb.co.uk/c--- setting-strips---glassine-paper-roll) [ ![Setting Strips - GLASSINE PAPER on a roll](https://cdn.wwb.co.uk/image/cache/data/Ento EQ/Setting tapes A 5597-150x150.jpg) ](https://www.wwb.co.uk/c---setting-strips---glassine-paper- roll) Unavailable for years - now available again. New larger reels. Availability: NOW [ View Info ](https://www.wwb.co.uk/c---setting-strips---glassine-paper-roll) Add to Cart [ CEBALLOSI subspecies of Graellsia isabellae eggs ](https://www.wwb.co.uk/ceballosi-subspecies-of-graellsia-isabellae) [ ![CEBALLOSI subspecies of Graellsia isabellae eggs](https://cdn.wwb.co.uk/image/cache/data/Saturniidae/Isabellae ceballosi female Sm-150x150.jpg) ](https://www.wwb.co.uk/ceballosi-subspecies-of- graellsia-isabellae) A subspecies first described in recent years. Extremely hard to obtain!! Availability: May/June [ View Info ](https://www.wwb.co.uk/ceballosi-subspecies-of-graellsia- isabellae) Add to Cart [ Spanish Moon Moth G isabellae eggs ](https://www.wwb.co.uk/spanish-moon- moth-g-isabellae-eggs) [ ![Spanish Moon Moth G isabellae eggs](https://cdn.wwb.co.uk/image/cache/data/Saturniidae/Isabellae male 1 Sm Adj-150x150.jpg) ](https://www.wwb.co.uk/spanish-moon-moth-g-isabellae-eggs) Considered as perhaps the most beautiful and impressive of European moths. The larvae feed on pine and can be sleeved, with protection against heavy rain. Availability: May/June [ View Info ](https://www.wwb.co.uk/spanish-moon-moth-g-isabellae-eggs) Add to Cart [ Festoon Zerynthia polyxena pupae ](https://www.wwb.co.uk/festoon-zerynthia- polyxena-pupae) [ ![Festoon Zerynthia polyxena pupae ](https://cdn.wwb.co.uk/image/cache/data/Papilionidae/Polyxena on blue-150x150.jpg) ](https://www.wwb.co.uk/festoon-zerynthia-polyxena-pupae) A charming smaller member of the Swallowtail family. Larvae like miniature Birdwing caterpillars. Availability: NOW [ View Info ](https://www.wwb.co.uk/festoon-zerynthia-polyxena-pupae) Add to Cart [ European Swallowtail machaon gorganus pupae ](https://www.wwb.co.uk/european-swallowtail-machaon-gorganus-pupae) [ ![European Swallowtail machaon gorganus pupae ](https://cdn.wwb.co.uk/image/cache/data/Papilionidae/Gorganus 0054 Sm-150x150.jpg) ](https://www.wwb.co.uk/european-swallowtail-machaon-gorganus- pupae) Swallowtail pupae are becoming hard to obtain. We have a stock available at the moment. Availability: Autumn [ View Info ](https://www.wwb.co.uk/european-swallowtail-machaon-gorganus- pupae) Add to Cart [ Yellow-legged Tortoiseshell xanthomelas 10 larvae ](https://www.wwb.co.uk/yellow-legged-tortoiseshell-xanthomelas-10-larvae) [ ![Yellow-legged Tortoiseshell xanthomelas 10 larvae](https://cdn.wwb.co.uk/image/cache/data/Nymphalidae/Xanthomelas5615 Sm-150x150.jpg) ](https://www.wwb.co.uk/yellow-legged-tortoiseshell- xanthomelas-10-larvae) Not available most years. They will be available this year from May. Availability: Spring £29.95 [ View Info ](https://www.wwb.co.uk/yellow-legged-tortoiseshell- xanthomelas-10-larvae) Add to Cart [ Large Tortoiseshell polychloros 10 Larvae ](https://www.wwb.co.uk/large- tortoiseshell-polychloros-larvae) [ ![Large Tortoiseshell polychloros 10 Larvae ](https://cdn.wwb.co.uk/image/cache/data/Polychloros2-150x150.jpg) ](https://www.wwb.co.uk/large-tortoiseshell-polychloros-larvae) Very rare and now may be establishing in Britain. A chance to assist its recovery. Availability: May onwards £24.95 [ View Info ](https://www.wwb.co.uk/large-tortoiseshell-polychloros-larvae) Add to Cart [ Privet Hawk S ligustri Pupae SPECIAL OFFER! ](https://www.wwb.co.uk/privet- hawk-s-ligustri-5-pupae) [ ![Privet Hawk S ligustri Pupae SPECIAL OFFER!](https://cdn.wwb.co.uk/image/cache/data/Sphingidae/Ligustri spread pink + larva 4770 Sm-150x150.jpg) ](https://www.wwb.co.uk/privet-hawk-s- ligustri-5-pupae) Share in our bounteous harvest and buy these huge Hawkmoth pupae at SPECIAL PRICES! Availability: NOW [ View Info ](https://www.wwb.co.uk/privet-hawk-s-ligustri-5-pupae) Add to Cart [ Euritides marcellus Swordtail 5 pupae ](https://www.wwb.co.uk/marcellus- swordtail-pupa) [ ![Euritides marcellus Swordtail 5 pupae](https://cdn.wwb.co.uk/image/cache/data/MarcellusGeranium_thumb-150x150.jpg) ](https://www.wwb.co.uk/marcellus-swordtail-pupa) First time available for decades! Flies and breeds well in a hot house. Very variable larvae. Availability: NOW £69.95 [ View Info ](https://www.wwb.co.uk/marcellus-swordtail-pupa) Add to Cart [ The Giant Swallowtail Papilio cresphontes pupae ](https://www.wwb.co.uk/the- giant-swallowtail-papilio-cresphontes-4-pupae) [ ![The Giant Swallowtail Papilio cresphontes pupae](https://cdn.wwb.co.uk/image/cache/data/Cresphontes-150x150.jpg) ](https://www.wwb.co.uk/the-giant-swallowtail-papilio-cresphontes-4-pupae) Very large Swallowtail that flies well in a conservatory. Dormant pupae. Availability: NOW [ View Info ](https://www.wwb.co.uk/the-giant-swallowtail-papilio- cresphontes-4-pupae) Add to Cart [ Saturnia jonasii, Far East Russia 10 eggs ](https://www.wwb.co.uk/index.php?route=product/product&product_id=6300) [ ![Saturnia jonasii, Far East Russia 10 eggs](https://cdn.wwb.co.uk/image/cache/data/Saturniidae/Boisduvali young larva Sm 1030407-150x150.jpg) ](https://www.wwb.co.uk/index.php?route=product/product&product_id=6300) Winter eggs to hatch in spring. Very attractive larvae with several colour changes. Availability: NOW £17.95 [ View Info ](https://www.wwb.co.uk/index.php?route=product/product&product_id=6300) Add to Cart [ Ligurian Emperor Saturnia pavoniella Cocoons ](https://www.wwb.co.uk/saturnia-pavoniella-4-cocoons) [ ![Ligurian Emperor Saturnia pavoniella Cocoons ](https://cdn.wwb.co.uk/image/cache/data/Saturniidae/Pavoniella L5 1070357 2 Sm-150x150.jpg) ](https://www.wwb.co.uk/saturnia-pavoniella-4-cocoons) Large cocoons from wild stock. Larvae have amazing colour forms. Availability: Autumn [ View Info ](https://www.wwb.co.uk/saturnia-pavoniella-4-cocoons) Add to Cart [ Small Eggar Moth Eriogaster lanestris cocoons ](https://www.wwb.co.uk/index.php?route=product/product&product_id=6428) [ ![Small Eggar Moth Eriogaster lanestris cocoons](https://cdn.wwb.co.uk/image/cache/data/Moths/Lanestris m +f Sm-150x150.jpg) ](https://www.wwb.co.uk/index.php?route=product/product&product_id=6428) Extraordinary nut-like cocoons. The moth emerges inside and waits for the right moment in spring to emerge. Availability: Autumn [ View Info ](https://www.wwb.co.uk/index.php?route=product/product&product_id=6428) Add to Cart [ Elephant Hawk elpenor pupae ](https://www.wwb.co.uk/elephant-hawk-elpenor- pupae) [ ![Elephant Hawk elpenor pupae ](https://cdn.wwb.co.uk/image/cache/data/Sphingidae/Elpenor moth on Rosebay 4686 Sm-150x150.jpg) ](https://www.wwb.co.uk/elephant-hawk-elpenor-pupae) Winter pupae. Store cool until incubation in June. Extraordinary and characterful larvae. Availability: NOW [ View Info ](https://www.wwb.co.uk/elephant-hawk-elpenor-pupae) Add to Cart [ Willowherb Hawkmoth Proserpinus proserpina Pupae ](https://www.wwb.co.uk/proserpinus-proserpina-4-pupae) [ ![Willowherb Hawkmoth Proserpinus proserpina Pupae ](https://cdn.wwb.co.uk/image/cache/data/ProserpinaHW_thumb-150x150.jpg) ](https://www.wwb.co.uk/proserpinus-proserpina-4-pupae) Dormant pupae of this very attractive and scarce Hawkmoth. Incubate in May. Availability: Autumn [ View Info ](https://www.wwb.co.uk/proserpinus-proserpina-4-pupae) Add to Cart [ Cinnabar Moth Hipocrita jacobaeae pupae ](https://www.wwb.co.uk/index.php?route=product/product&product_id=6513) [ ![Cinnabar Moth Hipocrita jacobaeae pupae](https://cdn.wwb.co.uk/image/cache/data/Moths/Cinnabar wings spread 0009 Sm-150x150.jpg) ](https://www.wwb.co.uk/index.php?route=product/product&product_id=6513) Store pupae refrigerated to emerge in June. Very pretty both as moths and larvae. Availability: NOW [ View Info ](https://www.wwb.co.uk/index.php?route=product/product&product_id=6513) Add to Cart [ Tau Emperor Aglia tau Pupae ](https://www.wwb.co.uk/tau-emperor-a- tau-6-pupae) [ ![Tau Emperor Aglia tau Pupae ](https://cdn.wwb.co.uk/image/cache/data/Saturniidae/Tau Male 9349 Sm-150x150.jpg) ](https://www.wwb.co.uk/tau-emperor-a-tau-6-pupae) Dormant pupae to emerge early in spring. Fabulous horned larvae! Availability: Autumn [ View Info ](https://www.wwb.co.uk/tau-emperor-a-tau-6-pupae) Add to Cart [ Goodden GEMLIGHT SUPER ](https://www.wwb.co.uk/index.php?route=product/product&product_id=6953) [ ![Goodden GEMLIGHT SUPER](https://cdn.wwb.co.uk/image/cache/data/Moth Traps/GemLight Super in hand illuminated 4449 Sm-150x150.jpg) ](https://www.wwb.co.uk/index.php?route=product/product&product_id=6953) Completely new design. Superbly miniaturised. Three different LEDs. Runs all night on a tiny power bank. Amazing! Availability: NOW [ View Info ](https://www.wwb.co.uk/index.php?route=product/product&product_id=6953) Add to Cart [ Moonlander Moth Trap with Supports and Goodden GemLight SUPER ](https://www.wwb.co.uk/index.php?route=product/product&product_id=5705) [ ![Moonlander Moth Trap with Supports and Goodden GemLight SUPER](https://cdn.wwb.co.uk/image/cache/data/Moth Traps/Moonlander and bag + GLS Sm P1060361 adj-250x250 copy-150x150.jpg) ](https://www.wwb.co.uk/index.php?route=product/product&product_id=5705) Now available with the ground-breaking newly designed Gemlight SUPER! Availability: NOW [ View Info ](https://www.wwb.co.uk/index.php?route=product/product&product_id=5705) Add to Cart [ Morpho helenor. South America pupae ](https://www.wwb.co.uk/index.php?route=product/product&product_id=6713) [ ![Morpho helenor. South America pupae](https://cdn.wwb.co.uk/image/cache/data/Morpho/Helenor 67223041 adj Sm-150x150.jpg) ](https://www.wwb.co.uk/index.php?route=product/product&product_id=6713) In a tropical enclosure or conservatory these are just magnificent in flight. An experience never forgotten! Availability: NOW [ View Info ](https://www.wwb.co.uk/index.php?route=product/product&product_id=6713) Add to Cart [ Citrus Swallowtail POT LUCK collection of 15 eggs or 10 larvae, according to availability ](https://www.wwb.co.uk/index.php?route=product/product&product_id=6178) [ ![Citrus Swallowtail POT LUCK collection of 15 eggs or 10 larvae, according to availability](https://cdn.wwb.co.uk/image/cache/data/Papilionidae/Citrus POT LUCK Sm-150x150.jpg) ](https://www.wwb.co.uk/index.php?route=product/product&product_id=6178) Eggs are now being laid and orders are being sent out. Availability: NOW £12.95 [ View Info ](https://www.wwb.co.uk/index.php?route=product/product&product_id=6178) Add to Cart [ Robinson Mercury Vapour Mains Electric Trap - complete electrics with 50m cable and choke ](https://www.wwb.co.uk/index.php?route=product/product&product_id=6344) [ ![Robinson Mercury Vapour Mains Electric Trap - complete electrics with 50m cable and choke ](https://cdn.wwb.co.uk/image/cache/data/Moth Traps/Trap Robinson Sm-150x150.jpg) ](https://www.wwb.co.uk/index.php?route=product/product&product_id=6344) The most powerful moth trap. Undoubtedly the best mains supply trap. Availability: Not always in stock £450.00 [ View Info ](https://www.wwb.co.uk/index.php?route=product/product&product_id=6344) Add to Cart [ Owl Butterfly Caligo species 10 larvae ](https://www.wwb.co.uk/index.php?route=product/product&product_id=6689) [ ![Owl Butterfly Caligo species 10 larvae](https://cdn.wwb.co.uk/image/cache/data/Caligo/Eurilochus larvae Jay 4 Sm copy-150x150.jpg) ](https://www.wwb.co.uk/index.php?route=product/product&product_id=6689) Eggs and larvae available immediately. Extraordinary larvae, producing amazing pupae like wrapped leaves. Availability: NOW £12.95 [ View Info ](https://www.wwb.co.uk/index.php?route=product/product&product_id=6689) Add to Cart [ Size 5A Plastic Box Shallow version of Size 5 174 x 115 x 41mm. Carton of 3. ](https://www.wwb.co.uk/index.php?route=product/product&product_id=6883) [ ![Size 5A Plastic Box Shallow version of Size 5 174 x 115 x 41mm. Carton of 3.](https://cdn.wwb.co.uk/image/cache/data/Plastic boxes/Size 5A three boxes1090684 Sm-150x150.jpg) ](https://www.wwb.co.uk/index.php?route=product/product&product_id=6883) New size of Plastic Rearing Container, shallower version of the ever popular Size 5. Availability: NOW £19.95 [ View Info ](https://www.wwb.co.uk/index.php?route=product/product&product_id=6883) Add to Cart [ Great Water Dock Rumex hydropathalum Seeds. Foodplant of the Large Copper Butterfly ](https://www.wwb.co.uk/index.php?route=product/product&product_id=6860) [ ![Great Water Dock Rumex hydropathalum Seeds. Foodplant of the Large Copper Butterfly](https://cdn.wwb.co.uk/image/cache/data/Plants/Dispar Docks and Canal A 2217 Sm-150x150.jpg) ](https://www.wwb.co.uk/index.php?route=product/product&product_id=6860) Foodplant of the Large Copper in its natural habitat. Easily grown at water's edge or in pots standing in water. Availability: NOW £4.95 [ View Info ](https://www.wwb.co.uk/index.php?route=product/product&product_id=6860) Add to Cart [ Milk Parsley Peucedanum palustre Packet of seed ](https://www.wwb.co.uk/index.php?route=product/product&product_id=6381) [ ![Milk Parsley Peucedanum palustre Packet of seed](https://cdn.wwb.co.uk/image/cache/data/Plants/Peucedanum leaf P1040556 Sm-150x150.jpg) ](https://www.wwb.co.uk/index.php?route=product/product&product_id=6381) Seldom available. Milk Parsley seed, foodplant of the Swallowtail Papilio machaon. Germinates rapidly and easy to grow. Availability: NOW £6.95 [ View Info ](https://www.wwb.co.uk/index.php?route=product/product&product_id=6381) Add to Cart [ Vapourer Moth antiqua eggs. ](https://www.wwb.co.uk/vapourer-moth-antiqua--- a-cluster-of-eggs) [ ![Vapourer Moth antiqua eggs.](https://cdn.wwb.co.uk/image/cache/data/Moths/Antiqua larvae group 1070808 Sm-150x150.jpg) ](https://www.wwb.co.uk/vapourer-moth-antiqua--- a-cluster-of-eggs) Exceptionally attractive larvae. Extraordinary fat wingless females, and males that can find them from miles away! Availability: NOW [ View Info ](https://www.wwb.co.uk/vapourer-moth-antiqua---a-cluster-of- eggs) Add to Cart [ WORLD SWALLOWTAIL PUPA COLLECTION 10 pupae ](https://www.wwb.co.uk/index.php?route=product/product&product_id=5778) [ ![WORLD SWALLOWTAIL PUPA COLLECTION 10 pupae](https://cdn.wwb.co.uk/image/cache/data/Papilionidae/Palinurus Sm 4349-150x150.jpg) ](https://www.wwb.co.uk/index.php?route=product/product&product_id=5778) After months of having no exotic butterfly pupae, this collection of World Swallowtails is now available again. Availability: NOW £38.50 [ View Info ](https://www.wwb.co.uk/index.php?route=product/product&product_id=5778) Add to Cart [ WORLD COLLECTION OF EXOTIC BUTTERFLIES Ten pupae ](https://www.wwb.co.uk/index.php?route=product/product&product_id=5779) [ ![WORLD COLLECTION OF EXOTIC BUTTERFLIES Ten pupae](https://cdn.wwb.co.uk/image/cache/data/Nymphalidae/Cyaniris 1060309 Sm-150x150.jpg) ](https://www.wwb.co.uk/index.php?route=product/product&product_id=5779) For the first time this year, due to Covid, exotic butterfly pupae have been impossible to obtain but we can now supply this collection again. Availability: NOW [ View Info ](https://www.wwb.co.uk/index.php?route=product/product&product_id=5779) Add to Cart [ SLEEVE PACK One each of Sizes 1, 3 and 4 with Velcro ](https://www.wwb.co.uk/index.php?route=product/product&product_id=6806) [ ![SLEEVE PACK One each of Sizes 1, 3 and 4 with Velcro](https://cdn.wwb.co.uk/image/cache/data/Ento EQ/Sleeve Size 4 copy Sm-150x150.jpg) ](https://www.wwb.co.uk/index.php?route=product/product&product_id=6806) The three most useful sizes, with reel of Velcro for securing the sleeve to the branch. Useful aid, giving the best chance of rearing success. Availability: NOW £35.50 [ View Info ](https://www.wwb.co.uk/index.php?route=product/product&product_id=6806) Add to Cart [ PUPAE NEST ](https://www.wwb.co.uk/index.php?route=product/product&product_id=6757) [ ![PUPAE NEST](https://cdn.wwb.co.uk/image/cache/data/Plastic boxes/Pupae Nest 9861 Sm-150x150.jpg) ](https://www.wwb.co.uk/index.php?route=product/product&product_id=6757) This WWB method of keeping underground pupae enables humidifying, inspection and good hygiene. Availability: NOW [ View Info ](https://www.wwb.co.uk/index.php?route=product/product&product_id=6757) Add to Cart [ Spring Frame Pocket Net - NEW SUPERIOR DESIGN ](https://www.wwb.co.uk/index.php?route=product/product&product_id=6756) [ ![Spring Frame Pocket Net - NEW SUPERIOR DESIGN](https://cdn.wwb.co.uk/image/cache/data/Nets and handles/Spring Frame open and folded 1387 blue-150x150.jpg) ](https://www.wwb.co.uk/index.php?route=product/product&product_id=6756) The best made and designed pocket net, compact and convenient for travel and field work. Introductory price! Availability: NOW £45.50 [ View Info ](https://www.wwb.co.uk/index.php?route=product/product&product_id=6756) Add to Cart [ OSIER A wonderful foodplant. Ten cuttings ](https://www.wwb.co.uk/osier-a- wonderful-foodplant-ten-cuttings) [ ![OSIER A wonderful foodplant. 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dog_eyes_green/canine-eyes-their-disorders.txt	Common Eye Problems in Dogs and How to Treat Them Â· The Wildest Skip to main content # Common Eye Problems in Dogs and How to Treat Them Your dog sees you as their best friend, so keep those eyes healthy. by Shauna S. Roberts, PhD opens in a new tab and Dr. Alycia Washington, DVM, MS opens in a new tab Updated November 28, 2023 ownza / Adobe Stock ## share article Twitter Opens a new window Facebook Opens a new window Pinterest Opens a new window Email Opens a new window Your pet wants you to read our newsletter. (Then give them a treat.) Enter email address I'm In Sign up for product updates, offers, and learn more about The Wildest, and other Mars Petcare brands . Must be over 16 years to sign up. See our privacy statement to find out how we collect and use your data, to contact us with privacy questions or to exercise your personal data rights. Dogs are susceptible to a variety of eye disorders, some of which can be serious and lead to vision loss. Eye diseases seen in dogs include conjunctivitis, dry eye, corneal ulcers, cataracts, glaucoma, and retinal disorders. Early detection and treatment are essential for the best outcome. If you notice any changes in your dogâs eyes, such as redness, swelling, discharge, squinting, or tearing, it is important to see a veterinarian right away. â Puppy-dog eyes opens in a new tab â get dog parents every time. Itâs been proven that gazing opens in a new tab into your petâs eyes produces oxytocin and promotes bonding. They are the epitome of the âpleading faceâ emoji. Irresistible. It could be something more than cuteness, though. If your dogâs eyes have been looking a little red or cloudy lately or if youâve noticed theyâre pawing at, rubbing, or showing signs of irritation around their eyes, you might need to make an appointment with your vet.Â âAs a general practitioner, I was often presented with problems such as conjunctivitis, dry eye, and corneal ulcer,â says Dr. Christine Lim, a veterinarian in Chicago. âNow that I specialize in ophthalmology, I more often see cataracts, glaucoma, and retinal disorders.â Related article opens in a new tab ### Dogs Get Dry Eye Too...Some Breeds More Than Others opens in a new tab Eyes without tears are only for Cameron Diaz in The Holiday . ## What are the most common eye problems in dogs?Â Eye problems in dogs are no joke â dogs can suffer from a host of health conditions including glaucoma, conjunctivitis, dry eyes, cataracts, and more. Some eye disorders occur more often than others and a dogâs breed usually plays a role in that. Common eye problems in dogs include:Â 1. Eye infections 2. Dry eyeÂ 3. Cataracts 4. Glaucoma 5. Corneal ulcers 6. Uveitis 7. Conjunctivitis 8. Watery eyes 9. Entropion/Ectropion 10. Bulging EyesÂ 11. Cherry eye 12. Lazy eye 13. Retinal Disorders ## How dogsâ eyes work To understand eye problems in dogs, it helps to know a little bit about how their eyes function. A dogâs eyes work much like a camera. Light first enters through the clear cornea then passes through the pupil. The iris controls the amount of light allowed in through the pupil. Next, light goes through the lens, which focuses the light on the retina â a layer containing color-sensitive cones and motion- and light-sensitive rods, which convert light into electrical signals. The cones and rods send these signals via the optic nerve to the brain, which constructs an image from them. Dogs have only two types of cones, compared with the three types in human eyes. As a result, dogs donât see as many colors as people opens in a new tab do. Dog eyes also contain structures not found in a camera, such as the gel-like vitreous humor that fills the eyeball and gives it shape. Canine eyes are different from human eyes in that they have a third eyelid, called the nictitating membrane, which is a thin whitish-pink tissue that protects the eye. And unlike humans, dogs have a reflective lining behind the retina called the tapetum lucidum; itâs what makes dogsâ eyes glow eerily when light hits them. Itâs also what allows them to see in dimmer light. Related article opens in a new tab ### Dog Vision: What Colors Do Dogs See? opens in a new tab They canât take in as many colors as you can, but their world isnât just black and white. The visual streak is a horizontal band in the retina right above the optic nerve; this area has the highest concentration of rods and cones, and vision is sharpest here. The visual streak varies greatly among breeds, and studies suggest that different breeds see the world differently. In dogs with long heads like wolves, the streak is wide, with the nerves evenly distributed. The shorter a breedâs head, the narrower (more circular) the streak tends to be. Pugs, for example, have a small spot of sharp vision â an âarea centralisâ â like humans do. Even within breeds, the visual streak can vary from type to type. ## How well do dogs see? All of these features equip a dog to be a good hunter under various light conditions. The tapetum lucidum improves a dogâs vision in low light, as does the high proportion of rods to cones, giving dogs better vision at night opens in a new tab than humans. A rod-dense retina also makes dogs excellent at detecting motion and shapes. Because most dogsâ eyes angle slightly to the side, they have a wider field of view than humans. When a wide field of vision combines with a wide visual streak, as in a German Shepherd, a dog can see the whole horizon at once (instead of having to scan the eyes back and forth as humans do). With keen senses of smell and hearing, dogs donât need to see well up close; in fact, near vision is blurry in long-nosed dogs. Short-nosed dogs, with their human-like area centralis, do appear to see well up close. Though the area centralis may lessen their ability as hunters, it may make them better lap dogs, more able to âreadâ their parentsâ faces. Overall, dog vision is less sharp than human vision. ## What are the signs of eye problems in dogs? Dog parents may be cued into an issue with their dogâs eye if it changes in appearance or if their dog seems to be experiencing eye irritation. Any concerns about a dogâs eyes should not be ignored. Signs of eye problems in dogs include: * Squinting * Eye discharge (especially if it is not clear) * Eye redness * Cloudiness * Pawing at the eyeÂ * Sudden change in vision (bumping into things, anxiety, hesitation to walk) * Swollen eyes * Bulging eyes * Persistently dilated or constricted pupils Related article opens in a new tab ### Everything You Need to Know About Cataracts in Dogs opens in a new tab Hereâs how to spot the eye condition and help your dog see more clearly. ## What are the dog breeds prone to eye problems? While eye issues can affect any dog, certain breeds face a greater risk. Brachycephalic (smoosh faced) dogs breeds are prone to eye problems. Brachycephalic breeds opens in a new tab include Pugs, French Bulldogs, English Bulldogs, Boston Terriers, Lhasa Apsos, and Bullmastiffs. The skull shapes in these dogs not only contribute to a higher risk for respiratory problems, but they have a higher incidence of eye issues as well. Their eyes bulge out more, contributing to a host of issues often lumped together as brachycephalic ocular syndrome.Â Dogs with brachycephalic ocular syndrome tend to have shallow eye sockets, contributing to eyes that are more likely to pop out as a result of trauma (proptosis). They are also more likely to have dry eyes and corneal ulcers, either from low tear production or from an inability to close their eyes all the way. Eyelid issues like entropion and trichiasis cause facial hairs to constantly scrape the eyeâs surface, causing discomfort and trauma to the cornea.Â ### Common dog eye problems Dog eyes are susceptible to a variety of issues. Some can be easily addressed by your veterinarian while others may call for a referral to a veterinary ophthalmologist. Here are some of the most common eye problems in dogs: ### Eye infections Viral and bacterial eye infections are commonly diagnosed in dogs. Fungal eye infections occur in dogs but are less common. Eye infections can affect the conjunctiva (the pink tissue around the eye) or the eye itself. Symptoms of eye infections include yellow or green eye discharge, crusting around the eyes, redness, and discomfort. Treatment often involves administering medicated eye drops. Depending on the severity and type of infection, oral medications may be prescribed, too.Â Related article opens in a new tab ### Whatâs This Weird Red Bump On My Dogâs Eye? opens in a new tab That would be a cherry eye, and youâll want to see your vet. ### Dry eye Dry eye occurs when not enough tears are produced to keep the eyes properly lubricated. Dogs may inherit this condition; among the dog breeds at higher risk are the American Cocker Spaniel, English Bulldog, Pug, Lhasa Apso, Pekinese, Shih Tzu, and West Highland White Terrier. Small, flat-faced dogs sometimes have eyes that bulge so much that their eyelids cannot close, which makes the surface of the eyes to dry out. Dry eye opens in a new tab may also result from an immune system reaction, an injury, or a drug side effect. Dryness can be a serious problem for dogs because dry eyes are easily irritated and may develop conjunctivitis or corneal ulcers. Artificial tears, good eye hygiene, anti-inflammatory drugs, and/or cyclosporine ointment (Optimmune) may help. ### Cataracts The most common cause of blindness in dogs, a cataract is a clouding of the lens that obscures the dogâs vision. Most dogs with cataracts opens in a new tab inherited the tendency to develop them. Inherited cataracts can occur in the Afghan Hound, American Cocker Spaniel, Boston Terrier, Chesapeake Bay Retriever, German Shepherd, Golden Retriever, Labrador Retriever, Miniature Schnauzer, Norwegian Buhund, Old English Sheepdog, Schnauzer, Siberian Husky, Staffordshire Bull Terrier, Standard Poodle, Welsh Springer Spaniel, and West Highland White Terrier. Diabetes opens in a new tab , injuries, poor diet opens in a new tab , and aging can also lead to cataracts. Surgery is available to treat dogs with cataracts. Removing the lens allows light to enter the eye again. For best post-surgery vision, the natural lens is usually replaced by a plastic lens. âThe surgery itself is not too stressful for the majority of patients,â says Dr. Lim. However, âthe first few weeks postoperatively can be stressful because it is very intensive â the patient must wear an Elizabethan collar at all times, and several medications are required.â ### Glaucoma Glaucoma is the elevated pressure created by the fluid inside the eyeball draining more slowly than it is produced. Dogs with glaucoma can experience damage to the retina or optic nerve. Most often, dogs get glaucoma because they inherited an eye structure that leads to poor drainage. Dog breeds in which primary (inherited) glaucoma occurs include the Alaskan Malamute, American Cocker Spaniel, Basset Hound, Beagle, Boston Terrier, Bouvier des Flandres, Chow Chow, Dalmatian, English Cocker Spaniel, English Springer Spaniel, Great Dane, Labrador Retriever, Norwegian Elkhound, Poodle (all sizes), Samoyed, Shar-Pei, Shih Tzu, Siberian Husky, and Welsh Springer Spaniel. Primary glaucoma has no obvious cause, and it affects both eyes (although one eye may develop glaucoma earlier than the other). Secondary glaucoma is glaucoma that is caused by a dislocated lens, injury, tumor, or other problem that decreases fluid drainage in the eye; it may affect just one eye. Glaucoma treatments include surgery, pills, eye drops, or (rarely) removal of the eyeball. âGlaucoma is still one of the more difficult things to handle,â says Dr. Vainisi. âEven though there are literally dozens of glaucoma procedures, there still is not that ideal oneâ¦even in humans.â Related article opens in a new tab ### How to Find a Veterinary Specialist opens in a new tab Just like your doctor would refer to you a specialist for expert care for a complicated issue, your vet may do the same for your dog. ### Corneal ulcers Corneal ulcers are slow-healing sores on the dogâs cornea, accompanied by inflammation. Most ulcers are caused by injuries, and treatment often involves antibiotics. Small dog breeds with very short noses and big eyeballs are more prone to eye injuries, says Dr. Samuel J. Vainisi, DVM, ACVO of the Animal Eye Clinic in Denmark, Wisc. âBecause of that, we see a lot of ulcers on the eyes of breeds such as the Boston Terrier, the Pekinese, and the Shih Tzu.â ### Uveitis Uveitis opens in a new tab refers to inflammation inside of the eye. This inflammation typically stems from the eyeâs blood vessels. Uveitis usually develops secondary to another cause including trauma, infection, tick-borne disease, auto-immune disease, or metabolic disease. Uveitis can cause pain in dogs, and the symptoms often reflect this discomfort. Symptoms of uveitis in dogs include squinting, rubbing the eyes, and ocular discharge. The eyes can appear red or cloudy. Treating uveitis involves addressing the inflammation and treating the underlying cause.Â ### Conjunctivitis Conjunctivitis is a condition in which the lining of the eyelids and the sclera (the white of the eye) become inflamed. It can be caused by infection, an object in the dogâs eye, an allergic reaction, dry eye, a scratch, or even smoke or dust. It can also be a symptom of other diseases. Treatment depends on the cause, but often entails addressing inflammation and infection. ### Watery eyes Watery eyes, or epiphora, is commonly seen in dogs. Dogs develop epiphora for two reasons â either excess tear production from eye irritation or more tears present due to a lack of drainage. Eyes can become irritated from allergies opens in a new tab , trauma, or infection. Normally, tears from the eyes drain through the nasolacrimal duct into the nasal cavity. When drainage is obstructed or poor, tears run down a dog's face instead. Tears can stain the fur on the face, which is a cosmetic concern for some dog parents. Clear tears and clear eyes are typically not considered to be a medical issue. Excessive tears with signs of eye irritation should be evaluated by a veterinarian.Â Related article opens in a new tab ### Dog Vision: What Colors Do Dogs See? opens in a new tab They canât take in as many colors as you can, but their world isnât just black and white. #### Entropion/ectropion Entropion occurs when one or both eyelids are inverted inwards. Entropion in dogs can occur due to genetics, developmental abnormalities, or secondary to eyelid trauma. Entropion is most commonly diagnosed in young, large breed dogs. Breeds that are predisposed to entropion include Bull Mastiffs, Chow Chows, Labrador Retrievers, Standard Poodles, Chesapeake Bay Retrievers, and Shar Peis. Entropion can cause the eyelashes to rub on the cornea, causing pain and trauma. Treatment often involves surgical correction.Â Ectropion occurs when an eyelid is turned outward or when the lower eyelid sags, creating minimal contact with the eye. Ectropion in dogs is typically congenital. Breeds predisposed to ectropion include Saint Bernards, Bloodhounds, Great Danes, and Spaniels. Picture droopy eyed dogs. When they blink, their lower eyelids do not make adequate contact with their eyes and cannot help with lubricating the cornea or wiping away irritants. Over time, the eyes can become dry and inflamed. Treatment can range from temporary anti- inflammatory medications to chronic eye lubricant application to corrective surgery.Â ### Bulging eyesÂ Dogâs eyes can bulge as a result of trauma or underlying medical conditions like glaucoma. A bulgy eye appearance can be from proptosis (displacement of the eye) or buphthalmos (enlargement of the eye). A dogâs eyes should be the same size and rest comfortably in their eye sockets. Any change to this state is considered a medical emergency. ### Cherry eye Dogs have a nictitating membrane, commonly called the third eyelid, that aids in tear production and eye protection. When this gland becomes displaced and protrudes, itâs called a cherry eye opens in a new tab and looks like smooth, pink tissue protruding from the inside corner of the eye. This limits the tear production in the eye and can cause dryness and irritation. The exposed tissue also becomes inflamed. While mild cases may be treated medically, surgical replacement is often recommended to address cherry eye. Any dog can develop a cherry eye, but brachycephalic breeds like English Bulldogs and Shih Tzus have a higher risk.Â ### Lazy eye Strabismus refers to having eyes that donât face the same direction. This is usually due to incoordination of the eye muscles. Strabismus in dogs is often genetic and does not cause any health issues; most dogs born with a lazy eye do not require any treatment. A dog that suddenly develops a lazy eye should be evaluated. A sudden change in eye position can develop as a result of tumors in or near the eye, neurological problems, or trauma. Treatment for acute strabismus in dogs depends on the cause.Â ### Retinal disorders Progressive retinal atrophy (PRA) is the name for a group of retinal disorders in which rods and cones die off. There is no treatment for this condition. Dogs who get PRA do so because theyâve inherited a defective gene. Although PRA strikes more than 100 breeds of dogs, different genes can be responsible for it. Therefore, breeds differ in the age at which the condition appears, how fast the condition progresses, and the ratio of males to females among affected dogs.Â Related article opens in a new tab ### Everything You Need to Know About Cataracts in Dogs opens in a new tab Hereâs how to spot the eye condition and help your dog see more clearly. PRA appears during puppyhood in the Cardigan Welsh Corgi, Cairn Terrier, Collie, Gordon Setter, Great Dane, Irish Setter, Miniature Schnauzer and Norwegian Elkhound. In contrast, some breeds usually donât develop PRA until adulthood. These include the American Cocker Spaniel, English Cocker Spaniel, Labrador Retriever, Lhasa Apso, Miniature Poodle, Portuguese Water Dog, Tibetan Spaniel, and Tibetan Terrier. PRA occurs mostly in males in the Siberian Husky and Samoyed. Genetic tests for PRA are available for several breeds. Other retinal problems include detachment of the retina from the back of the eye, inflammation, and abnormal development. Causes include infection and injury. Some retinal disorders have no treatment, while others can be helped by surgery or treatment of the cause. Small dogs may be more prone to retinal detachment. According to Dr. Vainisi, several small breeds of dogs, including Boston Terriers, Jack Russell Terriers, and Shih Tzus, love to pick up toys and shake them hard. âFluid goes violently back and forth in the back of the eye, and it just rips the retina right off,â he says. âOne moment theyâre seeing, and the next moment they can be totally blind.â ### How to treat your dogâs eye problem The best way to protect your dogâs vision is to catch eye disorders early opens in a new tab , when they are most easily treated. A dog with eye or vision problems may paw at or scratch their eye, squint, bump into things, become afraid of the dark, or be frightened in situations that did not frighten them before. The dogâs eye may produce discharge, be red, look cloudy or be swollen. The nictitating membrane may partially cover the eye. If your dog seems to have an eye problem, take them to the veterinarian right away. Your vet may have the knowledge and equipment to diagnose and treat the problem immediately; if not, they may refer your dog to a veterinary ophthalmologist, a specialist in animal eyes and their disorders. Related article opens in a new tab ### Whatâs This Weird Red Bump On My Dogâs Eye? opens in a new tab That would be a cherry eye, and youâll want to see your vet. Only about 300 veterinarians in the United States have board certification from the American College of Veterinary Ophthalmologists. As a result, if your dog needs a veterinary ophthalmologist, you may need to travel to see one. Some, but not all, veterinary ophthalmologists see dogs only by referral. The bottom line: If your dog has an eye issue, make an appointment with your vet right away. That way, your dog wonât need to suffer or develop a worse issue unnecessarily. ## Can you prevent dog eye problems?Â The best thing dog parents can do to protect their dogâs eyes is to minimize risk of injury and prioritize overall health. Keep your dog away from other animals that may not want to play nice. Donât let them hang around smoke or any aerosols that can irritate their eyes.Â Keep your pup up to date on vaccinations and preventatives to avoid infections and tick-borne disease. Feed an appropriate diet and provide lots of exercise to help prevent metabolic diseases like diabetes. Proactive petcare overlaps with dog eye disease prevention. ## FAQs (People also ask): ### Can I use over-the-counter eye drops for my dog's eye problems? Never apply any human medications to your dogâs eyes without consulting a veterinarian first. Human medications are not formulated for dogs and may include ingredients that can worsen your dogâs eye condition.Â ### Is there any home remedy available for eye problems in dogs? If your dog has excessive eye discharge or crusty eye boogers, you can gently wipe it away with a cotton ball or washcloth soaked in warm water. Be sure to seek veterinary care to address the underlying cause of the discharge.Â ### When should I seek immediate veterinary care for my dog's eye issue? Any eye issue should be addressed as soon as possible before it progresses to something that can affect a dogâs vision. If your dogâs eyes change in appearance or your dog vision seems suddenly impaired, seek veterinary attention ASAP.Â ## References: * Oxytocin-Gaze Positive Loop and the Coevolution of Human-Dog Bonds opens in a new tab * Curiosities: How Well Do Dogs See at Night? opens in a new tab * A Common Problems Of Dog Eyes (A Review) opens in a new tab * Clinical Signs of Brachycephalic Ocular Syndrome in 93 Dogs opens in a new tab * Prevalence of the Breed-Related Glaucomas in Pure-Bred Dogs in North America opens in a new tab * Cote's Clinical veterinary Advisor: Dogs and Cats - E-Book opens in a new tab * Nasolacrimal and Lacrimal Apparatus in Animals opens in a new tab Tags * dog opens in a new tab * dog health opens in a new tab * senior dog opens in a new tab ## Shauna S. Roberts, PhD Shauna S. Roberts, PhD, is an award-winning science and medical writer and copyeditor who specializes in arthritis, diabetes and related subjects. Shauna S. Roberts, PhD opens in a new tab ## Dr. Alycia Washington, DVM, MS Alycia Washington, DVM, is a small animal emergency veterinarian based in North Carolina. She works as a relief veterinarian opens in a new tab and provides services to numerous emergency and specialty hospitals. Dr. Washington is also a childrenâs book author and freelance writer with a focus on veterinary medicine. She has a special fondness for turtles, honey bees, and penguins â none of which she treats. In her free time, Dr. Washington enjoys travel, good food, and good enough coffee.Â Dr. Alycia Washington, DVM, MS opens in a new tab Website ## Related articles * ### Diabetes in Dogs: Symptoms, Treatment, and Prevention Learn which breeds are at risk, the symptoms to look out for, and what treatment options are available. opens in a new tab * ### Why You Should Trim Your Dogâs Bangs Hint: they canât see. opens in a new tab * ### How to Do a DIY Dog Checkup in 7 Steps You can do a DIY exam on your dog from your couch. opens in a new tab * ### Dogs Get Dry Eye Too...Some Breeds More Than Others Eyes without tears are only for Cameron Diaz in The Holiday . opens in a new tab * ### How to Do a DIY Dog Checkup in 7 Steps You can do a DIY exam on your dog from your couch. opens in a new tab * ### How to Take Care of a Senior Dog As dogs age, itâs important to recognize both physical and mental changes they may be experiencing. opens in a new tab * Health opens in a new tab * Nutrition opens in a new tab * Behavior opens in a new tab * Lifestyle opens in a new tab * Grooming opens in a new tab * Shopping opens in a new tab * Tools opens in a new tab * New Pet opens in a new tab * * Poodle opens in a new tab * About Us opens in a new tab * Collective opens in a new tab * Contact Us opens in a new tab * * Accessibility Opens a new window * Terms of Service opens in a new tab * Ad Choice Opens a new window * Privacy Notice Opens a new window * Your Privacy Choices Opens a new window * Cookie Management opens in a new tab * Cookie Policy Opens a new window Enter email address Submit icon Sign up for product updates, offers, and learn more about The Wildest, and other Mars Petcare brands . Must be over 16 years to sign up. See our privacy statement to find out how we collect and use your data, to contact us with privacy questions or to exercise your personal data rights. Facebook Instagram Tiktok Twitter Â© 2024, Kinship Partners, Inc. an affiliate of Mars Incorporated \| Ver. f1ab5a4	biology	66246	https://no.wikipedia.org/wiki/Nova%20scotia%20duck%20tolling%20retriever	Nova scotia duck tolling retriever	Nova scotia duck tolling retriever, også kalt toller, er en vannapporterende hunderase som trolig oppsto i Nova Scotia-distriktet i Canada på siste halvdel av 1800-tallet. Tolleren er Nova Scotias provinshund. Opprinnelse og alder Nova scotia duck tolling retriever (toller) kan være et resultat av en krysning mellom en småvokst chesapeake bay retriever, golden retriever og en brun spanieltype, men dette vites ikke med sikkerhet. Andre teorier antyder at den kan være en krysning mellom en leverfarget flat coated retriever og en labrador retriever. Noen mener også at den kan være innblandet irsk setter og andre lokale hunder. Parker et al. (2017) dokumeterer imidlertid at rasen er nært beslektet med andre retrievere, irsk vannspaniel og newfoundlandshund, samt at rasen har blitt tilført gener fra collie og/eller shetland sheepdog, noe som også forklarer hvordan den arvelige øyelidelsen CEA (collie eye anomaly) har tatt seg til denne hunderasen. Om shetland sheepdog inngår kan dette også forklare hvorfor denne retrieveren er mindre enn de andre, men om det kun er collie så må den reduserte størrelsen forklares med noe annet. Rasen har fått sin utforming i Canada. CKC anerkjente rasen i 1945, som den første kennelklubben i verden. FCI anerkjente den som sådan i 1982 og AKC i 2001. Rasen kom til Norge først i 1986 (Danmark/1982 – Sverige/1984). Den har de senere årene blitt stadig mer populær i Norge. Utseende, anatomi og fysikk Tolleren er den minste av retrieverne. Hannene blir gjerne ca. 48-52 cm i mankehøyde, mens tispene blir ca. 45-48 cm. Vekten ligger normalt på ca. 20-23 kg for en hanne, mens tispene gjerne veier 17-20 kg. Tolleren skal gi et kraftfullt og kompakt inntrykk, uten å virke tung. Den er både mindre og lettere i kroppen enn de øvrige retrieverne, noe som gjør den smidigere og hurtigere enn disse. Hodet er kileformet og er kortere og lettere enn for de andre retrieverrasene. Tolleren kan ha både mørkt pigment (sort) eller lyst pigment (kjøttfarget) på snute, lepper og øyelokkrender. Begge varianter er like aksepterte, men det er viktig at den fargen hunden har på snuten også skal gjenspeiles i lepper og øyelokkrender. Pelsen er middels lang og består av en stri dekkpels (vannavstøtende) med tett og myk underpels. Beheng i brystet og på baksiden av frambena og bakbena. Halen er rikelig behåret og skal gi et tett og buskete inntrykk. Fargen varierer fra ganske lys oransje til mørk rød (mørkere over ryggen, mot noe lysere i buken) med hvite markeringer i brystet, på labbene (sokker), på hodet (bliss) og ytterst på halespissen. Brunrød farge, sorte hår i pelsen eller hvite markeringer på andre steder enn poter, bryst, hode og haletupp er særdeles uønsket. Bruksområde Tolleren er en meget utholdende og energisk hund, og en meget dyktig svømmer og apportør. Den er en allsidig brukshund med en rekke flotte egenskaper som gjør den velegnet for så å si alle hundesporter. For mange utgjør den dessuten en god og stødig familiehund, som også har vakthundegenskaper, men det må understrekes at tolleren ikke er avlet med tanke på vokting og det er store individuelle forskjeller når det gjelder vaktinstinkter. Tollerens spesialitet er som rasenavnet tilsier såkalt tollingjakt/lokkejakt på ender og gjess, der den med sitt lekfulle vesen og bevegelsesmønster lokker viltet inn på skuddhold for så å apportere det fra vann eller land. Det er denne typen jakt som rasen er avlet fram for, men den kan også brukes til alt fra duejakt til storviltjakt (da hovedsakelig ettersøk). Den er en særdeles god sporhund og rasen har hatt stor fremgang som ettersøkshund på skadet vilt, redningshund, m.m. Tolleren er dog meget allsidig, og egner seg også godt til f.eks. lydighet, agility, freestyle og andre aktiviteter. Lynne og væremåte Tolleren er en meget lojal og viljesterk hund som passer for aktive familier. Rasen kan være noe skeptisk til fremmede og er kjent for å varsle når slike kommer på besøk, men den er ingen utpreget vakthund. Referanser Eksterne lenker Norsk Retrieverklubb Hunderaser Retrievere	norwegian_bokmål	0.754641
dog_eyes_green/Choroid_plexus.txt	The choroid plexus, or plica choroidea, is a plexus of cells that arises from the tela choroidea in each of the ventricles of the brain. Regions of the choroid plexus produce and secrete most of the cerebrospinal fluid (CSF) of the central nervous system. The choroid plexus consists of modified ependymal cells surrounding a core of capillaries and loose connective tissue. Multiple cilia on the ependymal cells move to circulate the cerebrospinal fluid. Structure[edit] Location[edit] Scheme of roof of fourth ventricle. The arrow is in the median aperture.1: Inferior medullary velum2: Choroid plexus 3: Cisterna magna of subarachnoid space4: Central canal5: Corpora quadrigemina6: Cerebral peduncle7: Superior medullary velum8: Ependymal lining of ventricle9: Pontine cistern of subarachnoid space There is a choroid plexus in each of the four ventricles. In the lateral ventricles, it is found in the body, and continued in an enlarged amount in the atrium. There is no choroid plexus in the anterior horn. In the third ventricle, there is a small amount in the roof that is continuous with that in the body, via the interventricular foramina, the channels that connect the lateral ventricles with the third ventricle. A choroid plexus is in part of the roof of the fourth ventricle. Microanatomy[edit] The choroid plexus consists of a layer of cuboidal epithelial cells surrounding a core of capillaries and loose connective tissue. The epithelium of the choroid plexus is continuous with the ependymal cell layer (ventricular layer) that lines the ventricular system. Progenitor ependymal cells are monociliated but they differentiate into multiciliated ependymal cells. Unlike the ependyma, the choroid plexus epithelial layer has tight junctions between the cells on the side facing the ventricle (apical surface). These tight junctions prevent the majority of substances from crossing the cell layer into the cerebrospinal fluid (CSF); thus the choroid plexus acts as a blood–CSF barrier. The choroid plexus folds into many villi around each capillary, creating frond-like processes that project into the ventricles. The villi, along with a brush border of microvilli, greatly increase the surface area of the choroid plexus. CSF is formed as plasma is filtered from the blood through the epithelial cells. Choroid plexus epithelial cells actively transport sodium ions into the ventricles and water follows the resulting osmotic gradient. The choroid plexus consists of many capillaries, separated from the ventricles by choroid epithelial cells. Fluid filters through these cells from blood to become cerebrospinal fluid. There is also much active transport of substances into, and out of, the CSF as it is made. Function[edit] CSF circulation The choroid plexus regulates the production and composition of cerebrospinal fluid (CSF), that provides the protective buoyancy for the brain. CSF acts as a medium for the glymphatic filtration system that facilitates the removal of metabolic waste from the brain, and the exchange of biomolecules and xenobiotics into and out of the brain. In this way the choroid plexus has a very important role in helping to maintain the delicate extracellular environment required by the brain to function optimally. The choroid plexus is also a major source of transferrin secretion that plays a part in iron homeostasis in the brain. Blood–cerebrospinal fluid barrier[edit] See also: Glymphatic system The blood–cerebrospinal fluid barrier (BCSFB) is a fluid–brain barrier that is composed of a pair of membranes that separate blood from CSF at the capillary level and CSF from brain tissue. The blood–CSF boundary at the choroid plexus is a membrane composed of epithelial cells and tight junctions that link them. There is a CSF-brain barrier at the level of the pia mater, but only in the embryo. Similar to the blood–brain barrier, the blood–CSF barrier functions to prevent the passage of most blood-borne substances into the brain, while selectively permitting the passage of specific substances (such as nutrients) into the brain and facilitating the removal of brain metabolites and metabolic products into the blood. Despite the similar function between the BBB and BCSFB, each facilitates the transport of different substances into the brain due to the distinctive structural characteristics of each of the two barrier systems. For a number of substances, the BCSFB is the primary site of entry into brain tissue. The blood–cerebrospinal fluid barrier has also been shown to modulate the entry of leukocytes from the blood to the central nervous system. The choroid plexus cells secrete cytokines that recruit monocyte-derived macrophages, among other cells, to the brain. This cellular trafficking has implications both in normal brain homeostasis and in neuroinflammatory processes. Clinical significance[edit] Choroid plexus cysts[edit] Main article: Choroid plexus cysts See also: Triple test During fetal development, some choroid plexus cysts may form. These fluid-filled cysts can be detected by a detailed second trimester ultrasound. The finding is relatively common, with a prevalence of ~1%. Choroid plexus cysts are usually an isolated finding. The cysts typically disappear later during pregnancy, and are usually harmless. They have no effect on infant and early childhood development. Choroid plexus cysts are associated with a 1% risk of fetal aneuploidy. The risk of aneuploidy increases to 10.5-12% if other risk factors or ultrasound findings are noted. Size, location, disappearance or progression, and whether the cysts are found on both sides or not do not affect the risk of aneuploidy. 44-50% of Edwards syndrome (trisomy 18) cases will present with choroid plexus cysts, as well 1.4% of Down syndrome (trisomy 21) cases. ~75% of abnormal karyotypes associated with choroid plexus cysts are trisomy 18, while the remainder are trisomy 21. Other[edit] There are three graded types of choroid plexus tumor that mainly affect young children. These types of cancer are rare. Etymology[edit] Choroid plexus translates from the Latin plexus chorioides, which mirrors Ancient Greek χοριοειδές πλέγμα. The word chorion was used by Galen to refer to the outer membrane enclosing the fetus. Both meanings of the word plexus are given as pleating, or braiding. As often happens language changes and the use of both choroid or chorioid is both accepted. Nomina Anatomica (now Terminologia Anatomica) reflected this dual usage. Additional images[edit] Coronal section of inferior horn of lateral ventricle. Choroid plexus histology 40x Choroid plexus Choroid plexus Choroid plexus See also[edit] This article uses anatomical terminology. Choroid plexus papilloma Tela choroidea	biology	468651	https://sv.wikipedia.org/wiki/Blod-hj%C3%A4rnbarri%C3%A4ren	Blod-hjärnbarriären	Blod-hjärnbarriären är mycket tätt sammanfogade kapillärväggar i hjärnans blodkärl som skyddar hjärnvävnaden. Blod-hjärnbarriären hindrar vissa droger, läkemedel och celler (till exempel vita blodkroppar, mikroorganismer) från att lämna blodbanan och nå hjärnans nervceller. Blod-hjärnbarriären utgör ett skydd mot bland annat infektion i hjärnan och är essentiell för det centrala nervsystemets funktion. Det rika nätverket av kapillärer i hjärnan medför att en nervcell aldrig befinner sig mer än 50 µm från en kapillär. Många av de blodburna kemiska substanser som cirkulerar i kroppen hindras dock från att nå hjärnan och ryggmärgen tack vare blod-hjärnbarriären. Till skillnad från blodkärl i det perifera blodcirkulationssystemet, som är mycket genomsläppliga, tillåter blod-hjärnbarriären en begränsad upptagning av ämnen i blodet. Ämnen som regelbundet passerar in genom blod-hjärnbarriären till hjärnans extracellulära vätska är syre, glukos och aminosyror. Ett annat exempel på regelbunden transport gäller utträde av koldioxid och andra avfallsämnen genom blod-hjärnbarriären till blodcirkulationen. Det finns strategiska platser i hjärnan där blod-hjärnbarriären saknas. Områdenas kollektiva namn är circumventrikulära organ och avsaknaden av blod-hjärnbarriär på de platser som ingår i gruppen tillåter diffusion av blodburna molekyler. Genom diffusion på dessa områden regleras endokrina funktioner och även funktioner förknippade med det autonoma nervsystemet. Hypofysen är ett sådant område utan blod-hjärnbarriär och där utsöndras och upptas hormon. Vid tallkottkörteln saknas också blod-hjärnbarriär vilket möjliggör upptagning av hormoner som påverkar strukturens reglering av dygnsrytm. I area postrema leder avsaknaden av blod-hjärnbarriären till att kräkreflexen kan starta när giftiga substanser återfinns i blodet. Övriga områden som ingår i det kollektiva namnet circumventrikulära organ är subfornikala organ och subkomissurala organ. Det finns indikationer på att blod-hjärnbarriärens genomsläpplighet ökar med åldrandet. Särskilt stor ökning har funnits hos patienter med demens (i synnerhet vaskulärdemens) och patienter med ökande skador i vit substans. Struktur Blod-hjärnbarriären består av tre cellulära element: endotelceller (som utgör kapillären), astrocytutskott och pericyter. Allt tyder på att alla komponenter av blod-hjärnbarriären är viktiga för en fungerande och stabil blod-hjärnbarriär. Ibland ingår även extracellulär matrix och neuron i det som beskrivs som den neurovaskulära enheten blod-hjärnbarriären. Endotelceller Blod-hjärnbarriärens endotelceller skiljer sig nämnvärt från vävnad i perifera endotelceller. I blod-hjärnbarriären har endotelceller täta fogar och zonula adherens, som är en form av celladhesion. Täta fogar och celladhesion begränsar paracellulär genomsläpplighet och medför avsaknad av fenestration.Genom att de bildar en dragkedja mellan intilliggande celler begränsar täta fogarna och celladhesion genomsläpplighet av blodburna molekyler. Celladhesionen består av ett cadherin-cateninkomplex och ger stöd till cellens struktur. Strukturen får ytterligare stöd från basala lamina, en 30–40 nm tjock matrix, som består av typ IV kollagen, proteoglycans, fibronectin, laminin och andra proteiner i extracellulär matrix. De täta fogarna består av fibrer och omfattar tre sorter integralt membranprotein; claudiner, occludiner och celladhesionsmolekyler. De omfattar även ett antal cytoplasmiska proteiner som ZO-1, ZO-2, ZO-3 och cingulin. Tack vare täta fogar delas plasmamembranet upp i två skilda domäner. Ett apikalt membran som är riktat mot blodflödet och ett basolateralt membran som är riktat mot hjärnvävnad. Endotelceller i hjärnan har därför särskilda egenskaper som är unika i jämförelse med övrig endotelium. Utöver det ovan nämnda innebär de specifika egenskaperna en barriär mot enzymer, elektrisk transendotelisk resistens, minimal vesikulär transport och större volym och antal av mitokondriskt innehåll. Astrocytutskott Astrocyter, som är en typ av gliacell, är stjärnformade och fäster runt blodkärlet via fotliknande utskott. 80-90 % av kapillären täcks av astrocytutskotten. Tidigare ansåg man att astrocyter var avgörande för blod-hjärnbarriären när det gäller genomsläpplighet men dagens forskning pekar på att astrocytens största funktion är att upprätthålla kretsloppet av näring och avfall. Ett kretslopp mellan kapillärerna och hjärnans extracellullära vätska och nervceller.Astrocyterna håller kapillärerna och neuronerna skilda från varandra. Interaktionen mellan endotelcellerna och astrocyterna är viktig för blod-hjärnbarriären och det finns växande bevis för att endotelcellerna har en ömsesidig framkallande influens över astrocyterna. Molekulära faktorer som frigörs från gliaceller, som till exempel neurotrofisk faktor GDNF bidrar till stabiliteten i blod-hjärnbarriärens uniformitet. Pericyter Pericyter finns inbäddade i basala lamina och återfinns därav mellan endotelcellerna och astrocyterna. Det finns studier som visar på att pericyter kan framkalla att endotelceller tätnar genom att reglera täta fogarnas celldelning, differentiering och formation i endotelcellerna. Pericyter i blod-hjärnbarriären har visat en fagocyterande förmåga som kan vara tecken på att de är inblandade i neuroimmunologiska funktioner. Dessutom ger pericyter i blod-hjärnbarriären uttryck för ett antal receptorer för vasoaktiva ämnen vilket tyder på att de också kan vara inblandade i hjärnans självreglering. Funktion Enkel diffusion Trots att blod-hjärnbarriären är 50-100 gånger tätare än blodkärl i resten av kroppen och att många ämnen hindras från att komma in till extracellullär vätska i det centrala nervsystemet är det vissa molekyler som kan korsa blod-hjärnbarriären. Det finns två huvudsakliga sätt som blodburna molekyler kan ta sig igenom. Ett sätt kallas passivt eller enkelt och har att göra med molekylernas egenskaper vad gäller fettlöslighet och laddning. Små molekyler som syre och koldioxid är fettlösliga och inte joniserade och kan därför passera blod-hjärnbarriären fritt via diffusion längs deras koncentrationsgradient. Generellt gäller att ju mer fettlöslig en molekyl är (vilket ger ingen eller liten polär karaktär) desto lättare är det för den att passera in i eller ut från endotelcellerna i hjärnan. Receptormedierad diffusion Många viktiga metaboliska substanser är mycket polariserade och har därför ingen genomsläpplighet. Molekyler tillhörande glukos, aminosyror och andra näringsämnen är exempel på substanser som är nödvändiga för centrala nervsystemets funktion men som inte kan ta sig igenom blod-hjärnbarriären fritt. Den här typen av molekylers transportsystem är receptormedierade och kräver inte heller energi utan förflyttning sker längs ämnets koncentrationsgradiens. Diffusion sker i det här fallet genom bärare som transporterar specifika substanser. Lösta molekyler binds till specifika membranprotein som är bärare genom blod-hjärnbarriären. Det finns olika system för att tillgodose hjärnans metaboliska efterfrågan. Glukostransportör-1 (GLUT-1), L-systemet och A-systemet för aminosyrebärare, för att nämna några. Aktivt transportsystem Det andra sättet är via ett aktivt transportsystem som kräver energi. Dessa transportsystem består av jonkanaler lika dem i nervcellerna. Endocytos Det finns ännu en viktig mekanism när det gäller centrala nervsystemets upptagning av ämnen. Den heter endocytos och är en process där celler absorberar material genom att innesluta det i cellmembranet. Endocytos är begränsad i hjärnans vaskulära system jämfört med kapillärer i resten av kroppen. Det finns dock två typer av endocytos som tillåter centrala nervsystemet att selektiv uppta makromolekyler. Reglerad upptagning av hormoner, tillväxt faktorer, enzymer och insulin är möjliga genom dessa mekanismer som är högt specialiserade i blod-hjärnbarriären. Ökad genomsläpplighet Hjärnskador Att blod-hjärnbarriären tappar ogenomtränglighet och öppnar upp sig mer eller mindre är kritiskt för neurologiska sjukdomars utveckling och framskridande. Ökad genomsläpplighet i blod-hjärnbarriären är förknippat med en rad olika hjärnskador, som till exempel traumatisk hjärnskada, hjärninfarkt, hjärnblödning, inflammatoriska sjukdomar som hjärnhinneinflammation och allvarliga toxiska metaboliska rubbningar. Det finns också en rad patologiska förändringar av blod-hjärnbarriären som leder till nedbrytning av funktionen. Normalprocess Det finns dock modesta och reversibla förändringar i blod-hjärnbarriärens ogenomtränglighet som är en reglerad normalprocess och uppstår som svar på frigjorda agenter. I plasman finns till exempel faktorer som krävs för läkningsprocesser i hjärnan samt för immunologisk övervakning av centrala nervsystemet. De molekyler som kan påverka blod-hjärnbarriärens täthet kommer från tre källor; endotelium, astrocyter och nervterminaler som befinner sig i närheten av kapillärer. Många av dessa kemiska budbärare har identifierats, som till exempel glutamat, aspartat, taurin, ATP, endotelin-1, kväveoxid, tumörnekrosfaktor alpha och interleukin 1-beta. Andra humorala agenter som ökar genomsläpplighet är bradykinin, serotonin, histamin, och substans P. Den här typen av reglerad ökning av genomsläpplighet sker till följd av att de täta fogarnas paracellulära gångar tillfälligt öppnas. Referenser Centrala nervsystemet Neurologi	swedish	0.596809
dog_eyes_green/eye-structure-and-function-in-dogs.txt	honeypot link skip to main content skip to main content * MSD MANUAL Veterinary Manual VETERINARY CONTENT PET HEALTH RESOURCES QUIZZES ABOUT 1. Veterinary / 2. Dog Owners / 3. Eye Disorders of Dogs / 4. Eye Structure and Function in Dogs / PET OWNER VERSION # Eye Structure and Function in Dogs By Kirk N. Gelatt , VMD, DACVO , Department of Small Animal Clinical Sciences, College of Veterinary Medicine, University of Florida Reviewed/Revised Jun 2018 View the Professional Version * Physical Examination of the Eye \| * For More Information \| The eyes of animals, including dogs' eyes , function much like yours. Animals also develop many of the same eye problems that people can have, including cataracts, glaucoma, and other problems. It is important for your dog to receive good eye care to protect its sight and allow it to interact comfortably with its environment. The eye is an active organ that constantly adjusts the amount of light it lets in and focuses on objects near and far. It produces continuous images that are quickly relayed to the brain. ### Anatomy of the eye --- The bony cavity or socket that contains the eyeball is called the orbit . The orbit is a structure that is formed by several bones. The orbit also contains muscles, nerves, blood vessels, and the structures that produce and drain tears. The white of the eye is called the sclera . This is the relatively tough outer layer of the eye. It is covered by a thin membrane, called the conjunctiva , located near the front of the eye. The conjunctiva runs to the edge of the cornea and covers the inside of the eyelid. The cornea is a clear dome on the front surface of the eye that lets light in. The cornea not only protects the front of the eye, but also helps focus light on the retina at the back of the eye. The iris is the circular, colored area of the eye. It controls the amount of light that enters the eye by making the pupil larger or smaller. The pupil is the black area in the middle of the eye. The pupil is controlled by the circular sphincter muscle. When the environment is dark, the pupil enlarges to let in more light; when the environment is bright, the pupil becomes smaller to let in less light. The lens , which sits behind the iris, changes its shape to focus light onto the retina. Small muscles (ciliary muscles) contract to cause the lens to become thicker, which allows the lens to focus on nearby objects. The ciliary muscles relax to cause the lens to become thinner when it focuses on distant objects. These lens changes are limited in dogs. The retina contains the cells that sense light (photoreceptors). The most sensitive area of the retina is called the area centralis in dogs; this area contains thousands of tightly packed photoreceptors that make visual images sharp. Each photoreceptor is attached to a nerve fiber. All the nerve fibers are bundled together to form the optic nerve . The photoreceptors in the retina convert the image into electrical impulses, which are carried to the brain by the optic nerve. The upper and lower eyelids are thin folds of skin that can cover the eye and reflexively blink to protect the eye. Blinking also helps spread tears over the surface of the eye, keeping it moist and clearing away small particles. The eyes of a dog are protected not only by the same types of eyelids that people have, but also by the nictitating membrane , which is sometimes called the third eyelid. This additional eyelid is a whitish pink color, and it is found under the lower eyelids on the inside corner of the eye (near the nose). The third eyelid extends across the eye when needed to protect the eyeball from scratches (for example, while traveling through brush) or in response to inflammation. To function properly, eyes must be kept moist. Tears are the source of this needed moisture. Tears are comprised of water, oil, and mucus. Lacrimal glands produce the watery portion of tears. They are located at the top outer edge of each eye. Mucus glands in the conjunctiva (called goblet cells) produce mucus. Meibomian glands within the eyelids produce the oily portion. The mixture of water, oil, and mucus creates a more protective tear that is slower to evaporate. Nasolacrimal ducts allow tears to drain from each eye into the nose. Each of these ducts has openings at the edge of the upper and lower eyelids near the nose. ### Structures that protect the eye, dog --- ## Physical Examination of the Eye Because of the importance of sight to your dog, one of the critical aspects of any examination or checkup will be an examination of your pet’s eyes. Be prepared to provide any background or medical history (such as any previous injury to the eye, history of treatments or medications used, any signs of visual problems, and vaccination history) that might help with the diagnosis of any eye problem. The first step of the examination involves checking to be sure that the shape and outline of the eyes are normal and that there are no obvious abnormalities. Then, using light and magnification in a darkened room, the reflexes of the pupils and the front part of the eye are examined. Depending on these findings and the reasons for the checkup, additional tests may be needed. Some parts of the examination may require sedation or anesthesia. A test, called the Schirmer tear test, may be performed to ensure that the eyes are producing enough tears to keep them moist. This is a relatively simple test in which a small paper strip is inserted under the eyelid to measure the amount of moisture produced. Another common test involves placing a small drop of fluorescein stain into each eye, which allows defects—such as scratches in the cornea of the eye—to be detected. Pressure within the eye is measured painlessly using an instrument called a tonometer. (If eye pressure is too high, optic nerve damage can occur, leading to irreversible blindness.) A swab may also be done to culture for bacteria or fungi. The eyelids may be turned inside out to examine the underside. The nasolacrimal tear duct may be flushed to evaluate the external parts of the eye. Drops may be added to the eyes to allow the pupils to become dilated so that the veterinarian may examine the internal parts of the eye using an ophthalmoscope. ## For More Information Also see professional content regarding eye structure, function, and physical examination . Test your Knowledge now Take a Quiz! * About * Disclaimer * Cookie Preferences * * Copyright © 2024 Merck & Co., Inc., Rahway, NJ, USA and its affiliates. All rights reserved.	biology	14911	https://no.wikipedia.org/wiki/%C3%98ye	Øye	Øye (lat. oculus) er en biologisk innretning, som projiserer lys via en linse på synsnerver i netthinnen og omsetter signalene til impulser i synsnervene. Synsnervene videresender informasjoner om lyset til hjernens occipitallapper, som fortolker disse, og skaper et bilde. Menneskets øye Øyeeplet (lat. bulbus oculi) Øyeeplet er kuleformet og inneholder brytende medier som fokuserer lyset på netthinnen. Sanseceller i netthinnen omdanner lyset til nervesignaler. Hornhinnen Hornhinnen (lat. cornea) ligger fremste på øyeeplet når øyelokkene er åpne. Hornhinnen er blank og klart gjennomsiktig. Den har et større antall lag som særlig kan sees ved bruk av spaltelampe. Det ytterste laget av hornhinnen består av et cellelag som er en celle tykt. Sår i dette cellelaget oppstår ved fremmedlegeme på øyet, solblindhet, sveiseblink og enkelte virusinfeksjoner. Slike sår kan bli synlige ved å dryppe fargestoffet fluorescein på øyet. Fargestoffet er gult, men ved kontakt med hornhinnen under cellelaget, blir fargen grønn. (se også hornhinnebetennelse) Regnbuehinne Regnbuehinnen eller iris, er den fargede delen av øyet hos virveldyr, inkludert mennesker. Regnbuehinnen har et hull, pupillen, i midten og muskler som gjør at pupillens størrelse kan justeres etter lysintensiteten. Pupillen Pupillen er hullet midt i regnbuehinnen. Hullet eller pupillens størrelse justeres med muskler i regnbuehinnen. Størrelsen endres basert på mengde lys mot øyet. Gjennom pupillen slippes lyset inn i det indre øyet. Linsen befinner seg rett bak pupillen, i øyets lysåpning. Her blir lyset som utgjør det visuelle inntrykket vi oppfatter som det endelige bildet, snudd før det når netthinnen. Netthinnen Netthinnen (retina) fanger opp synsinntrykk og ligger som et bakteppe innvendig i øyet. Den består av celler utformet som tapper og staver. Tappene er med på å oppfatte farger og gir et skarpt syn. Stavene gir svart-hvitt-syn og syn i mørke. Netthinnen kan reflekte lys tilbake som rød refleks (se nedenfor), som hos katter og mange andre pattedyr. I tillegg til det visuelle systemets tapper og staver, er det lys-sensitive ganglier som registrer lysstyrke og -farge - selv hos mange totalt blinde mennesker som har minst ett øyeeple intakt. Lyset som registreres av disse cellene er det sterkeste av signalene som styrer døgnrytmen. Synsnerven forlater netthinnen ved den blinde flekk. Skarpsynet i netthinnen er lokalisert til den gule flekk (macula lutea), hvor det er særlig høy tetthet av tapper og staver. Orbita Øyehulen. Er større enn bulbus oculi, som gir plass til de ytre øyemusklene, tallrike årer og nerver, samt tårekjertelen. Gulvet i orbita grenser mot sinus maxillaris (kjevebihulen), taket mot sinus frontalis (pannebihulen) og kraniehulen. Bakveggen, som ligger i høyde med øvre del av hjernestammen, har åpninger til årer og nerver. De seks ytre øyemusklene beveger bulbus oculi. Tverrstripet muskelfibre. Øyemusklene er synkronisert og jobber sammen, bortsett fra når vi studerer noe som er svært nært. Her er de listet opp i forhold til hvilken nerve som forsyner dem: Nervus oculomotorius Musculus rectus superior – drar øyet oppover Musculus rectus inferior – drar øyet nedover Musculus rectus medialis – drar øyet innover Musculus obliquus inferior – roterer øyet utover og drar det litt oppover Nervus trochlearis Musculus obliquus superior – roterer øyet innover og drar det litt nedover Nervus abducens Musculus rectus lateralis – drar øyet mot siden Arteria ophtalmica går fra arteria carotis interna og deler seg til en rekke mindre grener som forsyner ulike deler i orbita. Den viktigste grenen er arteria centralis retinae, som følger nervus opticus inn i bulbus oculi til retina, og er hovedansvarlig for blod til fotoreseptorene. Nervus opticus (2. hjernenerve)leder afferente signaler fra fotoreseptorene Nervus oculomotorius (3. hjernenerve) leder efferente signaler til tverrstripet og glatt muskulatur – styrer øyemotorikken. Bulbus oculi beskyttes mekanisk av øyelokk og øyevipper. Lokkene inneholder stive plater av bindevev, kantene har en rand av hår og utallige kjertelåpninger. En muskel sørger for at øyet kan åpnes, mens ringformet muskelfiber sørger for at øyet kan forsnevres/lukkes. Innsiden er kledd med conjuctiva(tårehinnen) som slår seg over på sclera og dekker denne helt inn mot cornea. Tårekjertelen ligger diagonalt over på andre siden av tårekanalene og produserer tårevæske som smører og renser hornhinnen cornea. Irritasjon eller rusk fører til økt produksjon. Tårekanalene drenerer tårevæske til nesehulen Disse styres av parasympatiske nervefibre – det er ingen viljemessig kontroll over produksjonen, men den kan påvirkes av emosjonelle forhold. Den blinde flekk En annen test går ut på å lukke det ene øyet og holde en liten lys gjenstand et stykke rett foran det åpne øyet. Stirr på et punkt bak gjenstanden, og før den lyse gjenstanden ut til siden/samme side som det åpne øyet. Ca 15-20 grader ut til siden sees plutselig ikke den lyse gjenstanden. Bildet av den har truffet netthinnen på den blinde flekk. Rød refleks Når lys fra ett punkt i et ellers mørkt rom treffer et øye med stor pupill, vil lyset som samles på netthinnen også sendes tilbake, slik at hvis vi ser på øyet fra nesten samme retning som lyset kommer fra, vil vi se et rødt lys der vi vanligvis ser det sorte i pupillen i midten av øyet. Dette brukes til undersøkelser på helsestasjonen for å utelukke en sjelden kreftsykdom på netthinnen. Ved katarakt (grå stær), når øyets linse blir matt, vil vi ikke se rød refleks. Ved en del tilstander med puss eller uklarheter i øyets væske vil også rød refleks bli borte. Når vi kjører bil i mørke kan vi se dyr på langt hold som små lyspunkter som er rød refleks fra øynene. Senehinne og konjunktiva Øyeeplet er kledd av en senehinne (lat. sclera) som musklene (se under) festes i. Senehinnen dekker hele øyeeplet bortsett fra hornhinnen, som må være gjennomsiktig. Over den delen av senehinnen som ligger eksponert for luft ligger konjunktiva, som er et hudlag med blodårer og nerver. Konjunktiva dekker også innsiden av øyelokkene. (Se også konjunktivitt.) Menneskets øye i kunst, litteratur og filosofi Det blir av noen hevdet at «Øynene er sjelens speil» og at de kan utvise frykt, glede, sorg, tristhet, tankefullhet, hat, hevn og ondskap. De meste berømte øyne i billedkunsten er trolig øynene til Mona Lisa, portrettet Leonardo da Vinci malte. Øyet hos virveldyr Virveldyr har primært minst tre øyne, et på hver side fremme på neurokraniet, samt et såkalt panneøye eller parietaløye/pinealøye midt i pannen. Dette er fremdeles synlig som et lysfølsomt organ blant flere arter innen alle virveldyrklasser, med unntak av fugler og pattedyr hvor det uten unntak, er modifisert til en kjertel kalt pinealkjertelen. Øyet hos pattedyr Øyet hos andre pattedyr har en lik oppbygning som øyet hos mennesket, det er kulerundt og har samme anatomi. Noen pattedyr har bedre syn enn mennesket, særlig det å se når det er svakt lys, nattsyn. Øyet hos fugler Øyet hos fuglene har i motsetning til øyet hos pattedyr ikke en rund form, men er forstørret og avflatet inne i hodet, som en omvendt trakt. Dette gir mindre bevegelsesfrihet, men desto bedre syn. En ring av små bein rundt hvert øye gir feste for øyemuskler. Fugleøyet ser ut til å være det best utviklete av alle virveldyrøyne. Selv om de er utstyrt med både et øvre og et nedre øyelokk, benytter de fleste en blinkhinne ved blunking. Blinkhinnen beskytter øyet under flyging, og fungerer både som solbriller og beskyttelse mot vær og vind. Hos dykkende fugler kan den til og med brukes som dykkerbriller som bidrar til skarpt syn under vann, i tillegg til at disse fuglene ofte har en svært fleksibel linse som kan krummes nok til å se skarpt både i vann og i luft. Ugler er en av de få gruppene som blunker på samme måte som pattedyr. Fugler har er to fovea på netthinnen, i motsetning til mennesket, som bare har en. Dagaktive fugler kan dessuten oppfatte ultrafiolett og polarisert lys. Øyet hos fisker Øynene til slimåler er rudimentære og mangler linse. At noen av artene har mer utviklete øyne enn andre forteller at de dårlig utviklete øynene er en sekundær egenskap og en tilpasning til de mørke havdypene hvor de holder til. Øyet hos virvelløse dyr Leddyr Leddyr er en stor dyregruppe med mange, svært ulike arter, derfor er det variasjon i hvordan øynene er utformet. Generelt er det to slags øyne i denne dyregruppen. Fasettøyne og punktøye eller medianøye. Fasettøye, er et sammensatt øye som består av flere enkelt øyne (ommatidier) i en gruppe, ett «stort øye». Hvert slikt enkelt øye er sekskantet. Slike øyne er vanlig hos de fleste leddyr og forekommer hos de fleste insekter, krepsdyr, mangefotinger, dolkhaler og også i den fossile gruppen trilobitter. Enkelte arter kan ha fasettøyne med bare noen få øyne, eller fasetter. Men et fasettøye kan også bestå av opp til små sekskantete fasetter. Øynene er enten hårløse eller besatt av mengder av små korte rett utstående hår, mellom fasettene. Fasettene øverst på øyet kan hos noen arter være større enn fasettene nederst. Punktøyne / medianøyne (ocellus) er en type enkelt øyne. Punktøyne oppfatter bare lys eller mørke. De brukes derfor ikke til å se med, men mer som ekstraøyne. Mange leddyr har slike punkøyne oppe på hodet eller i pannen. Ofte er det tre punktøyer – som danner en trekant. Bildegalleri Se også Syn Blindhet Eksterne lenker Øyet: Derfor blir synet dårligere etter 40 1000 artikler enhver Wikipedia bør ha	norwegian_bokmål	0.533658
dog_eyes_green/dog-eye-anatomy.txt	Skip to content * About Us * How it works * What we stand for * Our Founders * Our experts * News * Endorsements * Research Menu * About Us * How it works * What we stand for * Our Founders * Our experts * News * Endorsements * Research * Zigzag App: Puppy Training Made Easy * About Us * How it works * What we stand for * Our Founders * Experts * Endorsements * News * Research * Blog * Contact * * Menu * Zigzag App: Puppy Training Made Easy * About Us * How it works * What we stand for * Our Founders * Experts * Endorsements * News * Research * Blog * Contact * * * Blog * Contact Menu * Blog * Contact Download now Download * * * * # Dogs Eye Anatomy : Everything You Need To Know #### By Zigzag Puppy Expert, Petrina Firth Fully Qualified COAPE Behaviourist and Registered Training Instructor with The Animal Behaviour and Training Council #### In this article: We’re not exaggerating – dogs’ eyes are a marvel of engineering. Their eyes allow them to see the way in the incredible way they do. Puppy eyes are much like our own eyes. They have a lot of components, although they work differently. In fact, in some aspects, dogs’ eyes are far superior to ours; they have a broader field of vision and can detect movement far better. In this article, we’ll keep your eyes peeled as we take a look at the anatomy of dogs’ eyes. We’ll go over how puppy eyes work, and answer all kinds of questions like how can dogs see in the dark, can dogs see colour, can dogs watch TV, and what colours dogs see best. We bet you’re dying to know. Check out the Zigzag puppy training app for more information on your puppy’s development, and learn much more about how they see the world. We’ve also got a team of top-class dog trainers and behaviourists to answer your questions. They’ll keep a (human) eye on you throughout your journey through puppyhood too. Photo by Jesse Collins on Unsplash ## What is the anatomy of dogs’ eyes? Dog eyes are made up of a cornea, iris, pupil, lens, retina, and sclera. They also have an upper and lower eyelid and a third eyelid on the outside of the eye for protection. Rods and cones are how images and light are processed and important for vision. Let’s take a closer look at how each of these works. ### Cornea The transparent dome-like structure that covers the front of the eye. It bends light as it enters the eye. ### Iris This is the coloured part of a dog’s eye. It’s the bit that makes them beautiful, essentially. It can be yellow, brown, blue or even white, which expands and contracts in low light or bright light. ### Pupil According to light intensity, the pupil opens and closes. ### Lens The lens focuses light into the retina ### Retina This transforms light signals into the optic nerve and off into the brain. ### Sclera This is the white part of the eye that surrounds the iris. ### Eyelids Dogs have three eyelids: an upper, a lower and then a third eyelid. They mainly serve to protect the eye, the third eyelid sweeping back and forth to spread tear film and keep the eye moisturised. ### Rods and Cones There are photoreceptors found in the retina, these process light signals. Cones allow dogs to see colours, while rods allow them to see shapes. ## How do puppy eyes work? Puppies are born with their eyelids closed because their eyes are not fully developed. It’s actually quite endearing. Because their eyes are still developing for the first two weeks, their eyelids remain closed to protect them. Puppy eyes open around 14 days and usually one at a time. Puppies do quite alright without their eyes being open at the start actually, they don’t need their vision much as newborns. All they need is to find their mother for milk, and they mainly rely on their sense of smell for this. When they first open their eyes, their vision will be poor, and their eyes will look grey or blueish and a little milky. As the weeks go by, their eyesight develops more, and they’ll start seeing more clearly and start recognising shapes better. Puppy eyes reach full development at around 8 weeks of age. Once developed, their eyes will work the same way as dogs’ eyes do. Light goes into the eye through the cornea, and is focused onto the lens by the pupil at the centre of the iris. The lens bounces the light around, and then focuses light onto the retina, which sends a signal through the optic nerve into the brain. But it’s really the rods and cones who control how puppies see. Rods are light-sensitive and are used for shape and motion perception; dogs have far more rods than humans do. Cones are what control colour perception, and are the responsible ones for the reputation of dogs being colourblind, as they only have around 20% of the cones that humans do. But in reality, puppies are no different in that the spectrum of colour they see is different to that of a human. Instead of seeing a full array of colours, they see things in a yellow-blue spectrum. Despite not being able to see a full spectrum of colour, puppy eyes are much more sensitive than ours at night, and they also have an excellent movement-activated vision. This is an evolutionary characteristic that would have been extremely useful for hunting and they retained it after domestication . Photo by Izabelly Marques on Unsplash ## Can dogs see in the dark? Well…kinda! Our dogs’ wild ancestors were crepuscular, meaning that they hunted at dawn and dusk. Dogs, as we know them today, have kept this interesting talent. Their ability to see in the dark is made possible due to a reflective system called the tapetum lucidum (easily confused with a Harry Potter spell), which sits behind the retina and helps to enhance visual sensitivity at low light levels. Dogs have light-sensitive rods in their eyes, which help them detect movement and light in low-light conditions. However, when it’s pitch black dogs will struggle to see as well as us, and will rely on their other powerful senses like their sense of smell to move around. ## Can dogs see colour? Dogs see in certain colours, but not all. While humans see the entire colour spectrum in trichromatic vision, dogs have a dichromatic vision and only see blue/yellow, plus shades of grey and brown. This is because we have three types of cones in our eyes, and dogs only have two. Dogs also only have around 20% of the cones that humans do, meaning that the colours they do see are more muted, whereas humans see the world in more vivid and bright colours. ## What colours do dogs see best? Dogs have dichromatic vision, which means that their eyes can best see the colours yellow and blue, along with combinations of the two. Blue, blue-green, and violet are all different shades of blue to a dog, and shades of red and green are likely to appear as browns and grayscale. This is the same across all breeds. They all have the same colour vision, although different breeds, due to their skull shape and eye position, will have better eyesight in terms of depth perception than others. This may help you figure out what colour toys to buy your dog, blue and yellow are definitely best as they’ll be able to find them and see them easily. Photo by Mathis Jrdl on Unsplash ## How to care for my dog’s eyes? Puppy eyes should be cleaned as part of a regular grooming routine , and the sooner you start, the better. You want them to get used to grooming when they’re young so you don’t face any hiccups when they’re older. Check your dog’s eyes daily, and wipe away any dirt or debris with a clean cotton pad. Some dogs will wake up with weird eye snot. Don’t rub their actual eyeballs, by the way! Just wipe away any dirt around them and on the corner, where it tends to accumulate. You shouldn’t need to use any harsh chemicals or specific cleaners for this, just cooled boiled water on a cotton pad is all you need to clean the eyes fully. If your dog’s eyes are runny , inflamed or bloodshot , you should see a vet instead of diagnosing them at home with eye drops. Dogs’ eyes are precious, so it’s worth taking care of them! Different breeds of dogs, such as Pugs and French Bulldogs , will likely need more care and attention paid to their eyes. Due to their flat faces, they have a higher risk of gunk getting in, because their eyes stick out more. They also have a lot of skin around their eyes, which can lead to eye problems like cherry eye , and also are more prone to ulcers. We love our little aliens, and keeping an eye will help make sure they actually keep their eyes. Hmm…too dark? We hope this has given you a good overview of how dogs and puppies see the world. We’ve covered how dogs see best in blue and yellow, and how you should use those colours for any toys you choose to treat them with. We’re sure you’re well-equipped to take care of your dog’s eyes well, but your vet will always be happy to help you if you notice any redness or soreness in the eye. Now that you’re here, why not read our guide all about how to brush your puppy’s teeth ? You’ll need to know what toothbrush and toothpaste to get for their dashing smile too, so be sure to check it out. Download the Zigzag app , and find much more helpful information on how to take care of your puppy, including grooming, and that step-by-step training programme you’ve been looking for all this time. We even have breed-specific training guides to give your puppy the best start and a team of professional trainers and behaviourists on hand to talk to, whenever you run into some trouble. #### By Petrina Firth, Zigzag Puppy Expert Fully Qualified COAPE Behaviourist and Registered Training Instructor with The Animal Behaviour and Training Council #### In this article: #### Zigzag App ### Fun & Easy Puppy Training App * Personal training schedule based on age & breed * 24/7 Puppy expert coaching for pawnic moments * 3-5 Daily dog exercises ## Have a pup they said. It will be fun they said. #### We go the extra mile for you. 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These cookies help provide information on metrics the number of visitors, bounce rate, traffic source, etc. Advertisement Advertisement Advertisement cookies are used to provide visitors with relevant ads and marketing campaigns. These cookies track visitors across websites and collect information to provide customized ads. Others Others Other uncategorized cookies are those that are being analyzed and have not been classified into a category as yet. SAVE & ACCEPT ### Zigzag Puppy Coach #1 Puppy Training App Install ## Be first in line! Just like you – we’re also training to get better. Therefore, we can’t let everybody in at once. Sign up below and we’ll let you know when there’s a spot available for you. Email Yes, I want in!	biology	429273	https://da.wikipedia.org/wiki/Staffordshire%20Bull%20Terrier	Staffordshire Bull Terrier	Staffordshire Bull Terrier ("Staffy'en") er en hunderace, der stammer fra Staffordshire i Storbritannien. De første eksemplarer af racen blev indregistreret i England i 1935, hvilket er 100 år efter at hundekamp blev forbudt. Racen er derfor udelukkende skabt som familiehund og udstillingshund. Racen blev i 2006 kåret til årets familiehund i England. Staffordshire bull terrier stammer formodentlig fra datidens bulldogracer og terrierracer, med vægt på bulldogracerne. I det berømte Staffordshire Regiment, er staffordshire bull terrier regimentsmaskot. Efter 2. verdenskrig blev det tradition, at regimentet ved parader havde en staffordshire bull terrier til at gå forrest. Den har et bredt hoved, med kort snudeparti og rosen-ører (ørekupering er ikke tilladt i Danmark), stærke kæber og øjne placeret så blikket er fremefter. Den har korte ben og en middel-lang hale, bredt bagparti og brede skuldre. Temperament Staffordshire Bull Terrier er loyal og hengiven overfor sin familie, og er særligt velfungerende med børn. Den trives med familielivet og nyder at dase i sofaen såvel som at gå lange ture. Den er energisk og evigt begejstret, uanset hvad den laver. Den er venlig af sind, følsom og intelligent. Racen er frygtløs og nysgerrig på alt omkring den. Det er skønt i hverdagen, men det kan også betyde at ejeren skal tænke på vegne af hunden. Ser en Staffordshire noget spændende i horisonten, så tænker den ikke over om den springer 2 meter ned fra en altan eller løber ud over en vej. Derfor er det også vigtigt at træne en Staffordshire Bull Terriers impulskontrol. Den er uegnet som vagthund, og selvom den godt kan sige vov, når der kommer gæster, så er den generelt utroligt venlig overfor fremmede. Mange har oplevet indbrud, hvor overvågningen har vidst Staffordshire Bull Terrieren slikke og ville lege med tyven. Efter kønsmodning kan nogle Staffordshire Bull Terriers godt være mindre sociale og legesyge overfor fremmede hunde, og særligt hunde af samme køn som dem selv. Ligesom med alt andet socialisering og træning, er det vigtigt at man som ejer præger sin hund på en positiv måde, og bidrager til at få en velafbalanceret hund. Aktivitetsniveau En Staffordshire Bull Terrier er en aktiv race. De er nysgerrige og har brug for at få tilfredsstillet deres nysgerrighed og fysiske behov for aktivitet. Et par gåture rundt i villakvarteret hver dag er sjældent tilstrækkeligt. Den vil gerne træne og den vil gerne ud på tur. Løbeture eller lange gåture i skoven vil være en stor glæde for racen. Racen er ikke altid god til at komme af med varmen om sommeren, derfor skal man være opmærksom på ikke at motionere når det er varmest, og sørge for at hjælpe hunden med at køle ned ved at give den rigeligt væske og eventuelt et køledækken. Tag gerne en drikkedunk med på gåturene. Da hunden er stærk og har utroligt meget energi, vil den oftest lege langt tid længere end man lige forestiller sig - og hvad den kan holde til. Derfor er det vigtigt at du sætter restriktioner på aktiviteten, selvom hunden virker glad for at leget i det uendelige, da det kan fremprovokere stress. Pelspleje Den helt korte og glatte pels har ingen underuld. Det betyder også, at den er dårlig til at holde på varmen om vinteren. Derfor er racen kuldskær og et lunt dækken vil være en fordel i vinterperioden. Pelsen er let at holde, og kan tørres af med et opvredet vaskeskind, for at fjerne eventuelle løse hår. Træning Det er en intelligent race, der gerne vil samarbejde og træne med sin fører. Den kan være stædig, så god tålmodighed og gode belønninger, samt generel positiv indlæring anbefales. Du får de bedste resultater med positiv forstærkning, og Staffordshire Bull Terrieren kan klare sig godt i forskellige hundesportsgrene som lydighed, rally, nosework og agility. Den er særdeles glad for at lege, både med sine mennesker og med andre hunde. Derfor er legetøj i træning en en stor fordel, og en motivationsfaktor. Da racen kan have tendens til at stresse, og have dårlig impulskontrol, vil det være en god idé at træne nedstressning og passivitetstræning. Dette gøres bedst ved at lege af kortere varighed, og rose hunden for at optræde roligt imellem legene. Farver og fysik Rød, fawn (lysebrun), hvid, sort, brindle (tigerstribet) eller blå. Alle aftegn kan være med hvide aftegninger. Højde: 35,5 cm - 40,5 cm Vægt hanner: 13-17 kg. Vægt tæver: 11-15 kg. Foder Når du vælger foder til din staffordshire bull terrier, er det vigtigt at du vælger et foder der dækker alle dens behov. Det er særlig vigtigt at hvalpen fodres korrekt det første år, da det har stor betydning for om den eventuelt udvikler ledsygdomme. Da racen kan være disponeret for hudproblemer, er det vigtigt at du er opmærksom på dette og giver et foder, der understøtter en sund hud. Er du i tvivl om, hvilket foder din hund skal have og hvilken mængde, så kan du altid spørge din dyrlæge til råds. Referencer Eksterne henvisninger Terriere Hunderacer fra England	danish	0.928583
dog_eyes_green/55-a-guide-to-common-eye-problems.txt	Please click here for the latest information on how to access our services. CLINIC CONTACT NUMBERS * Brighouse: 01484 404400 * Denby Dale: 01484 865845 * Dewsbury: 01924 465592 * Mirfield: 01924 492155 * Penistone: 01226 764764 * Sandal: 01924 258833 * Wakefield: 01924 372017 * Waterloo: 01484 469184 X Menu 24hr Emergency Vets 01924 465592 Book an Appointment Register your Pet Search Search * Home * About Us * Our Clinics * Careers * Graduate Development Programme * Offers * Development programmes * RVN Training * EMS Programme * Sustainability * Antibiotics Resistance Fact Sheet * Reviews * Cat Friendly Clinic * Procedures & Pricing * Our Services * Facilities * Ultrasound * 24 Hour Emergency Service * Dentistry * Cat Dental Care in Dewsbury and West Yorkshire * Dog Dental Care in Dewsbury and West Yorkshire * Rabbit Dental Care in Dewsbury and West Yorkshire * Cryopen * Bereavement Room * Video Consultation Service * Repeat Prescriptions * Consultations * Flea and Worm Treatment * Tick, Flea, and Worm Prevention for Cats * Tick, Flea, and Worm Prevention for Dogs * Microchipping * Vaccinations * Dog Vaccinations * Cat Vaccinations * Rabbit Vaccinations * Neutering * Annual Health Check * Veterinary Nurse Clinics * Pet Weight Management * Weight management for your Cat * Weight management for your Dog * Weight management for your Rabbit * Senior Pets * Senior Pets Wellness Clinic * Pet Health for Life Plan for Rabbits * Laparoscopic spay * Rehabilitation Centre * Pet Health for Life * Cat Pet Health for Life Plan * Dog Pet Health for Life Plan * Rehabilitation Centre * Pet Hydrotherapy * Physiotherapy * Laser Treatment * Meet the Team * Pet Owners * Find Your Nearest Clinic * Help & Advice * Dogs * Dietary Advice * Behaviour * Puppy Advice * Physiotherapy * Neutering * Eye Care * Medication * Vaccinations * Senior Dogs * Dental Advice * Parasites * Ear Conditions * Skin Care * Cats * Kitten Advice * Neutering & Microchipping * Medication * Eye Care * Dietary Advice * Senior Cats * Vaccinations * Behaviour * Dental Advice * Parasites * Rabbits * Dietary Advice * Young Rabbits * Senior Rabbits * Rabbit Flystrike * Rabbit Calcivirus * General Pet Advice * Pet FAQ's * Pet Health * Veterinary Procedures * Pet Travel * Pet Boarding * Case Studies * Advice for Pet Owners and COVID-19 (Coronavirus) * News * Contact Us * Book an Appointment * Register Your Pet * Lost and found pets * Our Services * * Home * Help & Advice * Dogs * Eye Care * A guide to common eye problems # A guide to common eye problems A healthy dog's eyes should be clear, bright, and free from dirt, discharge, and inflammation. However, it is quite common for dog eye problems to occur, here is a guide of how to spot eye problems in your dog and how to provide treatment. ## Looking After Your Dog's Eyes ### Common Eye Conditions and Symptoms * Keratoconjunctivitis Sicca (Dry Eye) - This occurs when your dog's tear glands do not produce enough tears, resulting in recurrent or chronic conjunctivitis and persistently sore eyes. If left untreated, this condition can even lead to blindness. Though all dogs are susceptible, certain breeds, such as West Highland Terriers, Cavalier King Charles Spaniels, and Cocker Spaniels, seem to be more prone to this problem. * Conjunctivitis - An inflammation of the membrane that covers both the inner lining of the eyelid and the white of the eye. It can be caused by infections, allergies, inadequate tear production, or irritation. * Corneal Ulceration - This can occur when the shiny surface of the cornea is scratched or damaged. * Epiphora - If your dog's eyes constantly "weep", or if the fur around them appears "stained", then the normal tear flow may be blocked, and you should contact your vet immediately. * Cataracts and Glaucoma \- Dogs are just as susceptible to these conditions as humans. Cataracts cloud the lens inside the eye, and are the most common cause of blindness in dogs. A hereditary condition in some breeds, early examination by your vet is vital, as such animals should not be bred. Glaucoma stems from too much pressure being exerted upon the eye's interior as a result of a decrease in the amount of fluid draining from it. ### Common Symptoms of Illness * Red inner eyelids * Matter on the surface or in the corner of the eye * Cloudiness within the eyeball * A dull eye surface * The "third eyelid" coming across the eye surface * Excessive tearing or unusual discharges * Tear-stained fur around the eyes ### Eye Tests to Help Diagnose Problems * Fluorescein helps to identify corneal ulcers * Schirmer Tear Test determines the level of tear production * Ocular pressure is used to detect glaucoma * Ophthalmoscopes can be used to see inside the eye chamber ### How To Treat Canine Eye Problems Many canine eye problems can be treated at home with regular administration of eye drops or ointment. When diagnosing treatment, our vets will tell you everything you need to know about applying the drops or ointment, and about dosages. But for ease of reference, we've prepared this handy guide. ### How To Administer Eye Drops * You may need to muzzle your dog * Remove any discharge from around the eye with a cotton ball moistened with warm water * Read the instructions on the bottle for dosage information, and shake if necessary * Use one hand to hold the bottle between your thumb and index finger, and place the other under your dog's jaw to support their head * Tilt their head back, and to prevent blinking, use your free fingers to hold the eyelids open * Hold the bottle of drops close to the eye, but don't touch the eye's surface * Squeeze the drops onto the eye, and once they're in, release the head * Your dog will blink, spreading the medication across the eye's surface ### How To Administer Eye Ointment * You may need to muzzle your dog * Remove any discharge from around the eye with a cotton ball moistened with warm water * Read the instructions on the tube for dosage information * Gently pull back the upper and lower eyelids * Hold the tube parallel to the lower eyelid, and squeeze the ointment onto the edge of the eyelid * Massage the upper and lower eyelids together to spread the medication * Release your dog's head and allow them to blink, further spreading the medication across the eye's surface If you have any questions or concerns about your dogs eyes, contact your local Calder Vets branch, we're always here to help. Pet Advice Categories * Dogs * Dietary Advice * Behaviour * Puppy Advice * Physiotherapy * Neutering * Eye Care * Medication * Vaccinations * Senior Dogs * Dental Advice * Parasites * Ear Conditions * Skin Care * Cats * Kitten Advice * Neutering & Microchipping * Medication * Eye Care * Dietary Advice * Senior Cats * Vaccinations * Behaviour * Dental Advice * Parasites * Rabbits * Dietary Advice * Young Rabbits * Senior Rabbits * Rabbit Flystrike * Rabbit Calcivirus * General Pet Advice * Pet FAQ's * Pet Health * Veterinary Procedures * Pet Travel * Pet Boarding * Case Studies * Advice for Pet Owners and COVID-19 (Coronavirus) * See our Offers * Join Pet Health for Life * Book Appointment Calder Vets is a multi clinic vets practice with 9 clinics in South and West Yorkshire. When you search for 'vet near me' you will find a convenient Calder vets ready to help. Click here to find your local vets * Home * About Us * Our Services * Pet Health for Life * Pet Owners * Help & Advice * News * Contact Us Select your local Calder Vets clinic: * Brighouse Vets * Denby Dale Vets * Dewsbury Vets * Mirfield Vets * Penistone Vets * Sandal Vets * Wakefield Vets * Waterloo Vets * * * * © 2024 Calder Vets Ltd, Part of Linnaeus, an Affiliate of Mars, Incorporated Website by Clickingmad * Legal Notice * Privacy Statement * Terms of Service * Cookies * Sitemap * Modern Slavery Act * Complaints * Custom Charter * Gender Pay Gap Report * Accessibility Cookie Settings	biology	2885454	https://sv.wikipedia.org/wiki/Platysenta%20hypocritica	Platysenta hypocritica	Platysenta hypocritica är en fjärilsart som beskrevs av Dyar 1907. Platysenta hypocritica ingår i släktet Platysenta och familjen nattflyn. Inga underarter finns listade i Catalogue of Life. Källor Nattflyn hypocritica	swedish	1.29661
dog_eyes_green/Tapetum_lucidum.txt	The tapetum lucidum (Latin for 'bright tapestry, coverlet'; /təˈpiːtəm ˈluːsɪdəm/ tə-PEE-təm LOO-sih-dəm; pl.: tapeta lucida) is a layer of tissue in the eye of many vertebrates and some other animals. Lying immediately behind the retina, it is a retroreflector. It reflects visible light back through the retina, increasing the light available to the photoreceptors (although slightly blurring the image). The tapetum lucidum contributes to the superior night vision of some animals. Many of these animals are nocturnal, especially carnivores, while others are deep sea animals. Similar adaptations occur in some species of spiders. Haplorhine primates, including humans, are diurnal and lack a tapetum lucidum. Function and mechanism[edit] Choroid dissected from a calf's eye, tapetum lucidum appearing iridescent blue The presence of a tapetum lucidum enables animals to see in dimmer light than would otherwise be possible. The tapetum lucidum, which is iridescent, reflects light roughly on the interference principles of thin-film optics, as seen in other iridescent tissues. However, the tapetum lucidum cells are leucophores, not iridophores. The tapetum functions as a retroreflector which reflects light directly back along the light path. This serves to match the original and reflected light, thus maintaining the sharpness and contrast of the image on the retina. The tapetum lucidum reflects with constructive interference, thus increasing the quantity of light passing through the retina. In the cat, the tapetum lucidum increases the sensitivity of vision by 44%, allowing the cat to see light that is imperceptible to human eyes. It has been speculated that some flashlight fish may use eyeshine both to detect and to communicate with other flashlight fish. American scientist Nathan H. Lents has proposed that the tapetum lucidum evolved in vertebrates, but not in cephalopods, which have a very similar eye, because of the backwards-facing nature of vertebrate photoreceptors. The tapetum boosts photosensitivity under conditions of low illumination, thus compensating for the suboptimal design of the vertebrate retina. Classification[edit] A classification of anatomical variants of tapeta lucida defines four types: Retinal tapetum, as seen in teleosts (with a variety of reflecting materials from lipids to phenols), crocodiles (with guanine), marsupials (with lipid spheres), and fruit bats (with phospholipids). The tapetum lucidum is within the retinal pigment epithelium; in the other three types the tapetum is within the choroid behind the retina. Two anatomical classes can be distinguished: occlusible and non-occlusible. The brownsnout spookfish has an extraordinary focusing mirror derived from a retinal tapetum. Choroidal guainine tapetum, as seen in cartilaginous fish The tapetum is a palisade of cells containing stacks of flat hexagonal crystals of guanine. Choroidal tapetum cellulosum, as seen in carnivores, rodents and cetacea. The tapetum consists of layers of cells containing organized, highly refractive crystals. These crystals are diverse in shape and makeup: dogs and ferrets use zinc, cats use riboflavin and zinc, and lemurs use only riboflavin. Choroidal tapetum fibrosum, as seen in cows, sheep, goats and horses. The tapetum is an array of extracellular fibers, most commonly collagen. The functional differences between these four structural classes of tapeta lucida are not known. This section is missing information about bird anatomy: are they all retinal? If so, they should be moved up to the 4-type list.. Please expand the section to include this information. Further details may exist on the talk page. (August 2023) This classification does not include tapeta lucida in birds. Kiwis, stone-curlews, the boat-billed heron, the flightless kākāpō and many nightjars, owls, and other night birds such as the swallow-tailed gull also possess a tapetum lucidum. Nightjars use a retinal tapetum lucidum composed of lipids. Like humans, some animals lack a tapetum lucidum and they usually are diurnal. These include haplorhine primates, squirrels, some birds, red kangaroo, and pigs. Strepsirrhine primates are mostly nocturnal and, with the exception of several diurnal Eulemur species, have a tapetum lucidum of riboflavin crystals. When a tapetum lucidum is present, its location on the eyeball varies with the placement of the eyeball in the head, such that in all cases the tapetum lucidum enhances night vision in the center of the animal's field of view. Apart from its eyeshine, the tapetum lucidum itself has a color. It is often described as iridescent. In tigers it is greenish. In ruminants it may be golden green with a blue periphery, or whitish or pale blue with a lavender periphery. In dogs it may be whitish with a blue periphery. The color in reindeer changes seasonally, allowing the animals to better avoid predators in low-light winter at the price of blurrier vision. Eyeshine[edit] Reflection of camera flash from the tapetum lucidum Eyeshine is a visible effect of the tapetum lucidum. When light shines into the eye of an animal having a tapetum lucidum, the pupil appears to glow. Eyeshine can be seen in many animals, in nature and in flash photographs. In low light, a hand-held flashlight is sufficient to produce eyeshine that is highly visible to humans (despite their inferior night vision). Eyeshine occurs in a wide variety of colors including white, blue, green, yellow, pink and red. However, since eyeshine is a type of iridescence, the color varies with the angle at which it is seen and the minerals which make up the reflective tapetum lucidum crystals. White eyeshine occurs in many fish, especially walleye; blue eyeshine occurs in many mammals such as horses; green eyeshine occurs in mammals such as cats, dogs, and raccoons; and red eyeshine occurs in coyote, rodents, opossums and birds. A three-month-old black Labrador puppy with apparent eyeshine Although human eyes lack a tapetum lucidum, they still exhibit a weak reflection from the choroid, as can be seen in photography with the red-eye effect and with near-infrared eyeshine. Another effect in humans and other animals that may resemble eyeshine is leukocoria, which is a white shine indicative of abnormalities such as cataracts and cancers. In blue-eyed cats and dogs[edit] This section does not cite any sources. Please help improve this section by adding citations to reliable sources. Unsourced material may be challenged and removed.Find sources: "Tapetum lucidum" – news · newspapers · books · scholar · JSTOR (November 2022) (Learn how and when to remove this template message) Odd-eyed cat with eyeshine, plus red-eye effect in one eye Red eyeshine from a siamese cat mix with blue eyes Cats and dogs with a blue eye color may display both eyeshine and red-eye effect. Both species have a tapetum lucidum, so their pupils may display eyeshine. In flash color photographs, however, individuals with blue eyes may also display a distinctive red eyeshine. Individuals with heterochromia may display red eyeshine in the blue eye and normal yellow/green/blue/white eyeshine in the other eye. These include odd-eyed cats and bi-eyed dogs. The red-eye effect is independent of the eyeshine: in some photographs of individuals with a tapetum lucidum and heterochromia, the eyeshine is dim, yet the pupil of the blue eye still appears red. This is most apparent when the individual is not looking into the camera because the tapetum lucidum is far less extensive than the retina. In spiders[edit] Most species of spider also have a tapetum, which is located only in their smaller, lateral eyes; the larger central eyes have no such structure. This consists of reflective crystalline deposits, and is thought to have a similar function to the structure of the same name in vertebrates. Four general patterns can be distinguished in spiders: Primitive type (e.g. Mesothelae, Orthognatha) – a simple sheet behind the retina Canoe-shape type (e.g. Araneidae, Theridiidae) – two lateral walls separated by a gap for the nerve fibres Grated type (e.g. Lycosidae, Pisauridae) – a relatively complex, grill-shaped structure No tapetum (e.g. Salticidae) Uses by humans[edit] In darkness, eyeshine reveals this raccoon Humans use scanning for reflected eyeshine to detect and identify the species of animals in the dark, and deploying trained search dogs and search horses at night, as these animals benefit from improved night vision through this effect. Using eyeshine to identify animals in the dark employs not only its color but also several other features. The color corresponds approximately to the type of tapetum lucidum, with some variation between species. Other features include the distance between pupils relative to their size; the height above ground; the manner of blinking (if any); and the movement of the eyeshine (bobbing, weaving, hopping, leaping, climbing, flying). Artificial tapetum lucidum[edit] Manufactured retroreflectors modeled after a tapetum lucidum are described in numerous patents and today have many uses. The earliest patent, first used in "Catseye" brand raised pavement markers, was inspired by the tapetum lucidum of a cat's eye. Pathology[edit] In dogs, certain drugs are known to disturb the precise organization of the crystals of the tapetum lucidum, thus compromising the dog's ability to see in low light. These drugs include ethambutol, macrolide antibiotics, dithizone, antimalarial medications, some receptor H2-antagonists, and cardiovascular agents. The disturbance "is attributed to the chelating action which removes zinc from the tapetal cells." Gallery[edit] Traditionally it has been difficult to take retinal images of animals with a tapetum lucidum because ophthalmoscopy devices designed for humans rely on a high level of on-axis illumination. This kind of illumination causes a great deal of reflex, or back-scatter, when it interacts with the tapetum. New devices with variable illumination can make this possible, however. Heterochromatic dog with red-eye effect in blue eye Aye-aye Sportive lemur Reflective eyes of a cat visible from a camera flash A domestic tabby cat's green tapetum lucidum, apparent with camera flash European nightjar Subway passengers photographed with camera flash on small camera See also[edit] Defense mechanism (biology) Emission theory (vision) Nocturnal bottleneck Walleye Notes[edit] ^ The one exception to this generalization is the neotropical night monkey genus Aotus; they are sometimes described as having a tapetum lucidum of collagen fibrils, but lack the reflective riboflavin crystals present in the eyes of nocturnal strepsirrhine primates.	biology	2630098	https://sv.wikipedia.org/wiki/Leurophyllum%20tenebrosum	Leurophyllum tenebrosum	Leurophyllum tenebrosum är en insektsart som först beskrevs av Brunner von Wattenwyl 1895. Leurophyllum tenebrosum ingår i släktet Leurophyllum och familjen vårtbitare. Inga underarter finns listade i Catalogue of Life. Källor Vårtbitare tenebrosum	swedish	1.078907
taste_electrons/Taste_receptor.txt	A taste receptor or tastant is a type of cellular receptor which facilitates the sensation of taste. When food or other substances enter the mouth, molecules interact with saliva and are bound to taste receptors in the oral cavity and other locations. Molecules which give a sensation of taste are considered "sapid". Vertebrate taste receptors are divided into two families: Visual, olfactive, "sapictive" (the perception of tastes), trigeminal (hot, cool), mechanical, all contribute to the perception of taste. Of these, transient receptor potential cation channel subfamily V member 1 (TRPV1) vanilloid receptors are responsible for the perception of heat from some molecules such as capsaicin, and a CMR1 receptor is responsible for the perception of cold from molecules such as menthol, eucalyptol, and icilin. Tissue distribution[edit] The gustatory system consists of taste receptor cells in taste buds. Taste buds, in turn, are contained in structures called papillae. There are three types of papillae involved in taste: fungiform papillae, foliate papillae, and circumvallate papillae. (The fourth type - filiform papillae do not contain taste buds). Beyond the papillae, taste receptors are also in the palate and early parts of the digestive system like the larynx and upper esophagus. There are three cranial nerves that innervate the tongue; the vagus nerve, glossopharyngeal nerve, and the facial nerve. The glossopharyngeal nerve and the chorda tympani branch of the facial nerve innervate the TAS1R and TAS2R taste receptors. Next to the taste receptors in on the tongue, the gut epithelium is also equipped with a subtle chemosensory system that communicates the sensory information to several effector systems involved in the regulation of appetite, immune responses, and gastrointestinal motility In 2010, researchers found bitter receptors in lung tissue, which cause airways to relax when a bitter substance is encountered. They believe this mechanism is evolutionarily adaptive because it helps clear lung infections, but could also be exploited to treat asthma and chronic obstructive pulmonary disease. The sweet taste receptor (T1R2/T1R3) can be found in various extra-oral organs throughout the human body such as the brain, heart, kidney, bladder, nasal respiratory epithelium and more. In most of the organs, the receptor function is unclear. The sweet taste receptor found in the gut and in the pancreas was found to play an important role in the metabolic regulation of the gut carbohydrate-sensing process and in insulin secretion. This receptor is also found in the bladder, suggesting that consumption of artificial sweeteners which activates this receptor might cause excessive bladder contraction. Function[edit] Taste helps to identify toxins, maintain nutrition, and regulate appetite, immune responses, and gastrointestinal motility. Five basic tastes are recognized today: salty, sweet, bitter, sour, and umami. Salty and sour taste sensations are both detected through ion channels. Sweet, bitter, and umami tastes, however, are detected by way of G protein-coupled taste receptors. In addition, some agents can function as taste modifiers, as miraculin or curculin for sweet or sterubin to mask bitter. Mechanism of action[edit] The standard bitter, sweet, or umami taste receptor is a G protein-coupled receptor with seven transmembrane domains. Ligand binding at the taste receptors activate second messenger cascades to depolarize the taste cell. Gustducin is the most common taste Gα subunit, having a major role in TAS2R bitter taste reception. Gustducin is a homologue for transducin, a G-protein involved in vision transduction. Additionally, taste receptors share the use of the TRPM5 ion channel, as well as a phospholipase PLCβ2. Savory or glutamates (Umami)[edit] The TAS1R1+TAS1R3 heterodimer receptor functions as an umami receptor, responding to L-amino acid binding, especially L-glutamate. The umami taste is most frequently associated with the food additive monosodium glutamate (MSG) and can be enhanced through the binding of inosine monophosphate (IMP) and guanosine monophosphate (GMP) molecules. TAS1R1+3 expressing cells are found mostly in the fungiform papillae at the tip and edges of the tongue and palate taste receptor cells in the roof of the mouth. These cells are shown to synapse upon the chorda tympani nerves to send their signals to the brain, although some activation of the glossopharyngeal nerve has been found. Alternative candidate umami taste receptors include splice variants of metabotropic glutamate receptors, mGluR4 and mGluR1, and the NMDA receptor. During the evolution of songbirds, the umami taste receptor has undergone structural modifications in the ligand binding site, enabling these birds to sense the sweet taste by this receptor. Sweet[edit] The diagram above depicts the signal transduction pathway of the sweet taste. Object A is a taste bud, object B is one taste cell of the taste bud, and object C is the neuron attached to the taste cell. I. Part I shows the reception of a molecule. 1. Sugar, the first messenger, binds to a protein receptor on the cell membrane. II. Part II shows the transduction of the relay molecules. 2. G Protein-coupled receptors, second messengers, are activated. 3. G Proteins activate adenylate cyclase, an enzyme, which increases the cAMP concentration. Depolarization occurs. 4. The energy, from step 3, is given to activate the K+, potassium, protein channels.III. Part III shows the response of the taste cell. 5. Ca+, calcium, protein channels is activated.6. The increased Ca+ concentration activates neurotransmitter vesicles. 7. The neuron connected to the taste bud is stimulated by the neurotransmitters. The TAS1R2+TAS1R3 heterodimer receptor functions as the sweet receptor by binding to a wide variety of sugars and sugar substitutes. TAS1R2+3 expressing cells are found in circumvallate papillae and foliate papillae near the back of the tongue and palate taste receptor cells in the roof of the mouth. These cells are shown to synapse upon the chorda tympani and glossopharyngeal nerves to send their signals to the brain. The TAS1R3 homodimer also functions as a sweet receptor in much the same way as TAS1R2+3 but has decreased sensitivity to sweet substances. Natural sugars are more easily detected by the TAS1R3 receptor than sugar substitutes. This may help explain why sugar and artificial sweeteners have different tastes. Genetic polymorphisms in TAS1R3 partly explain the difference in sweet taste perception and sugar consumption between people of African American ancestry and people of European and Asian ancestries. Sensing of the sweet taste has changed throughout the evolution of different animals. Mammals sense the sweet taste by transferring the signal through the heterodimer T1R2/T1R3, the sweet taste receptor. In birds, however, the T1R2 monomer does not exist and they sense the sweet taste through the heterodimer T1R1/T1R3, the umami taste receptor, which has gone through modifications during their evolution. A recently conducted study showed that along the evolution stages of songbirds, there was a decrease in the ability to sense the umami taste, and an increase in the ability to sense the sweet taste, whereas the primordial songbird parent could only sense the umami taste. Researchers found a possible explanation for this phenomenon to be a structural change in the ligand binding site of the umami receptor between the sweet taste sensing and non-sensing songbirds. It is assumed that a mutation in the binding site occurred over time, which allowed them to sense the sweet taste through the umami taste receptor. Bitter[edit] The TAS2R proteins (InterPro: IPR007960) function as bitter taste receptors. There are 43 human TAS2R genes, each of which (excluding the five pseudogenes) lacks introns and codes for a GPCR protein. These proteins, as opposed to TAS1R proteins, have short extracellular domains and are located in circumvallate papillae, palate, foliate papillae, and epiglottis taste buds, with reduced expression in fungiform papillae. Though it is certain that multiple TAS2Rs are expressed in one taste receptor cell, it is still debated whether mammals can distinguish between the tastes of different bitter ligands. Some overlap must occur, however, as there are far more bitter compounds than there are TAS2R genes. Common bitter ligands include cycloheximide, denatonium, PROP (6-n-propyl-2-thiouracil), PTC (phenylthiocarbamide), and β-glucopyranosides. Signal transduction of bitter stimuli is accomplished via the α-subunit of gustducin. This G protein subunit activates a taste phosphodiesterase and decreases cyclic nucleotide levels. Further steps in the transduction pathway are still unknown. The βγ-subunit of gustducin also mediates taste by activating IP3 (inositol triphosphate) and DAG (diglyceride). These second messengers may open gated ion channels or may cause release of internal calcium. Though all TAS2Rs are located in gustducin-containing cells, knockout of gustducin does not completely abolish sensitivity to bitter compounds, suggesting a redundant mechanism for bitter tasting (unsurprising given that a bitter taste generally signals the presence of a toxin). One proposed mechanism for gustducin-independent bitter tasting is via ion channel interaction by specific bitter ligands, similar to the ion channel interaction which occurs in the tasting of sour and salty stimuli. One of the best-researched TAS2R proteins is TAS2R38, which contributes to the tasting of both PROP and PTC. It is the first taste receptor whose polymorphisms are shown to be responsible for differences in taste perception. Current studies are focused on determining other such taste phenotype-determining polymorphisms. More recent studies show that genetic polymorphisms in other bitter taste receptor genes influence bitter taste perception of caffeine, quinine and denatonium benzoate. The diagram depicted above shows the signal transduction pathway of the bitter taste. Bitter taste has many different receptors and signal transduction pathways. Bitter indicates poison to animals. It is most similar to sweet. Object A is a taste bud, object B is one taste cell, and object C is a neuron attached to object B. I. Part I is the reception of a molecule.1. A bitter substance such as quinine, is consumed and binds to G Protein-coupled receptors.II. Part II is the transduction pathway 2. Gustducin, a G protein second messenger, is activated. 3. Phosphodiesterase, an enzyme, is then activated. 4. Cyclic nucleotide, cNMP, is used, lowering the concentration 5. Channels such as the K+, potassium, channels, close.III. Part III is the response of the taste cell. 6. This leads to increased levels of Ca+. 7. The neurotransmitters are activated. 8. The signal is sent to the neuron. This section may require cleanup to meet Wikipedia's quality standards. The specific problem is: Need to check tone and formatting in this following paragraph. Please help improve this section if you can. (September 2022) (Learn how and when to remove this template message) It has been demonstrated that bitterness receptors (TAS2R) play an important role in an innate immune system of airway (nose and sinuses) ciliated epithelium tissues. This innate immune system adds an "active fortress" to the physical Immune system surface barrier. This fixed immune system is activated by the binding of ligands to specific receptors. These natural ligands are bacterial markers, for TAS2R38 example: acyl-homoserine lactones or quinolones produced by Pseudomonas aeruginosa. To defend against predators, some plants have produced mimic bacterial markers substances. These plant mimes are interpreted by the tongue, and the brain, as being bitterness. The fixed immune system receptors are identical to the bitter taste receptors, TAS2R. Bitterness substances are agonist of TAS2R fixed immune system. The innate immune system uses nitric oxide and defensins which are capable of destroying bacteria, and also viruses. These fixed innate immune systems (Active Fortresses) are known in other epithelial tissues than upper airway (nose, sinuses, trachea, bronchi), for example: breast (mammary epithelial cells), gut and also human skin (keratinocytes) Bitter molecules, their associated bitter taste receptors, and the sequences and homology models of bitter taste receptors, are available via BitterDB. Sour[edit] See also: Taste § Sourness Historically it was thought that the sour taste was produced solely when free hydrogen ions (H) directly depolarised taste receptors. However, specific receptors for sour taste with other methods of action are now being proposed. The HCN channels were such a proposal; as they are cyclic nucleotide-gated channels. The two ion channels now suggested to contribute to sour taste are ASIC2 and TASK-1. The diagram depicts the signal transduction pathway of the sour or salty taste. Object A is a taste bud, object B is a taste receptor cell within object A, and object C is the neuron attached to object B. I. Part I is the reception of hydrogen ions or sodium ions. 1. If the taste is sour, H+ ions, from an acidic substances, pass through their specific ion channel. Some can go through the Na+ channels. If the taste is salty Na+, sodium, molecules pass through the Na+ channels. Depolarization takes place II. Part II is the transduction pathway of the relay molecules.2. Cation, such as K+, channels are opened. III. Part III is the response of the cell. 3. An influx of Ca+ ions is activated.4. The Ca+ activates neurotransmitters. 5. A signal is sent to the neuron attached to the taste bud. Salt[edit] See also: Taste § Saltiness Various receptors have also been proposed for salty tastes, along with the possible taste detection of lipids, complex carbohydrates, and water. Evidence for these receptors had been unconvincing in most mammal studies. For example, the proposed ENaC receptor for sodium detection can only be shown to contribute to sodium taste in Drosophila. However, proteolyzed forms of ENaC have been shown to function as a human salt taste receptor. Proteolysis is the process where a protein is cleaved. The mature form of ENaC is thought to be proteolyzed, however the characterization of which proteolyzed forms exist in which tissues is incomplete. Proteolysis of cells created to overexpress hetermulitmeric ENaC comprising alpha, beta and gamma subunits was used to identify compounds that selectively enhanced the activity of proteolyzed ENaC versus non-proteolyzed ENaC. Human sensory studies demonstrated that a compound that enhances proteolyzed ENaC functions to enhance the salty taste of table salt, or sodium chloride, confirming proteolyzed ENaC as the first human salt taste receptor. Carbonation[edit] An enzyme connected to the sour receptor transmits information about carbonated water. Fat[edit] A possible taste receptor for fat, CD36, has been identified. CD36 has been localized to the circumvallate and foliate papillae, which are present in taste buds and where lingual lipase is produced, and research has shown that the CD36 receptor binds long chain fatty acids. Differences in the amount of CD36 expression in human subjects was associated with their ability to taste fats, creating a case for the receptor's relationship to fat tasting. Further research into the CD36 receptor could be useful in determining the existence of a true fat-tasting receptor. Free fatty acid receptor 4 (also termed GPR120) and to a much lesser extent free fatty acid receptor 1 (also termed GPR40) have been implicated to respond to oral fat, and their absence leads to reduced fat preference and reduced neuronal response to orally administered fatty acids. TRPM5 has been shown to be involved in oral fat response and identified as a possible oral fat receptor, but recent evidence presents it as primarily a downstream actor. Types[edit] Human bitter taste receptor genes are named TAS2R1 to TAS2R64, with many gaps due to non-existent genes, pseudogenes or proposed genes that have not been annotated to the most recent human genome assembly. Many bitter taste receptor genes also have confusing synonym names with several different gene names referring to the same gene. See table below for full list of human bitter taste receptor genes: Class Gene Synonyms Aliases Locus Description type 1(sweet) TAS1R1 GPR70 1p36.23 TAS1R2 GPR71 1p36.23 TAS1R3 1p36 type 2(bitter) TAS2R1 5p15 TAS2R2 7p21.3 pseudogene TAS2R3 7q31.3-q32 TAS2R4 7q31.3-q32 TAS2R5 7q31.3-q32 TAS2R6 7 not annotated in human genome assembly TAS2R7 12p13 TAS2R8 12p13 TAS2R9 12p13 TAS2R10 12p13 TAS2R11 absent in humans TAS2R12 TAS2R26 12p13.2 pseudogene TAS2R13 12p13 TAS2R14 12p13 TAS2R15 12p13.2 pseudogene TAS2R16 7q31.1-q31.3 TAS2R17 absent in humans TAS2R18 12p13.2 pseudogene TAS2R19 TAS2R23, TAS2R48 12p13.2 TAS2R20 TAS2R49 12p13.2 TAS2R21 absent in humans TAS2R22 12 not annotated in human genome assembly TAS2R24 absent in humans TAS2R25 absent in humans TAS2R27 absent in humans TAS2R28 absent in humans TAS2R29 absent in humans TAS2R30 TAS2R47 12p13.2 TAS2R31 TAS2R44 12p13.2 TAS2R32 absent in humans TAS2R33 12 not annotated in human genome assembly TAS2R34 absent in humans TAS2R35 absent in humans TAS2R36 12 not annotated in human genome assembly TAS2R37 12 not annotated in human genome assembly TAS2R38 7q34 TAS2R39 7q34 TAS2R40 GPR60 7q34 TAS2R41 7q34 TAS2R42 12p13 TAS2R43 12p13.2 TAS2R45 GPR59 12 TAS2R46 12p13.2 TAS2R50 TAS2R51 12p13.2 TAS2R52 absent in humans TAS2R53 absent in humans TAS2R54 absent in humans TAS2R55 absent in humans TAS2R56 absent in humans TAS2R57 absent in humans TAS2R58 absent in humans TAS2R59 absent in humans TAS2R60 7 TAS2R62P 7q34 pseudogene TAS2R63P 12p13.2 pseudogene TAS2R64P 12p13.2 pseudogene Loss of function[edit] In many species, taste receptors have shown loss of functions. The evolutionary process in which taste receptors lost their function is believed to be an adaptive evolution where it is associated with feeding ecology to drive specialization and bifurcation of taste receptors. Out of all the taste receptors, bitter, sweet, and umami are shown to have a correlation between inactivation of taste receptors and feeding behavior. However, there are no strong evidences that support any vertebrates are missing the bitter taste receptor genes. The sweet taste receptor is one of the taste receptors where the function has been lost. In mammals, the predominant sweet taste receptor is the Type 1 taste receptor Tas1r2/Tas1r3. Some mammalian species such as cats and vampire bats have shown inability to taste sweet. In these species, the cause of loss of function of the sweet receptor is due to the pseudogenization of Tas1r2. The pseudogenization of Tas1r2 is also observed in non-mammalian species such as chickens and tongueless Western clawed frog, and these species also show the inability to taste sweet. The pseudogenization of Tas1r2 is widespread and independent in the order Carnivora. Many studies have shown that the pseudogenization of taste receptors is caused by a deleterious mutation in the open reading frames (ORF). In a study, it was found that in nonfeline carnivorous species, these species showed ORF-disrupting mutations of Tas1r2, and they occurred independently among the species. They also showed high variance in their lineages. It is hypothesized that the pseudogenization of Tas1r2 occurred through convergent evolution where carnivorous species lost their ability to taste sweet because of dietary behavior. Umami is also a taste receptor where the function has been lost in many species. The predominant umami taste receptors are Tas1r1/Tas1r3. In two lineages of aquatic mammals including dolphins and sea lions, Tas1r1 has been found to be pseudogenized. The pseudogenization of Tas1r1 has also been found in terrestrial, carnivorous species. While the panda belongs to the order Carnivora, it is herbivorous where 99% of its diet is bamboo, and it cannot taste umami. Genome sequence of the panda shows that its Tas1r1 gene is pseudogenized. In a study, it was found that in all species in the order Carnivora except the panda, the open reading frame was maintained. In panda, the nonsynonymous to synonymous substitutions ratio was found to be much higher than other species in order Carnivora. This data correlates with fossil records date of the panda to show where panda switched from carnivore to herbivore diet. Therefore, the loss of function of umami in panda is hypothesized to be caused by dietary change where the panda became less dependence on meat. However, these studies do not explain herbivores such as horses and cows that have retained the Tas1r1 receptor. Overall, the loss of function of the a taste receptor is an evolutionary process that occurred due to a dietary change in species. See also[edit] List of distinct cell types in the adult human body	biology	778013	https://da.wikipedia.org/wiki/G-protein-koblede%20receptorer	G-protein-koblede receptorer	GPCR er beskrevet som den mest livsnødvendige gruppe proteiner. Forkortelsen står for G-protein–coupled receptor, på dansk G-protein-koblede receptorer. Disse receptorer er prominente medlemmer af en familie af membramproteiner kaldet 7TM - et kort navn for 7 transmembrane receptorer. Dette navn kommer af, at receptormolekylet slynger sig som en slange syv gange gennem cellemembranen (se billederne). Alle G-protein-koblede receptorer sidder i cellemembranen og er populært sagt cellernes "dørvogtere". Ved binding af en ligand ændrer receptoren konformation og aktiverer et G-protein der udløser et biokemisk, cellulært respons, der kan tage mange veje og omtales som signaltransduktion. Ligander kan være fotoner, smagsstoffer, duftstoffer, hormoner, lægemidler, kemikalier. Hos mennesket og pattedyr er der en superfamilie af omkring 800 G-protein-koblede receptorer, der på det molekylære niveau tager vare på utallige vigtige reaktioner i og mellem organismens celler. Velkendte eksempler er syns-receptoren rhodopsin og hormonreceptoren for adrenalin. Selv om der ikke synes megen lighed mellem opfattelsen af sansindtryk og hormoners virkning, har de lignende receptorer: 7TM strukturen er fælles med homologi af aminosyresekvensen. Nobelprisen i kemi blev i 2012 tildelt Brian Kobilka og Robert Lefkowitz for deres arbejde med GPCR og deres funktion. Mange funktioner Lugt Smag Syn Neurotransmission Hormonsecretion Chemotaxi Exocytose Kontrol af blodtryk Embryogenese Cellevækst og differentiering Virusinfektion Carcinogenese Mange eksempler "The human protein atlas" beskriver 774 humane G-proteinkoblede receptorer her er nogle eksempler: Opioid-receptorer findes udbredt både i centralnervesystemet, det perifere nervesystem og i mave-tarm-kanalen og binder både endogene neuropeptider (opioid-peptiderne), andre opioider og opiater. Dopamin-receptorerne består af mindst to familier af G-protein-koblede receptorer i det centrale nervesystem (CNS) og spiller en rolle i mange neurologiske processer som motivation, glæde, kognition (tænkning), indlæring, hukommelse, bevægelseskontrol og modulering af neuroendocrin signalering. Cannabinoid-receptorerne CB1 og CB2, to G-protein-koblede receptorer i det endocannabinoide system, der er placeret i det centrale og perifere nervesystem . Receptorer for feromoner er lokaliseret i det vomeronasale organ og der er identificeret tre familier af receptorer: V1R (VN1R1; VN1R2; VN1R3; VN1R5), V2R og V3R. CXCR4, chemokin-receptor type 4 er en cytokinreceptor og findes på overfladen af celler i det centrale nervesystem og immunsystemet og vides at være involveret i 23 kræftformer og to immunsygdomme, hvorfor denne receptor er blevet studeret flittigt som mål for lægemidler. CCR5, chemokin-receptor type 5 eller CD195 er en cytokinreceptor og findes på overfladen af hvide blodceller bl.a. T-cellerne. For at trænge ind i T-cellerne binder HIV, en virus der forårsager AIDS, sig til CCR5. CCR5-delta32, CCR5-Δ32 er en meget sjælden mutation af receptoren CCR5, hvor 32 aminosyrer mangler, således at HIV ikke kan binde sig til receptoren og trænge ind i cellerne. OR2AT4 er receptor for et syntetisk duftstof kaldet sandalore, som starter en kaskade af molekylære signaler, der synes at inducere reparationen af skadet væv. Farmaka og GPCR Meget medicin retter sig mod GPCR og meget forskning drejer sig om GPCR på grund af deres mange vigtige funktioner. Antihistamin-allergimedicin virker ved at blokkere histaminreceptoren Antidepresiv medicin virker ved at reagere med serotoninreceptoren Betablokkere virker ved at reagere med adrenoreceptoren Mange antipsykotiske farmaka hæmmer dopaminreceptorerne Mange psykostimulerende farmaka aktiverer dopaminreceptorerne, se også LSD Andre virkningsmekanismer kan være farmaka som enzymhæmmere, der griber ind i en signalvej over en GPCR, som f.eks. aspirin, der hæmmer enzymet cyclooxygenase, der danner de smerte-signallerende molekyler kalder prostaglandiner. Se også Arakidonsyre Bakterierhodopsin Endocannabinoide system Serotonin Signaltransduktion Tetrahydrocannabinol Eksterne links og henvisninger Proteiner	danish	0.515492
taste_electrons/Depolarization.txt	In biology, depolarization or hypopolarization is a change within a cell, during which the cell undergoes a shift in electric charge distribution, resulting in less negative charge inside the cell compared to the outside. Depolarization is essential to the function of many cells, communication between cells, and the overall physiology of an organism. Most cells in higher organisms maintain an internal environment that is negatively charged relative to the cell's exterior. This difference in charge is called the cell's membrane potential. In the process of depolarization, the negative internal charge of the cell temporarily becomes more positive (less negative). This shift from a negative to a more positive membrane potential occurs during several processes, including an action potential. During an action potential, the depolarization is so large that the potential difference across the cell membrane briefly reverses polarity, with the inside of the cell becoming positively charged. The change in charge typically occurs due to an influx of sodium ions into a cell, although it can be mediated by an influx of any kind of cation or efflux of any kind of anion. The opposite of a depolarization is called a hyperpolarization. Usage of the term "depolarization" in biology differs from its use in physics, where it refers to situations in which any form of polarity ( i.e. the presence of any electrical charge, whether positive or negative) changes to a value of zero. Depolarization is sometimes referred to as "hypopolarization" (as opposed to hyperpolarization). Physiology[edit] This section does not cite any sources. Please help improve this section by adding citations to reliable sources. Unsourced material may be challenged and removed. (February 2015) (Learn how and when to remove this template message) The process of depolarization is entirely dependent upon the intrinsic electrical nature of most cells. When a cell is at rest, the cell maintains what is known as a resting potential. The resting potential generated by nearly all cells results in the interior of the cell having a negative charge compared to the exterior of the cell. To maintain this electrical imbalance, ions are transported across the cell's plasma membrane. The transport of the ions across the plasma membrane is accomplished through several different types of transmembrane proteins embedded in the cell's plasma membrane that function as pathways for ions both into and out of the cell, such as ion channels, sodium potassium pumps, and voltage-gated ion channels. Resting potential[edit] The resting potential must be established within a cell before the cell can be depolarized. There are many mechanisms by which a cell can establish a resting potential, however there is a typical pattern of generating this resting potential that many cells follow. The generation of a negative resting potential within the cell involves the utilization of ion channels, ion pumps, and voltage-gated ion channels by the cell. However, the process of generating the resting potential within the cell also creates an environment outside the cell that favors depolarization. The sodium potassium pump is largely responsible for the optimization of conditions on both the interior and the exterior of the cell for depolarization. By pumping three positively charged sodium ions (Na) out of the cell for every two positively charged potassium ions (K) pumped into the cell, not only is the resting potential of the cell established, but an unfavorable concentration gradient is created by increasing the concentration of sodium outside the cell and increasing the concentration of potassium within the cell. While there is an excessive amount of potassium in the cell and sodium outside the cell, the generated resting potential maintains the closure of voltage-gated ion channels in the plasma membrane. This not only prevents the diffusion of ions pumped across the membrane but also involves the activity of potassium leak channels, allowing a controlled passive efflux of potassium ions, which contributes to the establishment of the negative resting potential. Additionally, despite the high concentration of positively-charged potassium ions, most cells contain internal components (of negative charge), which accumulate to establish a negative inner charge. Depolarization[edit] Voltage-gated sodium channel. Open channel (top) carries an influx of Na ions, giving rise to depolarization. As the channel becomes closed/inactivated (bottom), the depolarization ends. After a cell has established a resting potential, that cell has the capacity to undergo depolarization. Depolarization is the process by which the membrane potential becomes less negative, facilitating the generation of an action potential. For this rapid change to take place within the interior of the cell, several events must occur along the plasma membrane of the cell. While the sodium–potassium pump continues to work, the voltage-gated sodium and calcium channels that had been closed while the cell was at resting potential are opened in response to an initial change in voltage. As a change in the neuronal charge leads to the opening of voltage-gated sodium channels, this results in an influx of sodium ions down their electrochemical gradient. Sodium ions enter the cell, and they contribute a positive charge to the cell interior, causing a change in the membrane potential from negative to positive. The initial sodium ion influx triggers the opening of additional sodium channels (positive-feedback loop), leading to further sodium ion transfer into the cell and sustaining the depolarization process until the positive equilibrium potential is reached. Sodium channels possess an inherent inactivation mechanism that prompts rapid reclosure, even as the membrane remains depolarized. During this equilibrium, the sodium channels enter an inactivated state, temporarily halting the influx of sodium ions until the membrane potential becomes negatively charged again.Once the cell's interior is sufficiently positively charged, depolarization concludes, and the channels close once more. Repolarization[edit] After a cell has been depolarized, it undergoes one final change in internal charge. Following depolarization, the voltage-gated sodium ion channels that had been open while the cell was undergoing depolarization close again. The increased positive charge within the cell now causes the potassium channels to open. Potassium ions (K) begin to move down the electrochemical gradient (in favor of the concentration gradient and the newly established electrical gradient). As potassium moves out of the cell the potential within the cell decreases and approaches its resting potential once more. The sodium potassium pump works continuously throughout this process. Hyperpolarization[edit] The process of repolarization causes an overshoot in the potential of the cell. Potassium ions continue to move out of the axon so much so that the resting potential is exceeded and the new cell potential becomes more negative than the resting potential. The resting potential is ultimately re-established by the closing of all voltage-gated ion channels and the activity of the sodium potassium ion pump. Neurons[edit] Structure of a neuron Depolarization is essential to the functions of many cells in the human body, which is exemplified by the transmission of stimuli both within a neuron and between two neurons. The reception of stimuli, neural integration of those stimuli, and the neuron's response to stimuli all rely upon the ability of neurons to utilize depolarization to transmit stimuli either within a neuron or between neurons. Response to stimulus[edit] Stimuli to neurons can be physical, electrical, or chemical, and can either inhibit or excite the neuron being stimulated. An inhibitory stimulus is transmitted to the dendrite of a neuron, causing hyperpolarization of the neuron. The hyperpolarization following an inhibitory stimulus causes a further decrease in voltage within the neuron below the resting potential. By hyperpolarizing a neuron, an inhibitory stimulus results in a greater negative charge that must be overcome for depolarization to occur. Excitation stimuli, on the other hand, increases the voltage in the neuron, which leads to a neuron that is easier to depolarize than the same neuron in the resting state. Regardless of it being excitatory or inhibitory, the stimulus travels down the dendrites of a neuron to the cell body for integration. Integration of stimuli[edit] Summation of stimuli at an axon hillock Once the stimuli have reached the cell body, the nerve must integrate the various stimuli before the nerve can respond. The stimuli that have traveled down the dendrites converge at the axon hillock, where they are summed to determine the neuronal response. If the sum of the stimuli reaches a certain voltage, known as the threshold potential, depolarization continues from the axon hillock down the axon. Response[edit] The surge of depolarization traveling from the axon hillock to the axon terminal is known as an action potential. Action potentials reach the axon terminal, where the action potential triggers the release of neurotransmitters from the neuron. The neurotransmitters that are released from the axon continue on to stimulate other cells such as other neurons or muscle cells. After an action potential travels down the axon of a neuron, the resting membrane potential of the axon must be restored before another action potential can travel the axon. This is known as the recovery period of the neuron, during which the neuron cannot transmit another action potential. Rod cells of the eye[edit] The importance and versatility of depolarization within cells can be seen in the relationship between rod cells in the eye and their associated neurons. When rod cells are in the dark, they are depolarized. In the rod cells, this depolarization is maintained by ion channels that remain open due to the higher voltage of the rod cell in the depolarized state. The ion channels allow calcium and sodium to pass freely into the cell, maintaining the depolarized state. Rod cells in the depolarized state constantly release neurotransmitters which in turn stimulate the nerves associated with rod cells. This cycle is broken when rod cells are exposed to light; the absorption of light by the rod cell causes the channels that had facilitated the entry of sodium and calcium into the rod cell to close. When these channels close, the rod cells produce fewer neurotransmitters, which is perceived by the brain as an increase in light. Therefore, in the case of rod cells and their associated neurons, depolarization actually prevents a signal from reaching the brain as opposed to stimulating the transmission of the signal. Vascular endothelium[edit] Endothelium is a thin layer of simple squamous epithelial cells that line the interior of both blood and lymph vessels. The endothelium that lines blood vessels is known as vascular endothelium, which is subject to and must withstand the forces of blood flow and blood pressure from the cardiovascular system. To withstand these cardiovascular forces, endothelial cells must simultaneously have a structure capable of withstanding the forces of circulation while also maintaining a certain level of plasticity in the strength of their structure. This plasticity in the structural strength of the vascular endothelium is essential to overall function of the cardiovascular system. Endothelial cells within blood vessels can alter the strength of their structure to maintain the vascular tone of the blood vessel they line, prevent vascular rigidity, and even help to regulate blood pressure within the cardiovascular system. Endothelial cells accomplish these feats by using depolarization to alter their structural strength. When an endothelial cell undergoes depolarization, the result is a marked decrease in the rigidity and structural strength of the cell by altering the network of fibers that provide these cells with their structural support. Depolarization in vascular endothelium is essential not only to the structural integrity of endothelial cells, but also to the ability of the vascular endothelium to aid in the regulation of vascular tone, prevention of vascular rigidity, and the regulation of blood pressure. Heart[edit] Electrocardiogram Depolarization occurs in the four chambers of the heart: both atria first, and then both ventricles. The sinoatrial (SA) node on the wall of the right atrium initiates depolarization in the right and left atria, causing contraction, which corresponds to the P wave on an electrocardiogram. The SA node sends the depolarization wave to the atrioventricular (AV) node which—with about a 100 ms delay to let the atria finish contracting—then causes contraction in both ventricles, seen in the QRS wave. At the same time, the atria re-polarize and relax. The ventricles are re-polarized and relaxed at the T wave. This process continues regularly, unless there is a problem in the heart. Depolarization blockers[edit] There are drugs, called depolarization blocking agents, that cause prolonged depolarization by opening channels responsible for depolarization and not allowing them to close, preventing repolarization. Examples include the nicotinic agonists, suxamethonium and decamethonium.	biology	114961	https://sv.wikipedia.org/wiki/Nervimpuls	Nervimpuls	En nervimpuls är det sammansatta elektrokemiska fenomen längs nervcellers utskott (processer) som följer till exempel på signalöverföringen i en synaps. Den är en snabb förändring av spänningen över en nervcells cellmembran. Den används för signalering mellan nervceller hos djur, men även i viss begränsad utsträckning växter. Dessa nervimpulser förflyttar sig längs nervtråden med en hastighet av 0,5–120 m/s, beroende på hur isolerat (myeliniserat) axonet är samt tjockleken på själva axonet. Själva impulsförflyttningen beskrivs ibland elektriskt som en aktionspotential. Något som är typiskt för nervceller är att de kan bilda, ta emot och leda impulser. Impulser är en form av elektriska urladdningar som uppstår i nervcellerna. Urladdningen beror på att natrium- och kaliumjoner snabbt passerar genom cellens yta, cellmembran. Impulsen sprids sedan i nervcellen och dess utskott, och fortsätter sedan till andra celler via synapser eller motoriska ändplattor. Mekanism Kontaktpunkten mellan två nervceller eller mellan en nervcell och en körtelcell kallas synaps medan kontaktpunkten mellan en nervcell och en muskelcell kallas motorisk ändplatta. När en impuls från en nervcell når synapsen kommer svaret resultera i att vesiklar, innehållande signalsubstanser, fuserar med membranet och interagerar med receptorer på mottagarcellen. Mottagarcellen kommer att påverkas genom att jonkanaler antingen ökar eller minskar sin transportförmåga vilket leder till en höjd eller sänkt vilomembranpotential. Den förändrade vilomembranpotentialen betyder i sin tur att mottagarcellen ökar eller sänker sin känslighet för ytterligare stimuli. Om cellen då stimuleras tillräckligt mycket uppstår en ny impuls som förs vidare till nästa nervcell. På så sätt kan en impuls färdas lång väg genom många nervceller innan den slutligen leder till något. Då synapsklyftan är liten och den kemikaliefrisättning som sker är över ett mycket litet avstånd, påverkas nervimpulsens hastighet inte i nämnvärd grad. Det är därför en signal från hjärnan kan passera flera synapser och färdas längre sträcka än nervcellens längd men med bibehållen hastighet. Aktionspotentialen alstras närhelst en tillräckligt stor depolarisering av cellen inträffar, på grund av signaler från andra nervceller eller på grund av specifika stimuli. Dessa stimuli kan exempelvis vara sträckning av nervcellen, och det är på det viset sträckreceptorer i musklerna känner av läget som en muskel befinner sig i. Membranpotentialen Normalt har nervcellen en negativ potential jämfört med den extracellulära miljön (miljön utanför cellen), hos humanceller är ett vanligt värde −70 mV. Potentialskillnaden uppstår på grund av att cellmembranet endast är permeabelt (genomsläppligt) för vissa joner. På grund av diffusion uppstår då en elektrokemisk jämvikt där koncentrationen kaliumjoner (K+) är betydligt högre intracellulärt än extracellulärt, samtidigt som koncentrationen natriumjoner (Na+) är högre extracellulärt (utanför cellen). När depolariseringen nått till ett visst tröskelvärde öppnas spänningskänsliga Na+-kanaler i cellmembranet, så att natriumjoner på grund av koncentrationsskillnaden strömmar in i cellen. Eftersom natriumjonerna är positivt laddade depolariseras cellen nu hastigt, vilket ger upphov till aktionspotentialens stigande del. På grund av depolariseringen av cellen öppnas även, men med en viss fördröjning, K+-specifika jonkanaler. Detta resulterar i att kaliumjoner strömmar ut ur cellen och återställer den negativa vilopotentialen. Under den slutgiltiga fasen av denna så kallade repolarisering når nervcellen ett potentialminimum som kallas för hyperpolariserat tillstånd vilket orsakas av membranets extrema permeabilitet för kaliumjoner. Hyperpolariseringen är kortvarig och cellen återgår till sin normala vilopotential som varierar mellan −50 mV och −120 mV. Aktionspotentialen fortplantar sig genom nervcellens axon genom passiv diffusion av laddningar, varigenom spänningskänsliga jonkanaler öppnas och en ny aktionspotential alstras längs axonet. Referenser Cellbiologi Nervsystemet	swedish	0.473858
taste_electrons/Brainport.txt	BrainPort is a technology whereby sensory information can be sent to one's brain through an electrode array which sits atop the tongue. It was initially developed by Paul Bach-y-Rita as an aid to people's sense of balance, particularly of stroke victims. Bach-y-Rita founded Wicab in 1998. It has also been developed for use as a visual aid, demonstrating its ability to allow a blind person to see his or her surroundings in polygonal and pixel form. In this scenario, a camera picks up the image of the surrounding, the information is processed by a chip which converts it into impulses which are sent through an electrode array, via the tongue, to the person's brain. The human brain is able to interpret these impulses as visual signals and they are then redirected to the visual cortex, allowing the person to "see." This is similar in part to how a cochlear implant works, in that it transmits electrical stimuli to a receiving device in the body. The BrainPort V100 oral electronic vision aid was approved by the Food and Drug Administration (FDA) on June 18, 2015. See also[edit] Sensory substitution Neuroplasticity	biology	1042019	https://no.wikipedia.org/wiki/Blindsyn	Blindsyn	Blindsyn er evnen til å identifisere eller lokalisere stimuli man ikke bevisst kan se. Blindsyn kan finnes hos mennesker som til tross for at de tilsynelatende er totalt blinde etter en skade i den primære visuelle korteks, responderer på visuelt stimuli. Mennesker som lider av blindsyn har ingen bevisst opplevelse av syn, men hvis de blir bedt om å gjette kan de blant annet korrekt rette øynene mot en lyskilde, identifisere objekter i bevegelse, eller skille mellom enkle visuelle former. De blir selv ofte overrasket over at de gjetter riktig på slike oppgaver. De første observasjonene av det vi i dag kjenner som blindsyn ble trolig gjort av den britiske militærlegen George Riddoch som behandlet sårede soldater under første verdenskrig. Han oppdaget noe fascinerende blant de soldatene som hadde fått skader på primær visuell cortex som ligger bakerst i den occipitale del av hjernen og er involvert i visuell prosessering. Ved skader i dette området vil man miste evnen til å registrere spesifikk synsinformasjon. Ikke overraskende hadde soldatene med denne form for skade mistet persepsjon i deler av det visuelle feltet og oppfattet seg som blinde. Det som derimot var overraskende var at soldatene responderte på bevegelse i de delene av det visuelle feltet som de hevdet å være blinde på. Begrepet blindsyn ble introdusert av den britiske neuropsykologen Lawrence Weiskrantz og hans kollegaer. Dette gjorde de etter grundige undersøkelser av en pasient som de kalte DB. Hos DB var høyre occipital cortex, inkludert mesteparten av primær visuell cortex blitt fjernet etter et kirurgisk inngrep. Etter operasjonen var DB blant annet i stand til å gjengi et visuelt stimulus som tidligere var blitt presentert i hans blinde område. I tillegg kunne han også identifisere lokalisasjonen. På tross av dette rapporterte han ingen bevisste opplevelser i sitt blinde felt. Pasienter som lider av blindsyn har som regel store skader på det primære visuelle cortex i hjernen (V1). Likevel er tapet av visuell bevissthet i blind feltet sannsynligvis ikke en direkte følge av disse skadene. Skader på V1 har en «knock- on» effekt gjennom hele det visuelle systemet, noe som fører til redusert aktivering av etterfølgende visuelle prosseseringsområder. Det er minst ti veier (pathways) fra øyet til hjernen . Flere av disse kan tas i bruk av blindsynpasienter, og dette kan være med å forklare mekanismen bak blindsyn. Forskning har vist at blindsynpasienter ofte kan ta i bruk en trakt som forbinder corpus geniculatum laterale med det ipsilaterale visuelle motion area V5/MT som går forbi V1. Kortikale mekanismer fremstår ikke som essensielle. Når blindsyn skal diagnostiseres og studeres fokuseres det på to ting. Det første er personenes subjektive tilbakemeldinger om at de ikke klarer å se visuelle stimuli som blir presentert i det blinde feltet. Det andre er en «tvunget- valg» test der pasientene blir bedt om å gjette om det visuelle stimuli er tilstede eller ikke, og evt peke på stimuli. Blindsyn defineres som det å benekte å kunne se visuelt stimuli samtidig med å score over gjennomsnittet på «tvunget-valg» tester. Det er forskjeller mellom pasientene som lider av blindsyn. Dette har ført til at blindsyn deles inn i tre undergrupper: Action- blindsight: Pasientene kan i noen grad gripe etter eller peke på objekter i sitt blinde felt. Attention- blindsight: Pasientene som lider av denne formen for blindsyn kan oppfatte objekter og bevegelse og har en svak bevisst følelse av objekter på tross av at de rapporterer at de ikke kan se dem. Agnosopsia: Denne typen pasienter nekter for å ha bevisst kjennskap til visuelt stimuli. De viser likevel en evne til å skille form og bølgelengde. Referanser Syn Nevrologi Nevrovitenskap	norwegian_bokmål	0.665855
taste_electrons/Electrical_conductor.txt	In physics and electrical engineering, a conductor is an object or type of material that allows the flow of charge (electric current) in one or more directions. Materials made of metal are common electrical conductors. The flow of negatively charged electrons generates electric current, positively charged holes, and positive or negative ions in some cases. In order for current to flow within a closed electrical circuit, one charged particle does not need to travel from the component producing the current (the current source) to those consuming it (the loads). Instead, the charged particle simply needs to nudge its neighbor a finite amount, who will nudge its neighbor, and on and on until a particle is nudged into the consumer, thus powering it. Essentially what is occurring is a long chain of momentum transfer between mobile charge carriers; the Drude model of conduction describes this process more rigorously. This momentum transfer model makes metal an ideal choice for a conductor; metals, characteristically, possess a delocalized sea of electrons which gives the electrons enough mobility to collide and thus affect a momentum transfer. As discussed above, electrons are the primary mover in metals; however, other devices such as the cationic electrolyte(s) of a battery, or the mobile protons of the proton conductor of a fuel cell rely on positive charge carriers. Insulators are non-conducting materials with few mobile charges that support only insignificant electric currents. Resistance and conductance[edit] A piece of resistive material with electrical contacts on both ends. Main article: Electrical resistance and conductance The resistance of a given conductor depends on the material it is made of, and on its dimensions. For a given material, the resistance is inversely proportional to the cross-sectional area. For example, a thick copper wire has lower resistance than an otherwise-identical thin copper wire. Also, for a given material, the resistance is proportional to the length; for example, a long copper wire has higher resistance than an otherwise-identical short copper wire. The resistance R and conductance G of a conductor of uniform cross section, therefore, can be computed as R = ρ ℓ A , G = σ A ℓ . {\displaystyle {\begin{aligned}R&=\rho {\frac {\ell }{A}},\\[6pt]G&=\sigma {\frac {A}{\ell }}.\end{aligned}}} where ℓ {\displaystyle \ell } is the length of the conductor, measured in metres [m], A is the cross-section area of the conductor measured in square metres [m], σ (sigma) is the electrical conductivity measured in siemens per meter (S·m), and ρ (rho) is the electrical resistivity (also called specific electrical resistance) of the material, measured in ohm-metres (Ω·m). The resistivity and conductivity are proportionality constants, and therefore depend only on the material the wire is made of, not the geometry of the wire. Resistivity and conductivity are reciprocals: ρ = 1 / σ {\displaystyle \rho =1/\sigma } . Resistivity is a measure of the material's ability to oppose electric current. This formula is not exact: It assumes the current density is totally uniform in the conductor, which is not always true in practical situation. However, this formula still provides a good approximation for long thin conductors such as wires. Another situation this formula is not exact for is with alternating current (AC), because the skin effect inhibits current flow near the center of the conductor. Then, the geometrical cross-section is different from the effective cross-section in which current actually flows, so the resistance is higher than expected. Similarly, if two conductors are near each other carrying AC current, their resistances increase due to the proximity effect. At commercial power frequency, these effects are significant for large conductors carrying large currents, such as busbars in an electrical substation, or large power cables carrying more than a few hundred amperes. Aside from the geometry of the wire, temperature also has a significant effect on the efficacy of conductors. Temperature affects conductors in two main ways, the first is that materials may expand under the application of heat. The amount that the material will expand is governed by the thermal expansion coefficient specific to the material. Such an expansion (or contraction) will change the geometry of the conductor and therefore its characteristic resistance. However, this effect is generally small, on the order of 10. An increase in temperature will also increase the number of phonons generated within the material. A phonon is essentially a lattice vibration, or rather a small, harmonic kinetic movement of the atoms of the material. Much like the shaking of a pinball machine, phonons serve to disrupt the path of electrons, causing them to scatter. This electron scattering will decrease the number of electron collisions and therefore will decrease the total amount of current transferred. Conductor materials[edit] Main article: Electrical resistivity and conductivity Further information: Copper conductor and Aluminum building wiring Material ρ [Ω·m] at 20°C σ [S/m] at 20°C Silver, Ag 1.59 × 10 6.30 × 10 Copper, Cu 1.68 × 10 5.96 × 10 Aluminum, Al 2.82 × 10 3.50 × 10 Conduction materials include metals, electrolytes, superconductors, semiconductors, plasmas and some nonmetallic conductors such as graphite and conductive polymers. Copper has a high conductivity. Annealed copper is the international standard to which all other electrical conductors are compared; the International Annealed Copper Standard conductivity is 58 MS/m, although ultra-pure copper can slightly exceed 101% IACS. The main grade of copper used for electrical applications, such as building wire, motor windings, cables and busbars, is electrolytic-tough pitch (ETP) copper (CW004A or ASTM designation C100140). If high conductivity copper must be welded or brazed or used in a reducing atmosphere, then oxygen-free high conductivity copper (CW008A or ASTM designation C10100) may be used. Because of its ease of connection by soldering or clamping, copper is still the most common choice for most light-gauge wires. Silver is 6% more conductive than copper, but due to cost it is not practical in most cases. However, it is used in specialized equipment, such as satellites, and as a thin plating to mitigate skin effect losses at high frequencies. Famously, 14,700 short tons (13,300 t) of silver on loan from the United States Treasury were used in the making of the calutron magnets during World War II due to wartime shortages of copper. Aluminum wire is the most common metal in electric power transmission and distribution. Although only 61% of the conductivity of copper by cross-sectional area, its lower density makes it twice as conductive by mass. As aluminum is roughly one-third the cost of copper by weight, the economic advantages are considerable when large conductors are required. The disadvantages of aluminum wiring lie in its mechanical and chemical properties. It readily forms an insulating oxide, making connections heat up. Its larger coefficient of thermal expansion than the brass materials used for connectors causes connections to loosen. Aluminum can also "creep", slowly deforming under load, which also loosens connections. These effects can be mitigated with suitably designed connectors and extra care in installation, but they have made aluminum building wiring unpopular past the service drop. Organic compounds such as octane, which has 8 carbon atoms and 18 hydrogen atoms, cannot conduct electricity. Oils are hydrocarbons, since carbon has the property of tetracovalency and forms covalent bonds with other elements such as hydrogen, since it does not lose or gain electrons, thus does not form ions. Covalent bonds are simply the sharing of electrons. Hence, there is no separation of ions when electricity is passed through it. Liquids made of compounds with only covalent bonds cannot conduct electricity. Certain organic ionic liquids, by contrast, can conduct an electric current. While pure water is not an electrical conductor, even a small portion of ionic impurities, such as salt, can rapidly transform it into a conductor. Wire size[edit] Wires are measured by their cross sectional area. In many countries, the size is expressed in square millimetres. In North America, conductors are measured by American wire gauge for smaller ones, and circular mils for larger ones. Conductor ampacity[edit] The ampacity of a conductor, that is, the amount of current it can carry, is related to its electrical resistance: a lower-resistance conductor can carry a larger value of current. The resistance, in turn, is determined by the material the conductor is made from (as described above) and the conductor's size. For a given material, conductors with a larger cross-sectional area have less resistance than conductors with a smaller cross-sectional area. For bare conductors, the ultimate limit is the point at which power lost to resistance causes the conductor to melt. Aside from fuses, most conductors in the real world are operated far below this limit, however. For example, household wiring is usually insulated with PVC insulation that is only rated to operate to about 60 °C, therefore, the current in such wires must be limited so that it never heats the copper conductor above 60 °C, causing a risk of fire. Other, more expensive insulation such as Teflon or fiberglass may allow operation at much higher temperatures. Isotropy[edit] If an electric field is applied to a material, and the resulting induced electric current is in the same direction, the material is said to be an isotropic electrical conductor. If the resulting electric current is in a different direction from the applied electric field, the material is said to be an anisotropic electrical conductor. See also[edit] Classification of materials based on permittivity εr″/εr′ Current conduction Field propagation 0 perfect dielectriclossless medium ≪ 1 low-conductivity materialpoor conductor low-loss mediumgood dielectric ≈ 1 lossy conducting material lossy propagation medium ≫ 1 high-conductivity materialgood conductor high-loss mediumpoor dielectric ∞ perfect conductor Bundle conductor Charge transfer complex Electrical cable Electrical resistivity and conductivity Fourth rail Overhead line Stephen Gray, first to identify electrical conductors and insulators Superconductivity Third rail	biology	19251	https://da.wikipedia.org/wiki/Elektrisk%20kondensator	Elektrisk kondensator	En elektrisk kondensator (også kaldet en kapacitor) er en elektronisk komponent, der er indrettet til at have en vis elektrisk kapacitet (fysisk størrelse som måles i farad) – en evne til (på kort sigt) at opbevare en vis mængde elektrisk energi. Groft sagt kan en kondensator sammenlignes med et opladeligt "batteri" (element) – en kondensator op- og aflades blot meget hurtigere og indeholder blot en forsvindende brøkdel af den elektriske energi der kan opbevares i et opladeligt element af tilsvarende rumlig størrelse. Sådan virker en kondensator Opbygning Figuren til højre viser hvordan en kondensator principielt er opbygget: (1) To elektrisk ledende plader er anbragt parallelt og ganske tæt på hinanden, dog adskilt af et dielektrikum. (2) Dielektrikummet er enten et vakuum eller et lag af et elektrisk isolerende stof. (3) Kondensatoren har to tilledninger, som er forbundet til hver sin elektrisk ledende plade. I praktiske kondensatorer er dette arrangement bygget eller støbt ind i en "indpakning" af plast, aluminium eller keramik, så blot de to tilledninger "stikker ud" af komponenten. Kondensatoren og DC-kilder(jævnspænding) Hvis man forbinder kondensatorens to tilledninger med en jævnspændingskilde, vil spændingkildens positive pol trække de frie elektroner ud af den ene plade, og fylde elektroner på den plade der er forbundet til kildens negative pol; der går altså en strøm i kredsløbet. Denne proces varer i praksis ganske kort; strømstyrken i kredsløbet falder eksponentielt mod noget nær nul. Den plade, der er tilsluttet den positive pol, har nu et underskud af frie elektroner, hvilket medfører en positiv elektrisk ladning. Denne positive ladning udøver en elektrisk tiltrækningskraft på det overskud af frie elektroner, som den anden (nu negativt ladede) plade har modtaget fra strømkildens negative pol. Afbrydes forbindelsen mellem kondensatoren og strømkilden, vil de elektriske kræfter holde de frie elektroner fast i den negativt ladede plade, og derfor ligger der over kondensatorens tilledninger en spændingsforskel meget nær ved strømkildens polspænding. I kondensatorer med kapaciteter under ca. 1 mikrofarad (1 μF = 10-6 farad) "siver" denne opbevarede ladning dog hurtigt, bl.a på grund af en indre, elektrisk "utæthed" (kaldet tabsmodstand) i kondensatoren. Med en kondensator på et par mF og en lille lommelygte-pære kan man demonstrere den oplagrede elektriske energi ved at koble en opladt kondensator til pæren, hvilket resulterer i, at lommelygten lyser op et kort øjeblik; i løbet af det øjeblik "undslipper" elektronerne i den negativt ladede plade ud gennem pærens glødetråd og ind i den positivt ladede plade, og derved udligner forskellen i antallet af frie elektroner i de to plader. For en kort stund tjener kondensatoren altså som en strømkilde, der trækker en jævnstrøm igennem pæren. Kondensatoren og vekselstrømme Strømmen fra en vekselstrømskilde skifter retning med en vis frekvens (regelmæssig hyppighed), så hvis man kobler en kondensator til vekselstrømskilden, vil strømkilden pumpe frie elektroner først fra den ene plade til den anden, og øjeblikket efter i den modsatte retning. Så i modsætning til situationen med jævnstrømskilden, bliver en vekselstrømskilde aldrig færdig med at fylde den ene og tømme den anden plade i kondensatoren for frie elektroner – selv om der hele tiden løber en vekselstrøm i kredsløbet. Det viser sig at kondensatoren – overfor en vekselstrømskilde – udøver en slags modstand. Til højre er givet den formelle sammenhæng; reaktansen afhænger af to ting: Kondensatorens elektriske kapacitet Vekselstrømmens frekvens (det antal gange strømmen skifter retning pr. tidsenhed) Denne egenskab anvendes i analoge kredsløb til at filtrere og sortere et signal efter frekvenser. Et eksempel er et stereoanlægs knapper for bas og diskant; her anvendes en variabel modstand (knappen) sammen med en kondensator til at forstærke eller dæmpe enten dybe eller høje toner (hhv. lave og høje frekvenser) mere eller mindre end andre toner/frekvenser. Mål og egenskaber for kondensatorer Den elektriske kapacitet for en given kondensator bestemmes af tre faktorer: Arealet af de to ledende plader; jo større areal, desto større elektrisk kapacitet. Afstanden mellem de ledende plader; jo mindre afstand, desto større elektrisk kapacitet En egenskab kaldet dielektricitetskonstanten, for det vakuum eller isolerende stof, der adskiller de ledende plader. For at begrænse materialeforbruget søger fabrikanter af kondensatorer bl.a. at gøre afstanden mellem de ledende plader mindst mulig, men et meget tyndt isolerende lag mellem pladerne sætter en grænse for hvor store elektriske spændinger (potentialforskelle) der kan være mellem de to plader. Overskrides denne grænse, ioniseres det ellers isolerende materiale, og der opstår en kortslutning mellem de to plader; en genvej som den oplagrede elektriske energi straks benytter til at udligne ladningsforskellen. Derved udvikles varme, som kan sammensvejse de to ledende plader så der opstår en permanent kortslutning i komponenten. Kondensatorer leveres i praksis med oplysninger (som evt. kan være påtrykt komponenten, eller angivet ved en farvekode på komponentens ydre) om både kondensatorens elektriske kapacitet, og den maksimale spændingsforskel der må være over tilledningerne – det sidste for at undgå ionisering i, og kortslutninger igennem det isolerende dielektrikum. Afladning af en kondensator Når en kondensator er fuldt opladt har den en ladning , der egentlig er ladningen på kondensatorens positive leder; samlet set er kondensatoren jo neutral. Når kondensatoren tilsluttes et kredsløb med resistansen eller modstanden , vil der ske et fald i ladningen eller, sagt på en anden måde, en negativ ændring . Denne ændring sker over en given tid , så ændring pr. tidsenhed bliver altså . Ændring i ladning pr. tidsenhed er definitionen på strømstyrke , så formlen lyder . Dette er strømstyrken i kredsløbet og ikke bare i kondensatoren, da en elektrisk strøm skal løbe for, at man kan tale om strømstyrke. Ved at lave lidt om på formlen, får man . Udover denne udvikling i elektrisk ladning er der også noget, der hedder kapacitor-ligningen ifølge hvilken, der gælder, at ladningen er lig kapacitansen gange spændingen eller . Dette kombineres med Ohms lov , så: Dette udtryk for ladningen differentieres; både og antages at være konstante i et givent kredsløb, så kun og differentieres, hvilket giver: Man indsætter nu førfundne udtryk for differentialet af : Man dividerer så med på begge sider: For at finde en funktionsforskrift for skal man bemærke, at den fundne formel har formen: Ifølge separation af de variable er løsningen på en sådan differentialligning: . Her er skæringen med y-aksen, mens er Eulers tal, der er en matematisk konstant. Bruges denne løsning til at finde et udtryk for strømstyrken, fås: Skæringen med y-aksen er nu strømstyrken ved tiden 0, og det vil sige strømstyrken lige, når kondensatoren tilsluttes et kredsløb. Denne værdi kan noteres . Man får da funktionsforskriften: Når en kondensator aflades, er strømstyrken i kredsløbet altså eksponentiel faldende efter ovenstående matematiske model. Med tanke på Ohms lov kan man gange med på begge sider, så man derved får: Man har da en funktionsforskrift for spændingen i kondensatoren som funktion af tiden: Det ses, at også spændingen er eksponentielt aftagende. Ud fra førfundne funktionsforskrift kan man også finde den gennemstrømmende energi pr. tidsenhed eller, med andre ord, effekten . Nu skal man bruge en formel, der siger, at effekten er lig resistansen gange kvadratet af strømstyrken, eller . Dette kombineres med med funktionsforskriften for strømstyrke: . Dette er altså et udtryk for effekten, der er positiv. Noget, der ikke er positivt, er energiændringen i kondensatoren, som må være faldende eller negativ for at kunne give en effekt. Differentialet af energien i kondensatoren som funktion af tiden er altså effektens negative modstykke. Dvs: Funktionsforskriften for effekten sættes ind i dette udtryk: Hvis man vil lave differentialet af energien om til energien, må ligningen integreres: Dette giver: Da energien nødvendigvis må gå mod nul, bliver konstanten k nødt til at være nul: . Energien i en kondensator Dette udtryk kan så igen bruges til at få et udtryk for den elektriske potentielle energi i kondensatoren. Da dette er energien, før kondensatoren får mulighed for at afgive noget af den, skal man bruge funktionsforskriften for energi og sætte tiden til nul: Udtrykket for energien i en opladet kondensator er altså: Der findes mange hjælpermidler på internettet til at lave disse energiberegninger. Forskellige typer kondensatorer Kondensatorer bruges i elektroniske kredsløb til en lang række forskelligartede formål, i kapaciteter fra omkring en pikofarad (1 pF = 10-12 farad) og op til nogle tiendedele farad, og med forskellige spændingsgrænser. Keramiske kondensatorer Keramiske kondensatorer har typisk kapaciteter fra 1 picofarad til omkring 100 nanofarad (1 nF = 10-9 farad), og består af to metalskiver forsynet med hver sin tilledning. Disse er adskilt og omgivet af et keramisk materiale, som derved tjener både som det isolerende dielektrikum og som "indpakning" af hensyn til komponentens mekaniske stabilitet. Da det anvendte keramiske materiale har en høj dielektricitetkonstant, kan denne type kondensator fremstilles med kapaciteter (og spændingsmæssige begrænsning) der er store set i forhold til komponentens rumlige dimensioner og simple konstruktion. Til gengæld varierer det keramiske materiales dielektricitetskonstant (og dermed også kondensatorens elektriske kapacitet) med spændingsforskellen mellem de to ledende plader, hvilket gør keramiske kondensatorer uegnede til visse anvendelser. Blokkondensatorer I denne type kondensatorer anvendes strimler af metal- og plastikfolier (to af hver slags, og med metalfolierne forbunder til hver sin tilledning), som er lagt sammen, og derefter viklet eller foldet sammen til en (som regel) firkantet blok, som rumligt fylder lidt i forhold til sin elektriske kapacitet og spændingsgrænse. Kondensatorer af denne slags har typisk kapaciteter fra ca. en nanofarad og op til cirka en mikrofarad (1 μF = 10-6 farad). Elektrolytkondensatorer Disse kondensatorer leveres typisk med kapaciteter fra lidt under en mikrofarad, og op til nogle tiendedele farad. Her udgøres den ene ledende plade af et stykke sammenrullet folie af aluminium, hvis overflade er blevet ætset ru – dette giver foliet et meget stort overfladeareal. Den ætsede overflade er blevet behandlet med ilt, så de yderste aluminiumatomer i foliet er gået i kemisk forbindelse med ilten og derved danner et isolerende og mikrometertyndt lag af aluminiumilte. Den anden plade udgøres af en elektrisk ledende pasta, som omgiver det sammenrullede folie og trænger ned i alle de ætsede fordybninger og ujævnheder i foliet, og derved danner en elektrisk leder med omtrent samme (store) areal som foliets. Pasta og folie er i praksis emballeret i en lille cylindrisk beholder af aluminium, som samtidig udgør den ene af kondensatorens to tilledninger. Det store areal og det mikrometer-tynde dielektrikum af aluminiumilte giver elektrolytkondensatoren en meget stor elektrisk kapacitet i forhold til det rumfang komponenten optager. Til gengæld er der også nogle ulemper ved elektrolytkondensatorer: Det meget tynde dielektrikum (laget af aluminiumilte) gør, at elektrolykondensatorer højest kan indrettes til at tåle nogle få hundrede volt, mens andre kondensatortyper kan laves til at klare adskillige tusinde volt. Spændingen over kondensatoren skal altid være polariseret sådan, at det ætsede folie er positivt ladet i forhold til den ydre aluminiumsbeholder og den mellemliggende, ledende pasta. Ved modsat polarisering ødelægges det tynde lag af aluminiumilte ad galvanisk vej, indtil der opstår en kortslutning mellem pastaen og aluminiumsfolien. Og da elektrolytkondensatorer netop har relativt store elektriske kapaciteter, er det betydelige mængder af elektrisk energi der "slipper igennem" en sådan kortslutning. Derved omsættes den evt. lagrede elektriske energi til varme, som kan få trykket i pastaen til at sprænge komponentens ydre indpakning. Da foliet er viklet sammen, fungerer det i sig selv (utilsigtet) som en spole, om end en spole med meget lille selvinduktion. Så længe kondensatoren bruges til at behandle enten jævnstrøm eller vekselstrøm med lave frekvenser er dette ikke noget problem, men ved frekvenser over nogle hundrede kilohertz begynder virkningen af denne spole at vise sig som en "dårlig forbindelse" til anode-foliet. I dag 2005 er det mange steder muligt at købe elektrolytkondensatorer der har lav spolevirkning. De hedder lav-ESR (ESR – Equivalent Series Resistance). Disse kondensatorer anvendes i højkvalitets-hifi-forstærkere og SMPS. Tantal-elektrolytkondensatorer Tantal-elektrolytkondensatorer benytter en teknik svarende til de "almindelige" elektrolytkondensatorer nævnt ovenfor, blot baseret på grundstoffet tantal. Med denne teknik kan man have samme elektriske kapacitet og spændingsgrænse indenfor mindre rumlige dimensioner. Desuden begynder problemerne som følge af selvinduktion først at vise sig ved højere frekvenser end for de almindelige elektrolytkondensatorer. Drejekondensator Drejekondensatoren er en pladekondensator, der består af en fast stator og en bevægelig rotor. Ved at variere den del af rotoren, der er drejet ind i statoren, kan drejekondensatorens kapacitet ændres. Stator og rotor kan yderligere være isoleret af et fast dielektrikum. En drejekondensator bruges til at indstille frekvensen for en svingningskreds, f.eks. til at indstille en radio. En særlig form for drejekondensator er trimmekondensatoren, der indstilles med en nøgle eller skruetrækker og derefter ikke indstilles (før svingningskredsen evt. skal justeres). Kondensator opmærkning og koder De fleste producenter af kondensatorer følger Electronic Industries Alliance (EIA) standarderne for navngivning af kondensatorers spænding, kaapcitet og tolerance. Den findes i dag som internal standard IEC 60062. DC spændingstabel: AC spændingstabel: En kondensator med koden 474J skal læses som 47 ganget med 3. tals værdi i tabellen herunder. I dette tilfælde er det så 47 * 10000 = 470000 pF = 470 nF = 0.47 uF med J som betyder 5% tolerance. Kapacitetskoder Fodnoter Se også Ultrakondensator Elektronik Elektroniske komponenter Elektrisk spole Elektrisk svingningskreds Kapacitetsdiode Passive elektronikkomponenter Elektrisk energilagring Dagens artikel	danish	0.548193
taste_electrons/Electricity.txt	Electricity is the set of physical phenomena associated with the presence and motion of matter possessing an electric charge. Electricity is related to magnetism, both being part of the phenomenon of electromagnetism, as described by Maxwell's equations. Common phenomena are related to electricity, including lightning, static electricity, electric heating, electric discharges and many others. The presence of either a positive or negative electric charge produces an electric field. The motion of electric charges is an electric current and produces a magnetic field. In most applications, Coulomb's law determines the force acting on an electric charge. Electric potential is the work done to move an electric charge from one point to another within an electric field, typically measured in volts. Electricity plays a central role in many modern technologies, serving in electric power where electric current is used to energise equipment, and in electronics dealing with electrical circuits involving active components such as vacuum tubes, transistors, diodes and integrated circuits, and associated passive interconnection technologies. The study of electrical phenomena dates back to antiquity, with theoretical understanding progressing slowly until the 17th and 18th centuries. The development of the theory of electromagnetism in the 19th century marked significant progress, leading to electricity's industrial and residential application by electrical engineers by the century's end. This rapid expansion in electrical technology at the time was the driving force for the Second Industrial Revolution, with electricity's versatility driving transformations in industry and society. Electricity is integral to applications spanning transport, heating, lighting, communications, and computation, making it the foundation of modern industrial society. History Thales, the earliest known researcher into electricity Main articles: History of electromagnetic theory and History of electrical engineering See also: Etymology of electricity Long before any knowledge of electricity existed, people were aware of shocks from electric fish. Ancient Egyptian texts dating from 2750 BCE referred to these fish as the "Thunderer of the Nile", and described them as the "protectors" of all other fish. Electric fish were again reported millennia later by ancient Greek, Roman and Arabic naturalists and physicians. Several ancient writers, such as Pliny the Elder and Scribonius Largus, attested to the numbing effect of electric shocks delivered by electric catfish and electric rays, and knew that such shocks could travel along conducting objects. Patients with ailments such as gout or headache were directed to touch electric fish in the hope that the powerful jolt might cure them. Ancient cultures around the Mediterranean knew that certain objects, such as rods of amber, could be rubbed with cat's fur to attract light objects like feathers. Thales of Miletus made a series of observations on static electricity around 600 BCE, from which he believed that friction rendered amber magnetic, in contrast to minerals such as magnetite, which needed no rubbing. Thales was incorrect in believing the attraction was due to a magnetic effect, but later science would prove a link between magnetism and electricity. According to a controversial theory, the Parthians may have had knowledge of electroplating, based on the 1936 discovery of the Baghdad Battery, which resembles a galvanic cell, though it is uncertain whether the artifact was electrical in nature. Benjamin Franklin conducted extensive research on electricity in the 18th century, as documented by Joseph Priestley (1767) History and Present Status of Electricity, with whom Franklin carried on extended correspondence. Electricity would remain little more than an intellectual curiosity for millennia until 1600, when the English scientist William Gilbert wrote De Magnete, in which he made a careful study of electricity and magnetism, distinguishing the lodestone effect from static electricity produced by rubbing amber. He coined the Neo-Latin word electricus ("of amber" or "like amber", from ἤλεκτρον, elektron, the Greek word for "amber") to refer to the property of attracting small objects after being rubbed. This association gave rise to the English words "electric" and "electricity", which made their first appearance in print in Thomas Browne's Pseudodoxia Epidemica of 1646. Further work was conducted in the 17th and early 18th centuries by Otto von Guericke, Robert Boyle, Stephen Gray and C. F. du Fay. Later in the 18th century, Benjamin Franklin conducted extensive research in electricity, selling his possessions to fund his work. In June 1752 he is reputed to have attached a metal key to the bottom of a dampened kite string and flown the kite in a storm-threatened sky. A succession of sparks jumping from the key to the back of his hand showed that lightning was indeed electrical in nature. He also explained the apparently paradoxical behavior of the Leyden jar as a device for storing large amounts of electrical charge in terms of electricity consisting of both positive and negative charges. Michael Faraday's discoveries formed the foundation of electric motor technology. In 1775, Hugh Williamson reported a series of experiments to the Royal Society on the shocks delivered by the electric eel; that same year the surgeon and anatomist John Hunter described the structure of the fish's electric organs. In 1791, Luigi Galvani published his discovery of bioelectromagnetics, demonstrating that electricity was the medium by which neurons passed signals to the muscles. Alessandro Volta's battery, or voltaic pile, of 1800, made from alternating layers of zinc and copper, provided scientists with a more reliable source of electrical energy than the electrostatic machines previously used. The recognition of electromagnetism, the unity of electric and magnetic phenomena, is due to Hans Christian Ørsted and André-Marie Ampère in 1819–1820. Michael Faraday invented the electric motor in 1821, and Georg Ohm mathematically analysed the electrical circuit in 1827. Electricity and magnetism (and light) were definitively linked by James Clerk Maxwell, in particular in his "On Physical Lines of Force" in 1861 and 1862. While the early 19th century had seen rapid progress in electrical science, the late 19th century would see the greatest progress in electrical engineering. Through such people as Alexander Graham Bell, Ottó Bláthy, Thomas Edison, Galileo Ferraris, Oliver Heaviside, Ányos Jedlik, William Thomson, 1st Baron Kelvin, Charles Algernon Parsons, Werner von Siemens, Joseph Swan, Reginald Fessenden, Nikola Tesla and George Westinghouse, electricity turned from a scientific curiosity into an essential tool for modern life. In 1887, Heinrich Hertz discovered that electrodes illuminated with ultraviolet light create electric sparks more easily. In 1905, Albert Einstein published a paper that explained experimental data from the photoelectric effect as being the result of light energy being carried in discrete quantized packets, energising electrons. This discovery led to the quantum revolution. Einstein was awarded the Nobel Prize in Physics in 1921 for "his discovery of the law of the photoelectric effect". The photoelectric effect is also employed in photocells such as can be found in solar panels. The first solid-state device was the "cat's-whisker detector" first used in the 1900s in radio receivers. A whisker-like wire is placed lightly in contact with a solid crystal (such as a germanium crystal) to detect a radio signal by the contact junction effect. In a solid-state component, the current is confined to solid elements and compounds engineered specifically to switch and amplify it. Current flow can be understood in two forms: as negatively charged electrons, and as positively charged electron deficiencies called holes. These charges and holes are understood in terms of quantum physics. The building material is most often a crystalline semiconductor. Solid-state electronics came into its own with the emergence of transistor technology. The first working transistor, a germanium-based point-contact transistor, was invented by John Bardeen and Walter Houser Brattain at Bell Labs in 1947, followed by the bipolar junction transistor in 1948. Concepts Electric charge Main article: Electric charge See also: Electron, Proton, and Ion Charge on a gold-leaf electroscope causes the leaves to visibly repel each other The presence of charge gives rise to an electrostatic force: charges exert a force on each other, an effect that was known, though not understood, in antiquity. A lightweight ball suspended by a fine thread can be charged by touching it with a glass rod that has itself been charged by rubbing with a cloth. If a similar ball is charged by the same glass rod, it is found to repel the first: the charge acts to force the two balls apart. Two balls that are charged with a rubbed amber rod also repel each other. However, if one ball is charged by the glass rod, and the other by an amber rod, the two balls are found to attract each other. These phenomena were investigated in the late eighteenth century by Charles-Augustin de Coulomb, who deduced that charge manifests itself in two opposing forms. This discovery led to the well-known axiom: like-charged objects repel and opposite-charged objects attract. The force acts on the charged particles themselves, hence charge has a tendency to spread itself as evenly as possible over a conducting surface. The magnitude of the electromagnetic force, whether attractive or repulsive, is given by Coulomb's law, which relates the force to the product of the charges and has an inverse-square relation to the distance between them. The electromagnetic force is very strong, second only in strength to the strong interaction, but unlike that force it operates over all distances. In comparison with the much weaker gravitational force, the electromagnetic force pushing two electrons apart is 10 times that of the gravitational attraction pulling them together. Charge originates from certain types of subatomic particles, the most familiar carriers of which are the electron and proton. Electric charge gives rise to and interacts with the electromagnetic force, one of the four fundamental forces of nature. Experiment has shown charge to be a conserved quantity, that is, the net charge within an electrically isolated system will always remain constant regardless of any changes taking place within that system. Within the system, charge may be transferred between bodies, either by direct contact, or by passing along a conducting material, such as a wire. The informal term static electricity refers to the net presence (or 'imbalance') of charge on a body, usually caused when dissimilar materials are rubbed together, transferring charge from one to the other. The charge on electrons and protons is opposite in sign, hence an amount of charge may be expressed as being either negative or positive. By convention, the charge carried by electrons is deemed negative, and that by protons positive, a custom that originated with the work of Benjamin Franklin. The amount of charge is usually given the symbol Q and expressed in coulombs; each electron carries the same charge of approximately −1.6022×10 coulomb. The proton has a charge that is equal and opposite, and thus +1.6022×10 coulomb. Charge is possessed not just by matter, but also by antimatter, each antiparticle bearing an equal and opposite charge to its corresponding particle. Charge can be measured by a number of means, an early instrument being the gold-leaf electroscope, which although still in use for classroom demonstrations, has been superseded by the electronic electrometer. Electric current Main article: Electric current The movement of electric charge is known as an electric current, the intensity of which is usually measured in amperes. Current can consist of any moving charged particles; most commonly these are electrons, but any charge in motion constitutes a current. Electric current can flow through some things, electrical conductors, but will not flow through an electrical insulator. By historical convention, a positive current is defined as having the same direction of flow as any positive charge it contains, or to flow from the most positive part of a circuit to the most negative part. Current defined in this manner is called conventional current. The motion of negatively charged electrons around an electric circuit, one of the most familiar forms of current, is thus deemed positive in the opposite direction to that of the electrons. However, depending on the conditions, an electric current can consist of a flow of charged particles in either direction, or even in both directions at once. The positive-to-negative convention is widely used to simplify this situation. An electric arc provides an energetic demonstration of electric current. The process by which electric current passes through a material is termed electrical conduction, and its nature varies with that of the charged particles and the material through which they are travelling. Examples of electric currents include metallic conduction, where electrons flow through a conductor such as metal, and electrolysis, where ions (charged atoms) flow through liquids, or through plasmas such as electrical sparks. While the particles themselves can move quite slowly, sometimes with an average drift velocity only fractions of a millimetre per second, the electric field that drives them itself propagates at close to the speed of light, enabling electrical signals to pass rapidly along wires. Current causes several observable effects, which historically were the means of recognising its presence. That water could be decomposed by the current from a voltaic pile was discovered by Nicholson and Carlisle in 1800, a process now known as electrolysis. Their work was greatly expanded upon by Michael Faraday in 1833. Current through a resistance causes localised heating, an effect James Prescott Joule studied mathematically in 1840. One of the most important discoveries relating to current was made accidentally by Hans Christian Ørsted in 1820, when, while preparing a lecture, he witnessed the current in a wire disturbing the needle of a magnetic compass. He had discovered electromagnetism, a fundamental interaction between electricity and magnetics. The level of electromagnetic emissions generated by electric arcing is high enough to produce electromagnetic interference, which can be detrimental to the workings of adjacent equipment. In engineering or household applications, current is often described as being either direct current (DC) or alternating current (AC). These terms refer to how the current varies in time. Direct current, as produced by example from a battery and required by most electronic devices, is a unidirectional flow from the positive part of a circuit to the negative. If, as is most common, this flow is carried by electrons, they will be travelling in the opposite direction. Alternating current is any current that reverses direction repeatedly; almost always this takes the form of a sine wave. Alternating current thus pulses back and forth within a conductor without the charge moving any net distance over time. The time-averaged value of an alternating current is zero, but it delivers energy in first one direction, and then the reverse. Alternating current is affected by electrical properties that are not observed under steady state direct current, such as inductance and capacitance. These properties however can become important when circuitry is subjected to transients, such as when first energised. Electric field Main article: Electric field See also: Electrostatics The concept of the electric field was introduced by Michael Faraday. An electric field is created by a charged body in the space that surrounds it, and results in a force exerted on any other charges placed within the field. The electric field acts between two charges in a similar manner to the way that the gravitational field acts between two masses, and like it, extends towards infinity and shows an inverse square relationship with distance. However, there is an important difference. Gravity always acts in attraction, drawing two masses together, while the electric field can result in either attraction or repulsion. Since large bodies such as planets generally carry no net charge, the electric field at a distance is usually zero. Thus gravity is the dominant force at distance in the universe, despite being much weaker. Field lines emanating from a positive charge above a plane conductor An electric field generally varies in space, and its strength at any one point is defined as the force (per unit charge) that would be felt by a stationary, negligible charge if placed at that point. The conceptual charge, termed a 'test charge', must be vanishingly small to prevent its own electric field disturbing the main field and must also be stationary to prevent the effect of magnetic fields. As the electric field is defined in terms of force, and force is a vector, having both magnitude and direction, it follows that an electric field is a vector field. The study of electric fields created by stationary charges is called electrostatics. The field may be visualised by a set of imaginary lines whose direction at any point is the same as that of the field. This concept was introduced by Faraday, whose term 'lines of force' still sometimes sees use. The field lines are the paths that a point positive charge would seek to make as it was forced to move within the field; they are however an imaginary concept with no physical existence, and the field permeates all the intervening space between the lines. Field lines emanating from stationary charges have several key properties: first, that they originate at positive charges and terminate at negative charges; second, that they must enter any good conductor at right angles, and third, that they may never cross nor close in on themselves. A hollow conducting body carries all its charge on its outer surface. The field is therefore 0 at all places inside the body. This is the operating principal of the Faraday cage, a conducting metal shell which isolates its interior from outside electrical effects. The principles of electrostatics are important when designing items of high-voltage equipment. There is a finite limit to the electric field strength that may be withstood by any medium. Beyond this point, electrical breakdown occurs and an electric arc causes flashover between the charged parts. Air, for example, tends to arc across small gaps at electric field strengths which exceed 30 kV per centimetre. Over larger gaps, its breakdown strength is weaker, perhaps 1 kV per centimetre. The most visible natural occurrence of this is lightning, caused when charge becomes separated in the clouds by rising columns of air, and raises the electric field in the air to greater than it can withstand. The voltage of a large lightning cloud may be as high as 100 MV and have discharge energies as great as 250 kWh. The field strength is greatly affected by nearby conducting objects, and it is particularly intense when it is forced to curve around sharply pointed objects. This principle is exploited in the lightning conductor, the sharp spike of which acts to encourage the lightning strike to develop there, rather than to the building it serves to protect. Electric potential Main article: Electric potential See also: Voltage and Battery (electricity) A pair of AA cells. The + sign indicates the polarity of the potential difference between the battery terminals. The concept of electric potential is closely linked to that of the electric field. A small charge placed within an electric field experiences a force, and to have brought that charge to that point against the force requires work. The electric potential at any point is defined as the energy required to bring a unit test charge from an infinite distance slowly to that point. It is usually measured in volts, and one volt is the potential for which one joule of work must be expended to bring a charge of one coulomb from infinity. This definition of potential, while formal, has little practical application, and a more useful concept is that of electric potential difference, and is the energy required to move a unit charge between two specified points. An electric field has the special property that it is conservative, which means that the path taken by the test charge is irrelevant: all paths between two specified points expend the same energy, and thus a unique value for potential difference may be stated. The volt is so strongly identified as the unit of choice for measurement and description of electric potential difference that the term voltage sees greater everyday usage. For practical purposes, it is useful to define a common reference point to which potentials may be expressed and compared. While this could be at infinity, a much more useful reference is the Earth itself, which is assumed to be at the same potential everywhere. This reference point naturally takes the name earth or ground. Earth is assumed to be an infinite source of equal amounts of positive and negative charge, and is therefore electrically uncharged—and unchargeable. Electric potential is a scalar quantity, that is, it has only magnitude and not direction. It may be viewed as analogous to height: just as a released object will fall through a difference in heights caused by a gravitational field, so a charge will 'fall' across the voltage caused by an electric field. As relief maps show contour lines marking points of equal height, a set of lines marking points of equal potential (known as equipotentials) may be drawn around an electrostatically charged object. The equipotentials cross all lines of force at right angles. They must also lie parallel to a conductor's surface, since otherwise there would be a force along the surface of the conductor that would move the charge carriers to even the potential across the surface. The electric field was formally defined as the force exerted per unit charge, but the concept of potential allows for a more useful and equivalent definition: the electric field is the local gradient of the electric potential. Usually expressed in volts per metre, the vector direction of the field is the line of greatest slope of potential, and where the equipotentials lie closest together. Electromagnets Main article: Electromagnets Magnetic field circles around a current Ørsted's discovery in 1821 that a magnetic field existed around all sides of a wire carrying an electric current indicated that there was a direct relationship between electricity and magnetism. Moreover, the interaction seemed different from gravitational and electrostatic forces, the two forces of nature then known. The force on the compass needle did not direct it to or away from the current-carrying wire, but acted at right angles to it. Ørsted's words were that "the electric conflict acts in a revolving manner." The force also depended on the direction of the current, for if the flow was reversed, then the force did too. Ørsted did not fully understand his discovery, but he observed the effect was reciprocal: a current exerts a force on a magnet, and a magnetic field exerts a force on a current. The phenomenon was further investigated by Ampère, who discovered that two parallel current-carrying wires exerted a force upon each other: two wires conducting currents in the same direction are attracted to each other, while wires containing currents in opposite directions are forced apart. The interaction is mediated by the magnetic field each current produces and forms the basis for the international definition of the ampere. The electric motor exploits an important effect of electromagnetism: a current through a magnetic field experiences a force at right angles to both the field and current. This relationship between magnetic fields and currents is extremely important, for it led to Michael Faraday's invention of the electric motor in 1821. Faraday's homopolar motor consisted of a permanent magnet sitting in a pool of mercury. A current was allowed through a wire suspended from a pivot above the magnet and dipped into the mercury. The magnet exerted a tangential force on the wire, making it circle around the magnet for as long as the current was maintained. Experimentation by Faraday in 1831 revealed that a wire moving perpendicular to a magnetic field developed a potential difference between its ends. Further analysis of this process, known as electromagnetic induction, enabled him to state the principle, now known as Faraday's law of induction, that the potential difference induced in a closed circuit is proportional to the rate of change of magnetic flux through the loop. Exploitation of this discovery enabled him to invent the first electrical generator in 1831, in which he converted the mechanical energy of a rotating copper disc to electrical energy. Faraday's disc was inefficient and of no use as a practical generator, but it showed the possibility of generating electric power using magnetism, a possibility that would be taken up by those that followed on from his work. Electric circuits Main article: Electric circuit A basic electric circuit. The voltage source V on the left drives a current I around the circuit, delivering electrical energy into the resistor R. From the resistor, the current returns to the source, completing the circuit. An electric circuit is an interconnection of electric components such that electric charge is made to flow along a closed path (a circuit), usually to perform some useful task. The components in an electric circuit can take many forms, which can include elements such as resistors, capacitors, switches, transformers and electronics. Electronic circuits contain active components, usually semiconductors, and typically exhibit non-linear behaviour, requiring complex analysis. The simplest electric components are those that are termed passive and linear: while they may temporarily store energy, they contain no sources of it, and exhibit linear responses to stimuli. The resistor is perhaps the simplest of passive circuit elements: as its name suggests, it resists the current through it, dissipating its energy as heat. The resistance is a consequence of the motion of charge through a conductor: in metals, for example, resistance is primarily due to collisions between electrons and ions. Ohm's law is a basic law of circuit theory, stating that the current passing through a resistance is directly proportional to the potential difference across it. The resistance of most materials is relatively constant over a range of temperatures and currents; materials under these conditions are known as 'ohmic'. The ohm, the unit of resistance, was named in honour of Georg Ohm, and is symbolised by the Greek letter Ω. 1 Ω is the resistance that will produce a potential difference of one volt in response to a current of one amp. The capacitor is a development of the Leyden jar and is a device that can store charge, and thereby storing electrical energy in the resulting field. It consists of two conducting plates separated by a thin insulating dielectric layer; in practice, thin metal foils are coiled together, increasing the surface area per unit volume and therefore the capacitance. The unit of capacitance is the farad, named after Michael Faraday, and given the symbol F: one farad is the capacitance that develops a potential difference of one volt when it stores a charge of one coulomb. A capacitor connected to a voltage supply initially causes a current as it accumulates charge; this current will however decay in time as the capacitor fills, eventually falling to zero. A capacitor will therefore not permit a steady state current, but instead blocks it. The inductor is a conductor, usually a coil of wire, that stores energy in a magnetic field in response to the current through it. When the current changes, the magnetic field does too, inducing a voltage between the ends of the conductor. The induced voltage is proportional to the time rate of change of the current. The constant of proportionality is termed the inductance. The unit of inductance is the henry, named after Joseph Henry, a contemporary of Faraday. One henry is the inductance that will induce a potential difference of one volt if the current through it changes at a rate of one ampere per second. The inductor's behaviour is in some regards converse to that of the capacitor: it will freely allow an unchanging current, but opposes a rapidly changing one. Electric power Main article: electric power Electric power is the rate at which electric energy is transferred by an electric circuit. The SI unit of power is the watt, one joule per second. Electric power, like mechanical power, is the rate of doing work, measured in watts, and represented by the letter P. The term wattage is used colloquially to mean "electric power in watts." The electric power in watts produced by an electric current I consisting of a charge of Q coulombs every t seconds passing through an electric potential (voltage) difference of V is P = work done per unit time = Q V t = I V {\displaystyle P={\text{work done per unit time}}={\frac {QV}{t}}=IV\,} where Q is electric charge in coulombs t is time in seconds I is electric current in amperes V is electric potential or voltage in volts Electric power is generally supplied to businesses and homes by the electric power industry. Electricity is usually sold by the kilowatt hour (3.6 MJ) which is the product of power in kilowatts multiplied by running time in hours. Electric utilities measure power using electricity meters, which keep a running total of the electric energy delivered to a customer. Unlike fossil fuels, electricity is a low entropy form of energy and can be converted into motion or many other forms of energy with high efficiency. Electronics Main article: electronics Surface-mount electronic components Electronics deals with electrical circuits that involve active electrical components such as vacuum tubes, transistors, diodes, sensors and integrated circuits, and associated passive interconnection technologies. The nonlinear behaviour of active components and their ability to control electron flows makes digital switching possible, and electronics is widely used in information processing, telecommunications, and signal processing. Interconnection technologies such as circuit boards, electronics packaging technology, and other varied forms of communication infrastructure complete circuit functionality and transform the mixed components into a regular working system. Today, most electronic devices use semiconductor components to perform electron control. The underlying principles that explain how semiconductors work are studied in solid state physics, whereas the design and construction of electronic circuits to solve practical problems are part of electronics engineering. Electromagnetic wave Main article: Electromagnetic wave Faraday's and Ampère's work showed that a time-varying magnetic field created an electric field, and a time-varying electric field created a magnetic field. Thus, when either field is changing in time, a field of the other is always induced. These variations are an electromagnetic wave. Electromagnetic waves were analysed theoretically by James Clerk Maxwell in 1864. Maxwell developed a set of equations that could unambiguously describe the interrelationship between electric field, magnetic field, electric charge, and electric current. He could moreover prove that in a vacuum such a wave would travel at the speed of light, and thus light itself was a form of electromagnetic radiation. Maxwell's equations, which unify light, fields, and charge are one of the great milestones of theoretical physics. The work of many researchers enabled the use of electronics to convert signals into high frequency oscillating currents and, via suitably shaped conductors, electricity permits the transmission and reception of these signals via radio waves over very long distances. Production, storage and uses Generation and transmission Main article: Electricity generation See also: Electric power transmission and Mains electricity Early 20th-century alternator made in Budapest, Hungary, in the power generating hall of a hydroelectric station (photograph by Prokudin-Gorsky, 1905–1915). In the 6th century BC the Greek philosopher Thales of Miletus experimented with amber rods: these were the first studies into the production of electricity. While this method, now known as the triboelectric effect, can lift light objects and generate sparks, it is extremely inefficient. It was not until the invention of the voltaic pile in the eighteenth century that a viable source of electricity became available. The voltaic pile, and its modern descendant, the electrical battery, store energy chemically and make it available on demand in the form of electricity. Electrical power is usually generated by electro-mechanical generators. These can be driven by steam produced from fossil fuel combustion or the heat released from nuclear reactions, but also more directly from the kinetic energy of wind or flowing water. The steam turbine invented by Sir Charles Parsons in 1884 is still used to convert the thermal energy of steam into a rotary motion that can be used by electro-mechanical generators. Such generators bear no resemblance to Faraday's homopolar disc generator of 1831, but they still rely on his electromagnetic principle that a conductor linking a changing magnetic field induces a potential difference across its ends. Electricity generated by solar panels rely on a different mechanism: solar radiation is converted directly into electricity using the photovoltaic effect. Wind power is of increasing importance in many countries. Demand for electricity grows with great rapidity as a nation modernises and its economy develops. The United States showed a 12% increase in demand during each year of the first three decades of the twentieth century, a rate of growth that is now being experienced by emerging economies such as those of India or China. Environmental concerns with electricity generation, in specific the contribution of fossil fuel burning to climate change, have led to an increased focus on generation from renewable sources. In the power sector, wind and solar have become cost effective, speeding up an energy transition away from fossil fuels. Transmission and storage The invention in the late nineteenth century of the transformer meant that electrical power could be transmitted more efficiently at a higher voltage but lower current. Efficient electrical transmission meant in turn that electricity could be generated at centralised power stations, where it benefited from economies of scale, and then be despatched relatively long distances to where it was needed. Normally, demand of electricity must match the supply, as storage of electricity is difficult. A certain amount of generation must always be held in reserve to cushion an electrical grid against inevitable disturbances and losses. With increasing levels of variable renewable energy (wind and solar energy) in the grid, it has become more challenging to match supply and demand. Storage plays an increasing role in bridging that gap. There are four types of energy storage technologies, each in varying states of technology readiness: batteries (electrochemical storage), chemical storage such as hydrogen, thermal or mechanical (such as pumped hydropower). Applications The incandescent light bulb, an early application of electricity, operates by Joule heating: the passage of current through resistance generating heat. Electricity is a very convenient way to transfer energy, and it has been adapted to a huge, and growing, number of uses. The invention of a practical incandescent light bulb in the 1870s led to lighting becoming one of the first publicly available applications of electrical power. Although electrification brought with it its own dangers, replacing the naked flames of gas lighting greatly reduced fire hazards within homes and factories. Public utilities were set up in many cities targeting the burgeoning market for electrical lighting. In the late 20th century and in modern times, the trend has started to flow in the direction of deregulation in the electrical power sector. The resistive Joule heating effect employed in filament light bulbs also sees more direct use in electric heating. While this is versatile and controllable, it can be seen as wasteful, since most electrical generation has already required the production of heat at a power station. A number of countries, such as Denmark, have issued legislation restricting or banning the use of resistive electric heating in new buildings. Electricity is however still a highly practical energy source for heating and refrigeration, with air conditioning/heat pumps representing a growing sector for electricity demand for heating and cooling, the effects of which electricity utilities are increasingly obliged to accommodate. Electrification is expected to play a major role in the decarbonisation of sectors that rely on direct fossil fuel burning, such as transport (using electric vehicles) and heating (using heat pumps). The effects of electromagnetism are most visibly employed in the electric motor, which provides a clean and efficient means of motive power. A stationary motor such as a winch is easily provided with a supply of power, but a motor that moves with its application, such as an electric vehicle, is obliged to either carry along a power source such as a battery, or to collect current from a sliding contact such as a pantograph. Electrically powered vehicles are used in public transportation, such as electric buses and trains, and an increasing number of battery-powered electric cars in private ownership. Electricity is used within telecommunications, and indeed the electrical telegraph, demonstrated commercially in 1837 by Cooke and Wheatstone, was one of its earliest applications. With the construction of first transcontinental, and then transatlantic, telegraph systems in the 1860s, electricity had enabled communications in minutes across the globe. Optical fibre and satellite communication have taken a share of the market for communications systems, but electricity can be expected to remain an essential part of the process. Electronic devices make use of the transistor, perhaps one of the most important inventions of the twentieth century, and a fundamental building block of all modern circuitry. A modern integrated circuit may contain many billions of miniaturised transistors in a region only a few centimetres square. Electricity and the natural world Physiological effects Main article: Electric shock A voltage applied to a human body causes an electric current through the tissues, and although the relationship is non-linear, the greater the voltage, the greater the current. The threshold for perception varies with the supply frequency and with the path of the current, but is about 0.1 mA to 1 mA for mains-frequency electricity, though a current as low as a microamp can be detected as an electrovibration effect under certain conditions. If the current is sufficiently high, it will cause muscle contraction, fibrillation of the heart, and tissue burns. The lack of any visible sign that a conductor is electrified makes electricity a particular hazard. The pain caused by an electric shock can be intense, leading electricity at times to be employed as a method of torture. Death caused by an electric shock—electrocution—is still used for judicial execution in some US states, though its use had become very rare by the end of the 20th century. Electrical phenomena in nature Main article: Electrical phenomena The electric eel, Electrophorus electricus Electricity is not a human invention, and may be observed in several forms in nature, notably lightning. Many interactions familiar at the macroscopic level, such as touch, friction or chemical bonding, are due to interactions between electric fields on the atomic scale. The Earth's magnetic field is due to the natural dynamo of circulating currents in the planet's core. Certain crystals, such as quartz, or even sugar, generate a potential difference across their faces when pressed. This phenomenon is known as piezoelectricity, from the Greek piezein (πιέζειν), meaning to press, and was discovered in 1880 by Pierre and Jacques Curie. The effect is reciprocal: when a piezoelectric material is subjected to an electric field it changes size slightly. Some organisms, such as sharks, are able to detect and respond to changes in electric fields, an ability known as electroreception, while others, termed electrogenic, are able to generate voltages themselves to serve as a predatory or defensive weapon; these are electric fish in different orders. The order Gymnotiformes, of which the best known example is the electric eel, detect or stun their prey via high voltages generated from modified muscle cells called electrocytes. All animals transmit information along their cell membranes with voltage pulses called action potentials, whose functions include communication by the nervous system between neurons and muscles. An electric shock stimulates this system, and causes muscles to contract. Action potentials are also responsible for coordinating activities in certain plants. Cultural perception It is said that in the 1850s, British politician William Gladstone asked the scientist Michael Faraday why electricity was valuable. Faraday answered, "One day sir, you may tax it." However, according to Snopes.com "the anecdote should be considered apocryphal because it isn't mentioned in any accounts by Faraday or his contemporaries (letters, newspapers, or biographies) and only popped up well after Faraday's death." In the 19th and early 20th century, electricity was not part of the everyday life of many people, even in the industrialised Western world. The popular culture of the time accordingly often depicted it as a mysterious, quasi-magical force that can slay the living, revive the dead or otherwise bend the laws of nature. This attitude began with the 1771 experiments of Luigi Galvani in which the legs of dead frogs were shown to twitch on application of animal electricity. "Revitalization" or resuscitation of apparently dead or drowned persons was reported in the medical literature shortly after Galvani's work. These results were known to Mary Shelley when she authored Frankenstein (1819), although she does not name the method of revitalization of the monster. The revitalization of monsters with electricity later became a stock theme in horror films. As the public familiarity with electricity as the lifeblood of the Second Industrial Revolution grew, its wielders were more often cast in a positive light, such as the workers who "finger death at their gloves' end as they piece and repiece the living wires" in Rudyard Kipling's 1907 poem Sons of Martha. Electrically powered vehicles of every sort featured large in adventure stories such as those of Jules Verne and the Tom Swift books. The masters of electricity, whether fictional or real—including scientists such as Thomas Edison, Charles Steinmetz or Nikola Tesla—were popularly conceived of as having wizard-like powers. With electricity ceasing to be a novelty and becoming a necessity of everyday life in the later half of the 20th century, it required particular attention by popular culture only when it stops flowing, an event that usually signals disaster. The people who keep it flowing, such as the nameless hero of Jimmy Webb's song "Wichita Lineman" (1968), are still often cast as heroic, wizard-like figures. See also Energy portalElectronics portal Ampère's circuital law, connects the direction of an electric current and its associated magnetic currents. 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(1990), "Historical Atlas of Crystallography", Zeitschrift für Kristallographie, Springer, 209 (12): 67, Bibcode:1994ZK....209.1008P, doi:10.1524/zkri.1994.209.12.1008a, ISBN 0-7923-0649-X ^ Ivancevic, Vladimir & Tijana (2005), Natural Biodynamics, World Scientific, p. 602, ISBN 981-256-534-5 ^ Kandel, E.; Schwartz, J.; Jessell, T. (2000), Principles of Neural Science, McGraw-Hill Professional, pp. 27–28, ISBN 0-8385-7701-6 ^ Davidovits, Paul (2007), Physics in Biology and Medicine, Academic Press, pp. 204–05, ISBN 978-0-12-369411-9 ^ Jackson, Mark (4 November 2013), Theoretical physics – like sex, but with no need to experiment, The Conversation, archived from the original on 4 April 2014, retrieved 26 March 2014 ^ Polymenis, Michael (December 2010). "Faraday on the fiscal benefits of science". Nature. 468 (7324): 634. doi:10.1038/468634d. ISSN 1476-4687. PMID 21124439. S2CID 4420175. ^ Heuer, Rolf (February 2011). "One Day, Sir, You May Tax It". CERN Bulletin (7–08/2011). ^ Mikkelson, David (25 November 2000). "Michael Faraday 'Tax' Quote". Snopes. ^ Van Riper, A. Bowdoin (2002), Science in popular culture: a reference guide, Westport: Greenwood Press, ISBN 0-313-31822-0	biology	781661	https://da.wikipedia.org/wiki/Elektrostatisk%20generator	Elektrostatisk generator	En elektrostatisk generator er en elektromekanisk generator og transducer, som omsætter mekanisk arbejde til elektrisk energi i form af statisk elektricitet, eller rettere elektricitet med højspænding og lav jævnstrøm, uden brug af statiske eller dynamiske magnetfelter. Viden om statisk elektricitet dateres tilbage til de tidligste civilisationer, men som i årtusinder kun er blevet opfattet som et interessant og mystisk fænomen uden en teori, der forklarer dets opførsel, og som ofte er blevet blandet sammen med magnetisme. Ved slutningen af det 17. århundrede havde forskere udviklet praktiske metoder til at generere elektricitet ved friktion, mens udviklingen af elektrostatiske maskiner først begyndte i det 18. århundrede, da de blev de grundlæggende instrumenter i udforskningen af den nye videnskab elektricitet. Elektrostatiske generatorer fungerer ved, at man omsætter mekanisk arbejde til elektrisk energi. Elektrostatiske generatorer genererer elektrostatiske ladninger med modsatte fortegn i to ledere ved kun at anvende elektriske kræfter, og arbejder ved at bevæge plader, tromler eller bælter til at overføre elektrisk ladning til elektroder med højspænding. Ladningen genereres enten ved triboelektriske effekter (friktionsbaserede elektrostatiske generatorer; "friktionmaskiner") eller elektrostatisk induktion (influensgeneratorer; "influensmaskiner"). Influensgeneratorer: elektrofor guld blads elektroskop Cavallo-generator Kelvingenerator Holtz-generator Schwedoff-generator Piche-generator (eller Bertsch-generator) Righi's elektrometer Leyser-generator Wimshurst-generator Lebiez-generator Voss-generator Pidgeon-generator Wehrsen-generator Moderne elektrostatiske generatorer: Van de Graaff-generator Pelletron Vingeløs ionvindsgenerator Twente elektrostatisk generator En meget simpel elektrostatisk vekselsspændingsgenerator er en kondensatormikrofon. Kilder/referencer Yderligere læsning Gottlieb Christoph Bohnenberger: Description of different electricity-doubler of a new device, along with a number of experiments on various subjects of electricity, etc.. Tübingen 1798. William Holtz: On a new electrical machine .. In: Johann Poggendorff, CG Barth (Eds.): Annals of physics and chemistry. 126, Leipzig 1865, p. 157 - 171st William Holtz: the higher charge on insulating surfaces by side pull and the transfer of this principle to the construction of induction machines .. In: Johann Poggendorff, CG Barth (eds): Annals of physics and chemistry. 130, Leipzig 1867, p. 128 - 136 William Holtz: The influence machine. In: F. Poske (Eds.): Annals of physics and chemistry. Julius Springer, Berlin 1904 (seventeenth year, the fourth issue). O. Lehmann: Dr. J. Frick's physical technique. 2, Friedrich Vieweg und Sohn, Braunschweig 1909, p. 797 (Section 2). F. Poske: New forms of influence machines .. In: F. Poske (eds) for the physical and chemical education. journal Julius Springer, Berlin 1893 (seventh year, second issue). C. L. Stong, "Electrostatic motors are powered by electric field of the Earth ". October, 1974. (PDF) Oleg D. Jefimenko, "Electrostatic Motors: Their History, Types, and Principles of Operation". Electret Scientific, Star City, 1973. G. W. Francis (author) and Oleg D. Jefimenko (editor), "Electrostatic Experiments: An Encyclopedia of Early Electrostatic Experiments, Demonstrations, Devices, and Apparatus". Electret Scientific, Star City, 2005. V. E. Johnson, "Modern High-Speed Influence Machines; Their principles, construction and applications to radiography, radio-telegraphy, spark photography, electro-culture, electro-therapeutics, high-tension gas ignition, and the testing of materials". ISBN B0000EFPCO Alfred W. Simon, "Quantitative Theory of the Influence Electrostatic Generator". Phys. Rev. 24, 690–696 (1924), Issue 6 – December 1924. J. Clerk Maxwell, Treatise on Electricity and Magnetism (2nd ed.,Oxford, 1881), vol. i. p. 294 Joseph David Everett, Electricity (expansion of part iii. of Augustin Privat-Deschanel's "Natural Philosophy") (London, 1901), ch. iv. p. 20 A. Winkelmann, Handbuch der Physik (Breslau, 1905), vol. iv. pp. 50–58 (contains a large number of references to original papers) J. Gray, "Electrical Influence Machines, Their Historical Development and Modern Forms [with instruction on making them]" (London, I903). (J. A. F.) Silvanus P. Thompson, The Influence Machine from Nicholson -1788 to 1888, Journ. Soc. Tel. Eng., 1888, 17, p. 569 John Munro, The Story Of Electricity (The Project Gutenberg Etext) A. D. Moore (Editor), "Electrostatics and its Applications". Wiley, New York, 1973. Oleg D. Jefimenko (with D. K. Walker), "Electrostatic motors". Phys. Teach. 9, 121-129 (1971). W. R. Pidgeon, "An Influence-Machine". Proc. Phys. Soc. London 12(1)1 (October 1892) 406–411 and 16(1) (October 1897) 253–257. Se også Elektrostatisk motor Elektrometer (også kendt som "elektroskop") Statisk elektricitet Eksterne henvisninger Electrostatic Generator - Interactive Java Tutorial National High Magnetic Field Laboratory "Electrical (or Electrostatic) Machine ". 1911 encyclopedia. "How it works : Electricity ". triquartz.co.uk. Antonio Carlos M. de Queiroz, "Electrostatic Machines ". "Operation of the Wimshurst machine ". Antonio Carlos M. de Queiroz Youtube Elektrostatik Elektriske generatorer	danish	0.34423
mints_make_your_mouth_feel_cold/Mentha.txt	Mentha (also known as mint, from Greek μίνθα míntha, Linear B mi-ta) is a genus of plants in the family Lamiaceae (mint family). The exact distinction between species is unclear; it is estimated that 13 to 24 species exist. Hybridization occurs naturally where some species' ranges overlap. Many hybrids and cultivars are known. The genus has a subcosmopolitan distribution across Europe, Africa – (Southern Africa), Asia, Australia – Oceania, North America and South America. Its species can be found in many environments, but most grow best in wet environments and moist soils. Description[edit] Flowering verticillasters of a spearmint. Mints are aromatic, almost exclusively perennial herbs. They have wide-spreading underground and overground stolons and erect, square, branched stems. Mints will grow 10–120 cm (4–48 inches) tall and can spread over an indeterminate area. Due to their tendency to spread unchecked, some mints are considered invasive. The leaves are arranged in opposite pairs, from oblong to lanceolate, often downy, and with a serrated margin. Leaf colors range from dark green and gray-green to purple, blue, and sometimes pale yellow. The flowers are produced in long bracts from leaf axils. They are white to purple and produced in false whorls called verticillasters. The corolla is two-lipped with four subequal lobes, the upper lobe usually the largest. The fruit is a nutlet, containing one to four seeds. Taxonomy[edit] Mentha is a member of the tribe Mentheae in the subfamily Nepetoideae. The tribe contains about 65 genera, and relationships within it remain obscure. Authors have disagreed on the circumscription of Mentha. For example, M. cervina has been placed in Pulegium and Preslia, and M. cunninghamii has been placed in Micromeria. In 2004, a molecular phylogenetic study indicated that both M. cervina and M. cunninghamii should be included in Mentha. However, M. cunninghamii was excluded in a 2007 treatment of the genus. More than 3,000 names have been published in the genus Mentha, at ranks from species to forms, the majority of which are regarded as synonyms or illegitimate names. The taxonomy of the genus is made difficult because many species hybridize readily, or are themselves derived from possibly ancient hybridization events. Seeds from hybrids give rise to variable offspring, which may spread through vegetative propagation. The variability has led to what has been described as "paroxysms of species and subspecific taxa"; for example, one taxonomist published 434 new mint taxa for central Europe alone between 1911 and 1916. Recent sources recognize between 18 and 24 species. Species[edit] As of December 2020, Plants of the World Online recognized the following species: Mentha alaica Boriss. Mentha aquatica L. – water mint, marsh mint Mentha arvensis L. – corn mint, wild mint, Japanese peppermint, field mint, banana mint Mentha atrolilacina B.J.Conn & D.J.Duval – slender mint Mentha australis R.Br. – Australian mint Mentha canadensis L. – Canada mint, American wild mint Mentha cervina L. – Hart's pennyroyal Mentha cunninghamii (Benth.) Benth. – New Zealand mint Mentha dahurica Fisch. ex Benth. – Dahurian thyme Mentha darvasica Boriss. Mentha diemenica Spreng. – slender mint Mentha gattefossei Maire Mentha grandiflora Benth. Mentha japonica (Miq.) Makino Mentha laxiflora Benth. – forest mint Mentha longifolia (L.) L. – horse mint Mentha micrantha (Fisch. ex Benth.) Heinr.Braun Mentha pamiroalaica Boriss. Mentha pulegium L. – pennyroyal Mentha requienii Benth. – Corsican mint Mentha royleana Wall. ex Benth. Mentha satureioides R.Br. – native pennyroyal Mentha spicata L. – spearmint, garden mint (a cultivar of spearmint) Mentha suaveolens Ehrh. – apple mint, pineapple mint (a variegated cultivar of apple mint) Other species[edit] There are a number of plants that have mint in the common English name but which do not belong to the genus Mentha: Agastache sp. – known as horse mints Calamintha sp. (syn. Clinopodium) – known as calamints Clinopodium acinos (syn. Acinos arvensis) – known as backle mint Elsholtzia ciliata – known as comb mint Melissa officinalis – known as balm mint Nepeta sp. – known as cat mint or catnip Origanum sp. – known as rock mint Sideritis montana – known as sider mint Hybrids[edit] The Mentha × piperita hybrid known as "chocolate mint" The mint genus has a large grouping of recognized hybrids. Those accepted by Plants of the World Online are listed below. Parent species are taken from Tucker & Naczi (2007). Synonyms, along with cultivars and varieties where available, are included within the specific nothospecies. Mentha × carinthiaca Host - M. arvensis × M. suaveolens Mentha × dalmatica Tausch - M. arvensis × M. longifolia Mentha × dumetorum Schult. - M. aquatica × M. longifolia Mentha × gayeri Trautm. - M. longifolia × M. spicata × M. suaveolens Mentha × gracilis Sole (syn. Mentha × gentilis) - M. arvensis × M. spicata – ginger mint, Scotch spearmint Mentha × kuemmerlei Trautm. - M. aquatica × M. spicata × M. suaveolens Mentha × locyana Borbás - M. longifolia × M. verticillata Mentha × piperita L. - M. aquatica × M. spicata – peppermint, chocolate mint Mentha × pyramidalis Ten. - M. aquatica × M. microphylla Mentha × rotundifolia (L.) Huds. - M. longifolia × M. suaveolens – false apple mint Mentha × suavis Guss. (syn. Mentha × amblardii, Mentha × lamiifolia, Mentha × langii, Mentha × mauponii, Mentha × maximilianea, Mentha × rodriguezii, Mentha × weissenburgensis) - M. aquatica × M. suaveolens Mentha × verticillata L. - M. aquatica × M. arvensis Mentha × villosa Huds. (syn. M. nemorosa) - M. spicata × M. suaveolens – large apple mint, foxtail mint, hairy mint, woolly mint, Cuban mint, mojito mint, and yerba buena in Cuba Mentha × villosa-nervata Opiz - M. longifolia × M. spicata – sharp-toothed mint Mentha × wirtgeniana F.W.Schultz (syn. Mentha × smithiana) - M. aquatica × M. arvensis × M. spicata – red raripila mint Common names and cultivars[edit] There are hundreds of common English names for species and cultivars of Mentha. These include: Apple mint - Mentha suaveolens and Mentha × rotundifolia Banana mint - Mentha arvensis 'Banana' Bowles mint - Mentha villosa and Mentha × villosa 'Alopecuroides' Canada mint - Mentha canadensis Chocolate mint - Mentha × piperita 'Chocolate' Corsican mint - Mentha requienii Cuba mint - Mentha x villosa Curly mint - Mentha spicata 'Curly' Eau de Cologne mint - Mentha × piperita 'Citrata' Field mint - Mentha arvensis Flea mint - Mentha requienii Ginger mint - Mentha × gracilis Gray mint - Mentha longifolia Green mint - Mentha spicata Grey mint - Mentha longifolia Japanese peppermint - Mentha arvensis var. piperascens Japanese mint or Japanese medicine mint - Mentha spicata 'Abura' Kiwi mint - Mentha cunninghamii Lemon mint - Mentha x piperita var. citrata and Mentha X gentilis Marsh mint - Mentha aquatica Meadow mint - Mentha x gracilis and Mentha arvensis Mojito mint - Mentha Spicata 'Mojito' Moroccan mint - Mentha spicata var. crispa 'Moroccan' and mints collected in Morocco Pennyroyal - Mentha pulegium Peppermint - Mentha × piperita and sometimes Mentha requienii Pineapple mint - Mentha suaveolens 'Variegata' and Mentha suaveolens 'Pineapple' Polemint - Mentha pulegium Red raripila mint - Mentha × wirtgeniana Round leaf mint - Mentha suaveolens Spearmint - Mentha spicata Strawberry mint - Mentha × piperita 'Strawberry' Swiss mint - Mentha × piperita 'Swiss' Tall mint - Mentha × wirtgeniana Tea mint - Mentha × verticillata Toothmint - Mentha × smithiana Water mint - Mentha aquatica Woolly mint - Mentha × rotundifolia Cultivation[edit] Mentha x gracilis and M. rotundifolia: The steel ring is to control the spread of the plant. All mints thrive near pools of water, lakes, rivers, and cool moist spots in partial shade. In general, mints tolerate a wide range of conditions, and can also be grown in full sun. Mint grows all year round. They are fast-growing, extending their reach along surfaces through a network of runners. Due to their speedy growth, one plant of each desired mint, along with a little care, will provide more than enough mint for home use. Some mint species are more invasive than others. Even with the less invasive mints, care should be taken when mixing any mint with any other plants, lest the mint take over. To control mints in an open environment, they should be planted in deep, bottomless containers sunk in the ground, or planted above ground in tubs and barrels. Some mints can be propagated by seed, but growth from seed can be an unreliable method for raising mint for two reasons: mint seeds are highly variable — one might not end up with what one supposed was planted — and some mint varieties are sterile. It is more effective to take and plant cuttings from the runners of healthy mints. The most common and popular mints for commercial cultivation are peppermint (Mentha × piperita), native spearmint (Mentha spicata), Scotch spearmint (Mentha x gracilis), and cornmint (Mentha arvensis); also (more recently) apple mint (Mentha suaveolens). Mints are supposed to make good companion plants, repelling pesty insects and attracting beneficial ones. They are susceptible to whitefly and aphids. Harvesting of mint leaves can be done at any time. Fresh leaves should be used immediately or stored up to a few days in plastic bags in a refrigerator. Optionally, leaves can be frozen in ice cube trays. Dried mint leaves should be stored in an airtight container placed in a cool, dark, dry area. Uses[edit] This section may lack focus or may be about more than one topic. In particular, it treats the genus Mentha ("mint") as if it were a single kind of plant, whereas many of the uses apply only to one species or cultivated variety of the genus. Please help improve this article, possibly by splitting the section, or discuss this issue on the talk page. (July 2019) Culinary[edit] A jar of mint jelly, a traditional condiment served with lamb dishes Limonana (mint lemonade) served in Damascus, Syria The leaf, fresh or dried, is the culinary source of mint. Fresh mint is usually preferred over dried mint when storage of the mint is not a problem. The leaves have a warm, fresh, aromatic, sweet flavor with a cool aftertaste, and are used in teas, beverages, jellies, syrups, candies, and ice creams. In Middle Eastern cuisine, mint is used in lamb dishes, while in British cuisine and American cuisine, mint sauce and mint jelly are used, respectively. Mint (pudina) is a staple in Indian cuisine, used for flavouring curries and other dishes. Mint is a necessary ingredient in Touareg tea, a popular tea in northern African and Arab countries. Alcoholic drinks sometimes feature mint for flavor or garnish, such as the mint julep and the mojito. Crème de menthe is a mint-flavored liqueur used in drinks such as the grasshopper. Mint essential oil and menthol are extensively used as flavorings in breath fresheners, drinks, antiseptic mouth rinses, toothpaste, chewing gum, desserts, and candies, such as mint (candy) and mint chocolate. The substances that give the mints their characteristic aromas and flavors are menthol (the main aroma of peppermint and Japanese peppermint) and pulegone (in pennyroyal and Corsican mint). The compound primarily responsible for the aroma and flavor of spearmint is L-carvone. Mints are used as food plants by the larvae of some Lepidoptera species, including buff ermine moths. It is also eaten by beetles such as Chrysolina coerulans (blue mint beetle) and Mint leaf beetle. Traditional medicine and cosmetics[edit] The ancient Greeks rubbed mint on their arms, believing it would make them stronger. Mint was originally used as a medicinal herb to treat stomach ache and chest pains. There are several uses in traditional medicine and preliminary research for possible use in treating irritable bowel syndrome. Menthol from mint essential oil (40–90%) is an ingredient of many cosmetics and some perfumes. Menthol and mint essential oil are also used in aromatherapy which may have clinical use to alleviate post-surgery nausea. Allergic reaction[edit] Although it is used in many consumer products, mint may cause allergic reactions in some people, inducing symptoms such as abdominal cramps, diarrhea, headaches, heartburn, tingling or numbing around the mouth, anaphylaxis or contact dermatitis. Insecticides[edit] Mint oil is also used as an environmentally friendly insecticide for its ability to kill some common pests such as wasps, hornets, ants, and cockroaches. Room scent and aromatherapy[edit] Known in Greek mythology as the herb of hospitality, one of mint's first known uses in Europe was as a room deodorizer. The herb was strewn across floors to cover the smell of the hard-packed soil. Stepping on the mint helped to spread its scent through the room. Today, it is more commonly used for aromatherapy through the use of essential oils. Diseases[edit] Main article: List of mint diseases Etymology of "mint"[edit] An example of mint leaves The word "mint" descends from the Latin word mentha or menta, which is rooted in the Greek words μίνθα mintha, μίνθη minthē or μίντη mintē meaning "spearmint". The plant was personified in Greek mythology as Minthe, a nymph who was beloved by Hades and was transformed into a mint plant by either Persephone or Demeter. This, in turn, ultimately derived from a proto-Indo-European root that is also the origin of the Sanskrit -mantha, mathana (premna serratifolia). References to "mint leaves", without a qualifier like "peppermint" or "apple mint", generally refer to spearmint leaves. In Spain and Central and South America, mint is known as menta. In Lusophone countries, especially in Portugal, mint species are popularly known as hortelã. In many Indo-Aryan languages, it is called pudīna: Hindi: पुदीना , Sindhi: ڦُودنو, Bengali: পুদিনা borrowed from Persian پودنه pudna or پونه puna meaning "pennyroyal". The taxonomic family Lamiaceae is known as the mint family. It includes many other aromatic herbs, including most of the more common cooking herbs, such as basil, rosemary, sage, oregano, and catnip. As an English colloquial term, any small mint-flavored confectionery item can be called a mint. In common usage, other plants with fragrant leaves may be called "mint", although they are not in the mint family: Vietnamese mint, commonly used in Southeast Asian cuisine is Persicaria odorata in the family Polygonaceae, collectively known as smartweeds or pinkweeds. Mexican mint marigold is Tagetes lucida in the sunflower family (Asteraceae). Fossil record[edit] †Mentha pliocenica fossil seeds have been excavated in Pliocene deposits of Dvorets on the right bank of the Dnieper river between the cities of Rechitsa and Loyew, in south-eastern Belarus. The fossil seeds are similar to the seeds of Mentha aquatica and Mentha arvensis.	biology	4641048	https://sv.wikipedia.org/wiki/Miconia%20cutucuensis	Miconia cutucuensis	Miconia cutucuensis är en tvåhjärtbladig växtart som beskrevs av John Julius Wurdack. Miconia cutucuensis ingår i släktet Miconia och familjen Melastomataceae. IUCN kategoriserar arten globalt som starkt hotad. Artens utbredningsområde är Ecuador. Inga underarter finns listade i Catalogue of Life. Källor Myrtenordningen cutucuensis	swedish	0.888569
mints_make_your_mouth_feel_cold/Cold.txt	Cold is the presence of low temperature, especially in the atmosphere. In common usage, cold is often a subjective perception. A lower bound to temperature is absolute zero, defined as 0.00 K on the Kelvin scale, an absolute thermodynamic temperature scale. This corresponds to −273.15 °C on the Celsius scale, −459.67 °F on the Fahrenheit scale, and 0.00 °R on the Rankine scale. Since temperature relates to the thermal energy held by an object or a sample of matter, which is the kinetic energy of the random motion of the particle constituents of matter, an object will have less thermal energy when it is colder and more when it is hotter. If it were possible to cool a system to absolute zero, all motion of the particles in a sample of matter would cease and they would be at complete rest in the classical sense. The object could be described as having zero thermal energy. Microscopically in the description of quantum mechanics, however, matter still has zero-point energy even at absolute zero, because of the uncertainty principle. Cooling[edit] Main article: Refrigeration Cooling refers to the process of becoming cold, or lowering in temperature. This could be accomplished by removing heat from a system, or exposing the system to an environment with a lower temperature. Coolants are fluids used to cool objects, prevent freezing and prevent erosion in machines. Air cooling is the process of cooling an object by exposing it to air. This will only work if the air is at a lower temperature than the object, and the process can be enhanced by increasing the surface area, increasing the coolant flow rate, or decreasing the mass of the object. Another common method of cooling is exposing an object to ice, dry ice, or liquid nitrogen. This works by conduction; the heat is transferred from the relatively warm object to the relatively cold coolant. Laser cooling and magnetic evaporative cooling are techniques used to reach very low temperatures. History[edit] Early history[edit] In ancient times, ice was not adopted for food preservation but used to cool wine which the Romans had also done. According to Pliny, Emperor Nero invented the ice bucket to chill wines instead of adding it to wine to make it cold as it would dilute it. Some time around 1700 BC Zimri-Lim, king of Mari Kingdom in northwest Iraq had created an "icehouse" called bit shurpin at a location close to his capital city on the banks of the Euphrates. In the 7th century BC the Chinese had used icehouses to preserve vegetables and fruits. During the Tang dynastic rule in China (618–907 AD) a document refers to the practice of using ice that was in vogue during the Eastern Chou Dynasty (770–256 BC) by 94 workmen employed for "Ice-Service" to freeze everything from wine to dead bodies. Shachtman says that in the 4th century AD, the brother of the Japanese emperor Nintoku gave him a gift of ice from a mountain. The Emperor was so happy with the gift that he named the first of June as the "Day of Ice" and ceremoniously gave blocks of ice to his officials. Even in ancient times, Shachtman says, in Egypt and India, night cooling by evaporation of water and heat radiation, and the ability of salts to lower the freezing temperature of water was practiced. The ancient people of Rome and Greece were aware that boiled water cooled quicker than the ordinary water; the reason for this is that with boiling of water carbon dioxide and other gases, which are deterrents to cooling, are removed; but this fact was not known till the 17th century. From the 17th century[edit] Shachtman says that King James VI and I supported the work of Cornelis Drebbel as a magician to perform tricks such as producing thunder, lightning, lions, birds, trembling leaves and so forth. In 1620 he gave a demonstration in Westminster Abbey to the king and his courtiers on the power of cold. On a summer day, Shachtman says, Drebbel had created a chill (lowered the temperature by several degrees) in the hall of the Abbey, which made the king shiver and run out of the hall with his entourage. This was an incredible spectacle, says Shachtman. Several years before, Giambattista della Porta had demonstrated at the Abbey "ice fantasy gardens, intricate ice sculptures" and also iced drinks for banquets in Florence. The only reference to the artificial freezing created by Drebbel was by Francis Bacon. His demonstration was not taken seriously as it was considered one of his magic tricks, as there was no practical application then. Drebbel had not revealed his secrets. Shachtman says that Lord Chancellor Bacon, an advocate of experimental science, had tried in Novum Organum, published in the late 1620s, to explain the artificial freezing experiment at Westminster Abbey, though he was not present during the demonstration, as "Nitre (or rather its spirit) is very cold, and hence nitre or salt when added to snow or ice intensifies the cold of the latter, the nitre by adding to its own cold, but the salt by supplying activity to the cold snow." This explanation on the cold inducing aspects of nitre and salt was tried then by many scientists. Shachtman says it was the lack of scientific knowledge in physics and chemistry that had held back progress in the beneficial use of ice until a drastic change in religious opinions in the 17th century. The intellectual barrier was broken by Francis Bacon and Robert Boyle who followed him in this quest for knowledge of cold. Boyle did extensive experimentation during the 17th century in the discipline of cold, and his research on pressure and volume was the forerunner of research in the field of cold during the 19th century. He explained his approach as "Bacon's identification of heat and cold as the right and left hands of nature". Boyle also refuted some of the theories mooted by Aristotle on cold by experimenting on transmission of cold from one material to the other. He proved that water was not the only source of cold but gold, silver and crystal, which had no water content, could also change to severe cold condition. 19th century[edit] Out In The Cold, Léon Bazille Perrault In the United States from about 1850 till end of 19th century export of ice was second only to cotton. The first ice box was developed by Thomas Moore, a farmer from Maryland in 1810 to carry butter in an oval shaped wooden tub. The tub was provided with a metal lining in its interior and surrounded by a packing of ice. A rabbit skin was used as insulation. Moore also developed an ice box for domestic use with the container built over a space of 6 cubic feet (0.17 m) which was filled with ice. In 1825, ice harvesting by use of a horse drawn ice cutting device was invented by Nathaniel J. Wyeth. The cut blocks of uniform size ice was a cheap method of food preservation widely practiced in the United States. Also developed in 1855 was a steam powered device to haul 600 tons of ice per hour. More innovations ensued. Devices using compressed air as a refrigerants were invented. 20th century[edit] Iceboxes were in widespread use from the mid-19th century to the 1930s, when the refrigerator was introduced into the home. Most municipally consumed ice was harvested in winter from snow-packed areas or frozen lakes, stored in ice houses, and delivered domestically as iceboxes became more common. In 1913, refrigerators for home use were invented. In 1923 Frigidaire introduced the first self-contained unit. The introduction of Freon in the 1920s expanded the refrigerator market during the 1930s. Home freezers as separate compartments (larger than necessary just for ice cubes) were introduced in 1940. Frozen foods, previously a luxury item, became commonplace. Physiological effects[edit] Cold has numerous physiological and pathological effects on the human body, as well as on other organisms. Cold environments may promote certain psychological traits, as well as having direct effects on the ability to move. Shivering is one of the first physiological responses to cold. Even at low temperatures, the cold can massively disrupt blood circulation. Extracellular water freezes and tissue is destroyed. It affects fingers, toes, nose, ears and cheeks particularly often. They discolor, swell, blister, and bleed. Local frostbite leads to so-called chilblains or even to the death of entire body parts. Only temporary cold reactions of the skin are without consequences. As blood vessels contract, they become cool and pale, with less oxygen getting into the tissue. Warmth stimulates blood circulation again and is painful but harmless. Comprehensive protection against the cold is particularly important for children and for sports. Extreme cold temperatures may lead to frostbite, sepsis, and hypothermia, which in turn may result in death. Common myths[edit] A common, but false, statement states that cold weather itself can induce the identically named common cold. No scientific evidence of this has been found, although the disease, alongside influenza and others, does increase in prevalence with colder weather. Notable cold locations and objects[edit] Boomerang Nebula Neptune's moon Triton The National Institute of Standards and Technology in Boulder, Colorado using a new technique, managed to chill a microscopic mechanical drum to 360 microkelvins, making it the coldest object on record. Theoretically, using this technique, an object could be cooled to absolute zero. The coldest known temperature ever achieved is a state of matter called the Bose–Einstein condensate which was first theorized to exist by Satyendra Nath Bose in 1924 and first created by Eric Cornell, Carl Wieman, and co-workers at JILA on 5 June 1995. They did this by cooling a dilute vapor consisting of approximately two thousand rubidium-87 atoms to below 170 nK (one nK or nanokelvin is a billionth (10) of a kelvin) using a combination of laser cooling (a technique that won its inventors Steven Chu, Claude Cohen-Tannoudji, and William D. Phillips the 1997 Nobel Prize in Physics) and magnetic evaporative cooling. 90377 Sedna is one of the coldest known objects within the Solar System. Orbiting at an average distance of 84 billion miles, Sedna has an average surface temperature of -400°F (-240°C). The lunar crater Hermite was described after a 2009 survey by NASA's Lunar Reconnaissance Orbiter as the "coldest known place in the Solar System", with temperatures at 26 kelvins (−413 °F, −247 °C). The Boomerang Nebula is the coldest known natural location in the universe, with a temperature that is estimated at 1 K (−272.15 °C, −457.87 °F). The Dwarf Planet Haumea is one of the coldest known objects in our solar system. With a Temperature of -401 degrees Fahrenheit or -241 degrees Celsius The Planck spacecraft's instruments are kept at 0.1 K (−273.05 °C, −459.49 °F) via passive and active cooling. Absent any other source of heat, the temperature of the Universe is roughly 2.725 kelvins, due to the Cosmic microwave background radiation, a remnant of the Big Bang. Neptune's moon Triton has a surface temperature of 38.15 K (−235 °C, −391 °F) Uranus with a black-body temperature of 58.2 K (−215.0 °C, −354.9 °F). Saturn with a black-body temperature of 81.1 K (−192.0 °C, −313.7 °F). Mercury, despite being close to the Sun, is actually cold during its night, with a temperature of about 93.15 K (−180 °C, −290 °F). Mercury is cold during its night because it has no atmosphere to trap in heat from the Sun. Jupiter with a black-body temperature of 110.0 K (−163.2 °C, −261.67 °F). Mars with a black-body temperature of 210.1 K (−63.05 °C, −81.49 °F). The coldest continent on Earth is Antarctica. The coldest place on Earth is the Antarctic Plateau, an area of Antarctica around the South Pole that has an altitude of around 3,000 metres (9,800 ft). The lowest reliably measured temperature on Earth of 183.9 K (−89.2 °C, −128.6 °F) was recorded there at Vostok Station on 21 July 1983. The Poles of Cold are the places in the Southern and Northern Hemispheres where the lowest air temperatures have been recorded. (See List of weather records). The cold deserts of the North Pole, known as the tundra region, experiences an annual snow fall of a few inches and temperatures recorded are as low as 203.15 K (−70 °C, −94 °F). Only a few small plants survive in the generally frozen ground (thaws only for a short spell). Cold deserts of the Himalayas are a feature of a rain-shadow zone created by the mountain peaks of the Himalaya range that runs from Pamir Knot extending to the southern border of the Tibetan plateau; however this mountain range is also the reason for the monsoon rain fall in the Indian subcontinent. This zone is located in an elevation of about 3,000 m, and covers Ladakh, Lahaul, Spiti and Pooh. In addition, there are inner valleys within the main Himalayas such as Chamoli, some areas of Kinnaur, Pithoragarh and northern Sikkim which are also categorized as cold deserts. Antarctica Cold desert of the Himalayas in Ladakh Tree with hoarfrost Frozen Saint Lawrence River Winter sea ice Ice climbing Mythology and culture[edit] Niflheim was a realm of primordial ice and cold with nine frozen rivers in Norse Mythology. The "Hell in Dante's Inferno" is stated as Cocytus a frozen lake where Virgil and Dante were deposited. See also[edit] Technical, scientific Chiller – Machine that removes heat from a liquid coolant via vapor compression Cryogenics – Study of the production and behaviour of materials at very low temperatures Cryosphere – Those portions of Earth's surface where water is in solid form Freezing point – Temperature at which a solid turns liquid Negative temperature – Physical systems hotter than any other Coldness – Measure of the coldness of a system Ultracold atom – Atoms kept at temperatures close to absolute zero Entertainment, myth Ice cream – Frozen dessert Indrid Cold Snowball – Spherical object made from compacted snow Snowman – Figure sculpted from snow Winter sport – Sports or recreational activities which are played on snow or icePages displaying short descriptions of redirect targetss Meteorological: Atmospheric inversion – Deviation from the normal change of an atmospheric property with altitude Cold front – Leading edge of a cooler mass of air Freezing rain – Rain maintained at temperatures below freezing Frost – Coating or deposit of ice Hail – Form of solid precipitation Sleet – Form of precipitation consisting of rain and melting snow Snow – Precipitation in the form of ice crystal flakes Geographical and climatological: Glacier – Persistent body of ice that is moving under its own weight Ice cap – Ice mass that covers less than 50,000 km² of land area Ice cap climate – Polar climate where no mean monthly temperature exceeds 0 °C (32 °F) Ice sheet – Large mass of glacial ice Portals: Earth sciences Geography Physics Science Weather	biology	6071749	https://sv.wikipedia.org/wiki/Misty%20Icefield	Misty Icefield	Misty Icefield är en glaciär i Kanada. Den ligger i provinsen British Columbia, i den sydvästra delen av landet, km väster om huvudstaden Ottawa. Misty Icefield ligger meter över havet. Terrängen runt Misty Icefield är huvudsakligen bergig, men den allra närmaste omgivningen är kuperad. Den högsta punkten i närheten är meter över havet, km norr om Misty Icefield. Runt Misty Icefield är det mycket glesbefolkat, med invånare per kvadratkilometer.. Det finns inga samhällen i närheten. Trakten runt Misty Icefield är permanent täckt av is och snö. Trakten ingår i den hemiboreala klimatzonen. Årsmedeltemperaturen i trakten är °C. Den varmaste månaden är augusti, då medeltemperaturen är °C, och den kallaste är december, med °C. Genomsnittlig årsnederbörd är millimeter. Den regnigaste månaden är december, med i genomsnitt mm nederbörd, och den torraste är juli, med mm nederbörd. Kommentarer Källor Isformationer i British Columbia Kontrollbehov inkommande wikilänkar	swedish	0.681102
mints_make_your_mouth_feel_cold/Mouth.txt	The mouth is the body orifice through which many animals ingest food and vocalize. The body cavity immediately behind the mouth opening, known as the oral cavity (or cavum oris in Latin), is also the first part of the alimentary canal, which leads to the pharynx and the gullet. In tetrapod vertebrates, the mouth is bounded on the outside by the lips and cheeks — thus the oral cavity is also known as the buccal cavity (from Latin bucca, meaning "cheek") — and contains the tongue on the inside. Except for some groups like birds and lissamphibians, vertebrates usually have teeth in their mouths, although some fish species have pharyngeal teeth instead of oral teeth. Most bilaterian phyla, including arthropods, molluscs and chordates, have a two-opening gut tube with a mouth at one end and an anus at the other. Which end forms first in ontogeny is a criterion used to classify bilaterian animals into protostomes and deuterostomes. Development[edit] Main articles: Protostome and Deuterostome Development of the mouth and anus in protostomes and deuterostomes In the first multicellular animals, there was probably no mouth or gut and food particles were engulfed by the cells on the exterior surface by a process known as endocytosis. The particles became enclosed in vacuoles into which enzymes were secreted and digestion took place intracellularly. The digestive products were absorbed into the cytoplasm and diffused into other cells. This form of digestion is used nowadays by simple organisms such as Amoeba and Paramecium and also by sponges which, despite their large size, have no mouth or gut and capture their food by endocytosis. However, most animals have a mouth and a gut, the lining of which is continuous with the epithelial cells on the surface of the body. A few animals which live parasitically originally had guts but have secondarily lost these structures. The original gut of diploblastic animals probably consisted of a mouth and a one-way gut. Some modern invertebrates still have such a system: food being ingested through the mouth, partially broken down by enzymes secreted in the gut, and the resulting particles engulfed by the other cells in the gut lining. Indigestible waste is ejected through the mouth. In animals at least as complex as an earthworm, the embryo forms a dent on one side, the blastopore, which deepens to become the archenteron, the first phase in the formation of the gut. In deuterostomes, the blastopore becomes the anus while the gut eventually tunnels through to make another opening, which forms the mouth. In the protostomes, it used to be thought that the blastopore formed the mouth (proto– meaning "first") while the anus formed later as an opening made by the other end of the gut. More recent research, however, shows that in protostomes the edges of the slit-like blastopore close up in the middle, leaving openings at both ends that become the mouth and anus. Anatomy[edit] Invertebrates[edit] Butterfly tongue Apart from sponges and placozoans, almost all animals have an internal gut cavity, which is lined with gastrodermal cells. In less advanced invertebrates such as the sea anemone, the mouth also acts as an anus. Circular muscles around the mouth are able to relax or contract in order to open or close it. A fringe of tentacles thrusts food into the cavity and it can gape widely enough to accommodate large prey items. Food passes first into a pharynx and digestion occurs extracellularly in the gastrovascular cavity. Annelids have simple tube-like guts, and the possession of an anus allows them to separate the digestion of their foodstuffs from the absorption of the nutrients. Many molluscs have a radula, which is used to scrape microscopic particles off surfaces. In invertebrates with hard exoskeletons, various mouthparts may be involved in feeding behaviour. Insects have a range of mouthparts suited to their mode of feeding. These include mandibles, maxillae and labium and can be modified into suitable appendages for chewing, cutting, piercing, sponging and sucking. Decapods have six pairs of mouth appendages, one pair of mandibles, two pairs of maxillae and three of maxillipeds. Sea urchins have a set of five sharp calcareous plates, which are used as jaws and are known as Aristotle's lantern. Vertebrates[edit] In vertebrates, the first part of the digestive system is the buccal cavity, commonly known as the mouth. The buccal cavity of a fish is separated from the opercular cavity by the gills. Water flows in through the mouth, passes over the gills and exits via the operculum or gill slits. Nearly all fish have jaws and may seize food with them but most feed by opening their jaws, expanding their pharynx and sucking in food items. The food may be held or chewed by teeth located in the jaws, on the roof of the mouth, on the pharynx or on the gill arches. Litoria chloris calling Nearly all amphibians are carnivorous as adults. Many catch their prey by flicking out an elongated tongue with a sticky tip and drawing it back into the mouth, where they hold the prey with their jaws. They then swallow their food whole without much chewing. They typically have many small hinged pedicellate teeth, the bases of which are attached to the jaws, while the crowns break off at intervals and are replaced. Most amphibians have one or two rows of teeth in both jaws but some frogs lack teeth in the lower jaw. In many amphibians, there are also vomerine teeth attached to the bone in the roof of the mouth. The mouths of reptiles are largely similar to those of mammals. The crocodilians are the only reptiles to have teeth anchored in sockets in their jaws. They are able to replace each of their approximately 80 teeth up to 50 times during their lives. Most reptiles are either carnivorous or insectivorous, but turtles are often herbivorous. Lacking teeth that are suitable for efficiently chewing of their food, turtles often have gastroliths in their stomach to further grind the plant material. Snakes have a very flexible lower jaw, the two halves of which are not rigidly attached, and numerous other joints in their skull. These modifications allow them to open their mouths wide enough to swallow their prey whole, even if it is wider than they are. Birds do not have teeth, relying instead on other means of gripping and macerating their food. Their beaks have a range of sizes and shapes according to their diet and are composed of elongated mandibles. The upper mandible may have a nasofrontal hinge allowing the beak to open wider than would otherwise be possible. The exterior surface of beaks is composed of a thin, horny sheath of keratin. Nectar feeders such as hummingbirds have specially adapted brushy tongues for sucking up nectar from flowers. In mammals, the buccal cavity is typically roofed by the hard and soft palates, floored by the tongue and surrounded by the cheeks, salivary glands, and upper and lower teeth. The upper teeth are embedded in the upper jaw and the lower teeth in the lower jaw, which articulates with the temporal bones of the skull. The lips are soft and fleshy folds which shape the entrance into the mouth. The buccal cavity empties through the pharynx into the oesophagus. Other functions of the mouth[edit] Crocodilians living in the tropics can gape with their mouths to provide cooling by evaporation from the mouth lining. Some mammals rely on panting for thermoregulation as it increases evaporation of water across the moist surfaces of the lungs, the tongue and mouth. Birds also avoid overheating by gular fluttering, flapping the wings near the gular (throat) skin, similar to panting in mammals. Tasmanian devil in defensive stance Various animals use their mouths in threat displays. They may gape widely, exhibit their teeth prominently, or flash the startling colours of the mouth lining. This display allows each potential combatant an opportunity to assess the weapons of their opponent and lessens the likelihood of actual combat being necessary. A number of species of bird use a gaping, open beak in their fear and threat displays. Some augment the display by hissing or breathing heavily, while others clap their beaks. Mouths are also used as part of the mechanism for producing sounds for communication. To produce sounds, air is forced from the lungs over vocal cords in the larynx. In humans, the pharynx, soft palate, hard palate, alveolar ridge, tongue, teeth and lips are termed articulators and play their part in the production of speech. Varying the position of the tongue in relation to the other articulators or moving the lips restricts the airflow from the lungs in different ways and changes the mouth's resonating properties, producing a range of different sounds. In frogs, the sounds can be amplified using sacs in the throat region. The vocal sacs can be inflated and deflated and act as resonators to transfer the sound to the outside world. A bird's song is produced by the flow of air over a vocal organ at the base of the trachea, the syrinx. For each burst of song, the bird opens its beak and closes it again afterwards. The beak may move slightly and may contribute to the resonance but the song originates elsewhere. See also[edit] Oral manifestations of systemic disease	biology	53408	https://no.wikipedia.org/wiki/Slanger	Slanger	ormeslanger Alethinophidia Slanger (Serpentes) er en gruppe skjellkledde krypdyr som kjennetegnes ved at de mangler synlige lemmer. De er en suksessrik gruppe med over arter, og verdensomspennende utbredelse. Øgler og ormeøgler er de nærmeste slektningene, og de tre gruppene utgjør til sammen skjellkrypdyrene. Mennesker betrakter ofte slanger med frykt, og denne frykten virker dypt iboende på tvers av kulturer. Trolig har mennesker, og mange andre dyr, opparbeidet en instinktiv frykt fordi slanger kan være giftige. Samtidig blir slanger beundret for vakre farger og grasiøse bevegelser. For biologer er slanger spesielt interessante, ettersom de har en rekke fysiologiske tilpasninger som ikke har sidestykke hos andre dyr. Utbredelse Slanger finnes på alle kontinenter unntatt Antarktis. De fleste artene lever likevel i tropiske og subtropiske strøk, og ingen finnes i polområdene. De marine havslangene forekommer i de varme delene av Det indiske hav og Stillehavet. Hvis en ser bort fra havslangene, så har ikke slanger samme evne til å krysse vide havstrekninger som mange øgler har. Flere store øyer mangler derfor slanger, for eksempel Island, Irland og New Zealand. De nordligste slangene finnes i Nord-Europa, der tre arter når 60° nord. Det er de samme tre artene som også finnes i Norge: hoggorm, buorm og slettsnok. Hoggormen er verdens nordligste slange, og finnes i Norge i hvert fall nord til Nordland. I Sverige, Finland og Russland går arten mye lenger nord, helt opp til 68°. Det finnes også et ubekreftet funn fra Sør-Varanger, som i tilfelle henger sammen med den finske og russiske bestanden. I Nord-Amerika finnes strømpebåndsnokene til 56° nord i Canada. Det er også usikre funn på samme breddegrad i Alaska. Den sørligste arten er antakelig lanseslangen Rhinocerophis ammodytoides, som finnes sør til 47° i Patagonia. Høyderekorden tilhører sannsynligvis snoken Thermophis baileyi, som lever mer enn 4000 meter over havet i Tibet. Beskrivelse Slanger er kjent for at de mangler lemmer, har en todelt tunge, og at de ikke blunker, men alle disse trekkene ved kroppsbygningen finnes også hos ulike grupper av øgler. De viktigste morfologiske trekkene som er unike for slangene, er oppbygningen av ryggraden og skallen. Skjelettet er sterkt omdannet i forhold til andre landlevende virveldyr. Skulder og forlemmer er helt forsvunnet. Alle nålevende slanger mangler korsbein, men noen har bevart rester av bekken og baklemmer. Ryggraden er forlenget, og består av mellom 120 og 320 ryggvirvler. Til hver ryggvirvel er det festet et par ribbein. Halen er forholdsvis kort, og halevirvlene har ikke ribbein. Hver ryggvirvel er forbundet med den foregående virvelen med hele ti leddflater. Dette danner et sterkt, men smidig system, som sammen med sterke muskler, gjør det mulig for slangene å bevege seg uten lemmer. Tennene er som regel lange, tynne og krumme for å kunne holde på byttet, og transportere det innover i munnen. Giftslanger har egne gifttenner, der plassering og oppbygning varierer mellom de ulike gruppene. Slanger kan ikke tygge, eller rive i stykker byttet, så det må svelges helt. Den opprinnelige diaspside skallen har mistet begge kinnbuene. Quadratum-beinet kan derfor bevege seg svært fritt. Kjevebeinene er festet med elastiske ledd. Disse bygningstrekkene, samt at det ikke finnes noe skulderbelte, gjør det mulig for slanger å svelge store byttedyr. Inne i kroppen, under muskler og ribbein, har slanger de samme indre organer som andre virveldyr, men de er modifisert i størrelse og plassering. Hos de fleste artene er den venstre lungen redusert, eller forsvunnet. Den venstre nyren ligger etter den høyre, og hos hannslanger ligger også testiklene etter hverandre. Noen slanger har en trakélunge, som er nyttig hvis den egentlige lungen klemmes sammen når et stor bytte svelges. De minste slangene er falske ormeslanger fra De små Antiller i slekten Leptotyphlops med en totallengde på omtrent . Den lengste nålevende arten er antakelig nettpyton (). Det finnes usikre rapporter om lengre anakondaer, og anakondaen er kraftigere bygd, og blir utvilsomt tyngre enn pytonene. Slangene er ikke de eneste lemmeløse virveldyr. Blant skjellkrypdyrene har flere grupper mistet lemmene, som ormeøgler, finnefotøgler, blindøgler, og mange stålormer og skinker. Alle lemmeløse øgler har i motsetning til slangene beholdt skulderbeltet. Ormepaddene er en lemmeløs gruppe av amfibier. I Norge finnes det en lemmeløs øgle, stålormen. Det genetiske grunnlaget for slangenes spesielle kroppsbygning er mutasjoner i Hox-genene. Denne gruppen av gener finnes hos alle flercellede dyr, og regulerer kroppsbygningen langs lengdeaksen. Genene Hox a10/c10 stopper dannelse av ribbein hos øgler, men hos slanger er de slått av så det dannes ribbein langs hele ryggraden. Genene Hox a13/d13 stopper lengdeveksten til kroppen, men er svekket hos slanger, så kroppen kan bli langstrakt. Hox-genene er uvanlig fleksible hos alle skjellkrypdyr, og det kan være forklaringen på at så mange ulike grupper har mistet lemmene. Hud Det ytterste laget av overhuden består av β-keratin, som danner et sterkt lag som beskytter mot ytre skader, og hindrer uttørking av kroppen. Huden er dekt med skjell som er fortykkelser i keratinlaget, og som er en integrert del av overhuden i motsetning til fiskeskjell. Det er en vanlig misforståelse at slanger har en slimet og fuktig hud. Slangenes hud er tørr, selv om skjellene gjør at huden er glatt og skinnende. Etter hvert som den ytterste huden blir utslitt, vokser det fram en ny hud på innsiden. Slangene vrenger av seg hele den gamle huden på en gang, i motsetning til de fleste øgler som skifter huden i deler. Skjellene overlapper hverandre som takstein, unntatt på hodet. Overflaten til skjellene kan være både glatt, med kjøl, eller kornet. De fleste slanger har brede og ekstra glatte skjell under buken, som er til hjelp når de beveger seg. Antall, form og størrelse på skjellene er svært viktige kjennetegn for å skille ulike arter av slanger fra hverandre. Slanger har i motsetning til mange øgler aldri beinplater (osteodermer) under skjellene. Keratin er i seg selv gjennomsiktig, men huden kan ha alle farger, unntatt blått og grønt, på grunn av pigmenter i de indre hudlagene. Blå farge er en strukturfarge, som dannes ved interferens i skjellene. Grønn farge oppstår når gul farge fra indre hudlag blandes med blått i skjellene. Mange ufarlige slanger i Amerika har røde, gule og svarte tverrstriper, og ligner på de giftige korallslangene. Fargetegningene gir sannsynligvis de ufarlige slangene en ekstra beskyttelse mot predatorer. Dette fenomenet kalles mimikry, og er mest kjent blant insekter. Stoffskifte Alle slanger er vekselvarme. Det vil si at kroppstemperaturen er avhengig av temperaturen i omgivelsen. Mange arter soler seg for å øke kroppstemperaturen. Slanger som lever i tempererte strøk, ligger i dvale om vinteren. En fordel med å være vekselvarm, er at behovet for næring er lavere, ettersom forbrenningen under hvile ligger på 10–20 % av det som er vanlig hos fugler og pattedyr med tilsvarende kroppsstørrelse. Sanser Det mest kjente sanseorganet hos slangene er den er tynne og todelte tunga, som har form omtrent som en Y. Den plukker opp duftmolekyler fra lufta og bakken, og brukes også som føleorgan. Slangene stikker tunga ut med spillende bevegelser, og fører den deretter inn i munnen så duften kan analyseres av Jacobsons organ. En åpning foran i munnen gjør at tunga kan beveges ut og inn, uten at slangen trenger å gape. Hos ormeslanger kan øynene bare brukes til å skille mellom lys og mørke. Mange dagaktive arter som lever på marka, eller oppe i trær, har derimot svært skarpt syn, men kan ha vanskelig for å se ting som ikke beveger seg. Øynene er dekket av gjennomsiktige skjell i stedet for øyelokk. Dette gjør at slangenes øyne alltid er åpne, og at de aldri blunker. Øynene og synssenteret i hjernen hos slanger har flere unike bygningstrekk, noe som antakelig skyldes at slangenes forfedre var gravende, og hadde et redusert syn. Når de vendte tilbake til et liv over jordoverflaten, måtte øynene utvikles på nytt med de reduserte øynene som utgangspunkt. Strålelegemet (corpus ciliare) er blitt til en stiv ring. Fokusering skjer ved at linsen beveges fram og tilbake i forhold til netthinnen, i stedet for at linsen strekkes. I netthinnen skilles det, som hos andre virveldyr, mellom to typer lysfølsomme celler. Staver fungerer godt ved lav lysstyrke, men kan ikke skille mellom farger. Tapper fungerer bare ved høy lysstyrke, og har flere fotopigmenter som har maksimal følsomhet ved ulike bølgelengder, slik at tappene kan gi fargesyn. Hos slanger har tappene en særpreget oppbygning, ettersom de er nyutviklet fra staver. En skiller også mellom doble og enkle tapper, slik at slanger har tre typer fotoreseptorer. Slanger har i motsetning til øgler og de fleste andre dyr aldri små oljedråper i tappene som beskytter mot skade fra ultrafiolett lys. Disse dråpene mangler forøvrig også hos placentale pattedyr, som antakelig mistet dem i en periode av utviklingen da de utelukkende var nattaktive. Ormeslangene har bare rester av staver, medlemmene i hoggormfamilien har både tapper og staver, og dagaktive snoker har bare tapper. Dagaktive slanger har en rund pupill, og en gul linse som reduserer kromatisk aberrasjon. Nattaktive arter har derimot en avlang, vertikal pupill, og klar linse. En studie av øynene til strømpebåndsnoken Thamnophis sirtalis viser at denne arten ikke har staver, men både enkle og doble tapper. Det er tre typer fotopigmenter med maksimal følsomhet for henholdsvis bølgelengdene , og . Den laveste bølgelengden ligger i det ultrafiolette området, og kan ha betydning for å finne feromonspor. Slanger har verken ytre øre eller trommehinne, men hørselen er likevel en viktig sans for dem, og det indre øret er bygd opp som hos andre landlevende virveldyr. Sneglehuset er forbundet til underkjeven, og når underkjeven ligger på bakken kan slangen oppfatte vibrasjoner med en amplitude helt ned til én ångstrøm. Slangen kan også skille mellom vibrasjoner som oppfanges av venstre og høyre side av kjeven, så retning til lydkilden kan bestemmes. Egne sanseorganer som registrerer infrarød stråling finnes hos noen slangegrupper. De er blitt utviklet flere ganger, én gang hos gruveslangene, og i flere tilfeller hos boa- og pytonslangene. Gruveslangene har en stor sansegrop på hver side av hodet, mens pyton- og boaslangene har tre eller flere sansegroper langs overleppen. Disse organene reagerer på varmestråling med bølgelengde 5–30 µm, og er så følsomme at de kan registrere temperaturforskjeller mindre enn . Sansegropene har et tett nettverk av kapillarer som regulerer temperaturen. Informasjonen går til synssenteret der den slås sammen med signaler fra øynene til et bredspektret bilde. Sansen brukes til å jakte på nattaktive, varmblodige pattedyr, men er også nyttig for å regulere kroppstemperaturen. Atferd Bevegelser Tapet av lemmene har ikke ført til at slangene har vanskelig for å ta seg fram. De beveger seg raskt både på marka, underjordisk, i vannet, og oppe i trær. Slangene har flere måter å bevege seg på. Den langsomste bevegelsesmåten er å bevege seg i rett linje ved flytte grupper av bukskjell samtidig. Skjellene løftes opp fra bakken, og settes ned lengre fram, slik at kroppen blir løftet etter. Ribbeina bidrar ikke til bevegelsen. Denne måten å bevege seg på brukes av store, kraftig bygde slanger som pytonslanger, boaslanger og hoggormer for å snike seg innpå byttet. Noen slanger vrir kanten av bukskjellene for å få feste når de klatrer oppover trestammer og bergvegger. De vanligste måtene å komme seg fram på omfatter at kroppen buktes vekselvis til venstre og høyre i en bølge som går bakover kroppen. Kroppen presses mot uregelmessigheter på underlaget, og skyves framover. På denne måten flytter slanger seg på marka, og klatrer i trær. Tilsvarende bevegelser brukes også til å svømme. Havslangene kan snu buktingen slik at de svømmer baklengs, og har i tillegg en hale som er flatklemt fra siden for å gi framdrift i vannet. En spesiell bevegelsesmåte som er utviklet fra sideveis bukting, er siderulling. Da skifter buktingene på hver side på å ha kontakt med bakken, mens buktingene på den andre siden er løftet opp. Dette fører til at slangen beveger seg på skrå av sin lengderetning. Denne metoden brukes på ensartede underlag der slangen ikke kan skyve fra mot uregelmessigheter. Slanger som lever i sandørkener, som hornhoggorm og noen klapperslanger, beveger seg slik, men metoden brukes også av snoker som ferdes på mudderflater. I regnskogene i Sørøst-Asia lever de glideflyvende snokene i slekten Chrysopelea. De skaper en bæreflate ved å klemme flat kroppen, og ved å bukte seg under glideflukten. Slik kan de glidefly opptil mellom trærne. Trekkspillbevegelse, der framdelen av kroppen skytes fram, før resten trekkes etter, brukes når slanger skal bevege seg i trange underjordiske ganger. Lignende bevegelser brukes også til å klatre i trær der stamme og greiner er for glatte til at sideveis bukting kan brukes. Ernæring Alle slanger er rovdyr, som fanger og dreper andre dyr, og det finnes ingen planteetende arter. Vanlige byttedyr er øgler, andre slanger, små pattedyr, fugler, egg, fisk, snegler og insekter. Hvis en ser bort fra ormeslangene, så tar alle slanger bytter som er ganske store i forhold til sin egen kroppsstørrelse, og det går lang tid mellom måltidene. Tilpasninger i skallen og stoffskiftet gjør dette mulig. Desto større slangen er, desto større bytte kan den ta. Pytonslanger svelger antiloper, hjortedyr, griser, og til og med krokodiller og malayabjørner. De fleste slanger er generalister, som eter alle dyr de klarer å fange. Men det finnes også spesialiserte arter; kongekobra tar for eksempel stort sett bare andre slanger, og afrikaeggsnok eter egg. Giftslanger dreper byttet med det giftige bittet. Andre slanger kveiler seg rundt byttet, som ikke dør av knusning, men av kvelning. Små pattedyr dør raskere enn forventet, og det kan tenkes at døden ikke skyldes kvelning, men økt blodtrykk. Denne metoden er mest kjent fra boa- og pytonslangene, men brukes også av andre, for eksempel slettsnok. En tredje måte å drepe byttet på er å svelge det helt, mens det ennå lever. Slanger er i stand til å drepe og svelge bytter med en kroppsvekt større enn sin egen. Når byttet skal fordøyes, kan forbrenningen øke 40 ganger, og de indre organene, inkludert hjertet, kan øke 40–100 % i størrelse. Proteinene som deltar i aerob forbrenning hos slangene er helt unike. Disse proteinene dannes i mitokondriene, og mitokondrielt DNA ser ut til å ha gjennomgått en rask og omfattende endring tidlig i slangenes utvikling. Forplantningsbiologi I paringstiden finner hannslangene hunnene ved å følge et duftspor fra analkjertelen hos hunnen. Hannene utkjemper rituelle kamper for å få pare seg med hunnene. Kampen foregår ofte ved at de løfter sitt eget hode, samtidig som de prøver å trykke ned hodet og nakken på motstanderen. Slangene har indre befruktning, og hannen fører den såkalte hemipenisen inn i hunnens kloakkåpning. Hannslanger har to hemipeniser, men under paringen brukes bare en hemipenis om gangen. Utseende på dette organet er et viktig bygningstrekk for å skille forskjellige arter. De fleste slanger legger egg med et mykt, pergamentaktig skall. Antall egg i kullet varierer mye. Ormeslangene legger bare 2–8 egg, mens nettpytonen normalt legger 20–40 egg og kan legge opptil 104 egg. Eggleggende arter legger eggene på et sted som har rett temperatur og fuktighet. Det kan for eksempel være i råtne trestammer, i sandjord, eller under en stein. Det er ofte begrenset utvalg av gode plasser for egglegging, så flere hunner legger egg på samme sted. Mange arter beholder eggene i kroppen helt fram til klekking, så ungene fødes levende. Dette kalles ovovivipari og er en fordel i kaldt klima ettersom eggene da kan utnytte hunnens kroppstemperatur mens de utvikles. Et eksempel er slettsnoken som føder levende unger. Den lever i Nord- og Mellom-Europa og i fjellene i Sør-Europa. Den nære slektningen hagesnok lever i lavlandet i Sør-Europa og legger egg. Ovovivipari forekommer hos nesten alle arter av boaslanger, havslanger, australske giftsnoker og hos medlemmene i hoggormfamilien. Noen få arter har utviklet seg et steg videre og er vivipare. Det vil si at den ufødte ungen får næring fra kroppen til mora gjennom en primitiv morkake (placenta), og ikke bare fra plommesekken. Dette gjelder blant annet de nordamerikanske strømpebåndsnokene og vannsnokene, og noen australske giftsnoker. Enkelte bestander av den ovovivipare aspishuggormen har utviklet seg i retning av semelparitet, og de fleste hunnene dør etter å ha formert seg bare én gang. Reproduksjonen er belastende for kroppen, og gravide hunner må sole seg mye og er ekstra utsatt for predatorer. I noen områder kan det derfor være en fordel å bruke kroppens ressurser på å få fram ett stort kull i stedet for flere små. Hos pytonslangene kveiler hunnen seg om eggene, og blir hos dem helt til de klekkes. Den indiske tigerpytonen er en av de få pytonene som også forekommer i tempererte strøk, og hunnene hos denne arten trekker sammen musklene i en slags skjelving. Dette øker kroppstemperaturen, slik at eggene blir ruget fram. Omsorg for eggene er ellers svært sjeldent hos slanger, og det er ingen arter som passer på ungene etter at de er klekket. Giftslanger Giftslangene produserer gift i modifiserte spyttkjertler på hver side av hodet under og bak øyet. Giften brukes for å drepe, eller lamme byttedyr, og sprøytes inn i byttet via spesielle gifttenner. Selv om giften hovedsakelig brukes til jakt, er den også nyttig når slangen skal forsvare seg. De omtrent 600 artene av giftige slanger utgjør ingen taksonomisk gruppe, og en har derfor antatt at slangegift er blitt utviklet flere ganger hos de avanserte slangene. Alle medlemmer av følgende familier er giftige: giftsnoker (inkludert havslanger), jordvipere og hoggormfamilien. Hos snokene finnes det både giftige og ikke-giftige arter. Nyere forskning tyder på at alle slanger, og mange øgler, produserer litt gift i spyttkjertlene, eller at de i hvert fall har pseudogener for giftproduksjon. Giftslangene skiller seg ut ved å ha utviklet denne egenskapen i ekstrem retning. Gifttennene Gifttennene sitter alltid i overkjeven, men oppbygning og plassering varierer. Hos giftige snoker sitter giftennene langt bak i munnen, og kan ha en fure som giften kan renne i (opisthoglyf). Hos giftsnokene er furen lukket til en rør, og gifttennene sitter framme i munnen (proteroglyf). Artene i hoggormfamilien har også hule gifttenner framme i munnen, men hos dem er gifttennene lengre, og de kan bøyes opp mot ganen når de ikke er i bruk (solenoglyf). Tennene hos slanger uten gifttenner betegnes som aglyfe. Blant de ulike artene av jordvipere finnes alle fire typer av tenner. Bak hver gifttann sitter det en reservetann, som overtar når den gamle tanna er utslitt. Kanalen som fører gift fra giftkjertelen må samtidig flytte seg. Giften presses ut ved hjelp av muskler som klemmer på giftkjertlene. Spyttekobraene kan sprute gift ut av tennene framover mot øynene og ansiktet til en angriper. Giftinnsprøytningen er viljestyrt, og giftslanger biter ofte «tørt» når formålet er å skremme, slik at giften ikke brukes opp. Giftsammensetning Slangegift er en blanding av proteiner, enzymer, cellegifter, nervegifter og koagulerende stoffer. Blandingen varierer mellom ulike grupper og arter av slanger. Etter virkemåten kan en skille mellom tre typer giftstoffer: hemotoksiske (virker på hjerte- og karsystem, for eksempel ved å forårsake hemolyse), nevrotoksiske (virker på hjernen og det øvrige nervesystemet), og cytotoksiske (bryter ned cellevev rundt bittet). Nesten all slangegift inneholder enzymet hyaluronidase, som hjelper giftstoffene med å trenge raskt inn i kroppsvevet. Giftens virkning Den sterkeste slangegiften finnes hos giftsnokene. Havslangene er avhengig av hurtigvirkende gift, så byttet ikke forsvinner i mørkt og grumset vann. Tennene hos medlemmene i hoggormfamilien er så effektive til å føre store mengder gift inn i byttet, at det ikke er nødvendig med like sterk gift. Å lage en liste over de giftigste slangene byr på en del metodiske problemer, og har liten praktisk nytte. Mengden gift i et bitt varierer mellom artene, og har naturligvis stor betydning for hvor farlig slangen er. Den australske herpetologen Bryan Grieg Fry har sammenstilt målinger av giftighet fra flere kilder. Gift fra ulike slanger er injisert i mus, og dosen der halvparten dør (LD50) er målt. Her er det to feilkilder; for det første kan det tenkes at mus i forhold til kroppsstørrelsen tåler mer eller mindre av ulike typer gift enn mennesker. Den andre utfordringen er å finne en måte å injisere giften på som tilsvarer et slangebitt. Hvis en ser på injeksjon under huden (subkutan), så er den australske innlandstaipanen (Oxyuranus microlepidotus) den giftigste slangen. Andre forskere mener at Belchers havslange (Hydrophis belcheri) er den giftigste arten. Når slangegift kommer inn i kroppen til dyr eller mennesker, vil immunforsvaret produsere antistoffer for å stanse forgiftningen. Antiserum (antivenom, antivenin) mot slangebitt produseres ved at små doser slangegift injiseres i for eksempel hester, sauer, geiter eller kaniner. Deretter kan serumet utvinnes fra blodet til dyret, og brukes til behandling av slangebitt. Den romerske dikteren Lucan omtaler så tidlig som i immunitet mot slangebitt hos den afrikanske stammen Psylli. Noen dyr som ofte jakter på slanger, tåler høye doser av slangegift. Dette gjelder blant annet piggsvin, honninggrevling, sekretærfugl og manguster. Slangebitt hos mennesker Forekomst Ingen slanger jakter på mennesker, og de angriper ikke før de blir skremt. Hvis en ser bort fra de store kvelerslangene, så er ikke-giftige slanger ufarlige for mennesker. De kan bite, men tennene gjør liten skade, selv om det er en viss infeksjonsfare i såret. Bitt av giftslanger er derimot et alvorlig helseproblem. Verdens helseorganisasjon antok i 2019 at på verdensbasis blir cirka 2,7 millioner mennesker bitt av slanger hvert år, og mellom 81 000 og 138 000 dør på grunn av slangegift. En studie fra 2008 har et lavere estimat på mellom 20 000 og 94 000 dødsfall i året, og det er tall herfra som brukes i resten av dette avsnittet. En må likevel være klar over at også den sistnevnte studien har en del mangler. De fleste bittene skjer i land med varmt klima, der det er mange slanger, og en stor del av befolkningen arbeider med jordbruk. I utviklingsland prøver de fleste først tradisjonell behandling, før de eventuelt oppsøker en lege som driver med vestlig medisin. I Europa er hoggormene i slekten Vipera de eneste giftige slangene, og slangebitt forekommer relativt sjeldent. De farligste bittene forårsakes av de storvokste artene i Sør-Europa, og en antar at 48–128 mennesker i Europa dør hvert år av hoggormbitt. I Nord-Afrika og Midtøsten lever det flere arter i hoggormfamilien som er farligere enn de europeiske, og i tillegg finnes det her potensielt farlige giftsnoker, som egyptisk kobra og ørkenkobra. Likevel forekommer farlige slangebitt forholdsvis sjeldent, og stikk av skorpioner er vanligere. Situasjonen i Nord-Amerika minner om Europa med få slangebitt, bortsett fra at klapperslangene overtar hoggormenes plass. I USA er det bare omtrent fem dødsfall i året på grunn av klapperslangebitt. Mokasinslanger biter ofte mennesker, men sjelden med dødelig resultat. I Mellom- og Sør-Amerika er derimot bitt av giftslanger vanlig, og årlig dødstall er mellom 540 og 2300. De farligste slangene her er klapperslangen Crotalus durissus og lanseslangene Bothrops atrox og B. asper. Korallslangene har en farlig gift, men de er sky, og biter sjelden mennesker. Helsevesenet er dårlig utbygd i de fleste afrikanske land sør for Sahara, og statistikken over slangebitt er derfor mangelfull. Slangebitt er vanlig, og forekommer både i jordbruksområder, og inne i storbyer. Nattviperen Causus maculatus er aggressiv, men ufarlig, og biter mange i bananplantasjer. Farlige arter er svarthalset spyttekobra, grønn mamba, svart mamba, gabonviper, puffadder og flere efaner. I denne verdensdelen finnes det også farlige snoker, som boomslangen. Dødeligheten antas å ligge mellom 3500 og 32 000 tilfeller i året. Antall slangebitt varierer mellom de ulike delene av Asia. I Øst-Asia er farlige bitt relativt sjeldne, og forårsakes i tilfelle av ulike gruveslanger. Sør-Asia er derimot det området i verden som har flest dødsfall på grunn av giftslanger. Her er befolkningstettheten stor, mulighet for medisinsk behandling mangler ofte, og det finnes mange giftige slangearter. Flest mennesker drepes av Russells hoggorm, efan, og i Sørøst-Asia gruveslangen Calloselasma rhodostoma. Andre farlige arter er indisk kobra og vanlig krait. Her lever også verdens største giftslange, kongekobraen, men den holder seg stort sett unna bebygde områder. En antar at det totale antallet dødsfall på grunn av slangebitt for hele Asia ligger mellom 15 000 og 58 000 i året. De australske giftsnokene har svært sterk gift, men i dette landet er det er få dødsfall på grunn av slangebitt. Her er helsevesenet forberedt på slangebitt, og har motgift lett tilgjengelig. Befolkningstettheten er liten, og slanger og mennesker kan unngå hverandre. Havslangene har en vid utbredelse, og er svært giftige. Likevel er farlige bitt sjeldne, ettersom de har små gifttenner, og er lite aggressive. Virkning på kroppen og behandling Virkningen av et giftslangebitt varierer avhengig av mange faktorer, som slangeart, hvor mye gift som ble injisert, hvilken kroppsdel som ble bitt, og helsetilstanden til offeret. Frykten som kommer av at en er blitt bitt, fører til kvalme og svimmelhet. Giften kan også utløse et anafylaktisk sjokk. Slangegift er alltid en blanding av en rekke ulike stoffer, og det er vanskelig å sette opp generelle regler for hvordan virkningen varierer mellom ulike grupper av giftslanger. En kan likevel si at bittet til de fleste giftsnoker virker sterkest på nervesystemet. Musklene lammes, og i verste fall stopper pusten, slik at offeret kveles. Bitt fra disse artene medfører som regel lite smerte og opphovning. Giften virker så raskt at mange dør før de har fått medisinsk behandling. Spyttekobraenes gift kan føre til blindhet, om en får den på øynene. Artene i hoggormfamilien har derimot et bitt som fører til sterk smerte, og hevelse og misfarging av huden. Giften virker på blodet slik at blodplatene ikke koagulerer, og offeret kan hoste opp blod, blø neseblod, og ha blod i urin og avføring. Andre giftstoffer fører til nekrose, som kan gjøre det nødvendig med amputasjon av kroppsdelen som er bitt. Det tar lengre tid å dø av et farlig bitt, så pasienten har større sjanse til å komme seg tidsnok til lege. Rester av nekrotisert vev i blodet kan føre til akutt nyresvikt, som må behandles med dialyse. Hvis en blir bitt av en slange, må en alltid oppsøke lege. Førstehjelp består hovedsakelig av å holde pasienten i ro, spesielt den legemsdelen som er blitt bitt. En må ikke prøve å fjerne giften ved å skjære i såret, eller suge på bittstedet. Det er uenighet blant fagfolk om en trykkbandasje kan begrense spredning av giften. Den eneste effektive behandling er å raskest mulig injisere antiserum intravenøst. Allergiske reaksjoner på grunn av antiserumet er vanlig, og kvalifisert medisinsk personell må utføre behandlingen. Evolusjon og fossiler Opprinnelse Slangene stammer fra øgler, eller i hvert fall en gruppe som stod øglene nær. Både varaner, ormeøgler og blindøgler har vært foreslått som slangenes nærmeste slektninger. Det er nå påvist at evnen som noen skjellkrypdyr har til å produsere gift, oppstod allerede i overgangen mellom trias og jura for omtrent 200 millioner år siden. Skjellkrypdyr som kan produsere gift, samles i gruppen Toxicofera, som omfatter Iguania, Anguimorpha og slanger. Det er av flere grunner vanskelig å studere slangenes evolusjon. Det er funnet få fossiler, og de som er funnet består som regel bare av spredte ryggvirvler. Mitokondrielt DNA hos slangene har utviklet seg annerledes enn hos andre dyr, og er vanskelig å bruke som molekylær klokke. Det er to konkurrerende teorier om hvordan slangene utviklet sine særtrekk. Den første teorien ble foreslått av Edward Drinker Cope allerede i 1869. Ifølge denne teorien har slangene en periode levd i havet, og mistet lemmer og øyelokk som en tilpasning til et slikt liv. Tilhengere av denne teorien peker ofte på de utdødde mosasaurene som slangenes nærmeste slektninger. Teorien støttes av at de eldste slangefossilene tilhører marine arter, og av flere likhetstrekk mellom øynene til slanger og akvatiske virveldyr. Et argument mot denne teorien er at varanene antas å være nære slektninger av mosasaurene, men genetiske studier viser at slanger og varaner ikke er nært beslektet. Den andre teorien har for tiden flest tilhengere. I den hevdes det at slangenes forfedre levde et underjordisk liv, og at kroppsbygningen er en tilpasning til dette. Gravende øgler har også reduserte, eller manglende, lemmer, og en langstrakt kropp. Tilpasning til et underjordisk liv kan også forklare at øyelokkene, og det ytre øret er forsvunnet. Det er likevel usikkert om slangenes forfedre var gravende, eller om de bare brukte huler som andre dyr hadde gravd ut. Den nålevende øglen øreløs varan, er delvis gravende og delvis akvatisk, og minner på flere måter om slanger. Likhetene skyldes antakelig konvergent evolusjon, men arten kan gi et bilde av hvordan slangene oppstod. Fossiler Fra begynnelsen av sen kritt er det kjent flere fossile slanger med bakbein. Eupodophis fra Libanon, og Haasiophis og Pachyrhachis fra Vestbredden, er alle funnet i marine avsetninger fra cenomanium. Den litt yngre Najash rionegrina fra Patagonia i Argentina levde derimot på land, og er den eneste kjente slangen med korsbein. De fossile slangene som er kjent fra slutten av sen kritt, mangler bakbein, for eksempel Dinilysia fra coniacium i Patagonia. Mange arter fra kritt og paleogen føres til madtsoiidene. Denne utdødde familien hadde en vid utbredelse i Gondwana, og er også funnet i Europa. Alle de nevnte artene har opprinnelige trekk, som ikke finnes hos nålevende slanger, og betraktes som tidlige grener på slangenes stamtre. De utdødde familiene Palaeopheidae og Nigerophiidae regnes til den nålevende gruppen Alethinophidia. Begge disse familiene hadde en vid utbredelse fra cenomanium i kritt til sen eocen, og ser ut til å ha levd i havet. Også mulige representanter for nålevende familier, som boaslanger og falske korallslanger, er kjent fra kritt. Masseutryddelsen i overgangen mellom kritt og paleogen, da blant annet dinosaurene forsvant, rammet også slangene, spesielt de store artene. Ikke alle fossile slanger lar seg plassere i nålevende grupper. Dette gjelder blant annet to arter fra USA, Tuscahomaophis fra sen paleocen i Mississippi, og Goinophis fra sen oligocen i Nebraska. Noen utdødde slanger var større enn de nålevende, som Gigantophis garstini og Palaeophis colossaeus fra eocen. Den største kjente fossile slangen er Titanoboa cerrejonensis fra paleocen i Colombia. Totallengden til denne arten er beregnet til , og vekten til . De første avanserte slangene tilhører den utdødde familien Russellophiidae som forekom fra cenomanium i kritt til sen eocen. En annen utdødd familie av avanserte slanger er Anomalophiidae som bare er kjent fra tidlig eocen. Den første snoken dukker opp i sen eocen, men giftsnoker og hoggormer er derimot først kjent fra miocen. Mangfoldet av avanserte slanger har utviklet seg forholdsvis nylig, i koevolusjon med smågnagerne, som er de viktigste byttedyrene. Havslangene og de australske giftsnokene er en ung gruppe, som har utviklet i løpet av de siste ti millioner år. Systematikk Slangene utgjør en godt definert naturlig gruppe, men det er ikke enighet om slektskapsforholdene innenfor gruppen. I linneansk systematikk regnes slangene som underordenen Serpentes (eller Ophidia). Nærmeste overordnede gruppe er ordenen Squamata (skjellkrypdyr). Det har vært vanlig å dele slangene i tre infraordener: ormeslanger, primitive slanger og avanserte slanger. Det har vist seg at primitive slanger er en parafyletisk gruppe, noe en ikke ønsker i fylogenetisk systematikk. Der blir nålevende slanger delt i to grupper, ormeslanger og Alethinophidia. Avanserte slanger er en delgruppe av Alethinophidia, og omfatter over 80 prosent av slangeartene. Antall familier av slanger varierer mellom de ulike oversiktene. Boaslanger, pytonslanger, mudderslanger, spisshodepyton og jordpyton blir ofte slått sammen til en stor familie av kvelerslanger med det vitenskapelige navnet Boidae. Den store snokefamilien med 1850 arter er sikkert parafyletisk, og det finnes flere forslag for å splitte den i naturlige grupper. Noen skiller av praktiske årsaker havslangene ut i en egen familie, selv om det er klart at de hører til midt i giftsnokene. Tidligere ble gruveslangene ofte plassert i en egen familie, men de fleste regner dem nå til hoggormfamilien. Følgende stamtre bygger på en studie av morfologi og molekylære data hos nålevende og utdødde arter publisert av Lee et. al. i 2007. Utdødde taxa er merket med et kors (†). Vidal & Hedges publiserte i 2009 en fylogenetisk studie der de hevder at evnen til å gape høyt (makrostomi) er en opprinnelig egenskap hos Alethinophidia. Dette får betydning for posisjonen til dvergboaene, som ifølge Vidal & Hedges danner gruppen Amerophidia sammen med falsk korallslange. Slanger og mennesker Se også: Slange (symbol) Mennesket utviklet seg i tropisk Afrika, i et miljø med store kvelerslanger, og mange giftslanger, og frykten for slanger ser ut til være medfødt hos mennesker og andre primater. Frykten er ikke viljestyrt, og kan virke irrasjonell. Å se et bilde av en slange kan være nok til å utløse fysiologiske reaksjoner, som økt puls og svette i håndflatene. Eksperimenter med små barn viser at både barn og voksne oppdager slanger raskere enn ufarlige objekter. Det er blitt hevdet at primatene utviklet bedre syn, og en større hjerne for lettere å kunne oppdage slanger. Mennesker og andre primater har vært både bytte, predatorer og konkurrenter for slangene. Med bakgrunn i dette kan en forstå både menneskers frykt og avsky for slanger, og at de opptrer som gudeaktige skapninger i mytologien hos mange folkeslag. Forestillingen om drager forekommer over nesten hele verden, og må være svært gammel. Dragen kan være en sammensmeltning av slange, ørn og store kattedyr, altså de tre predatorene som aper frykter mest. Funn av fossile dinosaurer har antakelig hatt mindre betydning for utvikling av myten. I mytologien til de australske aboriginene spiller Regnbueslangen en viktig rolle. Den fjærkledde slangen Quetzalcoatl var en mektig gud i flere mellomamerikanske indianerkulturer. I hinduistisk og buddhistisk mytologi finnes det en gruppe av gudeaktige slanger, kalt naga. I oldtidas Egypt symboliserte uraeusslangen kongemakt og guddommelig beskyttelse. Fåvne og Midgardsormen er kjente slanger fra norrøn mytologi. Etter Balders død ble Loke straffet ved å bli bundet fast i en hule. En orm drypper gift på hodet hans, men kona Sigyn samler opp giften i et kar. Når hun må tømme karet, drypper det på Loke, og han vrir seg i smerte og forårsaker jordskjelv. Sjøormer er store slangeaktige fabeldyr som lever i vann, og troen på dem holdt seg lenge. I Antikkens Hellas var slangen hellig. En mente at slangen ble født på nytt når den skiftet hud, og at den derfor var udødelig. Slik ble slangen forbundet med legeguden Asklepios. I templene til denne guden brukte man slanger i helbredelsesritualer, og det er slik æskulapsnoken har fått sitt navn. Attributten til Asklepios var en stav omslynget av en slange, og æskulapstaven brukes fortsatt som symbol for legekunsten. Asklepios' datter Hygiea var helsens gudinne. Hennes attributt var et beger med en slange, og hygieabegeret brukes som symbol for farmasien. Kristendommen og jødedommen har for det meste et svært negativt syn på slanger. Allerede i Første mosebok dukker det opp en slange som lokker Eva til å spise av Kunnskapens tre. I Andre mosebok er det to fortellinger om slanger. Moses forvandler staven sin til en slange for å vise Guds makt. Seinere lager han en bronseslange festet på en stav. Når noen ble bitt av en giftslange, kunne de helbredes ved å se på bronseslangen. Dette minner mye om æskulapstaven, og er en rest av en eldre slangekult, som er blitt en del av jødedommen. I Johannesevangeliet 3,14 bruker Jesus bronseslangen som et bilde på seg selv. Til slutt i Bibelen i Johannes' åpenbaring kalles Satan «den gamle slange». Spor av antikkens slangekulter finnes antakelig i Cocullo i den italienske Abruzzoregionen, og på den greske øya Kefalonia. Her brukes harmløse slanger i kristne ritualer på minnedagene for enkelte helgener. Hos enkelte pinsemenigheter i avsidesliggende strøk i USA brukes giftslanger under gudstjenestene. Dette gjøres med henvisning til Markusevangeliet 16,17–16,18 og Lukasevangeliet 10,19 der det heter at de troende ikke vil bli skadet av slanger. Slangetemmere har vært et vanlig syn i Nord-Afrika og India. Slangen oppbevares i en kurv, og blir tilsynelatende hypnotisert av et musikkinstrument under en forestilling på et torg eller lignende. Det er som regel kobraer som blir brukt, men det hender at hoggormer brukes i stedet. Det er vanlig å brekke av gifttennene, eller å sy igjen munnen til slangen så den ikke kan skade noen. Slangetemming ble forbudt ved lov i India i 1972, men finner fortsatt sted. De fleste kulturer betrakter ikke slanger som mat, men i Øst- og Sørøst-Asia blir slanger spist. Her tror man også at slangeblod øker viriliteten. I Midtvesten i USA er det mange steder vanlig å spise klapperslanger. Etymologi Ordet slange er et lånord, og kommer fra lavtysk slang(e). Det er samme ord som høytysk Schlange, og er nok beslektet med ordet slynge. Ordet for slange i norrønt var ormr. Dette ordet var nedarvet fra urindoeuropeisk, og har kognater i andre språk, for eksempel engelsk worm, tysk Wurm og latin vermes. I mange norske dialekter, og i nynorsk og svensk, er det eneste ordet for dyret slange fortsatt orm. Ordet lever også videre i artsnavn som hoggorm og stålorm. Norske og danske zoologer har brukt ordet orme(r) om den systematiske gruppen som Linné og Lamarck kalte Vermes. Denne gruppen omfattet alle virvelløse dyr som ikke var leddyr, og er for lenge siden gått ut av bruk. Et annet gammelt arveord er snok som kommer via den urgermanske formen snak-an- fra en urindoeuropeisk rot (s)nēg-o-. Roten hadde betydningen «å krype, kryp», og er også opphavet til verbet å snike. Kognater er blant annet engelsk snake og sanskrit naga. Referanser Litteratur Eksterne lenker Naturhistorisk museum – Farlige, giftige, levende slanger Søkbar digitalkopi av Slanger av Alexandra Parsons, utgitt av Aventura forlag 1990 Serpent Research – Herpetological Natural History with an Emphasis on Snakes Pet Snakes Ikke bare om terrariedyr, men også generell informasjon skrevet på en lettfattelig måte Ecology Asia – Snakes of Southeast Asia Thailand Snakes innovations report – Snakes can Hear Stereo Sound from the Sand Krypdyr 1000 artikler enhver Wikipedia bør ha Krypdyr formelt beskrevet i 1758 Dyr formelt beskrevet av Carl von Linné	norwegian_bokmål	0.779976
mints_make_your_mouth_feel_cold/Menthol.txt	Menthol is an organic compound, more specifically a monoterpenoid, made synthetically or obtained from the oils of corn mint, peppermint, or other mints. It is a waxy, clear or white crystalline substance, which is solid at room temperature and melts slightly above. The main form of menthol occurring in nature is (−)-menthol, which is assigned the (1R,2S,5R) configuration. Menthol has local anesthetic and counterirritant qualities, and it is widely used to relieve minor throat irritation. Menthol also acts as a weak κ-opioid receptor agonist. Structure[edit] Natural menthol exists as one pure stereoisomer, nearly always the (1R,2S,5R) form (bottom left corner of the diagram below). The eight possible stereoisomers are: In the natural compound, the isopropyl group is in the trans orientation to both the methyl and hydroxyl groups. Thus, it can be drawn in any of the ways shown: The (+)- and (−)-enantiomers of menthol are the most stable among these based on their cyclohexane conformations. With the ring itself in a chair conformation, all three bulky groups can orient in equatorial positions. The two crystal forms for racemic menthol have melting points of 28 °C and 38 °C. Pure (−)-menthol has four crystal forms, of which the most stable is the α form, the familiar broad needles. Biological properties[edit] This section needs additional citations to secondary or tertiary sources such as review articles, monographs, or textbooks. Please also establish the relevance for any primary research articles cited. Unsourced or poorly sourced material may be challenged and removed. (September 2018) (Learn how and when to remove this template message) A macro photograph of menthol crystals Menthol crystals at room temperature. Approx. 1 cm in length. Menthol's ability to chemically trigger the cold-sensitive TRPM8 receptors in the skin is responsible for the well-known cooling sensation it provokes when inhaled, eaten, or applied to the skin. In this sense, it is similar to capsaicin, the chemical responsible for the spiciness of hot chilis (which stimulates heat sensors, also without causing an actual change in temperature). Menthol's analgesic properties are mediated through a selective activation of κ-opioid receptors. Menthol blocks calcium channels and voltage-sensitive sodium channels, reducing neural activity that may stimulate muscles. Some studies show that menthol acts as a GABAA receptor positive allosteric modulator and increases GABAergic transmission in PAG neurons. Menthol has anesthetic properties similar to, though less potent than, propofol because it interacts with the same sites on the GABAA receptor. Menthol may also enhance the activity of glycine receptors and negatively modulate 5-HT3 receptors and nAChRs. Menthol is widely used in dental care as a topical antibacterial agent, effective against several types of streptococci and lactobacilli. Menthol also lowers blood pressure and antagonizes vasoconstriction through TRPM8 activation. Occurrence[edit] Mentha arvensis (wild mint) is the primary species of mint used to make natural menthol crystals and natural menthol flakes. This species is primarily grown in the Uttar Pradesh region in India. Menthol occurs naturally in peppermint oil (along with a little menthone, the ester menthyl acetate and other compounds), obtained from Mentha × piperita (peppermint). Japanese menthol also contains a small percentage of the 1-epimer neomenthol. Biosynthesis[edit] The biosynthesis of menthol has been investigated in Mentha × piperita and the enzymes involved in have been identified and characterized. It begins with the synthesis of the terpene limonene, followed by hydroxylation, and then several reduction and isomerization steps. More specifically, the biosynthesis of (−)-menthol takes place in the secretory gland cells of the peppermint plant. The steps of the biosynthetic pathway are as follows: Geranyl diphosphate synthase (GPPS) first catalyzes the reaction of IPP and DMAPP into geranyl diphosphate. (−)-limonene synthase (LS) catalyzes the cyclization of geranyl diphosphate to (−)-limonene. (−)-Limonene-3-hydroxylase (L3OH), using O2 and then nicotinamide adenine dinucleotide phosphate (NADPH) catalyzes the allylic hydroxylation of (−)-limonene at the 3 position to (−)-trans-isopiperitenol. (−)-trans-Isopiperitenol dehydrogenase (iPD) further oxidizes the hydroxyl group on the 3 position using NAD to make (−)-isopiperitenone. (−)-Isopiperitenone reductase (iPR) then reduces the double bond between carbons 1 and 2 using NADPH to form (+)-cis-isopulegone. (+)-cis-Isopulegone isomerase (iPI) then isomerizes the remaining double bond to form (+)-pulegone. (+)-Pulegone reductase (PR) reduces this double bond using NADPH to form (−)-menthone. (−)-Menthone reductase (MR) then reduces the carbonyl group using NADPH to form (−)-menthol. Production[edit] Natural menthol is obtained by freezing peppermint oil. The resultant crystals of menthol are then separated by filtration. Total world production of menthol in 1998 was 12,000 tonnes of which 2,500 tonnes was synthetic. In 2005, the annual production of synthetic menthol was almost double. Prices are in the $10–20/kg range with peaks in the $40/kg region but have reached as high as $100/kg. In 1985, it was estimated that China produced most of the world's supply of natural menthol, although it appears that India has pushed China into second place. Menthol is manufactured as a single enantiomer (94% e.e.) on the scale of 3,000 tonnes per year by Takasago International Corporation. The process involves an asymmetric synthesis developed by a team led by Ryōji Noyori, who won the 2001 Nobel Prize for Chemistry in recognition of his work on this process: The process begins by forming an allylic amine from myrcene, which undergoes asymmetric isomerisation in the presence of a BINAP rhodium complex to give (after hydrolysis) enantiomerically pure R-citronellal. This is cyclised by a carbonyl-ene-reaction initiated by zinc bromide to isopulegol [de], which is then hydrogenated to give pure (1R,2S,5R)-menthol. Another commercial process is the Haarmann–Reimer process (after the company Haarmann & Reimer, now part of Symrise) This process starts from m-cresol which is alkylated with propene to thymol. This compound is hydrogenated in the next step. Racemic menthol is isolated by fractional distillation. The enantiomers are separated by chiral resolution in reaction with methyl benzoate, selective crystallisation followed by hydrolysis. Racemic menthol can also be formed by hydrogenation of thymol, menthone, or pulegone. In both cases with further processing (crystallizative entrainment resolution of the menthyl benzoate conglomerate) it is possible to concentrate the L-enantiomer, however this tends to be less efficient, although the higher processing costs may be offset by lower raw material costs. A further advantage of this process is that D-menthol becomes inexpensively available for use as a chiral auxiliary, along with the more usual L-antipode. Applications[edit] This section is in list format but may read better as prose. You can help by converting this section, if appropriate. Editing help is available. (October 2022) Menthol is included in many products, and for a variety of reasons. Cosmetic[edit] In nonprescription products for short-term relief of minor sore throat and minor mouth or throat irritation e.g.: lip balms and cough medicines. In some beauty products such as hair conditioners, based on natural ingredients (e.g., St. ⁠Ives). Medical[edit] As an antipruritic to reduce itching. As a topical analgesic, it is used to relieve minor aches and pains, such as muscle cramps, sprains, headaches and similar conditions, alone or combined with chemicals such as camphor, eucalyptus oil or capsaicin. In Europe, it tends to appear as a gel or a cream, while in the U.S., patches and body sleeves are very frequently used, e.g.: Tiger Balm, or IcyHot patches or knee/elbow sleeves. As a penetration enhancer in transdermal drug delivery. In decongestants for chest and sinuses (cream, patch or nose inhaler). Examples: Vicks VapoRub, Mentholatum, Axe Brand, VapoRem, Mentisan. In certain medications used to treat sunburns, as it provides a cooling sensation (then often associated with aloe). Commonly used in oral hygiene products and bad-breath remedies, such as mouthwash, toothpaste, mouth and tongue sprays, and more generally as a food flavor agent; such as in chewing gum and candy. In first aid products such as "mineral ice" to produce a cooling effect as a substitute for real ice in the absence of water or electricity (pouch, body patch/sleeve or cream). Others[edit] In aftershave products to relieve razor burn. As a smoking tobacco additive in some cigarette brands, for flavor, and to reduce throat and sinus irritation caused by smoking. Menthol also increases nicotine receptor density, increasing the addictive potential of tobacco products. As a pesticide against tracheal mites of honey bees. In perfumery, menthol is used to prepare menthyl esters to emphasize floral notes (especially rose). In various patches ranging from fever-reducing patches applied to children's foreheads to "foot patches" to relieve numerous ailments (the latter being much more frequent and elaborate in Asia, especially Japan: some varieties use "functional protrusions", or small bumps to massage one's feet as well as soothing them and cooling them down). As an antispasmodic and smooth muscle relaxant in upper gastrointestinal endoscopy. Organic chemistry[edit] In organic chemistry, menthol is used as a chiral auxiliary in asymmetric synthesis. For example, sulfinate esters made from sulfinyl chlorides and menthol can be used to make enantiomerically pure sulfoxides by reaction with organolithium reagents or Grignard reagents. Menthol reacts with chiral carboxylic acids to give diastereomic menthyl esters, which are useful for chiral resolution. It can be used as a catalyst for sodium production for the amateur chemist via the alcohol catalysed magnesium reduction process. Menthol is potentially ergogenic (performance enhancing) for athletic performance in hot environments Reactions[edit] Menthol reacts in many ways like a normal secondary alcohol. It is oxidised to menthone by oxidising agents such as chromic acid or dichromate, though under some conditions the oxidation can go further and break open the ring. Menthol is easily dehydrated to give mainly 3-menthene, by the action of 2% sulfuric acid. Phosphorus pentachloride (PCl5) gives menthyl chloride. History[edit] In the West, menthol was first isolated in 1771, by the German, Hieronymus David Gaubius. Early characterizations were done by Oppenheim, Beckett, Moriya, and Atkinson. It was named by F. L. Alphons Oppenheim (1833–1877) in 1861. Compendial status[edit] United States Pharmacopeia 23 Japanese Pharmacopoeia 15 Food Chemicals Codex Safety[edit] The estimated lethal dose for menthol (and peppermint oil) in humans may be as low as 50–500 mg/kg, (LD50 Acute: 3300 mg/kg [Rat]. 3400 mg/kg [Mouse]. 800 mg/kg [Cat]). Survival after doses of 8 to 9 g has been reported. Overdose effects are abdominal pain, ataxia, atrial fibrillation, bradycardia, coma, dizziness, lethargy, nausea, skin rash, tremor, vomiting, and vertigo. See also[edit] Medicine portal Aroma compound Carvone Chlorobutanol Ethyl benzoate Ethyl salicylate Menthoxypropanediol Methyl salicylate Menthol cigarettes Menthyl isovalerate Menthyl nicotinate p-Menthane-3,8-diol Thujone Vapor pressure	biology	789767	https://no.wikipedia.org/wiki/Metylisocyanat	Metylisocyanat	Metylisocyanat (MIC) er en organisk forbindelse med molekylformelen C2H3NO, ordnet som H3C-N=C=O. Andre navn på denne forbindelsen er isocyanatmetan og metylkarbylamin. Metylisocyanat hører til gruppen isocyanater, som er flittig brukt innen kjemisk industri. Metylisocyanat er et mellomprodukt i produksjonen av pesticider med karbamat (slik som karbaryl, karbofuran, metomyl og aldikarb). Det har også blitt brukt i produksjon av gummi og lim. Som et svært giftig og irriterende stoff er metylisocyanat helsefarlig for mennesker, og stoffet kom særlig i søkelyset etter Bhopal-katastrofen som inntraff inntraff 3. desember 1984 i den indiske byen Bhopal. Industrikatastrofen, som regnes som en av historiens verste, tok livet av nesten 8 000 mennesker i løpet av de første dagene og om lag 17 000 mennesker totalt. Fysiske egenskaper Metylisocyanat (MIC) er en klar, fargeløs væske med skarp, tåregassaktig lukt. Den er svært brannfarlig, har et kokepunkt på 39,1 °C og et lavt flammepunkt. Den er reaktiv, flyktig og eksplosiv i blanding med luft. Terskelverdien er satt til 0,02 ppm. Metylisocyanat er vannløselig (6–10 deler per 100 deler), men den reagerer med vannet (se Reaksjoner). Fremstilling Metylisocyanat fremstilles vanligvis av monometylamin (CH3NH2) og fosgen (CCl2O). Disse substansene reagerer ved en rekke temperaturer, men for storskala produksjon er det en fordel å kombinere disse reaktantene ved høyere temperatur i gassform. En blanding av metylisocyanat og to mol hydrogenklorid dannes, men N-metylkarbamoylklorid (MCC) dannes som en sideeffekt når blandingen kondenserer og etterlater seg en mol av hydrogenklorid som gass. Sluttproduktet metylisocyanat fås ved å reagere MCC med et tertiært amin, som for eksempel dimetylanilin eller pyridin, eller ved å separere det ved hjelp av destillasjonsteknikker. Metylisocyanat kan også fremstilles av N-metylformadid og luft. I den sistnevnte prosessen brukes det opp med en gang i en reguleringssløyfe der målet er å produsere metomyl. Det er også blitt hevdet at andre fremstillingsmetoder finnes. Reaksjoner Metylisocyanat reagerer lett med mange substanser som inneholder NH- eller OH-grupper og noen andre forbindelser. Det reagerer også med seg selv for å danne en trimer eller polymerer med større molekylmasse. Metylisocyanat reagerer med vann for å danne 1,3-dimetylurea og karbondioksid med utviklingen av varme (325 cal/gr – 325 kalorier per gram MIC som reagerer). Ved 25 °C brukes halvparten av MIC i løpet av ni minutter, gitt at reaksjonen skjer i overskudd av vann; hvis varmen ikke fjernes effektiv fra blandingen vil reaksjonshastigheten øke og raskt føre til at MIC begynner å koke. Dersom MIC er i overskudd, dannes 1,3,5-trimethlbiuret sammen med karbondioksid. Forbindelser som inneholder hydrogen festet til nitrogen, slik som ammoniakk eller primære eller sekundære aminer, vil raskt reagere med metylisocyanat og danne substituerte ureaer. Andre NH-forbindelser som for eksempel amider og ureaer reagerer mye langsommere med MIC. Alkoholer og fenoler som inneholder en OH-gruppe reagerer sakte med MIC, men reaksjonen kan bli katalysert av trialkylaminer eller dialkyntin dikarboksylat. Oksimer, hydroksylaminer og enoler reagerer også med metylisocyanat slik at det dannes metylkarbamater. I disse reaksjonene dannes produktene som er omtalt nedenfor (Bruksområder). Dersom det brukes katalysatorer reagerer MIC med seg selv og danner en fast trimer, trimetylisocyanurat eller en polymer med større molekylmasse. Natriummetoksid, trietylfosfin, jernklorid og visse andre metallforbindelser katalyserer dannelsen av MIC-trimeren, mens reaksjonen der det dannes en polymer med større molekylmasse katalyseres av visse trialkylaminer. Siden reaksjonen der det dannes en MIC-trimer er eksoterm (298 cal/1 gr MIC), kan den føre til voldsomme koking av MIC. Polymeren med stor molekylmasse hydrolyserer i varmt vann og det dannes trimetylcyanurat. Siden katalytiske metallsalter kan bli dannet fra urenheter i vanlig MIC og stål, må ikke dette produktet lagres i ståltønner eller -tanker. Bruksområder Metylisocyanat er et mellomprodukt i produksjonen av karbamat-baserte pesticider, slik som karbaryl, karbofuran, metomyl og aldikarb. Forbindelsen har også blitt brukt i fremstillingen av gummi og lim. Farer Metylisocyanat (MIC) er svært giftig. Terskelverdien satt av American Conference on Government Industrial Hygienist var 0,02 ppm. MIC kan skade kroppen ved innånding, svelging og kontakt i så små mengder som 0,4 ppm. Den kan føre til blant annet hoste, brystsmerter, dyspné, astma, irritasjon i øyne, nese og strupe samt hudskader. Utsettes man for større mengder (>21 ppm) MIC kan det resultere i pulmonalt ødem eller lungeødem, emfysem og blødninger, bronkial lungebetennelse og død. Selv om lukten av metylisocyanat med en konsentrasjon på 5 ppm ikke kan merkes av de fleste mennesker, gir dens potente tåregassaktige egenskaper en god pekepinn på forbindelsens tilstedeværelse (ved en konsentrasjon på 2–4 ppm blir vedkommendes øyne irritert, og ved 21 ppm kan vedkommende ikke lenger tåle tilstedeværelsen av metylisocyanat i luften). Forholdsregler må tas når man lagrer metylisocyanat på grunn av forbindelsens lette eksotermiske polymerisering (se Reaksjoner) og dens lignende følsomhet for vann. Bare rustfritt stål eller glass kan trygt brukes; MIC må oppbevares ved temperaturer under 40 °C (104 °F) og helst ved 4 °C (39 °F). Forbindelsens toksiske effekt kom til syne i Bhopal-katastrofen, da rundt 42 tonn metylisocyanat og andre gasser lakk ut fra reservoarer under bakken ved en fabrikk tilhørende Union Carbide India Limited (UCIL) den 3. desember 1984 og spredte seg over et tett befolket område, noe som umiddelbart drepte tusener mennesker og tok livet av ytterligere titusener i de etterfølgende ukene og månedene. Referanser Eksterne lenker NIOSH Safety and Health Topic: Isocyanates – National Institute for Occupational Safety and Health (NIOSH) Methyl Isocyanate – Columbia Analytical Services Isocyanater Monomerer	norwegian_bokmål	0.5307
mints_make_your_mouth_feel_cold/Lamiaceae.txt	The Lamiaceae (/ˌleɪmiˈeɪsiːˌiː, -iˌaɪ/ LAY-mee-AY-see-ee, -⁠eye) or Labiatae are a family of flowering plants commonly known as the mint, deadnettle or sage family. Many of the plants are aromatic in all parts and include widely used culinary herbs like basil, mint, rosemary, sage, savory, marjoram, oregano, hyssop, thyme, lavender, and perilla, as well as other medicinal herbs such as catnip, salvia, bee balm, wild dagga, and oriental motherwort. Some species are shrubs, trees (such as teak), or, rarely, vines. Many members of the family are widely cultivated, not only for their aromatic qualities, but also their ease of cultivation, since they are readily propagated by stem cuttings. Besides those grown for their edible leaves, some are grown for decorative foliage. Others are grown for seed, such as Salvia hispanica (chia), or for their edible tubers, such as Plectranthus edulis, Plectranthus esculentus, Plectranthus rotundifolius, and Stachys affinis (Chinese artichoke). Many are also grown ornamentally, notably coleus, Plectranthus, and many Salvia species and hybrids. The family has a cosmopolitan distribution. The enlarged Lamiaceae contain about 236 genera and have been stated to contain 6,900 to 7,200 species, but the World Checklist lists 7,534. The largest genera are Salvia (900), Scutellaria (360), Stachys (300), Plectranthus (300), Hyptis (280), Teucrium (250), Vitex (250), Thymus (220), and Nepeta (200). Clerodendrum was once a genus of over 400 species, but by 2010, it had been narrowed to about 150. The family has traditionally been considered closely related to the Verbenaceae; in the 1990s, phylogenetic studies suggested that many genera classified in the Verbenaceae should be classified in the Lamiaceae or to other families in the order Lamiales. The alternative family name Labiatae refers to the flowers typically having petals fused into an upper lip and a lower lip (labia in Latin). The flowers are bilaterally symmetrical with five united petals and five united sepals. They are usually bisexual and verticillastrate (a flower cluster that looks like a whorl of flowers, but actually consists of two crowded clusters). Although this is still considered an acceptable alternative name, most botanists now use the name Lamiaceae in referring to this family. The leaves emerge oppositely, each pair at right angles to the previous one (decussate) or whorled. The stems are frequently square in cross section, but this is not found in all members of the family, and is sometimes found in other plant families. Genera[edit] Leucas aspera in Hyderabad, India Orthosiphon thymiflorus flower Oregano Plectranthus ecklonii The last revision of the entire family was published in 2004. It described and provided keys to 236 genera. These are marked with an asterisk () in the list below. A few genera have been established or resurrected since 2004. These are marked with a plus sign (+). Other genera have been synonymised. These are marked with a minus sign (-). The remaining genera in the list are mostly of historical interest only and are from a source that includes such genera without explanation. Few of these are recognized in modern treatments of the family. Kew Gardens provides a list of genera that includes additional information. A list at the Angiosperm Phylogeny Website is frequently updated. Acanthomintha Achyrospermum Acinos Acrocephalus Acrotome Acrymia Adelosa Aegiphila Aeollanthus Agastache Ajuga Ajugoides Alajja Alvesia Amasonia Amethystea Anisochilus Anisomeles Asterohyptis Ballota Basilicum Becium Benguellia Blephilia Bostrychanthera Bovonia Brachysola Brazoria Bystropogon Calamintha Callicarpa Capitanopsis Capitanya Caryopteris Catoferia Cedronella Ceratanthus Chaiturus Chamaesphacos Chaunostoma Chelonopsis Chloanthes Cleonia Clerodendrum Clinopodium Colebrookea Collinsonia Colquhounia Comanthosphace Congea Conradina Coridothymus Cornutia Craniotome Cryphia Cuminia Cunila Cyanostegia Cyclotrichium Cymaria Dauphinea Dicerandra Dicrastylis Discretitheca Dorystoechas Dracocephalum Drepanocaryum Elsholtzia Endostemon Englerastrum +Eplingiella Eremostachys Eriope Eriophyton Eriopidion Eriothymus Erythrochlamys Euhesperida Eurysolen Faradaya Fuerstia Galeopsis Garrettia Geniosporum Glechoma Glechon Glossocarya Gmelina Gomphostemma Gontscharovia Hanceola Haplostachys Haumaniastrum Hedeoma Hemiandra Hemigenia Hemiphora Hemizygia Hesperozygis Heterolamium Hoehnea Holmskioldia Holocheila Holostylon Horminum Hosea Hoslundia Huxleya Hymenocrater Hymenopyramis Hypenia Hypogomphia Hyptidendron Hyptis Hyssopus Isodictyophorus Isodon Isoleucas +Kalaharia Karomia Keiskea Killickia Kudrjaschevia Kurzamra Lachnostachys Lagochilus Lagopsis Lallemantia Lamiophlomis Lamium Lavandula Leocus Leonotis Leonurus Lepechinia Leucas Leucophae Leucosceptrum Limniboza Lophanthus Loxocalyx Lycopus Macbridea Madlabium Marmoritis +Martianthus Marrubium Marsypianthes Matsumurella Meehania Melissa Melittis Mentha Meriandra, syn. of Salvia Mesona Metastachydium Microcorys Micromeria Microtoena Minthostachys Moluccella Monarda Monardella Monochilus Mosla Neohyptis Neorapinia Nepeta Newcastelia Nosema Notochaete Obtegomeria Ocimum Octomeron Ombrocharis Oncinocalyx Origanum Orthosiphon Otostegia +Ovieda Oxera Panzerina Paralamium Paraphlomis Paravitex Peltodon Pentapleura Perilla Perillula Peronema -Perovskia Perrierastrum Petitia Petraeovitex Phlomidoschema Phlomis Phlomoides Phyllostegia Physopsis Physostegia Piloblephis Pitardia Pityrodia Platostoma Plectranthus Pogogyne Pogostemon Poliomintha Prasium Premna Prostanthera Prunella Pseuderemostachys Pseudocarpidium Pseudocaryopteris Pseudomarrubium Puntia Pycnanthemum Pycnostachys Rabdosiella Renschia Rhabdocaulon Rhaphiodon Rhododon -Rosmarinus Rostrinucula Rotheca Roylea Rubiteucris +Rydingia Sabaudia Saccocalyx Salazaria Salvia Satureja Schizonepeta Schnabelia Scutellaria Sideritis Siphocranion Solenostemon Spartothamnella Sphenodesme Stachydeoma Stachyopsis Stachys Stenogyne Sulaimania Suzukia Symphorema Symphostemon Synandra Syncolostemon Tectona Teijsmanniodendron +Tetraclea Tetradenia Teucridium Teucrium Thorncroftia Thuspeinanta Thymbra Thymus Tinnea Trichostema Tripora Tsoongia Vitex Viticipremna +Volkameria Warnockia Wenchengia Westringia Wiedemannia Wrixonia Xenopoma Zataria *Ziziphora Recent changes[edit] The circumscription of several genera has changed since 2004. Tsoongia, Paravitex, and Viticipremna have been sunk into synonymy with Vitex. Huxleya has been sunk into Volkameria. Kalaharia, Volkameria, Ovieda, and Tetraclea have been segregated from a formerly polyphyletic Clerodendrum. Rydingia has been separated from Leucas. The remaining Leucas is paraphyletic over four other genera. Subfamilies and tribes[edit] In 2004, the Lamiaceae were divided into seven subfamilies, plus 10 genera not placed in any of the subfamilies. The unplaced genera are: Tectona, Callicarpa, Hymenopyramis, Petraeovitex, Peronema, Garrettia, Cymaria, Acrymia, Holocheila, and Ombrocharis. The subfamilies are the Symphorematoideae, Viticoideae, Ajugoideae, Prostantheroideae, Nepetoideae, Scutellarioideae, and Lamioideae. The subfamily Viticoideae is probably not monophyletic. The Prostantheroideae and Nepetoideae are divided into tribes. These are shown in the phylogenetic tree below. Phylogeny[edit] Most of the genera of Lamiaceae have never been sampled for DNA for molecular phylogenetic studies. Most of those that have been are included in the following phylogenetic tree. The phylogeny depicted below is based on seven different sources. Lamiaceae Callicarpa Tectona Viticoideae (pro parte) Gmelina Premna Viticoideae (pro parte) Vitex Symphorematoideae Congea Symphorema Ajugoideae Rotheca Teucrium Ajuga Oxera Faradaya Kalaharia Clerodendrum Volkameria Ovieda Aegiphila Tetraclea Amasonia Prostantheroideae Chloantheae Chloanthes Westringieae Prostanthera Westringia Nepetoideae Ocimeae Lavandula Siphocranion Isodon Hanceola Hyptis Orthosiphon Ocimum Plectranthus Coleus Elsholtzieae Elsholtzia Perilla Mentheae Lepechinia Salvia Rosmarinus Prunella Nepeta Dracocephalum Agastache Origanum Thymus Mentha Satureja Clinopodium Bystropogon Pycnanthemum Monarda Dicerandra Conradina Scutellarioideae Holmskioldia Scutellaria Lamioideae Pogostemon Phlomis Lamium Stachys Sideritis Haplostachys Stenogyne Phyllostegia Leonurus Marrubium Moluccella Rydingia Leucas Leonotis	biology	4311	https://sv.wikipedia.org/wiki/Orkid%C3%A9er	Orkidéer	Orkidéer (Orchidaceae) är en familj av enhjärtbladiga växter som beskrevs av Antoine Laurent de Jussieu. Orkidéer ingår i sparrisordningen. Enligt Catalogue of Life omfattar familjen Orchidaceae 27 234 arter. Beskrivning Orkidéer är fleråriga örter med underjordiska jordstammar eller knöllika, näringslagrande rötter (amrötter); sällan utan klorofyll. Stjälk upprätt. Blad strödda eller sällan nästan motsatta, parallellnerviga, helbräddade. Blommor tvåkönade, oftast samlade i toppställda gles- eller mångblommiga ax eller klasar, någon gång ensamma. Familjen är en av jordens artrikaste med nästan 800 släkten och omkring 30 000 arter. I Sverige har man funnit 44 arter fördelade på 23 släkten. Samtliga svenska orkidéer är fridlysta i hela landet. De som i äldre tider samlade och pressade växter erfor att orkidéer i likhet med suckulenta växter, till exempel sedum, var mycket svåra att få torra. I dagsläget är dock samtliga orkidéarter i Sverige fridlysta. Moderna botaniker använder sig av fotografering för att dokumentera sina fynd. Odling Orkidéer är numera vanliga krukväxter i svenska hem, särskilt den så kallade brudorkidén (Phalaenopsis). Orkidéer skall inte planteras i vanlig krukväxtjord, utan i luftig kompost (särskild orkidéjord finns att köpa). De behöver inte vattnas ofta, någon gång varannan vecka räcker bra. Vid vattning sänks orkidén med odlingskrukan ner i rumstempererat vatten i ca fem min och får därefter droppa av ordentligt innan den sätts tillbaka i ytterkrukan. Viktigt att tänka på är att det absolut inte får komma vatten i bladrosetten då detta lätt förorsakar röta, speciellt viktigt under de kalla årstiderna med sämre avdunstning. Sedan brudorkidén har blommat, kan stängeln lämnas orörd. Ofta kommer då nya förgreningar och nya blommor. Först när en stängel vissnat och torkat in, tas den bort. Se också Semi-hydroponic för odling av orkideer. Detta gäller framförallt när blomstjälken saknar förgreningar, underarter med förgrenade blomstjälkar blommar mer sällan om på gamla stjälkar. Grundregeln får dock vara att inte klippa bort en stjälk helt förrän den är helt intorkad. Släkten sofronitissläktet (Sophronitis) Knottblomstersläktet (Microstylis) Enligt Catalogue of Life ingår följande släkten i familjen: Aa Abdominea Acampe Acanthephippium Acianthera Acianthus Acineta Acriopsis Acrochaene Acrolophia Acrorchis adasläktet - Ada Adamantinia Adenochilus Adenoncos Adrorhizon Aenhenrya Aerangis Aeranthes Aerides Aetheorhyncha Aganisia Aglossorrhyncha Agrostophyllum Alamania Alatiliparis Altensteinia Ambrella Amesiella Amitostigma Anacamptiplatanthera Anacamptis Anacamptorchis Anathallis Ancistrochilus Ancistrorhynchus Andinia Androcorys Angraecopsis Angraecum anguloasläktet - Anguloa Anoectochilus anselliasläktet - Ansellia Anthogonium Aphyllorchis Aplectrum Aporostylis Apostasia Appendicula Aracamunia Arachnis Archivea Arethusa Armodorum Arnottia Arpophyllum Arthrochilus Artorima Arundina Ascidieria Ascocentropsis glödvandasläktet - Ascocentrum Ascochilopsis Ascochilus Ascoglossum aspasiasläktet - Aspasia Aspidogyne Aulosepalum Auxopus Barbosella barkeriasläktet - Barkeria Bartholina Basiphyllaea Baskervilla Batemannia Beclardia Beloglottis Bensteinia Benthamia Benzingia Bhutanthera Biermannia bifrenariasläktet - Bifrenaria Bipinnula Bletia mikadoblomssläktet - Bletilla Bogoria Bolusiella Bonatea Brachionidium Brachtia Brachycorythis Brachypeza Brachystele Bracisepalum Braemia Brasiliorchis nattstjärnesläktet - Brassavola Brassia Brassocattleya Bromheadia Broughtonia Brownleea Bryobium Buchtienia bulbofyllumsläktet - Bulbophyllum Bulleyia Burnettia Caladenia kalantesläktet - Calanthe Calassodia Caleana Callostylis Calochilus Calopogon Caluera Calymmanthera Nornasläktet - Calypso Calyptrochilum Camaridium Campanulorchis Campylocentrum Capanemia Cardiochilos Catasetum cattleyasläktet - Cattleya catykliasläktet - Catyclia Caucaea Caularthron Centroglossa Centrostigma Cephalanthera Cephalantheropsis Cephalopactis Cephalorchis Ceratandra Ceratocentron Ceratochilus Ceratostylis Chamaeangis Chamaeanthus Chamaegastrodia Chamelophyton Dvärgyxnesläktet - Chamorchis Changnienia Chaseella Chaubardia Chaubardiella Chauliodon Cheiradenia Cheirostylis Chelonistele Chiloglottis Chilopogon Chiloschista Chloraea Chondrorhyncha Chondroscaphe Christensonella Christensonia Chroniochilus Chrysoglossum Chysis Chytroglossa Cirrhaea Cischweinfia Claderia Cladobium Cleisocentron Cleisomeria Cleisostoma Cleisostomopsis Cleistes Cleistesiopsis Clematepistephium Clowesia Coccineorchis Cochleanthes Codonorchis Coelia Coeliopsis drottningorkidésläktet - Coelogyne Coilochilus Collabium Comparettia Conchidium Constantia Cooktownia Korallrotssläktet - Corallorhiza Cordiglottis Coryanthes Corybas Corycium Corymborkis Cottonia Cotylolabium Cranichis Cremastra Crepidium Cribbia Crossoglossa Cryptarrhena Cryptocentrum Cryptochilus Cryptopus Cryptopylos Cryptostylis citronodontoglossumssläktet - Cuitlauzina Cyanaeorchis Cyanicula Cyanthera Cybebus Cyclopogon Cycnoches Cymbidiella cymbidiumsläktet - Cymbidium Cynorkis Cyphochilus Cypholoron guckuskosläktet - Cypripedium Cyrtidiorchis Cyrtochiloides Cyrtochilum Cyrtopodium Cyrtorchis Cyrtosia Cyrtostylis Cystorchis Dactylanthera Dactylocamptis Dactylodenia handnyckelsläktet - Dactylorhiza Dactylostalix Daiotyla Danhatchia Deceptor Degranvillea Deiregyne dendrobiumsläktet - Dendrobium Dendrochilum Dendrophylax Devogelia Diaphananthe Diceratostele Dichaea Dichromanthus Dickasonia Didymoplexiella Didymoplexiopsis Didymoplexis Dienia Diglyphosa Dilochia Dilochiopsis Dilomilis Dimerandra Dimorphorchis Dinema Dinklageella Diodonopsis Diplocentrum Diplomeris Diploprora Dipodium disasläktet - Disa Discyphus Disperis Distylodon Diuris Domingoa Dossinia Dracomonticola Draconanthes Dracula Drakaea Dresslerella Dressleria Dryadella Dryadorchis Drymoanthus Drymoda Duckeella Dunstervillea Dyakia Earina Echinorhyncha Echinosepala Eclecticus Eggelingia Eleorchis Elleanthus Eloyella Eltroplectris Elythranthera Embreea encykliasläktet - Encyclia Entomophobia Eparmatostigma Ephippianthus Epiblastus Epiblema epidendrumsläktet - Epidendrum Epilaeliopsis Epilyna knipprotssläktet - Epipactis Epipogium Epistephium Erasanthe Eria Eriaxis Ericksonella Eriochilus Eriodes Eriopsis Erycina Erythrodes Erythrorchis Esmeralda praktvandasläktet - Euanthe Eulophia Eulophiella Euryblema Eurycentrum Eurychone Eurystyles Evotella Fernandezia Frigidorchis Frondaria Fuertesiella Funkiella Galeandra Galearis Galeoglossum Galeola Galeottia Galeottiella Gastrochilus Gastrodia Gastrorchis Gavilea Geesinkorchis Gennaria Genoplesium Genyorchis Geoblasta Geodorum Glomera Glossodia Gomesa Gomphichis Gonatostylis Gongora knärotssläktet - Goodyera Govenia Grammangis Grammatophyllum Grandiphyllum Graphorkis Grobya Grosourdya Guanchezia narrcattleyasläktet - Guarianthe Gunnarella brudsporresläktet - Gymnadenia Gymnanacamptis Gymnotraunsteinera Gymplatanthera Gynoglottis Habenaria Hagsatera Halleorchis myggblomstersläktet - Hammarbya Hancockia Hapalorchis Haraella Hederorkis Helleriella Helonoma Hemipilia Hemipiliopsis Honungsblomstersläktet - Herminium Herpysma Hetaeria Heterotaxis Hexalectris Himantoglossum Hintonella Hippeophyllum Hoehneella Hofmeisterella Holcoglossum Holothrix Homalopetalum Horichia Horvatia Houlletia Huntleya Huttonaea Hygrochilus Hylaeorchis Hylophila Hymenorchis Imerinaea India Inti Ionopsis Ipsea Isabelia Ischnogyne Isochilus Isotria Ixyophora Jacquiniella Jejewoodia Jejosephia Jumellea Kefersteinia Kegeliella Kionophyton Koellensteinia Kraenzlinella Kreodanthus Kuhlhasseltia Lacaena Laelia Laeliocattleya Lankesterella Lecanorchis Lemurella Lemurorchis Leochilus Lepanthes Lepanthopsis Lepidogyne Leporella Leptoceras leptotessläktet - Leptotes Ligeophila Limodorum gulyxnesläktet - Liparis Listrostachys Lockhartia Loefgrenianthus juvelorkidésläktet - Ludisia Lueckelia Lueddemannia Luisia lykastesläktet - Lycaste Lycida Lycomormium Lyperanthus Lyroglossa makodessläktet - Macodes Macradenia Macroclinium Macropodanthus Malaxis Malleola Manniella Mapinguari Margelliantha masdevalliasläktet - Masdevallia maxillariasläktet - Maxillaria Maxillariella Mediocalcar Megalorchis Megalotus Megastylis Meiracyllium Mesadenella Mesadenus Mesospinidium Mexipedium Microchilus Microcoelia Microepidendrum Micropera Microsaccus Microtatorchis Microterangis Microthelys Microtis miltoniasläktet - Miltonia Miltonidium penséorkidésläktet - Miltoniopsis Mobilabium Monomeria Monophyllorchis Mormodes Mormolyca Mycaranthes Myoxanthus Myrmechis Myrmecolaelia Myrmecophila Myrosmodes Mystacidium Nabaluia Neobathiea Neobenthamia Neobolusia Neoclemensia Neocogniauxia Neofinetia Neogardneria Neogyna Neolindleya Neomoorea Neotinea nästrotssläktet - Neottia Neottianthe Nephelaphyllum Nephrangis Nervilia Neuwiedia Nidema Nitidobulbon Nohawilliamsia Notheria Nothodoritis Nothostele Notylia Notyliopsis Oberonia Oberonioides Octarrhena oktomeriasläktet - Octomeria Odisha Odontochilus Odontorrhynchus Oeceoclades Oeonia Oeoniella Oestlundia Oligophyton Oliveriana Omoea oncidiumsläktet - Oncidium Ophioglossella ofryssläktet - Ophrys Orchidactylorhiza Orchigymnadenia Orchimantoglossum Orchinea Orchipedum Orchiplatanthera nyckelsläktet - Orchis Orchiserapias Oreorchis Orestias Orleanesia Ornithidium Ornithocephalus Ornithochilus Ornithocidium Orthoceras Ossiculum Otochilus Otoglossum Otostylis Oxystophyllum Pabstia Pabstiella Pachites Pachyphyllum Pachyplectron Pachystoma Palmorchis Panisea Paphinia Paphiopedilum Papilionanthe Papillilabium Papuaea Paracaleana Paradisanthus Paralophia Paraphalaenopsis Parapteroceras Pecteilis Pedilochilus Pelatantheria Pelexia Penkimia Pennilabium Peristeranthus Peristeria Peristylus Pescatoria fajussläktet - Phaius brudorkidésläktet - Phalaenopsis Pheladenia Phloeophila Pholidota mandarinorkidésläktet - Phragmipedium Phragmorchis Phreatia Phymatidium Physoceras Physogyne Pilophyllum Pinalia Pityphyllum nattviolssläktet - Platanthera Platycoryne Platylepis Platyrhiza Platystele Platythelys Plectorrhiza Plectrelminthus Plectrophora jungfruskosläktet - Pleione Pleurothallis Pleurothallopsis Plocoglottis Poaephyllum Podangis Podochilus Pogonia Pogoniopsis Polycycnis Polyotidium Polystachya Pomatocalpa Ponera Ponerorchis Ponthieva Porolabium Porpax Porphyrodesme Porphyroglottis Porphyrostachys Porroglossum Porrorhachis Potosia Praecoxanthus Prasophyllum Prescottia Pristiglottis Promenaea bläckfiskorkidésläktet - Prosthechea Pseudadenia Pseudanthera Pseuderia Pseudinium Pseudocentrum Pseudogoodyera Pseudolaelia Pseudorchis Pseudorhiza Pseudovanilla Psilochilus Psychilis fjärilsoncidiumsläktet - Psychopsis Pterichis Pteroceras Pteroglossa Pterostemma Pterostylis Pterygodium Pygmaeorchis Pyrorchis Quekettia Quisqueya Rangaeris Rauhiella Raycadenco Renanthera Restrepia Restrepiella Rhaesteria Rhetinantha Rhinerrhiza Rhinerrhizopsis Rhipidoglossum Rhizanthella Rhomboda Rhynchogyna näbblaeliasläktet - Rhyncholaelia Rhynchostele Rhynchostylis Ridleyella Rimacola Risleya Robiquetia Rodriguezia Roeperocharis guldspetsorkidésläktet - Rossioglossum Rudolfiella Saccoglossum Saccolabiopsis Saccolabium Sacoila Samarorchis Sanderella Santotomasia Sarcanthopsis Sarcochilus Sarcoglottis Sarcoglyphis Sarcophyton Sarcostoma Satyrium Saundersia Sauroglossum Saurolophorkis Sauvetrea Scaphosepalum Scaphyglottis Schiedeella Schistotylus Schizochilus Schlimia Schoenorchis Schuitemania Schunkea Scuticaria Sedirea Sedirisia Seegeriella Seidenfadenia Seidenfadeniella Selenipedium Senghasiella Serapias Serapicamptis Serapirhiza Sertifera Sievekingia Silvorchis Singchia Sirhookera Sirindhornia Skeptrostachys Smithorchis Smithsonia Smitinandia Sobennikoffia Sobralia Solenangis Solenidium Solenocentrum Soterosanthus Sotoa Spathoglottis Specklinia Sphyrarhynchus Spiculaea skruvaxsläktet - Spiranthes Spongiola Stalkya Stanhopea Staurochilus Stelis Stenia Stenoglottis Stenoptera Stenorrhynchos Stenotyla Stephanothelys Stereochilus Stereosandra Steveniella Stichorkis Stigmatodactylus Stolzia Suarezia Sudamerlycaste Summerhayesia Sunipia Sutrina Svenkoeltzia Systeloglossum Taeniophyllum Taeniorrhiza Tainia Teagueia Telipogon Tetramicra Teuscheria Thaia Thecopus Thecostele Thelasis Thelymitra Thelyschista Thrixspermum Thulinia klockorkidésläktet - 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magnetic_plant/Magnetotactic_bacteria.txt	Magnetotactic bacteria (or MTB) are a polyphyletic group of bacteria that orient themselves along the magnetic field lines of Earth's magnetic field. Discovered in 1963 by Salvatore Bellini and rediscovered in 1975 by Richard Blakemore, this alignment is believed to aid these organisms in reaching regions of optimal oxygen concentration. To perform this task, these bacteria have organelles called magnetosomes that contain magnetic crystals. The biological phenomenon of microorganisms tending to move in response to the environment's magnetic characteristics is known as magnetotaxis. However, this term is misleading in that every other application of the term taxis involves a stimulus-response mechanism. In contrast to the magnetoreception of animals, the bacteria contain fixed magnets that force the bacteria into alignment—even dead cells are dragged into alignment, just like a compass needle. Introduction[edit] The first description of magnetotactic bacteria was in 1963 by Salvatore Bellini of the University of Pavia. While observing bog sediments under his microscope, Bellini noticed a group of bacteria that evidently oriented themselves in a unique direction. He realized these microorganisms moved according to the direction of the North Pole, and hence called them "magnetosensitive bacteria". The publications were academic (peer-reviewed by the Istituto di Microbiologia's editorial committee under responsibility of the Institute's Director Prof. L. Bianchi, as usual in European universities at the time) and communicated in Italian with English, French and German short summaries in the official journal of a well-known institution, yet unexplainedly seem to have attracted little attention until they were brought to the attention of Richard Frankel in 2007. Frankel translated them into English and the translations were published in the Chinese Journal of Oceanography and Limnology. Richard Blakemore, then a microbiology graduate student at the University of Massachusetts at Amherst, working in the Woods Hole Oceanographic Institution in whose collections the pertinent publications of the Institute of Microbiology of the University of Pavia were extant, observed microorganisms following the direction of Earth's magnetic field. Blakemore did not mention Bellini's research in his own report, which he published in Science, but was able to observe magnetosome chains using an electron microscope. Bellini's terms for this behavior, namely Italian: batteri magnetosensibili, French: bactéries magnétosensibles or bactéries aimantées, German: magnetisch empfindliche Bakterien and English: magnetosensitive bacteria (Bellini's first publication, last page), went forgotten, and Blakemore's "magnetotaxis" was adopted by the scientific community. These bacteria have been the subject of many experiments. They have even been aboard the Space Shuttle to examine their magnetotactic properties in the absence of gravity, but a definitive conclusion was not reached. The sensitivity of magnetotactic bacteria to the Earth's magnetic field arises from the fact these bacteria precipitate chains of crystals of magnetic minerals within their cells. To date, all magnetotactic bacteria are reported to precipitate either magnetite or greigite. These crystals, and sometimes the chains of crystals, can be preserved in the geological record as magnetofossils. The oldest unambiguous magnetofossils come from the Cretaceous chalk beds of southern England, though less certain reports of magnetofossils extend to 1.9 billion years old Gunflint chert. There have also been claims of their existence on Mars based on the shape of magnetite particles within the Martian meteorite ALH84001, but these claims are highly contested. Biology[edit] Several different morphologies (shapes) of MTB exist, differing in number, layout and pattern of the bacterial magnetic particles (BMPs) they contain. The MTBs can be subdivided into two categories, according to whether they produce particles of magnetite (Fe3O4) or of greigite (Fe3S4), although some species are capable of producing both. Magnetite possesses a magnetic moment with three times the magnitude of greigite. Magnetite-producing magnetotactic bacteria are usually found in an oxic-anoxic transition zone (OATZ), the transition zone between oxygen-rich and oxygen-starved water or sediment. Many MTB are able to survive only in environments with very limited oxygen, and some can exist only in completely anaerobic environments. It has been postulated that the evolutionary advantage of possessing a system of magnetosomes is linked to the ability to efficiently navigate within this zone of sharp chemical gradients by simplifying a potential three-dimensional search for more favorable conditions to a single dimension. (See § Magnetism for a description of this mechanism.) Some types of magnetotactic bacteria can produce magnetite even in anaerobic conditions, using nitric oxide, nitrate, or sulfate as a final acceptor for electrons. The greigite mineralizing MTBs are usually strictly anaerobic. It has been suggested MTB evolved in the early Archean Eon, as the increase in atmospheric oxygen meant that there was an evolutionary advantage for organisms to have magnetic navigation. Magnetosomes first evolved as a defense mechanism in response to the increase of reactive oxygen species (ROS) that resulted from the Great Oxygenation Event. Organisms began to store iron in some form, and this intracellular iron was later adapted to form magnetosomes for magnetotaxis. These early MTB may have participated in the formation of the first eukaryotic cells. Biogenic magnetite similar to that found in magnetotactic bacteria has been also found in higher organisms, from euglenoid algae to trout. Reports in humans and pigeons are far less advanced. Magnetotactic bacteria organize their magnetosomes in linear chains. The magnetic dipole moment of the cell is therefore the sum of the dipole moment of each BMP, which is then sufficient to passively orient the cell and overcome the casual thermal forces found in a water environment. In the presence of more than one chain, the inter-chain repulsive forces will push these structures to the edge of the cell, inducing turgor. Nearly all of the genes relevant to magnetotaxis in MTB are located in an approximately 80 kilobase region in the genome called the magnetosome island. There are three main operons in the magnetosome island: the mamAB operon, the mamGFDC operon, and the mms6 operon. There are 9 genes that are essential for the formation and function of modern magnetosomes: mamA, mamB, mamE, mamI, mamK, mamM, mamO, mamP, and mamQ. In addition to these 9 genes that are well conserved across all MTB, there are more than 30 total genes that contribute to magnetotaxis in MTB. These non-essential genes account for the variation in magnetite/greigite crystal size and shape, as well as the specific alignment of magnetosomes in the cell. The diversity of MTB is reflected by the high number of different morphotypes found in environmental samples of water or sediment. Commonly observed morphotypes include spherical or ovoid cells (cocci), rod-shaped (bacilli), and spiral bacteria of various dimensions. One of the more distinctive morphotypes is an apparently multicellular bacterium referred to as the many-celled magnetotactic prokaryote (MMP). Regardless of their morphology, all MTB studied so far are motile by means of flagella and are gram-negative bacteria of various phyla. Despite the majority of known species being Pseudomonadota, e.g. Magnetospirillum magneticum, an alphaproteobacterium, members of various phyla possess the magnetosome gene cluster, such as Candidatus Magnetobacterium bavaricum, a Nitrospira. The arrangement of flagella differs and can be polar, bipolar, or in tufts. The first phylogenetic analysis on magnetotactic bacteria using 16S rRNA gene sequence comparisons was performed by P. Eden et al. in 1991. Another trait that shows considerable diversity is the arrangement of magnetosomes inside the bacterial cell. In the majority of MTB, the magnetosomes are aligned in chains of various lengths and numbers along the cell's long axis, which is magnetically the most efficient orientation. However, dispersed aggregates or clusters of magnetosomes occur in some MTB, usually at one side of the cell, which often corresponds to the site of flagellar insertion. Besides magnetosomes, large inclusion bodies containing elemental sulfur, polyphosphate, or poly-β-hydroxybutyrate are common in MTB. The most abundant type of MTB occurring in environmental samples, especially sediments, are coccoid cells possessing two flagellar bundles on a somewhat flattened side. This "bilophotrichous" type of flagellation gave rise to the tentative genus "Bilophococcus" for these bacteria. In contrast, two of the morphologically more conspicuous MTB, regularly observed in natural samples, but never isolated in pure culture, are the MMP and a large rod containing copious amounts of hook-shaped magnetosomes (Magnetobacterium bavaricum). Magnetism[edit] The physical development of a magnetic crystal is governed by two factors: one is moving to align the magnetic force of the molecules in conjunction with the developing crystal, while the other reduces the magnetic force of the crystal, allowing an attachment of the molecule while experiencing an opposite magnetic force. In nature, this causes the existence of a magnetic domain, surrounding the perimeter of the domain, with a thickness of approximately 150 nm of magnetite, within which the molecules gradually change orientation. For this reason, the iron is not magnetic in the absence of an applied field. Likewise, extremely small magnetic particles do not exhibit signs of magnetisation at room temperature; their magnetic force is continuously altered by the thermal motions inherent in their composition. Instead, individual magnetite crystals in MTB are of a size between 35 and 120 nm, that is; large enough to have a magnetic field and at the same time small enough to remain a single magnetic domain. The MTB polarity model The inclination of the Earth's magnetic field in the two respective hemispheres selects one of the two possible polarities of the magnetotactic cells (with respect to the flagellated pole of the cell), orienting the biomineralisation of the magnetosomes. Aerotaxis is the response by which bacteria migrate to an optimal oxygen concentration in an oxygen gradient. Various experiments have clearly shown that magnetotaxis and aerotaxis work in conjunction in magnetotactic bacteria. It has been shown that, in water droplets, one-way swimming magnetotactic bacteria can reverse their swimming direction and swim backwards under reducing conditions (less than optimal oxygen concentration), as opposed to oxic conditions (greater than optimal oxygen concentration). The behaviour that has been observed in these bacterial strains has been referred to as magneto-aerotaxis. Two different magneto-aerotactic mechanisms—known as polar and axial—are found in different MTB strains. Some strains that swim persistently in one direction along the magnetic field (either north-seeking [NS] or south-seeking [SS])—mainly the magnetotactic cocci—are polar magneto-aerotactic. These magnetotactic bacteria will travel along the lines of the earth's magnetic field according to their orientation, but will swerve as a group and reverse direction if exposed to a local, more powerful and oppositely-oriented magnetic field. In this way, they continue to travel in the same magnetic direction, but relative instead to the local field. Those MTB that swim in either direction along magnetic field lines with frequent, spontaneous reversals of swimming direction without turning around—for example, freshwater spirilla—are axial magneto-aerotactic and the distinction between NS and SS does not apply to these bacteria. The magnetic field provides both an axis and a direction of motility for polar magneto-aerotactic bacteria, whereas it only provides an axis of motility for axial types of bacteria. In both cases, magnetotaxis increases the efficiency of aerotaxis in vertical concentration gradients by reducing a three-dimensional search to a single dimension. Scientists have also proposed an extension of the described model of magneto-aerotaxis to a more complex redoxtaxis. In this case, the unidirectional movement of MTB in a drop of water would be only one aspect of a sophisticated redox-controlled response. One hint for the possible function of polar magnetotaxis could be that most of the representative microorganisms are characterised by possessing either large sulfur inclusions or magnetosomes consisting of iron-sulfides. Therefore, it may be speculated that the metabolism of these bacteria, being either chemolithoautotrophic or mixotrophic, is strongly dependent on the uptake of reduced sulfur compounds, which occurs in many habitats only in deeper regions at or below the OATZ due to the rapid chemical oxidation of these reduced chemical species by oxygen or other oxidants in the upper layers. Microorganisms belonging to the genus Thioploca, for example, use nitrate, which is stored intracellularly, to oxidize sulfide, and have developed vertical sheaths in which bundles of motile filaments are located. It is assumed that Thioploca use these sheathes to move efficiently in a vertical direction in sediment, thereby accumulating sulfide in deeper layers and nitrate in upper layers. For some MTB, it might also be necessary to perform excursions to anoxic zones of their habitat to accumulate reduced sulfur compounds. Magnetosomes[edit] The biomineralisation of magnetite (Fe3O4) requires regulating mechanisms to control the concentration of iron, the crystal nucleation, the redox potential and the acidity (pH). This is achieved by means of compartmentalisation in structures known as magnetosomes that allow the biochemical control of the above-mentioned processes. After the genome of several MTB species had been sequenced, a comparative analysis of the proteins involved in the formation of the BMP became possible. Sequence homology with proteins belonging to the ubiquitous cation diffusion facilitator (CDF) family and the "Htr-like" serine proteases has been found. While the first group is exclusively dedicated to the transport of heavy metals, the second group consists of heat shock proteins (HSPs) involved in the degradation of badly folded proteins. Other than the serine protease domain, some proteins found in the magnetosomial membrane (MM) also contain PDZ domains, while several other MM proteins contain tetratricopeptide repeat (TPR) domains. TPR domain[edit] Main article: Tetratricopeptide repeat The TPR domains are characterized by a folding consisting of two α-helices and include a highly conserved consensus sequence of 8 amino acids (of the 34 possible), which is the most common in nature. Apart from these amino acids, the remainder of the structure is found to be specialised in relation to its functional significance. The more notable compounds that comprise TPR domains include: membrane-bound transport complexes conveying proteins within mitochondria and/or peroxisomes complexes that recognise DNA-binding proteins and repress DNA transcription the anaphase-promoting complex (APC). Examples of both the TPR-TPR interactions, as well as TPR-nonTPR interactions, have been reported. PDZ domain[edit] Main article: PDZ domain The PDZ domains are structures that consist of 6 β-filaments and 2 α-helices that recognise the C-terminal amino acids of proteins in a sequence-specific manner. Usually, the third residue from the C-terminal is phosphorylated, preventing interaction with the PDZ domain. The only conserved residues in these structures are those involved in the recognition of the carboxy terminal. PDZ domains are quite widespread in nature, since they constitute the basic structure upon which multiproteinic complexes are assembled. This is especially true for those associated with membrane proteins, such as the inward rectifier K channels or the β2-adrenergic receptors. Membrane and proteins[edit] The formation of the magnetosome requires at least three steps: Invagination of the magnetosome membrane (MM) Entrance of magnetite precursors into the newly formed vesicle Nucleation and growth of the magnetite crystal The first formation of an invagination in the cytoplasmic membrane is triggered by a GTPase. It is supposed this process can take place amongst eukaryotes, as well. The second step requires the entrance of ferric ions into the newly formed vesicles from the external environment. Even when cultured in a Fe deficient medium, MTB succeed at accumulating high intracellular concentrations of this ion. It has been suggested that they accomplish this by secreting, upon need, a siderophore, a low-molecular-weight ligand displaying an elevated affinity for Fe ions. The "Fe-siderophore" complex is subsequently moved in the cytoplasm, where it is cleaved. The ferric ions must then be converted into the ferrous form (Fe), to be accumulated within the BMP; this is achieved by means of a transmembrane transporter, which exhibits sequence homology with a Na/H antiporter. Furthermore, the complex is a H/Fe antiporter, which transports ions via the proton gradient. These transmembrane transporters are localised both in the cytoplasmic membrane and in the MM, but in an inverted orientation; this configuration allows them to generate an efflux of Fe ions at the cytoplasmic membrane, and an influx of this same ion at the MM. This step is strictly controlled by a cytochrome-dependent redox system, which is not yet fully explained and appears to be species-specific. During the final stage of the process, the magnetite crystal nucleation is by action of transmembrane proteins with acidic and basic domains. One of these proteins, called Mms6, has also been employed for the artificial synthesis of magnetite, where its presence allows the production of crystals homogeneous in shape and size. It is likely that many other proteins associated with the MM could be involved in other roles, such as generation of supersaturated concentrations of iron, maintenance of reducing conditions, oxidisation of iron, and partial reduction and dehydration of hydrated iron compounds. Biomineralisation[edit] Several clues led to the hypothesis that different genetic sets exist for the biomineralisation of magnetite and greigite. In cultures of Magnetospirillum magnetotacticum, iron can not be replaced with other transition metals (Ti, Cr, Co, Cu, Ni, Hg, Pb) commonly found in the soil. In a similar manner, oxygen and sulfur are not interchangeable as nonmetallic substances of the magnetosome within the same species. From a thermodynamic point of view, in the presence of a neutral pH and a low redox potential, the inorganic synthesis of magnetite is favoured when compared to those of other iron oxides. It would thus appear microaerophilic or anaerobic conditions create a suitable potential for the formation of BMPs. Moreover, all iron absorbed by the bacteria is rapidly converted into magnetite, indicating the formation of crystals is not preceded by the accumulation of intermediate iron compounds; this also suggests the structures and the enzymes necessary for biomineralisation are already present within the bacteria. These conclusions are also supported by the fact that MTB cultured in aerobic conditions (and thus nonmagnetic) contain amounts of iron comparable to any other species of bacteria. Symbiosis with other species[edit] Symbiosis with magnetotactic bacteria has been proposed as the explanation for magnetoreception in some marine protists. Research is underway on whether a similar relationship may underlie magnetoreception in vertebrates as well. Biotechnology applications[edit] In certain types of applications, bacterial magnetite offers several advantages compared to chemically synthesized magnetite. Bacterial magnetosome particles, unlike those produced chemically, have a consistent shape, a narrow size distribution within the single magnetic domain range, and a membrane coating consisting of lipids and proteins. The magnetosome envelope allows for easy couplings of bioactive substances to its surface, a characteristic important for many applications. Magnetotactic bacterial cells have been used to determine south magnetic poles in meteorites and rocks containing fine-grained magnetic minerals and for the separation of cells after the introduction of magnetotactic bacterial cells into granulocytes and monocytes by phagocytosis. Magnetotactic bacterial magnetite crystals have been used in studies of magnetic domain analysis and in many commercial applications including: the immobilisation of enzymes; the formation of magnetic antibodies, and the quantification of immunoglobulin G; the detection and removal of Escherichia coli cells with a fluorescein isothiocyanate conjugated monoclonal antibody, immobilised on magnetotactic bacterial magnetite particles; and the introduction of genes into cells, a technology in which magnetosomes are coated with DNA and "shot" using a particle gun into cells that are difficult to transform using more standard methods. However, the prerequisite for any large-scale commercial application is mass cultivation of magnetotactic bacteria or the introduction and expression of the genes responsible for magnetosome synthesis into a bacterium, e.g., E. coli, that can be grown relatively cheaply to extremely large yields. Although some progress has been made, the former has not been achieved with the available pure cultures. Further reading[edit] "The Formation of Iron Biominerals ", pp 159–184 in "Metals, Microbes and Minerals: The Biogeochemical Side of Life" (2021) pp xiv + 341. Walter de Gruyter, Berlin. Authors Uebe, René; Schüler, Dirk; Editors Kroneck, Peter M.H. and Sosa Torres, Martha. DOI 10.1515/9783110589771-006 Bibliography[edit] ^ Lin, Wei; Zhang, Wensi; Zhao, Xiang; Roberts, Andrew; Paterson, Greig; Bazylinski, Dennis; Pan, Yongxin (26 March 2018). "Genomic expansion of magnetotactic bacteria reveals an early common origin of magnetotaxis with lineage-specific evolution". The ISME Journal. 12 (6): 1508–1519. doi:10.1038/s41396-018-0098-9. PMC 5955933. PMID 29581530. ^ Dusenbery, David B. (2009). Living at micro scale : the unexpected physics of being small. Cambridge, Mass.: Harvard University Press. ISBN 978-0-674-03116-6. ^ Dusenbery, David B. (1996). "Life at Small Scale", pp. 100-101. Scientific American Library, New York. ISBN 0-7167-5060-0. ^ Bellini, S. (1963). Su di un particolare comportamento di batteri d'acqua dolce [On a unique behavior of freshwater bacteria] (PDF) (in Italian). Italy: Institute of Microbiology, University of Pavia. ^ Bellini, S. (1963). Ulteriori studi sui "batteri magnetosensibili" [Further studies on magnetosensitive bacteria] (PDF) (in Italian). Italy: Institute of Microbiology, University of Pavia. ^ Bellini, Salvatore (27 March 2009). "On a unique behavior of freshwater bacteria". Chinese Journal of Oceanology and Limnology. 27 (1): 3–5. Bibcode:2009ChJOL..27....3B. doi:10.1007/s00343-009-0003-5. S2CID 86828549. ^ Bellini, Salvatore (27 March 2009). "Further studies on "magnetosensitive bacteria"". Chinese Journal of Oceanology and Limnology. 27 (1): 6–12. Bibcode:2009ChJOL..27....6B. doi:10.1007/s00343-009-0006-2. S2CID 86147382. ^ Frankel, Richard B. (27 March 2009). "The discovery of magnetotactic/magnetosensitive bacteria". Chinese Journal of Oceanology and Limnology. 27 (1): 1–2. Bibcode:2009ChJOL..27....1F. CiteSeerX 10.1.1.922.5692. doi:10.1007/s00343-009-0001-7. S2CID 86672505. ^ Komeili, Arash (January 2012). "Molecular mechanisms of compartmentalization and biomineralization in magnetotactic bacteria". FEMS Microbiology Reviews. 36 (1): 232–255. doi:10.1111/j.1574-6976.2011.00315.x. PMC 3540109. PMID 22092030. ^ Schaechter, Moselio, Ed.-in-Chief (2009). Encyclopedia of Microbiology, 3rd Ed. Vol. V. Academic Press, Elsevier. p. 230.{{cite book}}: CS1 maint: multiple names: authors list (link) ^ Blakemore, Richard (1975). "Magnetotactic Bacteria". Science. 190 (4212): 377–379. Bibcode:1975Sci...190..377B. doi:10.1126/science.170679. PMID 170679. S2CID 5139699. ^ Urban (2000). "Adverse effects of microgravity on the magnetotactic bacterium Magnetospirillum magnetotacticum". Acta Astronautica. 47 (10): 775–780. 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"Controlled biomineralization of magnetic minerals by magnetotactic bacteria". Chemical Geology. 132 (1–4): 191–198. Bibcode:1996ChGeo.132..191B. doi:10.1016/S0009-2541(96)00055-1. ^ Lin, Wei; Paterson, Greig; Zhu, Qiyun; Wang, Yinzhao; Kopylova, Evguenia; Li, Ying; Rob, Knight (February 2017). "Origin of microbial biomineralization and magnetotaxis during the Archean". Proceedings of the National Academy of Sciences. 114 (9): 2171–2176. Bibcode:2017PNAS..114.2171L. doi:10.1073/pnas.1614654114. PMC 5338559. PMID 28193877. ^ Guo, Fang; Yang, Wei; Jiang, Wei; Geng, Shuang; Peng, Tao; Ji, Li (February 2012). "Magnetosomes eliminate intracellular reactive oxygen species in Magnetospirillum gryphiswaldense MSR-1". Environmental Microbiology. 14 (7): 1722–9. doi:10.1111/j.1462-2920.2012.02707.x. PMID 22360568. ^ Eder SH, Cadiou H, Muhamad A, McNaughton PA, Kirschvink JL, Winklhofer M (Jul 24, 2012). "Magnetic characterization of isolated candidate vertebrate magnetoreceptor cells". Proc Natl Acad Sci U S A. 109 (30): 12022–7. Bibcode:2012PNAS..10912022E. doi:10.1073/pnas.1205653109. PMC 3409731. PMID 22778440. ^ Treiber CD, Salzer MC, Riegler J, Edelman N, Sugar C, Breuss M, Pichler P, Cadiou H, Saunders M, Lythgoe M, Shaw J, Keays DA (Apr 11, 2012). "Clusters of iron-rich cells in the upper beak of pigeons are macrophages not magnetosensitive neurons". Nature. 484 (7394): 367–70. Bibcode:2012Natur.484..367T. doi:10.1038/nature11046. PMID 22495303. S2CID 205228624. ^ Schübbe, Sabrina; Kube, Michael; Scheffel, André; Wawer, Cathrin; Heyen, Udo; Meyerdierks, Anke; Madkour, Mohamed H.; Mayer, Frank; Reinhardt, Richard; Schüler, Dirk (1 October 2003). "Characterization of a spontaneous nonmagnetic mutant of Magnetospirillum gryphiswaldense reveals a large deletion comprising a putative magnetosome island". Journal of Bacteriology. 185 (19): 5779–5790. doi:10.1128/JB.185.19.5779-5790.2003. PMC 193972. PMID 13129949. ^ Lefèvre, Christopher T.; Trubitsyn, Denis; Abreu, Fernanda; Kolinko, Sebastian; Jogler, Christian; de Almeida, Luiz Gonzaga Paula; de Vasconcelos, Ana Tereza R.; Kube, Michael; Reinhardt, Richard; Lins, Ulysses; Pignol, David; Schüler, Dirk; Bazylinski, Dennis A.; Ginet, Nicolas (May 2013). "Comparative genomic analysis of magnetotactic bacteria from the Deltaproteobacteria provides new insights into magnetite and greigite magnetosome genes required for magnetotaxis". Environmental Microbiology. 25 (10): 2712–2735. doi:10.1111/1462-2920.12128. PMID 23607663. ^ Young KD (September 2006). "The selective value of bacterial shape". Microbiol Mol Biol Rev. 70 (3): 660–703. doi:10.1128/MMBR.00001-06. PMC 1594593. PMID 16959965. ^ Jogler, C.; Wanner, G.; Kolinko, S.; Niebler, M.; Amann, R.; Petersen, N.; Kube, M.; Reinhardt, R.; Schuler, D. (2010). "Conservation of proteobacterial magnetosome genes and structures in an uncultivated member of the deep-branching Nitrospira phylum". Proceedings of the National Academy of Sciences. 108 (3): 1134–1139. Bibcode:2011PNAS..108.1134J. doi:10.1073/pnas.1012694108. PMC 3024689. PMID 21191098. ^ Ruan J, Kato T, Santini CL, Miyata T, Kawamoto A, Zhang WJ, Bernadac A, Wu LF, Namba K (December 2012). "Architecture of a flagellar apparatus in the fast-swimming magnetotactic bacterium MO-1". Proc Natl Acad Sci U S A. 109 (50): 20643–8. Bibcode:2012PNAS..10920643R. doi:10.1073/pnas.1215274109. PMC 3528567. PMID 23184985. ^ Frankel, R. B., D. A. Bazylinski, and D. Schüler (1998). "Biomineralization of magnetic iron minerals in magnetotactic bacteria". J. Supramolecular Science. 5 (3–4): 383–390. doi:10.1016/S0968-5677(98)00036-4.{{cite journal}}: CS1 maint: multiple names: authors list (link) ^ Huettel, M., S. Forster, S. Kloser, and H. Fossing (1996). "Vertical migration in the sediment-dwelling sulfur bacteria Thioploca spp. in overcoming diffusion limitations". Appl. Environ. Microbiol. 62 (6): 1863–72. Bibcode:1996ApEnM..62.1863H. doi:10.1128/AEM.62.6.1863-1872.1996. PMC 1388866. PMID 16535328.{{cite journal}}: CS1 maint: multiple names: authors list (link) ^ Blatch GL, Lässle M (November 1999). "The tetratricopeptide repeat: a structural motif mediating protein-protein interactions". BioEssays. 21 (11): 932–9. doi:10.1002/(SICI)1521-1878(199911)21:11<932::AID-BIES5>3.0.CO;2-N. PMID 10517866. ^ Lamb, Tugendreich, Hieter (1995). "Tetratrico peptide repeat interactions: to TPR or not to TPR?". TIBS. 20 (7): 257–9. doi:10.1016/s0968-0004(00)89037-4. PMID 7667876.{{cite journal}}: CS1 maint: multiple names: authors list (link) ^ Sheng, Sala; Sala, C (2001). "PDZ domains and the organization of supramolecular complexes". Annu. Rev. Neurosci. 24: 1–29. doi:10.1146/annurev.neuro.24.1.1. PMID 11283303. ^ Matsunaga, Okamura; Okamura, Y (2003). "Genes and proteins involved in bacterial magnetic particle formation". Trends in Microbiology. 11 (11): 536–541. doi:10.1016/j.tim.2003.09.008. PMID 14607071. ^ Potential-pH diagrams for iron oxides in water ^ Schüler D.; Baeuerlein E. (January 1, 1998). "Dynamics of iron uptake and Fe3O4 biomineralization during aerobic and microaerobic growth of Magnetospirillum gryphiswaldense". Journal of Bacteriology. 180 (1): 159–62. doi:10.1128/JB.180.1.159-162.1998. PMC 106862. PMID 9422606. ^ Monteil, Caroline L.; Vallenet, David; Menguy, Nicolas; Benzerara, Karim; Barbe, Valérie; Fouteau, Stéphanie; Cruaud, Corinne; Floriani, Magali; Viollier, Eric; Adryanczyk, Géraldine; Leonhardt, Nathalie (July 2019). "Ectosymbiotic bacteria at the origin of magnetoreception in a marine protist". Nature Microbiology. 4 (7): 1088–1095. doi:10.1038/s41564-019-0432-7. ISSN 2058-5276. PMC 6697534. PMID 31036911. ^ Natan, Eviatar; Fitak, Robert Rodgers; Werber, Yuval; Vortman, Yoni (2020-09-28). "Symbiotic magnetic sensing: raising evidence and beyond". Philosophical Transactions of the Royal Society B: Biological Sciences. 375 (1808): 20190595. doi:10.1098/rstb.2019.0595. PMC 7435164. PMID 32772668. ^ Saiyed, Telang, Ramchand (2003). "Application of magnetic techniques in the field of drug discovery and biomedicine". Biomagnetic Research and Technology. 1 (1): 2. doi:10.1186/1477-044X-1-2. PMC 212320. PMID 14521720.{{cite journal}}: CS1 maint: multiple names: authors list (link) External links[edit] http://www.gps.caltech.edu/~jkirschvink/magnetofossil.html http://www.calpoly.edu/~rfrankel/mtbcalpoly.html Magnetotactic Bacteria Photo Gallery http://www.agu.org/revgeophys/moskow01/moskow01.html Archived 2007-01-11 at the Wayback Machine Comparative Genome Analysis of Four Magnetotactic Bacteria Reveals a Complex Set of Group-Specific Genes Implicated in Magnetosome Biomineralization and Function Journal of Bacteriology, July 2007	biology	164678	https://no.wikipedia.org/wiki/Mutualisme%20%28biologi%29	Mutualisme (biologi)	Mutualisme i biologi er en interaksjon mellom to arter der begge arter drar fordel av interaksjonen. Mutualisme en form for symbiose. Velkjente eksempler på mutualisme er: lav, der en sopp og en alge eller blågrønnbakterie lever sammen og soppen sørger for bl.a. vann, næringssalter og beskyttelse og algen/blågrønnbakterien sørger for karbohydrater via fotosyntese. Pussefisk som leppefisker som spiser parasitter fra større fisk. Dyrepollinering der pollinatoren skaffer seg en ressurs, ofte mat, og planta oppnår befruktning. Nitrogenfikserende bakterier som finnes i røttene til flere plantegrupper og som tilfører planta nitrogenoksider samtidig som bakteriene er beskytta mot luftas oksygen. Hvor tett koblingen er mellom de to organismene er varierer, i noen tilfelle er en eller begge totalt avhengig av mutualismen for å overleve eller reprodusere. Dette kalles obligat mutualisme. I andre tilfeller er avhengigheten ikke livsnødvendig, den er fakultativ. Eksempler på begge typer finnes inne pollinering. I de fleste tilfeller vil både planta og dyret kunne nyttiggjøre seg flere ulike arter og mutualismen mellom to bestemte arter er fakultativ. Imidlertid er det noen tilfeller der en planteart er helt avhengig av en insektart. Slik obligat mutalisme finnes mellom fiken og fikenveps og trolig mellom Madaskars stjerneorkide (Anaegraceum sesquipedale) og dens pollinator, Xanthopan morgani praedicta. Økologi	norwegian_bokmål	0.687766
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Order threshold must be met with pre-tax total. See our shipping page for more information about shipping rates and options. Location & Contact Leaf & Node LLC P.O. Box 595 Tipp City, OH 45371 Contact us via email: [email protected] Information & Policies Shipping Information Return Policy Wholesale Inquiries Sweepstakes Rules Privacy Policy Terms of Service Link List Email Sign-up How-to Guides Get Exclusive Discounts & Deals Enter email here Sign up for our email list to get exclusive discounts and new product announcements in your inbox. Leaf & Node sends 2-4 emails per month. Let's Be Friends on Social Facebook Instagram Follow us on social media! © 2024, Leaf & Node . All rights reserved. Powered by Shopify Country/region AUD $ EUR € EUR € CAD $ CZK Kč DKK kr. 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Finland (EUR €) France (EUR €) Germany (EUR €) Hong Kong SAR (HKD $) Ireland (EUR €) Israel (ILS ₪) Italy (EUR €) Japan (JPY ¥) Malaysia (MYR RM) Netherlands (EUR €) New Zealand (NZD $) Norway (USD $) Poland (PLN zł) Portugal (EUR €) Singapore (SGD $) South Korea (KRW ₩) Spain (EUR €) Sweden (SEK kr) Switzerland (CHF CHF) United Arab Emirates (AED د.إ) United Kingdom (GBP £) Payment methods Amazon American Express Apple Pay Diners Club Discover Meta Pay Google Pay Mastercard PayPal Shop Pay Venmo Visa Home Shop Shop Propagation Stations Indoor Plant Trellises Air Plant Holders Jewelry Decorative Plant Stakes Plant Magnets Contact About Blog Log in Facebook Instagram Home Shop Propagation Stations Indoor Plant Trellises Air Plant Holders Jewelry Decorative Plant Stakes Plant Magnets Contact About Blog Search our site Log in Cart Cart Home Shop Shop Propagation Stations Indoor Plant Trellises Air Plant Holders Jewelry Decorative Plant Stakes Plant Magnets Contact About Blog Log in Facebook Instagram Home Shop Shop Propagation Stations Indoor Plant Trellises Air Plant Holders Jewelry Decorative Plant Stakes Plant Magnets Contact About Blog Log in Facebook Instagram Home Shop Shop Propagation Stations Indoor Plant Trellises Air Plant Holders Jewelry Decorative Plant Stakes Plant Magnets Contact About Blog Log in Facebook Instagram Shop Propagation Stations Indoor Plant Trellises Air Plant Holders Jewelry Decorative Plant Stakes Plant Magnets Shop Propagation Stations Indoor Plant Trellises Air Plant Holders Jewelry Decorative Plant Stakes Plant Magnets Collection: Plant Magnets Make space on your magnetic surfaces for these functional and adorable wooden plant magnets ! Customers love using them on refrigerators , metal plant shelves , and greenhouse cabinets . Or, maybe you're s hopping for unique gift ideas for a plant lover you know? These plant themed décor items are perfect for gifting to plant moms and dads! 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Order threshold must be met with pre-tax total. See our shipping page for more information about shipping rates and options. Location & Contact Leaf & Node LLC P.O. Box 595 Tipp City, OH 45371 Contact us via email: [email protected] Information & Policies Shipping Information Return Policy Wholesale Inquiries Sweepstakes Rules Privacy Policy Terms of Service Link List Email Sign-up How-to Guides Get Exclusive Discounts & Deals Enter email here Sign up for our email list to get exclusive discounts and new product announcements in your inbox. Leaf & Node sends 2-4 emails per month. Let's Be Friends on Social Facebook Instagram Follow us on social media! © 2024, Leaf & Node . All rights reserved. Powered by Shopify Country/region AUD $ EUR € EUR € CAD $ CZK Kč DKK kr. EUR € EUR € EUR € HKD $ EUR € ILS ₪ EUR € JPY ¥ MYR RM EUR € NZD $ USD $ PLN zł EUR € SGD $ KRW ₩ EUR € SEK kr CHF CHF AED د.إ GBP £ USD $ Update country/region Country/region United States (USD $) United States (USD $) Australia (AUD $) Austria (EUR €) Belgium (EUR €) Canada (CAD $) Czechia (CZK Kč) Denmark (DKK kr.) Finland (EUR €) France (EUR €) Germany (EUR €) Hong Kong SAR (HKD $) Ireland (EUR €) Israel (ILS ₪) Italy (EUR €) Japan (JPY ¥) Malaysia (MYR RM) Netherlands (EUR €) New Zealand (NZD $) Norway (USD $) Poland (PLN zł) Portugal (EUR €) Singapore (SGD $) South Korea (KRW ₩) Spain (EUR €) Sweden (SEK kr) Switzerland (CHF CHF) United Arab Emirates (AED د.إ) United Kingdom (GBP £) Payment methods Amazon American Express Apple Pay Diners Club Discover Meta Pay Google Pay Mastercard PayPal Shop Pay Venmo Visa Collection: Plant Magnets Make space on your magnetic surfaces for these functional and adorable wooden plant magnets ! Customers love using them on refrigerators , metal plant shelves , and greenhouse cabinets . Or, maybe you're s hopping for unique gift ideas for a plant lover you know? These plant themed décor items are perfect for gifting to plant moms and dads! Collection: Plant Magnets Make space on your magnetic surfaces for these functional and adorable wooden plant magnets ! Customers love using them on refrigerators , metal plant shelves , and greenhouse cabinets . Or, maybe you're s hopping for unique gift ideas for a plant lover you know? These plant themed décor items are perfect for gifting to plant moms and dads! Collection: Plant Magnets Make space on your magnetic surfaces for these functional and adorable wooden plant magnets ! Customers love using them on refrigerators , metal plant shelves , and greenhouse cabinets . Or, maybe you're s hopping for unique gift ideas for a plant lover you know? These plant themed décor items are perfect for gifting to plant moms and dads! Collection: Plant Magnets Make space on your magnetic surfaces for these functional and adorable wooden plant magnets ! Customers love using them on refrigerators , metal plant shelves , and greenhouse cabinets . Or, maybe you're s hopping for unique gift ideas for a plant lover you know? These plant themed décor items are perfect for gifting to plant moms and dads! Make space on your magnetic surfaces for these functional and adorable wooden plant magnets ! Customers love using them on refrigerators , metal plant shelves , and greenhouse cabinets . Or, maybe you're s hopping for unique gift ideas for a plant lover you know? These plant themed décor items are perfect for gifting to plant moms and dads! Make space on your magnetic surfaces for these functional and adorable wooden plant magnets ! Customers love using them on refrigerators , metal plant shelves , and greenhouse cabinets . Or, maybe you're s hopping for unique gift ideas for a plant lover you know? These plant themed décor items are perfect for gifting to plant moms and dads! Customers love using them on refrigerators , metal plant shelves , and greenhouse cabinets . 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Dad - Lover Magnet Plant Lady - Dad - Lover Magnet Regular price $6.95 Regular price Sale price $6.95 Choose options Quick view Plant Magnets - "Starter Pack" (Set of 4) Plant Magnets - "Starter Pack" (Set of 4) 1 review Regular price $18.95 Regular price Sale price $18.95 5.0 / 5.0 (1) 1 total reviews Add to cart Quick view Hoya Plant Magnets (Set of 4) Hoya Plant Magnets (Set of 4) Regular price $18.95 Regular price Sale price $18.95 Add to cart Quick view Monstera Deliciosa “Swiss Cheese Plant” - Plant Magnet Monstera Deliciosa “Swiss Cheese Plant” - Plant Magnet Regular price $4.95 Regular price Sale price $4.95 Add to cart Quick view Pothos or Heartleaf Philodendron - Plant Magnet Pothos or Heartleaf Philodendron - Plant Magnet Regular price $4.95 Regular price Sale price $4.95 Add to cart Quick view Ficus Lyrata "Fiddle Leaf Fig" - Plant Magnet Ficus Lyrata "Fiddle Leaf Fig" - Plant Magnet Regular price $4.95 Regular price Sale price $4.95 Add to cart Quick view ZZ Plant - Plant Magnet ZZ Plant - Plant Magnet Regular price $4.95 Regular price Sale price $4.95 Add to cart Quick view Sansevieria "Snake Plant" - Plant Magnet Sansevieria "Snake Plant" - Plant Magnet Regular price $4.95 Regular price Sale price $4.95 Add to cart Quick view Philodendron (Squamiferum, Florida Green) - Plant Magnet Philodendron (Squamiferum, Florida Green) - Plant Magnet Regular price $4.95 Regular price Sale price $4.95 Add to cart Quick view Opuntia Cactus "Prickly Pear" - Plant Magnet Opuntia Cactus "Prickly Pear" - Plant Magnet Regular price $4.95 Regular price Sale price $4.95 Add to cart Quick view Hoya Kerrii ("Sweetheart Hoya") - Plant Magnet Hoya Kerrii ("Sweetheart Hoya") - Plant Magnet Regular price $4.95 Regular price Sale price $4.95 Add to cart Quick view Hoya Polyneura ("Fishtail Hoya") - Plant Magnet Hoya Polyneura ("Fishtail Hoya") - Plant Magnet Regular price $4.95 Regular price Sale price $4.95 Add to cart Quick view Hoya Obovata - Plant Magnet Hoya Obovata - Plant Magnet Regular price $4.95 Regular price Sale price $4.95 Add to cart Quick view Hoya Wayettii or Kentiana - Plant Magnet Hoya Wayettii or Kentiana - Plant Magnet Regular price $4.95 Regular price Sale price $4.95 Add to cart Quick view Plant Lady - Dad - Lover Magnet Plant Lady - Dad - Lover Magnet Regular price $6.95 Regular price Sale price $6.95 Choose options Quick view Plant Magnets - "Starter Pack" (Set of 4) Plant Magnets - "Starter Pack" (Set of 4) 1 review Regular price $18.95 Regular price Sale price $18.95 5.0 / 5.0 (1) 1 total reviews Add to cart Quick view Hoya Plant Magnets (Set of 4) Hoya Plant Magnets (Set of 4) Regular price $18.95 Regular price Sale price $18.95 Add to cart Quick view Monstera Deliciosa “Swiss Cheese Plant” - Plant Magnet Monstera Deliciosa “Swiss Cheese Plant” - Plant Magnet Regular price $4.95 Regular price Sale price $4.95 Add to cart Quick view Pothos or Heartleaf Philodendron - Plant Magnet Pothos or Heartleaf Philodendron - Plant Magnet Regular price $4.95 Regular price Sale price $4.95 Add to cart Quick view Ficus Lyrata "Fiddle Leaf Fig" - Plant Magnet Ficus Lyrata "Fiddle Leaf Fig" - Plant Magnet Regular price $4.95 Regular price Sale price $4.95 Add to cart Quick view ZZ Plant - Plant Magnet ZZ Plant - Plant Magnet Regular price $4.95 Regular price Sale price $4.95 Add to cart Quick view Sansevieria "Snake Plant" - Plant Magnet Sansevieria "Snake Plant" - Plant Magnet Regular price $4.95 Regular price Sale price $4.95 Add to cart Quick view Philodendron (Squamiferum, Florida Green) - Plant Magnet Philodendron (Squamiferum, Florida Green) - Plant Magnet Regular price $4.95 Regular price Sale price $4.95 Add to cart Quick view Opuntia Cactus "Prickly Pear" - Plant Magnet Opuntia Cactus "Prickly Pear" - Plant Magnet Regular price $4.95 Regular price Sale price $4.95 Add to cart Quick view Hoya Kerrii ("Sweetheart Hoya") - Plant Magnet Hoya Kerrii ("Sweetheart Hoya") - Plant Magnet Regular price $4.95 Regular price Sale price $4.95 Add to cart Quick view Hoya Polyneura ("Fishtail Hoya") - Plant Magnet Hoya Polyneura ("Fishtail Hoya") - Plant Magnet Regular price $4.95 Regular price Sale price $4.95 Add to cart Quick view Hoya Obovata - Plant Magnet Hoya Obovata - Plant Magnet Regular price $4.95 Regular price Sale price $4.95 Add to cart Quick view Hoya Wayettii or Kentiana - Plant Magnet Hoya Wayettii or Kentiana - Plant Magnet Regular price $4.95 Regular price Sale price $4.95 Add to cart Quick view Plant Lady - Dad - Lover Magnet Plant Lady - Dad - Lover Magnet Regular price $6.95 Regular price Sale price $6.95 Choose options Quick view Plant Magnets - "Starter Pack" (Set of 4) Plant Magnets - "Starter Pack" (Set of 4) 1 review Regular price $18.95 Regular price Sale price $18.95 5.0 / 5.0 (1) 1 total reviews Add to cart Quick view Hoya Plant Magnets (Set of 4) Hoya Plant Magnets (Set of 4) Regular price $18.95 Regular price Sale price $18.95 Add to cart Quick view Monstera Deliciosa “Swiss Cheese Plant” - Plant Magnet Monstera Deliciosa “Swiss Cheese Plant” - Plant Magnet Regular price $4.95 Regular price Sale price $4.95 Add to cart Quick view Pothos or Heartleaf Philodendron - Plant Magnet Pothos or Heartleaf Philodendron - Plant Magnet Regular price $4.95 Regular price Sale price $4.95 Add to cart Quick view Ficus Lyrata "Fiddle Leaf Fig" - Plant Magnet Ficus Lyrata "Fiddle Leaf Fig" - Plant Magnet Regular price $4.95 Regular price Sale price $4.95 Add to cart Quick view ZZ Plant - Plant Magnet ZZ Plant - Plant Magnet Regular price $4.95 Regular price Sale price $4.95 Add to cart Quick view Sansevieria "Snake Plant" - Plant Magnet Sansevieria "Snake Plant" - Plant Magnet Regular price $4.95 Regular price Sale price $4.95 Add to cart Quick view Philodendron (Squamiferum, Florida Green) - Plant Magnet Philodendron (Squamiferum, Florida Green) - Plant Magnet Regular price $4.95 Regular price Sale price $4.95 Add to cart Quick view Opuntia Cactus "Prickly Pear" - Plant Magnet Opuntia Cactus "Prickly Pear" - Plant Magnet Regular price $4.95 Regular price Sale price $4.95 Add to cart Quick view Hoya Kerrii ("Sweetheart Hoya") - Plant Magnet Hoya Kerrii ("Sweetheart Hoya") - Plant Magnet Regular price $4.95 Regular price Sale price $4.95 Add to cart Quick view Hoya Polyneura ("Fishtail Hoya") - Plant Magnet Hoya Polyneura ("Fishtail Hoya") - Plant Magnet Regular price $4.95 Regular price Sale price $4.95 Add to cart Quick view Hoya Obovata - Plant Magnet Hoya Obovata - Plant Magnet Regular price $4.95 Regular price Sale price $4.95 Add to cart Quick view Hoya Wayettii or Kentiana - Plant Magnet Hoya Wayettii or Kentiana - Plant Magnet Regular price $4.95 Regular price Sale price $4.95 Add to cart Quick view Plant Lady - Dad - Lover Magnet Plant Lady - Dad - Lover Magnet Regular price $6.95 Regular price Sale price $6.95 Choose options Quick view Plant Magnets - "Starter Pack" (Set of 4) Plant Magnets - "Starter Pack" (Set of 4) 1 review Regular price $18.95 Regular price Sale price $18.95 5.0 / 5.0 (1) 1 total reviews Add to cart Quick view Plant Magnets - "Starter Pack" (Set of 4) 1 review Regular price $18.95 Regular price Sale price $18.95 5.0 / 5.0 (1) 1 total reviews Add to cart Plant Magnets - "Starter Pack" (Set of 4) 1 review Regular price $18.95 Regular price Sale price $18.95 5.0 / 5.0 (1) 1 total reviews Hoya Plant Magnets (Set of 4) Hoya Plant Magnets (Set of 4) Regular price $18.95 Regular price Sale price $18.95 Add to cart Quick view Monstera Deliciosa “Swiss Cheese Plant” - Plant Magnet Monstera Deliciosa “Swiss Cheese Plant” - Plant Magnet Regular price $4.95 Regular price Sale price $4.95 Add to cart Quick view Monstera Deliciosa “Swiss Cheese Plant” - Plant Magnet Regular price $4.95 Regular price Sale price $4.95 Add to cart Pothos or Heartleaf Philodendron - Plant Magnet Pothos or Heartleaf Philodendron - Plant Magnet Regular price $4.95 Regular price Sale price $4.95 Add to cart Quick view Pothos or Heartleaf Philodendron - Plant Magnet Regular price $4.95 Regular price Sale price $4.95 Add to cart Ficus Lyrata "Fiddle Leaf Fig" - Plant Magnet Ficus Lyrata "Fiddle Leaf Fig" - Plant Magnet Regular price $4.95 Regular price Sale price $4.95 Add to cart Quick view Ficus Lyrata "Fiddle Leaf Fig" - Plant Magnet Regular price $4.95 Regular price Sale price $4.95 Add to cart ZZ Plant - Plant Magnet ZZ Plant - Plant Magnet Regular price $4.95 Regular price Sale price $4.95 Add to cart Quick view Sansevieria "Snake Plant" - Plant Magnet Sansevieria "Snake Plant" - Plant Magnet Regular price $4.95 Regular price Sale price $4.95 Add to cart Quick view Philodendron (Squamiferum, Florida Green) - Plant Magnet Philodendron (Squamiferum, Florida Green) - Plant Magnet Regular price $4.95 Regular price Sale price $4.95 Add to cart Quick view Philodendron (Squamiferum, Florida Green) - Plant Magnet Regular price $4.95 Regular price Sale price $4.95 Add to cart Philodendron (Squamiferum, Florida Green) - Plant Magnet Regular price $4.95 Regular price Sale price $4.95 Opuntia Cactus "Prickly Pear" - Plant Magnet Opuntia Cactus "Prickly Pear" - Plant Magnet Regular price $4.95 Regular price Sale price $4.95 Add to cart Quick view Opuntia Cactus "Prickly Pear" - Plant Magnet Regular price $4.95 Regular price Sale price $4.95 Add to cart Hoya Kerrii ("Sweetheart Hoya") - Plant Magnet Hoya Kerrii ("Sweetheart Hoya") - Plant Magnet Regular price $4.95 Regular price Sale price $4.95 Add to cart Quick view Hoya Kerrii ("Sweetheart Hoya") - Plant Magnet Regular price $4.95 Regular price Sale price $4.95 Add to cart Hoya Polyneura ("Fishtail Hoya") - Plant Magnet Hoya Polyneura ("Fishtail Hoya") - Plant Magnet Regular price $4.95 Regular price Sale price $4.95 Add to cart Quick view Hoya Polyneura ("Fishtail Hoya") - Plant Magnet Regular price $4.95 Regular price Sale price $4.95 Add to cart Hoya Obovata - Plant Magnet Hoya Obovata - Plant Magnet Regular price $4.95 Regular price Sale price $4.95 Add to cart Quick view Hoya Wayettii or Kentiana - Plant Magnet Hoya Wayettii or Kentiana - Plant Magnet Regular price $4.95 Regular price Sale price $4.95 Add to cart Quick view UNIQUE PLANT DECOR & GIFTS HANDMADE from quality woods like cherry, maple, and mahogany STRONG MAGNETS make these decor items both lovely AND functional ORIGINAL DESIGNS feature a variety of common and rare houseplants EASY GIFT idea for plant lovers for any gifting occasion UNIQUE PLANT DECOR & GIFTS HANDMADE from quality woods like cherry, maple, and mahogany STRONG MAGNETS make these decor items both lovely AND functional ORIGINAL DESIGNS feature a variety of common and rare houseplants EASY GIFT idea for plant lovers for any gifting occasion HANDMADE from quality woods like cherry, maple, and mahogany STRONG MAGNETS make these decor items both lovely AND functional ORIGINAL DESIGNS feature a variety of common and rare houseplants EASY GIFT idea for plant lovers for any gifting occasion HANDMADE from quality woods like cherry, maple, and mahogany STRONG MAGNETS make these decor items both lovely AND functional ORIGINAL DESIGNS feature a variety of common and rare houseplants EASY GIFT idea for plant lovers for any gifting occasion HANDMADE from quality woods like cherry, maple, and mahogany STRONG MAGNETS make these decor items both lovely AND functional ORIGINAL DESIGNS feature a variety of common and rare houseplants EASY GIFT idea for plant lovers for any gifting occasion Leaf & Node's free shipping offer applies to economy shipping in the continental U.S. only. Order threshold must be met with pre-tax total. See our shipping page for more information about shipping rates and options. Leaf & Node's free shipping offer applies to economy shipping in the continental U.S. only. Order threshold must be met with pre-tax total. See our shipping page for more information about shipping rates and options. Leaf & Node's free shipping offer applies to economy shipping in the continental U.S. only. Order threshold must be met with pre-tax total. See our shipping page for more information about shipping rates and options. Leaf & Node's free shipping offer applies to economy shipping in the continental U.S. only. Order threshold must be met with pre-tax total. See our shipping page for more information about shipping rates and options. Location & Contact Leaf & Node LLC P.O. Box 595 Tipp City, OH 45371 Contact us via email: [email protected] Information & Policies Shipping Information Return Policy Wholesale Inquiries Sweepstakes Rules Privacy Policy Terms of Service Link List Email Sign-up How-to Guides Get Exclusive Discounts & Deals Enter email here Sign up for our email list to get exclusive discounts and new product announcements in your inbox. Leaf & Node sends 2-4 emails per month. Let's Be Friends on Social Facebook Instagram Follow us on social media! © 2024, Leaf & Node . All rights reserved. Powered by Shopify Country/region AUD $ EUR € EUR € CAD $ CZK Kč DKK kr. EUR € EUR € EUR € HKD $ EUR € ILS ₪ EUR € JPY ¥ MYR RM EUR € NZD $ USD $ PLN zł EUR € SGD $ KRW ₩ EUR € SEK kr CHF CHF AED د.إ GBP £ USD $ Update country/region Country/region United States (USD $) United States (USD $) Australia (AUD $) Austria (EUR €) Belgium (EUR €) Canada (CAD $) Czechia (CZK Kč) Denmark (DKK kr.) Finland (EUR €) France (EUR €) Germany (EUR €) Hong Kong SAR (HKD $) Ireland (EUR €) Israel (ILS ₪) Italy (EUR €) Japan (JPY ¥) Malaysia (MYR RM) Netherlands (EUR €) New Zealand (NZD $) Norway (USD $) Poland (PLN zł) Portugal (EUR €) Singapore (SGD $) South Korea (KRW ₩) Spain (EUR €) Sweden (SEK kr) Switzerland (CHF CHF) United Arab Emirates (AED د.إ) United Kingdom (GBP £) Payment methods Amazon American Express Apple Pay Diners Club Discover Meta Pay Google Pay Mastercard PayPal Shop Pay Venmo Visa Location & Contact Leaf & Node LLC P.O. Box 595 Tipp City, OH 45371 Contact us via email: [email protected] Information & Policies Shipping Information Return Policy Wholesale Inquiries Sweepstakes Rules Privacy Policy Terms of Service Link List Email Sign-up How-to Guides Get Exclusive Discounts & Deals Enter email here Sign up for our email list to get exclusive discounts and new product announcements in your inbox. Leaf & Node sends 2-4 emails per month. Let's Be Friends on Social Facebook Instagram Follow us on social media! Location & Contact Leaf & Node LLC P.O. Box 595 Tipp City, OH 45371 Contact us via email: [email protected] Information & Policies Shipping Information Return Policy Wholesale Inquiries Sweepstakes Rules Privacy Policy Terms of Service Link List Email Sign-up How-to Guides Get Exclusive Discounts & Deals Enter email here Sign up for our email list to get exclusive discounts and new product announcements in your inbox. Leaf & Node sends 2-4 emails per month. Let's Be Friends on Social Facebook Instagram Follow us on social media! Location & Contact Leaf & Node LLC P.O. Box 595 Tipp City, OH 45371 Contact us via email: [email protected] Information & Policies Shipping Information Return Policy Wholesale Inquiries Sweepstakes Rules Privacy Policy Terms of Service Link List Email Sign-up How-to Guides Location & Contact Leaf & Node LLC P.O. Box 595 Tipp City, OH 45371 Contact us via email: [email protected] Information & Policies Shipping Information Return Policy Wholesale Inquiries Sweepstakes Rules Privacy Policy Terms of Service Link List Email Sign-up How-to Guides Get Exclusive Discounts & Deals Enter email here Sign up for our email list to get exclusive discounts and new product announcements in your inbox. Leaf & Node sends 2-4 emails per month. Let's Be Friends on Social Facebook Instagram Follow us on social media! Get Exclusive Discounts & Deals Enter email here Sign up for our email list to get exclusive discounts and new product announcements in your inbox. Leaf & Node sends 2-4 emails per month. Let's Be Friends on Social Facebook Instagram Follow us on social media! Get Exclusive Discounts & Deals Enter email here Sign up for our email list to get exclusive discounts and new product announcements in your inbox. Leaf & Node sends 2-4 emails per month. Let's Be Friends on Social Facebook Instagram Follow us on social media! Enter email here Sign up for our email list to get exclusive discounts and new product announcements in your inbox. Leaf & Node sends 2-4 emails per month. Let's Be Friends on Social Facebook Instagram Follow us on social media! Enter email here Sign up for our email list to get exclusive discounts and new product announcements in your inbox. Leaf & Node sends 2-4 emails per month. Sign up for our email list to get exclusive discounts and new product announcements in your inbox. Leaf & Node sends 2-4 emails per month. Sign up for our email list to get exclusive discounts and new product announcements in your inbox. Leaf & Node sends 2-4 emails per month. © 2024, Leaf & Node . All rights reserved. Powered by Shopify Country/region AUD $ EUR € EUR € CAD $ CZK Kč DKK kr. EUR € EUR € EUR € HKD $ EUR € ILS ₪ EUR € JPY ¥ MYR RM EUR € NZD $ USD $ PLN zł EUR € SGD $ KRW ₩ EUR € SEK kr CHF CHF AED د.إ GBP £ USD $ Update country/region Country/region United States (USD $) United States (USD $) Australia (AUD $) Austria (EUR €) Belgium (EUR €) Canada (CAD $) Czechia (CZK Kč) Denmark (DKK kr.) Finland (EUR €) France (EUR €) Germany (EUR €) Hong Kong SAR (HKD $) Ireland (EUR €) Israel (ILS ₪) Italy (EUR €) Japan (JPY ¥) Malaysia (MYR RM) Netherlands (EUR €) New Zealand (NZD $) Norway (USD $) Poland (PLN zł) Portugal (EUR €) Singapore (SGD $) South Korea (KRW ₩) Spain (EUR €) Sweden (SEK kr) Switzerland (CHF CHF) United Arab Emirates (AED د.إ) United Kingdom (GBP £) Payment methods Amazon American Express Apple Pay Diners Club Discover Meta Pay Google Pay Mastercard PayPal Shop Pay Venmo Visa © 2024, Leaf & Node . All rights reserved. Powered by Shopify Country/region AUD $ EUR € EUR € CAD $ CZK Kč DKK kr. EUR € EUR € EUR € HKD $ EUR € ILS ₪ EUR € JPY ¥ MYR RM EUR € NZD $ USD $ PLN zł EUR € SGD $ KRW ₩ EUR € SEK kr CHF CHF AED د.إ GBP £ USD $ Update country/region Country/region United States (USD $) United States (USD $) Australia (AUD $) Austria (EUR €) Belgium (EUR €) Canada (CAD $) Czechia (CZK Kč) Denmark (DKK kr.) Finland (EUR €) France (EUR €) Germany (EUR €) Hong Kong SAR (HKD $) Ireland (EUR €) Israel (ILS ₪) Italy (EUR €) Japan (JPY ¥) Malaysia (MYR RM) Netherlands (EUR €) New Zealand (NZD $) Norway (USD $) Poland (PLN zł) Portugal (EUR €) Singapore (SGD $) South Korea (KRW ₩) Spain (EUR €) Sweden (SEK kr) Switzerland (CHF CHF) United Arab Emirates (AED د.إ) United Kingdom (GBP £) Payment methods Amazon American Express Apple Pay Diners Club Discover Meta Pay Google Pay Mastercard PayPal Shop Pay Venmo Visa Country/region AUD $ EUR € EUR € CAD $ CZK Kč DKK kr. EUR € EUR € EUR € HKD $ EUR € ILS ₪ EUR € JPY ¥ MYR RM EUR € NZD $ USD $ PLN zł EUR € SGD $ KRW ₩ EUR € SEK kr CHF CHF AED د.إ GBP £ USD $ Update country/region Country/region United States (USD $) United States (USD $) Australia (AUD $) Austria (EUR €) Belgium (EUR €) Canada (CAD $) Czechia (CZK Kč) Denmark (DKK kr.) Finland (EUR €) France (EUR €) Germany (EUR €) Hong Kong SAR (HKD $) Ireland (EUR €) Israel (ILS ₪) Italy (EUR €) Japan (JPY ¥) Malaysia (MYR RM) Netherlands (EUR €) New Zealand (NZD $) Norway (USD $) Poland (PLN zł) Portugal (EUR €) Singapore (SGD $) South Korea (KRW ₩) Spain (EUR €) Sweden (SEK kr) Switzerland (CHF CHF) United Arab Emirates (AED د.إ) United Kingdom (GBP £) Payment methods Amazon American Express Apple Pay Diners Club Discover Meta Pay Google Pay Mastercard PayPal Shop Pay Venmo Visa Country/region AUD $ EUR € EUR € CAD $ CZK Kč DKK kr. EUR € EUR € EUR € HKD $ EUR € ILS ₪ EUR € JPY ¥ MYR RM EUR € NZD $ USD $ PLN zł EUR € SGD $ KRW ₩ EUR € SEK kr CHF CHF AED د.إ GBP £ USD $ Update country/region Country/region United States (USD $) United States (USD $) Australia (AUD $) Austria (EUR €) Belgium (EUR €) Canada (CAD $) Czechia (CZK Kč) Denmark (DKK kr.) Finland (EUR €) France (EUR €) Germany (EUR €) Hong Kong SAR (HKD $) Ireland (EUR €) Israel (ILS ₪) Italy (EUR €) Japan (JPY ¥) Malaysia (MYR RM) Netherlands (EUR €) New Zealand (NZD $) Norway (USD $) Poland (PLN zł) Portugal (EUR €) Singapore (SGD $) South Korea (KRW ₩) Spain (EUR €) Sweden (SEK kr) Switzerland (CHF CHF) United Arab Emirates (AED د.إ) United Kingdom (GBP £) Country/region AUD $ EUR € EUR € CAD $ CZK Kč DKK kr. EUR € EUR € EUR € HKD $ EUR € ILS ₪ EUR € JPY ¥ MYR RM EUR € NZD $ USD $ PLN zł EUR € SGD $ KRW ₩ EUR € SEK kr CHF CHF AED د.إ GBP £ USD $ Country/region United States (USD $) United States (USD $) Australia (AUD $) Austria (EUR €) Belgium (EUR €) Canada (CAD $) Czechia (CZK Kč) Denmark (DKK kr.) Finland (EUR €) France (EUR €) Germany (EUR €) Hong Kong SAR (HKD $) Ireland (EUR €) Israel (ILS ₪) Italy (EUR €) Japan (JPY ¥) Malaysia (MYR RM) Netherlands (EUR €) New Zealand (NZD $) Norway (USD $) Poland (PLN zł) Portugal (EUR €) Singapore (SGD $) South Korea (KRW ₩) Spain (EUR €) Sweden (SEK kr) Switzerland (CHF CHF) United Arab Emirates (AED د.إ) United Kingdom (GBP £) United States (USD $) United States (USD $) Australia (AUD $) Austria (EUR €) Belgium (EUR €) Canada (CAD $) Czechia (CZK Kč) Denmark (DKK kr.) Finland (EUR €) France (EUR €) Germany (EUR €) Hong Kong SAR (HKD $) Ireland (EUR €) Israel (ILS ₪) Italy (EUR €) Japan (JPY ¥) Malaysia (MYR RM) Netherlands (EUR €) New Zealand (NZD $) Norway (USD $) Poland (PLN zł) Portugal (EUR €) Singapore (SGD $) South Korea (KRW ₩) Spain (EUR €) Sweden (SEK kr) Switzerland (CHF CHF) United Arab Emirates (AED د.إ) United Kingdom (GBP £) Payment methods Amazon American Express Apple Pay Diners Club Discover Meta Pay Google Pay Mastercard PayPal Shop Pay Venmo Visa	biology	695560	https://no.wikipedia.org/wiki/HTC%20STRTrk	HTC STRTrk	HTC STRTrk er en Windows Mobile-basert mobiltelefon (smartphone) som ble produsert av HTC. Den er HTCs første smartphone som var flipptelefon, og ble lansert i juni 2006. Den er også solgt som Cingular 3125, Dopod S300, i-mate Smartflip og Qtek 8500. Spesifikasjoner Skjerm: 2,2 tommer Skjermoppløsning: 240 x 320 Kamera: 1,3 megapiksler 200 MHz TI OMAP prosessor Batteri: 750 mAh Standby: 150 timer Taletid: 5 timer RAM: 64 MB ROM: 64 MB microSD minnekort Operativsystem: Windows Mobile 5 GPRS, EDGE Quadband: GSM 850 / 900 / 1800 / 1900 SMS, MMS Quadband Bluetooth 1.2 Wifi: Nei Størrelse: 98,5 mm (h), 51,4 mm (b) 15,8 mm (d) Vekt: 99 g med batteri Eksterne lenker Smartphone History - HTC STRTrk STRTrk Mobiltelefoner introdusert i 2006	norwegian_bokmål	1.185804
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Here’s how it works . Home Gardening How To Gardening Tips & Information Magnetism And Plant Growth – How Do Magnets Help Plants Grow Sign up to our newsletter Newsletter magnet (Image credit: Talaj) By Bonnie L. Grant last updated 2 February 2023 Any gardener or farmer desires consistently bigger and better plants with higher yields. The seeking of these traits has scientists testing, theorizing and hybridizing plants in an effort to achieve the optimum growth. One of these theories regards magnetism and plant growth. Magnetic fields, such as that generated by our planet, are thought to enhance plant growth. Do magnets help plants grow? There are actually several ways exposure to magnets may direct plant growth. Let’s learn more. Do Magnets Help Plants Grow? Healthy plants are impossible without adequate intake of water and nutrients, and some studies show that magnetic exposure can enhance intake of these essential items. Why do plants react to magnets? Some of the explanation centers on a magnet’s ability to change molecules. This is an important characteristic when applied to heavily saline water. The earth’s magnetic field also has a powerful influence on all life on the planet – kind of like with the old-time gardening method of planting by the moon . Grade school level experiments are common where the students study the effect of magnets on seeds or plants. The general consensus is that no discernible benefits are noticed. If this is the case, why would the experiments even exist? The magnetic pull of the earth is known to have an effect on living organisms and the biological processes. The evidence indicates that the earth’s magnetic pull influences seed germination by acting as an auxin or plant hormone. The magnetic field also assists in ripening of such plants as tomatoes . Much of plant response is due to the cryptochromes, or blue light receptors, that plants bear. Animals also have cryptochromes, which are activated by light and then are sensitive to magnetic pull. How Magnets Affect Plant Growth Studies in Palestine have indicated that plant growth is enhanced with magnets. This doesn’t mean you directly apply a magnet to the plant, but instead, the technology involves magnetizing water. The water in the region is heavily salted, which interrupts plant uptake. By exposing the water to magnets, the salt ions change and dissolve, creating purer water that is more easily taken up by the plant. Studies on how magnets affect plant growth also show that magnetic treatment of seeds enhances germination by speeding up the formation of protein in the cells. Growth is more rapid and robust. Why Do Plants React to Magnets? The reasons behind plant response to magnets are a bit harder to understand. It seems that magnetic force pulls apart ions and changes the chemical composition of such things as salt. It also appears that magnetism and plant growth are tied together by biological impulse. Plants have the natural response to “feel” gravity and magnetic pull just as humans and animals. The effect of magnetism actually can change the mitochondria in cells and enhance plant metabolism. If this all sounds like mumbo jumbo, join the club. The why is not as important as the fact that magnetism does seem to drive improved plant performance. And as a gardener, this is the most important fact of all. I’ll leave the scientific explanations to a professional and enjoy the benefits. Gardening tips, videos, info and more delivered right to your inbox! Sign up for the Gardening Know How newsletter today and receive a free download of our most popular eBook "How to Grow Delicious Tomatoes." Contact me with news and offers from other Future brands Receive email from us on behalf of our trusted partners or sponsors By submitting your information you agree to the Terms & Conditions and Privacy Policy and are aged 16 or over. Bonnie L. Grant Social Links Navigation Writer Bonnie Grant is a professional landscaper with a Certification in Urban Gardening. She has been gardening and writing for 15 years. A former professional chef, she has a passion for edible landscaping. When you purchase through links on our site, we may earn an affiliate commission. Here’s how it works . When you purchase through links on our site, we may earn an affiliate commission. Here’s how it works . Home Gardening How To Gardening Tips & Information Magnetism And Plant Growth – How Do Magnets Help Plants Grow Sign up to our newsletter Newsletter magnet (Image credit: Talaj) By Bonnie L. Grant last updated 2 February 2023 Any gardener or farmer desires consistently bigger and better plants with higher yields. The seeking of these traits has scientists testing, theorizing and hybridizing plants in an effort to achieve the optimum growth. One of these theories regards magnetism and plant growth. Magnetic fields, such as that generated by our planet, are thought to enhance plant growth. Do magnets help plants grow? There are actually several ways exposure to magnets may direct plant growth. Let’s learn more. Do Magnets Help Plants Grow? Healthy plants are impossible without adequate intake of water and nutrients, and some studies show that magnetic exposure can enhance intake of these essential items. Why do plants react to magnets? Some of the explanation centers on a magnet’s ability to change molecules. This is an important characteristic when applied to heavily saline water. The earth’s magnetic field also has a powerful influence on all life on the planet – kind of like with the old-time gardening method of planting by the moon . Grade school level experiments are common where the students study the effect of magnets on seeds or plants. The general consensus is that no discernible benefits are noticed. If this is the case, why would the experiments even exist? The magnetic pull of the earth is known to have an effect on living organisms and the biological processes. The evidence indicates that the earth’s magnetic pull influences seed germination by acting as an auxin or plant hormone. The magnetic field also assists in ripening of such plants as tomatoes . Much of plant response is due to the cryptochromes, or blue light receptors, that plants bear. Animals also have cryptochromes, which are activated by light and then are sensitive to magnetic pull. How Magnets Affect Plant Growth Studies in Palestine have indicated that plant growth is enhanced with magnets. This doesn’t mean you directly apply a magnet to the plant, but instead, the technology involves magnetizing water. The water in the region is heavily salted, which interrupts plant uptake. By exposing the water to magnets, the salt ions change and dissolve, creating purer water that is more easily taken up by the plant. Studies on how magnets affect plant growth also show that magnetic treatment of seeds enhances germination by speeding up the formation of protein in the cells. Growth is more rapid and robust. Why Do Plants React to Magnets? The reasons behind plant response to magnets are a bit harder to understand. It seems that magnetic force pulls apart ions and changes the chemical composition of such things as salt. It also appears that magnetism and plant growth are tied together by biological impulse. Plants have the natural response to “feel” gravity and magnetic pull just as humans and animals. The effect of magnetism actually can change the mitochondria in cells and enhance plant metabolism. If this all sounds like mumbo jumbo, join the club. The why is not as important as the fact that magnetism does seem to drive improved plant performance. And as a gardener, this is the most important fact of all. I’ll leave the scientific explanations to a professional and enjoy the benefits. Gardening tips, videos, info and more delivered right to your inbox! Sign up for the Gardening Know How newsletter today and receive a free download of our most popular eBook "How to Grow Delicious Tomatoes." Contact me with news and offers from other Future brands Receive email from us on behalf of our trusted partners or sponsors By submitting your information you agree to the Terms & Conditions and Privacy Policy and are aged 16 or over. Bonnie L. Grant Social Links Navigation Writer Bonnie Grant is a professional landscaper with a Certification in Urban Gardening. She has been gardening and writing for 15 years. A former professional chef, she has a passion for edible landscaping. Home Gardening How To Gardening Tips & Information Magnetism And Plant Growth – How Do Magnets Help Plants Grow Sign up to our newsletter Newsletter Home Gardening How To Gardening Tips & Information Magnetism And Plant Growth – How Do Magnets Help Plants Grow Sign up to our newsletter Newsletter magnet (Image credit: Talaj) By Bonnie L. Grant last updated 2 February 2023 Any gardener or farmer desires consistently bigger and better plants with higher yields. The seeking of these traits has scientists testing, theorizing and hybridizing plants in an effort to achieve the optimum growth. One of these theories regards magnetism and plant growth. Magnetic fields, such as that generated by our planet, are thought to enhance plant growth. Do magnets help plants grow? There are actually several ways exposure to magnets may direct plant growth. Let’s learn more. Do Magnets Help Plants Grow? Healthy plants are impossible without adequate intake of water and nutrients, and some studies show that magnetic exposure can enhance intake of these essential items. Why do plants react to magnets? Some of the explanation centers on a magnet’s ability to change molecules. This is an important characteristic when applied to heavily saline water. The earth’s magnetic field also has a powerful influence on all life on the planet – kind of like with the old-time gardening method of planting by the moon . Grade school level experiments are common where the students study the effect of magnets on seeds or plants. The general consensus is that no discernible benefits are noticed. If this is the case, why would the experiments even exist? The magnetic pull of the earth is known to have an effect on living organisms and the biological processes. The evidence indicates that the earth’s magnetic pull influences seed germination by acting as an auxin or plant hormone. The magnetic field also assists in ripening of such plants as tomatoes . Much of plant response is due to the cryptochromes, or blue light receptors, that plants bear. Animals also have cryptochromes, which are activated by light and then are sensitive to magnetic pull. How Magnets Affect Plant Growth Studies in Palestine have indicated that plant growth is enhanced with magnets. This doesn’t mean you directly apply a magnet to the plant, but instead, the technology involves magnetizing water. The water in the region is heavily salted, which interrupts plant uptake. By exposing the water to magnets, the salt ions change and dissolve, creating purer water that is more easily taken up by the plant. Studies on how magnets affect plant growth also show that magnetic treatment of seeds enhances germination by speeding up the formation of protein in the cells. Growth is more rapid and robust. Why Do Plants React to Magnets? The reasons behind plant response to magnets are a bit harder to understand. It seems that magnetic force pulls apart ions and changes the chemical composition of such things as salt. It also appears that magnetism and plant growth are tied together by biological impulse. Plants have the natural response to “feel” gravity and magnetic pull just as humans and animals. The effect of magnetism actually can change the mitochondria in cells and enhance plant metabolism. If this all sounds like mumbo jumbo, join the club. The why is not as important as the fact that magnetism does seem to drive improved plant performance. And as a gardener, this is the most important fact of all. I’ll leave the scientific explanations to a professional and enjoy the benefits. Gardening tips, videos, info and more delivered right to your inbox! Sign up for the Gardening Know How newsletter today and receive a free download of our most popular eBook "How to Grow Delicious Tomatoes." Contact me with news and offers from other Future brands Receive email from us on behalf of our trusted partners or sponsors By submitting your information you agree to the Terms & Conditions and Privacy Policy and are aged 16 or over. Bonnie L. Grant Social Links Navigation Writer Bonnie Grant is a professional landscaper with a Certification in Urban Gardening. She has been gardening and writing for 15 years. A former professional chef, she has a passion for edible landscaping. magnet (Image credit: Talaj) By Bonnie L. Grant last updated 2 February 2023 Any gardener or farmer desires consistently bigger and better plants with higher yields. The seeking of these traits has scientists testing, theorizing and hybridizing plants in an effort to achieve the optimum growth. One of these theories regards magnetism and plant growth. Magnetic fields, such as that generated by our planet, are thought to enhance plant growth. Do magnets help plants grow? There are actually several ways exposure to magnets may direct plant growth. Let’s learn more. Do Magnets Help Plants Grow? Healthy plants are impossible without adequate intake of water and nutrients, and some studies show that magnetic exposure can enhance intake of these essential items. Why do plants react to magnets? Some of the explanation centers on a magnet’s ability to change molecules. This is an important characteristic when applied to heavily saline water. The earth’s magnetic field also has a powerful influence on all life on the planet – kind of like with the old-time gardening method of planting by the moon . Grade school level experiments are common where the students study the effect of magnets on seeds or plants. The general consensus is that no discernible benefits are noticed. If this is the case, why would the experiments even exist? The magnetic pull of the earth is known to have an effect on living organisms and the biological processes. The evidence indicates that the earth’s magnetic pull influences seed germination by acting as an auxin or plant hormone. The magnetic field also assists in ripening of such plants as tomatoes . Much of plant response is due to the cryptochromes, or blue light receptors, that plants bear. Animals also have cryptochromes, which are activated by light and then are sensitive to magnetic pull. How Magnets Affect Plant Growth Studies in Palestine have indicated that plant growth is enhanced with magnets. This doesn’t mean you directly apply a magnet to the plant, but instead, the technology involves magnetizing water. The water in the region is heavily salted, which interrupts plant uptake. By exposing the water to magnets, the salt ions change and dissolve, creating purer water that is more easily taken up by the plant. Studies on how magnets affect plant growth also show that magnetic treatment of seeds enhances germination by speeding up the formation of protein in the cells. Growth is more rapid and robust. Why Do Plants React to Magnets? The reasons behind plant response to magnets are a bit harder to understand. It seems that magnetic force pulls apart ions and changes the chemical composition of such things as salt. It also appears that magnetism and plant growth are tied together by biological impulse. Plants have the natural response to “feel” gravity and magnetic pull just as humans and animals. The effect of magnetism actually can change the mitochondria in cells and enhance plant metabolism. If this all sounds like mumbo jumbo, join the club. The why is not as important as the fact that magnetism does seem to drive improved plant performance. And as a gardener, this is the most important fact of all. I’ll leave the scientific explanations to a professional and enjoy the benefits. Gardening tips, videos, info and more delivered right to your inbox! Sign up for the Gardening Know How newsletter today and receive a free download of our most popular eBook "How to Grow Delicious Tomatoes." Contact me with news and offers from other Future brands Receive email from us on behalf of our trusted partners or sponsors By submitting your information you agree to the Terms & Conditions and Privacy Policy and are aged 16 or over. Bonnie L. Grant Social Links Navigation Writer Bonnie Grant is a professional landscaper with a Certification in Urban Gardening. She has been gardening and writing for 15 years. A former professional chef, she has a passion for edible landscaping. By Bonnie L. Grant last updated 2 February 2023 Any gardener or farmer desires consistently bigger and better plants with higher yields. The seeking of these traits has scientists testing, theorizing and hybridizing plants in an effort to achieve the optimum growth. One of these theories regards magnetism and plant growth. Magnetic fields, such as that generated by our planet, are thought to enhance plant growth. Do magnets help plants grow? There are actually several ways exposure to magnets may direct plant growth. Let’s learn more. Do Magnets Help Plants Grow? Healthy plants are impossible without adequate intake of water and nutrients, and some studies show that magnetic exposure can enhance intake of these essential items. Why do plants react to magnets? Some of the explanation centers on a magnet’s ability to change molecules. This is an important characteristic when applied to heavily saline water. The earth’s magnetic field also has a powerful influence on all life on the planet – kind of like with the old-time gardening method of planting by the moon . Grade school level experiments are common where the students study the effect of magnets on seeds or plants. The general consensus is that no discernible benefits are noticed. If this is the case, why would the experiments even exist? The magnetic pull of the earth is known to have an effect on living organisms and the biological processes. The evidence indicates that the earth’s magnetic pull influences seed germination by acting as an auxin or plant hormone. The magnetic field also assists in ripening of such plants as tomatoes . Much of plant response is due to the cryptochromes, or blue light receptors, that plants bear. Animals also have cryptochromes, which are activated by light and then are sensitive to magnetic pull. How Magnets Affect Plant Growth Studies in Palestine have indicated that plant growth is enhanced with magnets. This doesn’t mean you directly apply a magnet to the plant, but instead, the technology involves magnetizing water. The water in the region is heavily salted, which interrupts plant uptake. By exposing the water to magnets, the salt ions change and dissolve, creating purer water that is more easily taken up by the plant. Studies on how magnets affect plant growth also show that magnetic treatment of seeds enhances germination by speeding up the formation of protein in the cells. Growth is more rapid and robust. Why Do Plants React to Magnets? The reasons behind plant response to magnets are a bit harder to understand. It seems that magnetic force pulls apart ions and changes the chemical composition of such things as salt. It also appears that magnetism and plant growth are tied together by biological impulse. Plants have the natural response to “feel” gravity and magnetic pull just as humans and animals. The effect of magnetism actually can change the mitochondria in cells and enhance plant metabolism. If this all sounds like mumbo jumbo, join the club. The why is not as important as the fact that magnetism does seem to drive improved plant performance. And as a gardener, this is the most important fact of all. I’ll leave the scientific explanations to a professional and enjoy the benefits. Gardening tips, videos, info and more delivered right to your inbox! Sign up for the Gardening Know How newsletter today and receive a free download of our most popular eBook "How to Grow Delicious Tomatoes." Contact me with news and offers from other Future brands Receive email from us on behalf of our trusted partners or sponsors By submitting your information you agree to the Terms & Conditions and Privacy Policy and are aged 16 or over. By Bonnie L. Grant last updated 2 February 2023 Any gardener or farmer desires consistently bigger and better plants with higher yields. The seeking of these traits has scientists testing, theorizing and hybridizing plants in an effort to achieve the optimum growth. One of these theories regards magnetism and plant growth. Magnetic fields, such as that generated by our planet, are thought to enhance plant growth. Do magnets help plants grow? There are actually several ways exposure to magnets may direct plant growth. Let’s learn more. Do Magnets Help Plants Grow? Healthy plants are impossible without adequate intake of water and nutrients, and some studies show that magnetic exposure can enhance intake of these essential items. Why do plants react to magnets? Some of the explanation centers on a magnet’s ability to change molecules. This is an important characteristic when applied to heavily saline water. The earth’s magnetic field also has a powerful influence on all life on the planet – kind of like with the old-time gardening method of planting by the moon . Grade school level experiments are common where the students study the effect of magnets on seeds or plants. The general consensus is that no discernible benefits are noticed. If this is the case, why would the experiments even exist? The magnetic pull of the earth is known to have an effect on living organisms and the biological processes. The evidence indicates that the earth’s magnetic pull influences seed germination by acting as an auxin or plant hormone. The magnetic field also assists in ripening of such plants as tomatoes . Much of plant response is due to the cryptochromes, or blue light receptors, that plants bear. Animals also have cryptochromes, which are activated by light and then are sensitive to magnetic pull. How Magnets Affect Plant Growth Studies in Palestine have indicated that plant growth is enhanced with magnets. This doesn’t mean you directly apply a magnet to the plant, but instead, the technology involves magnetizing water. The water in the region is heavily salted, which interrupts plant uptake. By exposing the water to magnets, the salt ions change and dissolve, creating purer water that is more easily taken up by the plant. Studies on how magnets affect plant growth also show that magnetic treatment of seeds enhances germination by speeding up the formation of protein in the cells. Growth is more rapid and robust. Why Do Plants React to Magnets? The reasons behind plant response to magnets are a bit harder to understand. It seems that magnetic force pulls apart ions and changes the chemical composition of such things as salt. It also appears that magnetism and plant growth are tied together by biological impulse. Plants have the natural response to “feel” gravity and magnetic pull just as humans and animals. The effect of magnetism actually can change the mitochondria in cells and enhance plant metabolism. If this all sounds like mumbo jumbo, join the club. The why is not as important as the fact that magnetism does seem to drive improved plant performance. And as a gardener, this is the most important fact of all. I’ll leave the scientific explanations to a professional and enjoy the benefits. Gardening tips, videos, info and more delivered right to your inbox! Sign up for the Gardening Know How newsletter today and receive a free download of our most popular eBook "How to Grow Delicious Tomatoes." Contact me with news and offers from other Future brands Receive email from us on behalf of our trusted partners or sponsors By submitting your information you agree to the Terms & Conditions and Privacy Policy and are aged 16 or over. Any gardener or farmer desires consistently bigger and better plants with higher yields. The seeking of these traits has scientists testing, theorizing and hybridizing plants in an effort to achieve the optimum growth. One of these theories regards magnetism and plant growth. Magnetic fields, such as that generated by our planet, are thought to enhance plant growth. Do magnets help plants grow? There are actually several ways exposure to magnets may direct plant growth. Let’s learn more. Do Magnets Help Plants Grow? Healthy plants are impossible without adequate intake of water and nutrients, and some studies show that magnetic exposure can enhance intake of these essential items. Why do plants react to magnets? Some of the explanation centers on a magnet’s ability to change molecules. This is an important characteristic when applied to heavily saline water. The earth’s magnetic field also has a powerful influence on all life on the planet – kind of like with the old-time gardening method of planting by the moon . Grade school level experiments are common where the students study the effect of magnets on seeds or plants. The general consensus is that no discernible benefits are noticed. If this is the case, why would the experiments even exist? The magnetic pull of the earth is known to have an effect on living organisms and the biological processes. The evidence indicates that the earth’s magnetic pull influences seed germination by acting as an auxin or plant hormone. The magnetic field also assists in ripening of such plants as tomatoes . Much of plant response is due to the cryptochromes, or blue light receptors, that plants bear. Animals also have cryptochromes, which are activated by light and then are sensitive to magnetic pull. How Magnets Affect Plant Growth Studies in Palestine have indicated that plant growth is enhanced with magnets. This doesn’t mean you directly apply a magnet to the plant, but instead, the technology involves magnetizing water. The water in the region is heavily salted, which interrupts plant uptake. By exposing the water to magnets, the salt ions change and dissolve, creating purer water that is more easily taken up by the plant. Studies on how magnets affect plant growth also show that magnetic treatment of seeds enhances germination by speeding up the formation of protein in the cells. Growth is more rapid and robust. Why Do Plants React to Magnets? The reasons behind plant response to magnets are a bit harder to understand. It seems that magnetic force pulls apart ions and changes the chemical composition of such things as salt. It also appears that magnetism and plant growth are tied together by biological impulse. Plants have the natural response to “feel” gravity and magnetic pull just as humans and animals. The effect of magnetism actually can change the mitochondria in cells and enhance plant metabolism. If this all sounds like mumbo jumbo, join the club. The why is not as important as the fact that magnetism does seem to drive improved plant performance. And as a gardener, this is the most important fact of all. I’ll leave the scientific explanations to a professional and enjoy the benefits. Gardening tips, videos, info and more delivered right to your inbox! Sign up for the Gardening Know How newsletter today and receive a free download of our most popular eBook "How to Grow Delicious Tomatoes." Contact me with news and offers from other Future brands Receive email from us on behalf of our trusted partners or sponsors By submitting your information you agree to the Terms & Conditions and Privacy Policy and are aged 16 or over. Any gardener or farmer desires consistently bigger and better plants with higher yields. The seeking of these traits has scientists testing, theorizing and hybridizing plants in an effort to achieve the optimum growth. One of these theories regards magnetism and plant growth. Magnetic fields, such as that generated by our planet, are thought to enhance plant growth. Do magnets help plants grow? There are actually several ways exposure to magnets may direct plant growth. Let’s learn more. Healthy plants are impossible without adequate intake of water and nutrients, and some studies show that magnetic exposure can enhance intake of these essential items. Why do plants react to magnets? Some of the explanation centers on a magnet’s ability to change molecules. This is an important characteristic when applied to heavily saline water. The earth’s magnetic field also has a powerful influence on all life on the planet – kind of like with the old-time gardening method of planting by the moon . Grade school level experiments are common where the students study the effect of magnets on seeds or plants. The general consensus is that no discernible benefits are noticed. If this is the case, why would the experiments even exist? The magnetic pull of the earth is known to have an effect on living organisms and the biological processes. The evidence indicates that the earth’s magnetic pull influences seed germination by acting as an auxin or plant hormone. The magnetic field also assists in ripening of such plants as tomatoes . Much of plant response is due to the cryptochromes, or blue light receptors, that plants bear. Animals also have cryptochromes, which are activated by light and then are sensitive to magnetic pull. Studies in Palestine have indicated that plant growth is enhanced with magnets. This doesn’t mean you directly apply a magnet to the plant, but instead, the technology involves magnetizing water. The water in the region is heavily salted, which interrupts plant uptake. By exposing the water to magnets, the salt ions change and dissolve, creating purer water that is more easily taken up by the plant. Studies on how magnets affect plant growth also show that magnetic treatment of seeds enhances germination by speeding up the formation of protein in the cells. Growth is more rapid and robust. The reasons behind plant response to magnets are a bit harder to understand. It seems that magnetic force pulls apart ions and changes the chemical composition of such things as salt. It also appears that magnetism and plant growth are tied together by biological impulse. Plants have the natural response to “feel” gravity and magnetic pull just as humans and animals. The effect of magnetism actually can change the mitochondria in cells and enhance plant metabolism. If this all sounds like mumbo jumbo, join the club. The why is not as important as the fact that magnetism does seem to drive improved plant performance. And as a gardener, this is the most important fact of all. I’ll leave the scientific explanations to a professional and enjoy the benefits. Gardening tips, videos, info and more delivered right to your inbox! Sign up for the Gardening Know How newsletter today and receive a free download of our most popular eBook "How to Grow Delicious Tomatoes." Contact me with news and offers from other Future brands Receive email from us on behalf of our trusted partners or sponsors By submitting your information you agree to the Terms & Conditions and Privacy Policy and are aged 16 or over. Gardening tips, videos, info and more delivered right to your inbox! Sign up for the Gardening Know How newsletter today and receive a free download of our most popular eBook "How to Grow Delicious Tomatoes." Contact me with news and offers from other Future brands Receive email from us on behalf of our trusted partners or sponsors By submitting your information you agree to the Terms & Conditions and Privacy Policy and are aged 16 or over. Gardening tips, videos, info and more delivered right to your inbox! Sign up for the Gardening Know How newsletter today and receive a free download of our most popular eBook "How to Grow Delicious Tomatoes." Contact me with news and offers from other Future brands Receive email from us on behalf of our trusted partners or sponsors By submitting your information you agree to the Terms & Conditions and Privacy Policy and are aged 16 or over. Sign up for the Gardening Know How newsletter today and receive a free download of our most popular eBook "How to Grow Delicious Tomatoes." Bonnie L. Grant Social Links Navigation Writer Bonnie Grant is a professional landscaper with a Certification in Urban Gardening. She has been gardening and writing for 15 years. A former professional chef, she has a passion for edible landscaping. Bonnie L. Grant Social Links Navigation Writer Bonnie Grant is a professional landscaper with a Certification in Urban Gardening. She has been gardening and writing for 15 years. A former professional chef, she has a passion for edible landscaping. Bonnie Grant is a professional landscaper with a Certification in Urban Gardening. She has been gardening and writing for 15 years. A former professional chef, she has a passion for edible landscaping. Bonnie Grant is a professional landscaper with a Certification in Urban Gardening. She has been gardening and writing for 15 years. 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Visit our corporate site .	biology	170974	https://da.wikipedia.org/wiki/Plantefysiologi	Plantefysiologi	Plantefysiologi (eller – hvis fremmedordet skulle være konstrueret korrekt – fytofysiologi) er læren om planternes livsfunktioner. Det drejer sig for det første om forhold som spiring, vækst, blomstring og frøsætning. Men for det andet drejer det sig også om optagelse af vand og næringssalte, transportsystemer, oplagring af næring, opfangning af energi, beskyttelse og forsvar mod sygdomme og beskadigelser. Plantefysiologien drejer sig kort sagt om planterne som systemer, der etablerer en indre ligevægt og en balance overfor ydre vilkår i deres miljø. Videnskabens historie Den engelske filosof og videnskabsmand, Francis Bacon, offentliggjorde ét af de første plantefysiologiske forsøg i bogen Sylva Sylvarum (1627). Bacon dyrkede forskellige landplanter i vand, og han konkluderede, at jord kun var nødvendigt for at holde planten opret. I 1648 offentliggjorde Jan Baptist van Helmont det, som betragtes som det første nøjagtigt opmålte forsøg indenfor plantefysiologi. Han havde dyrket et piletræ i en krukke, der rummede 100 kg ovntørret jord. Jorden mistede kun nogle få gram tørvægt under forsøget, og van Helmont konkluderede, at planter får al deres vægtforøgelse fra vand og ikke jord. I 1699 offentliggjorde John Woodward nogle forsøg over vækst hos Grøn Mynte, når den blev dyrket i forskellige slags vand. Han opdagede, at planterne voksede meget bedre i vand med tilsat jord end i destilleret vand. Stephen Hales betragtes som plantefysiologiens fader på grund af de mange forsøg, han omtaler i bogen Vegetable Staticks fra . Julius von Sachs samlede de løsrevne stumper af plantefysiologien og skabte faget som en videnskabelig disciplin. Hans lærebog, Lehrbuch der Botanik blev tidens faglige bibel. Forskere inden for plantefysiologien opdagede i det 19. århundrede, at planterne optager nødvendige, mineralske næringsstoffer som uorganiske ioner, der er opløst i vand. Under naturlige forhold virker jorden som et reservoir for mineralske næringsstoffer, men jorden er i sig selv ikke nødvendig for planternes vækst. Når næringsstofferne bliver opløst i vand, kan planterødderne optage dem, og når man tilfører de nødvendige næringsstoffer kunstigt til vandet, er jorden ikke længere afgørende for plantens trivsel. Næsten alle landplanter kan dyrkes i vand med opløste næringssalte (hydroponik), men nogle klarer sig dog bedre end andre. Senere forskning har vist, at jordbundens biodiversitet kan være afgørende for plantens langsigtede trivsel i forhold til sygdomme og skadedyr. Derfor er det sjældent muligt at få held til at dyrke planter i vand over længere perioder. Økologisk fysiologi Tilpasning til miljøet Planternes udseende og virkemåde kan betragtes som tilpasninger til forholdene i de økologiske nicher, som de enkelte arter foretrækker. Det gælder både planternes udvikling af forskellige livsformer, deres tilpasning af rodsystemerne til miljøforholdene, de forskellige stængelformer, bladenes udseende, farve, behåring og indskæringer, og det gælder blomsters og frugters udseende og opbygning. Den økologiske tilpasning går dog videre, for den gælder også de symbioser, som planterne indgår i. Her kan blot nævnes nogle få, velkendte: Bælgplanternes kvælstofsamlende bakterier (Rhizobia) De tilsvarende strålebakterier, som lever sammen med bl.a. El (Frankia) De utallige eksempler på mykorrhizasymbioser mellem planter og svampe. Lavernes symbiose mellem svampe og grønalger Ofte udsættes planter for stress i form af for høje eller for lave temperaturer, tørke, salt, iltmangel omkring rødderne, luftforurening eller sygdomsangreb. Planter har på en række måder tilpasset sig disse ændringer i vækstbetingelserne. Bladtab er f.eks. en tilpasning, der skal mindske fordampningen ved vandmangel, ligesom dannelsen af "varme-stress"-proteiner er en stabilisering af plantens enzymer, så de kan tåle høje temperaturer. Planter er afhængige af lys for at kunne udføre fotosyntese, men lyset har også en vigtig betydning for reguleringen af planternes vækst og udvikling. Højere planters vækst og udvikling kræver effektiv kommunikation både mellem de enkelte celler og mellem plantens enkelte dele og styres af en række forskellige plantehormoner (auxiner, gibberelliner, cytokininer, ethylen, abscisinsyre og de såkaldte brassinosteroider) samt af en lang række signalstoffer. Tilpasning til konkurrence Med til den økologiske fysiologi hører også de allelopatiske virkemidler, som mange planter har udviklet. Det er f.eks. kateristisk for rørsumpe, at de er artsfattige, og det skyldes, at Almindelig Tagrør afgiver stoffer, som hæmmer andre planters spiring. Tilsvarende afgiver Thuja og Almindelig Valnød stoffer (henholdsvis thujon og juglandin, som hæmmer andre planters vækst. Vækst og udvikling En plantes udvikling og vækst begynder, når den befrugtede ægcelle deler sig, cellerne strækker sig og differentieres på en forud fastlagt måde, sådan at der dannes en kim og senere en fuldt udviklet, voksen plante. Allerede kimen har de meristemer (vækstpunkter), som bestemmer udviklingen af organer som rod og skud. Hos den fuldt udviklede plante dannes der nye meristemer, der sætter gang i dannelsen af blade eller siderødder – afhængigt af, hvor de er placeret. Både plantens form, dens udvikling og hele dens vækst er bestemt af celledelinger i de forskellige meristemer og af en senere strækning af de nye celler. Ud over disse indre systemer påvirkes plantens vækst og udvikling også af ydre faktorer som daglængde, dagrytme og temperatur. Plantens vækst og udvikling og dermed udbyttet fra kulturplanterne afhænger af vækstforholdene. Planternes cellevæg Selvom planter i modsætning til hvirveldyr ikke har et skelet, som kan afstive dem, er det alligevel blandt planterne, at Jordens største levende organismer findes. Det skyldes, at plantecellen i modsætning til dyrecellen er omgivet af en cellevæg. Denne cellevæg har i sig selv stor mekanisk styrke, som yderligere øges ved turgortrykket, dvs. at cellevæggen holdes udspilet af saftspændingen. Cellevæggen bestemmer den enkelte celles form og planter kan derfor ikke i samme grad som dyr ændre udseende. Ud over at give planten mekanisk styrke tjener cellevæggen også som et mekanisk forsvar mod sygdomsangreb. Når cellevæggen nedbrydes efter et sygdomsangreb, fungerer nogle af nedbrydningsprodukterne som signalstoffer, der får planten til at producere og transportere et utal af proteiner og planteindholdsstoffer målrettet derhen, hvor de kan standse sygdomsvolderens fremtrængen. Cellevæggen er opbygget som et laminat af polymerer, bl.a.f.eks. polysaccharider såsom cellulose, hemi-celluloser og pektin, polyfenolet lignin og af proteiner. Industrielt udnyttes plantecellevæggens polymerer til fremstilling af papir, tekstiler, fibre, lim og plastprodukter. Tilsvarende er jordbundens humus en blanding, som består af ufuldstændigt nedbrudte nedbrydningsprodukter fra plantecellevæggene og genanvendte fenoler, saccharider og uorganiske ioner. Blomstring og frøsætning Se hovedartiklen Blomsterinduktion Blomsterne er højt specialiserede formeringsorganer, som kan ses hos de énkimbladede og tokimbladede planter. Blomsterne har vidt forskellig udformning, men en nærmere undersøgelse viser, at de er bygget over samme skema: yderst har man bægerblade, så følger kronbladene og inde bag dem har man så de egentlige kønsanlæg: frugtanlægget (frugtknude, griffel og støvfang) og de pollenbærende støvdragere. Visse planter mangler dele af dette grundsystem, men det skyldes en senere tilpasning til bestemte bestøvningsforhold (vindbestøvning, vandbestøvning, fuglebestøvning osv.). Blomsterne dannes ved den proces i knopperne, som hedder blomsterinduktion. Under forhold omdannes vækstpunktet fra at producere forstadier til skud og blade til i stedet at danne blomsterforstadier. Blomsterinduktionen forudsætter bestemte hormonelle og næringsmæssige tilstande i planten, men den igangsættes ved nogle faktorer i miljøet, som udløser den senere blomstring på det rette tidspunkt. Hos nogle arter udløses blomsterdannelsen af korte dage (efterår), hos andre af lange dage (forår). Hos atter andre er det kulde (vinter), og hos nogle er det tørtid (vandmangel). Når pollenet er overført til støvfanget, sker befrugtningen ved, at pollenkornet sender en spire ned gennem griflen, sådan at der dannes en kanal, som sædcellen kan trænge ned gennem. I frugtknuden forenes sæd- og ægcelle, befrugtningen er gennemført, og frødannelsen tager fart. Den befrugtede ægcelle danner en kim, som moderplanten derefter omgiver med oplagsnæring og en passende frøkappe. Frøene spredes så ved modenhed ved udnyttelse af miljøfaktorer: vind, vand, dyr osv. Livsprocesser Fotosyntese Se hovedartiklen Fotosyntese Helt centralt i planters fysiologi er deres evne til at udføre fotosyntese, hvilket sætter dem i stand til at udnytte sollysets energi til at omdanne atmosfærens CO2) og vand til organiske forbindelser som stivelse og glukose under samtidig udvikling af ilt. Planters fotosyntese er en dynamisk proces, der er afhængig af at flere faktorer er tilgængelig. Men da adgangen til kuldioxid, vand og lys er afhængig af en række miljøfaktorer, og planterne er bundet til deres voksested via rødderne, må de altså fra denne fastlåste position kunne tilpasse væksten med henblik på at opnå bedst mulig forsyning med de vigtigste vækstfaktorer. Optagelse af mineralske stoffer Planter får deres forsyning af kvælstof i form af nitrat eller ammonium, som sammen med andre næringssalte optages gennem rødderne. Nogle planter har symbiose med nitrogenfikserende bakterier, hvilket sætter dem i stand til også at udnytte luftens kvælstof som nitrogenkilde. I modsætning til dyr kan planter selv fremstille alle de nødvendige, kvælstofholdige stoffer ud fra disse uorganiske nitrogenforbindelser. Planter er derfor fotoautotrofe organismer, dvs. at de kan producere alle øvrige forbindelser såsom aminosyrer, proteiner, DNA, RNA og polysaccharider ud fra uorganiske stoffer og lys. Vandhusholdning Som for alle andre levende organismer er vand livsnødvendigt for planter, men de trues i højere grad end andre levende organismer af udtørring og død pga. vandtab til atmosfæren. Dette skyldes, at planter bærer blade med et meget stort overfladeareal for at kunne indfange solenergi og kuldioxid, og det betyder, at vandtabet kan være betydeligt. Som værn mod dette livstruende problem har planter udviklet et effektivt system, således at vand kan optages fra jorden gennem rødderne og via ledningsstrenge (vedkar) videretransporteres til bladene. For at mindske vandtabet fra bladoverfladen producerer nogle planter en vandafvisende overfladevoks, mens andre dækker overfladen af blade og stængler med et tæt hårlag. Desuden har de udviklet justerbare spalteåbninger i bladoverfladen, hvorigennem kuldioxid kan optages, uden at tabet af vanddamp bliver for stort. Planternes cellevæg Selvom planter i modsætning til hvirveldyr ikke har et skelet, som kan afstive dem, er det alligevel blandt planterne, at Jordens største levende organismer findes. Det skyldes, at plantecellen i modsætning til dyrecellen er omgivet af en cellevæg. Denne cellevæg har i sig selv stor mekanisk styrke, som yderligere øges ved turgortrykket, dvs. at cellevæggen holdes udspilet af saftspændingen. Cellevæggen bestemmer den enkelte celles form og planter kan derfor ikke i samme grad som dyr ændre udseende. Ud over at give planten mekanisk styrke tjener cellevæggen også som et mekanisk forsvar mod sygdomsangreb. Når cellevæggen nedbrydes efter et sygdomsangreb, fungerer nogle af nedbrydningsprodukterne som signalstoffer, der får planten til at producere og transportere et utal af proteiner og planteindholdsstoffer målrettet derhen, hvor de kan standse sygdomsvolderens fremtrængen. Cellevæggen er opbygget som et laminat af polymerer, bl.a.f.eks. polysaccharider såsom cellulose, hemicelluloser og pektin, polyfenolet lignin og af proteiner. Industrielt udnyttes plantecellevæggens polymerer til fremstilling af papir, tekstiler, fibre, lim og plastprodukter. Tilsvarende er jordbundens humus en blanding, som består af ufuldstændigt nedbrudte nedbrydningsprodukter fra plantecellevæggene og genanvendte fenoler, saccharider og uorganiske ioner. Planteindholdsstoffer Mange planter bestøves af insekter, som det derfor er nødvendigt at kunne tiltrække. Denne tilpasning til og kommunikation med omgivelserne opnår planter gennem produktion af mere end 200.000 forskellige planteindholdsstoffer (naturstoffer). Mange af planteindholdsstofferne har komplekse kemiske strukturer, hvis eventuelle toksikologiske virkninger på mennesker er ukendte, mens deres påvirkning af insekter og mikroorganismer kan være meget markante Noter Eksterne henvisninger Kidnapning af bakterie blev starten på alle planter. Videnskab.dk Botanik Fysiologi	danish	0.653143
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More ABOUT COMPANY COMPANY About Houzz Houzz Credit Cards Gift Cards Careers Privacy & Notice Terms Cookie Policy Your Privacy Choices Mobile Apps Copyright & Trademark BUSINESS SERVICES BUSINESS SERVICES For Professionals Houzz vs. Houzz Pro Houzz Pro vs. Ivy Houzz Pro Advertising Reviews Houzz Pro 3D Floor Planner Reviews For Brands Trade Program Buttons & Badges GET HELP GET HELP Your Orders Shipping & Delivery Return Policy Houzz Canada Review Professionals Suggested Professionals Accessibility Houzz Support Contact Sign In CONNECT WITH US CONNECT WITH US Houzz Blog Twitter Facebook YouTube RSS PRIVACY & LEGAL Privacy & Notice Terms Cookie Policy Copyright & Trademark SETTINGS COUNTRY COUNTRY Explore Discussions Featured Home Discussions Featured Garden Discussions Garden Experiments Growing plants with magnets Dave_S 20 years ago I am trying an experiment of placing magnets near plants to see if there is any boost in their growth or production. Has anyone else tried this? Email Save Comment 52 Follow Featured Answer Steve Lng Islnd NY Z-7a SunSet Z-34 6 years ago Its been discovered that Water exposed to a south magnetic field has molecules that group in 6 molecules where when exposed to a North Magnetic field group in 12. I have exposed water to South Pole Magnet of a N52 Neodymium (50mmx50x25) for 24 hours and it definitely had very low surface tension compared to non-exposed. It was noticeably a different feeling on your hands as well. Like \| 2 Save Sort by: Oldest Newest Oldest Comments (52) See 2 more comments Dave_S Original Author 20 years ago I set up a South Pole vs North Pole vs Control on some seeds which haven't germinated yet. Also, I put a North and South combination on a tomato and pepper plant in the garden and will continue to monitor them throughout the season for any differences with their neighbor non-magnetized plants. Like \| 1 Save palyne 20 years ago So Dave... what ever happened on this? Anything? Palyne Like Save Related Professionals Glendora Landscape Architects & Landscape Designers · Roosevelt Landscape Architects & Landscape Designers · Fort Atkinson Landscape Contractors · Hampton Bays Landscape Contractors · Haverhill Landscape Contractors · Homewood Landscape Contractors · Medford Landscape Contractors · Tacoma Landscape Contractors · Vadnais Heights Landscape Contractors · Adrian Decks, Patios & Outdoor Enclosures · Fort Pierce Decks, Patios & Outdoor Enclosures · Novi Decks, Patios & Outdoor Enclosures · St John's Kirk Decks, Patios & Outdoor Enclosures · Kenosha Siding & Exteriors · South Laurel Siding & Exteriors tony_k_orlando 20 years ago Earth to Dave, come in please. What are the results? Tony Like Save atillathepun 20 years ago Maybe magnets make plants carnivorous? Like Save Scott Wallace 20 years ago Funny...my daughter is doing this same thing for her science fair project this year. She just started Monday...I'll try to update this thread every week. Like \| 1 Save watermanjeff 20 years ago Dave I found a fairly recent experiment using radish seeds which showed a significant increase in the growth of root hairs. There is also a chapter in the controversial book "The Secret Life Of Plants", by Christopher Bird and Peter Tompkins, which deals with an amazing (unbelievable?) series of experiments. I don't have the book now, but as i recall the authors claimed to grow plants without light by running copper wires from outside (daylight)into a basement (dark) and inserting them into the soil in the pots the plants were in. Like i said....controversial. Jeff Here is a link that might be useful: The Effects of Electromagnetic Field...etc. Like Save palyne 20 years ago I have that book Jeff--and that was the one that struck me as most amazing (and in need of validation) out of the whole book (which btw I think is great). I'll see if I can dig out that passage and post it here. It really didn't give enough useful info to replicate--I once went looking for this a couple years ago hoping to! Attilathepun--that was truly hilarious. FEED ME! Palyne Like Save tony_k_orlando 20 years ago I only have two things to say to all you tormentors of plants..... and its simple, listen close now.... Red is positive and black is negative. Thanks for the tip on the book "The Secret Life Of Plants" I ordered it from the library today. Cant wait to check it out. Like Save pickwick 20 years ago i think it makes plants more attractive Like Save janemccl 20 years ago I have never grown plants with magnets. However, my dentist made me get a water pick which helped some with gum infection, but I still had problems. Then the water pick broke, and the hygenist recommended a magnetic water pick. The water got magnetized as it went through the machine. The infection all disappeared in three months by the next check up, and has not come back. Because the water pick impressed me, I bought some magnets from the internet and started magnetizing my drinking water. At first I felt great, then, after a couple of months, not so great. The magnets are reputed to make hard water soft, so maybe they removed too much magnesium and potassium from the water and my body didn't get enough. I would like to go back to it though. I think a glass a day might be good. It may clear infections? Also, I put some flowers in magnetic water, and the water NEVER got yucky, and the flowers lasted a LONG time. The water stayed clear and sweet with no rot on the flower stems. What magnetic water does to sprouting seeds or growing plants, I don't know. Best, Jane Like Save pickwick 20 years ago interesting association,Jane...have used electrostatic sprayers -a device located at the nozzle which charges mist particles emitted from a sprayer resulting in greater coverage with less product Like Save Mathmom1 19 years ago Who has actually experimented with either north pole facing the water for plants or south pole facing water for plants and recorded results? I am about to plant just harvested amaryillis seed in three containers. I'll use magnetized water to water two flats and non magnetized in the third. The water will be in a jar with a magnet wrapped around the jar oriented north for one, south for the second and none for the third. I will refill the water after watering each time from the tap, note how much water each flat used, and record germination percents and heights of each plant. Any suggestions from this forum's users? Like Save gingerhill 19 years ago Hysterical, I thought the post said magets. I must drink more coffee. I was thinking ewww, why would anyone want to try that. Thank goodness it's magnets :) Like \| 1 Save Amino_X 19 years ago What type of magnets are you using? Standard Ferric Oxides? Rare Earth? or Neodymiums? I did some experiments with diametricly opposed neodymium magnetic levitation some years back, but never thought to apply it to plants! Hmmm... Let us know how it works out :D Best Wishes Amino-X Like Save jkirk3279 19 years ago When starting plants this spring, I put a big speaker magnet underneath some Physallis Mullaca seedlings. A day later they had doubled in size ! I decided to follow up on this, so I cut squares of magnetic backed material I use to make magnetic signs. I put it under the seedlings. And nothing happened. So maybe the magnetic sign stuff wasn't strong enough. If this DID have good effects on the seedlings at first, I couldn't repeat the results. Maybe stronger magnets -- or opposing polarity would help. Like Save the_alpha_wolf_rules 19 years ago lol! it's spelled "maggots" anyway. Like Save The_Tree 18 years ago You can increase the growth of plants with magnets. The best way is to put seeds on a flat magnet (about 1500-2500 gauss) for a period of 2-6 days before planting. You'll need to experiment to find the absolute best length of time to leave them on the magnet. Plant the seeds within a day after taking them off of the magnet. You can magnetize the water that you water the plants with too. The polarity of the magnet does matter. Usually the South pole will increase growth. Some plants actually do better with North pole energy. Magnets can be attached to the hose (south pole of magnet facing hose) and given to the roots only, not the foliage. Using magnetized water alone can significantly increase the growth. If you thoroughly look into the history of using magnets for growing plants, you'll come accross the information I've given you, but it's difficult to find. Remember, the side of the magnet you put the seeds on and the side of the magnet facing the hose makes all of the difference. Generally, plants that grow under ground (potatoes) prefer North pole energy, above ground plants prefer South pole energy. There are exceptions. Magnetizing your plants is well worth the effort. They'll taste better and have a higher yield. Like \| 1 Save The_Tree 18 years ago Find the scientist that first discovered that magnetism consists of two separate energies and you've found my source. If your skeptical that water can be magnetized, do a google search on 'U.S. government studies on magnetized water'. In 1973, there was a government study that confirmed that magnetic energy alters the properties of water. It also states that the Soviet Union has used magnetized water for many years with great economic benefit. Like Save The_Tree 18 years ago And now the answer you've all been waiting for... It was Albert Roy Davis and Walter C. Rawls that made these discoveries. Plant yields can be increased from 20% to 200%! The plants will have a higher concentration of nutrients too. I've done experiments myself. They wrote about these and other fascinating experiments in their first book, "Magnetism and Its Effects on the Living System". There are some species that will grow better with exposure to North AND South pole energy. For example, the North pole plants may give you the highest yield, but the South pole plants will have the most nutrients. In these cases both will have improved qualities over plants of the same species that haven't been exposed to either magnetic field. You can find more information about this discovery on the U.S. Patent and Trademark Office website, patent # 4,020,590. Like Save mistercross 18 years ago This sounds like a perfect test for the Mythbusters on the Discovery Channel, especially if they still have the ten greenhouses from the test of music on plant growth. I would suggest it to them, but I block cookies and apparently can't post there. Here is a long article on magnetic claims, but it only briefly mentions that plant growth is one claim. Here is a student science fair test, in PDF format, on the effect of magnetism on plant growth. Here is a link that might be useful: Discovery Channel: Mythbusters Like Save The_Tree 18 years ago Take a look at how an MRI works. http://www.ccmr.cornell.edu/education/ask/?quid=41 Like Save snorelas 18 years ago hey, i am also doing the magnet experiment and i need something to back up my oun result, would you be able to send me some of your results? Like Save wayne_5 zone 6a Central Indiana 18 years ago Now how about people magnetism....I read where it is best to have your bed situated so that your head [top of] is facing the north, and second best if headed south............................"? Like Save albert_135 39.17°N 119.76°W 4695ft. 18 years ago I read somewhere that native plants growing under high power transmission lines did better than the same plants nearby. I haven't been able to confirm this. I thought that the high power transmission lines might have rapidly reversing magnetic fields but haven't been able to confirm that either. Like Save ascalon 17 years ago Has anyone any information on exactly what should be done with magnets to water or the plants directly? Like what kind of magnets, and what to do with them, and where. Please feel free to email me information at [email protected]. Like Save kelly_r 15 years ago I'm doing the whole magnet and seed thing also, but im having trouble with my research report. Anyone know of any usefull websites i could use? Like Save dethcheez 15 years ago I can't say that I've ever tried anything or even thought about trying anything with plants and magnets... But now I'm going to have to, thanx a lot... If any of my Carns eat me I'm blaming you guys... LOL... My many interest is Carns & Neps which do best with distilled water as I'm sure most plant probably would... Can/does the magnet in the water have anything to do with it possibly attracting unwanted metals/minerals in the water??? Kind of like a filter / Helping to purify it & making it healthier for the plants??? Also in the soil, Attracting / Repelling minerals to or away from the plant??? ??? Just thought I'd throw my 2 cents in... Like Save maifleur01 15 years ago I will post a new topic as I don't want to highjack this thread. Like Save kayjones 15 years ago Here's the link to this patent number - very interesting! Here is a link that might be useful: Magnets and seeds Like Save noway_ever_com 13 years ago I personally conducted an experiment with 0, 4000, 8000, 12000, and 16000 gauss, with neodymium magnets at 2000 gauss each. I measured O2 released over a period of slightly under a week, with a 40w light source. All specimens were placed 20 cm away, so as not to have interference between magnetic fields (the measured angle of compass deflection was at 18 cm). up to 4000, there was no significant difference in the amount of O2 produced by the plant(in the technical term). 16000 gauss, however, was under 55% efficient: a significant difference (in the technical term). This is logical because the magnetism will disrupt the plant's electron transport chain- which is a vital step in photosynthesis and cellular respiration. the (rough) results were: 0 gauss: 100% efficiency (inherent) 4000 gauss: 100% efficiency 8000 gauss: 75% efficiency 12000 gauss: 66% efficiency 16000 gauss: 55% efficiency so, no, magnetism does not help your plants grow. It starves and suffocates them. Like Save gigadygig_yahoo_com 13 years ago sniff this Like Save kelly.jb9398 12 years ago I'm doing a science fair project for my school. I'm experimenting on the effects of magnetism on plant growth. I'll using three pots of Sweet Basil plants. One will be a regular plant. The others will be under some type of influence of magnetism. I don't know what yet, but i might just do magnetized water. Please share some ideas that you have. Like \| 1 Save kelly.jb9398 12 years ago I've decided to use rosemary instead. I placed four magnets next to a potted plant on my windowsill and it started doing some weird things. The branches began spiraling. Like \| 1 Save ElectricFertilizer 11 years ago In a book called Electroculture by George Hull, one experimented from the 1800s sowed seeds over a set of wires placed in the soil and experienced significant increases in growth. I would attribute this to the electromagnetic fields produced by the current flow in a wire. Perhaps the difference comes from the field lines being circular vs linear from a regular magnet?? Like Save coing 11 years ago Kelly, An experiment is most likely to reveal the truth of the question if there is a control (comparing treated to untreated plants in exactly equal conditions) and also if it is double-blinded. This means that one person would assign the treatments, but another person, blind to which pot was treated in which way, would do the observations. This would prevent the observer from something we all do without realizing it: seeing what we want to see. Good luck with your project, let us know how it came out. Coing Like Save Konrad___far_north 10 years ago It was around 40 years ago when I helped out on a farm in southern Alberta, seeding HUGE fields of wheat etc. The farmer had a large coil hooked up on a power source, he just run seeds through this devise. Anybody done this? Like \| 1 Save albert_135 39.17°N 119.76°W 4695ft. 10 years ago FYI, Harbor Freight has some approx. 1X1X3 inch magnets that are supposed to lift 200 lb. About $18 each. Like Save David.Sturtz 10 years ago I am a retired electronics tech. Only iron has strongly magnetic properties. Water in particular is unaffected by magnetism because it has two covanlent chemical bonds rather than an ionic bond. It is not possible to magnetize a non magnetic material such as water. Running water past a magnet will not magnetize it any more than it would glass. There is some evidence, however, that growing plants in a magnetic field, can affect growth. Like Save Mokinu 8 years ago last modified: 8 years ago So, how did everyone's science fair experiments turn out? I wouldn't be surprised if plants and seeds could sense magnetic fields to some degree in an effort to see what kind of climate they're growing in. Maybe magnetizing seeds can speed this process up. After all, birds can sense magnetic fields. Like Save Seysonn_ 8a-NC/HZ-7 8 years ago I have never heard of such a thing : i.e the effect of magnet on plants growth. Why don't you just fertilize ? You want oxygen to get into the roots, amend with organic matter. I add some fine pine bark, to improve drainage and get oxygen to the roots. Sey Like \| 1 Save Mokinu 8 years ago last modified: 8 years ago As I understand it, if there's an effect on plants with magnetism, it should likely be a cumulative effect, and not something that extra care of your plants is going to make completely irrelevant, whether or not that extra care is all your plants need. Since perhaps no one really knows the effect, though, it's a moot point whether the effect is cumulative until figured out. I think there's sufficient reason to study it. Like Save albert_135 39.17°N 119.76°W 4695ft. 8 years ago ''Why don't you just..." is usually what professionals call a micro rant: The Microcomplaint: Nothing Too Small to Whine About - The New York Times - The Microcomplaint: Nothing Too Small to Whine About Like \| 1 Save PRO husbands helper 8 years ago I know magnets shoot photons at each other which causes a magnetic field. These are the same photons that light uses to travel so I am very curious if that would speed up photosynthesis...but no spacific answers I can find Like \| 1 Save Mokinu 8 years ago last modified: 8 years ago Interesting thought. I got some magnets for my own experimentation (primarily their effect when used on seeds before planting). So, hopefully I'll have something to report by the end of next season. It sounds like you're interested in post-planting information. I might try stuff out there, too, but it's not my main priority. I would suggest experimenting using the magnets at night, if you're going to use them on plants. Like \| 1 Save Mokinu 8 years ago last modified: 8 years ago Check this out: http://www.ncbi.nlm.nih.gov/pubmed/18512697 It looks like we've got some proof, for chickpea seeds, anyway. A gauss is a tenth of an mT. So, 1000 gauss static magnet exposure for an hour should produce results in chickpeas, or 500 gauss for two hours or 1500 gauss for two hours. Like \| 1 Save Mokinu 8 years ago Here's another link to explain how it helps if water is exposed to magnets. Apparently, it's supposed to make saltier water easier for plants to absorb: https://www.usaid.gov/news-information/frontlines/feed-future/magnets-help-plants-grow Like \| 1 Save zen_man 5 years ago The earth is a big magnet, so a valid experiment would be to see how plants grow in the absence of a magnetic field. Isolating a plant from the earth's magnetic field might be a little hard to do, but maybe a Faraday Cage would do the trick. Like Save David 3 years ago Earth is not a magnet. Nothing in nature is polar. Like Save Set Apart Spirit 2 years ago If you expose what’s commonly called the north pole (N&S poles dont exist) to tomato seeds for 30min proir to gemination, your yield will be less acidic! 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Garage Building New Home Construction Basement Remodeling Stair & Railing Contractors Carpenters Cabinetry & Cabinet Makers Roofing & Gutter Contractors Window Contractors Exterior & Siding Contractors Carpet Contractors Carpet Installation Flooring Contractors Wood Floor Refinishing Tile Installation Tile & Stone Custom Countertops Quartz Countertops Cabinet Refinishing Custom Bathroom Vanities Finish Carpentry Cabinet Repair Custom Windows Window Treatment Services Window Repair Fireplace Contractors Painters Paint & Wall Covering Dealers Door Contractors Glass & Shower Door Contractors Landscape Architects & Landscape Designers Landscape Contractors Landscape Construction Land Clearing Garden & Landscape Supplies Deck & Patio Builders Deck Repair Patio Design Stone, Pavers, & Concrete Paver Installation Driveway & Paving Contractors Driveway Repair Asphalt Paving Garage Door Repair Fence Contractors Fence Installation Gate Repair Pergola Construction Spa & Pool Maintenance Swimming 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Lead Generation Invoicing & Billing Estimating Architect Software Project Management Custom Website Lead Generation Invoicing & Billing CRM Takeoff Software Lumber & Framing Takeoffs Steel Takeoffs Concrete Takeoffs Drywall Takeoffs Insulation Takeoffs Houzz Pro: One simple solution for contractors and design pros Join as a Pro History of Houzz Get Ideas Photos Kitchen & Dining Kitchen Dining Room Pantry Great Room Breakfast Nook Living Living Room Family Room Sunroom Bed & Bath Bathroom Powder Room Bedroom Storage & Closet Baby & Kids Utility Laundry Garage Mudroom Outdoor Landscape Patio Deck Pool Backyard Porch Exterior Outdoor Kitchen Front Yard Driveway Poolhouse Bar & Wine Home Bar Wine Cellar More Rooms Game Room Home Office Basement Craft Library Gym Popular Design Ideas Kitchen Backsplash Firepit Fireplace Deck Railing Pergola Privacy Fence Small Closet Stories Stories and Guides Popular Stories Renovation Cost Guides Fence Installation Cost Guide Window Installation Cost Guide Discussions Get Advice Design Dilemmas Before & After Houzz TV Houzz Research Find Professionals Popular Professionals Design & Planning Construction & Renovation Finishes & Fixtures Landscaping & Outdoor Systems & Appliances More Interior Designers & Decorators Architects & Building Designers Design-Build Firms Kitchen & Bathroom Designers General Contractors Kitchen & Bathroom Remodelers Home Builders Roofing & Gutters Cabinets & Cabinetry Tile & Stone Hardwood Flooring Dealers Painters Landscape Contractors Landscape Architects & Landscape Designers Home Stagers Swimming Pool Builders Architects & Building Designers Design-Build Firms Interior Designers & Decorators Kitchen & Bathroom Designers Lighting Designers and Suppliers 3D Rendering Sustainable Design Basement Design Architectural Design Universal Design Energy-Efficient Homes Multigenerational Homes House Plans General Contractors Home Builders Kitchen & Bathroom Remodelers Home Remodeling Home Additions Green Building 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Doors Home Improvement Sale Trending in Home Improvement View All Home Improvement Tabletop Dinnerware Serveware Flatware Cups & Glassware Kitchen & Table Linens Kitchen Storage and Org Kitchen Islands & Carts Food Containers & Canisters Pantry & Cabinet Organizers Pot Racks Wine Racks Kitchen Appliances Gas & Electric Ranges Range Hoods & Vents Beer & Wine Refrigerators Small Kitchen Appliances Cookware & Bakeware Tools & Gadgets Kitchen Fixtures Kitchen & Tabletop Sale Trending in Kitchen & Tabletop View All Kitchen & Tabletop Home Bar Storage & Organization Baby & Kids Housekeeping & Laundry Pet Supplies All Sales View All Products Looking for the perfect gift? 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Cancel Outdoor Sale Sale ON SALE - UP TO 75% OFF Bathroom Vanities Chandeliers Bar Stools Pendant Lights Rugs Living Room Chairs Dining Room Furniture Wall Lighting Coffee Tables Side & End Tables Home Office Furniture Sofas Bedroom Furniture Lamps Mirrors Outdoor Sale UP TO 60% OFF Pots and Planters UP TO 70% OFF Outdoor Rugs UP TO 60% OFF Season's Biggest Outdoor Sale UP TO 60% OFF Patio Furniture Sign In Join as a Pro Interior Design Software Project Management Custom Website Lead Generation Invoicing & Billing Proposals Landscape Contractor Software Project Management Custom Website Lead Generation Invoicing & Billing Estimating General Contractor Software Project Management Custom Website Lead Generation Invoicing & Billing Estimating Remodeler Software Project Management Custom Website Lead Generation Invoicing & Billing Estimating Builder Software Project Management Custom Website Lead Generation Invoicing & Billing Estimating Roofer Software Project Management Custom Website Lead Generation Invoicing & Billing Estimating Architect Software Project Management Custom Website Lead Generation Invoicing & Billing CRM Takeoff Software Lumber & Framing Takeoffs Steel Takeoffs Concrete Takeoffs Drywall Takeoffs Insulation Takeoffs Houzz Pro: One simple solution for contractors and design pros Join as a Pro History of Houzz Get Ideas Photos Kitchen & Dining Kitchen Dining Room Pantry Great Room Breakfast Nook Living Living Room Family Room Sunroom Bed & Bath Bathroom Powder Room Bedroom Storage & Closet Baby & Kids Utility Laundry Garage Mudroom Outdoor Landscape Patio Deck Pool Backyard Porch Exterior Outdoor Kitchen Front Yard Driveway Poolhouse Bar & Wine Home Bar Wine Cellar More Rooms Game Room Home Office Basement Craft Library Gym Popular Design Ideas Kitchen Backsplash Firepit Fireplace Deck Railing Pergola Privacy Fence Small Closet Stories Stories and Guides Popular Stories Renovation Cost Guides Fence Installation Cost Guide Window Installation Cost Guide Discussions Get Advice Design Dilemmas Before & After Houzz TV Houzz Research Find Professionals Popular Professionals Design & Planning Construction & Renovation Finishes & Fixtures Landscaping & Outdoor Systems & Appliances More Interior Designers & Decorators Architects & Building Designers Design-Build Firms Kitchen & Bathroom Designers General Contractors Kitchen & Bathroom Remodelers Home Builders Roofing & Gutters Cabinets & Cabinetry Tile & Stone Hardwood Flooring Dealers Painters Landscape Contractors Landscape Architects & Landscape Designers Home Stagers Swimming Pool Builders Architects & Building Designers Design-Build Firms Interior Designers & Decorators Kitchen & Bathroom Designers Lighting Designers and Suppliers 3D Rendering Sustainable Design Basement Design Architectural Design Universal Design Energy-Efficient Homes Multigenerational Homes House Plans General Contractors Home Builders Kitchen & Bathroom Remodelers Home Remodeling Home Additions Green Building Garage Building New Home Construction Basement Remodeling Stair & Railing Contractors Carpenters Cabinetry & Cabinet Makers Roofing & Gutter Contractors Window Contractors Exterior & Siding Contractors Carpet Contractors Carpet Installation Flooring Contractors Wood Floor Refinishing Tile Installation Tile & Stone Custom Countertops Quartz Countertops Cabinet Refinishing Custom Bathroom Vanities Finish Carpentry Cabinet Repair Custom Windows Window Treatment Services Window Repair Fireplace Contractors Painters Paint & Wall Covering Dealers Door Contractors Glass & Shower Door Contractors Landscape Architects & Landscape Designers Landscape Contractors Landscape Construction Land Clearing Garden & Landscape Supplies Deck & Patio Builders Deck Repair Patio Design Stone, Pavers, & Concrete Paver Installation Driveway & Paving Contractors Driveway Repair Asphalt Paving Garage Door Repair Fence Contractors Fence Installation Gate Repair Pergola Construction Spa & Pool Maintenance Swimming Pool Contractors Hot Tub Installation HVAC Contractors Plumbers Electricians Appliance Services Solar Energy Contractors Outdoor Lighting Installation Landscape Lighting Installation Outdoor Lighting & Audio/Visual Specialists Home Theater & Home Automation Services Handyman Services Closet Designers Professional Organizers Furniture & Accessories Retailers Furniture Repair & Upholstery Services Specialty Contractors Color Consulting Wine Cellar Designers & Builders Home Stagers Home Inspection Welding Blacksmith Custom Artists Columbus, OH Painters New York City, NY Landscapers San Diego, CA Bathroom Remodelers Minneapolis, MN Architects Portland, OR Tile Installers Kansas City, MO Flooring Contractors Denver, CO Countertop Installers San Francisco, CA New Home Builders All Professionals All Services For Professionals Shop Products Popular Furniture Bath Outdoor Rugs & Decor Lighting Home Improvement Kitchen & Tabletop More Bath Bathroom Vanities Bathroom Vanity Lighting Bathroom 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Outdoor Rugs 5 x 7 Rugs 8 x 10 Rugs 9 x 12 Rugs Hall & Stair Runners Rug Pads Home Decor & Accents Pillows & Throws Vases Clocks Decorative Storage Faux Florals Bedding Wall Decor Mirrors Wall Mirrors Artwork Wallpaper Wall Panels Window Treatments Curtains Curtain Rods Blackout Curtains Blinds & Shades Rugs & Decor Sale Trending in Rugs & Decor View All Rugs & Decor Ceiling Lighting Chandeliers Pendant Lights Flush-Mounts Ceiling Fans Track Lighting Wall Lighting Wall Sconces Swing Arm Wall Lights Display Lighting Lamps Table Lamps Floor Lamps Desk Lamps Lamp Shades Outdoor Lighting Lighting Sale Trending in Lighting View All Lighting Bathroom Remodel Bathroom Vanities Bathroom Faucets Bathroom Sinks Bathtubs Showers Toilets Kitchen Remodel Kitchen Faucets Kitchen Sinks Major Kitchen Appliances Cabinet Hardware Backsplash Tile Tile Mosaic Tile Wall & Floor Tile Accent, Trim & Border Tile Whole House Remodel Heating & Cooling Hardware Building Materials Windows Front Doors Interior Doors Home Improvement Sale Trending in Home Improvement View All Home Improvement Tabletop Dinnerware Serveware Flatware Cups & Glassware Kitchen & Table Linens Kitchen Storage and Org Kitchen Islands & Carts Food Containers & Canisters Pantry & Cabinet Organizers Pot Racks Wine Racks Kitchen Appliances Gas & Electric Ranges Range Hoods & Vents Beer & Wine Refrigerators Small Kitchen Appliances Cookware & Bakeware Tools & Gadgets Kitchen Fixtures Kitchen & Tabletop Sale Trending in Kitchen & Tabletop View All Kitchen & Tabletop Home Bar Storage & Organization Baby & Kids Housekeeping & Laundry Pet Supplies All Sales View All Products Looking for the perfect gift? Send a Houzz Gift Card! Cancel Outdoor Sale Sale ON SALE - UP TO 75% OFF Bathroom Vanities Chandeliers Bar Stools Pendant Lights Rugs Living Room Chairs Dining Room Furniture Wall Lighting Coffee Tables Side & End Tables Home Office Furniture Sofas Bedroom Furniture Lamps Mirrors Outdoor Sale UP TO 60% OFF Pots and Planters UP TO 70% OFF Outdoor Rugs UP TO 60% OFF Season's Biggest Outdoor Sale UP TO 60% OFF Patio Furniture Sign In Join as a Pro Interior Design Software Project Management Custom Website Lead Generation Invoicing & Billing Proposals Landscape Contractor Software Project Management Custom Website Lead Generation Invoicing & Billing Estimating General Contractor Software Project Management Custom Website Lead Generation Invoicing & Billing Estimating Remodeler Software Project Management Custom Website Lead Generation Invoicing & Billing Estimating Builder Software Project Management Custom Website Lead Generation Invoicing & Billing Estimating Roofer Software Project Management Custom Website Lead Generation Invoicing & Billing Estimating Architect Software Project Management Custom Website Lead Generation Invoicing & Billing CRM Takeoff Software Lumber & Framing Takeoffs Steel Takeoffs Concrete Takeoffs Drywall Takeoffs Insulation Takeoffs Houzz Pro: One simple solution for contractors and design pros Join as a Pro History of Houzz Get Ideas Photos Kitchen & Dining Kitchen Dining Room Pantry Great Room Breakfast Nook Living Living Room Family Room Sunroom Bed & Bath Bathroom Powder Room Bedroom Storage & Closet Baby & Kids Utility Laundry Garage Mudroom Outdoor Landscape Patio Deck Pool Backyard Porch Exterior Outdoor Kitchen Front Yard Driveway Poolhouse Bar & Wine Home Bar Wine Cellar More Rooms Game Room Home Office Basement Craft Library Gym Popular Design Ideas Kitchen Backsplash Firepit Fireplace Deck Railing Pergola Privacy Fence Small Closet Stories Stories and Guides Popular Stories Renovation Cost Guides Fence Installation Cost Guide Window Installation Cost Guide Discussions Get Advice Design Dilemmas Before & After Houzz TV Houzz Research Find Professionals Popular Professionals Design & Planning Construction & Renovation Finishes & Fixtures Landscaping & Outdoor Systems & Appliances More Interior Designers & Decorators Architects & Building Designers Design-Build Firms Kitchen & Bathroom Designers General Contractors Kitchen & Bathroom Remodelers Home Builders Roofing & Gutters Cabinets & Cabinetry Tile & Stone Hardwood Flooring Dealers Painters Landscape Contractors Landscape Architects & Landscape Designers Home Stagers Swimming Pool Builders Architects & Building Designers Design-Build Firms Interior Designers & Decorators Kitchen & Bathroom Designers Lighting Designers and Suppliers 3D Rendering Sustainable Design Basement Design Architectural Design Universal Design Energy-Efficient Homes Multigenerational Homes House Plans General Contractors Home Builders Kitchen & Bathroom Remodelers Home Remodeling Home Additions Green Building Garage Building New Home Construction Basement Remodeling Stair & Railing Contractors Carpenters Cabinetry & Cabinet Makers Roofing & Gutter Contractors Window Contractors Exterior & Siding Contractors Carpet Contractors Carpet Installation Flooring Contractors Wood Floor Refinishing Tile Installation Tile & Stone Custom Countertops Quartz Countertops Cabinet Refinishing Custom Bathroom Vanities Finish Carpentry Cabinet Repair Custom Windows Window Treatment Services Window Repair Fireplace Contractors Painters Paint & Wall Covering Dealers Door Contractors Glass & Shower Door Contractors Landscape Architects & Landscape Designers Landscape Contractors Landscape Construction Land Clearing Garden & Landscape Supplies Deck & Patio Builders Deck Repair Patio Design Stone, Pavers, & Concrete Paver Installation Driveway & Paving Contractors Driveway Repair Asphalt Paving Garage Door Repair Fence Contractors Fence Installation Gate Repair Pergola Construction Spa & Pool Maintenance Swimming Pool Contractors Hot Tub Installation HVAC Contractors Plumbers Electricians Appliance Services Solar Energy Contractors Outdoor Lighting Installation Landscape Lighting Installation Outdoor Lighting & Audio/Visual Specialists Home Theater & Home Automation Services Handyman Services Closet Designers Professional Organizers Furniture & Accessories Retailers Furniture Repair & Upholstery Services Specialty Contractors Color Consulting Wine Cellar Designers & Builders Home Stagers Home Inspection Welding Blacksmith Custom Artists Columbus, OH Painters New York City, NY Landscapers San Diego, CA Bathroom Remodelers Minneapolis, MN Architects Portland, OR Tile Installers Kansas City, MO Flooring Contractors Denver, CO Countertop Installers San Francisco, CA New Home Builders All Professionals All Services For Professionals Shop Products Popular Furniture Bath Outdoor Rugs & Decor Lighting Home Improvement Kitchen & Tabletop More Bath Bathroom Vanities Bathroom Vanity Lighting Bathroom Mirrors Bathroom Fixtures Bathtubs Bedroom Beds Nightstands & Bedside Tables Dressers Kitchen & Dining Bar Stools & Counter Stools Dining Chairs Dining Tables Buffets and Sideboards Kitchen Fixtures Decor Rugs Area Rugs Wall Mirrors Living Room Armchairs & Accent Chairs Coffee & Accent Tables Sofas & Sectionals Media Storage Outdoor Patio & Outdoor Furniture Fire Pits Outdoor Lighting Lighting Ceiling Lighting Chandeliers Pendant Lighting Wall Sconces Lamps Office Desks & Hutches Office Chairs View All Products Designer Picks Living Room Sofas & Sectionals Coffee & Accent Tables Side & End Tables Console Tables Armchairs & Accent Chairs Living Room Sets TV Stands Chaise Lounges Ottomans & Poufs Bedroom Furniture Beds Dressers Nightstands Headboards Bed Frames Bedroom Sets Mattresses Kitchen & Dining Bar Stools Dining Tables Dining Chairs Dining Room Sets Sideboards & Buffets Office Desks Bookcases File Cabinets Office Chairs Room Dividers Furniture Sale Trending in Furniture Living Room Bedroom Furniture Kitchen & Dining View All Furniture Bath Vanities Single Vanities Double Vanities Small Vanities Transitional Vanities Modern Vanities Houzz Curated Vanities Best Selling Vanities Bathroom Mirrors Bathroom Vanity Mirrors Medicine Cabinets Bathroom Vanity Lighting Bathroom Faucets Bathroom Sinks Bathroom Fixtures Bathtubs Toilets Shower Doors Showerheads & Body Sprays Bathroom Accessories Bathroom Storage Bath Sale Trending in Bath View All Bath Designer Picks Houzz x Jennifer Kizzee Houzz x Motivo Home How to Choose a Bathroom Vanity Patio Furniture Outdoor Dining Furniture Outdoor Lounge Furniture Outdoor Chairs Adirondack Chairs Outdoor Bar Furniture Outdoor Benches Outdoor Lighting Wall Lights & Sconces Outdoor Flush-Mounts Landscape Lighting Outdoor Flood & Spot Lights Outdoor Decor Outdoor Rugs Doormats Outdoor Cushions & Pillows Patio Umbrellas Lawn & Garden Garden Statues & Yard Art Planters & Pots Fire Pits Outdoor Sale Trending in Outdoor View All Outdoor Rugs 5 x 7 Rugs 8 x 10 Rugs 9 x 12 Rugs Hall & Stair Runners Rug Pads Home Decor & Accents Pillows & Throws Vases Clocks Decorative Storage Faux Florals Bedding Wall Decor Mirrors Wall Mirrors Artwork Wallpaper Wall Panels Window Treatments Curtains Curtain Rods Blackout Curtains Blinds & Shades Rugs & Decor Sale Trending in Rugs & Decor View All Rugs & Decor Ceiling Lighting Chandeliers Pendant Lights Flush-Mounts Ceiling Fans Track Lighting Wall Lighting Wall Sconces Swing Arm Wall Lights Display Lighting Lamps Table Lamps Floor Lamps Desk Lamps Lamp Shades Outdoor Lighting Lighting Sale Trending in Lighting View All Lighting Bathroom Remodel Bathroom Vanities Bathroom Faucets Bathroom Sinks Bathtubs Showers Toilets Kitchen Remodel Kitchen Faucets Kitchen Sinks Major Kitchen Appliances Cabinet Hardware Backsplash Tile Tile Mosaic Tile Wall & Floor Tile Accent, Trim & Border Tile Whole House Remodel Heating & Cooling Hardware Building Materials Windows Front Doors Interior Doors Home Improvement Sale Trending in Home Improvement View All Home Improvement Tabletop Dinnerware Serveware Flatware Cups & Glassware Kitchen & Table Linens Kitchen Storage and Org Kitchen Islands & Carts Food Containers & Canisters Pantry & Cabinet Organizers Pot Racks Wine Racks Kitchen Appliances Gas & Electric Ranges Range Hoods & Vents Beer & Wine Refrigerators Small Kitchen Appliances Cookware & Bakeware Tools & Gadgets Kitchen Fixtures Kitchen & Tabletop Sale Trending in Kitchen & Tabletop View All Kitchen & Tabletop Home Bar Storage & Organization Baby & Kids Housekeeping & Laundry Pet Supplies All Sales View All Products Looking for the perfect gift? 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Professionals Accessibility Houzz Support Contact Sign In CONNECT WITH US CONNECT WITH US Houzz Blog Twitter Facebook YouTube RSS PRIVACY & LEGAL Privacy & Notice Terms Cookie Policy Copyright & Trademark SETTINGS COUNTRY COUNTRY BACK HOME GET IDEAS GET IDEAS View all photos Photos Kitchen & Dining Kitchen Dining Room Pantry Great Room Breakfast Nook Living Living Room Family Room Sunroom Bed & Bath Bathroom Powder Room Bedroom Storage & Closet Baby & Kids Utility Laundry Garage Mudroom Outdoor Landscape Patio Deck Pool Backyard Porch Exterior Outdoor Kitchen Front Yard Driveway Poolhouse Bar & Wine Home Bar Wine Cellar More Rooms Game Room Home Office Basement Craft Library Gym Popular Design Ideas Kitchen Backsplash Firepit Fireplace Deck Railing Pergola Privacy Fence Small Closet Stories Stories and Guides Popular Stories Renovation Cost Guides Fence Installation Cost Guide Window Installation Cost Guide Discussions Get Advice Design Dilemmas Before & After Houzz TV Houzz Research FIND PROFESSIONALS FIND PROFESSIONALS View all pros View all services Popular Professionals Interior Designers & Decorators Architects & Building Designers Design-Build Firms Kitchen & Bathroom Designers General Contractors Kitchen & Bathroom Remodelers Home Builders Roofing & Gutters Cabinets & Cabinetry Tile & Stone Hardwood Flooring Dealers Painters Landscape Contractors Landscape Architects & Landscape Designers Home Stagers Swimming Pool Builders Design & Planning Architects & Building Designers Design-Build Firms Interior Designers & Decorators Kitchen & Bathroom Designers Lighting Designers and Suppliers 3D Rendering Sustainable Design Basement Design Architectural Design Universal Design Energy-Efficient Homes Multigenerational Homes House Plans Construction & Renovation General Contractors Home Builders Kitchen & Bathroom Remodelers Home Remodeling Home Additions Green Building Garage Building New Home Construction Basement Remodeling Stair & Railing Contractors Carpenters 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Invoicing & Billing CRM Takeoff Software Lumber & Framing Takeoffs Steel Takeoffs Concrete Takeoffs Drywall Takeoffs Insulation Takeoffs MAGAZINE MAGAZINE Stories & Guides Popular Stories Renovation Cost Guides Houzz TV LATEST FROM HOUZZ DISCUSSIONS DISCUSSIONS Get Advice Design Dilemmas Before & After HOUZZ DISCUSSIONS KITCHEN KITCHEN SHOP KITCHEN & DINING Kitchen & Dining Furniture Tile Sinks & Faucets Appliances Tabletop Kitchen Cabinets & Storage Knobs & Pulls Lighting Cookware & Bakeware Tools & Gadgets Kitchen Knives View More KITCHEN PHOTOS Kitchen Dining FIND KITCHEN PROS BATH BATH SHOP BATH Bathroom Vanities Lighting Tile Showers Bathtubs Faucets Sinks Bath Accessories Bath Linens Medicine Cabinets Toilets View More BATH PHOTOS Bathroom Powder Room FIND BATH PROS BEDROOM BEDROOM SHOP BEDROOM Beds & Headboards Bedding Bedroom Decor Lamps Dressers Nightstands Closet Storage Futons Benches Chaises Bedroom Vanities View More BEDROOM PHOTOS Bedroom Kids' Room FIND DESIGN PROS LIVING LIVING SHOP LIVING Home Decor Coffee & Accent Tables Rugs Sofas & Sectionals Armchairs & Accent Chairs Lamps Artwork Media Storage Bookcases Fireplaces & Accessories Ottomans View More LIVING PHOTOS Living Room Family Room FIND DESIGN PROS OUTDOOR OUTDOOR SHOP OUTDOOR Furniture Lighting Outdoor Decor Lawn & Garden Pool & Spa Fire Pits Grills Backyard Play View More OUTDOOR PHOTOS Landscape Patio Pool Porch Deck FIND LANDSCAPING PROS LIGHTING LIGHTING SHOP LIGHTING Chandeliers Pendant Lighting Bathroom & Vanity Wall Sconces Flush Mounts Ceiling Fans Table Lamps Floor Lamps Kitchen & Cabinet Outdoor Wall Lights Outdoor Hanging Lights Kids' Lighting View More DECOR DECOR SHOP DECOR Decorative Accents Rugs Mirrors Wall Mirrors Wall Decor Artwork Pillows & Throws Window Treatments Artificial Flowers & Plants Clocks Decorative Objects Screens & Room Dividers Wall Shelves View More ABOUT COMPANY COMPANY About Houzz Houzz Credit Cards Gift Cards Careers Privacy & Notice Terms Cookie Policy Your Privacy Choices Mobile Apps Copyright & Trademark BUSINESS SERVICES BUSINESS SERVICES For Professionals Houzz vs. Houzz Pro Houzz Pro vs. Ivy Houzz Pro Advertising Reviews Houzz Pro 3D Floor Planner Reviews For Brands Trade Program Buttons & Badges GET HELP GET HELP Your Orders Shipping & Delivery Return Policy Houzz Canada Review Professionals Suggested Professionals Accessibility Houzz Support Contact Sign In CONNECT WITH US CONNECT WITH US Houzz Blog Twitter Facebook YouTube RSS PRIVACY & LEGAL Privacy & Notice Terms Cookie Policy Copyright & Trademark SETTINGS COUNTRY COUNTRY HOME GET IDEAS GET IDEAS View all photos Photos Kitchen & Dining Kitchen Dining Room Pantry Great Room Breakfast Nook Living Living Room Family Room Sunroom Bed & Bath Bathroom Powder Room Bedroom Storage & Closet Baby & Kids Utility Laundry Garage Mudroom Outdoor Landscape Patio Deck Pool Backyard Porch Exterior Outdoor Kitchen Front Yard Driveway Poolhouse Bar & Wine Home Bar Wine Cellar More Rooms Game Room Home Office Basement Craft Library Gym Popular Design Ideas Kitchen Backsplash Firepit Fireplace Deck Railing Pergola Privacy Fence Small Closet Stories Stories and Guides Popular Stories Renovation Cost Guides Fence Installation Cost Guide Window Installation Cost Guide Discussions Get Advice Design Dilemmas Before & After Houzz TV Houzz Research FIND PROFESSIONALS FIND PROFESSIONALS View all pros View all services Popular Professionals Interior Designers & Decorators Architects & Building Designers Design-Build Firms Kitchen & Bathroom Designers General Contractors Kitchen & Bathroom Remodelers Home Builders Roofing & Gutters Cabinets & Cabinetry Tile & Stone Hardwood Flooring Dealers Painters Landscape Contractors Landscape Architects & Landscape Designers Home Stagers Swimming Pool Builders Design & Planning Architects & Building Designers Design-Build Firms Interior Designers & Decorators Kitchen & Bathroom Designers Lighting Designers and Suppliers 3D Rendering Sustainable Design Basement Design Architectural Design Universal Design Energy-Efficient Homes Multigenerational Homes House Plans Construction & Renovation General Contractors Home Builders Kitchen & Bathroom Remodelers Home Remodeling Home Additions Green Building Garage Building New Home Construction Basement Remodeling Stair & Railing Contractors Carpenters Cabinetry & Cabinet Makers Roofing & Gutter Contractors Window Contractors Exterior & Siding Contractors Finishes & Fixtures Carpet Contractors Carpet Installation Flooring Contractors Wood Floor Refinishing Tile Installation Tile & Stone Custom Countertops Quartz Countertops Cabinet Refinishing Custom Bathroom Vanities Finish Carpentry Cabinet Repair Custom Windows Window Treatment Services Window Repair Fireplace Contractors Painters Paint & Wall Covering Dealers Door Contractors Glass & Shower Door Contractors Landscaping & Outdoor Landscape Architects & Landscape Designers Landscape Contractors Landscape Construction Land Clearing Garden & Landscape Supplies Deck & Patio Builders Deck Repair Patio Design Stone, Pavers, & Concrete Paver Installation Driveway & Paving Contractors Driveway Repair Asphalt Paving Garage Door Repair Fence Contractors Fence Installation Gate Repair Pergola Construction Spa & Pool Maintenance Swimming Pool Contractors Hot Tub Installation Systems & Appliances HVAC Contractors Plumbers Electricians Appliance Services Solar Energy Contractors Outdoor Lighting Installation Landscape Lighting Installation Outdoor Lighting & Audio/Visual Specialists Home Theater & Home Automation Services More Handyman Services Closet Designers Professional Organizers Furniture & Accessories Retailers Furniture Repair & Upholstery Services Specialty Contractors Color Consulting Wine Cellar Designers & Builders Home Stagers Home Inspection Welding Blacksmith Custom Artists Columbus, OH Painters New York City, NY Landscapers San Diego, CA Bathroom Remodelers Minneapolis, MN Architects Portland, OR 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Has anyone else tried this? Email Save Comment 52 Follow Featured Answer Steve Lng Islnd NY Z-7a SunSet Z-34 6 years ago Its been discovered that Water exposed to a south magnetic field has molecules that group in 6 molecules where when exposed to a North Magnetic field group in 12. I have exposed water to South Pole Magnet of a N52 Neodymium (50mmx50x25) for 24 hours and it definitely had very low surface tension compared to non-exposed. It was noticeably a different feeling on your hands as well. Like \| 2 Save Sort by: Oldest Newest Oldest Comments (52) See 2 more comments Dave_S Original Author 20 years ago I set up a South Pole vs North Pole vs Control on some seeds which haven't germinated yet. Also, I put a North and South combination on a tomato and pepper plant in the garden and will continue to monitor them throughout the season for any differences with their neighbor non-magnetized plants. Like \| 1 Save palyne 20 years ago So Dave... what ever happened on this? Anything? Palyne Like Save Related Professionals Glendora Landscape Architects & Landscape Designers · Roosevelt Landscape Architects & Landscape Designers · Fort Atkinson Landscape Contractors · Hampton Bays Landscape Contractors · Haverhill Landscape Contractors · Homewood Landscape Contractors · Medford Landscape Contractors · Tacoma Landscape Contractors · Vadnais Heights Landscape Contractors · Adrian Decks, Patios & Outdoor Enclosures · Fort Pierce Decks, Patios & Outdoor Enclosures · Novi Decks, Patios & Outdoor Enclosures · St John's Kirk Decks, Patios & Outdoor Enclosures · Kenosha Siding & Exteriors · South Laurel Siding & Exteriors tony_k_orlando 20 years ago Earth to Dave, come in please. What are the results? Tony Like Save atillathepun 20 years ago Maybe magnets make plants carnivorous? Like Save Scott Wallace 20 years ago Funny...my daughter is doing this same thing for her science fair project this year. She just started Monday...I'll try to update this thread every week. Like \| 1 Save watermanjeff 20 years ago Dave I found a fairly recent experiment using radish seeds which showed a significant increase in the growth of root hairs. There is also a chapter in the controversial book "The Secret Life Of Plants", by Christopher Bird and Peter Tompkins, which deals with an amazing (unbelievable?) series of experiments. I don't have the book now, but as i recall the authors claimed to grow plants without light by running copper wires from outside (daylight)into a basement (dark) and inserting them into the soil in the pots the plants were in. Like i said....controversial. Jeff Here is a link that might be useful: The Effects of Electromagnetic Field...etc. Like Save palyne 20 years ago I have that book Jeff--and that was the one that struck me as most amazing (and in need of validation) out of the whole book (which btw I think is great). I'll see if I can dig out that passage and post it here. It really didn't give enough useful info to replicate--I once went looking for this a couple years ago hoping to! Attilathepun--that was truly hilarious. FEED ME! Palyne Like Save tony_k_orlando 20 years ago I only have two things to say to all you tormentors of plants..... and its simple, listen close now.... Red is positive and black is negative. Thanks for the tip on the book "The Secret Life Of Plants" I ordered it from the library today. Cant wait to check it out. Like Save pickwick 20 years ago i think it makes plants more attractive Like Save janemccl 20 years ago I have never grown plants with magnets. However, my dentist made me get a water pick which helped some with gum infection, but I still had problems. Then the water pick broke, and the hygenist recommended a magnetic water pick. The water got magnetized as it went through the machine. The infection all disappeared in three months by the next check up, and has not come back. Because the water pick impressed me, I bought some magnets from the internet and started magnetizing my drinking water. At first I felt great, then, after a couple of months, not so great. The magnets are reputed to make hard water soft, so maybe they removed too much magnesium and potassium from the water and my body didn't get enough. I would like to go back to it though. I think a glass a day might be good. It may clear infections? Also, I put some flowers in magnetic water, and the water NEVER got yucky, and the flowers lasted a LONG time. The water stayed clear and sweet with no rot on the flower stems. What magnetic water does to sprouting seeds or growing plants, I don't know. Best, Jane Like Save pickwick 20 years ago interesting association,Jane...have used electrostatic sprayers -a device located at the nozzle which charges mist particles emitted from a sprayer resulting in greater coverage with less product Like Save Mathmom1 19 years ago Who has actually experimented with either north pole facing the water for plants or south pole facing water for plants and recorded results? I am about to plant just harvested amaryillis seed in three containers. I'll use magnetized water to water two flats and non magnetized in the third. The water will be in a jar with a magnet wrapped around the jar oriented north for one, south for the second and none for the third. I will refill the water after watering each time from the tap, note how much water each flat used, and record germination percents and heights of each plant. Any suggestions from this forum's users? Like Save gingerhill 19 years ago Hysterical, I thought the post said magets. I must drink more coffee. I was thinking ewww, why would anyone want to try that. Thank goodness it's magnets :) Like \| 1 Save Amino_X 19 years ago What type of magnets are you using? Standard Ferric Oxides? Rare Earth? or Neodymiums? I did some experiments with diametricly opposed neodymium magnetic levitation some years back, but never thought to apply it to plants! Hmmm... Let us know how it works out :D Best Wishes Amino-X Like Save jkirk3279 19 years ago When starting plants this spring, I put a big speaker magnet underneath some Physallis Mullaca seedlings. A day later they had doubled in size ! I decided to follow up on this, so I cut squares of magnetic backed material I use to make magnetic signs. I put it under the seedlings. And nothing happened. So maybe the magnetic sign stuff wasn't strong enough. If this DID have good effects on the seedlings at first, I couldn't repeat the results. Maybe stronger magnets -- or opposing polarity would help. Like Save the_alpha_wolf_rules 19 years ago lol! it's spelled "maggots" anyway. Like Save The_Tree 18 years ago You can increase the growth of plants with magnets. The best way is to put seeds on a flat magnet (about 1500-2500 gauss) for a period of 2-6 days before planting. You'll need to experiment to find the absolute best length of time to leave them on the magnet. Plant the seeds within a day after taking them off of the magnet. You can magnetize the water that you water the plants with too. The polarity of the magnet does matter. Usually the South pole will increase growth. Some plants actually do better with North pole energy. Magnets can be attached to the hose (south pole of magnet facing hose) and given to the roots only, not the foliage. Using magnetized water alone can significantly increase the growth. If you thoroughly look into the history of using magnets for growing plants, you'll come accross the information I've given you, but it's difficult to find. Remember, the side of the magnet you put the seeds on and the side of the magnet facing the hose makes all of the difference. Generally, plants that grow under ground (potatoes) prefer North pole energy, above ground plants prefer South pole energy. There are exceptions. Magnetizing your plants is well worth the effort. They'll taste better and have a higher yield. Like \| 1 Save The_Tree 18 years ago Find the scientist that first discovered that magnetism consists of two separate energies and you've found my source. If your skeptical that water can be magnetized, do a google search on 'U.S. government studies on magnetized water'. In 1973, there was a government study that confirmed that magnetic energy alters the properties of water. It also states that the Soviet Union has used magnetized water for many years with great economic benefit. Like Save The_Tree 18 years ago And now the answer you've all been waiting for... It was Albert Roy Davis and Walter C. Rawls that made these discoveries. Plant yields can be increased from 20% to 200%! The plants will have a higher concentration of nutrients too. I've done experiments myself. They wrote about these and other fascinating experiments in their first book, "Magnetism and Its Effects on the Living System". There are some species that will grow better with exposure to North AND South pole energy. For example, the North pole plants may give you the highest yield, but the South pole plants will have the most nutrients. In these cases both will have improved qualities over plants of the same species that haven't been exposed to either magnetic field. You can find more information about this discovery on the U.S. Patent and Trademark Office website, patent # 4,020,590. Like Save mistercross 18 years ago This sounds like a perfect test for the Mythbusters on the Discovery Channel, especially if they still have the ten greenhouses from the test of music on plant growth. I would suggest it to them, but I block cookies and apparently can't post there. Here is a long article on magnetic claims, but it only briefly mentions that plant growth is one claim. Here is a student science fair test, in PDF format, on the effect of magnetism on plant growth. Here is a link that might be useful: Discovery Channel: Mythbusters Like Save The_Tree 18 years ago Take a look at how an MRI works. http://www.ccmr.cornell.edu/education/ask/?quid=41 Like Save snorelas 18 years ago hey, i am also doing the magnet experiment and i need something to back up my oun result, would you be able to send me some of your results? Like Save wayne_5 zone 6a Central Indiana 18 years ago Now how about people magnetism....I read where it is best to have your bed situated so that your head [top of] is facing the north, and second best if headed south............................"? Like Save albert_135 39.17°N 119.76°W 4695ft. 18 years ago I read somewhere that native plants growing under high power transmission lines did better than the same plants nearby. I haven't been able to confirm this. I thought that the high power transmission lines might have rapidly reversing magnetic fields but haven't been able to confirm that either. Like Save ascalon 17 years ago Has anyone any information on exactly what should be done with magnets to water or the plants directly? Like what kind of magnets, and what to do with them, and where. Please feel free to email me information at [email protected]. Like Save kelly_r 15 years ago I'm doing the whole magnet and seed thing also, but im having trouble with my research report. Anyone know of any usefull websites i could use? Like Save dethcheez 15 years ago I can't say that I've ever tried anything or even thought about trying anything with plants and magnets... But now I'm going to have to, thanx a lot... If any of my Carns eat me I'm blaming you guys... LOL... My many interest is Carns & Neps which do best with distilled water as I'm sure most plant probably would... Can/does the magnet in the water have anything to do with it possibly attracting unwanted metals/minerals in the water??? Kind of like a filter / Helping to purify it & making it healthier for the plants??? Also in the soil, Attracting / Repelling minerals to or away from the plant??? ??? Just thought I'd throw my 2 cents in... Like Save maifleur01 15 years ago I will post a new topic as I don't want to highjack this thread. Like Save kayjones 15 years ago Here's the link to this patent number - very interesting! Here is a link that might be useful: Magnets and seeds Like Save noway_ever_com 13 years ago I personally conducted an experiment with 0, 4000, 8000, 12000, and 16000 gauss, with neodymium magnets at 2000 gauss each. I measured O2 released over a period of slightly under a week, with a 40w light source. All specimens were placed 20 cm away, so as not to have interference between magnetic fields (the measured angle of compass deflection was at 18 cm). up to 4000, there was no significant difference in the amount of O2 produced by the plant(in the technical term). 16000 gauss, however, was under 55% efficient: a significant difference (in the technical term). This is logical because the magnetism will disrupt the plant's electron transport chain- which is a vital step in photosynthesis and cellular respiration. the (rough) results were: 0 gauss: 100% efficiency (inherent) 4000 gauss: 100% efficiency 8000 gauss: 75% efficiency 12000 gauss: 66% efficiency 16000 gauss: 55% efficiency so, no, magnetism does not help your plants grow. It starves and suffocates them. Like Save gigadygig_yahoo_com 13 years ago sniff this Like Save kelly.jb9398 12 years ago I'm doing a science fair project for my school. I'm experimenting on the effects of magnetism on plant growth. I'll using three pots of Sweet Basil plants. One will be a regular plant. The others will be under some type of influence of magnetism. I don't know what yet, but i might just do magnetized water. Please share some ideas that you have. Like \| 1 Save kelly.jb9398 12 years ago I've decided to use rosemary instead. I placed four magnets next to a potted plant on my windowsill and it started doing some weird things. The branches began spiraling. Like \| 1 Save ElectricFertilizer 11 years ago In a book called Electroculture by George Hull, one experimented from the 1800s sowed seeds over a set of wires placed in the soil and experienced significant increases in growth. I would attribute this to the electromagnetic fields produced by the current flow in a wire. Perhaps the difference comes from the field lines being circular vs linear from a regular magnet?? Like Save coing 11 years ago Kelly, An experiment is most likely to reveal the truth of the question if there is a control (comparing treated to untreated plants in exactly equal conditions) and also if it is double-blinded. This means that one person would assign the treatments, but another person, blind to which pot was treated in which way, would do the observations. This would prevent the observer from something we all do without realizing it: seeing what we want to see. Good luck with your project, let us know how it came out. Coing Like Save Konrad___far_north 10 years ago It was around 40 years ago when I helped out on a farm in southern Alberta, seeding HUGE fields of wheat etc. The farmer had a large coil hooked up on a power source, he just run seeds through this devise. Anybody done this? Like \| 1 Save albert_135 39.17°N 119.76°W 4695ft. 10 years ago FYI, Harbor Freight has some approx. 1X1X3 inch magnets that are supposed to lift 200 lb. About $18 each. Like Save David.Sturtz 10 years ago I am a retired electronics tech. Only iron has strongly magnetic properties. Water in particular is unaffected by magnetism because it has two covanlent chemical bonds rather than an ionic bond. It is not possible to magnetize a non magnetic material such as water. Running water past a magnet will not magnetize it any more than it would glass. There is some evidence, however, that growing plants in a magnetic field, can affect growth. Like Save Mokinu 8 years ago last modified: 8 years ago So, how did everyone's science fair experiments turn out? I wouldn't be surprised if plants and seeds could sense magnetic fields to some degree in an effort to see what kind of climate they're growing in. Maybe magnetizing seeds can speed this process up. After all, birds can sense magnetic fields. Like Save Seysonn_ 8a-NC/HZ-7 8 years ago I have never heard of such a thing : i.e the effect of magnet on plants growth. Why don't you just fertilize ? You want oxygen to get into the roots, amend with organic matter. I add some fine pine bark, to improve drainage and get oxygen to the roots. Sey Like \| 1 Save Mokinu 8 years ago last modified: 8 years ago As I understand it, if there's an effect on plants with magnetism, it should likely be a cumulative effect, and not something that extra care of your plants is going to make completely irrelevant, whether or not that extra care is all your plants need. Since perhaps no one really knows the effect, though, it's a moot point whether the effect is cumulative until figured out. I think there's sufficient reason to study it. Like Save albert_135 39.17°N 119.76°W 4695ft. 8 years ago ''Why don't you just..." is usually what professionals call a micro rant: The Microcomplaint: Nothing Too Small to Whine About - The New York Times - The Microcomplaint: Nothing Too Small to Whine About Like \| 1 Save PRO husbands helper 8 years ago I know magnets shoot photons at each other which causes a magnetic field. These are the same photons that light uses to travel so I am very curious if that would speed up photosynthesis...but no spacific answers I can find Like \| 1 Save Mokinu 8 years ago last modified: 8 years ago Interesting thought. I got some magnets for my own experimentation (primarily their effect when used on seeds before planting). So, hopefully I'll have something to report by the end of next season. It sounds like you're interested in post-planting information. I might try stuff out there, too, but it's not my main priority. I would suggest experimenting using the magnets at night, if you're going to use them on plants. Like \| 1 Save Mokinu 8 years ago last modified: 8 years ago Check this out: http://www.ncbi.nlm.nih.gov/pubmed/18512697 It looks like we've got some proof, for chickpea seeds, anyway. A gauss is a tenth of an mT. So, 1000 gauss static magnet exposure for an hour should produce results in chickpeas, or 500 gauss for two hours or 1500 gauss for two hours. Like \| 1 Save Mokinu 8 years ago Here's another link to explain how it helps if water is exposed to magnets. Apparently, it's supposed to make saltier water easier for plants to absorb: https://www.usaid.gov/news-information/frontlines/feed-future/magnets-help-plants-grow Like \| 1 Save zen_man 5 years ago The earth is a big magnet, so a valid experiment would be to see how plants grow in the absence of a magnetic field. Isolating a plant from the earth's magnetic field might be a little hard to do, but maybe a Faraday Cage would do the trick. Like Save David 3 years ago Earth is not a magnet. Nothing in nature is polar. Like Save Set Apart Spirit 2 years ago If you expose what’s commonly called the north pole (N&S poles dont exist) to tomato seeds for 30min proir to gemination, your yield will be less acidic! Like Save Related Stories FLOWERS AND PLANTS Agastache Rupestris, a Heat-Loving Hummingbird Magnet By Susan J Tweit Threadleaf giant hyssop adds color and fragrance to late-summer and fall xeric gardens Full Story 12 GARDENING GUIDES Great Design Plant: Grow Blueberries for Their Fruit and More By Ellen Sousa/Turkey Hill Brook Farm Eastern gardeners should consider growing blueberry plants for their delicious fruits, bee-friendly spring blooms and brilliant fall foliage Full Story 33 GARDENING GUIDES 8 Plants That Snobs Love to Hate — and You'll Love to Grow By Bill Marken Don't dismiss these common annuals, perennials and shrubs — there are reasons they've been popular for so long Full Story 39 SUMMER GARDENING How to Grow Basil By Marianne Lipanovich Bright color, quick growth and endless uses for cooking make this summer annual a winner in the garden or a pot Full Story 79 GARDENING GUIDES Great Design Plant: Dwarf Blue Indigo Offers Carefree Beauty By Benjamin Vogt / Monarch Gardens Drought tolerant and a bumblebee magnet, spiky Baptisia australis may be the easiest plant you ever grow Full Story 21 NATIVE PLANTS Great Native Plant: Grow Wild Quinine for Its Unique Clusters of Blooms By Benjamin Vogt / Monarch Gardens Get connoisseur cred and unique blooms with this uncommon plant. Bonus assets: It’s low maintenance and drought tolerant Full Story 24 GARDENING AND LANDSCAPING Grow a Lush Privacy Screen By Christine Tusher No need to wait forever for patio privacy the green way. These 10 ideas will get your screening up and running in no time Full Story 181 HERBS Herb Garden Essentials: How to Grow Chives By Marianne Lipanovich This decorative and delicately flavored herb from the onion family is easy to grow indoors and out Full Story 24 LANDSCAPE DESIGN 8 Ways to Grow More Plants in Small Spaces By Falon Mihalic Use plants to bring your pocket garden to life Full Story 19 GARDENING GUIDES 7 New Plants to Grow for Beautiful Foliage By Le jardinet Add color, structure and interest to your garden with these recently introduced plants that sport exceptional foliage Full Story 64 Sponsored Explore Discussions Featured Home Discussions Featured Garden Discussions Garden Experiments Growing plants with magnets Dave_S 20 years ago I am trying an experiment of placing magnets near plants to see if there is any boost in their growth or production. Has anyone else tried this? Email Save Comment 52 Follow Featured Answer Steve Lng Islnd NY Z-7a SunSet Z-34 6 years ago Its been discovered that Water exposed to a south magnetic field has molecules that group in 6 molecules where when exposed to a North Magnetic field group in 12. I have exposed water to South Pole Magnet of a N52 Neodymium (50mmx50x25) for 24 hours and it definitely had very low surface tension compared to non-exposed. It was noticeably a different feeling on your hands as well. Like \| 2 Save Sort by: Oldest Newest Oldest Comments (52) See 2 more comments Dave_S Original Author 20 years ago I set up a South Pole vs North Pole vs Control on some seeds which haven't germinated yet. Also, I put a North and South combination on a tomato and pepper plant in the garden and will continue to monitor them throughout the season for any differences with their neighbor non-magnetized plants. Like \| 1 Save palyne 20 years ago So Dave... what ever happened on this? Anything? Palyne Like Save Related Professionals Glendora Landscape Architects & Landscape Designers · Roosevelt Landscape Architects & Landscape Designers · Fort Atkinson Landscape Contractors · Hampton Bays Landscape Contractors · Haverhill Landscape Contractors · Homewood Landscape Contractors · Medford Landscape Contractors · Tacoma Landscape Contractors · Vadnais Heights Landscape Contractors · Adrian Decks, Patios & Outdoor Enclosures · Fort Pierce Decks, Patios & Outdoor Enclosures · Novi Decks, Patios & Outdoor Enclosures · St John's Kirk Decks, Patios & Outdoor Enclosures · Kenosha Siding & Exteriors · South Laurel Siding & Exteriors tony_k_orlando 20 years ago Earth to Dave, come in please. What are the results? Tony Like Save atillathepun 20 years ago Maybe magnets make plants carnivorous? Like Save Scott Wallace 20 years ago Funny...my daughter is doing this same thing for her science fair project this year. She just started Monday...I'll try to update this thread every week. Like \| 1 Save watermanjeff 20 years ago Dave I found a fairly recent experiment using radish seeds which showed a significant increase in the growth of root hairs. There is also a chapter in the controversial book "The Secret Life Of Plants", by Christopher Bird and Peter Tompkins, which deals with an amazing (unbelievable?) series of experiments. I don't have the book now, but as i recall the authors claimed to grow plants without light by running copper wires from outside (daylight)into a basement (dark) and inserting them into the soil in the pots the plants were in. Like i said....controversial. Jeff Here is a link that might be useful: The Effects of Electromagnetic Field...etc. Like Save palyne 20 years ago I have that book Jeff--and that was the one that struck me as most amazing (and in need of validation) out of the whole book (which btw I think is great). I'll see if I can dig out that passage and post it here. It really didn't give enough useful info to replicate--I once went looking for this a couple years ago hoping to! Attilathepun--that was truly hilarious. FEED ME! Palyne Like Save tony_k_orlando 20 years ago I only have two things to say to all you tormentors of plants..... and its simple, listen close now.... Red is positive and black is negative. Thanks for the tip on the book "The Secret Life Of Plants" I ordered it from the library today. Cant wait to check it out. Like Save pickwick 20 years ago i think it makes plants more attractive Like Save janemccl 20 years ago I have never grown plants with magnets. However, my dentist made me get a water pick which helped some with gum infection, but I still had problems. Then the water pick broke, and the hygenist recommended a magnetic water pick. The water got magnetized as it went through the machine. The infection all disappeared in three months by the next check up, and has not come back. Because the water pick impressed me, I bought some magnets from the internet and started magnetizing my drinking water. At first I felt great, then, after a couple of months, not so great. The magnets are reputed to make hard water soft, so maybe they removed too much magnesium and potassium from the water and my body didn't get enough. I would like to go back to it though. I think a glass a day might be good. It may clear infections? Also, I put some flowers in magnetic water, and the water NEVER got yucky, and the flowers lasted a LONG time. The water stayed clear and sweet with no rot on the flower stems. What magnetic water does to sprouting seeds or growing plants, I don't know. Best, Jane Like Save pickwick 20 years ago interesting association,Jane...have used electrostatic sprayers -a device located at the nozzle which charges mist particles emitted from a sprayer resulting in greater coverage with less product Like Save Mathmom1 19 years ago Who has actually experimented with either north pole facing the water for plants or south pole facing water for plants and recorded results? I am about to plant just harvested amaryillis seed in three containers. I'll use magnetized water to water two flats and non magnetized in the third. The water will be in a jar with a magnet wrapped around the jar oriented north for one, south for the second and none for the third. I will refill the water after watering each time from the tap, note how much water each flat used, and record germination percents and heights of each plant. Any suggestions from this forum's users? Like Save gingerhill 19 years ago Hysterical, I thought the post said magets. I must drink more coffee. I was thinking ewww, why would anyone want to try that. Thank goodness it's magnets :) Like \| 1 Save Amino_X 19 years ago What type of magnets are you using? Standard Ferric Oxides? Rare Earth? or Neodymiums? I did some experiments with diametricly opposed neodymium magnetic levitation some years back, but never thought to apply it to plants! Hmmm... Let us know how it works out :D Best Wishes Amino-X Like Save jkirk3279 19 years ago When starting plants this spring, I put a big speaker magnet underneath some Physallis Mullaca seedlings. A day later they had doubled in size ! I decided to follow up on this, so I cut squares of magnetic backed material I use to make magnetic signs. I put it under the seedlings. And nothing happened. So maybe the magnetic sign stuff wasn't strong enough. If this DID have good effects on the seedlings at first, I couldn't repeat the results. Maybe stronger magnets -- or opposing polarity would help. Like Save the_alpha_wolf_rules 19 years ago lol! it's spelled "maggots" anyway. Like Save The_Tree 18 years ago You can increase the growth of plants with magnets. The best way is to put seeds on a flat magnet (about 1500-2500 gauss) for a period of 2-6 days before planting. You'll need to experiment to find the absolute best length of time to leave them on the magnet. Plant the seeds within a day after taking them off of the magnet. You can magnetize the water that you water the plants with too. The polarity of the magnet does matter. Usually the South pole will increase growth. Some plants actually do better with North pole energy. Magnets can be attached to the hose (south pole of magnet facing hose) and given to the roots only, not the foliage. Using magnetized water alone can significantly increase the growth. If you thoroughly look into the history of using magnets for growing plants, you'll come accross the information I've given you, but it's difficult to find. Remember, the side of the magnet you put the seeds on and the side of the magnet facing the hose makes all of the difference. Generally, plants that grow under ground (potatoes) prefer North pole energy, above ground plants prefer South pole energy. There are exceptions. Magnetizing your plants is well worth the effort. They'll taste better and have a higher yield. Like \| 1 Save The_Tree 18 years ago Find the scientist that first discovered that magnetism consists of two separate energies and you've found my source. If your skeptical that water can be magnetized, do a google search on 'U.S. government studies on magnetized water'. In 1973, there was a government study that confirmed that magnetic energy alters the properties of water. It also states that the Soviet Union has used magnetized water for many years with great economic benefit. Like Save The_Tree 18 years ago And now the answer you've all been waiting for... It was Albert Roy Davis and Walter C. Rawls that made these discoveries. Plant yields can be increased from 20% to 200%! The plants will have a higher concentration of nutrients too. I've done experiments myself. They wrote about these and other fascinating experiments in their first book, "Magnetism and Its Effects on the Living System". There are some species that will grow better with exposure to North AND South pole energy. For example, the North pole plants may give you the highest yield, but the South pole plants will have the most nutrients. In these cases both will have improved qualities over plants of the same species that haven't been exposed to either magnetic field. You can find more information about this discovery on the U.S. Patent and Trademark Office website, patent # 4,020,590. Like Save mistercross 18 years ago This sounds like a perfect test for the Mythbusters on the Discovery Channel, especially if they still have the ten greenhouses from the test of music on plant growth. I would suggest it to them, but I block cookies and apparently can't post there. Here is a long article on magnetic claims, but it only briefly mentions that plant growth is one claim. Here is a student science fair test, in PDF format, on the effect of magnetism on plant growth. Here is a link that might be useful: Discovery Channel: Mythbusters Like Save The_Tree 18 years ago Take a look at how an MRI works. http://www.ccmr.cornell.edu/education/ask/?quid=41 Like Save snorelas 18 years ago hey, i am also doing the magnet experiment and i need something to back up my oun result, would you be able to send me some of your results? Like Save wayne_5 zone 6a Central Indiana 18 years ago Now how about people magnetism....I read where it is best to have your bed situated so that your head [top of] is facing the north, and second best if headed south............................"? Like Save albert_135 39.17°N 119.76°W 4695ft. 18 years ago I read somewhere that native plants growing under high power transmission lines did better than the same plants nearby. I haven't been able to confirm this. I thought that the high power transmission lines might have rapidly reversing magnetic fields but haven't been able to confirm that either. Like Save ascalon 17 years ago Has anyone any information on exactly what should be done with magnets to water or the plants directly? Like what kind of magnets, and what to do with them, and where. Please feel free to email me information at [email protected]. Like Save kelly_r 15 years ago I'm doing the whole magnet and seed thing also, but im having trouble with my research report. Anyone know of any usefull websites i could use? Like Save dethcheez 15 years ago I can't say that I've ever tried anything or even thought about trying anything with plants and magnets... But now I'm going to have to, thanx a lot... If any of my Carns eat me I'm blaming you guys... LOL... My many interest is Carns & Neps which do best with distilled water as I'm sure most plant probably would... Can/does the magnet in the water have anything to do with it possibly attracting unwanted metals/minerals in the water??? Kind of like a filter / Helping to purify it & making it healthier for the plants??? Also in the soil, Attracting / Repelling minerals to or away from the plant??? ??? Just thought I'd throw my 2 cents in... Like Save maifleur01 15 years ago I will post a new topic as I don't want to highjack this thread. Like Save kayjones 15 years ago Here's the link to this patent number - very interesting! Here is a link that might be useful: Magnets and seeds Like Save noway_ever_com 13 years ago I personally conducted an experiment with 0, 4000, 8000, 12000, and 16000 gauss, with neodymium magnets at 2000 gauss each. I measured O2 released over a period of slightly under a week, with a 40w light source. All specimens were placed 20 cm away, so as not to have interference between magnetic fields (the measured angle of compass deflection was at 18 cm). up to 4000, there was no significant difference in the amount of O2 produced by the plant(in the technical term). 16000 gauss, however, was under 55% efficient: a significant difference (in the technical term). This is logical because the magnetism will disrupt the plant's electron transport chain- which is a vital step in photosynthesis and cellular respiration. the (rough) results were: 0 gauss: 100% efficiency (inherent) 4000 gauss: 100% efficiency 8000 gauss: 75% efficiency 12000 gauss: 66% efficiency 16000 gauss: 55% efficiency so, no, magnetism does not help your plants grow. It starves and suffocates them. Like Save gigadygig_yahoo_com 13 years ago sniff this Like Save kelly.jb9398 12 years ago I'm doing a science fair project for my school. I'm experimenting on the effects of magnetism on plant growth. I'll using three pots of Sweet Basil plants. One will be a regular plant. The others will be under some type of influence of magnetism. I don't know what yet, but i might just do magnetized water. Please share some ideas that you have. Like \| 1 Save kelly.jb9398 12 years ago I've decided to use rosemary instead. I placed four magnets next to a potted plant on my windowsill and it started doing some weird things. The branches began spiraling. Like \| 1 Save ElectricFertilizer 11 years ago In a book called Electroculture by George Hull, one experimented from the 1800s sowed seeds over a set of wires placed in the soil and experienced significant increases in growth. I would attribute this to the electromagnetic fields produced by the current flow in a wire. Perhaps the difference comes from the field lines being circular vs linear from a regular magnet?? Like Save coing 11 years ago Kelly, An experiment is most likely to reveal the truth of the question if there is a control (comparing treated to untreated plants in exactly equal conditions) and also if it is double-blinded. This means that one person would assign the treatments, but another person, blind to which pot was treated in which way, would do the observations. This would prevent the observer from something we all do without realizing it: seeing what we want to see. Good luck with your project, let us know how it came out. Coing Like Save Konrad___far_north 10 years ago It was around 40 years ago when I helped out on a farm in southern Alberta, seeding HUGE fields of wheat etc. The farmer had a large coil hooked up on a power source, he just run seeds through this devise. Anybody done this? Like \| 1 Save albert_135 39.17°N 119.76°W 4695ft. 10 years ago FYI, Harbor Freight has some approx. 1X1X3 inch magnets that are supposed to lift 200 lb. About $18 each. Like Save David.Sturtz 10 years ago I am a retired electronics tech. Only iron has strongly magnetic properties. Water in particular is unaffected by magnetism because it has two covanlent chemical bonds rather than an ionic bond. It is not possible to magnetize a non magnetic material such as water. Running water past a magnet will not magnetize it any more than it would glass. There is some evidence, however, that growing plants in a magnetic field, can affect growth. Like Save Mokinu 8 years ago last modified: 8 years ago So, how did everyone's science fair experiments turn out? I wouldn't be surprised if plants and seeds could sense magnetic fields to some degree in an effort to see what kind of climate they're growing in. Maybe magnetizing seeds can speed this process up. After all, birds can sense magnetic fields. Like Save Seysonn_ 8a-NC/HZ-7 8 years ago I have never heard of such a thing : i.e the effect of magnet on plants growth. Why don't you just fertilize ? You want oxygen to get into the roots, amend with organic matter. I add some fine pine bark, to improve drainage and get oxygen to the roots. Sey Like \| 1 Save Mokinu 8 years ago last modified: 8 years ago As I understand it, if there's an effect on plants with magnetism, it should likely be a cumulative effect, and not something that extra care of your plants is going to make completely irrelevant, whether or not that extra care is all your plants need. Since perhaps no one really knows the effect, though, it's a moot point whether the effect is cumulative until figured out. I think there's sufficient reason to study it. Like Save albert_135 39.17°N 119.76°W 4695ft. 8 years ago ''Why don't you just..." is usually what professionals call a micro rant: The Microcomplaint: Nothing Too Small to Whine About - The New York Times - The Microcomplaint: Nothing Too Small to Whine About Like \| 1 Save PRO husbands helper 8 years ago I know magnets shoot photons at each other which causes a magnetic field. These are the same photons that light uses to travel so I am very curious if that would speed up photosynthesis...but no spacific answers I can find Like \| 1 Save Mokinu 8 years ago last modified: 8 years ago Interesting thought. I got some magnets for my own experimentation (primarily their effect when used on seeds before planting). So, hopefully I'll have something to report by the end of next season. It sounds like you're interested in post-planting information. I might try stuff out there, too, but it's not my main priority. I would suggest experimenting using the magnets at night, if you're going to use them on plants. Like \| 1 Save Mokinu 8 years ago last modified: 8 years ago Check this out: http://www.ncbi.nlm.nih.gov/pubmed/18512697 It looks like we've got some proof, for chickpea seeds, anyway. A gauss is a tenth of an mT. So, 1000 gauss static magnet exposure for an hour should produce results in chickpeas, or 500 gauss for two hours or 1500 gauss for two hours. Like \| 1 Save Mokinu 8 years ago Here's another link to explain how it helps if water is exposed to magnets. Apparently, it's supposed to make saltier water easier for plants to absorb: https://www.usaid.gov/news-information/frontlines/feed-future/magnets-help-plants-grow Like \| 1 Save zen_man 5 years ago The earth is a big magnet, so a valid experiment would be to see how plants grow in the absence of a magnetic field. Isolating a plant from the earth's magnetic field might be a little hard to do, but maybe a Faraday Cage would do the trick. Like Save David 3 years ago Earth is not a magnet. Nothing in nature is polar. Like Save Set Apart Spirit 2 years ago If you expose what’s commonly called the north pole (N&S poles dont exist) to tomato seeds for 30min proir to gemination, your yield will be less acidic! Like Save Related Stories FLOWERS AND PLANTS Agastache Rupestris, a Heat-Loving Hummingbird Magnet By Susan J Tweit Threadleaf giant hyssop adds color and fragrance to late-summer and fall xeric gardens Full Story 12 GARDENING GUIDES Great Design Plant: Grow Blueberries for Their Fruit and More By Ellen Sousa/Turkey Hill Brook Farm Eastern gardeners should consider growing blueberry plants for their delicious fruits, bee-friendly spring blooms and brilliant fall foliage Full Story 33 GARDENING GUIDES 8 Plants That Snobs Love to Hate — and You'll Love to Grow By Bill Marken Don't dismiss these common annuals, perennials and shrubs — there are reasons they've been popular for so long Full Story 39 SUMMER GARDENING How to Grow Basil By Marianne Lipanovich Bright color, quick growth and endless uses for cooking make this summer annual a winner in the garden or a pot Full Story 79 GARDENING GUIDES Great Design Plant: Dwarf Blue Indigo Offers Carefree Beauty By Benjamin Vogt / Monarch Gardens Drought tolerant and a bumblebee magnet, spiky Baptisia australis may be the easiest plant you ever grow Full Story 21 NATIVE PLANTS Great Native Plant: Grow Wild Quinine for Its Unique Clusters of Blooms By Benjamin Vogt / Monarch Gardens Get connoisseur cred and unique blooms with this uncommon plant. Bonus assets: It’s low maintenance and drought tolerant Full Story 24 GARDENING AND LANDSCAPING Grow a Lush Privacy Screen By Christine Tusher No need to wait forever for patio privacy the green way. These 10 ideas will get your screening up and running in no time Full Story 181 HERBS Herb Garden Essentials: How to Grow Chives By Marianne Lipanovich This decorative and delicately flavored herb from the onion family is easy to grow indoors and out Full Story 24 LANDSCAPE DESIGN 8 Ways to Grow More Plants in Small Spaces By Falon Mihalic Use plants to bring your pocket garden to life Full Story 19 GARDENING GUIDES 7 New Plants to Grow for Beautiful Foliage By Le jardinet Add color, structure and interest to your garden with these recently introduced plants that sport exceptional foliage Full Story 64 Sponsored Explore Discussions Featured Home Discussions Featured Garden Discussions Garden Experiments Growing plants with magnets Dave_S 20 years ago I am trying an experiment of placing magnets near plants to see if there is any boost in their growth or production. Has anyone else tried this? Email Save Comment 52 Follow Featured Answer Steve Lng Islnd NY Z-7a SunSet Z-34 6 years ago Its been discovered that Water exposed to a south magnetic field has molecules that group in 6 molecules where when exposed to a North Magnetic field group in 12. I have exposed water to South Pole Magnet of a N52 Neodymium (50mmx50x25) for 24 hours and it definitely had very low surface tension compared to non-exposed. It was noticeably a different feeling on your hands as well. Like \| 2 Save Sort by: Oldest Newest Oldest Comments (52) See 2 more comments Dave_S Original Author 20 years ago I set up a South Pole vs North Pole vs Control on some seeds which haven't germinated yet. Also, I put a North and South combination on a tomato and pepper plant in the garden and will continue to monitor them throughout the season for any differences with their neighbor non-magnetized plants. Like \| 1 Save palyne 20 years ago So Dave... what ever happened on this? Anything? Palyne Like Save Related Professionals Glendora Landscape Architects & Landscape Designers · Roosevelt Landscape Architects & Landscape Designers · Fort Atkinson Landscape Contractors · Hampton Bays Landscape Contractors · Haverhill Landscape Contractors · Homewood Landscape Contractors · Medford Landscape Contractors · Tacoma Landscape Contractors · Vadnais Heights Landscape Contractors · Adrian Decks, Patios & Outdoor Enclosures · Fort Pierce Decks, Patios & Outdoor Enclosures · Novi Decks, Patios & Outdoor Enclosures · St John's Kirk Decks, Patios & Outdoor Enclosures · Kenosha Siding & Exteriors · South Laurel Siding & Exteriors tony_k_orlando 20 years ago Earth to Dave, come in please. What are the results? Tony Like Save atillathepun 20 years ago Maybe magnets make plants carnivorous? Like Save Scott Wallace 20 years ago Funny...my daughter is doing this same thing for her science fair project this year. She just started Monday...I'll try to update this thread every week. Like \| 1 Save watermanjeff 20 years ago Dave I found a fairly recent experiment using radish seeds which showed a significant increase in the growth of root hairs. There is also a chapter in the controversial book "The Secret Life Of Plants", by Christopher Bird and Peter Tompkins, which deals with an amazing (unbelievable?) series of experiments. I don't have the book now, but as i recall the authors claimed to grow plants without light by running copper wires from outside (daylight)into a basement (dark) and inserting them into the soil in the pots the plants were in. Like i said....controversial. Jeff Here is a link that might be useful: The Effects of Electromagnetic Field...etc. Like Save palyne 20 years ago I have that book Jeff--and that was the one that struck me as most amazing (and in need of validation) out of the whole book (which btw I think is great). I'll see if I can dig out that passage and post it here. It really didn't give enough useful info to replicate--I once went looking for this a couple years ago hoping to! Attilathepun--that was truly hilarious. FEED ME! Palyne Like Save tony_k_orlando 20 years ago I only have two things to say to all you tormentors of plants..... and its simple, listen close now.... Red is positive and black is negative. Thanks for the tip on the book "The Secret Life Of Plants" I ordered it from the library today. Cant wait to check it out. Like Save pickwick 20 years ago i think it makes plants more attractive Like Save janemccl 20 years ago I have never grown plants with magnets. However, my dentist made me get a water pick which helped some with gum infection, but I still had problems. Then the water pick broke, and the hygenist recommended a magnetic water pick. The water got magnetized as it went through the machine. The infection all disappeared in three months by the next check up, and has not come back. Because the water pick impressed me, I bought some magnets from the internet and started magnetizing my drinking water. At first I felt great, then, after a couple of months, not so great. The magnets are reputed to make hard water soft, so maybe they removed too much magnesium and potassium from the water and my body didn't get enough. I would like to go back to it though. I think a glass a day might be good. It may clear infections? Also, I put some flowers in magnetic water, and the water NEVER got yucky, and the flowers lasted a LONG time. The water stayed clear and sweet with no rot on the flower stems. What magnetic water does to sprouting seeds or growing plants, I don't know. Best, Jane Like Save pickwick 20 years ago interesting association,Jane...have used electrostatic sprayers -a device located at the nozzle which charges mist particles emitted from a sprayer resulting in greater coverage with less product Like Save Mathmom1 19 years ago Who has actually experimented with either north pole facing the water for plants or south pole facing water for plants and recorded results? I am about to plant just harvested amaryillis seed in three containers. I'll use magnetized water to water two flats and non magnetized in the third. The water will be in a jar with a magnet wrapped around the jar oriented north for one, south for the second and none for the third. I will refill the water after watering each time from the tap, note how much water each flat used, and record germination percents and heights of each plant. Any suggestions from this forum's users? Like Save gingerhill 19 years ago Hysterical, I thought the post said magets. I must drink more coffee. I was thinking ewww, why would anyone want to try that. Thank goodness it's magnets :) Like \| 1 Save Amino_X 19 years ago What type of magnets are you using? Standard Ferric Oxides? Rare Earth? or Neodymiums? I did some experiments with diametricly opposed neodymium magnetic levitation some years back, but never thought to apply it to plants! Hmmm... Let us know how it works out :D Best Wishes Amino-X Like Save jkirk3279 19 years ago When starting plants this spring, I put a big speaker magnet underneath some Physallis Mullaca seedlings. A day later they had doubled in size ! I decided to follow up on this, so I cut squares of magnetic backed material I use to make magnetic signs. I put it under the seedlings. And nothing happened. So maybe the magnetic sign stuff wasn't strong enough. If this DID have good effects on the seedlings at first, I couldn't repeat the results. Maybe stronger magnets -- or opposing polarity would help. Like Save the_alpha_wolf_rules 19 years ago lol! it's spelled "maggots" anyway. Like Save The_Tree 18 years ago You can increase the growth of plants with magnets. The best way is to put seeds on a flat magnet (about 1500-2500 gauss) for a period of 2-6 days before planting. You'll need to experiment to find the absolute best length of time to leave them on the magnet. Plant the seeds within a day after taking them off of the magnet. You can magnetize the water that you water the plants with too. The polarity of the magnet does matter. Usually the South pole will increase growth. Some plants actually do better with North pole energy. Magnets can be attached to the hose (south pole of magnet facing hose) and given to the roots only, not the foliage. Using magnetized water alone can significantly increase the growth. If you thoroughly look into the history of using magnets for growing plants, you'll come accross the information I've given you, but it's difficult to find. Remember, the side of the magnet you put the seeds on and the side of the magnet facing the hose makes all of the difference. Generally, plants that grow under ground (potatoes) prefer North pole energy, above ground plants prefer South pole energy. There are exceptions. Magnetizing your plants is well worth the effort. They'll taste better and have a higher yield. Like \| 1 Save The_Tree 18 years ago Find the scientist that first discovered that magnetism consists of two separate energies and you've found my source. If your skeptical that water can be magnetized, do a google search on 'U.S. government studies on magnetized water'. In 1973, there was a government study that confirmed that magnetic energy alters the properties of water. It also states that the Soviet Union has used magnetized water for many years with great economic benefit. Like Save The_Tree 18 years ago And now the answer you've all been waiting for... It was Albert Roy Davis and Walter C. Rawls that made these discoveries. Plant yields can be increased from 20% to 200%! The plants will have a higher concentration of nutrients too. I've done experiments myself. They wrote about these and other fascinating experiments in their first book, "Magnetism and Its Effects on the Living System". There are some species that will grow better with exposure to North AND South pole energy. For example, the North pole plants may give you the highest yield, but the South pole plants will have the most nutrients. In these cases both will have improved qualities over plants of the same species that haven't been exposed to either magnetic field. You can find more information about this discovery on the U.S. Patent and Trademark Office website, patent # 4,020,590. Like Save mistercross 18 years ago This sounds like a perfect test for the Mythbusters on the Discovery Channel, especially if they still have the ten greenhouses from the test of music on plant growth. I would suggest it to them, but I block cookies and apparently can't post there. Here is a long article on magnetic claims, but it only briefly mentions that plant growth is one claim. Here is a student science fair test, in PDF format, on the effect of magnetism on plant growth. Here is a link that might be useful: Discovery Channel: Mythbusters Like Save The_Tree 18 years ago Take a look at how an MRI works. http://www.ccmr.cornell.edu/education/ask/?quid=41 Like Save snorelas 18 years ago hey, i am also doing the magnet experiment and i need something to back up my oun result, would you be able to send me some of your results? Like Save wayne_5 zone 6a Central Indiana 18 years ago Now how about people magnetism....I read where it is best to have your bed situated so that your head [top of] is facing the north, and second best if headed south............................"? Like Save albert_135 39.17°N 119.76°W 4695ft. 18 years ago I read somewhere that native plants growing under high power transmission lines did better than the same plants nearby. I haven't been able to confirm this. I thought that the high power transmission lines might have rapidly reversing magnetic fields but haven't been able to confirm that either. Like Save ascalon 17 years ago Has anyone any information on exactly what should be done with magnets to water or the plants directly? Like what kind of magnets, and what to do with them, and where. Please feel free to email me information at [email protected]. Like Save kelly_r 15 years ago I'm doing the whole magnet and seed thing also, but im having trouble with my research report. Anyone know of any usefull websites i could use? Like Save dethcheez 15 years ago I can't say that I've ever tried anything or even thought about trying anything with plants and magnets... But now I'm going to have to, thanx a lot... If any of my Carns eat me I'm blaming you guys... LOL... My many interest is Carns & Neps which do best with distilled water as I'm sure most plant probably would... Can/does the magnet in the water have anything to do with it possibly attracting unwanted metals/minerals in the water??? Kind of like a filter / Helping to purify it & making it healthier for the plants??? Also in the soil, Attracting / Repelling minerals to or away from the plant??? ??? Just thought I'd throw my 2 cents in... Like Save maifleur01 15 years ago I will post a new topic as I don't want to highjack this thread. Like Save kayjones 15 years ago Here's the link to this patent number - very interesting! Here is a link that might be useful: Magnets and seeds Like Save noway_ever_com 13 years ago I personally conducted an experiment with 0, 4000, 8000, 12000, and 16000 gauss, with neodymium magnets at 2000 gauss each. I measured O2 released over a period of slightly under a week, with a 40w light source. All specimens were placed 20 cm away, so as not to have interference between magnetic fields (the measured angle of compass deflection was at 18 cm). up to 4000, there was no significant difference in the amount of O2 produced by the plant(in the technical term). 16000 gauss, however, was under 55% efficient: a significant difference (in the technical term). This is logical because the magnetism will disrupt the plant's electron transport chain- which is a vital step in photosynthesis and cellular respiration. the (rough) results were: 0 gauss: 100% efficiency (inherent) 4000 gauss: 100% efficiency 8000 gauss: 75% efficiency 12000 gauss: 66% efficiency 16000 gauss: 55% efficiency so, no, magnetism does not help your plants grow. It starves and suffocates them. Like Save gigadygig_yahoo_com 13 years ago sniff this Like Save kelly.jb9398 12 years ago I'm doing a science fair project for my school. I'm experimenting on the effects of magnetism on plant growth. I'll using three pots of Sweet Basil plants. One will be a regular plant. The others will be under some type of influence of magnetism. I don't know what yet, but i might just do magnetized water. Please share some ideas that you have. Like \| 1 Save kelly.jb9398 12 years ago I've decided to use rosemary instead. I placed four magnets next to a potted plant on my windowsill and it started doing some weird things. The branches began spiraling. Like \| 1 Save ElectricFertilizer 11 years ago In a book called Electroculture by George Hull, one experimented from the 1800s sowed seeds over a set of wires placed in the soil and experienced significant increases in growth. I would attribute this to the electromagnetic fields produced by the current flow in a wire. Perhaps the difference comes from the field lines being circular vs linear from a regular magnet?? Like Save coing 11 years ago Kelly, An experiment is most likely to reveal the truth of the question if there is a control (comparing treated to untreated plants in exactly equal conditions) and also if it is double-blinded. This means that one person would assign the treatments, but another person, blind to which pot was treated in which way, would do the observations. This would prevent the observer from something we all do without realizing it: seeing what we want to see. Good luck with your project, let us know how it came out. Coing Like Save Konrad___far_north 10 years ago It was around 40 years ago when I helped out on a farm in southern Alberta, seeding HUGE fields of wheat etc. The farmer had a large coil hooked up on a power source, he just run seeds through this devise. Anybody done this? Like \| 1 Save albert_135 39.17°N 119.76°W 4695ft. 10 years ago FYI, Harbor Freight has some approx. 1X1X3 inch magnets that are supposed to lift 200 lb. About $18 each. Like Save David.Sturtz 10 years ago I am a retired electronics tech. Only iron has strongly magnetic properties. Water in particular is unaffected by magnetism because it has two covanlent chemical bonds rather than an ionic bond. It is not possible to magnetize a non magnetic material such as water. Running water past a magnet will not magnetize it any more than it would glass. There is some evidence, however, that growing plants in a magnetic field, can affect growth. Like Save Mokinu 8 years ago last modified: 8 years ago So, how did everyone's science fair experiments turn out? I wouldn't be surprised if plants and seeds could sense magnetic fields to some degree in an effort to see what kind of climate they're growing in. Maybe magnetizing seeds can speed this process up. After all, birds can sense magnetic fields. Like Save Seysonn_ 8a-NC/HZ-7 8 years ago I have never heard of such a thing : i.e the effect of magnet on plants growth. Why don't you just fertilize ? You want oxygen to get into the roots, amend with organic matter. I add some fine pine bark, to improve drainage and get oxygen to the roots. Sey Like \| 1 Save Mokinu 8 years ago last modified: 8 years ago As I understand it, if there's an effect on plants with magnetism, it should likely be a cumulative effect, and not something that extra care of your plants is going to make completely irrelevant, whether or not that extra care is all your plants need. Since perhaps no one really knows the effect, though, it's a moot point whether the effect is cumulative until figured out. I think there's sufficient reason to study it. Like Save albert_135 39.17°N 119.76°W 4695ft. 8 years ago ''Why don't you just..." is usually what professionals call a micro rant: The Microcomplaint: Nothing Too Small to Whine About - The New York Times - The Microcomplaint: Nothing Too Small to Whine About Like \| 1 Save PRO husbands helper 8 years ago I know magnets shoot photons at each other which causes a magnetic field. These are the same photons that light uses to travel so I am very curious if that would speed up photosynthesis...but no spacific answers I can find Like \| 1 Save Mokinu 8 years ago last modified: 8 years ago Interesting thought. I got some magnets for my own experimentation (primarily their effect when used on seeds before planting). So, hopefully I'll have something to report by the end of next season. It sounds like you're interested in post-planting information. I might try stuff out there, too, but it's not my main priority. I would suggest experimenting using the magnets at night, if you're going to use them on plants. Like \| 1 Save Mokinu 8 years ago last modified: 8 years ago Check this out: http://www.ncbi.nlm.nih.gov/pubmed/18512697 It looks like we've got some proof, for chickpea seeds, anyway. A gauss is a tenth of an mT. So, 1000 gauss static magnet exposure for an hour should produce results in chickpeas, or 500 gauss for two hours or 1500 gauss for two hours. Like \| 1 Save Mokinu 8 years ago Here's another link to explain how it helps if water is exposed to magnets. Apparently, it's supposed to make saltier water easier for plants to absorb: https://www.usaid.gov/news-information/frontlines/feed-future/magnets-help-plants-grow Like \| 1 Save zen_man 5 years ago The earth is a big magnet, so a valid experiment would be to see how plants grow in the absence of a magnetic field. Isolating a plant from the earth's magnetic field might be a little hard to do, but maybe a Faraday Cage would do the trick. Like Save David 3 years ago Earth is not a magnet. Nothing in nature is polar. Like Save Set Apart Spirit 2 years ago If you expose what’s commonly called the north pole (N&S poles dont exist) to tomato seeds for 30min proir to gemination, your yield will be less acidic! Like Save Related Stories FLOWERS AND PLANTS Agastache Rupestris, a Heat-Loving Hummingbird Magnet By Susan J Tweit Threadleaf giant hyssop adds color and fragrance to late-summer and fall xeric gardens Full Story 12 GARDENING GUIDES Great Design Plant: Grow Blueberries for Their Fruit and More By Ellen Sousa/Turkey Hill Brook Farm Eastern gardeners should consider growing blueberry plants for their delicious fruits, bee-friendly spring blooms and brilliant fall foliage Full Story 33 GARDENING GUIDES 8 Plants That Snobs Love to Hate — and You'll Love to Grow By Bill Marken Don't dismiss these common annuals, perennials and shrubs — there are reasons they've been popular for so long Full Story 39 SUMMER GARDENING How to Grow Basil By Marianne Lipanovich Bright color, quick growth and endless uses for cooking make this summer annual a winner in the garden or a pot Full Story 79 GARDENING GUIDES Great Design Plant: Dwarf Blue Indigo Offers Carefree Beauty By Benjamin Vogt / Monarch Gardens Drought tolerant and a bumblebee magnet, spiky Baptisia australis may be the easiest plant you ever grow Full Story 21 NATIVE PLANTS Great Native Plant: Grow Wild Quinine for Its Unique Clusters of Blooms By Benjamin Vogt / Monarch Gardens Get connoisseur cred and unique blooms with this uncommon plant. 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These 10 ideas will get your screening up and running in no time Full Story 181 HERBS Herb Garden Essentials: How to Grow Chives By Marianne Lipanovich This decorative and delicately flavored herb from the onion family is easy to grow indoors and out Full Story 24 LANDSCAPE DESIGN 8 Ways to Grow More Plants in Small Spaces By Falon Mihalic Use plants to bring your pocket garden to life Full Story 19 GARDENING GUIDES 7 New Plants to Grow for Beautiful Foliage By Le jardinet Add color, structure and interest to your garden with these recently introduced plants that sport exceptional foliage Full Story 64 Explore Discussions Featured Home Discussions Featured Garden Discussions Garden Experiments Growing plants with magnets Dave_S 20 years ago I am trying an experiment of placing magnets near plants to see if there is any boost in their growth or production. Has anyone else tried this? Email Save Comment 52 Follow I am trying an experiment of placing magnets near plants to see if there is any boost in their growth or production. Has anyone else tried this? I am trying an experiment of placing magnets near plants to see if there is any boost in their growth or production. Has anyone else tried this? Featured Answer Steve Lng Islnd NY Z-7a SunSet Z-34 6 years ago Its been discovered that Water exposed to a south magnetic field has molecules that group in 6 molecules where when exposed to a North Magnetic field group in 12. I have exposed water to South Pole Magnet of a N52 Neodymium (50mmx50x25) for 24 hours and it definitely had very low surface tension compared to non-exposed. It was noticeably a different feeling on your hands as well. Like \| 2 Save Sort by: Oldest Newest Oldest Comments (52) See 2 more comments Dave_S Original Author 20 years ago I set up a South Pole vs North Pole vs Control on some seeds which haven't germinated yet. Also, I put a North and South combination on a tomato and pepper plant in the garden and will continue to monitor them throughout the season for any differences with their neighbor non-magnetized plants. Like \| 1 Save palyne 20 years ago So Dave... what ever happened on this? Anything? Palyne Like Save Related Professionals Glendora Landscape Architects & Landscape Designers · Roosevelt Landscape Architects & Landscape Designers · Fort Atkinson Landscape Contractors · Hampton Bays Landscape Contractors · Haverhill Landscape Contractors · Homewood Landscape Contractors · Medford Landscape Contractors · Tacoma Landscape Contractors · Vadnais Heights Landscape Contractors · Adrian Decks, Patios & Outdoor Enclosures · Fort Pierce Decks, Patios & Outdoor Enclosures · Novi Decks, Patios & Outdoor Enclosures · St John's Kirk Decks, Patios & Outdoor Enclosures · Kenosha Siding & Exteriors · South Laurel Siding & Exteriors tony_k_orlando 20 years ago Earth to Dave, come in please. What are the results? Tony Like Save atillathepun 20 years ago Maybe magnets make plants carnivorous? Like Save Scott Wallace 20 years ago Funny...my daughter is doing this same thing for her science fair project this year. She just started Monday...I'll try to update this thread every week. Like \| 1 Save watermanjeff 20 years ago Dave I found a fairly recent experiment using radish seeds which showed a significant increase in the growth of root hairs. There is also a chapter in the controversial book "The Secret Life Of Plants", by Christopher Bird and Peter Tompkins, which deals with an amazing (unbelievable?) series of experiments. I don't have the book now, but as i recall the authors claimed to grow plants without light by running copper wires from outside (daylight)into a basement (dark) and inserting them into the soil in the pots the plants were in. Like i said....controversial. Jeff Here is a link that might be useful: The Effects of Electromagnetic Field...etc. Like Save palyne 20 years ago I have that book Jeff--and that was the one that struck me as most amazing (and in need of validation) out of the whole book (which btw I think is great). I'll see if I can dig out that passage and post it here. It really didn't give enough useful info to replicate--I once went looking for this a couple years ago hoping to! Attilathepun--that was truly hilarious. FEED ME! Palyne Like Save tony_k_orlando 20 years ago I only have two things to say to all you tormentors of plants..... and its simple, listen close now.... Red is positive and black is negative. Thanks for the tip on the book "The Secret Life Of Plants" I ordered it from the library today. Cant wait to check it out. Like Save pickwick 20 years ago i think it makes plants more attractive Like Save janemccl 20 years ago I have never grown plants with magnets. However, my dentist made me get a water pick which helped some with gum infection, but I still had problems. Then the water pick broke, and the hygenist recommended a magnetic water pick. The water got magnetized as it went through the machine. The infection all disappeared in three months by the next check up, and has not come back. Because the water pick impressed me, I bought some magnets from the internet and started magnetizing my drinking water. At first I felt great, then, after a couple of months, not so great. The magnets are reputed to make hard water soft, so maybe they removed too much magnesium and potassium from the water and my body didn't get enough. I would like to go back to it though. I think a glass a day might be good. It may clear infections? Also, I put some flowers in magnetic water, and the water NEVER got yucky, and the flowers lasted a LONG time. The water stayed clear and sweet with no rot on the flower stems. What magnetic water does to sprouting seeds or growing plants, I don't know. Best, Jane Like Save pickwick 20 years ago interesting association,Jane...have used electrostatic sprayers -a device located at the nozzle which charges mist particles emitted from a sprayer resulting in greater coverage with less product Like Save Mathmom1 19 years ago Who has actually experimented with either north pole facing the water for plants or south pole facing water for plants and recorded results? I am about to plant just harvested amaryillis seed in three containers. I'll use magnetized water to water two flats and non magnetized in the third. The water will be in a jar with a magnet wrapped around the jar oriented north for one, south for the second and none for the third. I will refill the water after watering each time from the tap, note how much water each flat used, and record germination percents and heights of each plant. Any suggestions from this forum's users? Like Save gingerhill 19 years ago Hysterical, I thought the post said magets. I must drink more coffee. I was thinking ewww, why would anyone want to try that. Thank goodness it's magnets :) Like \| 1 Save Amino_X 19 years ago What type of magnets are you using? Standard Ferric Oxides? Rare Earth? or Neodymiums? I did some experiments with diametricly opposed neodymium magnetic levitation some years back, but never thought to apply it to plants! Hmmm... Let us know how it works out :D Best Wishes Amino-X Like Save jkirk3279 19 years ago When starting plants this spring, I put a big speaker magnet underneath some Physallis Mullaca seedlings. A day later they had doubled in size ! I decided to follow up on this, so I cut squares of magnetic backed material I use to make magnetic signs. I put it under the seedlings. And nothing happened. So maybe the magnetic sign stuff wasn't strong enough. If this DID have good effects on the seedlings at first, I couldn't repeat the results. Maybe stronger magnets -- or opposing polarity would help. Like Save the_alpha_wolf_rules 19 years ago lol! it's spelled "maggots" anyway. Like Save The_Tree 18 years ago You can increase the growth of plants with magnets. The best way is to put seeds on a flat magnet (about 1500-2500 gauss) for a period of 2-6 days before planting. You'll need to experiment to find the absolute best length of time to leave them on the magnet. Plant the seeds within a day after taking them off of the magnet. You can magnetize the water that you water the plants with too. The polarity of the magnet does matter. Usually the South pole will increase growth. Some plants actually do better with North pole energy. Magnets can be attached to the hose (south pole of magnet facing hose) and given to the roots only, not the foliage. Using magnetized water alone can significantly increase the growth. If you thoroughly look into the history of using magnets for growing plants, you'll come accross the information I've given you, but it's difficult to find. Remember, the side of the magnet you put the seeds on and the side of the magnet facing the hose makes all of the difference. Generally, plants that grow under ground (potatoes) prefer North pole energy, above ground plants prefer South pole energy. There are exceptions. Magnetizing your plants is well worth the effort. They'll taste better and have a higher yield. Like \| 1 Save The_Tree 18 years ago Find the scientist that first discovered that magnetism consists of two separate energies and you've found my source. If your skeptical that water can be magnetized, do a google search on 'U.S. government studies on magnetized water'. In 1973, there was a government study that confirmed that magnetic energy alters the properties of water. It also states that the Soviet Union has used magnetized water for many years with great economic benefit. Like Save The_Tree 18 years ago And now the answer you've all been waiting for... It was Albert Roy Davis and Walter C. Rawls that made these discoveries. Plant yields can be increased from 20% to 200%! The plants will have a higher concentration of nutrients too. I've done experiments myself. They wrote about these and other fascinating experiments in their first book, "Magnetism and Its Effects on the Living System". There are some species that will grow better with exposure to North AND South pole energy. For example, the North pole plants may give you the highest yield, but the South pole plants will have the most nutrients. In these cases both will have improved qualities over plants of the same species that haven't been exposed to either magnetic field. You can find more information about this discovery on the U.S. Patent and Trademark Office website, patent # 4,020,590. Like Save mistercross 18 years ago This sounds like a perfect test for the Mythbusters on the Discovery Channel, especially if they still have the ten greenhouses from the test of music on plant growth. I would suggest it to them, but I block cookies and apparently can't post there. Here is a long article on magnetic claims, but it only briefly mentions that plant growth is one claim. Here is a student science fair test, in PDF format, on the effect of magnetism on plant growth. Here is a link that might be useful: Discovery Channel: Mythbusters Like Save The_Tree 18 years ago Take a look at how an MRI works. http://www.ccmr.cornell.edu/education/ask/?quid=41 Like Save snorelas 18 years ago hey, i am also doing the magnet experiment and i need something to back up my oun result, would you be able to send me some of your results? Like Save wayne_5 zone 6a Central Indiana 18 years ago Now how about people magnetism....I read where it is best to have your bed situated so that your head [top of] is facing the north, and second best if headed south............................"? Like Save albert_135 39.17°N 119.76°W 4695ft. 18 years ago I read somewhere that native plants growing under high power transmission lines did better than the same plants nearby. I haven't been able to confirm this. I thought that the high power transmission lines might have rapidly reversing magnetic fields but haven't been able to confirm that either. Like Save ascalon 17 years ago Has anyone any information on exactly what should be done with magnets to water or the plants directly? Like what kind of magnets, and what to do with them, and where. Please feel free to email me information at [email protected]. Like Save kelly_r 15 years ago I'm doing the whole magnet and seed thing also, but im having trouble with my research report. Anyone know of any usefull websites i could use? Like Save dethcheez 15 years ago I can't say that I've ever tried anything or even thought about trying anything with plants and magnets... But now I'm going to have to, thanx a lot... If any of my Carns eat me I'm blaming you guys... LOL... My many interest is Carns & Neps which do best with distilled water as I'm sure most plant probably would... Can/does the magnet in the water have anything to do with it possibly attracting unwanted metals/minerals in the water??? Kind of like a filter / Helping to purify it & making it healthier for the plants??? Also in the soil, Attracting / Repelling minerals to or away from the plant??? ??? Just thought I'd throw my 2 cents in... Like Save maifleur01 15 years ago I will post a new topic as I don't want to highjack this thread. Like Save kayjones 15 years ago Here's the link to this patent number - very interesting! Here is a link that might be useful: Magnets and seeds Like Save noway_ever_com 13 years ago I personally conducted an experiment with 0, 4000, 8000, 12000, and 16000 gauss, with neodymium magnets at 2000 gauss each. I measured O2 released over a period of slightly under a week, with a 40w light source. All specimens were placed 20 cm away, so as not to have interference between magnetic fields (the measured angle of compass deflection was at 18 cm). up to 4000, there was no significant difference in the amount of O2 produced by the plant(in the technical term). 16000 gauss, however, was under 55% efficient: a significant difference (in the technical term). This is logical because the magnetism will disrupt the plant's electron transport chain- which is a vital step in photosynthesis and cellular respiration. the (rough) results were: 0 gauss: 100% efficiency (inherent) 4000 gauss: 100% efficiency 8000 gauss: 75% efficiency 12000 gauss: 66% efficiency 16000 gauss: 55% efficiency so, no, magnetism does not help your plants grow. It starves and suffocates them. Like Save gigadygig_yahoo_com 13 years ago sniff this Like Save kelly.jb9398 12 years ago I'm doing a science fair project for my school. I'm experimenting on the effects of magnetism on plant growth. I'll using three pots of Sweet Basil plants. One will be a regular plant. The others will be under some type of influence of magnetism. I don't know what yet, but i might just do magnetized water. Please share some ideas that you have. Like \| 1 Save kelly.jb9398 12 years ago I've decided to use rosemary instead. I placed four magnets next to a potted plant on my windowsill and it started doing some weird things. The branches began spiraling. Like \| 1 Save ElectricFertilizer 11 years ago In a book called Electroculture by George Hull, one experimented from the 1800s sowed seeds over a set of wires placed in the soil and experienced significant increases in growth. I would attribute this to the electromagnetic fields produced by the current flow in a wire. Perhaps the difference comes from the field lines being circular vs linear from a regular magnet?? Like Save coing 11 years ago Kelly, An experiment is most likely to reveal the truth of the question if there is a control (comparing treated to untreated plants in exactly equal conditions) and also if it is double-blinded. This means that one person would assign the treatments, but another person, blind to which pot was treated in which way, would do the observations. This would prevent the observer from something we all do without realizing it: seeing what we want to see. Good luck with your project, let us know how it came out. Coing Like Save Konrad___far_north 10 years ago It was around 40 years ago when I helped out on a farm in southern Alberta, seeding HUGE fields of wheat etc. The farmer had a large coil hooked up on a power source, he just run seeds through this devise. Anybody done this? Like \| 1 Save albert_135 39.17°N 119.76°W 4695ft. 10 years ago FYI, Harbor Freight has some approx. 1X1X3 inch magnets that are supposed to lift 200 lb. About $18 each. Like Save David.Sturtz 10 years ago I am a retired electronics tech. Only iron has strongly magnetic properties. Water in particular is unaffected by magnetism because it has two covanlent chemical bonds rather than an ionic bond. It is not possible to magnetize a non magnetic material such as water. Running water past a magnet will not magnetize it any more than it would glass. There is some evidence, however, that growing plants in a magnetic field, can affect growth. Like Save Mokinu 8 years ago last modified: 8 years ago So, how did everyone's science fair experiments turn out? I wouldn't be surprised if plants and seeds could sense magnetic fields to some degree in an effort to see what kind of climate they're growing in. Maybe magnetizing seeds can speed this process up. After all, birds can sense magnetic fields. Like Save Seysonn_ 8a-NC/HZ-7 8 years ago I have never heard of such a thing : i.e the effect of magnet on plants growth. Why don't you just fertilize ? You want oxygen to get into the roots, amend with organic matter. I add some fine pine bark, to improve drainage and get oxygen to the roots. Sey Like \| 1 Save Mokinu 8 years ago last modified: 8 years ago As I understand it, if there's an effect on plants with magnetism, it should likely be a cumulative effect, and not something that extra care of your plants is going to make completely irrelevant, whether or not that extra care is all your plants need. Since perhaps no one really knows the effect, though, it's a moot point whether the effect is cumulative until figured out. I think there's sufficient reason to study it. Like Save albert_135 39.17°N 119.76°W 4695ft. 8 years ago ''Why don't you just..." is usually what professionals call a micro rant: The Microcomplaint: Nothing Too Small to Whine About - The New York Times - The Microcomplaint: Nothing Too Small to Whine About Like \| 1 Save PRO husbands helper 8 years ago I know magnets shoot photons at each other which causes a magnetic field. These are the same photons that light uses to travel so I am very curious if that would speed up photosynthesis...but no spacific answers I can find Like \| 1 Save Mokinu 8 years ago last modified: 8 years ago Interesting thought. I got some magnets for my own experimentation (primarily their effect when used on seeds before planting). So, hopefully I'll have something to report by the end of next season. It sounds like you're interested in post-planting information. I might try stuff out there, too, but it's not my main priority. I would suggest experimenting using the magnets at night, if you're going to use them on plants. Like \| 1 Save Mokinu 8 years ago last modified: 8 years ago Check this out: http://www.ncbi.nlm.nih.gov/pubmed/18512697 It looks like we've got some proof, for chickpea seeds, anyway. A gauss is a tenth of an mT. So, 1000 gauss static magnet exposure for an hour should produce results in chickpeas, or 500 gauss for two hours or 1500 gauss for two hours. Like \| 1 Save Mokinu 8 years ago Here's another link to explain how it helps if water is exposed to magnets. Apparently, it's supposed to make saltier water easier for plants to absorb: https://www.usaid.gov/news-information/frontlines/feed-future/magnets-help-plants-grow Like \| 1 Save zen_man 5 years ago The earth is a big magnet, so a valid experiment would be to see how plants grow in the absence of a magnetic field. Isolating a plant from the earth's magnetic field might be a little hard to do, but maybe a Faraday Cage would do the trick. Like Save David 3 years ago Earth is not a magnet. Nothing in nature is polar. Like Save Set Apart Spirit 2 years ago If you expose what’s commonly called the north pole (N&S poles dont exist) to tomato seeds for 30min proir to gemination, your yield will be less acidic! Like Save Featured Answer Steve Lng Islnd NY Z-7a SunSet Z-34 6 years ago Its been discovered that Water exposed to a south magnetic field has molecules that group in 6 molecules where when exposed to a North Magnetic field group in 12. I have exposed water to South Pole Magnet of a N52 Neodymium (50mmx50x25) for 24 hours and it definitely had very low surface tension compared to non-exposed. It was noticeably a different feeling on your hands as well. Like \| 2 Save Steve Lng Islnd NY Z-7a SunSet Z-34 6 years ago Its been discovered that Water exposed to a south magnetic field has molecules that group in 6 molecules where when exposed to a North Magnetic field group in 12. I have exposed water to South Pole Magnet of a N52 Neodymium (50mmx50x25) for 24 hours and it definitely had very low surface tension compared to non-exposed. It was noticeably a different feeling on your hands as well. Like \| 2 Save Steve Lng Islnd NY Z-7a SunSet Z-34 6 years ago Its been discovered that Water exposed to a south magnetic field has molecules that group in 6 molecules where when exposed to a North Magnetic field group in 12. I have exposed water to South Pole Magnet of a N52 Neodymium (50mmx50x25) for 24 hours and it definitely had very low surface tension compared to non-exposed. It was noticeably a different feeling on your hands as well. Its been discovered that Water exposed to a south magnetic field has molecules that group in 6 molecules where when exposed to a North Magnetic field group in 12. I have exposed water to South Pole Magnet of a N52 Neodymium (50mmx50x25) for 24 hours and it definitely had very low surface tension compared to non-exposed. It was noticeably a different feeling on your hands as well. Its been discovered that Water exposed to a south magnetic field has molecules that group in 6 molecules where when exposed to a North Magnetic field group in 12. I have exposed water to South Pole Magnet of a N52 Neodymium (50mmx50x25) for 24 hours and it definitely had very low surface tension compared to non-exposed. It was noticeably a different feeling on your hands as well. Its been discovered that Water exposed to a south magnetic field has molecules that group in 6 molecules where when exposed to a North Magnetic field group in 12. I have exposed water to South Pole Magnet of a N52 Neodymium (50mmx50x25) for 24 hours and it definitely had very low surface tension compared to non-exposed. It was noticeably a different feeling on your hands as well. Its been discovered that Water exposed to a south magnetic field has molecules that group in 6 molecules where when exposed to a North Magnetic field group in 12. I have exposed water to South Pole Magnet of a N52 Neodymium (50mmx50x25) for 24 hours and it definitely had very low surface tension compared to non-exposed. It was noticeably a different feeling on your hands as well. Its been discovered that Water exposed to a south magnetic field has molecules that group in 6 molecules where when exposed to a North Magnetic field group in 12. I have exposed water to South Pole Magnet of a N52 Neodymium (50mmx50x25) for 24 hours and it definitely had very low surface tension compared to non-exposed. It was noticeably a different feeling on your hands as well. See 2 more comments Dave_S Original Author 20 years ago I set up a South Pole vs North Pole vs Control on some seeds which haven't germinated yet. Also, I put a North and South combination on a tomato and pepper plant in the garden and will continue to monitor them throughout the season for any differences with their neighbor non-magnetized plants. Like \| 1 Save palyne 20 years ago So Dave... what ever happened on this? Anything? Palyne Like Save Related Professionals Glendora Landscape Architects & Landscape Designers · Roosevelt Landscape Architects & Landscape Designers · Fort Atkinson Landscape Contractors · Hampton Bays Landscape Contractors · Haverhill Landscape Contractors · Homewood Landscape Contractors · Medford Landscape Contractors · Tacoma Landscape Contractors · Vadnais Heights Landscape Contractors · Adrian Decks, Patios & Outdoor Enclosures · Fort Pierce Decks, Patios & Outdoor Enclosures · Novi Decks, Patios & Outdoor Enclosures · St John's Kirk Decks, Patios & Outdoor Enclosures · Kenosha Siding & Exteriors · South Laurel Siding & Exteriors tony_k_orlando 20 years ago Earth to Dave, come in please. What are the results? Tony Like Save atillathepun 20 years ago Maybe magnets make plants carnivorous? Like Save Scott Wallace 20 years ago Funny...my daughter is doing this same thing for her science fair project this year. She just started Monday...I'll try to update this thread every week. Like \| 1 Save watermanjeff 20 years ago Dave I found a fairly recent experiment using radish seeds which showed a significant increase in the growth of root hairs. There is also a chapter in the controversial book "The Secret Life Of Plants", by Christopher Bird and Peter Tompkins, which deals with an amazing (unbelievable?) series of experiments. I don't have the book now, but as i recall the authors claimed to grow plants without light by running copper wires from outside (daylight)into a basement (dark) and inserting them into the soil in the pots the plants were in. Like i said....controversial. Jeff Here is a link that might be useful: The Effects of Electromagnetic Field...etc. Like Save palyne 20 years ago I have that book Jeff--and that was the one that struck me as most amazing (and in need of validation) out of the whole book (which btw I think is great). I'll see if I can dig out that passage and post it here. It really didn't give enough useful info to replicate--I once went looking for this a couple years ago hoping to! Attilathepun--that was truly hilarious. FEED ME! Palyne Like Save tony_k_orlando 20 years ago I only have two things to say to all you tormentors of plants..... and its simple, listen close now.... Red is positive and black is negative. Thanks for the tip on the book "The Secret Life Of Plants" I ordered it from the library today. Cant wait to check it out. Like Save pickwick 20 years ago i think it makes plants more attractive Like Save janemccl 20 years ago I have never grown plants with magnets. However, my dentist made me get a water pick which helped some with gum infection, but I still had problems. Then the water pick broke, and the hygenist recommended a magnetic water pick. The water got magnetized as it went through the machine. The infection all disappeared in three months by the next check up, and has not come back. Because the water pick impressed me, I bought some magnets from the internet and started magnetizing my drinking water. At first I felt great, then, after a couple of months, not so great. The magnets are reputed to make hard water soft, so maybe they removed too much magnesium and potassium from the water and my body didn't get enough. I would like to go back to it though. I think a glass a day might be good. It may clear infections? Also, I put some flowers in magnetic water, and the water NEVER got yucky, and the flowers lasted a LONG time. The water stayed clear and sweet with no rot on the flower stems. What magnetic water does to sprouting seeds or growing plants, I don't know. Best, Jane Like Save pickwick 20 years ago interesting association,Jane...have used electrostatic sprayers -a device located at the nozzle which charges mist particles emitted from a sprayer resulting in greater coverage with less product Like Save Mathmom1 19 years ago Who has actually experimented with either north pole facing the water for plants or south pole facing water for plants and recorded results? I am about to plant just harvested amaryillis seed in three containers. I'll use magnetized water to water two flats and non magnetized in the third. The water will be in a jar with a magnet wrapped around the jar oriented north for one, south for the second and none for the third. I will refill the water after watering each time from the tap, note how much water each flat used, and record germination percents and heights of each plant. Any suggestions from this forum's users? Like Save gingerhill 19 years ago Hysterical, I thought the post said magets. I must drink more coffee. I was thinking ewww, why would anyone want to try that. Thank goodness it's magnets :) Like \| 1 Save Amino_X 19 years ago What type of magnets are you using? Standard Ferric Oxides? Rare Earth? or Neodymiums? I did some experiments with diametricly opposed neodymium magnetic levitation some years back, but never thought to apply it to plants! Hmmm... Let us know how it works out :D Best Wishes Amino-X Like Save jkirk3279 19 years ago When starting plants this spring, I put a big speaker magnet underneath some Physallis Mullaca seedlings. A day later they had doubled in size ! I decided to follow up on this, so I cut squares of magnetic backed material I use to make magnetic signs. I put it under the seedlings. And nothing happened. So maybe the magnetic sign stuff wasn't strong enough. If this DID have good effects on the seedlings at first, I couldn't repeat the results. Maybe stronger magnets -- or opposing polarity would help. Like Save the_alpha_wolf_rules 19 years ago lol! it's spelled "maggots" anyway. Like Save The_Tree 18 years ago You can increase the growth of plants with magnets. The best way is to put seeds on a flat magnet (about 1500-2500 gauss) for a period of 2-6 days before planting. You'll need to experiment to find the absolute best length of time to leave them on the magnet. Plant the seeds within a day after taking them off of the magnet. You can magnetize the water that you water the plants with too. The polarity of the magnet does matter. Usually the South pole will increase growth. Some plants actually do better with North pole energy. Magnets can be attached to the hose (south pole of magnet facing hose) and given to the roots only, not the foliage. Using magnetized water alone can significantly increase the growth. If you thoroughly look into the history of using magnets for growing plants, you'll come accross the information I've given you, but it's difficult to find. Remember, the side of the magnet you put the seeds on and the side of the magnet facing the hose makes all of the difference. Generally, plants that grow under ground (potatoes) prefer North pole energy, above ground plants prefer South pole energy. There are exceptions. Magnetizing your plants is well worth the effort. They'll taste better and have a higher yield. Like \| 1 Save The_Tree 18 years ago Find the scientist that first discovered that magnetism consists of two separate energies and you've found my source. If your skeptical that water can be magnetized, do a google search on 'U.S. government studies on magnetized water'. In 1973, there was a government study that confirmed that magnetic energy alters the properties of water. It also states that the Soviet Union has used magnetized water for many years with great economic benefit. Like Save The_Tree 18 years ago And now the answer you've all been waiting for... It was Albert Roy Davis and Walter C. Rawls that made these discoveries. Plant yields can be increased from 20% to 200%! The plants will have a higher concentration of nutrients too. I've done experiments myself. They wrote about these and other fascinating experiments in their first book, "Magnetism and Its Effects on the Living System". There are some species that will grow better with exposure to North AND South pole energy. For example, the North pole plants may give you the highest yield, but the South pole plants will have the most nutrients. In these cases both will have improved qualities over plants of the same species that haven't been exposed to either magnetic field. You can find more information about this discovery on the U.S. Patent and Trademark Office website, patent # 4,020,590. Like Save mistercross 18 years ago This sounds like a perfect test for the Mythbusters on the Discovery Channel, especially if they still have the ten greenhouses from the test of music on plant growth. I would suggest it to them, but I block cookies and apparently can't post there. Here is a long article on magnetic claims, but it only briefly mentions that plant growth is one claim. Here is a student science fair test, in PDF format, on the effect of magnetism on plant growth. Here is a link that might be useful: Discovery Channel: Mythbusters Like Save The_Tree 18 years ago Take a look at how an MRI works. http://www.ccmr.cornell.edu/education/ask/?quid=41 Like Save snorelas 18 years ago hey, i am also doing the magnet experiment and i need something to back up my oun result, would you be able to send me some of your results? Like Save wayne_5 zone 6a Central Indiana 18 years ago Now how about people magnetism....I read where it is best to have your bed situated so that your head [top of] is facing the north, and second best if headed south............................"? Like Save albert_135 39.17°N 119.76°W 4695ft. 18 years ago I read somewhere that native plants growing under high power transmission lines did better than the same plants nearby. I haven't been able to confirm this. I thought that the high power transmission lines might have rapidly reversing magnetic fields but haven't been able to confirm that either. Like Save ascalon 17 years ago Has anyone any information on exactly what should be done with magnets to water or the plants directly? Like what kind of magnets, and what to do with them, and where. Please feel free to email me information at [email protected]. Like Save kelly_r 15 years ago I'm doing the whole magnet and seed thing also, but im having trouble with my research report. Anyone know of any usefull websites i could use? Like Save dethcheez 15 years ago I can't say that I've ever tried anything or even thought about trying anything with plants and magnets... But now I'm going to have to, thanx a lot... If any of my Carns eat me I'm blaming you guys... LOL... My many interest is Carns & Neps which do best with distilled water as I'm sure most plant probably would... Can/does the magnet in the water have anything to do with it possibly attracting unwanted metals/minerals in the water??? Kind of like a filter / Helping to purify it & making it healthier for the plants??? Also in the soil, Attracting / Repelling minerals to or away from the plant??? ??? Just thought I'd throw my 2 cents in... Like Save maifleur01 15 years ago I will post a new topic as I don't want to highjack this thread. Like Save kayjones 15 years ago Here's the link to this patent number - very interesting! Here is a link that might be useful: Magnets and seeds Like Save noway_ever_com 13 years ago I personally conducted an experiment with 0, 4000, 8000, 12000, and 16000 gauss, with neodymium magnets at 2000 gauss each. I measured O2 released over a period of slightly under a week, with a 40w light source. All specimens were placed 20 cm away, so as not to have interference between magnetic fields (the measured angle of compass deflection was at 18 cm). up to 4000, there was no significant difference in the amount of O2 produced by the plant(in the technical term). 16000 gauss, however, was under 55% efficient: a significant difference (in the technical term). This is logical because the magnetism will disrupt the plant's electron transport chain- which is a vital step in photosynthesis and cellular respiration. the (rough) results were: 0 gauss: 100% efficiency (inherent) 4000 gauss: 100% efficiency 8000 gauss: 75% efficiency 12000 gauss: 66% efficiency 16000 gauss: 55% efficiency so, no, magnetism does not help your plants grow. It starves and suffocates them. Like Save gigadygig_yahoo_com 13 years ago sniff this Like Save kelly.jb9398 12 years ago I'm doing a science fair project for my school. I'm experimenting on the effects of magnetism on plant growth. I'll using three pots of Sweet Basil plants. One will be a regular plant. The others will be under some type of influence of magnetism. I don't know what yet, but i might just do magnetized water. Please share some ideas that you have. Like \| 1 Save kelly.jb9398 12 years ago I've decided to use rosemary instead. I placed four magnets next to a potted plant on my windowsill and it started doing some weird things. The branches began spiraling. Like \| 1 Save ElectricFertilizer 11 years ago In a book called Electroculture by George Hull, one experimented from the 1800s sowed seeds over a set of wires placed in the soil and experienced significant increases in growth. I would attribute this to the electromagnetic fields produced by the current flow in a wire. Perhaps the difference comes from the field lines being circular vs linear from a regular magnet?? Like Save coing 11 years ago Kelly, An experiment is most likely to reveal the truth of the question if there is a control (comparing treated to untreated plants in exactly equal conditions) and also if it is double-blinded. This means that one person would assign the treatments, but another person, blind to which pot was treated in which way, would do the observations. This would prevent the observer from something we all do without realizing it: seeing what we want to see. Good luck with your project, let us know how it came out. Coing Like Save Konrad___far_north 10 years ago It was around 40 years ago when I helped out on a farm in southern Alberta, seeding HUGE fields of wheat etc. The farmer had a large coil hooked up on a power source, he just run seeds through this devise. Anybody done this? Like \| 1 Save albert_135 39.17°N 119.76°W 4695ft. 10 years ago FYI, Harbor Freight has some approx. 1X1X3 inch magnets that are supposed to lift 200 lb. About $18 each. Like Save David.Sturtz 10 years ago I am a retired electronics tech. Only iron has strongly magnetic properties. Water in particular is unaffected by magnetism because it has two covanlent chemical bonds rather than an ionic bond. It is not possible to magnetize a non magnetic material such as water. Running water past a magnet will not magnetize it any more than it would glass. There is some evidence, however, that growing plants in a magnetic field, can affect growth. Like Save Mokinu 8 years ago last modified: 8 years ago So, how did everyone's science fair experiments turn out? I wouldn't be surprised if plants and seeds could sense magnetic fields to some degree in an effort to see what kind of climate they're growing in. Maybe magnetizing seeds can speed this process up. After all, birds can sense magnetic fields. Like Save Seysonn_ 8a-NC/HZ-7 8 years ago I have never heard of such a thing : i.e the effect of magnet on plants growth. Why don't you just fertilize ? You want oxygen to get into the roots, amend with organic matter. I add some fine pine bark, to improve drainage and get oxygen to the roots. Sey Like \| 1 Save Mokinu 8 years ago last modified: 8 years ago As I understand it, if there's an effect on plants with magnetism, it should likely be a cumulative effect, and not something that extra care of your plants is going to make completely irrelevant, whether or not that extra care is all your plants need. Since perhaps no one really knows the effect, though, it's a moot point whether the effect is cumulative until figured out. I think there's sufficient reason to study it. Like Save albert_135 39.17°N 119.76°W 4695ft. 8 years ago ''Why don't you just..." is usually what professionals call a micro rant: The Microcomplaint: Nothing Too Small to Whine About - The New York Times - The Microcomplaint: Nothing Too Small to Whine About Like \| 1 Save PRO husbands helper 8 years ago I know magnets shoot photons at each other which causes a magnetic field. These are the same photons that light uses to travel so I am very curious if that would speed up photosynthesis...but no spacific answers I can find Like \| 1 Save Mokinu 8 years ago last modified: 8 years ago Interesting thought. I got some magnets for my own experimentation (primarily their effect when used on seeds before planting). So, hopefully I'll have something to report by the end of next season. It sounds like you're interested in post-planting information. I might try stuff out there, too, but it's not my main priority. I would suggest experimenting using the magnets at night, if you're going to use them on plants. Like \| 1 Save Mokinu 8 years ago last modified: 8 years ago Check this out: http://www.ncbi.nlm.nih.gov/pubmed/18512697 It looks like we've got some proof, for chickpea seeds, anyway. A gauss is a tenth of an mT. So, 1000 gauss static magnet exposure for an hour should produce results in chickpeas, or 500 gauss for two hours or 1500 gauss for two hours. Like \| 1 Save Mokinu 8 years ago Here's another link to explain how it helps if water is exposed to magnets. Apparently, it's supposed to make saltier water easier for plants to absorb: https://www.usaid.gov/news-information/frontlines/feed-future/magnets-help-plants-grow Like \| 1 Save zen_man 5 years ago The earth is a big magnet, so a valid experiment would be to see how plants grow in the absence of a magnetic field. Isolating a plant from the earth's magnetic field might be a little hard to do, but maybe a Faraday Cage would do the trick. Like Save David 3 years ago Earth is not a magnet. Nothing in nature is polar. Like Save Set Apart Spirit 2 years ago If you expose what’s commonly called the north pole (N&S poles dont exist) to tomato seeds for 30min proir to gemination, your yield will be less acidic! Like Save Dave_S Original Author 20 years ago I set up a South Pole vs North Pole vs Control on some seeds which haven't germinated yet. Also, I put a North and South combination on a tomato and pepper plant in the garden and will continue to monitor them throughout the season for any differences with their neighbor non-magnetized plants. Like \| 1 Save Dave_S Original Author 20 years ago I set up a South Pole vs North Pole vs Control on some seeds which haven't germinated yet. Also, I put a North and South combination on a tomato and pepper plant in the garden and will continue to monitor them throughout the season for any differences with their neighbor non-magnetized plants. I set up a South Pole vs North Pole vs Control on some seeds which haven't germinated yet. Also, I put a North and South combination on a tomato and pepper plant in the garden and will continue to monitor them throughout the season for any differences with their neighbor non-magnetized plants. I set up a South Pole vs North Pole vs Control on some seeds which haven't germinated yet. Also, I put a North and South combination on a tomato and pepper plant in the garden and will continue to monitor them throughout the season for any differences with their neighbor non-magnetized plants. Related Professionals Glendora Landscape Architects & Landscape Designers · Roosevelt Landscape Architects & Landscape Designers · Fort Atkinson Landscape Contractors · Hampton Bays Landscape Contractors · Haverhill Landscape Contractors · Homewood Landscape Contractors · Medford Landscape Contractors · Tacoma Landscape Contractors · Vadnais Heights Landscape Contractors · Adrian Decks, Patios & Outdoor Enclosures · Fort Pierce Decks, Patios & Outdoor Enclosures · Novi Decks, Patios & Outdoor Enclosures · St John's Kirk Decks, Patios & Outdoor Enclosures · Kenosha Siding & Exteriors · South Laurel Siding & Exteriors Scott Wallace 20 years ago Funny...my daughter is doing this same thing for her science fair project this year. She just started Monday...I'll try to update this thread every week. Like \| 1 Save Scott Wallace 20 years ago Funny...my daughter is doing this same thing for her science fair project this year. She just started Monday...I'll try to update this thread every week. Funny...my daughter is doing this same thing for her science fair project this year. She just started Monday...I'll try to update this thread every week. Funny...my daughter is doing this same thing for her science fair project this year. She just started Monday...I'll try to update this thread every week. watermanjeff 20 years ago Dave I found a fairly recent experiment using radish seeds which showed a significant increase in the growth of root hairs. There is also a chapter in the controversial book "The Secret Life Of Plants", by Christopher Bird and Peter Tompkins, which deals with an amazing (unbelievable?) series of experiments. I don't have the book now, but as i recall the authors claimed to grow plants without light by running copper wires from outside (daylight)into a basement (dark) and inserting them into the soil in the pots the plants were in. Like i said....controversial. Jeff Here is a link that might be useful: The Effects of Electromagnetic Field...etc. Like Save watermanjeff 20 years ago Dave I found a fairly recent experiment using radish seeds which showed a significant increase in the growth of root hairs. There is also a chapter in the controversial book "The Secret Life Of Plants", by Christopher Bird and Peter Tompkins, which deals with an amazing (unbelievable?) series of experiments. I don't have the book now, but as i recall the authors claimed to grow plants without light by running copper wires from outside (daylight)into a basement (dark) and inserting them into the soil in the pots the plants were in. Like i said....controversial. Jeff Here is a link that might be useful: The Effects of Electromagnetic Field...etc. Dave I found a fairly recent experiment using radish seeds which showed a significant increase in the growth of root hairs. There is also a chapter in the controversial book "The Secret Life Of Plants", by Christopher Bird and Peter Tompkins, which deals with an amazing (unbelievable?) series of experiments. I don't have the book now, but as i recall the authors claimed to grow plants without light by running copper wires from outside (daylight)into a basement (dark) and inserting them into the soil in the pots the plants were in. Like i said....controversial. Jeff Here is a link that might be useful: The Effects of Electromagnetic Field...etc. Dave I found a fairly recent experiment using radish seeds which showed a significant increase in the growth of root hairs. There is also a chapter in the controversial book "The Secret Life Of Plants", by Christopher Bird and Peter Tompkins, which deals with an amazing (unbelievable?) series of experiments. I don't have the book now, but as i recall the authors claimed to grow plants without light by running copper wires from outside (daylight)into a basement (dark) and inserting them into the soil in the pots the plants were in. Like i said....controversial. Jeff palyne 20 years ago I have that book Jeff--and that was the one that struck me as most amazing (and in need of validation) out of the whole book (which btw I think is great). I'll see if I can dig out that passage and post it here. It really didn't give enough useful info to replicate--I once went looking for this a couple years ago hoping to! Attilathepun--that was truly hilarious. FEED ME! Palyne Like Save palyne 20 years ago I have that book Jeff--and that was the one that struck me as most amazing (and in need of validation) out of the whole book (which btw I think is great). I'll see if I can dig out that passage and post it here. It really didn't give enough useful info to replicate--I once went looking for this a couple years ago hoping to! Attilathepun--that was truly hilarious. FEED ME! Palyne I have that book Jeff--and that was the one that struck me as most amazing (and in need of validation) out of the whole book (which btw I think is great). I'll see if I can dig out that passage and post it here. It really didn't give enough useful info to replicate--I once went looking for this a couple years ago hoping to! Attilathepun--that was truly hilarious. FEED ME! Palyne I have that book Jeff--and that was the one that struck me as most amazing (and in need of validation) out of the whole book (which btw I think is great). I'll see if I can dig out that passage and post it here. It really didn't give enough useful info to replicate--I once went looking for this a couple years ago hoping to! tony_k_orlando 20 years ago I only have two things to say to all you tormentors of plants..... and its simple, listen close now.... Red is positive and black is negative. Thanks for the tip on the book "The Secret Life Of Plants" I ordered it from the library today. Cant wait to check it out. Like Save tony_k_orlando 20 years ago I only have two things to say to all you tormentors of plants..... and its simple, listen close now.... Red is positive and black is negative. Thanks for the tip on the book "The Secret Life Of Plants" I ordered it from the library today. Cant wait to check it out. I only have two things to say to all you tormentors of plants..... and its simple, listen close now.... Red is positive and black is negative. Thanks for the tip on the book "The Secret Life Of Plants" I ordered it from the library today. Cant wait to check it out. I only have two things to say to all you tormentors of plants..... and its simple, listen close now.... Red is positive and black is negative. Thanks for the tip on the book "The Secret Life Of Plants" I ordered it from the library today. Cant wait to check it out. janemccl 20 years ago I have never grown plants with magnets. However, my dentist made me get a water pick which helped some with gum infection, but I still had problems. Then the water pick broke, and the hygenist recommended a magnetic water pick. The water got magnetized as it went through the machine. The infection all disappeared in three months by the next check up, and has not come back. Because the water pick impressed me, I bought some magnets from the internet and started magnetizing my drinking water. At first I felt great, then, after a couple of months, not so great. The magnets are reputed to make hard water soft, so maybe they removed too much magnesium and potassium from the water and my body didn't get enough. I would like to go back to it though. I think a glass a day might be good. It may clear infections? Also, I put some flowers in magnetic water, and the water NEVER got yucky, and the flowers lasted a LONG time. The water stayed clear and sweet with no rot on the flower stems. What magnetic water does to sprouting seeds or growing plants, I don't know. Best, Jane Like Save janemccl 20 years ago I have never grown plants with magnets. However, my dentist made me get a water pick which helped some with gum infection, but I still had problems. Then the water pick broke, and the hygenist recommended a magnetic water pick. The water got magnetized as it went through the machine. The infection all disappeared in three months by the next check up, and has not come back. Because the water pick impressed me, I bought some magnets from the internet and started magnetizing my drinking water. At first I felt great, then, after a couple of months, not so great. The magnets are reputed to make hard water soft, so maybe they removed too much magnesium and potassium from the water and my body didn't get enough. I would like to go back to it though. I think a glass a day might be good. It may clear infections? Also, I put some flowers in magnetic water, and the water NEVER got yucky, and the flowers lasted a LONG time. The water stayed clear and sweet with no rot on the flower stems. What magnetic water does to sprouting seeds or growing plants, I don't know. Best, Jane I have never grown plants with magnets. However, my dentist made me get a water pick which helped some with gum infection, but I still had problems. Then the water pick broke, and the hygenist recommended a magnetic water pick. The water got magnetized as it went through the machine. The infection all disappeared in three months by the next check up, and has not come back. Because the water pick impressed me, I bought some magnets from the internet and started magnetizing my drinking water. At first I felt great, then, after a couple of months, not so great. The magnets are reputed to make hard water soft, so maybe they removed too much magnesium and potassium from the water and my body didn't get enough. I would like to go back to it though. I think a glass a day might be good. It may clear infections? Also, I put some flowers in magnetic water, and the water NEVER got yucky, and the flowers lasted a LONG time. The water stayed clear and sweet with no rot on the flower stems. What magnetic water does to sprouting seeds or growing plants, I don't know. Best, Jane I have never grown plants with magnets. However, my dentist made me get a water pick which helped some with gum infection, but I still had problems. Then the water pick broke, and the hygenist recommended a magnetic water pick. The water got magnetized as it went through the machine. The infection all disappeared in three months by the next check up, and has not come back. Because the water pick impressed me, I bought some magnets from the internet and started magnetizing my drinking water. At first I felt great, then, after a couple of months, not so great. The magnets are reputed to make hard water soft, so maybe they removed too much magnesium and potassium from the water and my body didn't get enough. I would like to go back to it though. I think a glass a day might be good. It may clear infections? Also, I put some flowers in magnetic water, and the water NEVER got yucky, and the flowers lasted a LONG time. The water stayed clear and sweet with no rot on the flower stems. pickwick 20 years ago interesting association,Jane...have used electrostatic sprayers -a device located at the nozzle which charges mist particles emitted from a sprayer resulting in greater coverage with less product Like Save pickwick 20 years ago interesting association,Jane...have used electrostatic sprayers -a device located at the nozzle which charges mist particles emitted from a sprayer resulting in greater coverage with less product interesting association,Jane...have used electrostatic sprayers -a device located at the nozzle which charges mist particles emitted from a sprayer resulting in greater coverage with less product interesting association,Jane...have used electrostatic sprayers -a device located at the nozzle which charges mist particles emitted from a sprayer resulting in greater coverage with less product Mathmom1 19 years ago Who has actually experimented with either north pole facing the water for plants or south pole facing water for plants and recorded results? I am about to plant just harvested amaryillis seed in three containers. I'll use magnetized water to water two flats and non magnetized in the third. The water will be in a jar with a magnet wrapped around the jar oriented north for one, south for the second and none for the third. I will refill the water after watering each time from the tap, note how much water each flat used, and record germination percents and heights of each plant. Any suggestions from this forum's users? Like Save Mathmom1 19 years ago Who has actually experimented with either north pole facing the water for plants or south pole facing water for plants and recorded results? I am about to plant just harvested amaryillis seed in three containers. I'll use magnetized water to water two flats and non magnetized in the third. The water will be in a jar with a magnet wrapped around the jar oriented north for one, south for the second and none for the third. I will refill the water after watering each time from the tap, note how much water each flat used, and record germination percents and heights of each plant. Any suggestions from this forum's users? Who has actually experimented with either north pole facing the water for plants or south pole facing water for plants and recorded results? I am about to plant just harvested amaryillis seed in three containers. I'll use magnetized water to water two flats and non magnetized in the third. The water will be in a jar with a magnet wrapped around the jar oriented north for one, south for the second and none for the third. I will refill the water after watering each time from the tap, note how much water each flat used, and record germination percents and heights of each plant. Any suggestions from this forum's users? Who has actually experimented with either north pole facing the water for plants or south pole facing water for plants and recorded results? I am about to plant just harvested amaryillis seed in three containers. I'll use magnetized water to water two flats and non magnetized in the third. The water will be in a jar with a magnet wrapped around the jar oriented north for one, south for the second and none for the third. I will refill the water after watering each time from the tap, note how much water each flat used, and record germination percents and heights of each plant. Any suggestions from this forum's users? gingerhill 19 years ago Hysterical, I thought the post said magets. I must drink more coffee. I was thinking ewww, why would anyone want to try that. Thank goodness it's magnets :) Like \| 1 Save gingerhill 19 years ago Hysterical, I thought the post said magets. I must drink more coffee. I was thinking ewww, why would anyone want to try that. Thank goodness it's magnets :) Hysterical, I thought the post said magets. I must drink more coffee. I was thinking ewww, why would anyone want to try that. Thank goodness it's magnets :) Hysterical, I thought the post said magets. I must drink more coffee. I was thinking ewww, why would anyone want to try that. Thank goodness it's magnets :) Amino_X 19 years ago What type of magnets are you using? Standard Ferric Oxides? Rare Earth? or Neodymiums? I did some experiments with diametricly opposed neodymium magnetic levitation some years back, but never thought to apply it to plants! Hmmm... Let us know how it works out :D Best Wishes Amino-X Like Save Amino_X 19 years ago What type of magnets are you using? Standard Ferric Oxides? Rare Earth? or Neodymiums? I did some experiments with diametricly opposed neodymium magnetic levitation some years back, but never thought to apply it to plants! Hmmm... Let us know how it works out :D Best Wishes Amino-X What type of magnets are you using? Standard Ferric Oxides? Rare Earth? or Neodymiums? I did some experiments with diametricly opposed neodymium magnetic levitation some years back, but never thought to apply it to plants! Hmmm... Let us know how it works out :D Best Wishes Amino-X I did some experiments with diametricly opposed neodymium magnetic levitation some years back, but never thought to apply it to plants! Hmmm... Let us know how it works out :D jkirk3279 19 years ago When starting plants this spring, I put a big speaker magnet underneath some Physallis Mullaca seedlings. A day later they had doubled in size ! I decided to follow up on this, so I cut squares of magnetic backed material I use to make magnetic signs. I put it under the seedlings. And nothing happened. So maybe the magnetic sign stuff wasn't strong enough. If this DID have good effects on the seedlings at first, I couldn't repeat the results. Maybe stronger magnets -- or opposing polarity would help. Like Save jkirk3279 19 years ago When starting plants this spring, I put a big speaker magnet underneath some Physallis Mullaca seedlings. A day later they had doubled in size ! I decided to follow up on this, so I cut squares of magnetic backed material I use to make magnetic signs. I put it under the seedlings. And nothing happened. So maybe the magnetic sign stuff wasn't strong enough. If this DID have good effects on the seedlings at first, I couldn't repeat the results. Maybe stronger magnets -- or opposing polarity would help. When starting plants this spring, I put a big speaker magnet underneath some Physallis Mullaca seedlings. A day later they had doubled in size ! I decided to follow up on this, so I cut squares of magnetic backed material I use to make magnetic signs. I put it under the seedlings. And nothing happened. So maybe the magnetic sign stuff wasn't strong enough. If this DID have good effects on the seedlings at first, I couldn't repeat the results. Maybe stronger magnets -- or opposing polarity would help. When starting plants this spring, I put a big speaker magnet underneath some Physallis Mullaca seedlings. A day later they had doubled in size ! I decided to follow up on this, so I cut squares of magnetic backed material I use to make magnetic signs. The_Tree 18 years ago You can increase the growth of plants with magnets. The best way is to put seeds on a flat magnet (about 1500-2500 gauss) for a period of 2-6 days before planting. You'll need to experiment to find the absolute best length of time to leave them on the magnet. Plant the seeds within a day after taking them off of the magnet. You can magnetize the water that you water the plants with too. The polarity of the magnet does matter. Usually the South pole will increase growth. Some plants actually do better with North pole energy. Magnets can be attached to the hose (south pole of magnet facing hose) and given to the roots only, not the foliage. Using magnetized water alone can significantly increase the growth. If you thoroughly look into the history of using magnets for growing plants, you'll come accross the information I've given you, but it's difficult to find. Remember, the side of the magnet you put the seeds on and the side of the magnet facing the hose makes all of the difference. Generally, plants that grow under ground (potatoes) prefer North pole energy, above ground plants prefer South pole energy. There are exceptions. Magnetizing your plants is well worth the effort. They'll taste better and have a higher yield. Like \| 1 Save The_Tree 18 years ago You can increase the growth of plants with magnets. The best way is to put seeds on a flat magnet (about 1500-2500 gauss) for a period of 2-6 days before planting. You'll need to experiment to find the absolute best length of time to leave them on the magnet. Plant the seeds within a day after taking them off of the magnet. You can magnetize the water that you water the plants with too. The polarity of the magnet does matter. Usually the South pole will increase growth. Some plants actually do better with North pole energy. Magnets can be attached to the hose (south pole of magnet facing hose) and given to the roots only, not the foliage. Using magnetized water alone can significantly increase the growth. If you thoroughly look into the history of using magnets for growing plants, you'll come accross the information I've given you, but it's difficult to find. Remember, the side of the magnet you put the seeds on and the side of the magnet facing the hose makes all of the difference. Generally, plants that grow under ground (potatoes) prefer North pole energy, above ground plants prefer South pole energy. There are exceptions. Magnetizing your plants is well worth the effort. They'll taste better and have a higher yield. You can increase the growth of plants with magnets. The best way is to put seeds on a flat magnet (about 1500-2500 gauss) for a period of 2-6 days before planting. You'll need to experiment to find the absolute best length of time to leave them on the magnet. Plant the seeds within a day after taking them off of the magnet. You can magnetize the water that you water the plants with too. The polarity of the magnet does matter. Usually the South pole will increase growth. Some plants actually do better with North pole energy. Magnets can be attached to the hose (south pole of magnet facing hose) and given to the roots only, not the foliage. Using magnetized water alone can significantly increase the growth. If you thoroughly look into the history of using magnets for growing plants, you'll come accross the information I've given you, but it's difficult to find. Remember, the side of the magnet you put the seeds on and the side of the magnet facing the hose makes all of the difference. Generally, plants that grow under ground (potatoes) prefer North pole energy, above ground plants prefer South pole energy. There are exceptions. Magnetizing your plants is well worth the effort. They'll taste better and have a higher yield. You can increase the growth of plants with magnets. The best way is to put seeds on a flat magnet (about 1500-2500 gauss) for a period of 2-6 days before planting. You'll need to experiment to find the absolute best length of time to leave them on the magnet. Plant the seeds within a day after taking them off of the magnet. You can magnetize the water that you water the plants with too. The polarity of the magnet does matter. Usually the South pole will increase growth. Some plants actually do better with North pole energy. Magnets can be attached to the hose (south pole of magnet facing hose) and given to the roots only, not the foliage. Using magnetized water alone can significantly increase the growth. If you thoroughly look into the history of using magnets for growing plants, you'll come accross the information I've given you, but it's difficult to find. Remember, the side of the magnet you put the seeds on and the side of the magnet facing the hose makes all of the difference. Generally, plants that grow under ground (potatoes) prefer North pole energy, above ground plants prefer South pole energy. There are exceptions. Magnetizing your plants is well worth the effort. They'll taste better and have a higher yield. The_Tree 18 years ago Find the scientist that first discovered that magnetism consists of two separate energies and you've found my source. If your skeptical that water can be magnetized, do a google search on 'U.S. government studies on magnetized water'. In 1973, there was a government study that confirmed that magnetic energy alters the properties of water. It also states that the Soviet Union has used magnetized water for many years with great economic benefit. Like Save The_Tree 18 years ago Find the scientist that first discovered that magnetism consists of two separate energies and you've found my source. If your skeptical that water can be magnetized, do a google search on 'U.S. government studies on magnetized water'. In 1973, there was a government study that confirmed that magnetic energy alters the properties of water. It also states that the Soviet Union has used magnetized water for many years with great economic benefit. Find the scientist that first discovered that magnetism consists of two separate energies and you've found my source. If your skeptical that water can be magnetized, do a google search on 'U.S. government studies on magnetized water'. In 1973, there was a government study that confirmed that magnetic energy alters the properties of water. It also states that the Soviet Union has used magnetized water for many years with great economic benefit. Find the scientist that first discovered that magnetism consists of two separate energies and you've found my source. If your skeptical that water can be magnetized, do a google search on 'U.S. government studies on magnetized water'. In 1973, there was a government study that confirmed that magnetic energy alters the properties of water. It also states that the Soviet Union has used magnetized water for many years with great economic benefit. The_Tree 18 years ago And now the answer you've all been waiting for... It was Albert Roy Davis and Walter C. Rawls that made these discoveries. Plant yields can be increased from 20% to 200%! The plants will have a higher concentration of nutrients too. I've done experiments myself. They wrote about these and other fascinating experiments in their first book, "Magnetism and Its Effects on the Living System". There are some species that will grow better with exposure to North AND South pole energy. For example, the North pole plants may give you the highest yield, but the South pole plants will have the most nutrients. In these cases both will have improved qualities over plants of the same species that haven't been exposed to either magnetic field. You can find more information about this discovery on the U.S. Patent and Trademark Office website, patent # 4,020,590. Like Save The_Tree 18 years ago And now the answer you've all been waiting for... It was Albert Roy Davis and Walter C. Rawls that made these discoveries. Plant yields can be increased from 20% to 200%! The plants will have a higher concentration of nutrients too. I've done experiments myself. They wrote about these and other fascinating experiments in their first book, "Magnetism and Its Effects on the Living System". There are some species that will grow better with exposure to North AND South pole energy. For example, the North pole plants may give you the highest yield, but the South pole plants will have the most nutrients. In these cases both will have improved qualities over plants of the same species that haven't been exposed to either magnetic field. You can find more information about this discovery on the U.S. Patent and Trademark Office website, patent # 4,020,590. And now the answer you've all been waiting for... It was Albert Roy Davis and Walter C. Rawls that made these discoveries. Plant yields can be increased from 20% to 200%! The plants will have a higher concentration of nutrients too. I've done experiments myself. They wrote about these and other fascinating experiments in their first book, "Magnetism and Its Effects on the Living System". There are some species that will grow better with exposure to North AND South pole energy. For example, the North pole plants may give you the highest yield, but the South pole plants will have the most nutrients. In these cases both will have improved qualities over plants of the same species that haven't been exposed to either magnetic field. You can find more information about this discovery on the U.S. Patent and Trademark Office website, patent # 4,020,590. And now the answer you've all been waiting for... It was Albert Roy Davis and Walter C. Rawls that made these discoveries. Plant yields can be increased from 20% to 200%! The plants will have a higher concentration of nutrients too. I've done experiments myself. They wrote about these and other fascinating experiments in their first book, "Magnetism and Its Effects on the Living System". There are some species that will grow better with exposure to North AND South pole energy. For example, the North pole plants may give you the highest yield, but the South pole plants will have the most nutrients. In these cases both will have improved qualities over plants of the same species that haven't been exposed to either magnetic field. You can find more information about this discovery on the U.S. Patent and Trademark Office website, patent # 4,020,590. mistercross 18 years ago This sounds like a perfect test for the Mythbusters on the Discovery Channel, especially if they still have the ten greenhouses from the test of music on plant growth. I would suggest it to them, but I block cookies and apparently can't post there. Here is a long article on magnetic claims, but it only briefly mentions that plant growth is one claim. Here is a student science fair test, in PDF format, on the effect of magnetism on plant growth. Here is a link that might be useful: Discovery Channel: Mythbusters Like Save mistercross 18 years ago This sounds like a perfect test for the Mythbusters on the Discovery Channel, especially if they still have the ten greenhouses from the test of music on plant growth. I would suggest it to them, but I block cookies and apparently can't post there. Here is a long article on magnetic claims, but it only briefly mentions that plant growth is one claim. Here is a student science fair test, in PDF format, on the effect of magnetism on plant growth. Here is a link that might be useful: Discovery Channel: Mythbusters This sounds like a perfect test for the Mythbusters on the Discovery Channel, especially if they still have the ten greenhouses from the test of music on plant growth. I would suggest it to them, but I block cookies and apparently can't post there. Here is a long article on magnetic claims, but it only briefly mentions that plant growth is one claim. Here is a student science fair test, in PDF format, on the effect of magnetism on plant growth. Here is a link that might be useful: Discovery Channel: Mythbusters This sounds like a perfect test for the Mythbusters on the Discovery Channel, especially if they still have the ten greenhouses from the test of music on plant growth. I would suggest it to them, but I block cookies and apparently can't post there. Here is a long article on magnetic claims, but it only briefly mentions that plant growth is one claim. The_Tree 18 years ago Take a look at how an MRI works. http://www.ccmr.cornell.edu/education/ask/?quid=41 Like Save The_Tree 18 years ago Take a look at how an MRI works. http://www.ccmr.cornell.edu/education/ask/?quid=41 snorelas 18 years ago hey, i am also doing the magnet experiment and i need something to back up my oun result, would you be able to send me some of your results? Like Save snorelas 18 years ago hey, i am also doing the magnet experiment and i need something to back up my oun result, would you be able to send me some of your results? hey, i am also doing the magnet experiment and i need something to back up my oun result, would you be able to send me some of your results? hey, i am also doing the magnet experiment and i need something to back up my oun result, would you be able to send me some of your results? wayne_5 zone 6a Central Indiana 18 years ago Now how about people magnetism....I read where it is best to have your bed situated so that your head [top of] is facing the north, and second best if headed south............................"? Like Save wayne_5 zone 6a Central Indiana 18 years ago Now how about people magnetism....I read where it is best to have your bed situated so that your head [top of] is facing the north, and second best if headed south............................"? Now how about people magnetism....I read where it is best to have your bed situated so that your head [top of] is facing the north, and second best if headed south............................"? Now how about people magnetism....I read where it is best to have your bed situated so that your head [top of] is facing the north, and second best if headed south............................"? albert_135 39.17°N 119.76°W 4695ft. 18 years ago I read somewhere that native plants growing under high power transmission lines did better than the same plants nearby. I haven't been able to confirm this. I thought that the high power transmission lines might have rapidly reversing magnetic fields but haven't been able to confirm that either. Like Save albert_135 39.17°N 119.76°W 4695ft. 18 years ago I read somewhere that native plants growing under high power transmission lines did better than the same plants nearby. I haven't been able to confirm this. I thought that the high power transmission lines might have rapidly reversing magnetic fields but haven't been able to confirm that either. I read somewhere that native plants growing under high power transmission lines did better than the same plants nearby. I haven't been able to confirm this. I thought that the high power transmission lines might have rapidly reversing magnetic fields but haven't been able to confirm that either. I read somewhere that native plants growing under high power transmission lines did better than the same plants nearby. I haven't been able to confirm this. I thought that the high power transmission lines might have rapidly reversing magnetic fields but haven't been able to confirm that either. ascalon 17 years ago Has anyone any information on exactly what should be done with magnets to water or the plants directly? Like what kind of magnets, and what to do with them, and where. Please feel free to email me information at [email protected]. Like Save ascalon 17 years ago Has anyone any information on exactly what should be done with magnets to water or the plants directly? Like what kind of magnets, and what to do with them, and where. Please feel free to email me information at [email protected]. Has anyone any information on exactly what should be done with magnets to water or the plants directly? Like what kind of magnets, and what to do with them, and where. Please feel free to email me information at [email protected]. Has anyone any information on exactly what should be done with magnets to water or the plants directly? Like what kind of magnets, and what to do with them, and where. Please feel free to email me information at [email protected]. kelly_r 15 years ago I'm doing the whole magnet and seed thing also, but im having trouble with my research report. Anyone know of any usefull websites i could use? Like Save kelly_r 15 years ago I'm doing the whole magnet and seed thing also, but im having trouble with my research report. Anyone know of any usefull websites i could use? I'm doing the whole magnet and seed thing also, but im having trouble with my research report. Anyone know of any usefull websites i could use? I'm doing the whole magnet and seed thing also, but im having trouble with my research report. Anyone know of any usefull websites i could use? dethcheez 15 years ago I can't say that I've ever tried anything or even thought about trying anything with plants and magnets... But now I'm going to have to, thanx a lot... If any of my Carns eat me I'm blaming you guys... LOL... My many interest is Carns & Neps which do best with distilled water as I'm sure most plant probably would... Can/does the magnet in the water have anything to do with it possibly attracting unwanted metals/minerals in the water??? Kind of like a filter / Helping to purify it & making it healthier for the plants??? Also in the soil, Attracting / Repelling minerals to or away from the plant??? ??? Just thought I'd throw my 2 cents in... Like Save dethcheez 15 years ago I can't say that I've ever tried anything or even thought about trying anything with plants and magnets... But now I'm going to have to, thanx a lot... If any of my Carns eat me I'm blaming you guys... LOL... My many interest is Carns & Neps which do best with distilled water as I'm sure most plant probably would... Can/does the magnet in the water have anything to do with it possibly attracting unwanted metals/minerals in the water??? Kind of like a filter / Helping to purify it & making it healthier for the plants??? Also in the soil, Attracting / Repelling minerals to or away from the plant??? ??? Just thought I'd throw my 2 cents in... I can't say that I've ever tried anything or even thought about trying anything with plants and magnets... But now I'm going to have to, thanx a lot... If any of my Carns eat me I'm blaming you guys... LOL... My many interest is Carns & Neps which do best with distilled water as I'm sure most plant probably would... Can/does the magnet in the water have anything to do with it possibly attracting unwanted metals/minerals in the water??? Kind of like a filter / Helping to purify it & making it healthier for the plants??? Also in the soil, Attracting / Repelling minerals to or away from the plant??? ??? Just thought I'd throw my 2 cents in... I can't say that I've ever tried anything or even thought about trying anything with plants and magnets... But now I'm going to have to, thanx a lot... If any of my Carns eat me I'm blaming you guys... LOL... My many interest is Carns & Neps which do best with distilled water as I'm sure most plant probably would... Can/does the magnet in the water have anything to do with it possibly attracting unwanted metals/minerals in the water??? Kind of like a filter / Helping to purify it & making it healthier for the plants??? kayjones 15 years ago Here's the link to this patent number - very interesting! Here is a link that might be useful: Magnets and seeds Like Save kayjones 15 years ago Here's the link to this patent number - very interesting! Here is a link that might be useful: Magnets and seeds Here's the link to this patent number - very interesting! Here is a link that might be useful: Magnets and seeds noway_ever_com 13 years ago I personally conducted an experiment with 0, 4000, 8000, 12000, and 16000 gauss, with neodymium magnets at 2000 gauss each. I measured O2 released over a period of slightly under a week, with a 40w light source. All specimens were placed 20 cm away, so as not to have interference between magnetic fields (the measured angle of compass deflection was at 18 cm). up to 4000, there was no significant difference in the amount of O2 produced by the plant(in the technical term). 16000 gauss, however, was under 55% efficient: a significant difference (in the technical term). This is logical because the magnetism will disrupt the plant's electron transport chain- which is a vital step in photosynthesis and cellular respiration. the (rough) results were: 0 gauss: 100% efficiency (inherent) 4000 gauss: 100% efficiency 8000 gauss: 75% efficiency 12000 gauss: 66% efficiency 16000 gauss: 55% efficiency so, no, magnetism does not help your plants grow. It starves and suffocates them. Like Save noway_ever_com 13 years ago I personally conducted an experiment with 0, 4000, 8000, 12000, and 16000 gauss, with neodymium magnets at 2000 gauss each. I measured O2 released over a period of slightly under a week, with a 40w light source. All specimens were placed 20 cm away, so as not to have interference between magnetic fields (the measured angle of compass deflection was at 18 cm). up to 4000, there was no significant difference in the amount of O2 produced by the plant(in the technical term). 16000 gauss, however, was under 55% efficient: a significant difference (in the technical term). This is logical because the magnetism will disrupt the plant's electron transport chain- which is a vital step in photosynthesis and cellular respiration. the (rough) results were: 0 gauss: 100% efficiency (inherent) 4000 gauss: 100% efficiency 8000 gauss: 75% efficiency 12000 gauss: 66% efficiency 16000 gauss: 55% efficiency so, no, magnetism does not help your plants grow. It starves and suffocates them. I personally conducted an experiment with 0, 4000, 8000, 12000, and 16000 gauss, with neodymium magnets at 2000 gauss each. I measured O2 released over a period of slightly under a week, with a 40w light source. All specimens were placed 20 cm away, so as not to have interference between magnetic fields (the measured angle of compass deflection was at 18 cm). up to 4000, there was no significant difference in the amount of O2 produced by the plant(in the technical term). 16000 gauss, however, was under 55% efficient: a significant difference (in the technical term). This is logical because the magnetism will disrupt the plant's electron transport chain- which is a vital step in photosynthesis and cellular respiration. the (rough) results were: 0 gauss: 100% efficiency (inherent) 4000 gauss: 100% efficiency 8000 gauss: 75% efficiency 12000 gauss: 66% efficiency 16000 gauss: 55% efficiency so, no, magnetism does not help your plants grow. It starves and suffocates them. I personally conducted an experiment with 0, 4000, 8000, 12000, and 16000 gauss, with neodymium magnets at 2000 gauss each. I measured O2 released over a period of slightly under a week, with a 40w light source. All specimens were placed 20 cm away, so as not to have interference between magnetic fields (the measured angle of compass deflection was at 18 cm). up to 4000, there was no significant difference in the amount of O2 produced by the plant(in the technical term). 16000 gauss, however, was under 55% efficient: a significant difference (in the technical term). This is logical because the magnetism will disrupt the plant's electron transport chain- which is a vital step in photosynthesis and cellular respiration. 0 gauss: 100% efficiency (inherent) 4000 gauss: 100% efficiency 8000 gauss: 75% efficiency 12000 gauss: 66% efficiency 16000 gauss: 55% efficiency kelly.jb9398 12 years ago I'm doing a science fair project for my school. I'm experimenting on the effects of magnetism on plant growth. I'll using three pots of Sweet Basil plants. One will be a regular plant. The others will be under some type of influence of magnetism. I don't know what yet, but i might just do magnetized water. Please share some ideas that you have. Like \| 1 Save kelly.jb9398 12 years ago I'm doing a science fair project for my school. I'm experimenting on the effects of magnetism on plant growth. I'll using three pots of Sweet Basil plants. One will be a regular plant. The others will be under some type of influence of magnetism. I don't know what yet, but i might just do magnetized water. Please share some ideas that you have. I'm doing a science fair project for my school. I'm experimenting on the effects of magnetism on plant growth. I'll using three pots of Sweet Basil plants. One will be a regular plant. The others will be under some type of influence of magnetism. I don't know what yet, but i might just do magnetized water. Please share some ideas that you have. I'm doing a science fair project for my school. I'm experimenting on the effects of magnetism on plant growth. I'll using three pots of Sweet Basil plants. One will be a regular plant. The others will be under some type of influence of magnetism. I don't know what yet, but i might just do magnetized water. Please share some ideas that you have. kelly.jb9398 12 years ago I've decided to use rosemary instead. I placed four magnets next to a potted plant on my windowsill and it started doing some weird things. The branches began spiraling. Like \| 1 Save kelly.jb9398 12 years ago I've decided to use rosemary instead. I placed four magnets next to a potted plant on my windowsill and it started doing some weird things. The branches began spiraling. I've decided to use rosemary instead. I placed four magnets next to a potted plant on my windowsill and it started doing some weird things. The branches began spiraling. I've decided to use rosemary instead. I placed four magnets next to a potted plant on my windowsill and it started doing some weird things. The branches began spiraling. ElectricFertilizer 11 years ago In a book called Electroculture by George Hull, one experimented from the 1800s sowed seeds over a set of wires placed in the soil and experienced significant increases in growth. I would attribute this to the electromagnetic fields produced by the current flow in a wire. Perhaps the difference comes from the field lines being circular vs linear from a regular magnet?? Like Save ElectricFertilizer 11 years ago In a book called Electroculture by George Hull, one experimented from the 1800s sowed seeds over a set of wires placed in the soil and experienced significant increases in growth. I would attribute this to the electromagnetic fields produced by the current flow in a wire. Perhaps the difference comes from the field lines being circular vs linear from a regular magnet?? In a book called Electroculture by George Hull, one experimented from the 1800s sowed seeds over a set of wires placed in the soil and experienced significant increases in growth. I would attribute this to the electromagnetic fields produced by the current flow in a wire. Perhaps the difference comes from the field lines being circular vs linear from a regular magnet?? In a book called Electroculture by George Hull, one experimented from the 1800s sowed seeds over a set of wires placed in the soil and experienced significant increases in growth. I would attribute this to the electromagnetic fields produced by the current flow in a wire. Perhaps the difference comes from the field lines being circular vs linear from a regular magnet?? coing 11 years ago Kelly, An experiment is most likely to reveal the truth of the question if there is a control (comparing treated to untreated plants in exactly equal conditions) and also if it is double-blinded. This means that one person would assign the treatments, but another person, blind to which pot was treated in which way, would do the observations. This would prevent the observer from something we all do without realizing it: seeing what we want to see. Good luck with your project, let us know how it came out. Coing Like Save coing 11 years ago Kelly, An experiment is most likely to reveal the truth of the question if there is a control (comparing treated to untreated plants in exactly equal conditions) and also if it is double-blinded. This means that one person would assign the treatments, but another person, blind to which pot was treated in which way, would do the observations. This would prevent the observer from something we all do without realizing it: seeing what we want to see. Good luck with your project, let us know how it came out. Coing Kelly, An experiment is most likely to reveal the truth of the question if there is a control (comparing treated to untreated plants in exactly equal conditions) and also if it is double-blinded. This means that one person would assign the treatments, but another person, blind to which pot was treated in which way, would do the observations. This would prevent the observer from something we all do without realizing it: seeing what we want to see. Good luck with your project, let us know how it came out. Coing Kelly, An experiment is most likely to reveal the truth of the question if there is a control (comparing treated to untreated plants in exactly equal conditions) and also if it is double-blinded. This means that one person would assign the treatments, but another person, blind to which pot was treated in which way, would do the observations. This would prevent the observer from something we all do without realizing it: seeing what we want to see. Konrad___far_north 10 years ago It was around 40 years ago when I helped out on a farm in southern Alberta, seeding HUGE fields of wheat etc. The farmer had a large coil hooked up on a power source, he just run seeds through this devise. Anybody done this? Like \| 1 Save Konrad___far_north 10 years ago It was around 40 years ago when I helped out on a farm in southern Alberta, seeding HUGE fields of wheat etc. The farmer had a large coil hooked up on a power source, he just run seeds through this devise. Anybody done this? It was around 40 years ago when I helped out on a farm in southern Alberta, seeding HUGE fields of wheat etc. The farmer had a large coil hooked up on a power source, he just run seeds through this devise. Anybody done this? It was around 40 years ago when I helped out on a farm in southern Alberta, seeding HUGE fields of wheat etc. The farmer had a large coil hooked up on a power source, he just run seeds through this devise. Anybody done this? albert_135 39.17°N 119.76°W 4695ft. 10 years ago FYI, Harbor Freight has some approx. 1X1X3 inch magnets that are supposed to lift 200 lb. About $18 each. Like Save albert_135 39.17°N 119.76°W 4695ft. 10 years ago FYI, Harbor Freight has some approx. 1X1X3 inch magnets that are supposed to lift 200 lb. About $18 each. FYI, Harbor Freight has some approx. 1X1X3 inch magnets that are supposed to lift 200 lb. About $18 each. FYI, Harbor Freight has some approx. 1X1X3 inch magnets that are supposed to lift 200 lb. About $18 each. David.Sturtz 10 years ago I am a retired electronics tech. Only iron has strongly magnetic properties. Water in particular is unaffected by magnetism because it has two covanlent chemical bonds rather than an ionic bond. It is not possible to magnetize a non magnetic material such as water. Running water past a magnet will not magnetize it any more than it would glass. There is some evidence, however, that growing plants in a magnetic field, can affect growth. Like Save David.Sturtz 10 years ago I am a retired electronics tech. Only iron has strongly magnetic properties. Water in particular is unaffected by magnetism because it has two covanlent chemical bonds rather than an ionic bond. It is not possible to magnetize a non magnetic material such as water. Running water past a magnet will not magnetize it any more than it would glass. There is some evidence, however, that growing plants in a magnetic field, can affect growth. I am a retired electronics tech. Only iron has strongly magnetic properties. Water in particular is unaffected by magnetism because it has two covanlent chemical bonds rather than an ionic bond. It is not possible to magnetize a non magnetic material such as water. Running water past a magnet will not magnetize it any more than it would glass. There is some evidence, however, that growing plants in a magnetic field, can affect growth. I am a retired electronics tech. Only iron has strongly magnetic properties. Water in particular is unaffected by magnetism because it has two covanlent chemical bonds rather than an ionic bond. It is not possible to magnetize a non magnetic material such as water. Running water past a magnet will not magnetize it any more than it would glass. There is some evidence, however, that growing plants in a magnetic field, can affect growth. Mokinu 8 years ago last modified: 8 years ago So, how did everyone's science fair experiments turn out? I wouldn't be surprised if plants and seeds could sense magnetic fields to some degree in an effort to see what kind of climate they're growing in. Maybe magnetizing seeds can speed this process up. After all, birds can sense magnetic fields. Like Save Mokinu 8 years ago last modified: 8 years ago So, how did everyone's science fair experiments turn out? I wouldn't be surprised if plants and seeds could sense magnetic fields to some degree in an effort to see what kind of climate they're growing in. Maybe magnetizing seeds can speed this process up. After all, birds can sense magnetic fields. So, how did everyone's science fair experiments turn out? I wouldn't be surprised if plants and seeds could sense magnetic fields to some degree in an effort to see what kind of climate they're growing in. Maybe magnetizing seeds can speed this process up. After all, birds can sense magnetic fields. I wouldn't be surprised if plants and seeds could sense magnetic fields to some degree in an effort to see what kind of climate they're growing in. Maybe magnetizing seeds can speed this process up. After all, birds can sense magnetic fields. Seysonn_ 8a-NC/HZ-7 8 years ago I have never heard of such a thing : i.e the effect of magnet on plants growth. Why don't you just fertilize ? You want oxygen to get into the roots, amend with organic matter. I add some fine pine bark, to improve drainage and get oxygen to the roots. Sey Like \| 1 Save Seysonn_ 8a-NC/HZ-7 8 years ago I have never heard of such a thing : i.e the effect of magnet on plants growth. Why don't you just fertilize ? You want oxygen to get into the roots, amend with organic matter. I add some fine pine bark, to improve drainage and get oxygen to the roots. Sey I have never heard of such a thing : i.e the effect of magnet on plants growth. Why don't you just fertilize ? You want oxygen to get into the roots, amend with organic matter. I add some fine pine bark, to improve drainage and get oxygen to the roots. Sey You want oxygen to get into the roots, amend with organic matter. I add some fine pine bark, to improve drainage and get oxygen to the roots. Mokinu 8 years ago last modified: 8 years ago As I understand it, if there's an effect on plants with magnetism, it should likely be a cumulative effect, and not something that extra care of your plants is going to make completely irrelevant, whether or not that extra care is all your plants need. Since perhaps no one really knows the effect, though, it's a moot point whether the effect is cumulative until figured out. I think there's sufficient reason to study it. Like Save Mokinu 8 years ago last modified: 8 years ago As I understand it, if there's an effect on plants with magnetism, it should likely be a cumulative effect, and not something that extra care of your plants is going to make completely irrelevant, whether or not that extra care is all your plants need. Since perhaps no one really knows the effect, though, it's a moot point whether the effect is cumulative until figured out. I think there's sufficient reason to study it. As I understand it, if there's an effect on plants with magnetism, it should likely be a cumulative effect, and not something that extra care of your plants is going to make completely irrelevant, whether or not that extra care is all your plants need. Since perhaps no one really knows the effect, though, it's a moot point whether the effect is cumulative until figured out. I think there's sufficient reason to study it. As I understand it, if there's an effect on plants with magnetism, it should likely be a cumulative effect, and not something that extra care of your plants is going to make completely irrelevant, whether or not that extra care is all your plants need. Since perhaps no one really knows the effect, though, it's a moot point whether the effect is cumulative until figured out. I think there's sufficient reason to study it. albert_135 39.17°N 119.76°W 4695ft. 8 years ago ''Why don't you just..." is usually what professionals call a micro rant: The Microcomplaint: Nothing Too Small to Whine About - The New York Times - The Microcomplaint: Nothing Too Small to Whine About Like \| 1 Save albert_135 39.17°N 119.76°W 4695ft. 8 years ago ''Why don't you just..." is usually what professionals call a micro rant: The Microcomplaint: Nothing Too Small to Whine About - The New York Times - The Microcomplaint: Nothing Too Small to Whine About ''Why don't you just..." is usually what professionals call a micro rant: The Microcomplaint: Nothing Too Small to Whine About - The New York Times - The Microcomplaint: Nothing Too Small to Whine About ''Why don't you just..." is usually what professionals call a micro rant: The Microcomplaint: Nothing Too Small to Whine About - The New York Times - The Microcomplaint: Nothing Too Small to Whine About PRO husbands helper 8 years ago I know magnets shoot photons at each other which causes a magnetic field. These are the same photons that light uses to travel so I am very curious if that would speed up photosynthesis...but no spacific answers I can find Like \| 1 Save husbands helper 8 years ago I know magnets shoot photons at each other which causes a magnetic field. These are the same photons that light uses to travel so I am very curious if that would speed up photosynthesis...but no spacific answers I can find I know magnets shoot photons at each other which causes a magnetic field. These are the same photons that light uses to travel so I am very curious if that would speed up photosynthesis...but no spacific answers I can find I know magnets shoot photons at each other which causes a magnetic field. These are the same photons that light uses to travel so I am very curious if that would speed up photosynthesis...but no spacific answers I can find Mokinu 8 years ago last modified: 8 years ago Interesting thought. I got some magnets for my own experimentation (primarily their effect when used on seeds before planting). So, hopefully I'll have something to report by the end of next season. It sounds like you're interested in post-planting information. I might try stuff out there, too, but it's not my main priority. I would suggest experimenting using the magnets at night, if you're going to use them on plants. Like \| 1 Save Mokinu 8 years ago last modified: 8 years ago Interesting thought. I got some magnets for my own experimentation (primarily their effect when used on seeds before planting). So, hopefully I'll have something to report by the end of next season. It sounds like you're interested in post-planting information. I might try stuff out there, too, but it's not my main priority. I would suggest experimenting using the magnets at night, if you're going to use them on plants. Interesting thought. I got some magnets for my own experimentation (primarily their effect when used on seeds before planting). So, hopefully I'll have something to report by the end of next season. It sounds like you're interested in post-planting information. I might try stuff out there, too, but it's not my main priority. I would suggest experimenting using the magnets at night, if you're going to use them on plants. Interesting thought. I got some magnets for my own experimentation (primarily their effect when used on seeds before planting). So, hopefully I'll have something to report by the end of next season. It sounds like you're interested in post-planting information. I might try stuff out there, too, but it's not my main priority. I would suggest experimenting using the magnets at night, if you're going to use them on plants. Mokinu 8 years ago last modified: 8 years ago Check this out: http://www.ncbi.nlm.nih.gov/pubmed/18512697 It looks like we've got some proof, for chickpea seeds, anyway. A gauss is a tenth of an mT. So, 1000 gauss static magnet exposure for an hour should produce results in chickpeas, or 500 gauss for two hours or 1500 gauss for two hours. Like \| 1 Save Mokinu 8 years ago last modified: 8 years ago Check this out: http://www.ncbi.nlm.nih.gov/pubmed/18512697 It looks like we've got some proof, for chickpea seeds, anyway. A gauss is a tenth of an mT. So, 1000 gauss static magnet exposure for an hour should produce results in chickpeas, or 500 gauss for two hours or 1500 gauss for two hours. Check this out: http://www.ncbi.nlm.nih.gov/pubmed/18512697 It looks like we've got some proof, for chickpea seeds, anyway. A gauss is a tenth of an mT. So, 1000 gauss static magnet exposure for an hour should produce results in chickpeas, or 500 gauss for two hours or 1500 gauss for two hours. It looks like we've got some proof, for chickpea seeds, anyway. A gauss is a tenth of an mT. So, 1000 gauss static magnet exposure for an hour should produce results in chickpeas, or 500 gauss for two hours or 1500 gauss for two hours. Mokinu 8 years ago Here's another link to explain how it helps if water is exposed to magnets. Apparently, it's supposed to make saltier water easier for plants to absorb: https://www.usaid.gov/news-information/frontlines/feed-future/magnets-help-plants-grow Like \| 1 Save Mokinu 8 years ago Here's another link to explain how it helps if water is exposed to magnets. Apparently, it's supposed to make saltier water easier for plants to absorb: https://www.usaid.gov/news-information/frontlines/feed-future/magnets-help-plants-grow Here's another link to explain how it helps if water is exposed to magnets. Apparently, it's supposed to make saltier water easier for plants to absorb: https://www.usaid.gov/news-information/frontlines/feed-future/magnets-help-plants-grow Here's another link to explain how it helps if water is exposed to magnets. Apparently, it's supposed to make saltier water easier for plants to absorb: https://www.usaid.gov/news-information/frontlines/feed-future/magnets-help-plants-grow zen_man 5 years ago The earth is a big magnet, so a valid experiment would be to see how plants grow in the absence of a magnetic field. Isolating a plant from the earth's magnetic field might be a little hard to do, but maybe a Faraday Cage would do the trick. Like Save zen_man 5 years ago The earth is a big magnet, so a valid experiment would be to see how plants grow in the absence of a magnetic field. Isolating a plant from the earth's magnetic field might be a little hard to do, but maybe a Faraday Cage would do the trick. The earth is a big magnet, so a valid experiment would be to see how plants grow in the absence of a magnetic field. Isolating a plant from the earth's magnetic field might be a little hard to do, but maybe a Faraday Cage would do the trick. The earth is a big magnet, so a valid experiment would be to see how plants grow in the absence of a magnetic field. Isolating a plant from the earth's magnetic field might be a little hard to do, but maybe a Faraday Cage would do the trick. Set Apart Spirit 2 years ago If you expose what’s commonly called the north pole (N&S poles dont exist) to tomato seeds for 30min proir to gemination, your yield will be less acidic! Like Save Set Apart Spirit 2 years ago If you expose what’s commonly called the north pole (N&S poles dont exist) to tomato seeds for 30min proir to gemination, your yield will be less acidic! If you expose what’s commonly called the north pole (N&S poles dont exist) to tomato seeds for 30min proir to gemination, your yield will be less acidic! If you expose what’s commonly called the north pole (N&S poles dont exist) to tomato seeds for 30min proir to gemination, your yield will be less acidic! 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COMPANY About Houzz Houzz Credit Cards Gift Cards Careers Privacy & Notice Terms Cookie Policy Mobile Apps Copyright & Trademark BUSINESS SERVICES For Professionals Houzz vs. Houzz Pro Houzz Pro vs. Ivy Houzz Pro Advertising Reviews Houzz Pro 3D Floor Planner Reviews For Brands Trade Program Buttons & Badges GET HELP Your Orders Shipping & Delivery Return Policy Houzz Canada Review Professionals Suggested Professionals Accessibility Houzz Support Contact Sign In CONNECT WITH US Houzz Blog Twitter Facebook YouTube RSS United States Select country United States United Kingdom Australia Deutschland France Россия 日本 Italia España Danmark Sverige Ireland Singapore New Zealand India © 2024 Houzz Inc. COMPANY About Houzz Houzz Credit Cards Gift Cards Careers Privacy & Notice Terms Cookie Policy Mobile Apps Copyright & Trademark BUSINESS SERVICES For Professionals Houzz vs. Houzz Pro Houzz Pro vs. Ivy Houzz Pro Advertising Reviews Houzz Pro 3D Floor Planner Reviews For Brands Trade Program Buttons & Badges GET HELP Your Orders Shipping & Delivery Return Policy Houzz Canada Review Professionals Suggested Professionals Accessibility Houzz Support Contact Sign In CONNECT WITH US Houzz Blog Twitter Facebook YouTube RSS United States Select country United States United Kingdom Australia Deutschland France Россия 日本 Italia España Danmark Sverige Ireland Singapore New Zealand India United States Select country United States United Kingdom Australia Deutschland France Россия 日本 Italia España Danmark Sverige Ireland Singapore New Zealand India	biology	4190904	https://sv.wikipedia.org/wiki/Retrophyllum	Retrophyllum	Retrophyllum är ett släkte av barrträd. Retrophyllum ingår i familjen Podocarpaceae. Kladogram enligt Catalogue of Life: Bildgalleri Källor Externa länkar Tallordningen Retrophyllum	swedish	1.199193
eye_focus/Accommodation_(vertebrate_eye).txt	Accommodation is the process by which the vertebrate eye changes optical power to maintain a clear image or focus on an object as its distance varies. In this, distances vary for individuals from the far point—the maximum distance from the eye for which a clear image of an object can be seen, to the near point—the minimum distance for a clear image. Accommodation usually acts like a reflex, including part of the accommodation-convergence reflex, but it can also be consciously controlled. The main ways animals may change focus are: Focusing mechanisms[edit] The path of light through the eye calculated using four refractive indexes, cornea and lens curvatures approximating components of real eyes. Note objects in some size ranges and distances do not require the light path to bend noticeably to achieve focus. Focusing the light scattered by objects in a three dimensional environment into a two dimensional collection of individual bright points of light requires the light to be bent. To get a good image of these points of light on a defined area requires a precise systematic bending of light called refraction. The real image formed from millions of these points of light is what animals see using their retinas. Very even systematic curvature of parts of the cornea and lens produces this systematic bending of light onto the retina. Virtual eye showing the contribution to focus of different components. Due to the nature of optics the focused image on the retina is always inverted relative to the object. Different animals live in different environments having different refractive indexes involving water, air and often both. The eyes are therefor required to bend light different amounts leading to different mechanisms of focus being used in different environments. The air/cornea interface involves a larger difference in refractive index than hydrated structures within the eye. As a result, animals living in air have most of the bending of light achieved at the air/cornea interface with the lens being involved in finer focus of the image. 3D reconstruction based on measurements taken from a 20 year old human male focusing from 26mm to infinity (4.85 dioptre change). Side & back views shown. Most image distortions near the center are due to model being limited to 512 faces to make up the lens. Peripheral distortions are also present in animal lenses though are typically covered by the iris (anatomy) The previous video of the eye lens changing shape with focus is placed into context as the lens in this video is placed into the context of a virtual eye. Generally mammals, birds and reptiles living in air vary their eyes' optical power by subtly and precisely changing the shape of the elastic lens using the ciliary body. The small difference in refractive index between water and the hydrated cornea means fish and amphibians need to bend the light more using the internal structures of the eye. Therefore, eyes evolved in water have a mechanism involving changing the distance between a rigid rounder more refractive lens and the retina using less uniform muscles rather than subtly changing the shape of the lens itself using circularly arranged muscles. Land based animals and the shape changing lens[edit] Varying forms of direct experimental proof outlined in this article show that most non-aquatic vertebrates achieve focus, at least in part, by changing the shapes of their lenses. What is less well understood is how the subtle, precise and very quick changes in lens shape are made. Direct experimental proof of any lens model is necessarily difficult as the vertebrate lens is transparent and only functions well in the living animals. When considering vertebrates, aspects of all models may play varying roles in lens focus. The models can be broadly divided into two camps. Those models that stress the importance of external forces acting on a more passively elastic lens and other models that include forces that may be generated by the lens internally. External forces[edit] The model of a shape changing lens of humans was proposed by Young in a lecture on the 27th Nov 1800. Others such as Helmholtz and Huxley refined the model in the mid-1800s explaining how the ciliary muscle contracts rounding the lens to focus near and this model was popularized by Helmholtz in 1909. The model may be summarized like this. Normally the lens is held under tension by its suspending ligaments and capsule being pulled tight by the pressure of the eyeball. At short focal distance the ciliary muscle contracts, stretching the ciliary body and relieving some of the tension on the suspensory ligaments, allowing the lens to elastically round up a bit, increasing refractive power. Changing focus to an object at a greater distance requires a thinner less curved lens. This is achieved by relaxing some of the sphincter like ciliary muscles allowing the ciliarly body to spring back, pulling harder on the lens making it less curved and thinner, so increasing the focal distance. There is a problem with the Helmholtz model in that despite mathematical models being tried none has come close enough to working using only the Helmholtz mechanisms. Schachar model of lens focus Schachar has proposed a model for land based vertebrates that was not well received. The theory allows mathematical modeling to more accurately reflect the way the lens focuses while also taking into account the complexities in the suspensory ligaments and the presence of radial as well as circular muscles in the ciliary body. In this model the ligaments may pull to varying degrees on the lens at the equator using the radial muscles, while the ligaments offset from the equator to the front and back are relaxed to varying degrees by contracting the circular muscles. These multiple actions operating on the elastic lens allows it to change lens shape at the front more subtly. Not only changing focus, but also correcting for lens aberrations that might otherwise result from the changing shape while better fitting mathematical modeling. The "catenary" model of lens focus proposed by Coleman demands less tension on the ligaments suspending the lens. Rather than the lens as a whole being stretched thinner for distance vision and allowed to relax for near focus, contraction of the circular ciliary muscles results in the lens having less hydrostatic pressure against its front. The lens front can then reform its shape between the suspensory ligaments in a similar way to a slack chain hanging between two poles might change its curve when the poles are moved closer together. This model requires precise fluid movement of the lens front only rather than trying to change the shape of the lens as a whole. While this concept may be involved in the focusing it has been shown by Scheimpflug photography that the rear of the lens also changes shape in the living eye. Internal forces[edit] Tracing of Scheimpflug photographs of 20 year old human lens being thicker focusing near and thinner when focusing far. Internal layering of the lens is also significant Wrinkled lens fibers in picture below compared to straight fibers above When Thomas Young proposed the changing of the human lens's shape as the mechanism for focal accommodation in 1801 he thought the lens may be a muscle capable of contraction. This type of model is termed intracapsular accommodation as it relies on activity within the lens. In a 1911 Nobel lecture Allvar Gullstrand spoke on "How I found the intracapsular mechanism of accommodation" and this aspect of lens focusing continues to be investigated. Young spent time searching for the nerves that could stimulate the lens to contract without success. Since that time it has become clear the lens is not a simple muscle stimulated by a nerve so the 1909 Helmholtz model took precedence. Pre-twentieth century investigators did not have the benefit of many later discoveries and techniques. Membrane proteins such as aquaporins which allow water to flow into and out of cells are the most abundant membrane protein in the lens. Connexins which allow electrical coupling of cells are also prevalent. Electron microscopy and immunofluorescent microscopy show fiber cells to be highly variable in structure and composition. Magnetic resonance imaging confirms a layering in the lens that may allow for different refractive plans within it. The refractive index of human lens varies from approximately 1.406 in the central layers down to 1.386 in less dense layers of the lens. This index gradient enhances the optical power of the lens. As more is learned about mammalian lens structure from in situ Scheimpflug photography, MRI and physiological investigations it is becoming apparent the lens itself is not responding entirely passively to the surrounding ciliary muscle but may be able to change its overall refractive index through mechanisms involving water dynamics in the lens still to be clarified. The accompanying micrograph shows wrinkled fibers from a relaxed sheep lens after it is removed from the animal indicating shortening of the lens fibers during near focus accommodation. The age related changes in the human lens may also be related to changes in the water dynamics in the lens. Human eyes[edit] Duane's classical curves showing the amplitude or width of accommodation as changing with age. Mean (B) and approximate lower (A) and upper (C) standard deviations are shown. The young human eye can change focus from distance (infinity) to as near as 6.5 cm from the eye. This dramatic change in focal power of the eye of approximately 15 dioptres (the reciprocal of focal length in metres) occurs as a consequence of a reduction in zonular tension induced by ciliary muscle contraction. This process can occur in as little as 224 ± 30 milliseconds in bright light. The amplitude of accommodation declines with age. By the fifth decade of life the accommodative amplitude can decline so that the near point of the eye is more remote than the reading distance. When this occurs the patient is presbyopic. Once presbyopia occurs, those who are emmetropic (i.e., do not require optical correction for distance vision) will need an optical aid for near vision; those who are myopic (nearsighted and require an optical correction for distance or far vision), will find that they see better at near without their distance correction; and those who are hyperopic (farsighted) will find that they may need a correction for both distance and near vision. Note that these effects are most noticeable when the pupil is large; i.e. in dim light. The age-related decline in accommodation occurs almost universally to less than 2 dioptres by the time a person reaches 45 to 50 years, by which time most of the population will have noticed a decrease in their ability to focus on close objects and hence require glasses for reading or bifocal lenses. Accommodation decreases to about 1 dioptre at the age of 70 years. The dependency of accommodation amplitude on age is graphically summarized by Duane's classical curves. Theories on how humans focus[edit] Helmholtz—The most widely held theory of accommodation is that proposed by Hermann von Helmholtz in 1855. When viewing a far object, the circularly arranged ciliary muscle relaxes allowing the lens zonules and suspensory ligaments to pull on the lens, flattening it. The source of the tension is the pressure that the vitreous and aqueous humours exert outwards onto the sclera. When viewing a near object, the ciliary muscles contract (resisting the outward pressure on the sclera) causing the lens zonules to slacken which allows the lens to spring back into a thicker, more convex, form. Schachar—Ronald A. Schachar has proposed in 1992 what has been called a "rather bizarre geometric theory" which claims that focus by the human lens is associated with increased tension on the lens via the equatorial zonules; that when the ciliary muscle contracts, equatorial zonular tension is increased, causing the central surfaces of the crystalline lens to steepen, the central thickness of the lens to increase (anterior-posterior diameter), and the peripheral surfaces of the lens to flatten. While the tension on equatorial zonules is increased during accommodation, the anterior and posterior zonules are simultaneously relaxing. The increased equatorial zonular tension keeps the lens stable and flattens the peripheral lens surface during accommodation. As a consequence, gravity does not affect the amplitude of accommodation and primary spherical aberration shifts in the negative direction during accommodation. The theory has not found much independent support. Catenary—D. Jackson Coleman proposes that the lens, zonule and anterior vitreous comprise a diaphragm between the anterior and vitreous chambers of the eye. Ciliary muscle contraction initiates a pressure gradient between the vitreous and aqueous compartments that support the anterior lens shape. It is in this lens shape that the mechanically reproducible state of a steep radius of curvature in the center of the lens with slight flattening of the peripheral anterior lens, i.e. the shape, in cross section, of a catenary occurs. The anterior capsule and the zonule form a trampoline shape or hammock shaped surface that is totally reproducible depending on the circular dimensions, i.e. the diameter of the ciliary body (Müeller's muscle). The ciliary body thus directs the shape like the pylons of a suspension bridge, but does not need to support an equatorial traction force to flatten the lens. Induced effects of accommodation[edit] When humans accommodate to a near object, they also converge their eyes and constrict their pupils. The combination of these three movements (accommodation, convergence and miosis) is under the control of the Edinger-Westphal nucleus and is referred to as the near triad, or accommodation reflex. While it is well understood that proper convergence is necessary to prevent diplopia, the functional role of the pupillary constriction remains less clear. Arguably, it may increase the depth of field by reducing the aperture of the eye, and thus reduce the amount of accommodation needed to bring the image in focus on the retina. There is a measurable ratio (Matthiessen's ratio) between how much convergence takes place because of accommodation (AC/A ratio, CA/C ratio). Abnormalities with this can lead to binocular vision problems. Anomalies of accommodation described in humans[edit] There are many types of accommodation anomalies. It can be broadly classified into two, decreased accommodation and increased accommodation. Decreased accommodation may occur due to physiological (presbyopia), pharmacological (cycloplegia) or pathological. Excessive accommodation and spasm of accommodation are types of increased accommodation. Presbyopia[edit] Presbyopia, physiological insufficiency of accommodation due to age related changes in lens (decreased elasticity and increased hardness) and ciliary muscle power is the commonest form of accommodative dysfunction. It will cause gradual decrease in near vision. Accommodative insufficiency[edit] Accommodative insufficiency is the condition where amplitude of accommodation of a person is lesser compared to physiological limits for their age. Premature sclerosis of lens or ciliary muscle weaknesses due to systemic or local cases may cause accommodative insufficiency. Accommodative insufficiency is further categorised into different categories. Ill-sustained accommodation[edit] Ill-sustained accommodation is a condition similar to accommodative insufficiency. In this, range of accommodation will be normal, but after excessive near work accommodative power will decrease. Paralysis of accommodation[edit] In paralysis of accommodation, amplitude of accommodation is either markedly reduced or completely absent (cycloplegia). It may occur due to ciliary muscle paralysis or occulomotor nerve paralysis. Parasympatholytic drugs like atropine will also cause paralysis of accommodation. Unequal accommodation[edit] If there is amplitude of accommodation between the eyes differ 0.5 dioptre or more, it is considered as unequal. Organic diseases, head trauma or functional amblyopia may be responsible for unequal accommodation. Accommodative infacility[edit] Accommodative infacility is also known as accommodative inertia. In this condition there will be difficulty in changing accommodation from one point to other. There may be difficulty in adjusting focus from distance from near. It is a comparatively rare condition. Spasm of accommodation[edit] Spasm of accommodation also known as ciliary spasm is a condition of abnormally excessive accommodation which is out of voluntary control of the person. Vision may be blurred due to induced pseudomyopia. Accommodative excess[edit] Accommodative excess occurs when an individual uses more than normal accommodation for performing certain near work. Modern definitions simply regard it as an inability to relax accommodation readily. Aquatic animals[edit] Diving bird (Cormorant) lens focusing can be up to 80 dioptres for clearer underwater vision. Bony fish eye. Note the harder more spherical lens than in land based animals and a none circular muscle to pull the lens backward Aquatic animals include some that also thrive in the air so focusing mechanisms vary more than in those that are only land based. Some whales and seals are able to focus above and below water having two areas of retina with high numbers of rods and cones rather than one as in humans. Having two high resolution area of retina presumably allows two axis of vision one for above and one for below water. In reptiles and birds, the ciliary body which supports the lens via suspensory ligaments also touches the lens with a number of pads on its inner surface. These pads compress and release the lens to modify its shape while focusing on objects at different distances; the suspensory ligaments usually perform this function in mammals. With vision in fish and amphibians, the lens is fixed in shape, and focusing is instead achieved by moving the lens forwards or backwards within the eye using a muscle called the retractor lentus. In cartilaginous fish, the suspensory ligaments are replaced by a membrane, including a small muscle at the underside of the lens. This muscle pulls the lens forward from its relaxed position when focusing on nearby objects. In teleosts, by contrast, a muscle projects from a vascular structure in the floor of the eye, called the falciform process, and serves to pull the lens backwards from the relaxed position to focus on distant objects. While amphibians move the lens forward, as do cartilaginous fish, the muscles involved are not similar in either type of animal. In frogs, there are two muscles, one above and one below the lens, while other amphibians have only the lower muscle. In the simplest vertebrates, the lampreys and hagfish, the lens is not attached to the outer surface of the eyeball at all. There is no aqueous humor in these fish, and the vitreous body simply presses the lens against the surface of the cornea. To focus its eyes, a lamprey flattens the cornea using muscles outside of the eye and pushes the lens backwards. While not vertebrate, brief mention is made here of the convergent evolution of vertebrate and Molluscan eyes. The most complex Molluscan eye is the Cephalopod eye which is superficially similar structure and function to a vertebrate eye, including accommodation, while differing in basic ways such as having a two part lens and no cornea. The fundamental requirements of optics must be filled by all eyes with lenses using the tissues at their disposal so superficially eyes all tend to look similar. It is the way optical requirements are met using different cell types and structural mechanisms that varies among animals. See also[edit] Disorders of and relating to accommodation[edit] Accommodative esotropia Latent hyperopia Myopia Pseudomyopia Other[edit] Accommodation in fish Adaptation (eye) Amplitude of accommodation Cycloplegia Cyclospasm Edinger-Westphal nucleus Mandelbaum Effect Negative relative accommodation Positive relative accommodation	biology	160509	https://no.wikipedia.org/wiki/Optikk	Optikk	Optikk, eller lyslære, er den grenen av fysikken som beskriver oppførselen og egenskapene til lys, herunder lysets interaksjon med materie og bygging av optiske instrumenter som bruker lys eller detekterer lys, samt menneskets syn. Optikk beskriver vanligvis oppførselen av synlig-, ultrafiolett- og infrarødt lys. Fordi lys er en type elektromagnetisk stråling, vil andre former for elektromagnetisk stråling som røntgenstråling, mikrobølgeer og radiobølger utvise lignende egenskaper. De fleste optiske fenomener kan forklares ved hjelp av den klassisk elektromagnetismes beskrivelse av lys. Komplette elektromagnetiske beskrivelser av lys er imidlertid ofte vanskelig å anvende i praksis. Praktisk optikk gjør derfor vanligvis bruk av forenklede modeller. Den vanligste av disse er geometrisk optikk som behandler lys som en samling av stråler som forplanter seg i rette linjer, blir avbøyd når de passerer gjennom eller reflekteres i overflater. Fysisk optikk innebærer en mer omfattende modell av lyset, som inkluderer bølgeeffekter som diffraksjon, som innebærer at lys som sendes gjennom spalter spres i mønstre og interferens, der forskjellige lysbølger kan forsterke eller svekke hverandre, noe som ikke blir gjort rede for i geometriske optikk. Historisk sett ble den strålebaserte modellen av lyset utviklet først, etterfulgt av bølgemodellen. Fremgang i utviklingen av teorien for elektromagnetisme på 1800-tallet førte til oppdagelsen av at lysbølger faktisk er elektromagnetisk stråling. Noen fenomener med lyset har både bølge og partikkel-lignende egenskaper. Forklaring på disse effektene krever anvendelse av kvantemekanikk. Når man vurderer lysets partikkel-lignende egenskaper, blir lyset modellert som en samling av partikler, kalt fotoner. Kvanteoptikk omhandler anvendelsen av kvantemekanikk på optiske systemer. Optisk vitenskap er relevant for og blir studert i mange beslektede disipliner av den rene optikk, som astronomi, flere ingeniørvitenskaper, fotografi og medisin (spesielt oftalmologi og optometri). Praktiske anvendelser av optikk finnes i en rekke teknologier. Utnyttelse av optiske fenomener gjøres i en rekke vanlige hjelpemidler som speil, linse, teleskop, mikroskop, laser og fiberoptikk. Historie De aller tidligste optiske hjelpemidler var linser som ble utviklet i høykulturene i oldtidens Egypt og Mesopotamia. De greske filosofene på sin side var opptatt av teorier for lysets natur, da spesielt synserfaringer. Platon mente at syn har sin årsak i stråler som blir sendt ut av øynene. Andre igjen hadde motsatt oppfatning, nemlig at det menneskelige synet skyldes stråler fra objektene og inn på øynene. Sammenhengen mellom øyet og hvordan et objekt oppfattes som syn har vært et vanskelig tema helt opp til moderne tid. Utover på 1600-tallet ble man i stand til å fremstille briller, uten at man egentlig hadde så mye kunnskap om optikk. Flere av opplysningstidens mest kjente fysikere har gitt viktige bidrag til optikken, spesielt Isaac Newton (1643 – 1727) brakte kunnskapen om lys et langt steg fremover på begynnelsen av 1700-tallet. Stadig mer avanserte oppdagelser ble gjort etter dette, og mange av dagens optiske instrumenter og teorier om lys ble utviklet på 1800-tallet. Oldtidens linser og filosofiske betraktninger om lysets natur Optikk begynte med utviklingen av linser i oldtidens Egypt og Mesopotamia. De tidligste kjente linser, laget av polert krystall, ofte kvarts, dateres fra så tidlig som 700 før Kristi fødsel for assyriske linser som Layard-/Nimrudlinsen. De gamle romerne og grekerne fylte glasskuler med vann for å lage objektiver. Disse praktiske innretningene ble fulgt av utviklingen av teorier for lys og syn av de gamle greske og indiske filosofene. Dette førte videre til utviklingen av geometrisk optikk i den antikke verden. Ordet optikk kommer fra gammelgreske ordet , som betyr «utseende, se». Gresk filosofi om optikk delte seg i to motstridene teorier om hvordan syn skjer, nemlig teorien om «visuell persepsjon» og «emisjonsteorien». Teorien om visuell persepsjon forklarte synet ved at gjenstander sender ut kopier av seg selv (kalt eidola) som blir fanget opp av øyet. Tilhengere av denne oppfatningen var filosofer som Demokrit, Epikur, Aristoteles og deres tilhengere igjen. Denne teorien har en viss relasjon til moderne teorier om hva syn egentlig er, men for de greske filosofene forble dette bare spekulasjoner uten noe eksperimentelt grunnlag. Platon var den første som formulerte emisjonsteorien, idéen går ut på at visuell persepsjon oppstår ved at stråler sendes ut av øynene. Han kommenterte også fenomenet med speilvending i Timaios Noen hundre år senere skrev Euklid en avhandling med tittelen Optikken der han knyttet syn til geometri, dermed skapte han en gren innenfor optikken kalt geometrisk optikk. Han baserte sitt arbeid på Platons emisjonsteori, hvor han beskrev de matematiske reglene for perspektiv. Han beskrev også effektene av lysbrytning kvalitativt, men han stilte også spørsmål ved at en lysstråle fra øyet umiddelbart skulle kunne lyse opp stjernene hver gang noen blunket. Klaudios Ptolemaios beskrev i sin avhandling Optikk en egen emisjonsteori for syn: En stråle (eller fluks) fra øyet danner en kjegle, toppunktet er inne i øyet, og basen definerer det visuelle feltet. Strålene mente han var følsomme, dermed formidlet de informasjon tilbake til observatøren mentalt om avstanden og retningen på overflater. Han oppsummerte mye av Euklid, og fortsatte med å beskrive en måte å måle brytningsvinkelen det som skjer med lys som går gjennom et medium. Imidlertid la han ikke merke til den empiriske sammenhengen mellom lysstrålene og innfallsvinkelen. Videre utvikling av optikk i middelalderen I middelalderen ble de greske idéene om optikk gjenopptatt og utvidet av forfattere i den muslimske verden. En av de tidligste av disse var Al-Kindi (801 – 73) som arbeidet videre med aristoteliske og euklidske ideer om optikk. Han vektlegger emisjonsteorien siden den bedre kan kvantifisere optiske fenomener. I 984 skrev den persiske matematikeren Abu Sad al-Ala ibn Sahl avhandlingen Om brennende speil og linser. Her blir en riktig lov om lysbryting tilsvarende Snells brytningslov formulert. Han anvender denne loven for å beregne optimale former for linser og sfæriske speil. På begynnelsen av 1000-tallet skrev Al-Haitham Boken om optikk (Kitab al-manazir) hvor han utforsket refleksjon og brytning. I tillegg foreslår han et nytt konsept for å forklare syn og lys basert på observasjon og eksperimenter. Han avviste emisjonsteorien der stråler slippes ut av øyet. I stedet legger han frem ideen om at lyset spres i alle retninger i rette linjer fra alle steder der objektene blir observert og deretter inn i øyet. Dette uten at han selv riktig var i stand til å forklare hvordan øyet fanget lysstråler. Al-Haithams arbeidet ble i stor grad ignorert i den arabiske verden, men det ble oversatt anonymt til latin rundt år 1200. Dermed ble verket videre oppsummert og utvidet av den polske munken Vitelo. På grunn av dette blir verket en standardtekst innenfor optikk i Europa i de neste 400 år. På 1200-tallet skrev den engelske biskopen Robert Grosseteste tekster innenfor et bredt spekter av vitenskapelige temaer. Han diskuterer lys fra fire forskjellige perspektiver, som en erkjennelsesteori om lys, en metafysisk eller kosmogonisk, en etiologisk eller fysisk, og en teologisk, dette basert på verkene til Aristoteles og platonismen. Grossetestes mest berømte disippel Roger Bacon, skrev verker som siterer et bredt spekter av nylig oversatte optiske og filosofiske verker, inkludert de av Alhazen, Aristoteles, Avicenna, Averroës, Euclid al-Kindi, Ptolemaios, Tideus, og Konstantin den afrikanske. Bacon var i stand til å bruke deler av glasskuler som luper for å vise at lyset reflekteres fra objekter heller enn å sendes ut fra dem. De første bærbare linser for permanent bruk ble oppfunnet i Italia rundt 1286. Dette var starten på den optiske industrien for sliping og polering av objektiver for briller som utviklet seg i Venezia og Firenze på 1200-tallet. Senere oppstod denne produksjonen i både Nederland og Tyskland. Brillemakere laget forbedrede linsetyper for korreksjon av syn basert mer på empirisk kunnskap fra observasjoner av effekten av linsene. De benyttet seg ikke av datidens uferdige optiske teori. Teorien på denne tiden kunne knapt nok forklare hvordan briller egentlig fungerte. Den senere utviklingen av praktisk tilnærming og eksperimentering med linser førte til oppfinnelsen av mikroskopet rundt 1595. Senere i 1608 ble refraktorteleskoper oppfunnet. Begge disse oppfinnelsene oppstod i brillemakerverkstedene i Nederland. Utvikling av geometrisk optikk I begynnelsen av 1600-tallet utviklet Johannes Kepler den geometriske optikken videre i sine skrifter. Kepler dekket temaer som linser, refleksjon på flater og buede speil, prinsippene for camera obscura, samt den inverse kvadratlov. Denne loven forklarer hvordan intensiteten av lys reduseres med kvadratet av avstanden, gir optiske forklaringer på astronomiske fenomener som måne- og solformørkelse, samt astronomisk parallakse. Han var også i stand til å utlede rollen som netthinnen har som selve organ som skaper synet. Endelig kunne man vitenskapelig kvantifisere effektene av ulike typer linser som brillemakerne hadde observert over de foregående 300 årene. Etter oppfinnelsen av teleskopet kunne Kepler formulere det teoretiske grunnlaget for hvordan teleskopet virker. Han kunne også beskrive en forbedret versjon, kjent som Keplers teleskop, som består av to konvekse linser for å produsere høyere forstørrelse. Teorien for optikk fikk stor fremgang på midten av 1600-tallet med Avhandling om lys skrevet av filosofen René Descartes. Her forklares en rekke optiske fenomener som refleksjon og brytning ved en antagelse om at lys er noe som slippes ut av gjenstander som produser det. Dette skilte seg i hovedsak fra den gamle greske emisjonsteorien. På slutten av 1660-årene og begynnelsen av 1670-tallet utvidet Newton Descartes' ideer med emanasjonsteorien for lys. Denne er kjent for å hevde at lys i sin natur består av små partikler som han kalte korpuskler. Dessuten hevdet han at hvitt lys var en blanding av farger som kan deles inn i komponenter ved hjelp av et prisme. I 1690 foreslo Christiaan Huygens en bølgeteori for lys basert på idéer fra Robert Hooke i 1664. Hooke kritiserte offentlig Newtons teorier om lys og feiden mellom de to varte til Hooke døde. I 1704 publiserte Newton Opticks; blant annet på grunn av sin suksess i andre områder av fysikken, ble han generelt ansett for å være seierherren i debatten om lysets natur. Newtons optikk ble generelt akseptert før begynnelsen av 1800-tallet da Thomas Young og Augustin Fresnel utført eksperimenter på interferens med lys som forklarte lysets bølgenatur. Youngs kjente dobbeltspalte-eksperiment viste at lys kan overlagres. Dette har sammenheng med lysets bølgelignende egenskaper som Newtons teori ikke kunne forutsi. Arbeidet førte til en teori om diffraksjon for lys og åpnet et helt nytt område av studiet i fysisk optikk. Bølgeoptikk ble vellykket forent med James Clerk Maxwells elektromagnetisk teori i 1860. Utviklingen av kvanteoptikk Den neste utviklingen i optisk teori kom i 1899 da Max Planck korrekt greide å lage en modell for varmestråling. Her gjør han den viktige antagelsen om at utvekslingen av energi mellom lys og materie bare skjer i diskrete mengder som han kalte kvanter. I 1905 publisert Albert Einstein teorien om fotoelektrisk effekt som sier at lyset selv kan kvantiseres. I 1913 viste Niels Bohr at atomene bare kunne avgi diskrete mengder energi, dermed kunne de diskrete linjer sett i emisjons- og absorpsjonsspekteret forklares. Forståelse av samspillet mellom lys og materie som fulgte av denne utviklingen dannet ikke bare grunnlaget for kvanteoptikk, men var også avgjørende for utvikling av kvantemekanikken som helhet. Den ultimate høydepunktet kom med teorien om kvanteelektrodynamikk, som forklarer alle optiske- og elektromagnetiske prosesser generelt som følge av utveksling av reelle og virtuell fotoner. Kvanteoptikk fikk praktisk betydning med oppfinnelser av maseren i 1953 og av laseren i 1960. Ved å følge arbeidet til Paul Dirac i kvantefeltteori, kunne George Sudarshan, Roy J. Glauber og Leonard Mandel anvende kvanteteori for elektromagnetiske felter i 1950 og 1960. Dette førte til en mer detaljert forståelse av lys, samt statistikk for lys. Klassisk optikk Klassisk optikk er delt inn i to hovedgrener: geometrisk optikk og fysisk optikk. I geometrisk, eller stråleoptikk, betraktes lyset som om det forplanter seg i rette linjer, mens i fysisk- eller bølgeoptikk, betraktes lyset for å være en elektromagnetisk bølge. Geometrisk optikk kan ses på som en tilnærming av den fysikalske optikken. Denne kan anvendes når bølgelengden til lyset som anvendes er mye mindre enn størrelsen av de optiske elementer eller systemet som skal modelleres. Geometrisk optikk Geometrisk optikk eller stråleoptikk, beskriver bølgeforplantning av lys i form av «stråler» som går i rette linjer, hvis baner er underlagt lovene om refleksjon og brytning i grensesnittet mellom ulike medier. Disse lovene ble oppdaget empirisk så langt tilbake som 984 etter Kristus. De har blitt brukt i utformingen av optiske komponenter og instrumenter fra da av, og frem til i dag. Lovene kan oppsummeres slik: Når en lysstråle treffer grensen mellom to gjennomsiktige materialer, blir den oppdelt i en reflektert og avbøyd stråle (også kalt refraksjon). Loven om refleksjon sier at den reflekterte stråle ligger i innfallsplanet, og at refleksjonsvinkelen er lik innfallsvinkelen. Loven om refraksjon sier at den brutte stråle ligger i innfallsplanet, og sinus til vinkelen til brytningsstrålen dividert på sinus til innfallsvinkelen er konstant. Dette skrives matematisk slik: der n er konstant for hvilke som helst to materialer og en gitt lysfarge. Denne konstanten er kjent som brytningsindeksen og loven omtales som Snells brytningslov. Lovene om refleksjon og refraksjon kan utledes fra Fermats prinsipp som sier at «en lysstråle som beveger seg fra et punkt til et annet, velger den veien som leder raskest frem til målet». Approksimasjoner Geometrisk optikk er ofte forenklet ved at paraksial tilnærming. Matematiske betyr dette lineær oppførsel, slik at optiske komponenter og systemer kan beskrives ved hjelp av enkle matriser. Dette fører til teknikker for Gaussisk-optikk og paraksial strålesporing, som brukes til å finne grunnleggende egenskaper for optiske systemer, slik som omtrent bilde- og objektposisjoner og forstørrelser. Refleksjoner Refleksjoner kan deles inn i to typer: speilende refleksjon og diffus refleksjon. Speilende refleksjon beskriver glansen av overflater slik som speil, som reflekterer lys i en enkel og forutsigbar måte. Dette gir et reflekterte bilder som kan være forbundet med faktiske (reelt) eller ekstrapolert (virtuell) objekter plassert i rommet. Diffus refleksjon beskriver ugjennomsiktig materialer, som for eksempel papir eller mineraler. Refleksjonene fra slike flater kan bare beskrives statistisk, men den nøyaktige fordeling av det reflekterte lys avhenger av den mikroskopiske strukturen av materialet. Mange diffuse reflektorer kan beskrives eller tilnærmes av Lamberts cosinuslov, som beskriver flater som har lik luminans sett fra alle vinkler. Blanke overflater kan gi både speil- og diffus refleksjon. Ved speilende refleksjon blir retningen av den reflekterte stråle bestemt av vinkelen som innfallende stråle danner med overflatenormalen. Overflatenormalen er en linje vinkelrett på overflaten til det punktet hvor stråle treffer. Den innfallende- og reflekterte strålen, samt normalen, ligger i et enkelt plan, og vinkelen mellom den reflekterte stråle og overflatenormalen, er den samme som mellom den innfallende stråle og overflatenormalen. Dette er kjent som refleksjonsloven. For plane speil innebærer loven om refleksjon at speilbilder av objekter er oppreist og har samme avstand bak speilet som objektene har foran speilet. Bildestørrelsen er den samme som objektets størrelse. Loven innebærer også at speilbildet er paritets invertert, som en observatør vil oppfatte som en venstre-høyre inversjon. Bilder dannet av refleksjoner i to (eller likt antall) speil er ikke paritets invertert. En spesiell type reflektor er hjørnereflektoren som retroreflekterer lys, det vil si at de reflekterte strålene kastes tilbake i samme retning som de kom fra. Sfærisk speil kan modelleres i henhold til bølge-sporings fysikk og anvendelse av loven om refleksjon på ethvert punkt på overflaten. I parabolske speil vil parallelle lysstråler mot speilet reflekteres med stråler som konvergerer til et felles fokuspunkt. Andre buede overflater kan også fokusere lys, men på grunn av divergerende form vil fokus bli sprett ut i rommet. Ordet divergere brukes også for å beskrive linjer som løper fra hverandre. Spesielt sfæriske speil oppviser såkalt sfærisk aberrasjon. Krumme speil kan danne bilder med forstørrelse med større enn, eller mindre enn én, og forstørrelsen kan også være negative, noe som indikerer at bildet er invertert. Et oppreist bilde dannet av refleksjon i et speil er alltid virtuelle, mens et invertert bilde er ekte og kan projiseres på en skjerm. Refraksjon Lysbrytning oppstår når lyset går gjennom et område av rommet som gir en endring av brytningsindeksen: Dette prinsippet forklarer virkemåten til linser og fokusering av lyset. Den enkleste tilfellet med lysbrytning oppstår på en flate mellom et uniformt medium med brytningsindeks og et annet medium med brytningsindeks . I slike tilfeller beskriver Snells brytningslov den resulterende avbøyning av lysstrålen slik: der og er vinklene til normalen (i grensesnittet) og mellom henholdsvis det innkommende og brutte lyset, se illustrasjonen til høyre. Dette fenomenet er også forbundet med en endring av hastigheten til lys sett fra definisjonen av brytningsindeksen gitt ovenfor som innebærer: der og er bølgehastighetene gjennom de respektive mediene. En konsekvens av Snells brytningslov er at lysstråler som spres fra et materiale med en høy brytningsindeks til et materiale med lav brytningsindeks, er at interaksjon med grensesnittet kan resulterer i null transmisjon. Dette fenomenet kalles totalrefleksjon og er forklaringen bak teknologien kjent som fiberoptikk. Lyssignaler som går gjennom en fiberoptisk kabel gjennomgår total indre refleksjon, slik at praktisk talt ikke noe lys går tapt over kabelens lengde. Det er også mulig å fremstille polariserte lysstråler med en kombinasjon av refleksjon og refraksjon: Når en brutt stråle og dens reflekterte stråle danner en rett vinkel mellom seg er den reflekterte strålen «polarisert». Innfallsvinkelen som kreves for en slikt refleksjon er kjent som Brewsters vinkel. Snells brytningslov kan brukes til å forutsi graden av avbøyning som skjer med lysstråler som passerer gjennom «lineære media» så lenge brytningsindeks og geometriske forhold til mediet er kjent. For eksempel vil lys gjennom et prisme resulterer i at lysstrålen avbøyes avhengig av formen og orienteringen av prismet. I tillegg vil forskjellige frekvenser av lys ha litt forskjellig brytningsindeks i de fleste materialer, dermed kan brytning anvendes for å fremstille dispersjonsspektra som vises med regnbuens farger. Oppdagelsen av dette fenomenet tilskrives Isaac Newton. Noen medier har en brytningsindeks som varierer gradvis med posisjonen til lysstrålen. Dette resulterer i at lysstråler beskriver en kurve gjennom mediet i stedet for rette linjer. Denne effekten er forårsaker luftspeiling på varme dager, hvor den endrede brytningsindeksen for luft fører til at lysstrålene blir avbøyd. Dette skaper inntrykk av speilende refleksjoner på avstand, som for eksempel kan sees på overflaten av havet sett fra lang avstand. Materiale som har en varierende brytningsindeks kalles et gradient-indeksmateriale (GRIN) og har mange nyttige egenskaper som brukes i moderne optiske teknologier som kopimaskiner og skannere. Dette fagfeltet kalles gradient-indeksen optikk. En linse frembringer konvergerende eller divergerende lysstråler som følge av lysbrytning. Linser skaper knutepunkter på hver side som kan beregnes ved hjelp av linsemakerlikningen. Denne forteller at avstanden til fokus fra en linse i luft er gitt av: der er avstanden fra linsen til fokus, er brytningsindeksen for materialet til linsen, er radius til linsens kurvatur til overflaten nærmest lyskilden, er radius til linsens kurvatur til overflaten vekk fra lyskilden, og er tykkelsen til linsen. Denne er definert som distansen mellom overflatens toppunkter. Overflatepunktene er punktene hvor hver optisk overflate krysser den optiske akse. Se illustrasjonen til høyre som viser disse størrelsen. Generelt finnes det to typer linser: Konveks linser som får parallelle lysstråler til å konvergere og konkave linser som får parallelle lysstråler å divergere. I likhet med buede speil, vil lysbryting i linser beskrives av en enkel ligning, denne bestemmer plasseringen av bildene som gis en bestemt brennvidde () og objektavstand (): der er avstanden forbundet med bildet, se illustrasjon til høyre. Ut fra konvensjonen er fortegnet negativ hvis det virtuelle bildet er på samme side av linsen som objektet som betraktes og positiv hvis det er på motsatt side av objektivet. Brennvidden anses som negativ for konkave linser. Innkommende parallelle stråler blir fokusert av en konveks linse i et såkalt invertert ekte bilde en brennviddes avstand fra linsen, og på den andre siden av linsen. Stråler fra et objekt med gitt avstand blir fokusert lengre fra linsen enn brennvidde: Jo nærmere objektet er linsen jo lengre blir bildet fra linsen. Med konkave linser vil innkommende parallelle stråler divergere etter å ha gått gjennom linsen. Dette skjer slik at de synes å ha sin opprinnelse i et oppreist virtuelt bilde én brennvidde fra linsen og på samme side av den som strålene kom fra. Stråler fra et objekt i endelig avstand er forbundet med et virtuelt bilde som er nærmere linsen enn brennvidden, og på samme side av linsen som objektet. Jo nærmere objektet er linsen, jo nærmere kommer det virtuelle bildet av linsen. Forstørrelsen som en linse gir gitt av formelen: der det negative fortegnet etter konvensjonen indikere et oppreist objekt for positive verdier og et snudd objekt for negative verdier. I likhet med speil vil oppreiste bilder produsert av enkeltlinser være virtuelle, mens inverterte bilder er ekte. Linser har en type feil som kalles aberrasjon som forvrenger bilder og brennpunkter. Dette skyldes både geometriske feil, samt endret brytningsindeks for ulike bølgelengder av lys, noe som kalles kromatisk aberrasjon. Fysisk optikk I fysisk optikk anses lyset å forplante som en bølge. Denne modell kan forutsi fenomener som interferens og diffraksjon, som ikke kan forklares med geometrisk optikk. Lyshastigheten til bølger i luft er cirka 3,0×108 m/s (mer nøyaktig er denne hastigheten 299 792 458 m/s i vakuum). Bølgelengden til synlige lysbølger varierer mellom 400 og 700 nm, men begrepet «lys» er også ofte brukt om de usynlige kategoriene infrarød- (0,7-300 μm) og ultrafiolett lys (10-400 nm). Bølgemodellen kan brukes til å forutsi hvordan et optisk system vil oppføre seg uten at det kreves en forklaring på hva som egentlig er «bølgen» som forplanter seg i mediumet. Frem til midten av 1800-tallet snakket de fleste fysikere om eteren, et medium der lyset kunne spre seg. Eksistensen av elektromagnetiske bølger ble forutsakt i 1865 på grunnlag av Maxwells likninger. Disse bølgene forplanter seg med lyshastigheten og har varierende elektrisk- og magnetiske felt som står normalt på hverandre, og normalt på forplantningsretningen for bølgene. Lysbølger blir nå generelt behandlet som elektromagnetiske bølger, unntatt når kvantemekaniske effekter skal vurderes. Modellering og design av optiske systemer ved hjelp av fysisk optikk Mange forenklede tilnærmelser er utviklet for å analysere og utforme optiske systemer. De fleste av disse bruker et eneste skalart felt til å representere det elektriske feltet i lysbølgen, heller enn å bruke en vektorfelt med ortogonale elektriske- og magnetiske vektorer. Huygens-Fresnels prinsipp er basert på en slik modell. Denne ble utledet empirisk av Augustin Fresnel (1788-1827) i 1815 ved å benytte Huygens hypotese om at hvert punkt på en bølgefront genererer en ny bølgefront, som oppstår ved superposisjon av elementære kulebølger. Kirchhoffs diffraksjonformel som er utledet ved hjelp av Helmholtz-ligningen, setter Huygens-Fresnel-prinsippet på en mer solid teoretisk fundament. Mer rigorøse modeller som omfatter modellering av både elektriske og magnetiske felt i lysbølgen, er nødvendig ved håndtering av den detaljerte interaksjonen av lys med materialer der interaksjonen er avhengig av både elektriske og magnetiske egenskaper. For eksempel er oppførselen til en lysbølge som samvirker med en overflate av metall ganske forskjellig fra det som skjer ved vekselvirkning med et dielektrisk materiale. Dielektrisk materiale er for øvrig stoffer der transport av elektroner, elektronhull eller ioner normalt ikke skjer, men som allikevel kan bli polarisert av elektriske felter. En vektormodell må brukes til å modellere polarisert lys. Teknikker for numerisk modellering som for eksempel elementmetoden, Boundary element method og transmission-line matrix method kan anvendes for å modellere forplantningen av lyset i systemer der dette matematisk ikke kan løses analytisk. Slike modeller er beregningsmessig krevende og blir normalt bare brukes til å løse småskalaproblemer som krever nøyaktighet utover det som kan oppnås med analytiske løsninger. Alle resultatene fra geometrisk optikk kan også anvendes ved hjelp av teknikker fra såkalt Fourieroptikk. Fourieroptikk anvender mange av de samme matematiske og analytiske teknikker som brukes i akustisk og signalbehandling. Gaussisk stråleforplantning (spredning av lysstrålen følger normalfordeling) er en enkel modell fra paraksial fysikalsk optikk for spredning av koherent stråling, for eksempel laserstråler. Denne teknikken tar delvis hensyn til diffraksjon, slik at nøyaktige beregninger av den hastighet en laserstråle ekspanderer med over avstand, og den minimale størrelse som strålen kan fokuseres. Gaussisk stråleforplantning bygger en bro mellom den geometriske og fysiske optikk. Superposisjon og interferens Forskjellige lysbølger kan samvirke slik at det oppstår spesielle fenomener som det menneskelige øye oppfatter som mønstre. Denne interaksjonen mellom bølger er generelt betegnet interferens. Hvis to bølger med samme bølgelengde og frekvens er i fase, vil både bølgetoppene og bølgedalene være sammenfallende, se illustrasjon til høyre. Dette resulterer i konstruktiv interferens og en økning i amplituden til bølgene, som for lys er forbundet med sterkere lys i området. Motsatt fenomen oppstår hvis de to bølgene med samme bølgelengde og frekvens er ute av fase, da vil bølgetoppene være på linje med bølgedalene og vice versa. Dette resulterer i destruktiv interferens og en reduksjon i amplituden til bølgene. For lys er dette forbundet med en dimming av bølgeformen på det stedet. Siden Huygens-Fresnel-prinsippet forutsetter at et hvert punkt av en bølgefront er knyttet til produksjon av en ny forstyrrelse, er det mulig for en bølgefront å interferere med seg selv enten konstruktivt eller destruktivt på forskjellige steder. Noe som betyr at det oppstår lyse og mørke mønstre i regulære og forutsigbare mønstre. Interferometri er vitenskapen om måling av disse mønstrene. Vanligvis studeres slike fenomener for å gjøre presise forutsigelser om avstander eller optisk oppløsninger. Michelsons interferometer er et kjent instrument som brukte interferenseffekter til å måle lysets hastighet nøyaktig. Utseendet til tynne filmer og belegg er direkte berørt av interferens effekter. Antirefleksbelegg bruker destruktiv interferens for å redusere refleksjon på overflater, og kan brukes til å redusere gjenskinn og uønskede refleksjoner. I det enkleste tilfelle er det snakk om et enkelt lag med tykkelse på en fjerdedel av bølgelengden av det innfallende lyset. Den reflekterte bølge fra toppen av filmen og den reflekterte bølge fra film/material-grensesnittet er da nøyaktig 180° ute av fase, noe som forårsaker destruktiv interferens. Bølgene er bare akkurat ute av fase for en bølgelengde, som typisk ville bli valgt til å være i nærheten av sentrum av det synlige spektrum, cirka 550 nm. Mer komplekse design med flere lag kan brukes for å oppnå lav refleksjon over et bredt bånd, eller ekstremt lav refleksjon på en enkelt bølgelengde. Konstruktiv interferens i tynnfilmer kan skape sterke refleksjoner av lys i et intervall av bølgelengder som kan være smal eller bred, avhengig av utformingen av belegget. Disse filmene brukes til å lage dielektriske speil, interferensfilter, varmereflektorer, og filtre for fargeseparasjon i kameraer for fargefjernsyn. Denne interferenseffekten forårsaker også de fargerike regnbuemønstre som kan sees i oljesøl. Diffraksjon og optisk oppløsning Diffraksjon er et fenomen der interferens med lys kan observeres. Effekten ble først beskrevet i 1665 av Francesco Maria Grimaldi, som også innførte begrepet fra det latinske diffringere, «å bryte i stykker». Senere i samme århundre beskrev Robert Hooke og Isaac Newton også andre fenomener som nå omtales for å være diffraksjon, nemlig Newtons ringer, mens James Gregory dokumenterte sine observasjoner av diffraksjonsmønstre på fuglefjær. Diffraksjon er bøyning av lys rundt hjørnene av en hindring eller åpning, og skjer i området med «geometrisk skygge» bak hinderet. De to figurene til høyre viser hvordan bølger brer seg ut ved passering av et hull (øverst) og en spalte (nederst). Fenomenet opptrer for lys og andre bølger, som for eksempel bølger i vann. Det oppstår i neste omgang interferens mellom bølgene som gir seg utslag i forskjellige mønstre som kan observeres, for eksempel fargespill i fuglefjær. For enkle kontrollerte forsøk kan fenomenet observeres i et basseng der bølger sendes mot hindringer med for eksempel en eller flere spalter. Den første fysiske optiske modell av diffraksjon som støttet seg på Huygens-Fresnels prinsipp, ble utviklet i 1803 av Thomas Young i hans dobbeltspalteeksperiment der interferensmønstre mellom to spalter med tett avstand ble demonstrert. Young viste at hans resultater bare kan forklares hvis de to spaltene fungert som to unike kilder til bølger heller enn en enkeltkilde. I 1815 og 1818 etablert Fresnel en god matematisk redegjørelse for hvordan bølgeforstyrrelser kan forklare diffraksjon. De enkleste fysiske modeller for diffraksjon bruker ligningene som beskriver vinkelseparering av lyse og mørke mønstre på grunn av lys av en bestemt bølgelengde (λ). Generelt tar ligningen formen: hvor er avstanden mellom to kilder til bølgefronter (i tilfelle med Youngs eksperimenter var det to spalter som var kilden), er vinkelforskjellen mellom det sentrale mønsteret og er det m'te ordens mønster hvor det sentrale maksimum er . Se illustrasjonen nedenfor til høyre. Denne ligningen er modifisert noe for å ta hensyn til en rekke situasjoner for diffraksjon gjennom en enkelt spalte, diffraksjon gjennom flere spalter, eller diffraksjon gjennom et gitter som inneholder et stort antall spalter med lik innbyrdes avstand. Mer kompliserte modeller av diffraksjon krever anvendelse av matematikk som gjelder for Fresnel- eller Fraunhofer-diffraksjon. Røntgendiffraksjon forklares med det faktum at atomene i et krystall har lik avstand mellom hverandre og er i størrelsesorden av én angstrom. For å se diffraksjonsmønstre blir det send røntgenstråler med denne bølgelengden gjennom en krystall. Fordi krystallene er tredimensjonale objekter, i motsetning til et to-dimensjonale gitter, varierer de tilhørende diffraksjonsmønstere i to retninger i henhold til Bragg-refleksjon, med tilhørende lyse flekker som forekommer i unike mønstre og er to ganger avstanden mellom atomene. Diffraksjonseffekter begrenser muligheten for en optisk detektor til å kunne oppløse lys fra separate lyskilder. Generelt vil lys som passerer gjennom en apertur (blenderåpning) gjennomgå diffraksjon, og de beste bildene som kan opprettes fremstår som et sentralt sted med rundt lyse ringer, adskilt av mørke nullverdier: Dette mønsteret er kjent som et såkalt Airy-mønster og den sentrale lyse området som en Airy-disk, begge oppkalt etter den engelske astronom George Biddell Airy. Størrelsen på en slik skive er gitt ved: hvor q er vinkeloppløsningen, λ er bølgelengde av lyset, og D er diameter til blenderåpningen. Hvis vinkelseparasjonen av de to punktene er betydelig mindre enn den luftig skivens vinkelradius, kan ikke de to punktene løses opp i bildet. Hvis derimot deres vinkelseparasjon er mye større enn dette, dannes tydelige bilder av de to punktene og de kan derfor løses opp. John William Strutt definert noe vilkårlige Rayleigh-kriteriet om at to punkter med vinkelseparasjon som er lik den luftig skivens radius (målt til første null, det vil si til det første stedet hvor intet lys kan sees) kan anses å være oppløst. Det kan observeres at jo større diameteren av linsen eller dens åpning er, jo finere oppløsning oppstår. Et astronomisk interferometer med sin evne til å etterligne meget store utgangsåpninger, tillater størst mulig vinkeloppløsning. For bildebehandling innenfor astronomien er det et problem at atmosfæren hindrer at optimal oppløsning blir oppnådd i det synlige spekteret på grunn av atmosfæriske spredning. Dette forårsaker at stjerner tindrer. Astronomer refererer til denne effekten som seeing. Teknikker kjent som adaptiv optikk blir brukt for å eliminere den atmosfæriske forstyrrelser av bilder og for å oppnå resultater som nærmer seg diffraksjonsgrensen.<ref>Lucky Exposures: Diffraction limited astronomical imaging through the atmosphere by Robert Nigel Tubbs</ref> Spredning Refraktive fenomener kan observeres i grense mellom to stoffer med forskjellige optiske egenskaper, som en form for spredning. Den enkleste form for spredning er Thomson-spredning som oppstår når elektromagnetiske bølger avbøyes av enkeltpartikler. I yttergrensen for Thompson-spredning hvor den bølgelignende karakter til lyset er tydelig, blir lys brutt uavhengig av frekvensen, i motsetning til Compton-spredning, som er frekvensavhengig og en rent kvantemekanisk prosess. I statistisk forstand er elastisk spredning av lys på grunn av en stor mengde partikler mye mindre enn bølgelengden til lyset, en prosess som kalles Rayleigh-spredning. Motsatt er den tilsvarende prosessen for spredning av partikler som har lik eller større bølgelengde enn partiklene som forårsaker spredningen, kjent som Mie-spredning med Tyndall-effekten som et vanlig observert resultat. En liten andel av lysspredning fra atomer eller molekyler kan gjennomgå Raman-spredning, karakterisert ved frekvensendringer som skyldes eksitering av atomer og molekyler. Brillouin-spredning oppstår når frekvensen av lyset endres på grunn av lokale endringer med tid og bevegelser av et optisk tett materiale. Dipersjon Dispersjon oppstår når forskjellige frekvenser av lys har forskjellig fasefart, enten på grunn av materialegenskapene (materialdispersjon) eller på grunn av geometrien i en optisk bølgeleder (bølgeleder). Den mest kjente formen for dispersjon er en reduksjon i brytningsindeks med økende bølgelengde, noe som kan sees i de fleste transparente materialer. Dette kalles «normal dispersjon». Det forekommer i alle dielektriske materialer, i bølgelengdeområder der materialet absorberer ikke lys. I bølgelengdeområder hvor et medium har betydelig absorpsjon, kan brytningsindeksen øke med bølgelengden. Dette kalles anomal eller «unormal dispersjon». Separasjonen av farger i et prisme (lysbryting) er et eksempel på normal dispersjon. Mot overflatene på prismet forutsier Snells lov at innfallende lys i en vinkel θ til normalen vil bli brutt i en vinkel arcsin(sin (θ)/n). Således vil blått lys med høyere brytningsindeks, bli avbøyd sterkere enn rødt lys, noe som resulterer i det velkjente regnbuemønsteret. Materialdispersjon blir ofte beskrevet av Abbetallet, som gir et enkelt mål for spredning basert på brytningsindeksen ved tre bestemte bølgelengder. Bølgelederspredning er avhengig av forplantningskonstanten. Begge typer spredning føre til endringer i gruppekarakteristikken til bølgen, egenskapene i bølgepakken som endres med samme frekvens som amplitude av den elektromagnetiske bølgen. Gruppfartdispersjon manifesterer seg som en spredning av signalets (bølgens) "omhyllingskurve", den kan kvantifiseres med forsinkelsesparameteren for gruppedispersjonen: der er gruppefarten. For et uniform medium er gruppehastigheten: hvor n er brytningsindeksen og c er lysets hastighet i vakuum. Dette gir en enklere form for forsinkelsesparameter for gruppedispersjon: Dersom D er mindre enn null, sies mediet å ha positive dispersjon eller normal dispersjon. Dersom D er større enn null, har det medium negativ dispersjon. Hvis en lyspuls forplanter seg gjennom en normalt dispergerende medium, blir resultatet at de høyere frekvenskomponentene avtar mer enn de lavere frekvenskomponentene. Pulsen blir derfor positivt chirpet eller up-chirpet, det vil si at frekvensen øker med tiden. Dette fører til at spekteret som kommer ut av et prisme dukker opp med rødt lys der det brytes minst, og som blått/fiolett lys der det brytes mest. Hvis en bølge derimot går gjennom et unormalt (negativt) dispersivt medium, vil høye frekvenskomponenter bevege seg raskere enn de lavere, og pulsen blir negativt chirpet eller down-chirpet, noe som gjør at lyset minker i frekvens med tiden. Resultatet av gruppefartdispersjon, enten den er negativt eller positivt, er i siste instans tidsavhengig spredning av pulsen. Dette gjør styring av dispersjon svært viktig i optiske kommunikasjonssystemer basert på fiberoptiske kabler. Ellers vil dispersjon, om den blir for stor, føre til at grupper av lyspulser med informasjon bli spredd over tid og slå seg sammen, noe som gjør det umulig å trekke ut signalene. Polarisering Polarisasjon er en generell egenskap ved bølger som beskriver svingningenes orienteringen i rommet til. Mange elektromagnetiske bølger er transversalbølger der polarisering beskriver orienteringen av svingningene i planet vinkelrett på bølgeretningen. Svingningene kan være orientert i en enkelt retning (lineær polarisasjon), eller svingningens retning kan dreie seg når bølgen forplanter seg (sirkulær- eller elliptisk polarisasjon). Sirkulært polariserte bølger kan rotere mot høyre eller mot venstre i fartsretningen, og hvilke av disse to rotasjonene som er til stede i en bølge kalles for kiralitet. Den typiske måten å vurdere polarisering på er å holde rede på orienteringen av det elektriske feltets vektor når den elektromagnetiske bølgen forplanter seg, se illustrasjon nedenfor. Den elektriske feltvektoren i en plan bølge kan oppdeles vilkårlig i to vinkelrette vektorkomponenter merket x og y (med z som angir hastighetens retning). Formen som skapes i xy-planet av den elektriske feltetvektoren er en Lissajousfigur som beskriver polarisasjonstilstanden. Figurene nedenfor viser noen eksempler på utbredelsen av den elektriske feltvektoren (sort), med tiden (vertikale akser, z-akse), ved et spesielt punkt i rommet, sammen med dens x- og y- komponenter (rød/venstre og blå/høyre), og projeksjonen til vektoren i planet (lyseblå): Samme utbredelse ville oppstått om en ser kun på det elektriske felt på et bestemt tidspunkt, mens det utbrer seg i rommet med motsatt retning av forplantningsretningen. I figuren lengst til venstre er x- og y-komponentene av lysbølgen i fase. I dette tilfelle er forholdet mellom deres styrke konstant, slik at retningen av den elektriske vektoren (vektorsummen av de to komponentene) er konstant. Ettersom vektoren beskriver en enkelt linje i planet (nederst), kalles dette spesielt tilfelle lineær polarisasjon. Retningen av linjen er avhengig av de relative amplitudene til de to komponentene. I figuren i midten er det to ortogonale komponenter som har samme amplituder og er 90° ute av fase med hverandre. I dette tilfellet er en komponent null når den andre komponent har maksimal eller minimal amplitude. Det er to mulige faseforhold som tilfredsstiller denne tilstanden; nemlig at x-komponent kan være 90° foran y-komponenten, eller den kan være 90° bak y-komponenten. I dette spesielle tilfellet beskriver den elektriske vektoren en sirkel i planet, derfor kalles denne polarisering sirkulær polarisasjon. Rotasjonsretningen i sirkelen er avhengig av hvilken av de to faseforhold som eksisterer, og benevnes høyrehånds sirkulærpolarisering og venstreshånds sirkulærpolarisasjon. I det tredje tilfellet hvor de to komponentene enten ikke har samme amplituder og/eller deres faseforskjell hverken er null eller et multiplum av 90°, oppstår en polarisasjonen som kalles elliptisk polarisasjon. Årsaken til navnet er at den elektriske vektoren beskriver en ellipse i planet (en polariserings ellipse). Dette er vist i figuren over helt til høyre. Detaljerte matematisk beskrivelse av polarisering er gjort ved hjelp av såkalt Jones-beregninger, som videre beskrives av de såkalte Stokes' parametere. Elliptisk polarisering Sirkulær polarisering Lineær polarisering Endring av polarisering Medier som har ulike brytningsindekser for ulike polarisasjons-moduser kalles dobbeltbrytende. Velkjente sammenhenger der denne effekten skjer er i en optisk kompensator (lineære modi) og i faradayeffekt/optisk dreining (sirkulær modus). Dersom lengden av det dobbeltbrytende mediumet er tilstrekkelig, vil plane bølger gå ut av materialet med en signifikant annerledes forplantningsretning enn inn, dette på grunn av lysbrytning. For eksempel er dette tilfelle med makroskopiske krystaller av kalsitt, som gir observatøren to offset, det vil si ortogonalt polariserte bilder av det som sees gjennom det, se figur til høyre. Det var denne virkningen som førte til den første oppdagelse av polarisering av Rasmus Bartholin i 1669. I tillegg er faseforskyvningen, og således endringen i polarisasjonstilstanden, vanligvis frekvensavhengig noe som sammen med dikroisme ofte gir opphav til lyse farger og regnbuelignende effekter. I mineralogi er slike egenskaper kjent som pleokroisme, noe som ofte utnyttes for å identifisere mineraler ved hjelp av polariseringsmikroskoper. I tillegg er det mange plastmaterialer som normalt ikke er dobbeltbrytende, men som blir det når de utsettes for mekaniske påkjenninger, et fenomen som er grunnlaget for fotoelastisitet. Ikke-dobbeltbrytende metoder for å rotere lineær polarisering av lysstråler omfatter bruk av prismatiske polarisasjonsrotorer som anvender totalrefleksjon i et prismesett som er utformet for effektiv kolineære overføringer. Mediumer som reduserer amplituden til visse polarisasjonsmodi kalles dikroiske. Enheter som blokkerer nesten alle bølger i en modus kalles polarisasjonsfiltre eller bare polarisatorer. Malus' lov som er oppkalt etter Étienne-Louis Malus, sier at når en perfekt polarisator er plassert i en lineært polarisert lysstråle vil intensiteten I av lyset som passerer gjennom være gitt av: der I0 er den opprinnelige intensiteten og θi er vinkelen mellom lysets opprinnelige polarisasjonsretning og aksen til polarisatoren. En stråle av upolarisert lys kan betraktes som å inneholdende en ensartet blanding av lineære polarisasjoner i alle mulige vinkler. Siden den gjennomsnittlige verdien av er 1/2, blir transmisjonskoeffisienten: I praksis vil noe lys gå tapt i polarisatoren og selve overføringen av upolarisert lys vil bli noe lavere enn dette, rundt 38 % for Polaroid-type polarisator, men betydelig høyere (> 49,9 %) for noen dobbeltbrytende prismetyper. I tillegg til dobbeltbrytning og dikroisme i media med en viss utstrekning, kan polariseringseffekter også forekomme på (reflekterende) grensesnitt mellom to materialer med forskjellig brytningsindeks. Disse effektene blir behandlet av Fresnels ligninger. En del av bølgen blir overført, og en del reflekteres, idet forholdet avhenger av innfallsvinkelen og brytningsvinkelen. På denne måten gjenopptar den fysikalske optikken Brewsters vinkel. Når lyset reflekteres fra en tynnfilm på en overflate, kan interferens mellom refleksjonene fra filmens overflater produsere polarisering i det reflekterte og overførte lyset. Naturlig lys De fleste kilder til elektromagnetisk stråling inneholder et stort antall atomer eller molekyler som sender ut lys. Orienteringen av de elektriske feltene produsert av disse emitterne kan ikke være korrelert, i slike tilfeller sies lyset å være upolarisert. Hvis det er delvis korrelasjon mellom emitterne er lyset delvis polarisert. Hvis polariseringen er konsistent over hele spekteret til kilden, kan delvis polarisert lys beskrives som en superposisjon av en helt upolarisert komponent og en annen fullstendig polarisert komponent. En kan da beskrive lyset i form av graden av polarisering, og parametrene til polarisasjonens ellipse. Lys som reflekteres av glinsende transparente materialer er delvis eller fullstendig polarisert, bortsett fra når lyset er normalt (vinkelrett) på overflaten. Det var denne effekten som fikk matematikeren Étienne-Louis Malus (1775-1812) til å gjøre målinger for å kunne utvikle de første matematiske modeller for polarisert lys. Polarisering oppstår når lyset blir spredt i atmosfære. Det spredte lyset produserer lysstyrken og fargen på den klare himmelen. Delvis polarisering av spredt lys kan bli utnyttet ved å bruke polarisasjonsfiltre for å mørkne himmelen på bilder. Optisk polarisering er prinsipielt viktig i kjemien på grunn av sirkulærdikroisme og optisk rotasjon (sirkulær dobbeltbrytning) forårsaket ved optisk aktive molekyler (Kiralitet). Moderne optikk Moderne optikk omfatter fagområder innenfor optisk- og ingeniørvitenskap som ble populære på 1900-tallet. Disse områdene av optisk vitenskap relatere seg typisk til de elektromagnetiske eller kvantemekaniske egenskapene til lys, men tar også med andre emner. Et stor delfelt av moderne optikk er kvanteoptikk der det legges spesielt vekt på de kvantemekaniske egenskapene til lys. Kvanteoptikk er ikke bare teoretisk; noen moderne apparater som for eksempel laseren bygger på prinsipper som er avhengige av kvantemekanikk. Lysdetektorer som for eksempel fotomultiplikatorer og elektronmultiplikatorer er så følsomme at de er i stand til å reagere selv på bare enkelt fotoner. Elektroniske bildesensorer, som for eksempel CCD-er, gir en type støy som korresponderer med statistikk for hendelser relatert til enkeltfotoner. Lysdiodeer og solcelleer kan heller ikke forstås uten kvantemekanikk. I studiet av disse enhetene kan kvanteoptikk ofte overlapper med kvanteelektronikk. Spesialområder innenfor forskning på optikk omfatter studiet av hvordan lys samvirker med spesifikke materialer som i krystalloptikk og metamaterialer. Annen forskning fokuserer på fenomenologien i tilknytning til elektromagnetiske bølger som i singulære optikk, non-avbildningsoptikk, ikke-lineær optikk, statistisk optikk og radiometri. I tillegg har datateknologien hatt interesse for forskning på integrert optikk, maskinsyn og databehandling basert på lys som mulige komponenter i "neste generasjons datamaskiner. I dag er den rene vitenskapen om optikk kalt optisk vitenskap eller optisk fysikk for å skille den fra anvendte optiske fagfelt, som ofte kalles optiske ingeniørfag. Viktige fagfelter under de optiske ingeniørfagene inkluderer belysning, fotonikk og optoelektronikk med praktiske anvendelsesområder som konstruksjon av objektiver, andre optiske komponenter og bildebehandling. Noen av disse feltene overlapper, noe som betyr at fagfeltene betyr litt forskjellige ting i ulike deler av verden og i ulike deler av industrien. En profesjonelt fellesskap av forskere i lineære optikk har utviklet seg de siste tiårene på grunn av fremskritt innenfor laserteknologi. Lasere En laser er en enhet som emitterer lys (elektromagnetisk stråling) gjennom en prosess som kalles stimulert emisjon. Begrepet laser er en akronym for «Light Amplification by Stimulated Emission of Radiation». Laserlys er vanligvis romlig koherent, noe som betyr at lyset enten slippes ut i en smal, lavt-divergerende stråle, eller kan omdannes til en slik ved hjelp av optiske komponenter som linser. Enheter som avgir mikrobølger og radio kalles for masere. Den første brukbare laser ble demonstrert den 16. mai 1960 av Theodore Maiman (1927-2007) ved Hughes Research Laboratories. Etter at den ble oppfunnet ble laseren kalt «en løsning på jakt etter et problem.» Siden da har laserteknologi blitt storindustri, der disse nå finnes i tusenvis av svært forskjellige apparater og systemer. Den første bruken av lasere i dagliglivet var strekkode-skannerne brukt i dagligvarebutikker som ble introdusert i 1974. LaserDisc-spillerne som kom på markedet i 1978 var den første vellykkede forbrukerproduktene som inkluderte en laser, men CD-spilleren var den første laser-enhet fikk stor utbredelse blant vanlige forbrukere, noe som startet i 1982. Disse optiske lagringsenhetene bruker en halvleder laser, som er mindre enn én millimeter bred til å skanne overflaten av platen for registrering av lagringsdata. Fiberoptisk kommunikasjon er avhengig av lasere for å overføre store mengder informasjon med lysets hastighet. Andre vanlige anvendelser for lasere er laserskriveren og laser pennen. Lasere brukes innenfor medisin i felter som ublodige operasjoner, laseroperasjoner for synskorigering og laser capture mikrodisseksjon. Militære applikasjoner er systemer for rakettforsvar, direktivt infrarødt mottiltak (DIRCM) og LIDAR. Lasere brukes også i hologrammer, bubblegramer, laserlys-show og hårfjerning. Kapitsa-Dirac effekt Kapitsa Dirac-effekten bevirker at partikler diffraktere som et resultat av å utsettes for en stående bølge av lys. Oppfinnelsen av laseren muliggjorde produksjon av koherent lys, derfor kunne en få til å konstruere de stående bølger av lys, noe som er nødvendig for å observere effekten eksperimentelt. Tregt lys Når lyset forplanter seg gjennom et materiale beveger det seg med lavere fart enn i vakuum, c. Dette er en endring i fasehastigheten til lyset og kan sees som fysikalske effekter som for eksempel lysbrytning. Denne reduksjonen i hastigheten er kvantifisert ved forholdet mellom c og fasehastigheten, dette forholdet kalles som før nevnt brytningsindeksen for materialet. Tregt lys er et fysikt fenomen der gruppehastigheten til lyset er dramatisk redusert, ikke fasehastigheten. Trege lyseffekter oppstår imidlertid ikke på grunn av unormalt store brytningsindekser. Den enkleste bilde av lys er gitt av bølgemodellen i klassisk fysikk, der lys er en bølge eller forstyrrelse av det elektromagnetiske feltet. I en vakuum forutsier Maxwells ligninger at disse forstyrrelsene vil bevege seg med en bestemt hastighet, altså (c). Postulatet om lysets konstante hastighet i alle referansesystemer er basalt i den spesielle relativitetsteorien, dette har gitt opphav til en populær forestilling om at lysets hastighet alltid er den samme. Men i mange tilfeller er lys mer enn en forstyrrelse i det elektromagnetiske feltet, og lyshastigheten kan variere. Lysets bevegelse innenfor et medium er ikke lenger en forstyrrelse utelukkende av det elektromagnetiske feltet, men snarere en forstyrrelse av feltet, samt posisjonene og hastighetene av de ladede partikler (altså elektronene) i materialet. Bevegelsen til elektronene bestemmes av feltet som beskrives av Lorentz-kraften, men samtidig bestemmes feltet også av posisjonene og hastighetene av elektronene (gitt av Gauss' lov og Ampères lov). Oppførselen til en forstyrrelse gitt av denne kombinerte elektromagnetiske feltet og ladnignstettheten er fremdeles bestemt av Maxwells ligninger, men løsningene er kompliserte på grunn av den komplekse sammenheng mellom mediet og feltet. I 1998 ledet den danske fysikeren Lene Hau (1959-) forskere fra Harvard University og Rowland Institute for Science som lyktes i å bremse en lysstråle til rundt 17 meter per sekund. Hau har senere lyktes med å stoppe lyset helt, og utviklet metoder som kan stoppe lys, for derretter å starte det igjen senere. Dette har blant annet sammenheng med forskning for å utvikle datanettverk med større hastighet og kapasitet. Fysiologisk optikk og anvendelser Svært mange biologiske skapninger har syn eller andre visuelle systemer, noe som viser den sentrale rollen optikk spiller som en av de fem sanser. Fysiologisk optikk omfatter teoriene for syn, bildedannelse i øyet, etterbildedannelse, samt optiske illusjoner og andre effekter med det menneskelige syn. Den ligger i grenseområdet mellom fysikk, fysiologi, og psykologi. Mange mennesker dra nytte av briller eller kontaktlinser, og optikk er en integrert funksjon i mange forbruksvarer som for eksempel kameraer eller kikkerter. Regnbue og speiling er eksempler på optiske fenomener i atmosfæren. Optisk kommunikasjon er selve ryggraden for både Internett og moderne telefoni. Det menneskelige øyet Det menneskelige øyet fungerer ved å fokusere lys på et lag med fotoreseptorceller kalt netthinnen (Retina). Fokusering oppnås ved hjelp av en rekke transparente deler. Lyset inn i øyet passerer først gjennom hornhinnen (cornea), som bevirker mye av øyets optiske effekt. Lyset fortsetter gjennom et fluid like bak hornhinnen fremre øyekammer (Camera anterior bulbi oculi), deretter passerer det gjennom pupillen (Pupilla). Lyset passerer så gjennom øyelinsen (lens crystallin) som fokuserer lyset videre og foretar justering av fokus. Lyset passerer videre gjennom hoveddelen av fluidet i øye, det såkalte glasslegemet (humor vitreus), og treffer til slutt netthinnen. Cellene i netthinnen utgjør bakre overflate i øyet og er lysfølsom over det hele, bortsett fra der synsnerven (Nervus opticus) har sin utgang: Dette resulterer i en blind flekk. Aller mest lysfølsom er den gule flekk (Macula lutea) der øyets synsskarphet ivaretas. Det finnes to typer fotoreseptorceller som kalles tapper og staver. Disse er følsomme for ulike aspekter av lyset. Stavene er følsomme for intensiteten av lys over et bredt frekvensområde, og dermed er ansvarlig for svart/hvitt-synet. Stavceller er ikke tilstede på fovea, området av netthinnen som er ansvarlig for det sentrale synet, og er ikke så responsivt som tappcellene for romlige og tidsmessige endringer i synsinntrykket. Det er imidlertid tjue ganger flere stavceller enn tappceller i retina, men stavcellene på den andre siden er tilstede over et større område. På grunn av bredere utstrekning er stavene ansvarlig for sidesynet. I motsetning til stavene er tappcellene mindre følsom for den totale intensiteten av lyset, men finnes i tre varianter som er følsomme for forskjellige frekvensområder, dermed anvendes disse for oppfatningen av farge og fotopisk syn (høylys-syn). Tappene er sterkt konsentrert i fovea og har en høy synsskarphet, noe som betyr at de er bedre til romlig oppløsning enn stavcellene. Siden tappene ikke er så følsom for svakt lys som stavcellene, er nattsyn for en stor del begrenset til stavcellene. Siden tappcellene er i fovea er det disse som tar seg av sentralsynet, altså det som brukes for å gjøre det mest av lesning, studere fine detaljer som ved sying, eller nøye undersøkelse av objekter. Ciliærmuskelen rundt øyelinsen sørger for at øyets fokus justeres fortløpende, noe som kalles akkommodasjon. Nærfokus og fjernfokus definerer den nærmeste og fjerneste avstand fra øye som et objekt kan bringes i skarpt fokus. For en person med normalt syn, er fjernfokus uendelig langt unna. Posisjonen for nærfokus avhenger av hvor mye musklene er i stand til å øke krumningen på linsen, og hvor lite fleksibel linsen har blitt med alderen. Øyeleger og optikere vil vanligvis vurdere en hensiktsmessig nærfokus å være nærmere enn normal leseavstand, omtrent 25 cm Defekter på synet kan forklares ved hjelp av optiske prinsipper. Som menneskets alder øker blir linsen mindre fleksibel og området for nærfokus trekker seg fra øyet, en tilstand som kalles presbyopi. Mennesker som lider av hypermetropi kan ikke redusere brennvidden til øyets linse nok til at nærliggende objekter blir avbildet på deres netthinnen. Omvendt, personer som ikke kan øke brennvidden på øyelinsene nok til at fjerntliggende objekter å avbildes på netthinnen, sies å lide av nærsynthet (myopi). I dette tilfellet har personen fjernfokus som er betydelig nærmere enn uendelig. En tilstand som kalles astigmatisme resulterer i at hornhinnen ikke er sfærisk, men mer buet i én retning. Dette fører til at objekter med horisontalt utstrekning blir fokusert på ulike deler av netthinnen enn vertikalt utstrakte objekter, noe som resulterer i forvrengt syn. Alle disse forholdene kan rettes opp ved hjelp av korrigerende linser. For presbyopi og hyperopia vil en konvergerende linse gi den ekstra krumning som er nødvendig for å bringe nærfokus nærmere øyet. En divergerende linse brukes for nærsynthet og gir den kurvaturen som er nødvendig for å sende fjernfokus til uendelig avstand. Astigmatisme korrigeres med en sylindrisk linse som kurver sterkere i en retning enn i den andre for å kompensere for ulik form på hornhinnen. Den optiske effekten av korrigerende linser måles med enheten diopter, en verdi lik den resiproke av brennvidden målt i meter. En positiv brennvidde svarende til en konvergerende linse, og en negativ verdi for brennvidde svarende til en divergerende linse. For linser som korrigerer for astigmatisme i tillegg, må tre tall angis: Et tall for henholdsvis sfærisk og sylindrisk forsterkning, samt et for vinkelorientering av astigmatisme. Visuelle effekter Optiske illusjoner (også kalt optiske bedrag) er et fenomen der visuelt persiperte bilder skiller seg fra hvordan de er i virkeligheten. Informasjonen som samles inn med øyet blir behandlet i hjernen der en feilaktig persepsjon oppstår, altså noe som avviker fra objektet som synet egentlig registrerer. Optiske illusjoner kan være et resultat av en rekke fenomener inkludert fysiske effekter som skaper bilder som er forskjellig fra de objektene som i utgangspunktet skaper bildene en person ser. De fysiologiske virkningene på øynene og hjernen av overdreven stimulering (for eksempel lysstyrke, skråstilling, farge, bevegelse), og kognitive illusjoner hvor øyet og hjernen skaper såkalt bevisstløs inferens. Kognitive illusjoner består blant annet av noen effekter som har å gjøre med ubevisste feilbruk av visse optiske prinsipper. For eksempel Ames-rom, Hering-, Müller-Lyer-, Orbisons-, Ponzos-, Sanders- og Wundts illusjon er alle avhengige av oppfatningen av avstand ved hjelp av konvergerende og divergerende linjer. Dette på samme måte som parallelle lysstråler, eller hvilke som helst parallell linjer, ser ut til å samles i et forsvinningspunkt uendelig langt borte i et to-dimensjonalt bilde med perspektiv. Denne oppfatningen av avstand er også bakgrunnen for måneillusjonen hvor månen, til tross for at den i hovedsak har den samme størrelse, oppfattes som mye større i nærheten av horisonten enn det gjør i senit (rett opp). Denne illusjonen forvirret Klaudios Ptolemaios (90-168) så mye at han feilaktig tilskrev den til å være forårsaket av atmosfærisk brytning, noe han beskrev i sin avhandling Optikk. En annen type optisk illusjon utnytter «ødelagte mønstre» til å lure hjernen til å oppfatte symmetrier eller asymmetrier som ikke er til stede. Noen eksempler på slike er Café vegg-, Ehrenstein-, Fraser spiral-, Poggendorffs- og Zöllner illusjoner. Relaterte, men ikke strengt tatt illusjoner, er mønstre som oppstår på grunn av overlagring av periodiske strukturer. For eksempel transparente vevede stoffer med rutenettstruktur som produserer figurer kjent som moarémønster. Overlagring av periodiske gjennomsiktige mønstre oppfattes som parallelle ugjennomsiktig linjer eller kurver som produserer Line moiré-mønstre. Optiske instrumenter En enkelt linse alene benyttes i en rekke forskjellige apparater som objektiver i kameraer, synskorrigerende linser og forstørrelsesglass, mens ett enkelt speil brukes i parabolske speil og vanlige speil. En kombinasjon av en rekke speil, prismer og linser gir sammensatte optiske instrumenter som har mange praktiske anvendelsesområder. For eksempel har et periskop (til bruk på undervannsbåter) bare to plane speil innrettet for å muliggjøre syn over hindringer. De mest kjente sammensatte optiske instrumenter er mikroskop og teleskop. Disse ble begge oppfunnet i Nederland på sent 1500-tall. Mikroskopet ble først utviklet med bare to objektiver: objektivet og okularet. Objektivlinsen er i det vesentlige et forstørrelsesglass med meget liten brennvidde, mens okularet generelt har en lengre brennvidde. Effekten av dette blir et forstørret bilde av nære objekter. Vanligvis er en ekstern lyskilde nødvendig siden forstørrede bilder er svakere, dette kan forklares med energiprinsippet og spredning av lysstrålene over et større overflateareal. Moderne mikroskoper, også kjent som sammensatte mikroskop har mange objektiver (vanligvis fire) for å optimalisere funksjonalitet og forbedre bildestabiliteten. En litt annen type mikroskop er sammenligningsmikroskopet som benyttes for å se på like objekter plassert side ved side for å skape en stereoskopisk forstørrelse. For det menneskelige syn vises dermed et tredimensjonal bilde. De første teleskoper ble kalt refraktorer, og ble også utviklet med et enkelt objektiv og okular. I motsetning til mikroskopet, ble objektivlinsen på teleskopet utformet med stor brennvidde for å unngå optiske aberrasjoner. Objektivet fokuserer et bilde av en fjern gjenstand på sitt fokuspunkt som er justert for å være midtpunktet i et okular med en mye mindre brennvidde. Hovedmålet med et teleskop er ikke nødvendigvis forstørrelse, men i stedet å samle mest mulig lys, noe som er bestemt av den fysiske størrelsen av objektivlinsen. Dermed beskrives teleskoper vanligvis med diameteren av objektivet i stedet for sin forstørrelse. Forstørrelsen kan uansett endres ved å bytte okularer. På grunn av at forstørrelsen et teleskop gir er lik brennvidden til objektivet dividert med brennvidden til okularet, vil okularer med mindre brennlengde føre til større forstørrelse. Siden produksjon av store linser er mye vanskeligere enn å lage store speil, er de fleste moderne teleskoper speilteleskoper, det vil si at de bruker et primærspeil i stedet for et objektiv. De samme generelle optiske betraktninger gjelder for speilteleskoper som for refraktorer. Nemlig at jo større hovedspeil, jo mer lys blir samlet, og forstørrelsen er fremdeles lik brennvidden av det primære speilet dividert med brennvidden til okularet. Generelt har ikke profesjonelle teleskoper okular, i stedet plasseres en sensor (ofte en CCD) i fokus slik at en kan se bildet på en skjerm. Fotografering Fotografi involverer optikk både når det gjelder objektivet og mediet der den elektromagnetiske lyset blir registrert, enten det er snakk om en fotografisk film eller CCD. Ved fotografering må en vurdere gjensidighet mellom kameraet og eksponering som er oppsummert av forholdet: Eksponering ∝ Aperturets areal × eksponeringstid × motivets luminans der ∝ bety proporsjonal med. Med andre ord betyr dette at jo mindre blenderåpning, som også gir større dybdefokus, se bildene til høyre, jo mindre lys kommer inn. Dette betyr at for eksponering av et bilde må tidslengden økes, noe som fører til fare for uklarhet hvis motivet er i bevegelse. Et eksempel på bruk av loven om gjensidighet er f16-regelen som gir et grovt overslag for innstillingene som kreves for å estimere riktig eksponering i dagslys. Enkelt forklart går denne regelen ut på at eksponeringstiden stilles inn slik at den tilsvarer filmens ISO-tall, altså filmens lysfølsomhet. Er ISO-tallet 100 settes lukkertiden til 1/100 sekunder, ISO-tall 200 gir lukkertid 1/200 sekunder, og så videre. Neste trinn er å sette blenderåpningen i samsvar med lysforholdene: Sterkt solskin – 16, lett overskyet vær – 11, overskyet – 8, lite dagslys – 5,6 og ved solnedgang – 4. Regelen heter Sunny 16 på engelsk for at en lett skal huske at solskinn gir blenderåpning 16. Kameraets blenderåpning angis med det dimensjonsløse blendertallet eller f-nr, f/#, ofte skrevet bare som et tall gitt ved: der er brennvidde og er diameteren til blenderåpningen. Etter konvensjonen blir "f /#" behandlet som et enkelt symbol og bestemte verdier av f/# blir skrevet ved å erstatte nummertegnet med verdien. Det er to måter å øke f-nr på; enten ved å redusere diameteren på blenderåpningen eller endre til en lengre brennvidde (med en zoomlinse kan dette enkelt gjøres ved å justere objektivet). Høyere f-nr gir også en større dybdeskarphet som kan forklares med at objektivet nærmer seg å være et hullkamera (et kammer med et meget lite hull istedenfor linse). Et hullkamera er i stand til å fokusere alle bilder perfekt, uavhengig av avstand, men krever svært lange eksponeringstider. Synsfeltet til linsen vil forandres avhengig av brennvidden til den. Det er tre klassifikasjoner som er basert på forholdet mellom den diagonale størrelse på filmen (ofte 35 mm for amatørkameraer), eller sensorstørrelsen til kameraet, dividert på objektivets brennvidde: Normalobjektiv: synsvinkel på cirka 50° (kalt normal fordi denne vinkelen regnes omtrent å tilsvare menneskelig syn) og en brennvidde omtrent lik diagonalen av filmen eller sensoren. Vidvinkelobjektiv: synsvinkel bredere enn 60° og brennvidde kortere enn en vanlig linse. Lang fokuslinse: synsvinkel smalere enn vanlig linse. Et hvert objektiv med en brennvidde lengre enn diagonalen av filmen eller sensoren. Den vanligste typen lang fokuslinse er telelinseen med konstruksjon basert på en spesiell tele gruppe slik at den blir fysisk kortere enn brennvidden. Moderne zoomobjektiver kan ha noen eller alle av disse egenskapene. Den absolutte verdien for eksponeringstiden som kreves avhenger av hvor stor følsomhet filmen eller sensoren som brukes har. Dette måles ved hjelp av filmhastighet eller for digitale kameraer med kvanteutbyttet. I fotograferingens barndom ble det brukt film som hadde svært lav lysfølsomhet, dermed måtte eksponeringstidene være lange, selv for svært lyse bilder. Etterhvert som teknologien har blitt bedre har følsomheten til filmkameraer og digitale kameraer blitt betydelig større. Andre resultater overført fra fysisk og geometrisk optikk har å gjøre med kameraoptikk. For eksempel er den maksimale oppløsningsevnen til et bestemt kameraoppsett bestemt av diffraksjonsgrensen som er assosiert med størrelse av blenderåpningen og grovt angitt med Rayleigh-kriteriet. Atmosfæreoptikk De unike optiske egenskapene til atmosfæren forårsaker et bredt spekter av spektakulære optiske fenomener. Den blå fargen på himmelen er et direkte resultat av Rayleigh-spredning, noe som forårsaker omdirigering av sollys med høyere frekvenser (blått lys) tilbake til synsfeltet til observatøren på bakken. Fordi blått lys spres lettere enn rødt lys, får solen en rødaktig fargetone når den observeres gjennom en tykk atmosfære, for eksempel under en soloppgang eller solnedgang. Andre partikler i luften kan spre forskjellige farger i ulike vinkler og skape en fargerik glødende himmel ved skumring og daggry. Spredning av iskrystaller og andre partikler i atmosfæren kan forårsake halo, aftenrøde, korona, tussmørkestråler og bisol. Disse fenomenene har variasjoner på grunn av ulike partikkelstørrelser og geometri. Luftspeiling er et optiske fenomener der lysstråler blir avbøyd på grunn av termiske variasjoner i brytningsindeksen for luft. Dette gir forskjøvne eller sterkt forvrengte bilder av fjerne objekter. Andre mer dramatiske optiske fenomener knyttet til dette er blant annet Novaja Semlja-effekt hvor solen ser ut til å stige tidligere enn normal og med en forvrengt form. En spektakulær form for brytning oppstår ved temperaturinversjon, nemlig Fata morgana hvor objektene i horisonten eller bortenfor horisonten, for eksempel øyer, klipper, skip eller isfjell, virker strukket og forhøyet, som «eventyrslott» Regnbue er et resultat av en kombinasjon av intern refleksjon og spredt brytning av lyset i regndråper. En enkelt refleksjon på baksiden av regndråper gir en regnbue med en vinkelstørrelse på himmelen som varierer fra 40° til 42° med rødt på utsiden, se figuren til høyre. Doble regnbuer oppstår med to interne refleksjoner mellom regndråper med vinkelstørrelse på 50,5° til 54° med fiolett på utsiden. Fordi regnbuer oppstår med solen 180° fra sentrum av regnbuen, er fenomenet mer fremtredende jo nærmere solen er horisonten. Se også Optisk hjelpemiddel Optisk kommunikasjon Optisk tetthet Optisk tykkelse Referanser Litteratur Eksterne lenker Fundamental Optics – Melles Griot Technical Guide Physics of Light and Optikk - Brigham Young University Undergraduate Optikk og fotonikk: fysikk endrer våre liv etter *Institute av fysikk publikasjoner European Optical Society The Optical Society SPIE Optikk Elektromagnetisk stråling	norwegian_bokmål	0.582325
eye_focus/Inanearsightedtheima.txt	In a nearsighted the image of a far object is focused in front of the retina while in a farsighted the image is focused behind the retina. How are you going to correct these eye defect s using diverging and converging lenses? Explain. Sort Profile photo for Malcolm Maciver Malcolm Maciver Optometrist & AcademicAuthor has 429 answers and 779K answer views · 3y Well - while not the most eloquently asked - I think this is a good point to begin an explanation. Principle of refractive error while the question is correct- light entering the eye from optical infinity (ie distance) comes to focus in front of the retina in myopia, and forms an “apparent “ focus behind the retina in hyperopia, to understand correction we need to consider the same situation, but with a slight tweak. But before then we need to also understand the principle of reversibility in ray tracing, and lens orientation. Lenses refract light in order to alter the vergence, I have written mo Sponsored by Online Shopping Tools Amazon Hates When Prime Members Do This, But They Can't Stop You. This simple trick can save tons of money on Amazon, but most Prime members are ignoring it. Related questions How do diverging lenses correct nearsightedness? How does focused light in front of the retina make us near-sighted and not otherwise? Does it have anything to do with image formation? Why does light focusing in front of the retina mostly cause problems with seeing objects that are far (nearsightedness), and light focusing past the retina causes problems with seeing objects that are close (farsightedness)? How do one’s eyes go from farsighted to nearsighted? I am a farsighted person but my lenses is for nearsighted. Will this affect my eyes? Profile photo for Xaun Loc Xaun Loc Adult With an IQ Above Room Temperature! (1948–present)Author has 6K answers and 6.5M answer views · 2y Originally Answered: In a nearsighted the image of a far object is focused in front of the retina while in a farsighted the image is focused behind the retina. How are you going to correct these eye defect s using diverging and converging lenses? Explain. A2A: In a nearsighted person, the image of a far object is focused in front of the retina while in a farsighted person, the image is focused behind the retina. How would you correct these eye defects using diverging and converging lenses? Sorry, Layne Xen, but you need to learn to do your own schoolwork. Especially by the time you are getting ass... Profile photo for Bill Otto Bill Otto Top Writer Eyesight & Optometry at QuoraAuthor has 8.2K answers and 66.2M answer views · 1y Related Why does the eye lense refraction error of myopia, issue of focal point being before the retina, only occur when objects are far away. Why shouldn't it occur regardless of whether an object is near or far? Image distance is a function of object distance. Closer objects always focus further away from the lens. It is possible for an object to be close enough that it happens to focus on the retina in myopes. Profile photo for Assistant Assistant Bot · Nov 28 To correct nearsightedness, which is also known as myopia, a diverging lens is used. This type of lens spreads out the light rays before they enter the eye, which helps to move the focal point back to the retina. This allows the individual to see distant objects more clearly. On the other hand, to correct farsightedness, also known as hyperopia, a converging lens is used. This type of lens brings the light rays together before they enter the eye, which helps to move the focal point forward to the retina. This allows the individual to see nearby objects more clearly. In both cases, the goal is to Sponsored by Grammarly Hit the mark with every message. Predict how your reader will react, see how you sound, and get the response you want—with Grammarly. Related questions For a nearsighted person, is the image focused in front of the retina? True or False? Myopia and hyperopia causes are explainable by the eye lense getting stretched or not, but how does by focal condition occur? Can mild hyperopia/farsightedness be reversed without the use of corrective lenses or surgery? Why is my eye bleeding behind the retina? Which one is worse: being nearsighted or farsighted? Profile photo for Don Vater Don Vater Studied Optometry at Indiana University (Graduated 1970)Author has 551 answers and 793K answer views · 3y Related How do diverging lenses correct nearsightedness? With nearsightedness (myopia) the eyeball length is too long and the light rays focus in front of the retina. Divergent (negative/concave) lenses make the light rays diverge to focus back further on the retina. Profile photo for Brian Park Brian Park BS in Electrical Engineering (BSEE) & Physics, Optics, Mechanics, University of Akron (Graduated 1973)Author has 378 answers and 136.6K answer views · 1y Related Why does the eye lense refraction error of myopia, issue of focal point being before the retina, only occur when objects are far away. Why shouldn't it occur regardless of whether an object is near or far? Actually, for every different object distance a DIFFERENT refraction power is required. The minimum refraction required is for objects at infinite distance. More is required the closer object gets. The eye is set up so this minimum is when eye lens muscles are in relaxed state. The refraction power can only be increased by the muscles. For a myope, the refraction power is already too high to focus distant object. As the object gets closer, there will be point where the (excess for distance) refraction is just right. Objects beyond this point will be out-of-focus. At & within this point, the eye Promoted by Asana Profile photo for Victoria J. Chin Victoria J. Chin Former Head of Product Marketing, Growth & Scale at Asana (company) (2020–2023) · 3y What is the best project management tool? I might be a little biased, but as an Asana employee, I believe Asana is the best project management tool. With Asana, my entire team has a central source of truth so they know exactly who’s doing what by when. We can track all of our tasks and stay aligned on our team goals. This has been especially important recently, since it’s enabled our team to manage shifting priorities and take any new challenges in stride. Every team is different, so your team might not use Asana exactly like my team does. But every team can benefit from more clarity, coordination, and collaboration at work. Here are f Profile photo for Valente Hernandez Perez Valente Hernandez Perez Reduced my myopia naturallyAuthor has 3.4K answers and 3.5M answer views · 3y Related How do diverging lenses correct nearsightedness? Nearsightedness occurs when the eye can only see near objects but not far objects. This is because the light coming from far objects focus in front of the retina, rather than on the retina. Diverging lenses, also called concave lenses, move the converging point of the light backwards towards the retina. Therefore, diverging lenses correct nearsightedness by focusing the light coming from far objects onto the retina. Profile photo for Sharon Breivogel-Leonard Sharon Breivogel-Leonard Optician and Contact Lens Practitioner licensed in N.Y.Author has 3K answers and 14.5M answer views · 4y Related Shouldn’t elongated eye lens converge the rays of light behind retina? If yes, then how is elongation of eye lens a cause of myopia? “Shouldn’t elongated eye lens converge the rays of light behind retina? If yes, then how is elongation of eye lens a cause of myopia?” It’s not the “…elongated eye lens…” that causes myopia, but the elongated globe, or eye ball. The lens has some ability to fine tune the focus of the eye from near to far vision (which diminishes with age), but not enough to permanently correct for a globe that is too long axially (myopia), or one that is too short (hyperopia). This analogy might help to explain: Think of the back of the eye ball as a movie screen, and the lens as the film projector. If you move Promoted by The Penny Hoarder Profile photo for Lisa Dawson Lisa Dawson Founder at The Penny Hoarder (2010–present) · Updated 3h What are some expenses that frugal people never waste money on? You’ve mastered the art of cutting back – brewing your own coffee, avoiding Target dollar-spot temptations, and resisting the allure of avocado toast (cut to: millennial eye-roll). Yet, those pesky monthly bills remain. We get it, and we’re here to spill the beans on how to break free from the shackles of rent, utilities, cell phone bills, insurance, and grocery expenses. Ready to free up some cash? Read on for the ultimate frugal playbook 1. Insurance: Cancel Your Car Insurance Here’s the thing: your current car insurance company is probably overcharging you. But don’t waste your time hopping aro Profile photo for Raphael Raphael An African student optometrist · 7y Related Can you cure far-sightedness by looking at objects up-close? The answer is simply no.Far-sightedness(hypermetropia) can be diagnosed only when one is looking at far(6m and beyond)...this why your optometrist asks you to look at a test chart(VA) placed at 6m from ur examination chair.During looking at far your lens is relaxed and there is no accommodation.When looking at near,your lens contracts temporarily to help you obtain a clear focus of the near object,for people of the same age,the far-sighted's lens will contract more than one who is not when looking at near objects and this does not mean that the far-sighted's vision can be corrected. Profile photo for Bill Otto Bill Otto Top Writer Eyesight & Optometry at QuoraAuthor has 8.2K answers and 66.2M answer views · Feb 21 Related Why and how are long-distance images blurry in myopia and opposite in hypermyopia? I think you meant to write “hyperopia.” I would use a camera analogy but not very many people use manually focused camera lenses anymore. So think of binoculars. If you focus them near, then things in the distance are blurry. If you focus them at far objects, then nearer ones are blurry. A normal young eye, focuses on distant objects and accommodation allows automatic focusing on near objects. Hyperopia is when your eyes are focused beyond far so nothing is in focus. Your accommodation can add enough focusing power to just see far objects clearly. If you have myopia, your eyes are focused up close Promoted by monday.com Profile photo for monday.com monday.com One platform for managing any project, task, and workflow. · 10mo What are the benefits of using a work management platform for product managers? As a product manager, you are the driving force behind your product's strategic development and the one-stop-shop for all questions, ideas, suggestions, and requests about your products within your organization. Without a work management platform, it is impossible to retain, coordinate and communicate all that information. A good work management platform will help you develop, plan, manage, organize, and communicate the high-level strategy for your product. With over 180,000 customers worldwide, monday.com \| A new way of working's customization capabilities make it a leader when it comes to se Profile photo for Valente Hernandez Perez Valente Hernandez Perez Reduced my myopia naturallyAuthor has 3.4K answers and 3.5M answer views · 1y Related Why does the eye lense refraction error of myopia, issue of focal point being before the retina, only occur when objects are far away. Why shouldn't it occur regardless of whether an object is near or far? You need to look at the fundamental principles of optics. When the light pases through a convex, converging lens, which for the eye is the crystalline lens, you will see that the light converging point will depend on the distance from where the light is coming from. This because as the light passes through the lens, refraction happens and the direction of light when it leaves the lens depends on the direction and distance of the light before it enters the lens. Profile photo for Muthusamy Piramanayagam ( முத்துசாமி பிரமநாயகம்) Muthusamy Piramanayagam ( முத்துசாமி பிரமநாயகம்) M.Sc. Retired as Head of Department of Physics. Government of Tamilnadu, lndia.Author has 10.2K answers and 6.9M answer views · 3y Related A myopia patient could see objects blurred. So if the image is formed before retina (which works as a screen) then how that person could see the object even blur. if the image is not forming in retina then how it could be possible to see image? The image is formed before the retina. If a screen is placed at this position, the image will be clear and sharp. Why? Approximate size of retina is 1100 (mm)^2 . The biggest screen in a cinema hall is 72 * 98 (ft )^2 655,523,850( mm)^ 2 That is the cinema screen is 94320 times greater than an average retina. When the retina is in the correct focal plane, the linage of the cinema screen is clear and sharp. It is because Each point in the cinema screen forms a point image on the retina (in correct position) Note that 1 mm^2 circle on cine screen forms ( 1/94320) (mm)^2 a minute point on the retina. If t Promoted by Talkspace Profile photo for Talkspace Talkspace Online Therapy Platform · Jan 31 What role does therapy play in treating anxiety? A therapist can help you understand the roots of your anxiety and develop coping strategies so you’ll feel less anxious and be able to manage anxiety episodes more effectively. This might include helping you identify the underlying beliefs that lead to anxiety, or episodes from your past that result in anxiety today. Once you understand the sources of your anxiety and what triggers anxious episodes, your therapist will partner with you on strategies to reduce it. These might include journaling, breathing exercises, and cognitive behavioral therapy (CBT) techniques such as thought stopping or r Profile photo for Francis Vincent Francis Vincent Author has 7.2K answers and 6.3M answer views 3y Related My right eye sees far objects better but cannot focus as well on nearer objects as my left eye does. The opposite is on my left eye (cannot see far objects, better on near). Is this normal? Having one far sighted eye and one near sighted eye is called antimetropia and isn't very common. I had that when I was younger. My optometrist said I didn't need glasses as long as it wasn't bothering me. At 30 when I started using computers 8+ hours/day the eyestrain of only eye in focus did bother me so I got spectacles. We tend to get more farsighted as we age so I no longer have antimetropia. Now I have one slightly farsighted eye and one very farsighted eye. Having significantly different levels of the same refractive error is instead called antisomitropia. I would get an eye exam if I w Related questions How do diverging lenses correct nearsightedness? How does focused light in front of the retina make us near-sighted and not otherwise? Does it have anything to do with image formation? Why does light focusing in front of the retina mostly cause problems with seeing objects that are far (nearsightedness), and light focusing past the retina causes problems with seeing objects that are close (farsightedness)? How do one’s eyes go from farsighted to nearsighted? I am a farsighted person but my lenses is for nearsighted. Will this affect my eyes? For a nearsighted person, is the image focused in front of the retina? True or False? Myopia and hyperopia causes are explainable by the eye lense getting stretched or not, but how does by focal condition occur? Can mild hyperopia/farsightedness be reversed without the use of corrective lenses or surgery? Why is my eye bleeding behind the retina? Which one is worse: being nearsighted or farsighted? Can you explain the difference between nearsightedness (myopia) and farsightedness (hyperopia), and how are these vision problems treated? What is the possible disease if one retina is larger than the retina in other eye? If you have presbyopia, does far object focus in front of the retina and close object focus behind the retina? A nearsighted person has a near point of 12 cm and a far point of 17 cm. If the corrective lens is 2.0 cm from his eye, what lens power will enable this person to see distant objects clearly (answer should be in diopters)? Where does the image form in the eye of a nearsighted person? Related questions How do diverging lenses correct nearsightedness? How does focused light in front of the retina make us near-sighted and not otherwise? Does it have anything to do with image formation? Why does light focusing in front of the retina mostly cause problems with seeing objects that are far (nearsightedness), and light focusing past the retina causes problems with seeing objects that are close (farsightedness)? How do one’s eyes go from farsighted to nearsighted? I am a farsighted person but my lenses is for nearsighted. Will this affect my eyes? For a nearsighted person, is the image focused in front of the retina? True or False? AboutCareersPrivacyTermsContactLanguagesYour Ad ChoicesPress© Quora, Inc. 2024	biology	1938767	https://no.wikipedia.org/wiki/Linosomus	Linosomus	Linosomus er en slekt av biller som hører til underfamilien storkortvinger (Staphylininae) i familien kortvinger (Staphylinidae). Utseende Ganske små (kroppslengde 3-5,5 millimeter), lange og slanke, kortbeinte, blanke kortvinger. Kroppen er sparsomt hårete, svart med brunlige dekkvinger og mer eller mindre rødlige antenner og bein. De ligner særlig på slekten Xantholinus, men kan skilles fra disse på at hodet har fire lengdefurer i den fremre delen, og på at maksillarpalpenes ytterste ledd er fint og krumt. Hodet er forholdsvis stort og flatt, tydelig lengre enn bredt, svart, svært blankt og grovt punktert, med markerte, omtrent rettvinklede bakhjørner og tydelig "hals". Pronotum er rektangulært, tydelig lengre enn bredt, også svært blankt, med to buede rekker av grove punktgroper. Dekkvingene har avrundede "skuldre", er til sammen litt bredere enn pronotum med rette, parallelle ytterkanter. Innerkantene, som danner sømmen i midten, er litt buede, men ikke så tydelig som hos Xantholinus-artene. Levevis Som den slanke, kortbeinte kroppsformen kunne tyde på, er Linosomus-artene gravende og tilbringer mye av tiden under jorda. De kan også finnes under steiner. Som vanlig for kortvinger er de rovdyr som lever av ulike slags smådyr. Utbredelse Slekten er utbredt i Australia og Sør-Afrika. Systematisk inndeling Ordenen biller, Coleoptera Underordenen Polyphaga Overfamilien åtsel- og rovbiller, Staphylinoidea Familien kortvinger (Staphylinidae) Latreille, 1802 Underfamilien storkortvinger Staphylininae Latreille, 1802 Stammen Xantholinini Slekten Linosomus Kraatz, 1857 Linosomus bifurcatus Bordoni, 2016 Linosomus brincki (Scheerpeltz, 1974) Linosomus endrodyi Bordoni, 2016 Linosomus fumipennis (Casey, 1906) Linosomus grossulus (Casey, 1906) Linosomus hottentottus (Sachse, 1852) Linosomus mhlanlanensis Bordoni, 2016 Linosomus septentrionalis Bordoni, 2016 Linosomus socius (Fauvel, 1877) Linosomus tenuicornis (Nordmann, 1837) Eksterne lenker Linosomus på GBIF Atlas of Living Australia - Linosomus Storkortvinger Biller formelt beskrevet i 1857 Australias insekter Sør-Afrikas insekter	norwegian_bokmål	1.407393
eye_focus/myopiassoy.txt	[ ![AOA logo](/AOA/Images/Logos/Header%20Logo.png) ](/healthy-eyes) * [ What's a Doctor of Optometry? ](/healthy-eyes/whats-a-doctor-of-optometry "What's a Doctor of Optometry?") * [ Find a Doctor ](/healthy-eyes/find-a-doctor "Find a Doctor") * [ AOA.org ](/ "AOA.org") * ![Search](Content/img/svg/icon-search-black.svg) Search: ![Search](Content/img/svg/icon-search-black.svg) [ Eye and Vision Conditions ](/healthy-eyes/eye-and-vision-conditions "Eye and Vision Conditions") * [ Acanthamoeba ](/healthy-eyes/eye-and-vision-conditions/acanthamoeba "Acanthamoeba ") * [ Accommodative Dysfunction ](/healthy-eyes/eye-and-vision-conditions/accommodative-dysfunction "Accommodative Dysfunction") * [ Amblyopia ](/healthy-eyes/eye-and-vision-conditions/amblyopia "Amblyopia ") * [ Anterior Uveitis ](/healthy-eyes/eye-and-vision-conditions/anterior-uveitis "Anterior Uveitis ") * [ Astigmatism ](/healthy-eyes/eye-and-vision-conditions/astigmatism "Astigmatism") * [ Blepharitis ](/healthy-eyes/eye-and-vision-conditions/blepharitis "Blepharitis ") * [ Cataract ](/healthy-eyes/eye-and-vision-conditions/cataract "Cataract") * [ Chalazion ](/healthy-eyes/eye-and-vision-conditions/chalazion "Chalazion ") * [ Color Vision Deficiency ](/healthy-eyes/eye-and-vision-conditions/color-vision-deficiency "Color Vision Deficiency ") * [ Computer Vision Syndrome ](/healthy-eyes/eye-and-vision-conditions/computer-vision-syndrome "Computer Vision Syndrome") * [ Concussions ](/healthy-eyes/eye-and-vision-conditions/concussions "Concussions") * [ Conjunctivitis ](/healthy-eyes/eye-and-vision-conditions/conjunctivitis "Conjunctivitis ") * [ Convergence Insufficiency ](/healthy-eyes/eye-and-vision-conditions/convergence-insufficiency "Convergence Insufficiency") * [ Corneal Abrasion ](/healthy-eyes/eye-and-vision-conditions/corneal-abrasion "Corneal Abrasion ") * [ Diabetic Retinopathy ](/healthy-eyes/eye-and-vision-conditions/diabetic-retinopathy "Diabetic Retinopathy ") * [ Dry Eye ](/healthy-eyes/eye-and-vision-conditions/dry-eye "Dry Eye") * [ Eye Coordination ](/healthy-eyes/eye-and-vision-conditions/eye-coordination "Eye Coordination") * [ Floaters & Spots ](/healthy-eyes/eye-and-vision-conditions/floaters-and-spots "Floaters & Spots") * [ Glaucoma ](/healthy-eyes/eye-and-vision-conditions/glaucoma "Glaucoma") * [ Hordeolum ](/healthy-eyes/eye-and-vision-conditions/hordeolum "Hordeolum") * [ Hyperopia ](/healthy-eyes/eye-and-vision-conditions/hyperopia "Hyperopia") * [ Keratitis ](/healthy-eyes/eye-and-vision-conditions/keratitis "Keratitis") * [ Keratoconus ](/healthy-eyes/eye-and-vision-conditions/keratoconus "Keratoconus") * [ Macular Degeneration ](/healthy-eyes/eye-and-vision-conditions/macular-degeneration "Macular Degeneration") * [ Migraine with Aura ](/healthy-eyes/eye-and-vision-conditions/migraine-with-aura "Migraine with Aura") * [ Myokymia ](/healthy-eyes/eye-and-vision-conditions/myokymia "Myokymia") * [ Nystagmus ](/healthy-eyes/eye-and-vision-conditions/nystagmus "Nystagmus") * [ Ocular Allergies ](/healthy-eyes/eye-and-vision-conditions/ocular-allergies "Ocular Allergies") * [ Ocular Hypertension ](/healthy-eyes/eye-and-vision-conditions/ocular-hypertension "Ocular Hypertension") * [ Ocular Migraine ](/healthy-eyes/eye-and-vision-conditions/ocular-migraine "Ocular Migraine") * [ Pinguecula ](/healthy-eyes/eye-and-vision-conditions/pinguecula "Pinguecula") * [ Presbyopia ](/healthy-eyes/eye-and-vision-conditions/presbyopia "Presbyopia") * [ Pterygium ](/healthy-eyes/eye-and-vision-conditions/pterygium "Pterygium") * [ Ptosis ](/healthy-eyes/eye-and-vision-conditions/ptosis "Ptosis") * [ Retinal Detachment ](/healthy-eyes/eye-and-vision-conditions/retinal-detachment "Retinal Detachment") * [ Retinoblastoma ](/healthy-eyes/eye-and-vision-conditions/retinoblastoma "Retinoblastoma ") * [ Retinitis Pigmentosa ](/healthy-eyes/eye-and-vision-conditions/retinitis-pigmentosa "Retinitis Pigmentosa") * [ Strabismus ](/healthy-eyes/eye-and-vision-conditions/strabismus "Strabismus") * [ Subconjunctival Hemorrhage ](/healthy-eyes/eye-and-vision-conditions/subconjunctival-hemorrhage "Subconjunctival Hemorrhage") * [ Vision-Related Learning Problems ](/healthy-eyes/eye-and-vision-conditions/vision-related-learning-problems "Vision-Related Learning Problems") [ Healthy Eyes ](/healthy-eyes "Healthy Eyes") / [ Eye and Vision Conditions ](/healthy-eyes/eye-and-vision-conditions "Eye and Vision Conditions") / [ Myopia ](/healthy-eyes/eye-and-vision-conditions/myopia "Myopia") # Myopia (nearsightedness) Nearsightedness, or myopia, as it is medically termed, is a vision condition in which people can see close objects clearly, but objects farther away appear blurred. ![Myopia](/AOA/Images/Patients/Eye%20Conditions/Myopia.jpg) Myopia occurs if the eyeball is too long or the cornea (the clear front cover of the eye) is too curved. As a result, the light entering the eye isn't focused correctly, and distant objects look blurred. Myopia affects nearly 30% of the U.S. population. While the exact cause of myopia is unknown, there is significant evidence that many people inherit myopia, or at least the tendency to develop myopia. If one or both parents are nearsighted, there is an increased chance their children will be nearsighted. Even though the tendency to develop myopia may be inherited, its actual development may be affected by how a person uses his or her eyes. Individuals who spend considerable time reading, working at a computer, playing video games or doing other intense close visual work may be more likely to develop myopia. In fact, high levels of screen time on smart devices (i.e. looking at a smart phone) is associated with around a 30% higher risk of myopia and, when combined with excessive computer use, that risk rose to around 80%. ## Causes & risk factors Myopia may also occur due to environmental factors or other health problems: * Some people may experience blurred distance vision only at night. With "night myopia," low light makes it difficult for the eyes to focus properly. Or the increased pupil size during dark conditions allows more peripheral, unfocused light rays to enter the eye. * People who do an excessive amount of near-vision work may experience a false or "pseudo" myopia. Their blurred distance vision is caused by overuse of the eyes' focusing mechanism. After long periods of near work, their eyes are unable to refocus to see clearly in the distance. Clear distance vision usually returns after resting the eyes. However, constant visual stress may lead to a permanent reduction in distance vision over time. * Symptoms of myopia may also be a sign of variations in blood sugar levels in people with diabetes or maybe an early indication of a developing cataract. ## Symptoms People with myopia can have difficulty clearly seeing a movie or TV screen, a whiteboard in school or while driving. Generally, myopia first occurs in [ school-age children ](/healthy-eyes/eye-health-for-life/school-aged-vision "School-aged Vision") . Because the eye continues to grow during childhood, it typically progresses until about age 20. However, myopia may also develop in adults due to visual stress or health conditions such as diabetes. ## Diagnosis Testing for myopia may use several procedures to measure how the eyes focus light and to determine the power of any optical lenses needed to correct the reduced vision. As part of the testing, you will identify letters on a distance chart. This test measures [ visual acuity ](/healthy-eyes/vision-and- vision-correction/visual-acuity "Visual Acuity") , which is written as a fraction, such as 20/40. The top number of the fraction is the standard distance at which testing is performed (20 feet). The bottom number is the smallest letter size read. A person with 20/40 visual acuity would have to get within 20 feet to identify a letter that could be seen clearly at 40 feet in a "normal" eye. Normal distance visual acuity is 20/20, although many people have 20/15 (better) vision. Using an instrument called a phoropter, a doctor of optometry places a series of lenses in front of your eyes and measures how they focus light using a handheld lighted instrument called a retinoscope. Or the doctor may choose to use an automated instrument that evaluates the focusing power of the eye. The power is then refined based on your responses to determine the lenses that allow the clearest vision. Your doctor can conduct this testing without using eye drops to determine how the eyes respond under normal seeing conditions. In some cases, such as for patients who can't respond verbally or when some of the eye's focusing power may be hidden, a doctor may use eye drops. The eye drops temporarily keep the eyes from changing focus during testing. Using the information from these tests, along with the results of other tests of eye focusing and eye teaming, your doctor can determine if you have myopia. He or she will also determine the power of any lens correction needed to provide a clearer vision. Once testing is complete, your doctor can discuss treatment options. ## Treatment People with myopia have several options available to regain clear distance vision. They include: * Eyeglasses. For most people with myopia, eyeglasses are the primary choice for correction. Depending on the amount of myopia, you may only need to wear glasses for certain activities, like watching a movie or driving a car. Or, if you are very nearsighted, you may need to wear them all the time. Generally, a single-vision lens is prescribed to provide clear vision at all distances. However, patients over age 40, or children and adults whose myopia is due to the stress of near vision work, may need a bifocal or progressive addition lens. These multifocal lenses provide different powers or strengths throughout the lens to allow for clear vision in the distance and up close. * Contact lenses. For some individuals, [ contact lenses ](/healthy-eyes/vision-and-vision-correction/contact-lens-care "Contact Lenses") offer clearer vision and a wider field of view than eyeglasses. However, since contact lenses are worn directly on the eyes, they require proper evaluation and care to safeguard eye health. * Ortho-k or CRT. Another option for treating myopia is [ orthokeratology (ortho-k) ](/healthy-eyes/caring-for-your-eyes/corneal-modifications "Corneal Modifications") , also known as corneal refractive therapy (CRT). In this nonsurgical procedure, you wear a series of specially designed rigid contact lenses to gradually reshape the curvature of your cornea, the front outer surface of the eye. The lenses place pressure on the cornea to flatten it. This changes how light entering the eye is focused. You wear the contact lenses for limited periods, such as overnight, and then remove them. People with mild myopia may be able to temporarily obtain clear vision for most of their daily activities. * Laser procedures. Laser procedures such as [ LASIK (laser in situ keratomileusis) or PRK (photorefractive keratectomy) ](/healthy-eyes/caring-for-your-eyes/corneal-modifications "Corneal Modifications") are also possible treatment options for myopia in adults. A laser beam of light reshapes the cornea by removing a small amount of corneal tissue. The amount of myopia that PRK or LASIK can correct is limited by the amount of corneal tissue that can be safely removed. In PRK, a laser removes a thin layer of tissue from the surface of the cornea in order to change its shape and refocus light entering the eye. LASIK removes tissue from the inner layers, but not from the surface, of the cornea. To do this, a section of the outer corneal surface is lifted and folded back to expose the inner tissue. A laser then removes the precise amount of corneal tissue needed to reshape the eye. Then, the flap of outer tissue is placed back in position to heal. * Other refractive surgery procedures. People who are highly nearsighted or whose corneas are too thin for laser procedures may be able to have their myopia surgically corrected. A doctor may be able to implant small lenses with the desired optical correction in their eyes. The implant can be placed just in front of the natural lens (phakic intraocular lens implant), or the implant can replace the natural lens (clear lens extraction with intraocular lens implantation). This clear lens extraction procedure is similar to cataract surgery but occurs before a cataract is present. * Vision therapy for people with stress-related myopia. Vision therapy is an option for people whose blurred distance vision is caused by a spasm of the muscles that control eye focusing. Various eye exercises can improve poor eye focusing ability and regain clear distance vision. People with myopia have a variety of options to correct vision problems. A doctor of optometry will help select the treatment that best meets the visual and lifestyle needs of the patient. ## Prevention Children who are at high risk of progressive myopia (family history, early age of onset, and extended periods of near work) may benefit from treatment options that have been shown to reduce the progression of myopia. These treatments include the prescription of bifocal spectacle or contact lenses, orthokeratology, eye drops, or a combination of these. Because persons with high myopia are at a greater risk of developing [ cataracts ](/healthy- eyes/eye-and-vision-conditions/cataract "Cataracts") , [ glaucoma ](/healthy- eyes/eye-and-vision-conditions/glaucoma "Glaucoma") and myopic macular degeneration, myopia management may help preserve eye health. Find a Doctor of Optometry Zip Code Distance 5 Miles 10 Miles 25 Miles 50 Miles 100 Miles 200 Miles Search [ Advanced Search ](/healthy-eyes/find-a-doctor "Find A Doctor Results") [ Eye and Vision Conditions ](javascript:void$0$; "Eye and Vision Conditions") * [ Acanthamoeba ](/healthy-eyes/eye-and-vision-conditions/acanthamoeba "Acanthamoeba ") * [ Accommodative Dysfunction ](/healthy-eyes/eye-and-vision-conditions/accommodative-dysfunction "Accommodative Dysfunction") * [ Amblyopia ](/healthy-eyes/eye-and-vision-conditions/amblyopia "Amblyopia ") * [ Anterior Uveitis ](/healthy-eyes/eye-and-vision-conditions/anterior-uveitis "Anterior Uveitis ") * [ Astigmatism ](/healthy-eyes/eye-and-vision-conditions/astigmatism "Astigmatism") * [ Blepharitis ](/healthy-eyes/eye-and-vision-conditions/blepharitis "Blepharitis ") * [ Cataract ](/healthy-eyes/eye-and-vision-conditions/cataract "Cataract") * [ Chalazion ](/healthy-eyes/eye-and-vision-conditions/chalazion "Chalazion ") * [ Color Vision Deficiency ](/healthy-eyes/eye-and-vision-conditions/color-vision-deficiency "Color Vision Deficiency ") * [ Computer Vision Syndrome ](/healthy-eyes/eye-and-vision-conditions/computer-vision-syndrome "Computer Vision Syndrome") * [ Concussions ](/healthy-eyes/eye-and-vision-conditions/concussions "Concussions") * [ Conjunctivitis ](/healthy-eyes/eye-and-vision-conditions/conjunctivitis "Conjunctivitis ") * [ Convergence Insufficiency ](/healthy-eyes/eye-and-vision-conditions/convergence-insufficiency "Convergence Insufficiency") * [ Corneal Abrasion ](/healthy-eyes/eye-and-vision-conditions/corneal-abrasion "Corneal Abrasion ") * [ Diabetic Retinopathy ](/healthy-eyes/eye-and-vision-conditions/diabetic-retinopathy "Diabetic Retinopathy ") * [ Dry Eye ](/healthy-eyes/eye-and-vision-conditions/dry-eye "Dry Eye") * [ Eye Coordination ](/healthy-eyes/eye-and-vision-conditions/eye-coordination "Eye Coordination") * [ Floaters & Spots ](/healthy-eyes/eye-and-vision-conditions/floaters-and-spots "Floaters & Spots") * [ Glaucoma ](/healthy-eyes/eye-and-vision-conditions/glaucoma "Glaucoma") * [ Hordeolum ](/healthy-eyes/eye-and-vision-conditions/hordeolum "Hordeolum") * [ Hyperopia ](/healthy-eyes/eye-and-vision-conditions/hyperopia "Hyperopia") * [ Keratitis ](/healthy-eyes/eye-and-vision-conditions/keratitis "Keratitis") * [ Keratoconus ](/healthy-eyes/eye-and-vision-conditions/keratoconus "Keratoconus") * [ Macular Degeneration ](/healthy-eyes/eye-and-vision-conditions/macular-degeneration "Macular Degeneration") * [ Migraine with Aura ](/healthy-eyes/eye-and-vision-conditions/migraine-with-aura "Migraine with Aura") * [ Myokymia ](/healthy-eyes/eye-and-vision-conditions/myokymia "Myokymia") * [ Nystagmus ](/healthy-eyes/eye-and-vision-conditions/nystagmus "Nystagmus") * [ Ocular Allergies ](/healthy-eyes/eye-and-vision-conditions/ocular-allergies "Ocular Allergies") * [ Ocular Hypertension ](/healthy-eyes/eye-and-vision-conditions/ocular-hypertension "Ocular Hypertension") * [ Ocular Migraine ](/healthy-eyes/eye-and-vision-conditions/ocular-migraine "Ocular Migraine") * [ Pinguecula ](/healthy-eyes/eye-and-vision-conditions/pinguecula "Pinguecula") * [ Presbyopia ](/healthy-eyes/eye-and-vision-conditions/presbyopia "Presbyopia") * [ Pterygium ](/healthy-eyes/eye-and-vision-conditions/pterygium "Pterygium") * [ Ptosis ](/healthy-eyes/eye-and-vision-conditions/ptosis "Ptosis") * [ Retinal Detachment ](/healthy-eyes/eye-and-vision-conditions/retinal-detachment "Retinal Detachment") * [ Retinoblastoma ](/healthy-eyes/eye-and-vision-conditions/retinoblastoma "Retinoblastoma ") * [ Retinitis Pigmentosa ](/healthy-eyes/eye-and-vision-conditions/retinitis-pigmentosa "Retinitis Pigmentosa") * [ Strabismus ](/healthy-eyes/eye-and-vision-conditions/strabismus "Strabismus") * [ Subconjunctival Hemorrhage ](/healthy-eyes/eye-and-vision-conditions/subconjunctival-hemorrhage "Subconjunctival Hemorrhage") * [ Vision-Related Learning Problems ](/healthy-eyes/eye-and-vision-conditions/vision-related-learning-problems "Vision-Related Learning Problems") ## Find a Doctor of Optometry Zip Code Distance 5 Miles 10 Miles 25 Miles 50 Miles 100 Miles 200 Miles Search [ Advanced Search ](/healthy-eyes/find-a-doctor "Find A Doctor Results") Share This __ __ __ Related Articles * * * ![](/AOA/Images/Patients/Eye%20Conditions/Acanthamoeba.jpg) ### [ Acanthamoeba ](/healthy-eyes/eye-and-vision-conditions/acanthamoeba "Acanthamoeba ") Acanthamoeba is one of the most common organisms in the environment. Although it rarely causes infection, when it does occur, it can threaten your vision. ![](/AOA/Images/Patients/Eye%20Conditions/Accommodative-dysfunction.jpg) ### [ Accommodative dysfunction ](/healthy-eyes/eye-and-vision- conditions/accommodative-dysfunction "Accommodative Dysfunction") Accommodative dysfunction is an eye-focusing problem resulting in blurred vision—up close and/or far away— frequently found in children or adults who have extended near-work demand. ![](/AOA/Images/Patients/Eye%20Conditions/Amblyopia.jpg) ### [ Amblyopia (lazy eye) ](/healthy-eyes/eye-and-vision- conditions/amblyopia "Amblyopia ") Amblyopia—also known as lazy eye—is the loss or lack of development of clear vision in one or both eyes. 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eye_focus/8579myopianearsighte.txt	* [ 800.223.2273 ](tel:800.223.2273) * [ 100 Years of Cleveland Clinic ](https://my.clevelandclinic.org/about/history) * [ MyChart ](https://my.clevelandclinic.org/online-services/mychart) * [ Need Help? ](https://my.clevelandclinic.org/help) * [ Giving ](https://my.clevelandclinic.org/giving) * [ Careers ](https://jobs.clevelandclinic.org) * [ ![Search Icon Blue](/health/_next/static/media/search--blue.a23a2bb9.svg?w=32&q=75) Search ](https://my.clevelandclinic.org/search) [ ![Cleveland Clinic logo](/health/_next/static/media/logo- ccf.a7ea0118.svg?w=3840&q=75) ](https://my.clevelandclinic.org/) [ ![Search Icon](/health/_next/static/media/search-- gray.86f52a63.svg?w=48&q=75) ](https://my.clevelandclinic.org/search) * [ ClevelandClinic.org ](https://my.clevelandclinic.org) * [ Find A Doctor ](https://my.clevelandclinic.org/staff) * [ Locations & Directions ](https://my.clevelandclinic.org/locations) * [ Patients & Visitors ](https://my.clevelandclinic.org/patients) * [ Health Library ](https://my.clevelandclinic.org/health) * [ Institutes & Departments ](https://my.clevelandclinic.org/departments) * [ Appointments ](https://my.clevelandclinic.org/patients/information/access) ![](//zdbb.net/l/Dnl1wmWs8xCCpvWNCt9Egf/?w=16&q=75) [ Home ](https://my.clevelandclinic.org) / [ Health Library ](https://my.clevelandclinic.org/health) / [ Diseases & Conditions ](https://my.clevelandclinic.org/health/diseases) / Myopia (Nearsightedness) Advertisement Advertisement Advertisement # Myopia (Nearsightedness) Myopia (nearsightedness) is a common condition that’s usually diagnosed before age 20. It affects your distance vision — you can see objects that are near, but you have trouble viewing objects that are farther away like grocery store aisle markers or road signs. Myopia treatments include glasses, contact lenses or surgery. Contents Arrow Down Overview Symptoms and Causes Diagnosis and Tests Management and Treatment Prevention Outlook / Prognosis Living With Additional Common Questions Contents Arrow Down Overview Symptoms and Causes Diagnosis and Tests Management and Treatment Prevention Outlook / Prognosis Living With Additional Common Questions ## Overview Learn the signs of nearsightedness and what to do about it. ### What is myopia? Myopia is the medical name for nearsightedness, which means that you can see objects that are near clearly but have difficulty seeing objects that are farther away. For example, if you’re nearsighted, you may not be able to make out highway signs until they’re just a few feet away. Myopia affects a significant percentage of people. It’s an [ eye ](https://my.clevelandclinic.org/health/body/21823-eyes) focus disorder that’s normally corrected with eyeglasses, contact lenses or surgery. #### How common is myopia? Myopia is common. According to one estimate, more than 40% of people in the U.S. are nearsighted. This number is rapidly rising, especially among school- aged children. Eye experts expect this trend to continue in the coming decades. One in four parents has a child with some degree of nearsightedness. Some eye experts believe that if your child spends a great deal of time engaged in “near” activities, such as reading or using smartphones and computers, it may raise their risk of developing myopia. #### Are there types of myopia? [ Eye specialists ](https://my.clevelandclinic.org/health/articles/8607-eye- care-specialists) divide myopia broadly into simple myopia and pathologic myopia. Pathologic myopia is a newer name for degenerative myopia. People with simple myopia have contact lenses or eyeglasses that help provide clear vision, while those with pathologic myopia may not be able to have clear [ vision ](https://my.clevelandclinic.org/health/articles/21204-vision) even with corrective lenses. Advertisement Cleveland Clinic is a non-profit academic medical center. Advertising on our site helps support our mission. We do not endorse non-Cleveland Clinic products or services. [ Policy ](https://health.clevelandclinic.org/advertising) ## Symptoms and Causes ![A blurry street sign with myopia $nearsighted$ vs. a clear street sign with normal vision.](https://my.clevelandclinic.org/-/scassets/images/org/health/articles/myopia- nearsightedness) Focus that happens in front of the retina of your eye instead of at the retina results in myopia (nearsightedness). ### What are the symptoms of myopia? If you’re nearsighted, you may notice: * Faraway objects look blurred or fuzzy. * Close items appear clear. * [ Headaches ](https://my.clevelandclinic.org/health/diseases/9639-headaches) . * [ Eye strain ](https://my.clevelandclinic.org/health/diseases/21059-eye-strain) . * Squinting. * Tiredness when driving, playing sports or looking more than a few feet away. Some additional symptoms of myopia to watch for in your children include: * Poor performance in school. * Shortened attention span. * Holding objects close to their face. Most cases of myopia are mild and easily managed with [ eyeglasses ](https://my.clevelandclinic.org/health/articles/8593-eyeglasses) , [ contact lenses ](https://my.clevelandclinic.org/health/articles/10737-contact-lenses) or refractive surgery. ### What causes myopia? If you have myopia, more than likely, at least one or both of your biological parents do, too. Eye experts are still unsure of the exact cause of myopia, but believe it to be a mix of hereditary and environmental factors. It’s possible that you can inherit the ability to be myopic. If your lifestyle produces just the right conditions, you’ll develop it. For example, if you use your eyes for a lot of close-up work, like reading or working on a computer, you may develop myopia. Myopia usually appears in childhood. Typically, the condition can worsen in early childhood but tends to level off by the end of teen years. Because the light coming into your eyes doesn’t focus correctly, images are unclear. Think of it as being a little like a misdirected spotlight. If you shine a spotlight on the incorrect place in the distance, you won’t be able to see the correct object clearly. #### What are the risk factors for myopia? Risk factors for nearsightedness may include: * A family history of myopia. * Spending a lot of time doing “close-up” work, like reading or using screens like those on smartphones or computers. * Not spending a lot of time outdoors. Certain studies indicate that this may be a factor in developing myopia. * Ethnicity. Some groups of people have higher rates of myopia than others. Advertisement ### What are the complications of myopia? In most cases, providers can treat nearsightedness with glasses, contact lenses or corrective surgery, like LASIK. However, some cases of pathologic myopia can lead to more serious eye conditions, including: * Cataracts. * Glaucoma. * Optic neuropathy. * Neovascularization. * Retinal detachment. Pathologic myopia may make you more vulnerable to other more serious eye conditions. These include: * Developing unwanted blood vessels in your eye ( [ neovascularization ](https://my.clevelandclinic.org/health/diseases/24131-neovascularization-of-the-eye) ). * [ Glaucoma ](https://my.clevelandclinic.org/health/diseases/4212-glaucoma) . * Myopic optic neuropathy. * [ Retinal detachment ](https://my.clevelandclinic.org/health/diseases/10705-retinal-detachment) . * [ Cataracts ](https://my.clevelandclinic.org/health/diseases/8589-cataracts-age-related) . High myopia happens when your child’s eyeballs are too long, or their corneas are too steep. ## Diagnosis and Tests ### How is myopia diagnosed? An eye care provider can diagnose myopia using standard [ eye exams ](https://my.clevelandclinic.org/health/diagnostics/10738-eye-examinations- what-to-expect) . Providers usually diagnose myopia in childhood, but it can also develop in adults because of visual stress or diabetes. #### Testing an adult for myopia Your provider will evaluate how your eyes focus light and measure the power of any corrective lenses you may need. First, they’ll test your visual acuity (sharpness) by asking you to read letters on an eye chart. Then, they’ll use a lighted retinoscope to measure how your retina reflects light. Your provider may also use a phoropter. A phoropter is an instrument that measures the amount of your refractive error by placing a series of lenses in front of your eyes. This is how your provider measures the lens strength you need. #### Testing your child for myopia Your [ pediatrician ](https://my.clevelandclinic.org/health/articles/21716-what-is-a-pediatrician) will check your child’s eyes at each well-child visit. A [ first eye exam ](https://health.clevelandclinic.org/when-should-your-child-have-a-first-eye- exam-2/) should be before age 1, if possible. If your child has no evident eye problems, then schedule a repeat eye exam before kindergarten. As myopia runs in families, if your child has family members with vision issues, it’s even more important to test their eyes early. If you or your pediatrician notice any vision issues, your child may be referred to an [ optometrist ](https://my.clevelandclinic.org/health/articles/24219-optometrist) or pediatric [ ophthalmologist ](https://my.clevelandclinic.org/health/articles/22159-ophthalmologist) . During a children’s eye exam, your eye care provider will do a physical examination of your child’s eyes and check for a regular light reflex. For children between the ages of 3 and 5 years, your provider will also conduct vision screenings using eye chart tests, pictures, letters or the “tumbling E game,” also called the “Random E’s Visual Acuity Test.” As your child’s vision continues to change as they grow, continue to make sure they get vision screenings by their pediatrician or eye care provider before first grade and every two years thereafter. While most schools conduct eye screenings, they’re usually not complete enough to diagnose myopia. Providers diagnose most children when they’re between the ages of 3 and 12. Your provider may mention categories — mild, moderate or high myopia. These terms refer to the degree of nearsightedness as measured by [ refractive error ](https://my.clevelandclinic.org/health/diseases/24224-refractive-errors) . Refractive errors are issues with the natural shape of your eyes that make your [ vision blurry ](https://my.clevelandclinic.org/health/symptoms/24262-blurred-vision) . It’s possible to have myopia and another refractive error, like [ astigmatism ](https://my.clevelandclinic.org/health/diseases/8576-astigmatism) . Advertisement ## Management and Treatment ### How is myopia treated? Glasses or contact lenses can correct myopia in children and adults. For adults only (with rare exceptions for children), there are several types of refractive surgeries that can also correct myopia. With myopia, your prescription for glasses or contact lenses is a negative number, such as -3.00. The higher the number, the stronger your lenses will be. The prescription helps your eye focus light on your retina, clearing up your distance vision. * Eyeglasses: The most popular way for most people to correct myopia is with [ eyeglasses ](https://my.clevelandclinic.org/health/articles/8593-eyeglasses) . Depending on the degree of vision correction needed, you’ll wear eyeglasses either daily or only when you need distance vision. You may only need glasses for driving. Some kids with myopia may only need glasses to play ball, watch a movie or view the chalkboard. Some people may need to wear glasses constantly to see clearly. **** A single-vision lens will make distance vision clearer. But people over 40 who have myopia may require a bifocal or [ progressive lens ](https://my.clevelandclinic.org/health/treatments/progressive-lenses) to see clearly both near and far. * Contact lenses: Some people find that their distance vision is sharper and wider with [ contact lenses ](https://my.clevelandclinic.org/health/articles/10737-contact-lenses) . A potential downside is they require more care to keep clean. Ask your provider which type might be right for your myopia level and other refractive errors. * Ortho-k or CRT: Some people with mild myopia may be candidates for temporary corneal refractive contact lenses that you wear to bed to reshape your cornea temporarily, long enough to see for your daily activities. * LASIK is a laser-assisted in situ keratomileus procedure, the most common surgery to correct nearsightedness. In a [ LASIK ](https://my.clevelandclinic.org/health/treatments/21805-lasik-eye-surgery) procedure, your ophthalmologist uses a laser to cut a flap through the top of your cornea, reshape the inner corneal tissue and then drop the flap back into place. * LASEK is a laser-assisted subepithelial keratectomy procedure. In a LASEK procedure, your ophthalmologist uses a laser to cut a flap through only the top layer (epithelium) of your cornea, reshape the outer layers, and then close the flap. * [ PRK ](https://my.clevelandclinic.org/health/treatments/8596-photorefractive-keratectomy-prk-eye-surgery) is short for “photorefractive keratectomy,” which is a type of laser eye surgery used to correct mild or moderate nearsightedness. It may also correct farsightedness and/or astigmatism. In a PRK procedure, your ophthalmologist cuts off the front surface of your cornea and uses a laser to reshape the surface, which flattens it and allows light rays to focus on your retina. Unlike LASIK, the ophthalmologist doesn’t cut a flap, and your cornea will regrow its top layer in one to two weeks. PRK is better for people with corneas that are thinner or have a rough surface because it disrupts less corneal tissue than a comparable LASIK surgery. * Phakic intraocular lenses: These are an option for people who have high myopia or whose corneas are too thin for PRK or LASIK. Your provider places phakic intraocular lenses inside of your eye just in front of your natural lens. * Intraocular lens implant: This allows your ophthalmologist to surgically insert a new lens in your eye, replacing your natural one. This procedure happens before a cataract develops. * Vision therapy: This is an option if spasms of your focusing muscles cause myopia. You can strengthen the muscles through eye exercises and improve your focus. This treatment isn’t appropriate for everyone with myopia. After an eye exam, your ophthalmologist will let you know if it’s an option for you. Care at Cleveland Clinic [ Schedule an Eye Exam ](https://my.clevelandclinic.org/services/annual-eye- exams) [ Find a Doctor and Specialists ](https://my.clevelandclinic.org/services/annual-eye-exams#featured-provider- panel) [ Make an Appointment ](https://my.clevelandclinic.org/webappointment) ## Prevention ### Can myopia be prevented? You can’t prevent myopia as it’s a condition that tends to run in families, but you may be able to lower your risk of nearsightedness in some ways. #### How can I lower my risk of developing myopia? Some eye experts believe that you may be able to decrease your or your child’s risk of developing myopia by getting enough time outside and limiting the amount of time spent in front of screens. You may also want to be mindful of the amount of time doing close work like reading or sewing. ## Outlook / Prognosis ### What can I expect if I have myopia? Myopia is a condition that doesn’t go away. Treatments include using glasses or contact lenses. You may be able to get surgery to correct your vision. ### What is the outlook for myopia? The outlook for being nearsighted may differ depending on the type of myopia. Usually, providers can treat simple myopia easily. In rare cases of high myopia or pathologic myopia, your outlook may be different. High myopia usually stops getting worse between the ages of 20 and 30. You’ll still be able to get glasses or contact lenses or you may be able to have surgery. High myopia may lead to pathologic myopia and the possibility of more serious sight conditions later in life. These complications can lead to loss of sight. Regular eye exams are important for everyone but are especially if you have high myopia or pathologic myopia. You should follow the schedule set out by your eye care provider. ## Living With ### How can you prevent myopia from getting worse? Though there’s no cure for myopia, there are everyday steps you can take that can support your overall eye health. These days, it’s especially important to set limits for your children (and yourself) on activities that lead to eye strain. Try these sight-saving tips: * Limit time on digital devices. * Take screen breaks to stretch your eye muscles. * Don’t read or work in dim light. * Go outdoors and wear sunglasses when you’re out. * Wear protective eye gear for sports/hobbies. * [ Stop smoking ](https://my.clevelandclinic.org/health/articles/8699-quitting-smoking) . * Schedule regular eye exams. * Ask your provider about atropine eye drops to slow progression. * Ask your provider about dual-focus contact lenses to slow progression in kids. ### Which foods should I eat to keep my eyes as healthy as possible? Everyone’s eyes rely on nutrients from the foods we eat to maintain vital eye tissues and functions. Nutrition is especially essential to your child’s vision as their eyes grow and develop. In addition to limiting caffeinated colas and other soft drinks, keep hydrated by drinking enough water. Also, try to eat foods that are rich in: * Vitamin A. You need enough of the antioxidant vitamin A in your diet to maintain the surface of your eyes and healthy vision. There are vitamin A-rich sources for every diet preference. Plant-based choices include vegetables like sweet potatoes, leafy green vegetables and carrots. Or choose animal-based foods, such as cheese, oily fish or liver. * Vitamin C. The best foods for getting a daily dose of vitamin C are fruits and vegetables, including oranges, grapefruit, strawberries and broccoli. * Lutein. Eat leafy green vegetables to make sure to get enough lutein, which helps your eyes filter harmful blue light that can damage retinas. You can supplement your or your child’s diet with a multivitamin if you think you or they aren’t getting enough vitamins and minerals. Remember, though, that your body doesn’t absorb vitamins in pills as well as vitamins that occur naturally in foods. And it’s important to check with your healthcare provider before starting any supplements. Taking safe care of your and your family’s vision means regular eye exams, a good eye care routine and a healthy diet. Keeping those healthy habits will help you all to see a future filled with all the things you love. ### When should I see a doctor about myopia? Regular eye exams are important for everyone. It’s especially important to contact an eye care provider if you have any type of change in your vision. If you have kids and you notice that they squint a lot or pull things close to their faces to see them, make an appointment. In any case of extreme changes in vision — like a sudden loss of vision or noticing a significant increase in the number of floaters or flashes of light you see — get immediate medical help. Some conditions, like retinal detachment, are medical emergencies. ## Additional Common Questions ### Does myopia get worse with age? Yes, it can. Especially during growth spurts of the pre-teen and teen years, when your body grows quickly. At the age of 20, myopia usually levels off. You can also get a myopia diagnosis as an adult. When this happens, it’s usually due to visual stress or a disease like diabetes or cataracts. You can experience visual stress by spending too much time doing up-close activities, such as reading or doing computer work. Eye experts believe that your focusing muscles may get stuck in “near gear” from overusing them this way. If you’re an adult experiencing sudden nearsightedness, [ floaters ](https://my.clevelandclinic.org/health/articles/14209-floaters--flashers) (spots that appear in your field of vision), flashes of light or shadows, or a sudden loss of sight in one eye, contact an eye care provider immediately to rule out a more serious health condition. ### A note from Cleveland Clinic Many people will get a diagnosis of myopia (nearsightedness). Today, there are treatments that make it possible to obtain sharp vision despite this condition. It’s important to make and keep regular eye appointments. Diagnosing and treating any vision issue early is best. And remember, try not to let your or your child’s eyes get stuck in “near gear” from spending too much time on computers or smartphones. Get outside. Take a walk. Fresh air does the body, and eyes, good. [ ](mailto:?subject=Cleveland Clinic - Myopia $Nearsightedness$&body=https://my.clevelandclinic.org/health/diseases/8579-myopia- nearsightedness) Medically Reviewed Last reviewed by a Cleveland Clinic medical professional on 10/13/2023. Learn more about our [ editorial process ](https://my.clevelandclinic.org/about/website/editorial-policy) . #### References Advertisement Cleveland Clinic is a non-profit academic medical center. Advertising on our site helps support our mission. We do not endorse non-Cleveland Clinic products or services. 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All Rights Reserved.	biology	2903919	https://sv.wikipedia.org/wiki/Ocalaria%20dioptica	Ocalaria dioptica	Ocalaria dioptica är en fjärilsart som beskrevs av Walker 1865. Ocalaria dioptica ingår i släktet Ocalaria och familjen nattflyn. Inga underarter finns listade i Catalogue of Life. Källor Nattflyn dioptica	swedish	1.259925
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nearsightedness * Share * * * * Nearsightedness is when light entering the eye is focused incorrectly. This makes distant objects appear blurred. Nearsightedness is a type of refractive error of the eye. If you are nearsighted, you have trouble seeing things that are far away. ![Visual acuity test](https://ssl.adam.com/graphics/images/en/1124.jpg) Visual acuity tests may be performed in many different ways. It is a quick way to detect vision problems and is frequently used in schools or for mass screening. Driver license bureaus often use a small device that can test the eyes both together and individually. ![Normal, nearsightedness, and farsightedness](https://ssl.adam.com/graphics/images/en/19511.jpg) Normal vision occurs when light is focused directly on the retina rather than in front or behind it. A person with normal vision can see objects clearly near and faraway. Nearsightedness results in blurred vision when the visual image is focused in front of the retina, rather than directly on it. It occurs when the physical length of the eye is greater than the optical length. For this reason, nearsightedness often develops in the rapidly growing school-aged child or teenager, and progresses during the growth years, requiring frequent changes in glasses or contact lenses. A nearsighted person sees near objects clearly, while objects in the distance are blurred. Farsightedness is the result of the visual image being focused behind the retina rather than directly on it. It may be caused by the eyeball being too small or the focusing power being too weak. Farsightedness is often present from birth, but children can often tolerate moderate amounts without difficulty and most outgrow the condition. A farsighted person sees faraway objects clearly, while objects that are near are blurred. ![Lasik eye surgery - series - Normal anatomy](https://ssl.adam.com/graphics/images/en/19559.jpg) The cornea is the transparent part of the eye that covers the iris. It is also the main light bending part of the eye. ## Causes People are able to see because the front part of the eye bends (refracts) light and focuses it on the retina. This is the inside of the back surface of the eye. Nearsightedness occurs when there is a mismatch between the focusing power of the eye and the length of the eye. Light rays are focused in front of the retina, rather than directly on it. As a result, what you see is blurry. Most of the eye's focusing power comes from the cornea. Nearsightedness affects males and females equally. People who have a family history of nearsightedness are more likely to develop it. Most eyes with nearsightedness are healthy. However, a small number of people with severe nearsightedness develop a form of retinal degeneration. The predominant wavelength of light in your environment may affect the development of myopia. Recent research suggests that more time outdoors may lead to less myopia. ## Symptoms A nearsighted person sees close-up objects clearly, but objects in the distance are blurred. Squinting will tend to make far away objects seem clearer. Nearsightedness is often first noticed in school-aged children or teenagers. Children often cannot read the blackboard, but they can easily read a book. Nearsightedness gets worse during the growth years. People who are nearsighted may need to change glasses or contact lenses often. Nearsightedness most often stops progressing as a person stops growing in his or her early twenties. Other symptoms may include: * Eyestrain * [ Headaches ](/health-library/symptoms/headache) (uncommon) ## Exams and Tests A nearsighted person can easily read the Jaeger eye chart (the chart for near reading), but has trouble reading the Snellen eye chart (the chart for distance). A general eye exam, or [ standard ophthalmic exam ](/health- library/tests/standard-ophthalmic-exam) may include: * Eye pressure measurement ( [ tonometry ](/health-library/tests/tonometry) ) * [ Refraction test ](/health-library/tests/refraction-test) , to determine the correct prescription for glasses * Retinal examination * [ Slit-lamp exam ](/health-library/tests/slit-lamp-exam) of the structures at the front of the eyes * [ Test of color vision ](/health-library/tests/color-vision-test) , to look for possible color blindness * Tests of the muscles that move the eyes * Visual acuity, both at a distance (Snellen), and close up (Jaeger) ## Treatment Wearing eyeglasses or contact lenses can help shift the focus of the light image directly onto the retina. This will produce a clearer image. The most common surgery to correct myopia is [ LASIK ](/health- library/surgery/lasik-eye-surgery) . An excimer laser is used to reshape (flatten) the cornea, shifting the focus. A newer type of laser refractive surgery called SMILE (Small Incision Lenticule Extraction) is also approved for use in the United States. ## Outlook (Prognosis) Early diagnosis of nearsightedness is important. A child can suffer socially and educationally by not being able to see well at a distance. ## Possible Complications Complications may include: * [ Corneal ulcers and infections ](/health-library/diseases-conditions/corneal-ulcers-and-infections) may occur in people who use contact lenses. * Rarely, complications of laser vision correction may occur. These can be serious. * People with myopia, in rare cases, develop [ retinal detachments ](/health-library/diseases-conditions/retinal-detachment) or retinal degeneration. ## When to Contact a Medical Professional Contact your health care provider if your child shows these signs, which may indicate a vision problem: * Having difficulty reading the blackboard in school or signs on a wall * Holding books very close when reading * Sitting close to the television Contact your eye doctor if you or your child is nearsighted and experiences signs of a possible retinal tear or detachment, including: * Flashing lights * Floating spots * Sudden loss of any part of the field of vision ## Prevention It has been generally believed that there is no way to prevent nearsightedness. Reading and watching television do not cause nearsightedness. During the Covid-19 pandemic of 2020, when most school-aged children were learning from home, there was an increase in the development of nearsightedness over what had been seen before. In the past, dilating eye drops were proposed as a treatment to slow the development of nearsightedness in children, but those early studies were inconclusive. However, there is recent information that certain dilating eyedrops used in certain children at just the right time, may decrease the total amount of nearsightedness that they will develop. The use of glasses or contact lenses does not affect the normal progression of myopia -- they simply focus the light so the nearsighted person can see distant objects clearly. However, it is important to not prescribe glasses or contact lenses that are too strong. Hard contact lenses will sometimes hide the progression of nearsightedness, but vision will still get worse "under" the contact lens. ## References Chia A, Chua WH, Wen L, Fong A, Goon YY, Tan D. Atropine for the treatment of childhood myopia: changes after stopping atropine 0.01%, 0.1% and 0.5%. _Am J Ophthalmol_ . 2014;157(2):451-457. PMID: 24315293 pubmed.ncbi.nlm.nih.gov/24315293/ . Kanellopoulos AJ. Topography-guided LASIK versus small incision lenticule extraction (SMILE) for myopia and myopic astigmatism: a randomized, prospective, contralateral eye study. _J Refract Surg_ . 2017;33(5):306-312. PMID: 28486721 pubmed.ncbi.nlm.nih.gov/28486721/ . Nischal KK. Ophthalmology. In: Zitelli BJ, McIntire SC, Nowalk AJ, Garrison J, eds. _Zitelli and Davis' Atlas of Pediatric Physical Diagnosis_ . 8th ed. Philadelphia, PA: Elsevier; 2023:chap 20. Olitsky SE, Marsh JD. Abnormalities of refraction and accommodation. In: Kliegman RM, St. Geme JW, Blum NJ, Shah SS, Tasker RC, Wilson KM, eds. _Nelson Textbook of Pediatrics_ . 21st ed. Philadelphia, PA: Elsevier; 2020:chap 638. Torii H, Ohnuma K, Kurihara T, Tsubota K, Negishi K. Violet light transmission is related to myopia progression in adult high myopia. _Sci Rep_ . 2017;7(1):14523. PMID: 29109514 pubmed.ncbi.nlm.nih.gov/29109514/ . Wang J, Li Y, Musch DC, et al. Progression of myopia in school-aged children after COVID-19 home confinement. _JAMA Ophthalmol_ . 2021;139(3):293-300. PMID: 33443542 pubmed.ncbi.nlm.nih.gov/33443542/ . ## Version Info Last reviewed on: 8/22/2022 Reviewed by: Franklin W. Lusby, MD, Ophthalmologist, Lusby Vision Institute, La Jolla, CA. Also reviewed by David C. Dugdale, MD, Medical Director, Brenda Conaway, Editorial Director, and the A.D.A.M. 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Utseende En middelsstor (ca. 15 millimeter), langbeint, brunsvart gullbasse, kroppen er sparsomt kledt med skjell, ofte med noe metallisk glans. Hannens panne er firkantet forlenget, uten horn, hos denne arten forholdsvis kort. Utbredelse Arten lever på Borneo (Sabah). Systematisk plassering Ordenen biller, Coleoptera Underordenen Polyphaga Overfamilien skarabider, Scarabaeoidea Familien skarabider, (Scarabaeidae) Latreille, 1806 (eventuelt Cetoniidae) Underfamilien Cetoniinae Fleming, 1821 Stammen Goliathini Griffith & Pidgeon, 1832, eventuelt Phaedimini Slekten Philistina MacLeay, 1838 Underslekten Rhinacosmus Kraatz, 1895 Philistina inermis (Janson, 1903) Kilder Janson, O.E. (1903) On the genus Theodosia and other Eastern Goliathides, with descriptions of some new species. Transactions of the Entomological Society. London : 303-310. Krikken, J. (1979) Taxonomic review of the Southeast Asian genus Rhinacosmus Kraatz (Coleoptera: Cetoniidae). Zoologische Mededelingen 54: 281-290. Eksterne lenker Gullbasser Biller formelt beskrevet i 1903 Dyr formelt beskrevet av Oliver Erichson Janson Borneos insekter	norwegian_bokmål	1.233229
neanderthals_vitamin_C_diet/L-gulonolactone_oxidase.txt	2989 Gulonolactone oxidase deficiency[edit] The non-functional gulonolactone oxidase pseudogene (GULOP) was mapped to human chromosome 8p21, which corresponds to an evolutionarily conserved segment on either porcine chromosome 4 (SSC4) or 14 (SSC14). GULO produces the precursor to ascorbic acid, which spontaneously converts to the vitamin itself. The loss of activity of the gene encoding L-gulonolactone oxidase (GULO) has occurred separately in the history of several species. GULO activity has been lost in some species of bats, but others retain it. The loss of this enzyme activity is responsible for the inability of guinea pigs to enzymatically synthesize vitamin C. Both these events happened independently of the loss in the haplorrhine suborder of primates, which includes humans. The remnant of this non-functional gene with many mutations is still present in the genomes of guinea pigs and humans. It is unknown if remains of the gene exist in the bats who lack GULO activity. The function of GULO appears to have been lost several times, and possibly re-acquired, in several lines of passerine birds, where ability to make vitamin C varies from species to species. Loss of GULO activity in the primate order occurred about 63 million years ago, at about the time it split into the suborders Haplorhini (which lost the enzyme activity) and Strepsirrhini (which retained it). The haplorhine ("simple-nosed") primates, which cannot make vitamin C enzymatically, include the tarsiers and the simians (apes, monkeys and humans). The strepsirrhine ("bent-nosed" or "wet-nosed") primates, which can still make vitamin C enzymatically, include lorises, galagos, pottos, and, to some extent, lemurs. L-Gulonolactone oxidase deficiency has been called "hypoascorbemia" and is described by OMIM (Online Mendelian Inheritance in Man) as "a public inborn error of metabolism", as it affects all humans. There exists a wide discrepancy between the amounts of ascorbic acid other primates consume and what are recommended as "reference intakes" for humans. In its patently pathological form, the effects of ascorbate deficiency are manifested as scurvy. Consequences of loss[edit] It is likely that some level of adaptation occurred after the loss of the GULO gene by primates. Erythrocyte Glut1 and associated dehydroascorbic acid uptake modulated by stomatin switch are unique traits of humans and the few other mammals that have lost the ability to synthesize ascorbic acid from glucose. As GLUT transporters and stomatin are ubiquitously distributed in different human cell types and tissues, similar interactions may occur in human cells other than erythrocytes. Linus Pauling observed that after the loss of endogenous ascorbate production, apo(a) and Lp(a) were greatly favored by evolution, acting as ascorbate surrogate, since the frequency of occurrence of elevated Lp(a) plasma levels in species that had lost the ability to synthesize ascorbate is great. Also, only primates share regulation of CAMP gene expression by vitamin D, which occurred after the loss of GULO gene. Johnson et al. have hypothesized that the mutation of the GULOP pseudogene so that it stopped producing GULO may have been of benefit to early primates by increasing uric acid levels and enhancing fructose effects on weight gain and fat accumulation. With a shortage of food supplies this gave mutants a survival advantage. Animal models[edit] Studies of human diseases have benefited from the availability of small laboratory animal models. However, the tissues of animal models with a GULO gene generally have high levels of ascorbic acid and so are often only slightly influenced by exogenous vitamin C. This is a major handicap for studies involving the endogenous redox systems of primates and other animals that lack this gene. Guinea pigs are a popular human model. They lost the ability to make GULO 20 million years ago. In 1999, Maeda et al. genetically engineered mice with inactivated GULO gene. The mutant mice, like humans, entirely depend on dietary vitamin C, and they show changes indicating that the integrity of their vasculature is compromised. GULO mice have been used as a human model in multiple subsequent studies. There have been successful attempts to activate lost enzymatic function in different animal species. Various GULO mutants were also identified. Plant models[edit] In plants, the importance of vitamin C in regulating whole plant morphology, cell structure, and plant development has been clearly established via characterization of low vitamin C mutants of Arabidopsis thaliana, potato, tobacco, tomato, and rice. Elevating vitamin C content by overexpressing inositol oxygenase and gulono-1,4-lactone oxidase in A. thaliana leads to enhanced biomass and tolerance to abiotic stresses. Alternative substrates and related enzymes[edit] GULO belongs to a family of sugar-1,4-lactone oxidases, which also contains the yeast enzyme D-arabinono-1,4-lactone oxidase (ALO). ALO produces erythorbic acid when acting on its canonical substrate. This family is in turn a subfamily under more sugar-1,4-lactone oxidases, which also includes the bacterial L-gulono-1,4-lactone dehydrogenase and the plant galactonolactone dehydrogenase. All these aldonolactone oxidoreductases play a role in some form of vitamin C synthesis, and some (including GULO and ALO) accept substrates of other members. See also[edit] Vitamin C (ascorbic acid) Oxidoreductase Scurvy	biology	998	https://da.wikipedia.org/wiki/Art	Art	Arten (species, forkortet sp., flertal: spp.) er den grundlæggende systematiske enhed inden for biologien. Arten defineres ofte som en naturlig gruppe af populationer, hvor udveksling af gener finder sted (eller kan finde sted) og som i forhold til forplantning er isoleret fra andre grupper. Det vil sige at kun individer inden for samme art kan parre sig og få forplantningsdygtigt afkom. Dette kaldes det biologiske artsbegreb. For organismer, der formerer sig ukønnet eller ved selvbestøvning, må arter afgrænses ud fra ligheder og forskelle mellem forskellige individer. Nogle dyrearter kan i fangenskab hybridisere og få fertilt afkom, men da dette ikke vil ske i naturen, selv om de mødes her, betragtes de som forskellige arter. Eksempel To heste kan parre sig og få et føl, der igen kan få føl med andre heste – hestene tilhører derfor samme art. En hest og et æsel kan også parre sig og deres unger kaldes enten muldyr eller mulæsel, afhængig af hvem der er moren, men muldyret eller mulæselet kan (normalt) ikke få unger, da de oftest er sterile. Af den grund regnes hest og æsel som to forskellige arter. Det samme princip gælder også for planterne. Denne naturskabte afgrænsning mellem to arter kaldes en artsbarriere. Den kan af og til gennembrydes, når ellers sterile krydsninger spontant eller kunstigt får gennemført en kromosomfordobling. Se f.eks. Vadegræs (Spartina pectinata). Arter over for hybrider Man kan dog godt komme ud for, at arter kan krydses og får blandet afkom, men hybriden vil kun kunne bestå på steder, hvor ingen af forældrearterne kan klare sig. Dette er et særligt udpræget problem med Rododendron (Rhododendron) og Tjørn (Crataegus), fordi disse slægter breder sig voldsomt efter skovbrand eller stormfald. Da hybriderne bliver frugtbare i en yngre alder end arterne, kan de dominere i en periode, men når skoven lukker sig, så fortrænges hybriderne og kun de specialiserede arter kan overleve i skovens dybe skygge eller ude i lyset i sumpe, på ur og i kalksten, m.m. Flere artsbegreber Fordi det biologiske artsbegreb kan være besværligt at anvende i praksis, er der efterhånden skabt en række andre artsbegreber: Morfologisk artsbegreb Arterne adskiller sig fra hinanden ved deres bygning. Dette begreb er blevet meget anvendt gennem tiden. Økologisk artsbegreb Definerer en art som en gruppe af organismer, der udfylder samme niche. Krydsninger mellem to nærtstående arter vil ikke være optimalt tilpasset til forældrearternes nicher og vil ikke klare sig i konkurrencen. Evolutionære artsbegreb Også kaldet det kladistiske eller fylogenetiske artsbegreb. Naturen er dynamisk, ikke statisk - alle arter ændrer sig med tiden og bliver, hvis de ikke uddør som følge af konkurrence, naturkatastrofer m.v., til én eller flere nye arter. Det evolutionære artsbegreb minder om det biologiske, men inddrager tidsdimensionen, det vil sige at en art udvikler sig over tid og at nye arter opstår ved artsdannelse. Individer der fylogenetisk har samme stamfader tilhører samme art. Pluralistisk artsbegreb En art er et samfund af populationer, der formerer sig og lever inden for en bestemt niche i naturen. Se også Systematik Evolutionsteori Kilder Lars Skipper: Hvad er en art? Citat: "...Arten er den eneste [klassifikations-kategori] der eksisterer i virkeligheden, alle andre (slægter, familier, ordener m.v.) er indført for overskuelighedens skyld..." Eksterne henvisninger 2003-12-31, ScienceDaily: Working On The 'Porsche Of Its Time': New Model For Species Determination Offered Citat: "...two species of dinosaur that are members of the same genera varied from each other by just 2.2 percent. Translation of the percentage into an actual number results in an average of just three skeletal differences out of the total 338 bones in the body. Amazingly, 58 percent of these differences occurred in the skull alone. "This is a lot less variation than I'd expected," said Novak..." 2003-08-08, ScienceDaily: Cross-species Mating May Be Evolutionarily Important And Lead To Rapid Change, Say Indiana University Researchers Citat: "...the sudden mixing of closely related species may occasionally provide the energy to impel rapid evolutionary change..." 2004-01-09 ScienceDaily: Mayo Researchers Observe Genetic Fusion Of Human, Animal Cells; May Help Explain Origin Of AIDS Citat: "...The researchers have discovered conditions in which pig cells and human cells can fuse together in the body to yield hybrid cells that contain genetic material from both species..."What we found was completely unexpected," says Jeffrey Platt, M.D..." 2000-09-18, ScienceDaily: Scientists Unravel Ancient Evolutionary History Of Photosynthesis Citat: "...gene-swapping was common among ancient bacteria early in evolution..." 2004-06-07, Sciencedaily: Parting Genomes: University Of Arizona Biologists Discover Seeds Of Speciation Citat: "...There's a huge amount of biodiversity out there, and we don't know where it comes from. Evolutionary biologists are excited to figure out what causes what we see out there--the relative forces of selection and drift--whether things are adapting to their environment or variation is random..." 2005-07-05, Sciencedaily: Trees, Vines And Nets -- Microbial Evolution Changes Its Face Citat: "... EBI researchers have changed our view of 4 billion years of microbial evolution...In all, more than 600,000 vertical transfers are observed, coupled with 90,000 gene loss events and approximately 40,000 horizontal gene transfers...A few species, including beneficial nitrogen-fixing soil bacteria, appear to be 'champions'of horizontal gene transfer; "it's entirely possible that apparently harmless organisms are quietly spreading antibiotic resistance under our feet," concludes Christos Ouzounis..." 2005-11-11, Sciencedaily: Lateral Thinking Produces First Map Of Gene Transmission Citat: "...Their results clearly show genetic modification of organisms by lateral transfer is a widespread natural phenomenon, and it can occur even between distantly related organisms... it was assumed that transfer of genes could only be vertical, i.e. from parents to offspring..." Økologi Biologi	danish	0.791178
neanderthals_vitamin_C_diet/Healthy_diet.txt	A healthy diet is a diet that maintains or improves overall health. A healthy diet provides the body with essential nutrition: fluid, macronutrients such as protein, micronutrients such as vitamins, and adequate fibre and food energy. A healthy diet may contain fruits, vegetables, and whole grains, and may include little to no ultra-processed foods or sweetened beverages. The requirements for a healthy diet can be met from a variety of plant-based and animal-based foods, although additional sources of vitamin B12 are needed for those following a vegan diet. Various nutrition guides are published by medical and governmental institutions to educate individuals on what they should be eating to be healthy. Nutrition facts labels are also mandatory in some countries to allow consumers to choose between foods based on the components relevant to health. Recommendations World Health Organization The World Health Organization (WHO) makes the following five recommendations with respect to both populations and individuals: Maintain a healthy weight by eating roughly the same number of calories that your body is using. Limit intake of fats to no more than 30% of total caloric intake, preferring unsaturated fats to saturated fats. Avoid trans fats. Eat at least 400 grams of fruits and vegetables per day (not counting potatoes, sweet potatoes, cassava, and other starchy roots). A healthy diet also contains legumes (e.g. lentils, beans), whole grains, and nuts. Limit the intake of simple sugars to less than 10% of caloric intake (below 5% of calories or 25 grams may be even better). Limit salt/sodium from all sources and ensure that salt is iodized. Less than 5 grams of salt per day can reduce the risk of cardiovascular disease. The WHO has stated that insufficient vegetables and fruit is the cause of 2.8% of deaths worldwide. Other WHO recommendations include: ensuring that the foods chosen have sufficient vitamins and certain minerals; avoiding directly poisonous (e.g. heavy metals) and carcinogenic (e.g. benzene) substances; avoiding foods contaminated by human pathogens (e.g. E. coli, tapeworm eggs); and replacing saturated fats with polyunsaturated fats in the diet, which can reduce the risk of coronary artery disease and diabetes. United States Department of Agriculture Main article: History of USDA nutrition guides Main article: MyPlate The Dietary Guidelines for Americans by the United States Department of Agriculture (USDA) recommends three healthy patterns of diet, summarized in the table below, for a 2000 kcal diet. These guidelines are increasingly adopted by various groups and institutions for recipe and meal plan development. The guidelines emphasize both health and environmental sustainability and a flexible approach. The committee that drafted it wrote: "The major findings regarding sustainable diets were that a diet higher in plant-based foods, such as vegetables, fruits, whole grains, legumes, nuts, and seeds, and lower in calories and animal-based foods is more health promoting and is associated with less environmental impact than is the current U.S. diet. This pattern of eating can be achieved through a variety of dietary patterns, including the "Healthy U.S.-style Pattern", the "Healthy Vegetarian Pattern" and the "Healthy Mediterranean-style Pattern". Food group amounts are per day, unless noted per week. The three healthy patterns Food group/subgroup (units) U.S. style Vegetarian Med-style Fruits (cup eq) 2 2 2.5 Vegetables (cup eq) 2.5 2.5 2.5 Dark green 1.5/wk 1.5/wk 1.5/wk Red/orange 5.5/wk 5.5/wk 5.5/wk Starchy 5/wk 5/wk 5/wk Legumes 1.5/wk 3/wk 1.5/wk Others 4/wk 4/wk 4/wk Grains (oz eq) 6 6.5 6 Whole 3 3.5 3 Refined 3 3 3 Dairy (cup eq) 3 3 2 Protein Foods (oz eq) 5.5 3.5 6.5 Meat (red and processed) 12.5/wk – 12.5/wk Poultry 10.5/wk – 10.5/wk Seafood 8/wk – 15/wk Eggs 3/wk 3/wk 3/wk Nuts/seeds 4/wk 7/wk 4/wk Processed Soy (including tofu) 0.5/wk 8/wk 0.5/wk Oils (grams) 27 27 27 Solid fats limit (grams) 18 21 17 Added sugars limit (grams) 30 36 29 American Heart Association / World Cancer Research Fund / American Institute for Cancer Research The American Heart Association, World Cancer Research Fund, and American Institute for Cancer Research recommend a diet that consists mostly of unprocessed plant foods, with emphasis on a wide range of whole grains, legumes, and non-starchy vegetables and fruits. This healthy diet includes a wide range of non-starchy vegetables and fruits which provide different colors including red, green, yellow, white, purple, and orange. The recommendations note that tomato cooked with oil, allium vegetables like garlic, and cruciferous vegetables like cauliflower, provide some protection against cancer. This healthy diet is low in energy density, which may protect against weight gain and associated diseases. Finally, limiting consumption of sugary drinks, limiting energy-rich foods, including "fast foods" and red meat, and avoiding processed meats improves health and longevity. Overall, researchers and medical policymakers conclude that this healthy diet can reduce the risk of chronic disease and cancer. It is recommended that children consume 25 grams or less of added sugar (100 calories) per day. Other recommendations include no extra sugars in those under two years old and less than one soft drink per week. As of 2017, decreasing total fat is no longer recommended, but instead, the recommendation to lower risk of cardiovascular disease is to increase consumption of monounsaturated fats and polyunsaturated fats, while decreasing consumption of saturated fats. Harvard School of Public Health The Nutrition Source of Harvard School of Public Health (HSPH) makes the following dietary recommendations: Eat healthy fats: healthy fats are necessary and beneficial for health. HSPH "recommends the opposite of the low-fat message promoted for decades by the USDA" and "does not set a maximum on the percentage of calories people should get each day from healthy sources of fat." Healthy fats include polyunsaturated and monounsaturated fats, found in vegetable oils, nuts, seeds, and fish. Foods containing trans fats are to be avoided, while foods high in saturated fats like red meat, butter, cheese, ice cream, coconut and palm oil negatively impact health and should be limited. Eat healthy protein: the majority of protein should come from plant sources when possible: lentils, beans, nuts, seeds, whole grains; avoid processed meats like bacon. Eat mostly vegetables, fruit, and whole grains. Drink water. Consume sugary beverages, juices, and milk only in moderation. Artificially sweetened beverages contribute to weight gain because sweet drinks cause cravings. 100% fruit juice is high in calories. The ideal amount of milk and calcium is not known today. Pay attention to salt intake from commercially prepared foods: most of the dietary salt comes from processed foods, "not from salt added to cooking at home or even from salt added at the table before eating." Vitamins and minerals: must be obtained from food because they are not produced in our body. They are provided by a diet containing healthy fats, healthy protein, vegetables, fruit, milk and whole grains. Pay attention to the carbohydrates package: the type of carbohydrates in the diet is more important than the amount of carbohydrates. Good sources for carbohydrates are vegetables, fruits, beans, and whole grains. Avoid sugared sodas, 100% fruit juice, artificially sweetened drinks, and other highly processed food. Other than nutrition, the guide recommends staying active and maintaining a healthy body weight. Others David L. Katz, who reviewed the most prevalent popular diets in 2014, noted: The weight of evidence strongly supports a theme of healthful eating while allowing for variations on that theme. A diet of minimally processed foods close to nature, predominantly plants, is decisively associated with health promotion and disease prevention and is consistent with the salient components of seemingly distinct dietary approaches. Efforts to improve public health through diet are forestalled not for want of knowledge about the optimal feeding of Homo sapiens but for distractions associated with exaggerated claims, and our failure to convert what we reliably know into what we routinely do. Knowledge in this case is not, as of yet, power; would that it were so. Marion Nestle expresses the mainstream view among scientists who study nutrition: The basic principles of good diets are so simple that I can summarize them in just ten words: eat less, move more, eat lots of fruits and vegetables. For additional clarification, a five-word modifier helps: go easy on junk foods. Follow these precepts and you will go a long way toward preventing the major diseases of our overfed society—coronary heart disease, certain cancers, diabetes, stroke, osteoporosis, and a host of others.... These precepts constitute the bottom line of what seem to be the far more complicated dietary recommendations of many health organizations and national and international governments—the forty-one "key recommendations" of the 2005 Dietary Guidelines, for example. ... Although you may feel as though advice about nutrition is constantly changing, the basic ideas behind my four precepts have not changed in half a century. And they leave plenty of room for enjoying the pleasures of food. Historically, a healthy diet was defined as a diet comprising more than 55% of carbohydrates, less than 30% of fat and about 15% of proteins. This view is currently shifting towards a more comprehensive framing of dietary needs as a global need of various nutrients with complex interactions, instead of per nutrient type needs. Specific conditions Diabetes A healthy diet in combination with being active can help those with diabetes keep their blood sugar in check. The US CDC advises individuals with diabetes to plan for regular, balanced meals and to include more nonstarchy vegetables, reduce added sugars and refined grains, and focus on whole foods instead of highly processed foods. Generally, people with diabetes and those at risk are encouraged to increase their fiber intake. Hypertension A low-sodium diet is beneficial for people with high blood pressure. A 2008 Cochrane review concluded that a long-term (more than four weeks) low-sodium diet lowers blood pressure, both in people with hypertension (high blood pressure) and in those with normal blood pressure. The DASH diet (Dietary Approaches to Stop Hypertension) is a diet promoted by the National Heart, Lung, and Blood Institute (part of the NIH, a United States government organization) to control hypertension. A major feature of the plan is limiting intake of sodium, and the diet also generally encourages the consumption of nuts, whole grains, fish, poultry, fruits, and vegetables while lowering the consumption of red meats, sweets, and sugar. It is also "rich in potassium, magnesium, and calcium, as well as protein". The Mediterranean diet, which includes limiting consumption of red meat and using olive oil in cooking, has also been shown to improve cardiovascular outcomes. Obesity Further information: Dieting Healthy diets in combination with physical exercise can be used by people who are overweight or obese to lose weight, although this approach is not by itself an effective long-term treatment for obesity and is primarily effective for only a short period (up to one year), after which some of the weight is typically regained. A meta-analysis found no difference between diet types (low-fat, low-carbohydrate, and low-calorie), with a 2–4 kilograms (4.4–8.8 lb) weight loss. This level of weight loss is by itself insufficient to move a person from an 'obese' body mass index (BMI) category to a 'normal' BMI. Gluten-related disorders Further information: Gluten-free diet Gluten, a mixture of proteins found in wheat and related grains including barley, rye, oat, and all their species and hybrids (such as spelt, kamut, and triticale), causes health problems for those with gluten-related disorders, including celiac disease, non-celiac gluten sensitivity, gluten ataxia, dermatitis herpetiformis, and wheat allergy. In these people, the gluten-free diet is the only available treatment. Epilepsy Further information: Ketogenic diet The ketogenic diet is a treatment to reduce epileptic seizures for adults and children when managed by a health care team. Research Further information: Diet and cancer Preliminary research indicated that a diet high in fruit and vegetables may decrease the risk of cardiovascular disease and death, but not cancer. Eating a healthy diet and getting enough exercise can maintain body weight within the normal range and reduce the risk of obesity in most people. A 2021 scientific review of evidence on diets for lowering the risk of atherosclerosis found that: low consumption of salt and foods of animal origin, and increased intake of plant-based foods—whole grains, fruits, vegetables, legumes, and nuts—are linked with reduced atherosclerosis risk. The same applies for the replacement of butter and other animal/tropical fats with olive oil and other unsaturated-fat-rich oil. [...] With regard to meat, new evidence differentiates processed and red meat—both associated with increased CVD risk—from poultry, showing a neutral relationship with CVD for moderate intakes. [...] New data endorse the replacement of most high glycemic index (GI) foods with both whole grain and low GI cereal foods. Scientific research is also investigating impacts of nutrition on health- and lifespans beyond any specific range of diseases. This section is transcluded from Life extension#Healthy diet. (edit \| history) Research suggests that increasing adherence to Mediterranean diet patterns is associated with a reduction in total and cause-specific mortality, extending health- and lifespan. Research is identifying the key beneficial components of the Mediterranean diet. Studies suggest dietary changes are a factor of national relative rises in life-span. Optimal diet See also: Sustainable consumption § Sustainable food consumption Approaches to develop optimal diets for health- and lifespan (or "longevity diets") include: modifying the Mediterranean diet as the baseline via nutrition science. For instance, via: (additional) increase in plant-based foods alongside additional restriction of meat intake – meat reduction is (or can be) typically healthy, keeping alcohol consumption of any type at a minimum – conventional Mediterranean diets include alcohol consumption (i.e. of wine), which is under research due to data suggesting negative long-term brain impacts even at low/moderate consumption levels. fully replacing refined grains – some guidelines of Mediterranean diets do not clarify or include the principle of whole-grain consumption instead of refined grains. Whole grains are included in Mediterranean diets. Moreover, not only do the components of diets matter but the total caloric content and eating patterns may also impact health – dietary restriction such as caloric restriction is considered to be potentially healthy to include in eating patterns in various ways in terms of health- and lifespan. Unhealthy diets An unhealthy diet is a major risk factor for a number of chronic diseases including: high blood pressure, high cholesterol, diabetes, abnormal blood lipids, overweight/obesity, cardiovascular diseases, and cancer. The World Health Organization has estimated that 2.7 million deaths each year are attributable to a diet low in fruit and vegetables during the 21st century. Globally, such diets are estimated to cause about 19% of gastrointestinal cancer, 31% of ischaemic heart disease, and 11% of strokes, thus making it one of the leading preventable causes of death worldwide, and the 4th leading risk factor for any disease. As an example, the Western pattern diet is "rich in red meat, dairy products, processed and artificially sweetened foods, and salt, with minimal intake of fruits, vegetables, fish, legumes, and whole grains," contrasted by the Mediterranean diet which is associated with less morbidity and mortality. Dietary patterns that lead to non-communicable diseases generate productivity losses. A true cost accounting (TCA) assessment on the hidden impacts of agrifood systems estimated that unhealthy dietary patterns generate more than USD 9 trillion in health-related hidden costs in 2020, which is 73 percent of the total quantified hidden costs of global agrifood systems (USD 12.7 trillion). Globally, the average productivity losses per person from dietary intake is equivalent to 7 percent of GDP purchasing power parity (PPP) in 2020; low-income countries report the lowest value (4 percent), while other income categories report 7 percent or higher. Fad diet Further information: Fad diet Some publicized diets, often referred to as fad diets, make exaggerated claims of fast weight loss or other health advantages, such as longer life or detoxification without clinical evidence; many fad diets are based on highly restrictive or unusual food choices. Celebrity endorsements (including celebrity doctors) are frequently associated with such diets, and the individuals who develop and promote these programs often profit considerably. Public health Most of the people unable to afford a healthy diet in 2021 lived in southern Asia, and in eastern and western Africa Consumers are generally aware of the elements of a healthy diet, but find nutrition labels and diet advice in popular media confusing. Vending machines are criticized for being avenues of entry into schools for junk food promoters, but there is little in the way of regulation and it is difficult for most people to properly analyze the real merits of a company referring to itself as "healthy." The Committee of Advertising Practice in the United Kingdom launched a proposal to limit media advertising for food and soft drink products high in fat, salt, or sugar. The British Heart Foundation released its own government-funded advertisements, labeled "Food4Thought", which were targeted at children and adults to discourage unhealthy habits of consuming junk food. From a psychological and cultural perspective, a healthier diet may be difficult to achieve for people with poor eating habits. This may be due to tastes acquired in childhood and preferences for sugary, salty, and fatty foods. In 2018, the UK chief medical officer recommended that sugar and salt be taxed to discourage consumption. The UK government 2020 Obesity Strategy encourages healthier choices by restricting point-of-sale promotions of less-healthy foods and drinks. The effectiveness of population-level health interventions has included food pricing strategies, mass media campaigns and worksite wellness programs. One peso per liter of sugar-sweetened beverages (SSB) price intervention implemented in Mexico produced a 12% reduction in SSB purchasing. Mass media campaigns in Pakistan and the USA aimed at increasing vegetable and fruit consumption found positive changes in dietary behavior. Reviews of the effectiveness of worksite wellness interventions found evidence linking the programs to weight loss and increased fruit and vegetable consumption. Other animals Animals that are kept by humans also benefit from a healthy diet, but the requirements of such diets may be very different from the ideal human diet. See also Food portal Commercial determinants of health Healthy eating pyramid List of diets Meals Nutritionism Nutrition scale Nutritional rating systems Planetary Health Diet Plant-based diet Table of food nutrients	biology	56375	https://sv.wikipedia.org/wiki/Atkinsdieten	Atkinsdieten	Atkinsdieten är en diet för viktminskning lanserad av den amerikanske läkaren Robert Atkins på 1960-talet. Dieten bygger på en kolhydratfattig kost vilket medför att fet mat och kött är tillåtet så länge inte kolhydratintaget är för stort. Kolhydrater, protein samt fett är de huvudsakliga näringsämnena i vår föda som ger bränsle/energi till kroppen. Tanken är att ca 50–75 % av kroppens behov av energi, ska komma från protein och fett – resten av energibehovet från intag av kolhydrater. Atkins teser Atkins menade att det finns två huvudsakliga fel i dagens västerländska diet: dels att man äter för mycket raffinerade kolhydrater (särskilt socker, mjöl och sirap), dels att man generellt är för rädd för mättat fett. Enligt Atkins är det transfetter som ska undvikas snarare än mättat fett. Tyngdpunkten i dieten ligger på kosten, men i kostplanen lägger man även vikt vid näringstillskott och daglig motion. Dietplanen Atkinsdieten begränsar intaget av kolhydrater i syfte att få kroppen att ställa om från förbränning av främst glukos till förmån för förbränning av kroppsfetter. Denna process (lipolys) tar vid när kroppen går ner i ketos efter det att den gjort slut på överskott av kolhydrater att bränna. Enligt Atkins innebär detta att kroppen gör av med mer energi för att tillgodose kroppens näringsbehov. Atkinsdieten fokuserar på att minimera intaget av kolhydrater som har effekt på blodsockret. Atkins förordar att man äter livsmedel som bearbetats så lite som möjligt och som har lågt glykemiskt index. Atkinsdieten har fyra faser: Induktionsfas, viktminskningsfas, fas mellan viktminskning och underhållsfas, och underhållsfasen. I induktionsfasen (som Atkinsdieten mest är känd för) så syftar dieten till att försätta kroppen i ketos. Kolhydratintaget begränsas till 20 gram per dag (12–15 gram av dessa 20 gram kolhydrater, bör komma i form av bladgrönsaker). Tillåten mat är obegränsad mängd kött, fisk, skaldjur, ägg, olivolja, majonnäs, ost och vissa grönsaker; t.ex. gurka och sallad. Enbart grönsaker som är gröna och växer ovan mark får ätas i denna fas. Det som ska väljas bort i kosten är socker, mjölk, frukt, pasta, ris, flingor, bönor, potatis och andra rotfrukter. Upp till 110 gram hårdost får ätas per dag. Alkohol ska inte intas i denna fas. Koffein begränsas. Dagligt intag av multivitamintabletter rekommenderas. Motion förordas. Fasen pågår i två veckor eller tills bantaren tappat 10 % av sin övervikt. Under viktminskningsfasen ökas kolhydratintaget med 2 gram per vecka. Nu minskar restriktionerna och man får då äta alla sorters grönsaker och små mängder spannmål, men socker av alla de slag är fortfarande förbjudet. I den här fasen ska bantaren försöka hitta vilken nivå på kolhydratintag som är kritisk för viktminskning och bedöma vilka livsmedel som förorsakar personliga ätbegär. Nu bromsas viktminskningen genom att intaget av nettokolhydrater gradvis ökar. Nettokolhydrater är kolhydrater som påverkar blodsockret och därmed produktionen av det fettlagrande hormonet insulin. Denna fas pågår till dess att bantaren är cirka 4 kilo ifrån sin målvikt. Nästa fas går ut på att hitta en balansnivå för kolhydratintag. Bantaren ökar kolhydratintaget med 10 gram per vecka och följer upp var gränsen går innan bantaren börjar att öka i vikt igen. Nu anses det inte längre viktigt att kroppen är i ketos. När du närmar dig din målvikt kan du börja äta andra kolhydrater från t.ex. frukt och fullkornsprodukter. Även grönsaker med stärkelse, till exempel morötter, majs eller squash. Underhållsfasen är avsedd att vara livslång. Bantaren ska fortsätta äta enligt de vanor han eller hon skaffat sig under de tidigare faserna. Huvudprincipen för dieten är fortfarande att graden av bearbetning av de livsmedel man förtär ska vara så låg som möjligt. Om vikten börjar öka igen kan bantaren börja om från början med induktionsfasen. Tillåtna födoämnen Kött Fisk Grönsaker Ägg Mjölkprodukter Ej tillåtna livsmedel Potatis Bröd Ris Pasta Socker/Sockrade livsmedel Studier Flera ettårstudier har visat att de som äter enligt Atkinsdieten har gått ner i vikt i samma utsträckning eller mer än bantare som äter enligt andra dietplaner. I ettårsperspektivet har inga negativa hälsokonsekvenser påfunnits. Den kortsiktiga viktminskningen tros, snarare än förändring av metabolismen, bero på att dieten dämpar hungerkänslorna och att den genom sitt låga innehåll av socker och stärkelse reducerar den vattenbindande glukosreserven och därigenom minskar mängden vatten i kroppen.. Senare studier har visat att högt proteinintag har just denna hungerdämpande effekt, medan fettrik mat inte alls är verksam på detta plan.. Positiva resultat med Atkinsmetoden beror således i huvudsak på att en proteinrik födas hungerdämpande effekt ger ett lägre kaloriintag än på förändringar i metabolismen En större studie publicerades i JAMA i mars 2007 av Gardner vid Stanforduniversitetet och visade att överviktiga men i övrigt friska kvinnor i åldrarna 25–50 år tappat mer vikt med Atkinsdieten än med bantningsmetoder som tillåter ett högre kolhydratintag. Viktminskningen med Atkins hade varit 4,7 kilo i genomsnitt, att jämföra med 2,6 kilo för dem som ätit enligt "LEARN", 2,2 kilo för "Ornish" och 1,6 kilo för "the Zone". När värden för HDL (det så kallade goda kolesterolet), triglycerider och blodtryck jämfördes fanns en klar fördel för Atkinsdieten. Studien omfattade två månader med uppföljning under ytterligare 10 månader. En forskningsrapport stödjer att mättat fett under vissa förutsättningar kan skydda hjärtat hos kvinnor som genomgått klimakteriet, vilket ifrågasätter men dock inte omkullkastar, den allmänt vedertagna uppfattning och sambandet mellan mättat fett och hjärt- och kärlsjukdom. Se även Glykemiskt index Annika Dahlqvist Noter Bantning	swedish	0.712836
neanderthals_vitamin_C_diet/Neanderthal.txt	Neanderthals (/niˈændərˌtɑːl, neɪ-, -ˌθɑːl/ nee-AN-də(r)-TAHL, nay-, -⁠THAHL; Homo neanderthalensis or H. sapiens neanderthalensis) are an extinct group of archaic humans (generally regarded as a distinct species, though some regard it as a subspecies of Homo sapiens) who lived in Eurasia until about 40,000 years ago. The type specimen, Neanderthal 1, was found in 1856 in the Neander Valley in present-day Germany. It is not clear when the line of Neanderthals split from that of modern humans; studies have produced various times ranging from 315,000 to more than 800,000 years ago. The date of divergence of Neanderthals from their ancestor H. heidelbergensis is also unclear. The oldest potential Neanderthal bones date to 430,000 years ago, but the classification remains uncertain. Neanderthals are known from numerous fossils, especially from after 130,000 years ago. The reasons for Neanderthal extinction are disputed. Theories for their extinction include demographic factors such as small population size and inbreeding, competitive replacement, interbreeding and assimilation with modern humans, change of climate, disease, or a combination of these factors. For much of the early 20th century, European researchers depicted Neanderthals as primitive, unintelligent and brutish. Although knowledge and perception of them has markedly changed since then in the scientific community, the image of the unevolved caveman archetype remains prevalent in popular culture. In truth, Neanderthal technology was quite sophisticated. It includes the Mousterian stone-tool industry as well as the abilities to create fire, build cave hearths (to cook food, keep warm, defend themselves from animals, placing it at the centre of their homes), make adhesive birch bark tar, craft at least simple clothes similar to blankets and ponchos, weave, go seafaring through the Mediterranean, make use of medicinal plants, treat severe injuries, store food, and use various cooking techniques such as roasting, boiling, and smoking. Neanderthals consumed a wide array of food, mainly hoofed mammals, but also megafauna, plants, small mammals, birds, and aquatic and marine resources. Although they were probably apex predators, they still competed with cave lions, cave hyenas and other large predators. A number of examples of symbolic thought and Palaeolithic art have been inconclusively attributed to Neanderthals, namely possible ornaments made from bird claws and feathers, shells, collections of unusual objects including crystals and fossils, engravings, music production (possibly indicated by the Divje Babe flute), and Spanish cave paintings contentiously dated to before 65,000 years ago. Some claims of religious beliefs have been made. Neanderthals were likely capable of speech, possibly articulate, although the complexity of their language is not known. Compared with modern humans, Neanderthals had a more robust build and proportionally shorter limbs. Researchers often explain these features as adaptations to conserve heat in a cold climate, but they may also have been adaptations for sprinting in the warmer, forested landscape that Neanderthals often inhabited. They had cold-specific adaptations, such as specialised body-fat storage and an enlarged nose to warm air (although the nose could have been caused by genetic drift). Average Neanderthal men stood around 165 cm (5 ft 5 in) and women 153 cm (5 ft 0 in) tall, similar to pre-industrial modern Europeans. The braincases of Neanderthal men and women averaged about 1,600 cm (98 cu in) and 1,300 cm (79 cu in), respectively, which is considerably larger than the modern human average (1,260 cm (77 cu in) and 1,130 cm (69 cu in), respectively). The Neanderthal skull was more elongated and the brain had smaller parietal lobes and cerebellum, but larger temporal, occipital and orbitofrontal regions. The total population of Neanderthals remained low, proliferating weakly harmful gene variants and precluding effective long-distance networks. Despite this, there is evidence of regional cultures and regular communication between communities. They may have frequented caves and moved between them seasonally. Neanderthals lived in a high-stress environment with high trauma rates, and about 80% died before the age of 40. The 2010 Neanderthal genome project's draft report presented evidence for interbreeding between Neanderthals and modern humans. It possibly occurred 316,000 to 219,000 years ago, but more likely 100,000 years ago and again 65,000 years ago. Neanderthals also appear to have interbred with Denisovans, a different group of archaic humans, in Siberia. Around 1–4% of genomes of Eurasians, Indigenous Australians, Melanesians, Native Americans and North Africans is of Neanderthal ancestry, while most inhabitants of sub-Saharan Africa have around 0.3% of Neanderthal genes, save possible traces from early sapiens-to-Neanderthal gene flow and/or more recent back-migration of Eurasians to Africa. In all, about 20% of distinctly Neanderthal gene variants survive in modern humans. Although many of the gene variants inherited from Neanderthals may have been detrimental and selected out, Neanderthal introgression appears to have affected the modern human immune system, and is also implicated in several other biological functions and structures, but a large portion appears to be non-coding DNA. Neanderthals are named after the Neander Valley in which the first identified specimen was found. The valley was spelled Neanderthal and the species was spelled Neanderthaler in German until the spelling reform of 1901. The spelling Neandertal for the species is occasionally seen in English, even in scientific publications, but the scientific name, H. neanderthalensis, is always spelled with th according to the principle of priority. The vernacular name of the species in German is always Neandertaler ("inhabitant of the Neander Valley"), whereas Neandertal always refers to the valley. The valley itself was named after the late 17th century German theologian and hymn writer Joachim Neander, who often visited the area. His name in turn means 'new man', being a learned Graecisation of the German surname Neumann. Neanderthal can be pronounced using the /t/ (as in /niˈændərtɑːl/) or the standard English pronunciation of th with the fricative /θ/ (as /niˈændərθɔːl/). Neanderthal 1, the type specimen, was known as the "Neanderthal cranium" or "Neanderthal skull" in anthropological literature, and the individual reconstructed on the basis of the skull was occasionally called "the Neanderthal man". The binomial name Homo neanderthalensis—extending the name "Neanderthal man" from the individual specimen to the entire species, and formally recognising it as distinct from humans—was first proposed by Irish geologist William King in a paper read to the 33rd British Science Association in 1863. However, in 1864, he recommended that Neanderthals and modern humans be classified in different genera as he compared the Neanderthal braincase to that of a chimpanzee and argued that they were "incapable of moral and [theistic] conceptions". The first Neanderthal remains—Engis 2 (a skull)—were discovered in 1829 by Dutch/Belgian prehistorian Philippe-Charles Schmerling in the Grottes d'Engis, Belgium. He concluded that these "poorly developed" human remains must have been buried at the same time and by the same causes as the co-existing remains of extinct animal species. In 1848, Gibraltar 1 from Forbes' Quarry was presented to the Gibraltar Scientific Society by their Secretary Lieutenant Edmund Henry Réné Flint, but was thought to be a modern human skull. In 1856, local schoolteacher Johann Carl Fuhlrott recognised bones from Kleine Feldhofer Grotte in Neander Valley—Neanderthal 1 (the holotype specimen)—as distinct from modern humans, and gave them to German anthropologist Hermann Schaaffhausen to study in 1857. It comprised the cranium, thigh bones, right arm, left humerus and ulna, left ilium (hip bone), part of the right shoulder blade, and pieces of the ribs. Following Charles Darwin's On the Origin of Species, Fuhlrott and Schaaffhausen argued the bones represented an ancient modern human form; Schaaffhausen, a social Darwinist, believed that humans linearly progressed from savage to civilised, and so concluded that Neanderthals were barbarous cave-dwellers. Fuhlrott and Schaaffhausen met opposition namely from the prolific pathologist Rudolf Virchow who argued against defining new species based on only a single find. In 1872, Virchow erroneously interpreted Neanderthal characteristics as evidence of senility, disease and malformation instead of archaicness, which stalled Neanderthal research until the end of the century. By the early 20th century, numerous other Neanderthal discoveries were made, establishing H. neanderthalensis as a legitimate species. The most influential specimen was La Chapelle-aux-Saints 1 ("The Old Man") from La Chapelle-aux-Saints, France. French palaeontologist Marcellin Boule authored several publications, among the first to establish palaeontology as a science, detailing the specimen, but reconstructed him as slouching, ape-like, and only remotely related to modern humans. The 1912 'discovery' of Piltdown Man (a hoax), appearing much more similar to modern humans than Neanderthals, was used as evidence that multiple different and unrelated branches of primitive humans existed, and supported Boule's reconstruction of H. neanderthalensis as a far distant relative and an evolutionary dead-end. He fuelled the popular image of Neanderthals as barbarous, slouching, club-wielding primitives; this image was reproduced for several decades and popularised in science fiction works, such as the 1911 The Quest for Fire by J.-H. Rosny aîné and the 1927 The Grisly Folk by H. G. Wells in which they are depicted as monsters. In 1911, Scottish anthropologist Arthur Keith reconstructed La Chapelle-aux-Saints 1 as an immediate precursor to modern humans, sitting next to a fire, producing tools, wearing a necklace, and having a more humanlike posture, but this failed to garner much scientific rapport, and Keith later abandoned his thesis in 1915. By the middle of the century, based on the exposure of Piltdown Man as a hoax as well as a reexamination of La Chapelle-aux-Saints 1 (who had osteoarthritis which caused slouching in life) and new discoveries, the scientific community began to rework its understanding of Neanderthals. Ideas such as Neanderthal behaviour, intelligence and culture were being discussed, and a more humanlike image of them emerged. In 1939, American anthropologist Carleton Coon reconstructed a Neanderthal in a modern business suit and hat to emphasise that they would be, more or less, indistinguishable from modern humans had they survived into the present. William Golding's 1955 novel The Inheritors depicts Neanderthals as much more emotional and civilised. However, Boule's image continued to influence works until the 1960s. In modern-day, Neanderthal reconstructions are often very humanlike. Hybridisation between Neanderthals and early modern humans had been suggested early on, such as by English anthropologist Thomas Huxley in 1890, Danish ethnographer Hans Peder Steensby in 1907, and Coon in 1962. In the early 2000s, supposed hybrid specimens were discovered: Lagar Velho 1 and Muierii 1. However, similar anatomy could also have been caused by adapting to a similar environment rather than interbreeding. Neanderthal admixture was found to be present in modern populations in 2010 with the mapping of the first Neanderthal genome sequence. This was based on three specimens in Vindija Cave, Croatia, which contained almost 4% archaic DNA (allowing for near complete sequencing of the genome). However, there was approximately 1 error for every 200 letters (base pairs) based on the implausibly high mutation rate, probably due to the preservation of the sample. In 2012, British-American geneticist Graham Coop hypothesised that they instead found evidence of a different archaic human species interbreeding with modern humans, which was disproven in 2013 by the sequencing of a high-quality Neanderthal genome preserved in a toe bone from Denisova Cave, Siberia. Neanderthals are hominids in the genus Homo, humans, and generally classified as a distinct species, H. neanderthalensis, although sometimes as a subspecies of modern human as Homo sapiens neanderthalensis. This would necessitate the classification of modern humans as H. sapiens sapiens. A large part of the controversy stems from the vagueness of the term "species", as it is generally used to distinguish two genetically isolated populations, but admixture between modern humans and Neanderthals is known to have occurred. However, the absence of Neanderthal-derived patrilineal Y-chromosome and matrilineal mitochondrial DNA (mtDNA) in modern humans, along with the underrepresentation of Neanderthal X chromosome DNA, could imply reduced fertility or frequent sterility of some hybrid crosses, representing a partial biological reproductive barrier between the groups, and therefore species distinction. In 2014 geneticist Svante Pääbo summarised the controversy, describing such "taxonomic wars" as unresolvable, "since there is no definition of species perfectly describing the case". Neanderthals are thought to have been more closely related to Denisovans than to modern humans. Likewise, Neanderthals and Denisovans share a more recent last common ancestor (LCA) than to modern humans, based on nuclear DNA (nDNA). However, Neanderthals and modern humans share a more recent mitochondrial LCA (observable by studying mtDNA). This likely resulted from an interbreeding event subsequent to the Neanderthal/Denisovan split which introduced another mtDNA line. This involved either introgression coming from an unknown archaic human into Denisovans, or introgression from an earlier unidentified modern human wave from Africa into Neanderthals. It is largely thought that H. heidelbergensis was the last common ancestor of Neanderthals, Denisovans and modern humans before populations became isolated in Europe, Asia and Africa, respectively. The taxonomic distinction between H. heidelbergensis and Neanderthals is mostly based on a fossil gap in Europe between 300 and 243,000 years ago during marine isotope stage 8. "Neanderthals", by convention, are fossils which date to after this gap. However, 430,000-year-old bones at Sima de los Huesos could represent early Neanderthals or a closely related group, and the 400,000-year-old Aroeira 3 could represent a transitional phase. Ancestral and derived morphs could have lived concurrently. It is also possible that there was gene flow between Western Europe and Africa during the Middle Pleistocene, obscuring Neanderthal characteristics in such specimens, namely from Ceprano, Italy, and Sićevo Gorge, Serbia. The fossil record is much more complete from 130,000 years ago onwards, and specimens from this period make up the bulk of known Neanderthal skeletons. Dental remains from the Italian Visogliano and Fontana Ranuccio sites indicate that Neanderthal dental features had evolved by around 450–430,000 years ago during the Middle Pleistocene. There are two main hypotheses regarding the evolution of Neanderthals following the Neanderthal/human split: two-phase and accretion. Two-phase argues that a single major environmental event—such as the Saale glaciation—caused European H. heidelbergensis to increase rapidly in body size and robustness, as well as undergoing a lengthening of the head (phase 1), which then led to other changes in skull anatomy (phase 2). However, Neanderthal anatomy may not have been driven entirely by adapting to cold weather. Accretion holds that Neanderthals slowly evolved over time from the ancestral H. heidelbergensis, divided into four stages: early-pre-Neanderthals (MIS 12, Elster glaciation), pre-Neanderthals sensu lato (MIS 11–9, Holstein interglacial), early Neanderthals (MIS 7–5, Saale glaciation–Eemian), and classic Neanderthals sensu stricto (MIS 4–3, Würm glaciation). Numerous dates for the Neanderthal/human split have been suggested. The date of around 250,000 years ago cites "H. helmei" as being the last common ancestor (LCA), and the split is associated with the Levallois technique of making stone tools. The date of about 400,000 years ago uses H. heidelbergensis as the LCA. Estimates of 600,000 years ago assume that "H. rhodesiensis" was the LCA, which split off into modern human lineage and a Neanderthal/H. heidelbergensis lineage. Eight hundred thousand years ago has H. antecessor as the LCA, but different variations of this model would push the date back to 1 million years ago. However, a 2020 analysis of H. antecessor enamel proteomes suggests that H. antecessor is related but not a direct ancestor. DNA studies have yielded various results for the Neanderthal/human divergence time, such as 538–315, 553–321, 565–503, 654–475, 690–550, 765–550, 741–317, and 800–520,000 years ago; and a dental analysis concluded before 800,000 years ago. Neanderthals and Denisovans are more closely related to each other than they are to modern humans, meaning the Neanderthal/Denisovan split occurred after their split with modern humans. Assuming a mutation rate of 1 × 10 or 0.5 × 10 per base pair (bp) per year, the Neanderthal/Denisovan split occurred around either 236–190,000 or 473–381,000 years ago, respectively. Using 1.1 × 10 per generation with a new generation every 29 years, the time is 744,000 years ago. Using 5 × 10 nucleotide sites per year, it is 616,000 years ago. Using the latter dates, the split had likely already occurred by the time hominins spread out across Europe, and unique Neanderthal features had begun evolving by 600–500,000 years ago. Before splitting, Neanderthal/Denisovans (or "Neandersovans") migrating out of Africa into Europe apparently interbred with an unidentified "superarchaic" human species who were already present there; these superarchaics were the descendants of a very early migration out of Africa around 1.9 mya. Pre- and early Neanderthals, living before the Eemian interglacial (130,000 years ago), are poorly known and come mostly from Western European sites. From 130,000 years ago onwards, the quality of the fossil record increases dramatically with classic Neanderthals, who are recorded from Western, Central, Eastern and Mediterranean Europe, as well as Southwest, Central and Northern Asia up to the Altai Mountains in southern Siberia. Pre- and early Neanderthals, on the other hand, seem to have continuously occupied only France, Spain and Italy, although some appear to have moved out of this "core-area" to form temporary settlements eastward (although without leaving Europe). Nonetheless, southwestern France has the highest density of sites for pre-, early and classic Neanderthals. The Neanderthals were the first human species to permanently occupy Europe as the continent was only sporadically occupied by earlier humans. The southernmost find was recorded at Shuqba Cave, Levant; reports of Neanderthals from the North African Jebel Irhoud and Haua Fteah have been reidentified as H. sapiens. Their easternmost presence is recorded at Denisova Cave, Siberia 85°E; the southeast Chinese Maba Man, a skull, shares several physical attributes with Neanderthals, although these may be the result of convergent evolution rather than Neanderthals extending their range to the Pacific Ocean. The northernmost bound is generally accepted to have been 55°N, with unambiguous sites known between 50–53°N, although this is difficult to assess because glacial advances destroy most human remains, and palaeoanthropologist Trine Kellberg Nielsen has argued that a lack of evidence of Southern Scandinavian occupation is (at least during the Eemian interglacial) due to the former explanation and a lack of research in the area. Middle Palaeolithic artefacts have been found up to 60°N on the Russian plains, but these are more likely attributed to modern humans. A 2017 study claimed the presence of Homo at the 130,000-year-old Californian Cerutti Mastodon site in North America, but this is largely considered implausible. It is unknown how the rapidly fluctuating climate of the last glacial period (Dansgaard–Oeschger events) impacted Neanderthals, as warming periods would produce more favourable temperatures but encourage forest growth and deter megafauna, whereas frigid periods would produce the opposite. However, Neanderthals may have preferred a forested landscape. Stable environments with mild mean annual temperatures may have been the most suitable Neanderthal habitats. Populations may have peaked in cold but not extreme intervals, such as marine isotope stages 8 and 6 (respectively, 300,000 and 191,000 years ago during the Saale glaciation). It is possible their range expanded and contracted as the ice retreated and grew, respectively, to avoid permafrost areas, residing in certain refuge zones during glacial maxima. In 2021, Israeli anthropologist Israel Hershkovitz and colleagues suggested the 140- to 120,000-year-old Israeli Nesher Ramla remains, which feature a mix of Neanderthal and more ancient H. erectus traits, represent one such source population which recolonised Europe following a glacial period. Like modern humans, Neanderthals probably descended from a very small population with an effective population—the number of individuals who can bear or father children—of 3,000 to 12,000 approximately. However, Neanderthals maintained this very low population, proliferating weakly harmful genes due to the reduced effectivity of natural selection. Various studies, using mtDNA analysis, yield varying effective populations, such as about 1,000 to 5,000; 5,000 to 9,000 remaining constant; or 3,000 to 25,000 steadily increasing until 52,000 years ago before declining until extinction. Archaeological evidence suggests that there was a tenfold increase in the modern human population in Western Europe during the period of the Neanderthal/modern human transition, and Neanderthals may have been at a demographic disadvantage due to a lower fertility rate, a higher infant mortality rate, or a combination of the two. Estimates giving a total population in the higher tens of thousands are contested. A consistently low population may be explained in the context of the "Boserupian Trap": a population's carrying capacity is limited by the amount of food it can obtain, which in turn is limited by its technology. Innovation increases with population, but if the population is too low, innovation will not occur very rapidly and the population will remain low. This is consistent with the apparent 150,000 year stagnation in Neanderthal lithic technology. In a sample of 206 Neanderthals, based on the abundance of young and mature adults in comparison to other age demographics, about 80% of them above the age of 20 died before reaching 40. This high mortality rate was probably due to their high-stress environment. However, it has also been estimated that the age pyramids for Neanderthals and contemporary modern humans were the same. Infant mortality was estimated to have been very high for Neanderthals, about 43% in northern Eurasia. Neanderthals had more robust and stockier builds than typical modern humans, wider and barrel-shaped rib cages; wider pelvises; and proportionally shorter forearms and forelegs. Based on 45 Neanderthal long bones from 14 men and 7 women, the average height was 164 to 168 cm (5 ft 5 in to 5 ft 6 in) for males and 152 to 156 cm (5 ft 0 in to 5 ft 1 in) for females. For comparison, the average height of 20 males and 10 females Upper Palaeolithic humans is, respectively, 176.2 cm (5 ft 9.4 in) and 162.9 cm (5 ft 4.1 in), although this decreases by 10 cm (4 in) nearer the end of the period based on 21 males and 15 females; and the average in the year 1900 was 163 cm (5 ft 4 in) and 152.7 cm (5 ft 0 in), respectively. The fossil record shows that adult Neanderthals varied from about 147.5 to 177 cm (4 ft 10 in to 5 ft 10 in) in height, although some may have grown much taller (73.8 to 184.8 cm based on footprint length and from 65.8 to 189.3 cm based on footprint width). For Neanderthal weight, samples of 26 specimens found an average of 77.6 kg (171 lb) for males and 66.4 kg (146 lb) for females. Using 76 kg (168 lb), the body mass index for Neanderthal males was calculated to be 26.9–28.2, which in modern humans correlates to being overweight. This indicates a very robust build. The Neanderthal LEPR gene concerned with storing fat and body heat production is similar to that of the woolly mammoth, and so was likely an adaptation for cold climate. The neck vertebrae of Neanderthals are thicker from the front to the rear and transversely than those of (most) modern humans, leading to stability, possibly to accommodate a different head shape and size. Although the Neanderthal thorax (where the ribcage is) was similar in size to modern humans, the longer and straighter ribs would have equated to a widened mid-lower thorax and stronger breathing in the lower thorax, which are indicative of a larger diaphragm and possibly greater lung capacity. The lung capacity of Kebara 2 was estimated to have been 9.04 L (2.39 US gal), compared to the average human capacity of 6 L (1.6 US gal) for males and 4.7 L (1.2 US gal) for females. The Neanderthal chest was also more pronounced (expanded front-to-back, or antero-posteriorly). The sacrum (where the pelvis connects to the spine) was more vertically inclined, and was placed lower in relation to the pelvis, causing the spine to be less curved (exhibit less lordosis) and to fold in on itself somewhat (to be invaginated). In modern populations, this condition affects just a proportion of the population, and is known as a lumbarized sacrum. Such modifications to the spine would have enhanced side-to-side (mediolateral) flexion, better supporting the wider lower thorax. It is claimed by some that this feature would be normal for all Homo, even tropically-adapted Homo ergaster or erectus, with the condition of a narrower thorax in most modern humans being a unique characteristic. Body proportions are usually cited as being "hyperarctic" as adaptations to the cold, because they are similar to those of human populations which developed in cold climates—the Neanderthal build is most similar to that of Inuit and Siberian Yupiks among modern humans—and shorter limbs result in higher retention of body heat. Nonetheless, Neanderthals from more temperate climates—such as Iberia—still retain the "hyperarctic" physique. In 2019, English anthropologist John Stewart and colleagues suggested Neanderthals instead were adapted for sprinting, because of evidence of Neanderthals preferring warmer wooded areas over the colder mammoth steppe, and DNA analysis indicating a higher proportion of fast-twitch muscle fibres in Neanderthals than in modern humans. He explained their body proportions and greater muscle mass as adaptations to sprinting as opposed to the endurance-oriented modern human physique, as persistence hunting may only be effective in hot climates where the hunter can run prey to the point of heat exhaustion (hyperthermia). They had longer heel bones, reducing their ability for endurance running, and their shorter limbs would have reduced moment arm at the limbs, allowing for greater net rotational force at the wrists and ankles, causing faster acceleration. In 1981, American palaeoanthropologist Erik Trinkaus made note of this alternate explanation, but considered it less likely. Neanderthals had less developed chins, sloping foreheads, and longer, broader, more projecting noses. The Neanderthal skull is typically more elongated, but also wider, and less globular than that of most modern humans, and features much more of an occipital bun, or "chignon", a protrusion on the back of the skull, although it is within the range of variation for modern humans who have it. It is caused by the cranial base and temporal bones being placed higher and more towards the front of the skull, and a flatter skullcap. The Neanderthal face is characterized by mid-facial prognathism, where the zygomatic arches are positioned in a rearward location relative to modern humans, while their maxillary bones and nasal bones are positioned in a more forward direction, by comparison. Neanderthal eyeballs are larger than those of modern humans. One study proposed that this was due to Neanderthals having enhanced visual abilities, at the expense of neocortical and social development. However, this study was rejected by other researchers who concluded that eyeball size does not offer any evidence for the cognitive abilities of Neanderthal or modern humans. The projected Neanderthal nose and paranasal sinuses have generally been explained as having warmed air as it entered the lungs and retained moisture ("nasal radiator" hypothesis); if their noses were wider, it would differ to the generally narrowed shape in cold-adapted creatures, and that it would have been caused instead by genetic drift. Also, the sinuses reconstructed wide are not grossly large, being comparable in size to those of modern humans. However, if sinus size is not an important factor for breathing cold air, then the actual function would be unclear, so they may not be a good indicator of evolutionary pressures to evolve such a nose. Further, a computer reconstruction of the Neanderthal nose and predicted soft tissue patterns shows some similarities to those of modern Arctic peoples, potentially meaning the noses of both populations convergently evolved for breathing cold, dry air. Neanderthals featured a rather large jaw which was once cited as a response to a large bite force evidenced by heavy wearing of Neanderthal front teeth (the "anterior dental loading" hypothesis), but similar wearing trends are seen in contemporary humans. It could also have evolved to fit larger teeth in the jaw, which would better resist wear and abrasion, and the increased wear on the front teeth compared to the back teeth probably stems from repetitive use. Neanderthal dental wear patterns are most similar to those of modern Inuit. The incisors are large and shovel-shaped, and, compared to modern humans, there was an unusually high frequency of taurodontism, a condition where the molars are bulkier due to an enlarged pulp (tooth core). Taurodontism was once thought to have been a distinguishing characteristic of Neanderthals which lent some mechanical advantage or stemmed from repetitive use, but was more likely simply a product of genetic drift. The bite force of Neanderthals and modern humans is now thought to be about the same, about 285 N (64 lbf) and 255 N (57 lbf) in modern human males and females, respectively. The Neanderthal braincase averages 1,640 cm (100 cu in) for males and1,460 cm (89 cu in) for females, which is significantly larger than the averages for all groups of extant humans; for example, modern European males average 1,362 cm (83.1 cu in) and females 1,201 cm (73.3 cu in). For 28 modern human specimens from 190,000 to 25,000 years ago, the average was about 1,478 cm (90.2 cu in) disregarding sex, and modern human brain size is suggested to have decreased since the Upper Palaeolithic. The largest Neanderthal brain, Amud 1, was calculated to be 1,736 cm (105.9 cu in), one of the largest ever recorded in hominids. Both Neanderthal and human infants measure about 400 cm (24 cu in). When viewed from the rear, the Neanderthal braincase has lower, wider, rounder appearance than in anatomically modern humans. This characteristic shape is referred to as "en bombe" (bomb-like), and is unique to Neanderthals, with all other hominid species (including most modern humans) generally having narrow and relatively upright cranial vaults, when viewed from behind. The Neanderthal brain would have been characterized by relatively smaller parietal lobes and a larger cerebellum. Neanderthal brains also have larger occipital lobes (relating to the classic occurrence of an occipital bun in Neanderthal skull anatomy, as well as the greater width of their skulls), which implies internal differences in the proportionality of brain-internal regions, relative to Homo sapiens, consistent with external measurements obtained with fossil skulls. Their brains also have larger temporal lobe poles, wider orbitofrontal cortex, and larger olfactory bulbs, suggesting potential differences in language comprehension and associations with emotions (temporal functions), decision making (the orbitofrontal cortex) and sense of smell (olfactory bulbs). Their brains also show different rates of brain growth and development. Such differences, while slight, would have been visible to natural selection and may underlie and explain differences in the material record in things like social behaviors, technological innovation and artistic output. The lack of sunlight most likely led to the proliferation of lighter skin in Neanderthals, although it has been recently claimed that light skin in modern Europeans was not particularly prolific until perhaps the Bronze Age. Genetically, BNC2 was present in Neanderthals, which is associated with light skin colour; however, a second variation of BNC2 was also present, which in modern populations is associated with darker skin colour in the UK Biobank. DNA analysis of three Neanderthal females from southeastern Europe indicates that they had brown eyes, dark skin colour and brown hair, with one having red hair. In modern humans, skin and hair colour is regulated by the melanocyte-stimulating hormone—which increases the proportion of eumelanin (black pigment) to phaeomelanin (red pigment)—which is encoded by the MC1R gene. There are five known variants in modern humans of the gene which cause loss-of-function and are associated with light skin and hair colour, and another unknown variant in Neanderthals (the R307G variant) which could be associated with pale skin and red hair. The R307G variant was identified in a Neanderthal from Monti Lessini, Italy, and possibly Cueva del Sidrón, Spain. However, as in modern humans, red was probably not a very common hair colour because the variant is not present in many other sequenced Neanderthals. Maximum natural lifespan and the timing of adulthood, menopause and gestation were most likely very similar to modern humans. However, it has been hypothesised, based on the growth rates of teeth and tooth enamel, that Neanderthals matured faster than modern humans, although this is not backed up by age biomarkers. The main differences in maturation are the atlas bone in the neck as well as the middle thoracic vertebrae fused about 2 years later in Neanderthals than in modern humans, but this was more likely caused by a difference in anatomy rather than growth rate. Generally, models on Neanderthal caloric requirements report significantly higher intakes than those of modern humans because they typically assume Neanderthals had higher basal metabolic rates (BMRs) due to higher muscle mass, faster growth rate and greater body heat production against the cold; and higher daily physical activity levels (PALs) due to greater daily travelling distances while foraging. However, using a high BMR and PAL, American archaeologist Bryan Hockett estimated that a pregnant Neanderthal would have consumed 5,500 calories per day, which would have necessitated a heavy reliance on big game meat; such a diet would have caused numerous deficiencies or nutrient poisonings, so he concluded that these are poorly warranted assumptions to make. Neanderthals may have been more active during dimmer light conditions rather than broad daylight because they lived in regions with reduced daytime hours in the winter, hunted large game (such predators typically hunt at night to enhance ambush tactics), and had large eyes and visual processing neural centres. Genetically, colour blindness (which may enhance mesopic vision) is typically correlated with northern-latitude populations, and the Neanderthals from Vindija Cave, Croatia, had some substitutions in the Opsin genes which could have influenced colour vision. However, the functional implications of these substitutions are inconclusive. Neanderthal-derived alleles near ASB1 and EXOC6 are associated with being an evening person, narcolepsy and day-time napping. Neanderthals suffered a high rate of traumatic injury, with an estimated 79–94% of specimens showing evidence of healed major trauma, of which 37–52% were severely injured, and 13–19% injured before reaching adulthood. One extreme example is Shanidar 1, who shows signs of an amputation of the right arm likely due to a nonunion after breaking a bone in adolescence, osteomyelitis (a bone infection) on the left clavicle, an abnormal gait, vision problems in the left eye, and possible hearing loss (perhaps swimmer's ear). In 1995, Trinkaus estimated that about 80% succumbed to their injuries and died before reaching 40, and thus theorised that Neanderthals employed a risky hunting strategy ("rodeo rider" hypothesis). However, rates of cranial trauma are not significantly different between Neanderthals and Middle Palaeolithic modern humans (although Neanderthals seem to have had a higher mortality risk), there are few specimens of both Upper Palaeolithic modern humans and Neanderthals who died after the age of 40, and there are overall similar injury patterns between them. In 2012, Trinkaus concluded that Neanderthals instead injured themselves in the same way as contemporary humans, such as by interpersonal violence. A 2016 study looking at 124 Neanderthal specimens argued that high trauma rates were instead caused by animal attacks, and found that about 36% of the sample were victims of bear attacks, 21% big cat attacks, and 17% wolf attacks (totalling 92 positive cases, 74%). There were no cases of hyena attacks, although hyenas still nonetheless probably attacked Neanderthals, at least opportunistically. Such intense predation probably stemmed from common confrontations due to competition over food and cave space, and from Neanderthals hunting these carnivores. Low population caused a low genetic diversity and probably inbreeding, which reduced the population's ability to filter out harmful mutations (inbreeding depression). However, it is unknown how this affected a single Neanderthal's genetic burden and, thus, if this caused a higher rate of birth defects than in modern humans. It is known, however, that the 13 inhabitants of Sidrón Cave collectively exhibited 17 different birth defects likely due to inbreeding or recessive disorders. Likely due to advanced age (60s or 70s), La Chapelle-aux-Saints 1 had signs of Baastrup's disease, affecting the spine, and osteoarthritis. Shanidar 1, who likely died at about 30 or 40, was diagnosed with the most ancient case of diffuse idiopathic skeletal hyperostosis (DISH), a degenerative disease which can restrict movement, which, if correct, would indicate a moderately high incident rate for older Neanderthals. Neanderthals were subject to several infectious diseases and parasites. Modern humans likely transmitted diseases to them; one possible candidate is the stomach bacteria Helicobacter pylori. The modern human papillomavirus variant 16A may descend from Neanderthal introgression. A Neanderthal at Cueva del Sidrón, Spain, shows evidence of a gastrointestinal Enterocytozoon bieneusi infection. The leg bones of the French La Ferrassie 1 feature lesions that are consistent with periostitis—inflammation of the tissue enveloping the bone—likely a result of hypertrophic osteoarthropathy, which is primarily caused by a chest infection or lung cancer. Neanderthals had a lower cavity rate than modern humans, despite some populations consuming typically cavity-causing foods in great quantity, which could indicate a lack of cavity-causing oral bacteria, namely Streptococcus mutans. Two 250,000-year-old Neanderthaloid children from Payré, France, present the earliest known cases of lead exposure of any hominin. They were exposed on two distinct occasions either by eating or drinking contaminated food or water, or inhaling lead-laced smoke from a fire. There are two lead mines within 25 km (16 mi) of the site. Neanderthals likely lived in more sparsely distributed groups than contemporary modern humans, but group size is thought to have averaged 10 to 30 individuals, similar to modern hunter-gatherers. Reliable evidence of Neanderthal group composition comes from Cueva del Sidrón, Spain, and the footprints at Le Rozel, France: the former shows 7 adults, 3 adolescents, 2 juveniles and an infant; whereas the latter, based on footprint size, shows a group of 10 to 13 members where juveniles and adolescents made up 90%. A Neanderthal child's teeth analysed in 2018 showed it was weaned after 2.5 years, similar to modern hunter gatherers, and was born in the spring, which is consistent with modern humans and other mammals whose birth cycles coincide with environmental cycles. Indicated from various ailments resulting from high stress at a low age, such as stunted growth, British archaeologist Paul Pettitt hypothesised that children of both sexes were put to work directly after weaning; and Trinkaus said that, upon reaching adolescence, an individual may have been expected to join in hunting large and dangerous game. However, the bone trauma is comparable to modern Inuit, which could suggest a similar childhood between Neanderthals and contemporary modern humans. Further, such stunting may have also resulted from harsh winters and bouts of low food resources. Sites showing evidence of no more than three individuals may have represented nuclear families or temporary camping sites for special task groups (such as a hunting party). Bands likely moved between certain caves depending on the season, indicated by remains of seasonal materials such as certain foods, and returned to the same locations generation after generation. Some sites may have been used for over 100 years. Cave bears may have greatly competed with Neanderthals for cave space, and there is a decline in cave bear populations starting 50,000 years ago onwards (although their extinction occurred well after Neanderthals had died out). Neanderthals also had a preference for caves whose openings faced towards the south. Although Neanderthals are generally considered to have been cave dwellers, with 'home base' being a cave, open-air settlements near contemporaneously inhabited cave systems in the Levant could indicate mobility between cave and open-air bases in this area. Evidence for long-term open-air settlements is known from the 'Ein Qashish site in Israel, and Moldova I in Ukraine. Although Neanderthals appear to have had the ability to inhabit a range of environments—including plains and plateaux—open-air Neanderthals sites are generally interpreted as having been used as slaughtering and butchering grounds rather than living spaces. In 2022, remains of the first-known Neanderthal family (six adults and five children) were excavated from Chagyrskaya Cave in the Altai Mountains of southern Siberia in Russia. The family, which included a father, a daughter, and what appear to be cousins, most likely died together, presumably from starvation. Canadian ethnoarchaeologist Brian Hayden calculated a self-sustaining population that avoids inbreeding to consist of about 450–500 individuals, which would necessitate these bands to interact with 8–53 other bands, but more likely the larger estimate given low population density. Analysis of the mtDNA of the Neanderthals of Cueva del Sidrón, Spain, showed that the three adult men belonged to the same maternal lineage, while the three adult women belonged to different ones. This suggests a patrilocal residence (that a woman moved out of her group to live with her partner). However, the DNA of a Neanderthal from Denisova Cave, Russia, shows that she had an inbreeding coefficient of 1⁄8 (her parents were either half-siblings with a common mother, double first cousins, an uncle and niece or aunt and nephew, or a grandfather and granddaughter or grandmother and grandson) and the inhabitants of Cueva del Sidrón show several defects, which may have been caused by inbreeding or recessive disorders. Considering most Neanderthal artifacts were sourced no more than 5 km (3.1 mi) from the main settlement, Hayden considered it unlikely these bands interacted very often, and mapping of the Neanderthal brain and their small group size and population density could indicate that they had a reduced ability for inter-group interaction and trade. However, a few Neanderthal artefacts in a settlement could have originated 20, 30, 100 and 300 km (12.5, 18.5, 60 and 185 mi) away. Based on this, Hayden also speculated that macro-bands formed which functioned much like those of the low-density hunter-gatherer societies of the Western Desert of Australia. Macro-bands collectively encompass 13,000 km (5,000 sq mi), with each band claiming 1,200–2,800 km (460–1,080 sq mi), maintaining strong alliances for mating networks or to cope with leaner times and enemies. Similarly, British anthropologist Eiluned Pearce and Cypriot archaeologist Theodora Moutsiou speculated that Neanderthals were possibly capable of forming geographically expansive ethnolinguistic tribes encompassing upwards of 800 people, based on the transport of obsidian up to 300 km (190 mi) from the source compared to trends seen in obsidian transfer distance and tribe size in modern hunter-gatherers. However, according to their model Neanderthals would not have been as efficient at maintaining long-distance networks as modern humans, probably due to a significantly lower population. Hayden noted an apparent cemetery of six or seven individuals at La Ferrassie, France, which, in modern humans, is typically used as evidence of a corporate group which maintained a distinct social identity and controlled some resource, trading, manufacturing and so on. La Ferrassie is also located in one of the richest animal-migration routes of Pleistocene Europe. Genetic analysis indicates there were at least three distinct geographical groups—Western Europe, the Mediterranean coast, and east of the Caucasus—with some migration among these regions. Post-Eemian Western European Mousterian lithics can also be broadly grouped into three distinct macro-regions: Acheulean-tradition Mousterian in the southwest, Micoquien in the northeast, and Mousterian with bifacial tools (MBT) in between the former two. MBT may actually represent the interactions and fusion of the two different cultures. Southern Neanderthals exhibit regional anatomical differences from northern counterparts: a less protrusive jaw, a shorter gap behind the molars, and a vertically higher jawbone. These all instead suggest Neanderthal communities regularly interacted with neighbouring communities within a region, but not as often beyond. Nonetheless, over long periods of time, there is evidence of large-scale cross-continental migration. Early specimens from Mezmaiskaya Cave in the Caucasus and Denisova Cave in the Siberian Altai Mountains differ genetically from those found in Western Europe, whereas later specimens from these caves both have genetic profiles more similar to Western European Neanderthal specimens than to the earlier specimens from the same locations, suggesting long-range migration and population replacement over time. Similarly, artefacts and DNA from Chagyrskaya and Okladnikov Caves, also in the Altai Mountains, resemble those of eastern European Neanderthal sites about 3,000–4,000 km (1,900–2,500 mi) away more than they do artefacts and DNA of the older Neanderthals from Denisova Cave, suggesting two distinct migration events into Siberia. Neanderthals seem to have suffered a major population decline during MIS 4 (71–57,000 years ago), and the distribution of the Micoquian tradition could indicate that Central Europe and the Caucasus were repopulated by communities from a refuge zone either in eastern France or Hungary (the fringes of the Micoquian tradition) who dispersed along the rivers Prut and Dniester. There is also evidence of inter-group conflict: a skeleton from La Roche à Pierrot, France, showing a healed fracture on top of the skull apparently caused by a deep blade wound, and another from Shanidar Cave, Iraq, found to have a rib lesion characteristic of projectile weapon injuries. It is sometimes suggested that, since they were hunters of challenging big game and lived in small groups, there was no sexual division of labour as seen in modern hunter-gatherer societies. That is, men, women and children all had to be involved in hunting, instead of men hunting with women and children foraging. However, with modern hunter-gatherers, the higher the meat dependency, the higher the division of labour. Further, tooth-wearing patterns in Neanderthal men and women suggest they commonly used their teeth for carrying items, but men exhibit more wearing on the upper teeth, and women the lower, suggesting some cultural differences in tasks. It is controversially proposed that some Neanderthals wore decorative clothing or jewellery—such as a leopard skin or raptor feathers—to display elevated status in the group. Hayden postulated that the small number of Neanderthal graves found was because only high-ranking members would receive an elaborate burial, as is the case for some modern hunter-gatherers. Trinkaus suggested that elderly Neanderthals were given special burial rites for lasting so long given the high mortality rates. Alternatively, many more Neanderthals may have received burials, but the graves were infiltrated and destroyed by bears. Given that 20 graves of Neanderthals aged under 4 have been found—over a third of all known graves—deceased children may have received greater care during burial than other age demographics. Looking at Neanderthal skeletons recovered from several natural rock shelters, Trinkaus said that, although Neanderthals were recorded as bearing several trauma-related injuries, none of them had significant trauma to the legs that would debilitate movement. He suggested that self worth in Neanderthal culture derived from contributing food to the group; a debilitating injury would remove this self-worth and result in near-immediate death, and individuals who could not keep up with the group while moving from cave to cave were left behind. However, there are examples of individuals with highly debilitating injuries being nursed for several years, and caring for the most vulnerable within the community dates even further back to H. heidelbergensis. Especially given the high trauma rates, it is possible that such an altruistic strategy ensured their survival as a species for so long. Neanderthals were once thought of as scavengers, but are now considered to have been apex predators. In 1980, it was hypothesised that two piles of mammoth skulls at La Cotte de St Brelade, Jersey, at the base of a gulley were evidence of mammoth drive hunting (causing them to stampede off a ledge), but this is contested. Living in a forested environment, Neanderthals were likely ambush hunters, getting close to and attacking their target—a prime adult—in a short burst of speed, thrusting in a spear at close quarters. Younger or wounded animals may have been hunted using traps, projectiles, or pursuit. Some sites show evidence that Neanderthals slaughtered whole herds of animals in large, indiscriminate hunts and then carefully selected which carcasses to process. Nonetheless, they were able to adapt to a variety of habitats. They appear to have eaten predominantly what was abundant within their immediate surroundings, with steppe-dwelling communities (generally outside of the Mediterranean) subsisting almost entirely on meat from large game, forest-dwelling communities consuming a wide array of plants and smaller animals, and waterside communities gathering aquatic resources, although even in more southerly, temperate areas such as the southeastern Iberian Peninsula, large game still featured prominently in Neanderthal diets. Contemporary humans, in contrast, seem to have used more complex food extraction strategies and generally had a more diverse diet. Nonetheless, Neanderthals still would have had to have eaten a varied enough diet to prevent nutrient deficiencies and protein poisoning, especially in the winter when they presumably ate mostly lean meat. Any food with high contents of other essential nutrients not provided by lean meat would have been vital components of their diet, such as fat-rich brains, carbohydrate-rich and abundant underground storage organs (including roots and tubers), or, like modern Inuit, the stomach contents of herbivorous prey items. For meat, they appear to have fed predominantly on hoofed mammals, namely red deer and reindeer as these two were the most abundant game, but also on other Pleistocene megafauna such as chamois, ibex, wild boar, steppe wisent, aurochs, woolly mammoth, straight-tusked elephant, woolly rhinoceros, wild horse, and so on. There is evidence of directed cave and brown bear hunting both in and out of hibernation, as well as butchering. Analysis of Neanderthal bone collagen from Vindija Cave, Croatia, shows nearly all of their protein needs derived from animal meat. Some caves show evidence of regular rabbit and tortoise consumption. At Gibraltar sites, there are remains of 143 different bird species, many ground-dwelling such as the common quail, corn crake, woodlark, and crested lark. Scavenging birds such as corvids and eagles were commonly exploited. Neanderthals also exploited marine resources on the Iberian, Italian and Peloponnesian Peninsulas, where they waded or dived for shellfish, as early as 150,000 years ago at Cueva Bajondillo, Spain, similar to the fishing record of modern humans. At Vanguard Cave, Gibraltar, the inhabitants consumed Mediterranean monk seal, short-beaked common dolphin, common bottlenose dolphin, Atlantic bluefin tuna, sea bream and purple sea urchin; and at Gruta da Figueira Brava, Portugal, there is evidence of large-scale harvest of shellfish, crabs and fish. Evidence of freshwater fishing was found in Grotte di Castelcivita, Italy, for trout, chub and eel; Abri du Maras, France, for chub and European perch; Payré, France; and Kudaro Cave, Russia, for Black Sea salmon. Edible plant and mushroom remains are recorded from several caves. Neanderthals from Cueva del Sidrón, Spain, based on dental tartar, likely had a meatless diet of mushrooms, pine nuts and moss, indicating they were forest foragers. Remnants from Amud Cave, Israel, indicates a diet of figs, palm tree fruits and various cereals and edible grasses. Several bone traumas in the leg joints could possibly suggest habitual squatting, which, if the case, was likely done while gathering food. Dental tartar from Grotte de Spy, Belgium, indicates the inhabitants had a meat-heavy diet including woolly rhinoceros and mouflon sheep, while also regularly consuming mushrooms. Neanderthal faecal matter from El Salt, Spain, dated to 50,000 years ago—the oldest human faecal matter remains recorded—show a diet mainly of meat but with a significant component of plants. Evidence of cooked plant foods—mainly legumes and, to a far lesser extent, acorns—was discovered in Kebara Cave, Israel, with its inhabitants possibly gathering plants in spring and fall and hunting in all seasons except fall, although the cave was probably abandoned in late summer to early fall. At Shanidar Cave, Iraq, Neanderthals collected plants with various harvest seasons, indicating they scheduled returns to the area to harvest certain plants, and that they had complex food-gathering behaviours for both meat and plants. Neanderthals probably could employ a wide range of cooking techniques, such as roasting, and they may have been able to heat up or boil soup, stew, or animal stock. The abundance of animal bone fragments at settlements may indicate the making of fat stocks from boiling bone marrow, possibly taken from animals that had already died of starvation. These methods would have substantially increased fat consumption, which was a major nutritional requirement of communities with low carbohydrate and high protein intake. Neanderthal tooth size had a decreasing trend after 100,000 years ago, which could indicate an increased dependence on cooking or the advent of boiling, a technique that would have softened food. At Cueva del Sidrón, Spain, Neanderthals likely cooked and possibly smoked food, as well as used certain plants—such as yarrow and camomile—as flavouring, although these plants may have instead been used for their medicinal properties. At Gorham's Cave, Gibraltar, Neanderthals may have been roasting pinecones to access pine nuts. At Grotte du Lazaret, France, a total of twenty-three red deer, six ibexes, three aurochs, and one roe deer appear to have been hunted in a single autumn hunting season, when strong male and female deer herds would group together for rut. The entire carcasses seem to have been transported to the cave and then butchered. Because this is such a large amount of food to consume before spoilage, it is possible these Neanderthals were curing and preserving it before winter set in. At 160,000 years old, it is the oldest potential evidence of food storage. The great quantities of meat and fat which could have been gathered in general from typical prey items (namely mammoths) could also indicate food storage capability. With shellfish, Neanderthals needed to eat, cook, or in some manner preserve them soon after collection, as shellfish spoils very quickly. At Cueva de los Aviones, Spain, the remains of edible, algae eating shellfish associated with the alga Jania rubens could indicate that, like some modern hunter gatherer societies, harvested shellfish were held in water-soaked algae to keep them alive and fresh until consumption. Competition from large Ice Age predators was rather high. Cave lions likely targeted horses, large deer and wild cattle; and leopards primarily reindeer and roe deer; which heavily overlapped with Neanderthal diet. To defend a kill against such ferocious predators, Neanderthals may have engaged in a group display of yelling, arm waving, or stone throwing; or quickly gathered meat and abandoned the kill. However, at Grotte de Spy, Belgium, the remains of wolves, cave lions and cave bears—which were all major predators of the time—indicate Neanderthals hunted their competitors to some extent. Neanderthals and cave hyenas may have exemplified niche differentiation, and actively avoided competing with each other. Although they both mainly targeted the same groups of creatures—deer, horses and cattle—Neanderthals mainly hunted the former and cave hyenas the latter two. Further, animal remains from Neanderthal caves indicate they preferred to hunt prime individuals, whereas cave hyenas hunted weaker or younger prey, and cave hyena caves have a higher abundance of carnivore remains. Nonetheless, there is evidence that cave hyenas stole food and leftovers from Neanderthal campsites and scavenged on dead Neanderthal bodies. There are several instances of Neanderthals practising cannibalism across their range. The first example came from the Krapina, Croatia site, in 1899, and other examples were found at Cueva del Sidrón and Zafarraya in Spain; and the French Grotte de Moula-Guercy, Les Pradelles, and La Quina. For the five cannibalised Neanderthals at the Grottes de Goyet, Belgium, there is evidence that the upper limbs were disarticulated, the lower limbs defleshed and also smashed (likely to extract bone marrow), the chest cavity disemboweled, and the jaw dismembered. There is also evidence that the butchers used some bones to retouch their tools. The processing of Neanderthal meat at Grottes de Goyet is similar to how they processed horse and reindeer. About 35% of the Neanderthals at Marillac-le-Franc, France, show clear signs of butchery, and the presence of digested teeth indicates that the bodies were abandoned and eaten by scavengers, likely hyaenas. These cannibalistic tendencies have been explained as either ritual defleshing, pre-burial defleshing (to prevent scavengers or foul smell), an act of war, or simply for food. Due to a small number of cases, and the higher number of cut marks seen on cannibalised individuals than animals (indicating inexperience), cannibalism was probably not a very common practice, and it may have only been done in times of extreme food shortages as in some cases in recorded human history. Neanderthals used ochre, a clay earth pigment. Ochre is well documented from 60 to 45,000 years ago in Neanderthal sites, with the earliest example dating to 250–200,000 years ago from Maastricht-Belvédère, the Netherlands (a similar timespan to the ochre record of H. sapiens). It has been hypothesised to have functioned as body paint, and analyses of pigments from Pech de l'Azé, France, indicates they were applied to soft materials (such as a hide or human skin). However, modern hunter gatherers, in addition to body paint, also use ochre for medicine, for tanning hides, as a food preservative, and as an insect repellent, so its use as decorative paint for Neanderthals is speculative. Containers apparently used for mixing ochre pigments were found in Peștera Cioarei, Romania, which could indicate modification of ochre for solely aesthetic purposes. Neanderthals collected uniquely shaped objects and are suggested to have modified them into pendants, such as a fossil Aspa marginata sea snail shell possibly painted red from Grotta di Fumane, Italy, transported over 100 km (62 mi) to the site about 47,500 years ago; three shells, dated to about 120–115,000 years ago, perforated through the umbo belonging to a rough cockle, a Glycymeris insubrica, and a Spondylus gaederopus from Cueva de los Aviones, Spain, the former two associated with red and yellow pigments, and the latter a red-to-black mix of hematite and pyrite; and a king scallop shell with traces of an orange mix of goethite and hematite from Cueva Antón, Spain. The discoverers of the latter two claim that pigment was applied to the exterior to make it match the naturally vibrant inside colouration. Excavated from 1949 to 1963 from the French Grotte du Renne, Châtelperronian beads made from animal teeth, shells and ivory were found associated with Neanderthal bones, but the dating is uncertain and Châtelperronian artefacts may actually have been crafted by modern humans and simply redeposited with Neanderthal remains. Gibraltarian palaeoanthropologists Clive and Geraldine Finlayson suggested that Neanderthals used various bird parts as artistic mediums, specifically black feathers. In 2012, the Finlaysons and colleagues examined 1,699 sites across Eurasia, and argued that raptors and corvids, species not typically consumed by any human species, were overrepresented and show processing of only the wing bones instead of the fleshier torso, and thus are evidence of feather plucking of specifically the large flight feathers for use as personal adornment. They specifically noted the cinereous vulture, red-billed chough, kestrel, lesser kestrel, alpine chough, rook, jackdaw and the white tailed eagle in Middle Palaeolithic sites. Other birds claimed to present evidence of modifications by Neanderthals are the golden eagle, rock pigeon, common raven and the bearded vulture. The earliest claim of bird bone jewellery is a number of 130,000-year-old white tailed eagle talons found in a cache near Krapina, Croatia, speculated, in 2015, to have been a necklace. A similar 39,000-year-old Spanish imperial eagle talon necklace was reported in 2019 at Cova Foradà in Spain, though from the contentious Châtelperronian layer. In 2017, 17 incision-decorated raven bones from the Zaskalnaya VI rock shelter, Ukraine, dated to 43–38,000 years ago were reported. Because the notches are more-or-less equidistant to each other, they are the first modified bird bones that cannot be explained by simple butchery, and for which the argument of design intent is based on direct evidence. Discovered in 1975, the so-called Mask of la Roche-Cotard, a mostly flat piece of flint with a bone pushed through a hole on the midsection—dated to 32, 40, or 75,000 years ago—has been purported to resemble the upper half of a face, with the bone representing eyes. It is contested whether it represents a face, or if it even counts as art. In 1988, American archaeologist Alexander Marshack speculated that a Neanderthal at Grotte de L'Hortus, France, wore a leopard pelt as personal adornment to indicate elevated status in the group based on a recovered leopard skull, phalanges and tail vertebrae. As of 2014, 63 purported engravings have been reported from 27 different European and Middle Eastern Lower-to-Middle Palaeolithic sites, of which 20 are on flint cortexes from 11 sites, 7 are on slabs from 7 sites, and 36 are on pebbles from 13 sites. It is debated whether or not these were made with symbolic intent. In 2012, deep scratches on the floor of Gorham's Cave, Gibraltar, were discovered, dated to older than 39,000 years ago, which the discoverers have interpreted as Neanderthal abstract art. The scratches could have also been produced by a bear. In 2021, an Irish elk phalanx with five engraved offset chevrons stacked above each other was discovered at the entrance to the Einhornhöhle cave in Germany, dating to about 51,000 years ago. In 2018, some red-painted dots, disks, lines and hand stencils on the cave walls of the Spanish La Pasiega, Maltravieso, and Doña Trinidad were dated to be older than 66,000 years ago, at least 20,000 years prior to the arrival of modern humans in Western Europe. This would indicate Neanderthal authorship, and similar iconography recorded in other Western European sites—such as Les Merveilles, France, and Cueva del Castillo, Spain—could potentially also have Neanderthal origins. However, the dating of these Spanish caves, and thus attribution to Neanderthals, is contested. Neanderthals are known to have collected a variety of unusual objects—such as crystals or fossils—without any real functional purpose or any indication of damage caused by use. It is unclear if these objects were simply picked up for their aesthetic qualities, or if some symbolic significance was applied to them. These items are mainly quartz crystals, but also other minerals such as cerussite, iron pyrite, calcite and galena. A few findings feature modifications, such as a mammoth tooth with an incision and a fossil nummulite shell with a cross etched in from Tata, Hungary; a large slab with 18 cupstones hollowed out from a grave in La Ferrassie, France; and a geode from Peștera Cioarei, Romania, coated with red ochre. A number of fossil shells are also known from French Neanderthals sites, such as a rhynchonellid and a Taraebratulina from Combe Grenal; a belemnite beak from Grottes des Canalettes; a polyp from Grotte de l'Hyène; a sea urchin from La Gonterie-Boulouneix; and a rhynchonella, feather star and belemnite beak from the contentious Châtelperronian layer of Grotte du Renne. Purported Neanderthal bone flute fragments made of bear long bones were reported from Potočka zijalka, Slovenia, in the 1920s, and Istállós-kői-barlang, Hungary, and Mokriška jama, Slovenia, in 1985; but these are now attributed to modern human activities. The 43,000-year-old Divje Babe Flute from Slovenia, found in 1995, has been attributed by some researchers to Neanderthals, and Canadian musicologist Robert Fink said the original flute had either a diatonic or pentatonic musical scale. However, the date also overlaps with modern human immigration into Europe, which means it is also possible it was not manufactured by Neanderthals. In 2015, zoologist Cajus Diedrich argued that it was not a flute at all, and the holes were made by a scavenging hyaena as there is a lack of cut marks stemming from whittling, but in 2018, Slovenian archaeologist Matija Turk and colleagues countered that it is highly unlikely the punctures were made by teeth, and cut marks are not always present on bone flutes. Despite the apparent 150,000-year stagnation in Neanderthal lithic innovation, there is evidence that Neanderthal technology was more sophisticated than was previously thought. However, the high frequency of potentially debilitating injuries could have prevented very complex technologies from emerging, as a major injury would have impeded an expert's ability to effectively teach a novice. Neanderthals made stone tools, and are associated with the Mousterian industry. The Mousterian is also associated with North African H. sapiens as early as 315,000 years ago and was found in Northern China about 47–37,000 years ago in caves such as Jinsitai or Tongtiandong. It evolved around 300,000 years ago with the Levallois technique which developed directly from the preceding Acheulean industry (invented by H. erectus about 1.8 mya). Levallois made it easier to control flake shape and size, and as a difficult-to-learn and unintuitive process, the Levallois technique may have been directly taught generation to generation rather than via purely observational learning. There are distinct regional variants of the Mousterian industry, such as: the Quina and La Ferrassie subtypes of the Charentian industry in southwestern France, Acheulean-tradition Mousterian subtypes A and B along the Atlantic and northwestern European coasts, the Micoquien industry of Central and Eastern Europe and the related Sibiryachikha variant in the Siberian Altai Mountains, the Denticulate Mousterian industry in Western Europe, the racloir industry around the Zagros Mountains, and the flake cleaver industry of Cantabria, Spain, and both sides of the Pyrenees. In the mid-20th century, French archaeologist François Bordes debated against American archaeologist Lewis Binford to explain this diversity (the "Bordes–Binford debate"), with Bordes arguing that these represent unique ethnic traditions and Binford that they were caused by varying environments (essentially, form vs. function). The latter sentiment would indicate a lower degree of inventiveness compared to modern humans, adapting the same tools to different environments rather than creating new technologies. A continuous sequence of occupation is well documented in Grotte du Renne, France, where the lithic tradition can be divided into the Levallois–Charentian, Discoid–Denticulate (43,300 ±929 – 40,900 ±719 years ago), Levallois Mousterian (40,200 ±1,500 – 38,400 ±1,300 years ago) and Châtelperronian (40,930 ±393 – 33,670 ±450 years ago). There is some debate if Neanderthals had long-ranged weapons. A wound on the neck of an African wild ass from Umm el Tlel, Syria, was likely inflicted by a heavy Levallois-point javelin, and bone trauma consistent with habitual throwing has been reported in Neanderthals. Some spear tips from Abri du Maras, France, may have been too fragile to have been used as thrusting spears, possibly suggesting their use as darts. The Châtelperronian in central France and northern Spain is a distinct industry from the Mousterian, and is controversially hypothesised to represent a culture of Neanderthals borrowing (or by process of acculturation) tool-making techniques from immigrating modern humans, crafting bone tools and ornaments. In this frame, the makers would have been a transitional culture between the Neanderthal Mousterian and the modern human Aurignacian. The opposing viewpoint is that the Châtelperronian was manufactured by modern humans instead. Abrupt transitions similar to the Mousterian/Châtelperronian could also simply represent natural innovation, like the La Quina–Neronian transition 50,000 years ago featuring technologies generally associated with modern humans such as bladelets and microliths. Other ambiguous transitional cultures include the Italian Uluzzian industry, and the Balkan Szeletian industry. Before immigration, the only evidence of Neanderthal bone tools are animal rib lissoirs—which are rubbed against hide to make it more supple or waterproof—although this could also be evidence for modern humans immigrating earlier than expected. In 2013, two 51,400- to 41,100-year-old deer rib lissoirs were reported from Pech-de-l'Azé and the nearby Abri Peyrony in France. In 2020, five more lissoirs made of aurochs or bison ribs were reported from Abri Peyrony, with one dating to about 51,400 years ago and the other four to 47,700–41,100 years ago. This indicates the technology was in use in this region for a long time. Since reindeer remains were the most abundant, the use of less abundant bovine ribs may indicate a specific preference for bovine ribs. Potential lissoirs have also been reported from Grosse Grotte, Germany (made of mammoth), and Grottes des Canalettes, France (red deer). The Neanderthals in 10 coastal sites in Italy (namely Grotta del Cavallo and Grotta dei Moscerini) and Kalamakia Cave, Greece, are known to have crafted scrapers using smooth clam shells, and possibly hafted them to a wooden handle. They probably chose this clam species because it has the most durable shell. At Grotta dei Moscerini, about 24% of the shells were gathered alive from the seafloor, meaning these Neanderthals had to wade or dive into shallow waters to collect them. At Grotta di Santa Lucia, Italy, in the Campanian volcanic arc, Neanderthals collected the porous volcanic pumice, which, for contemporary humans, was probably used for polishing points and needles. The pumices are associated with shell tools. At Abri du Maras, France, twisted fibres and a 3-ply inner-bark-fibre cord fragment associated with Neanderthals show that they produced string and cordage, but it is unclear how widespread this technology was because the materials used to make them (such as animal hair, hide, sinew, or plant fibres) are biodegradable and preserve very poorly. This technology could indicate at least a basic knowledge of weaving and knotting, which would have made possible the production of nets, containers, packaging, baskets, carrying devices, ties, straps, harnesses, clothes, shoes, beds, bedding, mats, flooring, roofing, walls and snares, and would have been important in hafting, fishing and seafaring. Dating to 52–41,000 years ago, the cord fragment is the oldest direct evidence of fibre technology, although 115,000-year-old perforated shell beads from Cueva Antón possibly strung together to make a necklace are the oldest indirect evidence. In 2020, British archaeologist Rebecca Wragg Sykes expressed cautious support for the genuineness of the find, but pointed out that the string would have been so weak that it would have had limited functions. One possibility is as a thread for attaching or stringing small objects. The archaeological record shows that Neanderthals commonly used animal hide and birch bark, and may have used them to make cooking containers, although this is based largely on circumstantial evidence, because neither fossilizes well. It is possible that the Neanderthals at Kebara Cave, Israel, used the shells of the spur-thighed tortoise as containers. At the Italian Poggetti Vecchi site, there is evidence that they used fire to process boxwood branches to make digging sticks, a common implement in hunter-gatherer societies. Many Mousterian sites have evidence of fire, some for extended periods of time, though it is unclear whether they were capable of starting fire or simply scavenged from naturally occurring wildfires. Indirect evidence of fire-starting ability includes pyrite residue on a couple of dozen bifaces from late Mousterian (c. 50,000 years ago) northwestern France (which could indicate they were used as percussion fire starters), and collection of manganese dioxide by late Neanderthals which can lower the combustion temperature of wood. They were also capable of zoning areas for specific activities, such as for knapping, butchering, hearths and wood storage. Many Neanderthal sites lack evidence for such activity perhaps due to natural degradation of the area over tens of thousands of years, such as by bear infiltration after abandonment of the settlement. In a number of caves, evidence of hearths has been detected. Neanderthals likely considered air circulation when making hearths as a lack of proper ventilation for a single hearth can render a cave uninhabitable in several minutes. Abric Romaní rock shelter, Spain, indicates eight evenly spaced hearths lined up against the rock wall, likely used to stay warm while sleeping, with one person sleeping on either side of the fire. At Cueva de Bolomor, Spain, with hearths lined up against the wall, the smoke flowed upwards to the ceiling, and led to outside the cave. In Grotte du Lazaret, France, smoke was probably naturally ventilated during the winter as the interior cave temperature was greater than the outside temperature; likewise, the cave was likely only inhabited in the winter. In 1990, two 176,000-year-old ring structures, several metres wide, made of broken stalagmite pieces, were discovered in a large chamber more than 300 m (980 ft) from the entrance within Grotte de Bruniquel, France. One ring was 6.7 m × 4.5 m (22 ft × 15 ft) with stalagmite pieces averaging 34.4 cm (13.5 in) in length, and the other 2.2 m × 2.1 m (7.2 ft × 6.9 ft) with pieces averaging 29.5 cm (11.6 in). There were also four other piles of stalagmite pieces for a total of 112 m (367 ft) or 2.2 t (2.4 short tons) worth of stalagmite pieces. Evidence of the use of fire and burnt bones also suggest human activity. A team of Neanderthals was likely necessary to construct the structure, but the chamber's actual purpose is uncertain. Building complex structures so deep in a cave is unprecedented in the archaeological record, and indicates sophisticated lighting and construction technology, and great familiarity with subterranean environments. The 44,000-year-old Moldova I open-air site, Ukraine, shows evidence of a 7 m × 10 m (23 ft × 33 ft) ring-shaped dwelling made out of mammoth bones meant for long-term habitation by several Neanderthals, which would have taken a long time to build. It appears to have contained hearths, cooking areas and a flint workshop, and there are traces of woodworking. Upper Palaeolithic modern humans in the Russian plains are thought to have also made housing structures out of mammoth bones. Neanderthal produced the adhesive birch bark tar, using the bark of birch trees, for hafting. It was long believed that birch bark tar required a complex recipe to be followed, and that it thus showed complex cognitive skills and cultural transmission. However, a 2019 study showed it can be made simply by burning birch bark beside smooth vertical surfaces, such as a flat, inclined rock. Thus, tar making does not require cultural processes per se. However, at Königsaue (Germany), Neanderthals did not make tar with such an aboveground method but rather employed a technically more demanding underground production method. This is one of our best indicators that some of their techniques were conveyed by cultural processes. Neanderthals were likely able to survive in a similar range of temperatures to modern humans while sleeping: about 32 °C (90 °F) while naked in the open and windspeed 5.4 km/h (3.4 mph), or 27–28 °C (81–82 °F) while naked in an enclosed space. Since ambient temperatures were markedly lower than this—averaging, during the Eemian interglacial, 17.4 °C (63.3 °F) in July and 1 °C (34 °F) in January and dropping to as a low as −30 °C (−22 °F) on the coldest days—Danish physicist Bent Sørensen hypothesised that Neanderthals required tailored clothing capable of preventing airflow to the skin. Especially during extended periods of travelling (such as a hunting trip), tailored footwear completely enwrapping the feet may have been necessary. Nonetheless, as opposed to the bone sewing-needles and stitching awls assumed to have been in use by contemporary modern humans, the only known Neanderthal tools that could have been used to fashion clothes are hide scrapers, which could have made items similar to blankets or ponchos, and there is no direct evidence they could produce fitted clothes. Indirect evidence of tailoring by Neanderthals includes the ability to manufacture string, which could indicate weaving ability, and a naturally-pointed horse metatarsal bone from Cueva de los Aviones, Spain, which was speculated to have been used as an awl, perforating dyed hides, based on the presence of orange pigments. Whatever the case, Neanderthals would have needed to cover up most of their body, and contemporary humans would have covered 80–90%. Since human/Neanderthal admixture is known to have occurred in the Middle East, and no modern body louse species descends from their Neanderthal counterparts (body lice only inhabit clothed individuals), it is possible Neanderthals (and/or humans) in hotter climates did not wear clothes, or Neanderthal lice were highly specialised. Remains of Middle Palaeolithic stone tools on Greek islands indicate early seafaring by Neanderthals in the Ionian Sea possibly starting as far back as 200–150,000 years ago. The oldest stone artefacts from Crete date to 130–107,000 years ago, Cephalonia 125,000 years ago, and Zakynthos 110–35,000 years ago. The makers of these artefacts likely employed simple reed boats and made one-day crossings back and forth. Other Mediterranean islands with such remains include Sardinia, Melos, Alonnisos, and Naxos (although Naxos may have been connected to land), and it is possible they crossed the Strait of Gibraltar. If this interpretation is correct, Neanderthals' ability to engineer boats and navigate through open waters would speak to their advanced cognitive and technical skills. Given their dangerous hunting and extensive skeletal evidence of healing, Neanderthals appear to have lived lives of frequent traumatic injury and recovery. Well-healed fractures on many bones indicate the setting of splints. Individuals with severe head and rib traumas (which would have caused massive blood loss) indicate they had some manner of dressing major wounds, such as bandages made from animal skin. By and large, they appear to have avoided severe infections, indicating good long-term treatment of such wounds. Their knowledge of medicinal plants was comparable to that of contemporary humans. An individual at Cueva del Sidrón, Spain, seems to have been medicating a dental abscess using poplar—which contains salicylic acid, the active ingredient in aspirin—and there were also traces of the antibiotic-producing Penicillium chrysogenum. They may also have used yarrow and camomile, and their bitter taste—which should act as a deterrent as it could indicate poison—means it was likely a deliberate act. In Kebara Cave, Israel, plant remains which have historically been used for their medicinal properties were found, including the common grape vine, the pistachios of the Persian turpentine tree, ervil seeds and oak acorns. The degree of language complexity is difficult to establish, but given that Neanderthals achieved some technical and cultural complexity, and interbred with humans, it is reasonable to assume they were at least fairly articulate, comparable to modern humans. A somewhat complex language—possibly using syntax—was likely necessary to survive in their harsh environment, with Neanderthals needing to communicate about topics such as locations, hunting and gathering, and tool-making techniques. The FOXP2 gene in modern humans is associated with speech and language development. FOXP2 was present in Neanderthals, but not the gene's modern human variant. Neurologically, Neanderthals had an expanded Broca's area—operating the formulation of sentences, and speech comprehension, but out of a group of 48 genes believed to affect the neural substrate of language, 11 had different methylation patterns between Neanderthals and modern humans. This could indicate a stronger ability in modern humans than in Neanderthals to express language. In 1971, cognitive scientist Philip Lieberman attempted to reconstruct the Neanderthal vocal tract and concluded that it was similar to that of a newborn and incapable of producing a large range of speech sounds, due to the large size of the mouth and the small size of the pharyngeal cavity (according to his reconstruction), thus no need for a descended larynx to fit the entire tongue inside the mouth. He claimed that they were anatomically unable to produce the sounds /a/, /i/, /u/, /ɔ/, /g/, and /k/ and thus lacked the capacity for articulate speech, though were still able to speak at a level higher than non-human primates. However, the lack of a descended larynx does not necessarily equate to a reduced vowel capacity. The 1983 discovery of a Neanderthal hyoid bone—used in speech production in humans—in Kebara 2 which is almost identical to that of humans suggests Neanderthals were capable of speech. Also, the ancestral Sima de los Huesos hominins had humanlike hyoid and ear bones, which could suggest the early evolution of the modern human vocal apparatus. However, the hyoid does not definitively provide insight into vocal tract anatomy. Subsequent studies reconstruct the Neanderthal vocal apparatus as comparable to that of modern humans, with a similar vocal repertoire. In 2015, Lieberman hypothesized that Neanderthals were capable of syntactical language, although nonetheless incapable of mastering any human dialect. It is debated if behavioural modernity is a recent and uniquely modern human innovation, or if Neanderthals also possessed it. Although Neanderthals did bury their dead, at least occasionally—which may explain the abundance of fossil remains—the behavior is not indicative of a religious belief of life after death because it could also have had non-symbolic motivations, such as great emotion or the prevention of scavenging. Estimates made regarding the number of known Neanderthal burials range from thirty-six to sixty. The oldest confirmed burials do not seem to occur before approximately 70,000 years ago. The small number of recorded Neanderthal burials implies that the activity was not particularly common. The setting of inhumation in Neanderthal culture largely consisted of simple, shallow graves and pits. Sites such as La Ferrassie in France or Shanidar in Iraq may imply the existence of mortuary centers or cemeteries in Neanderthal culture due to the number of individuals found buried at them. The debate on Neanderthal funerals has been active since the 1908 discovery of La Chapelle-aux-Saints 1 in a small, artificial hole in a cave in southwestern France, very controversially postulated to have been buried in a symbolic fashion. Another grave at Shanidar Cave, Iraq, was associated with the pollen of several flowers that may have been in bloom at the time of deposition—yarrow, centaury, ragwort, grape hyacinth, joint pine and hollyhock. The medicinal properties of the plants led American archaeologist Ralph Solecki to claim that the man buried was some leader, healer, or shaman, and that "The association of flowers with Neanderthals adds a whole new dimension to our knowledge of his humanness, indicating that he had 'soul' ". However, it is also possible the pollen was deposited by a small rodent after the man's death. The graves of children and infants, especially, are associated with grave goods such as artefacts and bones. The grave of a newborn from La Ferrassie, France, was found with three flint scrapers, and an infant from Dederiyeh [de] Cave, Syria, was found with a triangular flint placed on its chest. A 10-month-old from Amud Cave, Israel, was associated with a red deer mandible, likely purposefully placed there given other animal remains are now reduced to fragments. Teshik-Tash 1 from Uzbekistan was associated with a circle of ibex horns, and a limestone slab argued to have supported the head. A child from Kiik-Koba, Crimea, Ukraine, had a flint flake with some purposeful engraving on it, likely requiring a great deal of skill. Nonetheless, these contentiously constitute evidence of symbolic meaning as the grave goods' significance and worth are unclear. It was once argued that the bones of the cave bear, particularly the skull, in some European caves were arranged in a specific order, indicating an ancient bear cult that killed bears and then ceremoniously arranged the bones. This would be consistent with bear-related rituals of modern human Arctic hunter-gatherers, but the alleged peculiarity of the arrangement could also be sufficiently explained by natural causes, and bias could be introduced as the existence of a bear cult would conform with the idea that totemism was the earliest religion, leading to undue extrapolation of evidence. It was also once thought that Neanderthals ritually hunted, killed and cannibalised other Neanderthals and used the skull as the focus of some ceremony. In 1962, Italian palaeontologist Alberto Blanc believed a skull from Grotta Guattari, Italy, had evidence of a swift blow to the head—indicative of ritual murder—and a precise and deliberate incising at the base to access the brain. He compared it to the victims of headhunters in Malaysia and Borneo, putting it forward as evidence of a skull cult. However, it is now thought to have been a result of cave hyaena scavengery. Although Neanderthals are known to have practiced cannibalism, there is unsubstantial evidence to suggest ritual defleshing. In 2019, Gibraltarian palaeoanthropologists Stewart, Geraldine and Clive Finlayson and Spanish archaeologist Francisco Guzmán speculated that the golden eagle had iconic value to Neanderthals, as exemplified in some modern human societies because they reported that golden eagle bones had a conspicuously high rate of evidence of modification compared to the bones of other birds. They then proposed some "Cult of the Sun Bird" where the golden eagle was a symbol of power. There is evidence from Krapina, Croatia, from wear use and even remnants of string, that suggests that raptor talons were worn as personal ornaments. The first Neanderthal genome sequence was published in 2010, and strongly indicated interbreeding between Neanderthals and early modern humans. The genomes of all studied modern populations contain Neanderthal DNA. Various estimates exist for the proportion, such as 1–4% or 3.4–7.9% in modern Eurasians, or 1.8–2.4% in modern Europeans and 2.3–2.6% in modern East Asians. Pre-agricultural Europeans appear to have had similar, or slightly higher, percentages to modern East Asians, and the numbers may have decreased in the former due to dilution with a group of people which had split off before Neanderthal introgression. Typically, studies have reported finding no significant levels of Neanderthal DNA in Sub-Saharan Africans, but a 2020 study detected 0.3-0.5% in the genomes of five African sample populations, likely the result of Eurasians back-migrating and interbreeding with Africans, as well as human-to-neanderthal gene flow from dispersals of Homo sapiens preceding the larger Out-of-Africa migration, and also showed more equal Neanderthal DNA percentages for European and Asian populations. Such low percentages of Neanderthal DNA in all present day populations indicate infrequent past interbreeding, unless interbreeding was more common with a different population of modern humans which did not contribute to the present day gene pool. Of the inherited Neanderthal genome, 25% in modern Europeans and 32% in modern East Asians may be related to viral immunity. In all, approximately 20% of the Neanderthal genome appears to have survived in the modern human gene pool. However, due to their small population and resulting reduced effectivity of natural selection, Neanderthals accumulated several weakly harmful mutations, which were introduced to and slowly selected out of the much larger modern human population; the initial hybridised population may have experienced up to a 94% reduction in fitness compared to contemporary humans. By this measure, Neanderthals may have substantially increased in fitness. A 2017 study focusing on archaic genes in Turkey found associations with coeliac disease, malaria severity and Costello syndrome. Nonetheless, some genes may have helped modern East Asians adapt to the environment; the putatively Neanderthal Val92Met variant of the MC1R gene, which may be weakly associated with red hair and UV radiation sensitivity, is primarily found in East Asian, rather than European, individuals. Some genes related to the immune system appear to have been affected by introgression, which may have aided migration, such as OAS1, STAT2, TLR6, TLR1, TLR10, and several related to immune response. In addition, Neanderthal genes have also been implicated in the structure and function of the brain, keratin filaments, sugar metabolism, muscle contraction, body fat distribution, enamel thickness and oocyte meiosis. Nonetheless, a large portion of surviving introgression appears to be non-coding ("junk") DNA with few biological functions. Due to the absence of Neanderthal-derived mtDNA (which is passed on from mother to child) in modern populations, it has been suggested that the progeny of Neanderthal females who mated with modern human males were either rare, absent, or sterile—that is to say, admixture stems from the progeny of Neanderthal males with modern human females. Due to the lack of Neanderthal-derived Y-chromosomes in modern humans (which is passed on from father to son), it has also been suggested that the hybrids that contributed ancestry to modern populations were predominantly females, or the Neanderthal Y-chromosome was not compatible with H. sapiens and became extinct. According to linkage disequilibrium mapping, the last Neanderthal gene flow into the modern human genome occurred 86–37,000 years ago, but most likely 65–47,000 years ago. It is thought that Neanderthal genes which contributed to the present day human genome stemmed from interbreeding in the Near East rather than the entirety of Europe. However, interbreeding still occurred without contributing to the modern genome. The approximately 40,000-year-old modern human Oase 2 was found, in 2015, to have had 6–9% (point estimate 7.3%) Neanderthal DNA, indicating a Neanderthal ancestor up to four to six generations earlier, but this hybrid population does not appear to have made a substantial contribution to the genomes of later Europeans. In 2016, the DNA of Neanderthals from Denisova Cave revealed evidence of interbreeding 100,000 years ago, and interbreeding with an earlier dispersal of H. sapiens may have occurred as early as 120,000 years ago in places such as the Levant. The earliest H. sapiens remains outside of Africa occur at Misliya Cave 194–177,000 years ago, and Skhul and Qafzeh 120–90,000 years ago. The Qafzeh humans lived at approximately the same time as the Neanderthals from the nearby Tabun Cave. The Neanderthals of the German Hohlenstein-Stadel have deeply divergent mtDNA compared to more recent Neanderthals, possibly due to introgression of human mtDNA between 316,000 and 219,000 years ago, or simply because they were genetically isolated. Whatever the case, these first interbreeding events have not left any trace in modern human genomes. Detractors of the interbreeding model argue that the genetic similarity is only a remnant of a common ancestor instead of interbreeding, although this is unlikely as it fails to explain why sub-Saharan Africans do not have Neanderthal DNA. In December 2023, scientists reported that genes inherited by modern humans from Neanderthals and Denisovans may biologically influence the daily routine of modern humans. Although nDNA confirms that Neanderthals and Denisovans are more closely related to each other than they are to modern humans, Neanderthals and modern humans share a more recent maternally-transmitted mtDNA common ancestor, possibly due to interbreeding between Denisovans and some unknown human species. The 400,000-year-old Neanderthal-like humans from Sima de los Huesos in northern Spain, looking at mtDNA, are more closely related to Denisovans than Neanderthals. Several Neanderthal-like fossils in Eurasia from a similar time period are often grouped into H. heidelbergensis, of which some may be relict populations of earlier humans, which could have interbred with Denisovans. This is also used to explain an approximately 124,000-year-old German Neanderthal specimen with mtDNA that diverged from other Neanderthals (except for Sima de los Huesos) about 270,000 years ago, while its genomic DNA indicated divergence less than 150,000 years ago. Sequencing of the genome of a Denisovan from Denisova Cave has shown that 17% of its genome derives from Neanderthals. This Neanderthal DNA more closely resembled that of a 120,000-year-old Neanderthal bone from the same cave than that of Neanderthals from Vindija Cave, Croatia, or Mezmaiskaya Cave in the Caucasus, suggesting that interbreeding was local. For the 90,000-year-old Denisova 11, it was found that her father was a Denisovan related to more recent inhabitants of the region, and her mother a Neanderthal related to more recent European Neanderthals at Vindija Cave, Croatia. Given how few Denisovan bones are known, the discovery of a first-generation hybrid indicates interbreeding was very common between these species, and Neanderthal migration across Eurasia likely occurred sometime after 120,000 years ago. The extinction of Neanderthals was part of the broader Late Pleistocene megafaunal extinction event. Whatever the cause of their extinction, Neanderthals were replaced by modern humans, indicated by near full replacement of Middle Palaeolithic Mousterian stone technology with modern human Upper Palaeolithic Aurignacian stone technology across Europe (the Middle-to-Upper Palaeolithic Transition) from 41,000 to 39,000 years ago. By between 44,200 to 40,600 BP, Neanderthals vanished from northwestern Europe. However, it is postulated that Iberian Neanderthals persisted until about 35,000 years ago, as indicated by the date range of transitional lithic assemblages—Châtelperronian, Uluzzian, Protoaurignacian and Early Aurignacian. The latter two are attributed to modern humans, but the former two have unconfirmed authorship, potentially products of Neanderthal/modern human cohabitation and cultural transmission. Further, the appearance of the Aurignacian south of the Ebro River has been dated to roughly 37,500 years ago, which has prompted the "Ebro Frontier" hypothesis which states that the river presented a geographic barrier preventing modern human immigration, and thus prolonging Neanderthal persistence. However, the dating of the Iberian Transition is debated, with a contested timing of 43,000–40,800 years ago at Cueva Bajondillo, Spain. The Châtelperronian appears in northeastern Iberia about 42,500–41,600 years ago. Some Neanderthals in Gibraltar were dated to much later than this—such as Zafarraya (30,000 years ago) and Gorham's Cave (28,000 years ago)—which may be inaccurate as they were based on ambiguous artefacts instead of direct dating. A claim of Neanderthals surviving in a polar refuge in the Ural Mountains is loosely supported by Mousterian stone tools dating to 34,000 years ago from the northern Siberian Byzovaya site at a time when modern humans may not yet have colonised the northern reaches of Europe; however, modern human remains are known from the nearby Mamontovaya Kurya site dating to 40,000 years ago. Indirect dating of Neanderthals remains from Mezmaiskaya Cave reported a date of about 30,000 years ago, but direct dating instead yielded 39,700 ±1,100 years ago, more in line with trends exhibited in the rest of Europe. The earliest indication of Upper Palaeolithic modern human immigration into Europe is the Balkan Bohunician industry beginning 48,000 years ago, likely deriving from the Levantine Emiran industry, and the earliest bones in Europe date to roughly 45–43,000 years ago in Bulgaria, Italy, and Britain. This wave of modern humans replaced Neanderthals. However, Neanderthals and H. sapiens have a much longer contact history. DNA evidence indicates H. sapiens contact with Neanderthals and admixture as early as 120–100,000 years ago. A 2019 reanalysis of 210,000-year-old skull fragments from the Greek Apidima Cave assumed to have belonged to a Neanderthal concluded that they belonged to a modern human, and a Neanderthal skull dating to 170,000 years ago from the cave indicates H. sapiens were replaced by Neanderthals until returning about 40,000 years ago. This identification was refuted by a 2020 study. Archaeological evidence suggests that Neanderthals displaced modern humans in the Near East around 100,000 years ago until about 60–50,000 years ago. Historically, modern human technology was viewed as vastly superior to that of Neanderthals, with more efficient weaponry and subsistence strategies, and Neanderthals simply went extinct because they could not compete. The discovery of Neanderthal/modern human introgression has caused the resurgence of the multiregional hypothesis, wherein the present day genetic makeup of all humans is the result of complex genetic contact among several different populations of humans dispersed across the world. By this model, Neanderthals and other recent archaic humans were simply assimilated into the modern human genome – that is, they were effectively bred out into extinction. Modern humans coexisted with Neanderthals in Europe for around 3,000 to 5,000 years. Their ultimate extinction coincides with Heinrich event 4, a period of intense seasonality; later Heinrich events are also associated with massive cultural turnovers when European human populations collapsed. This climate change may have depopulated several regions of Neanderthals, like previous cold spikes, but these areas were instead repopulated by immigrating humans, leading to Neanderthal extinction. In southern Iberia, there is evidence that Neanderthal populations declined during H4 and the associated proliferation of Artemisia-dominated desert-steppes. It has also been proposed that climate change was the primary driver, as their low population left them vulnerable to any environmental change, with even a small drop in survival or fertility rates possibly quickly leading to their extinction. However, Neanderthals and their ancestors had survived through several glacial periods over their hundreds of thousands of years of European habitation. It is also proposed that around 40,000 years ago, when Neanderthal populations may have already been dwindling from other factors, the Campanian Ignimbrite Eruption in Italy could have led to their final demise, as it produced 2–4 °C (3.6–7.2 °F) cooling for a year and acid rain for several more years. Modern humans may have introduced African diseases to Neanderthals, contributing to their extinction. A lack of immunity, compounded by an already low population, was potentially devastating to the Neanderthal population, and low genetic diversity could have also rendered fewer Neanderthals naturally immune to these new diseases ("differential pathogen resistance" hypothesis). However, compared to modern humans, Neanderthals had a similar or higher genetic diversity for 12 major histocompatibility complex (MHC) genes associated with the adaptive immune system, casting doubt on this model. Low population and inbreeding depression may have caused maladaptive birth defects, which could have contributed to their decline (mutational meltdown). In late-20th-century New Guinea, due to cannibalistic funerary practices, the Fore people were decimated by transmissible spongiform encephalopathies, specifically kuru, a highly virulent disease spread by ingestion of prions found in brain tissue. However, individuals with the 129 variant of the PRNP gene were naturally immune to the prions. Studying this gene led to the discovery that the 129 variant was widespread among all modern humans, which could indicate widespread cannibalism at some point in human prehistory. Because Neanderthals are known to have practised cannibalism to an extent and to have co-existed with modern humans, British palaeoanthropologist Simon Underdown speculated that modern humans transmitted a kuru-like spongiform disease to Neanderthals, and, because the 129 variant appears to have been absent in Neanderthals, it quickly killed them off. Neanderthals have been portrayed in popular culture including appearances in literature, visual media and comedy. The "caveman" archetype often mocks Neanderthals and depicts them as primitive, hunchbacked, knuckle-dragging, club-wielding, grunting, nonsocial characters driven solely by animal instinct. "Neanderthal" can also be used as an insult. In literature, they are sometimes depicted as brutish or monstrous, such as in H. G. Wells' The Grisly Folk and Elizabeth Marshall Thomas' The Animal Wife, but sometimes with a civilised but unfamiliar culture, as in William Golding's The Inheritors, Björn Kurtén's Dance of the Tiger, and Jean M. Auel's Clan of the Cave Bear and her Earth's Children series. Template:Authority control Taxonomy[edit] See also: Human taxonomy Etymology[edit] The site of Kleine Feldhofer Grotte where Neanderthal 1 was discovered Neanderthals are named after the Neander Valley in which the first identified specimen was found. The valley was spelled Neanderthal and the species was spelled Neanderthaler in German until the spelling reform of 1901. The spelling Neandertal for the species is occasionally seen in English, even in scientific publications, but the scientific name, H. neanderthalensis, is always spelled with th according to the principle of priority. The vernacular name of the species in German is always Neandertaler ("inhabitant of the Neander Valley"), whereas Neandertal always refers to the valley. The valley itself was named after the late 17th century German theologian and hymn writer Joachim Neander, who often visited the area. His name in turn means 'new man', being a learned Graecisation of the German surname Neumann. Neanderthal can be pronounced using the /t/ (as in /niˈændərtɑːl/) or the standard English pronunciation of th with the fricative /θ/ (as /niˈændərθɔːl/). Neanderthal 1, the type specimen, was known as the "Neanderthal cranium" or "Neanderthal skull" in anthropological literature, and the individual reconstructed on the basis of the skull was occasionally called "the Neanderthal man". The binomial name Homo neanderthalensis—extending the name "Neanderthal man" from the individual specimen to the entire species, and formally recognising it as distinct from humans—was first proposed by Irish geologist William King in a paper read to the 33rd British Science Association in 1863. However, in 1864, he recommended that Neanderthals and modern humans be classified in different genera as he compared the Neanderthal braincase to that of a chimpanzee and argued that they were "incapable of moral and [theistic] conceptions". Ernst Haeckel's Primate family tree showing H. stupidus (Neanderthal) as the ancestor to H. sapiens Research history[edit] Skullcap of Neanderthal 1, the type specimen, at the Musée de l'Homme, Paris The first Neanderthal remains—Engis 2 (a skull)—were discovered in 1829 by Dutch/Belgian prehistorian Philippe-Charles Schmerling in the Grottes d'Engis, Belgium. He concluded that these "poorly developed" human remains must have been buried at the same time and by the same causes as the co-existing remains of extinct animal species. In 1848, Gibraltar 1 from Forbes' Quarry was presented to the Gibraltar Scientific Society by their Secretary Lieutenant Edmund Henry Réné Flint, but was thought to be a modern human skull. In 1856, local schoolteacher Johann Carl Fuhlrott recognised bones from Kleine Feldhofer Grotte in Neander Valley—Neanderthal 1 (the holotype specimen)—as distinct from modern humans, and gave them to German anthropologist Hermann Schaaffhausen to study in 1857. It comprised the cranium, thigh bones, right arm, left humerus and ulna, left ilium (hip bone), part of the right shoulder blade, and pieces of the ribs. Following Charles Darwin's On the Origin of Species, Fuhlrott and Schaaffhausen argued the bones represented an ancient modern human form; Schaaffhausen, a social Darwinist, believed that humans linearly progressed from savage to civilised, and so concluded that Neanderthals were barbarous cave-dwellers. Fuhlrott and Schaaffhausen met opposition namely from the prolific pathologist Rudolf Virchow who argued against defining new species based on only a single find. In 1872, Virchow erroneously interpreted Neanderthal characteristics as evidence of senility, disease and malformation instead of archaicness, which stalled Neanderthal research until the end of the century. By the early 20th century, numerous other Neanderthal discoveries were made, establishing H. neanderthalensis as a legitimate species. The most influential specimen was La Chapelle-aux-Saints 1 ("The Old Man") from La Chapelle-aux-Saints, France. French palaeontologist Marcellin Boule authored several publications, among the first to establish palaeontology as a science, detailing the specimen, but reconstructed him as slouching, ape-like, and only remotely related to modern humans. The 1912 'discovery' of Piltdown Man (a hoax), appearing much more similar to modern humans than Neanderthals, was used as evidence that multiple different and unrelated branches of primitive humans existed, and supported Boule's reconstruction of H. neanderthalensis as a far distant relative and an evolutionary dead-end. He fuelled the popular image of Neanderthals as barbarous, slouching, club-wielding primitives; this image was reproduced for several decades and popularised in science fiction works, such as the 1911 The Quest for Fire by J.-H. Rosny aîné and the 1927 The Grisly Folk by H. G. Wells in which they are depicted as monsters. In 1911, Scottish anthropologist Arthur Keith reconstructed La Chapelle-aux-Saints 1 as an immediate precursor to modern humans, sitting next to a fire, producing tools, wearing a necklace, and having a more humanlike posture, but this failed to garner much scientific rapport, and Keith later abandoned his thesis in 1915. By the middle of the century, based on the exposure of Piltdown Man as a hoax as well as a reexamination of La Chapelle-aux-Saints 1 (who had osteoarthritis which caused slouching in life) and new discoveries, the scientific community began to rework its understanding of Neanderthals. Ideas such as Neanderthal behaviour, intelligence and culture were being discussed, and a more humanlike image of them emerged. In 1939, American anthropologist Carleton Coon reconstructed a Neanderthal in a modern business suit and hat to emphasise that they would be, more or less, indistinguishable from modern humans had they survived into the present. William Golding's 1955 novel The Inheritors depicts Neanderthals as much more emotional and civilised. However, Boule's image continued to influence works until the 1960s. In modern-day, Neanderthal reconstructions are often very humanlike. Hominin timelineThis box: viewtalkedit−10 —–−9 —–−8 —–−7 —–−6 —–−5 —–−4 —–−3 —–−2 —–−1 —–0 —MiocenePliocenePleistoceneHomininiNakalipithecusSamburupithecusOuranopithecus(Ou. turkae)(Ou. macedoniensis)ChororapithecusOreopithecusSivapithecusSahelanthropusGraecopithecusOrrorin(O. praegens)(O. tugenensis)Ardipithecus(Ar. kadabba)(Ar. ramidus)Australopithecus(Au. africanus)(Au. afarensis)(Au. anamensis)H. habilis(H. rudolfensis)(Au. garhi)H. erectus(H. antecessor)(H. ergaster)(Au. sediba)H. heidelbergensisHomo sapiensNeanderthalsDenisovans ←Earlier apes←Gorilla split←Chimpanzee split←Earliest bipedal←Earliest sign of Ardipithecus←Earliest sign of Australopithecus←Earliest stone tools←Earliest sign of Homo←Dispersal beyond Africa←Earliest fire / cooking←Earliest rock art←Earliest clothes←Modern humansHominidsParanthropus(million years ago) Hybridisation between Neanderthals and early modern humans had been suggested early on, such as by English anthropologist Thomas Huxley in 1890, Danish ethnographer Hans Peder Steensby in 1907, and Coon in 1962. In the early 2000s, supposed hybrid specimens were discovered: Lagar Velho 1 and Muierii 1. However, similar anatomy could also have been caused by adapting to a similar environment rather than interbreeding. Neanderthal admixture was found to be present in modern populations in 2010 with the mapping of the first Neanderthal genome sequence. This was based on three specimens in Vindija Cave, Croatia, which contained almost 4% archaic DNA (allowing for near complete sequencing of the genome). However, there was approximately 1 error for every 200 letters (base pairs) based on the implausibly high mutation rate, probably due to the preservation of the sample. In 2012, British-American geneticist Graham Coop hypothesised that they instead found evidence of a different archaic human species interbreeding with modern humans, which was disproven in 2013 by the sequencing of a high-quality Neanderthal genome preserved in a toe bone from Denisova Cave, Siberia. Classification[edit] Homo sapiens Denisovan from Denisova Cave Denisovan from Baishiya Karst Cave Neanderthal from Denisova Cave Neanderthal from Sidrón Cave Neanderthal from Vindija Cave 2019 phylogeny based on comparison of ancient proteomes and genomes with those of modern species. Neanderthals are hominids in the genus Homo, humans, and generally classified as a distinct species, H. neanderthalensis, although sometimes as a subspecies of modern human as Homo sapiens neanderthalensis. This would necessitate the classification of modern humans as H. sapiens sapiens. A large part of the controversy stems from the vagueness of the term "species", as it is generally used to distinguish two genetically isolated populations, but admixture between modern humans and Neanderthals is known to have occurred. However, the absence of Neanderthal-derived patrilineal Y-chromosome and matrilineal mitochondrial DNA (mtDNA) in modern humans, along with the underrepresentation of Neanderthal X chromosome DNA, could imply reduced fertility or frequent sterility of some hybrid crosses, representing a partial biological reproductive barrier between the groups, and therefore species distinction. In 2014 geneticist Svante Pääbo summarised the controversy, describing such "taxonomic wars" as unresolvable, "since there is no definition of species perfectly describing the case". Neanderthals are thought to have been more closely related to Denisovans than to modern humans. Likewise, Neanderthals and Denisovans share a more recent last common ancestor (LCA) than to modern humans, based on nuclear DNA (nDNA). However, Neanderthals and modern humans share a more recent mitochondrial LCA (observable by studying mtDNA). This likely resulted from an interbreeding event subsequent to the Neanderthal/Denisovan split which introduced another mtDNA line. This involved either introgression coming from an unknown archaic human into Denisovans, or introgression from an earlier unidentified modern human wave from Africa into Neanderthals. Evolution[edit] Stage 1: early-pre-Neanderthal, possibly H. erectus (Tautavel Man, 450,000 years ago)Stage 2: archaic Neanderthal, possibly H. heidelbergensis (Miguelón, 430,000 years ago)Stage 3: early Neanderthal (Saccopastore I, 130,000 years ago)Stage 4: classic European Neanderthal (La Chapelle-aux-Saints 1, 50,000 years ago)The accretion model It is largely thought that H. heidelbergensis was the last common ancestor of Neanderthals, Denisovans and modern humans before populations became isolated in Europe, Asia and Africa, respectively. The taxonomic distinction between H. heidelbergensis and Neanderthals is mostly based on a fossil gap in Europe between 300 and 243,000 years ago during marine isotope stage 8. "Neanderthals", by convention, are fossils which date to after this gap. However, 430,000-year-old bones at Sima de los Huesos could represent early Neanderthals or a closely related group, and the 400,000-year-old Aroeira 3 could represent a transitional phase. Ancestral and derived morphs could have lived concurrently. It is also possible that there was gene flow between Western Europe and Africa during the Middle Pleistocene, obscuring Neanderthal characteristics in such specimens, namely from Ceprano, Italy, and Sićevo Gorge, Serbia. The fossil record is much more complete from 130,000 years ago onwards, and specimens from this period make up the bulk of known Neanderthal skeletons. Dental remains from the Italian Visogliano and Fontana Ranuccio sites indicate that Neanderthal dental features had evolved by around 450–430,000 years ago during the Middle Pleistocene. There are two main hypotheses regarding the evolution of Neanderthals following the Neanderthal/human split: two-phase and accretion. Two-phase argues that a single major environmental event—such as the Saale glaciation—caused European H. heidelbergensis to increase rapidly in body size and robustness, as well as undergoing a lengthening of the head (phase 1), which then led to other changes in skull anatomy (phase 2). However, Neanderthal anatomy may not have been driven entirely by adapting to cold weather. Accretion holds that Neanderthals slowly evolved over time from the ancestral H. heidelbergensis, divided into four stages: early-pre-Neanderthals (MIS 12, Elster glaciation), pre-Neanderthals sensu lato (MIS 11–9, Holstein interglacial), early Neanderthals (MIS 7–5, Saale glaciation–Eemian), and classic Neanderthals sensu stricto (MIS 4–3, Würm glaciation). Numerous dates for the Neanderthal/human split have been suggested. The date of around 250,000 years ago cites "H. helmei" as being the last common ancestor (LCA), and the split is associated with the Levallois technique of making stone tools. The date of about 400,000 years ago uses H. heidelbergensis as the LCA. Estimates of 600,000 years ago assume that "H. rhodesiensis" was the LCA, which split off into modern human lineage and a Neanderthal/H. heidelbergensis lineage. Eight hundred thousand years ago has H. antecessor as the LCA, but different variations of this model would push the date back to 1 million years ago. However, a 2020 analysis of H. antecessor enamel proteomes suggests that H. antecessor is related but not a direct ancestor. DNA studies have yielded various results for the Neanderthal/human divergence time, such as 538–315, 553–321, 565–503, 654–475, 690–550, 765–550, 741–317, and 800–520,000 years ago; and a dental analysis concluded before 800,000 years ago. Neanderthals and Denisovans are more closely related to each other than they are to modern humans, meaning the Neanderthal/Denisovan split occurred after their split with modern humans. Assuming a mutation rate of 1 × 10 or 0.5 × 10 per base pair (bp) per year, the Neanderthal/Denisovan split occurred around either 236–190,000 or 473–381,000 years ago, respectively. Using 1.1 × 10 per generation with a new generation every 29 years, the time is 744,000 years ago. Using 5 × 10 nucleotide sites per year, it is 616,000 years ago. Using the latter dates, the split had likely already occurred by the time hominins spread out across Europe, and unique Neanderthal features had begun evolving by 600–500,000 years ago. Before splitting, Neanderthal/Denisovans (or "Neandersovans") migrating out of Africa into Europe apparently interbred with an unidentified "superarchaic" human species who were already present there; these superarchaics were the descendants of a very early migration out of Africa around 1.9 mya. Demographics[edit] Further information: Neanderthals in Southwest Asia, Neanderthals in Gibraltar, and List of Neanderthal sites Range[edit] Neanderthal skull from Tabun Cave, Israel, at the Israel Museum Pre- and early Neanderthals, living before the Eemian interglacial (130,000 years ago), are poorly known and come mostly from Western European sites. From 130,000 years ago onwards, the quality of the fossil record increases dramatically with classic Neanderthals, who are recorded from Western, Central, Eastern and Mediterranean Europe, as well as Southwest, Central and Northern Asia up to the Altai Mountains in southern Siberia. Pre- and early Neanderthals, on the other hand, seem to have continuously occupied only France, Spain and Italy, although some appear to have moved out of this "core-area" to form temporary settlements eastward (although without leaving Europe). Nonetheless, southwestern France has the highest density of sites for pre-, early and classic Neanderthals. The Neanderthals were the first human species to permanently occupy Europe as the continent was only sporadically occupied by earlier humans. The southernmost find was recorded at Shuqba Cave, Levant; reports of Neanderthals from the North African Jebel Irhoud and Haua Fteah have been reidentified as H. sapiens. Their easternmost presence is recorded at Denisova Cave, Siberia 85°E; the southeast Chinese Maba Man, a skull, shares several physical attributes with Neanderthals, although these may be the result of convergent evolution rather than Neanderthals extending their range to the Pacific Ocean. The northernmost bound is generally accepted to have been 55°N, with unambiguous sites known between 50–53°N, although this is difficult to assess because glacial advances destroy most human remains, and palaeoanthropologist Trine Kellberg Nielsen has argued that a lack of evidence of Southern Scandinavian occupation is (at least during the Eemian interglacial) due to the former explanation and a lack of research in the area. Middle Palaeolithic artefacts have been found up to 60°N on the Russian plains, but these are more likely attributed to modern humans. A 2017 study claimed the presence of Homo at the 130,000-year-old Californian Cerutti Mastodon site in North America, but this is largely considered implausible. It is unknown how the rapidly fluctuating climate of the last glacial period (Dansgaard–Oeschger events) impacted Neanderthals, as warming periods would produce more favourable temperatures but encourage forest growth and deter megafauna, whereas frigid periods would produce the opposite. However, Neanderthals may have preferred a forested landscape. Stable environments with mild mean annual temperatures may have been the most suitable Neanderthal habitats. Populations may have peaked in cold but not extreme intervals, such as marine isotope stages 8 and 6 (respectively, 300,000 and 191,000 years ago during the Saale glaciation). It is possible their range expanded and contracted as the ice retreated and grew, respectively, to avoid permafrost areas, residing in certain refuge zones during glacial maxima. In 2021, Israeli anthropologist Israel Hershkovitz and colleagues suggested the 140- to 120,000-year-old Israeli Nesher Ramla remains, which feature a mix of Neanderthal and more ancient H. erectus traits, represent one such source population which recolonised Europe following a glacial period. Map of Europe during the Würm glaciation 70–20,000 years ago Population[edit] Like modern humans, Neanderthals probably descended from a very small population with an effective population—the number of individuals who can bear or father children—of 3,000 to 12,000 approximately. However, Neanderthals maintained this very low population, proliferating weakly harmful genes due to the reduced effectivity of natural selection. Various studies, using mtDNA analysis, yield varying effective populations, such as about 1,000 to 5,000; 5,000 to 9,000 remaining constant; or 3,000 to 25,000 steadily increasing until 52,000 years ago before declining until extinction. Archaeological evidence suggests that there was a tenfold increase in the modern human population in Western Europe during the period of the Neanderthal/modern human transition, and Neanderthals may have been at a demographic disadvantage due to a lower fertility rate, a higher infant mortality rate, or a combination of the two. Estimates giving a total population in the higher tens of thousands are contested. A consistently low population may be explained in the context of the "Boserupian Trap": a population's carrying capacity is limited by the amount of food it can obtain, which in turn is limited by its technology. Innovation increases with population, but if the population is too low, innovation will not occur very rapidly and the population will remain low. This is consistent with the apparent 150,000 year stagnation in Neanderthal lithic technology. In a sample of 206 Neanderthals, based on the abundance of young and mature adults in comparison to other age demographics, about 80% of them above the age of 20 died before reaching 40. This high mortality rate was probably due to their high-stress environment. However, it has also been estimated that the age pyramids for Neanderthals and contemporary modern humans were the same. Infant mortality was estimated to have been very high for Neanderthals, about 43% in northern Eurasia. class=notpageimage\| Locations of Neanderthal finds in Europe and the Levant.View referencesShow map of Europeclass=notpageimage\| Locations of Neanderthal finds in Eurasia (note, part of Spain is cut off)View referencesShow map of Asia Anatomy[edit] Main article: Neanderthal anatomy Build[edit] Comparisons of a modern Eurasian male example (left) and a Neanderthal (right) skull reconstruction at the Cleveland Museum of Natural HistoryNeanderthal skull features Neanderthals had more robust and stockier builds than typical modern humans, wider and barrel-shaped rib cages; wider pelvises; and proportionally shorter forearms and forelegs. Based on 45 Neanderthal long bones from 14 men and 7 women, the average height was 164 to 168 cm (5 ft 5 in to 5 ft 6 in) for males and 152 to 156 cm (5 ft 0 in to 5 ft 1 in) for females. For comparison, the average height of 20 males and 10 females Upper Palaeolithic humans is, respectively, 176.2 cm (5 ft 9.4 in) and 162.9 cm (5 ft 4.1 in), although this decreases by 10 cm (4 in) nearer the end of the period based on 21 males and 15 females; and the average in the year 1900 was 163 cm (5 ft 4 in) and 152.7 cm (5 ft 0 in), respectively. The fossil record shows that adult Neanderthals varied from about 147.5 to 177 cm (4 ft 10 in to 5 ft 10 in) in height, although some may have grown much taller (73.8 to 184.8 cm based on footprint length and from 65.8 to 189.3 cm based on footprint width). For Neanderthal weight, samples of 26 specimens found an average of 77.6 kg (171 lb) for males and 66.4 kg (146 lb) for females. Using 76 kg (168 lb), the body mass index for Neanderthal males was calculated to be 26.9–28.2, which in modern humans correlates to being overweight. This indicates a very robust build. The Neanderthal LEPR gene concerned with storing fat and body heat production is similar to that of the woolly mammoth, and so was likely an adaptation for cold climate. Neanderthal hunters depicted in the Gallo-Roman Museum, Tongeren The neck vertebrae of Neanderthals are thicker from the front to the rear and transversely than those of (most) modern humans, leading to stability, possibly to accommodate a different head shape and size. Although the Neanderthal thorax (where the ribcage is) was similar in size to modern humans, the longer and straighter ribs would have equated to a widened mid-lower thorax and stronger breathing in the lower thorax, which are indicative of a larger diaphragm and possibly greater lung capacity. The lung capacity of Kebara 2 was estimated to have been 9.04 L (2.39 US gal), compared to the average human capacity of 6 L (1.6 US gal) for males and 4.7 L (1.2 US gal) for females. The Neanderthal chest was also more pronounced (expanded front-to-back, or antero-posteriorly). The sacrum (where the pelvis connects to the spine) was more vertically inclined, and was placed lower in relation to the pelvis, causing the spine to be less curved (exhibit less lordosis) and to fold in on itself somewhat (to be invaginated). In modern populations, this condition affects just a proportion of the population, and is known as a lumbarized sacrum. Such modifications to the spine would have enhanced side-to-side (mediolateral) flexion, better supporting the wider lower thorax. It is claimed by some that this feature would be normal for all Homo, even tropically-adapted Homo ergaster or erectus, with the condition of a narrower thorax in most modern humans being a unique characteristic. Body proportions are usually cited as being "hyperarctic" as adaptations to the cold, because they are similar to those of human populations which developed in cold climates—the Neanderthal build is most similar to that of Inuit and Siberian Yupiks among modern humans—and shorter limbs result in higher retention of body heat. Nonetheless, Neanderthals from more temperate climates—such as Iberia—still retain the "hyperarctic" physique. In 2019, English anthropologist John Stewart and colleagues suggested Neanderthals instead were adapted for sprinting, because of evidence of Neanderthals preferring warmer wooded areas over the colder mammoth steppe, and DNA analysis indicating a higher proportion of fast-twitch muscle fibres in Neanderthals than in modern humans. He explained their body proportions and greater muscle mass as adaptations to sprinting as opposed to the endurance-oriented modern human physique, as persistence hunting may only be effective in hot climates where the hunter can run prey to the point of heat exhaustion (hyperthermia). They had longer heel bones, reducing their ability for endurance running, and their shorter limbs would have reduced moment arm at the limbs, allowing for greater net rotational force at the wrists and ankles, causing faster acceleration. In 1981, American palaeoanthropologist Erik Trinkaus made note of this alternate explanation, but considered it less likely. Face[edit] Neanderthal man reconstruction, Natural History Museum, London. Neanderthals had less developed chins, sloping foreheads, and longer, broader, more projecting noses. The Neanderthal skull is typically more elongated, but also wider, and less globular than that of most modern humans, and features much more of an occipital bun, or "chignon", a protrusion on the back of the skull, although it is within the range of variation for modern humans who have it. It is caused by the cranial base and temporal bones being placed higher and more towards the front of the skull, and a flatter skullcap. The Neanderthal face is characterized by mid-facial prognathism, where the zygomatic arches are positioned in a rearward location relative to modern humans, while their maxillary bones and nasal bones are positioned in a more forward direction, by comparison. Neanderthal eyeballs are larger than those of modern humans. One study proposed that this was due to Neanderthals having enhanced visual abilities, at the expense of neocortical and social development. However, this study was rejected by other researchers who concluded that eyeball size does not offer any evidence for the cognitive abilities of Neanderthal or modern humans. The projected Neanderthal nose and paranasal sinuses have generally been explained as having warmed air as it entered the lungs and retained moisture ("nasal radiator" hypothesis); if their noses were wider, it would differ to the generally narrowed shape in cold-adapted creatures, and that it would have been caused instead by genetic drift. Also, the sinuses reconstructed wide are not grossly large, being comparable in size to those of modern humans. However, if sinus size is not an important factor for breathing cold air, then the actual function would be unclear, so they may not be a good indicator of evolutionary pressures to evolve such a nose. Further, a computer reconstruction of the Neanderthal nose and predicted soft tissue patterns shows some similarities to those of modern Arctic peoples, potentially meaning the noses of both populations convergently evolved for breathing cold, dry air. Neanderthals featured a rather large jaw which was once cited as a response to a large bite force evidenced by heavy wearing of Neanderthal front teeth (the "anterior dental loading" hypothesis), but similar wearing trends are seen in contemporary humans. It could also have evolved to fit larger teeth in the jaw, which would better resist wear and abrasion, and the increased wear on the front teeth compared to the back teeth probably stems from repetitive use. Neanderthal dental wear patterns are most similar to those of modern Inuit. The incisors are large and shovel-shaped, and, compared to modern humans, there was an unusually high frequency of taurodontism, a condition where the molars are bulkier due to an enlarged pulp (tooth core). Taurodontism was once thought to have been a distinguishing characteristic of Neanderthals which lent some mechanical advantage or stemmed from repetitive use, but was more likely simply a product of genetic drift. The bite force of Neanderthals and modern humans is now thought to be about the same, about 285 N (64 lbf) and 255 N (57 lbf) in modern human males and females, respectively. Reconstruction of an elderly Neanderthal man Brain[edit] The Neanderthal braincase averages 1,640 cm (100 cu in) for males and1,460 cm (89 cu in) for females, which is significantly larger than the averages for all groups of extant humans; for example, modern European males average 1,362 cm (83.1 cu in) and females 1,201 cm (73.3 cu in). For 28 modern human specimens from 190,000 to 25,000 years ago, the average was about 1,478 cm (90.2 cu in) disregarding sex, and modern human brain size is suggested to have decreased since the Upper Palaeolithic. The largest Neanderthal brain, Amud 1, was calculated to be 1,736 cm (105.9 cu in), one of the largest ever recorded in hominids. Both Neanderthal and human infants measure about 400 cm (24 cu in). When viewed from the rear, the Neanderthal braincase has lower, wider, rounder appearance than in anatomically modern humans. This characteristic shape is referred to as "en bombe" (bomb-like), and is unique to Neanderthals, with all other hominid species (including most modern humans) generally having narrow and relatively upright cranial vaults, when viewed from behind. The Neanderthal brain would have been characterized by relatively smaller parietal lobes and a larger cerebellum. Neanderthal brains also have larger occipital lobes (relating to the classic occurrence of an occipital bun in Neanderthal skull anatomy, as well as the greater width of their skulls), which implies internal differences in the proportionality of brain-internal regions, relative to Homo sapiens, consistent with external measurements obtained with fossil skulls. Their brains also have larger temporal lobe poles, wider orbitofrontal cortex, and larger olfactory bulbs, suggesting potential differences in language comprehension and associations with emotions (temporal functions), decision making (the orbitofrontal cortex) and sense of smell (olfactory bulbs). Their brains also show different rates of brain growth and development. Such differences, while slight, would have been visible to natural selection and may underlie and explain differences in the material record in things like social behaviors, technological innovation and artistic output. Hair and skin colour[edit] The lack of sunlight most likely led to the proliferation of lighter skin in Neanderthals, although it has been recently claimed that light skin in modern Europeans was not particularly prolific until perhaps the Bronze Age. Genetically, BNC2 was present in Neanderthals, which is associated with light skin colour; however, a second variation of BNC2 was also present, which in modern populations is associated with darker skin colour in the UK Biobank. DNA analysis of three Neanderthal females from southeastern Europe indicates that they had brown eyes, dark skin colour and brown hair, with one having red hair. In modern humans, skin and hair colour is regulated by the melanocyte-stimulating hormone—which increases the proportion of eumelanin (black pigment) to phaeomelanin (red pigment)—which is encoded by the MC1R gene. There are five known variants in modern humans of the gene which cause loss-of-function and are associated with light skin and hair colour, and another unknown variant in Neanderthals (the R307G variant) which could be associated with pale skin and red hair. The R307G variant was identified in a Neanderthal from Monti Lessini, Italy, and possibly Cueva del Sidrón, Spain. However, as in modern humans, red was probably not a very common hair colour because the variant is not present in many other sequenced Neanderthals. Metabolism[edit] Maximum natural lifespan and the timing of adulthood, menopause and gestation were most likely very similar to modern humans. However, it has been hypothesised, based on the growth rates of teeth and tooth enamel, that Neanderthals matured faster than modern humans, although this is not backed up by age biomarkers. The main differences in maturation are the atlas bone in the neck as well as the middle thoracic vertebrae fused about 2 years later in Neanderthals than in modern humans, but this was more likely caused by a difference in anatomy rather than growth rate. Generally, models on Neanderthal caloric requirements report significantly higher intakes than those of modern humans because they typically assume Neanderthals had higher basal metabolic rates (BMRs) due to higher muscle mass, faster growth rate and greater body heat production against the cold; and higher daily physical activity levels (PALs) due to greater daily travelling distances while foraging. However, using a high BMR and PAL, American archaeologist Bryan Hockett estimated that a pregnant Neanderthal would have consumed 5,500 calories per day, which would have necessitated a heavy reliance on big game meat; such a diet would have caused numerous deficiencies or nutrient poisonings, so he concluded that these are poorly warranted assumptions to make. Neanderthals may have been more active during dimmer light conditions rather than broad daylight because they lived in regions with reduced daytime hours in the winter, hunted large game (such predators typically hunt at night to enhance ambush tactics), and had large eyes and visual processing neural centres. Genetically, colour blindness (which may enhance mesopic vision) is typically correlated with northern-latitude populations, and the Neanderthals from Vindija Cave, Croatia, had some substitutions in the Opsin genes which could have influenced colour vision. However, the functional implications of these substitutions are inconclusive. Neanderthal-derived alleles near ASB1 and EXOC6 are associated with being an evening person, narcolepsy and day-time napping. Pathology[edit] Neanderthals suffered a high rate of traumatic injury, with an estimated 79–94% of specimens showing evidence of healed major trauma, of which 37–52% were severely injured, and 13–19% injured before reaching adulthood. One extreme example is Shanidar 1, who shows signs of an amputation of the right arm likely due to a nonunion after breaking a bone in adolescence, osteomyelitis (a bone infection) on the left clavicle, an abnormal gait, vision problems in the left eye, and possible hearing loss (perhaps swimmer's ear). In 1995, Trinkaus estimated that about 80% succumbed to their injuries and died before reaching 40, and thus theorised that Neanderthals employed a risky hunting strategy ("rodeo rider" hypothesis). However, rates of cranial trauma are not significantly different between Neanderthals and Middle Palaeolithic modern humans (although Neanderthals seem to have had a higher mortality risk), there are few specimens of both Upper Palaeolithic modern humans and Neanderthals who died after the age of 40, and there are overall similar injury patterns between them. In 2012, Trinkaus concluded that Neanderthals instead injured themselves in the same way as contemporary humans, such as by interpersonal violence. A 2016 study looking at 124 Neanderthal specimens argued that high trauma rates were instead caused by animal attacks, and found that about 36% of the sample were victims of bear attacks, 21% big cat attacks, and 17% wolf attacks (totalling 92 positive cases, 74%). There were no cases of hyena attacks, although hyenas still nonetheless probably attacked Neanderthals, at least opportunistically. Such intense predation probably stemmed from common confrontations due to competition over food and cave space, and from Neanderthals hunting these carnivores. La Ferrassie 1 at the Musée de l'Homme, Paris Low population caused a low genetic diversity and probably inbreeding, which reduced the population's ability to filter out harmful mutations (inbreeding depression). However, it is unknown how this affected a single Neanderthal's genetic burden and, thus, if this caused a higher rate of birth defects than in modern humans. It is known, however, that the 13 inhabitants of Sidrón Cave collectively exhibited 17 different birth defects likely due to inbreeding or recessive disorders. Likely due to advanced age (60s or 70s), La Chapelle-aux-Saints 1 had signs of Baastrup's disease, affecting the spine, and osteoarthritis. Shanidar 1, who likely died at about 30 or 40, was diagnosed with the most ancient case of diffuse idiopathic skeletal hyperostosis (DISH), a degenerative disease which can restrict movement, which, if correct, would indicate a moderately high incident rate for older Neanderthals. Neanderthals were subject to several infectious diseases and parasites. Modern humans likely transmitted diseases to them; one possible candidate is the stomach bacteria Helicobacter pylori. The modern human papillomavirus variant 16A may descend from Neanderthal introgression. A Neanderthal at Cueva del Sidrón, Spain, shows evidence of a gastrointestinal Enterocytozoon bieneusi infection. The leg bones of the French La Ferrassie 1 feature lesions that are consistent with periostitis—inflammation of the tissue enveloping the bone—likely a result of hypertrophic osteoarthropathy, which is primarily caused by a chest infection or lung cancer. Neanderthals had a lower cavity rate than modern humans, despite some populations consuming typically cavity-causing foods in great quantity, which could indicate a lack of cavity-causing oral bacteria, namely Streptococcus mutans. Two 250,000-year-old Neanderthaloid children from Payré, France, present the earliest known cases of lead exposure of any hominin. They were exposed on two distinct occasions either by eating or drinking contaminated food or water, or inhaling lead-laced smoke from a fire. There are two lead mines within 25 km (16 mi) of the site. Culture[edit] Main article: Neanderthal behavior Social structure[edit] Group dynamics[edit] Skeleton of a Neanderthal child discovered in Roc de Marsal near Les Eyzies, France, on display at the Hall of Human Origins, Washington, D.C. Neanderthals likely lived in more sparsely distributed groups than contemporary modern humans, but group size is thought to have averaged 10 to 30 individuals, similar to modern hunter-gatherers. Reliable evidence of Neanderthal group composition comes from Cueva del Sidrón, Spain, and the footprints at Le Rozel, France: the former shows 7 adults, 3 adolescents, 2 juveniles and an infant; whereas the latter, based on footprint size, shows a group of 10 to 13 members where juveniles and adolescents made up 90%. A Neanderthal child's teeth analysed in 2018 showed it was weaned after 2.5 years, similar to modern hunter gatherers, and was born in the spring, which is consistent with modern humans and other mammals whose birth cycles coincide with environmental cycles. Indicated from various ailments resulting from high stress at a low age, such as stunted growth, British archaeologist Paul Pettitt hypothesised that children of both sexes were put to work directly after weaning; and Trinkaus said that, upon reaching adolescence, an individual may have been expected to join in hunting large and dangerous game. However, the bone trauma is comparable to modern Inuit, which could suggest a similar childhood between Neanderthals and contemporary modern humans. Further, such stunting may have also resulted from harsh winters and bouts of low food resources. Sites showing evidence of no more than three individuals may have represented nuclear families or temporary camping sites for special task groups (such as a hunting party). Bands likely moved between certain caves depending on the season, indicated by remains of seasonal materials such as certain foods, and returned to the same locations generation after generation. Some sites may have been used for over 100 years. Cave bears may have greatly competed with Neanderthals for cave space, and there is a decline in cave bear populations starting 50,000 years ago onwards (although their extinction occurred well after Neanderthals had died out). Neanderthals also had a preference for caves whose openings faced towards the south. Although Neanderthals are generally considered to have been cave dwellers, with 'home base' being a cave, open-air settlements near contemporaneously inhabited cave systems in the Levant could indicate mobility between cave and open-air bases in this area. Evidence for long-term open-air settlements is known from the 'Ein Qashish site in Israel, and Moldova I in Ukraine. Although Neanderthals appear to have had the ability to inhabit a range of environments—including plains and plateaux—open-air Neanderthals sites are generally interpreted as having been used as slaughtering and butchering grounds rather than living spaces. In 2022, remains of the first-known Neanderthal family (six adults and five children) were excavated from Chagyrskaya Cave in the Altai Mountains of southern Siberia in Russia. The family, which included a father, a daughter, and what appear to be cousins, most likely died together, presumably from starvation. Inter-group relations[edit] Neanderthal mother with child depicted in the Anthropos Pavilion of the Moravian Museum Canadian ethnoarchaeologist Brian Hayden calculated a self-sustaining population that avoids inbreeding to consist of about 450–500 individuals, which would necessitate these bands to interact with 8–53 other bands, but more likely the larger estimate given low population density. Analysis of the mtDNA of the Neanderthals of Cueva del Sidrón, Spain, showed that the three adult men belonged to the same maternal lineage, while the three adult women belonged to different ones. This suggests a patrilocal residence (that a woman moved out of her group to live with her partner). However, the DNA of a Neanderthal from Denisova Cave, Russia, shows that she had an inbreeding coefficient of 1⁄8 (her parents were either half-siblings with a common mother, double first cousins, an uncle and niece or aunt and nephew, or a grandfather and granddaughter or grandmother and grandson) and the inhabitants of Cueva del Sidrón show several defects, which may have been caused by inbreeding or recessive disorders. Considering most Neanderthal artifacts were sourced no more than 5 km (3.1 mi) from the main settlement, Hayden considered it unlikely these bands interacted very often, and mapping of the Neanderthal brain and their small group size and population density could indicate that they had a reduced ability for inter-group interaction and trade. However, a few Neanderthal artefacts in a settlement could have originated 20, 30, 100 and 300 km (12.5, 18.5, 60 and 185 mi) away. Based on this, Hayden also speculated that macro-bands formed which functioned much like those of the low-density hunter-gatherer societies of the Western Desert of Australia. Macro-bands collectively encompass 13,000 km (5,000 sq mi), with each band claiming 1,200–2,800 km (460–1,080 sq mi), maintaining strong alliances for mating networks or to cope with leaner times and enemies. Similarly, British anthropologist Eiluned Pearce and Cypriot archaeologist Theodora Moutsiou speculated that Neanderthals were possibly capable of forming geographically expansive ethnolinguistic tribes encompassing upwards of 800 people, based on the transport of obsidian up to 300 km (190 mi) from the source compared to trends seen in obsidian transfer distance and tribe size in modern hunter-gatherers. However, according to their model Neanderthals would not have been as efficient at maintaining long-distance networks as modern humans, probably due to a significantly lower population. Hayden noted an apparent cemetery of six or seven individuals at La Ferrassie, France, which, in modern humans, is typically used as evidence of a corporate group which maintained a distinct social identity and controlled some resource, trading, manufacturing and so on. La Ferrassie is also located in one of the richest animal-migration routes of Pleistocene Europe. Genetically, Neanderthals can be grouped into three distinct regions (above). Dots indicate sampled specimens. Genetic analysis indicates there were at least three distinct geographical groups—Western Europe, the Mediterranean coast, and east of the Caucasus—with some migration among these regions. Post-Eemian Western European Mousterian lithics can also be broadly grouped into three distinct macro-regions: Acheulean-tradition Mousterian in the southwest, Micoquien in the northeast, and Mousterian with bifacial tools (MBT) in between the former two. MBT may actually represent the interactions and fusion of the two different cultures. Southern Neanderthals exhibit regional anatomical differences from northern counterparts: a less protrusive jaw, a shorter gap behind the molars, and a vertically higher jawbone. These all instead suggest Neanderthal communities regularly interacted with neighbouring communities within a region, but not as often beyond. Nonetheless, over long periods of time, there is evidence of large-scale cross-continental migration. Early specimens from Mezmaiskaya Cave in the Caucasus and Denisova Cave in the Siberian Altai Mountains differ genetically from those found in Western Europe, whereas later specimens from these caves both have genetic profiles more similar to Western European Neanderthal specimens than to the earlier specimens from the same locations, suggesting long-range migration and population replacement over time. Similarly, artefacts and DNA from Chagyrskaya and Okladnikov Caves, also in the Altai Mountains, resemble those of eastern European Neanderthal sites about 3,000–4,000 km (1,900–2,500 mi) away more than they do artefacts and DNA of the older Neanderthals from Denisova Cave, suggesting two distinct migration events into Siberia. Neanderthals seem to have suffered a major population decline during MIS 4 (71–57,000 years ago), and the distribution of the Micoquian tradition could indicate that Central Europe and the Caucasus were repopulated by communities from a refuge zone either in eastern France or Hungary (the fringes of the Micoquian tradition) who dispersed along the rivers Prut and Dniester. There is also evidence of inter-group conflict: a skeleton from La Roche à Pierrot, France, showing a healed fracture on top of the skull apparently caused by a deep blade wound, and another from Shanidar Cave, Iraq, found to have a rib lesion characteristic of projectile weapon injuries. Social hierarchy[edit] Reconstruction of an elderly Neanderthal man and child in the Natural History Museum, Vienna It is sometimes suggested that, since they were hunters of challenging big game and lived in small groups, there was no sexual division of labour as seen in modern hunter-gatherer societies. That is, men, women and children all had to be involved in hunting, instead of men hunting with women and children foraging. However, with modern hunter-gatherers, the higher the meat dependency, the higher the division of labour. Further, tooth-wearing patterns in Neanderthal men and women suggest they commonly used their teeth for carrying items, but men exhibit more wearing on the upper teeth, and women the lower, suggesting some cultural differences in tasks. It is controversially proposed that some Neanderthals wore decorative clothing or jewellery—such as a leopard skin or raptor feathers—to display elevated status in the group. Hayden postulated that the small number of Neanderthal graves found was because only high-ranking members would receive an elaborate burial, as is the case for some modern hunter-gatherers. Trinkaus suggested that elderly Neanderthals were given special burial rites for lasting so long given the high mortality rates. Alternatively, many more Neanderthals may have received burials, but the graves were infiltrated and destroyed by bears. Given that 20 graves of Neanderthals aged under 4 have been found—over a third of all known graves—deceased children may have received greater care during burial than other age demographics. Looking at Neanderthal skeletons recovered from several natural rock shelters, Trinkaus said that, although Neanderthals were recorded as bearing several trauma-related injuries, none of them had significant trauma to the legs that would debilitate movement. He suggested that self worth in Neanderthal culture derived from contributing food to the group; a debilitating injury would remove this self-worth and result in near-immediate death, and individuals who could not keep up with the group while moving from cave to cave were left behind. However, there are examples of individuals with highly debilitating injuries being nursed for several years, and caring for the most vulnerable within the community dates even further back to H. heidelbergensis. Especially given the high trauma rates, it is possible that such an altruistic strategy ensured their survival as a species for so long. Food[edit] See also: Pleistocene human diet Hunting and gathering[edit] Red deer, the most commonly hunted Neanderthal game Neanderthals were once thought of as scavengers, but are now considered to have been apex predators. In 1980, it was hypothesised that two piles of mammoth skulls at La Cotte de St Brelade, Jersey, at the base of a gulley were evidence of mammoth drive hunting (causing them to stampede off a ledge), but this is contested. Living in a forested environment, Neanderthals were likely ambush hunters, getting close to and attacking their target—a prime adult—in a short burst of speed, thrusting in a spear at close quarters. Younger or wounded animals may have been hunted using traps, projectiles, or pursuit. Some sites show evidence that Neanderthals slaughtered whole herds of animals in large, indiscriminate hunts and then carefully selected which carcasses to process. Nonetheless, they were able to adapt to a variety of habitats. They appear to have eaten predominantly what was abundant within their immediate surroundings, with steppe-dwelling communities (generally outside of the Mediterranean) subsisting almost entirely on meat from large game, forest-dwelling communities consuming a wide array of plants and smaller animals, and waterside communities gathering aquatic resources, although even in more southerly, temperate areas such as the southeastern Iberian Peninsula, large game still featured prominently in Neanderthal diets. Contemporary humans, in contrast, seem to have used more complex food extraction strategies and generally had a more diverse diet. Nonetheless, Neanderthals still would have had to have eaten a varied enough diet to prevent nutrient deficiencies and protein poisoning, especially in the winter when they presumably ate mostly lean meat. Any food with high contents of other essential nutrients not provided by lean meat would have been vital components of their diet, such as fat-rich brains, carbohydrate-rich and abundant underground storage organs (including roots and tubers), or, like modern Inuit, the stomach contents of herbivorous prey items. For meat, they appear to have fed predominantly on hoofed mammals, namely red deer and reindeer as these two were the most abundant game, but also on other Pleistocene megafauna such as chamois, ibex, wild boar, steppe wisent, aurochs, woolly mammoth, straight-tusked elephant, woolly rhinoceros, wild horse, and so on. There is evidence of directed cave and brown bear hunting both in and out of hibernation, as well as butchering. Analysis of Neanderthal bone collagen from Vindija Cave, Croatia, shows nearly all of their protein needs derived from animal meat. Some caves show evidence of regular rabbit and tortoise consumption. At Gibraltar sites, there are remains of 143 different bird species, many ground-dwelling such as the common quail, corn crake, woodlark, and crested lark. Scavenging birds such as corvids and eagles were commonly exploited. Neanderthals also exploited marine resources on the Iberian, Italian and Peloponnesian Peninsulas, where they waded or dived for shellfish, as early as 150,000 years ago at Cueva Bajondillo, Spain, similar to the fishing record of modern humans. At Vanguard Cave, Gibraltar, the inhabitants consumed Mediterranean monk seal, short-beaked common dolphin, common bottlenose dolphin, Atlantic bluefin tuna, sea bream and purple sea urchin; and at Gruta da Figueira Brava, Portugal, there is evidence of large-scale harvest of shellfish, crabs and fish. Evidence of freshwater fishing was found in Grotte di Castelcivita, Italy, for trout, chub and eel; Abri du Maras, France, for chub and European perch; Payré, France; and Kudaro Cave, Russia, for Black Sea salmon. Edible plant and mushroom remains are recorded from several caves. Neanderthals from Cueva del Sidrón, Spain, based on dental tartar, likely had a meatless diet of mushrooms, pine nuts and moss, indicating they were forest foragers. Remnants from Amud Cave, Israel, indicates a diet of figs, palm tree fruits and various cereals and edible grasses. Several bone traumas in the leg joints could possibly suggest habitual squatting, which, if the case, was likely done while gathering food. Dental tartar from Grotte de Spy, Belgium, indicates the inhabitants had a meat-heavy diet including woolly rhinoceros and mouflon sheep, while also regularly consuming mushrooms. Neanderthal faecal matter from El Salt, Spain, dated to 50,000 years ago—the oldest human faecal matter remains recorded—show a diet mainly of meat but with a significant component of plants. Evidence of cooked plant foods—mainly legumes and, to a far lesser extent, acorns—was discovered in Kebara Cave, Israel, with its inhabitants possibly gathering plants in spring and fall and hunting in all seasons except fall, although the cave was probably abandoned in late summer to early fall. At Shanidar Cave, Iraq, Neanderthals collected plants with various harvest seasons, indicating they scheduled returns to the area to harvest certain plants, and that they had complex food-gathering behaviours for both meat and plants. Food preparation[edit] Neanderthals probably could employ a wide range of cooking techniques, such as roasting, and they may have been able to heat up or boil soup, stew, or animal stock. The abundance of animal bone fragments at settlements may indicate the making of fat stocks from boiling bone marrow, possibly taken from animals that had already died of starvation. These methods would have substantially increased fat consumption, which was a major nutritional requirement of communities with low carbohydrate and high protein intake. Neanderthal tooth size had a decreasing trend after 100,000 years ago, which could indicate an increased dependence on cooking or the advent of boiling, a technique that would have softened food. Yarrow growing in Spain At Cueva del Sidrón, Spain, Neanderthals likely cooked and possibly smoked food, as well as used certain plants—such as yarrow and camomile—as flavouring, although these plants may have instead been used for their medicinal properties. At Gorham's Cave, Gibraltar, Neanderthals may have been roasting pinecones to access pine nuts. At Grotte du Lazaret, France, a total of twenty-three red deer, six ibexes, three aurochs, and one roe deer appear to have been hunted in a single autumn hunting season, when strong male and female deer herds would group together for rut. The entire carcasses seem to have been transported to the cave and then butchered. Because this is such a large amount of food to consume before spoilage, it is possible these Neanderthals were curing and preserving it before winter set in. At 160,000 years old, it is the oldest potential evidence of food storage. The great quantities of meat and fat which could have been gathered in general from typical prey items (namely mammoths) could also indicate food storage capability. With shellfish, Neanderthals needed to eat, cook, or in some manner preserve them soon after collection, as shellfish spoils very quickly. At Cueva de los Aviones, Spain, the remains of edible, algae eating shellfish associated with the alga Jania rubens could indicate that, like some modern hunter gatherer societies, harvested shellfish were held in water-soaked algae to keep them alive and fresh until consumption. Competition[edit] Cave hyena skeleton Competition from large Ice Age predators was rather high. Cave lions likely targeted horses, large deer and wild cattle; and leopards primarily reindeer and roe deer; which heavily overlapped with Neanderthal diet. To defend a kill against such ferocious predators, Neanderthals may have engaged in a group display of yelling, arm waving, or stone throwing; or quickly gathered meat and abandoned the kill. However, at Grotte de Spy, Belgium, the remains of wolves, cave lions and cave bears—which were all major predators of the time—indicate Neanderthals hunted their competitors to some extent. Neanderthals and cave hyenas may have exemplified niche differentiation, and actively avoided competing with each other. Although they both mainly targeted the same groups of creatures—deer, horses and cattle—Neanderthals mainly hunted the former and cave hyenas the latter two. Further, animal remains from Neanderthal caves indicate they preferred to hunt prime individuals, whereas cave hyenas hunted weaker or younger prey, and cave hyena caves have a higher abundance of carnivore remains. Nonetheless, there is evidence that cave hyenas stole food and leftovers from Neanderthal campsites and scavenged on dead Neanderthal bodies. Cannibalism[edit] Neandertal remains from the Troisième caverne of Goyet Caves (Belgium). The remains have scrape marks, indicating that they were butchered, with cannibalism being the "most parsimonious explanation". There are several instances of Neanderthals practising cannibalism across their range. The first example came from the Krapina, Croatia site, in 1899, and other examples were found at Cueva del Sidrón and Zafarraya in Spain; and the French Grotte de Moula-Guercy, Les Pradelles, and La Quina. For the five cannibalised Neanderthals at the Grottes de Goyet, Belgium, there is evidence that the upper limbs were disarticulated, the lower limbs defleshed and also smashed (likely to extract bone marrow), the chest cavity disemboweled, and the jaw dismembered. There is also evidence that the butchers used some bones to retouch their tools. The processing of Neanderthal meat at Grottes de Goyet is similar to how they processed horse and reindeer. About 35% of the Neanderthals at Marillac-le-Franc, France, show clear signs of butchery, and the presence of digested teeth indicates that the bodies were abandoned and eaten by scavengers, likely hyaenas. These cannibalistic tendencies have been explained as either ritual defleshing, pre-burial defleshing (to prevent scavengers or foul smell), an act of war, or simply for food. Due to a small number of cases, and the higher number of cut marks seen on cannibalised individuals than animals (indicating inexperience), cannibalism was probably not a very common practice, and it may have only been done in times of extreme food shortages as in some cases in recorded human history. The arts[edit] See also: Prehistoric art and Art of the Middle Paleolithic Personal adornment[edit] Neanderthals used ochre, a clay earth pigment. Ochre is well documented from 60 to 45,000 years ago in Neanderthal sites, with the earliest example dating to 250–200,000 years ago from Maastricht-Belvédère, the Netherlands (a similar timespan to the ochre record of H. sapiens). It has been hypothesised to have functioned as body paint, and analyses of pigments from Pech de l'Azé, France, indicates they were applied to soft materials (such as a hide or human skin). However, modern hunter gatherers, in addition to body paint, also use ochre for medicine, for tanning hides, as a food preservative, and as an insect repellent, so its use as decorative paint for Neanderthals is speculative. Containers apparently used for mixing ochre pigments were found in Peștera Cioarei, Romania, which could indicate modification of ochre for solely aesthetic purposes. Decorated king scallop shell from Cueva Antón, Spain. Interior (left) with natural red colouration, and exterior (right) with traces of unnatural orange pigmentation Neanderthals collected uniquely shaped objects and are suggested to have modified them into pendants, such as a fossil Aspa marginata sea snail shell possibly painted red from Grotta di Fumane, Italy, transported over 100 km (62 mi) to the site about 47,500 years ago; three shells, dated to about 120–115,000 years ago, perforated through the umbo belonging to a rough cockle, a Glycymeris insubrica, and a Spondylus gaederopus from Cueva de los Aviones, Spain, the former two associated with red and yellow pigments, and the latter a red-to-black mix of hematite and pyrite; and a king scallop shell with traces of an orange mix of goethite and hematite from Cueva Antón, Spain. The discoverers of the latter two claim that pigment was applied to the exterior to make it match the naturally vibrant inside colouration. Excavated from 1949 to 1963 from the French Grotte du Renne, Châtelperronian beads made from animal teeth, shells and ivory were found associated with Neanderthal bones, but the dating is uncertain and Châtelperronian artefacts may actually have been crafted by modern humans and simply redeposited with Neanderthal remains. Speculative reconstruction of white-tailed eagle talon jewellery from Krapina, Croatia (arrows indicate cut marks) Gibraltarian palaeoanthropologists Clive and Geraldine Finlayson suggested that Neanderthals used various bird parts as artistic mediums, specifically black feathers. In 2012, the Finlaysons and colleagues examined 1,699 sites across Eurasia, and argued that raptors and corvids, species not typically consumed by any human species, were overrepresented and show processing of only the wing bones instead of the fleshier torso, and thus are evidence of feather plucking of specifically the large flight feathers for use as personal adornment. They specifically noted the cinereous vulture, red-billed chough, kestrel, lesser kestrel, alpine chough, rook, jackdaw and the white tailed eagle in Middle Palaeolithic sites. Other birds claimed to present evidence of modifications by Neanderthals are the golden eagle, rock pigeon, common raven and the bearded vulture. The earliest claim of bird bone jewellery is a number of 130,000-year-old white tailed eagle talons found in a cache near Krapina, Croatia, speculated, in 2015, to have been a necklace. A similar 39,000-year-old Spanish imperial eagle talon necklace was reported in 2019 at Cova Foradà in Spain, though from the contentious Châtelperronian layer. In 2017, 17 incision-decorated raven bones from the Zaskalnaya VI rock shelter, Ukraine, dated to 43–38,000 years ago were reported. Because the notches are more-or-less equidistant to each other, they are the first modified bird bones that cannot be explained by simple butchery, and for which the argument of design intent is based on direct evidence. Discovered in 1975, the so-called Mask of la Roche-Cotard, a mostly flat piece of flint with a bone pushed through a hole on the midsection—dated to 32, 40, or 75,000 years ago—has been purported to resemble the upper half of a face, with the bone representing eyes. It is contested whether it represents a face, or if it even counts as art. In 1988, American archaeologist Alexander Marshack speculated that a Neanderthal at Grotte de L'Hortus, France, wore a leopard pelt as personal adornment to indicate elevated status in the group based on a recovered leopard skull, phalanges and tail vertebrae. Abstraction[edit] The scratched floor of Gorham's Cave, Gibraltar As of 2014, 63 purported engravings have been reported from 27 different European and Middle Eastern Lower-to-Middle Palaeolithic sites, of which 20 are on flint cortexes from 11 sites, 7 are on slabs from 7 sites, and 36 are on pebbles from 13 sites. It is debated whether or not these were made with symbolic intent. In 2012, deep scratches on the floor of Gorham's Cave, Gibraltar, were discovered, dated to older than 39,000 years ago, which the discoverers have interpreted as Neanderthal abstract art. The scratches could have also been produced by a bear. In 2021, an Irish elk phalanx with five engraved offset chevrons stacked above each other was discovered at the entrance to the Einhornhöhle cave in Germany, dating to about 51,000 years ago. In 2018, some red-painted dots, disks, lines and hand stencils on the cave walls of the Spanish La Pasiega, Maltravieso, and Doña Trinidad were dated to be older than 66,000 years ago, at least 20,000 years prior to the arrival of modern humans in Western Europe. This would indicate Neanderthal authorship, and similar iconography recorded in other Western European sites—such as Les Merveilles, France, and Cueva del Castillo, Spain—could potentially also have Neanderthal origins. However, the dating of these Spanish caves, and thus attribution to Neanderthals, is contested. Neanderthals are known to have collected a variety of unusual objects—such as crystals or fossils—without any real functional purpose or any indication of damage caused by use. It is unclear if these objects were simply picked up for their aesthetic qualities, or if some symbolic significance was applied to them. These items are mainly quartz crystals, but also other minerals such as cerussite, iron pyrite, calcite and galena. A few findings feature modifications, such as a mammoth tooth with an incision and a fossil nummulite shell with a cross etched in from Tata, Hungary; a large slab with 18 cupstones hollowed out from a grave in La Ferrassie, France; and a geode from Peștera Cioarei, Romania, coated with red ochre. A number of fossil shells are also known from French Neanderthals sites, such as a rhynchonellid and a Taraebratulina from Combe Grenal; a belemnite beak from Grottes des Canalettes; a polyp from Grotte de l'Hyène; a sea urchin from La Gonterie-Boulouneix; and a rhynchonella, feather star and belemnite beak from the contentious Châtelperronian layer of Grotte du Renne. Music[edit] See also: Prehistoric music The Divje Babe Flute in the National Museum of Slovenia Purported Neanderthal bone flute fragments made of bear long bones were reported from Potočka zijalka, Slovenia, in the 1920s, and Istállós-kői-barlang, Hungary, and Mokriška jama, Slovenia, in 1985; but these are now attributed to modern human activities. The 43,000-year-old Divje Babe Flute from Slovenia, found in 1995, has been attributed by some researchers to Neanderthals, and Canadian musicologist Robert Fink said the original flute had either a diatonic or pentatonic musical scale. However, the date also overlaps with modern human immigration into Europe, which means it is also possible it was not manufactured by Neanderthals. In 2015, zoologist Cajus Diedrich argued that it was not a flute at all, and the holes were made by a scavenging hyaena as there is a lack of cut marks stemming from whittling, but in 2018, Slovenian archaeologist Matija Turk and colleagues countered that it is highly unlikely the punctures were made by teeth, and cut marks are not always present on bone flutes. Technology[edit] Despite the apparent 150,000-year stagnation in Neanderthal lithic innovation, there is evidence that Neanderthal technology was more sophisticated than was previously thought. However, the high frequency of potentially debilitating injuries could have prevented very complex technologies from emerging, as a major injury would have impeded an expert's ability to effectively teach a novice. Stone tools[edit] Mousterian projectile pointLevallois technique Neanderthals made stone tools, and are associated with the Mousterian industry. The Mousterian is also associated with North African H. sapiens as early as 315,000 years ago and was found in Northern China about 47–37,000 years ago in caves such as Jinsitai or Tongtiandong. It evolved around 300,000 years ago with the Levallois technique which developed directly from the preceding Acheulean industry (invented by H. erectus about 1.8 mya). Levallois made it easier to control flake shape and size, and as a difficult-to-learn and unintuitive process, the Levallois technique may have been directly taught generation to generation rather than via purely observational learning. There are distinct regional variants of the Mousterian industry, such as: the Quina and La Ferrassie subtypes of the Charentian industry in southwestern France, Acheulean-tradition Mousterian subtypes A and B along the Atlantic and northwestern European coasts, the Micoquien industry of Central and Eastern Europe and the related Sibiryachikha variant in the Siberian Altai Mountains, the Denticulate Mousterian industry in Western Europe, the racloir industry around the Zagros Mountains, and the flake cleaver industry of Cantabria, Spain, and both sides of the Pyrenees. In the mid-20th century, French archaeologist François Bordes debated against American archaeologist Lewis Binford to explain this diversity (the "Bordes–Binford debate"), with Bordes arguing that these represent unique ethnic traditions and Binford that they were caused by varying environments (essentially, form vs. function). The latter sentiment would indicate a lower degree of inventiveness compared to modern humans, adapting the same tools to different environments rather than creating new technologies. A continuous sequence of occupation is well documented in Grotte du Renne, France, where the lithic tradition can be divided into the Levallois–Charentian, Discoid–Denticulate (43,300 ±929 – 40,900 ±719 years ago), Levallois Mousterian (40,200 ±1,500 – 38,400 ±1,300 years ago) and Châtelperronian (40,930 ±393 – 33,670 ±450 years ago). There is some debate if Neanderthals had long-ranged weapons. A wound on the neck of an African wild ass from Umm el Tlel, Syria, was likely inflicted by a heavy Levallois-point javelin, and bone trauma consistent with habitual throwing has been reported in Neanderthals. Some spear tips from Abri du Maras, France, may have been too fragile to have been used as thrusting spears, possibly suggesting their use as darts. Organic tools[edit] The Châtelperronian in central France and northern Spain is a distinct industry from the Mousterian, and is controversially hypothesised to represent a culture of Neanderthals borrowing (or by process of acculturation) tool-making techniques from immigrating modern humans, crafting bone tools and ornaments. In this frame, the makers would have been a transitional culture between the Neanderthal Mousterian and the modern human Aurignacian. The opposing viewpoint is that the Châtelperronian was manufactured by modern humans instead. Abrupt transitions similar to the Mousterian/Châtelperronian could also simply represent natural innovation, like the La Quina–Neronian transition 50,000 years ago featuring technologies generally associated with modern humans such as bladelets and microliths. Other ambiguous transitional cultures include the Italian Uluzzian industry, and the Balkan Szeletian industry. Before immigration, the only evidence of Neanderthal bone tools are animal rib lissoirs—which are rubbed against hide to make it more supple or waterproof—although this could also be evidence for modern humans immigrating earlier than expected. In 2013, two 51,400- to 41,100-year-old deer rib lissoirs were reported from Pech-de-l'Azé and the nearby Abri Peyrony in France. In 2020, five more lissoirs made of aurochs or bison ribs were reported from Abri Peyrony, with one dating to about 51,400 years ago and the other four to 47,700–41,100 years ago. This indicates the technology was in use in this region for a long time. Since reindeer remains were the most abundant, the use of less abundant bovine ribs may indicate a specific preference for bovine ribs. Potential lissoirs have also been reported from Grosse Grotte, Germany (made of mammoth), and Grottes des Canalettes, France (red deer). Smooth clam shell scrapers from Grotta dei Moscerini, Italy The Neanderthals in 10 coastal sites in Italy (namely Grotta del Cavallo and Grotta dei Moscerini) and Kalamakia Cave, Greece, are known to have crafted scrapers using smooth clam shells, and possibly hafted them to a wooden handle. They probably chose this clam species because it has the most durable shell. At Grotta dei Moscerini, about 24% of the shells were gathered alive from the seafloor, meaning these Neanderthals had to wade or dive into shallow waters to collect them. At Grotta di Santa Lucia, Italy, in the Campanian volcanic arc, Neanderthals collected the porous volcanic pumice, which, for contemporary humans, was probably used for polishing points and needles. The pumices are associated with shell tools. At Abri du Maras, France, twisted fibres and a 3-ply inner-bark-fibre cord fragment associated with Neanderthals show that they produced string and cordage, but it is unclear how widespread this technology was because the materials used to make them (such as animal hair, hide, sinew, or plant fibres) are biodegradable and preserve very poorly. This technology could indicate at least a basic knowledge of weaving and knotting, which would have made possible the production of nets, containers, packaging, baskets, carrying devices, ties, straps, harnesses, clothes, shoes, beds, bedding, mats, flooring, roofing, walls and snares, and would have been important in hafting, fishing and seafaring. Dating to 52–41,000 years ago, the cord fragment is the oldest direct evidence of fibre technology, although 115,000-year-old perforated shell beads from Cueva Antón possibly strung together to make a necklace are the oldest indirect evidence. In 2020, British archaeologist Rebecca Wragg Sykes expressed cautious support for the genuineness of the find, but pointed out that the string would have been so weak that it would have had limited functions. One possibility is as a thread for attaching or stringing small objects. The archaeological record shows that Neanderthals commonly used animal hide and birch bark, and may have used them to make cooking containers, although this is based largely on circumstantial evidence, because neither fossilizes well. It is possible that the Neanderthals at Kebara Cave, Israel, used the shells of the spur-thighed tortoise as containers. At the Italian Poggetti Vecchi site, there is evidence that they used fire to process boxwood branches to make digging sticks, a common implement in hunter-gatherer societies. Fire and construction[edit] Many Mousterian sites have evidence of fire, some for extended periods of time, though it is unclear whether they were capable of starting fire or simply scavenged from naturally occurring wildfires. Indirect evidence of fire-starting ability includes pyrite residue on a couple of dozen bifaces from late Mousterian (c. 50,000 years ago) northwestern France (which could indicate they were used as percussion fire starters), and collection of manganese dioxide by late Neanderthals which can lower the combustion temperature of wood. They were also capable of zoning areas for specific activities, such as for knapping, butchering, hearths and wood storage. Many Neanderthal sites lack evidence for such activity perhaps due to natural degradation of the area over tens of thousands of years, such as by bear infiltration after abandonment of the settlement. In a number of caves, evidence of hearths has been detected. Neanderthals likely considered air circulation when making hearths as a lack of proper ventilation for a single hearth can render a cave uninhabitable in several minutes. Abric Romaní rock shelter, Spain, indicates eight evenly spaced hearths lined up against the rock wall, likely used to stay warm while sleeping, with one person sleeping on either side of the fire. At Cueva de Bolomor, Spain, with hearths lined up against the wall, the smoke flowed upwards to the ceiling, and led to outside the cave. In Grotte du Lazaret, France, smoke was probably naturally ventilated during the winter as the interior cave temperature was greater than the outside temperature; likewise, the cave was likely only inhabited in the winter. The ring structures in Grotte de Bruniquel, France In 1990, two 176,000-year-old ring structures, several metres wide, made of broken stalagmite pieces, were discovered in a large chamber more than 300 m (980 ft) from the entrance within Grotte de Bruniquel, France. One ring was 6.7 m × 4.5 m (22 ft × 15 ft) with stalagmite pieces averaging 34.4 cm (13.5 in) in length, and the other 2.2 m × 2.1 m (7.2 ft × 6.9 ft) with pieces averaging 29.5 cm (11.6 in). There were also four other piles of stalagmite pieces for a total of 112 m (367 ft) or 2.2 t (2.4 short tons) worth of stalagmite pieces. Evidence of the use of fire and burnt bones also suggest human activity. A team of Neanderthals was likely necessary to construct the structure, but the chamber's actual purpose is uncertain. Building complex structures so deep in a cave is unprecedented in the archaeological record, and indicates sophisticated lighting and construction technology, and great familiarity with subterranean environments. The 44,000-year-old Moldova I open-air site, Ukraine, shows evidence of a 7 m × 10 m (23 ft × 33 ft) ring-shaped dwelling made out of mammoth bones meant for long-term habitation by several Neanderthals, which would have taken a long time to build. It appears to have contained hearths, cooking areas and a flint workshop, and there are traces of woodworking. Upper Palaeolithic modern humans in the Russian plains are thought to have also made housing structures out of mammoth bones. Birch tar[edit] Neanderthal produced the adhesive birch bark tar, using the bark of birch trees, for hafting. It was long believed that birch bark tar required a complex recipe to be followed, and that it thus showed complex cognitive skills and cultural transmission. However, a 2019 study showed it can be made simply by burning birch bark beside smooth vertical surfaces, such as a flat, inclined rock. Thus, tar making does not require cultural processes per se. However, at Königsaue (Germany), Neanderthals did not make tar with such an aboveground method but rather employed a technically more demanding underground production method. This is one of our best indicators that some of their techniques were conveyed by cultural processes. Clothes[edit] Neanderthals were likely able to survive in a similar range of temperatures to modern humans while sleeping: about 32 °C (90 °F) while naked in the open and windspeed 5.4 km/h (3.4 mph), or 27–28 °C (81–82 °F) while naked in an enclosed space. Since ambient temperatures were markedly lower than this—averaging, during the Eemian interglacial, 17.4 °C (63.3 °F) in July and 1 °C (34 °F) in January and dropping to as a low as −30 °C (−22 °F) on the coldest days—Danish physicist Bent Sørensen hypothesised that Neanderthals required tailored clothing capable of preventing airflow to the skin. Especially during extended periods of travelling (such as a hunting trip), tailored footwear completely enwrapping the feet may have been necessary. Two racloir side scrapers from Le Moustier, France Nonetheless, as opposed to the bone sewing-needles and stitching awls assumed to have been in use by contemporary modern humans, the only known Neanderthal tools that could have been used to fashion clothes are hide scrapers, which could have made items similar to blankets or ponchos, and there is no direct evidence they could produce fitted clothes. Indirect evidence of tailoring by Neanderthals includes the ability to manufacture string, which could indicate weaving ability, and a naturally-pointed horse metatarsal bone from Cueva de los Aviones, Spain, which was speculated to have been used as an awl, perforating dyed hides, based on the presence of orange pigments. Whatever the case, Neanderthals would have needed to cover up most of their body, and contemporary humans would have covered 80–90%. Since human/Neanderthal admixture is known to have occurred in the Middle East, and no modern body louse species descends from their Neanderthal counterparts (body lice only inhabit clothed individuals), it is possible Neanderthals (and/or humans) in hotter climates did not wear clothes, or Neanderthal lice were highly specialised. Seafaring[edit] Remains of Middle Palaeolithic stone tools on Greek islands indicate early seafaring by Neanderthals in the Ionian Sea possibly starting as far back as 200–150,000 years ago. The oldest stone artefacts from Crete date to 130–107,000 years ago, Cephalonia 125,000 years ago, and Zakynthos 110–35,000 years ago. The makers of these artefacts likely employed simple reed boats and made one-day crossings back and forth. Other Mediterranean islands with such remains include Sardinia, Melos, Alonnisos, and Naxos (although Naxos may have been connected to land), and it is possible they crossed the Strait of Gibraltar. If this interpretation is correct, Neanderthals' ability to engineer boats and navigate through open waters would speak to their advanced cognitive and technical skills. Medicine[edit] Given their dangerous hunting and extensive skeletal evidence of healing, Neanderthals appear to have lived lives of frequent traumatic injury and recovery. Well-healed fractures on many bones indicate the setting of splints. Individuals with severe head and rib traumas (which would have caused massive blood loss) indicate they had some manner of dressing major wounds, such as bandages made from animal skin. By and large, they appear to have avoided severe infections, indicating good long-term treatment of such wounds. Their knowledge of medicinal plants was comparable to that of contemporary humans. An individual at Cueva del Sidrón, Spain, seems to have been medicating a dental abscess using poplar—which contains salicylic acid, the active ingredient in aspirin—and there were also traces of the antibiotic-producing Penicillium chrysogenum. They may also have used yarrow and camomile, and their bitter taste—which should act as a deterrent as it could indicate poison—means it was likely a deliberate act. In Kebara Cave, Israel, plant remains which have historically been used for their medicinal properties were found, including the common grape vine, the pistachios of the Persian turpentine tree, ervil seeds and oak acorns. Language[edit] Reconstruction of the Kebara 2 skeleton at the Natural History Museum, London The degree of language complexity is difficult to establish, but given that Neanderthals achieved some technical and cultural complexity, and interbred with humans, it is reasonable to assume they were at least fairly articulate, comparable to modern humans. A somewhat complex language—possibly using syntax—was likely necessary to survive in their harsh environment, with Neanderthals needing to communicate about topics such as locations, hunting and gathering, and tool-making techniques. The FOXP2 gene in modern humans is associated with speech and language development. FOXP2 was present in Neanderthals, but not the gene's modern human variant. Neurologically, Neanderthals had an expanded Broca's area—operating the formulation of sentences, and speech comprehension, but out of a group of 48 genes believed to affect the neural substrate of language, 11 had different methylation patterns between Neanderthals and modern humans. This could indicate a stronger ability in modern humans than in Neanderthals to express language. In 1971, cognitive scientist Philip Lieberman attempted to reconstruct the Neanderthal vocal tract and concluded that it was similar to that of a newborn and incapable of producing a large range of speech sounds, due to the large size of the mouth and the small size of the pharyngeal cavity (according to his reconstruction), thus no need for a descended larynx to fit the entire tongue inside the mouth. He claimed that they were anatomically unable to produce the sounds /a/, /i/, /u/, /ɔ/, /g/, and /k/ and thus lacked the capacity for articulate speech, though were still able to speak at a level higher than non-human primates. However, the lack of a descended larynx does not necessarily equate to a reduced vowel capacity. The 1983 discovery of a Neanderthal hyoid bone—used in speech production in humans—in Kebara 2 which is almost identical to that of humans suggests Neanderthals were capable of speech. Also, the ancestral Sima de los Huesos hominins had humanlike hyoid and ear bones, which could suggest the early evolution of the modern human vocal apparatus. However, the hyoid does not definitively provide insight into vocal tract anatomy. Subsequent studies reconstruct the Neanderthal vocal apparatus as comparable to that of modern humans, with a similar vocal repertoire. In 2015, Lieberman hypothesized that Neanderthals were capable of syntactical language, although nonetheless incapable of mastering any human dialect. It is debated if behavioural modernity is a recent and uniquely modern human innovation, or if Neanderthals also possessed it. Religion[edit] See also: Paleolithic religion and History of religion Funerals[edit] Reconstruction of the grave of La Chapelle-aux-Saints 1 at the Musée de La Chapelle-aux-Saints Although Neanderthals did bury their dead, at least occasionally—which may explain the abundance of fossil remains—the behavior is not indicative of a religious belief of life after death because it could also have had non-symbolic motivations, such as great emotion or the prevention of scavenging. Estimates made regarding the number of known Neanderthal burials range from thirty-six to sixty. The oldest confirmed burials do not seem to occur before approximately 70,000 years ago. The small number of recorded Neanderthal burials implies that the activity was not particularly common. The setting of inhumation in Neanderthal culture largely consisted of simple, shallow graves and pits. Sites such as La Ferrassie in France or Shanidar in Iraq may imply the existence of mortuary centers or cemeteries in Neanderthal culture due to the number of individuals found buried at them. The debate on Neanderthal funerals has been active since the 1908 discovery of La Chapelle-aux-Saints 1 in a small, artificial hole in a cave in southwestern France, very controversially postulated to have been buried in a symbolic fashion. Another grave at Shanidar Cave, Iraq, was associated with the pollen of several flowers that may have been in bloom at the time of deposition—yarrow, centaury, ragwort, grape hyacinth, joint pine and hollyhock. The medicinal properties of the plants led American archaeologist Ralph Solecki to claim that the man buried was some leader, healer, or shaman, and that "The association of flowers with Neanderthals adds a whole new dimension to our knowledge of his humanness, indicating that he had 'soul' ". However, it is also possible the pollen was deposited by a small rodent after the man's death. The graves of children and infants, especially, are associated with grave goods such as artefacts and bones. The grave of a newborn from La Ferrassie, France, was found with three flint scrapers, and an infant from Dederiyeh [de] Cave, Syria, was found with a triangular flint placed on its chest. A 10-month-old from Amud Cave, Israel, was associated with a red deer mandible, likely purposefully placed there given other animal remains are now reduced to fragments. Teshik-Tash 1 from Uzbekistan was associated with a circle of ibex horns, and a limestone slab argued to have supported the head. A child from Kiik-Koba, Crimea, Ukraine, had a flint flake with some purposeful engraving on it, likely requiring a great deal of skill. Nonetheless, these contentiously constitute evidence of symbolic meaning as the grave goods' significance and worth are unclear. Cults[edit] It was once argued that the bones of the cave bear, particularly the skull, in some European caves were arranged in a specific order, indicating an ancient bear cult that killed bears and then ceremoniously arranged the bones. This would be consistent with bear-related rituals of modern human Arctic hunter-gatherers, but the alleged peculiarity of the arrangement could also be sufficiently explained by natural causes, and bias could be introduced as the existence of a bear cult would conform with the idea that totemism was the earliest religion, leading to undue extrapolation of evidence. It was also once thought that Neanderthals ritually hunted, killed and cannibalised other Neanderthals and used the skull as the focus of some ceremony. In 1962, Italian palaeontologist Alberto Blanc believed a skull from Grotta Guattari, Italy, had evidence of a swift blow to the head—indicative of ritual murder—and a precise and deliberate incising at the base to access the brain. He compared it to the victims of headhunters in Malaysia and Borneo, putting it forward as evidence of a skull cult. However, it is now thought to have been a result of cave hyaena scavengery. Although Neanderthals are known to have practiced cannibalism, there is unsubstantial evidence to suggest ritual defleshing. In 2019, Gibraltarian palaeoanthropologists Stewart, Geraldine and Clive Finlayson and Spanish archaeologist Francisco Guzmán speculated that the golden eagle had iconic value to Neanderthals, as exemplified in some modern human societies because they reported that golden eagle bones had a conspicuously high rate of evidence of modification compared to the bones of other birds. They then proposed some "Cult of the Sun Bird" where the golden eagle was a symbol of power. There is evidence from Krapina, Croatia, from wear use and even remnants of string, that suggests that raptor talons were worn as personal ornaments. Interbreeding[edit] Main article: Archaic human admixture with modern humans Interbreeding with modern humans[edit] Further information: Neanderthal genetics Map of western Eurasia showing areas and estimated dates of possible Neandertal–modern human hybridisation (in red) based on fossil samples from indicated sites The first Neanderthal genome sequence was published in 2010, and strongly indicated interbreeding between Neanderthals and early modern humans. The genomes of all studied modern populations contain Neanderthal DNA. Various estimates exist for the proportion, such as 1–4% or 3.4–7.9% in modern Eurasians, or 1.8–2.4% in modern Europeans and 2.3–2.6% in modern East Asians. Pre-agricultural Europeans appear to have had similar, or slightly higher, percentages to modern East Asians, and the numbers may have decreased in the former due to dilution with a group of people which had split off before Neanderthal introgression. Typically, studies have reported finding no significant levels of Neanderthal DNA in Sub-Saharan Africans, but a 2020 study detected 0.3-0.5% in the genomes of five African sample populations, likely the result of Eurasians back-migrating and interbreeding with Africans, as well as human-to-neanderthal gene flow from dispersals of Homo sapiens preceding the larger Out-of-Africa migration, and also showed more equal Neanderthal DNA percentages for European and Asian populations. Such low percentages of Neanderthal DNA in all present day populations indicate infrequent past interbreeding, unless interbreeding was more common with a different population of modern humans which did not contribute to the present day gene pool. Of the inherited Neanderthal genome, 25% in modern Europeans and 32% in modern East Asians may be related to viral immunity. In all, approximately 20% of the Neanderthal genome appears to have survived in the modern human gene pool. Reconstruction of the upper Palaeolithic human Oase 2 with around 7.3% Neanderthal DNA (from an ancestor 4–6 generations back) However, due to their small population and resulting reduced effectivity of natural selection, Neanderthals accumulated several weakly harmful mutations, which were introduced to and slowly selected out of the much larger modern human population; the initial hybridised population may have experienced up to a 94% reduction in fitness compared to contemporary humans. By this measure, Neanderthals may have substantially increased in fitness. A 2017 study focusing on archaic genes in Turkey found associations with coeliac disease, malaria severity and Costello syndrome. Nonetheless, some genes may have helped modern East Asians adapt to the environment; the putatively Neanderthal Val92Met variant of the MC1R gene, which may be weakly associated with red hair and UV radiation sensitivity, is primarily found in East Asian, rather than European, individuals. Some genes related to the immune system appear to have been affected by introgression, which may have aided migration, such as OAS1, STAT2, TLR6, TLR1, TLR10, and several related to immune response. In addition, Neanderthal genes have also been implicated in the structure and function of the brain, keratin filaments, sugar metabolism, muscle contraction, body fat distribution, enamel thickness and oocyte meiosis. Nonetheless, a large portion of surviving introgression appears to be non-coding ("junk") DNA with few biological functions. Due to the absence of Neanderthal-derived mtDNA (which is passed on from mother to child) in modern populations, it has been suggested that the progeny of Neanderthal females who mated with modern human males were either rare, absent, or sterile—that is to say, admixture stems from the progeny of Neanderthal males with modern human females. Due to the lack of Neanderthal-derived Y-chromosomes in modern humans (which is passed on from father to son), it has also been suggested that the hybrids that contributed ancestry to modern populations were predominantly females, or the Neanderthal Y-chromosome was not compatible with H. sapiens and became extinct. According to linkage disequilibrium mapping, the last Neanderthal gene flow into the modern human genome occurred 86–37,000 years ago, but most likely 65–47,000 years ago. It is thought that Neanderthal genes which contributed to the present day human genome stemmed from interbreeding in the Near East rather than the entirety of Europe. However, interbreeding still occurred without contributing to the modern genome. The approximately 40,000-year-old modern human Oase 2 was found, in 2015, to have had 6–9% (point estimate 7.3%) Neanderthal DNA, indicating a Neanderthal ancestor up to four to six generations earlier, but this hybrid population does not appear to have made a substantial contribution to the genomes of later Europeans. In 2016, the DNA of Neanderthals from Denisova Cave revealed evidence of interbreeding 100,000 years ago, and interbreeding with an earlier dispersal of H. sapiens may have occurred as early as 120,000 years ago in places such as the Levant. The earliest H. sapiens remains outside of Africa occur at Misliya Cave 194–177,000 years ago, and Skhul and Qafzeh 120–90,000 years ago. The Qafzeh humans lived at approximately the same time as the Neanderthals from the nearby Tabun Cave. The Neanderthals of the German Hohlenstein-Stadel have deeply divergent mtDNA compared to more recent Neanderthals, possibly due to introgression of human mtDNA between 316,000 and 219,000 years ago, or simply because they were genetically isolated. Whatever the case, these first interbreeding events have not left any trace in modern human genomes. Detractors of the interbreeding model argue that the genetic similarity is only a remnant of a common ancestor instead of interbreeding, although this is unlikely as it fails to explain why sub-Saharan Africans do not have Neanderthal DNA. In December 2023, scientists reported that genes inherited by modern humans from Neanderthals and Denisovans may biologically influence the daily routine of modern humans. Interbreeding with Denisovans[edit] Chris Stringer's Homo family tree. The horizontal axis represents geographic location, and the vertical time in millions of years ago. Although nDNA confirms that Neanderthals and Denisovans are more closely related to each other than they are to modern humans, Neanderthals and modern humans share a more recent maternally-transmitted mtDNA common ancestor, possibly due to interbreeding between Denisovans and some unknown human species. The 400,000-year-old Neanderthal-like humans from Sima de los Huesos in northern Spain, looking at mtDNA, are more closely related to Denisovans than Neanderthals. Several Neanderthal-like fossils in Eurasia from a similar time period are often grouped into H. heidelbergensis, of which some may be relict populations of earlier humans, which could have interbred with Denisovans. This is also used to explain an approximately 124,000-year-old German Neanderthal specimen with mtDNA that diverged from other Neanderthals (except for Sima de los Huesos) about 270,000 years ago, while its genomic DNA indicated divergence less than 150,000 years ago. Sequencing of the genome of a Denisovan from Denisova Cave has shown that 17% of its genome derives from Neanderthals. This Neanderthal DNA more closely resembled that of a 120,000-year-old Neanderthal bone from the same cave than that of Neanderthals from Vindija Cave, Croatia, or Mezmaiskaya Cave in the Caucasus, suggesting that interbreeding was local. For the 90,000-year-old Denisova 11, it was found that her father was a Denisovan related to more recent inhabitants of the region, and her mother a Neanderthal related to more recent European Neanderthals at Vindija Cave, Croatia. Given how few Denisovan bones are known, the discovery of a first-generation hybrid indicates interbreeding was very common between these species, and Neanderthal migration across Eurasia likely occurred sometime after 120,000 years ago. Extinction[edit] Main article: Neanderthal extinction Transition[edit] Map emphasising the Ebro River in northern Spain The extinction of Neanderthals was part of the broader Late Pleistocene megafaunal extinction event. Whatever the cause of their extinction, Neanderthals were replaced by modern humans, indicated by near full replacement of Middle Palaeolithic Mousterian stone technology with modern human Upper Palaeolithic Aurignacian stone technology across Europe (the Middle-to-Upper Palaeolithic Transition) from 41,000 to 39,000 years ago. By between 44,200 to 40,600 BP, Neanderthals vanished from northwestern Europe. However, it is postulated that Iberian Neanderthals persisted until about 35,000 years ago, as indicated by the date range of transitional lithic assemblages—Châtelperronian, Uluzzian, Protoaurignacian and Early Aurignacian. The latter two are attributed to modern humans, but the former two have unconfirmed authorship, potentially products of Neanderthal/modern human cohabitation and cultural transmission. Further, the appearance of the Aurignacian south of the Ebro River has been dated to roughly 37,500 years ago, which has prompted the "Ebro Frontier" hypothesis which states that the river presented a geographic barrier preventing modern human immigration, and thus prolonging Neanderthal persistence. However, the dating of the Iberian Transition is debated, with a contested timing of 43,000–40,800 years ago at Cueva Bajondillo, Spain. The Châtelperronian appears in northeastern Iberia about 42,500–41,600 years ago. Some Neanderthals in Gibraltar were dated to much later than this—such as Zafarraya (30,000 years ago) and Gorham's Cave (28,000 years ago)—which may be inaccurate as they were based on ambiguous artefacts instead of direct dating. A claim of Neanderthals surviving in a polar refuge in the Ural Mountains is loosely supported by Mousterian stone tools dating to 34,000 years ago from the northern Siberian Byzovaya site at a time when modern humans may not yet have colonised the northern reaches of Europe; however, modern human remains are known from the nearby Mamontovaya Kurya site dating to 40,000 years ago. Indirect dating of Neanderthals remains from Mezmaiskaya Cave reported a date of about 30,000 years ago, but direct dating instead yielded 39,700 ±1,100 years ago, more in line with trends exhibited in the rest of Europe. Bohunician scrapers in the Moravian Museum, Czech Republic The earliest indication of Upper Palaeolithic modern human immigration into Europe is the Balkan Bohunician industry beginning 48,000 years ago, likely deriving from the Levantine Emiran industry, and the earliest bones in Europe date to roughly 45–43,000 years ago in Bulgaria, Italy, and Britain. This wave of modern humans replaced Neanderthals. However, Neanderthals and H. sapiens have a much longer contact history. DNA evidence indicates H. sapiens contact with Neanderthals and admixture as early as 120–100,000 years ago. A 2019 reanalysis of 210,000-year-old skull fragments from the Greek Apidima Cave assumed to have belonged to a Neanderthal concluded that they belonged to a modern human, and a Neanderthal skull dating to 170,000 years ago from the cave indicates H. sapiens were replaced by Neanderthals until returning about 40,000 years ago. This identification was refuted by a 2020 study. Archaeological evidence suggests that Neanderthals displaced modern humans in the Near East around 100,000 years ago until about 60–50,000 years ago. Cause[edit] Modern humans[edit] Successive dispersals of Homo erectus (yellow), Neanderthals (ochre) and modern humans (red). Historically, modern human technology was viewed as vastly superior to that of Neanderthals, with more efficient weaponry and subsistence strategies, and Neanderthals simply went extinct because they could not compete. The discovery of Neanderthal/modern human introgression has caused the resurgence of the multiregional hypothesis, wherein the present day genetic makeup of all humans is the result of complex genetic contact among several different populations of humans dispersed across the world. By this model, Neanderthals and other recent archaic humans were simply assimilated into the modern human genome – that is, they were effectively bred out into extinction. Modern humans coexisted with Neanderthals in Europe for around 3,000 to 5,000 years. Climate change[edit] Their ultimate extinction coincides with Heinrich event 4, a period of intense seasonality; later Heinrich events are also associated with massive cultural turnovers when European human populations collapsed. This climate change may have depopulated several regions of Neanderthals, like previous cold spikes, but these areas were instead repopulated by immigrating humans, leading to Neanderthal extinction. In southern Iberia, there is evidence that Neanderthal populations declined during H4 and the associated proliferation of Artemisia-dominated desert-steppes. Dispersal of deposits during the Campanian Ignimbrite Eruption around 40,000 years ago. It has also been proposed that climate change was the primary driver, as their low population left them vulnerable to any environmental change, with even a small drop in survival or fertility rates possibly quickly leading to their extinction. However, Neanderthals and their ancestors had survived through several glacial periods over their hundreds of thousands of years of European habitation. It is also proposed that around 40,000 years ago, when Neanderthal populations may have already been dwindling from other factors, the Campanian Ignimbrite Eruption in Italy could have led to their final demise, as it produced 2–4 °C (3.6–7.2 °F) cooling for a year and acid rain for several more years. Disease[edit] Modern humans may have introduced African diseases to Neanderthals, contributing to their extinction. A lack of immunity, compounded by an already low population, was potentially devastating to the Neanderthal population, and low genetic diversity could have also rendered fewer Neanderthals naturally immune to these new diseases ("differential pathogen resistance" hypothesis). However, compared to modern humans, Neanderthals had a similar or higher genetic diversity for 12 major histocompatibility complex (MHC) genes associated with the adaptive immune system, casting doubt on this model. Low population and inbreeding depression may have caused maladaptive birth defects, which could have contributed to their decline (mutational meltdown). In late-20th-century New Guinea, due to cannibalistic funerary practices, the Fore people were decimated by transmissible spongiform encephalopathies, specifically kuru, a highly virulent disease spread by ingestion of prions found in brain tissue. However, individuals with the 129 variant of the PRNP gene were naturally immune to the prions. Studying this gene led to the discovery that the 129 variant was widespread among all modern humans, which could indicate widespread cannibalism at some point in human prehistory. Because Neanderthals are known to have practised cannibalism to an extent and to have co-existed with modern humans, British palaeoanthropologist Simon Underdown speculated that modern humans transmitted a kuru-like spongiform disease to Neanderthals, and, because the 129 variant appears to have been absent in Neanderthals, it quickly killed them off. In popular culture[edit] Main article: Neanderthals in popular culture Cavemen in The Black Terror #16 (1946) Neanderthals have been portrayed in popular culture including appearances in literature, visual media and comedy. The "caveman" archetype often mocks Neanderthals and depicts them as primitive, hunchbacked, knuckle-dragging, club-wielding, grunting, nonsocial characters driven solely by animal instinct. "Neanderthal" can also be used as an insult. In literature, they are sometimes depicted as brutish or monstrous, such as in H. G. Wells' The Grisly Folk and Elizabeth Marshall Thomas' The Animal Wife, but sometimes with a civilised but unfamiliar culture, as in William Golding's The Inheritors, Björn Kurtén's Dance of the Tiger, and Jean M. Auel's Clan of the Cave Bear and her Earth's Children series. See also[edit] Denisovan – Asian archaic human Early human migrations Early European modern humans – Earliest anatomically modern humans in EuropePages displaying short descriptions of redirect targets Homo floresiensis – Archaic human from Flores, Indonesia Homo luzonensis – Archaic human from Luzon, Philippines Homo naledi – South African archaic human species Human timeline Footnotes[edit] ^ After being mined for limestone, the cave caved in and was lost by 1900. It was rediscovered in 1997 by archaeologists Ralf Schmitz and Jürgen Thissen. ^ The German spelling Thal ("valley") was current until 1901 but has been Tal since then. (The German noun is cognate with English dale.) The German /t/ phoneme was frequently spelled th from the 15th to 19th centuries, but the spelling Tal became standardized in 1901 and the old spellings of the German names Neanderthal for the valley and Neanderthaler for the species were both changed to the spellings without h. ^ In Mettmann, "Neander Valley", there is a local idiosyncrasy in use of the outdated spellings with th, such as with the Neanderthal Museum (but the name is in English [German would require Neandertalermuseum]), the Neanderthal station (Bahnhof Neanderthal), and some other rare occasions meant for tourists. Beyond these, city convention is to use th when referring to the species. ^ King made a typo and said "theositic". ^ The bones were discovered by workers of Wilhelm Beckershoff and Friedrich Wilhelm Pieper. Initially, the workers threw the bones out as debris, but Beckershoff then told them to store the bones. Pieper asked Fuhlrott to come up to the cave and investigate the bones, which Beckershoff and Pieper believed belonged to a cave bear. ^ OAS1 and STAT2 both are associated with fighting viral inflections (interferons), and the listed toll-like receptors (TLRs) allow cells to identify bacterial, fungal, or parasitic pathogens. African origin is also correlated with a stronger inflammatory response. ^ Higher levels of Neanderthal-derived genes are associated with an occipital and parietal bone shape reminiscent to that of Neanderthals, as well as modifications to the visual cortex and the intraparietal sulcus (associated with visual processing). ^ Homo floresiensis originated in an unknown location from unknown ancestors and reached remote parts of Indonesia. Homo erectus spread from Africa to western Asia, then east Asia and Indonesia; its presence in Europe is uncertain, but it gave rise to Homo antecessor, found in Spain. Homo heidelbergensis originated from Homo erectus in an unknown location and dispersed across Africa, southern Asia and southern Europe (other scientists interpret fossils, here named heidelbergensis, as late erectus). Modern humans spread from Africa to western Asia and then to Europe and southern Asia, eventually reaching Australia and the Americas. In addition to Neanderthals and Denisovans, a third gene flow of archaic Africa origin is indicated at the right. The chart is missing superarchaic (which diverged from erectus 1.9 mya) introgression into Neanderthal/Denisovan common ancestor.	biology	2495865	https://sv.wikipedia.org/wiki/Nyctophilus%20walkeri	Nyctophilus walkeri	Nyctophilus walkeri är en fladdermusart som beskrevs av Thomas 1892. Nyctophilus walkeri ingår i släktet Nyctophilus och familjen läderlappar. IUCN kategoriserar arten globalt som livskraftig. Inga underarter finns listade i Catalogue of Life. Denna fladdermus förekommer i norra Australien i nordöstra Western Australia, norra Northern Territory och nordvästra Queensland. Habitatet utgörs av dammar i klippiga områden med växter av släktena Melaleuca och Pandanus samt av galleriskogar, främst med palmer av släktet Livistona. Källor Externa länkar Läderlappar walkeri Däggdjur i australiska regionen	swedish	0.886077
neanderthals_vitamin_C_diet/Human.txt	Humans (Homo sapiens) or modern humans are the most common and widespread species of primate, and the last surviving species of the genus Homo. They are great apes characterized by their hairlessness, bipedalism, and high intelligence. Humans have large brains, enabling more advanced cognitive skills that enable them to thrive and adapt in varied environments, develop highly complex tools, and form complex social structures and civilizations. Humans are highly social, with individual humans tending to belong to a multi-layered network of cooperating, distinct, or even competing social groups – from families and peer groups to corporations and political states. As such, social interactions between humans have established a wide variety of values, social norms, languages, and traditions (collectively termed institutions), each of which bolsters human society. Humans are also highly curious: the desire to understand and influence phenomena has motivated humanity's development of science, technology, philosophy, mythology, religion, and other frameworks of knowledge; humans also study themselves through such domains as anthropology, social science, history, psychology, and medicine. As of March 2024, there are estimated to be more than 8 billion humans alive. Although some scientists equate the term "humans" with all members of the genus Homo, in common usage it generally refers to Homo sapiens, the only extant member. Extinct members of the genus Homo are known as archaic humans, and the term "modern human" is used to distinguish Homo sapiens from archaic humans. Anatomically modern humans emerged around 300,000 years ago in Africa, evolving from Homo heidelbergensis or a similar species. Migrating out of Africa, they gradually replaced and interbred with local populations of archaic humans. Multiple hypotheses for the extinction of archaic human species such as Neanderthals include competition, violence, interbreeding with Homo sapiens, or inability to adapt to climate change. For most of their history, humans were nomadic hunter-gatherers. Humans began exhibiting behavioral modernity about 160,000–60,000 years ago. The Neolithic Revolution, which began in Southwest Asia around 13,000 years ago (and separately in a few other places), saw the emergence of agriculture and permanent human settlement; in turn, this led to the development of civilization and kickstarted a period of continuous (and ongoing) population growth and rapid technological change. Since then, a number of civilizations have risen and fallen, while a number of sociocultural and technological developments have resulted in significant changes to the human lifestyle. Genes and the environment influence human biological variation in visible characteristics, physiology, disease susceptibility, mental abilities, body size, and life span. Though humans vary in many traits (such as genetic predispositions and physical features), humans are among the least genetically diverse primates. Any two humans are at least 99% genetically similar. Humans are sexually dimorphic: generally, males have greater body strength and females have a higher body fat percentage. At puberty, humans develop secondary sex characteristics. Females are capable of pregnancy, usually between puberty, at around 12 years old, and menopause, around the age of 50. Humans are omnivorous, capable of consuming a wide variety of plant and animal material, and have used fire and other forms of heat to prepare and cook food since the time of Homo erectus. Humans can survive for up to eight weeks without food and several days without water. Humans are generally diurnal, sleeping on average seven to nine hours per day. Childbirth is dangerous, with a high risk of complications and death. Often, both the mother and the father provide care for their children, who are helpless at birth. Humans have a large, highly developed, and complex prefrontal cortex, the region of the brain associated with higher cognition. Humans are highly intelligent and capable of episodic memory; they have flexible facial expressions, self-awareness, and a theory of mind. The human mind is capable of introspection, private thought, imagination, volition, and forming views on existence. This has allowed great technological advancements and complex tool development through complex reasoning and the transmission of knowledge to subsequent generations through language. Humans' advanced technology has enabled them to spread to all the continents of the globe as well as to outer space, and to command profound influence on the biosphere and environment. The latter has prompted some geologists to demarcate the time from the emergence of human civilization till present as a separate geological epoch: the Anthropocene (with anthropo- deriving from the Ancient Greek word for "human", ἄνθρωπος). Etymology and definition Further information: Names for the human species and Human taxonomy Carl Linnaeus coined the name Homo sapiens and is the type specimen of the species All modern humans are classified into the species Homo sapiens, coined by Carl Linnaeus in his 1735 work Systema Naturae. The generic name "Homo" is a learned 18th-century derivation from Latin homō, which refers to humans of either sex. The word human can refer to all members of the Homo genus, although in common usage it generally just refers to Homo sapiens, the only extant species. The name "Homo sapiens" means 'wise man' or 'knowledgeable man'. There is disagreement if certain extinct members of the genus, namely Neanderthals, should be included as a separate species of humans or as a subspecies of H. sapiens. Human is a loanword of Middle English from Old French humain, ultimately from Latin hūmānus, the adjectival form of homō ('man' – in the sense of humanity). The native English term man can refer to the species generally (a synonym for humanity) as well as to human males. It may also refer to individuals of either sex. Despite the fact that the word animal is colloquially used as an antonym for human, and contrary to a common biological misconception, humans are animals. The word person is often used interchangeably with human, but philosophical debate exists as to whether personhood applies to all humans or all sentient beings, and further if one can lose personhood (such as by going into a persistent vegetative state). Evolution Main article: Human evolution Humans are apes (superfamily Hominoidea). The lineage of apes that eventually gave rise to humans first split from gibbons (family Hylobatidae) and orangutans (genus Pongo), then gorillas (genus Gorilla), and finally, chimpanzees and bonobos (genus Pan). The last split, between the human and chimpanzee–bonobo lineages, took place around 8–4 million years ago, in the late Miocene epoch. During this split, chromosome 2 was formed from the joining of two other chromosomes, leaving humans with only 23 pairs of chromosomes, compared to 24 for the other apes. Following their split with chimpanzees and bonobos, the hominins diversified into many species and at least two distinct genera. All but one of these lineages – representing the genus Homo and its sole extant species Homo sapiens – are now extinct. Reconstruction of Lucy, the first Australopithecus afarensis skeleton found The genus Homo evolved from Australopithecus. Though fossils from the transition are scarce, the earliest members of Homo share several key traits with Australopithecus. The earliest record of Homo is the 2.8 million-year-old specimen LD 350-1 from Ethiopia, and the earliest named species are Homo habilis and Homo rudolfensis which evolved by 2.3 million years ago. H. erectus (the African variant is sometimes called H. ergaster) evolved 2 million years ago and was the first archaic human species to leave Africa and disperse across Eurasia. H. erectus also was the first to evolve a characteristically human body plan. Homo sapiens emerged in Africa around 300,000 years ago from a species commonly designated as either H. heidelbergensis or H. rhodesiensis, the descendants of H. erectus that remained in Africa. H. sapiens migrated out of the continent, gradually replacing or interbreeding with local populations of archaic humans. Humans began exhibiting behavioral modernity about 160,000–70,000 years ago, and possibly earlier. The "out of Africa" migration took place in at least two waves, the first around 130,000 to 100,000 years ago, the second (Southern Dispersal) around 70,000 to 50,000 years ago. H. sapiens proceeded to colonize all the continents and larger islands, arriving in Eurasia 125,000 years ago, Australia around 65,000 years ago, the Americas around 15,000 years ago, and remote islands such as Hawaii, Easter Island, Madagascar, and New Zealand in the years 300 to 1280 CE. Human evolution was not a simple linear or branched progression but involved interbreeding between related species. Genomic research has shown that hybridization between substantially diverged lineages was common in human evolution. DNA evidence suggests that several genes of Neanderthal origin are present among all non sub-Saharan-African populations, and Neanderthals and other hominins, such as Denisovans, may have contributed up to 6% of their genome to present-day non sub-Saharan-African humans. Human evolution is characterized by a number of morphological, developmental, physiological, and behavioral changes that have taken place since the split between the last common ancestor of humans and chimpanzees. The most significant of these adaptations are hairlessness, obligate bipedalism, increased brain size and decreased sexual dimorphism (neoteny). The relationship between all these changes is the subject of ongoing debate. Hominoidea (hominoids, apes) Hylobatidae (gibbons) Hominidae (hominids, great apes) Ponginae Pongo (orangutans) Pongo abelii Pongo tapanuliensis Pongo pygmaeus Homininae (hominines) Gorillini Gorilla (gorillas) Gorilla gorilla Gorilla beringei Hominini (hominins) Panina Pan (chimpanzees) Pan troglodytes Pan paniscus Hominina (homininans) Homo sapiens (humans) History Main article: Human history Prehistory Main article: Prehistory Overview map of the peopling of the world by early human migration during the Upper Paleolithic, following to the Southern Dispersal paradigm Until about 12,000 years ago, all humans lived as hunter-gatherers. The Neolithic Revolution (the invention of agriculture) first took place in Southwest Asia and spread through large parts of the Old World over the following millennia. It also occurred independently in Mesoamerica (about 6,000 years ago), China, Papua New Guinea, and the Sahel and West Savanna regions of Africa. Access to food surplus led to the formation of permanent human settlements, the domestication of animals and the use of metal tools for the first time in history. Agriculture and sedentary lifestyle led to the emergence of early civilizations. Ancient Main article: Ancient history Great Pyramids of Giza, Egypt An urban revolution took place in the 4th millennium BCE with the development of city-states, particularly Sumerian cities located in Mesopotamia. It was in these cities that the earliest known form of writing, cuneiform script, appeared around 3000 BCE. Other major civilizations to develop around this time were Ancient Egypt and the Indus Valley Civilisation. They eventually traded with each other and invented technology such as wheels, plows and sails. Astronomy and mathematics were also developed and the Great Pyramid of Giza was built. There is evidence of a severe drought lasting about a hundred years that may have caused the decline of these civilizations, with new ones appearing in the aftermath. Babylonians came to dominate Mesopotamia while others, such as the Poverty Point culture, Minoans and the Shang dynasty, rose to prominence in new areas. The Late Bronze Age collapse around 1200 BCE resulted in the disappearance of a number of civilizations and the beginning of the Greek Dark Ages. During this period iron started replacing bronze, leading to the Iron Age. In the 5th century BCE, history started being recorded as a discipline, which provided a much clearer picture of life at the time. Between the 8th and 6th century BCE, Europe entered the classical antiquity age, a period when ancient Greece and ancient Rome flourished. Around this time other civilizations also came to prominence. The Maya civilization started to build cities and create complex calendars. In Africa, the Kingdom of Aksum overtook the declining Kingdom of Kush and facilitated trade between India and the Mediterranean. In West Asia, the Achaemenid Empire's system of centralized governance became the precursor to many later empires, while the Gupta Empire in India and the Han dynasty in China have been described as golden ages in their respective regions. Medieval Main article: Post-classical history Medieval French manuscript illustration of the three classes of medieval society from the 13th-century Li Livres dou Santé Following the fall of the Western Roman Empire in 476, Europe entered the Middle Ages. During this period, Christianity and the Church would provide centralized authority and education. In the Middle East, Islam became the prominent religion and expanded into North Africa. It led to an Islamic Golden Age, inspiring achievements in architecture, the revival of old advances in science and technology, and the formation of a distinct way of life. The Christian and Islamic worlds would eventually clash, with the Kingdom of England, the Kingdom of France and the Holy Roman Empire declaring a series of holy wars to regain control of the Holy Land from Muslims. In the Americas, complex Mississippian societies would arise starting around 800 CE, while further south, the Aztecs and Incas would become the dominant powers. The Mongol Empire would conquer much of Eurasia in the 13th and 14th centuries. Over this same time period, the Mali Empire in Africa grew to be the largest empire on the continent, stretching from Senegambia to Ivory Coast. Oceania would see the rise of the Tuʻi Tonga Empire which expanded across many islands in the South Pacific. Modern Main articles: Early modern period and Late modern period James Watt's steam engine The early modern period in Europe and the Near East (c. 1450–1800) began with the final defeat of the Byzantine Empire, and the rise of the Ottoman Empire. Meanwhile, Japan entered the Edo period, the Qing dynasty rose in China and the Mughal Empire ruled much of India. Europe underwent the Renaissance, starting in the 15th century, and the Age of Discovery began with the exploring and colonizing of new regions. This includes the British Empire expanding to become the world's largest empire and the colonization of the Americas. This expansion led to the Atlantic slave trade and the genocide of Native American peoples. This period also marked the Scientific Revolution, with great advances in mathematics, mechanics, astronomy and physiology. The late modern period (1800–present) saw the Technological and Industrial Revolution bring such discoveries as imaging technology, major innovations in transport and energy development. The United States of America underwent great change, going from a small group of colonies to one of the global superpowers. The Napoleonic Wars raged through Europe in the early 1800s, Spain lost most of its colonies in the New World, while Europeans continued expansion into Africa – where European control went from 10% to almost 90% in less than 50 years – and Oceania. A tenuous balance of power among European nations collapsed in 1914 with the outbreak of the First World War, one of the deadliest conflicts in history. In the 1930s, a worldwide economic crisis led to the rise of authoritarian regimes and a Second World War, involving almost all of the world's countries. The war's destruction led to the collapse of most global empires, leading to widespread decolonization. Contemporary Main article: Contemporary history Following the conclusion of the Second World War in 1945, the Cold War between the USSR and the United States saw a struggle for global influence, including a nuclear arms race and a space race, ending in the collapse of the Soviet Union. The current Information Age, spurred by the development of the Internet and Artificial Intelligence systems, sees the world becoming increasingly globalized and interconnected. Habitat and population Further information: Human geography and Demography Population statisticsMosaic cartogram showing the distribution of the global population based on 2018 UN data. Each of the 15,266 pixels represents the home country of 500,000 people – cartogram by Max Roser for Our World in DataChoropleth showing Population density (people per square kilometer) estimates by 30 arc-second grid in 2020World population8.1 billionPopulation density16/km (41/sq mi) by total area54/km (140/sq mi) by land areaLargest citiesTokyo, Delhi, Shanghai, São Paulo, Mexico City, Cairo, Mumbai, Beijing, Dhaka, Osaka, New York-Newark, Karachi, Buenos Aires, Chongqing, Istanbul, Kolkata, Manila, Lagos, Rio de Janeiro, Tianjin, Kinshasa, Guangzhou, Los Angeles-Long Beach-Santa Ana, Moscow, Shenzhen, Lahore, Bangalore, Paris, Jakarta, Chennai, Lima, Bogota, Bangkok, London Early human settlements were dependent on proximity to water and – depending on the lifestyle – other natural resources used for subsistence, such as populations of animal prey for hunting and arable land for growing crops and grazing livestock. Modern humans, however, have a great capacity for altering their habitats by means of technology, irrigation, urban planning, construction, deforestation and desertification. Human settlements continue to be vulnerable to natural disasters, especially those placed in hazardous locations and with low quality of construction. Grouping and deliberate habitat alteration is often done with the goals of providing protection, accumulating comforts or material wealth, expanding the available food, improving aesthetics, increasing knowledge or enhancing the exchange of resources. Humans are one of the most adaptable species, despite having a low or narrow tolerance for many of the earth's extreme environments. Currently the species is present in all eight biogeographical realms, although their presence in the Antarctic realm is very limited to research stations and annually there is a population decline in the winter months of this realm. Humans established their nation-states in the other seven realms, such as for example South Africa, India, Russia, Australia, Fiji, United States and Brazil (each located in a different biogeographical realm). By using advanced tools and clothing, humans have been able to extend their tolerance to a wide variety of temperatures, humidities, and altitudes. As a result, humans are a cosmopolitan species found in almost all regions of the world, including tropical rainforest, arid desert, extremely cold arctic regions, and heavily polluted cities; in comparison, most other species are confined to a few geographical areas by their limited adaptability. The human population is not, however, uniformly distributed on the Earth's surface, because the population density varies from one region to another, and large stretches of surface are almost completely uninhabited, like Antarctica and vast swathes of the ocean. Most humans (61%) live in Asia; the remainder live in the Americas (14%), Africa (14%), Europe (11%), and Oceania (0.5%). Within the last century, humans have explored challenging environments such as Antarctica, the deep sea, and outer space. Human habitation within these hostile environments is restrictive and expensive, typically limited in duration, and restricted to scientific, military, or industrial expeditions. Humans have briefly visited the Moon and made their presence felt on other celestial bodies through human-made robotic spacecraft. Since the early 20th century, there has been continuous human presence in Antarctica through research stations and, since 2000, in space through habitation on the International Space Station. Humans and their domesticated animals represent 96% of all mammalian biomass on earth, whereas all wild mammals represent only 4%. Estimates of the population at the time agriculture emerged in around 10,000 BC have ranged between 1 million and 15 million. Around 50–60 million people lived in the combined eastern and western Roman Empire in the 4th century AD. Bubonic plagues, first recorded in the 6th century AD, reduced the population by 50%, with the Black Death killing 75–200 million people in Eurasia and North Africa alone. Human population is believed to have reached one billion in 1800. It has since then increased exponentially, reaching two billion in 1930 and three billion in 1960, four in 1975, five in 1987 and six billion in 1999. It passed seven billion in 2011 and passed eight billion in November 2022. It took over two million years of human prehistory and history for the human population to reach one billion and only 207 years more to grow to 7 billion. The combined biomass of the carbon of all the humans on Earth in 2018 was estimated at 60 million tons, about 10 times larger than that of all non-domesticated mammals. In 2018, 4.2 billion humans (55%) lived in urban areas, up from 751 million in 1950. The most urbanized regions are Northern America (82%), Latin America (81%), Europe (74%) and Oceania (68%), with Africa and Asia having nearly 90% of the world's 3.4 billion rural population. Problems for humans living in cities include various forms of pollution and crime, especially in inner city and suburban slums. Humans have had a dramatic effect on the environment. They are apex predators, being rarely preyed upon by other species. Human population growth, industrialization, land development, overconsumption and combustion of fossil fuels have led to environmental destruction and pollution that significantly contributes to the ongoing mass extinction of other forms of life. Biology Anatomy and physiology Main article: Human body Diagram of the human skeleton Most aspects of human physiology are closely homologous to corresponding aspects of animal physiology. The dental formula of humans is: 2.1.2.32.1.2.3. Humans have proportionately shorter palates and much smaller teeth than other primates. They are the only primates to have short, relatively flush canine teeth. Humans have characteristically crowded teeth, with gaps from lost teeth usually closing up quickly in young individuals. Humans are gradually losing their third molars, with some individuals having them congenitally absent. Humans share with chimpanzees a vestigial tail, appendix, flexible shoulder joints, grasping fingers and opposable thumbs. Humans also have a more barrel-shaped chests in contrast to the funnel shape of other apes, an adaptation for bipedal respiration. Apart from bipedalism and brain size, humans differ from chimpanzees mostly in smelling, hearing and digesting proteins. While humans have a density of hair follicles comparable to other apes, it is predominantly vellus hair, most of which is so short and wispy as to be practically invisible. Humans have about 2 million sweat glands spread over their entire bodies, many more than chimpanzees, whose sweat glands are scarce and are mainly located on the palm of the hand and on the soles of the feet. It is estimated that the worldwide average height for an adult human male is about 171 cm (5 ft 7 in), while the worldwide average height for adult human females is about 159 cm (5 ft 3 in). Shrinkage of stature may begin in middle age in some individuals but tends to be typical in the extremely aged. Throughout history, human populations have universally become taller, probably as a consequence of better nutrition, healthcare, and living conditions. The average mass of an adult human is 59 kg (130 lb) for females and 77 kg (170 lb) for males. Like many other conditions, body weight and body type are influenced by both genetic susceptibility and environment and varies greatly among individuals. Humans have a far faster and more accurate throw than other animals. Humans are also among the best long-distance runners in the animal kingdom, but slower over short distances. Humans' thinner body hair and more productive sweat glands help avoid heat exhaustion while running for long distances. Compared to other apes, the human heart produces greater stroke volume and cardiac output and the aorta is proportionately larger. Genetics Main article: Human genetics A graphical representation of the standard human karyotype, including both the female (XX) and male (XY) sex chromosomes (bottom right), as well as the mitochondrial genome (shown to scale as "MT" at bottom left). Further information: Karyotype Like most animals, humans are a diploid and eukaryotic species. Each somatic cell has two sets of 23 chromosomes, each set received from one parent; gametes have only one set of chromosomes, which is a mixture of the two parental sets. Among the 23 pairs of chromosomes, there are 22 pairs of autosomes and one pair of sex chromosomes. Like other mammals, humans have an XY sex-determination system, so that females have the sex chromosomes XX and males have XY. Genes and environment influence human biological variation in visible characteristics, physiology, disease susceptibility and mental abilities. The exact influence of genes and environment on certain traits is not well understood. While no humans – not even monozygotic twins – are genetically identical, two humans on average will have a genetic similarity of 99.5%-99.9%. This makes them more homogeneous than other great apes, including chimpanzees. This small variation in human DNA compared to many other species suggests a population bottleneck during the Late Pleistocene (around 100,000 years ago), in which the human population was reduced to a small number of breeding pairs. The forces of natural selection have continued to operate on human populations, with evidence that certain regions of the genome display directional selection in the past 15,000 years. The human genome was first sequenced in 2001 and by 2020 hundreds of thousands of genomes had been sequenced. In 2012 the International HapMap Project had compared the genomes of 1,184 individuals from 11 populations and identified 1.6 million single nucleotide polymorphisms. African populations harbor the highest number of private genetic variants. While many of the common variants found in populations outside of Africa are also found on the African continent, there are still large numbers that are private to these regions, especially Oceania and the Americas. By 2010 estimates, humans have approximately 22,000 genes. By comparing mitochondrial DNA, which is inherited only from the mother, geneticists have concluded that the last female common ancestor whose genetic marker is found in all modern humans, the so-called mitochondrial Eve, must have lived around 90,000 to 200,000 years ago. Life cycle See also: Childbirth and Life expectancy A 10 mm human embryo at 5 weeks Most human reproduction takes place by internal fertilization via sexual intercourse, but can also occur through assisted reproductive technology procedures. The average gestation period is 38 weeks, but a normal pregnancy can vary by up to 37 days. Embryonic development in the human covers the first eight weeks of development; at the beginning of the ninth week the embryo is termed a fetus. Humans are able to induce early labor or perform a caesarean section if the child needs to be born earlier for medical reasons. In developed countries, infants are typically 3–4 kg (7–9 lb) in weight and 47–53 cm (19–21 in) in height at birth. However, low birth weight is common in developing countries, and contributes to the high levels of infant mortality in these regions. Compared with other species, human childbirth is dangerous, with a much higher risk of complications and death. The size of the fetus's head is more closely matched to the pelvis than in other primates. The reason for this is not completely understood, but it contributes to a painful labor that can last 24 hours or more. The chances of a successful labor increased significantly during the 20th century in wealthier countries with the advent of new medical technologies. In contrast, pregnancy and natural childbirth remain hazardous ordeals in developing regions of the world, with maternal death rates approximately 100 times greater than in developed countries. Both the mother and the father provide care for human offspring, in contrast to other primates, where parental care is mostly done by the mother. Helpless at birth, humans continue to grow for some years, typically reaching sexual maturity at 15 to 17 years of age. The human life span has been split into various stages ranging from three to twelve. Common stages include infancy, childhood, adolescence, adulthood and old age. The lengths of these stages have varied across cultures and time periods but is typified by an unusually rapid growth spurt during adolescence. Human females undergo menopause and become infertile at around the age of 50. It has been proposed that menopause increases a woman's overall reproductive success by allowing her to invest more time and resources in her existing offspring, and in turn their children (the grandmother hypothesis), rather than by continuing to bear children into old age. The life span of an individual depends on two major factors, genetics and lifestyle choices. For various reasons, including biological/genetic causes, women live on average about four years longer than men. As of 2018, the global average life expectancy at birth of a girl is estimated to be 74.9 years compared to 70.4 for a boy. There are significant geographical variations in human life expectancy, mostly correlated with economic development – for example, life expectancy at birth in Hong Kong is 87.6 years for girls and 81.8 for boys, while in the Central African Republic, it is 55.0 years for girls and 50.6 for boys. The developed world is generally aging, with the median age around 40 years. In the developing world, the median age is between 15 and 20 years. While one in five Europeans is 60 years of age or older, only one in twenty Africans is 60 years of age or older. In 2012, the United Nations estimated that there were 316,600 living centenarians (humans of age 100 or older) worldwide. Human life stages Infant boy and girl Boy and girl before puberty (children) Adolescent male and female Adult man and woman Elderly man and woman Diet Main article: Human nutrition Humans living in Bali, Indonesia, preparing a meal Humans are omnivorous, capable of consuming a wide variety of plant and animal material. Human groups have adopted a range of diets from purely vegan to primarily carnivorous. In some cases, dietary restrictions in humans can lead to deficiency diseases; however, stable human groups have adapted to many dietary patterns through both genetic specialization and cultural conventions to use nutritionally balanced food sources. The human diet is prominently reflected in human culture and has led to the development of food science. Until the development of agriculture, Homo sapiens employed a hunter-gatherer method as their sole means of food collection. This involved combining stationary food sources (such as fruits, grains, tubers, and mushrooms, insect larvae and aquatic mollusks) with wild game, which must be hunted and captured in order to be consumed. It has been proposed that humans have used fire to prepare and cook food since the time of Homo erectus. Human domestication of wild plants began about 11,700 years ago, leading to the development of agriculture, a gradual process called the Neolithic Revolution. These dietary changes may also have altered human biology; the spread of dairy farming provided a new and rich source of food, leading to the evolution of the ability to digest lactose in some adults. The types of food consumed, and how they are prepared, have varied widely by time, location, and culture. In general, humans can survive for up to eight weeks without food, depending on stored body fat. Survival without water is usually limited to three or four days, with a maximum of one week. In 2020 it is estimated 9 million humans die every year from causes directly or indirectly related to starvation. Childhood malnutrition is also common and contributes to the global burden of disease. However, global food distribution is not even, and obesity among some human populations has increased rapidly, leading to health complications and increased mortality in some developed and a few developing countries. Worldwide, over one billion people are obese, while in the United States 35% of people are obese, leading to this being described as an "obesity epidemic." Obesity is caused by consuming more calories than are expended, so excessive weight gain is usually caused by an energy-dense diet. Biological variation Main article: Human genetic variation Changes in the number and order of genes (A–D) create genetic diversity within and between population. There is biological variation in the human species – with traits such as blood type, genetic diseases, cranial features, facial features, organ systems, eye color, hair color and texture, height and build, and skin color varying across the globe. The typical height of an adult human is between 1.4 and 1.9 m (4 ft 7 in and 6 ft 3 in), although this varies significantly depending on sex, ethnic origin, and family bloodlines. Body size is partly determined by genes and is also significantly influenced by environmental factors such as diet, exercise, and sleep patterns. There is evidence that populations have adapted genetically to various external factors. The genes that allow adult humans to digest lactose are present in high frequencies in populations that have long histories of cattle domestication and are more dependent on cow milk. Sickle cell anemia, which may provide increased resistance to malaria, is frequent in populations where malaria is endemic. Populations that have for a very long time inhabited specific climates tend to have developed specific phenotypes that are beneficial for those environments – short stature and stocky build in cold regions, tall and lanky in hot regions, and with high lung capacities or other adaptations at high altitudes. Some populations have evolved highly unique adaptations to very specific environmental conditions, such as those advantageous to ocean-dwelling lifestyles and freediving in the Bajau. Human hair ranges in color from red to blond to brown to black, which is the most frequent. Hair color depends on the amount of melanin, with concentrations fading with increased age, leading to grey or even white hair. Skin color can range from darkest brown to lightest peach, or even nearly white or colorless in cases of albinism. It tends to vary clinally and generally correlates with the level of ultraviolet radiation in a particular geographic area, with darker skin mostly around the equator. Skin darkening may have evolved as protection against ultraviolet solar radiation. Light skin pigmentation protects against depletion of vitamin D, which requires sunlight to make. Human skin also has a capacity to darken (tan) in response to exposure to ultraviolet radiation. A Libyan, a Nubian, a Syrian, and an Egyptian, drawing by an unknown artist after a mural of the tomb of Seti I There is relatively little variation between human geographical populations, and most of the variation that occurs is at the individual level. Much of human variation is continuous, often with no clear points of demarcation. Genetic data shows that no matter how population groups are defined, two people from the same population group are almost as different from each other as two people from any two different population groups. Dark-skinned populations that are found in Africa, Australia, and South Asia are not closely related to each other. Genetic research has demonstrated that human populations native to the African continent are the most genetically diverse and genetic diversity decreases with migratory distance from Africa, possibly the result of bottlenecks during human migration. These non-African populations acquired new genetic inputs from local admixture with archaic populations and have much greater variation from Neanderthals and Denisovans than is found in Africa, though Neanderthal admixture into African populations may be underestimated. Furthermore, recent studies have found that populations in sub-Saharan Africa, and particularly West Africa, have ancestral genetic variation which predates modern humans and has been lost in most non-African populations. Some of this ancestry is thought to originate from admixture with an unknown archaic hominin that diverged before the split of Neanderthals and modern humans. Humans are a gonochoric species, meaning they are divided into male and female sexes. The greatest degree of genetic variation exists between males and females. While the nucleotide genetic variation of individuals of the same sex across global populations is no greater than 0.1%–0.5%, the genetic difference between males and females is between 1% and 2%. Males on average are 15% heavier and 15 cm (6 in) taller than females. On average, men have about 40–50% more upper body strength and 20–30% more lower body strength than women at the same weight, due to higher amounts of muscle and larger muscle fibers. Women generally have a higher body fat percentage than men. Women have lighter skin than men of the same population; this has been explained by a higher need for vitamin D in females during pregnancy and lactation. As there are chromosomal differences between females and males, some X and Y chromosome-related conditions and disorders only affect either men or women. After allowing for body weight and volume, the male voice is usually an octave deeper than the female voice. Women have a longer life span in almost every population around the world. There are intersex conditions in the human population, however these are rare. Psychology Main article: Psychology Drawing of the human brain, showing several important structures The human brain, the focal point of the central nervous system in humans, controls the peripheral nervous system. In addition to controlling "lower", involuntary, or primarily autonomic activities such as respiration and digestion, it is also the locus of "higher" order functioning such as thought, reasoning, and abstraction. These cognitive processes constitute the mind, and, along with their behavioral consequences, are studied in the field of psychology. Humans have a larger and more developed prefrontal cortex than other primates, the region of the brain associated with higher cognition. This has led humans to proclaim themselves to be more intelligent than any other known species. Objectively defining intelligence is difficult, with other animals adapting senses and excelling in areas that humans are unable to. There are some traits that, although not strictly unique, do set humans apart from other animals. Humans may be the only animals who have episodic memory and who can engage in "mental time travel". Even compared with other social animals, humans have an unusually high degree of flexibility in their facial expressions. Humans are the only animals known to cry emotional tears. Humans are one of the few animals able to self-recognize in mirror tests and there is also debate over to what extent humans are the only animals with a theory of mind. Sleep and dreaming Main articles: Sleep and Dream Humans are generally diurnal. The average sleep requirement is between seven and nine hours per day for an adult and nine to ten hours per day for a child; elderly people usually sleep for six to seven hours. Having less sleep than this is common among humans, even though sleep deprivation can have negative health effects. A sustained restriction of adult sleep to four hours per day has been shown to correlate with changes in physiology and mental state, including reduced memory, fatigue, aggression, and bodily discomfort. During sleep humans dream, where they experience sensory images and sounds. Dreaming is stimulated by the pons and mostly occurs during the REM phase of sleep. The length of a dream can vary, from a few seconds up to 30 minutes. Humans have three to five dreams per night, and some may have up to seven. Dreamers are more likely to remember the dream if awakened during the REM phase. The events in dreams are generally outside the control of the dreamer, with the exception of lucid dreaming, where the dreamer is self-aware. Dreams can at times make a creative thought occur or give a sense of inspiration. Consciousness and thought Main articles: Consciousness and Cognition Human consciousness, at its simplest, is sentience or awareness of internal or external existence. Despite centuries of analyses, definitions, explanations and debates by philosophers and scientists, consciousness remains puzzling and controversial, being "at once the most familiar and most mysterious aspect of our lives". The only widely agreed notion about the topic is the intuition that it exists. Opinions differ about what exactly needs to be studied and explained as consciousness. Some philosophers divide consciousness into phenomenal consciousness, which is sensory experience itself, and access consciousness, which can be used for reasoning or directly controlling actions. It is sometimes synonymous with 'the mind', and at other times, an aspect of it. Historically it is associated with introspection, private thought, imagination and volition. It now often includes some kind of experience, cognition, feeling or perception. It may be 'awareness', or 'awareness of awareness', or self-awareness. There might be different levels or orders of consciousness, or different kinds of consciousness, or just one kind with different features. The process of acquiring knowledge and understanding through thought, experience, and the senses is known as cognition. The human brain perceives the external world through the senses, and each individual human is influenced greatly by his or her experiences, leading to subjective views of existence and the passage of time. The nature of thought is central to psychology and related fields. Cognitive psychology studies cognition, the mental processes underlying behavior. Largely focusing on the development of the human mind through the life span, developmental psychology seeks to understand how people come to perceive, understand, and act within the world and how these processes change as they age. This may focus on intellectual, cognitive, neural, social, or moral development. Psychologists have developed intelligence tests and the concept of intelligence quotient in order to assess the relative intelligence of human beings and study its distribution among population. Motivation and emotion Main articles: Motivation and Emotion Illustration of grief from Charles Darwin's 1872 book The Expression of the Emotions in Man and Animals Human motivation is not yet wholly understood. From a psychological perspective, Maslow's hierarchy of needs is a well-established theory that can be defined as the process of satisfying certain needs in ascending order of complexity. From a more general, philosophical perspective, human motivation can be defined as a commitment to, or withdrawal from, various goals requiring the application of human ability. Furthermore, incentive and preference are both factors, as are any perceived links between incentives and preferences. Volition may also be involved, in which case willpower is also a factor. Ideally, both motivation and volition ensure the selection, striving for, and realization of goals in an optimal manner, a function beginning in childhood and continuing throughout a lifetime in a process known as socialization. Emotions are biological states associated with the nervous system brought on by neurophysiological changes variously associated with thoughts, feelings, behavioral responses, and a degree of pleasure or displeasure. They are often intertwined with mood, temperament, personality, disposition, creativity, and motivation. Emotion has a significant influence on human behavior and their ability to learn. Acting on extreme or uncontrolled emotions can lead to social disorder and crime, with studies showing criminals may have a lower emotional intelligence than normal. Emotional experiences perceived as pleasant, such as joy, interest or contentment, contrast with those perceived as unpleasant, like anxiety, sadness, anger, and despair. Happiness, or the state of being happy, is a human emotional condition. The definition of happiness is a common philosophical topic. Some define it as experiencing the feeling of positive emotional affects, while avoiding the negative ones. Others see it as an appraisal of life satisfaction or quality of life. Recent research suggests that being happy might involve experiencing some negative emotions when humans feel they are warranted. Sexuality and love Main articles: Human sexuality and Love Human parents often display familial love for their children. For humans, sexuality involves biological, erotic, physical, emotional, social, or spiritual feelings and behaviors. Because it is a broad term, which has varied with historical contexts over time, it lacks a precise definition. The biological and physical aspects of sexuality largely concern the human reproductive functions, including the human sexual response cycle. Sexuality also affects and is affected by cultural, political, legal, philosophical, moral, ethical, and religious aspects of life. Sexual desire, or libido, is a basic mental state present at the beginning of sexual behavior. Studies show that men desire sex more than women and masturbate more often. Humans can fall anywhere along a continuous scale of sexual orientation, although most humans are heterosexual. While homosexual behavior occurs in some other animals, only humans and domestic sheep have so far been found to exhibit exclusive preference for same-sex relationships. Most evidence supports nonsocial, biological causes of sexual orientation, as cultures that are very tolerant of homosexuality do not have significantly higher rates of it. Research in neuroscience and genetics suggests that other aspects of human sexuality are biologically influenced as well. Love most commonly refers to a feeling of strong attraction or emotional attachment. It can be impersonal (the love of an object, ideal, or strong political or spiritual connection) or interpersonal (love between humans). When in love dopamine, norepinephrine, serotonin and other chemicals stimulate the brain's pleasure center, leading to side effects such as increased heart rate, loss of appetite and sleep, and an intense feeling of excitement. Culture Main articles: Culture and Cultural universal Human society statisticsMost widely spoken languagesEnglish, Mandarin Chinese, Hindi, Spanish, Standard Arabic, Bengali, French, Russian, Portuguese, UrduMost practiced religionsChristianity, Islam, Hinduism, Buddhism, folk religions, Sikhism, Judaism, unaffiliated Humanity's unprecedented set of intellectual skills were a key factor in the species' eventual technological advancement and concomitant domination of the biosphere. Disregarding extinct hominids, humans are the only animals known to teach generalizable information, innately deploy recursive embedding to generate and communicate complex concepts, engage in the "folk physics" required for competent tool design, or cook food in the wild. Teaching and learning preserves the cultural and ethnographic identity of human societies. Other traits and behaviors that are mostly unique to humans include starting fires, phoneme structuring and vocal learning. Language Main article: Language Principal language families of the world (and in some cases geographic groups of families). For greater detail, see Distribution of languages in the world. While many species communicate, language is unique to humans, a defining feature of humanity, and a cultural universal. Unlike the limited systems of other animals, human language is open – an infinite number of meanings can be produced by combining a limited number of symbols. Human language also has the capacity of displacement, using words to represent things and happenings that are not presently or locally occurring but reside in the shared imagination of interlocutors. Language differs from other forms of communication in that it is modality independent; the same meanings can be conveyed through different media, audibly in speech, visually by sign language or writing, and through tactile media such as braille. Language is central to the communication between humans, and to the sense of identity that unites nations, cultures and ethnic groups. There are approximately six thousand different languages currently in use, including sign languages, and many thousands more that are extinct. The arts Main article: The arts Human arts can take many forms including visual, literary, and performing. Visual art can range from paintings and sculptures to film, fashion design, and architecture. Literary arts can include prose, poetry, and dramas. The performing arts generally involve theatre, music, and dance. Humans often combine the different forms (for example, music videos). Other entities that have been described as having artistic qualities include food preparation, video games, and medicine. As well as providing entertainment and transferring knowledge, the arts are also used for political purposes. The Deluge tablet of the Gilgamesh epic in Akkadian Art is a defining characteristic of humans and there is evidence for a relationship between creativity and language. The earliest evidence of art was shell engravings made by Homo erectus 300,000 years before modern humans evolved. Art attributed to H. sapiens existed at least 75,000 years ago, with jewellery and drawings found in caves in South Africa. There are various hypotheses as to why humans have adapted to the arts. These include allowing them to better problem solve issues, providing a means to control or influence other humans, encouraging cooperation and contribution within a society or increasing the chance of attracting a potential mate. The use of imagination developed through art, combined with logic may have given early humans an evolutionary advantage. Evidence of humans engaging in musical activities predates cave art and so far music has been practiced by virtually all known human cultures. There exists a wide variety of music genres and ethnic musics; with humans' musical abilities being related to other abilities, including complex social human behaviours. It has been shown that human brains respond to music by becoming synchronized with the rhythm and beat, a process called entrainment. Dance is also a form of human expression found in all cultures and may have evolved as a way to help early humans communicate. Listening to music and observing dance stimulates the orbitofrontal cortex and other pleasure sensing areas of the brain. Unlike speaking, reading and writing does not come naturally to humans and must be taught. Still, literature has been present before the invention of words and language, with 30,000-year-old paintings on walls inside some caves portraying a series of dramatic scenes. One of the oldest surviving works of literature is the Epic of Gilgamesh, first engraved on ancient Babylonian tablets about 4,000 years ago. Beyond simply passing down knowledge, the use and sharing of imaginative fiction through stories might have helped develop humans' capabilities for communication and increased the likelihood of securing a mate. Storytelling may also be used as a way to provide the audience with moral lessons and encourage cooperation. Tools and technologies Main articles: Tool and Technology The SCMaglev, the fastest train in the world clocking in at 603 km/h (375 mph) as of 2015 Stone tools were used by proto-humans at least 2.5 million years ago. The use and manufacture of tools has been put forward as the ability that defines humans more than anything else and has historically been seen as an important evolutionary step. The technology became much more sophisticated about 1.8 million years ago, with the controlled use of fire beginning around 1 million years ago. The wheel and wheeled vehicles appeared simultaneously in several regions some time in the fourth millennium BC. The development of more complex tools and technologies allowed land to be cultivated and animals to be domesticated, thus proving essential in the development of agriculture – what is known as the Neolithic Revolution. China developed paper, the printing press, gunpowder, the compass and other important inventions. The continued improvements in smelting allowed forging of copper, bronze, iron and eventually steel, which is used in railways, skyscrapers and many other products. This coincided with the Industrial Revolution, where the invention of automated machines brought major changes to humans' lifestyles. Modern technology is observed as progressing exponentially, with major innovations in the 20th century including: electricity, penicillin, semiconductors, internal combustion engines, the Internet, nitrogen fixing fertilisers, airplanes, computers, automobiles, contraceptive pills, nuclear fission, the green revolution, radio, scientific plant breeding, rockets, air conditioning, television and the assembly line. Religion and spirituality Main articles: Religion and Spirituality Shango, the Orisha of fire, lightning, and thunder, in the Yoruba religion, depicted on horseback Definitions of religion vary; according to one definition, a religion is a belief system concerning the supernatural, sacred or divine, and practices, values, institutions and rituals associated with such belief. Some religions also have a moral code. The evolution and the history of the first religions have become areas of active scientific investigation. Credible evidence of religious behaviour dates to the Middle Paleolithic era (45–200 thousand years ago). It may have evolved to play a role in helping enforce and encourage cooperation between humans. Religion manifests in diverse forms. Religion can include a belief in life after death, the origin of life, the nature of the universe (religious cosmology) and its ultimate fate (eschatology), and moral or ethical teachings. Views on transcendence and immanence vary substantially; traditions variously espouse monism, deism, pantheism, and theism (including polytheism and monotheism). Although measuring religiosity is difficult, a majority of humans profess some variety of religious or spiritual belief. In 2015 the plurality were Christian followed by Muslims, Hindus and Buddhists. As of 2015, about 16%, or slightly under 1.2 billion humans, were irreligious, including those with no religious beliefs or no identity with any religion. Science and philosophy Main articles: Science and Philosophy The Dunhuang map, a star map showing the North Polar region. China circa 700. An aspect unique to humans is their ability to transmit knowledge from one generation to the next and to continually build on this information to develop tools, scientific laws and other advances to pass on further. This accumulated knowledge can be tested to answer questions or make predictions about how the universe functions and has been very successful in advancing human ascendancy. Aristotle has been described as the first scientist, and preceded the rise of scientific thought through the Hellenistic period. Other early advances in science came from the Han Dynasty in China and during the Islamic Golden Age. The scientific revolution, near the end of the Renaissance, led to the emergence of modern science. A chain of events and influences led to the development of the scientific method, a process of observation and experimentation that is used to differentiate science from pseudoscience. An understanding of mathematics is unique to humans, although other species of animals have some numerical cognition. All of science can be divided into three major branches, the formal sciences (e.g., logic and mathematics), which are concerned with formal systems, the applied sciences (e.g., engineering, medicine), which are focused on practical applications, and the empirical sciences, which are based on empirical observation and are in turn divided into natural sciences (e.g., physics, chemistry, biology) and social sciences (e.g., psychology, economics, sociology). Philosophy is a field of study where humans seek to understand fundamental truths about themselves and the world in which they live. Philosophical inquiry has been a major feature in the development of humans' intellectual history. It has been described as the "no man's land" between definitive scientific knowledge and dogmatic religious teachings. Philosophy relies on reason and evidence, unlike religion, but does not require the empirical observations and experiments provided by science. Major fields of philosophy include metaphysics, epistemology, logic, and axiology (which includes ethics and aesthetics). Society Main article: Society Humans often live in family-based social structures Society is the system of organizations and institutions arising from interaction between humans. Humans are highly social and tend to live in large complex social groups. They can be divided into different groups according to their income, wealth, power, reputation and other factors. The structure of social stratification and the degree of social mobility differs, especially between modern and traditional societies. Human groups range from the size of families to nations. The first form of human social organization is thought to have resembled hunter-gatherer band societies. Gender Main article: Gender Human societies typically exhibit gender identities and gender roles that distinguish between masculine and feminine characteristics and prescribe the range of acceptable behaviours and attitudes for their members based on their sex. The most common categorisation is a gender binary of men and women. Many societies recognise a third gender, or less commonly a fourth or fifth. In some other societies, non-binary is used as an umbrella term for a range of gender identities that are not solely male or female. Gender roles are often associated with a division of norms, practices, dress, behavior, rights, duties, privileges, status, and power, with men enjoying more rights and privileges than women in most societies, both today and in the past. As a social construct, gender roles are not fixed and vary historically within a society. Challenges to predominant gender norms have recurred in many societies. Little is known about gender roles in the earliest human societies. Early modern humans probably had a range of gender roles similar to that of modern cultures from at least the Upper Paleolithic, while the Neanderthals were less sexually dimorphic and there is evidence that the behavioural difference between males and females was minimal. Kinship Main article: Kinship All human societies organize, recognize and classify types of social relationships based on relations between parents, children and other descendants (consanguinity), and relations through marriage (affinity). There is also a third type applied to godparents or adoptive children (fictive). These culturally defined relationships are referred to as kinship. In many societies, it is one of the most important social organizing principles and plays a role in transmitting status and inheritance. All societies have rules of incest taboo, according to which marriage between certain kinds of kin relations are prohibited, and some also have rules of preferential marriage with certain kin relations. Ethnicity Main article: Ethnic group Human ethnic groups are a social category that identifies together as a group based on shared attributes that distinguish them from other groups. These can be a common set of traditions, ancestry, language, history, society, culture, nation, religion, or social treatment within their residing area. Ethnicity is separate from the concept of race, which is based on physical characteristics, although both are socially constructed. Assigning ethnicity to a certain population is complicated, as even within common ethnic designations there can be a diverse range of subgroups, and the makeup of these ethnic groups can change over time at both the collective and individual level. Also, there is no generally accepted definition of what constitutes an ethnic group. Ethnic groupings can play a powerful role in the social identity and solidarity of ethnopolitical units. This has been closely tied to the rise of the nation state as the predominant form of political organization in the 19th and 20th centuries. Government and politics Main articles: Government and Politics The United Nations headquarters in New York City, which houses one of the world's largest political organizations As farming populations gathered in larger and denser communities, interactions between these different groups increased. This led to the development of governance within and between the communities. Humans have evolved the ability to change affiliation with various social groups relatively easily, including previously strong political alliances, if doing so is seen as providing personal advantages. This cognitive flexibility allows individual humans to change their political ideologies, with those with higher flexibility less likely to support authoritarian and nationalistic stances. Governments create laws and policies that affect the citizens that they govern. There have been many forms of government throughout human history, each having various means of obtaining power and the ability to exert diverse controls on the population. Approximately 47% of humans live in some form of a democracy, 17% in a hybrid regime, and 37% in an authoritarian regime. Many countries belong to international organizations and alliances; the largest of these is the United Nations, with 193 member states. Trade and economics Main articles: Trade and Economics The Silk Road (red) and spice trade routes (blue) Trade, the voluntary exchange of goods and services, is seen as a characteristic that differentiates humans from other animals and has been cited as a practice that gave Homo sapiens a major advantage over other hominids. Evidence suggests early H. sapiens made use of long-distance trade routes to exchange goods and ideas, leading to cultural explosions and providing additional food sources when hunting was sparse, while such trade networks did not exist for the now extinct Neanderthals. Early trade likely involved materials for creating tools like obsidian. The first truly international trade routes were around the spice trade through the Roman and medieval periods. Early human economies were more likely to be based around gift giving instead of a bartering system. Early money consisted of commodities; the oldest being in the form of cattle and the most widely used being cowrie shells. Money has since evolved into governmental issued coins, paper and electronic money. Human study of economics is a social science that looks at how societies distribute scarce resources among different people. There are massive inequalities in the division of wealth among humans; the eight richest humans are worth the same monetary value as the poorest half of all the human population. Conflict Further information: War and Violence American troops landing at Normandy, WWII. Humans commit violence on other humans at a rate comparable to other primates, but have an increased preference for killing adults, infanticide being more common among other primates. Phylogenetic analysis predicts that 2% of early H. sapiens would be murdered, rising to 12% during the medieval period, before dropping to below 2% in modern times. There is great variation in violence between human populations with rates of homicide in societies that have legal systems and strong cultural attitudes against violence at about 0.01%. The willingness of humans to kill other members of their species en masse through organized conflict (i.e., war) has long been the subject of debate. One school of thought holds that war evolved as a means to eliminate competitors, and has always been an innate human characteristic. Another suggests that war is a relatively recent phenomenon and has appeared due to changing social conditions. While not settled, current evidence indicates warlike predispositions only became common about 10,000 years ago, and in many places much more recently than that. War has had a high cost on human life; it is estimated that during the 20th century, between 167 million and 188 million people died as a result of war. War casualty data is less reliable for pre-medieval times, especially global figures. But compared with any period over the past 600 years, the last ~80 years (post 1946), has seen a very significant drop in global military and civilian death rates due to armed conflict. See also Mammals portalEvolutionary biology portalScience portal List of human evolution fossils Timeline of human evolution Notes ^ The world population and population density statistics are updated automatically from a template that uses the CIA World Factbook and United Nations World Population Prospects. ^ Cities with over 10 million inhabitants as of 2018. ^ Traditionally this has been explained by conflicting evolutionary pressures involved in bipedalism and encephalization (called the obstetrical dilemma), but recent research suggest it might be more complicated than that.	biology	494108	https://no.wikipedia.org/wiki/Menneske	Menneske	? H. s. denisova † H. s. idaltu H. s. sapiens Menneske (Homo sapiens) er en art med tobeinte primater (Primates) i familien av store aper (Hominidae) og tilhører menneskeslekten (Homo). Det vitenskapelige navnet kommer fra latin og betyr «det tenkende mennesket». Nålevende mennesker tilhører underarten H. s. sapiens, alle tidligere underarter av vår art er dødd ut eller absorbert i den moderne befolkningen. Menneske kan være både primærkonsument, sekundærkonsument, tertiærkonsument og toppkonsument i en næringskjede. Karakteristisk for mennesker er artens kombinasjon av å gå på to bein (tobeint), tilpasningsevne (som klær og verktøy), finmotorikk (hender og fingre), evne til å tenke abstrakt (å vise følelser og empati [medfølelse]), skjelne årsakssammenheng (kausalitet), tolke språk og symboler og eventuelt selvbevissthet. Ingen av disse egenskapene er egentlig unike for mennesker individuelt, men finnes også i ulike dyrearter – fra insekter til andre primater og hvaler. Sammen har de satt mennesket i stand til å utvikle samfunn, filosofi, religion, vitenskap, teknologi og kunst. Mennesker har utviklet seg i forhold til andre arter og har over tid kommet til å dominere utviklingen på planeten Jorden. Som et sosialt vesen har dets strukturer for sivilisasjon og samfunn blitt styrt ved hjelp av politikk, dens kultur og oppfatning av omverdenen ved hjelp av fenomener som religion, filosofi og vitenskapelig utvikling. Gjennom språket har arten også kunnet dokumentere funn, oppdagelser, oppfinnelser og sin egen historie. Studiet av mennesker er vanligvis delt inn i ulike fagområder. Studiet av mennesker kalles antropologi og studiet av menneskelig evolusjon kalles paleoantropologi. Studiet av menneskelig atferd kan gjøres innenfor psykologi og sosiologi, mens studiet basert på nøytrale etologiske perspektiver (atferdsbiologi) kalles humanetologi. Studiet av menneskelig språk kalles lingvistikk. Studiet av menneskers helse og mer kalles menneskelig medisin, og studiet av dens kropp kan beskrives i menneskelig anatomi og fysiologi. Menneskelig reproduksjon er relatert til både genetikk og seksualitet. Biologi Det moderne mennesket har mulighet for å bruke språk på et meget høyt nivå, og har en høyt utviklet hjerne som er i stand til utstrakt abstrakt tenkning og bevissthet. Denne mentale kapasiteten, kombinert med en oppreist kroppsholdning som frigjør dets øvre lemmer til andre aktiviteter enn gange, har gjort mennesket i stand til å bruke verktøy i større grad enn noen annen kjent dyreart. DNA-baserte beviser indikerer at moderne mennesker oppstod i Afrika for omtrent år siden. Mennesker befolker nå samtlige kontinenter og har per 2022 en total populasjon på over 7.8 milliarder individer. Studiet av mennesket skjer både i naturvitenskapene (humanbiologi), samfunnsvitenskapene (antropologi) og medisin (inkl. psykologi). Beskrivelse Et voksent menneske har ca. 1,8 m² hud, 32 tenner, ca. 600 muskler, 206 knokler, over 100 ledd, km blodårer samt 13 milliarder nerveceller. Mennesket har 4–6 liter blod som inneholder omtrent 25 billioner røde blodlegemer. Hjernen veier gjennomsnittlig gram. Mennesket har opp til 5 millioner hår, like mange som en sjimpanse eller gorilla. I motsetning til hos dem, er kroppshårene hos menneske tynne og kortvokste, slik at mennesket framstår som nakent i forhold til sine slektninger. Mennesket er en svært variabel art. Gjennomsnittsvekten på voksne individer varierer mellom 40 kg hos noen tropiske folkeslag til opp mot 70 kg hos enkelte nordlige grupper. Størrelsesforskjellen på kjønnene er omkring 20 %, større enn hos sjimpanse, men mindre enn det vi finner hos gorilla og orangutang. Med unntak av ryggsøylen og den store hjerneskallen er menneskekroppen lite spesialisert, og likner den vi finner hos de fleste primater. Øynene er foroverrettet. Tannsettet er noe redusert i forhold til primitive pattedyr, og mangler de lange hjørnetennene som er vanlig for øvrige primater. Hele tannarden er relativt liten og tilbaketrukket i forhold til slektningene, slik at den nederste del av underkjeven stikker fram som en hake. Dette er trolig en tilpasning til å spise mat som må tygges «sideveis», slik som frø og røtter. Fordøyelsessystemet er ganske enkelt og mangler tilpasninger for mer næringsfattig kost slik vi finner det hos gressetere. Som andre primater har mennesket relativt lite spesialiserte lemmer med fem fingre/tær på hver ekstremitet og kragebein. Menneskets føtter er tilpasset til å gå på hele fotsålen (sålegjenger), og mangler tilpasning til klatring slik vi finner hos andre primater. Evolusjon og systematikk Biologisk sett utgjør helheten av alle mennesker en art. Denne ga Linné det vitenskapelige navnet Homo sapiens (latin: i betydningen «det kloke mennesket»). Menneskets plass i naturen Menneskets plass i naturen har fra oldtiden av vært et stridstema. I mange religioner, eksempelvis åsatru, gresk mytologi, kristendom og islam blir mennesket beskrevet som en skapning som er skapt (eller har oppstått) spesielt og løsrevet fra den øvrige naturen. Likevel er likhetene med andre levende organismer ikke til å overse, og allerede Aristoteles grupperte mennesket i dyreriket. Linné plasserte i sitt verk Systema Naturae menneskene blant herredyrene (primater), i samme biologiske slekt som sjimpanse og orangutang. Denne plasseringen var omstridt i hans samtid, men på forespørsel fra biskopen i Uppsala, skrev han: Jeg kan ikke se at det er noen generiske forskjeller. Med «generisk» viste han til de egenskapene som skiller en slekt (genus på latin) fra en annen. Ideen om mennesket som en primat har holdt stand også i lys av de siste to hundre års forskning. Med Charles Darwins evolusjonsteori fikk man for første gang en etterprøvbar teori om stamtrær og slektskap, og menneskets fortid er i dag ganske godt beskrevet gjennom fossilfunn. Klassifikasjon Rike: Animalia (dyreriket) Rekke: Chordata (ryggstrengdyr) Klasse: Mammalia (pattedyr) Orden: Primates (primater) Familie: Hominidae (store aper) Slekt: Homo (menneskeslekten) Art: H. sapiens (menneske) Underart: H. s. sapiens (det moderne mennesket) Menneske hører også med i en rekke grupper som faller mellom de formelle kategoriene, slik som infraordenen høyere aper, underklassen placentale pattedyr, overklassen amniondyr, overrekken deuterostomier, gruppene opisthokonter og eukaryoter. Spredning av mennesker Menneskeaper Blant menneskeapene er sjimpanser menneskets nærmeste slektninger. Inntil for om lag 12 millioner år siden delte menneskene sin evolusjonære historie med sjimpansene og gorilla. Mennesket og sjimpansene har hatt en komplisert artsdannelsesprosess fra 8 til 4 millioner år siden, der populasjoner ser ut til å ha skilt lag for så å blande seg igjen i flere omganger. Etter dette «skilte de lag», dvs. at menneskene fikk en stamform som de ikke deler med andre menneskeaper. Det finnes flere fossiler som er kandidat til stamformen til menneske og sjimpanser, men disse er svært fragmentariske og det er per i dag usikkert nøyaktig hvem som representerer våre forfedre, sjimpansens forfedre og utdødde sidegreiner. Det finnes derimot godt med fossilt materiale fra utdødde arter som står nærmere mennesker enn andre aper, slik som Australopithecus afarensis og Homo erectus. Noen av disse er utdødde sidegrener, som vil si at de ikke etterlot seg avkom som har overlevd til i dag. Andre er menneskenes direkte stamformer. Disse er ikke i egentlig forstand «dødd ut» (fordi de jo har etterlatt seg avkom), men har gjennomgått så store endringer at de ikke lenger er gjenkjennelige, såkalte krono-arter. For mange av disse fossile artene er imidlertid statusen usikker. Det vil si at man ikke med sikkerhet vet om de representerte en sidegren, eller om de kan ha bidratt med avkom til nåtidens menneskeart. Hva som har utgjort arter og hva som bare har vært variasjoner innfor en gruppe er også usikkert. Førmennesker (Australopithecus) Noen av Australopithecus-artene, som levde for 4,2–1,2 millioner år siden, er f.eks. med sikkerhet sidegrener (bl.a. A. boisei og A. robustus), andre kan ha vært menneskenes stamformer (bl.a. A. anamensis og A. afarensis). De mindre robuste A. afarensis og A. africanus er vanligvis regnet som de linjene som leder til slekten menneskeslekten. Slekten Homo oppsto med bruk av de første steinredskapene for rundt 2,5 millioner år siden, men Australopithecus fortsatte å eksistere. De yngste restene vi kjenner av denne slekten er rundt 1,2 millioner år gamle. Mennesker (Homo) Gjennom tidene har det vært flere teorier om det moderne menneskets opprinnelse. I dag er de fleste forskere enige om at moderne Homo sapiens ble utviklet på den afrikanske savannen for mellom og år siden. For om lag år siden vandret grupper ut fra Afrika og spredte seg, først i tropiske strøk, og for kanskje så mye som år siden begynte de også å besette kaldere områder. I prosessen delvis fortrengte de, delvis blandet seg med tidligere utvandringsbølger (neandertalere, denisovere, Homo erectus). Mennesket nådde polare områder for rundt år siden og nådde derved de amerikanske kontinentene via Sibir. I dag er mennesket naturlig utbredt på alle kontinenter utenom Antarktis. Etter hvert som mennesket spredte seg, fortrengte det de tidligere menneskeartene, neandertalere i Europa, Mapa-folket i Asia, Homo erectus i Sørøst-Asia og Homo floresiensis på øya Flores. Den første representanten for nåtidsmennesket er i Europa Cro-Magnon-mennesket, oppkalt etter et funnsted i Frankrike. Der fant man de første restene etter disse menneskene i 1868. Cro-Magnon spredte seg trolig inn i Europa for omkring år siden. Menneske (H. sapiens) Man regner i dag med kun én nålevende underart av mennesket, nåtidsmennesket Homo sapiens sapiens. Utdødde underarter inkluderer Homo sapiens idaltu, funnene fra Omo og skjelettene fra Qafzeh-hulen i Israel. Det eksisterer imidlertid ikke en enhetlig taksonomi som alle er enige i. Disse funnene kan være vanskelige å skille fra eldre slekninger av vår art, men alle har en trekantet forhøyning midt på underkjeven som utgjør haken hos moderne mennesker. Eldre Homo-arter mangler dette tydelige trekket. Tidligere delte antropologer mennesket inn i raser, men det har man sluttet med (se menneskeraser). Menneskelig variasjon eksisterer (se menneskets kropp), men av politiske og etiske årsaker, spesielt på grunn av misbruk av rasebiologien på første halvdel av 1900-tallet, har man altså sluttet med å dele inn mennesket i annet enn etnisitet. Referanser Eksterne lenker Pattedyr i Norge 1000 artikler enhver Wikipedia bør ha	norwegian_bokmål	0.472136
neanderthals_vitamin_C_diet/Vitamin_C.txt	Vitamin C (also known as ascorbic acid and ascorbate) is a water-soluble vitamin found in citrus and other fruits, berries and vegetables. It is also a generic prescription medication and in some countries is sold as a non-prescription dietary supplement. As a therapy, it is used to prevent and treat scurvy, a disease caused by vitamin C deficiency. Vitamin C is an essential nutrient involved in the repair of tissue, the formation of collagen, and the enzymatic production of certain neurotransmitters. It is required for the functioning of several enzymes and is important for immune system function. It also functions as an antioxidant. Vitamin C may be taken by mouth or by intramuscular, subcutaneous or intravenous injection. Various health claims exist on the basis that moderate vitamin C deficiency increases disease risk, such as for the common cold, cancer or COVID-19. There are also claims of benefits from vitamin C supplementation in excess of the recommended dietary intake for people who are not considered vitamin C deficient. Vitamin C is generally well-tolerated. Large doses may cause gastrointestinal discomfort, headache, trouble sleeping, and flushing of the skin. The United States Institute of Medicine recommends against consuming large amounts. Most animals are able to synthesize their own vitamin C. However, apes (including humans) and monkeys (but not all primates), most bats, most fish, some rodents, and certain other animals must acquire it from dietary sources because a gene for a synthesis enzyme has mutations that render it dysfunctional. Vitamin C was discovered in 1912, isolated in 1928, and in 1933, was the first vitamin to be chemically produced. Partly for its discovery, Albert Szent-Györgyi was awarded the 1937 Nobel Prize in Physiology or Medicine. The name "vitamin C" always refers to the l-enantiomer of ascorbic acid and its oxidized form, dehydroascorbate (DHA). Therefore, unless written otherwise, "ascorbate" and "ascorbic acid" refer in the nutritional literature to l-ascorbate and l-ascorbic acid respectively. Ascorbic acid is a weak sugar acid structurally related to glucose. In biological systems, ascorbic acid can be found only at low pH, but in solutions above pH 5 is predominantly found in the ionized form, ascorbate. Numerous analytical methods have been developed for ascorbic acid detection. For example, vitamin C content of a food sample such as fruit juice can be calculated by measuring the volume of the sample required to decolorize a solution of dichlorophenolindophenol (DCPIP) and then calibrating the results by comparison with a known concentration of vitamin C. Plasma vitamin C is the most widely applied test for vitamin C status. Adequate levels are defined as near 50 μmol/L. Hypovitaminosis of vitamin C is defined as less than 23 μmol/L, and deficiency as less than 11.4 μmol/L. For people 20 years of age or above, data from the US 2017-18 National Health and Nutrition Examination Survey showed mean serum concentrations of 53.4 μmol/L. The percent of people reported as deficient was 5.9%. Globally, vitamin C deficiency is common in low and middle-income countries, and not uncommon in high income countries. In the latter, prevalence is higher in males than in females. Plasma levels are considered saturated at about 65 μmol/L, achieved by intakes of 100 to 200 mg/day, which are well above the recommended intakes. Even higher oral intake does not further raise plasma nor tissue concentrations because absorption efficiency decreases and any excess that is absorbed is excreted in urine. Vitamin C content in plasma is used to determine vitamin status. For research purposes, concentrations can be assessed in leukocytes and tissues, which are normally maintained at an order of magnitude higher than in plasma via an energy-dependent transport system, depleted slower than plasma concentrations during dietary deficiency and restored faster during dietary repletion, but these analysis are difficult to measure, and hence not part of standard diagnostic testing. Recommendations for vitamin C intake by adults have been set by various national agencies: In 2000, the chapter on Vitamin C in the North American Dietary Reference Intake was updated to give the Recommended Dietary Allowance (RDA) as 90 milligrams per day for adult men, 75 mg/day for adult women, and setting a Tolerable upper intake level (UL) for adults of 2,000 mg/day. The table (right) shows RDAs for the United States and Canada for children, and for pregnant and lactating women, as well as the ULs for adults. For the European Union, the EFSA set higher recommendations for adults, and also for children: 20 mg/day for ages 1–3, 30 mg/day for ages 4–6, 45 mg/day for ages 7–10, 70 mg/day for ages 11–14, 100 mg/day for males ages 15–17, 90 mg/day for females ages 15–17. For pregnancy 100 mg/day; for lactation 155 mg/day. Cigarette smokers and people exposed to secondhand smoke have lower serum vitamin C levels than nonsmokers. The thinking is that inhalation of smoke causes oxidative damage, depleting this antioxidant vitamin. The US Institute of Medicine estimated that smokers need 35 mg more vitamin C per day than nonsmokers, but did not formally establish a higher RDA for smokers. An inverse relationship between vitamin C intake and lung cancer was observed, although the conculsion was that more research is needed to confirm this observation. The US National Center for Health Statistics conducts biannual National Health and Nutrition Examination Survey (NHANES) to assess the health and nutritional status of adults and children in the United States. Some results are reported as What We Eat In America. The 2013–2014 survey reported that for adults ages 20 years and older, men consumed on average 83.3 mg/d and women 75.1 mg/d. This means that half the women and more than half the men are not consuming the RDA for vitamin C. The same survey stated that about 30% of adults reported they consumed a vitamin C dietary supplement or a multi-vitamin/mineral supplement that included vitamin C, and that for these people total consumption was between 300 and 400 mg/d. In 2000, the Institute of Medicine of the US National Academy of Sciences set a Tolerable upper intake level (UL) for adults of 2,000 mg/day. The amount was chosen because human trials had reported diarrhea and other gastrointestinal disturbances at intakes of greater than 3,000 mg/day. This was the Lowest-Observed-Adverse-Effect Level (LOAEL), meaning that other adverse effects were observed at even higher intakes. ULs are progressively lower for younger and younger children. In 2006, the European Food Safety Authority (EFSA) also pointed out the disturbances at that dose level, but reached the conclusion that there was not sufficient evidence to set a UL for vitamin C, as did the Japan National Institute of Health and Nutrition in 2010. For US food and dietary supplement labeling purposes, the amount in a serving is expressed as a percent of Daily Value (%DV). For vitamin C labeling purposes, 100% of the Daily Value was 60 mg, but as of May 27, 2016, it was revised to 90 mg to bring it into agreement with the RDA. A table of the old and new adult daily values is provided at Reference Daily Intake. European Union regulations require that labels declare energy, protein, fat, saturated fat, carbohydrates, sugars, and salt. Voluntary nutrients may be shown if present in significant amounts. Instead of Daily Values, amounts are shown as percent of Reference Intakes (RIs). For vitamin C, 100% RI was set at 80 mg in 2011. Although also present in other plant-derived foods, the richest natural sources of vitamin C are fruits and vegetables. Vitamin C is the most widely taken dietary supplement. The following table is approximate and shows the relative abundance in different raw plant sources. The amount is given in milligrams per 100 grams of the edible portion of the fruit or vegetable: Compared to plant sources, animal-sourced foods do not provide so great an amount of vitamin C, and what there is, is largely destroyed by the heat used when it is cooked. For example, raw chicken liver contains 17.9 mg/100 g, but fried, the content is reduced to 2.7 mg/100 g. Vitamin C is present in human breast milk at 5.0 mg/100 g. Cow's milk contains 1.0 mg/100 g, but the heat of pasteurization destroys it. Vitamin C chemically decomposes under certain conditions, many of which may occur during the cooking of food. Vitamin C concentrations in various food substances decrease with time in proportion to the temperature at which they are stored. Cooking can reduce the vitamin C content of vegetables by around 60%, possibly due to increased enzymatic destruction. Longer cooking times may add to this effect. Another cause of vitamin C loss from food is leaching, which transfers vitamin C to the cooking water, which is decanted and not consumed. Vitamin C dietary supplements are available as tablets, capsules, drink mix packets, in multi-vitamin/mineral formulations, in antioxidant formulations, and as crystalline powder. Vitamin C is also added to some fruit juices and juice drinks. Tablet and capsule content ranges from 25 mg to 1500 mg per serving. The most commonly used supplement compounds are ascorbic acid, sodium ascorbate and calcium ascorbate. Vitamin C molecules can also be bound to the fatty acid palmitate, creating ascorbyl palmitate, or else incorporated into liposomes. Countries fortify foods with nutrients to address known deficiencies. While many countries mandate or have voluntary programs to fortify wheat flour, maize (corn) flour or rice with vitamins, none include vitamin C in those programs. As described in Vitamin C Fortification of Food Aid Commodities (1997), the United States provides rations to international food relief programs, later under the asupices of the Food for Peace Act and the Bureau for Humanitarian Assistance. Vitamin C is added to corn-soy blend and wheat-soy blend products at 40 mg/100 grams. (along with minerals and other vitamins). Supplemental rations of these highly fortified, blended foods are provided to refugees and displaced persons in camps and to beneficiaries of development feeding programs that are targeted largely toward mothers and children. The report adds: "The stability of vitamin C (L-ascorbic acid) is of concern because this is one of the most labile vitamins in foods. Its main loss during processing and storage is from oxidation, which is accelerated by light, oxygen, heat, increased pH, high moisture content (water activity), and the presence of copper or ferrous salts. To reduce oxidation, the vitamin C used in commodity fortification is coated with ethyl cellulose (2.5 percent). Oxidative losses also occur during food processing and preparation, and additional vitamin C may be lost if it dissolves into cooking liquid and is then discarded." Ascorbic acid and some of its salts and esters are common additives added to various foods, such as canned fruits, mostly to slow oxidation and enzymatic browning. It may be used as a flour treatment agent used in breadmaking. As food additives, they are assigned E numbers, with safety assessment and approval the responsibility of the European Food Safety Authority. The relevant E numbers are: The stereoisomers of Vitamin C have a similar effect in food despite their lack of efficacy in humans. They include erythorbic acid and its sodium salt (E315, E316). Pharmacodynamics is the study of how the drug – in this instance vitamin C – affects the organism, whereas pharmacokinetics is the study of how an organism affects the drug. Pharmacodynamics includes enzymes for which vitamin C is a cofactor, with function potentially compromised in a deficiency state, and any enzyme cofactor or other physiological function affected by administration of vitamin C, orally or injected, in excess of normal requirements. At normal physiological concentrations, vitamin C serves as an enzyme substrate or cofactor and an electron donor antioxidant. The enzymatic functions include the synthesis of collagen, carnitine, and neurotransmitters; the synthesis and catabolism of tyrosine; and the metabolism of microsomes. In nonenzymatic functions it acts as a reducing agent, donating electrons to oxidized molecules and preventing oxidation in order to keep iron and copper atoms in their reduced states. At non-physiological concentrations achieved by intravenous dosing, vitamin C may function as a pro-oxidant, with therapeutic toxicity against cancer cells. Vitamin C functions as a cofactor for the following enzymes: As an antioxidant, ascorbate scavenges reactive oxygen and nitrogen compounds, thus neutralizing the potential tissue damage of these free radical compounds. Dehydroascorbate, the oxidized form, is then recycled back to ascorbate by endogenous antioxidants such as glutathione. In the eye, ascorbate is thought to protect against photolytically generated free-radical damage; higher plasma ascorbate is associated with lower risk of cateracts. Ascorbate may also provide antioxidant protection indirectly by regenerating other biological antioxidants such as α-tocopherol back to an active state. In addition, ascorbate also functions as a non-enzymatic reducing agent for mixed-function oxidases in the microsomal drug-metabolizing system that inactivates a wide variety of substrates such as drugs and environmental carcinogens. Ascorbic acid is absorbed in the body by both simple diffusion and active transport. Approximately 70%–90% of vitamin C is absorbed at moderate intakes of 30–180 mg/day. However, at doses above 1,000 mg/day, absorption falls to less than 50% as the active transport system becomes saturated. Active transport is managed by Sodium-Ascorbate Co-Transporter proteins (SVCTs) and Hexose Transporter proteins (GLUTs). SVCT1 and SVCT2 import ascorbate across plasma membranes. The Hexose Transporter proteins GLUT1, GLUT3 and GLUT4 transfer only the oxydized dehydroascorbic acid (DHA) form of vitamin C. The amount of DHA found in plasma and tissues under normal conditions is low, as cells rapidly reduce DHA to ascorbate. SVCTs are the predominant system for vitamin C transport within the body. In both vitamin C synthesizers (example: rat) and non-synthesizers (example: human) cells maintain ascorbic acid concentrations much higher than the approximately 50 micromoles/liter (µmol/L) found in plasma. For example, the ascorbic acid content of pituitary and adrenal glands can exceed 2,000 µmol/L, and muscle is at 200–300 µmol/L. The known coenzymatic functions of ascorbic acid do not require such high concentrations, so there may be other, as yet unknown functions. A consequence of all this high concentration organ content is that plasma vitamin C is not a good indicator of whole-body status, and people may vary in the amount of time needed to show symptoms of deficiency when consuming a diet very low in vitamin C. Excretion (via urine) is as ascorbic acid and metabolites. The fraction that is excreted as unmetabolized ascorbic acid increases as intake increases. In addition, ascorbic acid converts (reversibly) to DHA and from that compound non-reversibly to 2,3-diketogulonate and then oxalate. These three metabolites are also excreted via urine. During times of low dietary intake, vitamin C is reabsorbed by the kidneys rather than excreted. This salvage process delays onset of deficiency. Humans are better than guinea pigs at converting DHA back to ascorbate, and thus take much longer to become vitamin C deficient. Most animals and plants are able to synthesize vitamin C through a sequence of enzyme-driven steps, which convert monosaccharides to vitamin C. Yeasts do not make l-ascorbic acid but rather its stereoisomer, erythorbic acid. In plants, synthesis is accomplished through the conversion of mannose or galactose to ascorbic acid. In animals, the starting material is glucose. In some species that synthesize ascorbate in the liver (including mammals and perching birds), the glucose is extracted from glycogen; ascorbate synthesis is a glycogenolysis-dependent process. In humans and in animals that cannot synthesize vitamin C, the enzyme l-gulonolactone oxidase (GULO), which catalyzes the last step in the biosynthesis, is highly mutated and non-functional. There is some information on serum vitamin C concentrations maintained in animal species that are able to synthesize vitamin C. One study of several breeds of dogs reported an average of 35.9 μmol/L. A report on goats, sheep and cattle reported ranges of 100–110, 265–270 and 160–350 μmol/L, respectively. The biosynthesis of ascorbic acid in vertebrates starts with the formation of UDP-glucuronic acid. UDP-glucuronic acid is formed when UDP-glucose undergoes two oxidations catalyzed by the enzyme UDP-glucose 6-dehydrogenase. UDP-glucose 6-dehydrogenase uses the co-factor NAD as the electron acceptor. The transferase UDP-glucuronate pyrophosphorylase removes a UMP and glucuronokinase, with the cofactor ADP, removes the final phosphate leading to d-glucuronic acid. The aldehyde group of this compound is reduced to a primary alcohol using the enzyme glucuronate reductase and the cofactor NADPH, yielding l-gulonic acid. This is followed by lactone formation—utilizing the hydrolase gluconolactonase—between the carbonyl on C1 and hydroxyl group on C4. l-Gulonolactone then reacts with oxygen, catalyzed by the enzyme L-gulonolactone oxidase (which is nonfunctional in humans and other Haplorrhini primates; see Unitary pseudogenes) and the cofactor FAD+. This reaction produces 2-oxogulonolactone (2-keto-gulonolactone), which spontaneously undergoes enolization to form ascorbic acid. Reptiles and older orders of birds make ascorbic acid in their kidneys. Recent orders of birds and most mammals make ascorbic acid in their liver. Some mammals have lost the ability to synthesize vitamin C, including simians and tarsiers, which together make up one of two major primate suborders, Haplorhini. This group includes humans. The other more primitive primates (Strepsirrhini) have the ability to make vitamin C. Synthesis does not occur in some species in the rodent family Caviidae, which includes guinea pigs and capybaras, but does occur in other rodents, including rats and mice. Synthesis does not occur in most bat species, but there are at least two species, frugivorous bat Rousettus leschenaultii and insectivorous bat Hipposideros armiger, that retain (or regained) their ability of vitamin C production. A number of species of passerine birds also do not synthesize, but not all of them, and those that do not are not clearly related; it has been proposed that the ability was lost separately a number of times in birds. In particular, the ability to synthesize vitamin C is presumed to have been lost and then later re-acquired in at least two cases. The ability to synthesize vitamin C has also been lost in about 96% of extant fish (the teleosts). On a milligram consumed per kilogram of body weight basis, simian non-synthesizer species consume the vitamin in amounts 10 to 20 times higher than what is recommended by governments for humans. This discrepancy constituted some of the basis of the controversy on human recommended dietary allowances being set too low. However, simian consumption does not indicate simian requirements. Merck's veterinary manual states that daily intake of vitamin C at 3–6 mg/kg prevents scurvy in non-human primates. By way of comparison, across several countries, the recommended dietary intake for adult humans is in the range of 1–2 mg/kg. Ascorbic acid is a common enzymatic cofactor in mammals used in the synthesis of collagen, as well as a powerful reducing agent capable of rapidly scavenging a number of reactive oxygen species (ROS). Given that ascorbate has these important functions, it is surprising that the ability to synthesize this molecule has not always been conserved. In fact, anthropoid primates, Cavia porcellus (guinea pigs), teleost fishes, most bats, and some passerine birds have all independently lost the ability to internally synthesize vitamin C in either the kidney or the liver. In all of the cases where genomic analysis was done on an ascorbic acid auxotroph, the origin of the change was found to be a result of loss-of-function mutations in the gene that encodes L-gulono-γ-lactone oxidase, the enzyme that catalyzes the last step of the ascorbic acid pathway outlined above. One explanation for the repeated loss of the ability to synthesize vitamin C is that it was the result of genetic drift; assuming that the diet was rich in vitamin C, natural selection would not act to preserve it. In the case of the simians, it is thought that the loss of the ability to make vitamin C may have occurred much farther back in evolutionary history than the emergence of humans or even apes, since it evidently occurred soon after the appearance of the first primates, yet sometime after the split of early primates into the two major suborders Haplorrhini (which cannot make vitamin C) and its sister suborder of non-tarsier prosimians, the Strepsirrhini ("wet-nosed" primates), which retained the ability to make vitamin C. According to molecular clock dating, these two suborder primate branches parted ways about 63 to 60 million years ago. Approximately three to five million years later (58 million years ago), only a short time afterward from an evolutionary perspective, the infraorder Tarsiiformes, whose only remaining family is that of the tarsier (Tarsiidae), branched off from the other haplorrhines. Since tarsiers also cannot make vitamin C, this implies the mutation had already occurred, and thus must have occurred between these two marker points (63 to 58 million years ago). It has also been noted that the loss of the ability to synthesize ascorbate strikingly parallels the inability to break down uric acid, also a characteristic of primates. Uric acid and ascorbate are both strong reducing agents. This has led to the suggestion that, in higher primates, uric acid has taken over some of the functions of ascorbate. There are many different biosynthesis pathways to ascorbic acid in plants. Most proceed through products of glycolysis and other metabolic pathways. For example, one pathway utilizes plant cell wall polymers. The principal plant ascorbic acid biosynthesis pathway seems to be via l-galactose. The enzyme l-galactose dehydrogenase catalyzes the overall oxidation to the lactone and isomerization of the lactone to the C4-hydroxyl group, resulting in l-galactono-1,4-lactone. l-Galactono-1,4-lactone then reacts with the mitochondrial flavoenzyme l-galactonolactone dehydrogenase to produce ascorbic acid. l-Ascorbic acid has a negative feedback on l-galactose dehydrogenase in spinach. Ascorbic acid efflux by embryos of dicot plants is a well-established mechanism of iron reduction and a step obligatory for iron uptake. All plants synthesize ascorbic acid. Ascorbic acid functions as a cofactor for enzymes involved in photosynthesis, synthesis of plant hormones, as an antioxidant and regenerator of other antioxidants. Plants use multiple pathways to synthesize vitamin C. The major pathway starts with glucose, fructose or mannose (all simple sugars) and proceeds to l-galactose, l-galactonolactone and ascorbic acid. This biosynthesis is regulated following a diurnal rhythm. Enzyme expression peaks in the morning to supporting biosynthesis for when mid-day sunlight intensity demands high ascorbic acid concentrations. Minor pathways may be specific to certain parts of plants; these can be either identical to the vertebrate pathway (including the GLO enzyme), or start with inositol and get to ascorbic acid via l-galactonic acid to l-galactonolactone. Vitamin C can be produced from glucose by two main routes. The no longer utilized Reichstein process, developed in the 1930s, used a single fermentation followed by a purely chemical route. The modern two-step fermentation process, originally developed in China in the 1960s, uses additional fermentation to replace part of the later chemical stages. The Reichstein process and the modern two-step fermentation processes both use glucose as the starting material, convert that to sorbitol, and then to sorbose using fermentation. The two-step fermentation process then converts sorbose to 2-keto-l-gulonic acid (KGA) through another fermentation step, avoiding an extra intermediate. Both processes yield approximately 60% vitamin C from the glucose starting point. Researchers are exploring means for one-step fermentation. China produces about 70% of the global vitamin C market. The rest is split among European Union, India and North America. The global market is expected to exceed 141 thousand metric tons in 2024. Cost per metric ton (1000 kg) in US dollars was $2,220 in Shanghai, $2,850 in Hamburg and $3,490 in the US. Vitamin C has a definitive role in treating scurvy, which is a disease caused by vitamin C deficiency. Beyond that, a role for vitamin C as prevention or treatment for various diseases is disputed, with reviews often reporting conflicting results. No effect of vitamin C supplementation reported for overall mortality. It is on the World Health Organization's List of Essential Medicines and on the World Health Organization's Model Forumulary. In 2021, it was the 255th most commonly prescribed medication in the United States, with more than 1 million prescriptions. Scurvy is a disease resulting from a deficiency of vitamin C. Without this vitamin, collagen made by the body is too unstable to perform its function and several other enzymes in the body do not operate correctly. Early symptoms are malaise and lethargy, progressing to shortness of breath, bone pain and susceptibility to bruising. As the disease progressed, it is characterized by spots on and bleeding under the skin and bleeding gums. The skin lesions are most abundant on the thighs and legs. A person with the ailment looks pale, feels depressed, and is partially immobilized. In advanced scurvy there is fever, old wounds may become open and suppurating, loss of teeth, convulsions and, eventually, death. Until quite late in the disease the damage is reversible, as healthy collagen replaces the defective collagen with vitamin C repletion. Notable human dietary studies of experimentally induced scurvy were conducted on conscientious objectors during World War II in Britain and on Iowa state prisoners in the late 1960s to the 1980s. Men in the prison study developed the first signs of scurvy about four weeks after starting the vitamin C-free diet, whereas in the earlier British study, six to eight months were required, possibly due to the pre-loading of this group with a 70 mg/day supplement for six weeks before the scorbutic diet was fed. Men in both studies had blood levels of ascorbic acid too low to be accurately measured by the time they developed signs of scurvy. These studies both reported that all obvious symptoms of scurvy could be completely reversed by supplementation of only 10 mg a day. Treatment of scurvy can be with vitamin C-containing foods or dietary supplements or injection. People in sepsis may have micronutrient deficiencies, including low levels of vitamin C. An intake of 3.0 g/day, which requires intravenous administration, appears to be needed to maintain normal plasma concentrations in people with sepsis or severe burn injury. Sepsis mortality is reduced with administration of intravenous vitamin C. Research on vitamin C in the common cold has been divided into effects on prevention, duration, and severity. Oral intakes of more than 200 mg/day taken on a regular basis was not effective in prevention of the common cold. Restricting analysis to trials that used at least 1000 mg/day also saw no prevention benefit. However, taking a vitamin C supplement on a regular basis did reduce the average duration of the illness by 8% in adults and 14% in children, and also reduced the severity of colds. Vitamin C taken on a regular basis reduced the duration of severe symptoms but had no effect on the duration of mild symptoms. Therapeutic use, meaning that the vitamin was not started unless people started to feel the beginnings of a cold, had no effect on the duration or severity of the illness. Vitamin C distributes readily in high concentrations into immune cells, promotes natural killer cell activities, promotes lymphocyte proliferation, and is depleted quickly during infections, effects suggesting a prominent role in immune system function. The European Food Safety Authority concluded there is a cause and effect relationship between the dietary intake of vitamin C and functioning of a normal immune system in adults and in children under three years of age. During March through July 2020, vitamin C was the subject of more US FDA warning letters than any other ingredient for claims for prevention and/or treatment of COVID-19. In April 2021, the US National Institutes of Health (NIH) COVID-19 Treatment Guidelines stated that "there are insufficient data to recommend either for or against the use of vitamin C for the prevention or treatment of COVID-19." In an update posted December 2022, the NIH position was unchanged: For people hospitalized with severe COVID-19 there are reports of a significant reduction in the risk of all-cause, in-hospital mortality with the administration of vitamin C relative to no vitamin C. There were no significant differences in ventilation incidence, hospitalization duration or length of intensive care unit stay between the two groups. The majority of the trials incorporated into these meta-analyses used intravenous administration of the vitamin. Acute kidney injury was lower in people treated with vitamin C treatment. There were no differences in the frequency of other adverse events due to the vitamin. The conclusion was that further large-scale studies are needed to affirm its mortality benefits before issuing updated guidelines and recommendations. There is no evidence that vitamin C supplementation reduces the risk of lung cancer in healthy people or those at high risk due to smoking or asbestos exposure. It has no effect on the risk of prostate cancer, and there is no good evidence vitamic C supplementation affects the risk of colorectal cancer or breast cancer. There is research investigating whether high dose intravenous vitamin C administration as a co-treatment will suppress cancer stem cells, which are responsible for tumor recurrence, metastasis and chemoresistance. There is no evidence that vitamin C supplementation decreases the risk cardiovascular disease, although there may be an association between higher circulating vitamin C levels or dietary vitamin C and a lower risk of stroke. There is a positive effect of vitamin C on endothelial dysfunction when taken at doses greater than 500 mg per day. (The endothelium is a layer of cells that line the interior surface of blood vessels.) Serum vitamin C was reported to be 15.13 μmol/L lower in people with hypertension compared to normotensives. The vitamin was inversely associated with both systolic blood pressure (SBP) and diastolic blood pressure (DBP). Oral supplementation of the vitamin resulted in a very modest but statistically significant decrease in SBP in people with hypertension. The proposed explanation is that vitamin C increases intracellular concentrations of tetrahydrobiopterin, an endothelial nitric oxide synthase cofactor that promotes the production of nitric oxide, which is a potent vasodilator. Vitamin C supplementation might also reverse the nitric oxide synthase inhibitor NG-monomethyl-L-arginine 1, and there is also evidence cited that vitamin C directly enhances the biological activity of nitric oxide, a vasodilator. There are contradictory reviews. From one, vitamin C supplementation cannot be recommended for management of type 2 diabetes. However, another reported that supplementation with high doses of vitamin C can decrease blood glucose, insulin and hemoglobin A1c. One of the causes of iron-deficiency anemia is reduced absorption of iron. Iron absorption can be enhanced through ingestion of vitamin C alongside iron-containing food or supplements. Vitamin C helps to keep iron in the reduced ferrous state, which is more soluble and more easily absorbed. Human skin contains vitamin C, which supports collagen synthesis, decreases collagen degradation, and assists in antioxidant protection against UV-induced photo-aging, including photocarcinogenesis. This knowledge is often used as a rationale for the marketing of vitamin C as a topical "serum" ingredient to prevent or treat facial skin aging, melasma (dark pigmented spots) and wrinkles. The purported mechanism is that it functions as an antioxidant, neutralizing free radicals from sunlight exposure, air pollutants or normal metabolic processes. The efficacy of topical treatment, as opposed to oral intake is poorly understood. The clinical trial literature is characterized as insufficient to support health claims, one reason being put forward was that "All the studies used vitamin C in combination with other ingredients or therapeutic mechanisms, thereby complicating any specific conclusions regarding the efficacy of vitamin C." More research is needed. Lower plasma vitamin C concentrations were reported in people with cognitive impairment and Alzheimer's disease compared to people with normal cognition. Higher dietary intake of vitamin C was associated with lower risk of age-related cataracts. Vitamin C supplementation did not prevent age-related macular degeneration. Low intake and low serum concentration were associated with greater progression of periodontal disease. Oral intake as dietary supplements in excess of requirements are poorly absorbed, and excesses in the blood rapidly excreted in the urine, so it exhibits low acute toxicity. More than two to three grams, consumed orally, may cause nausea, abdominal cramps and diarrhea. These effects are attributed to the osmotic effect of unabsorbed vitamin C passing through the intestine. In theory, high vitamin C intake may cause excessive absorption of iron. A summary of reviews of supplementation in healthy subjects did not report this problem, but left as untested the possibility that individuals with hereditary hemochromatosis might be adversely affected. There is a longstanding belief among the mainstream medical community that vitamin C increases risk of kidney stones. "Reports of kidney stone formation associated with excess ascorbic acid intake are limited to individuals with renal disease". A review states that "data from epidemiological studies do not support an association between excess ascorbic acid intake and kidney stone formation in apparently healthy individuals", although one large, multi-year trial did report a nearly two-fold increase in kidney stones in men who regularly consumed a vitamin C supplement. There is extensive research on the purported benefits of intravenous vitamin C for treatment of sepsis, severe COVID-19 and cancer. Reviews list trials with doses as high as 24 grams per day. Concerns about possible adverse effects are that intravenous high-dose vitamin C leads to a supraphysiological level of vitamin C followed by oxidative degradation to dehydroascorbic acid and hence to oxalate, increasing the risk of oxalate kidney stones and oxalate nephropathy. The risk may be higher in people with renal impairment, as kidneys efficiently excrete excess vitamin C. Second, treatment with high dose vitamin C should be avoided in patients with glucose-6-phosphate dehydrogenase deficiency as it can lead to acute hemolysis. Third, treatment might interfere with the accuracy of glucometer measurement of blood glucose levels, as both vitamin C and glucose have similar molecular structure, which could lead to false high blood glucose readings. Despite all these concerns, meta-analyses of patients in intensive care for sepsis, septic shock, COVID-19 and other acute conditions reported no increase in new-onset kidney stones, acute kidney injury or requirement for renal replacement therapy for patients receiving short-term, high-dose, intravenous vitamin C treatment. This suggests that intravenous vitamin C is safe under these short-term applications. Scurvy was known to Hippocrates, described in book two of his Prorrheticorum and in his Liber de internis affectionibus, and cited by James Lind. Symptoms of scurvy were also described by Pliny the Elder: (i) Pliny. "49". Naturalis historiae. Vol. 3.; and (ii) Strabo, in Geographicorum, book 16, cited in the 1881 International Encyclopedia of Surgery. In the 1497 expedition of Vasco da Gama, the curative effects of citrus fruit were known. In the 1500s, Portuguese sailors put in to the island of Saint Helena to avail themselves of planted vegetable gardens and wild-growing fruit trees. Authorities occasionally recommended plant food to prevent scurvy during long sea voyages. John Woodall, the first surgeon to the British East India Company, recommended the preventive and curative use of lemon juice in his 1617 book, The Surgeon's Mate. In 1734, the Dutch writer Johann Bachstrom gave the firm opinion, "scurvy is solely owing to a total abstinence from fresh vegetable food, and greens." Scurvy had long been a principal killer of sailors during the long sea voyages. According to Jonathan Lamb, "In 1499, Vasco da Gama lost 116 of his crew of 170; In 1520, Magellan lost 208 out of 230;...all mainly to scurvy." The first attempt to give scientific basis for the cause of this disease was by a ship's surgeon in the Royal Navy, James Lind. While at sea in May 1747, Lind provided some crew members with two oranges and one lemon per day, in addition to normal rations, while others continued on cider, vinegar, sulfuric acid or seawater, along with their normal rations, in one of the world's first controlled experiments. The results showed that citrus fruits prevented the disease. Lind published his work in 1753 in his Treatise on the Scurvy. Fresh fruit was expensive to keep on board, whereas boiling it down to juice allowed easy storage but destroyed the vitamin (especially if boiled in copper kettles). It was 1796 before the British navy adopted lemon juice as standard issue at sea. In 1845, ships in the West Indies were provided with lime juice instead, and in 1860 lime juice was used throughout the Royal Navy, giving rise to the American use of the nickname "limey" for the British. Captain James Cook had previously demonstrated the advantages of carrying "Sour krout" on board, by taking his crew on a 1772-75 Pacific Ocean voyage without losing any of his men to scurvy. For his report on his methods the British Royal Society awarded him the Copley Medal in 1776. The name antiscorbutic was used in the eighteenth and nineteenth centuries for foods known to prevent scurvy. These foods included lemons, limes, oranges, sauerkraut, cabbage, malt, and portable soup. In 1928, the Canadian Arctic anthropologist Vilhjalmur Stefansson showed that the Inuit avoided scurvy on a diet of largely raw meat. Later studies on traditional food diets of the Yukon First Nations, Dene, Inuit, and Métis of Northern Canada showed that their daily intake of vitamin C averaged between 52 and 62 mg/day. Vitamin C was discovered in 1912, isolated in 1928 and synthesized in 1933, making it the first vitamin to be synthesized. Shortly thereafter Tadeus Reichstein succeeded in synthesizing the vitamin in bulk by what is now called the Reichstein process. This made possible the inexpensive mass-production of vitamin C. In 1934, Hoffmann–La Roche bought the Reichstein process patent, trademarked synthetic vitamin C under the brand name Redoxon, and began to market it as a dietary supplement. In 1907, a laboratory animal model which would help to identify the antiscorbutic factor was discovered by the Norwegian physicians Axel Holst and Theodor Frølich, who when studying shipboard beriberi, fed guinea pigs their test diet of grains and flour and were surprised when scurvy resulted instead of beriberi. Unknown at that time, this species did not make its own vitamin C (being a caviomorph), whereas mice and rats do. In 1912, the Polish biochemist Casimir Funk developed the concept of vitamins. One of these was thought to be the anti-scorbutic factor. In 1928, this was referred to as "water-soluble C", although its chemical structure had not been determined. From 1928 to 1932, Albert Szent-Györgyi and Joseph L. Svirbely's Hungarian team, and Charles Glen King's American team, identified the anti-scorbutic factor. Szent-Györgyi isolated hexuronic acid from animal adrenal glands, and suspected it to be the antiscorbutic factor. In late 1931, Szent-Györgyi gave Svirbely the last of his adrenal-derived hexuronic acid with the suggestion that it might be the anti-scorbutic factor. By the spring of 1932, King's laboratory had proven this, but published the result without giving Szent-Györgyi credit for it. This led to a bitter dispute over priority. In 1933, Walter Norman Haworth chemically identified the vitamin as l-hexuronic acid, proving this by synthesis in 1933. Haworth and Szent-Györgyi proposed that L-hexuronic acid be named a-scorbic acid, and chemically l-ascorbic acid, in honor of its activity against scurvy. The term's etymology is from Latin, "a-" meaning away, or off from, while -scorbic is from Medieval Latin scorbuticus (pertaining to scurvy), cognate with Old Norse skyrbjugr, French scorbut, Dutch scheurbuik and Low German scharbock. Partly for this discovery, Szent-Györgyi was awarded the 1937 Nobel Prize in Medicine, and Haworth shared that year's Nobel Prize in Chemistry. In 1957, J. J. Burns showed that some mammals are susceptible to scurvy as their liver does not produce the enzyme l-gulonolactone oxidase, the last of the chain of four enzymes that synthesize vitamin C. American biochemist Irwin Stone was the first to exploit vitamin C for its food preservative properties. He later developed the idea that humans possess a mutated form of the l-gulonolactone oxidase coding gene. Stone introduced Linus Pauling to the theory that humans needed to consume vitamin C in quantities far higher than what was considered a recommended daily intake in order to optimize health. In 2008, researchers discovered that in humans and other primates the red blood cells have evolved a mechanism to more efficiently utilize the vitamin C present in the body by recycling oxidized l-dehydroascorbic acid (DHA) back into ascorbic acid for reuse by the body. The mechanism was not found to be present in mammals that synthesize their own vitamin C. Vitamin C megadosage is a term describing the consumption or injection of vitamin C in doses comparable to or higher than the amounts produced by the livers of mammals which are able to synthesize vitamin C. An argument for this, although not the actual term, was described in 1970 in an article by Linus Pauling. Briefly, his position was that for optimal health, humans should be consuming at least 2,300 mg/day to compensate for the inability to synthesize vitamin C. The recommendation also fell into the consumption range for gorillas – a non-synthesizing near-relative to humans. A second argument for high intake is that serum ascorbic acid concentrations increase as intake increases until it plateaus at about 190 to 200 micromoles per liter (µmol/L) once consumption exceeds 1,250 milligrams. As noted, government recommendations are a range of 40 to 110 mg/day and normal plasma is approximately 50 µmol/L, so 'normal' is about 25% of what can be achieved when oral consumption is in the proposed megadose range. Pauling popularized the concept of high dose vitamin C as prevention and treatment of the common cold in 1970. A few years later he proposed that vitamin C would prevent cardiovascular disease, and that 10 grams/day, initially administered intravenously and thereafter orally, would cure late-stage cancer. Mega-dosing with ascorbic acid has other champions, among them chemist Irwin Stone and the controversial Matthias Rath and Patrick Holford, who both have been accused of making unsubstantiated treatment claims for treating cancer and HIV infection. The idea that large amounts of intravenous ascorbic acid can be used to treat late-stage cancer or ameliorate the toxicity of chemotherapy is – some forty years after Pauling's seminal paper – still considered unproven and still in need of high quality research. Chemistry[edit] ascorbic acid(reduced form)dehydroascorbic acid(oxidized form) Main article: Chemistry of ascorbic acid The name "vitamin C" always refers to the l-enantiomer of ascorbic acid and its oxidized form, dehydroascorbate (DHA). Therefore, unless written otherwise, "ascorbate" and "ascorbic acid" refer in the nutritional literature to l-ascorbate and l-ascorbic acid respectively. Ascorbic acid is a weak sugar acid structurally related to glucose. In biological systems, ascorbic acid can be found only at low pH, but in solutions above pH 5 is predominantly found in the ionized form, ascorbate. Numerous analytical methods have been developed for ascorbic acid detection. For example, vitamin C content of a food sample such as fruit juice can be calculated by measuring the volume of the sample required to decolorize a solution of dichlorophenolindophenol (DCPIP) and then calibrating the results by comparison with a known concentration of vitamin C. Deficiency[edit] Plasma vitamin C is the most widely applied test for vitamin C status. Adequate levels are defined as near 50 μmol/L. Hypovitaminosis of vitamin C is defined as less than 23 μmol/L, and deficiency as less than 11.4 μmol/L. For people 20 years of age or above, data from the US 2017-18 National Health and Nutrition Examination Survey showed mean serum concentrations of 53.4 μmol/L. The percent of people reported as deficient was 5.9%. Globally, vitamin C deficiency is common in low and middle-income countries, and not uncommon in high income countries. In the latter, prevalence is higher in males than in females. Plasma levels are considered saturated at about 65 μmol/L, achieved by intakes of 100 to 200 mg/day, which are well above the recommended intakes. Even higher oral intake does not further raise plasma nor tissue concentrations because absorption efficiency decreases and any excess that is absorbed is excreted in urine. Diagnostic testing[edit] Vitamin C content in plasma is used to determine vitamin status. For research purposes, concentrations can be assessed in leukocytes and tissues, which are normally maintained at an order of magnitude higher than in plasma via an energy-dependent transport system, depleted slower than plasma concentrations during dietary deficiency and restored faster during dietary repletion, but these analysis are difficult to measure, and hence not part of standard diagnostic testing. Diet[edit] Recommended consumption[edit] Recommendations for vitamin C intake by adults have been set by various national agencies: 40 mg/day: India National Institute of Nutrition, Hyderabad 45 mg/day or 300 mg/week: the World Health Organization 80 mg/day: the European Commission Council on nutrition labeling 90 mg/day (males) and 75 mg/day (females): Health Canada 2007 90 mg/day (males) and 75 mg/day (females): United States National Academy of Sciences 100 mg/day: Japan National Institute of Health and Nutrition 110 mg/day (males) and 95 mg/day (females): European Food Safety Authority US vitamin C recommendations (mg per day) RDA (children ages 1–3 years) 15 RDA (children ages 4–8 years) 25 RDA (children ages 9–13 years) 45 RDA (girls ages 14–18 years) 65 RDA (boys ages 14–18 years) 75 RDA (adult female) 75 RDA (adult male) 90 RDA (pregnancy) 85 RDA (lactation) 120 UL (adult female) 2,000 UL (adult male) 2,000 In 2000, the chapter on Vitamin C in the North American Dietary Reference Intake was updated to give the Recommended Dietary Allowance (RDA) as 90 milligrams per day for adult men, 75 mg/day for adult women, and setting a Tolerable upper intake level (UL) for adults of 2,000 mg/day. The table (right) shows RDAs for the United States and Canada for children, and for pregnant and lactating women, as well as the ULs for adults. For the European Union, the EFSA set higher recommendations for adults, and also for children: 20 mg/day for ages 1–3, 30 mg/day for ages 4–6, 45 mg/day for ages 7–10, 70 mg/day for ages 11–14, 100 mg/day for males ages 15–17, 90 mg/day for females ages 15–17. For pregnancy 100 mg/day; for lactation 155 mg/day. Cigarette smokers and people exposed to secondhand smoke have lower serum vitamin C levels than nonsmokers. The thinking is that inhalation of smoke causes oxidative damage, depleting this antioxidant vitamin. The US Institute of Medicine estimated that smokers need 35 mg more vitamin C per day than nonsmokers, but did not formally establish a higher RDA for smokers. An inverse relationship between vitamin C intake and lung cancer was observed, although the conculsion was that more research is needed to confirm this observation. The US National Center for Health Statistics conducts biannual National Health and Nutrition Examination Survey (NHANES) to assess the health and nutritional status of adults and children in the United States. Some results are reported as What We Eat In America. The 2013–2014 survey reported that for adults ages 20 years and older, men consumed on average 83.3 mg/d and women 75.1 mg/d. This means that half the women and more than half the men are not consuming the RDA for vitamin C. The same survey stated that about 30% of adults reported they consumed a vitamin C dietary supplement or a multi-vitamin/mineral supplement that included vitamin C, and that for these people total consumption was between 300 and 400 mg/d. Tolerable upper intake level[edit] In 2000, the Institute of Medicine of the US National Academy of Sciences set a Tolerable upper intake level (UL) for adults of 2,000 mg/day. The amount was chosen because human trials had reported diarrhea and other gastrointestinal disturbances at intakes of greater than 3,000 mg/day. This was the Lowest-Observed-Adverse-Effect Level (LOAEL), meaning that other adverse effects were observed at even higher intakes. ULs are progressively lower for younger and younger children. In 2006, the European Food Safety Authority (EFSA) also pointed out the disturbances at that dose level, but reached the conclusion that there was not sufficient evidence to set a UL for vitamin C, as did the Japan National Institute of Health and Nutrition in 2010. Food labeling[edit] For US food and dietary supplement labeling purposes, the amount in a serving is expressed as a percent of Daily Value (%DV). For vitamin C labeling purposes, 100% of the Daily Value was 60 mg, but as of May 27, 2016, it was revised to 90 mg to bring it into agreement with the RDA. A table of the old and new adult daily values is provided at Reference Daily Intake. European Union regulations require that labels declare energy, protein, fat, saturated fat, carbohydrates, sugars, and salt. Voluntary nutrients may be shown if present in significant amounts. Instead of Daily Values, amounts are shown as percent of Reference Intakes (RIs). For vitamin C, 100% RI was set at 80 mg in 2011. Sources[edit] Although also present in other plant-derived foods, the richest natural sources of vitamin C are fruits and vegetables. Vitamin C is the most widely taken dietary supplement. Plant sources[edit] For vitamin C content in ten common staple foods such as corn, rice, and wheat, see Staple food § Nutrition. The following table is approximate and shows the relative abundance in different raw plant sources. The amount is given in milligrams per 100 grams of the edible portion of the fruit or vegetable: Raw plant source Amount (mg / 100g) Kakadu plum 1000–5300 Camu camu 2800 Acerola 1677 Indian gooseberry 445 Rose hip 426 Common sea-buckthorn 400 Guava 228 Blackcurrant 200 Yellow bell pepper/capsicum 183 Red bell pepper/capsicum 128 Kale 120 Broccoli 90 Kiwifruit 90 Raw plant source Amount (mg / 100g) Green bell pepper/capsicum 80 Brussels sprouts 80 Loganberry, redcurrant 80 Cloudberry, elderberry 60 Strawberry 60 Papaya 60 Orange, lemon 53 Cauliflower 48 Pineapple 48 Cantaloupe 40 Passion fruit, raspberry 30 Grapefruit, lime 30 Cabbage, spinach 30 Raw plant source Amount (mg / 100g) Mango 28 Blackberry, cassava 21 Potato 20 Honeydew melon 20 Tomato 14 Cranberry 13 Blueberry, grape 10 Apricot, plum, watermelon 10 Avocado 8.8 Onion 7.4 Cherry, peach 7 Apple 6 Carrot, asparagus 6 Animal sources[edit] Compared to plant sources, animal-sourced foods do not provide so great an amount of vitamin C, and what there is, is largely destroyed by the heat used when it is cooked. For example, raw chicken liver contains 17.9 mg/100 g, but fried, the content is reduced to 2.7 mg/100 g. Vitamin C is present in human breast milk at 5.0 mg/100 g. Cow's milk contains 1.0 mg/100 g, but the heat of pasteurization destroys it. Food preparation[edit] Vitamin C chemically decomposes under certain conditions, many of which may occur during the cooking of food. Vitamin C concentrations in various food substances decrease with time in proportion to the temperature at which they are stored. Cooking can reduce the vitamin C content of vegetables by around 60%, possibly due to increased enzymatic destruction. Longer cooking times may add to this effect. Another cause of vitamin C loss from food is leaching, which transfers vitamin C to the cooking water, which is decanted and not consumed. Supplements[edit] Vitamin C dietary supplements are available as tablets, capsules, drink mix packets, in multi-vitamin/mineral formulations, in antioxidant formulations, and as crystalline powder. Vitamin C is also added to some fruit juices and juice drinks. Tablet and capsule content ranges from 25 mg to 1500 mg per serving. The most commonly used supplement compounds are ascorbic acid, sodium ascorbate and calcium ascorbate. Vitamin C molecules can also be bound to the fatty acid palmitate, creating ascorbyl palmitate, or else incorporated into liposomes. Food fortification[edit] Countries fortify foods with nutrients to address known deficiencies. While many countries mandate or have voluntary programs to fortify wheat flour, maize (corn) flour or rice with vitamins, none include vitamin C in those programs. As described in Vitamin C Fortification of Food Aid Commodities (1997), the United States provides rations to international food relief programs, later under the asupices of the Food for Peace Act and the Bureau for Humanitarian Assistance. Vitamin C is added to corn-soy blend and wheat-soy blend products at 40 mg/100 grams. (along with minerals and other vitamins). Supplemental rations of these highly fortified, blended foods are provided to refugees and displaced persons in camps and to beneficiaries of development feeding programs that are targeted largely toward mothers and children. The report adds: "The stability of vitamin C (L-ascorbic acid) is of concern because this is one of the most labile vitamins in foods. Its main loss during processing and storage is from oxidation, which is accelerated by light, oxygen, heat, increased pH, high moisture content (water activity), and the presence of copper or ferrous salts. To reduce oxidation, the vitamin C used in commodity fortification is coated with ethyl cellulose (2.5 percent). Oxidative losses also occur during food processing and preparation, and additional vitamin C may be lost if it dissolves into cooking liquid and is then discarded." Food preservation additive[edit] Ascorbic acid and some of its salts and esters are common additives added to various foods, such as canned fruits, mostly to slow oxidation and enzymatic browning. It may be used as a flour treatment agent used in breadmaking. As food additives, they are assigned E numbers, with safety assessment and approval the responsibility of the European Food Safety Authority. The relevant E numbers are: E300 ascorbic acid (approved for use as a food additive in the UK, US Canada, Australia and New Zealand) E301 sodium ascorbate (approved for use as a food additive in the UK, US, Canada, Australia and New Zealand) E302 calcium ascorbate (approved for use as a food additive in the UK, US Canada, Australia and New Zealand) E303 potassium ascorbate (approved in Australia and New Zealand, but not in the UK, US or Canada) E304 fatty acid esters of ascorbic acid such as ascorbyl palmitate (approved for use as a food additive in the UK, US, Canada, Australia and New Zealand) The stereoisomers of Vitamin C have a similar effect in food despite their lack of efficacy in humans. They include erythorbic acid and its sodium salt (E315, E316). Pharmacology[edit] See also: Chemistry of ascorbic acid Pharmacodynamics is the study of how the drug – in this instance vitamin C – affects the organism, whereas pharmacokinetics is the study of how an organism affects the drug. Pharmacodynamics[edit] Pharmacodynamics includes enzymes for which vitamin C is a cofactor, with function potentially compromised in a deficiency state, and any enzyme cofactor or other physiological function affected by administration of vitamin C, orally or injected, in excess of normal requirements. At normal physiological concentrations, vitamin C serves as an enzyme substrate or cofactor and an electron donor antioxidant. The enzymatic functions include the synthesis of collagen, carnitine, and neurotransmitters; the synthesis and catabolism of tyrosine; and the metabolism of microsomes. In nonenzymatic functions it acts as a reducing agent, donating electrons to oxidized molecules and preventing oxidation in order to keep iron and copper atoms in their reduced states. At non-physiological concentrations achieved by intravenous dosing, vitamin C may function as a pro-oxidant, with therapeutic toxicity against cancer cells. Vitamin C functions as a cofactor for the following enzymes: Three groups of enzymes (prolyl-3-hydroxylases, prolyl-4-hydroxylases, and lysyl hydroxylases) that are required for the hydroxylation of proline and lysine in the synthesis of collagen. These reactions add hydroxyl groups to the amino acids proline or lysine in the collagen molecule via prolyl hydroxylase and lysyl hydroxylase, both requiring vitamin C as a cofactor. The role of vitamin C as a cofactor is to oxidize prolyl hydroxylase and lysyl hydroxylase from Fe to Fe and to reduce it from Fe to Fe. Hydroxylation allows the collagen molecule to assume its triple helix structure, and thus vitamin C is essential to the development and maintenance of scar tissue, blood vessels, and cartilage. Two enzymes (ε-N-trimethyl-L-lysine hydroxylase and γ-butyrobetaine hydroxylase) are necessary for synthesis of carnitine. Carnitine is essential for the transport of fatty acids into mitochondria for ATP generation. Hypoxia-inducible factor-proline dioxygenase enzymes (isoforms: EGLN1, EGLN2, and EGLN3) allows cells to respond physiologically to low concentrations of oxygen. Dopamine beta-hydroxylase participates in the biosynthesis of norepinephrine from dopamine. Peptidylglycine alpha-amidating monooxygenase amidates peptide hormones by removing the glyoxylate residue from their c-terminal glycine residues. This increases peptide hormone stability and activity. As an antioxidant, ascorbate scavenges reactive oxygen and nitrogen compounds, thus neutralizing the potential tissue damage of these free radical compounds. Dehydroascorbate, the oxidized form, is then recycled back to ascorbate by endogenous antioxidants such as glutathione. In the eye, ascorbate is thought to protect against photolytically generated free-radical damage; higher plasma ascorbate is associated with lower risk of cateracts. Ascorbate may also provide antioxidant protection indirectly by regenerating other biological antioxidants such as α-tocopherol back to an active state. In addition, ascorbate also functions as a non-enzymatic reducing agent for mixed-function oxidases in the microsomal drug-metabolizing system that inactivates a wide variety of substrates such as drugs and environmental carcinogens. Pharmacokinetics[edit] Ascorbic acid is absorbed in the body by both simple diffusion and active transport. Approximately 70%–90% of vitamin C is absorbed at moderate intakes of 30–180 mg/day. However, at doses above 1,000 mg/day, absorption falls to less than 50% as the active transport system becomes saturated. Active transport is managed by Sodium-Ascorbate Co-Transporter proteins (SVCTs) and Hexose Transporter proteins (GLUTs). SVCT1 and SVCT2 import ascorbate across plasma membranes. The Hexose Transporter proteins GLUT1, GLUT3 and GLUT4 transfer only the oxydized dehydroascorbic acid (DHA) form of vitamin C. The amount of DHA found in plasma and tissues under normal conditions is low, as cells rapidly reduce DHA to ascorbate. SVCTs are the predominant system for vitamin C transport within the body. In both vitamin C synthesizers (example: rat) and non-synthesizers (example: human) cells maintain ascorbic acid concentrations much higher than the approximately 50 micromoles/liter (µmol/L) found in plasma. For example, the ascorbic acid content of pituitary and adrenal glands can exceed 2,000 µmol/L, and muscle is at 200–300 µmol/L. The known coenzymatic functions of ascorbic acid do not require such high concentrations, so there may be other, as yet unknown functions. A consequence of all this high concentration organ content is that plasma vitamin C is not a good indicator of whole-body status, and people may vary in the amount of time needed to show symptoms of deficiency when consuming a diet very low in vitamin C. Excretion (via urine) is as ascorbic acid and metabolites. The fraction that is excreted as unmetabolized ascorbic acid increases as intake increases. In addition, ascorbic acid converts (reversibly) to DHA and from that compound non-reversibly to 2,3-diketogulonate and then oxalate. These three metabolites are also excreted via urine. During times of low dietary intake, vitamin C is reabsorbed by the kidneys rather than excreted. This salvage process delays onset of deficiency. Humans are better than guinea pigs at converting DHA back to ascorbate, and thus take much longer to become vitamin C deficient. Synthesis[edit] Most animals and plants are able to synthesize vitamin C through a sequence of enzyme-driven steps, which convert monosaccharides to vitamin C. Yeasts do not make l-ascorbic acid but rather its stereoisomer, erythorbic acid. In plants, synthesis is accomplished through the conversion of mannose or galactose to ascorbic acid. In animals, the starting material is glucose. In some species that synthesize ascorbate in the liver (including mammals and perching birds), the glucose is extracted from glycogen; ascorbate synthesis is a glycogenolysis-dependent process. In humans and in animals that cannot synthesize vitamin C, the enzyme l-gulonolactone oxidase (GULO), which catalyzes the last step in the biosynthesis, is highly mutated and non-functional. Animal synthesis[edit] There is some information on serum vitamin C concentrations maintained in animal species that are able to synthesize vitamin C. One study of several breeds of dogs reported an average of 35.9 μmol/L. A report on goats, sheep and cattle reported ranges of 100–110, 265–270 and 160–350 μmol/L, respectively. The biosynthesis of ascorbic acid in vertebrates starts with the formation of UDP-glucuronic acid. UDP-glucuronic acid is formed when UDP-glucose undergoes two oxidations catalyzed by the enzyme UDP-glucose 6-dehydrogenase. UDP-glucose 6-dehydrogenase uses the co-factor NAD as the electron acceptor. The transferase UDP-glucuronate pyrophosphorylase removes a UMP and glucuronokinase, with the cofactor ADP, removes the final phosphate leading to d-glucuronic acid. The aldehyde group of this compound is reduced to a primary alcohol using the enzyme glucuronate reductase and the cofactor NADPH, yielding l-gulonic acid. This is followed by lactone formation—utilizing the hydrolase gluconolactonase—between the carbonyl on C1 and hydroxyl group on C4. l-Gulonolactone then reacts with oxygen, catalyzed by the enzyme L-gulonolactone oxidase (which is nonfunctional in humans and other Haplorrhini primates; see Unitary pseudogenes) and the cofactor FAD+. This reaction produces 2-oxogulonolactone (2-keto-gulonolactone), which spontaneously undergoes enolization to form ascorbic acid. Reptiles and older orders of birds make ascorbic acid in their kidneys. Recent orders of birds and most mammals make ascorbic acid in their liver. Non-synthesizers[edit] Some mammals have lost the ability to synthesize vitamin C, including simians and tarsiers, which together make up one of two major primate suborders, Haplorhini. This group includes humans. The other more primitive primates (Strepsirrhini) have the ability to make vitamin C. Synthesis does not occur in some species in the rodent family Caviidae, which includes guinea pigs and capybaras, but does occur in other rodents, including rats and mice. Synthesis does not occur in most bat species, but there are at least two species, frugivorous bat Rousettus leschenaultii and insectivorous bat Hipposideros armiger, that retain (or regained) their ability of vitamin C production. A number of species of passerine birds also do not synthesize, but not all of them, and those that do not are not clearly related; it has been proposed that the ability was lost separately a number of times in birds. In particular, the ability to synthesize vitamin C is presumed to have been lost and then later re-acquired in at least two cases. The ability to synthesize vitamin C has also been lost in about 96% of extant fish (the teleosts). On a milligram consumed per kilogram of body weight basis, simian non-synthesizer species consume the vitamin in amounts 10 to 20 times higher than what is recommended by governments for humans. This discrepancy constituted some of the basis of the controversy on human recommended dietary allowances being set too low. However, simian consumption does not indicate simian requirements. Merck's veterinary manual states that daily intake of vitamin C at 3–6 mg/kg prevents scurvy in non-human primates. By way of comparison, across several countries, the recommended dietary intake for adult humans is in the range of 1–2 mg/kg. Evolution of animal synthesis[edit] Ascorbic acid is a common enzymatic cofactor in mammals used in the synthesis of collagen, as well as a powerful reducing agent capable of rapidly scavenging a number of reactive oxygen species (ROS). Given that ascorbate has these important functions, it is surprising that the ability to synthesize this molecule has not always been conserved. In fact, anthropoid primates, Cavia porcellus (guinea pigs), teleost fishes, most bats, and some passerine birds have all independently lost the ability to internally synthesize vitamin C in either the kidney or the liver. In all of the cases where genomic analysis was done on an ascorbic acid auxotroph, the origin of the change was found to be a result of loss-of-function mutations in the gene that encodes L-gulono-γ-lactone oxidase, the enzyme that catalyzes the last step of the ascorbic acid pathway outlined above. One explanation for the repeated loss of the ability to synthesize vitamin C is that it was the result of genetic drift; assuming that the diet was rich in vitamin C, natural selection would not act to preserve it. In the case of the simians, it is thought that the loss of the ability to make vitamin C may have occurred much farther back in evolutionary history than the emergence of humans or even apes, since it evidently occurred soon after the appearance of the first primates, yet sometime after the split of early primates into the two major suborders Haplorrhini (which cannot make vitamin C) and its sister suborder of non-tarsier prosimians, the Strepsirrhini ("wet-nosed" primates), which retained the ability to make vitamin C. According to molecular clock dating, these two suborder primate branches parted ways about 63 to 60 million years ago. Approximately three to five million years later (58 million years ago), only a short time afterward from an evolutionary perspective, the infraorder Tarsiiformes, whose only remaining family is that of the tarsier (Tarsiidae), branched off from the other haplorrhines. Since tarsiers also cannot make vitamin C, this implies the mutation had already occurred, and thus must have occurred between these two marker points (63 to 58 million years ago). It has also been noted that the loss of the ability to synthesize ascorbate strikingly parallels the inability to break down uric acid, also a characteristic of primates. Uric acid and ascorbate are both strong reducing agents. This has led to the suggestion that, in higher primates, uric acid has taken over some of the functions of ascorbate. Plant synthesis[edit] Vitamin C biosynthesis in plants There are many different biosynthesis pathways to ascorbic acid in plants. Most proceed through products of glycolysis and other metabolic pathways. For example, one pathway utilizes plant cell wall polymers. The principal plant ascorbic acid biosynthesis pathway seems to be via l-galactose. The enzyme l-galactose dehydrogenase catalyzes the overall oxidation to the lactone and isomerization of the lactone to the C4-hydroxyl group, resulting in l-galactono-1,4-lactone. l-Galactono-1,4-lactone then reacts with the mitochondrial flavoenzyme l-galactonolactone dehydrogenase to produce ascorbic acid. l-Ascorbic acid has a negative feedback on l-galactose dehydrogenase in spinach. Ascorbic acid efflux by embryos of dicot plants is a well-established mechanism of iron reduction and a step obligatory for iron uptake. All plants synthesize ascorbic acid. Ascorbic acid functions as a cofactor for enzymes involved in photosynthesis, synthesis of plant hormones, as an antioxidant and regenerator of other antioxidants. Plants use multiple pathways to synthesize vitamin C. The major pathway starts with glucose, fructose or mannose (all simple sugars) and proceeds to l-galactose, l-galactonolactone and ascorbic acid. This biosynthesis is regulated following a diurnal rhythm. Enzyme expression peaks in the morning to supporting biosynthesis for when mid-day sunlight intensity demands high ascorbic acid concentrations. Minor pathways may be specific to certain parts of plants; these can be either identical to the vertebrate pathway (including the GLO enzyme), or start with inositol and get to ascorbic acid via l-galactonic acid to l-galactonolactone. Industrial synthesis[edit] Main article: Chemistry of ascorbic acid Vitamin C can be produced from glucose by two main routes. The no longer utilized Reichstein process, developed in the 1930s, used a single fermentation followed by a purely chemical route. The modern two-step fermentation process, originally developed in China in the 1960s, uses additional fermentation to replace part of the later chemical stages. The Reichstein process and the modern two-step fermentation processes both use glucose as the starting material, convert that to sorbitol, and then to sorbose using fermentation. The two-step fermentation process then converts sorbose to 2-keto-l-gulonic acid (KGA) through another fermentation step, avoiding an extra intermediate. Both processes yield approximately 60% vitamin C from the glucose starting point. Researchers are exploring means for one-step fermentation. China produces about 70% of the global vitamin C market. The rest is split among European Union, India and North America. The global market is expected to exceed 141 thousand metric tons in 2024. Cost per metric ton (1000 kg) in US dollars was $2,220 in Shanghai, $2,850 in Hamburg and $3,490 in the US. Medical uses[edit] Vitamin C supplements among other dietary supplements at a US drug store Vitamin C has a definitive role in treating scurvy, which is a disease caused by vitamin C deficiency. Beyond that, a role for vitamin C as prevention or treatment for various diseases is disputed, with reviews often reporting conflicting results. No effect of vitamin C supplementation reported for overall mortality. It is on the World Health Organization's List of Essential Medicines and on the World Health Organization's Model Forumulary. In 2021, it was the 255th most commonly prescribed medication in the United States, with more than 1 million prescriptions. Scurvy[edit] Main article: Scurvy Scurvy is a disease resulting from a deficiency of vitamin C. Without this vitamin, collagen made by the body is too unstable to perform its function and several other enzymes in the body do not operate correctly. Early symptoms are malaise and lethargy, progressing to shortness of breath, bone pain and susceptibility to bruising. As the disease progressed, it is characterized by spots on and bleeding under the skin and bleeding gums. The skin lesions are most abundant on the thighs and legs. A person with the ailment looks pale, feels depressed, and is partially immobilized. In advanced scurvy there is fever, old wounds may become open and suppurating, loss of teeth, convulsions and, eventually, death. Until quite late in the disease the damage is reversible, as healthy collagen replaces the defective collagen with vitamin C repletion. Notable human dietary studies of experimentally induced scurvy were conducted on conscientious objectors during World War II in Britain and on Iowa state prisoners in the late 1960s to the 1980s. Men in the prison study developed the first signs of scurvy about four weeks after starting the vitamin C-free diet, whereas in the earlier British study, six to eight months were required, possibly due to the pre-loading of this group with a 70 mg/day supplement for six weeks before the scorbutic diet was fed. Men in both studies had blood levels of ascorbic acid too low to be accurately measured by the time they developed signs of scurvy. These studies both reported that all obvious symptoms of scurvy could be completely reversed by supplementation of only 10 mg a day. Treatment of scurvy can be with vitamin C-containing foods or dietary supplements or injection. Sepsis[edit] People in sepsis may have micronutrient deficiencies, including low levels of vitamin C. An intake of 3.0 g/day, which requires intravenous administration, appears to be needed to maintain normal plasma concentrations in people with sepsis or severe burn injury. Sepsis mortality is reduced with administration of intravenous vitamin C. Common cold[edit] The Nobel Prize winner Linus Pauling advocated taking vitamin C for the common cold in a 1970 book. Research on vitamin C in the common cold has been divided into effects on prevention, duration, and severity. Oral intakes of more than 200 mg/day taken on a regular basis was not effective in prevention of the common cold. Restricting analysis to trials that used at least 1000 mg/day also saw no prevention benefit. However, taking a vitamin C supplement on a regular basis did reduce the average duration of the illness by 8% in adults and 14% in children, and also reduced the severity of colds. Vitamin C taken on a regular basis reduced the duration of severe symptoms but had no effect on the duration of mild symptoms. Therapeutic use, meaning that the vitamin was not started unless people started to feel the beginnings of a cold, had no effect on the duration or severity of the illness. Vitamin C distributes readily in high concentrations into immune cells, promotes natural killer cell activities, promotes lymphocyte proliferation, and is depleted quickly during infections, effects suggesting a prominent role in immune system function. The European Food Safety Authority concluded there is a cause and effect relationship between the dietary intake of vitamin C and functioning of a normal immune system in adults and in children under three years of age. COVID-19[edit] See also: COVID-19 drug repurposing research § Vitamin C, and COVID-19 misinformation § Vitamin C During March through July 2020, vitamin C was the subject of more US FDA warning letters than any other ingredient for claims for prevention and/or treatment of COVID-19. In April 2021, the US National Institutes of Health (NIH) COVID-19 Treatment Guidelines stated that "there are insufficient data to recommend either for or against the use of vitamin C for the prevention or treatment of COVID-19." In an update posted December 2022, the NIH position was unchanged: There is insufficient evidence for the COVID-19 Treatment Guidelines Panel (the Panel) to recommend either for or against the use of vitamin C for the treatment of COVID-19 in nonhospitalized patients. There is insufficient evidence for the Panel to recommend either for or against the use of vitamin C for the treatment of COVID-19 in hospitalized patients. For people hospitalized with severe COVID-19 there are reports of a significant reduction in the risk of all-cause, in-hospital mortality with the administration of vitamin C relative to no vitamin C. There were no significant differences in ventilation incidence, hospitalization duration or length of intensive care unit stay between the two groups. The majority of the trials incorporated into these meta-analyses used intravenous administration of the vitamin. Acute kidney injury was lower in people treated with vitamin C treatment. There were no differences in the frequency of other adverse events due to the vitamin. The conclusion was that further large-scale studies are needed to affirm its mortality benefits before issuing updated guidelines and recommendations. Cancer[edit] There is no evidence that vitamin C supplementation reduces the risk of lung cancer in healthy people or those at high risk due to smoking or asbestos exposure. It has no effect on the risk of prostate cancer, and there is no good evidence vitamic C supplementation affects the risk of colorectal cancer or breast cancer. There is research investigating whether high dose intravenous vitamin C administration as a co-treatment will suppress cancer stem cells, which are responsible for tumor recurrence, metastasis and chemoresistance. Cardiovascular disease[edit] There is no evidence that vitamin C supplementation decreases the risk cardiovascular disease, although there may be an association between higher circulating vitamin C levels or dietary vitamin C and a lower risk of stroke. There is a positive effect of vitamin C on endothelial dysfunction when taken at doses greater than 500 mg per day. (The endothelium is a layer of cells that line the interior surface of blood vessels.) Blood pressure[edit] Serum vitamin C was reported to be 15.13 μmol/L lower in people with hypertension compared to normotensives. The vitamin was inversely associated with both systolic blood pressure (SBP) and diastolic blood pressure (DBP). Oral supplementation of the vitamin resulted in a very modest but statistically significant decrease in SBP in people with hypertension. The proposed explanation is that vitamin C increases intracellular concentrations of tetrahydrobiopterin, an endothelial nitric oxide synthase cofactor that promotes the production of nitric oxide, which is a potent vasodilator. Vitamin C supplementation might also reverse the nitric oxide synthase inhibitor NG-monomethyl-L-arginine 1, and there is also evidence cited that vitamin C directly enhances the biological activity of nitric oxide, a vasodilator. Type 2 diabetes[edit] There are contradictory reviews. From one, vitamin C supplementation cannot be recommended for management of type 2 diabetes. However, another reported that supplementation with high doses of vitamin C can decrease blood glucose, insulin and hemoglobin A1c. Iron deficiency[edit] One of the causes of iron-deficiency anemia is reduced absorption of iron. Iron absorption can be enhanced through ingestion of vitamin C alongside iron-containing food or supplements. Vitamin C helps to keep iron in the reduced ferrous state, which is more soluble and more easily absorbed. Topical application to prevent signs of skin aging[edit] Human skin contains vitamin C, which supports collagen synthesis, decreases collagen degradation, and assists in antioxidant protection against UV-induced photo-aging, including photocarcinogenesis. This knowledge is often used as a rationale for the marketing of vitamin C as a topical "serum" ingredient to prevent or treat facial skin aging, melasma (dark pigmented spots) and wrinkles. The purported mechanism is that it functions as an antioxidant, neutralizing free radicals from sunlight exposure, air pollutants or normal metabolic processes. The efficacy of topical treatment, as opposed to oral intake is poorly understood. The clinical trial literature is characterized as insufficient to support health claims, one reason being put forward was that "All the studies used vitamin C in combination with other ingredients or therapeutic mechanisms, thereby complicating any specific conclusions regarding the efficacy of vitamin C." More research is needed. Cognitive impairment and Alzheimer's disease[edit] Lower plasma vitamin C concentrations were reported in people with cognitive impairment and Alzheimer's disease compared to people with normal cognition. Eye health[edit] Higher dietary intake of vitamin C was associated with lower risk of age-related cataracts. Vitamin C supplementation did not prevent age-related macular degeneration. Periodontal disease[edit] Low intake and low serum concentration were associated with greater progression of periodontal disease. Adverse effects[edit] Oral intake as dietary supplements in excess of requirements are poorly absorbed, and excesses in the blood rapidly excreted in the urine, so it exhibits low acute toxicity. More than two to three grams, consumed orally, may cause nausea, abdominal cramps and diarrhea. These effects are attributed to the osmotic effect of unabsorbed vitamin C passing through the intestine. In theory, high vitamin C intake may cause excessive absorption of iron. A summary of reviews of supplementation in healthy subjects did not report this problem, but left as untested the possibility that individuals with hereditary hemochromatosis might be adversely affected. There is a longstanding belief among the mainstream medical community that vitamin C increases risk of kidney stones. "Reports of kidney stone formation associated with excess ascorbic acid intake are limited to individuals with renal disease". A review states that "data from epidemiological studies do not support an association between excess ascorbic acid intake and kidney stone formation in apparently healthy individuals", although one large, multi-year trial did report a nearly two-fold increase in kidney stones in men who regularly consumed a vitamin C supplement. There is extensive research on the purported benefits of intravenous vitamin C for treatment of sepsis, severe COVID-19 and cancer. Reviews list trials with doses as high as 24 grams per day. Concerns about possible adverse effects are that intravenous high-dose vitamin C leads to a supraphysiological level of vitamin C followed by oxidative degradation to dehydroascorbic acid and hence to oxalate, increasing the risk of oxalate kidney stones and oxalate nephropathy. The risk may be higher in people with renal impairment, as kidneys efficiently excrete excess vitamin C. Second, treatment with high dose vitamin C should be avoided in patients with glucose-6-phosphate dehydrogenase deficiency as it can lead to acute hemolysis. Third, treatment might interfere with the accuracy of glucometer measurement of blood glucose levels, as both vitamin C and glucose have similar molecular structure, which could lead to false high blood glucose readings. Despite all these concerns, meta-analyses of patients in intensive care for sepsis, septic shock, COVID-19 and other acute conditions reported no increase in new-onset kidney stones, acute kidney injury or requirement for renal replacement therapy for patients receiving short-term, high-dose, intravenous vitamin C treatment. This suggests that intravenous vitamin C is safe under these short-term applications. History[edit] Scurvy was known to Hippocrates, described in book two of his Prorrheticorum and in his Liber de internis affectionibus, and cited by James Lind. Symptoms of scurvy were also described by Pliny the Elder: (i) Pliny. "49". Naturalis historiae. Vol. 3.; and (ii) Strabo, in Geographicorum, book 16, cited in the 1881 International Encyclopedia of Surgery. Scurvy at sea[edit] Limes, lemons and oranges were among foods identified early as preventing or treating scurvy on long sailing voyages. In the 1497 expedition of Vasco da Gama, the curative effects of citrus fruit were known. In the 1500s, Portuguese sailors put in to the island of Saint Helena to avail themselves of planted vegetable gardens and wild-growing fruit trees. Authorities occasionally recommended plant food to prevent scurvy during long sea voyages. John Woodall, the first surgeon to the British East India Company, recommended the preventive and curative use of lemon juice in his 1617 book, The Surgeon's Mate. In 1734, the Dutch writer Johann Bachstrom gave the firm opinion, "scurvy is solely owing to a total abstinence from fresh vegetable food, and greens." Scurvy had long been a principal killer of sailors during the long sea voyages. According to Jonathan Lamb, "In 1499, Vasco da Gama lost 116 of his crew of 170; In 1520, Magellan lost 208 out of 230;...all mainly to scurvy." James Lind, a British Royal Navy surgeon who, in 1747, identified that a quality in fruit prevented scurvy in one of the first recorded controlled experiments The first attempt to give scientific basis for the cause of this disease was by a ship's surgeon in the Royal Navy, James Lind. While at sea in May 1747, Lind provided some crew members with two oranges and one lemon per day, in addition to normal rations, while others continued on cider, vinegar, sulfuric acid or seawater, along with their normal rations, in one of the world's first controlled experiments. The results showed that citrus fruits prevented the disease. Lind published his work in 1753 in his Treatise on the Scurvy. Fresh fruit was expensive to keep on board, whereas boiling it down to juice allowed easy storage but destroyed the vitamin (especially if boiled in copper kettles). It was 1796 before the British navy adopted lemon juice as standard issue at sea. In 1845, ships in the West Indies were provided with lime juice instead, and in 1860 lime juice was used throughout the Royal Navy, giving rise to the American use of the nickname "limey" for the British. Captain James Cook had previously demonstrated the advantages of carrying "Sour krout" on board, by taking his crew on a 1772-75 Pacific Ocean voyage without losing any of his men to scurvy. For his report on his methods the British Royal Society awarded him the Copley Medal in 1776. The name antiscorbutic was used in the eighteenth and nineteenth centuries for foods known to prevent scurvy. These foods included lemons, limes, oranges, sauerkraut, cabbage, malt, and portable soup. In 1928, the Canadian Arctic anthropologist Vilhjalmur Stefansson showed that the Inuit avoided scurvy on a diet of largely raw meat. Later studies on traditional food diets of the Yukon First Nations, Dene, Inuit, and Métis of Northern Canada showed that their daily intake of vitamin C averaged between 52 and 62 mg/day. Discovery[edit] Further information: Vitamin § History Vitamin C was discovered in 1912, isolated in 1928 and synthesized in 1933, making it the first vitamin to be synthesized. Shortly thereafter Tadeus Reichstein succeeded in synthesizing the vitamin in bulk by what is now called the Reichstein process. This made possible the inexpensive mass-production of vitamin C. In 1934, Hoffmann–La Roche bought the Reichstein process patent, trademarked synthetic vitamin C under the brand name Redoxon, and began to market it as a dietary supplement. In 1907, a laboratory animal model which would help to identify the antiscorbutic factor was discovered by the Norwegian physicians Axel Holst and Theodor Frølich, who when studying shipboard beriberi, fed guinea pigs their test diet of grains and flour and were surprised when scurvy resulted instead of beriberi. Unknown at that time, this species did not make its own vitamin C (being a caviomorph), whereas mice and rats do. In 1912, the Polish biochemist Casimir Funk developed the concept of vitamins. One of these was thought to be the anti-scorbutic factor. In 1928, this was referred to as "water-soluble C", although its chemical structure had not been determined. Albert Szent-Györgyi, pictured here in 1948, was awarded the 1937 Nobel Prize in Medicine "for his discoveries in connection with the biological combustion processes, with special reference to vitamin C and the catalysis of fumaric acid". From 1928 to 1932, Albert Szent-Györgyi and Joseph L. Svirbely's Hungarian team, and Charles Glen King's American team, identified the anti-scorbutic factor. Szent-Györgyi isolated hexuronic acid from animal adrenal glands, and suspected it to be the antiscorbutic factor. In late 1931, Szent-Györgyi gave Svirbely the last of his adrenal-derived hexuronic acid with the suggestion that it might be the anti-scorbutic factor. By the spring of 1932, King's laboratory had proven this, but published the result without giving Szent-Györgyi credit for it. This led to a bitter dispute over priority. In 1933, Walter Norman Haworth chemically identified the vitamin as l-hexuronic acid, proving this by synthesis in 1933. Haworth and Szent-Györgyi proposed that L-hexuronic acid be named a-scorbic acid, and chemically l-ascorbic acid, in honor of its activity against scurvy. The term's etymology is from Latin, "a-" meaning away, or off from, while -scorbic is from Medieval Latin scorbuticus (pertaining to scurvy), cognate with Old Norse skyrbjugr, French scorbut, Dutch scheurbuik and Low German scharbock. Partly for this discovery, Szent-Györgyi was awarded the 1937 Nobel Prize in Medicine, and Haworth shared that year's Nobel Prize in Chemistry. In 1957, J. J. Burns showed that some mammals are susceptible to scurvy as their liver does not produce the enzyme l-gulonolactone oxidase, the last of the chain of four enzymes that synthesize vitamin C. American biochemist Irwin Stone was the first to exploit vitamin C for its food preservative properties. He later developed the idea that humans possess a mutated form of the l-gulonolactone oxidase coding gene. Stone introduced Linus Pauling to the theory that humans needed to consume vitamin C in quantities far higher than what was considered a recommended daily intake in order to optimize health. In 2008, researchers discovered that in humans and other primates the red blood cells have evolved a mechanism to more efficiently utilize the vitamin C present in the body by recycling oxidized l-dehydroascorbic acid (DHA) back into ascorbic acid for reuse by the body. The mechanism was not found to be present in mammals that synthesize their own vitamin C. History of large dose therapies[edit] Further information: Vitamin C megadosage and Intravenous ascorbic acid Vitamin C megadosage is a term describing the consumption or injection of vitamin C in doses comparable to or higher than the amounts produced by the livers of mammals which are able to synthesize vitamin C. An argument for this, although not the actual term, was described in 1970 in an article by Linus Pauling. Briefly, his position was that for optimal health, humans should be consuming at least 2,300 mg/day to compensate for the inability to synthesize vitamin C. The recommendation also fell into the consumption range for gorillas – a non-synthesizing near-relative to humans. A second argument for high intake is that serum ascorbic acid concentrations increase as intake increases until it plateaus at about 190 to 200 micromoles per liter (µmol/L) once consumption exceeds 1,250 milligrams. As noted, government recommendations are a range of 40 to 110 mg/day and normal plasma is approximately 50 µmol/L, so 'normal' is about 25% of what can be achieved when oral consumption is in the proposed megadose range. Pauling popularized the concept of high dose vitamin C as prevention and treatment of the common cold in 1970. A few years later he proposed that vitamin C would prevent cardiovascular disease, and that 10 grams/day, initially administered intravenously and thereafter orally, would cure late-stage cancer. Mega-dosing with ascorbic acid has other champions, among them chemist Irwin Stone and the controversial Matthias Rath and Patrick Holford, who both have been accused of making unsubstantiated treatment claims for treating cancer and HIV infection. The idea that large amounts of intravenous ascorbic acid can be used to treat late-stage cancer or ameliorate the toxicity of chemotherapy is – some forty years after Pauling's seminal paper – still considered unproven and still in need of high quality research. Notes[edit] ^ Dicot plants transport only ferrous iron (Fe), but if the iron circulates as ferric complexes (Fe), it has to undergo a reduction before it can be actively transported. Plant embryos efflux high amounts of ascorbate that chemically reduce iron(III) from ferric complexes.	biology	13707	https://da.wikipedia.org/wiki/Vitamin	Vitamin	Et vitamin er en organisk forbindelse og et livsnødvendigt næringsstof for en organisme. En organisk kemisk forbindelse (eller et relateret sæt af forbindelser) kaldes et vitamin, når en organisme ikke på egen hånd kan syntetisere forbindelsen i de nødvendige mængder, og det derfor bliver nødt til at få gennem kosten; derfor afhænger definitionen af et "vitamin" af omstændighederne og den pågældende organisme. Fx er ascorbinsyre (en variant af C-vitamin) et vitamin for mennesker, men ikke for mange andre. Mange vitaminer findes som kosttilskud, og mens kosttilskud er vigtige for behandlingen af bestemte helbredsproblemer, findes der ikke beviser på næringsmæssige fordele, når de bruges af sunde og raske mennesker. Opfattelsen er, at begrebet vitamin hverken inkluderer andre essentielle næringsstoffer som mineraler, fedtsyrer eller aminosyrer, som behøves i større mængder end vitaminer, eller det store antal andre næringsstoffer, der er sunde for kroppen, men som kun sjældnere kræves for at vedligeholde helbredet. I øjeblikket anerkendes 13 vitaminer universelt. Vitaminer klassificeres ved deres biologiske og kemiske aktivitet, ikke deres struktur. Derfor henviser hvert "vitamin" til et antal vitamer-forbindelser, der alle viser den biologiske aktivitet associeret med et bestemt vitamin. Sådan et sæt kemiske stoffer er grupperet under en alfabetiseret "generisk deskriptor"-titel som "A-vitamin" med forbindelserne retinal, retinol og fire kendte karotenoider. Vitamere kan pr. definition omdannes til den aktive form af vitaminet i kroppen og kan somme tider også omdannes til hinanden. Vitaminer har forskellige biokemiske funktioner: Nogle som D-vitamin har hormonlignende funktioner som regulatorer af mineralmetabolisme eller regulatorer af celle- og vævsvækst og -differentiering som nogle former for A-vitamin. Andre fungerer som antioxidanter som E-vitamin og visse C-vitaminer. Det største antal vitaminer, de komplekse B-vitaminer, fungerer som enzym-cofaktorer (coenzymer) eller udgangsstoffer for dem; coenzymer hjælper enzymer som katalysatorer i metabolisme. I denne rolle kan vitaminer bindes stramt til enzymer som en del af prostetiske grupper: Fx er biotin en del af enzymer involveret i dannelsen af fedtsyrer. De kan også være mindre stramt bundet til enzymkatalysatorer som coenzymer, adskillelige molekyler, hvis funktion er at transportere kemiske grupper eller elektroner mellem molekyler. For eksempel kan folsyre transportere methyl, aldehyd og methylen-grupper i cellen. Selvom disse roller i at assistere enzymsubstratreaktioner er vitaminernes bedst-kendte funktion, er de andre vitaminfunktioner lige så vigtige. Frem til midten af 1930'erne, da de første kommercielle B-vitaminer af gærekstrakt og semi-syntetiserede C-vitaminkosttilskudspiller blev solgt, blev vitaminer udelukkende indtaget gennem kosten, og forandringer i kosten (som kunne ske på en bestemt årstid) ændrede ofte voldsomt hvilke typer og mængder af vitaminer man indtog. Vitaminer er dog produceret som råt kemikalie og gjort meget tilgængeligt som billige semisyntetiserede og syntetiserede multivitamin-tilskud siden midten af det 20. århundrede. Studier i strukturel aktivitet, funktion og deres rolle i at vedligeholde helbredet kaldes vitaminologi. Ordet vitamin er en sammensætning og sammentrækning af vita (liv) og amin. Det blev første gang formuleret af Casimir Funk i 1912. Tilstedeværelsen af vitaminer kan være påkrævet for at optage andre stoffer fra maden. Fx optages mineralet kalk bedst ved tilstedeværelsen af D-vitamin. Liste over vitaminer Hvert vitamin bruges typisk i flere reaktioner, og derfor har de fleste flere funktioner. Helbredsmæssige effekter Vitaminer er essentielle for en multicellet organismes normale vækst og udvikling. Et foster begynder, fra det øjeblik, det undfanges, at udvikles ud fra sine forældres genetiske model ved hjælp af de næringsstoffer, det absorberer. Det kræver, at bestemte vitaminer og mineraler er til stede på bestemte tidspunkter. Disse næringsstoffer faciliterer de kemiske reaktioner, som blandt andet producerer hud, knogler og muskler. Hvis der er en alvorlig mangel på et eller flere af disse næringsstoffer, kan et barn udvikle en mangelsygdom. Selv mindre mangler kan forårsage permanent skade. For størstedelens vedkommende fås vitaminer gennem føden, men nogle få opnås på andre måder. Fx producerer mikroorganismer i tarmene — normalt kaldet "tarmflora" — K-vitamin og biotin, mens en type D-vitamin syntetiseres i huden ved hjælp af den naturlige ultraviolette bølgelængde fra sollys. Mennesker kan producere nogle vitaminer fra udgangsstoffer, som de indtager som A-vitamin produceret fra betakaroten, og niacin fra aminosyren tryptophan. Når vækst og udvikling er fuldendt, forbliver vitaminer essentielle næringsstoffer for en sund vedligeholdelse af cellerne, vævet og organismerne i en multicellet organisme; de lader også en multicellet livsform benytte den kemiske energi fra føden, den indtager, mere effektivt og hjælper med at bearbejde proteiner, kulhydrater og fedt, der kræves for respiration. Tilskud Hos individer, der ellers lever sundt, er der ikke meget bevis for, at tilskud har nogen gavnlig effekt, hvad angår kræft eller hjertekarsygdomme. Tilskud af A- og E-vitamin kan sågar øge dødeligheden hos sunde individer, omend de to store studier, som understøttede denne konklusion, medtog rygere, for hvem det allerede var kendt at betakaroten-tilskud kan være skadelige. Andre studier peger hen mod, at E-vitaminforgiftning er begrænset til overdosis af en bestemt type. Den Europæiske Union og andre europæiske lande har regelsæt, som definerer begrænsningerne af vitamin- (og mineral-) indtag, der kan bruges sikkert som kosttilskud. De fleste vitaminer, der sælges som kosttilskud, må ikke overstige en maksimal daglig dosis. Vitaminprodukter over disse foreskrevne grænser betragtes ikke som kosttilskud og skal registreres som enten receptpligtig medicin eller håndkøbslægemiddel pga. deres potentielle bivirkninger. Som følge heraf betragtes de fleste tilskud af de fedtopløselige vitaminer (som A-, D-, E- og K-vitamin) med mængder over det daglige indtag som medicin. Den daglige dosis for et vitamintilskud må for eksempel ikke overstige 300 % af det anbefalede daglige indtag, og for A-vitamin er denne begrænsning endnu lavere (200 %). Denne type reguleringerfinder sted i de fleste europæiske lande. Kosttilskud indeholder ofte vitaminer men kan også indeholde mineraler og urter. Videnskabelige undersøgelser bakker op om, at der er helbredsmæssige fordele ved kosttilskud til personer med bestemte helbredsmæssige problemer. I nogle tilfælde kan vitamintilskud have uønskede effekter, særligt hvis de tages før kirurgi sammen med andre kosttilskud eller medicin, eller hvis personen, der tager dem, har bestemte sundhedsmæssige forhold. De kan også indeholde vitaminniveauer, der er mange gange større, og i andre former, end man kan indtage gennem kost. Mangel Mennesker skal indtage vitaminer periodisk, men efter forskellige tidsplaner for at undgå vitaminmangel. Menneskekroppens depoter for de forskellige vitaminer varierer bredt; A- og B-vitamin og B12 opbevares i betragtelige mængder i menneskes legeme, hovedsageligt i leveren, og et voksent menneske kan undvære A- og D-vitamin i mange måneder, og i B12's tilfælde i flere år, før de udvikler mangeltilstand. Herimod opbevares vitamin B3 (niacin og niacinamid) ikke i menneskekroppen i særligt store mængder, så depoter kan ofte kun vare nogle uger. For C-vitamin er de første symptomer på skørbug i eksperimentelle studier med total C-vitamindeprivation varieret voldsomt, fra en måned til mere end seks måneder afhængig af den tidligere kostmæssige historie, som afgjorde kroppens depoter. Vitaminmangel klassificeres som enten primær eller sekundær. En primær mangel sker, når en organisme ikke får nok af vitaminet i sin kost. En sekundær mangel kan skyldes en dybereliggende tilstand, som forhindrer eller begrænser optagelsen eller brugen af vitaminet pga. en "livsstilsfaktor" som rygning, alkoholmisbrug eller brug af medicin, som forstyrrer optagelse eller brug af vitaminet. Folk, som indtager en varieret kost, udvikler kun meget sjældent en alvorlig primær vitaminmangel. I modsætning hertil kan restriktive kostplaner have potentiale til at skabe forlænget vitaminmangel, der kan føre til alvorlige sygdomme. Velkendte menneskelige vitaminmangler er tiamin (beriberi), niacin (pellagra), C-vitamin (skørbug) og D-vitamin (engelsk syge). I meget af den udviklede verden er sådanne mangelsygdomme sjældne; dette skyldes (1) et tilstrækkeligt forråd af mad og (2) tilsættelsen af vitaminer og mineraler til udbredte fødevarer, hvilket ofte kaldes berigelse. Udover disse klassiske mangelsygdomme har der også været tegn på forbindelse mellem vitaminmangel og en række andre lidelser. Bivirkninger I store doser har nogle vitaminer bivirkninger, som normalt bliver alvorligere, jo højere dosen er. Risikoen for at indtage for meget af et vitamin fra kosten er meget lille, men overdosis (vitaminforgiftning) fra vitamintilskud er set. Ved høje nok doser giver nogle vitaminer bivirkninger som kvalme, diarré og opkast. Når der fremkommer bivirkninger, kan man sædvanligvis komme problemet til livs ved at reducere dosis. Vitamindoserne er forskellige, da individuelle toleranceniveauer kan variere meget og lader til at være relaterede til alder og almen helbredstilstand. Farmakologi Vitaminer klassificeres enten som vandopløselige eller fedtopløselige. Der findes 13 vitaminer i mennesker: fire fedtopløselige (A, D, E og K) og ni vandopløselige (8 B-vitaminer og C-vitamin). Vandopløselige vitaminer opløses let i vand og udskilles generelt let fra kroppen, i en grad så niveau i urinen er en stærk indikator af vitaminindtagelse. Da de ikke lagres særlig nemt i kroppen, er det vigtigt at have et konstant indtag af dem. Mange typer af vandopløselige vitaminer syntetiseres af bakterier. Fedtopløselige vitaminer absorberes gennem mavetarmkanalen ved hjælp af lipider (fedt). De har en større risiko for at føre til hypervitaminose end de vandopløselige, da de har større tendens til at blive lagret i kroppen. Fedtopløselig vitaminregulering af særlig betydning i cystisk fibrose. Historie Værdien af at spise bestemte fødevarer for at vedligeholde et godt helbred blev anerkendt længe før vitaminerne blev identificeret. Man vidste allerede i det gamle Egypten, at ved at spise lever kunne man hjælpe til at kurere natteblindhed, en sygdom som det nu vides skyldes mangel på vitamin A. Havsejlads under Renæssancen resulterede i lange perioder uden adgang til frugter og grøntsager og gjorde vitaminmangelsygdomme udbredte i skibsbesætningerne. I 1747 opdagede den skotske kirurg James Lind, at citrusfrugter hjalp til at forhindre skørbug, en dødelig sygdom, hvor kollagen ikke dannes ordentligt, hvilket fører til dårlig sårheling, blødende tandkød, stærk smerte og død. I 1753 udgav Lind sin Treatise on the Scurvy, som anbefalede at bruge citroner og limefrugter for at undgå skørbug. Anbefalingen blev fulgt af den britiske Royal Navy, hvilket førte til udtrykket "limey" om sømænd. Linds opdagelse blev ikke bredt accepteret i Royal Navy's Arktis-ekspeditioner i det 19. århundrede, hvor mange mente, at skørbug kunne undgås ved god hygiejne, regelmæssig motion og ved at holde mandskabets gejst høj, snarere end ved frisk frugt. Som følge heraf fortsatte de arktiske ekspeditioner med at være plaget af skørbug og andre mangelsygdomme. I begyndelsen af det 20. århundrede, da Robert Falcon Scott foretog sine to ekspeditioner til Antarktis, var den fremherskende medicinske teori, at skørbug skyldtes "fordærvet" dåsemad. I slutningen af det 18. og begyndelsen af det 19. århundrede lod brugen af deprivationsstudier videnskabsfolk isolere og identificere en række vitaminer. Lipider fra fiskeolie blev brugt til at kurere engelsk syge (rakitis) hos rotter, og det fedtopløselige næringsstof blev oprindeligt kaldt "antirakitis A". På den måde blev den første "vitamin"-bioaktivitet, der nogensinde blev isoleret og kurerede rakitis, oprindeligt kaldt "A-vitamin"; i dag kaldes denne forbindelses bioaktivitet dog D-vitamin. I 1881 studerede den russiske kirurg Nikolai Lunin skørbugens effekter, mens han var ved Tartu Universitet (nu i Estland. Han fodrede mus med en kunstig mikstur af alle de separate bestanddele, der på daværende tidspunkt var identificeret i mælk, navnlig proteinerne, fedttyperne, kulhydraterne og saltene. De mus, der kun fik de individuelle bestanddele døde, mens de mus der fik mælk udviklede sig normalt. Han konkluderede, at "en naturlig føde som mælk derfor skal, udover disse kendte centrale bestanddele, indeholde små mængder ukendte substanser, som er essentielle for liv." Hans konklusioner blev dog afvist af hans rådgiver, Gustav von Bunge, selv efter andre studenter reproducerede hans resultater. Et lignende resultat af Cornelius Pekelharing blev beskrevet i en hollandsk medicinsk journal i 1905, men blev ikke publiceret særlig vidt. I Østasien, hvor polerede hvide ris var normal kost for middelklassen, var beriberi fra mangel på vitamin B1 endemisk. I 1884 observerede Takaki Kanehiro, en britisk-trænet læge fra den kejserlige japanske flåde, at beriberi var endemisk blandt lavtrangerende mandskab, som ofte ikke spiste andet end ris, men ikke blandt officerer som indtog en vestligt-inspireret kost. Med støtte fra den japanske flåde eksperimenterede han med besætningen på to krigsskibe: en besætning fik udelukkende hvide ris at spise, mens den anden fik kød, fisk, byg, ris og bønner. Den gruppe, som kun spiste hvide ris havde 161 besætningsmedlemmer med beriberi og 25 dødsfald, mens den anden gruppe kun havde 14 tilfælde af beriberi og ingen dødsfald. Det overbeviste Takaki og den japanske flåde om, at årsagen til beriberi skulle findes i kosten, men konkluderede fejlagtigt, at passende mængder protein ville forhindre det. At sygdomme kunne opstå fra kostmæssige mangler blev yderligere undersøgt af Christiaan Eijkman, som i 1897 opdagede, at man kunne forhindre beriberi i kyllinger ved at fodre dem med upolerede ris i stedet for polerede ris. Det følgende år postulerede Frederick Hopkins, at nogle madvarer indeholdt ekstra faktorer — udover proteiner, kulhydrater, fedt, etc. — som er nødvendige for menneskekroppens funktion. Hopkins og Eijkman blev tildelt Nobelprisen i fysiologi eller medicin i 1929 for deres opdagelser. I 1910 blev det første vitaminkompleks isoleret af den japanske videnskabsmand Umetaro Suzuki, som havde held med at udtrække et vandopløseligt kompleks af mikronæringsstoffer fra risklid og navngav det aberisk syre (senere Orizanin). Han offentliggjorde denne opdagelse i en japansk videnskabelig journal. Da artiklen blev oversat til tysk glemte man i oversættelsen at gøre opmærksom på, at det var et nyligt opdaget næringsstof, hvilket blev påstået i den oprindelige japanske artikel, og opdagelsen gik derfor relativt ubemærket hen. I 1912 isolerede den polskfødte biokemiker Casimir Funk i London det samme kompleks af mikronæringsstoffer og fremsatte forslag om, at man navngav komplekset "vitamin". Det blev senere kendt som B-vitamin3 (niacin), selv om han selv beskrev det som "anti-beri-beri-faktor" (som i dag ville blive kaldt tiamin eller vitamin B1). Funk fremsatte en hypotese om, at andre sygdomme, såsom engelsk syge, pellagra, cøliaki og skørbug også ville kunne kureres med vitaminer. Max Nierenstein foreslog angiveligt navnet "vitamin" (fra "vital amin").). Navnet blev snart efter synonymt med Hopkins' ekstra faktorer, og da det endelig blev påvist, at ikke alle vitaminer er aminer, sad navnet allerede fast. I 1930 afdækkede Paul Karrer betakarotens korrekte struktur, og identificerede andre karotenoider. Karrer og Norman Haworth bekræftede Albert Szent-Györgyis opdagelse af askorbinsyre og kom med anseelige bidrag til flaviners kemi, hvilket førte til identificeringen af laktoflavin. De modtog begge Nobelprisen i kemi i 1937 for deres undersøgelser af karotenoider, flaviner og vitamin A og B2. I 1931 havde Albert Szent-Györgyi og hans kollega Joseph Svirbely mistanke om, at "hexuronisk syre" faktisk var vitamin C, og gav en prøve til Charles Glen King, som beviste dets anti-skørbug-effekt. I 1937 blev Szent-Györgyi tildelt Nobelprisen i fysiologi eller medicin for sin opdagelse. I 1943 blev Edward Adelbert Doisy og Henrik Dam tildelt Nobelprisen i fysiologi eller medicin for deres opdagelse af vitamin K og dets kemiske struktur. I 1967 blev George Wald tildelt nobelprisen (sammen med Ragnar Granit og Haldan Keffer Hartline) for opdagelsen af at vitamin A kan deltage direkte i en fysiologisk proces. Navngivning Grunden til, at vitaminsættet springer direkte fra E til K, er, at vitaminerne der svarede til bogstaverne F–J enten blev omklassificeret, droppet som falske eller omdøbt på grund af deres forhold til vitamin B, som blev et kompleks af vitaminer. De tysktalende forskere, som isolerede og beskrev (og navngav) K-vitamin, valgte navnet fordi vitaminet er tæt involveret i koagulationen af blod efter at man pådrager sig sår (det tyske ord er, som det danske, Koagulation). På det tidspunkt var de fleste bogstaver fra F til J allerede brugt, så brugen af bogstavet K blev betragtet som fornuftig. Der findes andre manglende B-vitaminer som blev omklassificeret eller vurderet til ikke at være vitaminer. For eksempel er B9 folsyre og fem af folaterne er i rækken B11 til B16, former af vitaminer der allerede er opdaget, ikke krævet som et næringsstof af hele befolkningen (som B10, PABA til internt brug), biologisk inaktive, giftige, eller med uklassificerbare effekter i mennesker, eller ikke generelt anset som vitaminer af videnskaben, såsom det højest-nummererede, som nogle naturopater kalder B21 og B22. Der findes også ni B-kompleksvitaminer med bogstaver (såsom Bm). Der er andre D-vitaminer, som nu anerkendes som andre substanser, hvilket nogle kilder af samme type nummererer op til D7. Den kontroversielle kræftbehandling laetril var på et tidspunkt navngivet som vitamin B17. Der lader ikke til at være nogen konsensus om vitamin Q, R, T, V, W, X, Y eller Z, ligesom der heller ikke er substanser, der officielt er designeret vitamin N eller I. Noter Litteratur Henrik Dilling, Klar besked om vitaminer og mineraler, Aschehoug, . Eksterne henvisninger DTU Fødevareinstituttet: Fødevaredata Netdoktor: oversigt vitaminer Se også Bioforstærkning Mikrobiom Ernæring	danish	0.384841
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These two vital organs, though may not seem to be linked, share many similar features, particularly in the aspects of their blood vessels. The network of blood vessels at the back of the eye is closely related to heart health. These blood vessels at the back of the eye are the only visible vasculature accessible in a human body without relying on an invasive method. An eye examination with a careful viewing of the inner and outer part of the eye often can reveal early signs of cardiovascular disease (which may later present acutely as heart attack or stroke). ![](https://i0.wp.com/spm.um.edu.my/wp- content/uploads/2022/08/Picture1.png?resize=387%2C345&ssl=1) Photo 1 – Features at the back of the left eye with normal blood vessels ![](https://i0.wp.com/spm.um.edu.my/wp- content/uploads/2022/08/Picture2.png?resize=380%2C345&ssl=1) Photo 2 – Hypertensive changes at the back of the left eye (yellow arrow – death of nerve layer, red arrow – bleeding spot) Based on the results of the National Health and Morbidity Survey 2019, three in 10 Malaysians had high blood pressure. At the early stage, high blood pressure typically has no warning symptoms. Thus, many people are not aware of having high blood pressure until they develop end organ damage. An eye doctor may be able to discover early clues by recognizing changes in the eye’s blood vessels or small bleeding spots at the back of the eye. Sometimes, even a blocked artery with a blood clot leading to an impending eye stroke can be picked up by an experienced ophthalmologist. It is estimated that two out of 10 adults in Malaysia have diabetes. High blood sugar may damage the tiny blood vessels of the eye and cause leakage of fluid into the surrounding tissue. These conditions are known as diabetic retinopathy and diabetic macular oedema respectively; if untreated, may lead to vision impairment or ultimately blindness. Ideally, these reversible conditions should be identified before a visual loss occurs. For type 2 diabetes patients, diabetic retinopathy screening is recommended and should be carried out annually. ![](https://i0.wp.com/spm.um.edu.my/wp- content/uploads/2022/08/Picture3.png?resize=510%2C423&ssl=1) Photo 3 – Diabetic retinopathy to the left eye ![](https://i0.wp.com/spm.um.edu.my/wp- content/uploads/2022/08/Picture4.png?resize=383%2C384&ssl=1) Photo 4 – Diabetic macular oedema of the left eye, showing hard exudates around the macula Notably, four in 10 Malaysian adults have raised total cholesterol levels, with one in 4 being unaware of it. Fortunately, such conditions may occasionally manifest as small, yellowish soft bumps (called xanthelasma palpebrarum) around the eyelids. These aesthetically-unpleasing plagues rarely affect our vision but they may indicate a high cholesterol problem. Individuals who have such eye plaques should get their cholesterol levels checked. ![](https://i0.wp.com/spm.um.edu.my/wp- content/uploads/2022/08/2022-08-18.png?resize=447%2C237&ssl=1) In short, early detection and subsequent treatment of risk factors of cardiovascular disease (namely high blood pressure, diabetes, and high cholesterol) via an eye examination can reduce our risks of getting a heart attack or stroke in the near future. In line with the upcoming World Heart Day’s theme of “Use heart for every heart” and World Sight Day’s theme of “Love your eyes”, every Malaysian adult aged 40 years and above should do a medical checkup yearly with a comprehensive eye examination at the nearest medical facility. For the low-income group aged 40 years and above, PeKa B40 which is a free health screening through the health protection scheme is available for them. More details can be found at the official website of [ Protect Health – Peka B40 ](https://protecthealth.com.my/peka-b40/) . This write-up was prepared by Dr Yap Jun Fai (DrPH Candidate), Professor Dr [ Moy Foong Ming ](https://spm.um.edu.my/staff/moy-foong-ming/) and Dr [ Lim Yin Cheng ](https://spm.um.edu.my/staff/lim-yin-cheng/) from the Department of Social and Preventive Medicine, Faculty of Medicine, Universiti Malaya and Dr Alan Fong from the National Heart Association of Malaysia. This write-up is also published in the [ CodeBlue ](https://codeblue.galencentre.org/2022/08/12/our-eyes-are-the-windows-to-the- heart-dr-yap-jun-fai-prof-dr-moy-foong-ming-dr-lim-yin-cheng-dr-alan-fong/) , [ The Star ](https://www.thestar.com.my/opinion/letters/2022/08/15/windows- into-our-hearts) , [ New Straits Times ](https://www.nst.com.my/opinion/letters/2022/08/823586/eye-exam-gives-clues- heart-risks?fbclid=IwAR0-6NegRTjpOwnJ1rXSoCt6f9xE0PrcVtPqkOnKFi- LlqFIdOVpXHRLyO4) , and [ My Sin Chew ](https://www.sinchew.com.my/?p=4011284) . References 1. Ministry of Health Malaysia. Diabetic retinopathy screening – training module for healthcare providers. Ministry of health diabetic retinopathy screening team. 2017. Available [ here ](https://www.moh.gov.my/moh/resources/Penerbitan/2017/Rujukan/NCD%202017/Diabetic_Retinopathy_Screening_Module.pdf) . 2. Tsukikawa M, Stacey AW. A Review of Hypertensive Retinopathy and Chorioretinopathy. _Clin Optom (Auckl)_ . 2020;12:67-73. Available [ here ](https://www.ncbi.nlm.nih.gov/pmc/articles/PMC7211319/) . 3. Ishak A, Mohd Yusoff SS, Wan Abdullah W. Young Lady with Bilateral Yellowish Lesions on Her Eyelids. _Malays Fam Physician_ . 2018;13(3):44-46. Available [ here ](https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6382083/) . Please leave this field empty ![](https://i0.wp.com/spm.um.edu.my/wp-content/uploads/2020/12/PublicHealthUM- sqr.jpg?resize=227%2C0&ssl=1) ## Subscribe to our newsletter ## Sign up to receive an awesome Newsletter in your inbox, every month. 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Her journey into medicine started in […] [ ](https://spm.um.edu.my/2009/02/18/launch-of-centre-for-population- health-18-feb-2009/) ![](https://i0.wp.com/spm.um.edu.my/wp- content/uploads/2020/09/ceph-launch-2009.png?resize=510%2C510&ssl=1) [ ](https://spm.um.edu.my/wp-content/uploads/2020/09/ceph-launch-2009.png) Published [ 18 February 2009 ](https://spm.um.edu.my/2009/02/18/launch-of- centre-for-population-health-18-feb-2009/ "Permalink to: Launch of Centre for Population Health 18 Feb 2009") ## [ Launch of Centre for Population Health 18 Feb 2009 ](https://spm.um.edu.my/2009/02/18/launch-of-centre-for-population- health-18-feb-2009/) The Universiti Malaya and Queen’s University, Belfast jointly launched the Centre for Population Health (CePH) at the Chancellory Building on 18 February […] [ ](https://spm.um.edu.my/2020/04/30/talkshow-online-fakultas-psikologi-uin- ar-raniry/) ![Talkshow Online Fakultas Psikologi UIN Ar- Raniry](https://spm.um.edu.my/wp-content/themes/customizr- pro/assets/front/img/thumb-standard-empty.png) Published [ 30 April 2020 ](https://spm.um.edu.my/2020/04/30/talkshow-online- fakultas-psikologi-uin-ar-raniry/ "Permalink to: Talkshow Online Fakultas Psikologi UIN Ar-Raniry") ## [ Talkshow Online Fakultas Psikologi UIN Ar-Raniry ](https://spm.um.edu.my/2020/04/30/talkshow-online-fakultas-psikologi-uin-ar- raniry/) Fakultas Psikologi Universitas Islam Negeri (UIN) Ar-Raniry menggelar talkshow internasional selama dua hari, Senin (27/4) hingga Selasa 28 April 2020. Kegiatan itu […] ## Latest News * [ Congratulation Prof Dato’ Dr Yang Faridah Abdul Aziz ](https://spm.um.edu.my/2024/04/22/congratulation-prof-dato-dr-yang-faridah-abdul-aziz/) * [ Thank you Professor Dr April Camilla Roslani ](https://spm.um.edu.my/2024/04/22/thank-you-professor-dr-april-camilla-roslani/) * [ Nirmala Bhoo Pathy Recognised as a Distinguished Reviewer for JAMA Oncology! ](https://spm.um.edu.my/2024/04/19/nirmala-bhoo-pathy-recognised-as-a-distinguished-reviewer-for-jama-oncology/) * [ Congratulate Dr Malar Velli Segarmurthy for successfully completion of your DrPH viva voce ](https://spm.um.edu.my/2024/04/18/congratulate-dr-malar-velli-segarmurthy-for-successfully-completion-of-your-drph-viva-voce/) * [ Congratulation Dr Mohd Taufiq bin Abdul Ghani on the successfully completion of his Doctor of Public Health Viva Voce ](https://spm.um.edu.my/2024/04/17/congratulation-dr-mohd-taufiq-bin-abdul-ghani-on-the-successfully-completion-of-his-doctor-of-public-health-viva-voce/) ## Sign-up for our newsletter Please leave this field empty ![](https://spm.um.edu.my/wp-content/uploads/2020/12/PublicHealthUM-sqr.jpg) ## Subscribe to our newsletter ## Sign up to receive an awesome Newsletter in your inbox, every month. 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two_organs_but_not_all/21704heart.txt	Locations : [ Abu Dhabi ](https://www.clevelandclinicabudhabi.ae/) \| [ Canada ](https://my.clevelandclinic.org/canada) \| [ Florida ](https://my.clevelandclinic.org/florida) \| [ London ](https://clevelandcliniclondon.uk/) \| [ Nevada ](https://my.clevelandclinic.org/locations/nevada) \| [ Ohio ](https://my.clevelandclinic.org) \| ![Gray gradient](/health/_next/static/media/gray-gradient- left-16.59910877.svg?w=32&q=75) ![Gray gradient](/health/_next/static/media/gray-gradient- right-32.dd7ce4e5.svg?w=64&q=75) * [ 800.223.2273 ](tel:800.223.2273) * [ 100 Years of Cleveland Clinic ](https://my.clevelandclinic.org/about/history) * [ MyChart ](https://my.clevelandclinic.org/online-services/mychart) * [ Need Help? ](https://my.clevelandclinic.org/help) * [ Giving ](https://my.clevelandclinic.org/giving) * [ Careers ](https://jobs.clevelandclinic.org) * [ ![Search Icon Blue](/health/_next/static/media/search--blue.a23a2bb9.svg?w=32&q=75) Search ](https://my.clevelandclinic.org/search) [ ![Cleveland Clinic logo](/health/_next/static/media/logo- ccf.a7ea0118.svg?w=3840&q=75) ](https://my.clevelandclinic.org/) [ ![Search Icon](/health/_next/static/media/search-- gray.86f52a63.svg?w=48&q=75) ](https://my.clevelandclinic.org/search) * [ ClevelandClinic.org ](https://my.clevelandclinic.org) * [ Find A Doctor ](https://my.clevelandclinic.org/staff) * [ Locations & Directions ](https://my.clevelandclinic.org/locations) * [ Patients & Visitors ](https://my.clevelandclinic.org/patients) * [ Health Library ](https://my.clevelandclinic.org/health) * [ Institutes & Departments ](https://my.clevelandclinic.org/departments) * [ Appointments ](https://my.clevelandclinic.org/patients/information/access) ![](//zdbb.net/l/Dnl1wmWs8xCCpvWNCt9Egf/?w=16&q=75) [ Home ](https://my.clevelandclinic.org) / [ Health Library ](https://my.clevelandclinic.org/health) / [ Body Systems & Organs ](https://my.clevelandclinic.org/health/body) / Heart Advertisement Advertisement Advertisement # Heart Your muscular heart, the main organ in your cardiovascular system, is vital for life. Its parts work together to move blood through your body in a coordinated way. It constantly sends oxygen to your cells and takes away waste. Many conditions can affect this organ and keep it from working well. Contents Arrow Down Overview Function Anatomy Conditions and Disorders Care Additional Common Questions Contents Arrow Down Overview Function Anatomy Conditions and Disorders Care Additional Common Questions ## Overview ![The heart and the major arteries and veins going into and out of it.](https://my.clevelandclinic.org/-/scassets/images/org/health/articles/21704-heart- overview-outside) Your heart is a muscular organ that pumps blood to your body. ### What is the heart? The heart is a fist-sized organ that pumps [ blood ](https://my.clevelandclinic.org/health/body/24836-blood) throughout your body. It’s your [ circulatory system ](https://my.clevelandclinic.org/health/body/21775-circulatory-system) ’s main organ. Muscle and tissue make up this powerhouse organ. Your heart contains four muscular sections ( [ chambers ](https://my.clevelandclinic.org/health/body/23074-heart-chambers) ) that briefly hold blood before moving it. Electrical impulses make your heart beat, moving blood through these chambers. Your [ brain ](https://my.clevelandclinic.org/health/body/22638-brain) and [ nervous system ](https://my.clevelandclinic.org/health/articles/21202-nervous-system) direct your heart’s function. Care at Cleveland Clinic [ Cardiology Care ](https://my.clevelandclinic.org/services/cardiology-care) [ Cardiology Care for Children ](https://my.clevelandclinic.org/pediatrics/services/cardiology-care) [ Make an Appointment ](https://my.clevelandclinic.org/webappointment/what-to- expect) Advertisement Cleveland Clinic is a non-profit academic medical center. Advertising on our site helps support our mission. We do not endorse non-Cleveland Clinic products or services. [ Policy ](https://health.clevelandclinic.org/advertising) ## Function ### What is the function of the heart? Your heart’s main function is to move blood throughout your body. Blood brings oxygen and nutrients to your cells. It also takes away carbon dioxide and other waste so other organs can dispose of them. Your heart also: * Controls the rhythm and speed of your [ heart rate ](https://my.clevelandclinic.org/health/diagnostics/heart-rate) . * Maintains your [ blood pressure ](https://my.clevelandclinic.org/health/diseases/17649-blood-pressure) . Your heart works with these body systems to control your heart rate and other body functions: * Nervous system: Your nervous system helps control your heart rate. It sends signals that tell your heart to beat slower during rest and faster during stress. * Endocrine system: Your [ endocrine system ](https://my.clevelandclinic.org/health/articles/21201-endocrine-system) sends out [ hormones ](https://my.clevelandclinic.org/health/articles/22464-hormones) . These hormones tell your blood vessels to constrict or relax, which affects your blood pressure. Hormones from your [ thyroid ](https://my.clevelandclinic.org/health/body/23188-thyroid) gland can also tell your heart to beat faster or slower. ## Anatomy ![The chambers and valves of the heart.](https://my.clevelandclinic.org/-/scassets/images/org/health/articles/21704-heart- inside) Blood moves through chambers inside your heart. ### What are the parts of the heart? The parts of your heart are like the parts of a building. Your heart anatomy includes: * Walls. * Chambers that are like rooms. * [ Valves ](https://my.clevelandclinic.org/health/body/17067-heart-valves) that open and close like doors to the rooms. * [ Blood vessels ](https://my.clevelandclinic.org/health/body/21640-blood-vessels) like plumbing pipes that run through a building. * An electrical [ conduction system ](https://my.clevelandclinic.org/health/body/21648-heart-conduction-system) like electrical power that runs through a building. #### Heart walls Your heart walls are the muscles that contract (squeeze) and relax to send blood throughout your body. A layer of muscular tissue called the septum divides your heart walls into the left and right sides. Your heart walls have three layers: * Endocardium: Inner layer. * Myocardium: Muscular middle layer. * Epicardium: Protective outer layer. The epicardium is one layer of your [ pericardium ](https://my.clevelandclinic.org/health/body/23561-pericardium) . The pericardium is a protective sac that covers your entire heart. It produces fluid to lubricate your heart and keep it from rubbing against other organs. #### Heart chambers Your heart has four separate chambers. You have two chambers on the top (atrium, plural atria) and two on the bottom (ventricles), one on each side of your heart. * Right atrium: Two large veins deliver oxygen-poor blood to your right atrium. The superior [ vena cava ](https://my.clevelandclinic.org/health/body/22619-vena-cava) carries blood from your upper body. The inferior vena cava brings blood from your lower body. Then the right atrium pumps the blood to your right ventricle. * Right ventricle: The lower right chamber pumps the oxygen-poor blood to your [ lungs ](https://my.clevelandclinic.org/health/articles/8960-lungs-how-they-work) through the pulmonary artery. The lungs reload the blood with oxygen. * Left atrium: After the lungs fill your blood with oxygen, the pulmonary veins carry the blood to the left atrium. This upper chamber pumps the blood to your left ventricle. * Left ventricle: The left ventricle is slightly larger than the right. It pumps oxygen-rich blood to the rest of your body. #### Heart valves Your heart valves are like doors between your heart chambers. They open and close to allow blood to flow through. They also keep your blood from moving in the wrong direction. ##### Atrioventricular valves The atrioventricular (AV) valves open between your upper and lower heart chambers. They include: * Tricuspid valve: Door between your right atrium and right ventricle. * Mitral valve: Door between your left atrium and left ventricle. ##### Semilunar valves Semilunar (SL) valves open when blood flows out of your ventricles. They include: * Aortic valve: Opens when blood flows out of your left ventricle to your [ aorta ](https://my.clevelandclinic.org/health/articles/17058-aorta-anatomy) (artery that carries oxygen-rich blood to your body). * [ Pulmonary valve ](https://my.clevelandclinic.org/health/body/24273-pulmonary-valve) : Opens when blood flows from your right ventricle to your [ pulmonary arteries ](https://my.clevelandclinic.org/health/articles/21486-pulmonary-arteries) (the only arteries that carry oxygen-poor blood to your lungs). #### Blood vessels Your heart pumps blood through three types of blood vessels: * [ Arteries ](https://my.clevelandclinic.org/health/body/22896-arteries) carry oxygen-rich blood from your heart to your body’s tissues. The exception is your pulmonary arteries, which go to your lungs. * [ Veins ](https://my.clevelandclinic.org/health/body/23360-veins) carry oxygen-poor blood back to your heart. * [ Capillaries ](https://my.clevelandclinic.org/health/body/21988-capillaries) are small blood vessels where your body exchanges oxygen-rich and oxygen-poor blood. ##### Coronary arteries Your heart receives nutrients through a network of [ coronary arteries ](https://my.clevelandclinic.org/health/articles/17063-coronary-arteries) . These arteries run along your heart’s surface. They serve the heart itself and include the: * Left coronary artery: Divides into two branches (the circumflex artery and the left anterior descending artery). * [ Circumflex artery ](https://my.clevelandclinic.org/health/body/23926-circumflex-artery) : Supplies blood to the left atrium and the side and back of the left ventricle. * [ Left anterior descending artery ](https://my.clevelandclinic.org/health/body/23985-left-anterior-descending-artery) (LAD): Supplies blood to the front and bottom of the left ventricle and the front of the septum. * Right coronary artery (RCA): Supplies blood to the right atrium, right ventricle, bottom portion of the left ventricle and back of the septum. #### Electrical conduction system Your heart’s conduction system is like the electrical wiring of a building. It controls the rhythm and pace of your [ heartbeat ](https://my.clevelandclinic.org/health/articles/17064-heart-beat) . Signals start at the top of your heart and move down to the bottom. Your conduction system includes: * Sinoatrial (SA) node: Sends the signals that make your heart beat. * Atrioventricular (AV) node: Carries electrical signals from your heart’s upper chambers to its lower ones. * Left bundle branch: Sends electric impulses to your left ventricle. * Right bundle branch: Sends electric impulses to your right ventricle. * Bundle of His: Sends impulses from your AV node to the Purkinje fibers. * Purkinje fibers: Make your heart ventricles contract and pump out blood. Advertisement ### Where is your heart located? Your heart is in the front of your chest. It sits slightly behind and to the left of your sternum (breastbone), which is in the middle of your chest. Your heart is slightly on the left side of your body. It sits between your right and left lungs. The left lung is slightly smaller to make room for the heart in your left chest. Your rib cage protects your heart. ### What does your heart look like? Your heart looks a little bit like an upside-down pyramid with rounded edges. Large blood vessels go into and out of your heart to bring blood into and away from your heart. They connect your heart to the rest of your body, which it supplies with blood and oxygen. #### How big is your heart? Everyone’s heart is a slightly different size. Generally, your heart is about the same size as your fist. On average, an adult’s heart weighs about 10 ounces. Your heart may weigh a little more or a little less, depending on your body size and sex. Advertisement ## Conditions and Disorders ### What are the common conditions and disorders that affect your heart? Heart conditions are among the most common types of disorders. In the United States, heart disease is the leading cause of death. Common conditions that affect your heart include: * [ Arrhythmia ](https://my.clevelandclinic.org/health/diseases/16749-arrhythmia) : A heartbeat that’s too fast, too slow or beats with an irregular rhythm. * [ Cardiomyopathy ](https://my.clevelandclinic.org/health/diseases/16841-cardiomyopathy) : Unusual thickening, enlargement or stiffening of your heart muscle. * [ Congestive heart failure ](https://my.clevelandclinic.org/health/diseases/17069-heart-failure-understanding-heart-failure) : Your heart is too stiff or too weak to properly pump blood throughout your body. * [ Coronary artery disease ](https://my.clevelandclinic.org/health/diseases/16898-coronary-artery-disease) : Plaque buildup that leads to narrow coronary arteries. * [ Diabetes ](https://my.clevelandclinic.org/health/diseases/7104-diabetes) : Your blood sugar is higher than it should be. * [ Heart attack (myocardial infarction) ](https://my.clevelandclinic.org/health/diseases/16818-heart-attack-myocardial-infarction) : A sudden coronary artery blockage that cuts off oxygen to part of your heart muscle. * [ Heart valve disease ](https://my.clevelandclinic.org/health/diseases/17639-what-you-need-to-know-heart-valve-disease) : A valve in your heart isn’t working right. * [ High blood pressure ](https://my.clevelandclinic.org/health/diseases/4314-hypertension-high-blood-pressure) : Your blood is pushing too hard against your artery walls. * [ High cholesterol ](https://my.clevelandclinic.org/health/diseases/21656-hyperlipidemia) : Your blood has too many fats in it. * [ Pericarditis ](https://my.clevelandclinic.org/health/diseases/17353-pericarditis) : Inflammation in your heart’s lining (pericardium). #### Common signs or symptoms of heart conditions Symptoms of heart conditions include: * [ Chest pain ](https://my.clevelandclinic.org/health/symptoms/21209-chest-pain) . * [ Heart palpitations ](https://my.clevelandclinic.org/health/diseases/17084-heart-palpitations) . * [ Dizziness ](https://my.clevelandclinic.org/health/symptoms/6422-dizziness) . * [ Shortness of breath ](https://my.clevelandclinic.org/health/symptoms/16942-dyspnea) . * [ Fatigue ](https://my.clevelandclinic.org/health/symptoms/21206-fatigue) . * [ Swelling ](https://my.clevelandclinic.org/health/diseases/12564-edema) in your lower body. #### Common tests to check the health of your heart Tests to check your heart health include: * [ Blood pressure measurement ](https://my.clevelandclinic.org/health/diagnostics/25068-blood-pressure-measurement) . * [ Electrocardiogram ](https://my.clevelandclinic.org/health/diagnostics/16953-electrocardiogram-ekg) (EKG). * [ Echocardiogram ](https://my.clevelandclinic.org/health/diagnostics/16947-echocardiogram) . * [ Chest X-ray ](https://my.clevelandclinic.org/health/diagnostics/10228-chest-x-ray) . * [ Blood tests ](https://my.clevelandclinic.org/health/diagnostics/22207-cardiac-blood-tests) . * [ Cardiac catheterization ](https://my.clevelandclinic.org/health/diagnostics/16832-cardiac-catheterization) . * [ Computed tomography ](https://my.clevelandclinic.org/health/diagnostics/16834-cardiac-computed-tomography) (CT). * [ Heart MRI ](https://my.clevelandclinic.org/health/diagnostics/21961-heart-mri) (magnetic resonance imaging). * [ Stress test ](https://my.clevelandclinic.org/health/diagnostics/16984-exercise-stress-test) . ### Common treatments for the heart Treatments for heart conditions include: * Medicine to [ lower blood pressure ](https://my.clevelandclinic.org/health/treatments/21811-antihypertensives) or [ prevent clotting ](https://my.clevelandclinic.org/health/treatments/22288-anticoagulants) , for example. * Changes to daily habits, like what you eat and how much physical activity you get. * Medical devices like a [ pacemaker ](https://my.clevelandclinic.org/health/treatments/17360-permanent-pacemaker) . * Procedures like [ catheter ablation ](https://my.clevelandclinic.org/health/treatments/16851-catheter-ablation) or [ angioplasty ](https://my.clevelandclinic.org/health/treatments/22060-angioplasty) . * Operations like [ coronary artery bypass surgery ](https://my.clevelandclinic.org/health/treatments/16897-coronary-artery-bypass-surgery) or a [ valve replacement ](https://my.clevelandclinic.org/health/treatments/23966-heart-valve-replacement) . ## Care ### How can I keep my heart healthy? If you have a condition that affects your heart, follow your healthcare provider’s treatment plan. It’s important to take medications at the right times and in the right amounts. You can also make lifestyle changes to keep your heart healthy. You can strive to: * Achieve and maintain a weight that’s healthy for you. * Drink [ alcohol ](https://my.clevelandclinic.org/health/articles/16728-alcohol--your-heart-health) in moderation. * [ Eat heart-healthy foods ](https://my.clevelandclinic.org/health/articles/17079-heart-healthy-diet) like plenty of fruits, vegetables and whole grains. * Be physically active for at least 150 minutes per week. * Limit how much sodium you consume. * Manage your [ stress ](https://my.clevelandclinic.org/health/articles/11874-stress) with healthy strategies like [ meditation ](https://my.clevelandclinic.org/health/articles/17906-meditation) or journaling. * [ Quit smoking ](https://my.clevelandclinic.org/health/articles/8699-quitting-smoking) and/or using tobacco products and avoid [ secondhand smoke ](https://my.clevelandclinic.org/health/articles/10644-secondhand-smoke-dangers) . If you smoke, ask a healthcare provider for resources to help you quit. ## Additional Common Questions ### What should I ask my doctor about my heart? You may want to ask your healthcare provider: * How does my family history affect my heart health? * What can I do to lower my blood pressure? * How do my [ cholesterol levels ](https://my.clevelandclinic.org/health/articles/11920-cholesterol-numbers-what-do-they-mean) affect my heart? * What are the symptoms of a heart attack? * What foods should I eat to prevent heart disease? A note from Cleveland Clinic As the main organ of your circulatory system, your heart keeps you alive. It pumps blood throughout your body, bringing oxygen to your cells and tissues. Since your heart plays such a vital role, it’s important to take care of it. Conditions that affect your heart are very common, but you have the power to make changes for a stronger heart. Ask your healthcare provider how you can improve your heart health. [ ](mailto:?subject=Cleveland Clinic - Heart&body=https://my.clevelandclinic.org/health/body/21704-heart) Medically Reviewed Last reviewed by a Cleveland Clinic medical professional on 01/26/2024. Learn more about our [ editorial process ](https://my.clevelandclinic.org/about/website/editorial-policy) . #### References Advertisement Cleveland Clinic is a non-profit academic medical center. Advertising on our site helps support our mission. We do not endorse non-Cleveland Clinic products or services. 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All Rights Reserved.	biology	4090032	https://sv.wikipedia.org/wiki/Calochortus%20clavatus	Calochortus clavatus	Calochortus clavatus är en liljeväxtart som beskrevs av Sereno Watson. Calochortus clavatus ingår i släktet Calochortus och familjen liljeväxter. Artens utbredningsområde är Kalifornien. Underarter Arten delas in i följande underarter: C. c. avius C. c. clavatus C. c. gracilis C. c. pallidus C. c. recurvifolius Bildgalleri Källor Externa länkar Liljeväxter clavatus	swedish	1.351416
two_organs_but_not_all/PMC3640200.txt	Skip to main content U.S. flagAn official website of the United States government Here's how you know NIH NLM LogoLog in Access keysNCBI HomepageMyNCBI HomepageMain ContentMain Navigation Preview improvements coming to the PMC website in October 2024. Learn More or Try it out now. Search PMC Full-Text Archive Search PMC Full-Text Archive Search in PMC Advanced Search User Guide Journal List Eur Heart J PMC3640200 As a library, NLM provides access to scientific literature. Inclusion in an NLM database does not imply endorsement of, or agreement with, the contents by NLM or the National Institutes of Health. Learn more: PMC Disclaimer \| PMC Copyright Notice Logo of ehj Eur Heart J. 2013 May 1; 34(17): 1270–1278. Published online 2013 Feb 10. doi: 10.1093/eurheartj/eht023 PMCID: PMC3640200 PMID: 23401492 The eye and the heart Josef Flammer,1,* Katarzyna Konieczka,1 Rosa M. Bruno,2 Agostino Virdis,2 Andreas J. Flammer,3 and Stefano Taddei2 Author information Article notes Copyright and License information PMC Disclaimer Go to: Abstract The vasculature of the eye and the heart share several common characteristics. The easily accessible vessels of the eye are therefore—to some extent—a window to the heart. There is interplay between cardiovascular functions and risk factors and the occurrence and progression of many eye diseases. In particular, arteriovenous nipping, narrowing of retinal arteries, and the dilatation of retinal veins are important signs of increased cardiovascular risk. The pressure in the dilated veins is often markedly increased due to a dysregulation of venous outflow from the eye. Besides such morphological criteria, functional alterations might be even more relevant and may play an important role in future diagnostics. Via neurovascular coupling, flickering light dilates capillaries and small arterioles, thus inducing endothelium-dependent, flow-mediated dilation of larger retinal vessels. Risk factors for arteriosclerosis, such as dyslipidaemia, diabetes, or systemic hypertension, are also risk factors for eye diseases such as retinal arterial or retinal vein occlusions, cataracts, age-related macular degeneration, and increases in intraocular pressure (IOP). Functional alterations of blood flow are particularly relevant to the eye. The primary vascular dysregulation syndrome (PVD), which often includes systemic hypotension, is associated with disturbed autoregulation of ocular blood flow (OBF). Fluctuation of IOP on a high level or blood pressure on a low level leads to instable OBF and oxygen supply and therefore to oxidative stress, which is particularly involved in the pathogenesis of glaucomatous neuropathy. Vascular dysregulation also leads to a barrier dysfunction and thereby to small retinal haemorrhages. Keywords: Retinal vessels, Cardiovascular risk, Vascular dysregulation, Endothelial function, Systemic hypertension, Systemic hypotension, Retinal venous pressure, Retinal vein occlusion, Glaucoma Go to: Introduction The heart and the eye, two organs at first sight not linked to each other, have more in common than one would expect. The vasculature of the eye, although some peculiarities do exist, shares many features with the vasculature of the heart and is often exposed to the same intrinsic and environmental influences. Thus, the eye, with its easily accessible vasculature, may indeed be a window to the heart, but knowledge about some unique vascular features is necessary. It is the aim of this review (i) to describe the basic characteristics of the vasculature of the eye, (ii) to spark interest for the eye as a ‘vascular’ organ and the inherent advantages of depicting the microvasculature directly, and (iii) to make cardiologists aware of ophthalmologists' concerns about systemic conditions potentially aggravating eye diseases. Go to: Vasculature of the eye Blood supply to the eye faces the following challenges: (i) the retina has the highest oxygen consumption per volume in the body, (ii) the very exposed eye needs constant temperature to function, and (iii) the blood supply should not hinder the optical function. Nature has solved these needs in the following ways: (i) transparent parts such as the cornea and lens are supplied by a transparent aqueous humour; (ii) within the retina, oxygen transport is facilitated by intracellular haemoglobin; (iii) the translucent retina has only a few blood vessels and the photoreceptors receive their oxygen and nutrition from the choroid, which, in turn, has the highest blood flow (BF) per volume in the body; and (iv) the eye has no lymphatic vessels and it possesses an immune privilege. Go to: Anatomy of ocular circulation The circulation of the eye essentially comprises four parts: (i) the circulation of the anterior part of the eye, particularly the ciliary body that produces the aqueous humour; (ii) a retinal circulation similar to brain circulation but lacks autonomic innervation; (iii) a choroidal vasculature with fenestrated capillaries and the greatest density of autonomic innervations known in the body; and (iv) the optic nerve head (ONH);1 (Figure 1). An external file that holds a picture, illustration, etc. Object name is eht02301.jpg Figure 1 The ciliary body is highly perfused and produces the aqueous humour (left: photo taken from the back of the eye). The optic nerve head has a very dense network of long capillaries (middle). The retinal circulation is similar to brain circulation but without autonomic innervation. In contrast, the vasculature of the choroid is densely innervated (right). Go to: Regulation of ocular blood flow The retinal BF is auto-regulated2 and therefore—within a certain range—is independent of perfusion pressure (PP). The main regulators are the vascular endothelium cells and the neural and glial cells.3 A simplified function of neurovascular coupling (NVC) is depicted in Figure 2. If flickering light is projected onto the retina, both the arteries and veins dilate via a process mediated mainly by nitric oxide (NO). The visual stimulation of the retina primarily dilates capillaries and very small arterioles, thereby inducing a flow-mediated dilation of the larger retinal vessels, as observed with a retinal vessel analyser.4 Therefore, these tests also provide hints regarding the function of the vascular endothelium and may thus be particularly interesting for the cardiologist, as endothelial dysfunction is associated with most, if not all, cardiovascular risk factors.5 The densely innervated choroid (Figure 1) reacts to physical and psychological stressors as well as to temperature. If a cold airstream blows towards the eye, cold receptors in the sclera induce an increase in choroid BF.6 An external file that holds a picture, illustration, etc. Object name is eht02302.jpg Figure 2 The size of the retinal vessels is influenced by neural and glial cells (neurovascular coupling), shown in a simplified view on the left. Flickering light (green bar) leads to vasodilation of arteries (red) and veins (blue) in healthy subjects (middle) and to a lesser extent in subjects with vascular dysregulation (right). The green curves indicate the normal range. (Modified after Flammer J, Mozaffarieh M, Bebie H. Basic Sciences in Ophthalmology–Physics and Chemistry. Springer Publications, in print, with permission.) The ONH BF is influenced by the NVC but also by circulating molecules diffusing from the choroid into the ONH. Go to: Measurement of ocular blood flow A number of different methods are available to determine ocular blood flow (OBF), depending on the vessels of interest.7 Retroocular vessels are measured by colour Doppler imaging (Figure 3), while intraocular vessels can be observed directly by ophthalmoscopy or visualized with the help of fluorescence or indocyanine green angiography (Figure 4) and BF velocity can be quantified by Laser Doppler velocimetry. The BF in a capillary bed such as the ONH can be quantified by laser-flowmetry or laser-speckling. The bulk flow to the eye can be estimated by thermography8 (Figure 4). The dynamic changes over time can be observed with a retinal vessel analyser (Figure 2). An external file that holds a picture, illustration, etc. Object name is eht02303.jpg Figure 3 The vessels behind the eye (ophthalmic artery, central retinal artery, and the ciliary arteries) can be visualized and its flow quantified by colour Doppler imaging. Shown is the outcome from the ophthalmic artery of a healthy subject with normal resistivity (middle) and of a glaucoma patient with high resistivity (right). (Modified after Flammer J, Mozaffarieh M, Bebie H. Basic Sciences in Ophthalmology–Physics and Chemistry. Springer Publications, in print, with permission.) An external file that holds a picture, illustration, etc. Object name is eht02304.jpg Figure 4 The bulk flow can be quantified with the help of thermography. Left: A relatively cool eye of a subject with vascular dysregulation in relation to a normal control (middle left). The retinal circulation is visualized with fluorescence angiography (middle right) and choroid circulation with the indocyanine green angiography (right). Go to: Defective ocular blood flow As in all vascularized tissues, a marked reduction in OBF leads to an infarction, such as retinal infarction or ischaemic anterior optic neuropathy (Figure 5). The main causes are arteriosclerosis and emboli (originating from the carotid artery and the heart) or vasculitis such as giant cell arteritis. Arteriosclerosis frequently involves the retroocular vessels at early stages,9 probably due to the mechanical strain imposed by the rotating eye. In contrast, intraocular vessels may show some hyalinosis but not arteriosclerosis. An external file that holds a picture, illustration, etc. Object name is eht02305.jpg Figure 5 Classical ocular blood flow dysfunctions: (i) Anterior ischaemic neuropathy. (ii) Central retinal arterial occlusion. (iii) Embolus in a retinal artery. (iv) Retinal branch vein occlusion. Go to: Are retinal vessels a window to the heart? The cardiologist's perspective The retina is a unique site where the microcirculation can be imaged directly. Thus, it provides a window for detecting changes in microvasculature relating to the development of cardiovascular diseases such as arterial hypertension or coronary heart disease10 (Figure 6). Analysis of the retinal microvasculature provides information about the structure as well as the function of the vessels and this information can be easily obtained repeatedly over time. However, its clinical application has only recently gained some attention.11 An external file that holds a picture, illustration, etc. Object name is eht02306.jpg Figure 6 Examples of retinal vascular signs in patients with cardiovascular diseases. Black arrow: focal arteriolar narrowing. White arrow: arterio-venous nicking. Yellow arrow: haemorrhage. Blue arrow: micro-aneurysm. Red arrow: cotton wool spot. (From Liew and Wang,10 reused with permission from the author and the publisher.) Structural retinal changes Systemic cardiovascular diseases like arterial hypertension, coronary heart disease, or diabetes mellitus, as well as obesity are all associated with structural vascular changes in the retina. These include narrowing of arterioles, dilatation of veins, and a decrease in the arteriovenous ratio (AVR). According to the classification by Keith, Wagener, and Barker, four grades of retinal changes in hypertensive patients have been proposed: focal or general arteriolar narrowing (grade 1), arterio-venous nipping (grade 2), flame-shaped haemorrhages and exudates (grade 3), and papilledema (grade 4). At present, because of the often early diagnosis and treatment of hypertension, grades 3 and 4 are very rarely seen. In contrast, arteriolar narrowing and arterio-venous nipping are observed much more frequently. However, the clinical and prognostic significance of such mild degrees of retinopathy has been questioned,12–14 because these alterations appear to be largely non-specific arteriolar changes, except in young patients in whom modification from a normal retina should raise doubts. In contrast, grade 3 and 4 retinal changes are associated with an increased risk of cardiovascular events.15,16 Recent selective methodologies for investigating retinal changes in hypertension allow quantification of geometrical and topological properties of the arteriolar and venular tree. Evidence from both cross-sectional and longitudinal studies utilizing these new techniques documented an independent association between narrowed retinal arteriolar diameter and elevated blood pressure and showed that narrow retinal arterioles and smaller AVR may precede arterial hypertension and predict the development of hypertension in initially normotensive individuals.17–19 Structural alterations of peripheral small resistance arteries, as indicated by an increased media-to-lumen ratio (M/L), are frequently associated with several cardiovascular risk factors, including hypertension or diabetes mellitus, and contribute to the development of target organ damage.20 At present, the best methodological approach to detecting M/L in small resistance arteries is wire or pressure micromyography, which allows a demonstration that an increased M/L of subcutaneous small arteries relates to reduced coronary flow reserve and to some indexes of cardiac damage in hypertensive patients.21,22 In addition, the M/Ls of peripheral small arteries are independently associated with the occurrence of cardiovascular events, either in a high-risk population or in patients at low-moderate risk.23,24 Unfortunately, the invasive nature of this measurement, which requires a biopsy of subcutaneous fat from the glutaeal or omental regions, prevents larger-scale application of this method. In order to develop alternative non-invasive approaches for the evaluation of microvascular structure, the interest of many researchers was focused on the retinal vascular district. A recent and promising approach includes a confocal measurement of the external diameter of retinal arterioles and an evaluation of the internal diameter with a laser Doppler technique. From these two measurements, it is possible to calculate the wall-to-lumen (W/L) ratio of retinal arterioles.25 By this new approach, called scanning laser Doppler flowmetry (SLDF), the authors observed an increased W/L in essential hypertensive patients,26 an alteration even more evident in hypertensive patients with previous cardiovascular events.25 In a very recent report, the W/L of retinal arterioles evaluated by SLDF has been compared with the M/L of subcutaneous small arteries, assessed by the micromyographic technique, in the same subjects. A close correlation was observed between M/L and W/L, thus indicating that SLDF may provide similar information regarding microvascular morphology compared with invasive, but prognostically relevant, micromyographic measurements of the M/L of subcutaneous small arteries.27 Other interesting reports evidenced structural retinal changes as an early indicator of the presence28 and severity of coronary artery disease.29 Furthermore, there is a relation with coronary artery calcification and myocardial perfusion.30,31 Recently fractal analysis and quantification of microvascular branching has gained some interest in cardiovascular literature and has been recently demonstrated to predict cardiovascular mortality. Patients with suboptimal branching (very dense or very sparse) have an impaired prognosis.32 Future studies are needed to confirm the usefulness of such a non-invasive retinal microvascular approach to obtain a better stratification of cardiovascular risk and its prognostic relevance. A further advantage of retinal vessel analysis is the possibility of depicting not only arteries but also veins. Similar to arteries, veins are not mere passive vessels, but may also actively adapt to the vascular needs. Contrary to the retinal arteries, dilated venules bear a worse cardiovascular prognosis.33 These retinal veins, however, are often dilated by high retinal venous pressure (RVP) induced by local vasoconstriction at the level of the ONH. Functional retinal changes These morphological findings, however, should be supplemented by functional tests. As mentioned above, flicker light-induced vasodilation of the retinal vessel arteries and veins may give important functional information about the vascular endothelium. An impaired endothelial function is characteristic (although not pathognomonic) of atherosclerosis, a process beginning early in life and eventually leading to myocardial infarction, stroke, and other devastating vascular complications. Endothelial dysfunction precedes the development of morphological vascular changes, and thus, the assessment of endothelial function provides important diagnostic and prognostic information, particularly in patients with cardiovascular risk factors.5,34 In the past several years, invasive and non-invasive tools for in vivo assessment of endothelial function have been developed, all with their inherent advantages and disadvantages.35 Flicker light-induced vasodilatation in the retinal artery may be a valuable additional tool in this respect, particularly as it has been shown to be endothelium- and NO-dependent, however, independent from sympathetic innervations. Indeed, NO plays a role not only in the maintenance of retinal arterial and venous tone, but also in hyperaemic responses to flickering light, since the latter was abolished by systemic infusion of a NO-synthase inhibitor.36 Reduced flicker light-induced vasodilatation has already been demonstrated in patients with cardiovascular risk factors, such as diabetes, hypertension, obesity, and dyslipidaemia, and can be improved with the respective therapy.37–39 This was first demonstrated in essential hypertension. The increase in BF velocity in the central retinal artery and retinal capillary flow induced by flickering, as well as their decrease induced by NO-synthase inhibition, both present in healthy subjects, were abolished in young, untreated patients with uncomplicated hypertension.40 Interestingly, 7 days of treatment with an angiotensin receptor blocker can partially restore retinal endothelial function40,41 in parallel to what occurs in other districts.42 At the moment, these promising data are limited by small sample size and cross-sectional design. Future research should focus on the relationship between retinal vascular reactivity and other established techniques for the study of endothelial function, as well as on their possible prognostic significance, since this approach can provide unique insight into cerebral microcirculation, which is a crucial district for atherosclerotic, and in particular hypertensive, organ damage. Go to: Pathophysiology of tissue damage: an ophthalmologic perspective Cardiologists are concerned about potential consequences of cardiovascular risk factors and whether the eye could serve as a window for morphological and functional changes preceding the changes in the heart. On the other hand, ophthalmologists are concerned about systemic conditions inducing or aggravating eye diseases. For the optimal treatment of the patients, it is of importance for the cardiologist or internist to understand the vascular pathophysiology behind the most common eye diseases. Indeed, many prevalent eye diseases can be considered systemic diseases, e.g. diabetic or hypertensive retinopathy and, to some extent, also glaucoma. The impact of chronic hypoxia While acute and severe hypoxia leads to infarction, chronic hypoxia leads to an increase in Hypoxia-inducible factor (HIF)-1alpha (Figure 7) and thereby to an up-regulation of a number of molecules such as endothelin-1 (ET-1) and vascular endothelial growth factor (VEGF). This, in turn, has three potential consequences: stimulation of neovascularisation, weakening of the blood–retina barrier (BRB), and local vasoconstriction of veins. An external file that holds a picture, illustration, etc. Object name is eht02307.jpg Figure 7 Left: Under hypoxic condition hypoxia-inducible factor-1 alpha (HIF-1α) is increased and enhances expression of genes such as endothelin-1 or vascular endothelial growth factor. (From Flammer J, Mozaffarieh M, Bebie H. Basic Sciences in Ophthalmology–Physics and Chemistry. Springer Publications, in print, with permission.) This leads to weakening of the BRB (an example is the macular oedema, second from left) or to neovascularization (an example is wet age-related macular degeneration, second from right) Right: Antibody or antibody fragment injection into the eye binds VEGF, thereby restoring wet age-related macular degeneration in a dry age-related macular degeneration. This is best exemplified with age-related macular degeneration (AMD) normally remaining ‘dry’ and only moderately reducing visual acuity. One potential consequence of dry AMD is that hypoxia can induce growth of new vessels from the choroid into the retina thereby turning it to ‘wet’ AMD. One of the main stimuli involved is VEGF. Binding of VEGF by antibodies or fragments of antibodies thereby reduces symptoms relatively quickly (Figure 7). However, note that this treatment does not eliminate the underlying disease of the AMD or the hypoxia, and therefore, the treatment needs to be repeated. The impact of systemic hypertension As outlined above, severe arterial hypertension leads to hypertensive retinopathy. Hypertension and all other risk factors for arteriosclerosis,43 however, are also related to other eye diseases such as cataracts, AMD and increased intraocular pressure (IOP).44 The impact of systemic hypotension Arterial hypotension is also very important for the eye, but far less known. It is a particularly well-established risk factor for glaucomatous optic neuropathy (GON).45,46 As a consequence, blood pressure should not be lowered too rigorously in patients suffering from both systemic arterial hypertension and glaucoma. Spontaneous systemic hypotension [as it occurs particularly in the context of primary vascular dysregulation (PVD)] is very often observed in patients with normal tension glaucoma (NTG). Glaucoma patients with progression of GON despite a normal or normalized IOP may profit from a therapeutical increase in blood pressure, although unfortunately, controlled studies are not yet available. Besides systemic hypotension, nocturnal over- and non-dipping as well as increased blood pressure (BP) fluctuation are related to progression of GON. Hypotension is related to increased sensitivity to ET-1,47 which further reduces OBF. The relationship between PP or PP-fluctuation and GON-progression is now clearly established.48 Perfusion pressure is defined as arterial pressure minus venous pressure. However, in most of these studies, RVP was not measured but calculated based on the assumption that the venous pressure is equal to IOP, an assumption that is not correct in all cases. Retinal venous pressure RVP must be at least as high as the IOP (otherwise the vessels would collapse) and as high as the cerebrospinal fluid pressure, since the central retinal vein leaves the eye via the anterior optic nerve and then crosses the subarachnoid space. Retinal venous pressure is measured using a contact lens dynamometer.49 This pressure is sometimes higher than the IOP even in healthy subjects, but increases are quite often observed in conditions like glaucoma50 and diabetes mellitus, at high altitudes and in subjects with PVD. Retinal venous pressure varies over time and can be markedly influenced by drugs. Consequently, the PP is often smaller than previously assumed and pharmacological reduction of RVP is a promising approach to improving OBF. Whether increased venous pressure is a marker of increased cardiovascular risk is not known yet, but might deserve further evaluation. Go to: Dysregulation of blood flow In addition to responding to PP and structural changes in ocular blood vessels, OBF is markedly influenced by local regulation.51 Many determining factors for regulation are involved, meaning that different types of dysregulation can occur. We distinguish secondary from primary types of dysregulation.52 Secondary vascular dysregulation Pathological processes such as inflammations often lead to changes in the circulating blood and this, in turn, can have an effect in remote organs. One frequently encountered alteration is an increase in ET-1 level in circulating blood, and one of the remote tissues most often involved is the ONH. The reason for this is the fact that the blood–brain barrier in the ONH is partly abrogated by the proximity to the fenestrated vessels of the choroid (Figure 8). Increased ET-1 level in the circulating blood is found in patients with multiple sclerosis (MS)53 and transiently during optic neuritis,54 in rheumatoid arthritis55 and fibromyalgia.56 While increased ET-1 levels in the blood have little impact on brain or retinal BF, as long as the barrier is intact, it has a major influence on BF of the choroid and the ONH.57 The ONH, in such cases, sometimes appears slightly pale. In the case of giant cell arteritis, ET-1 is particularly increased in the subgroup of patients in which the eye is involved.58 In addition, in such cases, the ET-receptors are also up-regulated.59 The involvement of the ET system in giant cell arteritis explains why affected patients often indicate symptoms similar to amaurosis fugax, in addition to reporting a reduced feeling of thirst, both preceding the sudden blindness. An external file that holds a picture, illustration, etc. Object name is eht02308.jpg Figure 8 In the optic nerve head (ONH) (second from left), the blood–brain barrier is partly abrogated by the proximity to the fenestrated vessels of the choroid (left). Unstable oxygen supply in glaucoma patients increases superoxide anion (O2−) in the mitochondria of the axons. If neighbouring astrocytes are activated, nitric oxide (NO) diffuses into the axons resulting in the damaging peroxynitrite (ONOO−) (second from right). Indeed, visual field progression in glaucoma patients (right) increases not only with increasing intraocular pressure (green) but also with decreasing ocular blood flow (red). (From Flammer and Mozaffarieh,114 with permission.) Primary vascular dysregulation Even more important than the secondary vascular dysregulation is the so-called PVD syndrome.7,60 PVD is a predisposition to react differently to a number of stimuli like coldness61,62 or physical or emotional stress. The most prominent sign is the dysregulation of vessels, which gave the syndrome its name.63 However, PVD encompasses a number of additional signs and symptoms. In terms of blood vessels, vasospasms are the best known. This explains why, in the past, the term vasospastic syndrome64 was often used. We prefer the term PVD, as the syndrome can also include inappropriate vasodilation or barrier dysfunction, among other symptoms. Primary vascular dysregulation occurs more often in females than in males,65 in thin more than in obese subjects,65–67 in academics more than in blue-collar workers,68 and in Asians more than in Caucasians. Patients tend to be more active both physically and mentally. The main signs are arterial hypotension (particularly when they are young)69 and cold extremities with an increased response to coldness.61 In addition, patients often indicate altered drug sensitivity (partly due to altered expression of ABC-proteins),70 decreased sensations of thirst71 [ET-1 increases the prostaglandin (PG) E2 level in the centre of thirst], and prolonged sleep onset time72 (as we all can only fall asleep after warming up our feet). In terms of ocular perfusion, PVD subjects often have reduced autoregulation,73 increased spatial irregularities of retinal vessels, stiffer vessels (i.e. fast pulse wave propagation), and reduced NVC74,75 (Figure 2). Interestingly, in PVD subjects, OBF correlates with BF in the extremities,76,77 while such a correlation is absent in non-PVD subjects. Primary vascular dysregulation predisposes patients to certain eye diseases such as retinal arterial78 and vein occlusion79 or central serous chorioretinopathy.80 However, it is a clear risk factor for glaucoma, particularly NTG.81 Furthermore, subjects with PVD have an inverse response pattern regarding choroidal and ONH circulation with respect to blood gas perturbation.82 Primary vascular dysregulation has a particular impact on glaucoma.52 If glaucomatous damage occurs or progresses despite an IOP in the normal range, vascular factors are most often involved.83 Healthy subjects with PVD and glaucoma patients progressing despite a normal IOP have the following shared characteristics: reduced auto-regulation84,85 stiffer retinal vessels,86 reduced NVC,74,75 correlation between OBF and finger BF,87 increased level of ET-1,71 and altered gene expression in circulating lymphocytes.87 In addition, an increased level of DNA breaks,88 silent myocardial ischaemia,89 and nocturnal over-dipping90 occur particularly in glaucoma patients with PVD. Nocturnal hypotension might partly be due to decreased reuptake of sodium in the proximal renal tubuli91 due to stimulation of PGE2 by ET-1. Glaucoma patients have also demonstrated an abnormal ET-1 response to postural changes.92 Although PVD leads to vascular-induced damage in the eye, its impact on the heart, on the coronary microcirculation in particular, needs further study. Go to: Oxidative stress as a consequence of unstable ocular blood flow Oxidative stress plays a crucial role in many diseases. In case of glaucoma, the role of hypoxia in the pathogenesis of GON has long been debated.93 On the one hand, progression of GON is linked to reductions in OBF85 (Figure 8). On the other hand, hypoxia (as it occurs, for example, in the context of coronary artery disease or MS), while sometimes leading to mild atrophy of ONH, rarely leads to GON. The eye can adapt quite well to mild and stable hypoxia. In contrast, the eye can adapt less well to oxidative stress. Unstable oxygen supply increases oxidative stress, particularly in the mitochondria of the ONH. This, in turn, leads to GON if adjacent astrocytes are simultaneously activated and induced to overexpress NO synthase-2 (Figure 8). Oxygen supply can be unstable if oxygen saturation fluctuates, as occurs, for example, in sleep apnoea. The more frequent cause is an unstable OBF. The OBF, in turn, is unstable if IOP fluctuates at a high enough level or PP is low enough to exceed the capacity of autoregulation, or if autoregulation itself is disturbed. This is mainly the case in subjects with PVD. The involvement of PVD explains why NTG occurs more often in females than in males,94 but is also more frequent in Asian countries than in Europe or North America.95 Go to: Blood–retina barrier Like the brain, the retina can only properly function if the BRB is intact. The BRB is damaged by inflammation but also by hypoxia.96 Blood flow and barrier dysfunction are therefore linked. Molecules such as ET-1, which are involved in the regulation of the vessel size, also influence the barrier. Macular oedema is one potential manifestation of hypoxia97 (Figure 7). Go to: Retinal haemorrhages Haemorrhages occur if vessels are ruptured. These bleedings are normally large and can also break into the vitreous. Smaller haemorrhages, however, also occur if the BRB is opened at the level of both the endothelial cells (e.g. by VEGF or ET-1) and the basal membrane [by mettalloproteinase-9 (MMP-9)]98 (Figure 9). Indeed, the number of retinal haemorrhages in diabetes patients is correlated with the MMP-9 concentration in the vitreous.99,100 An external file that holds a picture, illustration, etc. Object name is eht02309.jpg Figure 9 Pathogenesis of optic disc splinter haemorrhages: Under normal conditions, the vessels in and around the optic nerve head are watertight. If the barrier is opened at the level of the endothelial cells, small molecules such as water as well as fluorescein can leak out. If, at the same time, the basal membrane in the same area is also weakened, erythrocytes can also escape. (Modified after Grieshaber and Flammer,115 with permission.) Splinter haemorrhages at the border of the ONH also occur in the context of glaucoma.101 In these patients, VEGF,102 ET-1,103 and MMP-9104 are indeed increased in the circulation blood, particularly in glaucoma patients with PVD, which explains the higher prevalence of such haemorrhages in NTG patients and in females. As mentioned before, these molecules can diffuse from the choroid into the neighbouring tissue (Figure 8). However, they can also be over-expressed by the local neural tissue in cases of local hypoxia, which explains why the frequency of haemorrhages, to some extent, is reduced after IOP reduction. If the BRB is opened at the level of the endothelial cells, this can allow the escape of water and small molecules such as fluorescein. If, at the same time, the basal membrane is also weakened by MMP-9, erythrocytes can also escape (Figure 9). Go to: Retinal vein occlusion Retinal vein occlusion (RVO) is often referred to as retinal venous thrombosis. However, increasing evidence now indicates that RVO might occur without thrombosis and that if thrombosis occurs, it might be secondary.105 The risk factors for RVO are similar to those for arterial occlusions, and anticoagulation treatments106 do not protect against RVO. Reduced OBF, glaucoma, PVD,107 and stress increase the risk of RVO and circulating ET-1 levels are increased in nearly all cases.79 In addition, OBF is also very often reduced and RVP increased in the contralateral clinically non-affected eye. Molecules from the circulating blood diffusing into the ONH, or produced locally either by the diseased arteries or by the hypoxic tissue, lead to a local venous constriction and thereby increase RVP.105 This leads to the so-called praestasis syndrome and eventually to a clinical picture of RVO (Figure 10). The weakened BRB further contributes to retinal oedema and haemorrhages. The positive clinical effect of anti-VEGF therapy in humans,108 as well as the positive effect of ET-1 blockers in experimental animals,109 supports this assumption. An external file that holds a picture, illustration, etc. Object name is eht02310.jpg Figure 10 Pathogenesis of retinal vein occlusion: At the lamina cribrosa, the central artery and central vein are topographically very close and share a common adventitia (middle). This enables a molecular cross talk between the two vessels (right). Endothelin-1 (blue), for example, can diffuse from the ailing artery as well as from the adjacent hypoxic tissue to the very sensitive vein, leading to venous constriction. [Modified after Fraenkl SA, Mozaffarieh M, Flammer J. (2010), Figures 1a, 2, 4). With kind permission from Springer Science + Business Media B.V.] Go to: Therapeutic aspects Treatments of diabetes (e.g. with insulin) or vasculitis (with steroids) and the elimination of risk factors for arteriosclerosis (such as reduction of BP in systemic hypertension) are the gold standards. Other treatment modalities, however, are also on the horizon. A very low BP in a patient with progressing GON should be raised with an increased salt intake91 or, in extreme cases, with a very low dose of fludrocortisone,110 although well-controlled intervention studies are not yet available. Magnesium111 and low doses of calcium antagonists112 improve vascular regulation of arteries and veins in the eye, particularly in patients with PVD. Oxidative stress in the mitochondria can be reduced, for example, by ginkgo biloba.113 Go to: Conclusion Ocular blood flow has many aspects in common with the systemic circulation, but also has some peculiarities. This includes the BRB, autoregulation, NVC, the influence of circulating molecules on BF of the ONH, and the lack of autonomic innervation of retinal vessels. In addition to structural vascular abnormalities, the dysregulation of arteries and veins is also important. Intraretinal haemorrhages are often a consequence of disturbed BRB. Venous dysregulation increases RVP and can lead to RVO. While hypoxia plays a major pathophysiological role in diabetic retinopathy and in wet AMD, an unstable oxygen supply contributes to GON by increasing the oxidative stress. While systemic hypertension increases the risk of infarctions or diabetic retinopathy, systemic hypotension and increased fluctuations in BP are risk factors for GON. 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[PubMed] [Google Scholar] Articles from European Heart Journal are provided here courtesy of Oxford University Press OTHER FORMATS PDF (1.3M) ACTIONS Cite Collections SHARE RESOURCES Similar articles Cited by other articles Links to NCBI Databases FOLLOW NCBI Connect with NLM National Library of Medicine 8600 Rockville Pike Bethesda, MD 20894 Web Policies FOIA HHS Vulnerability Disclosure Help Accessibility Careers NLM NIH HHS USA.gov Tell us what you think!Close	biology	1517898	https://sv.wikipedia.org/wiki/Propranolol	Propranolol	Propranolol är en antihypertensiv medicin som agerar på kroppens noradrenerga system. Den minskar aktiviteten hos kroppens sympatiska nervsystem genom att blockera adrenerga beta-receptorer, vilket bland annat leder till sänkt blodtryck. Propranolol skrivs framförallt ut för att behandla sjukdomar i kardiovaskulära systemet, till exempel hjärtinfarkt, högt blodtryck, angina pectoris, men även för giftstruma, migrän, tumörer i binjuremärgen och tremor. Den har även använts experimentellt mot posttraumatiskt stressyndrom, där den verkar minska symptomen på tillståndet. Eftersom betablockerare sänker blodsockret, kan propranolol ge hypoglykemi. Det kan också förvärra obstruktiva lungsjukdomar och sänka pH-värdet i blodet. Ökad drömaktivitet och mardrömmar förekommer vid behandling med propranolol. Dess påverkan på blodkärlen kan leda till vita fingrar. Agranulocytos är en allvarlig biverkning som kan uppkomma. Medicinsk användning Propranolol används för att behandla olika medicinska tillstånd, såsom: Kardiovaskulär Hypertoni Kärlkramp Hjärtinfarkt Takykardi Portahypertension Förebygga blödningar och ascites hos Esofagusvaricer Ångest Tidigare var propanolol en av de bästa behandlingar för hypertoni. Eftersom de inte kunde ge lika bra effekt som andra mediciner, särskilt bland de äldre, blev beta-blockeraren nedgraderad till fjärde-klass i juni 2006 i Storbritannien. Fler och fler bevis hos de mest frekvent använda beta-blockerare vid normal dosering har även påvisat att öka risken för Typ 2-diabetes. Psykiatri Propranolol används ibland till för att behandla scenskräck. Dock finns inte lika bra bevis på att behandla andra ångeststörningar. De utförda experiment i andra psykiatriska områden: Posttraumatiskt stressyndrom (PTSD) och specifika Fobier Förbättringar av sociala förmågor hos personer med Autismspektrumstörning Aggressivt beteende av patienter med Hjärnskada Behandling för överdrivet drickande av vätskor som orsakas av Polydipsi Syntes Propranolol framställs ur 1-naftol och epiklorhydrin. I första steget öppnas epoxid-ringen upp av nukleofil-attack från OH-gruppen i 1-naftol, samtidigt sker 2 stegs protonöverföring. Vätet som sitter på -OH hamnar nu på epoxidsyret. I det andra steget sker en SN2-reaktion, i det här fallet, en nukleofil substitution av isopropylamin på det kolet som binder till den hyfsat bra lämnande grupp -Cl. Därav bildas den önskade slutprodukten - propranolol. Man kan även använda sig av en stark bas som NaOH i det undre steget. Den starka basen NaOH hjälper till att deprotonera vätet som är bunden till OH-gruppen i 1-naftol, samtidigt hjälper den till att stabilisera den bildande alkoxid. Den nya natrium-1-naftolat intermediat som har bildats är en bra nukleofil. På samma sätt kommer den att attackera kolet som binder till -Cl på epiklorhydrin och en ny mellanprodukt bildas. Därefter görs en nukleofil-attack av isopropylamin på det elektrofila kolet som sitter på epoxidsyret. Vilket resulterar i en ringöppning och syret protoneras till en alkohol, därav fås slutprodukten - propranolol. Propranolol är en racematisk blandning – det vill säga, två enantiomerer, R(+) och S(-). S(-)-enantiomeren är ungefär 100 gånger bättre än R(+)-enantiomeren på att blockera adrenerga beta-receptorer. Syntesen ovan (1) visar ett generellt och billigt sätt att syntetisera propranolol. Men för att undvika racemat har forskare behövt hitta andra sätt. Som till exempel syntesen nedan (2) som är steoreoselektiv, vilket betyder att det mesta av produkten blir S(-)-propranolol. (I) K2CO3, CH2=CHCH2Br, acetone, reflux, 12 h; 97-99%; (II) cat-OsO4, (DHQD)2-PHAL, K3Fe(CN)6, K2CO3, t -BuOH:H2O, 0 °C, 12 h, 94-98%; 73-90% ee; (III) SOCl2, Et3N, CH2Cl2, 0 °C, 40 min.; 96-99%; (IV) cat. RuCl3.3H2O, NaIO4, CH3CN:H2O, 0 °C, 30 min., 94-98%; (V) LiBr, THF 25 °C, 2-3 h; (VI) 20% H2SO4, Et2O, 25 °C, 10 h; (VII) K2CO3, MeOH, 0 °C, 2 h, 80-85%; (VIII) iPr-NH2, H2O (cat.), reflux, 2 h, 99%. Referenser Noter Källor Inderal produktinformation på FASS Data sources include Micromedex® (updated Jan 4th, 2017), Cerner Multum™ (updated Jan 10th, 2017), Wolters Kluwer™ (updated Jan 6th, 2017) and others Betablockerare	swedish	0.588656
two_organs_but_not_all/Humaneye.txt	Jump to content Main menu Main menu move to sidebar hide Navigation * [ Main page ](/wiki/Main_Page "Visit the main page \[z\]") * [ Contents ](/wiki/Wikipedia:Contents "Guides to browsing Wikipedia") * [ Current events ](/wiki/Portal:Current_events "Articles related to current events") * [ Random article ](/wiki/Special:Random "Visit a randomly selected article \[x\]") * [ About Wikipedia ](/wiki/Wikipedia:About "Learn about Wikipedia and how it works") * [ Contact us ](//en.wikipedia.org/wiki/Wikipedia:Contact_us "How to contact Wikipedia") * [ Donate ](https://donate.wikimedia.org/wiki/Special:FundraiserRedirector?utm_source=donate&utm_medium=sidebar&utm_campaign=C13_en.wikipedia.org&uselang=en "Support us by donating to the Wikimedia Foundation") Contribute * [ Help ](/wiki/Help:Contents "Guidance on how to use and edit Wikipedia") * [ Learn to edit ](/wiki/Help:Introduction "Learn how to edit Wikipedia") * [ Community portal 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* 9 Images * 10 See also * 11 References * 12 External links Toggle the table of contents # Human eye 53 languages * [ العربية ](https://ar.wikipedia.org/wiki/%D8%B9%D9%8A%D9%86_%D8%A7%D9%84%D8%A5%D9%86%D8%B3%D8%A7%D9%86 "عين الإنسان – Arabic") * [ Авар ](https://av.wikipedia.org/wiki/%D0%93%D3%80%D0%B0%D0%B4%D0%B0%D0%BC%D0%B0%D1%81%D1%83%D0%BB_%D0%B1%D0%B5%D1%80 "ГӀадамасул бер – Avaric") * [ বাংলা ](https://bn.wikipedia.org/wiki/%E0%A6%AE%E0%A6%BE%E0%A6%A8%E0%A6%AC_%E0%A6%9A%E0%A7%8B%E0%A6%96 "মানব চোখ – Bangla") * [ Bân-lâm-gú ](https://zh-min-nan.wikipedia.org/wiki/J%C3%AEn-g%C3%A1n "Jîn-gán – Minnan") * [ Български ](https://bg.wikipedia.org/wiki/%D0%A7%D0%BE%D0%B2%D0%B5%D1%88%D0%BA%D0%BE_%D0%BE%D0%BA%D0%BE "Човешко око – Bulgarian") * [ Bosanski ](https://bs.wikipedia.org/wiki/Ljudsko_oko "Ljudsko oko – Bosnian") * [ Català ](https://ca.wikipedia.org/wiki/Sistema_visual_hum%C3%A0 "Sistema visual humà – Catalan") * [ Čeština ](https://cs.wikipedia.org/wiki/Lidsk%C3%A9_oko "Lidské oko – Czech") * [ ދިވެހިބަސް ](https://dv.wikipedia.org/wiki/%DE%8D%DE%AF "ލޯ – Divehi") * [ Español ](https://es.wikipedia.org/wiki/Ojo_humano "Ojo humano – Spanish") * [ فارسی ](https://fa.wikipedia.org/wiki/%DA%86%D8%B4%D9%85_%D8%A7%D9%86%D8%B3%D8%A7%D9%86 "چشم انسان – Persian") * [ Français ](https://fr.wikipedia.org/wiki/%C5%92il_humain "Œil humain – French") * [ Galego ](https://gl.wikipedia.org/wiki/Ollo_humano "Ollo humano – Galician") * [ 한국어 ](https://ko.wikipedia.org/wiki/%EB%88%88_$%EC%9D%B8%EC%B2%B4$ "눈 $인체$ – Korean") * [ Հայերեն ](https://hy.wikipedia.org/wiki/%D5%84%D5%A1%D6%80%D5%A4%D5%B8%D6%82_%D5%A1%D5%B9%D6%84 "Մարդու աչք – Armenian") * [ हिन्दी ](https://hi.wikipedia.org/wiki/%E0%A4%AE%E0%A4%BE%E0%A4%A8%E0%A4%B5_%E0%A4%A8%E0%A5%87%E0%A4%A4%E0%A5%8D%E0%A4%B0 "मानव नेत्र – Hindi") * [ Hrvatski ](https://hr.wikipedia.org/wiki/Ljudsko_oko "Ljudsko oko – Croatian") * [ Bahasa Indonesia ](https://id.wikipedia.org/wiki/Mata_manusia "Mata manusia – Indonesian") * [ Interlingua ](https://ia.wikipedia.org/wiki/Oculo_human "Oculo human – Interlingua") * [ Iñupiatun ](https://ik.wikipedia.org/wiki/Iri "Iri – Inupiaq") * [ עברית ](https://he.wikipedia.org/wiki/%D7%A2%D7%99%D7%9F_%D7%90%D7%A0%D7%95%D7%A9%D7%99%D7%AA "עין אנושית – Hebrew") * [ Jawa ](https://jv.wikipedia.org/wiki/Soca "Soca – Javanese") * [ ಕನ್ನಡ ](https://kn.wikipedia.org/wiki/%E0%B2%AE%E0%B2%BE%E0%B2%A8%E0%B2%B5%E0%B2%A8_%E0%B2%95%E0%B2%A3%E0%B3%8D%E0%B2%A3%E0%B3%81 "ಮಾನವನ ಕಣ್ಣು – Kannada") * [ Kurdî ](https://ku.wikipedia.org/wiki/%C3%87av%C3%AA_mirov "Çavê mirov – Kurdish") * [ Лакку ](https://lbe.wikipedia.org/wiki/%D0%98%D0%BD%D1%81%D0%B0%D0%BD%D0%BD%D0%B0%D0%BB_%D1%8F "Инсаннал я – Lak") * [ Lietuvių ](https://lt.wikipedia.org/wiki/%C5%BDmogaus_akis "Žmogaus akis – Lithuanian") * [ Magyar ](https://hu.wikipedia.org/wiki/Emberi_szem "Emberi szem – Hungarian") * [ Македонски ](https://mk.wikipedia.org/wiki/%D0%A7%D0%BE%D0%B2%D0%B5%D1%87%D0%BA%D0%BE_%D0%BE%D0%BA%D0%BE "Човечко око – Macedonian") * [ മലയാളം ](https://ml.wikipedia.org/wiki/%E0%B4%AE%E0%B4%A8%E0%B5%81%E0%B4%B7%E0%B5%8D%E0%B4%AF_%E0%B4%A8%E0%B5%87%E0%B4%A4%E0%B5%8D%E0%B4%B0%E0%B4%82 "മനുഷ്യ നേത്രം – Malayalam") * [ Bahasa Melayu ](https://ms.wikipedia.org/wiki/Mata_manusia "Mata manusia – Malay") * [ Nederlands ](https://nl.wikipedia.org/wiki/Menselijk_oog "Menselijk oog – Dutch") * [ नेपाली ](https://ne.wikipedia.org/wiki/%E0%A4%AE%E0%A4%BE%E0%A4%A8%E0%A4%B5_%E0%A4%86%E0%A4%81%E0%A4%96%E0%A4%BE "मानव आँखा – Nepali") * [ नेपाल भाषा ](https://new.wikipedia.org/wiki/%E0%A4%AE%E0%A4%A8%E0%A5%81%E0%A4%AF%E0%A4%BE%E0%A4%97%E0%A5%81_%E0%A4%AE%E0%A4%BF%E0%A4%96%E0%A4%BE "मनुयागु मिखा – Newari") * [ 日本語 ](https://ja.wikipedia.org/wiki/%E3%83%92%E3%83%88%E3%81%AE%E7%9C%BC "ヒトの眼 – Japanese") * [ Oʻzbekcha / ўзбекча ](https://uz.wikipedia.org/wiki/Odam_ko%CA%BBzi "Odam koʻzi – Uzbek") * [ ਪੰਜਾਬੀ ](https://pa.wikipedia.org/wiki/%E0%A8%AE%E0%A8%A8%E0%A9%81%E0%A9%B1%E0%A8%96%E0%A9%80_%E0%A8%85%E0%A9%B1%E0%A8%96 "ਮਨੁੱਖੀ ਅੱਖ – Punjabi") * [ Português ](https://pt.wikipedia.org/wiki/Olho_humano "Olho humano – Portuguese") * [ Română ](https://ro.wikipedia.org/wiki/Ochiul_uman "Ochiul uman – Romanian") * [ Русский ](https://ru.wikipedia.org/wiki/%D0%93%D0%BB%D0%B0%D0%B7_%D1%87%D0%B5%D0%BB%D0%BE%D0%B2%D0%B5%D0%BA%D0%B0 "Глаз человека – Russian") * [ සිංහල ](https://si.wikipedia.org/wiki/%E0%B6%B8%E0%B7%92%E0%B6%B1%E0%B7%92%E0%B7%83%E0%B7%8A_%E0%B6%87%E0%B7%83 "මිනිස් ඇස – Sinhala") * [ کوردی ](https://ckb.wikipedia.org/wiki/%DA%86%D8%A7%D9%88%DB%8C_%D9%85%D8%B1%DB%86%DA%A4 "چاوی مرۆڤ – Central Kurdish") * [ Српски / srpski ](https://sr.wikipedia.org/wiki/%D0%89%D1%83%D0%B4%D1%81%D0%BA%D0%BE_%D0%BE%D0%BA%D0%BE "Људско око – Serbian") * [ Srpskohrvatski / српскохрватски ](https://sh.wikipedia.org/wiki/Ljudsko_oko "Ljudsko oko – Serbo-Croatian") * [ Suomi ](https://fi.wikipedia.org/wiki/Ihmissilm%C3%A4 "Ihmissilmä – Finnish") * [ Tagalog ](https://tl.wikipedia.org/wiki/Mata_ng_tao "Mata ng tao – Tagalog") * [ தமிழ் ](https://ta.wikipedia.org/wiki/%E0%AE%AE%E0%AE%A9%E0%AE%BF%E0%AE%A4%E0%AE%95%E0%AF%8D_%E0%AE%95%E0%AE%A3%E0%AF%8D "மனிதக் கண் – Tamil") * [ ไทย ](https://th.wikipedia.org/wiki/%E0%B8%95%E0%B8%B2%E0%B8%A1%E0%B8%99%E0%B8%B8%E0%B8%A9%E0%B8%A2%E0%B9%8C "ตามนุษย์ – Thai") * [ Türkçe ](https://tr.wikipedia.org/wiki/%C4%B0nsan_g%C3%B6z%C3%BC "İnsan gözü – Turkish") * [ Türkmençe ](https://tk.wikipedia.org/wiki/Adam_g%C3%B6zi "Adam gözi – Turkmen") * [ Українська ](https://uk.wikipedia.org/wiki/%D0%9B%D1%8E%D0%B4%D1%81%D1%8C%D0%BA%D0%B5_%D0%BE%D0%BA%D0%BE "Людське око – Ukrainian") * [ Tiếng Việt ](https://vi.wikipedia.org/wiki/M%E1%BA%AFt_ng%C6%B0%E1%BB%9Di "Mắt người – Vietnamese") * [ 粵語 ](https://zh-yue.wikipedia.org/wiki/%E4%BA%BA%E7%9C%BC "人眼 – Cantonese") * [ 中文 ](https://zh.wikipedia.org/wiki/%E4%BA%BA%E7%9C%BC "人眼 – Chinese") [ Edit links ](https://www.wikidata.org/wiki/Special:EntityPage/Q430024#sitelinks-wikipedia "Edit interlanguage links") * [ Article 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[ Wikimedia Commons ](https://commons.wikimedia.org/wiki/Human_eye) * [ Wikiversity ](https://en.wikiversity.org/wiki/Human_eye_development) From Wikipedia, the free encyclopedia Sensory organ of vision This article is about the eyes of humans. For eyes in general, see [ Eye ](/wiki/Eye "Eye") . For other uses, see [ Eye (disambiguation) ](/wiki/Eye_$disambiguation$ "Eye $disambiguation$") . This article uses [ anatomical terminology ](/wiki/Anatomical_terminology "Anatomical terminology") . Human eye --- [ ![](//upload.wikimedia.org/wikipedia/commons/thumb/0/08/Human_eye%2C_anterior_view.jpg/250px- Human_eye%2C_anterior_view.jpg) ](/wiki/File:Human_eye,_anterior_view.jpg) The eye of the right side of the face, showing its visible components - a white [ sclera ](/wiki/Sclera "Sclera") , a light brown [ iris ](/wiki/Iris_$anatomy$ "Iris $anatomy$") , and the black [ pupil ](/wiki/Pupil "Pupil") , in its [ orbit ](/wiki/Orbit_$anatomy$ "Orbit $anatomy$") surrounded by the [ lids ](/wiki/Eyelid "Eyelid") and [ lashes ](/wiki/Eyelashes "Eyelashes") [ ![](//upload.wikimedia.org/wikipedia/commons/thumb/e/e8/Eye- diagram_no_circles_border.svg/250px-Eye-diagram_no_circles_border.svg.png) ](/wiki/File:Eye-diagram_no_circles_border.svg) 1\. [ vitreous body ](/wiki/Vitreous_body "Vitreous body") 2\. [ ora serrata ](/wiki/Ora_serrata "Ora serrata") 3\. [ ciliary muscle ](/wiki/Ciliary_muscle "Ciliary muscle") 4\. [ ciliary zonules ](/wiki/Zonule_of_Zinn "Zonule of Zinn") 5\. [ Schlemm's canal ](/wiki/Schlemm%27s_canal "Schlemm's canal") 6\. [ pupil ](/wiki/Pupil "Pupil") 7\. [ anterior chamber ](/wiki/Anterior_chamber_of_eyeball "Anterior chamber of eyeball") 8\. [ cornea ](/wiki/Cornea "Cornea") 9\. [ iris ](/wiki/Iris_$anatomy$ "Iris $anatomy$") 10\. [ lens cortex ](/wiki/Lens_cortex "Lens cortex") 11\. [ lens nucleus ](/wiki/Lens_nucleus "Lens nucleus") 12\. [ ciliary process ](/wiki/Ciliary_processes "Ciliary processes") 13\. [ conjunctiva ](/wiki/Conjunctiva "Conjunctiva") 14\. [ inferior oblique muscle ](/wiki/Inferior_oblique_muscle "Inferior oblique muscle") 15\. [ inferior rectus muscle ](/wiki/Inferior_rectus_muscle "Inferior rectus muscle") 16\. [ medial rectus muscle ](/wiki/Medial_rectus_muscle "Medial rectus muscle") 17\. [ retinal arteries and veins ](/wiki/Retinal_arteries_and_veins "Retinal arteries and veins") 18\. [ optic disc ](/wiki/Optic_disc "Optic disc") 19\. [ dura mater ](/wiki/Dura_mater "Dura mater") 20\. [ central retinal artery ](/wiki/Central_retinal_artery "Central retinal artery") 21\. [ central retinal vein ](/wiki/Central_retinal_vein "Central retinal vein") 22\. [ optic nerve ](/wiki/Optic_nerve "Optic nerve") 23\. [ vorticose vein ](/wiki/Vorticose_veins "Vorticose veins") 24\. [ bulbar sheath ](/wiki/Tenon%27s_capsule "Tenon's capsule") 25\. [ macula ](/wiki/Macula_of_retina "Macula of retina") 26\. [ fovea ](/wiki/Fovea_centralis "Fovea centralis") 27\. [ sclera ](/wiki/Sclera "Sclera") 28\. [ choroid ](/wiki/Choroid "Choroid") 29\. [ superior rectus muscle ](/wiki/Superior_rectus_muscle "Superior rectus muscle") 30\. [ retina ](/wiki/Retina "Retina") Details [ System ](/wiki/Organ_system "Organ system") \| [ Visual system ](/wiki/Visual_system "Visual system") Identifiers [ Latin ](/wiki/Latin "Latin") \| _oculus_ [ Greek ](/wiki/Ancient_Greek "Ancient Greek") \| _ἀνθρώπινος ὀφθαλμός_ [ MeSH ](/wiki/Medical_Subject_Headings "Medical Subject Headings") \| [ D005123 ](https://meshb.nlm.nih.gov/record/ui?ui=D005123) [ TA98 ](/wiki/Terminologia_Anatomica "Terminologia Anatomica") \| [ A01.1.00.007 ](https://ifaa.unifr.ch/Public/EntryPage/TA98%20Tree/Entity%20TA98%20EN/01.1.00.007%20Entity%20TA98%20EN.htm) [ A15.2.00.001 ](https://ifaa.unifr.ch/Public/EntryPage/TA98%20Tree/Entity%20TA98%20EN/15.2.00.001%20Entity%20TA98%20EN.htm) [ TA2 ](/wiki/Terminologia_Anatomica "Terminologia Anatomica") \| [ 113 ](https://ta2viewer.openanatomy.org/?id=113) , [ 6734 ](https://ta2viewer.openanatomy.org/?id=6734) [ FMA ](/wiki/Foundational_Model_of_Anatomy "Foundational Model of Anatomy") \| [ 54448 ](https://bioportal.bioontology.org/ontologies/FMA/?p=classes&conceptid=http%3A%2F%2Fpurl.org%2Fsig%2Font%2Ffma%2Ffma54448) [ Anatomical terminology ](/wiki/Anatomical_terminology "Anatomical terminology") [ [ edit on Wikidata ](https://www.wikidata.org/wiki/Q430024 "d:Q430024") ] The human eye is an [ organ ](/wiki/Organ_$biology$ "Organ $biology$") of the [ sensory nervous system ](/wiki/Sensory_nervous_system "Sensory nervous system") that reacts to [ visible light ](/wiki/Light "Light") and allows the use of visual information for various purposes including [ seeing things ](/wiki/Visual_perception "Visual perception") , [ keeping balance ](/wiki/Balance_$ability$ "Balance $ability$") , and maintaining [ circadian rhythm ](/wiki/Circadian_rhythm "Circadian rhythm") . [ ![](//upload.wikimedia.org/wikipedia/commons/thumb/9/9a/Arizona_eye_model.png/253px- Arizona_eye_model.png) ](/wiki/File:Arizona_eye_model.png) Arizona Eye Model. "A" is accommodation in diopters. The eye can be considered as a living [ optical device ](/wiki/Optics "Optics") . It is approximately spherical in shape, with its outer layers, such as the outermost, white part of the eye (the [ sclera ](/wiki/Sclera "Sclera") ) and one of its inner layers (the pigmented [ choroid ](/wiki/Choroid "Choroid") ) keeping the eye essentially [ light tight ](/wiki/Stray_light "Stray light") except on the eye's [ optic axis ](/wiki/Optic_axis "Optic axis") . In order, along the optic axis, the optical components consist of a first lens (the [ cornea—the clear part of the eye ](/wiki/Cornea "Cornea") ) that accounts for most of the optical power of the eye and accomplishes most of the [ focusing of light ](/wiki/Focus_$optics$ "Focus $optics$") from the outside world; then an [ aperture ](/wiki/Aperture "Aperture") (the [ pupil ](/wiki/Pupil "Pupil") ) in a [ diaphragm ](/wiki/Diaphragm_$optics$ "Diaphragm $optics$") (the [ iris—the coloured part of the eye ](/wiki/Iris_$anatomy$ "Iris $anatomy$") ) that controls the amount of light entering the interior of the eye; then another lens (the [ crystalline lens ](/wiki/Lens_$anatomy$ "Lens $anatomy$") ) that accomplishes the remaining focusing of light into [ images ](/wiki/Real_image "Real image") ; and finally a light-sensitive part of the eye (the [ retina ](/wiki/Retina "Retina") ), where the images fall and are processed. The retina makes a connection to the [ brain ](/wiki/Human_brain "Human brain") via the [ optic nerve ](/wiki/Optic_nerve "Optic nerve") . The remaining components of the eye keep it in its required shape, nourish and maintain it, and protect it. Three types of cells in the retina convert light energy into electrical energy used by the [ nervous system ](/wiki/Nervous_system "Nervous system") : [ rods ](/wiki/Rod_cell "Rod cell") respond to low intensity light and contribute to perception of low-resolution, black-and-white images; [ cones ](/wiki/Cone_cell "Cone cell") respond to high intensity light and contribute to perception of high-resolution, coloured images; and the recently discovered [ photosensitive ganglion cells ](/wiki/Photosensitive_ganglion_cell "Photosensitive ganglion cell") respond to a full range of light intensities and contribute to adjusting the amount of light reaching the retina, to regulating and suppressing the hormone [ melatonin ](/wiki/Melatonin "Melatonin") , and to [ entraining ](/wiki/Entrainment_$chronobiology$ "Entrainment $chronobiology$") [ circadian rhythm ](/wiki/Circadian_rhythm "Circadian rhythm") . [1] ## Structure [ [ edit ](/w/index.php?title=Human_eye&action=edit&section=1 "Edit section: Structure") ] [ ![A detailed depiction of eye using a 3D medical illustration](//upload.wikimedia.org/wikipedia/commons/thumb/7/76/3D_Medical_Animation_Eye_Structure.jpg/260px-3D_Medical_Animation_Eye_Structure.jpg) ](/wiki/File:3D_Medical_Animation_Eye_Structure.jpg) A detailed medical illustration of the eye [ ![](//upload.wikimedia.org/wikipedia/commons/thumb/6/61/MRI_of_human_eye.jpg/170px- MRI_of_human_eye.jpg) ](/wiki/File:MRI_of_human_eye.jpg) [ MRI ](/wiki/Magnetic_resonance_imaging "Magnetic resonance imaging") scan of the human eye Humans have two eyes, situated on the left and the right of the [ face ](/wiki/Face "Face") . The eyes sit in bony cavities called the [ orbits ](/wiki/Orbit_$anatomy$ "Orbit $anatomy$") , in the [ skull ](/wiki/Skull#Humans "Skull") . There are six [ extraocular muscles ](/wiki/Extraocular_muscles "Extraocular muscles") that control eye movements. The front visible part of the eye is made up of the whitish [ sclera ](/wiki/Sclera "Sclera") , a coloured [ iris ](/wiki/Iris_$anatomy$ "Iris $anatomy$") , and the [ pupil ](/wiki/Pupil_$eye$ "Pupil $eye$") . A thin layer called the [ conjunctiva ](/wiki/Conjunctiva "Conjunctiva") sits on top of this. The front part is also called the [ anterior ](/wiki/Anatomical_terms_of_location#Anterior_and_posterior "Anatomical terms of location") segment of the eye. The eye is not shaped like a perfect sphere; rather it is a fused two-piece unit, composed of an [ anterior (front) segment and the posterior (back) ](/wiki/Anatomical_terms_of_location#anterior "Anatomical terms of location") segment. The anterior segment is made up of the cornea, iris and lens. The cornea is transparent and more curved and is linked to the larger posterior segment, composed of the vitreous, retina, choroid and the outer white shell called the sclera. The cornea is typically about 11.5 mm (0.45 in) in diameter, and 0.5 mm (500 μm) in thickness near its centre. The posterior chamber constitutes the remaining five-sixths; its diameter is typically about 24 mm (0.94 in). An area termed the limbus connects the cornea and sclera. The iris is the pigmented circular structure concentrically surrounding the centre of the eye, the pupil, which appears to be black. The size of the pupil, which controls the amount of light entering the eye, is adjusted by the iris' [ dilator ](/wiki/Iris_dilator_muscle "Iris dilator muscle") and [ sphincter muscles ](/wiki/Iris_sphincter_muscle "Iris sphincter muscle") . Light energy enters the eye through the cornea, through the pupil and then through the lens. The lens shape is changed for near focus (accommodation) and is controlled by the ciliary muscle. Between the two lenses, there are four [ optical surfaces ](/wiki/Optical_surfaces "Optical surfaces") which each [ refract ](/wiki/Refraction "Refraction") light as it travels along the optical path. One basic model describing the geometry of the optical system is the Arizona Eye Model. [2] This model describes the accommodation of the eye geometrically. Photons of light falling on the light-sensitive cells of the retina ( [ photoreceptor cones and rods ](/wiki/Photoreceptor_cell "Photoreceptor cell") ) are converted into electrical signals that are transmitted to the brain by the optic nerve and interpreted as sight and vision. ### Size [ [ edit ](/w/index.php?title=Human_eye&action=edit&section=2 "Edit section: Size") ] The size of the eye differs among adults by only one or 2 millimetres. The eyeball is generally less tall than it is wide. The sagittal vertical (height) of a human adult eye is approximately 23.7 mm (0.93 in), the transverse horizontal diameter (width) is 24.2 mm (0.95 in) and the axial anteroposterior size (depth) averages 22.0–24.8 mm (0.87–0.98 in) with no significant difference between sexes and age groups. [3] Strong correlation has been found between the transverse diameter and the width of the orbit (r = 0.88). [3] The typical adult eye has an anterior to posterior diameter of 24 mm (0.94 in), and a volume of 6 cubic centimetres (0.37 cu in). [4] The eyeball grows rapidly, increasing from about 16–17 mm (0.63–0.67 in) diameter at birth to 22.5–23 mm (0.89–0.91 in) by three years of age. By age 12, the eye attains its full size. ### Components [ [ edit ](/w/index.php?title=Human_eye&action=edit&section=3 "Edit section: Components") ] [ ![](//upload.wikimedia.org/wikipedia/commons/thumb/1/1e/Schematic_diagram_of_the_human_eye_en.svg/250px- Schematic_diagram_of_the_human_eye_en.svg.png) ](/wiki/File:Schematic_diagram_of_the_human_eye_en.svg) Schematic diagram of the human eye. It shows a horizontal section through the right eye. The eye is made up of three coats, or layers, enclosing various anatomical structures. The outermost layer, known as the [ fibrous tunic ](/wiki/Fibrous_tunic_of_eyeball "Fibrous tunic of eyeball") , is composed of the [ cornea ](/wiki/Cornea "Cornea") and [ sclera ](/wiki/Sclera "Sclera") , which provide shape to the eye and support the deeper structures. The middle layer, known as the [ vascular tunic or uvea ](/wiki/Uvea "Uvea") , consists of the [ choroid ](/wiki/Choroid "Choroid") , [ ciliary body ](/wiki/Ciliary_body "Ciliary body") , pigmented epithelium and [ iris ](/wiki/Iris_$anatomy$ "Iris $anatomy$") . The innermost is the [ retina ](/wiki/Retina "Retina") , which gets its oxygenation from the blood vessels of the choroid (posteriorly) as well as the retinal vessels (anteriorly). The spaces of the eye are filled with the [ aqueous humour ](/wiki/Aqueous_humour "Aqueous humour") anteriorly, between the cornea and lens, and the [ vitreous body ](/wiki/Vitreous_body "Vitreous body") , a jelly-like substance, behind the lens, filling the entire posterior cavity. The aqueous humour is a clear watery fluid that is contained in two areas: the [ anterior chamber ](/wiki/Anterior_chamber_of_eyeball "Anterior chamber of eyeball") between the cornea and the iris, and the [ posterior chamber ](/wiki/Posterior_chamber_of_eyeball "Posterior chamber of eyeball") between the iris and the lens. The lens is suspended to the ciliary body by the suspensory ligament ( [ zonule of Zinn ](/wiki/Zonule_of_Zinn "Zonule of Zinn") ), made up of hundreds of fine transparent fibers which transmit muscular forces to change the shape of the lens for accommodation (focusing). The vitreous body is a clear substance composed of water and proteins, which give it a jelly-like and sticky composition. [5] [ ![](//upload.wikimedia.org/wikipedia/commons/thumb/a/a9/Gray892.png/208px- Gray892.png) ](/wiki/File:Gray892.png) The outer parts of the eye ### Extraocular muscles [ [ edit ](/w/index.php?title=Human_eye&action=edit&section=4 "Edit section: Extraocular muscles") ] Main article: [ Extraocular muscles ](/wiki/Extraocular_muscles "Extraocular muscles") Each eye has seven [ extraocular muscles ](/wiki/Extraocular_muscles "Extraocular muscles") located in its [ orbit ](/wiki/Orbit_$anatomy$ "Orbit $anatomy$") . [6] Six of these muscles control the [ eye movements ](/wiki/Eye_movements "Eye movements") , the seventh controls the movement of the upper [ eyelid ](/wiki/Eyelid "Eyelid") . The six muscles are four recti muscles – the [ lateral rectus ](/wiki/Lateral_rectus_muscle "Lateral rectus muscle") , the [ medial rectus ](/wiki/Medial_rectus_muscle "Medial rectus muscle") , the [ inferior rectus ](/wiki/Inferior_rectus_muscle "Inferior rectus muscle") , and the [ superior rectus ](/wiki/Superior_rectus_muscle "Superior rectus muscle") , and two oblique muscles the [ inferior oblique ](/wiki/Inferior_oblique_muscle "Inferior oblique muscle") , and the [ superior oblique ](/wiki/Superior_oblique_muscle "Superior oblique muscle") . The seventh muscle is the [ levator palpebrae superioris muscle ](/wiki/Levator_palpebrae_superioris_muscle "Levator palpebrae superioris muscle") . When the muscles exert different tensions, a torque is exerted on the globe that causes it to turn, in almost pure rotation, with only about one millimeter of translation. [7] Thus, the eye can be considered as undergoing rotations about a single point in the centre of the eye. * [ ![Eye and orbit anatomy with motor nerves](//upload.wikimedia.org/wikipedia/commons/thumb/c/cf/Eye_orbit_anterior.jpg/120px-Eye_orbit_anterior.jpg) ](/wiki/File:Eye_orbit_anterior.jpg "Eye and orbit anatomy with motor nerves") Eye and orbit anatomy with motor nerves * [ ![Image showing orbita with eye and nerves visible $periocular fat removed$](//upload.wikimedia.org/wikipedia/commons/thumb/9/90/Lateral_orbit_nerves.jpg/120px-Lateral_orbit_nerves.jpg) ](/wiki/File:Lateral_orbit_nerves.jpg "Image showing orbita with eye and nerves visible $periocular fat removed$") Image showing orbita with eye and nerves visible (periocular fat removed) * [ ![Image showing orbita with eye and periocular fat](//upload.wikimedia.org/wikipedia/commons/thumb/0/07/Lateral_orbit_anatomy_2.jpg/120px-Lateral_orbit_anatomy_2.jpg) ](/wiki/File:Lateral_orbit_anatomy_2.jpg "Image showing orbita with eye and periocular fat") Image showing orbita with eye and periocular fat * [ ![Normal anatomy of the human eye and orbit, anterior view](//upload.wikimedia.org/wikipedia/commons/thumb/8/87/Eye_orbit_anatomy_anterior2.jpg/120px-Eye_orbit_anatomy_anterior2.jpg) ](/wiki/File:Eye_orbit_anatomy_anterior2.jpg "Normal anatomy of the human eye and orbit, anterior view") Normal [ anatomy ](/wiki/Anatomy "Anatomy") of the human eye and orbit, anterior view ## Vision [ [ edit ](/w/index.php?title=Human_eye&action=edit&section=5 "Edit section: Vision") ] See also: [ Visual acuity ](/wiki/Visual_acuity "Visual acuity") , [ Eye § Visual acuity ](/wiki/Eye#Visual_acuity "Eye") , [ Fovea centralis § Angular size of foveal cones ](/wiki/Fovea_centralis#Angular_size_of_foveal_cones "Fovea centralis") , and [ Color vision § Physiology of color perception ](/wiki/Color_vision#Physiology_of_color_perception "Color vision") ### Field of view [ [ edit ](/w/index.php?title=Human_eye&action=edit&section=6 "Edit section: Field of view") ] [ ![](//upload.wikimedia.org/wikipedia/commons/thumb/d/d0/Mairead_cropped.png/220px- Mairead_cropped.png) ](/wiki/File:Mairead_cropped.png) Side-view of the human eye, viewed approximately 90° temporal, illustrating how the iris and pupil appear rotated towards the viewer due to the optical properties of the cornea and the aqueous humour The approximate [ field of view ](/wiki/Field_of_view "Field of view") of an individual human eye (measured from the fixation point, i.e., the point at which one's gaze is directed) varies by facial anatomy, but is typically 30° superior (up, limited by the brow), 45° nasal (limited by the nose), 70° inferior (down), and 100° temporal (towards the temple). [8] [9] [10] For both eyes, combined ( [ binocular vision ](/wiki/Binocular_vision "Binocular vision") ) visual field is approximately 100° vertical and a maximum 190° horizontal, approximately 120° of which makes up the binocular field of view (seen by both eyes) flanked by two uniocular fields (seen by only one eye) of approximately 40 degrees. [11] [12] It is an area of 4.17 [ steradians ](/wiki/Steradian "Steradian") or 13700 [ square degrees ](/wiki/Square_degree "Square degree") for binocular vision. [13] When viewed at large angles from the side, the iris and pupil may still be visible by the viewer, indicating the person has peripheral vision possible at that angle. [14] [15] [16] About 15° temporal and 1.5° below the horizontal is the [ blind spot ](/wiki/Blind_spot_$vision$ "Blind spot $vision$") created by the optic nerve nasally, which is roughly 7.5° high and 5.5° wide. [17] ### Dynamic range [ [ edit ](/w/index.php?title=Human_eye&action=edit&section=7 "Edit section: Dynamic range") ] The retina has a static [ contrast ratio ](/wiki/Contrast_ratio "Contrast ratio") of around 100:1 (about 6.5 [ f-stops ](/wiki/F-number#Stops,_f- stop_conventions,_and_exposure "F-number") ). As soon as the eye moves rapidly to acquire a target ( [ saccades ](/wiki/Saccade "Saccade") ), it re-adjusts its exposure by adjusting the iris, which adjusts the size of the pupil. Initial dark adaptation takes place in approximately four seconds of profound, uninterrupted darkness; full adaptation through adjustments in retinal rod photoreceptors is 80% complete in thirty minutes. The process is nonlinear and multifaceted, so an interruption by light exposure requires restarting the dark adaptation process over again. [ ![](//upload.wikimedia.org/wikipedia/commons/thumb/d/dc/Pupillary_light_reflex.jpg/300px- Pupillary_light_reflex.jpg) ](/wiki/File:Pupillary_light_reflex.jpg) The pupil of the human eye can range in size from 2 mm to over 8 mm to [ adapt ](/wiki/Adaptation_$eye$ "Adaptation $eye$") to the environment The human eye can detect a luminance from 10 −6 cd/m 2 , or one millionth (0.000001) of a [ candela ](/wiki/Candela "Candela") per square meter to 10 8 cd/m 2 or one hundred million (100,000,000) candelas per square meter. [18] [19] [20] (that is it has a range of 10 14 , or one hundred trillion 100,000,000,000,000, about 46.5 f-stops). This range does not include looking at the midday sun (10 9 cd/m 2 ) [21] or lightning discharge. At the low end of the range is the [ absolute threshold ](/wiki/Absolute_threshold "Absolute threshold") of vision for a steady light across a wide field of view, about 10 −6 cd/m 2 (0.000001 candela per square meter). [22] [23] The upper end of the range is given in terms of normal visual performance as 10 8 cd/m 2 (100,000,000 or one hundred million candelas per square meter). [24] [ ![](//upload.wikimedia.org/wikipedia/commons/thumb/b/b7/Voluntary_pupil_dilation.gif/220px- Voluntary_pupil_dilation.gif) ](/wiki/File:Voluntary_pupil_dilation.gif) Dilation and constriction of the pupil The eye includes a [ lens ](/wiki/Lens_$anatomy$ "Lens $anatomy$") similar to [ lenses ](/wiki/Lens_$optics$ "Lens $optics$") found in optical instruments such as cameras and the same physics principles can be applied. The [ pupil ](/wiki/Pupil "Pupil") of the human eye is its [ aperture ](/wiki/Aperture "Aperture") ; the iris is the diaphragm that serves as the aperture stop. Refraction in the [ cornea ](/wiki/Cornea "Cornea") causes the effective aperture (the [ entrance pupil ](/wiki/Entrance_pupil "Entrance pupil") ) to differ slightly from the physical pupil diameter. The entrance pupil is typically about 4 mm in diameter, although it can range from 2 mm ( f /8.3 ) in a brightly lit place to 8 mm ( f /2.1 ) in the dark. The latter value decreases slowly with age; older people's eyes sometimes dilate to not more than 5–6mm in the dark, and may be as small as 1mm in the light. [25] [26] ## Movement [ [ edit ](/w/index.php?title=Human_eye&action=edit&section=8 "Edit section: Movement") ] Main article: [ Eye movement ](/wiki/Eye_movement "Eye movement") [ ![](//upload.wikimedia.org/wikipedia/commons/thumb/3/37/Fundus_photograph_of_normal_right_eye.jpg/220px- Fundus_photograph_of_normal_right_eye.jpg) ](/wiki/File:Fundus_photograph_of_normal_right_eye.jpg) The light circle is the [ optic disc ](/wiki/Optic_disc "Optic disc") where the optic nerve exits the retina The visual system in the human brain is too slow to process information if images are slipping across the retina at more than a few degrees per second. [27] Thus, to be able to see while moving, the brain must compensate for the motion of the head by turning the eyes. Frontal-eyed animals have a small area of the retina with very high visual acuity, the [ fovea centralis ](/wiki/Fovea_centralis "Fovea centralis") . It covers about 2 degrees of visual angle in people. To get a clear view of the world, the brain must turn the eyes so that the image of the object of regard falls on the fovea. Any failure to make eye movements correctly can lead to serious visual degradation. Having two eyes allows the brain to determine the depth and distance of an object, called stereovision, and gives the sense of three-dimensionality to the vision. Both eyes must point accurately enough that the object of regard falls on corresponding points of the two retinas to stimulate stereovision; otherwise, double vision might occur. Some persons with congenitally crossed eyes tend to ignore one eye's vision, thus do not suffer double vision, and do not have stereovision. The movements of the eye are controlled by six muscles attached to each eye, and allow the eye to elevate, depress, converge, diverge and roll. These muscles are both controlled voluntarily and involuntarily to track objects and correct for simultaneous head movements. ### Rapid [ [ edit ](/w/index.php?title=Human_eye&action=edit&section=9 "Edit section: Rapid") ] Main article: [ Rapid eye movement sleep ](/wiki/Rapid_eye_movement_sleep "Rapid eye movement sleep") Rapid eye movement, REM, typically refers to the [ sleep ](/wiki/Sleep "Sleep") stage during which the most vivid dreams occur. During this stage, the eyes move rapidly. ### Saccadian [ [ edit ](/w/index.php?title=Human_eye&action=edit&section=10 "Edit section: Saccadian") ] Main article: [ Saccade ](/wiki/Saccade "Saccade") Saccades are quick, simultaneous movements of both eyes in the same direction controlled by the frontal lobe of the brain. ### Fixational [ [ edit ](/w/index.php?title=Human_eye&action=edit&section=11 "Edit section: Fixational") ] Main article: [ Fixation (visual) ](/wiki/Fixation_$visual$ "Fixation $visual$") Even when looking intently at a single spot, the eyes drift around. This ensures that individual photosensitive cells are continually stimulated in different degrees. Without changing input, these cells would otherwise stop generating output. Eye movements include drift, [ ocular tremor ](/wiki/Ocular_tremor "Ocular tremor") , and microsaccades. Some irregular drifts, movements smaller than a saccade and larger than a microsaccade, subtend up to one tenth of a degree. Researchers vary in their definition of [ microsaccades ](/wiki/Microsaccade "Microsaccade") by amplitude. Martin Rolfs [28] states that 'the majority of microsaccades observed in a variety of tasks have amplitudes smaller than 30 min-arc'. However, others state that the "current consensus has largely consolidated around a definition of microsaccades that includes magnitudes up to 1°." [29] ### Vestibulo-ocular [ [ edit ](/w/index.php?title=Human_eye&action=edit&section=12 "Edit section: Vestibulo-ocular") ] Main article: [ Vestibulo-ocular reflex ](/wiki/Vestibulo-ocular_reflex "Vestibulo-ocular reflex") The [ vestibulo-ocular reflex ](/wiki/Vestibulo-ocular_reflex "Vestibulo- ocular reflex") is a [ reflex ](/wiki/Reflex "Reflex") eye movement that stabilizes images on the [ retina ](/wiki/Retina "Retina") during head movement by producing an eye movement in the direction opposite to head movement in response to neural input from the vestibular system of the inner ear, thus maintaining the image in the centre of the visual field. For example, when the head moves to the right, the eyes move to the left. This applies for head movements up and down, left and right, and tilt to the right and left, all of which give input to the ocular muscles to maintain visual stability. ### Smooth pursuit [ [ edit ](/w/index.php?title=Human_eye&action=edit&section=13 "Edit section: Smooth pursuit") ] Main article: [ Pursuit movement ](/wiki/Pursuit_movement "Pursuit movement") Eyes can also follow a moving object around. This tracking is less accurate than the vestibulo-ocular reflex, as it requires the brain to process incoming visual information and supply [ feedback ](/wiki/Feedback "Feedback") . Following an object moving at constant speed is relatively easy, though the eyes will often make saccades to keep up. The smooth pursuit movement can move the eye at up to 100°/s in adult humans. It is more difficult to visually estimate speed in low light conditions or while moving, unless there is another point of reference for determining speed. ### Optokinetic [ [ edit ](/w/index.php?title=Human_eye&action=edit&section=14 "Edit section: Optokinetic") ] Main article: [ Optokinetic response ](/wiki/Optokinetic_response "Optokinetic response") The optokinetic reflex (or optokinetic nystagmus) stabilizes the image on the retina through visual feedback. It is induced when the entire visual scene drifts across the retina, eliciting eye rotation in the same direction and at a velocity that minimizes the motion of the image on the retina. When the gaze direction deviates too far from the forward heading, a compensatory saccade is induced to reset the gaze to the centre of the visual field. [30] For example, when looking out of the window at a moving train, the eyes can focus on a moving train for a short moment (by stabilizing it on the retina), until the train moves out of the field of vision. At this point, the eye is moved back to the point where it first saw the train (through a saccade). ## Near response [ [ edit ](/w/index.php?title=Human_eye&action=edit&section=15 "Edit section: Near response") ] The adjustment to close-range vision involves three processes to focus an image on the retina. ### Vergence movement [ [ edit ](/w/index.php?title=Human_eye&action=edit&section=16 "Edit section: Vergence movement") ] Main article: [ Vergence ](/wiki/Vergence "Vergence") [ ![](//upload.wikimedia.org/wikipedia/commons/thumb/0/0e/Stereogram_Tut_Eye_Convergence.png/220px- Stereogram_Tut_Eye_Convergence.png) ](/wiki/File:Stereogram_Tut_Eye_Convergence.png) The two eyes converge to point to the same object. When a creature with binocular vision looks at an object, the eyes must rotate around a vertical axis so that the projection of the image is in the centre of the retina in both eyes. To look at a nearby object, the eyes rotate 'towards each other' ( [ convergence ](/wiki/Convergence_$eye$ "Convergence $eye$") ), while for an object farther away they rotate 'away from each other' ( [ divergence ](/wiki/Divergence_$eye$ "Divergence $eye$") ). ### Pupil constriction [ [ edit ](/w/index.php?title=Human_eye&action=edit&section=17 "Edit section: Pupil constriction") ] Lenses cannot refract light rays at their edges as well as closer to the centre. The image produced by any lens is therefore somewhat blurry around the edges ( [ spherical aberration ](/wiki/Spherical_aberration "Spherical aberration") ). It can be minimized by screening out peripheral light rays and looking only at the better-focused centre. In the eye, the pupil serves this purpose by constricting while the eye is focused on nearby objects. Small apertures also give an increase in [ depth of field ](/wiki/Depth_of_field "Depth of field") , allowing a broader range of "in focus" vision. In this way the pupil has a dual purpose for near vision: to reduce spherical aberration and increase depth of field. [31] ### Lens accommodation [ [ edit ](/w/index.php?title=Human_eye&action=edit&section=18 "Edit section: Lens accommodation") ] Main article: [ Lens (vertebrate anatomy) ](/wiki/Lens_$vertebrate_anatomy$ "Lens $vertebrate anatomy$") Changing the curvature of the lens is carried out by the [ ciliary muscles ](/wiki/Ciliary_muscle "Ciliary muscle") surrounding the lens; this process is known as "accommodation". Accommodation narrows the inner diameter of the ciliary body, which actually relaxes the fibers of the suspensory ligament attached to the periphery of the lens, and also allows the lens to relax into a more convex, or globular, shape. A more convex lens refracts light more strongly and focuses divergent light rays from near objects onto the retina, allowing closer objects to be brought into better focus. [31] [32] ## Medicine [ [ edit ](/w/index.php?title=Human_eye&action=edit&section=19 "Edit section: Medicine") ] The human eye contains enough complexity to warrant specialized attention and care beyond the duties of a [ general practitioner ](/wiki/General_practitioner "General practitioner") . These specialists, or [ eye care professionals ](/wiki/Eye_care_professional "Eye care professional") , serve different functions in different countries. Eye care professionals can have overlap in their patient care privileges. For example, both an [ ophthalmologist ](/wiki/Ophthalmologist "Ophthalmologist") (M.D.) and [ optometrist ](/wiki/Optometrist "Optometrist") (O.D.) are professionals who diagnoses eye disease and can prescribe lenses to correct vision. Typically, only ophthalmologists are licensed to perform surgical procedures. Ophthalmologists may also specialize within a surgical area, such as [ cornea ](/wiki/Corneal_transplantation "Corneal transplantation") , [ cataracts ](/wiki/Cataract_surgery "Cataract surgery") , [ laser ](/wiki/Refractive_surgery "Refractive surgery") , [ retina ](/wiki/Retinal_detachment "Retinal detachment") , or [ oculoplastics ](/wiki/Oculoplastics "Oculoplastics") . Eye care professionals include: * [ Ocularists ](/wiki/Ocularist "Ocularist") * [ Ophthalmologists ](/wiki/Ophthalmology "Ophthalmology") * [ Optometrists ](/wiki/Optometry "Optometry") * [ Opticians ](/wiki/Opticianry "Opticianry") * [ Orthoptists ](/wiki/Orthoptics "Orthoptics") and [ vision therapists ](/wiki/Vision_therapy "Vision therapy") ## Irritation [ [ edit ](/w/index.php?title=Human_eye&action=edit&section=20 "Edit section: Irritation") ] See also: [ Irritation § Eye irritation ](/wiki/Irritation#Eye_irritation "Irritation") [ ![](//upload.wikimedia.org/wikipedia/commons/thumb/f/f5/Bloodshot.jpg/220px- Bloodshot.jpg) ](/wiki/File:Bloodshot.jpg) Conjunctival injection, or redness of the sclera surrounding the iris and pupil Eye irritation has been defined as "the magnitude of any stinging, scratching, burning, or other irritating sensation from the eye". [33] It is a common problem experienced by people of all ages. Related eye symptoms and signs of irritation are discomfort, dryness, excess tearing, itchiness, grating, foreign body sensation, ocular fatigue, pain, soreness, redness, swollen eyelids, and tiredness, etc. These eye symptoms are reported with intensities from mild to severe. It has been suggested that these eye symptoms are related to different causal mechanisms, and symptoms are related to the particular ocular anatomy involved. [34] Several suspected causal factors in our environment have been studied so far. [33] One hypothesis is that [ indoor air pollution ](/wiki/Indoor_air_quality "Indoor air quality") may cause eye and airway irritation. [35] [36] Eye irritation depends somewhat on destabilization of the outer-eye tear film, i.e. the formation of dry spots on the cornea, resulting in ocular discomfort. [35] [37] [38] Occupational factors are also likely to influence the perception of eye irritation. Some of these are lighting (glare and poor contrast), gaze position, reduced blink rate, limited number of breaks from visual tasking, and a constant combination of accommodation, musculoskeletal burden, and impairment of the visual nervous system. [39] [40] Another factor that may be related is work stress. [41] [42] In addition, psychological factors have been found in multivariate analyses to be associated with an increase in eye irritation among [ VDU ](/wiki/Visual_display_unit "Visual display unit") users. [43] [44] Other risk factors, such as chemical toxins/irritants (e.g. amines, formaldehyde, acetaldehyde, acrolein, N-decane, VOCs, ozone, pesticides and preservatives, allergens, etc.) might cause eye irritation as well. Certain [ volatile organic compounds ](/wiki/Volatile_organic_compound "Volatile organic compound") that are both chemically reactive and airway irritants may cause eye irritation. Personal factors (e.g. use of contact lenses, eye make-up, and certain medications) may also affect destabilization of the tear film and possibly result in more eye symptoms. [34] Nevertheless, if airborne particles alone should destabilize the tear film and cause eye irritation, their content of surface-active compounds must be high. [34] An integrated physiological risk model with [ blink ](/wiki/Blink "Blink") frequency, destabilization, and break-up of the eye tear film as inseparable phenomena may explain eye irritation among office workers in terms of occupational, climate, and eye-related physiological risk factors. [34] There are two major measures of eye irritation. One is blink frequency, which can be observed by human behavior. The other measures are break up time, tear flow, hyperemia (redness, swelling), tear fluid cytology, and epithelial damage (vital stains) etc., which are human beings' physiological reactions. Blink frequency is defined as the number of blinks per minute and it is associated with eye irritation. Blink frequencies are individual with mean frequencies of < 2–3 to 20–30 blinks/minute, and they depend on environmental factors including the use of [ contact lenses ](/wiki/Contact_lens "Contact lens") . Dehydration, mental activities, work conditions, room temperature, relative humidity, and illumination all influence blink frequency. Break-up time (BUT) is another major measure of eye irritation and tear film stability. [45] It is defined as the time interval (in seconds) between blinking and rupture. BUT is considered to reflect the stability of the tear film as well. In normal persons, the break-up time exceeds the interval between blinks, and, therefore, the tear film is maintained. [34] Studies have shown that blink frequency is correlated negatively with break-up time. This phenomenon indicates that perceived eye irritation is associated with an increase in blink frequency since the cornea and conjunctiva both have sensitive nerve endings that belong to the first trigeminal branch. [46] [47] Other evaluating methods, such as hyperemia, cytology etc. have increasingly been used to assess eye irritation. There are other factors that are related to eye irritation as well. Three major factors that influence the most are indoor air pollution, contact lenses and gender differences. Field studies have found that the prevalence of objective eye signs is often significantly altered among office workers in comparisons with random samples of the general population. [48] [49] [50] [51] These research results might indicate that indoor air pollution has played an important role in causing eye irritation. There are more and more people wearing contact lens now and dry eyes appear to be the most common complaint among contact lens wearers. [52] [53] [54] Although both contact lens wearers and spectacle wearers experience similar eye irritation symptoms, dryness, redness, and grittiness have been reported far more frequently among contact lens wearers and with greater severity than among spectacle wearers. [54] Studies have shown that incidence of dry eyes increases with age, [55] [56] especially among women. [57] Tear film stability (e.g. [ tear break-up time ](/wiki/Tear_break-up_time "Tear break-up time") ) is significantly lower among women than among men. In addition, women have a higher blink frequency while reading. [58] Several factors may contribute to gender differences. One is the use of eye make-up. Another reason could be that the women in the reported studies have done more VDU work than the men, including lower grade work. A third often-quoted explanation is related to the age-dependent decrease of tear secretion, particularly among women after 40 years of age. [57] [59] [60] In a study conducted by [ UCLA ](/wiki/UCLA "UCLA") , the frequency of reported symptoms in industrial buildings was investigated. [61] The study's results were that eye irritation was the most frequent symptom in industrial building spaces, at 81%. Modern office work with use of office equipment has raised concerns about possible adverse health effects. [62] Since the 1970s, reports have linked mucosal, skin, and general symptoms to work with self- copying paper. Emission of various particulate and volatile substances has been suggested as specific causes. These symptoms have been related to [ sick building syndrome ](/wiki/Sick_building_syndrome "Sick building syndrome") (SBS), which involves symptoms such as irritation to the eyes, skin, and upper airways, headache and fatigue. [63] Many of the symptoms described in SBS and [ multiple chemical sensitivity ](/wiki/Multiple_chemical_sensitivity "Multiple chemical sensitivity") (MCS) resemble the symptoms known to be elicited by airborne irritant chemicals. [64] A repeated measurement design was employed in the study of acute symptoms of eye and respiratory tract irritation resulting from occupational exposure to sodium borate dusts. [65] The symptom assessment of the 79 exposed and 27 unexposed subjects comprised interviews before the shift began and then at regular hourly intervals for the next six hours of the shift, four days in a row. [65] Exposures were monitored concurrently with a personal real time aerosol monitor. Two different exposure profiles, a daily average and short term (15 minute) average, were used in the analysis. Exposure- response relations were evaluated by linking incidence rates for each symptom with categories of exposure. [65] Acute incidence rates for nasal, eye, and [ throat irritation ](/wiki/Throat_irritation "Throat irritation") , and coughing and breathlessness were found to be associated with increased exposure levels of both exposure indices. Steeper exposure-response slopes were seen when short term exposure concentrations were used. Results from multivariate logistic regression analysis suggest that current smokers tended to be less sensitive to the exposure to airborne sodium borate dust. [65] Several actions can be taken to prevent eye irritation— * trying to maintain normal blinking by avoiding room temperatures that are too high; avoiding relative humidities that are too high or too low, because they reduce blink frequency or may increase water evaporation. [34] * trying to maintain an intact film of tears by the following actions: 1. Blinking and short breaks may be beneficial for VDU users. [66] [67] Increasing these two actions might help maintain the tear film. 2. Downward gazing is recommended to reduce ocular surface area and water evaporation. [68] [69] [70] 3. The distance between the VDU and keyboard should be kept as short as possible to minimize evaporation from the ocular surface area by a low direction of the gaze, [71] and 4. Blink training can be beneficial. [72] In addition, other measures are proper lid hygiene, avoidance of eye rubbing, [73] and proper use of personal products and medication. Eye make-up should be used with care. [74] ## Disease [ [ edit ](/w/index.php?title=Human_eye&action=edit&section=21 "Edit section: Disease") ] [ ![](//upload.wikimedia.org/wikipedia/commons/thumb/c/c9/Schematic_diagram_of_human_eye_multilingual.svg/360px- Schematic_diagram_of_human_eye_multilingual.svg.png) ](/wiki/File:Schematic_diagram_of_human_eye_multilingual.svg) Diagram of a human eye ( [ horizontal section ](/wiki/Transverse_plane "Transverse plane") of the right eye) 1\. [ Lens ](/wiki/Lens_$anatomy$ "Lens $anatomy$") , 2. [ Zonule of Zinn or Ciliary zonule ](/wiki/Zonule_of_Zinn "Zonule of Zinn") , 3. [ Posterior chamber ](/wiki/Posterior_chamber "Posterior chamber") and 4. [ Anterior chamber ](/wiki/Anterior_chamber "Anterior chamber") with 5. [ Aqueous humour ](/wiki/Aqueous_humour "Aqueous humour") flow; 6. [ Pupil ](/wiki/Pupil "Pupil") , 7. [ Corneosclera or Fibrous tunic ](/wiki/Fibrous_tunic_of_eyeball "Fibrous tunic of eyeball") with 8. [ Cornea ](/wiki/Cornea "Cornea") , 9. [ Trabecular meshwork ](/wiki/Trabecular_meshwork "Trabecular meshwork") and [ Schlemm's canal ](/wiki/Schlemm%27s_canal "Schlemm's canal") . 10. [ Corneal limbus ](/wiki/Corneal_limbus "Corneal limbus") and 11. [ Sclera ](/wiki/Sclera "Sclera") ; 12. [ Conjunctiva ](/wiki/Conjunctiva "Conjunctiva") , 13. [ Uvea ](/wiki/Uvea "Uvea") with 14. [ Iris ](/wiki/Iris_$anatomy$ "Iris $anatomy$") , 15. [ Ciliary body ](/wiki/Ciliary_body "Ciliary body") (with a: _pars plicata_ and b: _pars plana_ ) and 16. [ Choroid ](/wiki/Choroid "Choroid") ); 17. [ Ora serrata ](/wiki/Ora_serrata "Ora serrata") , 18. [ Vitreous humor ](/wiki/Vitreous_humor "Vitreous humor") with 19. [ Hyaloid canal/(old artery) ](/wiki/Hyaloid_artery "Hyaloid artery") , 20. [ Retina ](/wiki/Retina "Retina") with 21. [ Macula or macula lutea ](/wiki/Macula_of_retina "Macula of retina") , 22. [ Fovea ](/wiki/Fovea_centralis "Fovea centralis") and 23. [ Optic disc ](/wiki/Optic_disc "Optic disc") → [ blind spot ](/wiki/Blind_spot_$vision$ "Blind spot $vision$") ; 24. [ Visual axis (line of sight) ](/wiki/Line_of_sight "Line of sight") . 25. [ Optical axis ](/wiki/Optical_axis "Optical axis") . 26. [ Optic nerve ](/wiki/Optic_nerve "Optic nerve") with 27. [ Dural ](/wiki/Dura_mater "Dura mater") sheath, 28. [ Tenon's capsule or bulbar sheath ](/wiki/Tenon%27s_capsule "Tenon's capsule") , 29. Tendon. 30\. [ Anterior segment ](/wiki/Anterior_segment "Anterior segment") , 31. [ Posterior segment ](/wiki/Posterior_segment "Posterior segment") . 32\. [ Ophthalmic artery ](/wiki/Ophthalmic_artery "Ophthalmic artery") , 33. [ Artery ](/wiki/Central_retinal_artery "Central retinal artery") and [ central retinal vein ](/wiki/Central_retinal_vein "Central retinal vein") → 36. Blood vessels of the retina; [ Ciliary arteries ](/wiki/Ciliary_arteries "Ciliary arteries") (34. [ Short posterior ones ](/wiki/Short_posterior_ciliary_arteries "Short posterior ciliary arteries") , 35. [ Long posterior ones ](/wiki/Long_posterior_ciliary_arteries "Long posterior ciliary arteries") and 37. [ Anterior ones ](/wiki/Anterior_ciliary_artery "Anterior ciliary artery") ), 38. [ Lacrimal artery ](/wiki/Lacrimal_artery "Lacrimal artery") , 39. [ Ophthalmic vein ](/wiki/Ophthalmic_vein "Ophthalmic vein") , 40. [ Vorticose vein ](/wiki/Vorticose_vein "Vorticose vein") . 41\. [ Ethmoid bone ](/wiki/Ethmoid_bone "Ethmoid bone") , 42. [ Medial rectus muscle ](/wiki/Medial_rectus_muscle "Medial rectus muscle") , 43. [ Lateral rectus muscle ](/wiki/Lateral_rectus_muscle "Lateral rectus muscle") , 44. [ Sphenoid bone ](/wiki/Sphenoid_bone "Sphenoid bone") . There are many [ diseases ](/wiki/Eye_disease "Eye disease") , disorders, and [ age-related ](/wiki/Aging-associated_diseases "Aging-associated diseases") changes that may affect the eyes and surrounding structures. As the eye ages, certain changes occur that can be attributed solely to the aging process. Most of these anatomic and physiologic processes follow a gradual decline. With aging, the quality of vision worsens due to reasons independent of diseases of the aging eye. While there are many changes of significance in the non-diseased eye, the most functionally important changes seem to be a reduction in pupil size and the loss of accommodation or focusing capability ( [ presbyopia ](/wiki/Presbyopia "Presbyopia") ). The area of the pupil governs the amount of light that can reach the retina. The extent to which the pupil dilates decreases with age, leading to a substantial decrease in light received at the retina. In comparison to younger people, it is as though older persons are constantly wearing medium-density sunglasses. Therefore, for any detailed visually guided tasks on which performance varies with illumination, older persons require extra lighting. Certain ocular diseases can come from [ sexually transmitted infections ](/wiki/Sexually_transmitted_infection "Sexually transmitted infection") such as herpes and genital warts. If contact between the eye and area of infection occurs, the STI can be transmitted to the eye. [75] With aging, a prominent white ring develops in the periphery of the cornea called [ arcus senilis ](/wiki/Arcus_senilis "Arcus senilis") . Aging causes laxity, downward shift of eyelid tissues and atrophy of the orbital fat. These changes contribute to the etiology of several eyelid disorders such as [ ectropion ](/wiki/Ectropion "Ectropion") , [ entropion ](/wiki/Entropion "Entropion") , [ dermatochalasis ](/wiki/Dermatochalasis "Dermatochalasis") , and [ ptosis ](/wiki/Ptosis_$eyelid$ "Ptosis $eyelid$") . The vitreous gel undergoes liquefaction ( [ posterior vitreous detachment ](/wiki/Posterior_vitreous_detachment "Posterior vitreous detachment") or PVD) and its opacities — visible as [ floaters ](/wiki/Floater "Floater") — gradually increase in number. [ Eye care professionals ](/wiki/Eye_care_professional "Eye care professional") , including [ ophthalmologists ](/wiki/Ophthalmologist "Ophthalmologist") and [ optometrists ](/wiki/Optometrist "Optometrist") , are involved in the treatment and management of ocular and vision disorders. A [ Snellen chart ](/wiki/Snellen_chart "Snellen chart") is one type of [ eye chart ](/wiki/Eye_chart "Eye chart") used to measure [ visual acuity ](/wiki/Visual_acuity "Visual acuity") . At the conclusion of a complete [ eye examination ](/wiki/Eye_examination "Eye examination") , the eye doctor might provide the patient with an [ eyeglass prescription ](/wiki/Eyeglass_prescription "Eyeglass prescription") for [ corrective lenses ](/wiki/Corrective_lens "Corrective lens") . Some disorders of the eyes for which corrective lenses are prescribed include myopia ( [ near-sightedness ](/wiki/Near-sightedness "Near-sightedness") ), [ hyperopia ](/wiki/Hyperopia "Hyperopia") (far-sightedness), [ astigmatism ](/wiki/Astigmatism "Astigmatism") , and [ presbyopia ](/wiki/Presbyopia "Presbyopia") (the loss of focusing range during aging). ### Macular degeneration [ [ edit ](/w/index.php?title=Human_eye&action=edit&section=22 "Edit section: Macular degeneration") ] Main article: [ Macular degeneration ](/wiki/Macular_degeneration "Macular degeneration") Macular degeneration is especially prevalent in the U.S. and affects roughly 1.75 million Americans each year. [76] Having lower levels of lutein and zeaxanthin within the macula may be associated with an increase in the risk of age-related macular degeneration. [77] Lutein and zeaxanthin act as [ antioxidants ](/wiki/Antioxidant "Antioxidant") that protect the retina and macula from oxidative damage from high-energy light waves. [78] As the light waves enter the eye, they excite electrons that can cause harm to the cells in the eye, but they can cause oxidative damage that may lead to macular degeneration or cataracts. Lutein and zeaxanthin bind to the electron free radical and are reduced rendering the electron safe. There are many ways to ensure a diet rich in lutein and zeaxanthin, the best of which is to eat dark green vegetables including kale, spinach, broccoli and turnip greens. Nutrition is an important aspect of the ability to achieve and maintain proper eye health. [ Lutein ](/wiki/Lutein "Lutein") and [ zeaxanthin ](/wiki/Zeaxanthin "Zeaxanthin") are two major carotenoids, found in the macula of the eye, that are being researched to identify their role in the pathogenesis of eye disorders such as age-related [ macular degeneration ](/wiki/Macular_degeneration "Macular degeneration") and [ cataracts ](/wiki/Cataracts "Cataracts") . [79] ## Sexuality [ [ edit ](/w/index.php?title=Human_eye&action=edit&section=23 "Edit section: Sexuality") ] Human eyes (particularly the [ iris ](/wiki/Iris_$anatomy$ "Iris $anatomy$") and its [ color ](/wiki/Eye_color "Eye color") ) and the area surrounding the eye ( [ lids ](/wiki/Eyelid "Eyelid") , [ lashes ](/wiki/Eyelash "Eyelash") , [ brows ](/wiki/Eyebrow "Eyebrow") ) have long been a key component of [ physical attractiveness ](/wiki/Physical_attractiveness "Physical attractiveness") . [ Eye contact ](/wiki/Eye_contact "Eye contact") plays a significant role in human nonverbal communication. A prominent [ limbal ring ](/wiki/Limbal_ring "Limbal ring") (dark ring around the [ iris ](/wiki/Iris_$anatomy$ "Iris $anatomy$") of the eye) is considered attractive. [80] Additionally, long and full [ eyelashes ](/wiki/Eyelash "Eyelash") are coveted as a sign of beauty and are considered an attractive [ facial feature ](/wiki/Face "Face") . [81] Pupil size has also been shown to play an influential role in attraction and nonverbal communication, with [ dilated (larger) pupils ](/wiki/Mydriasis "Mydriasis") perceived to be more attractive. [82] It should also be noted that dilated pupils are a response to sexual arousal and stimuli. [83] In the [ Renaissance ](/wiki/Renaissance "Renaissance") , women used the juice of the berries of the [ belladonna ](/wiki/Atropa_belladonna "Atropa belladonna") plant in eyedrops to [ dilate the pupils ](/wiki/Pupillary_response "Pupillary response") and make the eyes appear more seductive. * [ ![Long, thick, and dark eyelashes are considered an attractive facial feature as they draw attention to the eyes. Subject exhibits trichomegaly $exceptionally long lashes$](//upload.wikimedia.org/wikipedia/commons/thumb/9/9e/Human_eyelashes.jpg/427px-Human_eyelashes.jpg) ](/wiki/File:Human_eyelashes.jpg "Long, thick, and dark eyelashes are considered an attractive facial feature as they draw attention to the eyes. Subject exhibits trichomegaly $exceptionally long lashes$") Long, thick, and dark eyelashes are considered an attractive facial feature as they draw attention to the eyes. Subject exhibits [ trichomegaly ](/wiki/Trichomegaly "Trichomegaly") (exceptionally long lashes) * [ ![A thick, dark, limbal ring is seen as an attractive feature](//upload.wikimedia.org/wikipedia/commons/thumb/9/96/Human_eye_with_limbal_ring%2C_anterior_view.jpg/427px-Human_eye_with_limbal_ring%2C_anterior_view.jpg) ](/wiki/File:Human_eye_with_limbal_ring,_anterior_view.jpg "A thick, dark, limbal ring is seen as an attractive feature") A thick, dark, limbal ring is seen as an attractive feature * [ ![Pupils dilate in response to sexual arousal and larger pupils are perceived to be more attractive](//upload.wikimedia.org/wikipedia/commons/thumb/1/19/Human_eye_in_dim_light.jpg/427px-Human_eye_in_dim_light.jpg) ](/wiki/File:Human_eye_in_dim_light.jpg "Pupils dilate in response to sexual arousal and larger pupils are perceived to be more attractive") Pupils dilate in response to sexual arousal and larger pupils are perceived to be more attractive ## Images [ [ edit ](/w/index.php?title=Human_eye&action=edit&section=24 "Edit section: Images") ] * [ ![Right eye without labels $horizontal section$](//upload.wikimedia.org/wikipedia/commons/thumb/a/a4/Diagram_of_human_eye_without_labels.svg/114px-Diagram_of_human_eye_without_labels.svg.png) ](/wiki/File:Diagram_of_human_eye_without_labels.svg "Right eye without labels $horizontal section$") Right eye without labels (horizontal section) * [ ![](//upload.wikimedia.org/wikipedia/commons/thumb/0/03/Blausen_0388_EyeAnatomy_01.png/120px-Blausen_0388_EyeAnatomy_01.png) ](/wiki/File:Blausen_0388_EyeAnatomy_01.png) * [ ![](//upload.wikimedia.org/wikipedia/commons/thumb/3/30/Blausen_0389_EyeAnatomy_02.png/120px-Blausen_0389_EyeAnatomy_02.png) ](/wiki/File:Blausen_0389_EyeAnatomy_02.png) * [ ![The structures of the eye labeled](//upload.wikimedia.org/wikipedia/commons/thumb/d/d0/Three_Main_Layers_of_the_Eye.png/120px-Three_Main_Layers_of_the_Eye.png) ](/wiki/File:Three_Main_Layers_of_the_Eye.png "The structures of the eye labeled") The structures of the eye labeled * [ ![Another view of the eye and the structures of the eye labeled](//upload.wikimedia.org/wikipedia/commons/thumb/e/e9/Three_Internal_chambers_of_the_Eye.svg/117px-Three_Internal_chambers_of_the_Eye.svg.png) ](/wiki/File:Three_Internal_chambers_of_the_Eye.svg "Another view of the eye and the structures of the eye labeled") Another view of the eye and the structures of the eye labeled ## See also [ [ edit ](/w/index.php?title=Human_eye&action=edit&section=25 "Edit section: See also") ] * [ ![icon](//upload.wikimedia.org/wikipedia/commons/thumb/1/10/Anatomy_posture_and_body_mechanics_08.web.jpg/18px-Anatomy_posture_and_body_mechanics_08.web.jpg) ](/wiki/File:Anatomy_posture_and_body_mechanics_08.web.jpg) [ Anatomy portal ](/wiki/Portal:Anatomy "Portal:Anatomy") * [ Eye colour ](/wiki/Eye_colour "Eye colour") * [ Eye development ](/wiki/Eye_development "Eye development") * [ Eye disease ](/wiki/Eye_disease "Eye disease") * [ Eye strain ](/wiki/Eye_strain "Eye strain") * [ Hyaloid canal ](/wiki/Hyaloid_canal "Hyaloid canal") * [ Iris recognition ](/wiki/Iris_recognition "Iris recognition") * [ Knobloch syndrome ](/wiki/Knobloch_syndrome "Knobloch syndrome") * [ Lacrimal caruncle ](/wiki/Lacrimal_caruncle "Lacrimal caruncle") * [ Rheum ](/wiki/Rheum "Rheum") * [ Spectral sensitivity ](/wiki/Spectral_sensitivity "Spectral sensitivity") ## References [ [ edit ](/w/index.php?title=Human_eye&action=edit&section=26 "Edit section: References") ] 1. ^ Zimmer, Carl (February 2012). [ "Our Strange, Important, Subconscious Light Detectors" ](https://www.discovermagazine.com/mind/the-brain-our-strange-important-subconscious-light-detectors) . Discover Magazine . Retrieved 2012-05-05 . 2. ^ Schwiegerling, Jim (2004). _Field guide to visual and ophthalmic optics_ . SPIE FG. Bellingham, Wash: SPIE Press. [ ISBN ](/wiki/ISBN_$identifier$ "ISBN $identifier$") [ 978-0-8194-5629-8 ](/wiki/Special:BookSources/978-0-8194-5629-8 "Special:BookSources/978-0-8194-5629-8") . 3. ^ _a _ _b _ [ "Variations in eyeball diameters of the healthy adults" ](http://www.pubfacts.com/detail/25431659/Variations-in-eyeball-diameters-of-the-healthy-adults) . 4. ^ Cunningham, Emmett T.; Riordan-Eva, Paul (2011-05-17). [ _Vaughan & Asbury's General Ophthalmology _ ](http://accessmedicine.com/resourceTOC.aspx?resourceID=720) (18th ed.). New York: McGraw-Hill Medical. [ ISBN ](/wiki/ISBN_$identifier$ "ISBN $identifier$") [ 978-0-07-163420-5 ](/wiki/Special:BookSources/978-0-07-163420-5 "Special:BookSources/978-0-07-163420-5") . 5. ^ "eye, human."Encyclopædia Britannica from [ Encyclopædia Britannica Ultimate Reference Suite ](/wiki/Encyclop%C3%A6dia_Britannica_Ultimate_Reference_Suite "Encyclopædia Britannica Ultimate Reference Suite") 2009 6. ^ Haładaj, R (2019). [ "Normal Anatomy and Anomalies of the Rectus Extraocular Muscles in Human: A Review of the Recent Data and Findings" ](https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6954479) . _BioMed Research International_ . 2019 : 8909162. [ doi ](/wiki/Doi_$identifier$ "Doi $identifier$") : [ 10.1155/2019/8909162 ](https://doi.org/10.1155%2F2019%2F8909162) . [ PMC ](/wiki/PMC_$identifier$ "PMC $identifier$") [ 6954479 ](https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6954479) . [ PMID ](/wiki/PMID_$identifier$ "PMID $identifier$") [ 31976329 ](https://pubmed.ncbi.nlm.nih.gov/31976329) . 7. ^ Carpenter, Roger H.S. (1988). _Movements of the eyes (2nd ed.)_ . London: Pion, Ltd [ ISBN ](/wiki/ISBN_$identifier$ "ISBN $identifier$") [ 0-85086-109-8 ](/wiki/Special:BookSources/0-85086-109-8 "Special:BookSources/0-85086-109-8") . 8. ^ Savino, Peter J.; Danesh-Meyer, Helen V. (2012). [ _Colour Atlas and Synopsis of Clinical Ophthalmology – Wills Eye Institute – Neuro-Ophthalmology_ ](https://books.google.com/books?id=6RgSZGWQZGIC&pg=PA12) . Lippincott Williams & Wilkins. p. 12. [ ISBN ](/wiki/ISBN_$identifier$ "ISBN $identifier$") [ 978-1-60913-266-8 ](/wiki/Special:BookSources/978-1-60913-266-8 "Special:BookSources/978-1-60913-266-8") . 9. ^ Ryan, Stephen J.; Schachat, Andrew P.; Wilkinson, Charles P.; David R. Hinton; SriniVas R. Sadda; [ Peter Wiedemann ](/wiki/Peter_Wiedemann "Peter Wiedemann") (2012). [ _Retina_ ](https://books.google.com/books?id=PdAsuzFRv5oC&pg=PT342) . Elsevier Health Sciences. p. 342. [ ISBN ](/wiki/ISBN_$identifier$ "ISBN $identifier$") [ 978-1-4557-3780-2 ](/wiki/Special:BookSources/978-1-4557-3780-2 "Special:BookSources/978-1-4557-3780-2") . 10. ^ Trattler, William B.; Kaiser, Peter K.; Friedman, Neil J. (2012). [ _Review of Ophthalmology: Expert Consult – Online and Print_ ](https://books.google.com/books?id=AazA_9TQnHYC&pg=PA255) . Elsevier Health Sciences. p. 255. [ ISBN ](/wiki/ISBN_$identifier$ "ISBN $identifier$") [ 978-1-4557-3773-4 ](/wiki/Special:BookSources/978-1-4557-3773-4 "Special:BookSources/978-1-4557-3773-4") . 11. ^ Dagnelie, Gislin (2011). [ _Visual Prosthetics: Physiology, Bioengineering, Rehabilitation_ ](https://archive.org/details/Gislin_Dagnelie_Visual_Prosthetics) . Springer Science & Business Media. p. [ 398 ](https://archive.org/details/Gislin_Dagnelie_Visual_Prosthetics/page/n401) . [ ISBN ](/wiki/ISBN_$identifier$ "ISBN $identifier$") [ 978-1-4419-0754-7 ](/wiki/Special:BookSources/978-1-4419-0754-7 "Special:BookSources/978-1-4419-0754-7") . 12. ^ Dohse, K.C. (2007). [ _Effects of Field of View and Stereo Graphics on Memory in Immersive Command and Control_ ](https://books.google.com/books?id=p2pSW2D4s7gC&pg=PA6) . p. 6. [ ISBN ](/wiki/ISBN_$identifier$ "ISBN $identifier$") [ 978-0-549-33503-0 ](/wiki/Special:BookSources/978-0-549-33503-0 "Special:BookSources/978-0-549-33503-0") . [ _[ permanent dead link ](/wiki/Wikipedia:Link_rot "Wikipedia:Link rot") _ ] 13. ^ Deering, Michael F. (1998). [ _The Limits of Human Vision_ ](http://michaelfrankdeering.org/Projects/EyeModel/limits.pdf) (PDF) . 14. ^ Spring, K. H.; Stiles, W. S. (1948). [ "Apparent shape and size of the pupil viewed obliquely" ](https://www.ncbi.nlm.nih.gov/pmc/articles/PMC510837) . _British Journal of Ophthalmology_ . 32 (6): 347–354. [ doi ](/wiki/Doi_$identifier$ "Doi $identifier$") : [ 10.1136/bjo.32.6.347 ](https://doi.org/10.1136%2Fbjo.32.6.347) . [ PMC ](/wiki/PMC_$identifier$ "PMC $identifier$") [ 510837 ](https://www.ncbi.nlm.nih.gov/pmc/articles/PMC510837) . [ PMID ](/wiki/PMID_$identifier$ "PMID $identifier$") [ 18170457 ](https://pubmed.ncbi.nlm.nih.gov/18170457) . 15. ^ Fedtke, Cathleen; Manns, Fabrice; Ho, Arthur (2010). [ "The entrance pupil of the human eye: a three-dimensional model as a function of viewing angle" ](https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3408927) . _Optics Express_ . 18 (21): 22364–22376. [ Bibcode ](/wiki/Bibcode_$identifier$ "Bibcode $identifier$") : [ 2010OExpr..1822364F ](https://ui.adsabs.harvard.edu/abs/2010OExpr..1822364F) . [ doi ](/wiki/Doi_$identifier$ "Doi $identifier$") : [ 10.1364/OE.18.022364 ](https://doi.org/10.1364%2FOE.18.022364) . [ PMC ](/wiki/PMC_$identifier$ "PMC $identifier$") [ 3408927 ](https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3408927) . [ PMID ](/wiki/PMID_$identifier$ "PMID $identifier$") [ 20941137 ](https://pubmed.ncbi.nlm.nih.gov/20941137) . 16. ^ Mathur, A.; Gehrmann, J.; Atchison, D. A. (2013). [ "Pupil shape as viewed along the horizontal visual field" ](https://doi.org/10.1167%2F13.6.3) . _Journal of Vision_ . 13 (6): 3. [ doi ](/wiki/Doi_$identifier$ "Doi $identifier$") : [ 10.1167/13.6.3 ](https://doi.org/10.1167%2F13.6.3) . [ PMID ](/wiki/PMID_$identifier$ "PMID $identifier$") [ 23648308 ](https://pubmed.ncbi.nlm.nih.gov/23648308) . 17. ^ [ MIL-STD-1472F, Military Standard, Human Engineering, Design Criteria For Military Systems, Equipment, And Facilities ](http://www.everyspec.com/MIL-STD/MIL-STD-1400-1499/MIL-STD-1472F_208/) . everyspec.com (1999) 18. ^ Ivergard, Toni; Hunt, Brian (2008). [ _Handbook of Control Room Design and Ergonomics: A Perspective for the Future, Second Edition_ ](https://books.google.com/books?id=DR9UyqLkgH8C&pg=PT108) . CRC Press. p. 90. [ ISBN ](/wiki/ISBN_$identifier$ "ISBN $identifier$") [ 978-1-4200-6434-6 ](/wiki/Special:BookSources/978-1-4200-6434-6 "Special:BookSources/978-1-4200-6434-6") . 19. ^ Kaschke, Michael; Donnerhacke, Karl-Heinz; Rill, Michael Stefan (2013). [ _Optical Devices in Ophthalmology and Optometry: Technology, Design Principles and Clinical Applications_ ](https://books.google.com/books?id=DPw8AgAAQBAJ&pg=PA26) . Vol. 19. p. 26. [ Bibcode ](/wiki/Bibcode_$identifier$ "Bibcode $identifier$") : [ 2014JBO....19g9901M ](https://ui.adsabs.harvard.edu/abs/2014JBO....19g9901M) . [ doi ](/wiki/Doi_$identifier$ "Doi $identifier$") : [ 10.1117/1.JBO.19.7.079901 ](https://doi.org/10.1117%2F1.JBO.19.7.079901) . [ ISBN ](/wiki/ISBN_$identifier$ "ISBN $identifier$") [ 978-3-527-64899-3 ](/wiki/Special:BookSources/978-3-527-64899-3 "Special:BookSources/978-3-527-64899-3") . [ S2CID ](/wiki/S2CID_$identifier$ "S2CID $identifier$") [ 117946411 ](https://api.semanticscholar.org/CorpusID:117946411) . ` {{ [ cite book ](/wiki/Template:Cite_book "Template:Cite book") }} ` : ` \|journal= ` ignored ( [ help ](/wiki/Help:CS1_errors#periodical_ignored "Help:CS1 errors") ) 20. ^ Banterle, Francesco; Artusi, Alessandro; Debattista, Kurt; Alan Chalmers (2011). [ _Advanced High Dynamic Range Imaging: Theory and Practice_ ](https://books.google.com/books?id=LL5orppYlJsC&pg=PA7) . CRC Press. p. 7. [ ISBN ](/wiki/ISBN_$identifier$ "ISBN $identifier$") [ 978-1-56881-719-4 ](/wiki/Special:BookSources/978-1-56881-719-4 "Special:BookSources/978-1-56881-719-4") . 21. ^ Pode, Ramchandra; Diouf, Boucar (2011). [ _Solar Lighting_ ](https://books.google.com/books?id=sqKUqfvDq_MC&pg=PA62) . Springer Science & Business Media. p. 62. 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[ S2CID ](/wiki/S2CID_$identifier$ "S2CID $identifier$") [ 12857616 ](https://api.semanticscholar.org/CorpusID:12857616) . ## External links [ [ edit ](/w/index.php?title=Human_eye&action=edit&section=27 "Edit section: External links") ] * [ Eye – Hilzbook ](https://web.archive.org/web/20150523224359/http://hilzbook.com/organs/head/eye/) * [ Retina – Hilzbook ](https://web.archive.org/web/20150524023842/http://hilzbook.com/organs/head/eye/retina/) * [ Interactive Tool to explore the Human Eye ](https://www.visiondirect.co.uk/the-human-eye) * [ ![](//upload.wikimedia.org/wikipedia/en/thumb/4/4a/Commons-logo.svg/12px-Commons-logo.svg.png) ](/wiki/File:Commons-logo.svg) Media related to [ Human eyes ](https://commons.wikimedia.org/wiki/Category:Human_eyes "commons:Category:Human eyes") at Wikimedia Commons * [ ![](//upload.wikimedia.org/wikipedia/commons/thumb/f/fa/Wikiquote-logo.svg/13px-Wikiquote-logo.svg.png) ](/wiki/File:Wikiquote-logo.svg) Quotations related to [ eyes ](https://en.wikiquote.org/wiki/eyes "wikiquote:eyes") at Wikiquote * [ v ](/wiki/Template:Orbital_anatomy "Template:Orbital anatomy") * [ t ](/wiki/Template_talk:Orbital_anatomy "Template talk:Orbital anatomy") * [ e ](/wiki/Special:EditPage/Template:Orbital_anatomy "Special:EditPage/Template:Orbital anatomy") The [ orbit ](/wiki/Orbit_$anatomy$ "Orbit $anatomy$") of the eye --- Bones \| * [ Frontal bone ](/wiki/Frontal_bone "Frontal bone") * [ Zygomatic bone ](/wiki/Zygomatic_bone "Zygomatic bone") * [ Maxillary bone ](/wiki/Maxilla "Maxilla") * [ Sphenoid bone ](/wiki/Sphenoid_bone "Sphenoid bone") * [ Ethmoid bone ](/wiki/Ethmoid_bone "Ethmoid bone") * [ Palatine bone ](/wiki/Palatine_bone "Palatine bone") * [ Lacrimal bone ](/wiki/Lacrimal_bone "Lacrimal bone") [ Muscles ](/wiki/Extraocular_muscles "Extraocular muscles") \| * [ Superior rectus muscle ](/wiki/Superior_rectus_muscle "Superior rectus muscle") * [ Inferior rectus muscle ](/wiki/Inferior_rectus_muscle "Inferior rectus muscle") * [ Lateral rectus muscle ](/wiki/Lateral_rectus_muscle "Lateral rectus muscle") * [ Medial rectus muscle ](/wiki/Medial_rectus_muscle "Medial rectus muscle") * [ Superior oblique muscle ](/wiki/Superior_oblique_muscle "Superior oblique muscle") * [ Trochlea of superior oblique ](/wiki/Trochlea_of_superior_oblique "Trochlea of superior oblique") * [ Inferior oblique muscle ](/wiki/Inferior_oblique_muscle "Inferior oblique muscle") [ Eyelid ](/wiki/Eyelid "Eyelid") \| * [ Levator palpebrae superioris muscle ](/wiki/Levator_palpebrae_superioris_muscle "Levator palpebrae superioris muscle") * [ Tarsus ](/wiki/Tarsus_$eyelids$ "Tarsus $eyelids$") * [ Medial palpebral ligament ](/wiki/Medial_palpebral_ligament "Medial palpebral ligament") * [ Epicanthic fold ](/wiki/Epicanthic_fold "Epicanthic fold") * [ Meibomian gland ](/wiki/Meibomian_gland "Meibomian gland") * [ Ciliary glands ](/wiki/Moll%27s_gland "Moll's gland") * [ Eyelash ](/wiki/Eyelash "Eyelash") * [ Palpebral fissure ](/wiki/Palpebral_fissure "Palpebral fissure") * [ Canthus ](/wiki/Canthus "Canthus") * [ Gland of Zeis ](/wiki/Gland_of_Zeis "Gland of Zeis") [ Lacrimal apparatus ](/wiki/Lacrimal_apparatus "Lacrimal apparatus") \| * [ Lacrimal canaliculi ](/wiki/Lacrimal_canaliculi "Lacrimal canaliculi") * [ Lacrimal caruncle ](/wiki/Lacrimal_caruncle "Lacrimal caruncle") * [ Lacrimal gland ](/wiki/Lacrimal_gland "Lacrimal gland") * [ Accessory lacrimal glands ](/wiki/Accessory_lacrimal_glands "Accessory lacrimal glands") * [ Krause's glands ](/wiki/Krause%27s_glands "Krause's glands") * [ Ciaccio's glands ](/wiki/Ciaccio%27s_glands "Ciaccio's glands") * [ Lacrimal lake ](/wiki/Lacrimal_lake "Lacrimal lake") * [ Lacrimal papilla ](/wiki/Lacrimal_papilla "Lacrimal papilla") * [ Lacrimal punctum ](/wiki/Lacrimal_punctum "Lacrimal punctum") * [ Lacrimal sac ](/wiki/Lacrimal_sac "Lacrimal sac") * [ Nasolacrimal duct ](/wiki/Nasolacrimal_duct "Nasolacrimal duct") Other \| * [ Eyebrow ](/wiki/Eyebrow "Eyebrow") * [ Unibrow ](/wiki/Unibrow "Unibrow") * [ Conjunctiva ](/wiki/Conjunctiva "Conjunctiva") * [ Plica semilunaris ](/wiki/Plica_semilunaris_of_conjunctiva "Plica semilunaris of conjunctiva") * [ Orbital septum ](/wiki/Orbital_septum "Orbital septum") * [ Periorbita ](/wiki/Periorbita "Periorbita") * [ Suspensory ligament of eyeball ](/wiki/Suspensory_ligament_of_eyeball "Suspensory ligament of eyeball") * [ Tenon's capsule ](/wiki/Tenon%27s_capsule "Tenon's capsule") * [ v ](/wiki/Template:Eye_proteins "Template:Eye proteins") * [ t ](/wiki/Template_talk:Eye_proteins "Template talk:Eye proteins") * [ e ](/wiki/Special:EditPage/Template:Eye_proteins "Special:EditPage/Template:Eye proteins") Eye [ proteins ](/wiki/Protein "Protein") --- [ Opsin ](/wiki/Opsin "Opsin") ( [ retinylidene protein ](/wiki/Retinylidene_protein "Retinylidene protein") ) \| \| [ visual ](/wiki/Vertebrate_visual_opsin "Vertebrate visual opsin") \| * [ Rhodopsin ](/wiki/Rhodopsin "Rhodopsin") * [ Cone opsins ](/wiki/Cone_opsin "Cone opsin") * [ OPN1LW ](/wiki/OPN1LW "OPN1LW") * [ OPN1MW ](/wiki/OPN1MW "OPN1MW") / [ OPN1MW2 ](/wiki/OPN1MW2 "OPN1MW2") * [ OPN1SW ](/wiki/OPN1SW "OPN1SW") ---\|--- [ nonvisual ](/wiki/Opsin#Novel_type_2_opsin_groups "Opsin") \| * [ Melanopsin ](/wiki/Melanopsin "Melanopsin") * [ OPN3 ](/wiki/OPN3 "OPN3") * [ OPN5 ](/wiki/OPN5 "OPN5") * [ RRH ](/wiki/RRH "RRH") * [ RGR ](/wiki/RGR_$gene$ "RGR $gene$") [ Crystallin ](/wiki/Crystallin "Crystallin") \| * [ Alpha ](/wiki/Alpha_crystallin "Alpha crystallin") ( [ A ](/wiki/CRYAA "CRYAA") * [ B ](/wiki/CRYAB "CRYAB") ) * [ Beta ](/wiki/Beta_gamma_crystallin "Beta gamma crystallin") ( [ A1 ](/wiki/Crystallin,_beta_A1 "Crystallin, beta A1") * [ A2 ](/w/index.php?title=CRYBA2&action=edit&redlink=1 "CRYBA2 $page does not exist$") * [ A4 ](/wiki/CRYBA4 "CRYBA4") * [ B1 ](/wiki/CRYBB1 "CRYBB1") * [ B2 ](/wiki/CRYBB2 "CRYBB2") * [ B3 ](/wiki/CRYBB3 "CRYBB3") ) * [ Gamma ](/wiki/Beta_gamma_crystallin "Beta gamma crystallin") ( [ A ](/wiki/CRYGA "CRYGA") * [ B ](/wiki/CRYGB "CRYGB") * [ C ](/wiki/CRYGC "CRYGC") * [ D ](/wiki/Crystallin,_gamma_D "Crystallin, gamma D") * [ N ](/w/index.php?title=CRYGN&action=edit&redlink=1 "CRYGN $page does not exist$") * [ S ](/wiki/CRYGS "CRYGS") ) Other \| * [ Arrestin ](/wiki/Arrestin "Arrestin") * [ Guanylate cyclase activator ](/wiki/Guanylate_cyclase_activator "Guanylate cyclase activator") * [ Recoverin ](/wiki/Recoverin "Recoverin") * [ Rhodopsin kinase ](/wiki/Rhodopsin_kinase "Rhodopsin kinase") * [ v ](/wiki/Template:Human_regional_anatomy "Template:Human regional anatomy") * [ t ](/wiki/Template_talk:Human_regional_anatomy "Template talk:Human regional anatomy") * [ e ](/wiki/Special:EditPage/Template:Human_regional_anatomy "Special:EditPage/Template:Human regional anatomy") [ Human regional anatomy ](/wiki/Human_body#Regional_groups "Human body") --- [ Body ](/wiki/Human_body "Human body") \| [ Skin ](/wiki/Human_skin "Human skin") [ Head ](/wiki/Human_head "Human head") \| * [ Hair ](/wiki/Hair "Hair") * [ Face ](/wiki/Face "Face") * [ Forehead ](/wiki/Forehead "Forehead") * [ Cheek ](/wiki/Cheek "Cheek") * [ Chin ](/wiki/Chin "Chin") * [ Eyebrow ](/wiki/Eyebrow "Eyebrow") * Eye * [ Eyelid ](/wiki/Eyelid "Eyelid") * [ Nose ](/wiki/Human_nose "Human nose") * [ Mouth ](/wiki/Human_mouth "Human mouth") * [ Lip ](/wiki/Lip "Lip") * [ Tongue ](/wiki/Tongue "Tongue") * [ Teeth ](/wiki/Human_tooth "Human tooth") * [ Ear ](/wiki/Ear "Ear") * [ Jaw ](/wiki/Jaw "Jaw") * [ Mandible ](/wiki/Mandible "Mandible") * [ Occiput ](/wiki/Occipital_bone "Occipital bone") * [ Scalp ](/wiki/Scalp "Scalp") * [ Temple ](/wiki/Temple_$anatomy$ "Temple $anatomy$") [ Neck ](/wiki/Neck "Neck") \| * [ Adam's apple ](/wiki/Adam%27s_apple "Adam's apple") * [ Throat ](/wiki/Throat "Throat") * [ Nape ](/wiki/Nape "Nape") [ Torso ](/wiki/Torso "Torso") (Trunk) \| * [ Abdomen ](/wiki/Abdomen "Abdomen") * [ Waist ](/wiki/Waist "Waist") * [ Midriff ](/wiki/Midriff "Midriff") * [ Navel ](/wiki/Navel "Navel") * [ Vertebral column ](/wiki/Vertebral_column "Vertebral column") * [ Back ](/wiki/Human_back "Human back") * [ Thorax ](/wiki/Thorax "Thorax") * [ Breast ](/wiki/Breast "Breast") * [ Nipple ](/wiki/Nipple "Nipple") * [ Pelvis ](/wiki/Pelvis "Pelvis") * [ Genitalia ](/wiki/Sex_organ "Sex organ") * [ Penis ](/wiki/Human_penis "Human penis") * [ Scrotum ](/wiki/Scrotum "Scrotum") * [ Vulva ](/wiki/Vulva "Vulva") * [ Anus ](/wiki/Human_anus "Human anus") [ Limbs ](/wiki/Limb_$anatomy$ "Limb $anatomy$") \| \| [ Arm ](/wiki/Arm "Arm") \| * [ Shoulder ](/wiki/Shoulder "Shoulder") * [ Axilla ](/wiki/Axilla "Axilla") * [ Elbow ](/wiki/Elbow "Elbow") * [ Forearm ](/wiki/Forearm "Forearm") * [ Wrist ](/wiki/Wrist "Wrist") * [ Hand ](/wiki/Hand "Hand") * [ Finger ](/wiki/Finger "Finger") * [ Fingernail ](/wiki/Nail_$anatomy$ "Nail $anatomy$") * [ Thumb ](/wiki/Thumb "Thumb") * [ Index ](/wiki/Index_finger "Index finger") * [ Middle ](/wiki/Middle_finger "Middle finger") * [ Ring ](/wiki/Ring_finger "Ring finger") * [ Little ](/wiki/Little_finger "Little finger") ---\|--- [ Leg ](/wiki/Human_leg "Human leg") \| * [ Buttocks ](/wiki/Buttocks "Buttocks") * [ Hip ](/wiki/Hip "Hip") * [ Thigh ](/wiki/Thigh "Thigh") * [ Knee ](/wiki/Knee "Knee") * [ Calf ](/wiki/Calf_$leg$ "Calf $leg$") * [ Foot ](/wiki/Foot "Foot") * [ Ankle ](/wiki/Ankle "Ankle") * [ Heel ](/wiki/Heel "Heel") * [ Toe ](/wiki/Toe "Toe") * [ Toenail ](/wiki/Nail_$anatomy$ "Nail $anatomy$") * [ Sole ](/wiki/Sole_$foot$ "Sole $foot$") * [ v ](/wiki/Template:Human_systems_and_organs "Template:Human systems and organs") * [ t ](/wiki/Template_talk:Human_systems_and_organs "Template talk:Human systems and organs") * [ e ](/wiki/Special:EditPage/Template:Human_systems_and_organs "Special:EditPage/Template:Human systems and organs") [ Human systems ](/wiki/Human_body "Human body") and [ organs ](/wiki/Organ_$biology$ "Organ $biology$") --- [ Musculoskeletal system ](/wiki/Human_musculoskeletal_system "Human musculoskeletal system") \| \| [ Skeletal system ](/wiki/Human_skeleton "Human skeleton") \| * [ Bone ](/wiki/Bone "Bone") * [ Carpus ](/wiki/Carpal_bones "Carpal bones") * [ Collar bone ](/wiki/Clavicle "Clavicle") (clavicle) * [ Thigh bone ](/wiki/Femur "Femur") (femur) * [ Fibula ](/wiki/Fibula "Fibula") * [ Humerus ](/wiki/Humerus "Humerus") * [ Mandible ](/wiki/Mandible "Mandible") * [ Metacarpus ](/wiki/Metacarpal_bones "Metacarpal bones") * [ Metatarsus ](/wiki/Metatarsal_bones "Metatarsal bones") * [ Ossicles ](/wiki/Ossicles "Ossicles") * [ Patella ](/wiki/Patella "Patella") * [ Phalanges ](/wiki/Phalanx_bone "Phalanx bone") * [ Radius ](/wiki/Radius_$bone$ "Radius $bone$") * [ Skull ](/wiki/Skull#Humans "Skull") * [ Tarsus ](/wiki/Tarsus_$skeleton$ "Tarsus $skeleton$") * [ Tibia ](/wiki/Tibia "Tibia") * [ Ulna ](/wiki/Ulna "Ulna") * [ Rib ](/wiki/Rib "Rib") * [ Vertebra ](/wiki/Vertebral_column "Vertebral column") * [ Pelvis ](/wiki/Pelvis "Pelvis") * [ Sternum ](/wiki/Sternum "Sternum") * [ Cartilage ](/wiki/Cartilage "Cartilage") ---\|--- [ Joints ](/wiki/Joint "Joint") \| * [ Fibrous joint ](/wiki/Fibrous_joint "Fibrous joint") * [ Cartilaginous joint ](/wiki/Cartilaginous_joint "Cartilaginous joint") * [ Synovial joint ](/wiki/Synovial_joint "Synovial joint") [ Muscular system ](/wiki/Muscular_system "Muscular system") \| * [ Muscle ](/wiki/Muscle "Muscle") * [ Tendon ](/wiki/Tendon "Tendon") * [ Diaphragm ](/wiki/Thoracic_diaphragm "Thoracic diaphragm") [ Circulatory system ](/wiki/Circulatory_system "Circulatory system") \| \| [ Cardiovascular system ](/wiki/Circulatory_system "Circulatory system") \| * _peripheral_ * [ Artery ](/wiki/Artery "Artery") * [ Vein ](/wiki/Vein "Vein") * [ Lymphatic vessel ](/wiki/Lymphatic_vessel "Lymphatic vessel") * [ Heart ](/wiki/Heart "Heart") ---\|--- [ Lymphatic system ](/wiki/Lymphatic_system "Lymphatic system") \| * _primary_ * [ Bone marrow ](/wiki/Bone_marrow "Bone marrow") * [ Thymus ](/wiki/Thymus "Thymus") * _secondary_ * [ Spleen ](/wiki/Spleen "Spleen") * [ Lymph node ](/wiki/Lymph_node "Lymph node") * _CNS equivalent_ * [ Glymphatic system ](/wiki/Glymphatic_system "Glymphatic system") [ Nervous system ](/wiki/Nervous_system "Nervous system") \| * * [ Brain ](/wiki/Human_brain "Human brain") * [ Spinal cord ](/wiki/Spinal_cord "Spinal cord") * [ Nerve ](/wiki/Nerve "Nerve") * [ Sensory system ](/wiki/Sensory_system "Sensory system") * [ Ear ](/wiki/Ear "Ear") * Eye * [ Somatic system ](/wiki/Somatic_nervous_system "Somatic nervous system") [ Integumentary system ](/wiki/Integumentary_system "Integumentary system") \| * [ Skin ](/wiki/Human_skin "Human skin") * [ Subcutaneous tissue ](/wiki/Subcutaneous_tissue "Subcutaneous tissue") * [ Breast ](/wiki/Breast "Breast") * [ Mammary gland ](/wiki/Mammary_gland "Mammary gland") [ Haematopoietic ](/wiki/Haematopoietic_system "Haematopoietic system") and [ immune systems ](/wiki/Immune_system "Immune system") \| * [ Myeloid ](/wiki/Myeloid "Myeloid") * [ Myeloid immune system ](/wiki/Immune_system "Immune system") * [ Lymphoid ](/wiki/Lymphocyte "Lymphocyte") * [ Lymphoid immune system ](/wiki/Immune_system "Immune system") [ Respiratory system ](/wiki/Respiratory_system "Respiratory system") \| * [ Upper ](/wiki/Respiratory_tract#Upper_respiratory_tract "Respiratory tract") * [ Nose ](/wiki/Human_nose "Human nose") * [ Nasopharynx ](/wiki/Pharynx#Nasopharynx "Pharynx") * [ Larynx ](/wiki/Larynx "Larynx") * [ Lower ](/wiki/Respiratory_tract#Lower_respiratory_tract "Respiratory tract") * [ Trachea ](/wiki/Trachea "Trachea") * [ Bronchus ](/wiki/Bronchus "Bronchus") * [ Lung ](/wiki/Lung "Lung") [ Digestive system ](/wiki/Human_digestive_system "Human digestive system") \| * [ Mouth ](/wiki/Human_mouth "Human mouth") * [ Salivary gland ](/wiki/Salivary_gland "Salivary gland") * [ Tongue ](/wiki/Tongue "Tongue") * [ Lip ](/wiki/Lip "Lip") * [ Tooth ](/wiki/Human_tooth "Human tooth") * _upper GI_ * [ Oropharynx ](/wiki/Pharynx "Pharynx") * [ Laryngopharynx ](/wiki/Pharynx "Pharynx") * [ Esophagus ](/wiki/Esophagus "Esophagus") * [ Stomach ](/wiki/Stomach "Stomach") * _lower GI_ * [ Small intestine ](/wiki/Small_intestine "Small intestine") * [ Appendix ](/wiki/Appendix_$anatomy$ "Appendix $anatomy$") * [ Colon ](/wiki/Large_intestine#Structure "Large intestine") * [ Rectum ](/wiki/Rectum "Rectum") * [ Anus ](/wiki/Human_anus "Human anus") * _[ accessory ](/wiki/Human_digestive_system "Human digestive system") _ * [ Liver ](/wiki/Liver "Liver") * [ Biliary tract ](/wiki/Biliary_tract "Biliary tract") * [ Pancreas ](/wiki/Pancreas "Pancreas") [ Urinary system ](/wiki/Urinary_system "Urinary system") \| * [ Genitourinary system ](/wiki/Genitourinary_system "Genitourinary system") * [ Kidney ](/wiki/Kidney "Kidney") * [ Ureter ](/wiki/Ureter "Ureter") * [ Bladder ](/wiki/Urinary_bladder "Urinary bladder") * [ Urethra ](/wiki/Urethra "Urethra") [ Reproductive system ](/wiki/Human_reproductive_system "Human reproductive system") \| * [ Male ](/wiki/Male_reproductive_system "Male reproductive system") * [ Scrotum ](/wiki/Scrotum "Scrotum") * [ Penis ](/wiki/Human_penis "Human penis") * [ Prostate ](/wiki/Prostate "Prostate") * [ Testicle ](/wiki/Testicle "Testicle") * [ Seminal vesicle ](/wiki/Seminal_vesicle "Seminal vesicle") * [ Female ](/wiki/Female_reproductive_system "Female reproductive system") * [ Uterus ](/wiki/Uterus "Uterus") * [ Vagina ](/wiki/Vagina "Vagina") * [ Vulva ](/wiki/Vulva "Vulva") * [ Ovary ](/wiki/Ovary "Ovary") * [ Placenta ](/wiki/Placenta "Placenta") [ Endocrine system ](/wiki/Endocrine_system "Endocrine system") \| * [ Pituitary ](/wiki/Pituitary_gland "Pituitary gland") * [ Pineal ](/wiki/Pineal_gland "Pineal gland") * [ Thyroid ](/wiki/Thyroid "Thyroid") * [ Parathyroid ](/wiki/Parathyroid_gland "Parathyroid gland") * [ Adrenal ](/wiki/Adrenal_gland "Adrenal gland") * [ Islets of Langerhans ](/wiki/Pancreatic_islets "Pancreatic islets") * [ v ](/wiki/Template:Eye_anatomy "Template:Eye anatomy") * [ t ](/wiki/Template_talk:Eye_anatomy "Template talk:Eye anatomy") * [ e ](/wiki/Special:EditPage/Template:Eye_anatomy "Special:EditPage/Template:Eye anatomy") Anatomy of the [ globe ](/wiki/Globe_$human_eye$ "Globe $human eye$") of the human eye --- [ Fibrous tunic ](/wiki/Fibrous_tunic_of_eyeball "Fibrous tunic of eyeball") (outer) \| \| [ Sclera ](/wiki/Sclera "Sclera") \| * [ Episcleral layer ](/wiki/Episcleral_layer "Episcleral layer") * [ Schlemm's canal ](/wiki/Schlemm%27s_canal "Schlemm's canal") * [ Trabecular meshwork ](/wiki/Trabecular_meshwork "Trabecular meshwork") ---\|--- [ Cornea ](/wiki/Cornea "Cornea") \| * [ Limbus ](/wiki/Corneal_limbus "Corneal limbus") * _layers_ * [ Epithelium ](/wiki/Corneal_epithelium "Corneal epithelium") * [ Bowman's ](/wiki/Bowman%27s_layer "Bowman's layer") * [ Stroma ](/wiki/Stroma_of_cornea "Stroma of cornea") * [ Dua's layer ](/wiki/Dua%27s_layer "Dua's layer") * [ Descemet's ](/wiki/Descemet%27s_membrane "Descemet's membrane") * [ Endothelium ](/wiki/Corneal_endothelium "Corneal endothelium") ![1:posterior segment 2:ora serrata 3:ciliary muscle 4:ciliary zonules 5:Schlemm's canal 6:pupil 7:anterior chamber 8:cornea 9:iris 10:lens cortex 11:lens nucleus 12:ciliary process 13:conjunctiva 14:inferior oblique muscule 15:inferior rectus muscule 16:medial rectus muscle 17:retinal arteries and veins 18:optic disc 19:dura mater 20:central retinal artery 21:central retinal vein 22:optic nerve 23:vorticose vein 24:bulbar sheath 25:macula 26:fovea 27:sclera 28:choroid 29:superior rectus muscle 30:retina](//upload.wikimedia.org/wikipedia/commons/thumb/e/e8/Eye- diagram_no_circles_border.svg/200px-Eye-diagram_no_circles_border.svg.png) 1:posterior segment 2:ora serrata 3:ciliary muscle 4:ciliary zonules 5:Schlemm's canal 6:pupil 7:anterior chamber 8:cornea 9:iris 10:lens cortex 11:lens nucleus 12:ciliary process 13:conjunctiva 14:inferior oblique muscule 15:inferior rectus muscule 16:medial rectus muscle 17:retinal arteries and veins 18:optic disc 19:dura mater 20:central retinal artery 21:central retinal vein 22:optic nerve 23:vorticose vein 24:bulbar sheath 25:macula 26:fovea 27:sclera 28:choroid 29:superior rectus muscle 30:retina [ Uvea / vascular tunic ](/wiki/Uvea "Uvea") (middle) \| \| [ Choroid ](/wiki/Choroid "Choroid") \| * [ Capillary lamina of choroid ](/wiki/Capillary_lamina_of_choroid "Capillary lamina of choroid") * [ Bruch's membrane ](/wiki/Bruch%27s_membrane "Bruch's membrane") * [ Sattler's layer ](/wiki/Sattler%27s_layer "Sattler's layer") ---\|--- [ Ciliary body ](/wiki/Ciliary_body "Ciliary body") \| * [ Ciliary processes ](/wiki/Ciliary_processes "Ciliary processes") * [ Ciliary muscle ](/wiki/Ciliary_muscle "Ciliary muscle") * [ Pars plicata ](/wiki/Pars_plicata "Pars plicata") * [ Pars plana ](/wiki/Pars_plana "Pars plana") [ Iris ](/wiki/Iris_$anatomy$ "Iris $anatomy$") \| * [ Stroma ](/wiki/Stroma_of_iris "Stroma of iris") * [ Pupil ](/wiki/Pupil "Pupil") * [ Iris dilator muscle ](/wiki/Iris_dilator_muscle "Iris dilator muscle") * [ Iris sphincter muscle ](/wiki/Iris_sphincter_muscle "Iris sphincter muscle") [ Retina ](/wiki/Retina "Retina") (inner) \| \| Layers \| * [ Inner limiting membrane ](/wiki/Inner_limiting_membrane "Inner limiting membrane") * [ Nerve fiber layer ](/wiki/Nerve_fiber_layer "Nerve fiber layer") * [ Ganglion cell layer ](/wiki/Ganglion_cell_layer "Ganglion cell layer") * [ Inner plexiform layer ](/wiki/Inner_plexiform_layer "Inner plexiform layer") * [ Inner nuclear layer ](/wiki/Inner_nuclear_layer "Inner nuclear layer") * [ Outer plexiform layer ](/wiki/Outer_plexiform_layer "Outer plexiform layer") * [ Outer nuclear layer ](/wiki/Outer_nuclear_layer "Outer nuclear layer") * [ External limiting membrane ](/wiki/External_limiting_membrane "External limiting membrane") * [ Layer of rods and cones ](/wiki/Layer_of_rods_and_cones "Layer of rods and cones") * [ Retinal pigment epithelium ](/wiki/Retinal_pigment_epithelium "Retinal pigment epithelium") ---\|--- Cells \| * [ Photoreceptor cells ](/wiki/Photoreceptor_cell "Photoreceptor cell") ( [ Cone cell ](/wiki/Cone_cell "Cone cell") , [ Rod cell ](/wiki/Rod_cell "Rod cell") ) → ( [ Horizontal cell ](/wiki/Retina_horizontal_cell "Retina horizontal cell") ) → [ Bipolar cell ](/wiki/Retina_bipolar_cell "Retina bipolar cell") → ( [ Amacrine cell ](/wiki/Amacrine_cell "Amacrine cell") ) → [ Retina ganglion cell ](/wiki/Retinal_ganglion_cell "Retinal ganglion cell") ( [ Midget cell ](/wiki/Midget_cell "Midget cell") , [ Parasol cell ](/wiki/Parasol_cell "Parasol cell") , [ Bistratified cell ](/wiki/Bistratified_cell "Bistratified cell") , [ Giant retina ganglion cells ](/wiki/Giant_retinal_ganglion_cells "Giant retinal ganglion cells") , [ Photosensitive ganglion cell ](/wiki/Intrinsically_photosensitive_retinal_ganglion_cells "Intrinsically photosensitive retinal ganglion cells") ) → _Diencephalon_ : [ P cell ](/wiki/Parvocellular_cell "Parvocellular cell") , [ M cell ](/wiki/Magnocellular_cell "Magnocellular cell") , [ K cell ](/wiki/Koniocellular_cell "Koniocellular cell") , [ Muller glia ](/wiki/Muller_glia "Muller glia") Other \| * [ Macula ](/wiki/Macula_of_retina "Macula of retina") * [ Perifoveal area ](/wiki/Perifovea "Perifovea") * [ Parafoveal area ](/wiki/Parafovea "Parafovea") * [ Fovea ](/wiki/Fovea_centralis "Fovea centralis") * [ Foveal avascular zone ](/wiki/Foveal_avascular_zone "Foveal avascular zone") * [ Foveola ](/wiki/Foveola "Foveola") * [ Optic disc ](/wiki/Optic_disc "Optic disc") * [ Optic cup ](/wiki/Optic_cup_$anatomical$ "Optic cup $anatomical$") * [ Ora serrata ](/wiki/Ora_serrata "Ora serrata") Anatomical regions of the eye \| \| [ Anterior segment ](/wiki/Anterior_segment_of_eyeball "Anterior segment of eyeball") \| * [ Adnexa ](/wiki/Accessory_visual_structures "Accessory visual structures") ( [ Eyebrow ](/wiki/Eyebrow "Eyebrow") , [ Eyelid ](/wiki/Eyelid "Eyelid") , [ Conjunctiva ](/wiki/Conjunctiva "Conjunctiva") , [ Lacrimal system ](/wiki/Lacrimal_system "Lacrimal system") , [ Orbit ](/wiki/Orbit_$anatomy$ "Orbit $anatomy$") ) * [ Fibrous tunic ](/wiki/Fibrous_tunic "Fibrous tunic") * [ Anterior chamber ](/wiki/Anterior_chamber_of_eyeball "Anterior chamber of eyeball") * [ Aqueous humour ](/wiki/Aqueous_humour "Aqueous humour") * [ Iris ](/wiki/Iris_$anatomy$ "Iris $anatomy$") * [ Posterior chamber ](/wiki/Posterior_chamber_of_eyeball "Posterior chamber of eyeball") * [ Ciliary body ](/wiki/Ciliary_body "Ciliary body") * [ Lens ](/wiki/Lens_$anatomy$ "Lens $anatomy$") * [ Capsule of lens ](/wiki/Capsule_of_lens "Capsule of lens") * [ Zonule of Zinn ](/wiki/Zonule_of_Zinn "Zonule of Zinn") ---\|--- [ Posterior segment ](/wiki/Posterior_segment_of_eyeball "Posterior segment of eyeball") \| * [ Vitreous chamber ](/wiki/Vitreous_chamber "Vitreous chamber") * [ Vitreous body ](/wiki/Vitreous_body "Vitreous body") * [ Retina ](/wiki/Retina "Retina") * [ Choroid ](/wiki/Choroid "Choroid") Other \| * [ Keratocytes ](/wiki/Corneal_keratocyte "Corneal keratocyte") * [ Ocular immune system ](/wiki/Ocular_immune_system "Ocular immune system") * [ Optical coherence tomography ](/wiki/Optical_coherence_tomography#Ophthalmology "Optical coherence tomography") * [ Eye care professional ](/wiki/Eye_care_professional "Eye care professional") * [ Eye disease ](/wiki/Eye_disease "Eye disease") * [ Refractive error ](/wiki/Refractive_error "Refractive error") * [ Accommodation ](/wiki/Accommodation_$eye$ "Accommodation $eye$") * _Physiological Optics_ * [ Visual perception ](/wiki/Visual_perception "Visual perception") [ Authority control databases ](/wiki/Help:Authority_control "Help:Authority control") [ ![Edit this at Wikidata](//upload.wikimedia.org/wikipedia/en/thumb/8/8a/OOjs_UI_icon_edit- ltr-progressive.svg/10px-OOjs_UI_icon_edit-ltr-progressive.svg.png) ](https://www.wikidata.org/wiki/Q430024#identifiers "Edit this at Wikidata") \| * [ Terminologia Anatomica ](http://tools.wmflabs.org/wikidata-externalid-url/?p=1323&url_prefix=https:%2F%2Fwww.unifr.ch%2Fifaa%2FPublic%2FEntryPage%2FTA98%20Tree%2FEntity%20TA98%20EN%2F&url_suffix=%20Entity%20TA98%20EN.htm&id=A01.1.00.007) * [ 2 ](http://tools.wmflabs.org/wikidata-externalid-url/?p=1323&url_prefix=https:%2F%2Fwww.unifr.ch%2Fifaa%2FPublic%2FEntryPage%2FTA98%20Tree%2FEntity%20TA98%20EN%2F&url_suffix=%20Entity%20TA98%20EN.htm&id=A15.2.00.001) ---\|--- ![](https://login.wikimedia.org/wiki/Special:CentralAutoLogin/start?type=1x1) Retrieved from " [ https://en.wikipedia.org/w/index.php?title=Human_eye&oldid=1219372703 ](https://en.wikipedia.org/w/index.php?title=Human_eye&oldid=1219372703) " [ Categories ](/wiki/Help:Category "Help:Category") : * [ Human eye ](/wiki/Category:Human_eye "Category:Human eye") * [ Facial features ](/wiki/Category:Facial_features "Category:Facial features") * [ Sensory organs ](/wiki/Category:Sensory_organs "Category:Sensory organs") * [ Ophthalmology ](/wiki/Category:Ophthalmology "Category:Ophthalmology") * [ Vision by taxon ](/wiki/Category:Vision_by_taxon "Category:Vision by taxon") * [ Visual system ](/wiki/Category:Visual_system "Category:Visual system") Hidden categories: * [ All articles with dead external links ](/wiki/Category:All_articles_with_dead_external_links "Category:All articles with dead external links") * [ Articles with dead external links from April 2024 ](/wiki/Category:Articles_with_dead_external_links_from_April_2024 "Category:Articles with dead external links from April 2024") * [ Articles with permanently dead external links ](/wiki/Category:Articles_with_permanently_dead_external_links "Category:Articles with permanently dead external links") * [ CS1 errors: periodical ignored ](/wiki/Category:CS1_errors:_periodical_ignored "Category:CS1 errors: periodical ignored") * [ Articles with short description ](/wiki/Category:Articles_with_short_description "Category:Articles with short description") * [ Short description is different from Wikidata ](/wiki/Category:Short_description_is_different_from_Wikidata "Category:Short description is different from Wikidata") * [ Commons category link is on Wikidata ](/wiki/Category:Commons_category_link_is_on_Wikidata "Category:Commons category link is on Wikidata") * [ Articles with TA98 identifiers ](/wiki/Category:Articles_with_TA98_identifiers "Category:Articles with TA98 identifiers") * This page was last edited on 17 April 2024, at 10:55 (UTC) . * Text is available under the [ Creative Commons Attribution-ShareAlike License 4.0 ](//en.wikipedia.org/wiki/Wikipedia:Text_of_the_Creative_Commons_Attribution-ShareAlike_4.0_International_License) [ ](//en.wikipedia.org/wiki/Wikipedia:Text_of_the_Creative_Commons_Attribution-ShareAlike_4.0_International_License) ; additional terms may apply. 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Wikipedia® is a registered trademark of the [ Wikimedia Foundation, Inc. ](//www.wikimediafoundation.org/) , a non-profit organization. * [ Privacy policy ](https://foundation.wikimedia.org/wiki/Special:MyLanguage/Policy:Privacy_policy) * [ About Wikipedia ](/wiki/Wikipedia:About) * [ Disclaimers ](/wiki/Wikipedia:General_disclaimer) * [ Contact Wikipedia ](//en.wikipedia.org/wiki/Wikipedia:Contact_us) * [ Code of Conduct ](https://foundation.wikimedia.org/wiki/Special:MyLanguage/Policy:Universal_Code_of_Conduct) * [ Developers ](https://developer.wikimedia.org) * [ Statistics ](https://stats.wikimedia.org/#/en.wikipedia.org) * [ Cookie statement ](https://foundation.wikimedia.org/wiki/Special:MyLanguage/Policy:Cookie_statement) * [ Mobile view ](//en.m.wikipedia.org/w/index.php?title=Human_eye&mobileaction=toggle_view_mobile) * [ ![Wikimedia Foundation](/static/images/footer/wikimedia-button.png) ](https://wikimediafoundation.org/) * [ ![Powered by MediaWiki](/static/images/footer/poweredby_mediawiki_88x31.png) ](https://www.mediawiki.org/) * Toggle limited content width [ v ]: View this template [ t ]: Discuss this template *[ e ]: Edit this template	biology	1593191	https://no.wikipedia.org/wiki/Heterorrhina%20sexmaculata	Heterorrhina sexmaculata	Heterorrhina sexmaculata er en bille som hører til gruppen gullbasser (Cetoniinae) i gruppen skarabider (Scarabaeoidea). Utseende En middelsstor (25-28 millimeter), bred, metallisk grønnfarget eller kobberfarget gullbasse, vanligvis med to svarte flekker på pronotum og fire på dekkvingene. Størrelsen på flekkene varierer mye, noen ganger er flekkene på dekkvingene utvidet til brede tverrbånd. Utbredelse Arten lever i Malaysia og Indonesia. Systematisk plassering Som for flere andre av gullbasse-slektene med navn som slutter på "-rhina" er det uklart om navnet bør staves med én (-"rhina") eller to (-"rrhina") r-er. Ordenen biller, Coleoptera Underordenen Polyphaga Overfamilien skarabider, Scarabaeoidea Familien skarabider, (Scarabaeidae) Latreille, 1806 (eventuelt Cetoniidae) Underfamilien Cetoniinae Fleming, 1821 Stammen Goliathini Griffith & Pidgeon, 1832 Slekten Heterorrhina Westwood, 1842 Heterorrhina sexmaculata (Fabricius, 1801) Heterorrhina sexmaculata dohrni Heterorrhina sexmaculata imperatrix Heterorrhina sexmaculata sexmaculata (Fabricius, 1801) Kilder Fabricius, J.C. (1801) Systema Eleutheratorum secundum ordines, genera, species: adiectis synonymis, locis, observationibus, descriptionibus. Tomus I, Impensis bibliopoli academici novi, Kiliae: 1-506. Eksterne lenker Heterorrhina på Encyclopedia of life Bilde av Heterorrhina sexmaculata dohrni Gullbasser Malaysias insekter Indonesias insekter Dyr formelt beskrevet av Johann Christian Fabricius Biller formelt beskrevet i 1801	norwegian_bokmål	1.059812
two_organs_but_not_all/Symmetry_in_biology.txt	Symmetry in biology refers to the symmetry observed in organisms, including plants, animals, fungi, and bacteria. External symmetry can be easily seen by just looking at an organism. For example, the face of a human being has a plane of symmetry down its centre, or a pine cone displays a clear symmetrical spiral pattern. Internal features can also show symmetry, for example the tubes in the human body (responsible for transporting gases, nutrients, and waste products) which are cylindrical and have several planes of symmetry. Biological symmetry can be thought of as a balanced distribution of duplicate body parts or shapes within the body of an organism. Importantly, unlike in mathematics, symmetry in biology is always approximate. For example, plant leaves – while considered symmetrical – rarely match up exactly when folded in half. Symmetry is one class of patterns in nature whereby there is near-repetition of the pattern element, either by reflection or rotation. While sponges and placozoans represent two groups of animals which do not show any symmetry (i.e. are asymmetrical), the body plans of most multicellular organisms exhibit, and are defined by, some form of symmetry. There are only a few types of symmetry which are possible in body plans. These are radial (cylindrical), bilateral, biradial and spherical symmetry. While the classification of viruses as an "organism" remains controversial, viruses also contain icosahedral symmetry. The importance of symmetry is illustrated by the fact that groups of animals have traditionally been defined by this feature in taxonomic groupings. The Radiata, animals with radial symmetry, formed one of the four branches of Georges Cuvier's classification of the animal kingdom. Meanwhile, Bilateria is a taxonomic grouping still used today to represent organisms with embryonic bilateral symmetry. Radial symmetry[edit] "Radial symmetry" redirects here. For radial symmetry in mathematics, see rotational symmetry. Organisms with radial symmetry show a repeating pattern around a central axis such that they can be separated into several identical pieces when cut through the central point, much like pieces of a pie. Typically, this involves repeating a body part 4, 5, 6 or 8 times around the axis – referred to as tetramerism, pentamerism, hexamerism and octamerism, respectively. Such organisms exhibit no left or right sides but do have a top and a bottom surface, or a front and a back. George Cuvier classified animals with radial symmetry in the taxon Radiata (Zoophytes), which is now generally accepted to be an assemblage of different animal phyla that do not share a single common ancestor (a polyphyletic group). Most radially symmetric animals are symmetrical about an axis extending from the center of the oral surface, which contains the mouth, to the center of the opposite (aboral) end. Animals in the phyla Cnidaria and Echinodermata generally show radial symmetry, although many sea anemones and some corals within the Cnidaria have bilateral symmetry defined by a single structure, the siphonoglyph. Radial symmetry is especially suitable for sessile animals such as the sea anemone, floating animals such as jellyfish, and slow moving organisms such as starfish; whereas bilateral symmetry favours locomotion by generating a streamlined body. Many flowers are also radially symmetric, or "actinomorphic". Roughly identical floral structures – petals, sepals, and stamens – occur at regular intervals around the axis of the flower, which is often the female reproductive organ containing the carpel, style and stigma. Lilium bulbiferum displays hexamerism with repeated parts arranged around the axis of the flower. Subtypes of radial symmetry[edit] Three-fold triradial symmetry was present in Trilobozoa from the Late Ediacaran period. Four-fold tetramerism appears in some jellyfish, such as Aurelia marginalis. This is immediately obvious when looking at the jellyfish due to the presence of four gonads, visible through its translucent body. This radial symmetry is ecologically important in allowing the jellyfish to detect and respond to stimuli (mainly food and danger) from all directions. Apple cut horizontally showing that pentamerism also occurs in fruit Flowering plants show five-fold pentamerism, in many of their flowers and fruits. This is easily seen through the arrangement of five carpels (seed pockets) in an apple when cut transversely. Among animals, only the echinoderms such as sea stars, sea urchins, and sea lilies are pentamerous as adults, with five arms arranged around the mouth. Being bilaterian animals, however, they initially develop with mirror symmetry as larvae, then gain pentaradial symmetry later. Hexamerism is found in the corals and sea anemones (class Anthozoa), which are divided into two groups based on their symmetry. The most common corals in the subclass Hexacorallia have a hexameric body plan; their polyps have six-fold internal symmetry and a number of tentacles that is a multiple of six. Octamerism is found in corals of the subclass Octocorallia. These have polyps with eight tentacles and octameric radial symmetry. The octopus, however, has bilateral symmetry, despite its eight arms. Icosahedral symmetry[edit] Gastroenteritis viruses have icosahedral symmetry Icosahedral symmetry occurs in an organism which contains 60 subunits generated by 20 faces, each an equilateral triangle, and 12 corners. Within the icosahedron there is 2-fold, 3-fold and 5-fold symmetry. Many viruses, including canine parvovirus, show this form of symmetry due to the presence of an icosahedral viral shell. Such symmetry has evolved because it allows the viral particle to be built up of repetitive subunits consisting of a limited number of structural proteins (encoded by viral genes), thereby saving space in the viral genome. The icosahedral symmetry can still be maintained with more than 60 subunits, but only in multiples of 60. For example, the T=3 Tomato bushy stunt virus has 60x3 protein subunits (180 copies of the same structural protein). Although these viruses are often referred to as 'spherical', they do not show true mathematical spherical symmetry. In the early 20th century, Ernst Haeckel described (Haeckel, 1904) a number of species of Radiolaria, some of whose skeletons are shaped like various regular polyhedra. Examples include Circoporus octahedrus, Circogonia icosahedra, Lithocubus geometricus and Circorrhegma dodecahedra. The shapes of these creatures should be obvious from their names. Tetrahedral symmetry is not present in Callimitra agnesae. Spherical symmetry[edit] Volvox is a microscopic green freshwater alga with spherical symmetry. Young colonies can be seen inside the larger ones. Spherical symmetry is characterised by the ability to draw an endless, or great but finite, number of symmetry axes through the body. This means that spherical symmetry occurs in an organism if it is able to be cut into two identical halves through any cut that runs through the organism's center. True spherical symmetry is not found in animal body plans. Organisms which show approximate spherical symmetry include the freshwater green alga Volvox. Bacteria are often referred to as having a 'spherical' shape. Bacteria are categorized based on their shapes into three classes: cocci (spherical-shaped), bacillus (rod-shaped) and spirochetes (spiral-shaped) cells. In reality, this is a severe over-simplification as bacterial cells can be curved, bent, flattened, oblong spheroids and many more shapes. Due to the huge number of bacteria considered to be cocci (coccus if a single cell), it is unlikely that all of these show true spherical symmetry. It is important to distinguish between the generalized use of the word 'spherical' to describe organisms at ease, and the true meaning of spherical symmetry. The same situation is seen in the description of viruses – 'spherical' viruses do not necessarily show spherical symmetry, being usually icosahedral. Bilateral symmetry[edit] "Bilateral symmetry" redirects here. For bilateral symmetry in mathematics, see reflection symmetry. Main article: Bilateria Organisms with bilateral symmetry contain a single plane of symmetry, the sagittal plane, which divides the organism into two roughly mirror image left and right halves – approximate reflectional symmetry. The small emperor moth, Saturnia pavonia, displays a deimatic pattern with bilateral symmetry. Flower of bee orchid (Ophrys apifera) is bilaterally symmetrical (zygomorphic). The lip of the flower resembles the (bilaterally symmetric) abdomen of a female bee; pollination occurs when a male bee attempts to mate with it. Animals with bilateral symmetry are classified into a large group called the bilateria which contains 99% of all animals (comprising over 32 phyla and 1 million described species). All bilaterians have some asymmetrical features; for example, the human heart and liver are positioned asymmetrically despite the body having external bilateral symmetry. The bilateral symmetry of bilaterians is a complex trait which develops due to the expression of many genes. The bilateria have two axes of polarity. The first is an anterior-posterior (AP) axis which can be visualised as an imaginary axis running from the head or mouth to the tail or other end of an organism. The second is the dorsal-ventral (DV) axis which runs perpendicular to the AP axis. During development the AP axis is always specified before the DV axis which is known as the second embryonic axis. The AP axis is essential in defining the polarity of bilateria and allowing the development of a front and back to give the organism direction. The front end encounters the environment before the rest of the body so sensory organs such as eyes tend to be clustered there. This is also the site where a mouth develops since it is the first part of the body to encounter food. Therefore, a distinct head, with sense organs connected to a central nervous system, tends to develop. This pattern of development (with a distinct head and tail) is called cephalization. It is also argued that the development of an AP axis is important in locomotion – bilateral symmetry gives the body an intrinsic direction and allows streamlining to reduce drag. In addition to animals, the flowers of some plants also show bilateral symmetry. Such plants are referred to as zygomorphic and include the orchid (Orchidaceae) and pea (Fabaceae) families, and most of the figwort family (Scrophulariaceae). The leaves of plants also commonly show approximate bilateral symmetry. Biradial symmetry[edit] Biradial symmetry is found in organisms which show morphological features (internal or external) of both bilateral and radial symmetry. Unlike radially symmetrical organisms which can be divided equally along many planes, biradial organisms can only be cut equally along two planes. This could represent an intermediate stage in the evolution of bilateral symmetry from a radially symmetric ancestor. The animal group with the most obvious biradial symmetry is the ctenophores. In ctenophores the two planes of symmetry are (1) the plane of the tentacles and (2) the plane of the pharynx. In addition to this group, evidence for biradial symmetry has even been found in the 'perfectly radial' freshwater polyp Hydra (a cnidarian). Biradial symmetry, especially when considering both internal and external features, is more common than originally accounted for. Evolution of symmetry[edit] Like all the traits of organisms, symmetry (or indeed asymmetry) evolves due to an advantage to the organism – a process of natural selection. This involves changes in the frequency of symmetry-related genes throughout time. Evolution of symmetry in plants[edit] Early flowering plants had radially symmetric flowers but since then many plants have evolved bilaterally symmetrical flowers. The evolution of bilateral symmetry is due to the expression of CYCLOIDEA genes. Evidence for the role of the CYCLOIDEA gene family comes from mutations in these genes which cause a reversion to radial symmetry. The CYCLOIDEA genes encode transcription factors, proteins which control the expression of other genes. This allows their expression to influence developmental pathways relating to symmetry. For example, in Antirrhinum majus, CYCLOIDEA is expressed during early development in the dorsal domain of the flower meristem and continues to be expressed later on in the dorsal petals to control their size and shape. It is believed that the evolution of specialized pollinators may play a part in the transition of radially symmetrical flowers to bilaterally symmetrical flowers. Evolution of symmetry in animals[edit] The Ediacaran Phylum Trilobozoa possess a wide variety of body shapes, mostly tri-radial symmetry, although its most famous member, Tribrachidium, possess a triskelion body shape. Symmetry is often selected for in the evolution of animals. This is unsurprising since asymmetry is often an indication of unfitness – either defects during development or injuries throughout a lifetime. This is most apparent during mating during which females of some species select males with highly symmetrical features. For example, facial symmetry influences human judgements of human attractiveness. Additionally, female barn swallows, a species where adults have long tail streamers, prefer to mate with males that have the most symmetrical tails. While symmetry is known to be under selection, the evolutionary history of different types of symmetry in animals is an area of extensive debate. Traditionally it has been suggested that bilateral animals evolved from a radial ancestor. Cnidarians, a phylum containing animals with radial symmetry, are the most closely related group to the bilaterians. Cnidarians are one of two groups of early animals considered to have defined structure, the second being the ctenophores. Ctenophores show biradial symmetry leading to the suggestion that they represent an intermediate step in the evolution of bilateral symmetry from radial symmetry. Interpretations based only on morphology are not sufficient to explain the evolution of symmetry. Two different explanations are proposed for the different symmetries in cnidarians and bilateria. The first suggestion is that an ancestral animal had no symmetry (was asymmetric) before cnidarians and bilaterians separated into different evolutionary lineages. Radial symmetry could have then evolved in cnidarians and bilateral symmetry in bilaterians. Alternatively, the second suggestion is that an ancestor of cnidarians and bilaterians had bilateral symmetry before the cnidarians evolved and became different by having radial symmetry. Both potential explanations are being explored and evidence continues to fuel the debate. Asymmetry[edit] Although asymmetry is typically associated with being unfit, some species have evolved to be asymmetrical as an important adaptation. Many members of the phylum Porifera (sponges) have no symmetry, though some are radially symmetric. Group/Species Asymmetrical Feature Adaptive Benefit Some owls Size and positioning of ears Allows the owl to more precisely determine the location of prey Flatfish Both eyes on the same side of their head Rest and swim on one side (to blend in with sand floor of the ocean) The scale-eating cichlid Perissodus microlepis Mouth and jaw asymmetry More effective at removing scales from their prey Humans Handedness and internal asymmetry of organs e.g. left lung is smaller than the right Handedness is an adaptation reflecting the asymmetries of the human brain. All vertebrates Internal asymmetry of heart and bowels Internal asymmetry is thought to be caused by a developmental axial twist. Further information: List of animals featuring external asymmetry Head of a male crossbill showing asymmetrical upper and lower beak A winter flounder, a type of flatfish, with both eyes on the same side of its head Hermit crabs have different sized claws A Roman snail and its helical shell Chicoreus palmarosae, a sea snail, illustrating asymmetry, which is seen in all gastropods in the form of a helical shell A red slug, clearly showing the pneumostome Male caribou usually possess one brow tine flattened into a shovel shape A life restoration of Stegosaurus stenops with its asymmetrical plates. Symmetry breaking[edit] The presence of these asymmetrical features requires a process of symmetry breaking during development, both in plants and animals. Symmetry breaking occurs at several different levels in order to generate the anatomical asymmetry which we observe. These levels include asymmetric gene expression, protein expression, and activity of cells. For example, left-right asymmetry in mammals has been investigated extensively in the embryos of mice. Such studies have led to support for the nodal flow hypothesis. In a region of the embryo referred to as the node there are small hair-like structures (monocilia) that all rotate together in a particular direction. This creates a unidirectional flow of signalling molecules causing these signals to accumulate on one side of the embryo and not the other. This results in the activation of different developmental pathways on each side, and subsequent asymmetry. Schematic diagram of signalling pathways on the left and right side of a chick embryo, ultimately leading to the development of asymmetry Much of the investigation of the genetic basis of symmetry breaking has been done on chick embryos. In chick embryos the left side expresses genes called NODAL and LEFTY2 that activate PITX2 to signal the development of left side structures. Whereas, the right side does not express PITX2 and consequently develops right side structures. A more complete pathway is shown in the image at the side of the page. For more information about symmetry breaking in animals please refer to the left-right asymmetry page. Plants also show asymmetry. For example the direction of helical growth in Arabidopsis, the most commonly studied model plant, shows left-handedness. Interestingly, the genes involved in this asymmetry are similar (closely related) to those in animal asymmetry – both LEFTY1 and LEFTY2 play a role. In the same way as animals, symmetry breaking in plants can occur at a molecular (genes/proteins), subcellular, cellular, tissue and organ level. Fluctuating asymmetry[edit] This section is an excerpt from Fluctuating asymmetry.[edit] Bilateral features in the face and body, such as left and right eyes, ears, lips, wrists and thighs, often show some extent of fluctuating asymmetry. Some individuals show greater asymmetry than others. Fluctuating asymmetry (FA), is a form of biological asymmetry, along with anti-symmetry and direction asymmetry. Fluctuating asymmetry refers to small, random deviations away from perfect bilateral symmetry. This deviation from perfection is thought to reflect the genetic and environmental pressures experienced throughout development, with greater pressures resulting in higher levels of asymmetry. Examples of FA in the human body include unequal sizes (asymmetry) of bilateral features in the face and body, such as left and right eyes, ears, wrists, breasts, testicles, and thighs. Research has exposed multiple factors that are associated with FA. As measuring FA can indicate developmental stability, it can also suggest the genetic fitness of an individual. This can further have an effect on mate attraction and sexual selection, as less asymmetry reflects greater developmental stability and subsequent fitness. Human physical health is also associated with FA. For example, young men with greater FA report more medical conditions than those with lower levels of FA. Multiple other factors can be linked to FA, such as intelligence and personality traits. See also[edit] Biological structures[edit] Standard anatomical position Anatomical terms of motion Anatomical terms of muscle Anatomical terms of bone Anatomical terms of neuroanatomy Glossary of botanical terms Glossary of plant morphology Glossary of leaf morphology Glossary of entomology terms Plant morphology Terms of orientation[edit] Handedness Laterality Proper right and proper left Reflection symmetry Sinistral and dextral Direction (disambiguation) Symmetry (disambiguation)	biology	26909	https://sv.wikipedia.org/wiki/Alger	Alger	För staden, se Alger, Algeriet. För andra betydelser, se Alger (olika betydelser). Alger () är de eukaryota organismer som utvinner energi ur ljus genom fotosyntes, vanligen lever i vatten och inte är fanerogamer (Fröväxter). De flesta alger använder klorofyll för fotosyntesen. De är släktskapsmässigt (fylogenetiskt) vitt åtskilda och tillhör alltså inte en taxonomisk grupp. Till algerna räknas många olika organismer, från mycket små och enkla encelliga till stora och komplexa flercelliga organismer, till exempel brunalger som kan bli 60 meter långa och väga 300 kg. Cyanobakterier kallades förr felaktigt för "blågröna alger", men de är bakterier och inte alger. Alger har traditionellt betraktats som enkla växter och en stor grupp av alger är besläktade med högre växter. De flesta algerna är protister. Till protisterna räknas även bland annat urdjur, (protozoa), som traditionellt ansetts mer djurlika. Alger utgör alltså inte en evolutionär gren. Algerna saknar ledningsvävnad för transport av vatten. Alla alger saknar blad, rötter och blommor och andra organ som utmärker växterna. De skiljer sig också från andra protozoer genom att i allmänhet vara fotoautotrofer. Detta är dock en otydlig distinktion eftersom några alger är mixotrofa, det vill säga de utvinner sin energi genom såväl fotosyntes som till exempel fagotrofi och osmotrofi. Hos några encelliga arter har fotosyntesapparaten helt tillbakabildats; dessa alger förlitar sig alltså helt på externa energikällor. Alla algers fotosyntetiska förmåga härstammar evolutionärt från cyanobakterierna. Algerna uppskattas stå för omkring 73–87 procent av den globala syreproduktionen. Alger lever vanligen i vatten eller på fuktiga ställen. De återfinns alltså både på land och i marina miljöer, men eftersom alger saknar den ledningsvävnad och andra egenskaper som ett liv på land kräver är de mer vanligt förekommande i haven och i tropiska miljöer. Lavar består av en alg i symbios med en svamp, och i lavar kan algen överleva även i torra miljöer. Algerna har en viktig roll i den marina ekologin. Mikroskopiska arter som svävar fritt i haven (i pelagialen eller vattenpelaren) kallas fytoplankton och utgör den marina näringskedjans primärproducenter och huvuddelen av havens växtplankton. Vid Sveriges kuster finns alger bland annat i form av grönslick närmast vattenytan. I mycket höga koncentrationer, så kallad algblomning, kan dessa alger konkurrera ut andra livsformer genom att förgifta dem och vara farliga för badande människor. Bentiska alger som tång växer framförallt i grunda vatten och används bland annat för tillverkning av agar och gödningsmedel. Den vetenskap som studerar alger kallas fykologi eller algologi. En forskare som studerar fykologi kallas algolog eller (mindre vanligt) fykolog. Relationerna mellan alggrupper Prokaryota alger Traditionellt har cyanobakterier kallats för blågrönalger eftersom man med "alger" avsåg alla fotosyntetiska organismer i havet. På senare tid räknas dock cyanobakterier inte till algerna. De tillhör de äldsta organismerna som hittats som fossil och tros härstamma från prekambrium (3,8 miljarder år sedan) då de producerade mycket av det syre som finns i jordens atmosfär idag. Cyanobakterierna har den prokaryota cellstruktur som kännetecknar bakterier, och deras fotosyntes äger rum inuti cytoplasman snarare än i specialiserade organeller. Några trådformiga cyanobakterier har specialiserade celler för kvävefixering kallade heterocyster. Eukaryota alger Alla andra alger är eukaryota och utför sin fotosyntes i särskilda membranförsedda organeller kallade kloroplaster. Kloroplaster innehåller DNA och har en struktur som gör att de liknar cyanobakterier. Man förmodar därför att kloroplaster en gång utvecklats utifrån så kallade endosymbionter, bakterier som inneslutits i en annan organism. Kloroplasternas funktion varierar mellan olika typer av alger, vilket återspeglar den repetitiva evolutionen av endosymbios. (Se vidare endosymbiontteorin). Hos tre grupper av alger finns primitiva, ursprungliga kloroplaster: Grönalger (tillsammans med embryofyter) Rödalger Glaukofyter I dessa grupper omges kloroplasten av två membran och har fömodligen uppstått ur en enda endosymbios. Hos rödalgerna har kloroplasterna ungefär samma pigmentation som cyanobakterierna medan pigmentet hos grönalgernas kloroplaster består av klorofyll a och b. Klorofyll b finns hos några enstaka cyanobakterier men saknas hos de flesta. Högre växter har ungefär samma pigmentation som grönalger och tros ha utvecklats ur dem. Två andra grupper har gröna kloroplaster som innehåller klorofyll b: Euglenider Chlorarachniophyta Deras kloroplaster omges av tre eller fyra membran och har förmodligen erhållits från en upptagen grönalg. Hos chlorarachniophyta innehåller kloroplasterna en liten neuklomorf, det vill säga en reducerad, eukaryot cellkärna som finns i vissa plastider (varav chlorarachniophyta är en). Det har spekulerats i att orsaken till att euglenidernas kloroplaster bara omges av tre membran ska vara att de upptagits genom myzocytos (svengelska?) snarare än fagocytos. De återstående algernas kloroplaster innehåller alla klorofyll a och c. Klorofyll c finns inte hos prokaryota eller primära kloroplaster, men man har hittat en genetisk överensstämmelse med rödalgerna vilket kan antyda att det där finns en släktskap. Bland dessa övriga alger finns: Stramenopiler Haptofyter Kryptofyter Dinoflagellater I de första tre av dessa grupper har kloroplasterna fyra membran (med en neuklomorf hos kryptfyterna) och förmodligen har de en gemensam förfader med samma typ av pigmentation. Typiskt nog har dinoflagellaternas kloroplaster tre membran, men mångfalden bland kloroplasterna inom gruppen är stor och några av dess medlemmar har förvärvat sina från olika håll. Apicomplexa, en närbesläktad grupp parasiter, har också plastider men inte egentliga kloroplaster och tycks har sitt ursprung gemensamt med dinoflagellaterna. Observera dock att många av dessa alggrupper innehåller medlemmar som inte längre är fotosyntetiska. Några innehåller plastider men inte kloroplaster och några saknar till och med kloroplaster. Referenser Denna artikel var ursprungligen en översättning av motsvarande engelskspråkiga artikel den 11 september 2006 Se även Lavar	swedish	0.850728
spider_venom_lethal/pnas2004516117.txt	PNAS Logo ARTICLES FRONT MATTER AUTHORS RESEARCH ARTICLE BIOLOGICAL SCIENCES FREE ACCESS SHARE ON Australian funnel-web spiders evolved human-lethal δ-hexatoxins for defense against vertebrate predators Volker Herzig https://orcid.org/0000-0003-2514-3983 [email protected], Kartik Sunagar https://orcid.org/0000-0003-0998-1581, David T. R. Wilson, +11, and Bryan G. Fry https://orcid.org/0000-0001-6661-1283 [email protected] Info & Affiliations Edited by David M. Hillis, The University of Texas at Austin, Austin, TX, and approved August 9, 2020 (received for review March 10, 2020) September 21, 2020 117 (40) 24920-24928 https://doi.org/10.1073/pnas.2004516117 13,088 21 Metrics Total views 13,088 Last 12 Months 2,248 Total citations 21 Last 12 Months 0 Vol. 117 \| No. 40 Significance Abstract Results Discussion Conclusion Materials and Methods Data Availability Acknowledgments Supporting Information References Information & Authors Metrics & Citations View Options References Media Share Significance The venom of Australian funnel-web spiders contains δ-hexatoxins (δ-HXTXs) that exert fatal neurotoxic effects in humans by inhibiting inactivation of voltage-gated sodium channels, but their precise ecological role remains unclear. Sequencing of venom-gland transcriptomes from 10 funnel-web species uncovered 22 δ-HXTXs. Evolutionary analysis revealed extreme conservation of these toxins, despite their ancient origin. We isolated the lethal δ-HXTX from venom of the Sydney funnel-web spider and showed that it induces pain in mice, suggesting a role in predator deterrence. Although humans are not the target of δ-HXTXs, these toxins likely evolved to deter vertebrate predators commonly encountered by these spiders, such as bandicoots, birds, and lizards. Thus, the lethal potency of δ-HXTXs against humans is an unfortunate evolutionary coincidence. Abstract Australian funnel-web spiders are infamous for causing human fatalities, which are induced by venom peptides known as δ-hexatoxins (δ-HXTXs). Humans and other primates did not feature in the prey or predator spectrum during evolution of these spiders, and consequently the primate lethality of δ-HXTXs remains enigmatic. Funnel-web envenomations are mostly inflicted by male spiders that wander from their burrow in search of females during the mating season, which suggests a role for δ-HXTXs in self-defense since male spiders rarely feed during this period. Although 35 species of Australian funnel-web spiders have been described, only nine δ-HXTXs from four species have been characterized, resulting in a lack of understanding of the ecological roles and molecular evolution of δ-HXTXs. Here, by profiling venom-gland transcriptomes of 10 funnel-web species, we report 22 δ-HXTXs. Phylogenetic and evolutionary assessments reveal a remarkable sequence conservation of δ-HXTXs despite their deep evolutionary origin within funnel-web spiders, consistent with a defensive role. We demonstrate that δ-HXTX-Ar1a, the lethal toxin from the Sydney funnel-web spider Atrax robustus, induces pain in mice by inhibiting inactivation of voltage-gated sodium (NaV) channels involved in nociceptive signaling. δ-HXTX-Ar1a also inhibited inactivation of cockroach NaV channels and was insecticidal to sheep blowflies. Considering their algogenic effects in mice, potent insecticidal effects, and high levels of sequence conservation, we propose that the δ-HXTXs were repurposed from an initial insecticidal predatory function to a role in defending against nonhuman vertebrate predators by male spiders, with their lethal effects on humans being an unfortunate evolutionary coincidence. Sign up for PNAS alerts. Get alerts for new articles, or get an alert when an article is cited. Despite their fearsome reputation, only a few species of spiders can cause death or serious harm to humans (1). An infamous exception is the Australian funnel-web spider, arguably the world’s deadliest spider (2). These spiders produce extraordinarily complex venoms, with each venom containing up to several thousand peptide toxins (3, 4). Despite this chemical complexity, a single family of toxins known as the δ-hexatoxins (δ-HXTXs) is responsible for the human envenomation syndrome (5). There are currently 35 described species of Australian funnel-web spiders and 38 species of related non-Australian funnel-web spiders in the genus Macrothele, but to date only 12 δ-HXTX sequences have been reported from six species within this broad clade. A homologous δ-actinopoditoxin (δ-AOTX) is present in the venom of the related Australian mouse spider Missulena bradleyi (6), which can cause serious human envenomations with symptoms resembling those from funnel-web spider bites (7). δ-HXTXs and δ-AOTX comprise 42 to 44 residues and contain four disulfide bonds, three of which are arranged in an inhibitor cystine knot (ICK) motif (8, 9). δ-HXTXs slow the inactivation of vertebrate tetrodotoxin-sensitive voltage-gated sodium (NaV) channels and insect NaV channels by binding to the voltage sensor in channel domain IV (10, 11). In human bite victims, δ-HXTXs cause disturbances in respiration, blood pressure, and heart rate, followed by severe hypotension. Without treatment with commercial antivenom (5), fatalities can occur by respiratory and circulatory failure within a few hours of the bite (12). Interestingly, in striking contrast to humans and other primates, some vertebrates such as dogs and cats are insensitive to funnel-web envenomation (13). Humans did not feature in the prey or predator spectrum during evolution of funnel-web spiders, as primates were not present 150 to 200 million y ago (MYA) when these spiders originated (14). Thus, the underlying reason for the peculiar susceptibility of humans to δ-HXTXs and the ecological role of these toxins remain enigmatic. The δ-HXTXs are insecticidal (15, 16), which might suggest a role in prey capture. However, in some species, these toxins are secreted in very low abundance in the venoms of female spiders and immature males, consistent with the fact that only sexually mature male spiders cause severe or lethal human envenomations (17). Moreover, it is hard to reconcile a role for these toxins in predation given that sexually mature males, in whose venom the toxins are most abundant, rarely feed during the mating season. Rather, the fact that adult males leave the safety of their burrows to search for female spiders (2), making them more susceptible to predators, suggests a role for the δ-HXTXs in predator deterrence. A well-documented strategy for defensive toxins is to induce pain (18–20), and pain is a common symptom following funnel-web envenomation (2, 17). Consistent with the idea that the δ-HXTXs serve a defensive role by inducing pain in vertebrate predators, Magi 4 from the venom of a Japanese funnel-web spider potentiates the activity of NaV1.1 and NaV1.6 (21), which are involved in pain signaling (19, 22). In the current study, we identified 22 δ-HXTX sequences from 10 species of Australian funnel-web spiders, and evaluated their molecular evolution, phylogenetic histories, insecticidal activity, and potency against human NaV channels involved in pain signaling. Taken together, our data provide strong evidence that the δ-HXTXs were recruited by funnel-web spiders as a weapon to deter vertebrate predators, and that their lethal effects on humans is an unfortunate evolutionary coincidence. Results δ-HXTX Sequences. δ-HXTXs from seven funnel-web spider species (Hadronyche infensa, Hadronyche valida, Hadronyche venenata, Hadronyche versuta, Atrax robustus, Atrax sutherlandi, and Illawarra wisharti) were sequenced via rapid amplification of cDNA (complementary DNA) ends (RACE) (SI Appendix). In addition, we generated cDNA libraries for H. infensa, Hadronyche modesta, Hadronyche cerberea, and Hadronyche formidabilis. Our complete dataset (Dataset S1), based on our RACE and transcriptomic data plus sequences available from the literature, comprised 169 mature peptide sequences and 167 corresponding nucleotide sequences (the latter were only missing for δ-HXTX-Hv1b and δ-AOTX-Mb1a). Our dataset contained 132 δ-HXTXs, 1 δ-AOTX, and 18 homologous U-HXTXs from H. infensa, 17 related barytoxins (U-BATXs) from Trittame loki, and 1 μ-HXTX from Macrothele gigas. Removal of 53 duplicate or incomplete sequences and the two peptide sequences that lacked a corresponding nucleotide sequence yielded a total of 114 nucleotide sequences for phylogenetic analysis. The data revealed 22 mature δ-HXTX sequences to complement the 12 published δ-HXTX sequences. Phylogenetic History and Molecular Evolution of δ-HXTXs. The identification of homologous sequences from the barychelid spider T. loki in this study reveals that these U-BATXs, μ-HXTX-Mg1c, and the δ-HXTXs were probably derived from a common ancestral toxin. However, there are also important differences between the U-BATXs and μ-HXTX-Mg1c in comparison with all δ-HXTXs from atracid and macrothelid funnel-web spiders. First, U-BATXs and μ-HXTX-Mg1c have only six Cys residues that form an ICK motif, whereas the δ-HXTXs usually contain eight Cys residues, with one additional disulfide bond. Second, the δ-HXTXs comprise a rare triplet of Cys residues in positions 14 to 16 (based on δ-HXTX-Ar1a), which is not present in μ-HXTX-Mg1c or any of the U-BATXs. Moreover, in the Bayesian phylogenetic analyses, all funnel-web spider sequences clustered together and were well-separated from the T. loki sequences (Fig. 1). All of these considerations taken together highlight the divergent evolution of δ-HXTXs in atracid and macrothelid funnel-web spiders following their phylogenetic separation from other mygalomorph lineages (Fig. 1). Fig. 1. Phylogenetic reconstruction of δ-HXTXs. Tree representing the phylogenetic history of δ-HXTXs as estimated by maximum-likelihood inference. The thickness of branches corresponds to node supports (thick branch, bootstrap ≥ 75; thin branch, bootstrap < 75), and various species are presented in distinct colors. The cysteine pattern (black lines) and activities (red lines) are annotated (Right). Fly and mouse icons indicate insecticidal and vertebrate activity, respectively. The underscore sequence numbers refer to the unique preprotoxin nomenclature used in the ArachnoServer database (23). In contrast to the massive sequence variations observed in most venom proteins, the δ-HXTXs are surprisingly well-conserved (Fig. 2). The signal peptide, propeptide, and mature peptide coding regions in the δ-HXTXs were characterized by extremely low omega (ω) values (i.e., the ratio of nonsynonymous to synonymous substitutions) (Fig. 2A and Table 1), indicative of strong sequence conservation despite being recruited into the venoms of funnel-web spiders around 150 to 200 MYA (14). Consistent with the findings of the maximum-likelihood method, the Bayesian approaches identified only three positively selected sites (2.6% of sites)—positions that rapidly diversify across time—while many sites (15.6%) were found to be evolving under the pervasive influence of negative selection, which ensures sequence conservation across time. A few amino acid sites (n = 7) were found to be experiencing diversifying selection, albeit in an episodic fashion (i.e., in short bursts across time) (Fig. 2 B–D). Fig. 2. Molecular evolution of δ-HXTXs. (A) Toxin precursor domains and their rate of evolution, indicated as ω values (i.e., nonsynonymous-to-synonymous substitution rate ratio). (B) Structure of δ-HXTX-Hv1a (Protein Data Bank ID code 1VTX) (8), depicting the locations of positively selected sites. (C) Sequence alignment of δ-HXTXs from representative species. The positions of the four disulfide bonds are indicated by lines above and below the sequence alignment, while the extent of evolutionary conservation of amino acids (calculated from the complete alignment of 114 sequences) is denoted by the illustrated color code. Note: Loop IV is not present in the plesiotypic T. loki sequence and is instead characteristic of the apotypic δ-HXTX sequences. (D) Statistics associated with selection analyses. eFast unconstrained Bayesian approximation (FUBAR); fsites experiencing episodic diversifying selection (0.05 significance) by the mixed-effects model evolution (MEME); gpositively selected sites detected by the Bayes empirical Bayes approach implemented in M8 of Phylogenetic Analysis by Maximum Likelihood (PAML); hnumber of sites under pervasive diversifying selection at posterior probability ≥0.95 (FUBAR); inumber of sites under pervasive purifying selection at posterior probability ≥0.95 (FUBAR). Table 1. Collection sites and species used for venom-gland library construction Species Collection site Number and sex of specimens Collector Atrax robustus Sydney, NSW 1 M/1 F Graham Nicholson Atrax sutherlandi Gerringong, NSW 1 M D.T.R.W. Hadronyche infensa Fraser Island and Toowoomba, QLD 5 F (RACE) D.T.R.W. Hadronyche infensa Fraser Island and Toowoomba, QLD 3 F (454) S.S.P. Hadronyche modesta Kalorama, Dandenong Ranges, VIC 4 F B.G.F. Hadronyche valida Binna Burra, QLD 1 juvenile M D.T.R.W. Hadronyche venenata Tooms Lake, TAS 1 F Glenn Gregg Hadronyche versuta Blue Mountains, NSW 1 F Graham Nicholson Hadronyche formidabilis South Tamborine, QLD 1 F/4 juveniles S.D. Hadronyche cerberea Blue Mountains, NSW 2 F S.D. Illawara wisharti Gerringong, NSW 1 M D.T.R.W. F, female; M, male. Cys Derivations and Codon Usage. The three-dimensional structure of many venom peptides, including the δ-HXTXs, relies heavily on the formation of disulfide bonds. Analysis of the arrangement of eight Cys residues in the δ-HXTXs (Fig. 3A) indicates that Cys residues 1 to 5 are extremely well conserved in all funnel-web spiders. However, many subtypes were discovered with either missing or novel cysteines, indicating the probable evolution of novel forms and functions. For instance, while one derivation each was found with a missing cysteine at positions 6 and 7, δ-HXTXs lacking Cys-8 were more common with 11 derivations in δ-HXTXs from H. infensa, with one of them even possessing a novel cysteine residue (which we refer to as position 9). The precursor peptides with the eighth Cys residue missing correspond to four mature toxin sequences, and comparison with combined matrix-assisted laser desorption/ionization (MALDI) and Orbitrap mass spectrometry (MS) data for H. infensa venom (4) reveals closely matching molecular masses for three of the monomers, one homodimer, and four heterodimers (Fig. 3B). Analysis of the codons used for Cys residues also revealed some genus-specific variations (Fig. 3C). In all funnel-web δ-HXTXs, Cys-2 is encoded by TGT, whereas Cys-3 is encoded by TGC. In Atrax and Illawarra, all other Cys residues are encoded only by TGT (except for Cys-8 in Illawarra being solely encoded by TGC). In Hadronyche, Cys-1, 5, 6, 7, and 8 are dominated by TGT and Cys-4 is preferentially encoded by TGC. In contrast to all other funnel-web spider genera, in Macrothele all Cys residues (except for Cys-2) are dominantly encoded by TGC. The observed codon bias could be important for the rapid expression of toxins in the venom gland. Fig. 3. Cys derivations and codon usage in δ-HXTXs. (A) Alignment of δ-HXTXs representing major changes in the Cys framework. (B) Expected and experimentally determined molecular masses for the seven Cys residue derivations of δ-HXTX homologs from H. infensa. Several masses closely matching either monomers or homo/heterodimers were observed using MALDI or Orbitrap mass spectrometry. (C) Codon usage for Cys residues in δ-HXTXs from different funnel-web genera. Lines at the top represent the four disulfide bonds in the prototypical Ar1a toxin. NaV Channel Subtype Selectivity of δ-HXTX-Ar1a. In order to examine the biological role of the δ-HXTXs, we used reversed-phase high-performance liquid chromatography (RP-HPLC) to isolate δ-HXTX-Ar1a (hereafter Ar1a) from the venom of A. robustus (Fig. 4). We then used a Fluorescent Imaging Plate Reader (FLIPR)-based fluorescence assay to assess the ability of Ar1a to potentiate currents from human NaV1.1 to NaV1.8 channels stably expressed in HEK293 cells. This assay was previously used to determine the pharmacological activity of the scorpion venom peptide OD1. OD1 activates several NaV channel subtypes and the potency and subtype selectivity of OD1 as determined by FLIPR was found to be comparable to data obtained using electrophysiological assays (24). Fig. 4. Isolation and purification of Ar1a from A. robustus venom. (A) Chromatogram from C18 RP-HPLC fractionation of A. robustus venom with the peak containing Ar1a highlighted in red. (A, Inset) Photo of a female A. robustus. (B) Chromatogram from hydrophobic interaction liquid chromatography (HILIC) of the Ar1a-containing peak from A. The dashed line indicates the solvent gradient, with the percentage of solvent B (90% acetonitrile/0.045% trifluoroacetic acid) indicated on the right ordinate axis. (B, Inset) MALDI-MS spectrum of purified Ar1a. Ar1a had no effect on NaV1.4, NaV1.5, NaV1.7, and NaV1.8 at concentrations up to 150 nM, whereas a concentration-dependent potentiation of veratridine-evoked responses was observed in cells expressing NaV1.1, NaV1.2, NaV1.3, and NaV1.6 (Fig. 5A). Ar1a was an equipotent potentiator of NaV1.1 (half-maximum effective concentration (EC50) of 30.2 nM), NaV1.2 (EC50 38.9 nM), NaV1.3 (EC50 38.9 nM), and NaV1.6 (EC50 91.2 nM) with comparable mean pEC50 (i.e., negative logarithm of the EC50) values of 7.52 ± 0.24, 7.41 ± 0.09, 7.41 ± 0.15, and 7.04 ± 0.08, respectively. Fig. 5. Biological characterization of Ar1a. (A) NaV subtype selectivity of Ar1a. The effect of Ar1a on NaV1.1 to NaV1.8 heterologously expressed in HEK293 cells in combination with the human b1 subunit was assessed using a membrane potential assay. Ar1a elicited a concentration-dependent increase in membrane potential in the presence of veratridine (5 µM) in cells expressing NaV1.1 (pEC50 7.52 ± 0.24), NaV1.2 (pEC50 7.41 ± 0.09), NaV1.3 (pEC50 7.41 ± 0.15), and NaV1.6 (pEC50 7.04 ± 0.08). Data are presented as mean ± SEM (n = 3). (B) Dose–response curve for paralysis of L. cuprina blowflies (shown in Inset) injected with Ar1a. Paralysis was assessed at 1 h postinjection. Error bars indicate SEM. The PD50 was determined as the mean ± SEM of three independent experiments. All paralytic effects were reversible within 24 h and no lethal effects were observed. (C) Dose-dependent inhibition of BgNaV1 fast inactivation by Ar1a. Representative sodium currents were elicited by a depolarization to −20 mV before (black) and after (red) addition of toxin from a holding potential of −90 mV. (D) Normalized conductance–voltage relationships (G/Gmax; black filled circles) and steady-state inactivation relationships (I/Imax; black open circles) of BgNaV1 before (black circles) and after (red circles) Ar1a application. Channel-expressing oocytes were depolarized in 5-mV steps from a holding potential of −90 mV. Error bars represent SEM; n = 3 to 5. Mammalian Nocifensive Responses. Administration of Ar1a (100 nM, 20 µL) by shallow subcutaneous (intraplantar) injection into the foot pad of male C57BL/6 mice elicited mild, transient nocifensive responses consisting of flinching, lifting, licking, and shaking of the hind paw. This nocifensive behavior was characterized by relatively slow onset (5 min postinjection) to a peak at 15 min postinjection with 10.5 ± 1.5 flinches per 5 min. No systemic effects, such as the muscle fasciculations, salivation, or other effects associated with the human envenomation syndrome, were observed at this dose. Toxicity of Ar1a in Blowflies. Injection of Ar1a into sheep blowflies (Lucilia cuprina) caused contractile paralysis with a median paralytic dose (PD50) of 319 ± 42 pmol/g at 1 h postinjection (Fig. 5B). However, even at the highest dose tested (which was limited by the amount of native δ-HXTX-Ar1a available), all flies fully recovered within 24 h, indicating that the toxin’s insecticidal effects in blowflies are reversible. Effect of Ar1a on BgNaV1. Given its activity on human NaV channels, we decided to examine if the insecticidal effects of Ar1a are due to potentiation of the activity of insect NaV channels. For this purpose, we examined the effects of Ar1a on the BgNaV1 channel from the German cockroach Blattella germanica expressed in Xenopus oocytes. At 1 nM, Ar1a had no effect on BgNaV1 currents whereas 10 nM Ar1a induced a substantial persistent current (Fig. 5C). BgNaV1 fast inactivation was completely inhibited by 100 nM Ar1a. Boltzmann fits of the normalized conductance–voltage relationships and steady-state inactivation relationships revealed no significant difference in V1/2 before and after addition of 1 or 10 nM Ar1a (t test, P ≥ 0.01) but 100 nM Ar1a caused substantial hyperpolarizing shifts in the V1/2 of both channel activation (from −37.2 ± 0.6 to −44.9 ± 0.7 mV) and steady-state inactivation (from −50.3 ± 0.1 to −63.3 ± 0.7 mV) (Fig. 5D). Discussion In the present study, we employed a multipronged approach involving venom-gland transcriptomics, molecular and phylogenetic analyses, and functional assays to determine the role of the lethal δ-HXTXs in the ecology of funnel-web spiders. Enigmatic Evolutionary Conservation of δ-HXTXs. Molecular evolutionary assessments revealed that the genes encoding for δ-HXTXs have remained nearly unchanged despite originating in the common ancestor of atracid and macrothelid funnel-web spiders 150 to 200 MYA (14). Together with our phylogenetic analysis, this indicates that despite the single early origin of δ-HXTXs in funnel-web spiders, they have diversified at a much slower evolutionary rate than many other spider toxins (25–29). The increased level of sequence conservation is consistent with a role for the δ-HXTXs in defense. Due to their relatively limited use and consequent exclusion from the typical Red Queen mode of competitive evolution, defensive toxins are theorized to evolve slower than their predatory counterparts (30). Our phylogenetic analysis demonstrates that all δ-HXTX sequences evolved from a common ancestral toxin scaffold, with early gene duplications and diversification present before the recently proposed split into the families Macrothelidae and Atracidae (31). Further support of a split between these families is provided by the nucleotide sequences used to encode the Cys residues, with Atracidae being dominated by TGT and Macrothelidae being dominated by TGC. Our phylogeny also provides evidence for at least two neofunctionalization events. The first event occurred during the early evolution of δ-HXTXs. μ-HXTX-Mg1c, the most basal of the funnel-web spider sequences included in our analysis, has an ICK motif but lacks the two Cys residues involved in the formation of the fourth disulfide bond (32). μ-HXTX-Mg1c is a homolog of μ-HXTX-Mg1a and μ-HXTX-Mg1b, which are both known to be insecticidal but not active against vertebrates (33). On the other hand, δ-HXTX-Mg1a, which is sister to the remaining δ-HXTX sequences, has both vertebrate and insecticidal activities (33). These activities would be consistent with a repurposing of δ-HXTXs from the purely insecticidal activity of their ancestral plesiotypic form to dual activity against both mammals and insects, which occurred around 150 to 200 MYA (14). Given the absence of primates in Australia at the time when δ-HXTXs originated [humans first populated Australia 65,000 y ago (34), and Australia lacks indigenous nonhuman primates], the primate toxicity of δ-HXTXs can only be regarded as coincidental. The second neofunctionalization event is apparent in the genus Hadronyche with multiple convergent losses of the last Cys residue. Such convergence points toward a strong selection pressure, possibly resulting in a change in selectivity or potency. The fact that an odd number of Cys residues is energetically unfavored led us to investigate whether these seven Cys residue derivations of δ-HXTXs form dimers. Mass spectrometry analysis of H. infensa venom (4) revealed the presence of masses corresponding to monomers and homo- and heterodimers. Unfortunately, nothing is yet known about the activities of these δ-HXTX derivations or the dimers that are formed, which provides an exciting area for future investigations. Clues from the Activity of Ar1a. δ-HXTXs were previously demonstrated to inflict potent but reversible paralysis in blowfly larvae and crickets (16). We found that Ar1a potently inhibits fast inactivation of the cockroach BgNaV channel, which is consistent with the contractile paralysis induced in blowflies and reminiscent of the effects of other toxins that target insect NaV channels (reviewed in ref. 35). Employing venom components to cause pain is a common evolutionary strategy for self-defense in venomous animals (19, 30, 36–38). Strong support for a defensive role of δ-HXTXs is therefore provided by the nocifensive response that Ar1a induced following intraplantar injections in mice. Although the lethal dose of δ-HXTXs varies considerably within vertebrates (13), we presume that high local tissue concentrations of δ-HXTXs resulting from a funnel-web spider bite will induce algogenic effects in a much wider range of vertebrates than half-maximum lethal dose (LD50) experiments might indicate. With regard to the subtype selectivity of δ-HXTXs, δ-HXTX-Mg1a (Magi 4) from the Japanese funnel-web spider preferentially activated rat NaV1.1 and NaV1.3 and mouse NaV1.6 while also showing weak activity on rat NaV1.2 channels (3). For Ar1a, we observed equipotent activity across NaV1.1, NaV1.2, NaV1.3, and NaV1.6. Overall, this is consistent with a defensive role, as both NaV1.1 and NaV1.6 are known to be involved in pain signaling (19, 22, 39). The activity of Ar1a at NaV1.6 is further consistent with the observed effects of Australian funnel-web venoms in the chick biventer assay (SI Appendix, Fig. S1) (40), as NaV1.6 is the predominant isoform at the nodes of Ranvier in motor neurons. Thus, inhibition of the inactivation of this NaV channel isoform could contribute to both sensory and motor effects in envenomed individuals, making δ-HXTXs a powerful weapon to deter predators. Differential Expression of δ-HXTXs. The clinical syndrome resulting from funnel-web spider envenomation of vertebrates is driven by the δ-HXTXs (5). Male A. robustus venom was reported to be at least six times more potent than the female venom (41). In addition, the venoms of six male funnel-web species were found to be more potent than females’ in inducing toxic effects in the chick biventer nerve-muscle preparation (40), consistent with increased expression of δ-HXTXs in male venoms. Male funnel-web spiders are more exposed to vertebrate predation once they leave the safety of their burrows to search for female mates, so increased expression of a defensive toxin would make ecological sense to allow adult males to defend against these predators. Moreover, since adult male mygalomorph spiders consume less food than females (42), the increased expression of δ-HXTXs in mature male spiders is inconsistent with a role for these toxins in prey capture. Conclusion In summary, our data suggest that the δ-HXTXs likely evolved from having an ancestral role in predation to a primary role in defense against ecologically important vertebrate predators, with their lethal potency against humans being an unfortunate evolutionary coincidence. Materials and Methods Australian funnel-web spiders were collected from various locations and states across Australia, as summarized in Table 1. The spiders were individually housed at ∼23 to 25 °C in dark cabinets until venom and venom glands were dissected. Nomenclature. Toxins were named according to the rational nomenclature described previously (43). Spider taxonomy was taken from World Spider Catalog version 21.0 (44). Messenger RNA Isolation and cDNA Library Construction. Messenger RNA and cDNA libraries were isolated and constructed using the protocols summarized in SI Appendix. For details of RACE, Sanger, and next-generation sequencing, see SI Appendix. Phylogenetics and Selection Analyses. Reconstruction of the phylogenetic history and molecular evolution of δ-HXTXs was performed as detailed in SI Appendix. RP-HPLC Purification of Ar1a. Milked lyophilized venom from male A. robustus specimens was supplied by the Australian Reptile Park. The venom was reconstituted in MilliQ water to a concentration of ∼5 mg/mL and Ar1a was purified using RP-HPLC as outlined in SI Appendix. Determination of the NaV Subtype Selectivity of Ar1a. The activity of Ar1a on human NaV channels stably expressed in HEK293 cells was determined using a FLIPRTetra assay (24) as described in SI Appendix. Algogenic Effects of Ar1a. Ethical approval for in vivo experiments was obtained from The University of Queensland Animal Ethics Committee (PHARM/512/12/RAMACIOTTI) and they were conducted in accordance with the Queensland Animal Care and Protection Act (2002), the Australian Code of Practice for the Care and Use of Animals for Scientific Purposes (eighth edition, 2013), and the International Association for the Study of Pain Guidelines for the Use of Animals in Research. Details of intraplantar administration of Ar1a and assessment of induced nocifensive behavior are detailed in SI Appendix. Insecticidal Effects of Ar1a. Native Ar1a was tested for insecticidal toxicity by injection into sheep blowflies (45) as described in SI Appendix. Activity of Ar1a on BgNaV1. Two-electrode voltage-clamp electrophysiology was used to determine the activity of Ar1a on BgNaV1 heterologously expressed in Xenopus oocytes, as outlined in SI Appendix. Data Availability Metadata and annotated nucleotide sequences generated in this paper were deposited in the European Nucleotide Archive under project accession nos. PRJEB6062 for H. infensa, PRJEB14734 for H. cerberea, and PRJEB14965 for H. formidabilis. All UniProt and ArachnoServer accessions for sequences used for phylogenetic analysis are listed in SI Appendix. Raw data have also been deposited in Figshare, 10.6084/m9.figshare.12798617. All study data are included in the article and SI Appendix. Acknowledgments We acknowledge support from the Australian National Health & Medical Research Council (Principal Research Fellowship APP1136889 and Program Grant APP1072113 to G.F.K.; Career Development Fellowship APP1162503 to I.V.), the Australian Research Council (Discovery Grant DP190100304 to B.G.F.; Future Fellowship FT190100482 to V.H.). K.S. was supported by the Department of Science and Technology (DST) INSPIRE Faculty Award (DST/INSPIRE/04/2017/000071), DST - Fund for Improvement of S&T Infrastructure in Higher Educational Institutions (DST-FIST) (SR/FST/LS-II/2018/233), and the Department of Biotechnology-Indian Institute of Science (DBT-IISc) Partnership Program. I.V. was supported by an Early Career Researcher (ECR) grant from The Clive & Vera Ramaciotti Foundation. We thank Dr. Roger Drinkwater for assistance with sequencing, Dr. Robert Raven (Queensland Museum) and Mr. Graham Wishart for specimen collection and identification, Mr. Glenn Gregg and Prof. Graham Nicholson for providing spiders, the Australian Reptile Park for provision of A. robustus venom, Geoff Brown (Department of Agriculture and Fisheries, Queensland) for blowflies, and Ke Dong (Michigan State University) for sharing BgNaV1/TipE clones. Supporting Information Appendix (PDF) DOWNLOAD 694.96 KB Dataset_S01 (XLSX) DOWNLOAD 32.24 KB References 1 T. J. Hauke, V. Herzig, Dangerous arachnids—Fake news or reality? Toxicon 138, 173–183 (2017). Go to reference Crossref PubMed Google Scholar 2 G. K. Isbister, H. W. Fan, Spider bite. Lancet 378, 2039–2047 (2011). Crossref PubMed Google Scholar 3 P. Escoubas, B. Sollod, G. F. King, Venom landscapes: Mining the complexity of spider venoms via a combined cDNA and mass spectrometric approach. Toxicon 47, 650–663 (2006). 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Go to reference Crossref PubMed Google Scholar 44 World Spider Catalog, version number 21.0. https://wsc.nmbe.ch, (Natural History Museum Bern, 2020). Go to reference Google Scholar 45 N. S. Bende et al., The insecticidal neurotoxin Aps III is an atypical knottin peptide that potently blocks insect voltage-gated sodium channels. Biochem. Pharmacol. 85, 1542–1554 (2013). Go to reference Crossref PubMed Google Scholar VIEW FULL TEXT\|DOWNLOAD PDF Further reading in this issue RESEARCH ARTICLESEPTEMBER 18, 2020 Learning probabilistic neural representations with randomly connected circuits Ori Maoz, Gašper Tkačik, [...]Elad Schneidman, RESEARCH ARTICLESEPTEMBER 14, 2020 Damage accelerates ice shelf instability and mass loss in Amundsen Sea Embayment Stef Lhermitte, Sainan Sun, [...]Thomas Nagler, RESEARCH ARTICLESEPTEMBER 21, 2020 Enabling early detection of osteoarthritis from presymptomatic cartilage texture maps via transport-based learning Shinjini Kundu, Beth G. 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[ Human Behavior ](https://www.livescience.com/human-behavior) [ ![Health without the hype: Subscribe to stay in the know.](/media/img/partners/livescience_health-not-hype-button.jpg) ](https://www2.smartbrief.com/signupSystem/subscribe.action?pageSequence=1&briefName=livescience&campaign=bb9da017) # Primates, Including Humans, Are the Most Violent Animals [ News ](https://www.livescience.com/news) By [ Christopher Wanjek ](https://www.livescience.com/author/christopher- wanjek) published 28 September 2016 * [ ](https://www.facebook.com/sharer/sharer.php?u=https://www.livescience.com/56306-primates-including-humans-are-the-most-violent-animals.html) * [ ](https://twitter.com/intent/tweet?text=Primates%2C%20Including%20Humans%2C%20Are%20the%20Most%20Violent%20Animals&url=https://www.livescience.com/56306-primates-including-humans-are-the-most-violent-animals.html) * [ ](whatsapp://send?text=Primates,%20Including%20Humans,%20Are%20the%20Most%20Violent%20Animalshttps://www.livescience.com/56306-primates-including-humans-are-the-most-violent-animals.html?fwa) * [ __ ](https://www.reddit.com/submit?url=https://www.livescience.com/56306-primates-including-humans-are-the-most-violent-animals.html&title=Primates,%20Including%20Humans,%20Are%20the%20Most%20Violent%20Animals) * [ ](https://pinterest.com/pin/create/button/?url=https://www.livescience.com/56306-primates-including-humans-are-the-most-violent-animals.html&media=https://cdn.mos.cms.futurecdn.net/btyKAp2iWbPRyj42Kfa9NN-1200-80.jpg) * [ ](https://share.flipboard.com/bookmarklet/popout?title=Primates%2C%20Including%20Humans%2C%20Are%20the%20Most%20Violent%20Animals&url=https%3A%2F%2Fwww.livescience.com%2F56306-primates-including-humans-are-the-most-violent-animals.html) * [ __ ](mailto:?subject=I%20found%20this%20webpage&body=Hi,%20I%20found%20this%20webpage%20and%20thought%20you%20might%20like%20it%20https://www.livescience.com/56306-primates-including-humans-are-the-most-violent-animals.html) ![Iraq, fighting, wars, soldiers](https://cdn.mos.cms.futurecdn.net/btyKAp2iWbPRyj42Kfa9NN-320-80.jpg) Iraq's location makes it fertile ground for battles. (Image credit: [ ChameleonsEye ](http://www.shutterstock.com/gallery-668929p1.html) \| [ Shutterstock ](URL) ) Why do humans kill each other? It's a question that has been posed for millennia. At least part of the answer may lie in the fact that humans have evolved from a particularly violent branch of [ the animal family tree ](https://www.livescience.com/33400-8-weird-animal-facts.html) , according to a new study. From the seemingly lovable lemur to the [ crafty chimpanzee ](https://www.livescience.com/46300-chimpanzee-evolution-dna-mutations.html) and mighty gorilla, the mammalian order of primates — to which humans belong — kill within their own species nearly six times more often than the average mammal does, Spanish researchers found. [ Whales ](https://www.livescience.com/animals/marine-mammals/whales) rarely kill each other; the same goes for bats and rabbits. Some species of felines and canines occasionally kill others within their own species — for example, when sparring over territory or mates. Yet most primates use lethal violence with greater frequency than these other animal groups, sometimes even killing their fellow species members in organized raids. [ [ Top 10 Things that Make Humans Special ](https://www.livescience.com/15689-evolution-human-special- species.html) ] Humans exhibit a level of [ lethal aggression ](https://www.livescience.com/5333-evolution-human-aggression.html) that fits this pattern in primates, the researchers determined, according to the findings, published today (Sept. 28) in the journal Nature. Humans are equally as violent to each other as most other primates are, and we have been this way pretty much since [ the dawn of humankind ](https://www.livescience.com/50030-oldest-human-fossil-photos.html) . But that doesn't mean we can't change our ways, the research also suggests. In an exhaustive study, researchers led by José María Gómez of Spain's Higher Council for Scientific Research (CSIC) analyzed data from more than 4 million deaths among the members of 1,024 mammal species from 137 taxonomic families, including about 600 human populations, ranging from about 50,000 years ago to the present. The researchers quantified the level of [ lethal violence ](https://www.livescience.com/53427-oldest-evidence-warfare-uncovered.html) in these species. The researchers calculated that about 2 percent of all human deaths have been caused by interpersonal violence — a figure that matches the observed values for prehistoric humans such as Neanderthals, and most other primates. [ [ 8 Humanlike Behaviors of Primates ](https://www.livescience.com/15309-humanlike- behaviors-primates.html) ] ## Sign up for the Live Science daily newsletter now Get the world’s most fascinating discoveries delivered straight to your inbox. Contact me with news and offers from other Future brands Receive email from us on behalf of our trusted partners or sponsors By submitting your information you agree to the [ Terms & Conditions ](http://www.futureplc.com/terms-conditions/) and [ Privacy Policy ](http://www.futureplc.com/privacy-policy/) and are aged 16 or over. "[This is a level of] violence we should have only considering our specific position in the mammalian phylogenetic [evolutionary] tree," Gómez told Live Science. "Within primates, humans are not unusually violent." Yet unlike violence among other mammals, the levels of lethal interpersonal [ human violence ](https://www.livescience.com/6535-laws-change-science- violence-explained.html) have fluctuated throughout history — from low levels during nomadic periods, to higher levels when plunder and conquest became profitable, to lower levels in the [ era of civilized societies ](https://www.livescience.com/44171-society-civilization-collapse-study.html) . This implies, perhaps optimistically, that [ human culture ](https://www.livescience.com/21478-what-is-culture-definition-of- culture.html) can influence our evolutionarily inherited level of lethal violence, the researchers said. In other words, we can control our propensity for violence — however deep-rooted it may be — better than other primates can. "This is a nifty study with important results that debunk the old 'killer ape' view of humanity," said Douglas Fry, professor and chair of anthropology at the University of Alabama at Birmingham. Fry pointed to earlier ideas, put forth by researchers including Harvard University evolutionary psychologist and author Steven Pinker, that human violence was much more common in [ human ancestors ](https://www.livescience.com/planet-earth/evolution) that lived in earlier epochs than it is now. "Employing an innovative approach that contextualizes human lethal aggression within a mammalian framework, Gomez and colleagues demonstrate that recent assertions by Steven Pinker and others that violent death in [ the Paleolithic ](https://www.livescience.com/53368-paleo-diet.html) was shockingly high are greatly exaggerated," said Fry, an expert on human evolution who was not involved with the new study. Other experts, however, have noted the limitations of the data. For instance, there can be an inherent underestimation of violent death in prehistoric humans given the lack of forensic evidence, as well as a difficulty in comparing such disparate data on living and dead mammalian populations, according to Richard Wrangham, a professor of biological anthropology at Harvard University who has researched the origins of human warfare but was not involved in the new study. Wrangham said he suspects that humans are more violent to each other than the study suggests. "Certainly, there is culturally derived variation across societies in the rate of killing adults; but as a species, we belong to a club…that kill[s] adults at an exceptionally high rate," Wrangham told Live Science. "It should not be taken to mean that humans are 'ordinary' with respect to levels of lethal violence. … Humans really are exceptional." Ironically, human violence may be a result of being social, Gómez said, as [ groups aim to protect themselves ](https://www.livescience.com/12781-ravens- group-living-stress.html) or otherwise secure resources and maintain order. "Territorial and social species showed significantly higher values of lethal violence than solitary and nonterritorial mammals," Gómez said. "This is something that should be explored in the future." _Follow Christopher Wanjek[ @wanjek ](https://twitter.com/wanjek) for daily tweets on health and science with a humorous edge. Wanjek is the author of "Food at Work" and "Bad Medicine." His column, [ Bad Medicine ](https://www.livescience.com/tag/bad-medicine) , appears regularly on Live Science. _ ![Christopher Wanjek](https://cdn.mos.cms.futurecdn.net/FAYRUhgsHHoW8R3GqQPK3A.jpeg) [ Christopher Wanjek ](https://www.livescience.com/author/christopher-wanjek) Social Links Navigation [ ](https://www.twitter.com/@wanjek) Live Science Contributor Christopher Wanjek is a Live Science contributor and a health and science writer. He is the author of three science books: Spacefarers (2020), Food at Work (2005) and Bad Medicine (2003). His "Food at Work" book and project, concerning workers' health, safety and productivity, was commissioned by the U.N.'s International Labor Organization. For Live Science, Christopher covers public health, nutrition and biology, and he has written extensively for The Washington Post and Sky & Telescope among others, as well as for the NASA Goddard Space Flight Center, where he was a senior writer. 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A service of the National Library of Medicine, National Institutes of Health. StatPearls [Internet]. Treasure Island (FL): StatPearls Publishing; 2024 Jan-. [ ![Cover of StatPearls](/corehtml/pmc/pmcgifs/bookshelf/thumbs/th-statpearls- lrg.png) ](/books/n/statpearls/ "Table of Contents Page") ## StatPearls [Internet]. Show details Treasure Island (FL): [ StatPearls Publishing ](https://www.statpearls.com/) ; 2024 Jan-. Search term # Funnel Web Spider Toxicity Justin T. Binstead ; Thomas M. Nappe . Author Information and Affiliations #### Authors Justin T. Binstead 1 ; Thomas M. Nappe 2 . #### Affiliations 1 St. Luke's University Hospital 2 St. Luke's University Health Network; Lewis Katz School of Medicine, Temple University Last Update: January 9, 2023 . ## Continuing Education Activity There are over 40 species of funnel-web spiders, with 3 genera restricted to Australia, including the Hadronyche, Illawarra, and the Atrax. Funnel-web spiders are medium to large in size and are dark in color, ranging from black to brown. Funnel-web spiders get their name from their funnel-shaped burrows they spin to trap prey. Funnel-web spiders have powerful, sharp fangs that have been known to penetrate fingernails and soft shoes. They are known to be among the most dangerous spiders in the world. This activity reviews the etiology, presentation, evaluation, and management/prevention of funnel web spider venom toxicity, and reviews the role of the interprofessional team in evaluating, diagnosing, and managing the condition. Objectives: * Outline the toxicokinetics and pathophysiology of funnel web spider venom toxicity. * Identify the presentation of a patient with funnel web spider venom toxicity, and potential differential diagnoses. * Describe the treatment and management strategies for addressing funnel web spider venom toxicity. * Review interprofessional team strategies for improving coordination and communication to advance the management of victims of funnel spider toxicity and improve outcomes. [ Access free multiple choice questions on this topic. ](https://www.statpearls.com/account/trialuserreg/?articleid=29295&utm_source=pubmed&utm_campaign=reviews&utm_content=29295) ## Introduction There are over 40 species of funnel-web spiders, with 3 genera restricted to Australia, including the _Hadronyche_ , _Illawarra_ , and the _Atrax_ . Of all Australian spiders, one species of the _Atrax_ genera, the _Atrax_ _robustu_ s, is implicated in the most human fatalities. The _Atrax robustus_ is known as the Sydney funnel-web spider and is native to eastern Australia. Funnel-web spiders are medium to large in size and are dark in color, ranging from black to brown. Funnel-web spiders get their name from their funnel-shaped burrows they spin to trap prey. These spiders reside in cool and relatively sheltered habitats. They are often found under rocks or in rock gardens, in various shrubberies, or under logs. Some funnel web spiders even reside in trees, sometimes several meters in the air. The bite of the Sydney funnel-web spider is potentially deadly, but since the development of the antivenom in 1981 and the advancement of modern first aid techniques, there has been only 1 death associated with this spider's bite and was likely a result of a delayed presentation. [1] Funnel-web spiders have powerful, sharp fangs that have been known to penetrate fingernails and soft shoes. They are known to be the most dangerous spiders in the world. The silk entrance to the burrow of a Sydney funnel-web spider has a "vestibule-like" structure, and the spider sits just within the vestibule and senses vibrations along the silk "trip lines" and reacts to inject venom into its prey. The tree-dwelling funnel-web spiders can reach 4 to 5 cm in length, with the largest species being the Northern Tree Funnel Web Spider. [2] ## Etiology All funnel-web spider bites should be treated as potentially life-threatening, even though only approximately 10% to 15% of bites are venomous. Since the venom from the funnel-web spider bite is highly toxic, all species should be considered potentially dangerous. [3] In all the fatalities where the gender of the spider was confirmed, the male funnel-web spider was responsible. Males are more active at night and have been known to enter homes. The onset of severe envenomation is rapid. In one study, the median time to onset of envenoming was 28 minutes, and only 2 cases had onset after 2 hours. In both cases, the bites had pressure immobilization bandages applied. Death may occur in 15 minutes (small children) to 3 days. [1] Younger patients and patients with underlying medical conditions have a higher incidence of death when they are bitten by a funnel-web spider. ## Epidemiology Data has been extracted to determine the species-specific envenomation rates and the severity of the funnel-web spider bites and to determine both the efficacy and the adverse events related to the antivenom. The data gathered revealed that there were 198 potential funnel-web spider bites identified. Of those, 138 were confirmed as a funnel-web spider, and 77 of those cases produced severe envenomation. All of the species related to the severe envenomations were attributed to species restricted to New South Wales and Southern Queensland. The antivenom was used in 75 patients, including 22 children, with a complete response in 97% of the positively identified cases. [3] There were 3 adverse reactions which were all in adults (one early mild, one early severe that require epinephrine, and a delayed serum sickness reaction). The researchers concluded that severe funnel-web spider envenomations were confined to New South Wales and southern Queensland, with the tree-dwelling funnel webs having the highest envenomation rates. The antivenom to funnel web spiders was safe and effective, and severe allergic reactions are uncommon. True necrotizing arachnidism appears to be quite rare. ## Toxicokinetics There are a large number of different toxins in the venom of these spiders. They are classified as atracotoxin. These neurotoxins induce the spontaneous and repetitive firing of action potentials in presynaptic autonomic and motor neurons, leading to catecholamine surge. The atracotoxin are also associated with voltage-gated sodium channel toxicity. [4] These are extremely toxic and believed to be the main cause of lethal envenomation syndrome following the bite of a funnel web spider. The venomous component primarily responsible for the envenomation syndrome of the _Atrax robustus_ is a single peptide known as delta-atracotoxin. [5] [6] ## History and Physical Early symptoms of a funnel-web spider envenomation include facial paresthesias, nausea, vomiting, profuse diaphoresis, drooling, and shortness of breath. Patients may become agitated, confused and ultimately comatose. This is associated with hypertension, metabolic acidosis, dilated pupils, muscle twitching and pulmonary and cerebral edema. Death results from pulmonary edema or progression to hypotension and circulatory collapse. [7] ## Evaluation There is no lab assay available to detect the venom of a funnel-web spider easily. Laboratory evaluation should include serum creatinine kinase, electrolytes, renal function, glucose; arterial or venous blood gas to assess for hypoxia; and coagulation studies to assess for disseminated intravascular coagulation. ## Treatment / Management The bite from a funnel-web spider can cause very severe symptoms that can worsen and progress rapidly, and the primary treatment is antivenom known as FWSAV. Therefore, all bites from large, black spiders in the endemic areas should be treated as funnel-web spider bites. First-aid treatment for a suspected funnel-web spider envenomation starts with cleansing the area with soap and tap water, then immediately applying a pressure immobilization bandage. This technique combines a light pressure bandage with immobilizing the affected area as if it were being splinted. This technique limits the spread of the venom throughout the body and minimizes the area affected by the bite. [3] There is also evidence suggesting that the applied pressure and prolonged localization inactivate the venom. Emergency medical treatment should be sought as soon as possible. It is critical to maintain the pressure immobilization bandage until the patient is evaluated by trained medical personnel in an emergency department. The pressure immobilization bandage should not be removed prematurely as this can cause systemic mobilization of the venom. Before removal of the pressure immobilization bandage, intravenous access should be established, and the patient should be connected to appropriate cardiorespiratory monitoring, while a supply of antivenom is obtained and readily available for administration. A patient who does not show any symptoms of systemic envenomation may deteriorate rapidly once the bandage is removed. [7] The primary treatment is antivenom FWSAV; however, other supportive measures may be indicated. Antivenom should be given at the earliest sign of systemic envenomation. For patients without any development of systemic symptoms, monitoring should occur for 4 to 6 hours from the time of the envenomation or, if pressure bandage applied, from the time of removal. Antivenom is not indicated if the patient only has localized symptoms after an appropriate observation period. ## Differential Diagnosis Differential diagnosis includes other insect or spider bites, cutaneous abscess (=/-) MRSA, anthrax, herpes zoster, pyoderma gangrenosum, Stevens- Johnson syndrome, and toxic epidermal necrolysis. ## Pearls and Other Issues * The _Atrax robustus_ is considered the deadliest spider in the world. * Since the development of the antivenom FWSAV in 1981, there have been no reported deaths with early administration. * Primary treatment is with antivenom FWSAV. * All patients should have immobilizing pressure dressing applied and transported immediately to the nearest emergency department. ## Enhancing Healthcare Team Outcomes Primary consultation should include a medical toxicologist or the local poison center. Critical care specialists should be consulted for inpatient monitoring for all symptomatic patients. Recommended follow-up with healthcare team including primary care, nursing, and medical toxicologist should occur for anyone given antivenom, to assure no development of serum sickness. All treating physicians and primary providers including nurse practitioners should educate on outdoor safety and close follow-up. ## Review Questions * [ Access free multiple choice questions on this topic. ](https://www.statpearls.com/account/trialuserreg/?articleid=29295&utm_source=pubmed&utm_campaign=reviews&utm_content=29295) * [ Comment on this article. ](https://www.statpearls.com/articlelibrary/commentarticle/29295/?utm_source=pubmed&utm_campaign=comments&utm_content=29295) [ ![Image ](/books/NBK535394/bin/funnelweb.gif) ](/books/NBK535394/figure/article-29295.image.f1/?report=objectonly "Figure") #### [ Figure ](/books/NBK535394/figure/article-29295.image.f1/?report=objectonly) Funnel-Web Spider Contributed by Steve Bhimji, MS, MD, PhD ## References 1\. Isbister GK, Gray MR, Balit CR, Raven RJ, Stokes BJ, Porges K, Tankel AS, Turner E, White J, Fisher MM. Funnel-web spider bite: a systematic review of recorded clinical cases. Med J Aust. 2005 Apr 18; 182 (8):407-11. [ [ PubMed : 15850438 ](https://pubmed.ncbi.nlm.nih.gov/15850438) ] 2\. Atkinson RK, Walker P. The effects of season of collection, feeding, maturation and gender on the potency of funnel-web spider (Atrax infensus) venom. Aust J Exp Biol Med Sci. 1985 Oct; 63 ( Pt 5) :555-61. [ [ PubMed : 4091761 ](https://pubmed.ncbi.nlm.nih.gov/4091761) ] 3\. Isbister GK. Antivenom efficacy or effectiveness: the Australian experience. Toxicology. 2010 Feb 09; 268 (3):148-54. [ [ PubMed : 19782716 ](https://pubmed.ncbi.nlm.nih.gov/19782716) ] 4\. Del Brutto OH. Neurological effects of venomous bites and stings: snakes, spiders, and scorpions. Handb Clin Neurol. 2013; 114 :349-68. [ [ PubMed : 23829924 ](https://pubmed.ncbi.nlm.nih.gov/23829924) ] 5\. Luch A. Mechanistic insights on spider neurotoxins. EXS. 2010; 100 :293-315. [ [ PubMed : 20358687 ](https://pubmed.ncbi.nlm.nih.gov/20358687) ] 6\. Alewood D, Birinyi-Strachan LC, Pallaghy PK, Norton RS, Nicholson GM, Alewood PF. Synthesis and characterization of delta-atracotoxin-Ar1a, the lethal neurotoxin from venom of the Sydney funnel-web spider (Atrax robustus). Biochemistry. 2003 Nov 11; 42 (44):12933-40. [ [ PubMed : 14596608 ](https://pubmed.ncbi.nlm.nih.gov/14596608) ] 7\. Braitberg G, Segal L. Spider bites - Assessment and management. Aust Fam Physician. 2009 Nov; 38 (11):862-7. [ [ PubMed : 19893831 ](https://pubmed.ncbi.nlm.nih.gov/19893831) ] 8\. Hedin M, Derkarabetian S, Ramírez MJ, Vink C, Bond JE. Phylogenomic reclassification of the world's most venomous spiders (Mygalomorphae, Atracinae), with implications for venom evolution. Sci Rep. 2018 Jan 26; 8 (1):1636. [ [ PMC free article : PMC5785998 ](/pmc/articles/PMC5785998/) ] [ [ PubMed : 29374214 ](https://pubmed.ncbi.nlm.nih.gov/29374214) ] 9\. Cardoso FC, Pineda SS, Herzig V, Sunagar K, Shaikh NY, Jin AH, King GF, Alewood PF, Lewis RJ, Dutertre S. The Deadly Toxin Arsenal of the Tree- Dwelling Australian Funnel-Web Spiders. Int J Mol Sci. 2022 Oct 28; 23 (21) [ [ PMC free article : PMC9658043 ](/pmc/articles/PMC9658043/) ] [ [ PubMed : 36361863 ](https://pubmed.ncbi.nlm.nih.gov/36361863) ] 10\. Nicholson GM, Little MJ, Tyler M, Narahashi T. Selective alteration of sodium channel gating by Australian funnel-web spider toxins. Toxicon. 1996 Nov- Dec; 34 (11-12):1443-53. [ [ PubMed : 9028001 ](https://pubmed.ncbi.nlm.nih.gov/9028001) ] 11\. Herzig V, Sunagar K, Wilson DTR, Pineda SS, Israel MR, Dutertre S, McFarland BS, Undheim EAB, Hodgson WC, Alewood PF, Lewis RJ, Bosmans F, Vetter I, King GF, Fry BG. Australian funnel-web spiders evolved human-lethal δ-hexatoxins for defense against vertebrate predators. Proc Natl Acad Sci U S A. 2020 Oct 06; 117 (40):24920-24928. [ [ PMC free article : PMC7547274 ](/pmc/articles/PMC7547274/) ] [ [ PubMed : 32958636 ](https://pubmed.ncbi.nlm.nih.gov/32958636) ] Disclosure: Justin Binstead declares no relevant financial relationships with ineligible companies. Disclosure: Thomas Nappe declares no relevant financial relationships with ineligible companies. [ Copyright ](/books/about/copyright/) © 2024, StatPearls Publishing LLC. This book is distributed under the terms of the Creative Commons Attribution- NonCommercial-NoDerivatives 4.0 International (CC BY-NC-ND 4.0) ( [ http://creativecommons.org/licenses/by-nc-nd/4.0/ ](https://creativecommons.org/licenses/by-nc-nd/4.0/) ), which permits others to distribute the work, provided that the article is not altered or used commercially. You are not required to obtain permission to distribute this article, provided that you credit the author and journal. Bookshelf ID: NBK535394 PMID: [ 30571015 ](https://pubmed.ncbi.nlm.nih.gov/30571015 "PubMed record of this page") Share ### Views * [ PubReader ](/books/NBK535394/?report=reader) * [ Print View ](/books/NBK535394/?report=printable) * Cite this Page Binstead JT, Nappe TM. Funnel Web Spider Toxicity. [Updated 2023 Jan 9]. In: StatPearls [Internet]. Treasure Island (FL): StatPearls Publishing; 2024 Jan-. ### In this Page * Continuing Education Activity * Introduction * Etiology * Epidemiology * Toxicokinetics * History and Physical * Evaluation * Treatment / Management * Differential Diagnosis * Pearls and Other Issues * Enhancing Healthcare Team Outcomes * Review Questions * References ### Bulk Download * [ Bulk download StatPearls data from FTP ](https://ftp.ncbi.nlm.nih.gov/pub/litarch/3d/12/) ### Related information * [ PMC ](/books/?Db=pmc&DbFrom=books&Cmd=Link&LinkName=books_pmc_refs&IdsFromResult=4681478) PubMed Central citations * [ PubMed ](/books/?Db=pubmed&DbFrom=books&Cmd=Link&LinkName=books_pubmed_refs&IdsFromResult=4681478) Links to PubMed ### Similar articles in PubMed * [ Clinical features and management of Hadronyche envenomation in man. ](/pubmed/10669029) [Toxicon. 2000] Clinical features and management of Hadronyche envenomation in man. _Miller MK, Whyte IM, White J, Keir PM._ _Toxicon. 2000 Mar; 38(3):409-27._ * [ Cross-reactivity of Sydney funnel-web spider antivenom: neutralization of the in vitro toxicity of other Australian funnel-web (Atrax and Hadronyche) spider venoms. ](/pubmed/11711122) [Toxicon. 2002] Cross-reactivity of Sydney funnel-web spider antivenom: neutralization of the in vitro toxicity of other Australian funnel-web (Atrax and Hadronyche) spider venoms. _Graudins A, Wilson D, Alewood PF, Broady KW, Nicholson GM._ _Toxicon. 2002 Mar; 40(3):259-66._ * [ The Deadly Toxin Arsenal of the Tree-Dwelling Australian Funnel-Web Spiders. ](/pubmed/36361863) [Int J Mol Sci. 2022] The Deadly Toxin Arsenal of the Tree-Dwelling Australian Funnel-Web Spiders. _Cardoso FC, Pineda SS, Herzig V, Sunagar K, Shaikh NY, Jin AH, King GF, Alewood PF, Lewis RJ, Dutertre S._ _Int J Mol Sci. 2022 Oct 28; 23(21). Epub 2022 Oct 28._ * [ Review The funnel web and common spider bites. ](/pubmed/15129470) [Aust Fam Physician. 2004] Review The funnel web and common spider bites. _Nimorakiotakis B, Winkel KD._ _Aust Fam Physician. 2004 Apr; 33(4):244-51._ * [ Review Funnel-web spider bite: a systematic review of recorded clinical cases. ](/pubmed/15850438) [Med J Aust. 2005] Review Funnel-web spider bite: a systematic review of recorded clinical cases. _Isbister GK, Gray MR, Balit CR, Raven RJ, Stokes BJ, Porges K, Tankel AS, Turner E, White J, Fisher MM._ _Med J Aust. 2005 Apr 18; 182(8):407-11._ [ See reviews... ](/sites/entrez?db=pubmed&cmd=link&linkname=pubmed_pubmed_reviews&uid=30571015) [ See all... ](/sites/entrez?db=pubmed&cmd=link&linkname=pubmed_pubmed&uid=30571015) ### Recent Activity [ Clear ](javascript:historyDisplayState$'ClearHT'$) [ Turn Off ](javascript:historyDisplayState$'HTOff'$) [ Turn On ](javascript:historyDisplayState$'HTOn'$) * [ Funnel Web Spider Toxicity - StatPearls ](/portal/utils/pageresolver.fcgi?recordid=66302118241a5058e6e557d5) Funnel Web Spider Toxicity - StatPearls Your browsing activity is empty. 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Nanodectes bulbicercus ingår i släktet Nanodectes och familjen vårtbitare. IUCN kategoriserar arten globalt som akut hotad. Inga underarter finns listade i Catalogue of Life. Källor Vårtbitare bulbicercus	swedish	1.071818
spider_venom_lethal/Delta_atracotoxin.txt	Delta atracotoxin (δ-ACTX-Ar1, robustoxin, or robustotoxin) is a low-molecular-weight neurotoxic polypeptide found in the venom of the Sydney funnel-web spider (Atrax robustus). Delta atracotoxin produces potentially fatal neurotoxic symptoms in primates, by slowing the inactivation of sodium ion channels in autonomic and motor neurons. In the spiders' intended insect prey, the toxin exerts this same activity upon potassium and calcium ion channels. The structure of atracotoxin comprises a core beta region with a cystine knot motif, a feature seen in other neurotoxic polypeptides. History[edit] Since 1927, records are kept of envenomations of humans by the Sydney funnel-web spider, and 14 deaths have been reported in medical literature between 1927 and 1981, when the antivenom became available. In all cases in which the sex of the spider was determined, death occurred after a bite from a male spider. Structure[edit] Delta atracotoxin is a 42-residue peptide toxin with the chemical formula C206H313N59O59S9. The amino acid sequence of delta atracotoxin is unusual in that it contains three consecutive cysteine residues at positions 14–16. The amino acid sequence of delta atracotoxin is: CAKKRNWCGK NEDCCCPMKC IYAWYNQQGS CQTTITGLFK KC Cysteine bridges exist between Cys1 and Cys15, Cys8 and Cys20, Cys14 and Cys31, and Cys16 and Cys42. The structure consists of a small triple-stranded beta-sheet stabilized by a disulfide knot, followed by a C-terminal extension comprising three classic or inverse y-turns. The disulfide knot is a ring consisting of two disulfide bonds (1-15 and 8-20) and the connecting backbone, through which a third disulfide bond (14-31) passes. The β-sheet, defined on the basis of inter-sheet hydrogen bonds, consists of residues 6-8 (strand I), 19-21 (strand II) and 29-32 (strand III), with a topology of +2x, —1. The two hydrogen bonds (one amide of which has a slowly exchanging amide proton) between strands I and III are distorted (NH to CO distance between 2.5 and 3.0 A). There are four hydrogen bonds between strands II and III (all of which have corresponding slowly exchanging amide protons), three being present in most of the structures and one in half of the structures. The structure contains a number of chain reversals. The first is not well defined and is either a type II β-turn (Lys3-Asn6) or a y-turn centered on Arg5. Chain reversal II is a y turn centered on Gly9. Chain reversal III is not well defined, being either a type I β-turn (Asnn-Cys14) or an inverse y-turn centered on Asn11. Chain reversal IV (Cys15-Met18) is not stabilized by a hydrogen bond but has a cis peptide bond between Cys16 and Pro17 and resembles a type Via turn. The fifth chain reversal occurs in the region of residues 22–28, which fulfill the criteria for an i2-loop. The C-terminal extension, stabilized by the Cys16-Cys42 disulfide bond, consists of three y-turns, VI-VIII, that are, respectively, an inverse turn, centered on Thr33, a classic turn centered on Ile35 and an inverse turn centered on Phe39. All three of the y-turn hydrogen bonds have slowly exchanging amide protons (although this is not the case for the other turns). The only slowly exchanging amide proton not accounted for by consensus hydrogen bonds in any secondary structure element is that of Gly37 (which hydrogen bonds to Thr34 in one of the structures). The conformations of the Cys1-Cys15 and Cys8-Cys20 disulfide bonds are well defined and have negative and positive Xss, respectively; the other two bonds have lower order parameters. The hydrophobic core of RBX is limited, consisting of essentially the disulfide knot cystine residues and the buried Met18. The 22-28 loop contains one apolar residue, Ala23, and three aromatics, Tyr22, Trp24 and Tyr25, and is flanked by Ile21 at its N-terminus and Trp7 near its C-terminus, so this region represents a significant non-polar surface on the molecule. RBX is highly positively charged, with one Arg (sequence position 5) and six Lys (3, 4, 10, 19, 40 and 41) residues, balanced only by Glu12 and Asp13. These charged residues form three patches on the surface. Patch A consists of the positively charged residues 3,4 and 5, patch B of residues 10, 12, 13 and the N-terminus (including possible salt bridges between Lys10 and Glu12 and Asp13 and the N-terminus), and patch C of 19, 40, 41 and the C-terminus. Mechanism of action[edit] Delta atracotoxin is responsible for the potentially lethal envenomation syndrome seen following funnel-web spider envenomation. d-Atracotoxins induce spontaneous, repetitive firing and prolongation of action potentials resulting in continuous acetylcholine neurotransmitter release from somatic and autonomic nerve endings. This will lead to slower voltage-gated sodium channel inactivation and a hyperpolarizing shift in the voltage-dependence of activation. This action is due to voltage-dependent binding to neurotoxin receptor site-3 in a similar, but not identical, fashion to scorpion a-toxins and sea anemone toxins. In the sea anemone and scorpion toxins, combinations of charged (especially cationic) and hydrophobic side-chains are important for binding to their receptor site (site 3) on the sodium channel. It will therefore be not surprising to find that the same applies to delta atracotoxin and versutoxin (a close homologue of delta atracotoxin). Delta atracotoxin presents three distinct charged patches on its surface, as well as a non-polar region centered on the 22-28 loop. Both of these structural features may play a role in its binding to the voltage-gated sodium channel, but further studies are necessary in defining which residues are important for interaction with the sodium channel so that a plausible model can be constructed of its binding site. Synthetic[edit] The availability of synthetic toxin has allowed scientists to further explore the biological activity of the toxin, resulting in the observation that d-ACTX-Ar1a causes repetitive firing and prolongation of the action potential. These actions underlie the clinical symptoms seen following envenomation and further contribute to the understanding of the molecular basis for activity of this potent neurotoxin on voltage-gated sodium channels. Under voltage-clamp conditions in dorsal root ganglion (DRG) neurons it was found that the effects of the synthetic toxin on sodium currents were not significantly different from those previously reported for the native toxin. Neither native nor synthetic d-ACTX-Ar1a had any effect on TTX-resistant sodium currents, but both exerted a potent selective modulation of TTX-sensitive sodium currents consistent with actions on neurotoxin receptor site-3. This includes a slowing of the sodium-channel inactivation, a hyperpolarizing shift in the voltage-dependence of activation and a hyperpolarizing shift in the steady-state sodium-channel inactivation. d-ACTX-Ar1a causes a prolongation of action potential duration, accompanied by spontaneous repetitive firing, but does not depolarize the resting membrane potential. Effects on the autonomic nervous system, including vomiting, profuse sweating, salivation, lachrymation, marked hypertension followed by hypotension, together with effect on the somatic nervous system to cause muscle fasciculation and dyspnea (shortness of breath) are presumably due to excessive transmitter release. To identify the sodium-channel binding surface of d-ACTX-Ar1a, scientist must synthesize analogues with selected residue changes. Studies will contribute to a more detailed mapping of site-3, the neurotoxin receptor site on the sodium-channel and provide structure-activity data critical for determining the phylaspecific actions of this and related atracotoxins. Toxicity[edit] The toxicity of the spider's venom is affected by the sex of the spider. The male funnel-web spider's venom appears to be six times more powerful than that of the female spider, based on minimum lethal dose determinations. In addition, different species of animals tend to react to the venom in various ways. For example, rats, rabbits and cats are unaffected by the bite of a female funnel-web spider, whereas for 20 percent of mice and guinea pigs the bite of a female was fatal. A bite of a male funnel-web spider, though, led to the death of almost all mice and guinea pigs. Although the male spider's venom seems to be more potent, male spider bites cause mild transient effects in dogs and cats. Most primates, including humans, appear to be extremely sensitive to the funnel-web spider's venom. The LD50 values have been determined in mice, for male spider venom 3.3 mg/kg body weight of the mouse and for female spider venom 50 mg/kg body weight were found. The LD50 value of pure delta atracotoxin which was isolated from a male spider, 0.15 mg/kg body weight was found. Signs and symptoms[edit] The bite of a Sydney funnel web spider is at first painful, due to the large fangs and acidic pH of the venom. If there is no immediate treatment symptoms may arise beginning ten minutes after the bite. Hypertension may occur, which is often followed by a prolonged hypotension and circulatory failure. Other symptoms include dyspnea and ultimately respiratory failure, generalized skeletal muscle fasciculation, salivation, lachrymation, sweating, nausea, vomiting, diarrhoea, pulmonary edema and pain. The progress of the envenomation is precisely studied in primates, which symptoms are very similar to those of humans. In the first 25 minutes after envenomation disturbances in respiration occur, which gradually become worse. Some monkeys required artificial ventilation. Initially, the blood pressure decreased, but then quickly rose, after which the blood pressure gradually declined. After 40–100 minutes severe hypotension occurred. Lachrymation started after 6–15 minutes and was followed by salivation. These symptoms were most severe during 15–35 minutes after envenomation. Skeletal muscle fasciculation started after 8–10 minutes and reached its peak between 20 and 45 minutes. It was accompanied with an increase in body temperature. Envenomation with the male venom produced mostly the same symptoms, although the onset of the symptoms was a little delayed. The female venom also produces the same symptoms, but far less severe. Antivenom[edit] The antivenom was developed by a team headed by Struan Sutherland at the Commonwealth Serum Laboratories in Melbourne. Since the antivenom became available in 1981, there have been no recorded fatalities from Sydney funnel-web spider bites. In September 2012, it was reported that stocks of antivenom were running low, and members of the public were asked to catch the spiders so that they could be milked for their venom. The venom is taken from the spiders by delicately stroking their fangs and collecting the tiny droplets of the deadly venom. The venom is needed to produce the antivenom. One dose of antivenom requires around 70 milkings from a spider. Funnel web spider antivenom is prepared from the plasma of rabbits immunized with the venom of the male funnel web spider (Atrax robustus). Each vial of the product contains 125 units of antivenom which has been standardized to neutralize 1.25 mg of funnel web spider venom. The product also contains glycine and other rabbit plasma proteins. Funnel web spider antivenom is a purified immunoglobulin (mainly immunoglobulin G), derived from rabbit plasma, which contains specific antibodies against the toxic substances in the venom of the funnel web spider, Atrax robustus. There is evidence to show that the antivenom is effective in the treatment of patients bitten by some other funnel web spiders of the genus Hadronyche (formerly Atrax). See also[edit] Atracotoxin	biology	4858253	https://sv.wikipedia.org/wiki/Cyphostemma%20anatomica	Cyphostemma anatomica	Cyphostemma anatomica är en vinväxtart som först beskrevs av C. A. Smith, och fick sitt nu gällande namn av Wild & R. B. Drumm.. Cyphostemma anatomica ingår i släktet Cyphostemma och familjen vinväxter. Inga underarter finns listade i Catalogue of Life. Källor Vinväxter anatomica	swedish	1.094665
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Image: David Wilson Scientists studying the most venomous spider in the world have found the venom of some varies depending on circumstances – which could provide insights into how they could be of use for human health. Dr Linda Hernández Duran from James Cook University’s Australian Institute of Tropical Health and Medicine led a study that examined the venom produced by different species of funnel-web under different conditions. She said funnel- webs are the most venomous spiders in the world. “Funnel-webs have the most complex venoms in the natural world, and they are valued for the therapeutics and natural bioinsecticides that are potentially hidden in their venom molecules. Knowing more about how they are produced is a step towards unlocking this potential,” said Dr Hernández Duran. The team collected four different species of funnel-web – the Border Ranges (Hadronyche valida), Darling Downs, (Hadronyche infensa), Southern tree- dwelling (Hadronyche cerberea) and Sydney funnel-web (Atrax robustus) – and subjected them to different tests, such as being prodded with tweezers and puffed with air. “We mapped their behaviour and measured their heart rate with a laser monitor to establish a proxy value for their metabolic rate. We then collected their venom and analysed it with a mass spectrometer,” said Dr Hernández Duran. She said researchers found that certain spiders had variations in their venom based on different factors such as defensiveness and heart rate. “With the Border Ranges funnel-web, the expression of some venom components was associated with heart rate and defensiveness. The other species didn’t demonstrate this, suggesting that particular associations may be species- specific,” said Dr Hernández Duran. She said the use of venom and the display of aggressive behaviours by spiders have metabolic costs. “As a result, spiders might use different behavioural strategies to compensate for these costs. Our results suggest spiders might increase their metabolic rate when they use venoms, and reduce their movement when facing a threat,” said Dr Hernández Duran. She said the findings highlight the link between behaviour, physiology, and venom composition in funnel-webs. “We showed for the first time how specific venom components are associated with particular behavioural and physiological variables and demonstrated that these relationships are context-dependent. 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cancer_not_communicable/PMC7150340.txt	Skip to main content U.S. flagAn official website of the United States government Here's how you know NIH NLM LogoLog in Access keysNCBI HomepageMyNCBI HomepageMain ContentMain Navigation Preview improvements coming to the PMC website in October 2024. Learn More or Try it out now. Search PMC Full-Text Archive Search PMC Full-Text Archive Search in PMC Advanced Search User Guide Journal List Elsevier - PMC COVID-19 Collection PMC7150340 As a library, NLM provides access to scientific literature. Inclusion in an NLM database does not imply endorsement of, or agreement with, the contents by NLM or the National Institutes of Health. Learn more: PMC Disclaimer \| PMC Copyright Notice Logo of pheelsevier International Encyclopedia of Public Health. 2017 : 22–39. Published online 2016 Oct 24. doi: 10.1016/B978-0-12-803678-5.00516-6 PMCID: PMC7150340 Principles of Infectious Diseases: Transmission, Diagnosis, Prevention, and Control Jean Maguire van Seventer Boston University School of Public Health, Boston, MA, USA Natasha S. Hochberg Guest Editor (s): Stella R. Quah Copyright and License information PMC Disclaimer Go to: Abstract Infectious disease control and prevention relies on a thorough understanding of the factors determining transmission. This article summarizes the fundamental principles of infectious disease transmission while highlighting many of the agent, host, and environmental determinants of these diseases that are of particular import to public health professionals. Basic principles of infectious disease diagnosis, control, and prevention are also reviewed. Keywords: Control, Environment, Epidemic, Epidemiology, Host, Infection, Infectious disease, One health, Outbreak, Prevention, Public health, Reservoir, Transmission, Vector, Zoonosis Go to: Introduction An infectious disease can be defined as an illness due to a pathogen or its toxic product, which arises through transmission from an infected person, an infected animal, or a contaminated inanimate object to a susceptible host. Infectious diseases are responsible for an immense global burden of disease that impacts public health systems and economies worldwide, disproportionately affecting vulnerable populations. In 2013, infectious diseases resulted in over 45 million years lost due to disability and over 9 million deaths (Naghavi et al., 2015). Lower respiratory tract infections, diarrheal diseases, HIV/AIDS, malaria, and tuberculosis (TB) are among the top causes of overall global mortality (Vos et al., 2015). Infectious diseases also include emerging infectious diseases; diseases that have newly appeared (e.g., Middle East Respiratory Syndrome) or have existed but are rapidly increasing in incidence or geographic range (e.g., extensively drug-resistant tuberculosis (XDR TB) and Zika virus (Morse, 1995). Infectious disease control and prevention relies on a thorough understanding of the factors determining transmission. This article summarizes some of the fundamental principles of infectious disease transmission while highlighting many of the agent, host, and environmental determinants of these diseases that are of particular import to public health professionals. Go to: The Epidemiological Triad: Agent–Host–Environment A classic model of infectious disease causation, the epidemiological triad (Snieszko, 1974), envisions that an infectious disease results from a combination of agent (pathogen), host, and environmental factors (Figure 1 ). Infectious agents may be living parasites (helminths or protozoa), fungi, or bacteria, or nonliving viruses or prions. Environmental factors determine if a host will become exposed to one of these agents, and subsequent interactions between the agent and host will determine the exposure outcome. Agent and host interactions occur in a cascade of stages that include infection, disease, and recovery or death (Figure 2(a) ). Following exposure, the first step is often colonization, the adherence and initial multiplication of a disease agent at a portal of entry such as the skin or the mucous membranes of the respiratory, digestive, or urogenital tract. Colonization, for example, with methicillin-resistant Staphylococcus aureus in the nasal mucosa, does not cause disease in itself. For disease to occur, a pathogen must infect (invade and establish within) host tissues. Infection will always cause some disruption within a host, but it does not always result in disease. Disease indicates a level of disruption and damage to a host that results in subjective symptoms and objective signs of illness. For example, latent TB infection is only infection – evidenced by a positive tuberculin skin test or interferon gamma release assay – but with a lack of symptoms (e.g., cough or night sweats) or signs (e.g., rales on auscultation of the chest) of disease. This is in contrast to active pulmonary TB (disease), which is accompanied by disease symptoms and signs. An external file that holds a picture, illustration, etc. Object name is f00516-01-9780128036785.jpg Figure 1 The epidemiological triad model of infectious disease causation. The triad consists of an agent (pathogen), a susceptible host, and an environment (physical, social, behavioral, cultural, political, and economic factors) that brings the agent and host together, causing infection and disease to occur in the host. An external file that holds a picture, illustration, etc. Object name is f00516-02-9780128036785.jpg Figure 2 Potential outcomes of host exposure to an infectious agent. (a) Following an exposure, the agent and host interact in a cascade of stages the can result in infection, disease, and recovery or death. (b) Progression from one stage to the next is dependent upon both agent properties of infectivity, pathogenicity, and virulence, and host susceptibility to infection and disease, which is in large part due to both protective and adverse effects of the host immune response. Credit: Modification of original by Barbara Mahon, MD, MPH. Recovery from infection can be either complete (elimination of the agent) or incomplete. Incomplete recovery can result in both chronic infections and latent infections. Chronic infections are characterized by the continued detectable presence of an infectious agent. In contrast, latent infections are distinguished by an agent which can remain quiescent in host cells and can later undergo reactivation. For example, varicella zoster virus, the agent causing chicken pox, may reactivate many years after a primary infection to cause shingles. From a public health standpoint, latent infections are significant in that they represent silent reservoirs of infectious agent for future transmission. Determinants of Infectious Disease When a potential host is exposed to an infectious agent, the outcome of that exposure is dependent upon the dynamic relationship between agent determinants of infectivity, pathogenicity, and virulence, and intrinsic host determinants of susceptibility to infection and to disease (Figure 2(b)). Environmental factors, both physical and social behavioral, are extrinsic determinants of host vulnerability to exposure. Agent Factors Infectivity is the likelihood that an agent will infect a host, given that the host is exposed to the agent. Pathogenicity refers to the ability of an agent to cause disease, given infection, and virulence is the likelihood of causing severe disease among those with disease. Virulence reflects structural and/or biochemical properties of an infectious agent. Notably, the virulence of some infectious agents is due to the production of toxins (endotoxins and/or exotoxins) such as the cholera toxin that induces a profuse watery diarrhea. Some exotoxins cause disease independent of infection, as for example, the staphylococcal enterotoxins that can cause foodborne diseases. Agent characteristics can be measured in various ways. Infectivity is often quantified in terms of the infectious dose 50 (ID 50), the amount of agent required to infect 50% of a specified host population. ID50 varies widely, from 10 organisms for Shigella dysenteriae to 106–1011 for Vibrio cholerae (Gama et al., 2012; FDA, 2012). Infectivity and pathogenicity can be measured by the attack rate, the number of exposed individuals who develop disease (as it may be difficult to determine if someone has been infected if they do not have outward manifestations of disease). Virulence is often measured by the case fatality rate or proportion of diseased individuals who die from the disease. Host Factors The outcome of exposure to an infectious agent depends, in part, upon multiple host factors that determine individual susceptibility to infection and disease. Susceptibility refers to the ability of an exposed individual (or group of individuals) to resist infection or limit disease as a result of their biological makeup. Factors influencing susceptibility include both innate, genetic factors and acquired factors such as the specific immunity that develops following exposure or vaccination. The malaria resistance afforded carriers of the sickle cell trait exemplifies how genetics can influence susceptibility to infectious disease (Aidoo et al., 2002). Susceptibility is also affected by extremes of age, stress, pregnancy, nutritional status, and underlying diseases. These latter factors can impact immunity to infection, as illustrated by immunologically naïve infant populations, aging populations experiencing immune senescence, and immunocompromised HIV/AIDS patients. Mechanical and chemical surface barriers such as the skin, the flushing action of tears, and the trapping action of mucus are the first host obstacles to infection. For example, wound infection and secondary sepsis are serious complications of severe burns which remove the skin barrier to microbial entry. Lysozyme, secreted in saliva, tears, milk, sweat, and mucus, and gastric acid have bactericidal properties, and vaginal acid is microbicidal for many agents of sexually transmitted infections (STIs). Microbiome-resident bacteria (a.k.a. commensal bacteria, normal flora) can also confer host protection by using available nutrients and space to prevent pathogenic bacteria from taking up residence. The innate and adaptive immune responses are critical components of the host response to infectious agents (Table 1 ). Each of these responses is carried out by cells of a distinct hematopoietic stem cell lineage: the myeloid lineage gives rise to innate immune cells (e.g., neutrophils, macrophages, dendritic cells) and the lymphoid lineage gives rise to adaptive immune cells (e.g., T cells, B cells). The innate immune response is an immediate, nonspecific response to broad groups of pathogens. By contrast, the adaptive immune response is initially generated over a period of 3–4 days, it recognizes specific pathogens, and it consists of two main branches: (1) T cell-mediated immunity (a.k.a. cell-mediated immunity) and (2) B cell-mediated immunity (a.k.a. humoral or antibody-mediated immunity). The innate and adaptive responses also differ in that the latter has memory, whereas the former does not. As a consequence of adaptive immune memory, if an infectious agent makes a second attempt to infect a host, pathogen-specific memory T cells, memory B cells, and antibodies will mount a secondary immune response that is much more rapid and intense than the initial, primary response and, thus, better able to inhibit infection and disease. Immune memory is the basis for the use of vaccines that are given in an attempt to stimulate an individual's adaptive immune system to generate pathogen-specific immune memory. Of note, in some cases the response of the immune system to an infectious agent can contribute to disease progress. For example, immunopathology is thought to be responsible for the severe acute disease that can occur following infection with a dengue virus that is serotypically distinct from that causing initial dengue infection (Screaton et al., 2015). Table 1 Comparison of innate and adaptive immunity Innate Immune Response Adaptive Immune Response Immediate response; initiated within seconds Gradual response; initially generated over 3–4 days (primary response) Targets groups of pathogens Targets-specific pathogens No memory Memory Open in a separate window An immune host is someone protected against a specific pathogen (because of previous infection or vaccination) such that subsequent infection will not take place or, if infection does occur, the severity of disease is diminished. The duration and efficacy of immunity following immunization by natural infection or vaccination varies depending upon the infecting agent, quality of the vaccine, type of vaccine (i.e., live or inactivated virus, subunit, etc.), and ability of the host to generate an immune response. For example, a single yellow fever vaccination appears to confer lifelong immunity, whereas immune protection against tetanus requires repeat vaccination every 10 years (Staples et al., 2015; Broder et al., 2006). In malaria-endemic areas, natural immunity to malaria usually develops by 5 years of age and, while protective from severe disease and death, it is incomplete and short-lived (Langhorne et al., 2008). Functionally, there are two basic types of immunization, active and passive. Active immunization refers to the generation of immune protection by a host's own immune response. In contrast, passive immunization is conferred by transfer of immune effectors, most commonly antibody (a.k.a. immunoglobulin, antisera), from a donor animal or human. For example, after exposure to a dog bite, an individual who seeks medical care will receive both active and passive postexposure immune prophylaxis consisting of rabies vaccine (to induce the host immune response) and rabies immune globulin (to provide immediate passive protection against rabies). An example of natural passive immunization is the transfer of immunity from mother to infant during breastfeeding. Vaccination does not always result in active immunization; failure of vaccination can be due to either host or vaccine issues. Individuals who are immunosuppressed as, for example, a result of HIV infection, malnutrition, immunosuppressive therapy, or immune senescence might not mount a sufficient response after vaccination so as to be adequately immunized (protected). Similarly, vaccination with an inadequate amount of vaccine or a vaccine of poor quality (e.g., due to break in cold chain delivery) might prevent even a healthy individual from becoming immunized. Environmental Factors Environmental determinants of vulnerability to infectious diseases include physical, social, behavioral, cultural, political, and economic factors. In some cases, environmental influences increase risk of exposure to an infectious agent. For example, following an earthquake, environmental disruption can increase the risk of exposure to Clostridium tetani and result in host traumatic injuries that provide portals of entry for the bacterium. Environmental factors promoting vulnerability can also lead to an increase in susceptibility to infection by inducing physiological changes in an individual. For example, a child living in a resource-poor setting and vulnerable to malnutrition may be at increased risk of infection due to malnutrition-induced immunosuppression. Table 2 provides examples of some of the many environmental factors that can facilitate the emergence and/or spread of specific infectious diseases. Table 2 Environmental factors facilitating emergence and/or spread of specific infectious diseases Environmental factor facilitating transmission Mechanism Disease References Climate/weather EI Niño- persistent, above-normal rainfall EI Niño-persistent, above-normal rainfall Flooding Increased vegetation promoting increase in rodent reservoir Expansion of vertically infected mosquitoes and secondary vectors Promotes exposure to contaminated rat urine and water Hantavirus pulmonary syndrome Rift Valley fever Leptospirosis, cholera Engelthaler et al. (1999) Anyamba et al. (2010) Cann et al. (2013) Natural disaster Tsunami, earthquake Tornado Environmental disruption promoting exposure Environmental disruption promoting exposure Tetanus Cutaneous mucormycosis Afshar et al. (2011) Neblett Fanfair et al. (2012) Infrastructure Engineering infrastructure Water treatment plant Engineered water systems Defective plumbing promoting viral dispersal Inadequate microbial barriers Reservoir and distribution SARS Cryptosporidiosis Legionellosis Yu et el. (2004) Widerstrom et al. (2014) Ashbolt (2015) Development/change in land use Water resource development and management Water resource development and management Water resource development and management Forest fragmentation Deforestation Deforestation Dams, irrigation schemes, mining expanding intermediate host habitat Dams, irrigation schemes expanding vector habitat Expansion of irrigated rice farming creating vector breeding sites Loss of biodiversity expanding natural reservoir Creation of vector breeding sites Driving contact with reservoir host Schistosomiasis Malaria Japanese encephalitis Lyme Malaria Hendra Steinmann et al. (2006) Keiser et al. (2005) Erlanger et al. (2009) Granter et al. (2014) Yasuoka and Levins (2007) Plowright et al. (2011) Technology and industry Medical technology Medical technology Food processing Globilization of food industry Food storage Crop introduction Animal husbandry Inappropriate use of antibiotics driving genetic change Transfusion of contaminated blood Undercooked hamburger Transport contaminated seed from Egypt to Germany and France Improper storage of maize Maize cultivation promoting vector abundance Small-scale poultry farming facilitating animal-to-human virus transfer Antibiotic-resistant infections Chagas E. coli O157:H7 outbreak E. coli O104:H4 outbreak Acute aflatoxicosis Malaria H5N1 avian influenza Goossens et al. (2005) Angheben et al. (2015) Bell et al. (1994) EFSA (2011) Azziz-Baumgartner et al. (2005) Kebede et al. (2005) Halpin (2005) Travel and commerce Visiting friends and family Recreational Commercial Commercial Import of virus Exposure while rafting, kayaking Import of infected animals Contamination ice cream premix during tanker trailer transport Chikungunya Schistosomiasis Monkeypox Salmonellosis Rezza et al. (2007) Morgan et al. (2010) CDC (2003a) Hennessyet al. (1996) Politics Government response Denial of viral etiology epidemic HIV/AIDS Simelela et al. (2015) Economics Low income Resource-poor environment Poor urban environment Lack of protection against vector Inadequate WASH promoting transmission Poor WASH promoting vector expansion Dengue Trachoma Lymphatic filariasis Brunkard et al. (2007) Taylor et al. (2014) Simonsen and Mwakitalu (2013) War and conflict Displaced persons camps Displaced persons camps Inadequate WASH Inadequate WASH Cholera Cutaneous leishmaniasis CDC (1996) Alawieh et al. (2014) Social/behavioral Injection drug use Sexual practices Cultural practices Consumptive behaviors Forest encroachment, bushmeat hunting Live-animal markets Sharing contaminated injection equipment High-risk sexual behavior among truckers Unsafe burial practices Consumption of raw or undercooked marine fish or squid Exposure to infected bush animals Close contact facilitating animal virus jumping species to humans Hepatitis C HIV-1 infection Ebola Anisakidosis Ebola SARS Nelson et al. (2011) Rakwar et al. (1999) Hewlett and Amola (2003) Hochberg and Hamer (2010) Pourrut et al. (2005) Peiris et al. (2004) Open in a separate window WASH, water, sanitation, and hygiene; E. coli, Escherichia coli; SARS, severe acute respiratory syndrome. Go to: Transmission Basics A unique characteristic of many infectious diseases is that exposure to certain infectious agents can have consequences for other individuals, because an infected person can act as a source of exposure. Some pathogens (e.g., STI agents) are directly transmitted to other people, while others (e.g., vectorborne disease (VBD) agents) are transmitted indirectly. From a public health standpoint, it is useful to define stages of an infectious disease with respect to both clinical disease and potential for transmission (Figure 3 ). With respect to disease, the incubation period is defined as the time from exposure to an infectious agent until the time of first signs or symptoms of disease. The incubation period is followed by the period of clinical illness which is the duration between first and last disease signs or symptoms. With respect to transmission of an infectious agent, the latent (preinfectious) period is the duration of time between exposure to an agent and the onset of infectiousness. It is followed by the infectious period (a.k.a. period of communicability) which is the time period when an infected person can transmit an infectious agent to other individuals. In parasitic infections, the latent and infectious periods are commonly referred to as the prepatent period and patent period, respectively. An external file that holds a picture, illustration, etc. Object name is f00516-03-9780128036785.jpg Figure 3 Stages of infectious disease. The stages of an infectious disease can be identified with relation to signs and symptoms of illness in the host (incubating and clinically ill), and the host's ability to transmit the infectious agent (latent and infectious). The red bar indicates when an individual is infectious but asymptomatic. The relationship between stages is an important determinant of carrier states and, thus, the ease of spread of an infectious disease through a population. (a) Patients infected with Ebola virus do not become infectious until they show signs of disease. (b) In some cases, varicella (chicken pox)-infected individuals can act as incubatory carriers and become infectious before the onset of symptoms (e.g., rash). (c) Some patients with Vibrio cholerae infection remain infectious as convalescent carriers after recovery. (d) Salmonella Typhi infection can result in an apparently healthy carrier that never shows signs or symptoms of disease. The duration of disease stages is unique for each type of infection and it can vary widely for a given type of infection depending upon agent, host, and environmental factors that affect, for example, dose of the inoculated agent, route of exposure, host susceptibility, and agent infectivity and virulence. Knowledge of the timing of disease stages is of key importance in the design of appropriate control and prevention strategies to prevent the spread of an infectious disease. For example, efforts to control the recent Ebola West Africa outbreak through contact tracing and quarantine were based on knowledge that the infectious period for Ebola does not begin until the start of the period of clinical illness, which occurs up to 21 days following exposure (Figure 3(a); Pandey et al., 2014). A carrier is, by definition, an infectious individual who is not showing clinical evidence of disease and, thus, might unknowingly facilitate the spread of an infectious agent through a population. Incubatory carriers exist when the incubation period overlaps with the infectious period, as can occur in some cases of chicken pox (Figure 3(b)). Convalescent carriers occur when the period of infectiousness extends beyond the period of clinical illness (Figure 3(c)). Carriers of this type can be a significant issue in promoting the spread of certain enteric infections, such as those caused by the bacterium, V. cholerae. Healthy carriers, infected individuals that remain asymptomatic but are capable of transmitting an infectious agent, occur commonly with many infectious diseases (e.g., meningococcal meningitis and typhoid fever) and are also significant challenges to disease control (Figure 3(d)). Go to: Dynamics of Infectious Diseases within Populations A variety of terms are used to describe the occurrence of an infectious disease within a specific geographic area or population. Sporadic diseases occur occasionally and unpredictably, while endemic diseases occur with predictable regularity. Levels of endemicity can be classified as holoendemic, hyperendemic, mesoendemic, or hypoendemic depending upon whether a disease occurs with, respectively, extreme, high, moderate, or low frequency. For some infectious diseases, such as malaria, levels of endemicity are well defined and used as parameters for identifying disease risk and implementing control activities. Malaria endemicity is quantified based upon rates of palpable enlarged spleens in a defined (usually pediatric) age group: holoendemic >75%, hyperendemic 51–75%, mesoendemic 11–50%, and hypoendemic <10% (Hay et al., 2008). An epidemic refers to an, often acute, increase in disease cases above the baseline level. An epidemic may reflect an escalation in the occurrence of an endemic disease or the appearance of a disease that did not previously exist in a population. The term outbreak is often used synonymously with epidemic but can occasionally refer to an epidemic occurring in a more limited geographical area; for example, a foodborne illness associated with a group gathering. By contrast, a pandemic is an epidemic that has spread over a large geographic region, encompassing multiple countries or continents, or extending worldwide. Influenza commonly occurs as a seasonal epidemic, but periodically it gives rise to a global pandemic, as was the case with 2009 H1N1 influenza. Two fundamental measures of disease frequency are prevalence and incidence. Prevalence is an indicator of the number of existing cases in a population as it describes the proportion of individuals who have a particular disease, measured either at a given point in time (point prevalence) or during a specified time period (period prevalence). In contrast, incidence (a.k.a. incidence rate) is a measurement of the rate at which new cases of a disease occur (or are detected) in a population over a given time period. Usually measured as a proportion (number infected/number exposed), attack rates are often calculated during an outbreak. In some circumstances, a secondary attack rate is calculated to quantify the spread of disease to susceptible exposed persons from an index case (the case first introducing an agent into a setting) in a circumscribed population, such as in a household or hospital. During the 2003 SARS epidemic, secondary attack rates in Toronto hospitals were high but varied from 25% to 40% depending upon the hospital ward (CDC, 2003b). The basic reproductive number (basic reproductive ratio; R 0) is a measure of the potential for an infectious disease to spread through an immunologically naïve population. It is defined as the average number of secondary cases generated by a single, infectious case in a completely susceptible population. In reality, for most infectious diseases entering into a community, some proportion of the population is usually immune (and nonsusceptible) due to previous infection and/or immunization. Thus, a more accurate reflection of the potential for community disease spread is the effective reproductive number (R) which measures the average number of new infections due to a single infection. In general, for an epidemic to occur in a population, R must be >1 so that the number of cases continues to increase. Herd immunity (a.k.a. community immunity) refers to population-level resistance to an infectious disease that occurs when there are enough immune individuals to block the chain of infection/transmission. As a result of herd immunity, susceptible individuals who are not immune themselves are indirectly protected from infection (Figure 4 ). Vaccine hesitancy, the choice of individuals or their caregivers to delay or decline vaccination, can lead to overall lower levels of herd immunity. Outbreaks of measles in the United States, including a large 2014 measles outbreak at an amusement park in California, highlight the phenomena of vaccine refusal and associated increased risk for vaccine-preventable diseases among both nonvaccinated and fully vaccinated (but not fully protected) individuals (Phadke et al., 2016). An external file that holds a picture, illustration, etc. Object name is f00516-04-9780128036785.jpg Figure 4 Herd immunity occurs when one is protected from infection by immunization occurring in the community. Using influenza as an example, the top box shows a population with a few infected individuals (shown in red) and the rest healthy but unimmunized (shown in blue); influenza spreads easily through the population. The middle box depicts the same population but with a small number who are immunized (shown in yellow); those who are immunized do not become infected, but a large proportion of the population becomes infected. In the bottom box, a large proportion of the population is immunized; this prevents significant transmission, including to those who are unimmunized. Source: National Institute of Allergy and Infectious Diseases (NIAID). An important public health consequence of herd immunity is that immunization coverage does not need to be 100% for immunization programs to be successful. The equation R = R0(1 − x) (where x equals the immune portion of the population) indicates the level of immunization required to prevent the spread of an infectious disease through a population. The proportion that needs to be immunized depends on the pathogen (Table 3 ). When the proportion immunized (x) reaches a level such that R < 1, a chain of infection cannot be sustained. Thus, Ro and R can be used to calculate the target immunization coverage needed for the success of vaccination programs. Table 3 Herd immunity thresholds for selected infectious diseases Disease Ro Herd immunity threshold (%) Diphtheria 6–7 83–86 Ebola (West Africa) 1.5–2.5a 33–60 Measles 12–18 92–94 Mumps 4–7 75–86 Polio 5–7 80–86 Rubella 6–7 83–85 Smallpox 5–7 80–85 Open in a separate window aAlthaus (2014). Source: Modification of table from CDC, WHO, 2001. Course: “Smallpox: Disease, Prevention, and Intervention” [Online]. The Centers for Disease Control and Prevention and the World Health Organization. Available: http://www.emergency.cdc.gov/agent/smallpox/training/overview/ (accessed and retrieved 28.04.16.) unless otherwise indicated. Go to: Infectious Disease Diagnosis Proper diagnosis of infectious illnesses is essential for both appropriate treatment of patients and carrying out prevention and control surveillance activities. Two important properties that should be considered for any diagnostic test utilized are sensitivity and specificity. Sensitivity refers to the ability of the test to correctly identify individuals infected with an agent (‘positive in disease’). A test that is very sensitive is more likely to pick up individuals with the disease (and possibly some without the disease); a very sensitive test will have few false negatives. Specificity is the ability of the test to correctly identify individuals not infected by a particular agent (‘negative in health’); high specificity implies few false positives. Often, screening tests are highly sensitive (to capture any possible cases), and confirmatory tests are more specific (to rule out false-positive screening tests). Broadly, laboratory diagnosis of infectious diseases is based on tests that either directly identify an infectious agent or provide evidence that infection has occurred by documenting agent-specific immunity in the host (Figure 5 ). Identification of an infecting agent involves either direct examination of host specimens (e.g., blood, tissue, urine) or environmental specimens, or examination following agent culture and isolation from such specimens. The main categories of analyses used in pathogen identification can be classified as phenotypic, revealing properties of the intact agent, nucleic acid-based, determining agent nucleic acid (DNA or RNA) characteristics and composition, and immunologic, detecting microbial antigen or evidence of immune response to an agent (Figure 5). Direct phenotypic analyses include both macroscopic and/or microscopic examination of specimens to determine agent morphology and staining properties. Cultured material containing large quantities of agent can undergo analyses to determine characteristics, such as biochemical enzymatic activity (enzymatic profile) and antimicrobial sensitivity, and to perform phage typing, a technique which differentiates bacterial strains according to the infectivity of strain-specific bacterial viruses (a.k.a. bacteriophages). Nucleic acid–based tests often make use of the polymerase chain reaction (PCR) to amplify agent DNA or complementary DNA (cDNA) synthesized from messenger RNA (mRNA). The ability of pathogen-specific PCR primers to generate an amplification product can confirm or rule out involvement of a specific pathogen. Sequencing of amplified DNA fragments can also assist with pathogen identification. Restriction fragment analysis, as by pulse-field gel electrophoresis of restriction enzyme-digested genomic DNA isolated from cultured material, can yield distinct ‘DNA fingerprints’ that can be used for comparing the identities of bacteria. The CDC PulseNet surveillance program uses DNA fingerprinting as the basis for detecting and defining foodborne disease outbreaks that can sometimes be quite widely dispersed (CDC, 2013). Most recently, next-generation sequencing technologies have made whole-genome sequencing a realistic subtyping method for use in foodborne outbreak investigation and surveillance (Deng et al., 2016). The objective of immunologic analysis of specimens is to reveal evidence of an agent through detection of its antigenic components with agent-specific antibodies. Serotyping refers to the grouping of variants of species of bacteria or viruses based on shared surface antigens that are identified using immunologic methodologies such as enzyme-linked immunosorbent assay (ELISA) and Western blotting. An external file that holds a picture, illustration, etc. Object name is f00516-05-9780128036785.jpg Figure 5 Methods of infectious disease diagnosis. Laboratory methods for infectious disease diagnosis focus on either analyzing host specimens or environmental samples for an agent (upper section), or analyzing the host for evidence of immunity to an agent (lower section). Closed solid bullets, category of test; open bullets, examples of tests. PCR, polymerase chain reaction; ELISA, enzyme-linked immunosorbent assay; PFGE, pulsed-field gel electrophoresis. Immunologic assays are also used to look for evidence that an agent-specific immune response has occurred in an exposed or potentially exposed individual. Serologic tests detect pathogen-specific B cell–secreted antibodies in serum or other body fluids. Some serologic assays simply detect the ability of host antibodies to bind to killed pathogen or components of pathogen (e.g., ELISA). Others rely on the ability of antibodies to actually neutralize the activity of live microbes; as, for example, the plaque reduction neutralization test which determines the ability of serum antibodies to neutralize virus. Antibody titer measures the amount of a specific antibody present in serum or other fluid, expressed as the greatest dilution of serum that still gives a positive test in whatever assay is being employed. Intradermal tests for identification of T cell–mediated immediate type (Type I) hypersensitivity or delayed type (Type IV) hypersensitivity responses to microbial antigen can be used to diagnose or support the diagnosis of some bacterial, fungal, and parasitic infections, such as, the Mantoux (tuberculin) test for TB. Go to: Infectious Disease Control and Prevention Based on the classic model of Leavell and Clark (1965), infectious disease prevention activities can be categorized as primary, secondary, or tertiary. Primary prevention occurs at the predisease phase and aims to protect populations, so that infection and disease never occur. For example, measles immunization campaigns aim to decrease susceptibility following exposure. The goal of secondary prevention is to halt the progress of an infection during its early, often asymptomatic stages so as to prevent disease development or limit its severity; steps important for not only improving the prognosis of individual cases but also preventing infectious agent transmission. For example, interventions for secondary prevention of hepatitis C in injection drug user populations include early diagnosis and treatment by active surveillance and screening (Miller and Dillon, 2015). Tertiary prevention focuses on diseased individuals with the objective of limiting impact through, for example, interventions that decrease disease progression, increase functionality, and maximize quality of life. Broadly, public health efforts to control infectious diseases focus on primary and secondary prevention activities that reduce the potential for exposure to an infectious agent and increase host resistance to infection. The objective of these activities can extend beyond disease control, as defined by the 1997 Dahlem Workshop on the Eradication of Infectious Diseases, to reach objectives of elimination and eradication (Dowdle, 1998; Box 1 ). Box 1 Hierarchy of public health efforts targeting infectious diseases The 1997 Dahlem Workshop on the Eradication of Infectious Diseases defined a continuum of outcomes due to public health interventions targeting infectious diseases: “1) control, the reduction of disease incidence, prevalence, morbidity or mortality to a locally acceptable level as a result of deliberate efforts; continued intervention measures are required to maintain the reduction (e.g. diarrheal diseases), 2) elimination of disease, reduction to zero of the incidence of a specified disease in a defined geographical area as a result of deliberate efforts; continued intervention measures are required (e.g. neonatal tetanus), 3) elimination of infections, reduction to zero of the incidence of infection caused by a specific agent in a defined geographical area as a result of deliberate efforts; continued measures to prevent re-establishment of transmission are required (e.g. measles, poliomyelitis),4) eradication, permanent reduction to zero of the worldwide incidence of infection caused by a specific agent as a result of deliberate efforts; intervention measures are no longer needed (e.g. smallpox), and 5) extinction, the specific infectious agent no longer exists in nature or in the laboratory (e.g. none)” (Dowdle, 1998). As noted earlier, the causation and spread of an infectious disease is determined by the interplay between agent, host, and environmental factors. For any infectious disease, this interplay requires a specific linked sequence of events termed the chain of infection or chain of transmission (Figure 6 ). The chain starts with the infectious agent residing and multiplying in some natural reservoir; a human, animal, or part of the environment such as soil or water that supports the existence of the infectious agent in nature. The infectious agent leaves the reservoir via a portal of exit and, using some mode of transmission, moves to reach a portal of entry into a susceptible host. A thorough understanding of the chain of infection is crucial for the prevention and control of any infectious disease, as breaking a link anywhere along the chain will stop transmission of the infectious agent. Often more than one intervention can be effective in controlling a disease, and the approach selected will depend on multiple factors such as economics and ease with which an intervention can be executed in a given setting. It is important to realize that the potential for rapid and far-reaching movement of infectious agents that has accompanied globalization means that coordination of intervention activities within and between nations is required for optimal prevention and control of certain diseases. An external file that holds a picture, illustration, etc. Object name is f00516-06-9780128036785.jpg Figure 6 The chain of infection (a.k.a. chain of transmission). One way to visualize the transmission of an infectious agent though a population is through the interconnectedness of six elements linked in a chain. Public health control and prevention efforts focus on breaking one or more links of the chain in order to stop disease spread. The Infectious Agent and Its Reservoir The cause of any infectious disease is the infectious agent. As discussed earlier, many types of agents exist, and each can be characterized by its traits of infectivity, pathogenicity, and virulence. A reservoir is often, but not always, the source from which the agent is transferred to a susceptible host. For example, bats are both the reservoir for Marburg virus and a source of infection for humans and bush animals including African gorillas. However, because morbidity and mortality due to Marburg infection is significant among these bush animals, they cannot act as a reservoir to sustain the virus in nature (they die too quickly), although they can act as a source to transmit Marburg to humans. Infectious agents can exist in more than one type of reservoir. The number and types of reservoirs are important determinants of how easily an infectious disease can be prevented, controlled, and, in some cases, eliminated or eradicated. Animal, particularly wild animal, reservoirs, and environmental reservoirs in nature can be difficult to manage and, thus, can pose significant challenges to public health control efforts. In contrast, infectious agents that only occur in human reservoirs are among those most easily targeted, as illustrated by the success of smallpox eradication. Humans are the reservoir for many common infectious diseases including STIs (e.g., HIV, syphilis) and respiratory diseases (e.g., influenza). Humans also serve as a reservoir, although not always a primary reservoir, for many neglected tropical diseases (NTDs) as, for example, dracunculiasis (a.k.a. Guinea worm). From a public health standpoint, an important feature of human reservoirs is that they might not show signs of illness and, thus, can potentially act as unrecognized carriers of disease within communities. The classic example of a human reservoir is the cook Mary Mallon (Typhoid Mary); an asymptomatic chronic carrier of Salmonella enterica serovar Typhi who was linked to at least 53 cases of typhoid fever (Soper, 1939). Animals are a reservoir for many human infectious diseases. Zoonosis is the term used to describe any infectious disease that is naturally transmissible from animals to humans. These diseases make up approximately 60% of all infectious diseases, and an estimated 75% of recently emerging infectious diseases (Burke et al., 2012). Zoonotic reservoirs and sources of human disease agents include both domestic (companion and production) animals (e.g., dogs and cows) and wildlife. Control and prevention of zoonotic diseases requires the concerted efforts of professionals of multiple disciplines and is the basis for what has become known as the One Health approach (Gibbs, 2014). This approach emphasizes the interconnectedness of human health, animal health, and the environment and recognizes the necessity of multidisciplinary collaboration in order to prevent and respond to public health threats. Inanimate matter in the environment, such as soil and water, can also act as a reservoir of human infectious disease agents. The causative agents of tetanus and botulism (Clostridium tetani and C. botulinum) are examples of environmental pathogens that can survive for years within soil and still remain infectious to humans. Legionella pneumophila, the etiologic agent of Legionnaires' disease, is part of the natural flora of freshwater rivers, streams, and other bodies. However, the pathogen particularly thrives in engineered aquatic reservoirs such as cooling towers, fountains, and central air conditioning systems, which provide conditions that promote bacterial multiplication and are frequently linked to outbreaks. Soil and water are also sources of infection for several protozoa and helminth species which, when excreted by a human reservoir host, can often survive for weeks to months. Outbreaks of both cryptosporidiosis and giardiasis commonly occur during summer months as a result of contact with contaminated recreational water. Soil containing roundworm (Ascaris lumbricoides) eggs is an important source of soil-transmitted helminth infections in children. Targeting the Agent and Reservoir Early steps in preventing exposure to an infectious agent include interventions to control or eliminate the agent within its reservoir, to neutralize or destroy the reservoir, and/or to stop the agent from exiting its reservoir. Central to these interventions are surveillance activities that routinely identify disease agents within reservoirs. When humans are the reservoir, or source, of an infectious agent, early and rapid diagnosis and treatment are key to decreasing the duration of infection and risk of transmission. Both active surveillance and passive surveillance are used to detect infected cases and carriers. Some readily communicable diseases, such as Ebola, can require isolation of infected individuals to minimize the risk of transmission. As part of the global effort to eradicate dracunculiasis, several endemic countries have established case containment centers to provide treatment and support to patients with emerging Guinea worms to keep them from contaminating water sources and, thereby, exposing others (Hochberg et al., 2008). Contact tracing and quarantine are other activities employed in the control of infections originating from a human reservoir or source. During the West Africa Ebola outbreak, key control efforts focused on the tracing and daily follow-up of healthy individuals who had come in contact with Ebola patients and were potentially infected with the virus (Pandey et al., 2014). One Health emphasizes the importance of surveillance and monitoring for zoonotic pathogens in animal populations. For some diseases (e.g., Rift Valley fever) epizootics (analogous to epidemics, but in animal populations) can actually serve as sentinel events for forecasting impending human epidemics. Once animal reservoirs (and sources) of infection are identified, approaches to prevention and control include reservoir elimination and prevention of reservoir infection. Zoonotic diseases exist in nature in predictably regular, enzootic cycles and/or epizootic cycles and are transmitted to humans via distinct pathways. The focus of prevention and control activities for these diseases reflects the extent to which a zoonotic pathogen has evolved to become established in human populations (Wolfe et al., 2007). For some zoonotic diseases (e.g. anthrax, Nipah, rabies), primary transmission always occurs from animals, with humans acting as incidental (dead end) hosts; control of these diseases thus concentrates on preventing animal-to-animal and, ultimately, animal-to-human transmission. Currently, most human cases of avian influenza are the result of human infection from birds; human-to-human transmission is extremely rare. Thus, reservoir elimination by culling infected poultry flocks is a recommended measure for controlling avian influenza in birds and preventing sporadic infection of humans (CDC, 2015). Other zoonotic diseases demonstrate varying degrees of secondary human-to-human transmission following primary transmission (a.k.a. spillover) from animals. Both rates of spillover and the ability to sustain human-to-human transmission can vary widely between zoonoses and, in consequence, control strategies can also be quite different. For example, outbreaks of Ebola arise following an initial bush animal-to-human transmission event, and subsequent human-to-human transmission is often limited (Feldmann and Geisbert, 2011). In contrast, the four dengue viruses originally emerged from a sylvatic cycle between non-human primates and mosquitoes, and are now sustained by a continuous human-mosquito-human cycle of transmission with outbreaks occurring as a result of infected individuals entering into naïve populations (Vasilakis et al., 2011). Thus, while Ebola outbreak prevention efforts would include limiting contact with bush animals, such efforts would not be useful for prevention of dengue outbreaks. HIV is an example of a virus that emerged from an ancestral animal virus, simian immunodeficiency virus, but has evolved so that it is now HIV is an example of a virus that emerged from an ancestral animal virus, simian immunodeficiency virus, but has evolved so that it is now only transmitted human to human (Faria et al., 2014). Portal of Exit Infectious agents exit human and animal reservoirs and sources via one of several routes which often reflect the primary location of disease; respiratory disease agents (e.g., influenza virus) usually exit within respiratory secretions, whereas gastrointestinal disease agents (e.g., rotavirus, Cryptosporidium spp.) commonly exit in feces. Other portals of exits include sites from which urine, blood, breast milk, and semen leave the host. For some infectious diseases, infection can naturally occur as a result of contact with more than one type of bodily fluid, each of which uses a different portal of exit. While infection with the SARS virus most frequently occurred via contact with respiratory secretions, a large community outbreak was caused by the spread of virus in a plume of diarrhea (Yu et al., 2004). Control interventions targeting portals of exit and entry are discussed below. Modes of Transmission There are a variety of ways in which infectious agents move from a natural reservoir to a susceptible host, and several different classification schemes are used. The scheme below categorizes transmission as direct transmission, if the infective form of the agent is transferred directly from a reservoir to an infected host, and indirect transmission, if transfer takes place via a live or inanimate intermediary (Box 2 ). Box 2 Modes of transmission of infectious agents Modes of Direct Transmission (infective form of agent transferred directly from reservoir or host): 1. Direct contact 2. Direct spread of droplets 3. Direct exposure to an infectious agent in the environment 4. Bite 5. Transplacental/perinatal Modes of Indirect Transmission (infective form of agent transferred indirectly from reservoir or infected host): 1. Biological • Biological vector • Intermediate host 2. Mechanical • Mechanical vector • Vehicle 3. Airborne Modes of Direct Transmission Direct physical contact between the skin or mucosa of an infected person and that of a susceptible individual allows direct transfer of infectious agents. This is a mode of transmission for most STIs and many other infectious agents, such as bacterial and viral conjunctivitis (a.k.a. pink eye) and Ebola virus disease. Direct droplet transmission occurs after sneezing, coughing, or talking projects a spray of agent-containing droplets that are too large to remain airborne over large distances or for prolonged periods of time. The infectious droplets traverse a space of generally less than 1 m to come in contact with the skin or mucosa of a susceptible host. Many febrile childhood diseases, including the common cold, are transferred this way. Diseases spread by direct contact and droplet transmission require close proximity of infected and susceptible individuals and, thus, commonly occur in settings such as households, schools, institutions of incarceration, and refugee/displaced person camps. Infectious agents spread exclusively in this manner are often unable to survive for long periods outside of a host; direct transmission helps to ensure transfer of a large infective dose. Direct contact to an agent in the environment is a means of exposure to infectious agents maintained in environmental reservoirs. Diseases commonly transmitted in this manner include those in which the infectious agent enters a susceptible host via inhalation (e.g., histoplasmosis) or through breaks in the skin following a traumatic event (e.g., tetanus). Animal bites are another way in which some infectious agents are directly transferred, through broken skin. This is the most common means of infection with rabies virus. Transplacental (a.k.a. congenital, vertical) and perinatal transmissions occur during pregnancy and delivery or breastfeeding, respectively. Classic examples include mother-to-child transmission of the protozoa Toxoplasma gondii during pregnancy, HIV during pregnancy, delivery, or breastfeeding, and Zika virus during pregnancy (Rasmussen et al., 2016). Targeting Directly Transmitted Infectious Diseases Case finding and contact tracing are public health prevention and control activities aimed at stopping the spread of infectious diseases transmitted by either direct contact or direct spread of droplets. Once identified, further activities to limit transmission to susceptible individuals can involve definitive diagnosis, treatment, and, possibly, isolation of active cases and carriers, and observation, possible quarantine, or prophylactic vaccination or treatment of contacts. Patient education is an important feature of any communicable infectious disease control effort. Environmental changes, such as decreasing overcrowded areas and increasing ventilation, can also contribute to limiting the spread of some infectious diseases, particularly respiratory diseases. Central to prevention of transplacental and perinatal infectious disease transmission is avoidance of maternal infection and provision of early diagnosis and treatment of infected women prior to or during pregnancy. For example, public health efforts targeting congenital toxoplasmosis focus on preventing pregnant women from consuming undercooked meat or contacting cat feces that may be contaminated. Current WHO guidelines for prevention of mother-to-child HIV transmission recommend that HIV-infected pregnant and breastfeeding women should be maintained on antiretrovirals (WHO, 2013). Modes of Indirect Transmission There are three main categories of indirect transmission: biological, mechanical, and airborne. Box 3 provides definitions of the different types of hosts, vectors, and vehicles involved in the life cycle of agents that are transmitted indirectly. Box 3 Hosts, vectors, and vehicles involved in the life cycle of infectious agents transmitted indirectly Definitive host: A host in which a parasite reproduces sexually. Humans are definitive hosts for roundworms. By strict definition, mosquitoes are the definitive host of malaria as they are the organism in which sexual reproduction of the agent protozoa, Plasmodium spp., occurs. Reservoir host: A host that serves to sustain an infectious pathogen as a potential source of infection for transmission to humans. Note that a reservoir host will not succumb to infection. Lowland gorillas and chimpanzees can be infected by Ebola virus, but they are not a reservoir host as they suffer devastating losses from infection. Bats are a suspected reservoir for Ebola virus. Intermediate host: A host in which larval or intermediate stages of an infectious agent develop but sexual reproduction does not take place. An intermediate host does not directly transfer an agent to the definitive host. Snails are an intermediate host in the lifecycle of Schistosoma spp. Dead-end host: A host from which infectious agents cannot be transmitted to other susceptible hosts. Humans are a dead-end host for West Nile virus which normally circulates between mosquitoes and certain avian species. Vector: A generic term for a living organism (e.g., biological vector or intermediate host) involved in the indirect transmission of an infectious agent from a reservoir or infected host to a susceptible host. Biological vector: A vector (often arthropod) in which an infectious organism must develop or multiply before the vector can transmit the organism to a susceptible host. Aedes spp. mosquitoes are a biological vector for dengue, chikungunya, and Zika. Mechanical vector: A vector (often arthropod) that transmits an infectious organism from one host to another but is not essential to the life cycle of the organism. The house fly is a mechanical vector in the diarrheal disease shigellosis as it carries feces contaminated with the Shigella spp. bacterium to a susceptible person. Vehicles: Inanimate objects that serve as an intermediate in the indirect transmission of a pathogen from a reservoir or infected host to a susceptible host. These include food, water, and fomites such as doorknobs, surgical instruments, and used needles. Biological transmission occurs when multiplication and/or development of a pathogenic agent within a vector (e.g., biological vector or intermediate host) is required for the agent to become infectious to humans. The time that is necessary for these events to occur is known as the extrinsic incubation period; in contrast to the intrinsic incubation period which is the time required for an exposed human host to become infectious. Indirect transmission by mosquito vectors is the primary mode of transmission of a large number of viruses (arthropod-borne viruses or arboviruses) of public health concern (e.g., West Nile, Zika). A number of NTDs are also transmitted by biological vectors including lymphatic filariasis (a.k.a. elephantiasis) by mosquitoes. Ticks are biological vectors for many bacterial etiological agents (e.g., Lyme disease and ehrlichiosis), and the parasitic agent causing babesiosis. The infectious agent of the helminthic NTDs, schistosomiasis, and dracunculiasis are transmitted indirectly via intermediate freshwater snail and copepod hosts, respectively. Mechanical transmission does not require pathogen multiplication or development within a living organism. It occurs when an infectious agent is physically transferred by a live entity (mechanical vector) or inanimate object (vehicle) to a susceptible host. Classic examples of diseases spread by mechanical vector transmission are shigellosis (transmission of Shigella spp. on the appendages of flies) and plague (transmission of Yersinia pestis by fleas). Many diarrheal diseases are transmitted by the fecal-oral route with food and water often acting as vehicles (Figure 7 ). Other types of vehicles for infectious disease agents are biologic products (e.g., blood, organs for transplant) and fomites (inanimate objects such as needles, surgical instruments, door handles, and bedding). Transfusion-related protozoal infection resulting in Chagas disease has been of increasing concern to the US blood banks that have instituted screening measures (CDC, 2007). An external file that holds a picture, illustration, etc. Object name is f00516-07-9780128036785.jpg Figure 7 The ‘F-diagram’ illustrates major direct and indirect pathways of fecal–oral pathogen transmission and depicts the roles of water, sanitation, and hygiene interventions in providing barriers to transmission. Primary barriers prevent contact with feces, and secondary barriers prevent ingestion of feces. Source: Water, Engineering and Development Centre (WEDC), Loughborough University. Airborne transmission involves aerosolized suspensions of residue (less than five microns in size, from evaporated aerosol droplets) or particles containing agents that can be transported over time and long distance and still remain infective. TB is a classic example of an infectious disease often spread by airborne transmission. Targeting Indirectly Transmitted Infectious Diseases VBDs comprise approximately 17% of the global burden of infectious diseases (Townson et al., 2005). For some diseases (e.g., dengue, Zika, Chagas), chemoprophylaxis and immunoprophylaxis are not prevention and control options, leaving vector control as the primary means of preventing disease transmission. Integrated vector management is defined by the WHO as, “a rational decision-making process to optimize the use of resources for vector control” (WHO, 2012). There are four major categories of IVM vector control strategies: biological, chemical, environmental, and mechanical. IVM interventions are chosen from these categories based upon available resources, local patterns of disease transmission, and ecology of local disease vectors. Two key elements of IVM are collaboration within the health sector and with other sectors (e.g., agriculture, engineering) to plan and carry out vector control activities, and community engagement to promote program sustainability. Another core element is the integrated approach which often permits concurrent targeting of multiple VBDs, as some diseases are transmitted by a single, common vector, and some vector control interventions can target several different vectors. In addition, combining interventions serves not only to reduce reliance on any single intervention, but also to reduce the selection pressure for insecticide and drug resistance. Table 4 , adapted from the 2012 WHO Handbook for IVM, illustrates some of the many types of IVM activities and provides examples of VBDs that might be controlled by such interventions (WHO, 2012). Table 4 Methods used to control vectorborne diseases examples of various types of IVM activities and some of the VBDs they might control and prevent Category Method Chagas disease Dengue Trypanosomiasis Japanese encephalitis Leishmaniasis Lymphatic filariasis Malaria Onchocerciasis Schistosomiasis Trachoma Environmental Source reduction + + + + Habitat manipulation + + + Irrigation management and design + + + + Proximity of livestock + + + Waste management + + Mechanical House improvement + + + + Removal trapping + + + Polystyrene beads + Biological Natural enemy conservation + + + + Biological larvicides + + + + + Fungi Botanicals + + Chemical Insecticide-treated bednets + + + + + Indoor residual spraying + + + Insecticidal treatment of habitat + + + + + Insecticide-treated targets + Biorational methodsa + + Chemical repellants + + + Open in a separate window aFor example, pheromones to trap pests or disrupt mating. Source: Modification of table from WHO, 2012. Handbook for Integrated Vector Management. WHO Press, France. Diarrheal diseases primarily result from oral contact with water, food, or other vehicles contaminated with pathogenic agents originating from human or animal feces. Most (∼88%) of diarrhea-associated deaths are attributable to unsafe drinking water, inadequate sanitation, and insufficient hygiene (Black et al., 2003; Prüss-Üstün et al., 2008). Interruption of fecal–oral transmission through provision of safe water and adequate sanitation, and promotion of personal and domestic hygiene are fundamental to diarrhea prevention and control. Fecal–oral transmission of a diarrheal agent can occur via one of several routes. In 1958, Wagner and Lanoix developed a model of major transmission depicted in what has become known as the ‘F-diagram,’ based on steps within the fecal–oral flow of transmission starting with the letter ‘F’: fluids (drinking water), fingers, flies, fields (crops and soil), floods (representative of surface water in general), and food (Wagner and Lanoix, 1958; Figure 7). Other F's that can be considered include facilities (e.g., settings where transmission is likely to occur such as daycare centers) and fornication. The F-diagram is useful for depicting where water, sanitation, and hygiene (WASH) interventions act as barriers in the fecal–oral flow of diarrheal pathogens. Safe excreta disposal and handling act as primary barriers to transmission by preventing fecal pathogens from entering the environment. Once the environment has become contaminated with pathogen-containing feces, secondary and tertiary barriers to transmission include water treatment, safe transport and storage of water, provision of sewage systems to control flooding, fly control, and good personal and domestic hygiene (e.g., food hygiene) practices (requiring adequate water quantity) (Figure 7). As with IVM, the control of diarrheal diseases increases with integration of control measures to achieve multiple barriers to fecal–oral transmission. The basic approach to preventing transmission of an infectious agent from a contaminated vehicle is to prevent contamination of, decontaminate, or eliminate the vehicle. Food is a common vehicle for infectious agents, and it can potentially become contaminated at any step along the food production chain of production, processing, distribution, and preparation. Production refers to the growing of plants for harvest and raising animals for food. An example of contamination at this step includes the use of fecally contaminated water for crop irrigation. Processing refers to steps such as the chopping, grinding, or pasteurizing of food to convert it into a consumer product; if the external surface of a melon is contaminated, chopping it into pieces for sale can result in contamination of the fruit. Distribution, in which food is transferred from the place where it was produced and/or processed to the consumer, can result in contamination if, for example, the transportation vehicle is not clean. Finally, preparation is the step in which food is made ready to eat; not cleaning a cutting board after cutting raw chicken can result in microbial pathogen cross-contamination of other food items. Food hygiene is the term used to describe the conditions and activities employed to prevent or limit microbial contamination of food in order to ensure food safety. Decontamination includes sterilization, the destruction of all microbial agents, and disinfection, the destruction of specific agents. Control of airborne diseases focuses on regulating environmental airflow and air quality to minimize contact with infectious droplet nuclei. In health-care settings, negative pressure isolation rooms and exhaust vents can be used to manipulate airflow. Recirculating, potentially infectious air can undergo high-efficiency particulate air (HEPA) filtration and/or be mixed with ‘clean’ (noncontaminated) air to remove or dilute the concentration of infectious particle to below the infectious dose. Health-care workers should use N95 masks. On commercial aircraft, airborne pathogen transmission is minimized by methods including regulating airflow to prevent widespread dispersal of airborne microbes throughout the cabin, HEPA filtering recirculating air, and mixing recirculating air with fresh air (considered sterile) (Dowdall et al., 2010). Portal of Entry The portal of entry refers to the site at which the infectious agent enters a susceptible host and gains access to host tissues. Many portals of entry are the same as portals of exit and include the gastrointestinal, genitourinary, and respiratory tracts, as well as compromised skin and mucous membrane surfaces. Some infectious agents can naturally enter a susceptible host by more than one portal. For example, the three forms of human anthrax can be distinguished according to the route of agent entry: cutaneous anthrax due to entry through the skin, gastrointestinal anthrax resulting from ingestion of spores, and pulmonary anthrax following inhalation of spores. Targeting Portals of Exit and Entry Standard infection control practices target portals of exit (and entry) of infectious agents from human reservoirs and sources. CDC guidelines suggest two levels of precautions to stop transmission of infectious agents: Standard Precautions and transmission-based precautions (Siegel et al., 2007). Standard Precautions prevent transmission of infectious agents that can be acquired by contact with blood, body fluids, nonintact skin, and mucous membranes. They can be used to prevent transmission in both health-care and non-health-care settings, regardless of whether infection is suspected or confirmed. Hand hygiene is a major component of these precautions, along with use of personal protective equipment (PPE). Common PPE include gloves, gowns, face protection (e.g., eye-protecting face shields), and respiratory protection using N95 masks to prevent inhalation of airborne infectious particles (e.g., from Mycobacterium tuberculosis). Of note, depending on the circumstance, PPE can be used to prevent dispersal of infectious agents from their source by providing a barrier to the portal of exit, or to protect a susceptible individual by placing a barrier to a portal of entry. Respiratory hygiene/cough etiquette is used to prevent spread of infection by respiratory droplets. Main elements of respiratory hygiene/cough etiquette include covering the nose and mouth area with one's elbow during coughing or sneezing or using a surgical mask to limit dissemination of infectious respiratory secretions, and hand hygiene after contact with respiratory secretions. Other components of standard precautions include needle stick and sharp injury prevention, safe injection practices, cleaning and disinfection of potentially contaminated equipment and other objects, and safe waste management. The Susceptible Host A susceptible host is an individual who is at risk of infection and disease following exposure to an infectious agent. As discussed previously, there are many determinants of host susceptibility, including both innate factors determined by the genetic makeup of the host and, acquired factors such as agent-specific immunity and malnutrition. Targeting the Susceptible Host Important prevention and control interventions that target the susceptible host include both those that address determinants of susceptibility in the host (e.g., immunoprophylaxis, provision of adequate nutrition, treatment of underlying diseases) and those that target an infecting agent (e.g., chemoprophylaxis). Immunoprophylaxis encompasses both active immunization by vaccination and passive immunization through provision of pathogen-specific immunoglobulin. Malnutrition is a strong risk factor for morbidity and mortality due to diarrheal disease, and a vicious cycle exists between infectious diarrheal disease leading to malnutrition and impaired immune function which, in turn, promotes increased susceptibility to infection (Keusch et al., 2006). Consequently, breastfeeding and safe complementary feeding play crucial roles in protecting infants and young children from infectious diseases, particularly in resource-poor settings. Micronutrients are required for normal immune function, and vitamin A and zinc supplementations have been shown to decrease some types of infections in children deficient in these micronutrients (Mayo-Wilson et al., 2014; Imdad et al., 2010). In certain circumstances, chemoprophylaxis is employed to protect a susceptible host in anticipation of, or following exposure to an infectious agent. Antimalarial drugs are routinely used in combination with personal protective measures to prevent malaria in travelers and established guidelines exist for antibiotic prophylaxis prior to surgery. Another important element in the prevention and control of infections is the recognition and management of patients with underlying diseases and conditions that can weaken host barriers to infection. For example, TB is the leading opportunistic infection in HIV-infected individuals, and antiretroviral therapy reduces risk of developing TB and mortality due to TB disease. Infectious complications are a major cause of morbidity and mortality in cancer and transplant patients, often resulting from immunosuppression that can be primary or related to drug and/or radiation therapy. Infectious disease control is also critical in individuals with compromised physical barriers to microbes as, for example, burn patients and patients with cystic fibrosis. Go to: Concluding Remarks Dr William H Stewart, the one-time Surgeon General of the United States, has been quoted (perhaps mistakenly) as saying in the 1960s “It is time to close the book on infectious diseases, and declare the war against pestilence won (Spellberg, 2008).” These words clearly do not hold true today, and public health practitioners wage an ever-growing fight against emerging pathogens, drug-resistant organisms, and vaccine-preventable diseases. In this light, it is all the more important that we have the tools needed to understand transmission dynamics and implement effective prevention and control programs. Clear definitions of terminology and elucidation of fundamental principles lay the foundation for effective public health interventions. Hopefully, this article helps strengthen the armamentarium of the public health practitioner. Go to: See also Arboviruses; Bacterial Infections: Overview; Biostatistics; Cholera and Other Vibrioses; Clinical Epidemiology; Dengue; Ebola and Other Viral Hemorrhagic Fevers; Emergence of Novel Human Infections: New Insights and New Challenges; Epidemiology of the Acquired Immunodeficiency Syndrome; Foodborne Diseases; HIV Prevention and Treatment in Children and Adolescents; Helminthic Diseases: Dracunculiasis; Helminthic Diseases: Intestinal Nematode Infections; Intestinal Infections: Overview; Measles; Measurement and Modeling: Infectious Disease Modeling; Parasitic Diseases, an Overview; Plague, Historical; Protozoan Diseases: Cryptosporidiosis, Giardiasis, and Other Intestinal Protozoan Diseases; Protozoan Diseases: Malaria Clinical Features, Management, and Prevention; Rabies; Re-emerging Diseases: Overview; Reproductive Health: Sexually Transmitted Infections – Overview; Salmonella; Severe Acute Respiratory Syndrome (SARS); Shigellosis; Smallpox; Tetanus; Tuberculosis Epidemiology; Typhoid Fever; Viral Infections, an Overview with a Focus on Prevention of Transmission; Waterborne Diseases. Go to: Biographies An external file that holds a picture, illustration, etc. Object name is u00516-01-9780128036785.jpg Jean Maguire van Seventer, VMD, is a graduate of Stanford University and University of Pennsylvania School of Veterinary Medicine. She received postdoctoral training in comparative and veterinary pathology at Harvard Medical School and in immunology at the National Institutes of Health. Dr van Seventer worked as a biomedical research scientist in the Department of Pathology at University of Chicago Medical School and in the Department of Environmental Health at Boston University School of Public Health, investigating regulation of human T cell and dendritic cell differentiation and activation. Dr van Seventer is a clinical associate professor of Environmental Health at the Boston University School of Public Health and director of the school's Infectious Disease Certificate Program. She has a special interest in the role of the environment in infectious disease emergence and spread and teaches two graduate courses focused on Environmental Determinants of Infectious Diseases and Analysis of Emerging Infections Using the One Health Approach. An external file that holds a picture, illustration, etc. Object name is u00516-02-9780128036785.jpg Natasha S. Hochberg, MD, MPH, is a graduate of Harvard University and Case Western Reserve University School of Medicine. After completing internal medicine residency at the Brigham and Women's Hospital, Dr Hochberg spent two years as an Epidemic Intelligence Service (EIS) officer in the Division of Parasitic Diseases at the Centers for Disease Control and Prevention, conducting studies in Niger, Haiti, Bangladesh and the United States. Dr Hochberg completed a Masters in Public Health and Infectious Diseases fellowship at Emory University. Dr Hochberg is an assistant professor of Medicine and Epidemiology at the Boston University Schools of Medicine and Public Health. She is codirector of the Travel Clinic at Boston Medical Center and teaches courses for MPH students on Infectious Disease Epidemiology and Outbreak Investigations. Her research interests include the study of tuberculosis and tuberculosis-parasite coinfections in the United States, India, and Brazil. Go to: References Afshar M., Raju M., Ansell D., Bleck T.P. Narrative review: tetanus-a health threat after natural disasters in developing countries. Ann. Intern. Med. 2011;154:329–335. [PubMed] [Google Scholar] Aidoo M., Terlouw D.J., Kolczak M.S., Mcelroy P.D., Ter Kuile F.O., Kariuki S., Nahlen B.L., Lal A.A., Udhayakumar V. Protective effects of the sickle cell gene against malaria morbidity and mortality. Lancet. 2002;359:1311–1312. [PubMed] [Google Scholar] Alawieh A., Musharrafieh U., Jaber A., Berry A., Ghosn N., Bizri A.R. 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[PubMed] [Google Scholar] Articles from International Encyclopedia of Public Health are provided here courtesy of Elsevier OTHER FORMATS PDF (2.8M) ACTIONS Cite Collections SHARE RESOURCES Similar articles Cited by other articles Links to NCBI Databases FOLLOW NCBI Connect with NLM National Library of Medicine 8600 Rockville Pike Bethesda, MD 20894 Web Policies FOIA HHS Vulnerability Disclosure Help Accessibility Careers NLM NIH HHS USA.gov Tell us what you think!Close	biology	1054494	https://da.wikipedia.org/wiki/Asymptomatisk%20b%C3%A6rer	Asymptomatisk bærer	En asymptomatisk bærer er en person eller anden organisme, der er blevet inficeret med et patogen, men som er uden tegn eller symptomer. Selvom bærere ikke er påvirket af patogenet, kan de overføre det til andre eller udvikle symptomer i senere stadier af sygdommen. Asymptomatiske bærere spiller en kritisk rolle i transmission af almindelige infektiøse sygdomme som tyfus, HIV, C. difficile, influenza, kolera, tuberkulose og COVID-19, skønt sidstnævnte ofte er forbundet med "robust T-celleimmunitet" hos mere end en fjerdedel af de undersøgte patienter. Mens mekanismen for at være sygdomsbærende (disease-carrying) stadig er ukendt, har forskere gjort fremskridt i forståelsen af, hvordan visse patogener kan forblive sovende hos et menneske i en periode. En bedre forståelse af bærere af asymptomatiske sygdomme er afgørende for områder inden for lægevidenskab og folkesundhed, da de arbejder på at afbøde spredningen af almindelige smitsomme sygdomme. Noter og referencer Noter Referencer Se også Immunforsvar − Uspecifikt immunforsvar − T-celle Eksterne henvisninger "Retningslinjer for håndtering af COVID-19 i sundhedsvæsenet" 21. oktober 2020 − Omtaler også asymptomatiske bærere "Robust T Cell Immunity in Convalescent Individuals with Asymptomatic or Mild COVID-19" fra Sciencedirect.com Symptomer Immunologi Infektionssygdomme	danish	0.582738
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](/cancer/risk-prevention/genetics/genetic-testing-for-cancer-risk/what-happens-during-genetic-testing-for-cancer.html) * [ Radiation Exposure ](/cancer/risk-prevention/radiation-exposure.html) __ * [ X-rays and Gamma Rays ](/cancer/risk-prevention/radiation-exposure/x-rays-gamma-rays.html) __ * [ What Are X-rays and Gamma Rays? ](/cancer/risk-prevention/radiation-exposure/x-rays-gamma-rays/what-are-xrays-and-gamma-rays.html) * [ How Are People Exposed to X-rays and Gamma Rays? ](/cancer/risk-prevention/radiation-exposure/x-rays-gamma-rays/how-are-people-exposed.html) * [ Do X-rays and Gamma Rays Cause Cancer? ](/cancer/risk-prevention/radiation-exposure/x-rays-gamma-rays/do-xrays-and-gamma-rays-cause-cancer.html) * [ Do X-rays and Gamma Rays Cause Health Problems Other than Cancer? ](/cancer/risk-prevention/radiation-exposure/x-rays-gamma-rays/other-health-problems.html) * [ Can I Avoid or Limit My Exposure to X-rays and Gamma Rays? ](/cancer/risk-prevention/radiation-exposure/x-rays-gamma-rays/avoiding-exposure.html) * [ Radon ](/cancer/risk-prevention/radiation-exposure/radon.html) * [ Radiofrequency (RF) Radiation ](/cancer/risk-prevention/radiation-exposure/radiofrequency-radiation.html) * [ Power Lines, Electrical Devices, and Extremely Low Frequency Radiation ](/cancer/risk-prevention/radiation-exposure/extremely-low-frequency-radiation.html) * [ Cellular (Cell) Phones ](/cancer/risk-prevention/radiation-exposure/cellular-phones.html) * [ Cell Phone Towers ](/cancer/risk-prevention/radiation-exposure/cellular-phone-towers.html) * [ Smart Meters ](/cancer/risk-prevention/radiation-exposure/smart-meters.html) * [ Chemicals ](/cancer/risk-prevention/chemicals.html) __ * [ Acrylamide ](/cancer/risk-prevention/chemicals/acrylamide.html) * [ Agent Orange ](/cancer/risk-prevention/chemicals/agent-orange-and-cancer.html) * [ Antiperspirants ](/cancer/risk-prevention/chemicals/antiperspirants-and-breast-cancer-risk.html) * [ Arsenic ](/cancer/risk-prevention/chemicals/arsenic.html) * [ Asbestos ](/cancer/risk-prevention/chemicals/asbestos.html) * [ Aspartame ](/cancer/risk-prevention/chemicals/aspartame.html) * [ Benzene ](/cancer/risk-prevention/chemicals/benzene.html) * [ Cosmetics ](/cancer/risk-prevention/chemicals/cosmetics.html) * [ Diesel Exhaust ](/cancer/risk-prevention/chemicals/diesel-exhaust-and-cancer.html) * [ Firefighting ](/cancer/risk-prevention/chemicals/firefighting.html) * [ Formaldehyde ](/cancer/risk-prevention/chemicals/formaldehyde.html) * [ Hair Dyes ](/cancer/risk-prevention/chemicals/hair-dyes.html) * [ Military Burn Pits ](/cancer/risk-prevention/chemicals/burn-pits.html) * [ Recombinant Bovine Growth Hormone ](/cancer/risk-prevention/chemicals/recombinant-bovine-growth-hormone.html) * [ PFOA, PFOS, and Related PFAS Chemicals ](/cancer/risk-prevention/chemicals/teflon-and-perfluorooctanoic-acid-pfoa.html) * [ Talcum Powder ](/cancer/risk-prevention/chemicals/talcum-powder-and-cancer.html) * [ Water Fluoridation ](/cancer/risk-prevention/chemicals/water-fluoridation-and-cancer-risk.html) * [ Infections ](/cancer/risk-prevention/infections.html) __ * [ Infections that Can Lead to Cancer ](/cancer/risk-prevention/infections/infections-that-can-lead-to-cancer.html) __ * [ Can Infections Cause Cancer? ](/cancer/risk-prevention/infections/infections-that-can-lead-to-cancer/intro.html) * [ Viruses that Can Lead to Cancer ](/cancer/risk-prevention/infections/infections-that-can-lead-to-cancer/viruses.html) * [ Bacteria that Can Lead to Cancer ](/cancer/risk-prevention/infections/infections-that-can-lead-to-cancer/bacteria.html) * [ Parasites that Can Lead to Cancer ](/cancer/risk-prevention/infections/infections-that-can-lead-to-cancer/parasites.html) * [ HIV Infection and Cancer ](/cancer/risk-prevention/infections/hiv-infection-aids.html) __ * [ What Are HIV and AIDS? ](/cancer/risk-prevention/infections/hiv-infection-aids/what-are-hiv-and-aids.html) * [ HIV and Cancer ](/cancer/risk-prevention/infections/hiv-infection-aids/hiv-aids-and-cancer.html) * [ Medical Treatments ](/cancer/risk-prevention/medical-treatments.html) __ * [ Abortion and Breast Cancer Risk ](/cancer/risk-prevention/medical-treatments/abortion-and-breast-cancer-risk.html) * [ DES Exposure: Questions and Answers ](/cancer/risk-prevention/medical-treatments/des-exposure.html) * [ Menopausal Hormone Therapy and Cancer Risk ](/cancer/risk-prevention/medical-treatments/menopausal-hormone-replacement-therapy-and-cancer-risk.html) __ __ Back [ __ Download Section as PDF ](/content/dam/CRC/PDF/Public/6141.00.pdf) # Viruses that Can Lead to Cancer On this page [ show ] [ hide ] * Human papillomaviruses (HPVs) * Epstein-Barr virus (EBV) * Hepatitis B virus (HBV) and hepatitis C virus (HCV) * Human immunodeficiency virus (HIV) * Human herpes virus 8 (HHV-8) * Human T-lymphotrophic virus-1 (HTLV-1) * Merkel cell polyomavirus (MCV) * Viruses with uncertain or unproven links to cancer in humans Viruses are very small organisms; most can’t even be seen with an ordinary microscope. They are made up of a small number of genes in the form of DNA or RNA surrounded by a protein coating. A virus must enter a living cell and take over the cell’s machinery in order to reproduce and make more viruses. Some viruses do this by inserting their own DNA (or RNA) into that of the host cell. When the DNA or RNA affects the host cell’s genes, it can push the cell toward becoming cancer. In general, each type of virus tends to infect only a certain type of cell in the body. (For example, the viruses that cause the common cold only infect the cells lining the nose and throat.) Several viruses are linked with cancer in humans. Our growing knowledge of the role of viruses as a cause of cancer has led to the development of vaccines to help prevent certain human cancers. But these vaccines can only protect against infections if they are given before the person is exposed to the cancer-promoting virus. ## Human papillomaviruses (HPVs) [ Human papillomaviruses (HPVs) ](/cancer/risk-prevention/hpv.html) are a group of more than 150 related viruses. They are called _papillomaviruses_ because some of them cause papillomas, which are more commonly known as warts. Some types of HPV only grow in skin, while others grow in mucous membranes such as the mouth, throat, or vagina. All types of HPV are spread by contact (touch). More than 40 types of HPV can be passed on through sexual contact. Most sexually active people are infected with one or more of these HPV types at some point in their lives. At least a dozen of these HPV types are known to cause cancer. While HPV infections are very common, cancer caused by HPV is not. Most people infected with HPV will not develop a cancer related to the infection. However, some people with long-lasting infections of high-risk HPV types are at risk of developing cancer. HPV infections of the mucous membranes can cause genital warts, but they usually have no symptoms. There are no effective medicines or other treatments for HPV, other than removing or destroying cells that are known to be infected. But in most people, the body’s immune system controls the HPV infection or gets rid of it over time. To learn more, see [ HPV and HPV Testing ](/cancer/risk-prevention/hpv/hpv-and-hpv-testing.html) . ### HPV and cervical cancer A few types of HPV are the main causes of [ cervical cancer ](/cancer/types/cervical-cancer.html) , which is the second most common cancer among women worldwide. Cervical cancer has become much less common in the United States because the Pap test has been widely available for many years. This test can show pre-cancer in cells of the cervix that might be caused by HPV infection. These pre-cancer cells can then be destroyed or removed, if needed. This can keep cancer from developing. Doctors can now also test for HPV as part of cervical cancer screening, which can tell them if someone might be at higher risk for cervical cancer. Nearly all individuals with cervical cancer show signs of HPV infection on lab tests. Even though doctors can test for HPV, there is no treatment directed at HPV itself. If the HPV causes abnormal cells to start growing, these cells can be removed or destroyed. See [ HPV and HPV Testing ](/cancer/risk-prevention/hpv/hpv-and-hpv- testing.html) for more information on this topic. ### HPV and other cancers HPV also has a role in causing some cancers of the [ penis ](/cancer/types/penile-cancer.html) , [ anus ](/cancer/types/anal-cancer.html) , [ vagina ](/cancer/types/vaginal-cancer.html) , [ vulva ](/cancer/types/vulvar-cancer.html) , and [ mouth and throat ](/cancer/types/oral-cavity-and-oropharyngeal-cancer.html) . [ Smoking ](/cancer/risk-prevention/tobacco.html) , which is also linked with some of these cancers, may work with HPV to increase cancer risk. Other genital infections may also increase the risk that HPV will cause cancer. You can get more details in [ HPV and Cancer ](/cancer/risk- prevention/hpv/hpv-and-cancer-info.html) . ### Vaccines against HPV Vaccines are now available to help protect children and young adults against infection from the main cancer-causing HPV types. HPV vaccination can help prevent more than 90% of HPV cancers. These vaccines are approved for use in females and males and are given as a series of injections (shots). The vaccines can only be used to help prevent HPV infection – they do not stop or help treat an existing infection. To be most effective, the vaccine series should be given before a person becomes sexually active (has sex with another person). American Cancer Society recommendations for HPV vaccination * HPV vaccination works best when given to boys and girls between ages 9 and 12. * Children and young adults age 13 through 26 who have not been vaccinated, or who haven’t gotten all their doses, should get the vaccine as soon as possible. Vaccination of young adults will not prevent as many cancers as vaccination of children and teens. * ACS does not recommend HPV vaccination for persons older than 26 years. See [ HPV Vaccines ](/cancer/risk-prevention/hpv.html) for more on this. ## Epstein-Barr virus (EBV) EBV is a type of herpes virus. It is probably best known for causing infectious mononucleosis, often called “mono” or the “kissing disease.” In addition to kissing, EBV can be passed from person to person by coughing, sneezing, or by sharing drinking or eating utensils. Most people in the United States are infected with EBV by the end of their teen years, although not everyone develops the symptoms of mono. As with other herpes virus infections, EBV infection is life-long, even though most people have no symptoms after the first few weeks. EBV infects and stays in certain white blood cells in the body called _B lymphocytes_ (also called _B_ _cells_ ). There are no medicines or other treatments to get rid of EBV, nor are there vaccines to help prevent it, but EBV infection doesn’t cause serious problems in most people. EBV infection increases a person’s risk of getting [ nasopharyngeal cancer ](/cancer/types/nasopharyngeal-cancer.html) (cancer of the area in the back of the nose) and certain types of fast-growing [ lymphomas ](/cancer/types/non- hodgkin-lymphoma.html) such as Burkitt lymphoma. It may also be linked to [ Hodgkin lymphoma ](/cancer/types/hodgkin-lymphoma.html) and some cases of [ stomach cancer ](/cancer/types/stomach-cancer.html) . EBV-related cancers are more common in Africa and parts of Southeast Asia. Overall, very few people who have been infected with EBV will ever develop these cancers. ## Hepatitis B virus (HBV) and hepatitis C virus (HCV) Both HBV and HCV cause viral hepatitis, a type of liver infection. Other viruses can also cause hepatitis (hepatitis A virus, for example), but only HBV and HCV can cause the long-term (chronic) infections that increase a person’s chance of [ liver cancer ](/cancer/types/liver-cancer.html) . In the United States, less than half of liver cancers are linked to HBV or HCV infection. But this number is much higher in some other countries, where both viral hepatitis and liver cancer are much more common. Some research also suggests that long-term HCV infection might be linked with some other cancers, such as [ non-Hodgkin lymphoma ](/cancer/types/non-hodgkin-lymphoma.html) . HBV and HCV are spread from person to person in much the same way as HIV (see the section on HIV below) — through sharing needles (such as during injection drug use), unprotected sex, or childbirth. They can also be passed on through blood transfusions, but this is rare in the United States because donated blood is tested for these viruses. Of the 2 viruses, infection with HBV is more likely to cause symptoms, such as a flu-like illness and jaundice (yellowing of the eyes and skin). Most adults recover completely from HBV infection within a few months. Only a very small portion of adults go on to have chronic HBV infections, but this risk is higher in young children. People with chronic HBV infections have a higher risk for liver cancer. HCV is less likely to cause symptoms than HBV, but it is more likely to cause chronic infection, which can lead to liver damage or even cancer. Millions of people in the United States have chronic HCV infections, and most of these people don’t even know they have it. To help find some of these unknown chronic HBV and HCV infections, the US Centers for Disease Control and Prevention (CDC) recommends that all people 18 years of age or older get tested for HBV and HCV at least once during their lifetime, and that some groups of people get tested at a younger age and/or more often. (For detailed lists of who should get tested for HBV and HCV and how often, visit the CDC website at: [ https://www.cdc.gov/hepatitis/hbv/bfaq.htm ](https://www.cdc.gov/hepatitis/hbv/bfaq.htm) and [ https://www.cdc.gov/hepatitis/hcv/cfaq.htm ](https://www.cdc.gov/hepatitis/hcv/cfaq.htm) .) If an infection is found, treatment and preventive measures can be used to slow liver damage and reduce cancer risk. Both hepatitis B and C infections can be treated with drugs. Treating chronic hepatitis C infection with a combination of drugs for at least a few months can get rid of HCV in many people. A number of drugs can also be used to help treat chronic hepatitis B. Although they don’t cure the disease, they can lower the risk of liver damage and might lower the risk of liver cancer as well. There is a vaccine to prevent HBV infection, but none for HCV. In the United States, the CDC recommends the HBV vaccine for all children and adults up to age 59, as well as those who are older and at risk of HBV exposure. This includes people infected with HIV, men who have sex with men, injection drug users, people in certain group homes, people with certain medical conditions and occupations (such as health care workers), and others. (For a more complete list of who should get the HBV vaccine, visit the CDC website at: [ https://www.cdc.gov/hepatitis/hbv/bfaq.htm ](https://www.cdc.gov/hepatitis/hbv/bfaq.htm) .) ## Human immunodeficiency virus (HIV) HIV, the virus that causes acquired immune deficiency syndrome (AIDS), doesn’t appear to cause cancers directly. But HIV infection increases a person’s risk of getting several types of cancer, especially some linked to other viruses. HIV can be spread through semen, vaginal fluids, blood, and breast milk from an HIV-infected person. Known routes of spread include: * Unprotected sex (oral, vaginal, or anal) with an HIV-infected person * Injections with needles or injection equipment previously used by an HIV-infected person * Prenatal (before birth) and perinatal (during birth) exposure of infants from mothers with HIV * Breastfeeding by mothers with HIV * Transfusion of blood products containing HIV (the risk of HIV from a transfusion is less than 1 in a million in the United States due to blood testing and donor screening) * Organ transplants from an HIV-infected person (donors are now tested for HIV) * Penetrating injuries or accidents (usually needle sticks) in health care workers while caring for HIV-infected patients or handling their blood HIV is not spread by insects, through water, or by casual contact such as talking, shaking hands, hugging, coughing, sneezing, or from sharing dishes, bathrooms, kitchens, phones, or computers. It is not spread through saliva, tears, or sweat. HIV infects and destroys white blood cells known as helper T-cells, which weakens the body’s immune system. This might let some other viruses, such as HPV, thrive, which might lead to cancer. Many scientists believe that the immune system is also important in attacking and destroying newly formed cancer cells. A weak immune system might let new cancer cells survive long enough to grow into a serious, life-threatening tumor. HIV infection has been linked to a higher risk of developing [ Kaposi sarcoma ](/cancer/types/kaposi-sarcoma.html) and [ cervical cancer ](/cancer/types/cervical-cancer.html) . It’s also linked to certain kinds of [ non-Hodgkin lymphoma ](/cancer/types/non-hodgkin-lymphoma.html) , especially central nervous system lymphoma. Other types of cancer that may be more likely to develop in people with HIV infection include: * [ Anal cancer ](/cancer/types/anal-cancer.html) * [ Hodgkin disease ](/cancer/types/hodgkin-lymphoma.html) * [ Lung cancer ](/cancer/types/lung-cancer.html) * [ Cancers of the mouth and throat ](/cancer/types/oral-cavity-and-oropharyngeal-cancer.html) * Some types of [ skin cancer ](/cancer/types/skin-cancer.html) * [ Liver cancer ](/cancer/types/liver-cancer.html) Some other, less common types of cancer may also be more likely to develop in people with HIV. Because HIV infection often has no symptoms for years, a person can have HIV for a long time and not know it. The CDC recommends that everyone between the ages of 13 and 64 be tested for HIV at least once as part of their routine health care. There is no vaccine to prevent HIV. But there are ways to lower your risk of getting it, such as not having unprotected sex or sharing needles with someone who has HIV. For people who are at high risk of HIV infection, such as injection drug users and people whose partners have HIV, taking medicine (as a pill every day) is another way to help lower your risk of infection. For people already infected with HIV, taking anti-HIV drugs can help slow the damage to the immune system, which may help reduce the risk of getting some of the cancers above. For more information, see [ HIV and Cancer ](/cancer/risk- prevention/infections/hiv-infection-aids.html) . ## Human herpes virus 8 (HHV-8) HHV-8, also known as Kaposi sarcoma–associated herpes virus (KSHV) , has been found in nearly all tumors in patients with Kaposi sarcoma (KS). KS is a rare, slow-growing cancer that often appears as reddish-purple or blue-brown tumors just underneath the skin. In KS, the cells that line blood and lymph vessels are infected with HHV-8. The infection makes them divide too much and live longer than they should. These types of changes may eventually turn them into cancer cells. HHV-8 is transmitted through sex and appears to be spread other ways, such as through blood and saliva, as well. Studies have shown that fewer than 10% of people in the US are infected with this virus. HHV-8 infection is life-long (as with other herpes viruses), but it does not appear to cause disease in most healthy people. Many more people are infected with HHV-8 than ever develop KS, so it’s likely that other factors are also needed for it to develop. Having a weakened immune system appears to be one such factor. In the US, almost all people who develop KS have other conditions that have weakened their immune system, such as HIV infection or immune suppression after an organ transplant. KS was rare in the United States until it started appearing in people with AIDS in the early 1980s. The number of people with KS has dropped in the US since peaking in the early 1990s, most likely because of better treatment of HIV infection. For more information on KS, see [ Kaposi Sarcoma ](/cancer/types/kaposi- sarcoma.html) _._ HHV-8 infection has also been linked to some rare blood cancers, such as primary effusion __ lymphoma. The virus has also been found in many people with multicentric Castleman disease _,_ an overgrowth of lymph nodes that acts very much like and often develops into cancer of the lymph nodes (lymphoma). Further study is needed to better understand the role of HHV-8 in these diseases. ## Human T-lymphotrophic virus-1 (HTLV-1) HTLV-1 has been linked with a type of lymphocytic leukemia and non-Hodgkin lymphoma called adult T-cell leukemia/lymphoma (ATL) . This cancer is found mostly in southern Japan, the Caribbean, central Africa, parts of South America, and in some immigrant groups in the southeastern United States. In addition to ATL, this virus can cause other health problems, although many people with HTLV-1 don’t have any of them. HTLV-1 belongs to a class of viruses called _retroviruses_ . These viruses use RNA (instead of DNA) for their genetic code. To reproduce, they must go through an extra step to change their RNA genes into DNA. Some of the new DNA genes can then become part of the chromosomes of the human cell infected by the virus. This can change how the cell grows and divides, which can sometimes lead to cancer. HTLV-1 is something like HIV, which is another human retrovirus. But HTLV-1 cannot cause AIDS. In humans, HTLV-1 is spread in the same ways as HIV, such as unprotected sex with an HTLV-1-infected partner or injection with a needle after an infected person has used it. Mothers infected with HTLV-1 can also pass on the virus to their children, although this risk can be reduced if the mother doesn’t breastfeed. Infection with HTLV-1 is rare in the United States. Fewer than 1% of people in the US are infected with HTLV-1, but this rate is much higher in groups of people at high risk (such as injection drug users). Since 1988, all blood donated in the United States has been screened for HTLV-1. This has greatly reduced the chance of infection through transfusion, and has also helped control the potential spread of HTLV-1 infection. Once infected with HTLV-1, a person’s chance of developing ATL can be up to about 5%, usually after a long time with no symptoms (20 or more years). ## Merkel cell polyomavirus (MCV) MCV was discovered in 2008 in samples from a rare and aggressive type of skin cancer called Merkel cell carcinoma . Most people are infected with MCV at some point (often in childhood), and it usually causes no symptoms. But in a few people with this infection, the virus can affect the DNA inside cells, which can lead to Merkel cell cancer. Nearly all Merkel cell cancers are now thought to be linked to this infection. It is not yet clear how people become infected with this virus, but it has been found in a number of places in the body, including normal skin and saliva. For more information, see [ Merkel Cell Skin Cancer ](/cancer/types/merkel- cell-skin-cancer.html) . ## Viruses with uncertain or unproven links to cancer in humans ### Simian virus 40 (SV40) SV40 is a virus that usually infects monkeys. __ Some polio vaccines prepared between 1955 and 1963 were made from monkey cells and were later found to be contaminated with SV40. Some older studies suggested that infection with SV40 might increase a person’s risk of developing [ mesothelioma ](/cancer/types/malignant- mesothelioma.html) (a rare cancer of the lining of the lungs or abdomen), as well as some [ brain tumors ](/cancer/types/brain-spinal-cord-tumors- adults.html) , [ bone cancers ](/cancer/types/bone-cancer.html) , and [ lymphomas ](/cancer/types/lymphoma.html) . But the accuracy of these older studies has been questioned. Scientists have found that some lab animals, such as hamsters, developed mesotheliomas when they were intentionally infected with SV40. Researchers have also noticed that SV40 can make mouse cells grown in the lab become cancerous. Other researchers have studied biopsy specimens of certain human cancers and found fragments of DNA that look like they might be from SV40. But not all researchers have found this, and fragments much like these can also be found in human tissues that show no signs of cancer. So far, the largest studies looking at this issue have not found any increased risk for mesothelioma or other cancers among people who got the contaminated polio vaccines as children. For example, the recent increase in lung mesothelioma cases has been seen mainly in men aged 75 and older, most of whom would not have received the vaccine. Among the age groups who were known to have gotten the vaccine, mesothelioma rates have actually gone down. And even though women were just as likely to have had the vaccine, many more men continue to be diagnosed with mesothelioma. The bottom line: even though SV40 causes cancer in some lab animals, the evidence so far suggests that it does not cause cancer in humans. __ 1. Written by 2. References __ ![](/adobe/dynamicmedia/deliver/dm-aid--4f092b60-0db4-41fd- ad58-43ddc71ff4fd/logo-fpo.png?preferwebp=true&quality=82) [ The American Cancer Society medical and editorial content team ](/cancer/acs-medical-content-and-news-staff.html) Our team is made up of doctors and oncology certified nurses with deep knowledge of cancer care as well as journalists, editors, and translators with extensive experience in medical writing. Armstrong GL, Wasley A, Simard EP, et al. The prevalence of Hepatitis C Virus infection in the United States, 1999 through 2002. _Ann Int Med_ . 2006;144;705–714. Ault KA. 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Risk factors for HIV-1 transmission from HIV-seropositive male blood donors to their regular female partners in northern Thailand. _AIDS_ . 1997;11:1765–1772. National Cancer Institute. HIV Infection and Cancer Risk. 2011. Accessed at www.cancer.gov/cancertopics/factsheet/Risk/hiv-infection on September 22, 2014. National Cancer Institute. HPV and Cancer. 2012. Accessed at www.cancer.gov/cancertopics/factsheet/Risk/HPV on September 22, 2014. National Cancer Institute. _Simian Virus 40 and Human Cancer: Fact Sheet_ . Accessed at www.cancer.gov/cancertopics/factsheet/simian-virs-40 on August 29, 2011. Content no longer available. National Cancer Institute. Studies find no evidence that SV40 is related to human cancer. Accessed at www.cancer.gov/newscenter/newsfromnci/2004/sv40 on September 22, 2014. Poiesz BJ, Papsidero LD, Ehrlich G, et al. Prevalence of HTLV-I-associated T-cell lymphoma. _Am J Hematol_ . 2001;66:32–38. Qu L, Jenkins F, Triulzi DJ. Human herpesvirus 8 genomes and seroprevalence in United States blood donors. _Transfusion._ 2010;50:1050–1056. Rodig SJ, Cheng J, Wardzala J, et al. Improved detection suggests all Merkel cell carcinomas harbor Merkel polyomavirus. _J Clin Invest_ . 2012;122:4645-4653. Sahasrabuddhe VV, Shiels MS, McGlynn KA, Engels EA. The risk of hepatocellular carcinoma among individuals with acquired immunodeficiency syndrome in the United States. _Cancer_ . 2012;118:6226–6233. Smith BD, Morgan RL, Beckett GA, et al; Centers for Disease Control and Prevention. Recommendations for the identification of chronic hepatitis C virus infection among persons born during 1945-1965. _MMWR Recomm Rep._ 2012 Aug 17;61(RR-4):1–32. Strickler HD, Goedert JJ, Devesa SS, et al. Trends in U.S. pleural mesothelioma incidence rates following simian virus 40 contamination of early poliovirus vaccines. _J Natl Cancer Inst_ . 2003;95:38–45. Vilchez RA, Kozinetz CA, Butel JS. Conventional epidemiology and the link between SV40 and human cancers. _Lancet Oncol_ . 2003;4:188–191. Last Revised: March 21, 2023 American Cancer Society medical information is copyrighted material. For reprint requests, please see our [ Content Usage Policy ](/about- us/policies/content-usage.html) . #### American Cancer Society Emails Sign up to stay up-to-date with news, valuable information, and ways to get involved with the American Cancer Society. [ Sign Up for Email ](/about-us/email-sign-up.html) __ Back to Top ### Help us end cancer as we know it, for everyone. 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All rights reserved. The American Cancer Society is a qualified 501(c)(3) tax-exempt organization. Tax ID Number: 13-1788491. Cancer.org is provided courtesy of the Leo and Gloria Rosen family.	biology	3148788	https://sv.wikipedia.org/wiki/Rhabdomastix%20californiensis	Rhabdomastix californiensis	Rhabdomastix californiensis är en tvåvingeart som beskrevs av Alexander 1921. Rhabdomastix californiensis ingår i släktet Rhabdomastix och familjen småharkrankar. Inga underarter finns listade i Catalogue of Life. Källor Småharkrankar californiensis	swedish	1.400086
cancer_not_communicable/Clonally_transmissible_cancer.txt	A transmissible cancer is a cancer cell or cluster of cancer cells that can be transferred between individuals without the involvement of an infectious agent, such as an Oncovirus. The evolution of transmissible cancer has occurred naturally in other animal species, but human cancer transmission is rare. This transfer is typically between members of the same species or closely related species. General mechanism[edit] Transmissible cancers require a specific combination of related circumstances to occur. These conditions involve both the host species and the tumors being transferred. These typically include, low genetic diversity among individuals, effective physical and environmental transport system, effective dose of infective material and ideal micro-environments. The cancers reproduce faster in larger quantities with different means of reproduction tend to be favored for transmission if host conditions are met. Transmissible cancers follow the general pattern of cancer spread, starting with the growth of primary cancer cells at tumor sites followed by invasion of surrounding tissue and subsequent spread throughout the organism. The main hurdles for surviving cells of a successful spread to a new host are histocompatibility barriers. The cancers have to bypass the self recognition system, survive the difference in nutrients and induce the correct response in the new hosts to begin the cycle anew. Transmissible cancers behave as true parasites, relying primarily on transport systems like direct contact, environmental transport and vectors, rather than hematogenous and lymphatic carriers to spread between organisms. The amount of shredded cancer cells from initial host has to be high enough to increase survival probability. Direct contact transmissions through sexual or general contact such as in DFTD and CVTD ensures a higher potential for transmission. Population factors also play an important role. A dense population of available and uninfected potential hosts is ideal for the tumors given the complexity and difficulty of the overall process, hence its virulence and potency must be adequately controlled. Humans[edit] In humans, a significant fraction of Kaposi's sarcoma occurring after transplantation may be due to tumorous outgrowth of donor cells. Although Kaposi's sarcoma is caused by a virus (Kaposi's sarcoma-associated herpesvirus), in these cases, it appears likely that transmission of virus-infected tumor cells—rather than the free virus—caused tumors in the transplant recipients. In 2007, four people (three women and one man) received different organ transplants (liver, both lungs and kidneys) from a 53-year-old woman who had recently died from intracranial bleeding. Before transplantation, the organ donor was deemed to have no signs of cancer upon medical examination. The organ recipients developed metastatic breast cancer from the organs and three of them died from the cancer between 2009–2017. In 2014, a case of parasite-to-host cancer transmission occurred in a 41-year-old man in Colombia with a compromised immune system due to HIV. The man's tumor cells were shown to have originated from the dwarf tapeworm, Hymenolepis nana. In the 1990s, an undifferentiated pleomorphic sarcoma was transmitted from a 32-year-old patient to his 53-year-old surgeon when the surgeon injured his hand during an operation. Within five months, a tumor had developed on the hand of the surgeon and was subsequently excised. Histologic examinations of the tumor tissues from the patient and surgeon showed that both were morphologically identical. In 1986, a 19-year-old laboratory worker mistakenly punctured her hand with a needle previously used to extract human colonic cancer cells. No injection of the substance occurred, and the worker suffered a small puncture wound with bleeding. Within 19 days, she had developed a small cancerous nodule on her hand. The tumor was removed soon after, and has since shown no sign of reoccurrence. Other animals[edit] Contagious cancers are known to occur in dogs, Tasmanian devils, Syrian hamsters, and some marine bivalves including soft-shell clams. These cancers have a relatively stable genome as they are transmitted. Recent studies have tested whether other highly prevalent wildlife cancers, such as urogenital carcinomas in Californian sea lions, could also be contagious but so far there is no evidence for this. Clonally transmissible cancer, caused by a clone of malignant cells rather than a virus, is an extremely rare disease modality, with few transmissible cancers being known. The evolution of transmissible cancer is unlikely, because the cell clone must be adapted to survive a physical transmission of living cells between hosts, and must be able to survive in the environment of a new host's immune system. Animals that have undergone population bottlenecks may be at greater risks of contracting transmissible cancers due to a lack of overall genetic diversity. Infectious cancers may also evolve to circumvent immune response by means of natural selection in order to spread. Because of their transmission, it was initially thought that these diseases were caused by the transfer of oncoviruses, in the manner of cervical cancer caused by human papillomavirus. However, canine transmissible venereal tumor mutes the expression of the immune response, whereas the Syrian hamster disease spreads due to lack of genetic diversity. Canine transmissible venereal tumor[edit] Main article: Canine transmissible venereal tumor Canine transmissible venereal tumor (CTVT) is sexually transmitted cancer which induces cancerous tumors on the genitalia of both male and female dogs, typically during mating. It was first described medically by a veterinary practitioner in London in 1810. It was experimentally transplanted between dogs in 1876 by M. A. Novinsky (1841–1914). A single malignant clone of CTVT cells has colonized dogs worldwide, representing the oldest known malignant cell line in continuous propagation, a fact that was uncovered in 2006. Researchers deduced that the CTVT went through 2 million mutations to reach its actual state, and inferred it started to develop in ancient dog species 11 000 years ago. Contagious reticulum cell sarcoma[edit] Main article: Contagious reticulum cell sarcoma Contagious reticulum cell sarcoma of the Syrian hamster can be transmitted from one Syrian hamster to another through various mechanisms. It has been seen to spread within a laboratory population, presumably through gnawing at tumours and cannibalism. It can also be spread by means of the bite of the mosquito Aedes aegypti. Devil facial tumour disease[edit] Main article: Devil facial tumour disease Devil facial tumour disease (DFTD) is a transmissible parasitic cancer in the Tasmanian devil. Since its discovery in 1996, DFTD has spread and infected 4/5 of all Tasmanian devils and threatens them with extinction. DFTD has a near 100% fatality rate, and has killed up to 90% of Tasmanian devil populations living in some reserves. A new DFTD tumor-type cancer was recently uncovered on 5 Tasmanian devils (DFT2), histologically different from DFT1, leading researchers to believe that the Tasmanian devil "is particularly prone to the emergence of transmissible cancers". Bivalves[edit] Soft-shell clams, Mya arenaria, have been found to be vulnerable to a transmissible neoplasm of the hemolymphatic system — effectively, leukemia. The cells have infected clam beds hundreds of miles from each other, making this clonally transmissible cancer the only one that does not require contact for transmission. Horizontally transmitted cancers have also been discovered in three other species of marine bivalves: bay mussels (Mytilus trossulus), common cockles (Cerastoderma edule) and golden carpet shell clams (Polititapes aureus). The golden carpet shell clam cancer was found to have been transmitted from another species, the pullet carpet shell (Venerupis corrugata). See also[edit] Allotransplantation Anne-Maree Pearse, originator of the allograft theory of transmissible cancer Myxosporea – SCANDAL hypothesis	biology	4360113	https://sv.wikipedia.org/wiki/Rhipsalis%20oblonga	Rhipsalis oblonga	Rhipsalis oblonga är en kaktusväxtart som beskrevs av Johan Albert o Constantin Loefgren. Rhipsalis oblonga ingår i släktet Rhipsalis och familjen kaktusväxter. Inga underarter finns listade i Catalogue of Life. Bildgalleri Källor Externa länkar Kaktusväxter oblonga	swedish	1.228404
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A service of the National Library of Medicine, National Institutes of Health. StatPearls [Internet]. Treasure Island (FL): StatPearls Publishing; 2024 Jan-. [ ![Cover of StatPearls](/corehtml/pmc/pmcgifs/bookshelf/thumbs/th-statpearls- lrg.png) ](/books/n/statpearls/ "Table of Contents Page") ## StatPearls [Internet]. Show details Treasure Island (FL): [ StatPearls Publishing ](https://www.statpearls.com/) ; 2024 Jan-. Search term # Epidemiology of Prevention of Communicable Diseases Peter F. Edemekong ; Ben Huang . Author Information and Affiliations #### Authors Peter F. Edemekong 1 ; Ben Huang 2 . #### Affiliations 1 University of Texas Medical Branch - Galveston 2 Marian Un College of Osteopathic Med Last Update: October 24, 2022 . ## Continuing Education Activity Communicable diseases are illnesses caused by viruses or bacteria that people spread to one another through contact with contaminated surfaces, bodily fluids, blood products, insect bites, or through the air. There are many examples of communicable diseases, some of which require reporting to appropriate health departments or government agencies in the locality of the outbreak. Some examples of the communicable disease include HIV, hepatitis A, B and C, measles, salmonella, measles, and blood-borne illnesses. Most common forms of spread include fecal-oral, food, sexual intercourse, insect bites, contact with contaminated fomites, droplets, or skin contact. This activity reviews the epidemiology of communicable diseases and discusses the role of the interprofessional team in preventing communicable diseases and educating patients on techniques to avoid the transmission of communicable diseases. Objectives: * Explain the meaning of a communicable disease. * Summarize the common communicable diseases. * Describe the most common forms of spread of communicable diseases. * Review the epidemiology of communicable diseases and the role of the interprofessional team in preventing communicable diseases and educating patients on techniques to avoid the transmission of communicable diseases. [ Access free multiple choice questions on this topic. ](https://www.statpearls.com/account/trialuserreg/?articleid=21205&utm_source=pubmed&utm_campaign=reviews&utm_content=21205) ## Introduction Communicable diseases are illnesses caused by viruses or bacteria that people spread to one another through contact with contaminated surfaces, bodily fluids, blood products, insect bites, or through the air. [1] There are many examples of communicable diseases, some of which require reporting to appropriate health departments or government agencies in the locality of the outbreak. Some examples of the communicable disease include HIV, hepatitis A, B and C, measles, salmonella, measles and blood-borne illnesses. Most common forms of spread include fecal-oral, food, sexual intercourse, insect bites, contact with contaminated fomites, droplets, or skin contact. [2] [3] [4] Specifically, hepatitis is a form of a communicable disease that is spread through the oral-fecal route. An individual is exposed to hepatitis by coming in contact with blood products, consuming contaminated water, having sex with another infected person (oral and intercourse), or eating food that is contaminated by the virus. There are six criteria that need to be met to diagnose a hepatitis infection. These criteria include an infection agent, in this case, the hepatitis virus, a reservoir, route of infection, transmission mode, route of entry, and a susceptible subject who becomes infected with the virus. Hepatitis A virus (HAV) is a communicable disease that is preventable through vaccination. It affects the liver causing jaundice. It is transmitted person- to-person through consumption of food, oral sexual contact, poor hand hygiene after using the bathroom or changing diapers, and water that is contaminated. It is one of the most reported outbreaks in the United States. It is self- limited after ingestion through contaminated food sources. The virus replicates in the liver, is excreted in bile, and can reach high concentrations in the stool. Stool concentrations are the highest 2 weeks after transmission. Patients are considered non-infectious about a week after inoculation or the onset of jaundice. Patients who are symptomatic most often present with acute onset fever, malaise, jaundice, hepatomegaly, and abdominal pain. Jaundice is often followed with marked elevated of serum aminotransferases that is greater than 1000 units/L. The test of choice is IgM anti-hepatitis A virus for diagnostic purposes. There is no specific therapy available. Presently, supportive and conservative management is the mainstay of treatments. Prevention includes personal hygiene or with active or passive immunization. [5] [6] ## Function There are four major patterns of HAV infections worldwide divided into areas of high, intermediate, low, or very low prevalence. Endemic areas of high prevalence include parts of Africa, Asia, and Latin America. Most infections in these areas occur in early childhood. Areas of low prevalence and very low prevalence include North America and Western Europe with few infections during childhood and majority of the population are susceptible throughout adulthood. In the United States, HAV is one of the most reported diseases among vaccine- preventable diseases. Over 30,000 cases were reported in 1997. An estimated 270,000 HAV infections are said to have occurred each year between 1980 and 1999. A total of 1390 cases of hepatitis A were reported from 50 states to the Centers for Disease Control and Prevention (CDC) in 2015. There was a 12.2% increase from reported cases of HAV in 2014. Of note, the overall incidence in 2015 was 0.4 cases per 100,000 population which was the same as in 2014 (CDC, 2017). Since 1996, the declining incidence in the United States is attributed to the widespread use of HAV vaccination for populations considered high-risk. An incidence of 1 case per 10,000 was notably the lowest recorded in 2007. States with routine vaccination for children also noticeably made the most noticeable difference (Epocrartes, 2017). Overall, there has been a 95% decline in HAV in the United States since the vaccine for HAV became available in 1995. Globally, the epidemiology of HAV is evolving, in part attributed to improved sanitation standards and living conditions mostly noticeable in developing countries. This has undoubtedly contributed to the global decline in the number of infected children globally. However, the incidence among adults has increased due to the larger population of an adult who lacks antibodies that are protective against HAV. [7] [8] ## Issues of Concern Recently, the Division of Disease Control and Health Protection issued a Healthcare Provider Advisory note on HAV in the State of Florida indicating that 217 cases have been in reported in the State of Florida alone since January 2017, a significant increase when compared to the past 5-year average of 94 cases. Of note was the fact that most HAV cases did not have international travel exposure. Southeast Florida (e.g., Broward and Miami-Dade counties) had the most cases of HAV with 69% among males (most had male sexual contact). The median age of reported cases was 38 years with the highest rates of Hepatitis A disease recorded among people ages 25 to 44 years. About 60% of the cases of HAV in Florida required hospitalization. Also of note is the fact that nearly 1200 outbreaks of HAV were recorded among individuals who are homeless, use intravenous (IV) drugs, men who have sex with men, and their close or direct contacts as investigated by the health departments in Arizona, California, Colorado, Michigan, New York and Utah (DOH, Florida 2017). ## Clinical Significance History and Physical Examination * Acute onset fever * Fatigue * Malaise * Nausea and vomiting * Jaundice * Hepatomegaly * Right upper quadrant pain * Joint pain * Clay-colored bowel movements Other Clinical Factors * Headache * Fatigue * Dark urine * Pruritus * Rash * Arthralgias and myalgias * Cough * Bradycardia * Diarrhea * Constipation * Splenomegaly * Posterior cervical lymphadenopathy Diagnostic Tests * Serum aminotransferases * Serum bilirubin * BUN * Serum Creatinine * Prothrombin time * IgM anti-hepatitis A virus (HAV) * IgG anti-hepatitis A virus (HAV) * Stool and body fluid electron microscopy * Hepatitis A virus RNA Treatment Options Presumptive: If unvaccinated with recent exposure to HAV less than 2 weeks: HAV or immune globulin Acute presentation HAV infection * Confirmed HAV: Supportive and conservative management * Worsening jaundice and encephalopathy: liver transplant Recommendations of the Advisory Committee on Immunization Practices: DOH Florida, 2017. * All children at age 1 year * Persons who are at increased risk for infection * Persons who are at increased risk for complications from HAV * Any person wishing to obtain immunity ## Other Issues Recommendation for two-dose HAV vaccine, 6 to 12 months apart for the following persons: * Men who have sex with men * Injection and non-injection drugs users * Persons with chronic liver disease * Persons traveling to or working in countries with high or intermediate endemicity of hepatitis A * Persons with clotting-factor disorders * Household members and other close personal contacts of adopted children newly arriving from countries with high or intermediate hepatitis A endemicity * Persons with direct contact with persons who have hepatitis A ## Enhancing Healthcare Team Outcomes Communicable diseases are illnesses caused by viruses or bacteria that people spread to one another through contact with contaminated surfaces, bodily fluids, blood products, insect bites, or through the air. There are many examples of communicable diseases. Health professionals need to be aware that some require reporting to appropriate health departments or government agencies in the locality of the outbreak. Some examples of reportable communicable disease include HIV, hepatitis A, B and C, measles, salmonella, measles, and blood-borne illnesses. Most common forms of spread include fecal- oral, food, sexual intercourse, insect bites, contact with contaminated fomites, droplets, or skin contact. Improving health professional understanding of communicable diseases that must be reported will lead to better patient outcomes. In the hospital setting, the nurse educators and infectious disease nurse play a crucial role in educating the clinicians and nurses in avoiding spreading communicable disease. Further, the infectious disease nurse assists in identifying concerns and reporting issues to the interprofessional team managing a patients care. Often this involves more stringent infection prevention precautions and guiding the interprofessional team caring for the patient to avoid further spread of disease an obtain the best outcomes. [Level V] ## Review Questions * [ Access free multiple choice questions on this topic. ](https://www.statpearls.com/account/trialuserreg/?articleid=21205&utm_source=pubmed&utm_campaign=reviews&utm_content=21205) * [ Comment on this article. ](https://www.statpearls.com/articlelibrary/commentarticle/21205/?utm_source=pubmed&utm_campaign=comments&utm_content=21205) ## References 1\. Wang P, Li Z, Jones A, Bodner ME, Dean E. Discordance between lifestyle- related health behaviors and beliefs of urban mainland Chinese: A questionnaire study with implications for targeting health education. AIMS Public Health. 2019; 6 (1):49-66. [ [ PMC free article : PMC6433611 ](/pmc/articles/PMC6433611/) ] [ [ PubMed : 30931342 ](https://pubmed.ncbi.nlm.nih.gov/30931342) ] 2\. Moein D, Masoud D, Mahmood N, Abbas D. Epidemiological Trend of Cutaneous Leishmaniasis in an Endemic Focus Disease During 2009-2016, Central Iran. Turkiye Parazitol Derg. 2019 Jun 17; 43 (2):55-59. [ [ PubMed : 31204455 ](https://pubmed.ncbi.nlm.nih.gov/31204455) ] 3\. Heller O, Somerville C, Suggs LS, Lachat S, Piper J, Aya Pastrana N, Correia JC, Miranda JJ, Beran D. The process of prioritization of non-communicable diseases in the global health policy arena. Health Policy Plan. 2019 Jun 01; 34 (5):370-383. [ [ PMC free article : PMC6736081 ](/pmc/articles/PMC6736081/) ] [ [ PubMed : 31199439 ](https://pubmed.ncbi.nlm.nih.gov/31199439) ] 4\. Zhou S, Davison K, Qin F, Lin KF, Chow BC, Zhao JX. The roles of exercise professionals in the health care system: A comparison between Australia and China. J Exerc Sci Fit. 2019 Jul; 17 (3):81-90. [ [ PMC free article : PMC6517258 ](/pmc/articles/PMC6517258/) ] [ [ PubMed : 31193075 ](https://pubmed.ncbi.nlm.nih.gov/31193075) ] 5\. McNamara LA, Potts CC, Blain A, Topaz N, Apostol M, Alden NB, Petit S, Farley MM, Harrison LH, Triden L, Muse A, Poissant T, Wang X, MacNeil JR. Invasive Meningococcal Disease due to Nongroupable _Neisseria meningitidis_ -Active Bacterial Core Surveillance Sites, 2011-2016. Open Forum Infect Dis. 2019 May; 6 (5):ofz190. [ [ PMC free article : PMC6524832 ](/pmc/articles/PMC6524832/) ] [ [ PubMed : 31123695 ](https://pubmed.ncbi.nlm.nih.gov/31123695) ] 6\. Guerra CA, Kang SY, Citron DT, Hergott DEB, Perry M, Smith J, Phiri WP, Osá Nfumu JO, Mba Eyono JN, Battle KE, Gibson HS, García GA, Smith DL. Human mobility patterns and malaria importation on Bioko Island. Nat Commun. 2019 May 27; 10 (1):2332. [ [ PMC free article : PMC6536527 ](/pmc/articles/PMC6536527/) ] [ [ PubMed : 31133635 ](https://pubmed.ncbi.nlm.nih.gov/31133635) ] 7\. Phillips JA. Chlamydia Infections. Workplace Health Saf. 2019 Jul; 67 (7):375-376. [ [ PubMed : 31179859 ](https://pubmed.ncbi.nlm.nih.gov/31179859) ] 8\. Whitty CJM, Ansah E. Malaria control stalls in high incidence areas. BMJ. 2019 May 21; 365 :l2216. [ [ PubMed : 31113780 ](https://pubmed.ncbi.nlm.nih.gov/31113780) ] Disclosure: Peter Edemekong declares no relevant financial relationships with ineligible companies. Disclosure: Ben Huang declares no relevant financial relationships with ineligible companies. [ Copyright ](/books/about/copyright/) © 2024, StatPearls Publishing LLC. This book is distributed under the terms of the Creative Commons Attribution- NonCommercial-NoDerivatives 4.0 International (CC BY-NC-ND 4.0) ( [ http://creativecommons.org/licenses/by-nc-nd/4.0/ ](https://creativecommons.org/licenses/by-nc-nd/4.0/) ), which permits others to distribute the work, provided that the article is not altered or used commercially. You are not required to obtain permission to distribute this article, provided that you credit the author and journal. 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They are the result of pathogens, such as viruses and bacteria. Communicable diseases include colds and flu. Communicable diseases can transmit through contact with bodily fluids, insect bites, contaminated surfaces, water, and foods, or through the air. This article will discuss communicable diseases, their symptoms, and how to avoid them. ## What are communicable diseases? ![An image of a crowd of people walking through a public space](//i0.wp.com/post.medicalnewstoday.com/wp- content/uploads/sites/3/2022/05/blur-crowd-communicable-diseases- header-1024x575.jpg?w=1155&h=1528) [ Share on Pinterest ](https://www.pinterest.com/pin/create/button/?url=https%3A%2F%2Fwww.medicalnewstoday.com%2Farticles%2Fcommunicable- diseases&media=https%3A%2F%2Fpost.medicalnewstoday.com%2Fwp- content%2Fuploads%2Fsites%2F3%2F2022%2F05%2Fblur-crowd-communicable-diseases- header-1024x575.jpg&description=Communicable%20diseases%3A%20Types%2C%20symptoms%2C%20prevention%2C%20and%20treatment "Share on Pinterest") sebastian-julian/Getty Images A communicable disease is any disease that passes between people or animals. People sometimes refer to communicable diseases as “infectious” or “transmissible” diseases. Pathogens, including bacteria, viruses, fungi, and protozoa, cause communicable diseases. [ Learn more about the different types of pathogens here. ](https://www.medicalnewstoday.com/articles/pathogens-definition) ### Symptoms Once a pathogen has entered a person’s body, it often will begin replicating. The individual may then begin to experience symptoms. Symptoms will vary depending on the disease. Some people will not experience any symptoms. However, they can still transmit the pathogen. Some symptoms are a direct result of the pathogen damaging the body’s cells. Others are due to the body’s immune response to the infection. Some communicable diseases may be mild, and symptoms pass after a few days. However, some can be serious and potentially life threatening. Symptom severity may vary depending on a person’s overall health and immune function. ## Types and symptoms Four main types of pathogens cause infection: Viruses, bacteria, fungi, and protozoa. ### Viruses [ Viruses ](https://www.medicalnewstoday.com/articles/158179) are tiny pathogens that contain genetic material. Unlike other pathogens, they lack the complex structure of a cell. To replicate, they must enter the cells of other living beings. Once inside, they use the cell’s machinery to make copies of themselves. ### Bacteria [ Bacteria ](https://www.medicalnewstoday.com/articles/157973) are microscopic, single-celled organisms. They exist in almost every environment on earth, including inside the human body. Many bacteria are harmless, and some help the body to function. However, bacteria can also cause infections that damage the body. ### Fungi [ Fungi ](https://www.medicalnewstoday.com/articles/158134) are a type of organism that includes yeasts, molds, and mushrooms. There are [ millions ](https://www.cdc.gov/fungal/features/fungal-infections.html) of different fungi. However, only around 300 cause harmful illnesses. [ Fungal infections ](https://www.medicalnewstoday.com/articles/317970) can occur anywhere in the body. However, they commonly affect the skin and mucus membranes. ### Protozoa Protozoa are microscopic organisms that typically consist of a single cell. Some protozoa are parasitic, meaning they live on or inside another organism and use the organism’s nutrients for their own survival. Parasitic protozoa can cause various diseases. [ Learn more about parasitic infections here. ](https://www.medicalnewstoday.com/articles/220302) ## Common communicable diseases Common viral, bacterial, fungal, and protozoa diseases include: ### Rhinoviruses Rhinoviruses are a group of viruses that are the [ most common ](https://www.cdc.gov/features/rhinoviruses/index.html) cause of the [ common cold ](https://www.medicalnewstoday.com/articles/166606) . Symptoms of a cold may [ include ](https://www.cdc.gov/features/rhinoviruses/) : * a [ stuffy ](https://www.medicalnewstoday.com/articles/313808) or [ runny nose ](https://www.medicalnewstoday.com/articles/325248) * [ sore throat ](https://www.medicalnewstoday.com/articles/311449) * [ headache ](https://www.medicalnewstoday.com/articles/73936) A person can catch a rhinovirus by inhaling contaminated droplets from the cough or sneeze of another person. Similarly, rhinoviruses are spread by people touching their nose, eyes, or mouth after touching items or surfaces that have come into contact with the virus. ### Coronaviruses [ Coronaviruses ](https://www.medicalnewstoday.com/articles/covid-19) are a large group of viruses that [ affect the respiratory system ](https://www.niaid.nih.gov/diseases-conditions/coronaviruses) . This family includes the SARS-CoV-2 virus. Some coronaviruses can cause common cold and flu symptoms, while others can cause more severe outcomes. ### Coronavirus resources For more advice on COVID-19 prevention and treatment, visit our [ coronavirus hub ](https://www.medicalnewstoday.com/coronavirus) . Was this helpful? ### Influenza [ Influenza ](https://www.medicalnewstoday.com/articles/15107) viruses are infections that attack the respiratory system. Some [ potential symptoms ](https://www.cdc.gov/flu/symptoms/symptoms.htm) include: * [ fever ](https://www.medicalnewstoday.com/articles/168266) or [ chills ](https://www.medicalnewstoday.com/articles/chills) * [ stuffy or runny nose ](https://www.medicalnewstoday.com/articles/313808) * sore throat * [ cough ](https://www.medicalnewstoday.com/articles/220349) * [ headaches ](https://www.medicalnewstoday.com/articles/headaches) * muscle or [ body aches ](https://www.medicalnewstoday.com/articles/319985) * [ fatigue ](https://www.medicalnewstoday.com/articles/248002) A person can catch influenza viruses in the same way they may catch rhinoviruses. ### HIV [ HIV ](https://www.medicalnewstoday.com/articles/17131) attacks the immune system of its host. This makes the person vulnerable to other infections and diseases. A person can contract HIV as a result of contact with blood or other body fluids containing the virus. The symptoms of HIV may [ develop gradually ](https://www.cdc.gov/hiv/basics/) and in stages. They can [ include ](https://www.hiv.gov/hiv-basics/overview/about-hiv-and-aids/symptoms-of-hiv) : * fever * chills * [ rash ](https://www.medicalnewstoday.com/articles/315963) * [ mouth sores ](https://www.medicalnewstoday.com/articles/323849) * sore throat * [ swollen lymph nodes ](https://www.medicalnewstoday.com/articles/316336) * [ night sweats ](https://www.medicalnewstoday.com/articles/296818) * [ muscle aches ](https://www.medicalnewstoday.com/articles/322869) * fatigue The only way a person can be certain they have HIV is to have an HIV test. Although there is no cure for HIV, [ medications ](https://www.medicalnewstoday.com/articles/324300) can help to keep the virus under control or make it undetectable. Without such treatment, HIV can develop into [ AIDS ](https://www.medicalnewstoday.com/articles/17131) . [ Learn more about undetectable HIV here. ](https://www.medicalnewstoday.com/articles/undetectable-hiv) Other medications can help prevent a person from contracting HIV. People at high risk of HIV and those who believe they may have had exposure to it should speak with their primary healthcare professional about these options. ### HIV and AIDS resources For more in-depth information and resources on HIV and AIDS, visit our [ dedicated hub ](https://www.medicalnewstoday.com/hiv-and-aids) . Was this helpful? ### _Salmonella_ and _Escherichia coli_ Nontyphoidal _[ Salmonella ](https://www.medicalnewstoday.com/articles/160942) _ and [ _Escherichia coli_ _(E. coli)_ ](https://www.medicalnewstoday.com/articles/68511) are two different types of bacteria that can infect the digestive system. Another form of salmonella, _Salmonella typhi,_ can also cause [ typhoid ](https://www.medicalnewstoday.com/articles/156859) . They typically spread through [ contaminated foods ](https://www.hhs.gov/answers/public-health-and-safety/what-is-the-difference- between-salmonella-and-e-coli/index.html) , such as uncooked meats and eggs, unwashed fruits and vegetables, and contaminated water sources. Salmonella [ can also spread ](https://www.food.gov.uk/safety- hygiene/salmonella) through contact with live animals, including chickens, and through person-to-person contact. Some symptoms of these infections include: * abdominal cramps * [ diarrhea ](https://www.medicalnewstoday.com/articles/158634) * fever * headache ### Tuberculosis [ Tuberculosis (TB) ](https://www.medicalnewstoday.com/articles/8856) is a bacterial infection that primarily attacks the lungs. It may cause the following symptoms: * a cough continuing for more than [ 3 weeks ](https://www.lung.org/lung-health-diseases/lung-disease-lookup/tuberculosis/symptoms-diagnosis) * [ loss of appetite ](https://www.medicalnewstoday.com/articles/324011) * [ unintentional weight loss ](https://www.medicalnewstoday.com/articles/326417) * fever * chills * night sweats A person can catch TB by inhaling tiny droplets or “aerosols” from the cough or sneeze of a person who has the infection. ### Ringworm [ Ringworm ](https://www.medicalnewstoday.com/articles/158004) is a [ common ](https://www.nhs.uk/conditions/ringworm/) fungal infection of the skin. The characteristic symptom of ringworm is a ring-shaped rash. It may be dry, scaly, or itchy. People may contract ringworm through: * close contact with a person who has ringworm * sharing towels, bedding, or other personal items with a person who has ringworm * close contact with animals with ringworm, typically cats Without treatment, ringworm [ may spread ](https://www.aad.org/public/diseases/a-z/ringworm-overview) to other parts of the body. ### Athlete’s foot [ Athlete’s foot ](https://www.medicalnewstoday.com/articles/261244) is a common fungal infection that affects the skin on the feet. It typically causes sore or itchy white patches between the toes. People can contract athlete’s foot through direct contact with someone who has the fungus or surfaces that have been in contact with the fungus. For example, an individual might contract athlete’s foot after walking barefoot in locker rooms, showers, or swimming pools. ### Plasmodium The protozoa _Plasmodium_ _genus_ causes the tropical disease [ malaria ](https://www.medicalnewstoday.com/articles/150670) . The parasite primarily [ transmits ](https://www.who.int/news-room/fact-sheets/detail/malaria) through [ mosquito bites ](https://www.medicalnewstoday.com/articles/311485) . Malaria causes symptoms such as: * fever and chills * headaches * vomiting * diarrhea * muscle pains Without proper treatment, malaria can be life threatening. Vaccination programs are also effectively protecting people from malaria fatalities. ### Lyme disease Lyme disease is a potentially serious infection that black-legged ticks can pass to humans. It is the [ most common ](https://www.cdc.gov/lyme/index.html) carrier-spread disease in the United States. The bacteria _Borrelia burgdorferi_ causes the majority of Lyme disease cases. However, the bacteria _Borrelia mayonii_ may also cause the disease. Symptoms of Lym disease include: * headache * fatigue * fever * skin rash Lyme disease can spread to the joints, heart, and nervous system if a person does not treat it. [ Learn more about Lyme disease here ](https://www.medicalnewstoday.com/articles/150479) . ## Causes A person may develop a communicable disease after becoming infected by the pathogen. This may happen through: * direct contact with a person carrying the pathogen * contact with bodily fluids containing pathogens * inhaling pathogen-containing droplets from another person’s cough or sneeze * receiving a bite from an animal or insect carrying the pathogen * consuming contaminated water or foods ## How to prevent transmission People can reduce their risk of contracting or transmitting disease-causing pathogens by following the steps below: * [ washing their hands thoroughly ](https://www.medicalnewstoday.com/articles/proper-hand-washing) and regularly * disinfecting surfaces at home often, especially doorknobs and food areas * disinfecting personal items such as phones * cooking meats, eggs, and other foods thoroughly * practicing good hygiene when preparing and handling food * avoiding eating spoiled food * avoiding touching wild animals * receiving available vaccinations * taking antimalarial medications when traveling where there is a malaria risk * check for ticks and other parasites ## Treatment for communicable diseases Some communicable diseases cause only mild symptoms that disappear without treatment. Others may cause severe symptoms or potentially life threatening complications. Patients require different treatment depending on disease process and clinical presentation. ### Viral infections Vaccines are a highly effective method for preventing specific viral infections. There are several [ different types ](https://www.hhs.gov/immunization/basics/types/index.html) of vaccines. When a person receives a vaccine, they are receiving a form of the virus. The immune system responds by producing antibodies capable of killing an active form of the virus in the future. If a person already has a virus, they may require antiviral medications to keep the virus under control. ### Bacterial infections Bacterial infections can range from mild to life threatening. A person who has a bacterial infection may require a course of [ antibiotics ](https://www.medicalnewstoday.com/articles/10278) to help control the infection. These medications can help to kill bacteria or slow them down so the immune system can counteract them. However, many bacteria are developing a resistance to antibiotics, which poses a major health risk. More than [ 2.8 million ](https://www.cdc.gov/drugresistance/biggest-threats.html) antibiotic- resistant infections occur in the U.S. every year. A person should only ever take antibiotics on a medical recommendation. ### Fungal infections A severe or chronic fungal infection may require prescription [ antifungal medications ](https://www.medicalnewstoday.com/articles/antifungal) and, in rare cases, intravenous medication. However, people can treat many mild infections, such as ringworm and athlete’s foot, with over-the-counter topical ointments. ## Summary Communicable diseases are diseases that can pass from person to person. The pathogens that cause these diseases can spread in various ways, such as through the air, contact with contaminated substances or surfaces, or from animal and insect bites. Many communicable diseases cause mild symptoms that go away without treatment. Others require treatment to prevent them from becoming more serious. There are steps a person can take to reduce their risk of contracting and transmitting disease-causing pathogens. These include receiving available vaccinations, practicing regular handwashing, and maintaining good hygiene at home. Last medically reviewed on May 10, 2022 * [ Public Health ](https://www.medicalnewstoday.com/categories/public-health) * [ Infectious Diseases / Bacteria / Viruses ](https://www.medicalnewstoday.com/categories/infectious_diseases) ### How we reviewed this article: Sources Medical News Today has strict sourcing guidelines and draws only from peer- reviewed studies, academic research institutions, and medical journals and associations. We avoid using tertiary references. We link primary sources — including studies, scientific references, and statistics — within each article and also list them in the resources section at the bottom of our articles. You can learn more about how we ensure our content is accurate and current by reading our [ editorial policy ](https://www.medicalnewstoday.com/articles/process) . * 2019 AR Threats report. (2021). [ https://www.cdc.gov/drugresistance/biggest-threats.html ](https://www.cdc.gov/drugresistance/biggest-threats.html) * Common colds: Protect yourself and others. (2021). [ https://www.cdc.gov/features/rhinoviruses/ ](https://www.cdc.gov/features/rhinoviruses/) * Coronaviruses. (2022). [ https://www.niaid.nih.gov/diseases-conditions/coronaviruses ](https://www.niaid.nih.gov/diseases-conditions/coronaviruses) * Flu symptoms and complications. (2021). [ https://www.cdc.gov/flu/symptoms/symptoms.htm ](https://www.cdc.gov/flu/symptoms/symptoms.htm) * Fungal infections: Protect your health. (2022). [ https://www.cdc.gov/fungal/features/fungal-infections.html ](https://www.cdc.gov/fungal/features/fungal-infections.html) * HIV basics. (2019). [ https://www.cdc.gov/hiv/basics/ ](https://www.cdc.gov/hiv/basics/) * Malaria. (2022). [ https://www.who.int/news-room/fact-sheets/detail/malaria ](https://www.who.int/news-room/fact-sheets/detail/malaria) * Ringworm. (2020). [ https://www.nhs.uk/conditions/ringworm ](https://www.nhs.uk/conditions/ringworm) * Ringworm: Overview. (n.d.). [ https://www.aad.org/public/diseases/a-z/ringworm-overview ](https://www.aad.org/public/diseases/a-z/ringworm-overview) * Symptoms of HIV. (2020). [ https://www.hiv.gov/hiv-basics/overview/about-hiv-and-aids/symptoms-of-hiv ](https://www.hiv.gov/hiv-basics/overview/about-hiv-and-aids/symptoms-of-hiv) * Tuberculosis (TB). (n.d.). [ https://www.lung.org/lung-health-diseases/lung-disease-lookup/tuberculosis ](https://www.lung.org/lung-health-diseases/lung-disease-lookup/tuberculosis) * Vaccine types. (2021). [ https://www.hhs.gov/immunization/basics/types/index.html ](https://www.hhs.gov/immunization/basics/types/index.html) * What is the difference between Salmonella and E.Coli? (2014). [ https://www.hhs.gov/answers/public-health-and-safety/what-is-the-difference- between-salmonella-and-e-coli/index.html ](https://www.hhs.gov/answers/public- health-and-safety/what-is-the-difference-between-salmonella-and-e- coli/index.html) Share this article [ ](https://www.facebook.com/sharer/sharer.php?u=https%3A%2F%2Fwww.medicalnewstoday.com%2Farticles%2Fcommunicable- diseases%3Futm_medium%3Dsocial%26utm_source%3Dfacebook%26utm_campaign%3Dsocial- sharebar-referred-desktop "Share on Facebook") [ ](https://twitter.com/intent/tweet?via=mnt&text=Communicable%20diseases%3A%20Types%2C%20symptoms%2C%20prevention%2C%20and%20treatment&url=https%3A%2F%2Fwww.medicalnewstoday.com%2Farticles%2Fcommunicable- diseases%3Futm_medium%3Dsocial%26utm_source%3Dtwitter%26utm_campaign%3Dsocial- sharebar-referred-desktop "Share on Twitter") ![](//i0.wp.com/post.medicalnewstoday.com/wp-content/uploads/2022/02/Michaela- Murphy-500x500-Bio.png?w=105&h=105) Medically reviewed by Michaela Murphy, PA-C — By Aaron Kandola — Updated on November 17, 2023 ## Latest news * [ ](https://www.medicalnewstoday.com/articles/wearable-tech-detects-cardiac-arrhythmia-before-onset) [ Wearable tech uses AI to detect cardiac arrhythmia 30 minutes before onset ](https://www.medicalnewstoday.com/articles/wearable-tech-detects-cardiac- arrhythmia-before-onset) * [ ](https://www.medicalnewstoday.com/articles/artificial-sweetener-neotame-may-have-potential-damage-gut-ibs) [ Artificial sweetener neotame may have potential to damage gut, lead to IBS ](https://www.medicalnewstoday.com/articles/artificial-sweetener-neotame-may- have-potential-damage-gut-ibs) * [ ](https://www.medicalnewstoday.com/articles/ai-tool-may-help-detect-cancer-few-minutes-drop-blood) [ AI tool may help detect cancer in a few minutes with a drop of blood ](https://www.medicalnewstoday.com/articles/ai-tool-may-help-detect-cancer- few-minutes-drop-blood) * [ ](https://www.medicalnewstoday.com/articles/regularly-eating-avocado-linked-to-lower-diabetes-risk-in-women) [ Regularly eating avocado linked to lower diabetes risk in women ](https://www.medicalnewstoday.com/articles/regularly-eating-avocado-linked- to-lower-diabetes-risk-in-women) * [ ](https://www.medicalnewstoday.com/articles/misplaced-your-keys-how-to-distinguish-dementia-from-normal-age-related-memory-loss) [ Misplaced your keys? How to distinguish dementia from normal age-related memory loss ](https://www.medicalnewstoday.com/articles/misplaced-your-keys- how-to-distinguish-dementia-from-normal-age-related-memory-loss) ### Related Coverage * [ ](https://www.medicalnewstoday.com/articles/317632?utm_source=ReadNext) [ What to know about airborne diseases ](https://www.medicalnewstoday.com/articles/317632?utm_source=ReadNext) Medically reviewed by [ Stacy Sampson, D.O. ](https://www.medicalnewstoday.com/reviewers) [ Airborne diseases transmit between people when droplets containing microorganisms remain suspended in the air, for example, after a person coughs… ](https://www.medicalnewstoday.com/articles/317632?utm_source=ReadNext) [ READ MORE ](https://www.medicalnewstoday.com/articles/317632?utm_source=ReadNext) * * [ ](https://www.medicalnewstoday.com/articles/317970?utm_source=ReadNext) [ What you need to know about fungal infections ](https://www.medicalnewstoday.com/articles/317970?utm_source=ReadNext) Medically reviewed by [ Kevin Martinez, M.D. ](https://www.medicalnewstoday.com/reviewers) [ Some fungi occur naturally in the body, and they can be helpful or harmful. An infection occurs when an invasive fungus becomes too much for the… ](https://www.medicalnewstoday.com/articles/317970?utm_source=ReadNext) [ READ MORE ](https://www.medicalnewstoday.com/articles/317970?utm_source=ReadNext) * [ ](https://www.medicalnewstoday.com/articles/septicemic-plague?utm_source=ReadNext) [ What to know about septicemic plague ](https://www.medicalnewstoday.com/articles/septicemic- plague?utm_source=ReadNext) [ Septicemic plague occurs when plague-causing bacteria directly cause infection in the blood or as a complication of other types of plague. 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Sygdommen kan overføres til mennesker via flåtbid, fra moder til foster i forbindelse med graviditet og via blodtransfusion. Babesia er almindelig i det nordøstlige USA. Parasitten forekommer også i flåter i Danmark. Babesiose Symptomerne på babesiose minder om malaria-symptomer, bl.a. feber, kulderystelser, muskel- og ledsmerter, blodmangel og blodig urin. Men det er også muligt at have sygdommen uden symptomer. Test for babesiose Blodudstrygning (negativt resultat udelukker ikke Babesia) FISH (Fluorescent In-Situ Hybridization) Western Blot, immunblot ELISA (IgM, IgA, IgG) PCR Patienten kan sagtens have babesiose, selvom der ikke er tegn på infektion i blodprøverne. Parasitten er svær at finde, og antistoftest og PCR for Babesia viser ikke altid tegn på parasitten, selvom patienten har babesiose. Bemærk, at der findes flere hundrede arter af diverse flåt-/vektorbårne sygdomme, hvorfor en test ikke kan udelukke sygdom, når den kun tester for få undertyper. Co-infektioner Ved klinisk mistanke om borreliose eller anden flåt-/vektorbåren sygdom er det en god idé at teste for Babesiose, da en del patienter med borreliose er smittet med flere såkaldte co-infektioner, heriblandt babesia. Eksempelvis kan der testes for: Borrelia Babesia Bartonella Mycoplasma Pneumoniae Mycoplasma Haemofelis Chlamydia Pneumoniae Rickettsia Ehrlichia Anaplasma Toxoplasma Francisella tularensis Syfilis TBE (Tick Borne Encephalitis) HIV/AIDS Kilder Eksterne henvisninger Humanbiologi Infektionssygdomme 2 tilfælde af Babesia-smitte fra mor til foster, kongenital Babesia: https://www.ncbi.nlm.nih.gov/pubmed/28992325 1 tilfælde af Babesia-smitte fra mor til foster, kongenital Babesia: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2687033/ Babesia-smitte via blodtransfusion: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3708872/ Co-infection with Babesia divergens and Anaplasma phagocytophilum in cattle (Bos taurus), Sweden: https://www.ncbi.nlm.nih.gov/pubmed/28869191	danish	0.899185
plant_light_pho/PMC9846745.txt	Skip to main content U.S. flagAn official website of the United States government Here's how you know NIH NLM LogoLog in Access keysNCBI HomepageMyNCBI HomepageMain ContentMain Navigation Preview improvements coming to the PMC website in October 2024. Learn More or Try it out now. Search PMC Full-Text Archive Search PMC Full-Text Archive Search in PMC Advanced Search User Guide Journal List Front Microbiol PMC9846745 As a library, NLM provides access to scientific literature. Inclusion in an NLM database does not imply endorsement of, or agreement with, the contents by NLM or the National Institutes of Health. Learn more: PMC Disclaimer \| PMC Copyright Notice Logo of frontmicrobio Front Microbiol. 2022; 13: 1112301. Published online 2023 Jan 4. doi: 10.3389/fmicb.2022.1112301 PMCID: PMC9846745 PMID: 36687569 Editorial: Algal photosynthesis Weimin Ma,corresponding author 1 , * Lu-Ning Liu,corresponding author 2 , * Qiang Wang,corresponding author 3 , * Deqiang Duanmu,corresponding author 4 , * and Bao-Sheng Qiucorresponding author 5 , * Author information Article notes Copyright and License information PMC Disclaimer Algae are a diverse group of predominantly aquatic photosynthetic organisms, including cyanobacteria, green algae and other eukaryotic algae. They account for more than 50% of the photosynthesis that takes place on Earth. Photosynthetic efficiency is generally higher in algae than in higher plants, because of a wide range of antenna pigments to harvest more solar energy and a variety of carbon dioxide-concentrating systems to increase carbon dioxide (CO2) concentration around ribulose-1,5-bisphosphate carboxylase/oxygenase (Rubisco). Apart from their natural role as primary producers in the global carbon cycle, algae also feature in biotechnology for the production of a range of high-value natural products and a sustainable source of protein. This Research Topic aims to gather knowledge on understanding the working mechanisms of efficient photosynthesis in algae and contains 12 papers of which 8 are original research, 3 are reviews or mini-reviews, and one is a perspective. The oligomeric states of cyanobacterial photosystem I (PSI) are diverse and at least consist of its monomer, dimer, trimer and tetramer. Such diversity is of significant importance for the survival of cyanobacterial cells under changing ecological environments. Chen, Liu, et al. review the implications of structural and oligomeric diversity among cyanobacterial PSI supercomplexes. Through biochemical and biophysical characterization and cryo-EM single-particle analysis, Chen, He, et al. further identified two novel oligomeric states of PSI, hexamer and octamer, from the filamentous cyanobacterium Anabaena sp. PCC 7120 grown in a low light environment. Du et al. construct a photo-bio-electrochemical system and in this system, purified reaction center-light harvesting (RC-LH) complex as a mediator can accept the electron from hydroxymethylferrocene (FcMeOH) and transfer to the overlapped fluorine-doped tin oxide (FTO) electrode, being composed of a FTO glass as the front electrode and a Pt-coated FTO glass as the counter electrode. This indicates that purified RC-LH complex can operate in this in vitro system. In addition, the activity and stability of PSI are significantly reduced and phototropic growth is significantly attenuated in a Chlamydomonas reinhardtii heme oxygenase 1 mutant (hmox1) that is deficient in bilin biosynthesis. Zhang et al. reveal the presence of an alternative bilin biosynthetic pathway independent of heme oxygenase 1 in the chloroplast by a hmox1 suppressor screening in Chlamydomonas cells. Photosynthetic ferredoxin:plastoquinone oxidoreductase (NDH-1) is predominantly, if not totally, located in the thylakoid membrane, accepts electrons from reduced ferredoxin by PSI, and participates in a variety of bio-energetic reactions, including cyclic electron transfer around PSI, CO2 acquisition, and cellular respiration. Mi describes the current advances and possible regulatory mechanisms of cyanobacterial NDH-1 in photosynthesis. Translocation of chloroplast-located genes to mitochondria or nucleus is considered to be a safety strategy that impedes mutation of photosynthetic genes and maintains their household function during evolution. Yu et al. propose that the organelle translocation strategy of photosynthetic NDH-1 genes during evolution is necessary to maintain the function of photosynthetic NDH-1 as an important antioxidant mechanism for efficient photosynthesis. Cyanobacteria use an inorganic carbon-concentrating mechanism (CCM) to increase inorganic carbon concentration around Rubisco for efficient CO2 fixation. Tang et al. reveal distinct molecular components and organization of CCM in thermophilic cyanobacteria using the comparative genomic analysis. Their findings provide insights into the CCM components of thermophilic cyanobacteria and fundamental knowledge for further research regarding photosynthetic improvement and biomass yield of thermophilic cyanobacteria with important biotechnological potentials. In addition, through structural analyses and molecular dynamic simulations, Min et al. reveal a previously unrecognized mechanism for the uncommon intermolecular Coenzyme A (CoA) transfer reaction, a key reaction intermediate for carbon fixation. This discovery not only broadens the knowledge on the catalytic mechanisms of CoA transferases, but also contributes to enzyme engineering of the 3-hydroxypropionate cycle for synthesis of high-value chemicals. During algal evolution, a variety of antioxidant mechanisms are developed to protect algal photosynthesis under harsh environment conditions. Iron-stress-induced protein A (IsiA) is the major chlorophyll-containing protein in iron-starved cyanobacteria, binding up to 50% of the chlorophyll in these cells. Jia et al. describe progress in understanding the regulation and functions of IsiA based on laboratory research using model cyanobacteria. Abscisic acid (ABA) is known as a stress related hormone and plays a critical role in the regulation of various types of stress responses. Yang et al. propose that ABA is synthesized in Neopyropia yezoensis possibly via the carotenoid, mevalonate (MVA) and 2-C-methyl-D-erythritol 4-phosphate (MEP) pathways and the up-regulation of antioxidase genes under high salinity is mediated by the ABA signaling pathway. A greater plasticity of metabolic pathways in response to the trophic growth mode is of significant importance for cyanobacterial growth and environmental acclimation. Muth-Pawlak et al. propose the regulatory patterning of carbon metabolism in cyanobacterial cells grown under different trophic modes (including low-carbon autotrophy, carbon-rich autotrophy, photomixotrophy and light-activated heterotrophy) via a comparative proteomic strategy. On Earth, far-red light derived photosynthesis occurs in cyanobacteria living in environments where visible light is strongly attenuated. Billi et al. identify the endolithic, extremotolerant cyanobacterium Chroococcidiopsis sp. CCMEE 010 capable of far-red light photoacclimation (FaRLiP) with a significantly reduced FaRLiP cluster, which has implications for the possibility of oxygenic photosynthesis on exoplanets. Collectively, this volume of the Research Topic provides exiting works in the area of the catalytic and antioxidant mechanisms of algal photosynthesis, ranging from the structure, biogenesis, metabolism, signaling, regulation and evolution of photosynthesis in algae to the molecular components and modules of efficient photosynthesis in algae. With the efforts of many researchers worldwide, the frontiers of this topic keep evolving at a rapid pace. Go to: Author contributions All authors listed have made a substantial, direct, and intellectual contribution to the work and approved it for publication. Go to: Acknowledgments We thank all the authors and reviewers that have contributed to this Research Topic. Go to: Funding Statement WM was supported by the National Natural Science Foundation of China (Grant No. 32170257). Go to: Conflict of interest The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest. Go to: Publisher's note All claims expressed in this article are solely those of the authors and do not necessarily represent those of their affiliated organizations, or those of the publisher, the editors and the reviewers. Any product that may be evaluated in this article, or claim that may be made by its manufacturer, is not guaranteed or endorsed by the publisher. Articles from Frontiers in Microbiology are provided here courtesy of Frontiers Media SA OTHER FORMATS PDF (90K) ACTIONS Cite Collections SHARE RESOURCES Similar articles Cited by other articles Links to NCBI Databases FOLLOW NCBI Connect with NLM National Library of Medicine 8600 Rockville Pike Bethesda, MD 20894 Web Policies FOIA HHS Vulnerability Disclosure Help Accessibility Careers NLM NIH HHS USA.gov Tell us what you think!Close	biology	952209	https://da.wikipedia.org/wiki/Kromosom%203%20%28mennesket%29	Kromosom 3 (mennesket)	Kromosom 3 er et af menneskets 23 kromosompar, og menneskets celler indeholder sædvanligvis to kopier af dette kromosom. Kromosom 3 omfatter mere end 198 millioner basepar (DNA's byggesten) og repræsenterer omkring 6.5% af det samlede DNA i cellerne. Identificering af generne på hvert kromosom er et aktivt område inden for genforskningen. Eftersom forskerne benytter forskellige metoder til at anslå antallet af gener på hvert kromsom, findes der varierende angivelser af antallet. Kromosom 3 indeholder sandsynligvis i omegnen af 1.026 til 1.085 protein kodende gener. Gener De følgende gener findes på kromosom 3: p-arm De følgende er nogle af de gener der findes på p-armen (den korte arm) af det mennesklige kromosom 3: ALAS1: aminolevulinate, delta-, synthase 1 APEH: kodende enzym Acylamino-acid-releasing enzym ARPP-21: Cyclic AMP-regulerende phosphoprotein, 21 kDa AZI2: kodende protein 5-azacytidine-induced protein 2 BRK1: SCAR/WAVE actin nucleating complex subunit BRPF1: bromodomain og PHD finger containing 1 BTD: biotinidase C3orf60/NDUFAF3: kodende enzym NADH dehydrogenase [ubiquinone] 1 alpha subcomplex assembly factor 3 CACNA2D3: calcium channel, voltage-dependent, alpha 2/delta subunit 3 CCR5: chemokine (C-C motif) receptor 5 CGGBP1: CGG triplet repeat binding protein 1 CNTN4: Contactin 4 COL7A1: Collagen, type VII, alpha 1 (epidermolysis bullosa, dystrophic, dominant og recessive) DCLK3: Doublecortin like kinase 3 EAF1: ELL associated factor 1 ENTPD3: ectonucleoside triphosphate diphosphohydrolase 3 FBXL2: F-box og leucine rich repeat protein 2 FOXP1: Forkhead Box Protein P1 GMPPB: GDP-mannose pyrophosphorylase B HEMK1: kodende protein HemK methyltransferase family member 1 HIGD1A: HIG1 domain family member 1A LARS2: leucyl-tRNA synthetase, mitochondrial LIMD1: LIM domain-containing protein 1 MITF: microphthalmia-associated transcription factor MLH1: mutL homolog 1, colon cancer, nonpolyposis type 2 (E. coli) MYRIP: Myosin VIIA og Rab interacting protein NBEAL2: Neurobeachin-like 2 NKTR: NK-tumor recognition protein NPRL2: Nitrogen permease regulator 2-like protein OXTR: oxytocin receptor PTHR1: parathyroid hormone receptor 1 QRICH1: kodende protein QRICH1, also known as Glutamine-rich protein 1, RBM6: RNA-binding protein 6 RPP14: Ribonuclease P protein subunit p14 SCN5A: sodium channel, voltage-gated, type V, alpha (long QT syndrome 3) SETD5: SET domain containing 5 SFMBT1: Scm-like with four mbt domains 1 SLC25A20: solute carrier family 25 (carnitine/acylcarnitine translocase), member 20 STT3B: catalytic subunit of the oligosaccharyltransferase complex SYNPR: synaptoporin TDGF1: Teratocarcinoma-derived growth factor 1 TMEM158: Transmembrane protein 158 TMIE: transmembrane inner ear TRAK1: trafficking kinesin-binding protein 1 TRANK1: kodende protein Tetratricopeptide repeat og ankyrin repeat containing 1 TUSC2: tumor suppressor candidate 2 UCN2: Urocortin-2 VGLL3: vestigial-like family member 3 VHL: von Hippel-Lindau tumor suppressor ZMYND10: zinc finger MYND-type containing 10 ZNF502: kodende protein Zinc finger protein 502 ZNF621: kodende protein Zinc finger protein 621 q-arm De følgende er nogle af de gener der findes på q-armen (den lange arm) af det mennesklige kromosom 3: ADIPOQ: adiponectin AMOTL2: kodende protein Angiomotin-like protein 2 ARHGAP31: Rho GRPase activating protein 31 CAMPD1: Camptodactyly CCDC80: Coiled-coil domain containing protein 80 CD200R1: Cell surface glycoprotein CD200 receptor 1 CLDND1: Claudin domain containing 1 CPN2: Carboxypeptidase N subunit 2 CPOX: coproporphyrinogen oxidase (coproporphyria, harderoporphyria) DPPA2: Developmental pluripotency associated 2 EAF2: ELL associated factor 2 EFCC1: EF-hand og coiled-coil domain containing 1 ETM1: Essential tremor 1 ETV5: ETS variant 5 FAM43A: family with sequence similarity 43 member A FAM162A: family with sequence similarity 162 member A GYG1: Glycogenin-1 HGD: homogentisate 1,2-dioxygenase (homogentisate oxidase) IFT122: intraflagellar transport gene 122 KIAA1257: KIAA1257 LMLN: kodende protein Leishmanolysin-like (metallopeptidase M8 family) LRRC15: leucine rich repeat containing 15 LSG1: large subunit GTPase 1 homolog MB21D2: kodende protein Mab-21 domain containing 2 MCCC1: methylcrotonoyl-Coenzym A carboxylase 1 (alpha) MYLK: Telokin NFKBIZ: NF-kappa-B inhibitor zeta PCCB: propionyl Coenzym A carboxylase, beta polypeptide PDCD10: programmeret cell død 10 PIK3CA: phosphoinositide-3-kinase, catalytic, alpha polypeptide PROSER1: Proline og serine rich protein 1 RAB7: RAB7, member RAS oncogene family RETNLB: resistin-like beta RHO: rhodopsin visual pigment RIOX2: Ribosomal oxygenase 2 SELT: Selenoprotein T SENP7: Sentrin-specific protease 7 SERP1: Stress-associated endoplasmic reticulum protein 1 SOX2: transcription factor SOX2OT: SOX2 overlapende transcript SRPRB: Signal recognition particle receptor subunit beta TM4SF1: Transmembrane 4 L6 family member 1 TRAT1: T-cell receptor-associated transmembrane adapter 1 USH3A: Usher syndrome 3A ZBED2: kodende protein Zinc finger BED-type containing 2 ZNF9: zinc finger protein 9 (a cellular retroviral nucleic acid binding protein) Relaterede sygdomme og uregelmæssigheder Nedenstående sygdomme har sammenhæng med varianter i gener, som hører til kromosom 3: Kilder Kromosomer Homo sapiens	danish	0.635924
plant_light_pho/Chlorophyll.txt	Chlorophyll is any of several related green pigments found in cyanobacteria and in the chloroplasts of algae and plants. Its name is derived from the Greek words χλωρός, khloros ("pale green") and φύλλον, phyllon ("leaf"). Chlorophyll allows plants to absorb energy from light. Chlorophylls absorb light most strongly in the blue portion of the electromagnetic spectrum as well as the red portion. Conversely, it is a poor absorber of green and near-green portions of the spectrum. Hence chlorophyll-containing tissues appear green because green light, diffusively reflected by structures like cell walls, is less absorbed. Two types of chlorophyll exist in the photosystems of green plants: chlorophyll a and b. History[edit] Chlorophyll was first isolated and named by Joseph Bienaimé Caventou and Pierre Joseph Pelletier in 1817. The presence of magnesium in chlorophyll was discovered in 1906, and was the first detection of that element in living tissue. After initial work done by German chemist Richard Willstätter spanning from 1905 to 1915, the general structure of chlorophyll a was elucidated by Hans Fischer in 1940. By 1960, when most of the stereochemistry of chlorophyll a was known, Robert Burns Woodward published a total synthesis of the molecule. In 1967, the last remaining stereochemical elucidation was completed by Ian Fleming, and in 1990 Woodward and co-authors published an updated synthesis. Chlorophyll f was announced to be present in cyanobacteria and other oxygenic microorganisms that form stromatolites in 2010; a molecular formula of C55H70O6N4Mg and a structure of (2-formyl)-chlorophyll a were deduced based on NMR, optical and mass spectra. Photosynthesis[edit] Absorbance spectra of free chlorophyll a (blue) and b (red) in a solvent. The spectra of chlorophyll molecules are slightly modified in vivo depending on specific pigment-protein interactions. Chlorophyll a Chlorophyll b Chlorophyll is vital for photosynthesis, which allows plants to absorb energy from light. Chlorophyll molecules are arranged in and around photosystems that are embedded in the thylakoid membranes of chloroplasts. In these complexes, chlorophyll serves three functions: The function of the vast majority of chlorophyll (up to several hundred molecules per photosystem) is to absorb light. Having done so, these same centers execute their second function: The transfer of that energy by resonance energy transfer to a specific chlorophyll pair in the reaction center of the photosystems. This specific pair performs the final function of chlorophylls: Charge separation, which produces the unbound protons (H) and electrons (e) that separately propel biosynthesis. The two currently accepted photosystem units are photosystem I and photosystem II, which have their own distinct reaction centres, named P700 and P680, respectively. These centres are named after the wavelength (in nanometers) of their red-peak absorption maximum. The identity, function and spectral properties of the types of chlorophyll in each photosystem are distinct and determined by each other and the protein structure surrounding them. The function of the reaction center of chlorophyll is to absorb light energy and transfer it to other parts of the photosystem. The absorbed energy of the photon is transferred to an electron in a process called charge separation. The removal of the electron from the chlorophyll is an oxidation reaction. The chlorophyll donates the high energy electron to a series of molecular intermediates called an electron transport chain. The charged reaction center of chlorophyll (P680) is then reduced back to its ground state by accepting an electron stripped from water. The electron that reduces P680 ultimately comes from the oxidation of water into O2 and H through several intermediates. This reaction is how photosynthetic organisms such as plants produce O2 gas, and is the source for practically all the O2 in Earth's atmosphere. Photosystem I typically works in series with Photosystem II; thus the P700 of Photosystem I is usually reduced as it accepts the electron, via many intermediates in the thylakoid membrane, by electrons coming, ultimately, from Photosystem II. Electron transfer reactions in the thylakoid membranes are complex, however, and the source of electrons used to reduce P700 can vary. The electron flow produced by the reaction center chlorophyll pigments is used to pump H ions across the thylakoid membrane, setting up a proton-motive force a chemiosmotic potential used mainly in the production of ATP (stored chemical energy) or to reduce NADP to NADPH. NADPH is a universal agent used to reduce CO2 into sugars as well as other biosynthetic reactions. Reaction center chlorophyll–protein complexes are capable of directly absorbing light and performing charge separation events without the assistance of other chlorophyll pigments, but the probability of that happening under a given light intensity is small. Thus, the other chlorophylls in the photosystem and antenna pigment proteins all cooperatively absorb and funnel light energy to the reaction center. Besides chlorophyll a, there are other pigments, called accessory pigments, which occur in these pigment–protein antenna complexes. Chemical structure[edit] Space-filling model of the chlorophyll a molecule Several chlorophylls are known. All are defined as derivatives of the parent chlorin by the presence of a fifth, ketone-containing ring beyond the four pyrrole-like rings. Most chlorophylls are classified as chlorins, which are reduced relatives of porphyrins (found in hemoglobin). They share a common biosynthetic pathway with porphyrins, including the precursor uroporphyrinogen III. Unlike hemes, which contain iron bound to the N4 center, most chlorophylls bind magnesium. The axial ligands attached to the Mg center are often omitted for clarity. Appended to the chlorin ring are various side chains, usually including a long phytyl chain (C20H39O). The most widely distributed form in terrestrial plants is chlorophyll a. The only difference between chlorophyll a and chlorophyll b is that the former has a methyl group where the latter has a formyl group. This difference causes a considerable difference in the absorption spectrum, allowing plants to absorb a greater portion of visible light. The structures of chlorophylls are summarized below: Chlorophyll a Chlorophyll b Chlorophyll c1 Chlorophyll c2 Chlorophyll d Chlorophyll f Molecular formula C55H72O5N4Mg C55H70O6N4Mg C35H30O5N4Mg C35H28O5N4Mg C54H70O6N4Mg C55H70O6N4Mg C2 group −CH3 −CH3 −CH3 −CH3 −CH3 −CHO C3 group −CH=CH2 −CH=CH2 −CH=CH2 −CH=CH2 −CHO −CH=CH2 C7 group −CH3 −CHO −CH3 −CH3 −CH3 −CH3 C8 group −CH2CH3 −CH2CH3 −CH2CH3 −CH=CH2 −CH2CH3 −CH2CH3 C17 group −CH2CH2COO−Phytyl −CH2CH2COO−Phytyl −CH=CHCOOH −CH=CHCOOH −CH2CH2COO−Phytyl −CH2CH2COO−Phytyl C17−C18 bond Single(chlorin) Single(chlorin) Double(porphyrin) Double(porphyrin) Single(chlorin) Single(chlorin) Occurrence Universal Mostly plants Various algae Various algae Cyanobacteria Cyanobacteria Structures of chlorophylls chlorophyll a chlorophyll b chlorophyll c1 chlorophyll c2 chlorophyll d chlorophyll f Chlorophyll e is reserved for a pigment that has been extracted from algae in 1966 but not chemically described. Besides the lettered chlorophylls, a wide variety of sidechain modifications to the chlorophyll structures are known in the wild. For example, Prochlorococcus, a cyanobacterium, uses 8-vinyl Chl a and b. Measurement of chlorophyll content[edit] Chlorophyll forms deep green solutions in organic solvents. Chlorophylls can be extracted from the protein into organic solvents. In this way, the concentration of chlorophyll within a leaf can be estimated. Methods also exist to separate chlorophyll a and chlorophyll b. In diethyl ether, chlorophyll a has approximate absorbance maxima of 430 nm and 662 nm, while chlorophyll b has approximate maxima of 453 nm and 642 nm. The absorption peaks of chlorophyll a are at 465 nm and 665 nm. Chlorophyll a fluoresces at 673 nm (maximum) and 726 nm. The peak molar absorption coefficient of chlorophyll a exceeds 10 M cm, which is among the highest for small-molecule organic compounds. In 90% acetone-water, the peak absorption wavelengths of chlorophyll a are 430 nm and 664 nm; peaks for chlorophyll b are 460 nm and 647 nm; peaks for chlorophyll c1 are 442 nm and 630 nm; peaks for chlorophyll c2 are 444 nm and 630 nm; peaks for chlorophyll d are 401 nm, 455 nm and 696 nm. Ratio fluorescence emission can be used to measure chlorophyll content. By exciting chlorophyll a fluorescence at a lower wavelength, the ratio of chlorophyll fluorescence emission at 705±10 nm and 735±10 nm can provide a linear relationship of chlorophyll content when compared with chemical testing. The ratio F735/F700 provided a correlation value of r 0.96 compared with chemical testing in the range from 41 mg m up to 675 mg m. Gitelson also developed a formula for direct readout of chlorophyll content in mg m. The formula provided a reliable method of measuring chlorophyll content from 41 mg m up to 675 mg m with a correlation r value of 0.95. Biosynthesis[edit] Main article: Chlorophyllide In some plants, chlorophyll is derived from glutamate and is synthesised along a branched biosynthetic pathway that is shared with heme and siroheme. Chlorophyll synthase is the enzyme that completes the biosynthesis of chlorophyll a: chlorophyllide a + phytyl diphosphate ⇌ {\displaystyle \rightleftharpoons } chlorophyll a + diphosphate This conversion forms an ester of the carboxylic acid group in chlorophyllide a with the 20-carbon diterpene alcohol phytol. Chlorophyll b is made by the same enzyme acting on chlorophyllide b. The same is known for chlorophyll d and f, both made from corresponding chlorophyllides ultimately made from chlorophyllide a. In Angiosperm plants, the later steps in the biosynthetic pathway are light-dependent. Such plants are pale (etiolated) if grown in darkness. Non-vascular plants and green algae have an additional light-independent enzyme and grow green even in darkness. Chlorophyll is bound to proteins. Protochlorophyllide, one of the biosynthetic intermediates, occurs mostly in the free form and, under light conditions, acts as a photosensitizer, forming free radicals, which can be toxic to the plant. Hence, plants regulate the amount of this chlorophyll precursor. In angiosperms, this regulation is achieved at the step of aminolevulinic acid (ALA), one of the intermediate compounds in the biosynthesis pathway. Plants that are fed by ALA accumulate high and toxic levels of protochlorophyllide; so do the mutants with a damaged regulatory system. Senescence and the chlorophyll cycle[edit] The process of plant senescence involves the degradation of chlorophyll: for example the enzyme chlorophyllase (EC 3.1.1.14) hydrolyses the phytyl sidechain to reverse the reaction in which chlorophylls are biosynthesised from chlorophyllide a or b. Since chlorophyllide a can be converted to chlorophyllide b and the latter can be re-esterified to chlorophyll b, these processes allow cycling between chlorophylls a and b. Moreover, chlorophyll b can be directly reduced (via 7-hydroxychlorophyll a) back to chlorophyll a, completing the cycle. In later stages of senescence, chlorophyllides are converted to a group of colourless tetrapyrroles known as nonfluorescent chlorophyll catabolites (NCC's) with the general structure: These compounds have also been identified in ripening fruits and they give characteristic autumn colours to deciduous plants. Distribution[edit] The chlorophyll maps show milligrams of chlorophyll per cubic meter of seawater each month. Places where chlorophyll amounts were very low, indicating very low numbers of phytoplankton, are blue. Places where chlorophyll concentrations were high, meaning many phytoplankton were growing, are yellow. The observations come from the Moderate Resolution Imaging Spectroradiometer (MODIS) on NASA's Aqua satellite. Land is dark gray, and places where MODIS could not collect data because of sea ice, polar darkness, or clouds are light gray. The highest chlorophyll concentrations, where tiny surface-dwelling ocean plants are thriving, are in cold polar waters or in places where ocean currents bring cold water to the surface, such as around the equator and along the shores of continents. It is not the cold water itself that stimulates the phytoplankton. Instead, the cool temperatures are often a sign that the water has welled up to the surface from deeper in the ocean, carrying nutrients that have built up over time. In polar waters, nutrients accumulate in surface waters during the dark winter months when plants cannot grow. When sunlight returns in the spring and summer, the plants flourish in high concentrations. Culinary use[edit] Synthetic chlorophyll is registered as a food additive colorant, and its E number is E140. Chefs use chlorophyll to color a variety of foods and beverages green, such as pasta and spirits. Absinthe gains its green color naturally from the chlorophyll introduced through the large variety of herbs used in its production. Chlorophyll is not soluble in water, and it is first mixed with a small quantity of vegetable oil to obtain the desired solution. Biological use[edit] A 2002 study found that "leaves exposed to strong light contained degraded major antenna proteins, unlike those kept in the dark, which is consistent with studies on the illumination of isolated proteins". This appeared to the authors as support for the hypothesis that "active oxygen species play a role in vivo" in the short-term behaviour of plants. See also[edit] Wikimedia Commons has media related to Chlorophyll. Bacteriochlorophyll, related compounds in phototrophic bacteria Chlorophyllin, a semi-synthetic derivative of chlorophyll Deep chlorophyll maximum Chlorophyll fluorescence, to measure plant stress	biology	2629445	https://sv.wikipedia.org/wiki/Typophyllum%20chlorophyllum	Typophyllum chlorophyllum	Typophyllum chlorophyllum är en insektsart som beskrevs av Bolívar, I. 1890. Typophyllum chlorophyllum ingår i släktet Typophyllum och familjen vårtbitare. Inga underarter finns listade i Catalogue of Life. Källor Vårtbitare chlorophyllum	swedish	0.496307
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Science & Tech ](/Science-Tech) [ Biographies ](/Biographies) [ Animals & Nature ](/Animals-Nature) [ Geography & Travel ](/Geography-Travel) [ Arts & Culture ](/Arts-Culture) [ Money ](/money) [ Videos ](/videos) __ [ algae ](https://www.britannica.com/science/algae) __ Table of Contents * [ Introduction & Top Questions ](/science/algae) * __ [ Physical and ecological features of algae ](/science/algae/Physical-and-ecological-features-of-algae) * [ Size range and diversity of structure ](/science/algae/Physical-and-ecological-features-of-algae#ref31712) * [ Distribution and abundance ](/science/algae/Physical-and-ecological-features-of-algae#ref31713) * [ Ecological and commercial importance ](/science/algae/Ecological-and-commercial-importance) * [ Toxicity ](/science/algae/Toxicity) * __ [ Form and function of algae ](/science/algae/Form-and-function-of-algae) * [ The algal cell ](/science/algae/Form-and-function-of-algae#ref31717) * [ Flagella ](/science/algae/Flagella) * [ Mitosis ](/science/algae/Flagella#ref31719) * [ Cellular respiration ](/science/algae/Flagella#ref31720) * [ Photosynthesis and light-absorbing pigments ](/science/algae/Photosynthesis-and-light-absorbing-pigments) * [ The effects of water on light absorption ](/science/algae/Photosynthesis-and-light-absorbing-pigments#ref272721) * [ Nutrient storage ](/science/algae/Nutrient-storage) * [ Alternative methods of nutrient absorption ](/science/algae/Nutrient-storage#ref272723) * [ Reproduction and life histories ](/science/algae/Reproduction-and-life-histories) * [ Evolution and paleontology of algae ](/science/algae/Evolution-and-paleontology-of-algae) * __ [ Classification of algae ](/science/algae/Classification-of-algae) * [ Diagnostic features ](/science/algae/Classification-of-algae#ref31726) * [ Annotated classification ](/science/algae/Classification-of-algae#ref31727) [ References & Edit History ](https://www.britannica.com/science/algae/additional-info) [ Quick Facts & Related Topics ](/facts/algae) [ Images & Videos ](https://www.britannica.com/science/algae/images-videos) [ ![“mermaid's wine glass” algae](https://cdn.britannica.com/57/13657-004-BEC2EC63/genus-algae-shape- wine-glass-mermaid-Acetabularia.jpg) ](https://cdn.britannica.com/57/13657-004-BEC2EC63/genus-algae-shape-wine- glass-mermaid-Acetabularia.jpg) [ ![sea lettuce](https://cdn.britannica.com/19/4019-004-B3672DFA/lactuca-green-algae- Ulva-sea-lettuce-tide.jpg) ](https://cdn.britannica.com/19/4019-004-B3672DFA/lactuca-green-algae-Ulva- sea-lettuce-tide.jpg) [ ![toothed wrack](https://cdn.britannica.com/71/5471-004-C5DDEB35/serratus-Fucus- wrack.jpg) ](https://cdn.britannica.com/71/5471-004-C5DDEB35/serratus-Fucus- wrack.jpg) [ ![Halimeda discoidea](https://cdn.britannica.com/69/5469-004-D417E170/Halimeda-discoidea- green-algae.jpg) ](https://cdn.britannica.com/69/5469-004-D417E170/Halimeda- discoidea-green-algae.jpg) [ ![Volvox](https://cdn.britannica.com/04/40604-004-AFBDAA4A/Colonies-thousands- cells-Volvox-globator-flagella-cell.jpg) ](https://cdn.britannica.com/04/40604-004-AFBDAA4A/Colonies-thousands-cells- Volvox-globator-flagella-cell.jpg) [ ![Investigate various types of phytoplankton, their anatomies, and their means of photosynthesis](https://cdn.britannica.com/70/73070-138-346BD2F6/plantlike- algae-water-oceans-bodies-organisms-diatoms.jpg?w=400&h=225&c=crop) __ ](/video/73070/plantlike-algae-water-oceans-bodies-organisms-diatoms) [ ![What causes algae blooms?](https://cdn.britannica.com/15/253815-138-6C1BA71C/algae- blooms-red-tides-botany.jpg?w=400&h=225&c=crop) __ ](/video/253815/algae- blooms-red-tides-botany) [ ![red tide](https://cdn.britannica.com/65/43765-004-13A5F389/Red-tide-Tampa-Bay- Florida-dinoflagellates-fish.jpg) ](https://cdn.britannica.com/65/43765-050-00423EC7/Red-tide-Tampa-Bay-Florida- dinoflagellates-fish.jpg) [ ![Turning sewage into green crude oil: How does it work?](https://cdn.britannica.com/37/179837-138-867F5CEB/efforts-crude-oil- algae.jpg?w=400&h=225&c=crop) __ ](/video/179837/efforts-crude-oil-algae) [ ![drying edible algae](https://cdn.britannica.com/65/11665-004-F234D43B/algae- beach-Hisanohama-Japan-Fukushima-ken.jpg) ](https://cdn.britannica.com/65/11665-004-F234D43B/algae-beach-Hisanohama- Japan-Fukushima-ken.jpg) For Students [ ![sea lettuce](https://cdn.britannica.com/19/4019-004-B3672DFA/lactuca- green-algae-Ulva-sea-lettuce-tide.jpg?w=200&h=200&c=crop) ](/summary/algae) [ algae summary ](/summary/algae) Quizzes [ ![Mushrooms growing in forest. $vegetable; fungus; mushroom; macrofungi; epigeous$](https://cdn.britannica.com/19/158119-131-8AF57DBB/porcini- mushrooms-number-Northern-Hemisphere-tree-species.jpg?w=200&h=200&c=crop) ](/quiz/science-at-random-quiz) [ Science at Random Quiz ](/quiz/science-at-random-quiz) [ ![Diversity among heteropterans. lace bug, termite bug, coreid bug, bat bug, toad bug, water strider, backswimmer, bedbug, stinkbug, water scorpion, plant bug, insects](https://cdn.britannica.com/31/51831-131-39C41686/Diversity- heteropterans-lace-bug-coreid-termite-bat.jpg?w=200&h=200&c=crop) ](/quiz/all- about-biology-quiz) [ All About Biology Quiz ](/quiz/all-about-biology-quiz) Related Questions * [ Are algae toxic? ](/question/Are-algae-toxic) * [ Why are algae important? ](/question/Why-are-algae-important) Read Next [ ![Army of deadly Microbes](https://cdn.britannica.com/60/196560-131-C44ACE30/Army- Microbes.jpg?w=200&h=200&c=crop) ](/list/meet-the-microbes-5-tiny-protozoans- and-algae) [ Meet the Microbes: 5 Tiny Protozoans and Algae ](/list/meet-the- microbes-5-tiny-protozoans-and-algae) [ ![algae. Lake Erie. Dead fish in harmful algal bloom along the southeast Lake Erie shore of Pelee Island, Ontario, Canada, 5 miles north of the international line Aug. 19, 2011. Toxic algae blooms, drinking water, 4th largest of 5 Great Lakes](https://cdn.britannica.com/47/178347-131-DD740A7C/algae-fish-Lake-Erie- bloom-shore-line-Aug-19-2011.jpg?w=200&h=200&c=crop) ](/story/harmful-algal- blooms) [ Harmful Algal Blooms ](/story/harmful-algal-blooms) Discover [ ![Community service - volunteers picking up garbage in a park during a spring cleanup. Environmentalism](https://cdn.britannica.com/41/193741-050-9F292343/Volunteers- garbage-park-spring-cleanup.jpg?w=200&h=200&c=crop) ](/story/a-timeline-of- environmental-history) [ A Timeline of Environmental History ](/story/a-timeline-of-environmental- history) [ ![King Cobra snake in Malaysia. $reptile$](https://cdn.britannica.com/68/152568-131-E6B869A4/King-cobra- world-snake.jpg?w=200&h=200&c=crop) ](/list/9-of-the-worlds-deadliest-snakes) [ 9 of the World’s Deadliest Snakes ](/list/9-of-the-worlds-deadliest-snakes) [ ![Close up of books. Stack of books, pile of books, literature, reading. Homepage 2010, arts and entertainment, history and society](https://cdn.britannica.com/55/142355-131-EFF621AF/books-Stack- literature-pile-reading-entertainment-society-2010.jpg?w=200&h=200&c=crop) ](/list/12-novels-considered-the-greatest-book-ever-written) [ 12 Novels Considered the “Greatest Book Ever Written” ](/list/12-novels- considered-the-greatest-book-ever-written) [ ![Shadow of a man holding large knife in his hand inside of some dark, spooky buiding](https://cdn.britannica.com/51/212551-131-CCA62CB1/Shadow-man- spooky-building-knife.jpg?w=200&h=200&c=crop) ](/list/7-of-historys-most- notorious-serial-killers) [ 7 of History's Most Notorious Serial Killers ](/list/7-of-historys-most- notorious-serial-killers) [ ![The Titanic. $disasters, ships$](https://cdn.britannica.com/79/4679-131-183F83F8/Titanic.jpg?w=200&h=200&c=crop) ](/story/timeline-of-the-titanics-final-hours) [ Timeline of the _Titanic_ ’s Final Hours ](/story/timeline-of-the-titanics- final-hours) [ ![Cheetah $Acinonyx jubatus$ standing on rock, side view, Masai Mara National Reserve, Kenya](https://cdn.britannica.com/00/152300-131-FEE1926E/Cheetah-Maasai-Mara- National-Reserve-Kenya.jpg?w=200&h=200&c=crop) ](/list/the-fastest-animals-on- earth) [ The Fastest Animals on Earth ](/list/the-fastest-animals-on-earth) [ ![William Shakespeare](https://cdn.britannica.com/26/189426-131-EFA4D7E9/William- Shakespeare.jpg?w=200&h=200&c=crop) ](/story/400th-anniversary-of- shakespeares-death) [ The Death of Shakespeare ](/story/400th-anniversary-of-shakespeares-death) __ __ Contents [ Home ](/) [ Science ](/browse/Science) [ Biology ](/browse/Biology) [ Fungi, Protists & Viruses ](/browse/Fungi-Protists-Viruses) # Toxicity [ ![sea sparkle](https://cdn.britannica.com/70/30670-004-9F8354EF/species- dinoflagellate-substances-sea-sparkle-algae-Noctiluca.jpg?w=300) __ ](https://cdn.britannica.com/70/30670-004-9F8354EF/species-dinoflagellate- substances-sea-sparkle-algae-Noctiluca.jpg) [ sea sparkle ](https://cdn.britannica.com/70/30670-004-9F8354EF/species- dinoflagellate-substances-sea-sparkle-algae-Noctiluca.jpg) A species of dinoflagellate known as _Noctiluca scintillans_ , commonly called sea sparkle, is a type of algae that can aggregate into an algal bloom, producing substances that are potentially toxic to marine life. (more) Some algae can be harmful to humans. A few [ species ](https://www.britannica.com/science/species-taxon) produce toxins that may be concentrated in [ shellfish ](https://www.britannica.com/animal/shellfish- animal) and finfish, which are thereby rendered unsafe or poisonous for human [ consumption ](https://www.merriam-webster.com/dictionary/consumption) . The [ dinoflagellates ](https://www.britannica.com/science/dinoflagellate) (class Dinophyceae) are the most [ notorious ](https://www.merriam- webster.com/dictionary/notorious) producers of toxins. [ Paralytic ](https://www.britannica.com/science/paralytic-shellfish-poisoning) [ shellfish poisoning ](https://www.britannica.com/science/shellfish-poisoning) is caused by the neurotoxin [ saxitoxin ](https://www.britannica.com/science/saxitoxin) or any of at least 12 related [ compounds ](https://www.merriam-webster.com/dictionary/compounds) , often produced by the dinoflagellates _Alexandrium tamarense_ and _Gymnodinium catenatum_ . Diarrheic shellfish poisoning is caused by okadaic acids that are produced by several kinds of algae, especially species of _Dinophysis_ . Neurotoxic shellfish poisoning, caused by toxins produced in _ [ Gymnodinium breve ](https://www.britannica.com/science/Gymnodinium-breve) _ , is notorious for fish kills and shellfish poisoning along the coast of Florida in the [ United States ](https://www.britannica.com/place/United-States) . When the [ red tide ](https://www.britannica.com/science/red-tide) blooms are blown to shore, wind-sprayed toxic cells can cause health problems for humans and other animals that breathe the air. Not all shellfish poisons are produced by dinoflagellates. Amnesic shellfish poisoning is caused by domoic acid produced by diatoms (class Bacillariophyceae), such as _Nitzschia pungens_ and _N. pseudodelicatissima_ . Symptoms of this poisoning in humans progress from abdominal cramps to vomiting to memory loss to disorientation and finally to death. [ Ciguatera ](https://www.britannica.com/science/ciguatera) is a disease of humans caused by consumption of [ tropical fish ](https://www.britannica.com/animal/tropical-fish) that have fed on the alga _Gambierdiscus_ or _Ostreopsis_ . Unlike many other algal toxins, [ ciguatoxin ](https://www.britannica.com/science/ciguatoxin) and maitotoxin are concentrated in finfish rather than shellfish. Levels as low as one part per billion in fish can be sufficient to cause human intoxication. Several algae produce toxins lethal to [ fish ](https://www.britannica.com/animal/fish) . _ [ Prymnesium parvum ](https://www.britannica.com/science/Prymnesium-parvum) _ (class Prymnesiophyceae) has caused massive die-offs in ponds where fish are [ cultured ](https://www.merriam-webster.com/dictionary/cultured) , and _Chrysochromulina polylepis_ (class Prymnesiophyceae) has caused major fish kills along the coasts of the [ Scandinavian ](https://www.britannica.com/place/Scandinavia) countries. Other algae, such as _Heterosigma_ (class Raphidophyceae) and _Dictyocha_ (class Dictyochophyceae), are suspected fish killers as well. [ ![Streptococcus pyogenes](https://cdn.britannica.com/26/123226-050-0DFE8193/bacteria- Photomicrograph-Streptococcus-pyogenes-scarlet-fever.jpg) More From Britannica microbiology: Algae ](/science/microbiology/Types-of- microorganisms#ref498568) Algae can cause human [ diseases ](https://www.britannica.com/science/human- disease) by directly attacking human tissues, although the frequency is rare. Protothecosis, caused by the chloroplast-lacking green alga, _ Prototheca _ , can result in waterlogged skin lesions, in which the pathogen grows. _Prototheca_ organisms may eventually spread to the lymph glands from these subcutaneous lesions. _Prototheca_ is also believed to be responsible for ulcerative [ dermatitis ](https://www.britannica.com/science/dermatitis) in the [ platypus ](https://www.britannica.com/animal/platypus) . Very rarely, similar infections in humans and cattle can be caused by chloroplast-bearing species of [ _Chlorella_ ](https://www.britannica.com/science/Chlorella) . Some seaweeds contain high concentrations of [ arsenic ](https://www.britannica.com/science/arsenic) and when eaten may cause [ arsenic poisoning ](https://www.britannica.com/science/arsenic-poisoning) . The brown alga _Hizikia_ , for example, contains [ sufficient ](https://www.britannica.com/dictionary/sufficient) arsenic to be used as a rat poison.	biology	2420433	https://sv.wikipedia.org/wiki/Lamprologus%20kungweensis	Lamprologus kungweensis	Lamprologus kungweensis är en fiskart som beskrevs av Poll, 1956. Lamprologus kungweensis ingår i släktet Lamprologus och familjen Cichlidae. IUCN kategoriserar arten globalt som akut hotad. Inga underarter finns listade i Catalogue of Life. Källor Externa länkar Abborrartade fiskar kungweensis	swedish	0.977593
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[ Browse ](/browse "Hidden") 2. [ Blogs ](/browse/blogs "Hidden") 3. Blog Viewer # Blog Viewer ## Nature at Your Desk: The Hidden Health Boosts of Office Plants #### ![](https://d2x5ku95bkycr3.cloudfront.net/App_Themes/Common/images/profile/1_200.png) By [ SRAI News ](https://www.srainternational.org/people/srai-news) posted 12-13-2023 01:26 PM [ 0 ](javascript:void$0$ "Nbr of recommenders") [ Recommend ](javascript:WebForm_DoPostBackWithOptions$new WebForm_PostBackOptions\("ctl00$MainCopy$ctl03$ucPermission$BlogItemRating$lbLike", "", true, "", "", false, true$\) "Recommend this item.") ![](https://higherlogicdownload.s3.amazonaws.com/SRAINTERNATIONAL/UploadedImages/Fcl0AV5kSUWrpfi0wGoX_Desk With Plants.jpeg) ## Nature at Your Desk: The Hidden Health Boosts of Office Plants Interior landscapes such as office spaces can impact creativity and productivity by using live plants to create urban green spaces. Research on plants in workplaces shows there are numerous benefits to incorporating indoor plants. Here are two distinct advantages of designing a green space in your workplace. Health Benefits : * _Improved Air Quality_ : Plants act as natural air purifiers by absorbing pollutants and releasing oxygen during photosynthesis. They can help remove toxins such as benzene, formaldehyde, and trichloroethylene from the air, creating a healthier indoor environment. * _Humidity Regulation_ : When plants release moisture through a process called transpiration, they help maintain optimal humidity levels in indoor spaces. This is particularly beneficial in environments with air conditioning or heating systems that tend to dry out the air. * _Stress Reduction_ : The presence of plants has been linked to reduced stress levels and increased feelings of well-being. Greenery in the office can create a more relaxed atmosphere and contribute to a positive work environment. * _Increased Productivity_ : Studies have suggested that having plants in the workplace can enhance productivity and concentration. The visual appeal of plants and the connection to nature may help reduce mental fatigue and improve focus. * _Noise Reduction_ : Some larger plants can absorb and diffract sound waves, contributing to a quieter and more peaceful work setting. This is especially helpful in open office layouts where noise can be a challenge. Aesthetic Benefits : * _Enhanced Aesthetics_ : Live plants add a natural and aesthetically pleasing element to the office decor. They work to soften the harsh lines of modern office furniture and contribute to a more visually appealing workspace. * _Biophilic Design_ : Incorporating elements of nature, such as live plants, aligns with the principles of biophilic design. This design philosophy recognizes the innate human need for connection with nature and seeks to integrate natural elements into the built environment. * _Customizable Decor_ : Plants come in various shapes, sizes, and colors, allowing for a wide range of design possibilities. Businesses can tailor office decor to match the company's branding or employees’ preferences. When selecting plants for an office environment consider factors such as lighting conditions, maintenance requirements, and potential allergies among employees. Regular care, watering, and providing adequate light will contribute to the vigor of the plants and maximize their benefits in the workplace. You could network with colleagues for backup plant care. Studies show that live indoor plants or window views of green spaces have a significant positive effect on workers' perceptions and job satisfaction compared to workplaces without them. The workplace is also perceived as a healthy and productive space when interior plants are present. Plants Best Suited for Offices : * Snake Plant ( _Sansevieria_ ): Known for its air-purifying qualities and low maintenance requirements. * Spider Plant ( _Chlorophytum comosum_ ): A resilient plant that helps improve air quality and is easy to care for. * ZZ Plant ( _Zamioculcas zamiifolia_ ): Tolerant of low light conditions and requires minimal watering. * Pothos ( _Epipremnum aureum_ ): Versatile and adaptable, able to thrive in various light conditions. * Peace Lily ( _Spathiphyllum_ ): Known for its elegant white blooms and effective air purification. * Rubber Plant ( _Ficus elastica_ ): Adds a touch of greenery and is relatively low maintenance. * Weeping Fig ( _Ficus benjamina_ ): Versatile low maintenance, drought resistant plant suitable for office spaces. * Succulents * Select Orchids * Select Ferns * * * Authored by Rani Muthukrishnan , Director of Research Compliance Texas A&M University San Antonio [ #December2023 ](https://www.srainternational.org/search?s=%23December2023&executesearch=true) 0 comments 5 views ## Permalink ![SRAI-Logo- White.png](https://higherlogicdownload.s3.amazonaws.com/SRAINTERNATIONAL/47435d22-1632-4f94-ae7e-26ffbad74c98/UploadedImages/Logos/SRAI- Logo-White.png) Society of Research Administrators International 1560 Wilson Blvd, Suite 310 Arlington, VA 22209 [ [email protected] ](mailto:[email protected]) Phone: +1 703-741-0140 [ __ ](https://www.facebook.com/SocResAdminINTL) [ __ ](https://twitter.com/SocietyRAIntl) [ __ ](https://www.linkedin.com/company/society-of-research-administrators- international/) [ Partner with SRAI ](partnerships) [ Donate to SRAI ](support-society) [ Career Center ](career) [ Privacy Statement ](privacy) [ Online Community Rules & Etiquette ](http://www.srainternational.org/termsandconditions) Copyright ©2024 SRA International. All rights reserved. Site by [ eConverse Media ](http://econversemedia.com) [ Powered by Higher Logic ](http://www.higherlogic.com) ![](https://d2x5ku95bkycr3.cloudfront.net/img/loading.gif)	biology	4595713	https://sv.wikipedia.org/wiki/Passiflora%20punctata	Passiflora punctata	Passiflora punctata är en passionsblomsväxtart som beskrevs av Carl von Linné. Passiflora punctata ingår i släktet passionsblommor, och familjen passionsblomsväxter. Inga underarter finns listade i Catalogue of Life. Bildgalleri Källor Externa länkar Passionsblommor punctata	swedish	1.32851
more_than_two_sexes/sexualreproduction.txt	Skip to content [ ![Logo for OPEN SLCC](https://slcc.pressbooks.pub/app/uploads/2020/04/SLCClogo- BrandColors2015.png) ](https://slcc.pressbooks.pub/) Toggle Menu Primary Navigation * [ Home ](https://slcc.pressbooks.pub/collegebiology1) * [ Read ](https://slcc.pressbooks.pub/collegebiology1/front-matter/introduction/) * [ Sign in ](https://slcc.pressbooks.pub/collegebiology1/wp-login.php?redirect_to=https%3A%2F%2Fslcc.pressbooks.pub%2Fcollegebiology1%2Fchapter%2Fsexual-reproduction%2F) * Search in book: Search Want to create or adapt books like this? [ Learn more ](https://pressbooks.com/adapt-open- textbooks?utm_source=book&utm_medium=banner&utm_campaign=bbc) about how Pressbooks supports open publishing practices. [ ](javascript:void) Book Contents Navigation Contents 1. [ Introduction ](https://slcc.pressbooks.pub/collegebiology1/front-matter/introduction/) 2. I . What is Life? 1. [ 1.1 Major Groups of Living Organisms ](https://slcc.pressbooks.pub/collegebiology1/chapter/chapter-1-what-is-life/) 1. [ Groups of Life ](https://slcc.pressbooks.pub/collegebiology1/chapter/chapter-1-what-is-life/#chapter-40-section-1) 2. [ Properties of all cells ](https://slcc.pressbooks.pub/collegebiology1/chapter/chapter-1-what-is-life/#chapter-40-section-2) 2. [ 1.2 Levels of Biological Organization ](https://slcc.pressbooks.pub/collegebiology1/chapter/1-2-levels-of-biological-organization/) 1. [ Organization from Atoms to Cells ](https://slcc.pressbooks.pub/collegebiology1/chapter/1-2-levels-of-biological-organization/#chapter-45-section-1) 2. [ Cells ](https://slcc.pressbooks.pub/collegebiology1/chapter/1-2-levels-of-biological-organization/#chapter-45-section-2) 3. [ Organization from Cells to Organisms ](https://slcc.pressbooks.pub/collegebiology1/chapter/1-2-levels-of-biological-organization/#chapter-45-section-3) 4. [ Organization from Organisms to the Biosphere ](https://slcc.pressbooks.pub/collegebiology1/chapter/1-2-levels-of-biological-organization/#chapter-45-section-4) 3. [ 1.3 Properties of Life ](https://slcc.pressbooks.pub/collegebiology1/chapter/1-3-properties-of-life/) 1. [ Properties of Cellular Life ](https://slcc.pressbooks.pub/collegebiology1/chapter/1-3-properties-of-life/#chapter-47-section-1) 3. II . The Process of Science 1. [ 2.1 Scientific Inquiry ](https://slcc.pressbooks.pub/collegebiology1/chapter/chapter-1/) 4. III . Evolution 1 1. [ 3.1 Darwin and Natural Selection ](https://slcc.pressbooks.pub/collegebiology1/chapter/evolution/) 1. [ Pre-Darwinian Ideas ](https://slcc.pressbooks.pub/collegebiology1/chapter/evolution/#chapter-160-section-1) 2. [ Charles Darwin ](https://slcc.pressbooks.pub/collegebiology1/chapter/evolution/#chapter-160-section-2) 3. [ Natural Selection ](https://slcc.pressbooks.pub/collegebiology1/chapter/evolution/#chapter-160-section-3) 2. [ 3.2 Variation and Adaptation ](https://slcc.pressbooks.pub/collegebiology1/chapter/variation-adaptation/) 3. [ 3.3 Adaptive Evolution ](https://slcc.pressbooks.pub/collegebiology1/chapter/adaptive-evolution/) 1. [ Stabilizing Selection ](https://slcc.pressbooks.pub/collegebiology1/chapter/adaptive-evolution/#chapter-1608-section-1) 2. [ Directional Selection ](https://slcc.pressbooks.pub/collegebiology1/chapter/adaptive-evolution/#chapter-1608-section-2) 3. [ Diversifying Selection ](https://slcc.pressbooks.pub/collegebiology1/chapter/adaptive-evolution/#chapter-1608-section-3) 4. [ No Perfect Organisms ](https://slcc.pressbooks.pub/collegebiology1/chapter/adaptive-evolution/#chapter-1608-section-4) 4. [ 3.4 Evidence for Evolution ](https://slcc.pressbooks.pub/collegebiology1/chapter/evidence-for-evolution/) 1. [ Fossils ](https://slcc.pressbooks.pub/collegebiology1/chapter/evidence-for-evolution/#chapter-1611-section-1) 2. [ Anatomy ](https://slcc.pressbooks.pub/collegebiology1/chapter/evidence-for-evolution/#chapter-1611-section-2) 3. [ Embryology ](https://slcc.pressbooks.pub/collegebiology1/chapter/evidence-for-evolution/#chapter-1611-section-3) 4. [ Biogeography ](https://slcc.pressbooks.pub/collegebiology1/chapter/evidence-for-evolution/#chapter-1611-section-4) 5. [ Molecular Biology ](https://slcc.pressbooks.pub/collegebiology1/chapter/evidence-for-evolution/#chapter-1611-section-5) 6. [ Direct Observations of Evolution ](https://slcc.pressbooks.pub/collegebiology1/chapter/evidence-for-evolution/#chapter-1611-section-6) 5. IV . Fundamentals of Chemistry 1. [ 4.1 The Composition of Organisms ](https://slcc.pressbooks.pub/collegebiology1/chapter/4-1-the-composition-of-organisms/) 2. [ 4.2 The Structure of Atoms ](https://slcc.pressbooks.pub/collegebiology1/chapter/4-2-the-structure-of-atoms/) 1. [ Atomic Structure ](https://slcc.pressbooks.pub/collegebiology1/chapter/4-2-the-structure-of-atoms/#chapter-125-section-1) 2. [ Atomic Number ](https://slcc.pressbooks.pub/collegebiology1/chapter/4-2-the-structure-of-atoms/#chapter-125-section-2) 3. [ Electron Shells and the Bohr Model ](https://slcc.pressbooks.pub/collegebiology1/chapter/4-2-the-structure-of-atoms/#chapter-125-section-3) 3. [ 4.3 Covalent Bonds ](https://slcc.pressbooks.pub/collegebiology1/chapter/4-3-chemical-bonds/) 1. [ Chemical Bonds ](https://slcc.pressbooks.pub/collegebiology1/chapter/4-3-chemical-bonds/#chapter-132-section-1) 2. [ Covalent Bonds ](https://slcc.pressbooks.pub/collegebiology1/chapter/4-3-chemical-bonds/#chapter-132-section-2) 4. [ 4.4 Non-covalent bonds ](https://slcc.pressbooks.pub/collegebiology1/chapter/4-4-non-covalent-bonds/) 1. [ Ionic Bonds ](https://slcc.pressbooks.pub/collegebiology1/chapter/4-4-non-covalent-bonds/#chapter-157-section-1) 2. [ Hydrogen Bonds ](https://slcc.pressbooks.pub/collegebiology1/chapter/4-4-non-covalent-bonds/#chapter-157-section-2) 3. [ Van Der Waals Interactions ](https://slcc.pressbooks.pub/collegebiology1/chapter/4-4-non-covalent-bonds/#chapter-157-section-3) 6. V . Life in Water 1. [ 5.1 Water is Polar ](https://slcc.pressbooks.pub/collegebiology1/chapter/5-1-the-polar-nature-of-water/) 2. [ 5.2 Water's Interactions with Other Molecules ](https://slcc.pressbooks.pub/collegebiology1/chapter/5-2-waters-interactions-with-other-molecules/) 1. [ Water’s Solvent Properties ](https://slcc.pressbooks.pub/collegebiology1/chapter/5-2-waters-interactions-with-other-molecules/#chapter-269-section-1) 2. [ Water’s Cohesive and Adhesive Properties ](https://slcc.pressbooks.pub/collegebiology1/chapter/5-2-waters-interactions-with-other-molecules/#chapter-269-section-2) 3. [ 5.3 Other Properties of Water ](https://slcc.pressbooks.pub/collegebiology1/chapter/5-3-properties-of-water/) 1. [ Water’s States: Gas, Liquid, and Solid ](https://slcc.pressbooks.pub/collegebiology1/chapter/5-3-properties-of-water/#chapter-196-section-1) 2. [ Water’s High Heat Capacity ](https://slcc.pressbooks.pub/collegebiology1/chapter/5-3-properties-of-water/#chapter-196-section-2) 3. [ Water’s Heat of Vaporization ](https://slcc.pressbooks.pub/collegebiology1/chapter/5-3-properties-of-water/#chapter-196-section-3) 4. [ 5.4 pH, Acids, and Bases ](https://slcc.pressbooks.pub/collegebiology1/chapter/5-4-ph-acids-and-bases/) 1. [ Dissociation of Water ](https://slcc.pressbooks.pub/collegebiology1/chapter/5-4-ph-acids-and-bases/#chapter-198-section-1) 2. [ Acids and Bases ](https://slcc.pressbooks.pub/collegebiology1/chapter/5-4-ph-acids-and-bases/#chapter-198-section-2) 3. [ The pH Scale ](https://slcc.pressbooks.pub/collegebiology1/chapter/5-4-ph-acids-and-bases/#chapter-198-section-3) 4. [ Buffers ](https://slcc.pressbooks.pub/collegebiology1/chapter/5-4-ph-acids-and-bases/#chapter-198-section-4) 7. VI . Carbon and Biomolecules 1. [ 6.1 Hydrocarbons ](https://slcc.pressbooks.pub/collegebiology1/chapter/6-1-hydrocarbons/) 1. [ Carbon ](https://slcc.pressbooks.pub/collegebiology1/chapter/6-1-hydrocarbons/#chapter-287-section-1) 2. [ Hydrocarbons ](https://slcc.pressbooks.pub/collegebiology1/chapter/6-1-hydrocarbons/#chapter-287-section-2) 2. [ 6.2 Functional Groups ](https://slcc.pressbooks.pub/collegebiology1/chapter/6-2-functional-groups/) 1. [ Functional Groups ](https://slcc.pressbooks.pub/collegebiology1/chapter/6-2-functional-groups/#chapter-285-section-1) 3. [ 6.3 Synthesis of Biological Macromolecules ](https://slcc.pressbooks.pub/collegebiology1/chapter/6-3-synthesis-of-biological-macromolecules/) 1. [ Dehydration Synthesis ](https://slcc.pressbooks.pub/collegebiology1/chapter/6-3-synthesis-of-biological-macromolecules/#chapter-294-section-1) 2. [ Hydrolysis ](https://slcc.pressbooks.pub/collegebiology1/chapter/6-3-synthesis-of-biological-macromolecules/#chapter-294-section-2) 8. VII . Proteins 1. [ 7.1 Protein Function ](https://slcc.pressbooks.pub/collegebiology1/chapter/7-1-protein-function/) 2. [ 7.2 Amino Acids ](https://slcc.pressbooks.pub/collegebiology1/chapter/7-2-amino-acids/) 3. [ 7.3 Protein Structure ](https://slcc.pressbooks.pub/collegebiology1/chapter/7-3-protein-structure/) 1. [ Protein Structure ](https://slcc.pressbooks.pub/collegebiology1/chapter/7-3-protein-structure/#chapter-355-section-1) 4. [ 7.4 Protein Folding, Regulation, and Denaturation ](https://slcc.pressbooks.pub/collegebiology1/chapter/7-4-protein-folding-regulation-and-denaturation/) 1. [ Protein Folding ](https://slcc.pressbooks.pub/collegebiology1/chapter/7-4-protein-folding-regulation-and-denaturation/#chapter-392-section-1) 2. [ Protein Regulation ](https://slcc.pressbooks.pub/collegebiology1/chapter/7-4-protein-folding-regulation-and-denaturation/#chapter-392-section-2) 3. [ Denaturation ](https://slcc.pressbooks.pub/collegebiology1/chapter/7-4-protein-folding-regulation-and-denaturation/#chapter-392-section-3) 9. VIII . Enzymes 1. [ 8.1 Metabolic Pathways ](https://slcc.pressbooks.pub/collegebiology1/chapter/8-1-metabolic-pathways/) 1. [ Metabolism ](https://slcc.pressbooks.pub/collegebiology1/chapter/8-1-metabolic-pathways/#chapter-418-section-1) 2. [ Anabolic and Catabolic Pathways ](https://slcc.pressbooks.pub/collegebiology1/chapter/8-1-metabolic-pathways/#chapter-418-section-2) 2. [ 8.2 Enzyme Function ](https://slcc.pressbooks.pub/collegebiology1/chapter/8-2-enzyme-function/) 1. [ What is an Enzyme? ](https://slcc.pressbooks.pub/collegebiology1/chapter/8-2-enzyme-function/#chapter-420-section-1) 2. [ Enzyme Active Site and Substrate Specificity ](https://slcc.pressbooks.pub/collegebiology1/chapter/8-2-enzyme-function/#chapter-420-section-2) 3. [ Induced Fit and Enzyme Function ](https://slcc.pressbooks.pub/collegebiology1/chapter/8-2-enzyme-function/#chapter-420-section-3) 3. [ 8.3 Enzyme Activity ](https://slcc.pressbooks.pub/collegebiology1/chapter/8-3-molecular-regulation-of-enzymes/) 1. [ Environmental Influences on Enzyme Activity ](https://slcc.pressbooks.pub/collegebiology1/chapter/8-3-molecular-regulation-of-enzymes/#chapter-422-section-1) 2. [ Enzyme Inhibition ](https://slcc.pressbooks.pub/collegebiology1/chapter/8-3-molecular-regulation-of-enzymes/#chapter-422-section-2) 3. [ Cofactors and Coenzymes ](https://slcc.pressbooks.pub/collegebiology1/chapter/8-3-molecular-regulation-of-enzymes/#chapter-422-section-3) 4. [ Enzyme Compartmentalization ](https://slcc.pressbooks.pub/collegebiology1/chapter/8-3-molecular-regulation-of-enzymes/#chapter-422-section-4) 4. [ 8.4 Feedback Inhibition of Metabolic Pathways ](https://slcc.pressbooks.pub/collegebiology1/chapter/8-4-feedback-inhibition-of-metabolic-pathways/) 1. [ Feedback Inhibition ](https://slcc.pressbooks.pub/collegebiology1/chapter/8-4-feedback-inhibition-of-metabolic-pathways/#chapter-424-section-1) 10. IX . Lipids and Membranes 1. [ 9.1 Lipids ](https://slcc.pressbooks.pub/collegebiology1/chapter/lipids/) 1. [ Lipids ](https://slcc.pressbooks.pub/collegebiology1/chapter/lipids/#chapter-1081-section-1) 2. [ 9.2 The Plasma Membrane ](https://slcc.pressbooks.pub/collegebiology1/chapter/the-plasma-membrane/) 1. [ Fluid Mosaic Model ](https://slcc.pressbooks.pub/collegebiology1/chapter/the-plasma-membrane/#chapter-1085-section-1) 2. [ Phospholipids ](https://slcc.pressbooks.pub/collegebiology1/chapter/the-plasma-membrane/#chapter-1085-section-2) 3. [ Proteins ](https://slcc.pressbooks.pub/collegebiology1/chapter/the-plasma-membrane/#chapter-1085-section-3) 4. [ Carbohydrates ](https://slcc.pressbooks.pub/collegebiology1/chapter/the-plasma-membrane/#chapter-1085-section-4) 5. [ Membrane Fluidity ](https://slcc.pressbooks.pub/collegebiology1/chapter/the-plasma-membrane/#chapter-1085-section-5) 3. [ 9.3 The Endomembrane System ](https://slcc.pressbooks.pub/collegebiology1/chapter/the-endomembrane-system/) 1. [ The Nuclear Envelope ](https://slcc.pressbooks.pub/collegebiology1/chapter/the-endomembrane-system/#chapter-1089-section-1) 2. [ The Endoplasmic Reticulum ](https://slcc.pressbooks.pub/collegebiology1/chapter/the-endomembrane-system/#chapter-1089-section-2) 3. [ The Golgi Apparatus ](https://slcc.pressbooks.pub/collegebiology1/chapter/the-endomembrane-system/#chapter-1089-section-3) 4. [ Lysosomes ](https://slcc.pressbooks.pub/collegebiology1/chapter/the-endomembrane-system/#chapter-1089-section-4) 11. X . Membrane Transport 1. [ 10.1 Passive Transport ](https://slcc.pressbooks.pub/collegebiology1/chapter/passive-transport/) 1. [ Selective Permeability ](https://slcc.pressbooks.pub/collegebiology1/chapter/passive-transport/#chapter-1172-section-1) 2. [ Diffusion ](https://slcc.pressbooks.pub/collegebiology1/chapter/passive-transport/#chapter-1172-section-2) 3. [ Facilitated diffusion ](https://slcc.pressbooks.pub/collegebiology1/chapter/passive-transport/#chapter-1172-section-3) 2. [ 10.2 Osmosis ](https://slcc.pressbooks.pub/collegebiology1/chapter/osmosis/) 1. [ Mechanism ](https://slcc.pressbooks.pub/collegebiology1/chapter/osmosis/#chapter-1194-section-1) 2. [ Tonicity ](https://slcc.pressbooks.pub/collegebiology1/chapter/osmosis/#chapter-1194-section-2) 3. [ Tonicity in Living Systems ](https://slcc.pressbooks.pub/collegebiology1/chapter/osmosis/#chapter-1194-section-3) 3. [ 10.3 Active Transport ](https://slcc.pressbooks.pub/collegebiology1/chapter/active-transport/) 1. [ Moving Against a Gradient ](https://slcc.pressbooks.pub/collegebiology1/chapter/active-transport/#chapter-1296-section-1) 2. [ Primary Active Transport ](https://slcc.pressbooks.pub/collegebiology1/chapter/active-transport/#chapter-1296-section-2) 3. [ Secondary Active Transport (Co-transport) ](https://slcc.pressbooks.pub/collegebiology1/chapter/active-transport/#chapter-1296-section-3) 4. [ 10.4 Bulk Transport ](https://slcc.pressbooks.pub/collegebiology1/chapter/bulk-transport/) 1. [ Endocytosis ](https://slcc.pressbooks.pub/collegebiology1/chapter/bulk-transport/#chapter-1299-section-1) 2. [ Exocytosis ](https://slcc.pressbooks.pub/collegebiology1/chapter/bulk-transport/#chapter-1299-section-2) 12. XI . Cell Signaling 1. [ 11.1 Ligands and Receptors ](https://slcc.pressbooks.pub/collegebiology1/chapter/ligands-and-receptors/) 1. [ Steps of Cell Signaling ](https://slcc.pressbooks.pub/collegebiology1/chapter/ligands-and-receptors/#chapter-1692-section-1) 2. [ Ligands ](https://slcc.pressbooks.pub/collegebiology1/chapter/ligands-and-receptors/#chapter-1692-section-2) 3. [ Receptors ](https://slcc.pressbooks.pub/collegebiology1/chapter/ligands-and-receptors/#chapter-1692-section-3) 2. [ 11.2 Types of Cell Signaling ](https://slcc.pressbooks.pub/collegebiology1/chapter/types-of-cell-signaling/) 1. [ Direct Signaling ](https://slcc.pressbooks.pub/collegebiology1/chapter/types-of-cell-signaling/#chapter-1691-section-1) 2. [ Paracrine Signaling ](https://slcc.pressbooks.pub/collegebiology1/chapter/types-of-cell-signaling/#chapter-1691-section-2) 3. [ Endocrine Signaling ](https://slcc.pressbooks.pub/collegebiology1/chapter/types-of-cell-signaling/#chapter-1691-section-3) 3. [ 11.3 Signal Transduction ](https://slcc.pressbooks.pub/collegebiology1/chapter/signal-transduction/) 1. [ Binding Initiates a Signaling Pathway ](https://slcc.pressbooks.pub/collegebiology1/chapter/signal-transduction/#chapter-1727-section-1) 2. [ Methods of Intracellular Signaling ](https://slcc.pressbooks.pub/collegebiology1/chapter/signal-transduction/#chapter-1727-section-2) 4. [ 11.4 Response to the Signal and Termination ](https://slcc.pressbooks.pub/collegebiology1/chapter/response-to-the-signal/) 1. [ Response to the Signal ](https://slcc.pressbooks.pub/collegebiology1/chapter/response-to-the-signal/#chapter-1729-section-1) 2. [ Termination of the Signal ](https://slcc.pressbooks.pub/collegebiology1/chapter/response-to-the-signal/#chapter-1729-section-2) 13. XII . Nucleic Acids and DNA Replication 1. [ 12.1 Functions of Nucleic Acids ](https://slcc.pressbooks.pub/collegebiology1/chapter/nucleic-acids/) 1. [ DNA and RNA ](https://slcc.pressbooks.pub/collegebiology1/chapter/nucleic-acids/#chapter-514-section-1) 2. [ 12.2 DNA Structure ](https://slcc.pressbooks.pub/collegebiology1/chapter/dna-structure/) 1. [ Nucleotides ](https://slcc.pressbooks.pub/collegebiology1/chapter/dna-structure/#chapter-521-section-1) 2. [ Polynucleotides ](https://slcc.pressbooks.pub/collegebiology1/chapter/dna-structure/#chapter-521-section-2) 3. [ The Double Helix ](https://slcc.pressbooks.pub/collegebiology1/chapter/dna-structure/#chapter-521-section-3) 3. [ 12.3 Organization of DNA in the cell ](https://slcc.pressbooks.pub/collegebiology1/chapter/organization-of-dna-in-the-cell/) 1. [ The Genome ](https://slcc.pressbooks.pub/collegebiology1/chapter/organization-of-dna-in-the-cell/#chapter-551-section-1) 2. [ Chromatin and Chromosomes ](https://slcc.pressbooks.pub/collegebiology1/chapter/organization-of-dna-in-the-cell/#chapter-551-section-2) 3. [ Genes ](https://slcc.pressbooks.pub/collegebiology1/chapter/organization-of-dna-in-the-cell/#chapter-551-section-3) 4. [ 12.4 DNA Replication ](https://slcc.pressbooks.pub/collegebiology1/chapter/dna-replication/) 1. [ DNA Replication is Semi-Conservative ](https://slcc.pressbooks.pub/collegebiology1/chapter/dna-replication/#chapter-556-section-1) 2. [ The Process of DNA Replication ](https://slcc.pressbooks.pub/collegebiology1/chapter/dna-replication/#chapter-556-section-2) 14. XIII . Transcription 1. [ 13.1 The Central Dogma ](https://slcc.pressbooks.pub/collegebiology1/chapter/central-dogma/) 1. [ The Central Dogma: DNA Encodes RNA; RNA Encodes Protein ](https://slcc.pressbooks.pub/collegebiology1/chapter/central-dogma/#chapter-614-section-1) 2. [ 13.2 Prokaryotic Transcription ](https://slcc.pressbooks.pub/collegebiology1/chapter/prokaryotic-transcription/) 1. [ Transcription ](https://slcc.pressbooks.pub/collegebiology1/chapter/prokaryotic-transcription/#chapter-616-section-1) 2. [ Regulation of Transcription ](https://slcc.pressbooks.pub/collegebiology1/chapter/prokaryotic-transcription/#chapter-616-section-2) 3. [ 13.3 Eukaryotic Transcription ](https://slcc.pressbooks.pub/collegebiology1/chapter/eukaryotic-transcription/) 1. [ RNA Polymerase II Promoters and Transcription Factors ](https://slcc.pressbooks.pub/collegebiology1/chapter/eukaryotic-transcription/#chapter-618-section-1) 2. [ Enhancers and Transcription ](https://slcc.pressbooks.pub/collegebiology1/chapter/eukaryotic-transcription/#chapter-618-section-2) 3. [ Eukaryotic Elongation and Termination ](https://slcc.pressbooks.pub/collegebiology1/chapter/eukaryotic-transcription/#chapter-618-section-3) 4. [ 13.4 mRNA Processing ](https://slcc.pressbooks.pub/collegebiology1/chapter/mrna-processing/) 1. [ mRNA Processing ](https://slcc.pressbooks.pub/collegebiology1/chapter/mrna-processing/#chapter-620-section-1) 15. XIV . Translation 1. [ 14.1 The Genetic Code ](https://slcc.pressbooks.pub/collegebiology1/chapter/the-genetic-code/) 1. [ Codons specify amino acids ](https://slcc.pressbooks.pub/collegebiology1/chapter/the-genetic-code/#chapter-698-section-1) 2. [ The Genetic Code Is Degenerate ](https://slcc.pressbooks.pub/collegebiology1/chapter/the-genetic-code/#chapter-698-section-2) 3. [ The genetic code is nearly universal. ](https://slcc.pressbooks.pub/collegebiology1/chapter/the-genetic-code/#chapter-698-section-3) 2. [ 14.2 The Protein Synthesis Machinery ](https://slcc.pressbooks.pub/collegebiology1/chapter/the-protein-synthesis-machinery/) 1. [ The Protein Synthesis Machinery ](https://slcc.pressbooks.pub/collegebiology1/chapter/the-protein-synthesis-machinery/#chapter-702-section-1) 3. [ 14.3 The Mechanism of Protein Synthesis ](https://slcc.pressbooks.pub/collegebiology1/chapter/the-mechanism-of-protein-synthesis/) 1. [ Protein Synthesis ](https://slcc.pressbooks.pub/collegebiology1/chapter/the-mechanism-of-protein-synthesis/#chapter-704-section-1) 2. [ Protein Folding, Modification, and Targeting ](https://slcc.pressbooks.pub/collegebiology1/chapter/the-mechanism-of-protein-synthesis/#chapter-704-section-2) 16. XV . Evolution 2 1. [ 15.1 Variation and Evolution ](https://slcc.pressbooks.pub/collegebiology1/chapter/variation/) 2. [ 15.2 Causes of Mutation ](https://slcc.pressbooks.pub/collegebiology1/chapter/causes-of-mutation/) 3. [ 15.3 Types of Mutation ](https://slcc.pressbooks.pub/collegebiology1/chapter/types-of-mutation/) 17. XVI . Cell Division and the Cell Cycle 1. [ 16.1 Cell Division and Genomic DNA ](https://slcc.pressbooks.pub/collegebiology1/chapter/cell-division-and-genomic-dna/) 2. [ 16.2 The Cell Cycle ](https://slcc.pressbooks.pub/collegebiology1/chapter/the-cell-cycle/) 1. [ The Cell Cycle ](https://slcc.pressbooks.pub/collegebiology1/chapter/the-cell-cycle/#chapter-850-section-1) 2. [ Interphase ](https://slcc.pressbooks.pub/collegebiology1/chapter/the-cell-cycle/#chapter-850-section-2) 3. [ The Mitotic Phase ](https://slcc.pressbooks.pub/collegebiology1/chapter/the-cell-cycle/#chapter-850-section-3) 3. [ 16.3 Mitosis and Cytokinesis ](https://slcc.pressbooks.pub/collegebiology1/chapter/mitosis/) 1. [ Mitosis ](https://slcc.pressbooks.pub/collegebiology1/chapter/mitosis/#chapter-872-section-1) 2. [ Cytokinesis ](https://slcc.pressbooks.pub/collegebiology1/chapter/mitosis/#chapter-872-section-2) 4. [ 16.4 The Cytoskeleton ](https://slcc.pressbooks.pub/collegebiology1/chapter/the-cytoskeleton/) 18. XVII . Regulation of the Cell Cycle and Cancer 1. [ 17.1 Cell Cycle Checkpoints ](https://slcc.pressbooks.pub/collegebiology1/chapter/cell-cycle-checkpoints/) 1. [ Regulation at Internal Checkpoints ](https://slcc.pressbooks.pub/collegebiology1/chapter/cell-cycle-checkpoints/#chapter-901-section-1) 2. [ Apoptosis ](https://slcc.pressbooks.pub/collegebiology1/chapter/cell-cycle-checkpoints/#chapter-901-section-2) 2. [ 17.2 Regulator Molecules of the Cell Cycle ](https://slcc.pressbooks.pub/collegebiology1/chapter/regulator-molecules-of-the-cell-cycle/) 1. [ Timing of the Cell Cycle ](https://slcc.pressbooks.pub/collegebiology1/chapter/regulator-molecules-of-the-cell-cycle/#chapter-912-section-1) 2. [ Regulation of the Cell Cycle by External Events ](https://slcc.pressbooks.pub/collegebiology1/chapter/regulator-molecules-of-the-cell-cycle/#chapter-912-section-2) 3. [ Intracellular Cell Cycle Regulators ](https://slcc.pressbooks.pub/collegebiology1/chapter/regulator-molecules-of-the-cell-cycle/#chapter-912-section-3) 3. [ 17.3 Cancer ](https://slcc.pressbooks.pub/collegebiology1/chapter/cancer/) 1. [ What is Cancer? ](https://slcc.pressbooks.pub/collegebiology1/chapter/cancer/#chapter-939-section-1) 2. [ How Does Cancer Develop? ](https://slcc.pressbooks.pub/collegebiology1/chapter/cancer/#chapter-939-section-2) 4. [ 17.4 Cancer and the Cell Cycle ](https://slcc.pressbooks.pub/collegebiology1/chapter/cancer-and-the-cell-cycle/) 1. [ Cancer and the Cell Cycle ](https://slcc.pressbooks.pub/collegebiology1/chapter/cancer-and-the-cell-cycle/#chapter-915-section-1) 2. [ Proto-oncogenes ](https://slcc.pressbooks.pub/collegebiology1/chapter/cancer-and-the-cell-cycle/#chapter-915-section-2) 3. [ Tumor Suppressor Genes ](https://slcc.pressbooks.pub/collegebiology1/chapter/cancer-and-the-cell-cycle/#chapter-915-section-3) 19. XVIII . Sexual Reproduction and Meiosis 1. [ 18.1 Sexual Reproduction ](https://slcc.pressbooks.pub/collegebiology1/chapter/sexual-reproduction/) 2. [ 18.2 Life Cycles of Sexually Reproducing Organisms ](https://slcc.pressbooks.pub/collegebiology1/chapter/life-cycles-of-sexually-reproducing-organisms/) 3. [ 18.3 Meiosis ](https://slcc.pressbooks.pub/collegebiology1/chapter/meiosis/) 1. [ Overview ](https://slcc.pressbooks.pub/collegebiology1/chapter/meiosis/#chapter-970-section-1) 2. [ Meiosis I ](https://slcc.pressbooks.pub/collegebiology1/chapter/meiosis/#chapter-970-section-2) 3. [ Meiosis II ](https://slcc.pressbooks.pub/collegebiology1/chapter/meiosis/#chapter-970-section-3) 4. [ Comparing Meiosis and Mitosis ](https://slcc.pressbooks.pub/collegebiology1/chapter/meiosis/#chapter-970-section-4) 4. [ 18.4 Nondisjunction ](https://slcc.pressbooks.pub/collegebiology1/chapter/nondisjunction/) 1. [ Chromosome Number Abnormalities ](https://slcc.pressbooks.pub/collegebiology1/chapter/nondisjunction/#chapter-993-section-1) 2. [ Aneuploidy ](https://slcc.pressbooks.pub/collegebiology1/chapter/nondisjunction/#chapter-993-section-2) 3. [ Sex Chromosome Nondisjunction in Humans ](https://slcc.pressbooks.pub/collegebiology1/chapter/nondisjunction/#chapter-993-section-3) 20. XIX . Genetics 1 1. [ 19.1 Foundations of Modern Genetics ](https://slcc.pressbooks.pub/collegebiology1/chapter/foundations-of-modern-genetics/) 1. [ Before Mendel ](https://slcc.pressbooks.pub/collegebiology1/chapter/foundations-of-modern-genetics/#chapter-780-section-1) 2. [ About Gregor Mendel ](https://slcc.pressbooks.pub/collegebiology1/chapter/foundations-of-modern-genetics/#chapter-780-section-2) 3. [ Traits, Genotypes, and Phenotypes ](https://slcc.pressbooks.pub/collegebiology1/chapter/foundations-of-modern-genetics/#chapter-780-section-3) 2. [ 19.2 Segregation ](https://slcc.pressbooks.pub/collegebiology1/chapter/segregation/) 1. [ Mendel’s model organism ](https://slcc.pressbooks.pub/collegebiology1/chapter/segregation/#chapter-784-section-1) 2. [ Mendelian Crosses ](https://slcc.pressbooks.pub/collegebiology1/chapter/segregation/#chapter-784-section-2) 3. [ Mendelian Cross Results ](https://slcc.pressbooks.pub/collegebiology1/chapter/segregation/#chapter-784-section-3) 3. [ 19.3 Punnett Squares and Laws of Probability ](https://slcc.pressbooks.pub/collegebiology1/chapter/punnett-squares-and-laws-of-probability/) 1. [ Probability Basics ](https://slcc.pressbooks.pub/collegebiology1/chapter/punnett-squares-and-laws-of-probability/#chapter-795-section-1) 2. [ The Punnett Square Approach for a Monohybrid Cross ](https://slcc.pressbooks.pub/collegebiology1/chapter/punnett-squares-and-laws-of-probability/#chapter-795-section-2) 4. [ 19.4 Independent Assortment ](https://slcc.pressbooks.pub/collegebiology1/chapter/independent-assortment/) 1. [ Identifying All Gamete Types Based on a Parental Genotype ](https://slcc.pressbooks.pub/collegebiology1/chapter/independent-assortment/#chapter-791-section-1) 2. [ Linked Genes ](https://slcc.pressbooks.pub/collegebiology1/chapter/independent-assortment/#chapter-791-section-2) 21. XX . Genetics 2 1. [ 20.1 Incomplete Dominance, Codominance, and Multiple Alleles ](https://slcc.pressbooks.pub/collegebiology1/chapter/incomplete-dominance-and-codominance/) 1. [ Alternatives to Dominance and Recessiveness ](https://slcc.pressbooks.pub/collegebiology1/chapter/incomplete-dominance-and-codominance/#chapter-1070-section-1) 2. [ Codominance ](https://slcc.pressbooks.pub/collegebiology1/chapter/incomplete-dominance-and-codominance/#chapter-1070-section-2) 3. [ Multiple Alleles ](https://slcc.pressbooks.pub/collegebiology1/chapter/incomplete-dominance-and-codominance/#chapter-1070-section-3) 2. [ 20.2 Sex-linked traits ](https://slcc.pressbooks.pub/collegebiology1/chapter/sex-linked-traits/) 3. [ 20.3 Pedigree Analysis ](https://slcc.pressbooks.pub/collegebiology1/chapter/pedigree-analysis/) 1. [ What is a pedigree? ](https://slcc.pressbooks.pub/collegebiology1/chapter/pedigree-analysis/#chapter-1074-section-1) 2. [ Pedigree Analysis ](https://slcc.pressbooks.pub/collegebiology1/chapter/pedigree-analysis/#chapter-1074-section-2) 4. [ 20.4 Polygenic Inheritance and Epistasis ](https://slcc.pressbooks.pub/collegebiology1/chapter/polygenic-inheritance-and-epistasis/) 1. [ Epistasis ](https://slcc.pressbooks.pub/collegebiology1/chapter/polygenic-inheritance-and-epistasis/#chapter-1076-section-1) 2. [ Polygenic Inheritance ](https://slcc.pressbooks.pub/collegebiology1/chapter/polygenic-inheritance-and-epistasis/#chapter-1076-section-2) 22. XXI . Energy and the ATP Cycle 1. [ 21.1 Metabolism ](https://slcc.pressbooks.pub/collegebiology1/chapter/metabolism/) 1. [ Organisms and Metabolism ](https://slcc.pressbooks.pub/collegebiology1/chapter/metabolism/#chapter-1363-section-1) 2. [ Metabolic Reactions ](https://slcc.pressbooks.pub/collegebiology1/chapter/metabolism/#chapter-1363-section-2) 2. [ 21.2 The Laws of Thermodynamics ](https://slcc.pressbooks.pub/collegebiology1/chapter/22-2-the-laws-of-thermodynamics/) 1. [ The First Law of Thermodynamics ](https://slcc.pressbooks.pub/collegebiology1/chapter/22-2-the-laws-of-thermodynamics/#chapter-1388-section-1) 2. [ The Second Law of Thermodynamics ](https://slcc.pressbooks.pub/collegebiology1/chapter/22-2-the-laws-of-thermodynamics/#chapter-1388-section-2) 3. [ 21.3 Energy ](https://slcc.pressbooks.pub/collegebiology1/chapter/energy/) 1. [ Potential and Kinetic Energy ](https://slcc.pressbooks.pub/collegebiology1/chapter/energy/#chapter-1378-section-1) 2. [ Free Energy ](https://slcc.pressbooks.pub/collegebiology1/chapter/energy/#chapter-1378-section-2) 3. [ Endergonic Reactions and Exergonic Reactions ](https://slcc.pressbooks.pub/collegebiology1/chapter/energy/#chapter-1378-section-3) 4. [ 21.4 The ATP cycle ](https://slcc.pressbooks.pub/collegebiology1/chapter/the-atp-cycle/) 23. XXII . Chemiosmosis 1. [ 22.1 The Energy Transformations that Sustain Life ](https://slcc.pressbooks.pub/collegebiology1/chapter/22-1-the-energy-transformations-that-sustain-life/) 2. [ 22.2 Chemiosmosis and ATP Synthase ](https://slcc.pressbooks.pub/collegebiology1/chapter/atp-synthase/) 1. [ Chemiosmosis ](https://slcc.pressbooks.pub/collegebiology1/chapter/atp-synthase/#chapter-1418-section-1) 3. [ 22.3 Electron Transport Chains ](https://slcc.pressbooks.pub/collegebiology1/chapter/electron-transport-chain/) 1. [ Redox Reactions ](https://slcc.pressbooks.pub/collegebiology1/chapter/electron-transport-chain/#chapter-1430-section-1) 2. [ Electrons and Energy ](https://slcc.pressbooks.pub/collegebiology1/chapter/electron-transport-chain/#chapter-1430-section-2) 3. [ Electron Transport Chains ](https://slcc.pressbooks.pub/collegebiology1/chapter/electron-transport-chain/#chapter-1430-section-3) 4. [ 22.4 Electron Transport Chains in Respiration and Photosynthesis ](https://slcc.pressbooks.pub/collegebiology1/chapter/etcs-in-respiration-and-photosynthesis/) 1. [ The Electron Transport Chain in the Mitochondrion ](https://slcc.pressbooks.pub/collegebiology1/chapter/etcs-in-respiration-and-photosynthesis/#chapter-1448-section-1) 2. [ The Electron Transport Chain in the Chloroplast ](https://slcc.pressbooks.pub/collegebiology1/chapter/etcs-in-respiration-and-photosynthesis/#chapter-1448-section-2) 3. [ Comparing the Electron Transport Chain in the Mitochondrion and Chloroplast ](https://slcc.pressbooks.pub/collegebiology1/chapter/etcs-in-respiration-and-photosynthesis/#chapter-1448-section-3) 24. XXIII . Cellular Respiration 1. [ 23.1 Overview of Cellular Respiration ](https://slcc.pressbooks.pub/collegebiology1/chapter/overview-of-cellular-respiration/) 1. [ Electron Carriers ](https://slcc.pressbooks.pub/collegebiology1/chapter/overview-of-cellular-respiration/#chapter-1475-section-1) 2. [ The Mitochondrion ](https://slcc.pressbooks.pub/collegebiology1/chapter/overview-of-cellular-respiration/#chapter-1475-section-2) 2. [ 23.2 Glycolysis ](https://slcc.pressbooks.pub/collegebiology1/chapter/glycolysis/) 1. [ Overview of Glycolysis ](https://slcc.pressbooks.pub/collegebiology1/chapter/glycolysis/#chapter-1508-section-1) 2. [ Outcomes of Glycolysis ](https://slcc.pressbooks.pub/collegebiology1/chapter/glycolysis/#chapter-1508-section-2) 3. [ Steps of Glycolysis ](https://slcc.pressbooks.pub/collegebiology1/chapter/glycolysis/#chapter-1508-section-3) 3. [ 23.3 Pyruvate Oxidation and the Citric Acid Cycle ](https://slcc.pressbooks.pub/collegebiology1/chapter/pyruvate-oxidation-and-the-citric-acid-cycle/) 1. [ Pyruvate Oxidation ](https://slcc.pressbooks.pub/collegebiology1/chapter/pyruvate-oxidation-and-the-citric-acid-cycle/#chapter-1519-section-1) 2. [ The Citric Acid Cycle ](https://slcc.pressbooks.pub/collegebiology1/chapter/pyruvate-oxidation-and-the-citric-acid-cycle/#chapter-1519-section-2) 3. [ Products of the Citric Acid Cycle ](https://slcc.pressbooks.pub/collegebiology1/chapter/pyruvate-oxidation-and-the-citric-acid-cycle/#chapter-1519-section-3) 25. XXIV . Photosynthesis 1. [ 24.1 Overview of Photosynthesis ](https://slcc.pressbooks.pub/collegebiology1/chapter/25-1-capturing-light-energy/) 1. [ Photosynthetic Structures ](https://slcc.pressbooks.pub/collegebiology1/chapter/25-1-capturing-light-energy/#chapter-1538-section-1) 2. [ The Two Parts of Photosynthesis ](https://slcc.pressbooks.pub/collegebiology1/chapter/25-1-capturing-light-energy/#chapter-1538-section-2) 2. [ 24.2 Light Energy ](https://slcc.pressbooks.pub/collegebiology1/chapter/light-energy/) 1. [ What Is Light Energy? ](https://slcc.pressbooks.pub/collegebiology1/chapter/light-energy/#chapter-1557-section-1) 2. [ Absorption of Light ](https://slcc.pressbooks.pub/collegebiology1/chapter/light-energy/#chapter-1557-section-2) 3. [ Pigments ](https://slcc.pressbooks.pub/collegebiology1/chapter/light-energy/#chapter-1557-section-3) 3. [ 24.3 The Light-Dependent Reactions ](https://slcc.pressbooks.pub/collegebiology1/chapter/the-light-dependent-reactions/) 4. [ 24.4 The Calvin Cycle ](https://slcc.pressbooks.pub/collegebiology1/chapter/the-calvin-cycle/) 1. [ The Calvin Cycle ](https://slcc.pressbooks.pub/collegebiology1/chapter/the-calvin-cycle/#chapter-1589-section-1) 2. [ Respiration and Photosynthesis: the reactions that sustain the biosphere ](https://slcc.pressbooks.pub/collegebiology1/chapter/the-calvin-cycle/#chapter-1589-section-2) 26. [ Appendix ](https://slcc.pressbooks.pub/collegebiology1/back-matter/appendix/) # [ College Biology I ](https://slcc.pressbooks.pub/collegebiology1/) # 18.1 Sexual Reproduction The ability to reproduce is a basic characteristic of all organisms. Although many unicellular organisms and a few multicellular organisms can produce genetically identical clones of themselves through _asexual reproduction_ , many single-celled organisms and most multicellular organisms reproduce regularly using another method— _sexual reproduction_ . This highly evolved method involves the production by parents of two haploid cells and the fusion of two haploid cells to form a single diploid cell—a genetically unique organism. Haploid cells that are part of the sexual reproductive cycle are produced by a type of cell division called meiosis . Sexual reproduction, involving both meiosis and fertilization, introduces variation into offspring that may account for the evolutionary success of sexual reproduction. The vast majority of eukaryotic organisms, both multicellular and unicellular, can or must employ some form of meiosis and fertilization to reproduce. ![Sexual reproduction generalized life cycle](https://slcc.pressbooks.pub/app/uploads/sites/20/2021/02/Sexual- Reproduction-911x1024.png) Although many details vary in sexual lifestyles, they all involve the alternation of fertilization and meiosis. Fertilization unites two haploid cells to make a diploid zygote. Meiosis reduces ploidy to produces haploid gametes. Some organisms have higher levels of ploidy, but alternation of diploid and haploid is most common. (Sexual reproduction by Melissa Hardy is used under a [ Creative Commons Attribution-NonCommercial license ](https://creativecommons.org/licenses/by-nc/4.0/) ). Sexual reproduction requires the union of two specialized cells, called gametes , each of which contains one set of chromosomes. When two gametes unite, they form a zygote , or fertilized egg that contains two sets of chromosomes. (Note: Cells that contain one set of chromosomes are called haploid ; cells containing two sets of chromosomes are called diploid .) Since fertilization combines the genetic contents of two cells (egg and sperm) to produce the next generation of organisms, sexual reproduction must involve a nuclear division that reduces the number of chromosome sets by half. Otherwise each new generation of individuals would contain double the chromosome number of the previous generation. This type of cell division is called meiosis . Most animals and plants and many unicellular organisms are diploid and therefore have two sets of chromosomes per somatic cell (all cells of a multicellular organism except the gametes or reproductive cells). The two copies of each chromosome type are homologous with respect to one another, meaning that they contain the same genes in identical locations along their lengths. Diploid organisms inherit one copy of each chromosome type from each parent. Sexual reproduction was likely an early evolutionary innovation after the appearance of eukaryotic cells. It appears to have been very successful because most eukaryotes are able to reproduce sexually and, in many animal species, it is the only mode of reproduction. And yet, scientists also recognize some real disadvantages to sexual reproduction. For instance, if the parent organism is successfully occupying a habitat, genetically identical offspring with the same traits should be similarly successful. Furthermore, asexual reproduction does not require another individual of the opposite sex. Indeed, some organisms that lead a solitary lifestyle have retained the ability to reproduce asexually. Theoretically, in asexual populations, reproduction would occur twice as quickly since sexual populations require two individuals to reproduce. Nevertheless, multicellular organisms that exclusively depend on asexual reproduction are exceedingly rare. Why sexual reproductive strategies so common? These are important (and as yet unanswered) questions in biology, even though they have been the focus of much research beginning in the latter half of the 20th century. There are several possible explanations, one of which is that the genetic variation that sexual reproduction creates among offspring is very important to the survival and reproduction of the population. Thus, on average, a sexually reproducing population will leave more descendants than an otherwise similar asexually reproducing population. The major (and sometimes only) source of genetic variation in asexual organisms is mutation. Mutations are also the ultimate source of variation in sexually reproducing organisms. However, in contrast to mutation during asexual reproduction, these mutations during sexual reproduction can be continually reshuffled from one generation to the next when different parents combine their unique genomes to produce different combinations of genetic variation. ![Two geckos mating](https://slcc.pressbooks.pub/app/uploads/sites/20/2021/02/682px- Hemidactylus_frenatus_mating_ventral_view.jpg) Most animals, such as these Common House Geckos, reproduce sexually. ( [ _Hemidactylus frenatus_ mating ](https://commons.wikimedia.org/wiki/File:Hemidactylus_frenatus_mating,_ventral_view.jpg) by [ Basile Morin ](https://commons.wikimedia.org/wiki/User:Basile_Morin) is used under a [ Creative Commons Attribution license ](https://creativecommons.org/licenses/by/4.0/) ). * * * Text adapted from OpenStax Biology 2e and used under a [ Creative Commons Attribution License 4.0 ](https://creativecommons.org/licenses/by/4.0/) . Access for free at [ https://openstax.org/books/biology-2e/pages/1-introduction ](https://openstax.org/books/biology-2e/pages/1-introduction) definition haploid reproductive cell (sperm or egg) that fuses with another haploid cell during fertilization × Close definition a cell formed by the union of two gametes; the first cell of a new individual × Close definition type of cell division that results in cells with half of the genetic material of the parent cell; used to produce gametes × Close definition cell, nucleus, or organism containing two sets of chromosomes (2n) × Close definition chromosomes of the same morphology with the same genes in the same location; diploid organisms have pairs of homologous chromosomes (homologs), with each homolog derived from a different parent × Close definition Previous/next navigation [ Previous: 17.4 Cancer and the Cell Cycle ](https://slcc.pressbooks.pub/collegebiology1/chapter/cancer-and-the-cell- cycle/ "Previous: 17.4 Cancer and the Cell Cycle") [ Next: 18.2 Life Cycles of Sexually Reproducing Organisms ](https://slcc.pressbooks.pub/collegebiology1/chapter/life-cycles-of-sexually- reproducing-organisms/ "Next: 18.2 Life Cycles of Sexually Reproducing Organisms") Back to top ## License ![Icon for the Creative Commons Attribution-NonCommercial 4.0 International License](https://slcc.pressbooks.pub/app/themes/pressbooks- book/packages/buckram/assets/images/cc-by-nc.svg) [ College Biology I ](https://slcc.pressbooks.pub/collegebiology1) Copyright © by Melissa Hardy is licensed under a [ Creative Commons Attribution- NonCommercial 4.0 International License ](https://creativecommons.org/licenses/by-nc/4.0/) , except where otherwise noted. 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These findings are part of a larger project that includes findings from six focus groups on [ the experiences and views of transgender and nonbinary adults ](https://www.pewresearch.org/social-trends/2022/06/07/the-experiences- challenges-and-hopes-of-transgender-and-nonbinary-u-s-adults/) and estimates of the [ share of U.S. adults who say their gender is different from the sex they were assigned at birth ](https://www.pewresearch.org/short- reads/2022/06/07/about-5-of-young-adults-in-the-u-s-say-their-gender-is- different-from-their-sex-assigned-at-birth/) . This analysis is based on a survey of 10,188 U.S. adults. The data was collected as a part of a larger survey conducted May 16-22, 2022. Everyone who took part is a member of the Center’s American Trends Panel (ATP), an online survey panel that is recruited through national, random sampling of residential addresses. This way, nearly all U.S. adults have a chance of selection. The survey is weighted to be representative of the U.S. adult population by gender, race, ethnicity, partisan affiliation, education and other categories. Read more about the [ ATP’s methodology ](https://www.pewresearch.org/our-methods/u-s-surveys/the-american-trends- panel/) . See here to read more about the [ questions used for this report ](https://www.pewresearch.org/social-trends/wp- content/uploads/sites/3/2022/06/PSD_06.28.22_gender.identity.topline.pdf) and the [ report’s methodology ](https://www.pewresearch.org/social- trends/2022/06/28/methodology) . Terminology _ _ _ _ References to White, Black and Asian adults include only those who are not Hispanic and identify as only one race. Hispanics are of any race. All references to party affiliation include those who lean toward that party. Republicans include those who identify as Republicans and those who say they lean toward the Republican Party. Democrats include those who identify as Democrats and those who say they lean toward the Democratic Party. References to college graduates or people with a college degree comprise those with a bachelor’s degree or more. “Some college” includes those with an associate degree and those who attended college but did not obtain a degree. The terms “transgender” and “trans” are used interchangeably throughout this report to refer to people whose gender is different from the sex they were assigned at birth. [ ![A chart showing Most favor protecting trans people from discrimination, even as growing share say gender is determined by sex at birth](https://www.pewresearch.org/wp- content/uploads/sites/20/2022/06/PSDT_06.28.22_Gender_Identity_0_0.png?w=620) ](https://www.pewresearch.org/social-trends/2022/06/28/americans-complex- views-on-gender-identity-and-transgender- issues/psdt_06-28-22_gender_identity_0_0-png/) As the United States addresses issues of transgender rights and the broader landscape around gender identity continues to shift, the American public holds a complex set of views around these issues, according to a new Pew Research Center survey. Roughly eight-in-ten U.S. adults say there is at least some discrimination against transgender people in our society, and a majority favor laws that would protect transgender individuals from discrimination in jobs, housing and public spaces. At the same time, 60% say a person’s gender is determined by their sex assigned at birth, up from 56% in 2021 and 54% in 2017. The public is divided over the extent to which our society has accepted people who are transgender: 38% say society has gone too far in accepting them, while a roughly equal share (36%) say society hasn’t gone far enough. About one-in- four say things have been about right. Underscoring the public’s ambivalence around these issues, even among those who see at least some discrimination against trans people, a majority (54%) say society has either gone too far or been about right in terms of acceptance. The fundamental belief about whether gender can differ from sex assigned at birth is closely aligned with opinions on transgender issues. Americans who say a person’s gender _can_ be different from their sex at birth are more likely than others to see discrimination against trans people and a lack of societal acceptance. They’re also more likely to say that our society hasn’t gone far enough in accepting people who are transgender. But even among those who say a person’s gender is determined by their sex at birth, there is a diversity of viewpoints. Half of this group say they would favor laws that protect trans people from discrimination in certain realms of life. And about one-in-four say forms and online profiles should include options other than “male” or “female” for people who don’t identify as either. _Related:_ [ _The Experiences, Challenges and Hopes of Transgender and Nonbinary U.S. adults_ ](https://www.pewresearch.org/social- trends/2022/06/07/the-experiences-challenges-and-hopes-of-transgender-and- nonbinary-u-s-adults/) [ ![Chart showing Young adults, Democrats more likely to say society hasn’t gone far enough in accepting people who are transgender](https://www.pewresearch.org/wp- content/uploads/sites/20/2022/06/PSDT_06.28.22_Gender_Identity_0_1.png?w=620) ](https://www.pewresearch.org/social-trends/2022/06/28/americans-complex- views-on-gender-identity-and-transgender- issues/psdt_06-28-22_gender_identity_0_1-png/) When it comes to issues surrounding gender identity, young adults are at the leading edge of change and acceptance. Half of adults ages 18 to 29 say someone can be a man or a woman even if that differs from the sex they were assigned at birth. This compares with about four-in-ten of those ages 30 to 49 and about a third of those 50 and older. Adults younger than 30 are also more likely than older adults to say society hasn’t gone far enough in accepting people who are transgender (47% vs. 39% of 30- to 49-year-olds and 31% of those 50 and older) These views differ even more sharply by partisanship. Democrats and those who lean to the Democratic Party are more than four times as likely as Republicans and Republican leaners to say that a person’s gender can be different from the sex they were assigned at birth (61% vs. 13%). Democrats are also much more likely than Republicans to say our society hasn’t gone far enough in accepting people who are transgender (59% vs. 10%). For their part, 66% of Republicans say society has gone _too far_ in accepting people who are transgender. Amid a national conversation over these issues, many states are considering or have put in place [ laws or policies ](https://www.washingtonpost.com/politics/2022/03/25/lgbtq-rights-gop-bills- dont-say-gay/) that would directly affect the lives of transgender and nonbinary people – that is, those who don’t identify as a man or a woman. Some of these laws would limit protections for transgender and nonbinary people; others are aimed at safeguarding them. The survey finds that a majority of U.S. adults (64%) say they would favor laws that would protect transgender individuals from discrimination in jobs, housing and public spaces such as restaurants and stores. But there is also a fair amount of support for specific proposals that would limit how trans people can participate in certain activities and navigate their day-to-day lives. Roughly six-in-ten adults (58%) favor proposals that would require transgender athletes to compete on teams that match the sex they were assigned at birth (17% oppose this, 24% neither favor nor oppose). 1 And 46% favor making it illegal for health care professionals to provide someone younger than 18 with medical care for a gender transition (31% oppose). The public is more evenly split when it comes to making it illegal for public school districts to teach about gender identity in elementary schools (41% favor and 38% oppose) and investigating parents for child abuse if they help someone younger than 18 get medical care for a gender transition (37% favor and 36% oppose). Across the board, views on these policies are deeply divided by party. [ ![Views of laws and policies related to transgender issues differ widely by party](https://www.pewresearch.org/wp- content/uploads/sites/20/2022/06/PSDT_06.28.22_Gender_Identity_0_2.png?w=640) ](https://www.pewresearch.org/social-trends/2022/06/28/americans-complex- views-on-gender-identity-and-transgender- issues/psdt_06-28-22_gender_identity_0_2-png/) When asked what has influenced their views on gender identity – specifically, whether they believe a person can be a different gender than the sex they were assigned at birth – those who believe gender can be different from sex at birth and those who do not point to different factors. For the former group, the most influential factors shaping their views are what they’ve learned from science (40% say this has influenced their views a great deal or a fair amount) and knowing someone who is transgender (38%). Some 46% of those who say gender is determined by sex at birth also point to what they’ve learned from science, but this group is far more likely than those who say a person’s gender can be different from their sex at birth to say their religious beliefs have had at least a fair amount of influence on their opinion (41% vs. 9%). The nationally representative survey of 10,188 U.S. adults was conducted May 16-22, 2022. [ Previously published findings from the survey ](https://www.pewresearch.org/short-reads/2022/06/07/about-5-of-young-adults- in-the-u-s-say-their-gender-is-different-from-their-sex-assigned-at-birth/) show that 1.6% of U.S. adults are trans or nonbinary, and the share is higher among adults younger than 30. More than four-in-ten U.S. adults know someone who is trans and 20% know someone who is nonbinary. Among the other key findings in this report: Nearly half of U.S. adults (47%) say it’s extremely or very important to use a person’s new name if they transition to a gender that is different from the sex they were assigned at birth and change their name. A smaller share (34%) say the same about using someone’s new pronouns (such as “he” instead of “she”). A majority of Democrats (64%) – compared with 28% of Republicans – say it’s at least very important to use someone’s new name if they go through a gender transition and change their name. And while 51% of Democrats say it’s extremely or very important to use someone’s new pronouns, just 14% of Republicans say the same. Many Americans express discomfort with the pace of change around issues of gender identity. Some 43% say views on issues related to people who are transgender or nonbinary are changing too quickly, while 26% say things aren’t changing quickly enough and 28% say the pace of change is about right. Adults ages 65 and older are the most likely to say views on these issues are changing too quickly; conversely, those younger than 30 are the most likely to say they’re not changing quickly enough. More than four-in-ten (44%) say forms and online profiles that ask about a person’s gender should include options other than “male” and “female” for people who don’t identify as either. Some 38% say the same about government documents such as passports and driver’s licenses. Half of adults younger than 30 say government documents that ask about a person’s gender should provide more than two gender options, compared with about four-in-ten or fewer among those in older age groups. Views differ even more widely by party: While majorities of Democrats say forms and online profiles (64%) and government documents (58%) should offer options other than “male” and “female,” about eight-in-ten Republicans say they should _not_ (79% say this about forms and online profiles and 83% say this about government documents). Democrats and Republicans who agree that a person’s gender is determined by their sex at birth often have different views on transgender issues. A majority (61%) of Democrats – but just 31% of Republicans – who say a person’s gender is determined by the sex they were assigned at birth say there is at least a fair amount of discrimination against transgender people in our society today. And while 62% of Democrats who say gender is determined by sex at birth say they would favor policies that protect trans individuals against discrimination, fewer than half of their Republican counterparts say the same. Democrats’ views on some transgender issues vary by age. Among Democrats younger than 30, about seven-in-ten (72%) say someone can be a man or a woman even if that’s different from the sex they were assigned at birth, and 66% say society hasn’t gone far enough in accepting people who are transgender. Smaller majorities of Democrats 30 and older express these views. Age is less of a factor among Republicans. In fact, similar shares of Republicans ages 18 to 29 and those 65 and older say a person’s gender is determined by their sex at birth (88% each) and that society has gone too far in accepting people who are transgender (67% of Republicans younger than 30 and 69% of those 65 and older). About three-in-ten parents of K-12 students (29%) say at least one of their children has learned about people who are transgender or nonbinary from a teacher or another adult at their school. Similar shares across regions and in urban, suburban and rural areas say their children have learned about this in school, as do similar shares of Republican and Democratic parents. Views on whether it’s good or bad that their children have or haven’t learned about people who are trans or nonbinary at school vary by party and by children’s age. For example, among parents of children in elementary school, 45% say either that their children _have_ learned about this and that’s a _bad_ thing or that they _haven’t_ learned about it and that’s a _good_ thing. A smaller share of parents of middle and high schoolers (34%) say the same. Republican parents are much more likely than Democratic parents to say this, regardless of their child’s age. ### A rising share say a person’s gender is determined by their sex at birth [ ![Majority of U.S. adults say gender is determined by sex assigned at birth](https://www.pewresearch.org/wp- content/uploads/sites/20/2022/06/PSDT_06.28.22_Gender_Identity_0_3.png?w=620) ](https://www.pewresearch.org/social-trends/2022/06/28/americans-complex- views-on-gender-identity-and-transgender- issues/psdt_06-28-22_gender_identity_0_3-png/) Six-in-ten U.S. adults say that whether a person is a man or a woman is determined by their sex assigned at birth. This is up from 56% [ one year ago ](https://www.pewresearch.org/short-reads/2021/07/27/rising-shares-of-u-s- adults-know-someone-who-is-transgender-or-goes-by-gender-neutral-pronouns/) and 54% in [ 2017 ](https://www.pewresearch.org/short- reads/2017/11/08/transgender-issues-divide-republicans-and-democrats/) . No single demographic group is driving this change, and patterns in who is more likely to say this are similar to what they were in past years. Today, half or more in all age groups say that gender is determined by sex assigned at birth, but this is a less common view among younger adults. Half of adults younger than 30 say this, lower than the 60% of 30- to 49-year-olds who say the same. Even higher shares of those 50 to 64 (66%) and those 65 and older (64%) say a person’s gender is determined by their sex at birth. The party gap on this issue remains wide. The vast majority of Republicans and those who lean toward the GOP say gender is determined by sex assigned at birth (86%), compared with 38% of Democrats and Democratic leaners. Most Democrats say that whether a person is a man or a woman can be different from their sex at birth (61% vs. just 13% of Republicans). Liberal Democrats are particularly likely to hold this view – 79% say a person’s gender can be different from sex at birth, compared with 45% of moderate or conservative Democrats. Meanwhile, 92% of conservative Republicans say gender is determined by sex at birth and 74% of moderate or liberal Republicans agree. Democrats ages 18 to 29 are also substantially more likely than older Democrats to say that someone’s gender can be different from their sex assigned at birth, although majorities of Democrats across age groups share this view. About seven-in-ten Democrats younger than 30 say this (72%), compared with about six-in-ten or fewer in the older age groups. Among Republicans, there is no clear pattern by age. About eight-in-ten or more Republicans across age groups – including 88% each among those ages 18 to 29 and those 65 and older – say a person’s gender is determined by their sex at birth. The view that a person’s gender is determined by their sex assigned at birth is more common among those with lower levels of educational attainment and those living in rural areas or in the Midwest or South. This view is also more prevalent among men and Black Americans. A solid majority of those who do _not_ know a transgender person say that whether a person is a man or a woman is determined by sex assigned at birth (68%), while those who _do_ know a trans person are more evenly split. About half say gender is determined by sex assigned at birth (51%), while 48% say gender and sex assigned at birth can be different. Though Republicans who know a trans person are more likely than Republicans who don’t to say gender can be different from sex assigned at birth, more than eight-in-ten in both groups (83% and 88%, respectively) say gender is determined by sex at birth. Meanwhile, there are large differences between Democrats who do and do _not_ know a transgender person. A majority of Democrats who _do_ know a trans person (72%) say someone can be a man or a woman even if that differs from their sex assigned at birth, while those who don’t know anyone who is transgender are about evenly split (48% say gender is determined by sex assigned at birth while 51% say it can be different). #### Many Americans point to science when asked what has influenced their views on whether gender can differ from sex assigned at birth When asked about factors that have influenced their views about whether someone’s gender can be different from the sex they were assigned at birth, 44% say what they’ve learned from science has had a great deal or a fair amount of influence. About three-in-ten (28%) point to their religious views and about two-in-ten (22%) say knowing someone who is transgender has influenced their views at least a fair amount. Smaller shares say what they’ve heard or read in the news (15%) or on social media (14%) has had a great deal or a fair amount of influence on their views. [ ![Chart showing More than four-in-ten U.S. adults say science has influenced their views of gender and sex at least a fair amount](https://www.pewresearch.org/wp- content/uploads/sites/20/2022/06/PSDT_06.28.22_Gender_Identity_0_4.png?w=640) ](https://www.pewresearch.org/social-trends/2022/06/28/americans-complex- views-on-gender-identity-and-transgender- issues/psdt_06-28-22_gender_identity_0_4-png/) The factors people point to on this topic differ by whether or not they say gender is determined by sex at birth. Among those who say that whether someone is a man or a woman is determined by the sex they were assigned at birth, 46% say what they’ve learned from science has influenced their views on this at least a fair amount, while 41% say the same about their religious views. About one-in-ten point to what they’ve heard or read in the news (12%), what they’ve heard or read on social media (11%) or knowing someone who’s transgender (11%). Among those who say someone can be a man or a woman even if that’s different from the sex they were assigned at birth, 40% say their views on this topic have been influenced at least a fair amount by what they’ve learned from science. A similar share say the same about knowing a transgender person (38%). Smaller shares in this group say what they’ve heard or read in the news (19%) or on social media (18%) or their religious views (9%) have had a great deal or a fair amount of influence. Among those who say gender is determined by sex assigned at birth, adults younger than 30 stand out as being more likely than their older counterparts to say their knowledge of science (60%), what they’ve heard or read on social media (22%) or knowing someone who is trans (17%) influenced this view a great deal or a fair amount. In turn, those ages 65 and older tend to be more likely than younger age groups to cite their religious views (51% in the older group say this has had at least a fair amount of influence). Republicans who say gender is determined by sex assigned at birth are more likely than Democrats with the same view to say their knowledge of science (52% vs. 40%) and their religious views (45% vs. 34%) have had at least a fair amount of influence, while Democrats are more likely than Republicans to say the news (17% vs. 10%), social media (16% vs. 10%) and knowing someone who is trans (15% vs. 9%) have influenced them – though the shares are still small among both groups. [ ![U.S. adults with different viewpoints on gender and sex say their opinions have been influenced by different factors](https://www.pewresearch.org/wp- content/uploads/sites/20/2022/06/PSDT_06.28.22_Gender_Identity_0_5.png?w=620) ](https://www.pewresearch.org/social-trends/2022/06/28/americans-complex- views-on-gender-identity-and-transgender- issues/psdt_06-28-22_gender_identity_0_5-png/) On the flip side, among those who say someone’s gender can be _different_ from the sex they were assigned at birth, adults younger than 30 are also more likely than older adults to say social media has contributed to this view at least a fair amount (33% vs. 15% or fewer among older age groups). Adults ages 65 and older are more likely than their younger counterparts to say what they’ve learned from science has influenced their view (46% vs. 40% or fewer). Democrats who say whether someone is a man or a woman can be different from their sex at birth are more likely than Republicans with the same view to say that what they’ve learned from science (43% vs. 26%) and knowing someone who is transgender (40% vs. 26%) has influenced their view a great deal or a fair amount. ### Public sees discrimination against trans people and limited acceptance Roughly eight-in-ten Americans say transgender people face at least some discrimination, and relatively few believe our society is extremely or very accepting of people who are trans. These views differ widely by partisanship and by beliefs about whether someone’s gender can differ from the sex they were assigned at birth. Overall, 57% of adults say there is a great deal or a fair amount of discrimination against transgender people in our society today. An additional 21% say there is some discrimination against trans people, and 14% say there is a little or none at all. There are modest differences in views on this issue across demographic groups. Women (62%) are more likely than men (52%) to say there is a great deal or a fair amount of discrimination against transgender people, and college graduates (62%) are more likely than those with less education (55%) to say the same. [ ![Chart showing Most Americans say there is at least some discrimination against trans people in the U.S.](https://www.pewresearch.org/wp- content/uploads/sites/20/2022/06/PSDT_06.28.22_Gender_Identity_0_6.png?w=640) ](https://www.pewresearch.org/social-trends/2022/06/28/americans-complex- views-on-gender-identity-and-transgender- issues/psdt_06-28-22_gender_identity_0_6-png/) There is, however, a wide partisan divide in these views: While 76% of Democrats and those who lean to the Democratic Party say there is a great deal or a fair amount of discrimination against trans people, 35% of Republicans and Republican leaners share that assessment. One-in-four Republicans see little or no discrimination against this group, compared with 5% of Democrats. These views are also linked with underlying opinions about whether a person’s gender can be different from their sex assigned at birth. Among those who say someone can be a man or a woman even if that’s different from the sex they were assigned at birth, 83% say there is a great deal or a fair amount of discrimination against trans people. Even so, some 42% of those who hold the alternative point of view – that gender is determined by sex assigned at birth – also see at least a fair amount of discrimination. Among Democrats who say gender is determined by sex at birth, that share rises to 61%. Relatively few adults (14%) say society is extremely or very accepting, while about a third (35%) say it is somewhat accepting. A plurality (44%) says our society is a little or not at all accepting of trans people. [ ![Chart showing Plurality of Americans say there is little or no societal acceptance of transgender people](https://www.pewresearch.org/wp- content/uploads/sites/20/2022/06/PSDT_06.28.22_Gender_Identity_0_7.png?w=640) ](https://www.pewresearch.org/social-trends/2022/06/28/americans-complex- views-on-gender-identity-and-transgender- issues/psdt_06-28-22_gender_identity_0_7-png/) Again, these views are strongly linked with partisanship. Democrats have a much more negative view than Republicans, with 54% of Democrats saying society is a little accepting or not at all accepting of transgender people, compared with a third of Republicans. And, as with views of discrimination, assessments of societal acceptance are linked to underlying views about how gender is determined. Those who say one’s gender can be different from the sex they were assigned at birth see less acceptance: 56% say society is a little accepting or not accepting at all of people who are transgender. This compares with 37% among those who say gender is determined by sex at birth. Republicans who say gender is determined by sex at birth are more likely than Democrats who say the same to believe that society is at least somewhat accepting of people who are transgender (61% vs. 47%). #### About four-in-ten say society has gone too far in accepting trans people While a majority of Americans see at least a fair amount of discrimination against transgender people and relatively few see widespread acceptance, 38% say our society has gone too far in accepting them. Some 36% say society has not gone far enough in accepting people who are trans, and 23% say the level of acceptance has been about right. These views differ along demographic and partisan lines. Young adults (ages 18 to 29) and those with a bachelor’s degree or more education are among the most likely to say society hasn’t gone far enough in accepting people who are trans. Men, White adults and those without a four-year college degree are among the most likely to say society has gone too far in this regard. [ ![Chart showing Public is divided over whether society has gone too far or not far enough in accepting transgender people](https://www.pewresearch.org/wp- content/uploads/sites/20/2022/06/PSDT_06.28.22_Gender_Identity_0_8.png?w=620) ](https://www.pewresearch.org/social-trends/2022/06/28/americans-complex- views-on-gender-identity-and-transgender- issues/psdt_06-28-22_gender_identity_0_8-png/) There is a wide partisan divide as well. Roughly six-in-ten Democrats (59%) say society hasn’t gone far enough in accepting people who are transgender, while 15% say it has gone too far (24% say it’s been about right). Republicans’ views are almost the inverse: 10% say society hasn’t gone far enough and 66% say it’s gone too far (22% say it’s been about right). Even among those who see at least some discrimination against trans people, a majority (54%) say society has either gone too far in accepting trans people or been about right; 44% say society hasn’t gone far enough. ### Many say it’s important to use someone’s new name, pronouns when they’ve gone through a gender transition [ ![Nearly half of adults say it’s important to use someone’s new name if they change their name as part of a gender transition](https://www.pewresearch.org/wp- content/uploads/sites/20/2022/06/PSDT_06.28.22_Gender_Identity_0_9.png?w=640) ](https://www.pewresearch.org/social-trends/2022/06/28/americans-complex- views-on-gender-identity-and-transgender- issues/psdt_06-28-22_gender_identity_0_9-png/) Nearly half of adults (47%) say it’s extremely or very important that if a person who transitions to a gender that’s different from their sex assigned at birth changes their name, others refer to them by their new name. An additional 22% say this is somewhat important. Three-in-ten say this is a little or not at all important (18%) or that it shouldn’t be done (12%). Smaller shares say that if a person transitions to a gender that’s different from their sex assigned at birth and starts going by different pronouns (such as “she” instead of “he”), it’s important that others refer to them by their new pronouns. About a third (34%) say this is extremely or very important, and 21% say this is somewhat important. More than four-in-ten say this is a little or not at all important (26%) or it should not be done (18%). These views differ along many of the same dimensions as other topics asked about. While 80% of those who believe someone’s gender can be different from their sex assigned at birth also say it’s extremely or very important to use a person’s new name when they’ve gone through a gender transition, 27% of those who think gender is determined by one’s sex assigned at birth share this opinion. The pattern is similar when it comes to use of preferred pronouns. Democrats are much more likely than Republicans to say it’s extremely or very important to refer to a person using their new name or pronouns. When it comes to pronouns, a majority of Republicans (55%), compared with only 17% of Democrats, say using someone’s new pronouns when they’ve been through a gender transition is not at all important or should not be done. [ ![Chart showing People who know a trans person place more importance on using a person’s new name, pronouns if they transition](https://www.pewresearch.org/wp- content/uploads/sites/20/2022/06/PSDT_06.28.22_Gender_Identity_0_10.png?w=618) ](https://www.pewresearch.org/social-trends/2022/06/28/americans-complex- views-on-gender-identity-and-transgender- issues/psdt_06-28-22_gender_identity_0_10-png/) There are some demographic differences as well, with women more likely than men and those with a four-year college degree more likely than those with less education to say it’s extremely or very important to use a person’s new name or pronouns when referring to them. In addition, people who say they know someone who is trans are more likely than those who do not to say this is extremely or very important. Even so, substantial shares of those who don’t know a trans person view this as important. For example, 39% of those who don’t know someone who is transgender say it’s extremely or very important to refer to a person who goes through a gender transition and changes their name by their new name. ### Plurality of adults say views on gender identity issues are changing too quickly Many Americans are not comfortable with the pace of change that’s occurring around issues involving gender identity. Some 43% say views on issues related to people who are transgender and nonbinary are changing too quickly. About one-in-four (26%) say things are not changing quickly enough, and 28% say they are changing at about the right speed. Women (30%) are more likely than men (21%) to say views on these issues are not changing quickly enough, and adults younger than 30 are more likely than their older counterparts to say the same. Among those ages 18 to 29, 37% say views on these issues are not changing quickly enough; this compares with 26% of those ages 30 to 49, 22% of those ages 50 to 64 and 19% of those 65 and older. At the same time, White adults (46%) are more likely than Black (34%), Hispanic (39%) or Asian (31%) adults to say views are changing _too quickly_ . [ ![Chart showing More than four-in-ten Americans say societal views on gender identity are changing too quickly](https://www.pewresearch.org/wp- content/uploads/sites/20/2022/06/PSDT_06.28.22_Gender_Identity_0_11.png?w=620) ](https://www.pewresearch.org/social-trends/2022/06/28/americans-complex- views-on-gender-identity-and-transgender- issues/psdt_06-28-22_gender_identity_0_11-png/) Opinions also differ sharply by partisanship. Among Democrats, a plurality (42%) say views on issues involving transgender and nonbinary people are not changing fast enough, and 21% say they are changing too quickly. About a third (35%) say the speed is about right. By contrast, 70% of Republicans say views on these issues are changing too quickly, while only 7% say views aren’t changing fast enough. About one-in-five Republicans (21%) say they’re changing at about the right speed. Respondents were asked in an open-ended format why they think views are changing too quickly or not quickly enough, when it comes to issues surrounding transgender and nonbinary people. For those who say things are changing too quickly, responses fell into several different categories. Some indicated that new ways of thinking about gender were inconsistent with their religious beliefs. Others expressed concern that the long-term consequences of medical gender transitions are not well-known, or that changing views on gender identity are merely a fad that’s being pushed by the media. Still others said they worry that there’s too much discussion of these issues in schools these days. For those who say views are not changing quickly enough, some pointed to discrimination and a lack of acceptance of trans and nonbinary people. Others pointed to legislative initiatives in some states aimed at restricting the rights of trans and nonbinary people. Many also said that too many people in our society aren’t open to change when it comes to these issues. 2 #### In their own words: Why do some people think views on issues related to transgender people and those who don’t identify as a man or a woman are changing _too quickly_ ? __General concerns about the pace of change_ _ _“The issue is so new to me I can’t keep up. I don’t know what to think about all of this new information. I’m baffled by so many changes.”_ _“It takes quite a bit of time for society to accept changes. I have not been aware of this issue for very long. I am relatively conservative and feel that changes need time to be accepted.”_ __Religious reasons_ _ _“People now believe everyone should just forget about their birth identity and just go along with what they think they are. God made us all for a reason and if He intended us to pick our gender then there would be no reason to be born with specific male or female parts_ .” _“I have a personal religious belief that sex is an essential part of our eternal identity and that identifying as something other than you are … just doesn’t make a lot of sense.”_ _“I believe GOD created a man and a woman. We have overstepped our bounds in messing with the miracle of life. I side with my creator.”_ __Concerns about long-term medical consequences_ _ _“We do not know the long-term health problems of hormone therapy, especially in young children.”_ _“More time needs to pass to study mental, physical, emotional ramifications of medications & surgeries, especially when done before puberty and/or adulthood.” _ _“Accepting gender fluidity, especially for younger children, seems quick. Also, medical treatments related to gender for people under 18 seems to be being accepted without longer term studies.”_ __It’s a fad/Driven by the media_ _ _“I respect people’s views about themselves, and I will refer to them in the way they want to be referred to, but I believe it’s become trendy because it’s being pushed so much in culture, especially for children.”_ _“News media, social media and entertainment media companies are trying to change, and it seems they have been succeeding in changing public opinion on this issue for many people.”_ _“It is encouraging kids who are easily influenced to participate in the ‘in’ fad when their brains are not fully developed.”_ __Concerns about schools_ _ _“Elementary school students should not be subjected to instruction on sex identity, any questions the child asks should be referred to a parent.”_ _“I think that young people are exposed to these issues at too early an age. I believe that it is up to the parents, and I oppose schools that want to include it in the ‘curriculum.’”_ _“It’s being pushed on society and especially on younger children, confusing them all the more. This is not something that should be taught in schools.”_ #### In their own words: Why do some people think views on issues related to transgender people and those who don’t identify as a man or a woman are changing _too slowly_ ? __Discrimination_ _ _“There is far too much discrimination, hate, and violence directed toward people who are brave enough to stand up for who they truly are. We, as a country and as a society, need to respect how people want to identify themselves and be kind toward one another, end of story.”_ _“Protections for basic rights to self-determination in identity, health care choices, privacy, and consensual relationships should be a bare minimum that our society can provide for everyone – transgender people included_ . _”_ _“There’s too much discrimination. People need to quit controlling other people’s private lives. I consider them very brave for having the courage to be who they identify with_ . _”_ _“Equal protection has not kept up with trans issues, including trans youth and the right to gender-affirming care.”_ __Legislative efforts_ _ _“Acceptance is not changing quick enough. There remains discrimination and elected officials are passing laws that make it more difficult for transgender individuals in society to live, work and exist.”_ _“We are going backwards with all the anti-gay & -trans legislation that is being passed.” _ _“For every step forward, it feels like there are two steps back with reactive conservative laws.”_ _“These laws are working to restrict the rights of trans and nonbinary people, and also discrimination is still very high which results in elevated rates of suicide, poverty, violence and homelessness especially for people of color.”_ _“The spate of laws being proposed that would take away the rights of transgender people is evidence that we’re a long way from treating them right.”_ __Society is not open to change_ _ _“Too many people are simply stuck in the binary. We, as a society, need to just accept that someone else’s gender identity is whatever they say it is and it rarely has any bearing on the lives of others.”_ _“These are people. Who they say they are is all that matters. Society, mostly conservatives, doesn’t understand change in any form. So, they fight it. And they hinder the ability for others to learn about themselves and others, which slows growing as a society to a crawl.”_ _“It’s an issue that has been in the closet for centuries. It’s time to acknowledge and accept that gender identity is a spectrum and not binary.”_ _“We are not accepting the changes. We refuse to see what is in front of us. We care too much about not changing the status quo as we know it.”_ _“Society often views this as a phase or a period of uncertainty in their life. Instead, it’s about a person bringing their gender identity in line with what they have experienced internally all their life.”_ ### Most say they’re not paying close attention to news about bills related to transgender people [ ![Chart showing Liberal Democrats are more likely than other groups to be following news about bills related to trans people closely](https://www.pewresearch.org/wp- content/uploads/sites/20/2022/06/PSDT_06.28.22_Gender_Identity_0_12.png?w=618) ](https://www.pewresearch.org/social-trends/2022/06/28/americans-complex- views-on-gender-identity-and-transgender- issues/psdt_06-28-22_gender_identity_0_12-png/) Many states are [ considering legislation ](https://www.washingtonpost.com/politics/2022/03/25/lgbtq-rights-gop-bills- dont-say-gay/) related to people who are transgender, but a relatively small share of U.S. adults (8%) say they’re following news about these bills extremely or very closely. Another 24% say they’re following this somewhat closely, while about two-thirds say they’re following it either a little closely (23%) or not all closely (44%). 3 Only about one-in-ten or less across age, racial and ethnic groups, and across levels of educational attainment, say they are following news about bills related to people who are transgender extremely or very closely. Six-in-ten or more across demographic groups say they’re following news about these bills a little closely or not closely at all. Liberal Democrats and Democratic-leaning independents (46%) are more likely than moderate and conservative Democrats (29%) to say they are following news about state bills related to people who are transgender at least somewhat closely. Conservative Republicans and Republican leaners (31%) are more likely than their moderate and liberal counterparts (24%) – but less likely than liberal Democrats – to be following news about these bills at least somewhat closely. Still, half or more among each of these groups say they have been following news about this a little or not at all closely. ### About six-in-ten would favor requiring that transgender athletes compete on teams that match their sex at birth The survey asked respondents how they feel about some current laws and policies that are either in place or being considered across the U.S. related to transgender issues. Only two of seven items are either endorsed or rejected by a majority: 64% say they would favor policies that protect transgender individuals from discrimination in jobs, housing, and public spaces such as restaurants and stores, and 58% say they would favor policies that require that transgender athletes compete on teams that match the sex they were assigned at birth rather than the gender they identify with. [ ![Chart showing Most Americans say they would favor laws that would protect transgender people from discrimination in jobs, housing and public spaces](https://www.pewresearch.org/wp- content/uploads/sites/20/2022/06/PSDT_06.28.22_Gender_Identity_0_13.png?w=640) ](https://www.pewresearch.org/social-trends/2022/06/28/americans-complex- views-on-gender-identity-and-transgender- issues/psdt_06-28-22_gender_identity_0_13-png-2/) Even though there is not a majority consensus on most of these laws or policies, there are gaps of at least 10 percentage points on three items. Some 46% say they would favor making it illegal for health care professionals to provide someone younger than 18 with medical care for gender transitions, and 41% would favor requiring transgender individuals to use public bathrooms that match the sex they were assigned at birth rather than the gender they identify with; 31% say they would oppose each of these. Meanwhile, more say they would _oppose_ (44%) than say they would favor (27%) requiring health insurance companies to cover medical care for gender transitions. Views are more divided when it comes to laws and policies that would make it illegal for public school districts to teach about gender identity in elementary schools (41% favor and 38% oppose) or that would investigate parents for child abuse if they helped someone younger than 18 get medical care for a gender transition (37% favor and 36% oppose). Some 21% and 27%, respectively, say they’d neither favor nor oppose these policies. #### Views on many policies related to transgender issues vary by age, party, and race and ethnicity Majorities of U.S. adults across age groups express support for laws and policies that would protect transgender individuals from discrimination in jobs, housing, and public spaces such as restaurants and stores. About seven- in-ten adults ages 18 to 29 (70%) and 30 to 49 (68%) say they favor such protections, as do about six-in-ten adults ages 50 to 64 (60%) and 65 and older (59%). But adults younger than 30 are more likely than those in each of the older age groups to say they favor laws or policies that would require health insurance companies to cover medical care for gender transitions (37% among those younger than 30 vs. about a quarter among each of the older age groups). They’re also less likely than older adults to express support for bills and policies that would restrict the rights of people who are transgender or limit what schools teach about gender identity. On most items, those ages 50 to 64 and those 65 and older express similar views. [ ![Chart showing Views of laws and policies related to transgender issues differ by age](https://www.pewresearch.org/wp- content/uploads/sites/20/2022/06/PSDT_06.28.22_Gender_Identity_0_14.png?w=640) ](https://www.pewresearch.org/social-trends/2022/06/28/americans-complex- views-on-gender-identity-and-transgender- issues/psdt_06-28-22_gender_identity_0_14-png/) Views differ even more widely along party lines. For example, eight-in-ten Democrats say they favor laws or policies that would protect trans individuals from discrimination, compared with 48% of Republicans. Conversely, by margins of about 40 percentage points or more, Republicans are more likely than Democrats to express support for laws or policies that would do each of the following: require trans athletes to compete on teams that match the sex they were assigned at birth (85% of Republicans vs. 37% of Democrats favor); make it illegal for health care professionals to provide someone younger than 18 with medical care for a gender transition (72% vs. 26%); make it illegal for public school districts to teach about gender identity in elementary schools (69% vs. 18%); require transgender individuals to use public bathrooms that match the sex they were assigned at birth (67% vs. 20%); and investigate parents for child abuse if they help someone younger than 18 get medical care for a gender transition (59% vs. 17%). Overall, White adults tend to be more likely than Black, Hispanic and Asian adults to express support for laws and policies that would restrict the rights of transgender people or limit what schools can teach about gender identity. But among Democrats, White adults are often _less_ likely than other groups to favor such laws and policies, particularly compared with their Black and Hispanic counterparts. And White Democrats are more likely than Black, Hispanic and Asian Democrats to say they favor protecting trans individuals from discrimination and requiring health insurance companies to cover medical care for gender transitions. ### Sizable shares say forms and government documents should include options other than ‘male’ and ‘female’ [ ![Chart showing About four-in-ten or more say forms and government documents should offer options other than ‘male’ and ‘female’](https://www.pewresearch.org/wp- content/uploads/sites/20/2022/06/PSDT_06.28.22_Gender_Identity_0_15.png?w=620) ](https://www.pewresearch.org/social-trends/2022/06/28/americans-complex- views-on-gender-identity-and-transgender- issues/psdt_06-28-22_gender_identity_0_15-png/) About four-in-ten Americans (38%) say government documents such as passports and driver’s licenses that ask about a person’s gender should include options other than “male” and “female” for people who don’t identify as either; a larger share (44%) say the same about forms and online profiles that ask about a person’s gender. Half of adults younger than 30 say government documents that ask about gender should include options other than “male” and “female,” compared with 39% of those ages 30 to 49, 35% of those 50 to 64 and 33% of adults 65 and older. When it comes to forms and online profiles, 54% of adults younger than 30 and 47% of those ages 30 to 49 say these forms should include more than two gender options; smaller shares of adults ages 50 to 64 and 65 and older (37% each) say the same. Views on this vary considerably by party. A majority of Democrats and Democratic-leaning independents say forms and online profiles (64%) and government documents (58%) that ask about a person’s gender should include options other than “male” and “female.” In contrast, about eight-in-ten or more Republicans and Republican leaners say forms and online profiles (79%) and government documents (83%) should _not_ include more than these two gender options. Those who say they know someone who is nonbinary are more likely than those who don’t know anyone who’s nonbinary to say forms and government documents should include gender options other than “male” and “female.” Still, 39% of those who don’t know anyone who’s nonbinary say forms and online profiles shouldinclude other gender options, and 33% say the same about government documents that ask about a person’s gender. Conversely, 31% of those who say they know someone who’s nonbinary say forms and online profiles should _not_ include options other than “male” and “female,” and 41% say this about government documents. ### About three-in-ten parents of K-12 students say their children have learned about people who are trans or nonbinary at school In recent months, lawmakers in several states have introduced legislation that would [ prohibit or limit instruction on sexual orientation or gender identity ](https://www.edweek.org/leadership/whats-driving-the-push-to-restrict- schools-on-lgbtq-issues/2022/04) in schools. The survey asked parents of K-12 students whether any of their children have learned about people who are transgender or who don’t identify as a boy or a girl from a teacher or another adult at their school and how they feel about the fact that their children have or have not learned about this. Some 37% of parents with children in middle or high school say their middle or high schoolers have learned about people who are transgender or who don’t identify as a boy or a girl from a teacher or another adult at their school; a much smaller share of parents of elementary school students (16%) say the same. Overall, 29% of parents with children in elementary, middle or high school say at least one of their K-12 children have learned about this at school. Similar shares of parents of K-12 students in urban (31%), suburban (27%) and rural (32%) areas – and in the Northeast (34%), Midwest (33%), South (26%) and West (28%) – say their school-age children have learned about people who are transgender or who don’t identify as a boy or a girl. And Republican (27%) and Democratic (31%) parents are also about equally likely to say their children have learned about this in school. None of these differences are statistically significant. [ ![Chart showing Views on children learning about people who are trans or nonbinary at school differ by party, children’s age](https://www.pewresearch.org/wp- content/uploads/sites/20/2022/06/PSDT_06.28.22_Gender_Identity_0_16.png?w=640) ](https://www.pewresearch.org/social-trends/2022/06/28/americans-complex- views-on-gender-identity-and-transgender- issues/psdt_06-28-22_gender_identity_0_16-png-2/) Many parents of K-12 students don’t think it’s good for their children to learn about people who are transgender or nonbinary from their teachers or other adults at school. Among parents of elementary school students, 45% either say their children have learned about people who are trans or nonbinary at school and see this is a _bad_ thing or say their children have _not_ learned about this and say this is a _good_ thing. A far smaller share (13%) say it’s a good thing that their elementary school children have learned about people who are trans or nonbinary or that it’s a bad thing that they _haven’t_ learned about this. And about four-in-ten (41%) say it’s neither good nor bad that their elementary school children have or haven’t learned about people who are transgender or nonbinary. Among parents with children in middle or high school, 34% say it’s a bad thing that their children have learned about people who are trans or nonbinary at school _or_ that it’s a good thing that they haven’t; 14% say it’s good that their middle or high schoolers have learned about this _or_ that it’s bad that they haven’t; and 51% say it’s neither good nor bad that their children have or haven’t learned about this in school. Republican and Republican-leaning parents with children in elementary, middle and high school are more likely than their Democratic and Democratic-leaning counterparts to say it’s a bad thing that their children have learned about people who are trans or nonbinary at school or that it’s a good thing that they haven’t. In turn, Democratic parents are more likely to say it’s _good_ that their children _have_ learned about this or _bad_ that they _haven’t_ . They are also more likely to say it’s neither good nor bad that their children have or haven’t learned about people who are trans or nonbinary at school. [ Acknowledgments ](https://www.pewresearch.org/social- trends/2022/06/28/acknowledgments-59/) ← Prev Page [ 2 ](https://www.pewresearch.org/social- trends/2022/06/28/acknowledgments-59/) [ 3 ](https://www.pewresearch.org/social-trends/2022/06/28/methodology-51/) [ Next Page → ](https://www.pewresearch.org/social- trends/2022/06/28/acknowledgments-59/) 1. For each policy item, respondents were also given the option of answering “neither favor nor oppose.” ↩ 2. Open-ended responses (quotations) have been lightly edited for clarity and length. ↩ 3. The shares who say they are following news about this a little or not at all closely do not add up to the combined share shown in the chart due to rounding. ↩ ![](https://www.pewresearch.org/wp-content/plugins/prc-block- library/blocks/promo/assets/weekly.svg) ### Sign up for our weekly newsletter Fresh data delivery Saturday mornings Sign Up ![](https://www.pewresearch.org/wp-content/plugins/prc-block- library/blocks/promo/assets/journalism.svg) ### Sign up for The Briefing Weekly updates on the world of news & information Sign Up Topics * [ Discrimination & Prejudice ](https://www.pewresearch.org/topic/politics-policy/political-issues/discrimination-prejudice/) * [ Gender Identity ](https://www.pewresearch.org/topic/gender-lgbtq/lgbtq-attitudes-experiences/gender-identity/) * [ K-12 ](https://www.pewresearch.org/topic/other-topics/education/k-12/) * [ LGBTQ Acceptance ](https://www.pewresearch.org/topic/politics-policy/political-issues/lgbtq-acceptance/) * [ Parenthood ](https://www.pewresearch.org/topic/family-relationships/parenthood/) Share This Link: * [ X ](https://pewrsr.ch/3OQ7Zg6) * [ Facebook ](https://pewrsr.ch/3OQ7Zg6) * [ Threads ](https://pewrsr.ch/3OQ7Zg6) * [ LinkedIn ](https://pewrsr.ch/3OQ7Zg6) * [ WhatsApp ](https://pewrsr.ch/3OQ7Zg6) [ Share _ _ ](https://www.pewresearch.org/social-trends/2022/06/28/americans- complex-views-on-gender-identity-and-transgender-issues/) ### Related report Apr 2, 2024 [ ](https://www.pewresearch.org/2024/04/02/rising-numbers-of-americans-say- jews-and-muslims-face-a-lot-of-discrimination/) ## [ Rising Numbers of Americans Say Jews and Muslims Face a Lot of Discrimination ](https://www.pewresearch.org/2024/04/02/rising-numbers-of- americans-say-jews-and-muslims-face-a-lot-of-discrimination/) short read Apr 2, 2024 [ ](https://www.pewresearch.org/short-reads/2024/04/02/how-us-muslims-are- experiencing-the-israel-hamas-war/) ## [ How U.S. Muslims are experiencing the Israel-Hamas war ](https://www.pewresearch.org/short-reads/2024/04/02/how-us-muslims-are- experiencing-the-israel-hamas-war/) short read Apr 2, 2024 [ ](https://www.pewresearch.org/short-reads/2024/04/02/how-us-jews-are- experiencing-the-israel-hamas-war/) ## [ How U.S. Jews are experiencing the Israel-Hamas war ](https://www.pewresearch.org/short-reads/2024/04/02/how-us-jews-are- experiencing-the-israel-hamas-war/) short read Dec 8, 2023 [ ](https://www.pewresearch.org/short-reads/2023/12/08/striking-findings- from-2023/) ## [ Striking findings from 2023 ](https://www.pewresearch.org/short- reads/2023/12/08/striking-findings-from-2023/) report Dec 8, 2023 [ ](https://www.pewresearch.org/politics/2023/12/08/americans-views-of-the- israel-hamas-war/) ## [ Americans’ Views of the Israel-Hamas War ](https://www.pewresearch.org/politics/2023/12/08/americans-views-of-the- israel-hamas-war/) ### Most Popular 1 [ In Tight Presidential Race, Voters Are Broadly Critical of Both Biden and Trump ](https://www.pewresearch.org/politics/2024/04/24/in-tight-presidential- race-voters-are-broadly-critical-of-both-biden-and-trump/) 2 [ A growing share of Americans have little or no confidence in Netanyahu ](https://www.pewresearch.org/short-reads/2024/04/25/a-growing-share-of- americans-have-little-or-no-confidence-in-netanyahu/) 3 [ What the data says about abortion in the U.S. ](https://www.pewresearch.org/short-reads/2024/03/25/what-the-data-says-about- abortion-in-the-us/) 4 [ What Are Americans’ Top Foreign Policy Priorities? ](https://www.pewresearch.org/global/2024/04/23/what-are-americans-top- foreign-policy-priorities/) 5 [ Americans’ Social Media Use ](https://www.pewresearch.org/internet/2024/01/31/americans-social-media-use/) ## Report Materials * _ _ [ Topline ](https://www.pewresearch.org/wp-content/uploads/sites/20/2022/06/PSD_06.28.22_gender.identity.topline.pdf) * _ _ [ Report PDF ](https://www.pewresearch.org/wp-content/uploads/sites/20/2022/06/PSDT_06.28.22_GenderID_fullreport.pdf) ## Table of Contents ## Table of Contents \+ * [ Americans’ Complex Views on Gender Identity and Transgender Issues ](https://www.pewresearch.org/social-trends/2022/06/28/americans-complex-views-on-gender-identity-and-transgender-issues/) * A rising share say a person’s gender is determined by their sex at birth * Many Americans point to science when asked what has influenced their views on whether gender can differ from sex assigned at birth * Public sees discrimination against trans people and limited acceptance * About four-in-ten say society has gone too far in accepting trans people * Plurality of adults say views on gender identity issues are changing too quickly * Most say they’re not paying close attention to news about bills related to transgender people * About six-in-ten would favor requiring that transgender athletes compete on teams that match their sex at birth * Views on many policies related to transgender issues vary by age, party, and race and ethnicity * Sizable shares say forms and government documents should include options other than ‘male’ and ‘female’ * About three-in-ten parents of K-12 students say their children have learned about people who are trans or nonbinary at school * [ Acknowledgments ](https://www.pewresearch.org/social-trends/2022/06/28/acknowledgments-59/) * [ Methodology ](https://www.pewresearch.org/social-trends/2022/06/28/methodology-51/) * The American Trends Panel survey methodology * Overview * Panel recruitment * Sample design * Questionnaire development and testing * Incentives * Data collection protocol * Data quality checks * Weighting * Dispositions and response rates * A note about the Asian sample [ ](https://www.pewresearch.org) [ ](https://www.pewresearch.org) [ ](https://www.pewresearch.org) 1615 L St. NW, Suite 800 Washington, DC 20036 USA [ (+1) 202-419-4300 \| Main ](tel:+12024194300) [ (+1) 202-857-8562 \| Fax ](tel:+12028578562) [ (+1) 202-419-4372 \| Media Inquiries ](tel:+12024194372) #### Research Topics * [ Age & Generations ](https://www.pewresearch.org/topic/generations-age/) * [ Coronavirus (COVID-19) ](https://www.pewresearch.org/topic/coronavirus-disease-covid-19/) * [ Economy & Work ](https://www.pewresearch.org/topic/economy-work/) * [ Family & Relationships ](https://www.pewresearch.org/topic/family-relationships/) * [ Gender & LGBTQ ](https://www.pewresearch.org/topic/gender-lgbtq/) * [ Immigration & Migration ](https://www.pewresearch.org/topic/immigration-migration/) * [ International Affairs ](https://www.pewresearch.org/topic/international-affairs/) * [ Internet & Technology ](https://www.pewresearch.org/topic/internet-technology/) * [ Methodological Research ](https://www.pewresearch.org/topic/methodological-research/) * [ News Habits & Media ](https://www.pewresearch.org/topic/news-habits-media/) * [ Non-U.S. Governments ](https://www.pewresearch.org/topic/non-us-governments/) * [ Other Topics ](https://www.pewresearch.org/topic/other-topics/) * [ Politics & Policy ](https://www.pewresearch.org/topic/politics-policy/) * [ Race & Ethnicity ](https://www.pewresearch.org/topic/race-ethnicity/) * [ Religion ](https://www.pewresearch.org/topic/religion/) * [ Science ](https://www.pewresearch.org/topic/science/) #### Follow Us * [ Email Newsletters ](https://pewrsr.ch/3OQ7Zg6) * [ Facebook ](https://pewrsr.ch/3OQ7Zg6) * [ Twitter ](https://twitter.com) * [ Tumblr ](https://pewrsr.ch/3OQ7Zg6) * [ YouTube ](https://pewrsr.ch/3OQ7Zg6) * [ RSS Feed ](https://pewrsr.ch/3OQ7Zg6) [ ABOUT PEW RESEARCH CENTER ](https://www.pewresearch.org/about) Pew Research Center is a nonpartisan fact tank that informs the public about the issues, attitudes and trends shaping the world. It conducts public opinion polling, demographic research, media content analysis and other empirical social science research. Pew Research Center does not take policy positions. It is a subsidiary of [ The Pew Charitable Trusts ](https://www.pewtrusts.org/) . Copyright 2024 Pew Research Center [ About ](https://www.pewresearch.org/about/) [ Terms & Conditions ](https://www.pewresearch.org/terms-and-conditions/) [ Privacy Policy ](https://www.pewresearch.org/privacy-policy/) Cookie Settings [ Reprints, Permissions & Use Policy ](https://www.pewresearch.org/about/use- policy/) [ Feedback ](https://www.pewresearch.org/contact-form/) [ Careers ](https://www.pewresearch.org/about/careers/)	biology	252621	https://da.wikipedia.org/wiki/Genderqueer	Genderqueer	Genderqueer eller nonbinær er et spektrum af kønsidentiteter. En genderqueer person er en person, der identificerer sig med et køn, der hverken er ”mand” eller ”kvinde” eller en, der identificerer sig som hverken-eller, begge eller en kombination heraf. I forhold til de binære køn ("mand" og "kvinde") identificerer genderqueers sig generelt mere som ”både/og” eller ”hverken/eller” frem for ”enten/eller”. Nogle genderqueers ser deres identitet som én ud af mange forskellige køn uden for mand og kvinde, andre ser det som et begreb, der omfatter alle kønsidentiteter uden for de binære køn, og atter andre mener, at det omfatter de binære køn imellem andre Nogle vil identificere sig som interkønnede eller akønnede og nogle ser det som et tredje køn, der lægges til de traditionelle to. Fællestrækket for alle genderqueers er, at de modsætter sig idéen om, at der kun findes to køn. Beskrivelsen genderqueer bruges lejlighedsvis også mere bredt som et tillægsord, der refererer til mennesker, der på en hvilken som helst måde er kønsoverskridere og kunne have en hvilken som helst kønsidentitet. Nogle genderqueer folk identificerer sig som transkønnede (i den forstand at det er et paraplybegreb for en bredere udstrækning af mennesker, der identificerer med et andet køn end det, de blev 'tildelt' ved fødslen) og nogle gør ikke. De to begreber er ikke fuldstændig ens, men de overlapper hinanden. Genderqueers kan transitionere fysisk med operationer, hormoner, elektrolyse og andre metoder eller vælge ikke at ændre deres kroppe ved disse metoder. De kan også transitionere socialt eller blive ved med at klæde sig og gå under deres 'tildelte' køn. Der er ikke kun én vej at gå som genderqueer. Betegnelsen genderqueer blev grundlæggende brugt til hovedsageligt hvide, middel- og overklasse-amerikanere, der var 'tildelt' hunkøn ved fødslen og på den ene eller anden måde på det FtM(female-to-male) eller transmaskuline spektrum, men der er også mange selvidentificerede genderqueers, som har radikalt forskellig etnicitet, klasse, køn og national baggrund. Imidlertid er personer der identificerer sig som genderqueers stadig uforholdsmæssigt fra den gruppe (?). Hvordan, genderqueers ser køn i det store hele og dets relation til dem selv, varierer. Nogle genderqueers ser køn som et kontinuum imellem mand og kvinde med de to traditionelle køn ved de to poler og deres eget genderqueer-ståsted som indenfor det kontinuum. Andre mener, at der er så mange køn, som der er mennesker. Igen andre mener, at de binære køn er en social konstruktion og vælger ikke at holde fast ved den konstruktion. Nogle genderqueers afviser enhver kønsteori som en gældende metode til at klassificere individer med. Nogle genderqueer personer foretrækker at bruge konventionelle binære pronomener så som ”han” eller ”hun”, imens andre foretrækker kønsneutrale pronomener som f.eks. "hen/hen/hens" eller "de/dem/deres" i stedet for, selvom sidstnævnte kan give misforståelser, da det hovedsageligt er en flertalsform. Den/den/dens er ikke i spil. Nogle genderqueers foretrækker, at folk skifter imellem ham og hende (og/eller pronomener), når der refereres til dem, og andre foretrækker, at der kun bruges deres navn og ingen betegnelser overhovedet. Nogen genderqueers skifter navn til mindre kønsstereotype navne. Kønsneutrale betegnelser er også i den sammenhæng et meget passende valg at bruge om hypotetiske personer frem for at bruge ”ham eller hende” til at referere hvem som helst, da det ikke forudsætter eller tillægger køn. Det opleves også som respektfuldt at bruge kønsneutrale betegnelser om nogen, hvis betegnelsespræference ikke er kendt af taleren, selv om det er bedst at finde den persons præference frem for at blive ved med at bruge betegnelser med hvilke, de måske ville eller måske ikke ville føle sig godt tilpas med. Begrebet panseksuel bruges specifikt til at fremhæve den opfattelse, at der findes mange køn, hvorimod ”biseksuel” antyder, at der kun findes to kønsidentiteter og to køn. Note: nogle ser ”genderqueer” som et mere bevidst politiseret version af begrebet androgyn, androgyne identificerer sig som både mænd og kvinder eller ingen af delene. Alternative betydninger: Betegnelsen genderqueer bliver også nogle gange brugt i en bredere forstand som et adjektiv, der referer til hvem som helst, der udfordrer kønsroller og binære klassifikationer af køn. Dette er er lidt på samme måde som homoseksuelle, biseksuelle og andre, der identificerer sig som queer som en bredere paraplybetegnelse. Men fordi genderqueer også refererer til mere specifikke kønsidentiteter er betegnelser som nonbinære mere passende at bruge som en bred betegnelse for folk, der ikke passer ind i rigide, binære kønsbokse. Se også Genderfuck Interkønnethed Transkønnethed Seksuel orientering Eksterne henvisninger Liste over kønsneutrale navne Gender Wiki Genderqueer Noter Sexologi LGBT	danish	0.760557
more_than_two_sexes/lgbtqrights.txt	Skip navigation [ Know your rights Back to Know Your Rights main page ](/know-your-rights) # LGBTQ Rights The legal landscape for LGBTQ people is constantly evolving. If you think you have been discriminated against and would like our assistance, please visit our Report LGBTQ and HIV Discrimination Page and we can help you figure out whether you are protected under federal or state laws. Share this issue: Print Select a scenario Select a scenario ![Collage of images that represent LGBT](https://www.aclu.org/wp- content/uploads/2019/02/lgbt-sm.png) ## Can an employer discriminate against me because of my sexual orientation or gender identity? ### Your rights Employers with 15 or more employees are prohibited by Title VII of the 1964 Civil Rights Act from discriminating on the basis of sex. Some courts have ruled that Title VII also bans discrimination based on sexual orientation or gender identity. The Supreme Court recently announced it will take up this question in three cases. In addition, many states and cities have laws that ban this kind of discrimination. ### If you believe that your rights have been violated If you think that you have experienced discrimination at work, you can file a complaint with the U.S. Equal Employment Opportunity Commission (EEOC), which has taken the position that LGBTQ people are protected under Title VII. Try to document everything like emails or HR papers that might be relevant. We encourage you to contact your local ACLU affiliate or the national ACLU LGBTQ & HIV Project for help weighing your options. ### Additional resources If you’ve been discriminated against based on sexual orientation or gender identity, the ACLU may be able to help. Contact us by filling out an intake form. Print: this section \| all sections Share this scenario: ## Can a landlord refuse to rent to me? ### Your rights The federal Fair Housing Act prohibits sex discrimination by most landlords and, as the Supreme Court held in 2020 ( _ Bostock v. Clayton County) _ , discrimination on the basis of sexual orientation and gender identity is sex discrimination. Thus, The Fair Housing Act prohibits discrimination on the basis of sexual orientation or gender identity. State and local laws where you live may also bar this discrimination. Housing discrimination against people with HIV/AIDS, or people perceived to have HIV/AIDS, is also illegal under the Fair Housing Act’s protections against disability discrimination. Housing providers that receive funding from the Department of Housing and Urban Development (HUD) or have loans insured by the Federal Housing Administration (FHA), as well as lenders insured by FHA, are subject to HUD’s Equal Access Rule, which bans discrimination in HUD programs on the basis of sexual orientation or gender identity. ### If you believe your rights have been violated What you can do depends largely on where the discrimination took place, whether any state or local laws there might apply to your situation, and where things stand under the current administration. It helps immensely if you document every interaction and exchange that could show what happened. We encourage you to contact your local ACLU affiliate or the national ACLU LGBTQ & HIV Project for help weighing your options. ### Additional resources If you’ve been treated unfairly in housing based on sexual orientation or gender identity, the ACLU may be able to help. Contact us by filling out an intake form. Print: this section \| all sections Share this scenario: ## Am I protected from discrimination in public accommodations, like shops and restaurants? ### Your rights There is no federal law that bans discrimination based on sexual orientation or gender identity in public accommodations, like restaurants, theaters and other businesses. However, state and local laws where you live may ban this kind of discrimination. ### Additional resources If you’ve been discriminated against based on sexual orientation or gender identity, the ACLU may be able to help. Contact us by filling out an intake form. Print: this section \| all sections Share this scenario: ## Are LGBTQ students protected from discrimination in schools? ### Your rights Title IX of the Education Amendments of 1972 bans discrimination on the basis of sex by public schools, and the Supreme Court held in 2020 ( _ Bostock v. Clayton County) _ that discrimination on the basis of sexual orientation and gender identity is sex discrimination. Thus, Title IX prohibits students from discrimination on the basis of sexual orientation or gender identity. Federal courts have held that Title IX requires public schools to respond to harassment based on appearance or behavior that doesn’t conform to gender stereotypes: boys who wear makeup, girls who wear pants, or students who are transgender or non-binary. The First Amendment right to free expression can also apply to school dress codes, especially when there are different rules for boys than there are for girls. Your constitutional right to privacy makes it illegal for your school to “out” you to anyone without your permission, even if you’re out to other people at school. The First Amendment protects your right to express yourself in public schools. That includes bringing a same-sex date to prom or any school event and talking about LGBTQ topics. Your right to be yourself in school includes the right to be transgender or non- binary, and to transition at school. While the law in this area is evolving, a growing number of courts have found that Title IX and the Constitution protect transgender students’ right to access sex-separated programs and facilities consistent with their gender identity. Some state and local laws also explicitly protect transgender students from discrimination in schools. ### If your rights are violated Document everything. Take notes and keep copies of any emails with school administrators, relevant school forms, etc. If anyone at school is harassing or threatening you, it’s crucial that you report every incident to a principal or counselor. Usually schools must be put on notice before they can be held legally responsible for protecting you. If you have reported harassment or any other kind of discrimination to your school officials and they have done little or nothing to stop it, we encourage you to contact your local ACLU affiliate or the national ACLU LGBTQ & HIV Project for help weighing your options. ### Additional resources If you’ve been discriminated against based on sexual orientation or gender identity, the ACLU may be able to help. Contact us at our national office [ here ](https://action.aclu.org/legal-intake/report-lgbtqhiv-discrimination) , or you can find your local ACLU office [ here ](https://www.aclu.org/about/affiliates) . Here are open letters on a variety of LGBTQ issues that you can use when advocating for your rights with school administrators. Print: this section \| all sections Share this scenario: ## Does the law protect my right to use the restroom consistent with my gender identity? ### Your rights State and local laws that prohibit discrimination based on gender identity or expression should protect transgender people’s right to use restrooms and locker rooms that match their gender identity. We believe that laws that ban sex discrimination should also be interpreted by the courts to protect transgender people. While federal law in this area is uncertain, most courts to address this question have found in favor of transgender people being able to access facilities most consistent with their gender identity. In some places, state and local nondiscrimination laws are much clearer about transgender people’s right to use gender identity-appropriate public restrooms. Many businesses, universities, and other public places are converting their restrooms to all-gender spaces. ### How the law varies in different states and cities Some places — for example, states like Colorado, Iowa, Oregon, and Washington, and cities like San Francisco and New York City — specifically grant transgender people the right to use gender identity-appropriate restrooms in public spaces. Other places, like Chicago, continue to allow businesses to decide whether transgender patron may access men’s or women’s restrooms based on the gender on their ID, which may or may not reflect accurately the person’s gender identity. Some cities — like Austin, Texas, New York City, Philadelphia, and West Hollywood — require that single-stall public restrooms be labeled as all- gender. ### If you believe your rights are violated What you can do depends largely on where the discrimination took place, whether any state or local laws there might apply to your situation, and where things are with federal lawsuits currently in play. We encourage you to contact your local ACLU affiliate or the national ACLU LGBT & HIV Project for help weighing your options. ### Additional resources If you’ve been discriminated against based on sexual orientation or gender identity, the ACLU may be able to help. Contact us by filling out an intake form. Print: this section \| all sections Share this scenario: ## How do I update the gender marker on my US passport? ### Your rights As of June 30, 2021, you no longer need to show medical documentation to establish or update the gender designation on your US passport. Simply fill out your passport application (typically Form DS-11) and check the M or F box that is most appropriate for you. The State Department will be adding an X designation on US passports, however it is not currently available. We expect to see additional information from the State Department on obtaining an X designation by the end of 2021 or early 2022. Once this designation is available you will be able to self-select an M, F, or X on your passport. ### Additional resources The State Department website has additional information about selecting your gender marker. Print: this section \| all sections Share this scenario: ## What if I have different gender markers on different IDs or records? ### Your rights There is no legal obligation to have consistent gender markers on various documents, and you should obtain the gender marker on each document that is most comfortable for you. Different gender markers on documents may cause administrative confusion if you show them at the same time, or if there is a discrepancy between the gender marker on your ID and the marker in your record. The confusion may be uncomfortable when interacting with an agent, but can usually be cleared up with a conversation. Print: this section \| all sections Share this scenario: * * * ### Other Know Your Rights Issues [ Abortion Supporters and Helpers ](abortion-supporters-and-helpers) [ Know Your Digital Rights: Digital Discrimination in Hiring ](know-your- digital-rights-digital-discrimination-in-hiring) [ Health Care Providers ](health-care-providers) [ Tribal Regalia ](tribal-regalia) [ What To Do When Encountering Questions from Law Enforcement ](what-do-when- encountering-law-enforcement-questioning) [ What to Do If You Think You're on the No Fly List ](what-do-if-you-think- youre-no-fly-list) [ Enforcement at the Airport ](what-do-when-encountering-law-enforcement- airports-and-other-ports-entry-us) [ Dreamers (DACA) ](know-your-rights-about-daca) [ Stopped by Police ](stopped-by-police) [ 100 Mile Border Zone ](border-zone)	biology	1234257	https://no.wikipedia.org/wiki/Diskrimineringsloven%20om%20seksuell%20orientering	Diskrimineringsloven om seksuell orientering	Lov om forbud mot diskriminering på grunn av seksuell orientering, kjønnsidentitet og kjønnsuttrykk, også kalt diskrimineringsloven om seksuell orientering, var en norsk lov. Den ble vedtatt av Stortinget 21. juni 2013. Formål og virkeområde Lovens formål var å fremme likestilling uavhengig av seksuell orientering, kjønnsidentitet og kjønnsuttrykk. Likestilling innebærer likeverd, like muligheter og rettigheter, tilgjengelighet og tilrettelegging. Loven kom til anvendelse på alle områder i samfunnet, med unntak av familieliv og andre rent personlige forhold. Diskrimieringsforbud Diskriminering på grunn av seksuell orientering, kjønnsidentitet eller kjønnsuttrykk er forbudt. Forbudet gjelder diskriminering på grunn av faktisk, antatt, tidligere eller fremtidig seksuell orientering, kjønnsidentitet eller kjønnsuttrykk. Forbudet gjelder også diskriminering på grunn av seksuell orientering, kjønnsidentitet eller kjønnsuttrykk til en person som den som diskrimineres har tilknytning til. Med diskriminering menes direkte og indirekte forskjellsbehandling som ikke er lovlig etter § 6 eller § 7. Med direkte forskjellsbehandling menes en handling eller unnlatelse som har som formål eller virkning at en person blir behandlet dårligere enn andre i tilsvarende situasjon, og at dette skyldes seksuell orientering, kjønnsidentitet eller kjønnsuttrykk. Med indirekte forskjellsbehandling menes enhver tilsynelatende nøytral bestemmelse, betingelse, praksis, handling eller unnlatelse som fører til at personer stilles dårligere enn andre, og at dette skjer på grunn av seksuell orientering, kjønnsidentitet eller kjønnsuttrykk. Unntak fra loven Forskjellsbehandling er ikke i strid med forbudet når den har et saklig formål, den er nødvendig for å oppnå formålet og det er et rimelig forhold mellom det man ønsker å oppnå og hvor inngripende forskjellsbehandlingen er for den eller de som stilles dårligere. Lovmaker har så langt ikke eksemplifisert hva disse unntakene skulle være, og det vil antakelig være opp til domstolene å avgrense hva som er «saklig formål» m.v. Positiv særbehandling Positiv særbehandling på grunn av seksuell orientering, kjønnsidentitet eller kjønnsuttrykk er ikke i strid med forbudet dersom særbehandlingen er egnet til å fremme lovens formål, det er et rimelig forhold mellom det man ønsker å oppnå og hvor inngripende forskjellsbehandlingen er for den eller de som stilles dårligere og særbehandlingen opphører når formålet med den er oppnådd. Regjeringen Solberg har varslet at den ønsker å harmonisere de ulike diskrimineringsrelaterte lovene i en felles diskrimineringslovgivning. Referanser Norske lover Transfobi Lover av 2013 Opphør i 2017	norwegian_bokmål	0.725216
more_than_two_sexes/Sexualreproduction.txt	Jump to content Main menu Main menu move to sidebar hide Navigation * [ Main page ](/wiki/Main_Page "Visit the main page \[z\]") * [ Contents ](/wiki/Wikipedia:Contents "Guides to browsing Wikipedia") * [ Current events ](/wiki/Portal:Current_events "Articles related to current events") * [ Random article ](/wiki/Special:Random "Visit a randomly selected article \[x\]") * [ About Wikipedia ](/wiki/Wikipedia:About "Learn about Wikipedia and how it works") * [ Contact us ](//en.wikipedia.org/wiki/Wikipedia:Contact_us "How to contact Wikipedia") * [ Donate ](https://donate.wikimedia.org/wiki/Special:FundraiserRedirector?utm_source=donate&utm_medium=sidebar&utm_campaign=C13_en.wikipedia.org&uselang=en "Support us by donating to the Wikimedia Foundation") Contribute * [ Help ](/wiki/Help:Contents "Guidance on how to use and edit Wikipedia") * [ Learn to edit ](/wiki/Help:Introduction "Learn how to edit Wikipedia") * [ Community portal 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account and log in; however, it is not mandatory") * [ Log in ](/w/index.php?title=Special:UserLogin&returnto=Sexual+reproduction "You're encouraged to log in; however, it's not mandatory. \[o\]") Pages for logged out editors [ learn more ](/wiki/Help:Introduction) * [ Contributions ](/wiki/Special:MyContributions "A list of edits made from this IP address \[y\]") * [ Talk ](/wiki/Special:MyTalk "Discussion about edits from this IP address \[n\]") ## Contents move to sidebar hide * (Top) * 1 Evolution * 2 Sexual selection * 3 Animals Toggle Animals subsection * 3.1 Arthropods * 3.1.1 Insects * 3.2 Mammals * 3.3 Fish * 4 Plants Toggle Plants subsection * 4.1 Flowering plants * 4.2 Ferns * 4.3 Bryophytes * 5 Fungi * 6 Bacteria and archaea * 7 See also * 8 References * 9 Further reading * 10 External links Toggle the table of contents # Sexual reproduction 71 languages * [ Alemannisch ](https://als.wikipedia.org/wiki/Geschlechtliche_Fortpflanzung "Geschlechtliche Fortpflanzung – Alemannic") * [ العربية ](https://ar.wikipedia.org/wiki/%D8%AA%D9%83%D8%A7%D8%AB%D8%B1_%D8%AC%D9%86%D8%B3%D9%8A "تكاثر جنسي – Arabic") * [ Asturianu ](https://ast.wikipedia.org/wiki/Reproducci%C3%B3n_sexual "Reproducción sexual – Asturian") * [ বাংলা ](https://bn.wikipedia.org/wiki/%E0%A6%AF%E0%A7%8C%E0%A6%A8_%E0%A6%AA%E0%A7%8D%E0%A6%B0%E0%A6%9C%E0%A6%A8%E0%A6%A8 "যৌন প্রজনন – Bangla") * [ 閩南語 / Bân-lâm-gú ](https://zh-min-nan.wikipedia.org/wiki/I%C3%BA-s%C3%A8ng_se%E2%81%BF-si%CC%8Dt "Iú-sèng seⁿ-si̍t – Minnan") * [ Беларуская ](https://be.wikipedia.org/wiki/%D0%9F%D0%B0%D0%BB%D0%B0%D0%B2%D0%BE%D0%B5_%D1%80%D0%B0%D0%B7%D0%BC%D0%BD%D0%B0%D0%B6%D1%8D%D0%BD%D0%BD%D0%B5 "Палавое размнажэнне – Belarusian") * [ Bikol Central ](https://bcl.wikipedia.org/wiki/Sekswal_na_reproduksyon "Sekswal na reproduksyon – Central Bikol") * [ Български ](https://bg.wikipedia.org/wiki/%D0%9F%D0%BE%D0%BB%D0%BE%D0%B2%D0%BE_%D1%80%D0%B0%D0%B7%D0%BC%D0%BD%D0%BE%D0%B6%D0%B0%D0%B2%D0%B0%D0%BD%D0%B5 "Полово размножаване – Bulgarian") * [ Bosanski ](https://bs.wikipedia.org/wiki/Spolno_razmno%C5%BEavanje "Spolno razmnožavanje – Bosnian") * [ Català ](https://ca.wikipedia.org/wiki/Reproducci%C3%B3_sexual "Reproducció sexual – Catalan") * [ Čeština ](https://cs.wikipedia.org/wiki/Pohlavn%C3%AD_rozmno%C5%BEov%C3%A1n%C3%AD "Pohlavní rozmnožování – Czech") * [ Dansk ](https://da.wikipedia.org/wiki/K%C3%B8nnet_formering "Kønnet formering – Danish") * [ Deutsch ](https://de.wikipedia.org/wiki/Geschlechtliche_Fortpflanzung "Geschlechtliche Fortpflanzung – German") * [ Eesti ](https://et.wikipedia.org/wiki/Suguline_sigimine "Suguline sigimine – Estonian") * [ Ελληνικά ](https://el.wikipedia.org/wiki/%CE%A3%CE%B5%CE%BE%CE%BF%CF%85%CE%B1%CE%BB%CE%B9%CE%BA%CE%AE_%CE%B1%CE%BD%CE%B1%CF%80%CE%B1%CF%81%CE%B1%CE%B3%CF%89%CE%B3%CE%AE "Σεξουαλική αναπαραγωγή – Greek") * [ Español ](https://es.wikipedia.org/wiki/Reproducci%C3%B3n_sexual "Reproducción sexual – Spanish") * [ Esperanto ](https://eo.wikipedia.org/wiki/Seksa_reproduktado "Seksa reproduktado – Esperanto") * [ Euskara ](https://eu.wikipedia.org/wiki/Sexu_ugalketa "Sexu ugalketa – Basque") * [ فارسی ](https://fa.wikipedia.org/wiki/%D8%AA%D9%88%D9%84%DB%8C%D8%AF%D9%85%D8%AB%D9%84_%D8%AC%D9%86%D8%B3%DB%8C "تولیدمثل جنسی – Persian") * [ Fiji Hindi ](https://hif.wikipedia.org/wiki/Biological_reproduction "Biological reproduction – Fiji Hindi") * [ Français ](https://fr.wikipedia.org/wiki/Sexualit%C3%A9_$reproduction$ "Sexualité $reproduction$ – French") * [ Gaeilge ](https://ga.wikipedia.org/wiki/At%C3%A1irgeadh_gn%C3%A9asach "Atáirgeadh gnéasach – Irish") * [ Galego ](https://gl.wikipedia.org/wiki/Reproduci%C3%B3n_sexual "Reprodución sexual – Galician") * [ 한국어 ](https://ko.wikipedia.org/wiki/%EC%9C%A0%EC%84%B1_%EC%83%9D%EC%8B%9D "유성 생식 – Korean") * [ Հայերեն ](https://hy.wikipedia.org/wiki/%D5%8D%D5%A5%D5%BC%D5%A1%D5%AF%D5%A1%D5%B6_%D5%A2%D5%A1%D5%A6%D5%B4%D5%A1%D6%81%D5%B8%D6%82%D5%B4 "Սեռական բազմացում – Armenian") * [ हिन्दी ](https://hi.wikipedia.org/wiki/%E0%A4%B2%E0%A5%88%E0%A4%82%E0%A4%97%E0%A4%BF%E0%A4%95_%E0%A4%9C%E0%A4%A8%E0%A4%A8 "लैंगिक जनन – Hindi") * [ Hrvatski ](https://hr.wikipedia.org/wiki/Spolno_razmno%C5%BEavanje "Spolno razmnožavanje – Croatian") * [ Bahasa Indonesia ](https://id.wikipedia.org/wiki/Reproduksi_seksual "Reproduksi seksual – Indonesian") * [ Íslenska ](https://is.wikipedia.org/wiki/Kyn%C3%A6xlun "Kynæxlun – Icelandic") * [ Italiano ](https://it.wikipedia.org/wiki/Riproduzione_sessuata "Riproduzione sessuata – Italian") * [ עברית ](https://he.wikipedia.org/wiki/%D7%A8%D7%91%D7%99%D7%99%D7%94_%D7%9E%D7%99%D7%A0%D7%99%D7%AA "רבייה מינית – Hebrew") * [ Қазақша ](https://kk.wikipedia.org/wiki/%D0%96%D1%8B%D0%BD%D1%8B%D1%81%D1%82%D1%8B_%D0%BA%D3%A9%D0%B1%D0%B5%D1%8E_%D0%B6%D3%99%D0%BD%D0%B5_%D2%B1%D1%80%D1%8B%D2%9B%D1%82%D0%B0%D0%BD%D1%83_%D0%B5%D1%80%D0%B5%D0%BA%D1%88%D0%B5%D0%BB%D1%96%D0%BA%D1%82%D0%B5%D1%80%D1%96 "Жынысты көбею және ұрықтану ерекшеліктері – Kazakh") * [ Kreyòl ayisyen ](https://ht.wikipedia.org/wiki/Repwodiksyon_seksy%C3%A8l "Repwodiksyon seksyèl – Haitian Creole") * [ Kurdî ](https://ku.wikipedia.org/wiki/Pirb%C3%BBna_zayend%C3%AE "Pirbûna zayendî – Kurdish") * [ Latviešu ](https://lv.wikipedia.org/wiki/Dzimumvairo%C5%A1an%C4%81s "Dzimumvairošanās – Latvian") * [ Magyar ](https://hu.wikipedia.org/wiki/Ivaros_szaporod%C3%A1s "Ivaros szaporodás – Hungarian") * [ മലയാളം ](https://ml.wikipedia.org/wiki/%E0%B4%B2%E0%B5%88%E0%B4%82%E0%B4%97%E0%B4%BF%E0%B4%95%E0%B4%AA%E0%B5%8D%E0%B4%B0%E0%B4%A4%E0%B5%8D%E0%B4%AF%E0%B5%81%E0%B5%BD%E0%B4%AA%E0%B5%8D%E0%B4%AA%E0%B4%BE%E0%B4%A6%E0%B4%A8%E0%B4%82 "ലൈംഗികപ്രത്യുൽപ്പാദനം – Malayalam") * [ مصرى ](https://arz.wikipedia.org/wiki/%D8%AA%D9%83%D8%A7%D8%AB%D8%B1_%D8%AC%D9%86%D8%B3%D9%89 "تكاثر جنسى – Egyptian Arabic") * [ Bahasa Melayu ](https://ms.wikipedia.org/wiki/Pembiakan_seks "Pembiakan seks – Malay") * [ မြန်မာဘာသာ ](https://my.wikipedia.org/wiki/%E1%80%9C%E1%80%AD%E1%80%84%E1%80%BA%E1%80%96%E1%80%BC%E1%80%84%E1%80%B7%E1%80%BA%E1%80%99%E1%80%BB%E1%80%AD%E1%80%AF%E1%80%B8%E1%80%95%E1%80%BD%E1%80%AC%E1%80%B8%E1%80%81%E1%80%BC%E1%80%84%E1%80%BA%E1%80%B8 "လိင်ဖြင့်မျိုးပွားခြင်း – Burmese") * [ Nederlands ](https://nl.wikipedia.org/wiki/Geslachtelijke_voortplanting "Geslachtelijke voortplanting – Dutch") * [ 日本語 ](https://ja.wikipedia.org/wiki/%E6%9C%89%E6%80%A7%E7%94%9F%E6%AE%96 "有性生殖 – Japanese") * [ Norsk bokmål ](https://no.wikipedia.org/wiki/Kj%C3%B8nnet_formering "Kjønnet formering – Norwegian Bokmål") * [ Norsk nynorsk ](https://nn.wikipedia.org/wiki/Kj%C3%B8nna_formeiring "Kjønna formeiring – Norwegian Nynorsk") * [ Oʻzbekcha / ўзбекча ](https://uz.wikipedia.org/wiki/Jinsiy_ko%CA%BBpayish "Jinsiy koʻpayish – Uzbek") * [ پنجابی ](https://pnb.wikipedia.org/wiki/%D8%AC%D9%86%D8%B3%DB%8C_%D8%AA%D9%88%D9%84%DB%8C%D8%AF "جنسی تولید – Western Punjabi") * [ پښتو ](https://ps.wikipedia.org/wiki/%D8%AC%D9%86%D8%B3%D9%8A_%D8%A8%DB%8C%D8%A7_%D8%AA%D9%88%D9%84%D9%8A%D8%AF "جنسي بیا توليد – Pashto") * [ Polski ](https://pl.wikipedia.org/wiki/Rozmna%C5%BCanie_p%C5%82ciowe "Rozmnażanie płciowe – Polish") * [ Português ](https://pt.wikipedia.org/wiki/Reprodu%C3%A7%C3%A3o_sexuada "Reprodução sexuada – Portuguese") * [ Română ](https://ro.wikipedia.org/wiki/Reproducere_sexuat%C4%83 "Reproducere sexuată – Romanian") * [ Русский ](https://ru.wikipedia.org/wiki/%D0%9F%D0%BE%D0%BB%D0%BE%D0%B2%D0%BE%D0%B5_%D1%80%D0%B0%D0%B7%D0%BC%D0%BD%D0%BE%D0%B6%D0%B5%D0%BD%D0%B8%D0%B5 "Половое размножение – Russian") * [ සිංහල ](https://si.wikipedia.org/wiki/%E0%B6%BD%E0%B7%92%E0%B6%82%E0%B6%9C%E0%B7%92%E0%B6%9A_%E0%B6%B4%E0%B7%8A%E2%80%8D%E0%B6%BB%E0%B6%A2%E0%B6%B1%E0%B6%B1%E0%B6%BA "ලිංගික ප්‍රජනනය – Sinhala") * [ Simple English ](https://simple.wikipedia.org/wiki/Sexual_reproduction "Sexual reproduction – Simple English") * [ Slovenčina ](https://sk.wikipedia.org/wiki/Pohlavn%C3%A9_rozmno%C5%BEovanie "Pohlavné rozmnožovanie – Slovak") * [ Slovenščina ](https://sl.wikipedia.org/wiki/Spolno_razmno%C5%BEevanje "Spolno razmnoževanje – Slovenian") * [ Српски / srpski ](https://sr.wikipedia.org/wiki/Polno_razmno%C5%BEavanje "Polno razmnožavanje – Serbian") * [ Suomi ](https://fi.wikipedia.org/wiki/Suvullinen_lis%C3%A4%C3%A4ntyminen "Suvullinen lisääntyminen – Finnish") * [ Svenska ](https://sv.wikipedia.org/wiki/Sexuell_f%C3%B6r%C3%B6kning "Sexuell förökning – Swedish") * [ Tagalog ](https://tl.wikipedia.org/wiki/Reproduksiyong_seksuwal "Reproduksiyong seksuwal – Tagalog") * [ தமிழ் ](https://ta.wikipedia.org/wiki/%E0%AE%AA%E0%AE%BE%E0%AE%B2%E0%AE%BF%E0%AE%AF%E0%AE%B2%E0%AF%8D_%E0%AE%87%E0%AE%A9%E0%AE%AA%E0%AF%8D%E0%AE%AA%E0%AF%86%E0%AE%B0%E0%AF%81%E0%AE%95%E0%AF%8D%E0%AE%95%E0%AE%AE%E0%AF%8D "பாலியல் இனப்பெருக்கம் – Tamil") * [ Taqbaylit ](https://kab.wikipedia.org/wiki/Amyaraw_azufan "Amyaraw azufan – Kabyle") * [ Татарча / tatarça ](https://tt.wikipedia.org/wiki/%D2%96%D0%B5%D0%BD%D1%81%D0%B8_%D2%AF%D1%80%D1%87%D2%AF "Җенси үрчү – Tatar") * [ ไทย ](https://th.wikipedia.org/wiki/%E0%B8%81%E0%B8%B2%E0%B8%A3%E0%B8%AA%E0%B8%B7%E0%B8%9A%E0%B8%9E%E0%B8%B1%E0%B8%99%E0%B8%98%E0%B8%B8%E0%B9%8C%E0%B9%81%E0%B8%9A%E0%B8%9A%E0%B8%AD%E0%B8%B2%E0%B8%A8%E0%B8%B1%E0%B8%A2%E0%B9%80%E0%B8%9E%E0%B8%A8 "การสืบพันธุ์แบบอาศัยเพศ – Thai") * [ Türkçe ](https://tr.wikipedia.org/wiki/E%C5%9Feyli_%C3%BCreme "Eşeyli üreme – Turkish") * [ Українська ](https://uk.wikipedia.org/wiki/%D0%A1%D1%82%D0%B0%D1%82%D0%B5%D0%B2%D0%B5_%D1%80%D0%BE%D0%B7%D0%BC%D0%BD%D0%BE%D0%B6%D0%B5%D0%BD%D0%BD%D1%8F "Статеве розмноження – Ukrainian") * [ اردو ](https://ur.wikipedia.org/wiki/%D8%AC%D9%86%D8%B3%DB%8C_%D8%AA%D9%88%D9%84%DB%8C%D8%AF "جنسی تولید – Urdu") * [ Tiếng Việt ](https://vi.wikipedia.org/wiki/Sinh_s%E1%BA%A3n_h%E1%BB%AFu_t%C3%ADnh "Sinh sản hữu tính – Vietnamese") * [ Võro ](https://fiu-vro.wikipedia.org/wiki/Sugulin%C3%B5_siginemine "Sugulinõ siginemine – Võro") * [ 吴语 ](https://wuu.wikipedia.org/wiki/%E6%9C%89%E6%80%A7%E7%94%9F%E6%AE%96 "有性生殖 – Wu") * [ 粵語 ](https://zh-yue.wikipedia.org/wiki/%E6%9C%89%E6%80%A7%E7%B9%81%E6%AE%96 "有性繁殖 – Cantonese") * [ 中文 ](https://zh.wikipedia.org/wiki/%E6%9C%89%E6%80%A7%E7%94%9F%E6%AE%96 "有性生殖 – Chinese") [ Edit links ](https://www.wikidata.org/wiki/Special:EntityPage/Q182353#sitelinks-wikipedia "Edit interlanguage links") * [ Article ](/wiki/Sexual_reproduction "View the content page \[c\]") * [ Talk ](/wiki/Talk:Sexual_reproduction "Discuss improvements to the content page \[t\]") English * [ Read ](/wiki/Sexual_reproduction) * [ Edit ](/w/index.php?title=Sexual_reproduction&action=edit "Edit this page \[e\]") * [ View history ](/w/index.php?title=Sexual_reproduction&action=history "Past revisions of this page \[h\]") Tools Tools move to sidebar hide Actions * [ Read ](/wiki/Sexual_reproduction) * [ Edit ](/w/index.php?title=Sexual_reproduction&action=edit "Edit this page \[e\]") * [ View history ](/w/index.php?title=Sexual_reproduction&action=history) General * [ What links here ](/wiki/Special:WhatLinksHere/Sexual_reproduction "List of all English Wikipedia pages containing links to this page \[j\]") * [ Related changes ](/wiki/Special:RecentChangesLinked/Sexual_reproduction "Recent changes in pages linked from this page \[k\]") * [ Upload file ](/wiki/Wikipedia:File_Upload_Wizard "Upload files \[u\]") * [ Special pages ](/wiki/Special:SpecialPages "A list of all special pages \[q\]") * [ Permanent link ](/w/index.php?title=Sexual_reproduction&oldid=1220742356 "Permanent link to this revision of this page") * [ Page information ](/w/index.php?title=Sexual_reproduction&action=info "More information about this page") * [ Cite this page ](/w/index.php?title=Special:CiteThisPage&page=Sexual_reproduction&id=1220742356&wpFormIdentifier=titleform "Information on how to cite this page") * [ Get shortened URL ](/w/index.php?title=Special:UrlShortener&url=https%3A%2F%2Fen.wikipedia.org%2Fwiki%2FSexual_reproduction) * [ Download QR code ](/w/index.php?title=Special:QrCode&url=https%3A%2F%2Fen.wikipedia.org%2Fwiki%2FSexual_reproduction) * [ Wikidata item ](https://www.wikidata.org/wiki/Special:EntityPage/Q182353 "Structured data on this page hosted by Wikidata \[g\]") Print/export * [ Download as PDF ](/w/index.php?title=Special:DownloadAsPdf&page=Sexual_reproduction&action=show-download-screen "Download this page as a PDF file") * [ Printable version ](/w/index.php?title=Sexual_reproduction&printable=yes "Printable version of this page \[p\]") In other projects * [ Wikimedia Commons ](https://commons.wikimedia.org/wiki/Category:Sexual_reproduction) From Wikipedia, the free encyclopedia Biological process [ ![](//upload.wikimedia.org/wikipedia/commons/thumb/d/df/Sexual_cycle_N-2N.svg/250px- Sexual_cycle_N-2N.svg.png) ](/wiki/File:Sexual_cycle_N-2N.svg) In the first stage of sexual reproduction, [ meiosis ](/wiki/Meiosis "Meiosis") , the number of chromosomes is reduced from a [ diploid ](/wiki/Diploid "Diploid") number (2n) to a [ haploid ](/wiki/Haploid "Haploid") number (n). During [ fertilisation ](/wiki/Fertilisation "Fertilisation") , haploid gametes come together to form a diploid [ zygote ](/wiki/Zygote "Zygote") , and the original number of chromosomes is restored. Sexual reproduction is a type of [ reproduction ](/wiki/Reproduction "Reproduction") that involves a complex [ life cycle ](/wiki/Biological_life_cycle "Biological life cycle") in which a [ gamete ](/wiki/Gamete "Gamete") ( [ haploid ](/wiki/Haploid "Haploid") reproductive cells, such as a [ sperm ](/wiki/Sperm "Sperm") or [ egg cell ](/wiki/Egg_cell "Egg cell") ) with a single set of [ chromosomes ](/wiki/Chromosome "Chromosome") combines with another gamete to produce a [ zygote ](/wiki/Zygote "Zygote") that develops into an organism composed of [ cells ](/wiki/Cell_$biology$ "Cell $biology$") with two sets of chromosomes ( [ diploid ](/wiki/Diploid "Diploid") ). [1] This is typical in animals, though the number of chromosome sets and how that number changes in sexual reproduction varies, especially among plants, fungi, and other [ eukaryotes ](/wiki/Eukaryote "Eukaryote") . [2] [3] Sexual reproduction is the most common life cycle in [ multicellular ](/wiki/Multicellular_organism "Multicellular organism") eukaryotes, such as [ animals ](/wiki/Animals "Animals") , [ fungi ](/wiki/Fungi "Fungi") and [ plants ](/wiki/Plants "Plants") . [4] [5] Sexual reproduction also occurs in some [ unicellular ](/wiki/Unicellular_organism "Unicellular organism") eukaryotes. [2] [6] Sexual reproduction does not occur in [ prokaryotes ](/wiki/Prokaryote "Prokaryote") , unicellular organisms without [ cell nuclei ](/wiki/Cell_nuclei "Cell nuclei") , such as [ bacteria ](/wiki/Bacteria "Bacteria") and [ archaea ](/wiki/Archaea "Archaea") . However, some processes in bacteria, including [ bacterial conjugation ](/wiki/Bacterial_conjugation "Bacterial conjugation") , [ transformation ](/wiki/Transformation_$genetics$ "Transformation $genetics$") and [ transduction ](/wiki/Transduction_$genetics$ "Transduction $genetics$") , may be considered analogous to sexual reproduction in that they incorporate new genetic information. [7] Some [ proteins ](/wiki/Protein "Protein") and other features that are key for sexual reproduction may have arisen in bacteria, but sexual reproduction is believed to have developed in an ancient eukaryotic ancestor. [8] In eukaryotes, diploid precursor cells divide to produce haploid cells in a process called [ meiosis ](/wiki/Meiosis "Meiosis") . In meiosis, DNA is replicated to produce a total of four copies of each chromosome. This is followed by two cell divisions to generate haploid gametes. After the DNA is replicated in meiosis, the [ homologous chromosomes ](/wiki/Homologous_chromosome "Homologous chromosome") pair up so that their [ DNA ](/wiki/DNA "DNA") sequences are aligned with each other. During this period before cell divisions, genetic information is exchanged between homologous chromosomes in [ genetic recombination ](/wiki/Genetic_recombination "Genetic recombination") . Homologous chromosomes contain highly similar but not identical information, and by exchanging similar but not identical regions, genetic recombination increases genetic diversity among future generations. [9] During sexual reproduction, two haploid gametes combine into one diploid cell known as a [ zygote ](/wiki/Zygote "Zygote") in a process called [ fertilization ](/wiki/Fertilisation "Fertilisation") . The nuclei from the gametes fuse, and each gamete contributes half of the genetic material of the zygote. Multiple cell divisions by [ mitosis ](/wiki/Mitosis "Mitosis") (without change in the number of chromosomes) then develop into a multicellular diploid phase or generation. In plants, the diploid phase, known as the [ sporophyte ](/wiki/Sporophyte "Sporophyte") , produces spores by meiosis. These spores then germinate and divide by mitosis to form a haploid multicellular phase, the [ gametophyte ](/wiki/Gametophyte "Gametophyte") , which produces gametes directly by mitosis. This type of life cycle, involving alternation between two multicellular phases, the sexual haploid gametophyte and asexual diploid sporophyte, is known as [ alternation of generations ](/wiki/Alternation_of_generations "Alternation of generations") . The [ evolution of sexual reproduction ](/wiki/Evolution_of_sexual_reproduction "Evolution of sexual reproduction") is considered paradoxical, [10] because [ asexual reproduction ](/wiki/Asexual_reproduction "Asexual reproduction") should be able to outperform it as every young organism created can bear its own young. This implies that an asexual population has an intrinsic capacity to grow more rapidly with each generation. [11] This 50% cost is a [ fitness ](/wiki/Fitness_$biology$ "Fitness $biology$") disadvantage of sexual reproduction. [12] The two-fold cost of sex includes this cost and the fact that any organism can only pass on 50% of its own genes to its offspring. However, one definite advantage of sexual reproduction is that it increases genetic diversity and impedes the accumulation of harmful genetic [ mutations ](/wiki/Mutation "Mutation") . [13] [9] [ Sexual selection ](/wiki/Sexual_selection "Sexual selection") is a mode of [ natural selection ](/wiki/Natural_selection "Natural selection") in which some individuals out-reproduce others of a population because they are better at securing [ mates ](/wiki/Mating "Mating") for sexual reproduction. [14] [ _[ failed verification ](/wiki/Wikipedia:Verifiability "Wikipedia:Verifiability") _ ] [15] It has been described as "a powerful evolutionary force that does not exist in asexual populations". [16] ## Evolution [ [ edit ](/w/index.php?title=Sexual_reproduction&action=edit&section=1 "Edit section: Evolution") ] Main article: [ Evolution of sexual reproduction ](/wiki/Evolution_of_sexual_reproduction "Evolution of sexual reproduction") The first [ fossilized ](/wiki/Fossil "Fossil") evidence of sexual reproduction in eukaryotes is from the [ Stenian ](/wiki/Stenian "Stenian") period, about 1.05 billion years old. [17] [18] Biologists studying [ evolution ](/wiki/Evolution "Evolution") propose several explanations for the development of sexual reproduction and its maintenance. These reasons include reducing the likelihood of the [ accumulation ](/wiki/Mullers_ratchet "Mullers ratchet") of deleterious mutations, increasing rate of [ adaptation to changing environments ](/wiki/Red_queen_hypothesis "Red queen hypothesis") , [19] [ dealing with competition ](/wiki/Tangled_bank_hypothesis "Tangled bank hypothesis") , [ DNA repair ](/wiki/DNA_repair "DNA repair") , masking deleterious mutations, and reducing genetic variation on the genomic level. [20] [21] [22] [23] All of these ideas about why sexual reproduction has been maintained are generally supported, but ultimately the size of the population determines if sexual reproduction is entirely beneficial. Larger [ populations ](/wiki/Population "Population") appear to respond more quickly to some of the benefits obtained through sexual reproduction than do smaller population sizes. [24] Maintenance of sexual reproduction has been explained by theories that work at several [ levels of selection ](/wiki/Levels_of_selection "Levels of selection") , though some of these models remain controversial. [ _[ citation needed ](/wiki/Wikipedia:Citation_needed "Wikipedia:Citation needed") _ ] However, newer models presented in recent years suggest a basic advantage for sexual reproduction in slowly reproducing [ complex organisms ](/wiki/Complex_organism "Complex organism") . Sexual reproduction allows these species to exhibit characteristics that depend on the specific [ environment ](/wiki/Natural_environment "Natural environment") that they inhabit, and the particular survival strategies that they employ. [25] ## Sexual selection [ [ edit ](/w/index.php?title=Sexual_reproduction&action=edit&section=2 "Edit section: Sexual selection") ] Main article: [ Sexual selection ](/wiki/Sexual_selection "Sexual selection") In order to reproduce sexually, both males and females need to find a [ mate ](/wiki/Mating "Mating") . Generally in animals [ mate choice ](/wiki/Mate_choice "Mate choice") is made by females while males compete to be chosen. This can lead [ organisms ](/wiki/Organism "Organism") to extreme efforts in order to reproduce, such as combat and display, or produce extreme features caused by a [ positive feedback ](/wiki/Positive_feedback "Positive feedback") known as a [ Fisherian runaway ](/wiki/Fisherian_runaway "Fisherian runaway") . Thus sexual reproduction, as a form of [ natural selection ](/wiki/Natural_selection "Natural selection") , has an effect on [ evolution ](/wiki/Evolution "Evolution") . [ Sexual dimorphism ](/wiki/Sexual_dimorphism "Sexual dimorphism") is where the basic [ phenotypic traits ](/wiki/Phenotypic_trait "Phenotypic trait") vary between males and females of the same [ species ](/wiki/Species "Species") . Dimorphism is found in both [ sex organs ](/wiki/Sex_organ "Sex organ") and in [ secondary sex characteristics ](/wiki/Secondary_sex_characteristics "Secondary sex characteristics") , body size, physical strength and morphology, [ biological ornamentation ](/wiki/Biological_ornament "Biological ornament") , [ behavior ](/wiki/Behavior "Behavior") and other bodily traits. However, sexual selection is only implied over an extended period of time leading to sexual dimorphism. [26] ## Animals [ [ edit ](/w/index.php?title=Sexual_reproduction&action=edit&section=3 "Edit section: Animals") ] Further information: [ Reproductive system § Animals ](/wiki/Reproductive_system#Animals "Reproductive system") , [ Fertilisation § Fertilisation in animals ](/wiki/Fertilisation#Fertilisation_in_animals "Fertilisation") , and [ Animal sexual behavior ](/wiki/Animal_sexual_behavior "Animal sexual behavior") ### Arthropods [ [ edit ](/w/index.php?title=Sexual_reproduction&action=edit&section=4 "Edit section: Arthropods") ] This section is an excerpt from [ Arthropod § Reproduction and development ](/wiki/Arthropod#Reproduction_and_development "Arthropod") . [ [ edit ](https://en.wikipedia.org/w/index.php?title=Arthropod&action=edit) ] [ ![](//upload.wikimedia.org/wikipedia/commons/thumb/1/11/Aphid-giving- birth.jpg/200px-Aphid-giving-birth.jpg) ](/wiki/File:Aphid-giving-birth.jpg) [ Aphid ](/wiki/Aphid "Aphid") giving birth to live young from an unfertilized egg [ ![](//upload.wikimedia.org/wikipedia/commons/thumb/b/bc/Harvestmen_mating_%2844325686201%29.jpg/200px- Harvestmen_mating_%2844325686201%29.jpg) ](/wiki/File:Harvestmen_mating_$44325686201$.jpg) [ Harvestmen ](/wiki/Opiliones "Opiliones") mating A few arthropods, such as [ barnacles ](/wiki/Barnacle "Barnacle") , are [ hermaphroditic ](/wiki/Hermaphroditic "Hermaphroditic") , that is, each can have the organs of both [ sexes ](/wiki/Sex "Sex") . However, individuals of most species remain of one sex their entire lives. [27] A few species of [ insects ](/wiki/Insect "Insect") and crustaceans can reproduce by [ parthenogenesis ](/wiki/Parthenogenesis "Parthenogenesis") , especially if conditions favor a "population explosion". However, most arthropods rely on sexual reproduction, and parthenogenetic species often revert to sexual reproduction when conditions become less favorable. [28] The ability to undergo [ meiosis ](/wiki/Meiosis "Meiosis") is widespread among arthropods including both those that reproduce sexually and those that reproduce [ parthenogenetically ](/wiki/Parthenogenesis "Parthenogenesis") . [29] Although meiosis is a major characteristic of arthropods, understanding of its fundamental adaptive benefit has long been regarded as an unresolved problem, [30] that appears to have remained unsettled. [ Aquatic ](/wiki/Aquatic_animal "Aquatic animal") arthropods may breed by external fertilization, as for example [ horseshoe crabs ](/wiki/Horseshoe_crab "Horseshoe crab") do, [31] or by [ internal fertilization ](/wiki/Internal_fertilization "Internal fertilization") , where the [ ova ](/wiki/Ovum "Ovum") remain in the female's body and the [ sperm ](/wiki/Sperm "Sperm") must somehow be inserted. All known terrestrial arthropods use internal fertilization. [ Opiliones ](/wiki/Opiliones "Opiliones") (harvestmen), [ millipedes ](/wiki/Millipede "Millipede") , and some crustaceans use modified appendages such as [ gonopods ](/wiki/Gonopod "Gonopod") or [ penises ](/wiki/Opiliones_penis "Opiliones penis") to transfer the sperm directly to the female. However, most male [ terrestrial ](/wiki/Terrestrial_animal "Terrestrial animal") arthropods produce [ spermatophores ](/wiki/Spermatophore "Spermatophore") , waterproof packets of [ sperm ](/wiki/Sperm "Sperm") , which the females take into their bodies. A few such species rely on females to find spermatophores that have already been deposited on the ground, but in most cases males only deposit spermatophores when complex [ courtship ](/wiki/Courtship "Courtship") rituals look likely to be successful. [27] [ ![](//upload.wikimedia.org/wikipedia/commons/thumb/2/28/Shrimp_nauplius.jpg/220px- Shrimp_nauplius.jpg) ](/wiki/File:Shrimp_nauplius.jpg) The nauplius larva of a [ penaeid shrimp ](/wiki/Penaeid_shrimp "Penaeid shrimp") Most arthropods lay eggs, [27] but scorpions are [ ovoviviparous ](/wiki/Ovoviviparity "Ovoviviparity") : they produce live young after the eggs have hatched inside the mother, and are noted for prolonged maternal care. [32] Newly born arthropods have diverse forms, and insects alone cover the range of extremes. Some hatch as apparently miniature adults (direct development), and in some cases, such as [ silverfish ](/wiki/Silverfish "Silverfish") , the hatchlings do not feed and may be helpless until after their first moult. Many insects hatch as grubs or [ caterpillars ](/wiki/Caterpillar "Caterpillar") , which do not have segmented limbs or hardened cuticles, and [ metamorphose ](/wiki/Metamorphosis "Metamorphosis") into adult forms by entering an inactive phase in which the larval tissues are broken down and re-used to build the adult body. [33] [ Dragonfly ](/wiki/Dragonfly "Dragonfly") larvae have the typical cuticles and jointed limbs of arthropods but are flightless water-breathers with extendable jaws. [34] Crustaceans commonly hatch as tiny [ nauplius ](/wiki/Nauplius_$larva$ "Nauplius $larva$") larvae that have only three segments and pairs of appendages. [27] #### Insects [ [ edit ](/w/index.php?title=Sexual_reproduction&action=edit&section=5 "Edit section: Insects") ] Further information: [ Insect § Reproduction and development ](/wiki/Insect#Reproduction_and_development "Insect") [ ![](//upload.wikimedia.org/wikipedia/commons/thumb/4/4d/Australian_Emperor_mating_and_laying.jpg/250px- Australian_Emperor_mating_and_laying.jpg) ](/wiki/File:Australian_Emperor_mating_and_laying.jpg) An [ Australian emperor dragonfly ](/wiki/Australian_emperor "Australian emperor") laying eggs, guarded by a male Insect species make up more than two-thirds of all [ extant ](/wiki/Extant_taxon "Extant taxon") animal species. Most insect species reproduce sexually, though some species are facultatively [ parthenogenetic ](/wiki/Parthenogenetic "Parthenogenetic") . Many insect species have [ sexual dimorphism ](/wiki/Sexual_dimorphism "Sexual dimorphism") , while in others the sexes look nearly identical. Typically they have two sexes with males producing spermatozoa and females ova. The ova develop into eggs that have a covering called the [ chorion ](/wiki/Chorion "Chorion") , which forms before internal fertilization. Insects have very diverse mating and reproductive strategies most often resulting in the male depositing a [ spermatophore ](/wiki/Spermatophore "Spermatophore") within the female, which she stores until she is ready for egg fertilization. After fertilization, and the formation of a zygote, and varying degrees of development, in many species the eggs are deposited outside the female; while in others, they develop further within the female and the young are born live. [35] ### Mammals [ [ edit ](/w/index.php?title=Sexual_reproduction&action=edit&section=6 "Edit section: Mammals") ] Main article: [ Mammalian reproduction ](/wiki/Mammalian_reproduction "Mammalian reproduction") See also: [ Human reproduction ](/wiki/Human_reproduction "Human reproduction") There are three extant kinds of mammals: [ monotremes ](/wiki/Monotreme "Monotreme") , [ placentals ](/wiki/Placental "Placental") and [ marsupials ](/wiki/Marsupial "Marsupial") , all with internal fertilization. In placental mammals, offspring are born as juveniles: complete animals with the [ sex organs ](/wiki/Sex_organ "Sex organ") present although not reproductively functional. After several months or years, depending on the species, the sex organs develop further to maturity and the animal becomes [ sexually mature ](/wiki/Sexual_maturity "Sexual maturity") . Most female mammals are only [ fertile ](/wiki/Fertility "Fertility") during certain periods during their [ estrous ](/wiki/Estrous "Estrous") cycle, at which point they are ready to mate. Individual male and female mammals meet and carry out [ copulation ](/wiki/Animal_sexual_behavior#Mammals "Animal sexual behavior") . [36] For most mammals, males and females [ exchange sexual partners throughout their adult lives ](/wiki/Promiscuity "Promiscuity") . [37] [38] [39] ### Fish [ [ edit ](/w/index.php?title=Sexual_reproduction&action=edit&section=7 "Edit section: Fish") ] Further information: [ Fish § Reproductive system ](/wiki/Fish#Reproductive_system "Fish") The vast majority of fish species lay eggs that are then fertilized by the male. [40] Some species lay their eggs on a substrate like a rock or on plants, while others scatter their eggs and the eggs are fertilized as they drift or sink in the water column. Some fish species use internal fertilization and then disperse the developing eggs or give birth to live offspring. Fish that have live-bearing offspring include the [ guppy ](/wiki/Guppy "Guppy") and mollies or _[ Poecilia ](/wiki/Poecilia "Poecilia") _ . Fishes that give birth to live young can be [ ovoviviparous ](/wiki/Ovoviviparous "Ovoviviparous") , where the eggs are fertilized within the female and the eggs simply hatch within the female body, or in [ seahorses ](/wiki/Seahorse "Seahorse") , the male carries the developing young within a pouch, and gives birth to live young. [41] Fishes can also be [ viviparous ](/wiki/Viviparous "Viviparous") , where the female supplies nourishment to the internally growing offspring. Some fish are [ hermaphrodites ](/wiki/Hermaphrodite "Hermaphrodite") , where a single fish is both male and female and can produce eggs and sperm. In hermaphroditic fish, some are male and female at the same time while in other fish they are serially hermaphroditic; starting as one sex and changing to the other. In at least one hermaphroditic species, self-fertilization occurs when the eggs and sperm are released together. Internal self-fertilization may occur in some other species. [42] One fish species does not reproduce by sexual reproduction but uses sex to produce offspring; _[ Poecilia formosa ](/wiki/Poecilia_formosa "Poecilia formosa") _ is a unisex species that uses a form of [ parthenogenesis ](/wiki/Parthenogenesis "Parthenogenesis") called [ gynogenesis ](/wiki/Gynogenesis "Gynogenesis") , where unfertilized eggs develop into embryos that produce female offspring. _Poecilia formosa_ mate with males of other fish species that use internal fertilization, the sperm does not fertilize the eggs but stimulates the growth of the eggs which develops into embryos. [43] ## Plants [ [ edit ](/w/index.php?title=Sexual_reproduction&action=edit&section=8 "Edit section: Plants") ] Main article: [ Plant reproduction ](/wiki/Plant_reproduction "Plant reproduction") Animals have life cycles with a single diploid multicellular phase that produces haploid gametes directly by meiosis. Male gametes are called sperm, and female gametes are called eggs or ova. In animals, fertilization of the ovum by a sperm results in the formation of a diploid zygote that develops by repeated mitotic divisions into a diploid adult. Plants have two multicellular life-cycle phases, resulting in an [ alternation of generations ](/wiki/Alternation_of_generations "Alternation of generations") . Plant zygotes germinate and divide repeatedly by mitosis to produce a diploid multicellular organism known as the sporophyte. The mature sporophyte produces haploid spores by meiosis that germinate and divide by mitosis to form a multicellular gametophyte phase that produces gametes at maturity. The gametophytes of different groups of plants vary in size. Mosses and other pteridophytic plants may have gametophytes consisting of several million cells, while [ angiosperms ](/wiki/Angiosperm "Angiosperm") have as few as three cells in each pollen grain. ### Flowering plants [ [ edit ](/w/index.php?title=Sexual_reproduction&action=edit&section=9 "Edit section: Flowering plants") ] [ ![](//upload.wikimedia.org/wikipedia/commons/thumb/3/37/Hosta3.jpg/220px- Hosta3.jpg) ](/wiki/File:Hosta3.jpg) Flowers contain the sexual organs of flowering plants. [ Flowering plants ](/wiki/Flowering_plant "Flowering plant") are the dominant plant form on land [44] : 168, 173 and they reproduce either sexually or asexually. Often their most distinctive feature is their reproductive organs, commonly called flowers. The [ anther ](/wiki/Stamen "Stamen") produces [ pollen grains ](/wiki/Pollen "Pollen") which contain the male [ gametophytes ](/wiki/Gametophyte "Gametophyte") that produce sperm nuclei. For pollination to occur, pollen grains must attach to the stigma of the female reproductive structure ( [ carpel ](/wiki/Carpel "Carpel") ), where the female gametophytes are located within ovules enclose within the [ ovary ](/wiki/Ovary "Ovary") . After the pollen tube grows through the carpel's style, the [ sex ](/wiki/Sex "Sex") cell nuclei from the pollen grain migrate into the ovule to fertilize the egg cell and endosperm nuclei within the female gametophyte in a process termed [ double fertilization ](/wiki/Double_fertilization "Double fertilization") . The resulting zygote develops into an embryo, while the triploid endosperm (one sperm cell plus two female cells) and female tissues of the ovule give rise to the surrounding tissues in the developing seed. The ovary, which produced the female gametophyte(s), then grows into a [ fruit ](/wiki/Fruit "Fruit") , which surrounds the seed(s). Plants may either [ self-pollinate ](/wiki/Self-pollination "Self-pollination") or [ cross- pollinate ](/wiki/Pollination "Pollination") . In 2013, flowers dating from the [ Cretaceous ](/wiki/Cretaceous "Cretaceous") (100 million years before present) were found encased in amber, the oldest evidence of sexual reproduction in a flowering plant. Microscopic images showed tubes growing out of pollen and penetrating the flower's stigma. The pollen was sticky, suggesting it was carried by insects. [45] ### Ferns [ [ edit ](/w/index.php?title=Sexual_reproduction&action=edit&section=10 "Edit section: Ferns") ] Further information: [ Alternation of generations ](/wiki/Alternation_of_generations "Alternation of generations") Ferns produce large diploid [ sporophytes ](/wiki/Sporophyte "Sporophyte") with [ rhizomes ](/wiki/Rhizome "Rhizome") , roots and leaves. Fertile leaves produce [ sporangia ](/wiki/Sporangia "Sporangia") that contain haploid [ spores ](/wiki/Spore "Spore") . The spores are released and germinate to produce small, thin gametophytes that are typically heart shaped and green in color. The gametophyte [ prothalli ](/wiki/Prothallus "Prothallus") , produce motile sperm in the [ antheridia ](/wiki/Antheridia "Antheridia") and egg cells in [ archegonia ](/wiki/Archegonia "Archegonia") on the same or different plants. [46] After rains or when dew deposits a film of water, the motile sperm are splashed away from the antheridia, which are normally produced on the top side of the thallus, and swim in the film of water to the archegonia where they fertilize the egg. To promote out crossing or cross fertilization the sperm are released before the eggs are receptive of the sperm, making it more likely that the sperm will fertilize the eggs of different thallus. After fertilization, a [ zygote ](/wiki/Zygote "Zygote") is formed which grows into a new sporophytic plant. The condition of having separate sporophyte and gametophyte plants is called [ alternation of generations ](/wiki/Alternation_of_generation "Alternation of generation") . ### Bryophytes [ [ edit ](/w/index.php?title=Sexual_reproduction&action=edit&section=11 "Edit section: Bryophytes") ] The [ bryophytes ](/wiki/Bryophyte "Bryophyte") , which include [ liverworts ](/wiki/Marchantiophyta "Marchantiophyta") , [ hornworts ](/wiki/Hornwort "Hornwort") and [ mosses ](/wiki/Moss "Moss") , reproduce both sexually and [ vegetatively ](/wiki/Vegetative_reproduction "Vegetative reproduction") . They are small plants found growing in moist locations and like ferns, have motile sperm with [ flagella ](/wiki/Flagella "Flagella") and need water to facilitate sexual reproduction. These plants start as a haploid spore that grows into the dominant gametophyte form, which is a multicellular haploid body with leaf-like structures that [ photosynthesize ](/wiki/Photosynthesis "Photosynthesis") . Haploid gametes are produced in antheridia (male) and archegonia (female) by mitosis. The sperm released from the antheridia respond to chemicals released by ripe archegonia and swim to them in a film of water and fertilize the egg cells thus producing a zygote. The [ zygote ](/wiki/Zygote "Zygote") divides by mitotic division and grows into a multicellular, diploid sporophyte. The sporophyte produces spore capsules ( [ sporangia ](/wiki/Sporangia "Sporangia") ), which are connected by stalks ( [ setae ](/wiki/Seta "Seta") ) to the archegonia. The spore capsules produce spores by meiosis and when ripe the capsules burst open to release the spores. Bryophytes show considerable variation in their reproductive structures and the above is a basic outline. Also in some species each plant is one sex ( [ dioicous ](/wiki/Dioicous "Dioicous") ) while other species produce both sexes on the same plant ( [ monoicous ](/wiki/Monoicous "Monoicous") ). [47] ## Fungi [ [ edit ](/w/index.php?title=Sexual_reproduction&action=edit&section=12 "Edit section: Fungi") ] Main article: [ Mating in fungi ](/wiki/Mating_in_fungi "Mating in fungi") Further information: [ Fungus § Reproduction ](/wiki/Fungus#Reproduction "Fungus") [ ![](//upload.wikimedia.org/wikipedia/commons/thumb/d/d1/Puffballs_emitting_spores.jpg/220px- Puffballs_emitting_spores.jpg) ](/wiki/File:Puffballs_emitting_spores.jpg) Puffballs emitting spores [ Fungi ](/wiki/Fungi "Fungi") are classified by the methods of sexual reproduction they employ. The outcome of sexual reproduction most often is the production of [ resting spores ](/wiki/Resting_spore "Resting spore") that are used to survive inclement times and to spread. There are typically three phases in the sexual reproduction of fungi: [ plasmogamy ](/wiki/Plasmogamy "Plasmogamy") , [ karyogamy ](/wiki/Karyogamy "Karyogamy") and [ meiosis ](/wiki/Meiosis "Meiosis") . The cytoplasm of two parent cells fuse during plasmogamy and the nuclei fuse during karyogamy. New haploid gametes are formed during meiosis and develop into spores. The adaptive basis for the maintenance of sexual reproduction in the [ Ascomycota ](/wiki/Ascomycota "Ascomycota") and [ Basidiomycota ](/wiki/Basidiomycota "Basidiomycota") ( [ dikaryon ](/wiki/Dikaryon "Dikaryon") ) [ fungi ](/wiki/Fungus "Fungus") was reviewed by Wallen and Perlin. [48] They concluded that the most plausible reason for maintaining this capability is the benefit of [ repairing DNA damage ](/wiki/DNA_repair "DNA repair") , caused by a variety of stresses, through [ recombination ](/wiki/Homologous_recombination "Homologous recombination") that occurs during [ meiosis ](/wiki/Meiosis "Meiosis") . [48] ## Bacteria and archaea [ [ edit ](/w/index.php?title=Sexual_reproduction&action=edit&section=13 "Edit section: Bacteria and archaea") ] Three distinct processes in [ prokaryotes ](/wiki/Prokaryote "Prokaryote") are regarded as similar to [ eukaryotic sex ](/wiki/Origin_and_function_of_meiosis "Origin and function of meiosis") : [ bacterial transformation ](/wiki/Bacterial_transformation "Bacterial transformation") , which involves the incorporation of foreign DNA into the bacterial chromosome; [ bacterial conjugation ](/wiki/Bacterial_conjugation "Bacterial conjugation") , which is a transfer of [ plasmid ](/wiki/Plasmid "Plasmid") DNA between bacteria, but the plasmids are rarely incorporated into the bacterial chromosome; and [ gene transfer and genetic exchange in archaea ](/wiki/Prokaryote#DNA_transfer "Prokaryote") . Bacterial transformation involves the [ recombination of genetic material ](/wiki/Genetic_recombination "Genetic recombination") and its function is mainly associated with [ DNA repair ](/wiki/Sexual_recombination#Recombinational_repair "Sexual recombination") . Bacterial transformation is a complex process encoded by numerous bacterial genes, and is a bacterial adaptation for DNA transfer. [20] [21] This process occurs naturally in at least 40 bacterial species. [49] For a bacterium to bind, take up, and recombine exogenous DNA into its chromosome, it must enter a special physiological state referred to as competence (see [ Natural competence ](/wiki/Natural_competence "Natural competence") ). Sexual reproduction in early single-celled eukaryotes may have evolved from bacterial transformation, [22] or from a similar process in [ archaea ](/wiki/Archaea "Archaea") (see below). On the other hand, bacterial conjugation is a type of direct transfer of DNA between two bacteria mediated by an external appendage called the conjugation pilus. [50] Bacterial conjugation is controlled by [ plasmid genes ](/wiki/Plasmid "Plasmid") that are adapted for spreading copies of the plasmid between bacteria. The infrequent integration of a plasmid into a host bacterial chromosome, and the subsequent transfer of a part of the host chromosome to another cell do not appear to be bacterial adaptations. [20] [51] Exposure of hyperthermophilic archaeal Sulfolobus species to DNA damaging conditions induces cellular aggregation accompanied by high frequency [ genetic marker ](/wiki/Genetic_marker "Genetic marker") exchange [52] [53] Ajon et al. [53] hypothesized that this cellular aggregation enhances species-specific DNA repair by homologous recombination. DNA transfer in _Sulfolobus_ may be an early form of sexual interaction similar to the more well-studied bacterial transformation systems that also involve species- specific DNA transfer leading to homologous recombinational repair of DNA damage. ## See also [ [ edit ](/w/index.php?title=Sexual_reproduction&action=edit&section=14 "Edit section: See also") ] * [ Amphimixis (psychology) ](/wiki/Amphimixis_$psychology$ "Amphimixis $psychology$") * [ Anisogamy ](/wiki/Anisogamy "Anisogamy") * [ Biological reproduction ](/wiki/Biological_reproduction "Biological reproduction") * [ Hermaphroditism ](/wiki/Hermaphroditism "Hermaphroditism") * [ Isogamy ](/wiki/Isogamy "Isogamy") * [ Mate choice ](/wiki/Mate_choice "Mate choice") * [ Mating in fungi ](/wiki/Mating_in_fungi "Mating in fungi") * [ Operational sex ratio ](/wiki/Operational_sex_ratio "Operational sex ratio") * [ Outcrossing ](/wiki/Outcrossing "Outcrossing") * [ Allogamy ](/wiki/Allogamy "Allogamy") * [ Self-incompatibility ](/wiki/Self-incompatibility "Self-incompatibility") * [ Sex ](/wiki/Sex "Sex") * [ Sexual intercourse ](/wiki/Sexual_intercourse "Sexual intercourse") * [ Transformation (genetics) ](/wiki/Transformation_$genetics$ "Transformation $genetics$") ## References [ [ edit ](/w/index.php?title=Sexual_reproduction&action=edit&section=15 "Edit section: References") ] 1. ^ John Maynard Smith & Eörz Szathmáry, The Major Transitions in Evolution, [ W. H. Freeman and Company ](/wiki/W._H._Freeman_and_Company "W. H. Freeman and Company") , 1995, p 149 2. ^ _a _ _b _ Chalker, Douglas (2013). [ "Epigenetics of Ciliates" ](https://cshperspectives.cshlp.org/content/5/12/a017764.full) . _Cold Spring Harbor Perspectives in Biology_ . 5 (12): a017764. [ doi ](/wiki/Doi_$identifier$ "Doi $identifier$") : [ 10.1101/cshperspect.a017764 ](https://doi.org/10.1101%2Fcshperspect.a017764) . [ PMC ](/wiki/PMC_$identifier$ "PMC $identifier$") [ 3839606 ](https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3839606) . [ PMID ](/wiki/PMID_$identifier$ "PMID $identifier$") [ 24296171 ](https://pubmed.ncbi.nlm.nih.gov/24296171) . [ Archived ](https://web.archive.org/web/20220913054521/https://cshperspectives.cshlp.org/content/5/12/a017764.full) from the original on 2022-09-13 . Retrieved 2022-09-13 – via Cold Spring Harbor. 3. ^ Can Song, ShaoJun Liu (2012). 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[ PMID ](/wiki/PMID_$identifier$ "PMID $identifier$") [ 27619703 ](https://pubmed.ncbi.nlm.nih.gov/27619703) . 5. ^ Woods, Kerry (June 19, 2012). [ "Flowering Plants" ](https://eol.org/docs/discover/flowering-plants) . _Encyclopedia of Life_ . [ Archived ](https://web.archive.org/web/20220913053019/https://eol.org/docs/discover/flowering-plants) from the original on September 13, 2022 . Retrieved September 12, 2022 . 6. ^ Knop, Michael (2011). [ "Yeast cell morphology and sexual reproduction – A short overview and some considerations" ](https://www.sciencedirect.com/science/article/pii/S1631069111001405) . _Comptes Rendus Biologies_ . 334 (8–9): 599–606. [ doi ](/wiki/Doi_$identifier$ "Doi $identifier$") : [ 10.1016/j.crvi.2011.05.007 ](https://doi.org/10.1016%2Fj.crvi.2011.05.007) (inactive 2024-03-22). [ PMID ](/wiki/PMID_$identifier$ "PMID $identifier$") [ 21819940 ](https://pubmed.ncbi.nlm.nih.gov/21819940) . 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[ PMID ](/wiki/PMID_$identifier$ "PMID $identifier$") [ 29619017 ](https://pubmed.ncbi.nlm.nih.gov/29619017) . 49. ^ Lorenz, M.G.; Wackernagel, W. (1994). [ "Bacterial gene transfer by natural genetic transformation in the environment" ](https://www.ncbi.nlm.nih.gov/pmc/articles/PMC372978) . _Microbiological Reviews_ . 58 (3): 563–602. [ doi ](/wiki/Doi_$identifier$ "Doi $identifier$") : [ 10.1128/mmbr.58.3.563-602.1994 ](https://doi.org/10.1128%2Fmmbr.58.3.563-602.1994) . [ PMC ](/wiki/PMC_$identifier$ "PMC $identifier$") [ 372978 ](https://www.ncbi.nlm.nih.gov/pmc/articles/PMC372978) . [ PMID ](/wiki/PMID_$identifier$ "PMID $identifier$") [ 7968924 ](https://pubmed.ncbi.nlm.nih.gov/7968924) . 50. ^ Lodé, T. (2012). [ "Have Sex or Not? Lessons from Bacteria" ](https://doi.org/10.1159%2F000342879) . _Sexual Development_ . 6 (6): 325–328. [ doi ](/wiki/Doi_$identifier$ "Doi $identifier$") : [ 10.1159/000342879 ](https://doi.org/10.1159%2F000342879) . [ PMID ](/wiki/PMID_$identifier$ "PMID $identifier$") [ 22986519 ](https://pubmed.ncbi.nlm.nih.gov/22986519) . 51. ^ Krebs, J. E.; Goldstein, E. S.; Kilpatrick, ST (2011). [ _Lewin's GENES X_ ](https://archive.org/details/lewinsgenesx0000unse/page/289) . Boston: Jones and Bartlett Publishers. pp. [ 289–292 ](https://archive.org/details/lewinsgenesx0000unse/page/289) . [ ISBN ](/wiki/ISBN_$identifier$ "ISBN $identifier$") [ 978-0-7637-6632-0 ](/wiki/Special:BookSources/978-0-7637-6632-0 "Special:BookSources/978-0-7637-6632-0") . 52. ^ Fröls, Sabrina; Ajon, Malgorzata; Wagner, Michaela; et al. (9 October 2008). [ "UV-inducible cellular aggregation of the hyperthermophilic archaeon Sulfolobus solfataricus is mediated by pili formation" ](https://doi.org/10.1111%2Fj.1365-2958.2008.06459.x) . _Molecular Microbiology_ . 70 (4). Wiley: 938–952. [ doi ](/wiki/Doi_$identifier$ "Doi $identifier$") : [ 10.1111/j.1365-2958.2008.06459.x ](https://doi.org/10.1111%2Fj.1365-2958.2008.06459.x) . [ ISSN ](/wiki/ISSN_$identifier$ "ISSN $identifier$") [ 0950-382X ](https://www.worldcat.org/issn/0950-382X) . [ PMID ](/wiki/PMID_$identifier$ "PMID $identifier$") [ 18990182 ](https://pubmed.ncbi.nlm.nih.gov/18990182) . [ S2CID ](/wiki/S2CID_$identifier$ "S2CID $identifier$") [ 12797510 ](https://api.semanticscholar.org/CorpusID:12797510) . 53. ^ _a _ _b _ Ajon, Małgorzata; Fröls, Sabrina; van Wolferen, Marleen; et al. (18 October 2011). [ "UV-inducible DNA exchange in hyperthermophilic archaea mediated by type IV pili" ](https://pure.rug.nl/ws/files/6771142/2011MolMicrobiolAjon.pdf) (PDF) . _Molecular Microbiology_ . 82 (4). Wiley: 807–817. [ doi ](/wiki/Doi_$identifier$ "Doi $identifier$") : [ 10.1111/j.1365-2958.2011.07861.x ](https://doi.org/10.1111%2Fj.1365-2958.2011.07861.x) . [ ISSN ](/wiki/ISSN_$identifier$ "ISSN $identifier$") [ 0950-382X ](https://www.worldcat.org/issn/0950-382X) . [ PMID ](/wiki/PMID_$identifier$ "PMID $identifier$") [ 21999488 ](https://pubmed.ncbi.nlm.nih.gov/21999488) . [ S2CID ](/wiki/S2CID_$identifier$ "S2CID $identifier$") [ 42880145 ](https://api.semanticscholar.org/CorpusID:42880145) . [ Archived ](https://web.archive.org/web/20211010101112/https://pure.rug.nl/ws/files/6771142/2011MolMicrobiolAjon.pdf) (PDF) from the original on 10 October 2021 . Retrieved 13 December 2019 . ## Further reading [ [ edit ](/w/index.php?title=Sexual_reproduction&action=edit&section=16 "Edit section: Further reading") ] * Pang, K. "Certificate Biology: New Mastering Basic Concepts", Hong Kong, 2004 * [ Journal of Biology of Reproduction ](http://www.biolreprod.org/) , accessed in August 2005. * [ "Sperm Use Heat Sensors To Find The Egg; Weizmann Institute Research Contributes To Understanding Of Human Fertilization" ](https://www.sciencedaily.com/releases/2003/02/030203071703.htm) , _Science Daily_ , 3 February 2003 * Michod, R. E.; Levin, B.E., eds. (1987). [ _The Evolution of sex: An examination of current ideas_ ](https://archive.org/details/evolutionofsexex0000unse) . Sunderland, Massachusetts: Sinauer Associates. [ ISBN ](/wiki/ISBN_$identifier$ "ISBN $identifier$") [ 978-0-87893-458-4 ](/wiki/Special:BookSources/978-0-87893-458-4 "Special:BookSources/978-0-87893-458-4") . * Michod, R. E. (1994). [ _Eros and Evolution: A Natural Philosophy of Sex_ ](https://archive.org/details/erosevolutionnat0000mich) . Perseus Books. [ ISBN ](/wiki/ISBN_$identifier$ "ISBN $identifier$") [ 978-0-201-40754-9 ](/wiki/Special:BookSources/978-0-201-40754-9 "Special:BookSources/978-0-201-40754-9") . ## External links [ [ edit ](/w/index.php?title=Sexual_reproduction&action=edit&section=17 "Edit section: External links") ] * [ Khan Academy, video lecture ](https://www.youtube.com/watch?v=kaSIjIzAtYA) * [ Sexual Reproduction and the Evolution of Sex ](https://www.nature.com/scitable/topicpage/sexual-reproduction-and-the-evolution-of-sex-824/) ( [ Archived (2023) ](https://archive.today/20231008141323/https://www.nature.com/scitable/topicpage/sexual-reproduction-and-the-evolution-of-sex-824/) ) − [ Nature journal ](/wiki/Nature_$journal$ "Nature $journal$") (2008) * [ v ](/wiki/Template:Sex_$biology$ "Template:Sex $biology$") * [ t ](/wiki/Template_talk:Sex_$biology$ "Template talk:Sex $biology$") * [ e ](/wiki/Special:EditPage/Template:Sex_$biology$ "Special:EditPage/Template:Sex $biology$") [ Sex ](/wiki/Sex "Sex") --- Biological terms \| * [ Sexual dimorphism ](/wiki/Sexual_dimorphism "Sexual dimorphism") * [ Male ](/wiki/Male "Male") * [ Female ](/wiki/Female "Female") * [ Sexual differentiation ](/wiki/Sexual_differentiation "Sexual differentiation") * [ Feminization ](/wiki/Feminization_$biology$ "Feminization $biology$") * [ Virilization ](/wiki/Virilization "Virilization") * [ Sex-determination system ](/wiki/Sex-determination_system "Sex-determination system") * [ XY ](/wiki/XY_sex-determination_system "XY sex-determination system") * [ ZW ](/wiki/ZW_sex-determination_system "ZW sex-determination system") * [ XO ](/wiki/XO_sex-determination_system "XO sex-determination system") * [ ZO ](/wiki/ZO_sex-determination_system "ZO sex-determination system") * [ Temperature-dependent ](/wiki/Temperature-dependent_sex_determination "Temperature-dependent sex determination") * [ Haplodiploidy ](/wiki/Haplodiploidy "Haplodiploidy") * [ Heterogametic sex / Homogametic sex ](/wiki/Heterogametic_sex "Heterogametic sex") * [ Sex chromosome ](/wiki/Sex_chromosome "Sex chromosome") * [ X chromosome ](/wiki/X_chromosome "X chromosome") * [ Y chromosome ](/wiki/Y_chromosome "Y chromosome") * [ Testis-determining factor ](/wiki/Testis-determining_factor "Testis-determining factor") * [ Hermaphrodite ](/wiki/Hermaphrodite "Hermaphrodite") * [ Sequential hermaphroditism ](/wiki/Sequential_hermaphroditism "Sequential hermaphroditism") * [ Simultaneous hermaphroditism ](/wiki/Simultaneous_hermaphroditism "Simultaneous hermaphroditism") * [ Intersex ](/wiki/Intersex "Intersex") * [ parasexuality ](/wiki/Parasexual_cycle "Parasexual cycle") * [ Sex as a biological variable ](/wiki/Sex_as_a_biological_variable "Sex as a biological variable") Sexual reproduction \| * [ Evolution of sexual reproduction ](/wiki/Evolution_of_sexual_reproduction "Evolution of sexual reproduction") * [ Anisogamy ](/wiki/Anisogamy "Anisogamy") * [ Isogamy ](/wiki/Isogamy "Isogamy") * [ Germ cell ](/wiki/Germ_cell "Germ cell") * [ Reproductive system ](/wiki/Reproductive_system "Reproductive system") * [ Sex organ ](/wiki/Sex_organ "Sex organ") * [ Mating ](/wiki/Mating "Mating") * [ Meiosis ](/wiki/Meiosis "Meiosis") * [ Gametogenesis ](/wiki/Gametogenesis "Gametogenesis") * [ Spermatogenesis ](/wiki/Spermatogenesis "Spermatogenesis") * [ Oogenesis ](/wiki/Oogenesis "Oogenesis") * [ Gamete ](/wiki/Gamete "Gamete") * [ spermatozoon ](/wiki/Spermatozoon "Spermatozoon") * [ ovum ](/wiki/Egg_cell "Egg cell") * [ Fertilization ](/wiki/Fertilisation "Fertilisation") * [ External ](/wiki/External_fertilization "External fertilization") * [ Internal ](/wiki/Internal_fertilization "Internal fertilization") * [ Sexual selection ](/wiki/Sexual_selection "Sexual selection") * [ Plant reproduction ](/wiki/Plant_reproduction "Plant reproduction") * [ Fungal reproduction ](/wiki/Mating_in_fungi "Mating in fungi") * [ Sexual reproduction in animals ](/wiki/Sexual_reproduction_in_animals "Sexual reproduction in animals") * [ Sexual intercourse ](/wiki/Sexual_intercourse "Sexual intercourse") * [ Penile-vaginal intercourse ](/wiki/Penile-vaginal_intercourse "Penile-vaginal intercourse") * [ Copulation ](/wiki/Copulation_$zoology$ "Copulation $zoology$") * [ Hormonal motivation ](/wiki/Effects_of_hormones_on_sexual_motivation "Effects of hormones on sexual motivation") * [ Human reproduction ](/wiki/Human_reproduction "Human reproduction") * [ Lordosis behavior ](/wiki/Lordosis_behavior "Lordosis behavior") * [ Pelvic thrust ](/wiki/Pelvic_thrust "Pelvic thrust") [ Sexuality ](/wiki/Human_sexuality "Human sexuality") \| * [ Plant sexuality ](/wiki/Plant_reproductive_morphology "Plant reproductive morphology") * [ Animal sexuality ](/wiki/Animal_sexual_behaviour "Animal sexual behaviour") * [ Human sexuality ](/wiki/Human_sexuality "Human sexuality") * [ Mechanics ](/wiki/Mechanics_of_human_sexuality "Mechanics of human sexuality") * [ Differentiation ](/wiki/Sexual_differentiation_in_humans "Sexual differentiation in humans") * [ Activity ](/wiki/Human_sexual_activity "Human sexual activity") * ![](//upload.wikimedia.org/wikipedia/en/thumb/9/96/Symbol_category_class.svg/16px-Symbol_category_class.svg.png) [ Category ](/wiki/Category:Sex "Category:Sex") * [ v ](/wiki/Template:Animal_sexual_behavior "Template:Animal sexual behavior") * [ t ](/wiki/Template_talk:Animal_sexual_behavior "Template talk:Animal sexual behavior") * [ e ](/wiki/Special:EditPage/Template:Animal_sexual_behavior "Special:EditPage/Template:Animal sexual behavior") [ Animal sexual behaviour ](/wiki/Animal_sexual_behaviour "Animal sexual behaviour") --- [ General ](/wiki/Animal_sexual_behaviour "Animal sexual behaviour") \| * [ Sexual selection ](/wiki/Sexual_selection "Sexual selection") * Sexual reproduction * [ evolution ](/wiki/Evolution_of_sexual_reproduction "Evolution of sexual reproduction") * [ reproductive system ](/wiki/Reproductive_system "Reproductive system") * [ hormonal motivation ](/wiki/Effects_of_hormones_on_sexual_motivation "Effects of hormones on sexual motivation") * [ Courtship display ](/wiki/Courtship_display "Courtship display") * [ sexual ornamentation ](/wiki/Biological_ornament "Biological ornament") * [ handicap principle ](/wiki/Handicap_principle "Handicap principle") * [ sexy son hypothesis ](/wiki/Sexy_son_hypothesis "Sexy son hypothesis") * [ Fisherian runaway ](/wiki/Fisherian_runaway "Fisherian runaway") * [ Mating systems ](/wiki/Mating_system "Mating system") * [ mate choice ](/wiki/Mate_choice "Mate choice") * [ mating call ](/wiki/Mating_call "Mating call") * [ mate guarding ](/wiki/Mate_guarding "Mate guarding") * [ mating plug ](/wiki/Mating_plug "Mating plug") * [ lek mating ](/wiki/Lek_mating "Lek mating") * [ Copulation ](/wiki/Copulation_$zoology$ "Copulation $zoology$") * [ cloacal kiss ](/wiki/Cloacal_kiss "Cloacal kiss") * [ sexual intercourse ](/wiki/Sexual_intercourse "Sexual intercourse") * [ Pelvic thrust ](/wiki/Pelvic_thrust "Pelvic thrust") * [ pseudocopulation ](/wiki/Pseudocopulation "Pseudocopulation") * [ Fertilisation ](/wiki/Fertilisation#Fertilisation_in_animals "Fertilisation") * [ internal ](/wiki/Internal_fertilization "Internal fertilization") * [ external ](/wiki/External_fertilization "External fertilization") * [ sperm competition ](/wiki/Sperm_competition "Sperm competition") * [ traumatic insemination ](/wiki/Traumatic_insemination "Traumatic insemination") * [ penile spines ](/wiki/Penile_spines "Penile spines") * [ Modes ](/wiki/Modes_of_reproduction "Modes of reproduction") * [ monogamy ](/wiki/Monogamy_in_animals "Monogamy in animals") * [ promiscuity ](/wiki/Promiscuity "Promiscuity") * [ polyandry ](/wiki/Polyandry_in_animals "Polyandry in animals") * [ polygyny ](/wiki/Polygyny_in_animals "Polygyny in animals") * [ polygynandry ](/wiki/Polygynandry "Polygynandry") * [ semelparity and iteroparity ](/wiki/Semelparity_and_iteroparity "Semelparity and iteroparity") * [ opportunistic ](/wiki/Opportunistic_breeder "Opportunistic breeder") * [ hermaphroditism ](/wiki/Hermaphrodite "Hermaphrodite") * [ cuckoldry ](/wiki/Cuckold "Cuckold") * [ seasonal ](/wiki/Seasonal_breeder "Seasonal breeder") * [ synchrony ](/wiki/Reproductive_synchrony "Reproductive synchrony") * [ Sexual dimorphism ](/wiki/Sexual_dimorphism "Sexual dimorphism") * [ anisogamy ](/wiki/Anisogamy "Anisogamy") * [ oogamy ](/wiki/Oogamy "Oogamy") * [ Bateman's principle ](/wiki/Bateman%27s_principle "Bateman's principle") * [ bimaturism ](/wiki/Sexual_bimaturism "Sexual bimaturism") * [ cannibalism ](/wiki/Sexual_cannibalism "Sexual cannibalism") * [ coercion ](/wiki/Sexual_coercion_among_animals "Sexual coercion among animals") * [ Sexual conflict ](/wiki/Sexual_conflict "Sexual conflict") * [ interlocus ](/wiki/Interlocus_sexual_conflict "Interlocus sexual conflict") * [ intralocus ](/wiki/Intralocus_sexual_conflict "Intralocus sexual conflict") * [ Interspecies breeding ](/wiki/Hybrid_$biology$ "Hybrid $biology$") * [ Non-reproductive behavior ](/wiki/Non-reproductive_sexual_behavior_in_animals "Non-reproductive sexual behavior in animals") * [ Fisher's principle ](/wiki/Fisher%27s_principle "Fisher's principle") [ Invertebrates ](/wiki/Animal_sexual_behaviour#Invertebrates "Animal sexual behaviour") \| * [ Arthropods ](/wiki/Arthropod#Reproduction_and_development "Arthropod") * [ crab ](/wiki/Crab#Reproduction_and_lifecycle "Crab") * [ spider ](/wiki/Spider#Reproduction_and_life_cycle "Spider") * [ scorpion ](/wiki/Scorpion#Reproduction "Scorpion") * [ beetle ](/wiki/Beetle#Mating "Beetle") * [ insect ](/wiki/Insect#Reproduction_and_development "Insect") * [ butterfly ](/wiki/Butterfly#Life_cycle "Butterfly") * [ Cephalopods ](/wiki/Cephalopod#Reproduction_and_life_cycle "Cephalopod") * [ octopus ](/wiki/Octopus#Reproduction "Octopus") * [ Cnidaria ](/wiki/Cnidaria#Sexual "Cnidaria") * [ sea anemone ](/wiki/Sea_anemone#Lifecycle "Sea anemone") * [ jellyfish ](/wiki/Jellyfish#Reproduction "Jellyfish") * [ coral ](/wiki/Coral#Sexual "Coral") * [ Echinoderms ](/wiki/Echinoderm#Reproduction "Echinoderm") * [ Gastropods ](/wiki/Mating_of_gastropods "Mating of gastropods") * [ apophallation ](/wiki/Apophallation "Apophallation") * [ love dart ](/wiki/Love_dart "Love dart") * [ Sponge ](/wiki/Sponge#Reproduction "Sponge") * Worms * [ earthworm ](/wiki/Earthworm#Reproduction "Earthworm") * [ epitoky ](/wiki/Epitoky "Epitoky") * [ penis fencing ](/wiki/Penis_fencing "Penis fencing") [ Fish ](/wiki/Fish_reproduction "Fish reproduction") \| * [ Spawning strategies ](/wiki/Spawn_$biology$#Spawning_strategies "Spawn $biology$") * [ Polyandry in fish ](/wiki/Polyandry_in_fish "Polyandry in fish") * [ Eels ](/wiki/Eel_life_history "Eel life history") * [ Salmon run ](/wiki/Salmon_run "Salmon run") * [ Seahorse ](/wiki/Seahorse#Reproduction "Seahorse") * [ Sharks ](/wiki/Shark#Life_history "Shark") [ Amphibians ](/wiki/Amphibian#Reproduction "Amphibian") \| * [ Sexual selection ](/wiki/Sexual_selection_in_amphibians "Sexual selection in amphibians") * [ frogs ](/wiki/Sexual_selection_in_amphibians "Sexual selection in amphibians") * [ Frog reproduction ](/wiki/Frog#Reproduction "Frog") * [ Salamanders ](/wiki/Salamander#Reproduction_and_development "Salamander") [ Reptiles ](/wiki/Reptile#Reproduction "Reptile") \| * [ Sexual selection in scaled reptiles ](/wiki/Sexual_selection_in_scaled_reptiles "Sexual selection in scaled reptiles") * [ lizards ](/wiki/Sexual_selection_in_scaled_reptiles "Sexual selection in scaled reptiles") * [ snakes ](/wiki/Sexual_selection_in_scaled_reptiles "Sexual selection in scaled reptiles") * [ side-blotched lizard ](/wiki/Common_side-blotched_lizard "Common side-blotched lizard") * [ Crocodilians ](/wiki/Crocodilia#Reproduction_and_parenting "Crocodilia") * [ Tuatara ](/wiki/Tuatara#Reproduction "Tuatara") [ Birds ](/wiki/Bird#Breeding "Bird") \| * [ Sexual selection ](/wiki/Sexual_selection_in_birds "Sexual selection in birds") * [ Breeding behaviour ](/wiki/Bird#Breeding "Bird") * [ golden eagle ](/wiki/Reproduction_and_life_cycle_of_the_golden_eagle "Reproduction and life cycle of the golden eagle") * [ seabirds ](/wiki/Seabird_breeding_behavior "Seabird breeding behavior") * [ Homosexual behavior ](/wiki/List_of_birds_displaying_homosexual_behavior "List of birds displaying homosexual behavior") [ Mammals ](/wiki/Mammalian_reproduction "Mammalian reproduction") \| * [ Sexual selection ](/wiki/Sexual_selection_in_mammals "Sexual selection in mammals") * [ rut ](/wiki/Rut_$mammalian_reproduction$ "Rut $mammalian reproduction$") * [ Lordosis behavior ](/wiki/Lordosis_behavior "Lordosis behavior") * [ Homosexual behavior ](/wiki/List_of_mammals_displaying_homosexual_behavior "List of mammals displaying homosexual behavior") * [ Canid ](/wiki/Canidae#Life_history "Canidae") * [ African wild dog ](/wiki/African_wild_dog#Social_and_reproductive_behaviour "African wild dog") * [ coyote ](/wiki/Coyote#Social_and_reproductive_behaviors "Coyote") * [ dingo ](/wiki/Dingo#Reproduction "Dingo") * [ domestic dog ](/wiki/Canine_reproduction#Copulation "Canine reproduction") * [ gray wolf ](/wiki/Wolf#Reproduction_and_development "Wolf") * [ red fox ](/wiki/Red_fox#Reproduction_and_development "Red fox") * [ Dolphin ](/wiki/Dolphin#Reproduction_and_sexuality "Dolphin") * [ Elephant ](/wiki/Elephant#Sexual_behaviour "Elephant") * [ European badger ](/wiki/European_badger#Reproduction_and_development "European badger") * [ Felidae ](/wiki/Felidae "Felidae") * [ lion ](/wiki/Lion#Reproduction_and_life_cycle "Lion") * [ tiger ](/wiki/Tiger#Reproduction "Tiger") * [ cheetah ](/wiki/Cheetah#Reproduction "Cheetah") * [ domestic cat ](/wiki/Cat#Reproduction "Cat") * [ Fossa ](/wiki/Fossa_$animal$#Breeding "Fossa $animal$") * [ Hippopotamus ](/wiki/Hippopotamus#Reproduction "Hippopotamus") * [ Spotted hyena ](/wiki/Spotted_hyena#Reproduction_and_development "Spotted hyena") * [ Marsupial ](/wiki/Marsupial#Reproductive_system "Marsupial") * [ kangaroo ](/wiki/Kangaroo#Sexual_behavior "Kangaroo") * [ Pinnipeds ](/wiki/Pinniped#Reproductive_behavior "Pinniped") * [ walrus ](/wiki/Walrus#Reproduction "Walrus") * Primates * [ human ](/wiki/Human_sexual_activity "Human sexual activity") * [ bonobo ](/wiki/Bonobo#Sociosexual_behaviour "Bonobo") * [ gorilla ](/wiki/Gorilla#Reproduction_and_parenting "Gorilla") * [ olive baboon ](/wiki/Olive_baboon#Reproduction_and_parenting "Olive baboon") * [ mandrill ](/wiki/Mandrill#Mating "Mandrill") * [ ringtailed lemur ](/wiki/Ring-tailed_lemur#Breeding_and_reproduction "Ring-tailed lemur") * [ sexual swelling ](/wiki/Sexual_swelling "Sexual swelling") * [ Raccoon ](/wiki/Raccoon#Reproduction "Raccoon") * [ Rodent ](/wiki/Rodent#Mating_strategies "Rodent") * [ Short-beaked echidna ](/wiki/Short-beaked_echidna#Reproduction "Short-beaked echidna") [ Portals ](/wiki/Wikipedia:Contents/Portals "Wikipedia:Contents/Portals") : * [ ![icon](//upload.wikimedia.org/wikipedia/commons/thumb/2/2d/Issoria_lathonia.jpg/21px-Issoria_lathonia.jpg) ](/wiki/File:Issoria_lathonia.jpg) [ Biology ](/wiki/Portal:Biology "Portal:Biology") * [ ![icon](//upload.wikimedia.org/wikipedia/commons/thumb/0/09/Tree_of_life.svg/21px-Tree_of_life.svg.png) ](/wiki/File:Tree_of_life.svg) [ evolutionary biology ](/wiki/Portal:Evolutionary_biology "Portal:Evolutionary biology") * [ ![icon](//upload.wikimedia.org/wikipedia/commons/thumb/8/8b/Nuvola_apps_kalzium.svg/19px-Nuvola_apps_kalzium.svg.png) ](/wiki/File:Nuvola_apps_kalzium.svg) [ Science ](/wiki/Portal:Science "Portal:Science") [ Authority control databases ](/wiki/Help:Authority_control "Help:Authority control") : National [ ![Edit this at Wikidata](//upload.wikimedia.org/wikipedia/en/thumb/8/8a/OOjs_UI_icon_edit- ltr-progressive.svg/10px-OOjs_UI_icon_edit-ltr-progressive.svg.png) 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E. Anderson, H. Crum och William Russell Buck 1990. Schistidium heterophyllum ingår i släktet blommossor, och familjen Grimmiaceae. Inga underarter finns listade i Catalogue of Life. Källor Externa länkar Blommossor heterophyllum	swedish	1.07315
more_than_two_sexes/Mating_type.txt	Mating types are the microorganism equivalent to sexes in multicellular lifeforms and are thought to be the ancestor to distinct sexes. They also occur in macro-organisms such as fungi. Definition[edit] Mating types are the microorganism equivalent to sex in higher organisms and occur in isogamous and anisogamous species. Depending on the group, different mating types are often referred to by numbers, letters, or simply "+" and "−" instead of "male" and "female", which refer to "sexes" or differences in size between gametes. Syngamy can only take place between gametes carrying different mating types. Occurrence[edit] Reproduction by mating types is especially prevalent in fungi. Filamentous ascomycetes usually have two mating types referred to as "MAT1-1" and "MAT1-2", following the yeast mating-type locus (MAT). Under standard nomenclature, MAT1-1 (which may informally be called MAT1) encodes for a regulatory protein with an alpha box motif, while MAT1-2 (informally called MAT2) encodes for a protein with a high motility-group (HMG) DNA-binding motif, as in the yeast mating type MATα1. The corresponding mating types in yeast, a non-filamentous ascomycete, are referred to as MATa and MATα. Mating type genes in ascomycetes are called idiomorphs rather than alleles due to the uncertainty of the origin by common descent. The proteins they encode are transcription factors which regulate both the early and late stages of the sexual cycle. Heterothallic ascomycetes produce gametes, which present a single Mat idiomorph, and syngamy will only be possible between gametes carrying complementary mating types. On the other hand, homothallic ascomycetes produce gametes that can fuse with every other gamete in the population (including its own mitotic descendants) most often because each haploid contains the two alternate forms of the Mat locus in its genome. Basidiomycetes can have thousands of different mating types. In the ascomycete Neurospora crassa matings are restricted to interaction of strains of opposite mating type. This promotes some degree of outcrossing. Outcrossing, through complementation, could provide the benefit of masking recessive deleterious mutations in genes which function in the dikaryon and/or diploid stage of the life cycle. Evolution[edit] Main article: Evolution of sexual reproduction Mating types likely predate anisogamy, and sexes evolved directly from mating types or independently in some lineages. In 2006 Japanese researchers found a gene in males of the alga Pleodorina starrii that’s an orthologue to a gene for a mating type in the alga Chlamydomonas reinhardtii, providing evidence for an evolutionary link between sexes and mating types. Secondary mating types evolved alongside simultaneous hermaphrodites in several lineages. In Volvocales, the plus mating type is the ancestor to female. In ciliates multiple mating types evolved from binary mating types in several lineages. As of 2019, genomic conflict has been considered the leading explanation for the evolution of two mating types. See also[edit] Mating in fungi Mating of yeast Mating-type locus Saccharomyces cerevisiae (a and α mating types) Schizophyllum commune (23,328 mating types) Tetrahymena (7 mating types)	biology	4488993	https://sv.wikipedia.org/wiki/Genista%20fasselata	Genista fasselata	Genista fasselata är en ärtväxtart som beskrevs av Joseph Decaisne. Genista fasselata ingår i släktet ginster, och familjen ärtväxter. IUCN kategoriserar arten globalt som livskraftig. Inga underarter finns listade i Catalogue of Life. Källor Externa länkar Ginster fasselata	swedish	0.99327
trees_grow_directions/Phototropism.txt	In biology, phototropism is the growth of an organism in response to a light stimulus. Phototropism is most often observed in plants, but can also occur in other organisms such as fungi. The cells on the plant that are farthest from the light contain a hormone called auxin that reacts when phototropism occurs. This causes the plant to have elongated cells on the furthest side from the light. Phototropism is one of the many plant tropisms, or movements, which respond to external stimuli. Growth towards a light source is called positive phototropism, while growth away from light is called negative phototropism. Negative phototropism is not to be confused with skototropism, which is defined as the growth towards darkness, whereas negative phototropism can refer to either the growth away from a light source or towards the darkness. Most plant shoots exhibit positive phototropism, and rearrange their chloroplasts in the leaves to maximize photosynthetic energy and promote growth. Some vine shoot tips exhibit negative phototropism, which allows them to grow towards dark, solid objects and climb them. The combination of phototropism and gravitropism allow plants to grow in the correct direction. Mechanism[edit] There are several signaling molecules that help the plant determine where the light source is coming from, and these activate several genes, which change the hormone gradients allowing the plant to grow towards the light. The very tip of the plant is known as the coleoptile, which is necessary in light sensing. The middle portion of the coleoptile is the area where the shoot curvature occurs. The Cholodny–Went hypothesis, developed in the early 20th century, predicts that in the presence of asymmetric light, auxin will move towards the shaded side and promote elongation of the cells on that side to cause the plant to curve towards the light source. Auxins activate proton pumps, decreasing the pH in the cells on the dark side of the plant. This acidification of the cell wall region activates enzymes known as expansins which disrupt hydrogen bonds in the cell wall structure, making the cell walls less rigid. In addition, increased proton pump activity leads to more solutes entering the plant cells on the dark side of the plant, which increases the osmotic gradient between the symplast and apoplast of these plant cells. Water then enters the cells along its osmotic gradient, leading to an increase in turgor pressure. The decrease in cell wall strength and increased turgor pressure above a yield threshold causes cells to swell, exerting the mechanical pressure that drives phototropic movement. Proteins encoded by a second group of genes, PIN genes, have been found to play a major role in phototropism. They are auxin transporters, and it is thought that they are responsible for the polarization of auxin location. Specifically PIN3 has been identified as the primary auxin carrier. It is possible that phototropins receive light and inhibit the activity of PINOID kinase (PID), which then promotes the activity of PIN3. This activation of PIN3 leads to asymmetric distribution of auxin, which then leads to asymmetric elongation of cells in the stem. pin3 mutants had shorter hypocotyls and roots than the wild-type, and the same phenotype was seen in plants grown with auxin efflux inhibitors. Using anti-PIN3 immunogold labeling, movement of the PIN3 protein was observed. PIN3 is normally localized to the surface of hypocotyl and stem, but is also internalized in the presence of Brefeldin A (BFA), an exocytosis inhibitor. This mechanism allows PIN3 to be repositioned in response to an environmental stimulus. PIN3 and PIN7 proteins were thought to play a role in pulse-induced phototropism. The curvature responses in the "pin3" mutant were reduced significantly, but only slightly reduced in "pin7" mutants. There is some redundancy among "PIN1", "PIN3", and "PIN7", but it is thought that PIN3 plays a greater role in pulse-induced phototropism. There are phototropins that are highly expressed in the upper region of coleoptiles. There are two main phototropism they are phot1 and phot2. phot2 single mutants have phototropic responses like that of the wild-type, but phot1 phot2 double mutants do not show any phototropic responses. The amounts of PHOT1 and PHOT2 present are different depending on the age of the plant and the intensity of the light. There is a high amount of PHOT2 present in mature Arabidopsis leaves and this was also seen in rice orthologs. The expression of PHOT1 and PHOT2 changes depending on the presence of blue or red light. There was a downregulation of PHOT1 mRNA in the presence of light, but upregulation of PHOT2 transcript. The levels of mRNA and protein present in the plant were dependent upon the age of the plant. This suggests that the phototropin expression levels change with the maturation of the leaves. Mature leaves contain chloroplasts that are essential in photosynthesis. Chloroplast rearrangement occurs in different light environments to maximize photosynthesis. There are several genes involved in plant phototropism including the NPH1 and NPL1 gene. They are both involved in chloroplast rearrangement. The nph1 and npl1 double mutants were found to have reduced phototropic responses. In fact, the two genes are both redundant in determining the curvature of the stem. Recent studies reveal that multiple AGC kinases, except for PHOT1 and PHOT2, are involved in plant phototropism. Firstly, PINOID, exhibiting a light-inducible expression pattern, determines the subcellular relocation of PIN3 during phototropic responses via a direct phosphorylation. Secondly, D6PK and its D6PKL homologs modulates the auxin transport activity of PIN3, likely through phosphorylation as well. Third, upstream of D6PK/D6PKLs, PDK1.1 and PDK1.2 acts an essential activator for these AGC kinases. Interestingly, different AGC kinases might participate in different steps during the progression of a phototropic response. D6PK/D6PKLs exhibit an ability to phosphorylate more phosphosites than PINOID. Five models of auxin distribution in phototropism[edit] In 2012, Sakai and Haga outlined how different auxin concentrations could be arising on shaded and lighted side of the stem, giving birth to phototropic response. Five models in respect to stem phototropism have been proposed, using Arabidopsis thaliana as the study plant. Five models showing how auxin is transported in the plant Arabidopsis. First model In the first model incoming light deactivates auxin on the light side of the plant allowing the shaded part to continue growing and eventually bend the plant over towards the light. Second model In the second model light inhibits auxin biosynthesis on the light side of the plant, thus decreasing the concentration of auxin relative to the unaffected side. Third model In the third model there is a horizontal flow of auxin from both the light and dark side of the plant. Incoming light causes more auxin to flow from the exposed side to the shaded side, increasing the concentration of auxin on the shaded side and thus more growth occurring. Fourth model In the fourth model it shows the plant receiving light to inhibit auxin basipetal down to the exposed side, causing the auxin to only flow down the shaded side. Fifth model Model five encompasses elements of both model 3 and 4. The main auxin flow in this model comes from the top of the plant vertically down towards the base of the plant with some of the auxin travelling horizontally from the main auxin flow to both sides of the plant. Receiving light inhibits the horizontal auxin flow from the main vertical auxin flow to the irradiated exposed side. And according to the study by Sakai and Haga, the observed asymmetric auxin distribution and subsequent phototropic response in hypocotyls seems most consistent with this fifth scenario. Effects of wavelength[edit] Phototropism in plants such as Arabidopsis thaliana is directed by blue light receptors called phototropins. Other photosensitive receptors in plants include phytochromes that sense red light and cryptochromes that sense blue light. Different organs of the plant may exhibit different phototropic reactions to different wavelengths of light. Stem tips exhibit positive phototropic reactions to blue light, while root tips exhibit negative phototropic reactions to blue light. Both root tips and most stem tips exhibit positive phototropism to red light. Cryptochromes are photoreceptors that absorb blue/ UV-A light, and they help control the circadian rhythm in plants and timing of flowering. Phytochromes are photoreceptors that sense red/far-red light, but they also absorb blue light; they can control flowering in adult plants and the germination of seeds, among other things. The combination of responses from phytochromes and cryptochromes allow the plant to respond to various kinds of light. Together phytochromes and cryptochromes inhibit gravitropism in hypocotyls and contribute to phototropism. Gallery[edit] The Thale Cress (Arabidopsis thaliana) is regulated by blue to UV light Phycomyces, a fungus, also exhibit phototropism Example on a Phalaenopsis Example on Azuki beans Ravenalas growing between two buildings in Kinshasa, Democratic Republic of Congo. The plane (here perpendicular to the north–south axis) of these two plants is orientated to maximize daylight absorption See also[edit] Scotobiology Cholodny–Went model	biology	796989	https://no.wikipedia.org/wiki/Herkogami	Herkogami	Herkogami er atskillelse av kjønnsfunksjoner i rom hos hermafrodittiske (tvekjønnete) organismer (for atskillelse i tid, se dichogami). Selv om hermafrodittiske organismer er i stand til å sjølbefrukte er dette som regel ufordelaktig, pga. innavlsdepresjon. Mange organismer har derfor evolvert mekanismer for å unngå sjølbefruktning og det å atskille hannlig og hunnlig funksjon i rom er en slik mekanisme. Herkogami er svært vanlig hos blomsterplantene der de fleste artene er hermafroditter. Herkogami vil si at pollen i utgangspunktet avleveres og mottas på ulike plasser i blomsten. Ofte er det pollinatorens bevegelse i blomsten som fører til at fremmed pollen avsettes og blomstens eget pollen fjernes, men det kan også være bevegelser i blomsterdeler som besørger dette. Formering	norwegian_bokmål	0.840231
trees_grow_directions/Apical_dominance.txt	In botany, apical dominance is the phenomenon whereby the main, central stem of the plant is dominant over (i.e., grows more strongly than) other side stems; on a branch the main stem of the branch is further dominant over its own side twigs. Plant physiology describes apical dominance as the control exerted by the terminal bud (and shoot apex) over the outgrowth of lateral buds. Overview[edit] Apical dominance occurs when the shoot apex inhibits the growth of lateral buds so that the plant may grow vertically. It is important for the plant to devote energy to growing upward so that it can get more light to undergo photosynthesis. If the plant utilizes available energy for growing upward, it may be able to outcompete other individuals in the vicinity. Plants that were capable of outcompeting neighboring plants likely had higher fitness. Apical dominance is therefore most likely adaptive. Typically, the end of a shoot contains an apical bud, which is the location where shoot growth occurs. The apical bud produces a plant hormone, auxin (IAA), that inhibits growth of the lateral buds further down on the stem towards the axillary bud. Auxin is predominantly produced in the growing shoot apex and is transported throughout the plant via the phloem and diffuses into lateral buds which prevents elongation. That auxin likely regulates apical dominance was first discovered in 1934. When the apical bud is removed, the lowered IAA concentration allows the lateral buds to grow and produce new shoots, which compete to become the lead growth. Weeping larch showing growth habit lacking apical dominance Apex removal[edit] Plant physiologists have identified four different stages the plant goes through after the apex is removed (Stages I-IV). The four stages are referred to as lateral bud formation, "imposition of inhibition" (apical dominance), initiation of lateral bud outgrowth following decapitation, and elongation and development of the lateral bud into a branch. These stages can also be defined by the hormones that are regulating the process which are as follows: Stage I, cytokinin promoted, causing the lateral bud to form since cytokinin plays a role in cell division; Stage II, auxin is promoted, resulting in apical dominance ("imposition of inhibition"); Stage III, cytokinin released resulting in outward growth of the lateral bud; and Stage IV, auxin is decreased and gibberellic acid is promoted which results in cell division, enabling the bud or branch to continue outward growth. More simply stated, lateral bud formation is inhibited by the shoot apical meristem (SAM). The lateral bud primordium (from which the lateral bud develops) is located below SAM. The shoot tip rising from the SAM inhibits the growth of the lateral bud by repressing auxin. When the shoot is cut off, the lateral bud begins to lengthen which is mediated by a release of cytokinin. Once the apical dominance has been lifted from the plant, elongation and lateral growth is promoted and the lateral buds grow into new branches. When lateral bud formation prevents the plant from growing upward, it is undergoing lateral dominance. Often, lateral dominance can be triggered by decapitating the SAM or artificially decreasing the concentration of auxin in plant tissues. Applications[edit] When apical meristems (apical buds) are continually removed, the shape of a tree or shrub can be manipulated remarkably, because newer, uninhibited, branches grow en masse almost anywhere on the tree or shrub.Topiary garden, Beckley Park manor, UK When the apical bud is removed, the lowered IAA concentration allows the lateral buds to grow and produce new shoots, which compete to become the lead growth. Pruning techniques such as coppicing and pollarding make use of this natural response to curtail direct plant growth and produce a desired shape, size, and/or productivity level for the plant. The principle of apical dominance is manipulated for espalier creation, hedge building, or artistic sculptures called topiary. If the SAM is removed, it stimulates growth in the lateral direction. By careful pruning, it is possible to create remarkable designs or patterns. Some fruit trees have strong apical dominance, and young trees can become "leggy", with poor side limb development. Apical dominance can be reduced in this case, or in cases where limbs are broken off by accident, by cutting off the auxin flow above side buds that one wishes to stimulate. This is often done by orchardists for young trees. Occasionally, strong apical dominance is advantageous, as in the "Ballerina" apple trees. These trees are intended to be grown in small gardens, and their strong apical dominance combined with a dwarfing rootstock gives a compact narrow tree with very short fruiting side branches. See also[edit] Meristem Fruit tree pruning	biology	4091945	https://sv.wikipedia.org/wiki/Lilium%20polyphyllum	Lilium polyphyllum	Lilium polyphyllum är en liljeväxtart som beskrevs av David Don. Lilium polyphyllum ingår i släktet liljor och familjen liljeväxter. Inga underarter finns listade. Arten förekommer i bergstrakter i Afghanistan, Pakistan och nordvästra Indien. Den växer vid 2100 till 3000 meter över havet. Denna blomma ingår i undervegetationen i skogar. Exemplar med blomställning är 10 till 12 år gamla. Beståndet hotas av skogsröjningar när jordbruksmark etableras eller när trafikleder byggs. Lilium polyphyllum plockas dessutom som prydnadsväxt. Några exemplar drabbas av svampen Botrytis cinerea. IUCN listar arten som akut hotad (CR). Bildgalleri Källor Externa länkar Liljor polyphyllum	swedish	1.108984
trees_grow_directions/Auxin.txt	Auxins (plural of auxin /ˈɔːksɪn/) are a class of plant hormones (or plant-growth regulators) with some morphogen-like characteristics. Auxins play a cardinal role in coordination of many growth and behavioral processes in plant life cycles and are essential for plant body development. The Dutch biologist Frits Warmolt Went first described auxins and their role in plant growth in the 1920s. Kenneth V. Thimann became the first to isolate one of these phytohormones and to determine its chemical structure as indole-3-acetic acid (IAA). Went and Thimann co-authored a book on plant hormones, Phytohormones, in 1937. Overview[edit] Auxins were the first of the major plant hormones to be discovered. They derive their name from the Greek word αυξειν (auxein – "to grow/increase"). Auxin is present in all parts of a plant, although in very different concentrations. The concentration in each position is crucial developmental information, so it is subject to tight regulation through both metabolism and transport. The result is the auxin creates "patterns" of auxin concentration maxima and minima in the plant body, which in turn guide further development of respective cells, and ultimately of the plant as a whole. The (dynamic and environment responsive) pattern of auxin distribution within the plant is a key factor for plant growth, its reaction to its environment, and specifically for development of plant organs (such as leaves or flowers). It is achieved through very complex and well-coordinated active transport of auxin molecules from cell to cell throughout the plant body—by the so-called polar auxin transport. Thus, a plant can (as a whole) react to external conditions and adjust to them, without requiring a nervous system. Auxins typically act in concert with, or in opposition to, other plant hormones. For example, the ratio of auxin to cytokinin in certain plant tissues determines initiation of root versus shoot buds. On the molecular level, all auxins are compounds with an aromatic ring and a carboxylic acid group. The most important member of the auxin family is indole-3-acetic acid (IAA), which generates the majority of auxin effects in intact plants, and is the most potent native auxin. And as native auxin, its equilibrium is controlled in many ways in plants, from synthesis, through possible conjugation to degradation of its molecules, always according to the requirements of the situation. Five naturally occurring (endogenous) auxins in plants include indole-3-acetic acid, 4-chloroindole-3-acetic acid, phenylacetic acid, indole-3-butyric acid, and indole-3-propionic acid. However, most of the knowledge described so far in auxin biology and as described in the sections which follow, apply basically to IAA; the other three endogenous auxins seems to have marginal importance for intact plants in natural environments. Alongside endogenous auxins, scientists and manufacturers have developed many synthetic compounds with auxinic activity. Synthetic auxins fall into four classes: dicamba quinolinecarboxylic acids, which includes quinclorac derivatives of pyridinecarboxylic acids, which includes picloram, triclopyr, clopyralid phenoxyacetic acid, phenoxypropionic acid, and phenoxybutyric acid, 1-naphthaleneacetic acid derivatives 2,4-D, 2,4-DP 2,4-DB 2,4,5-T MCPA MCPB, mecoprop Some synthetic auxins, such as 2,4-D and 2,4,5-trichlorophenoxyacetic acid (2,4,5-T), are sold as herbicides. Broad-leaf plants (dicots), such as dandelions, are much more susceptible to auxins than narrow-leaf plants (monocots) such as grasses and cereal crops, making these synthetic auxins valuable as herbicides. Discovery[edit] Charles Darwin[edit] In 1881, Charles Darwin and his son Francis performed experiments on coleoptiles, the sheaths enclosing young leaves in germinating grass seedlings. The experiment exposed the coleoptile to light from a unidirectional source, and observed that they bend towards the light. By covering various parts of the coleoptiles with a light-impermeable opaque cap, the Darwins discovered that light is detected by the coleoptile tip, but that bending occurs in the hypocotyl. However the seedlings showed no signs of development towards light if the tip was covered with an opaque cap, or if the tip was removed. The Darwins concluded that the tip of the coleoptile was responsible for sensing light, and proposed that a messenger is transmitted in a downward direction from the tip of the coleoptile, causing it to bend. Peter Boysen Jensen[edit] In 1910, Danish scientist Peter Boysen Jensen demonstrated that the phototropic stimulus in the oat coleoptile could propagate through an incision. These experiments were extended and published in greater detail in 1911 and 1913. He found that the tip could be cut off and put back on, and that a subsequent one-sided illumination was still able to produce a positive phototropic curvature in the basal part of the coleoptile. He demonstrated that the transmission could take place through a thin layer of gelatin separating the unilaterally illuminated tip from the shaded stump. By inserting a piece of mica he could block transmission in the illuminated and non-illuminated side of the tip, respectively, which allowed him to show that the transmission took place in the shaded part of the tip. Thus, the longitudinal half of the coleoptile that exhibits the greater rate of elongation during the phototropic curvature, was the tissue to receive the growth stimulus. In 1911, Boysen Jensen concluded from his experimental results that the transmission of the phototropic stimulus was not a physical effect (for example due to a change in pressure) but serait dû à une migration de substance ou d’ions (was caused by the transport of a substance or of ions). These results were fundamental for further work on the auxin theory of tropisms. Frits Went[edit] Main article: Frits Warmolt Went In 1928, the Dutch botanist Frits Warmolt Went showed that a chemical messenger diffuses from coleoptile tips. Went's experiment identified how a growth promoting chemical causes a coleoptile to grow towards the light. Went cut the tips of the coleoptiles and placed them in the dark, putting a few tips on agar blocks that he predicted would absorb the growth-promoting chemical. On control coleoptiles, he placed a block that lacked the chemical. On others, he placed blocks containing the chemical, either centered on top of the coleoptile to distribute the chemical evenly or offset to increase the concentration on one side. When the growth-promoting chemical was distributed evenly the coleoptile grew straight. If the chemical was distributed unevenly, the coleoptile curved away from the side with the cube, as if growing towards the light, even though it was grown in the dark. Went later proposed that the messenger substance is a growth-promoting hormone, which he named auxin, that becomes asymmetrically distributed in the bending region. Went concluded that auxin is at a higher concentration on the shaded side, promoting cell elongation, which results in coleoptiles bending towards the light. Hormonal activity[edit] Auxins help development at all levels in plants, from the cellular level, through organs, and ultimately to the whole plant. Molecular mechanisms[edit] When a plant cell comes into contact with auxin, it causes dramatic changes in gene expression, with many genes up- or down-regulated. The precise mechanisms by which this occurs are still an area of active research, but there is now a general consensus on at least two auxin signalling pathways. Perception[edit] The best-characterized auxin receptors are the TIR1/ AFB family of F-box proteins. F-box proteins target other proteins for degradation via the ubiquitin degradation pathway. When TIR1/ AFB proteins bind to auxin, the auxin acts as a 'molecular glue' that allows these proteins to then bind to their targets (see below). Another auxin-binding protein, ABP1 is now often regarded as an auxin receptor (at the apoplast), but it is generally considered to have a much more minor role than the TIR1/AFB signaling pathway, and much less is known about ABP1 signaling. Aux/IAA and ARF signalling modules[edit] The auxin signal cascade: In the absence of auxin, Aux/IAA bind to and suppress the transcriptional activity of ARFs. When auxin is present it forms a 'molecular glue' between TIR1 and Aux/IAAs, which leads to the degradation of these repressors. ARFs are then free to bind to DNA and to cause changes in transcription. Auxin response factors (ARFs) are a large group of transcription factors that act in auxin signaling. In the absence of auxin, ARFs bind to a class of repressors known as Aux/IAAs. Aux/IAA suppress the ability of ARFs to enhance gene transcription. Additionally, the binding of Aux/IAA to ARFs brings Aux/IAA into contact with the promoters of auxin-regulated genes. When at these promoters, Aux/IAA repress the expression of these genes through recruiting other factors to make modifications to the DNA structure. The binding of auxin to TIR1/AFBs allows them to bind to Aux/IAAs. When bound by TIR1/AFBs, Aux/IAAs are marked for degradation. The degradation of Aux/IAA frees ARF proteins, which are then able to activate or repress genes at whose promoters they are bound. The large number of Aux/IAA and ARF binding pairs possible, and their different distributions between cell types and across developmental age are thought to account for the astonishingly diverse responses that auxin produces. In June 2018, it was demonstrated that plant tissues can respond to auxin in a TIR1-dependent manner extremely quickly (probably too quickly to be explained by changes in gene expression). This has led some scientists to suggest that there is an as yet unidentified TIR1-dependent auxin-signalling pathway that differs from the well-known transcriptional response. On a cellular level[edit] Main article: Acid-growth hypothesis On the cellular level, auxin is essential for cell growth, affecting both cell division and cellular expansion. Auxin concentration level, together with other local factors, contributes to cell differentiation and specification of the cell fate. Depending on the specific tissue, auxin may promote axial elongation (as in shoots), lateral expansion (as in root swelling), or iso-diametric expansion (as in fruit growth). In some cases (coleoptile growth), auxin-promoted cellular expansion occurs in the absence of cell division. In other cases, auxin-promoted cell division and cell expansion may be closely sequenced within the same tissue (root initiation, fruit growth). In a living plant, auxins and other plant hormones nearly always appear to interact to determine patterns of plant development. Organ patterns[edit] Growth and division of plant cells together result in the growth of tissue, and specific tissue growth contributes to the development of plant organs. Auxin diffuses along the shaded side of the plant, and causes cellulose in the cell wall to break, allowing turgor (water pressure) to expand the cell. Growth of cells contributes to the plant's size, unevenly localized growth produces bending, turning and directionalization of organs- for example, stems turning toward light sources (phototropism), roots growing in response to gravity (gravitropism), and other tropisms originated because cells on one side grow faster than the cells on the other side of the organ. So, precise control of auxin distribution between different cells has paramount importance to the resulting form of plant growth and organization. Auxin transport and the uneven distribution of auxin[edit] Further information: Polar auxin transport To cause growth in the required domains, auxins must of necessity be active preferentially in them. Local auxin maxima can be formed by active biosynthesis in certain cells of tissues, for example via tryptophan-dependent pathways, but auxins are not synthesized in all cells (even if cells retain the potential ability to do so, only under specific conditions will auxin synthesis be activated in them). For that purpose, auxins have to be not only translocated toward those sites where they are needed but also they must have an established mechanism to detect those sites. Translocation is driven throughout the plant body, primarily from peaks of shoots to peaks of roots (from up to down). For long distances, relocation occurs via the stream of fluid in phloem vessels, but, for short-distance transport, a unique system of coordinated polar transport directly from cell to cell is exploited. This short-distance, active transport exhibits some morphogenetic properties. This process, polar auxin transport, is directional, very strictly regulated, and based in uneven distribution of auxin efflux carriers on the plasma membrane, which send auxins in the proper direction. While PIN-FORMED (PIN) proteins are vital in transporting auxin in a polar manner, the family of AUXIN1/LIKE-AUX1 (AUX/LAX) genes encodes for non-polar auxin influx carriers. The regulation of PIN protein localisation in a cell determines the direction of auxin transport from cell, and concentrated effort of many cells creates peaks of auxin, or auxin maxima (regions having cells with higher auxin – a maximum). Proper and timely auxin maxima within developing roots and shoots are necessary to organise the development of the organ. PINs are regulated by multiple pathways, at both the transcriptional and the post-translational levels. PIN proteins can be phosphorylated by PINOID, which determines their apicobasal polarity and thereby the directionality of auxin fluxes. In addition, other AGC kinases, such as D6PK, phosphorylate and activate PIN transporters. AGC kinases, including PINOID and D6PK, target to the plasma membrane via binding to phospholipids. Upstream of D6PK, 3'-phosphoinositide dependent protein kinase 1 (PDK1) acts as a master regulator. PDK1 phosphorylates and activates D6PK at the basal side of plasma membrane, executing the activity of PIN-mediated polar auxin transport and subsequent plant development. Surrounding auxin maxima are cells with low auxin troughs, or auxin minima. For example, in the Arabidopsis fruit, auxin minima have been shown to be important for its tissue development. Auxin has a significant effect on spatial and temporal gene expressions during the growth of apical meristems. These interactions depend both on the concentration of Auxin as well as the spatial orientation during primordial positioning. Auxin relies on PIN1 which works as an auxin efflux carrier. PIN1 positioning upon membranes determines the directional flow of the hormone from higher to lower concentrations. Initiation of primordia in apical meristems is correlated to heightened auxin levels. Genes required to specify the identity of cells arrange and express based on levels of auxin. STM (SHOOT MERISTEMLESS), which helps maintain undifferentiated cells, is down-regulated in the presence of auxin. This allows growing cells to differentiate into various plant tissues. The CUC (CUP-SHAPED COTYLEDON) genes set the boundaries for growing tissues and promote growth. They are upregulated via auxin influx. Experiments making use of GFP (GREEN FLUORESCENCE PROTEIN) visualization in Arabidopsis have supported these claims. Organization of the plant[edit] Further information: Apical dominance As auxins contribute to organ shaping, they are also fundamentally required for proper development of the plant itself. Without hormonal regulation and organization, plants would be merely proliferating heaps of similar cells. Auxin employment begins in the embryo of the plant, where the directional distribution of auxin ushers in subsequent growth and development of primary growth poles, then forms buds of future organs. Next, it helps to coordinate proper development of the arising organs, such as roots, cotyledons, and leaves and mediates long-distance signals between them, contributing so to the overall architecture of the plant. Throughout the plant's life, auxin helps the plant maintain the polarity of growth, and actually "recognize" where it has its branches (or any organ) connected. An important principle of plant organization based upon auxin distribution is apical dominance, which means the auxin produced by the apical bud (or growing tip) diffuses (and is transported) downwards and inhibits the development of ulterior lateral bud growth, which would otherwise compete with the apical tip for light and nutrients. Removing the apical tip and its suppressively acting auxin allows the lower dormant lateral buds to develop, and the buds between the leaf stalk and stem produce new shoots which compete to become the lead growth. The process is actually quite complex because auxin transported downwards from the lead shoot tip has to interact with several other plant hormones (such as strigolactones or cytokinins) in the process on various positions along the growth axis in plant body to achieve this phenomenon. This plant behavior is used in pruning by horticulturists. Finally, the sum of auxin arriving from stems to roots influences the degree of root growth. If shoot tips are removed, the plant does not react just by the outgrowth of lateral buds — which are supposed to replace to original lead. It also follows that smaller amount of auxin arriving at the roots results in slower growth of roots and the nutrients are subsequently in higher degree invested in the upper part of the plant, which hence starts to grow faster. Effects[edit] A healthy Arabidopsis thaliana plant (left) next to an auxin signal-transduction mutant with a repressed response to auxin. Crown galls are caused by Agrobacterium tumefaciens bacteria; they produce and secrete auxin and cytokinin, which interfere with normal cell division and cause tumors. Auxin participates in phototropism, geotropism, hydrotropism and other developmental changes. The uneven distribution of auxin, due to environmental cues, such as unidirectional light or gravity force, results in uneven plant tissue growth, and generally, auxin governs the form and shape of the plant body, direction and strength of growth of all organs, and their mutual interaction. When the cells grow larger, their volume increases as the intracellular solute concentration increases with water moving into the cells from extracellular fluid. This auxin-stimulated intake of water causes turgor pressure on the cell walls, causing the plant to bend. Auxin stimulates cell elongation by stimulating wall-loosening factors, such as expansins, to loosen cell walls. The effect is stronger if gibberellins are also present. Auxin also stimulates cell division if cytokinins are present. When auxin and cytokinin are applied to callus, rooting can be generated with higher auxin to cytokinin ratios, shoot growth is induced by lower auxin to cytokinin ratios, and a callus is formed with intermediate ratios, with the exact threshold ratios depending on the species and the original tissue. Auxin also induces sugar and mineral accumulation at the site of application. Wound response[edit] Auxin induces the formation and organization of phloem and xylem. When the plant is wounded, the auxin may induce the cell differentiation and regeneration of the vascular tissues. Root growth and development[edit] Auxins promote root initiation. Auxin induces both growth of pre-existing roots and root branching (lateral root initiation), and also adventitious root formation. As more native auxin is transported down the stem to the roots, the overall development of the roots is stimulated. If the source of auxin is removed, such as by trimming the tips of stems, the roots are less stimulated accordingly, and growth of stem is supported instead. In horticulture, auxins, especially NAA and IBA, are commonly applied to stimulate root initiation when rooting cuttings of plants. However, high concentrations of auxin inhibit root elongation and instead enhance adventitious root formation. Removal of the root tip can lead to inhibition of secondary root formation. Apical dominance[edit] Main article: Apical dominance Auxin induces shoot apical dominance; the axillary buds are inhibited by auxin, as a high concentration of auxin directly stimulates ethylene synthesis in axillary buds, causing inhibition of their growth and potentiation of apical dominance. When the apex of the plant is removed, the inhibitory effect is removed and the growth of lateral buds is enhanced. This is called decapitation, usually performed in tea plantations and hedge-making. Auxin is sent to the part of the plant facing away from the light, where it promotes cell elongation, thus causing the plant to bend towards the light. Fruit growth and development[edit] Auxin is required for fruit growth and development and delays fruit senescence. When seeds are removed from strawberries, fruit growth is stopped; exogenous auxin stimulates the growth in fruits with seeds removed. For fruit with unfertilized seeds, exogenous auxin results in parthenocarpy ("virgin-fruit" growth). Fruits form abnormal morphologies when auxin transport is disturbed. In Arabidopsis fruits, auxin controls the release of seeds from the fruit (pod). The valve margins are a specialised tissue in pods that regulates when pod will open (dehiscence). Auxin must be removed from the valve margin cells to allow the valve margins to form. This process requires modification of the auxin transporters (PIN proteins). The evolutionary transition from diploid to triploid endosperms - and the production of antipodal cells - may have occurred due to a shift in gametophyte development which produced a new interaction with an auxin-dependent mechanism originating in the earliest angiosperms. Flowering[edit] Auxin plays also a minor role in the initiation of flowering and development of reproductive organs. In low concentrations, it can delay the senescence of flowers. A number of plant mutants have been described that affect flowering and have deficiencies in either auxin synthesis or transport. In maize, one example is bif2 barren inflorescence2. Ethylene biosynthesis[edit] In low concentrations, auxin can inhibit ethylene formation and transport of precursor in plants; however, high concentrations can induce the synthesis of ethylene. Therefore, the high concentration can induce femaleness of flowers in some species. Auxin inhibits abscission prior to the formation of the abscission layer, and thus inhibits senescence of leaves. Synthetic auxins include the following compounds2,4-Dichlorophenoxyacetic acid (2,4-D); active herbicide and main auxin in laboratory useα-Naphthalene acetic acid (α-NAA); often part of commercial rooting powders2-Methoxy-3,6-dichlorobenzoic acid (dicamba); active herbicide4-Amino-3,5,6-trichloropicolinic acid (tordon or picloram); active herbicide2,4,5-Trichlorophenoxyacetic acid (2,4,5-T) Synthetic auxins[edit] In the course of research on auxin biology, many compounds with noticeable auxin activity were synthesized. Many of them had been found to have economical potential for human-controlled growth and development of plants in agronomy. Auxins are toxic to plants in large concentrations; they are most toxic to dicots and less so to monocots. Because of this property, synthetic auxin herbicides, including 2,4-dichlorophenoxyacetic acid (2,4-D) and 2,4,5-trichlorophenoxyacetic acid (2,4,5-T), have been developed and used for weed control. However, some exogenously synthesized auxins, especially 1-naphthaleneacetic acid (NAA) and indole-3-butyric acid (IBA), are also commonly applied to stimulate root growth when taking cuttings of plants or for different agricultural purposes such as the prevention of fruit drop in orchards. Used in high doses, auxin stimulates the production of ethylene, also a native plant hormone. Excess ethylene can inhibit elongation growth, cause leaves to fall (abscission), and even kill the plant. Some synthetic auxins, such as 2,4-D and 2,4,5-T are marketed also as herbicides. Dicots, such as dandelions, are much more susceptible to auxins than monocots, such as grasses and cereal crops. So these synthetic auxins are valuable as synthetic herbicides. 2,4-D was the first widely used herbicide, and it is still in use. 2,4-D was first commercialized by the Sherwin-Williams company and saw use in the late 1940s. It is easy and inexpensive to manufacture. Triclopyr (3,5,6-TPA), while known as an herbicide, has also been shown to increase the size of fruit in plants. At increased concentrations, the hormone can be lethal. Dosing down to the correct concentration has been shown to alter photosynthetic pathways. This hindrance to the plant causes a response that increases carbohydrate production, leading to larger fruit. Herbicide manufacture[edit] Synthetic auxins are used as a kind of herbicide and overdosing of auxins will interrupt plants' growth and lead to their death. The defoliant Agent Orange, used extensively by British forces in the Malayan Emergency and American forces in the Vietnam War, was a mix of 2,4-D and 2,4,5-T. The compound 2,4-D is still in use and is thought to be safe, but 2,4,5-T was more or less banned by the U.S. Environmental Protection Agency in 1979. The dioxin TCDD is an unavoidable contaminant produced in the manufacture of 2,4,5-T. As a result of the integral dioxin contamination, the use of 2,4,5-T products has been implicated in leukemia, miscarriages, birth defects, liver damage, and other diseases. See also[edit] Auxin binding protein Fusicoccin Herbicide; specifically, see the section: §Auxin Phenoxy herbicide Pruning fruit trees Tropism Witch's broom Toshio Murashige Folke K. Skoog Kenneth V. Thimann	biology	4383336	https://sv.wikipedia.org/wiki/Physalis%20lignescens	Physalis lignescens	Physalis lignescens är en potatisväxtart som beskrevs av Umaldy Theodore Waterfall. Physalis lignescens ingår i släktet lyktörter, och familjen potatisväxter. Inga underarter finns listade i Catalogue of Life. Källor Lyktörter lignescens	swedish	1.042305
trees_grow_directions/Gravitropism.txt	Gravitropism (also known as geotropism) is a coordinated process of differential growth by a plant in response to gravity pulling on it. It also occurs in fungi. Gravity can be either "artificial gravity" or natural gravity. It is a general feature of all higher and many lower plants as well as other organisms. Charles Darwin was one of the first to scientifically document that roots show positive gravitropism and stems show negative gravitropism. That is, roots grow in the direction of gravitational pull (i.e., downward) and stems grow in the opposite direction (i.e., upwards). This behavior can be easily demonstrated with any potted plant. When laid onto its side, the growing parts of the stem begin to display negative gravitropism, growing (biologists say, turning; see tropism) upwards. Herbaceous (non-woody) stems are capable of a degree of actual bending, but most of the redirected movement occurs as a consequence of root or stem growth outside. The mechanism is based on the Cholodny–Went model which was proposed in 1927, and has since been modified. Although the model has been criticized and continues to be refined, it has largely stood the test of time. In roots[edit] In the process of plant roots growing in the direction of gravity by gravitropism, high concentrations of auxin move towards the cells on the bottom side of the root. This suppresses growth on this side, while allowing cell elongation on the top of the root. As a consequence of this, curved growth occurs and the root is directed downwards. Root growth occurs by division of stem cells in the root meristem located in the tip of the root, and the subsequent asymmetric expansion of cells in a shoot-ward region to the tip known as the elongation zone. Differential growth during tropisms mainly involves changes in cell expansion versus changes in cell division, although a role for cell division in tropic growth has not been formally ruled out. Gravity is sensed in the root tip and this information must then be relayed to the elongation zone so as to maintain growth direction and mount effective growth responses to changes in orientation to and continue to grow its roots in the same direction as gravity. Abundant evidence demonstrates that roots bend in response to gravity due to a regulated movement of the plant hormone auxin known as polar auxin transport. This was described in the 1920s in the Cholodny-Went model. The model was independently proposed by the Ukrainian scientist N. Cholodny of the University of Kyiv in 1927 and by Frits Went of the California Institute of Technology in 1928, both based on work they had done in 1926. Auxin exists in nearly every organ and tissue of a plant, but it has been reoriented in the gravity field, can initiate differential growth resulting in root curvature. Experiments show that auxin distribution is characterized by a fast movement of auxin to the lower side of the root in response to a gravity stimulus at a 90° degree angle or more. However, once the root tip reaches a 40° angle to the horizontal of the stimulus, auxin distribution quickly shifts to a more symmetrical arrangement. This behavior is described as a "tipping point" mechanism for auxin transport in response to a gravitational stimulus. In shoots[edit] Gravitropism is an integral part of plant growth, orienting its position to maximize contact with sunlight, as well as ensuring that the roots are growing in the correct direction. Growth due to gravitropism is mediated by changes in concentration of the plant hormone auxin within plant cells. As plant shoots grow, high concentrations of auxin moves towards the bottom of the shoot to initiate cell growth of those cells, while suppressing cell growth on the top of the shoot. This faster growth of the bottom cells results in upward curved growth and elongation, abusing the shootits cells, away from the direction of gravitational pull. As plants mature, gravitropism continues to guide growth and development along with phototropism. While amyloplasts continue to guide plants in the right direction, plant organs and function rely on Apex reorientation in Pinus pinaster during the first 24h after experimental inclination of the plant. phototropic responses to ensure that the leaves are receiving enough light to perform basic functions such as photosynthesis. In complete darkness, mature plants have little to no sense of gravity, unlike seedlings that can still orient themselves to have the shoots grow upward until light is reached when development can begin. Differential sensitivity to auxin helps explain Darwin's original observation that stems and roots respond in the opposite way to the forces of gravity. In both roots and stems, auxin accumulates towards the gravity vector on the lower side. In roots, this results in the inhibition of cell expansion on the lower side and the concomitant curvature of the roots towards gravity (positive gravitropism). In stems, the auxin also accumulates on the lower side, however in this tissue it increases cell expansion and results in the shoot curving up (negative gravitropism). A recent study showed that for gravitropism to occur in shoots, a lot of an inclination, instead of a weak gravitational force, is necessary. This finding sets aside gravity sensing mechanisms that would rely on detecting the pressure of the weight of statoliths. In fruit[edit] A few species of fruit exhibit negative geotropism. Bananas are one well-known example. Once the canopy that covers the fruit dries, the bananas will begin to curve upwards, towards sunlight, in what is known as phototropism. The specific chemical that initiates the upward curvature is a phytohormone in the banana called Auxin. When the banana is first exposed to sunlight after the leaf canopy dries, one face of the fruit is shaded. On exposure to sunlight, auxin in the banana migrates from the sunlight side to the shaded side. Since auxin is a powerful plant growth hormone, the increased concentration promotes cell division and causes the plant cells on the shaded side to grow. This asymmetrical distribution of auxin is responsible for the upward curvature of the banana. Gravity-sensing mechanisms[edit] Statoliths[edit] Banana fruit exhibiting negative geotropism. Plants possess the ability to sense gravity in several ways, one of which is through statoliths. Statoliths are dense amyloplasts, organelles that synthesize and store starch involved in the perception of gravity by the plant (gravitropism), that collect in specialized cells called statocytes. Statocytes are located in the starch parenchyma cells near vascular tissues in the shoots and in the columella in the caps of the roots. These specialized amyloplasts are denser than the cytoplasm and can sediment according to the gravity vector. The statoliths are enmeshed in a web of actin and it is thought that their sedimentation transmits the gravitropic signal by activating mechanosensitive channels. The gravitropic signal then leads to the reorientation of auxin efflux carriers and subsequent redistribution of auxin streams in the root cap and root as a whole. Auxin moves toward higher concentrations on the bottom side of the root and suppresses elongation. The asymmetric distribution of auxin leads to differential growth of the root tissues, causing the root to curve and follow the gravity stimuli. Statoliths are also found in the endodermic layer of the hypocotyl, stem, and inflorescence stock. The redistribution of auxin causes increased growth on the lower side of the shoot so that it orients in a direction opposite that of the gravity stimuli. Modulation by phytochrome[edit] Phytochromes are red and far-red photoreceptors that help induce changes in certain aspects of plant development. Apart being itself the tropic factor (phototropism), light may also suppress the gravitropic reaction. In seedlings, red and far-red light both inhibit negative gravitropism in seedling hypocotyls (the shoot area below the cotyledons) causing growth in random directions. However, the hypocotyls readily orient towards blue light. This process may be caused by phytochrome disrupting the formation of starch-filled endodermal amyloplasts and stimulating their conversion to other plastid types, such as chloroplasts or etiolaplasts. Compensation[edit] The compensation reaction of the bending Coprinus stem. C – the compensating part of the stem. Bending mushroom stems follow some regularities that are not common in plants. After turning into horizontal the normal vertical orientation the apical part (region C in the figure below) starts to straighten. Finally this part gets straight again, and the curvature concentrates near the base of the mushroom. This effect is called compensation (or sometimes, autotropism). The exact reason of such behavior is unclear, and at least two hypotheses exist. The hypothesis of plagiogravitropic reaction supposes some mechanism that sets the optimal orientation angle other than 90 degrees (vertical). The actual optimal angle is a multi-parameter function, depending on time, the current reorientation angle and from the distance to the base of the fungi. The mathematical model, written following this suggestion, can simulate bending from the horizontal into vertical position but fails to imitate realistic behavior when bending from the arbitrary reorientation angle (with unchanged model parameters). The alternative model supposes some “straightening signal”, proportional to the local curvature. When the tip angle approaches 30° this signal overcomes the bending signal, caused by reorientation, straightening resulting. Both models fit the initial data well, but the latter was also able to predict bending from various reorientation angles. Compensation is less obvious in plants, but in some cases it can be observed combining exact measurements with mathematical models. The more sensitive roots are stimulated by lower levels of auxin; higher levels of auxin in lower halves stimulate less growth, resulting in downward curvature (positive gravitropism). Gravitropic mutants[edit] Mutants with altered responses to gravity have been isolated in several plant species including Arabidopsis thaliana (one of the genetic model systems used for plant research). These mutants have alterations in either negative gravitropism in hypocotyls and/or shoots, or positive gravitropism in roots, or both. Mutants have been identified with varying effects on the gravitropic responses in each organ, including mutants which nearly eliminate gravitropic growth, and those whose effects are weak or conditional. In the same way that gravity has an effect on winding and circumnutating, thus aspects of morphogenesis have defects on the mutant. Once a mutant has been identified, it can be studied to determine the nature of the defect (the particular difference(s) it has compared to the non-mutant 'wildtype'). This can provide information about the function of the altered gene, and often about the process under study. In addition the mutated gene can be identified, and thus something about its function inferred from the mutant phenotype. Gravitropic mutants have been identified that affect starch accumulation, such as those affecting the PGM1 (which encodes the enzyme phosphoglucomutase) gene in Arabidopsis, causing plastids – the presumptive statoliths – to be less dense and, in support of the starch-statolith hypothesis, less sensitive to gravity. Other examples of gravitropic mutants include those affecting the transport or response to the hormone auxin. In addition to the information about gravitropism which such auxin-transport or auxin-response mutants provide, they have been instrumental in identifying the mechanisms governing the transport and cellular action of auxin as well as its effects on growth. There are also several cultivated plants that display altered gravitropism compared to other species or to other varieties within their own species. Some are trees that have a weeping or pendulate growth habit; the branches still respond to gravity, but with a positive response, rather than the normal negative response. Others are the lazy (i.e. ageotropic or agravitropic) varieties of corn (Zea mays) and varieties of rice, barley and tomatoes, whose shoots grow along the ground. See also[edit] Amyloplast – starch organelle involved in sensing gravitropism Astrobotany – the field of science concerned with plants in a spaceflight environment Clinostat – a device used to the effects of gravitational pull Random positioning machine – a device used to negate the effects of gravitational pull Free fall machine – a device used to negate the effects of gravitational pull Large diameter centrifuge – a device used to create a hyper-gravity pull Prolonged sine – reaction of plants to turning from their usual vertical orientation	biology	1166256	https://sv.wikipedia.org/wiki/R%C3%B6relsefenomen%20hos%20v%C3%A4xter	Rörelsefenomen hos växter	Denna artikel behandlar rörelsefenomen hos växter, i bemärkelsen växternas förmåga att utföra rörelser som medför en lägesförändring av någon del av växtkroppen, som stjälkar, blad, blommor, rötter, ståndare och fruktblad, samt och öppnings- och spridningsrörelser hos sporhus och frukter. Växters rörelser är en del i ämnet växtfysiologi. Vad är rörelser hos växter Alla livsföreteelser hos växter kan egentligen, eftersom växter är levande organismer, sägas vara förknippade med rörelse i en eller annan form. Exempelvis kräver växtens ämnesomsättning transport av näringsämnen från en växtdel till en annan. Till exempel upptas vatten genom rötterna och leds upp genom stammen och i bladen bildas kolhydrater som upplagras i andra organ, som rotknölar och stamknölar. Sådana diffusionsrörelser är dock inte direkt iakttagbara och behandlas inte närmare i denna artikel. Växandets fenomen i allmänhet, i meningen tillväxt genom nybildning av celler och vävnader, skulle också kunna uppfattas som en rörelse, men är irreversibelt och behandlas inte heller närmare i denna artikel. Inom botanik avses med "växtrörelser" sådana iakttagbara, om än ofta långsamma, rörelser som levande växter utför som medför en lägesförändring av någon del av växtkroppen. Det är i denna mening "växtrörelser" används i denna artikel. Växtrörelser Växter är i de flesta fall fastsittande organismer men strävar liksom alla levande organismer efter att erhålla gynnsammast möjliga livsbetingelser. Även om de inte är fritt rörliga utan bundna till växtplatsen har växter förmågan att orientera sig i livsrummet för att kunna nyttja de tillgängliga resurserna på gynnsammast möjliga sätt. Växter behöver exempelvis ljus för fotosyntes. Tillgången på ljus kan på en viss växtplats vara begränsad och det kan råda konkurrens om resursen. Som en följd av detta har växter utvecklat förmågan att växa i riktning mot ljuset för att få tillgång till så mycket ljus som möjligt. Även om växter i de flesta fall är fastsittande organismer är de alltså inte passiva utan orienterar sig aktivt i livsrummet. Denna förmåga är mycket viktig för växternas överlevnad. Man skiljer på vitala rörelser, det vill säga rörelser som fordrar medverkan av levande celler, som böjning eller vridning av fastsittande växter eller växtorgan, och mekaniska rörelser, som exempelvis innefattar hygroskopiska rörelser, en typ av rörelser som beror på variationer i fuktighetshalt. Beträffande orsaken till rörelserna skiljer man när det gäller vitala rörelser på autonoma rörelser som beror på inre förhållanden (som nutationer) och inducerade eller paratoniska rörelser, som framkallas av yttre förhållanden och utlöses genom specifika retningar (retningsrörelser). Om retningsrörelsernas riktning bestäms av retningens riktning kallas de för tropistiska rörelser (tropismer). Om retningsrörelsernas riktning däremot är oberoende av retningens riktning och endast beror på växtorganets byggnad kallas de för nastiska rörelser (nastier). Retningsrörelser vars riktning bestäms av retningens riktning förstås genom taxis, som innebär rörelse mot eller från ett visst slags stimulus (retning). Med hänsyn till mekanismen för växtrörelsers utförande skiljer man när det gäller vitala rörelser på turgorrörelser, som beror på förändringar i turgortrycket, eller saftspänningen, i växtorgan, och tillväxtrörelser, som beror på olika tillväxthastighet hos olika sidor av ett växtorgan. Tropismer Tropismer är växtrörelser som utlöses som svar på stimuli i form av till exempel ljus, temperatur eller beröring, och vars riktning bestäms av retningens riktning. Tropismer är vanligen tillväxtrörelser som åstadkoms genom olika tillväxthastighet hos motsatta sidor av ett växtorgan, i form av riktningsrörelser eller orienteringsrörelser. Tropismer benämns efter retningens art, däribland fototropism (ljus), gravitropism (tyngdkraft), termotropism (temperatur), hydrotropism (vatten), thigmotropism, haptotropism (för beröring, kontakt) och kemotropism (kemisk retning). Växtorganens reaktion på en retning kan vara positiv eller negativ och man skiljer därför på ortotropa organ som rör sig i riktning mot retningen (positiv reaktion) och plagiotropa organ som rör sig bort från retningen (negativ reaktion). Ett specialfall av plagiotropism är diatropism, då organet ställer sig vinkelrätt mot retningen. Fototropism och gravitropism (äldre benämning geotropism) förekommer hos nästan alla växter och är mycket viktiga för växternas förmåga att orientera sig. Oberoende av fröets orientering i marken kommer huvudroten att söka sig rakt nedåt i marken som ett svar på gravitationen och skottet att växa uppåt, delvis som svar på gravitationen, men också som svar på ljuset. Huvudroten är positivt gravitropisk, medan skottet är negativt gravitropiskt och positivt fototropiskt. Sidorötter och sidoskott brukar reagera plagiogeotropiskt, medan bladen ofta är diageotropiska och diafototropiska. Alla riktningsrörelser hos växter som framkallas av oliksidig tillväxt i växtorganen regleras av växthormoner, och tillväxtstimulerande auxin har en viktig betydelse. Både i frågan om fototropism och gravitropism har auxin en roll som reglerar tillväxten. Autotropism är en av växten själv framkallad strävan att motverka en genom yttre retning framkallad tropism. Vid tropistiska rörelser kan man när det gäller det retningsförloppet skilja på mottagandet av retningen (perception), retningens fortledning och de förändringar i protoplasman den närmast åstadkommer, samt reaktionen, det vill säga det synliga resultatet av retningen. Mellan perception och reaktion förlöper alltid en viss tid (reaktionstiden) och därtill måste retningen inverka under en minimitid (presentationstiden) för att överhuvudtaget reaktion skall ske. För perceptionen gäller inom vissa gränser den så kallade retmängdlagen, som innebär, att presentationstiden och retningens intensitet är omvänt proportionella. Nastier Nastier (nasti) är växtrörelser som utlöses som svar på stimuli i form av till exempel ljus, temperatur eller beröring, och vars riktning är oberoende av retningens riktning och bestäms av själva den stimulerade växtvävnadens konstruktion. Nastier förekommer både i form av tillväxt- och turgorrörelser. Nastier benämns liksom tropismer efter retningens art, som fotonasti (ljus), termonasti (temperatur), seismonasti, thigmonasti, haptonasti (för beröring, kontakt) och kemonasti (kemisk retning). Benämningen epinasti respektive hyponasti används för att beskriva en rörelse som härrör från en starkare tillväxt på översidan respektive undersidan av ett växtorgan. Av nastier är de seismonastiska rörelserna hos mimosor ett sedan gammalt känt exempel. Om man skakar plantan eller sårar ett av småbladen, fälls de dubbelt sammansatta bladen hastigt ihop och bladskaften sänker sig. På bladen finns fina känselhår som är mycket känsliga för beröring och såväl vid bladskaftens som vid de enskilda småbladens bas finns särskilda organ, leddynor, med vars hjälp rörelserna utförs. Mekanismen verkar genom att den mekaniska retningen av känselhåren utlöser en signal som medför en hastig förändring i saftspänning (turgortryck) i leddynorna. Växtrörelser som beror på förändringar i turgortryck kan vara mycket snabba, jämför med tillväxtrörelser. Utöver det nämnda exemplet med bladrörelserna hos mimosor är ett bra exempel Venus flugfälla, en köttätande växt, vars blad bildar en slagfälla som slår ihop snabbt nog för att kunna fånga små insekter. Hos en del växter, däribland hos många baljväxter och oxalisar, förekommer periodiska rörelser hos blad och blomblad i samband med växlingen mellan dag och natt, så kallad nyktinasti. Detta innebär att växtorganen under dygnet skiftar mellan en dagställning och en nattställning. Exempelvis att blad fäller ihop sig eller att blommor slutar sig över natten. Carl von Linné kallade detta fenomen för "växtsömn" och därför har dessa växtrörelser även kallats för "sömnrörelser". Hygroskopiska rörelser Hygroskopiska rörelser är en typ av rörelser som beror på variationer i fuktighetshalt. Dessa rörelser är inga retningsrörelser, eftersom de sker mekaniskt beroende på cellväggarnas eller membranskiktens olika utvidgning och skrumpnande vid variationer i luftens fuktighetshalt. Ett exempel på hygroskopiska rörelser är öppningsrörelserna hos en del växters frukter. Genom torka skapas spänningar i fruktväggen och när spänningen plötsligt utlöses slungas fröna iväg. Fruktsprötet hos skatnäva rätar ut sig i fuktig luft och vid torka vrider sig korkskruvslikt och borrar på så sätt ned fröet i marken och även detta är en hygroskopisk rörelse. Ytterligare ett exempel är att många ökenväxter har frukter som öppnas vid fuktig väderlek, se hygrochasi. Jerikorosor är en grupp växter som uppvisar kraftiga hygroskopiska rörelser. De kan överleva utan vatten mycket länge genom att rullar ihop sig till torra bollar. I detta torra tillstånd kan de se döda ut, men det är de inte utan de vecklar ut sig och grönskar åter när de får vatten igen. Källor Växtrörelser, Svensk uppslagsbok (1955) Växterna rörliga liv (naturfilm) Rörelser hos växter, KauTube. Externa länkar The movements of plants Växtfysiologi de:Pflanzenbewegung eo:Planta moviĝo	swedish	0.590709
trees_grow_directions/Tree.txt	In botany, a tree is a perennial plant with an elongated stem, or trunk, usually supporting branches and leaves. In some usages, the definition of a tree may be narrower, including only woody plants with secondary growth, plants that are usable as lumber or plants above a specified height. In wider definitions, the taller palms, tree ferns, bananas, and bamboos are also trees. Trees are not a monophyletic taxonomic group but consist of a wide variety of plant species that have independently evolved a trunk and branches as a way to tower above other plants to compete for sunlight. The majority of tree species are angiosperms or hardwoods; of the rest, many are gymnosperms or softwoods. Trees tend to be long-lived, some reaching several thousand years old. Trees have been in existence for 370 million years. It is estimated that there are around three trillion mature trees in the world. A tree typically has many secondary branches supported clear of the ground by the trunk, which typically contains woody tissue for strength, and vascular tissue to carry materials from one part of the tree to another. For most trees it is surrounded by a layer of bark which serves as a protective barrier. Below the ground, the roots branch and spread out widely; they serve to anchor the tree and extract moisture and nutrients from the soil. Above ground, the branches divide into smaller branches and shoots. The shoots typically bear leaves, which capture light energy and convert it into sugars by photosynthesis, providing the food for the tree's growth and development. Trees usually reproduce using seeds. Flowers and fruit may be present, but some trees, such as conifers, instead have pollen cones and seed cones. Palms, bananas, and bamboos also produce seeds, but tree ferns produce spores instead. Trees play a significant role in reducing erosion and moderating the climate. They remove carbon dioxide from the atmosphere and store large quantities of carbon in their tissues. Trees and forests provide a habitat for many species of animals and plants. Tropical rainforests are among the most biodiverse habitats in the world. Trees provide shade and shelter, timber for construction, fuel for cooking and heating, and fruit for food as well as having many other uses. In much of the world, forests are shrinking as trees are cleared to increase the amount of land available for agriculture. Because of their longevity and usefulness, trees have always been revered, with sacred groves in various cultures, and they play a role in many of the world's mythologies. Definition Diagram of secondary growth in a eudicot or coniferous tree showing idealised vertical and horizontal sections. A new layer of wood is added in each growing season, thickening the stem, existing branches and roots. Although "tree" is a term of common parlance, there is no universally recognised precise definition of what a tree is, either botanically or in common language. In its broadest sense, a tree is any plant with the general form of an elongated stem, or trunk, which supports the photosynthetic leaves or branches at some distance above the ground. Trees are also typically defined by height, with smaller plants from 0.5 to 10 m (1.6 to 32.8 ft) being called shrubs, so the minimum height of a tree is only loosely defined. Large herbaceous plants such as papaya and bananas are trees in this broad sense. A commonly applied narrower definition is that a tree has a woody trunk formed by secondary growth, meaning that the trunk thickens each year by growing outwards, in addition to the primary upwards growth from the growing tip. Under such a definition, herbaceous plants such as palms, bananas and papayas are not considered trees regardless of their height, growth form or stem girth. Certain monocots may be considered trees under a slightly looser definition; while the Joshua tree, bamboos and palms do not have secondary growth and never produce true wood with growth rings, they may produce "pseudo-wood" by lignifying cells formed by primary growth. Tree species in the genus Dracaena, despite also being monocots, do have secondary growth caused by meristem in their trunk, but it is different from the thickening meristem found in dicotyledonous trees. Aside from structural definitions, trees are commonly defined by use; for instance, as those plants which yield lumber. Overview "Saplings" redirects here. For the novel, see Saplings (novel). For the film, see The Saplings. For the episode, see Saplings (Weeds). The tree growth habit is an evolutionary adaptation found in different groups of plants: by growing taller, trees are able to compete better for sunlight. Trees tend to be tall and long-lived, some reaching several thousand years old. Several trees are among the oldest organisms now living. Trees have modified structures such as thicker stems composed of specialised cells that add structural strength and durability, allowing them to grow taller than many other plants and to spread out their foliage. They differ from shrubs, which have a similar growth form, by usually growing larger and having a single main stem; but there is no consistent distinction between a tree and a shrub, made more confusing by the fact that trees may be reduced in size under harsher environmental conditions such as on mountains and subarctic areas. The tree form has evolved separately in unrelated classes of plants in response to similar environmental challenges, making it a classic example of parallel evolution. With an estimated 60,000-100,000 species, the number of trees worldwide might total twenty-five per cent of all living plant species. The greatest number of these grow in tropical regions; many of these areas have not yet been fully surveyed by botanists, making tree diversity and ranges poorly known. Tall herbaceous monocotyledonous plants such as banana lack secondary growth, but are trees under the broadest definition. The majority of tree species are angiosperms or hardwoods. Of the rest, many are gymnosperms or softwood trees; these include conifers, cycads, ginkgophytes and gnetales, which produce seeds which are not enclosed in fruits, but in open structures such as pine cones, and many have tough waxy leaves, such as pine needles. Most angiosperm trees are eudicots, the "true dicotyledons", so named because the seeds contain two cotyledons or seed leaves. There are also some trees among the old lineages of flowering plants called basal angiosperms or paleodicots; these include Amborella, Magnolia, nutmeg and avocado, while trees such as bamboo, palms and bananas are monocots. Wood gives structural strength to the trunk of most types of tree; this supports the plant as it grows larger. The vascular system of trees allows water, nutrients and other chemicals to be distributed around the plant, and without it trees would not be able to grow as large as they do. Trees, as relatively tall plants, need to draw water up the stem through the xylem from the roots by the suction produced as water evaporates from the leaves. If insufficient water is available the leaves will die. The three main parts of trees include the root, stem, and leaves; they are integral parts of the vascular system which interconnects all the living cells. In trees and other plants that develop wood, the vascular cambium allows the expansion of vascular tissue that produces woody growth. Because this growth ruptures the epidermis of the stem, woody plants also have a cork cambium that develops among the phloem. The cork cambium gives rise to thickened cork cells to protect the surface of the plant and reduce water loss. Both the production of wood and the production of cork are forms of secondary growth. Trees are either evergreen, having foliage that persists and remains green throughout the year, or deciduous, shedding their leaves at the end of the growing season and then having a dormant period without foliage. Most conifers are evergreens, but larches (Larix and Pseudolarix) are deciduous, dropping their needles each autumn, and some species of cypress (Glyptostrobus, Metasequoia and Taxodium) shed small leafy shoots annually in a process known as cladoptosis. The crown is the spreading top of a tree including the branches and leaves, while the uppermost layer in a forest, formed by the crowns of the trees, is known as the canopy. A sapling is a young tree. Many tall palms are herbaceous monocots, which do not undergo secondary growth and never produce wood. In many tall palms, the terminal bud on the main stem is the only one to develop, so they have unbranched trunks with large spirally arranged leaves. Some of the tree ferns, order Cyatheales, have tall straight trunks, growing up to 20 metres (66 ft), but these are composed not of wood but of rhizomes which grow vertically and are covered by numerous adventitious roots. Distribution Further information: Forest The Daintree Rainforest The number of trees in the world, according to a 2015 estimate, is 3.04 trillion, of which 1.39 trillion (46%) are in the tropics or sub-tropics, 0.61 trillion (20%) in the temperate zones, and 0.74 trillion (24%) in the coniferous boreal forests. The estimate is about eight times higher than previous estimates, and is based on tree densities measured on over 400,000 plots. It remains subject to a wide margin of error, not least because the samples are mainly from Europe and North America. The estimate suggests that about 15 billion trees are cut down annually and about 5 billion are planted. In the 12,000 years since the start of human agriculture, the number of trees worldwide has decreased by 46%. There are approximately 64,100 known tree species in the world. With 43% of all tree species, South America has the highest biodiversity, followed by Eurasia (22%), Africa (16%), North America (15%), and Oceania (11%). In suitable environments, such as the Daintree Rainforest in Queensland, or the mixed podocarp and broadleaf forest of Ulva Island, New Zealand, forest is the more-or-less stable climatic climax community at the end of a plant succession, where open areas such as grassland are colonised by taller plants, which in turn give way to trees that eventually form a forest canopy. Conifers in the Swabian alps In cool temperate regions, conifers often predominate; a widely distributed climax community in the far north of the northern hemisphere is moist taiga or northern coniferous forest (also called boreal forest). Taiga is the world's largest land biome, forming 29% of the world's forest cover. The long cold winter of the far north is unsuitable for plant growth and trees must grow rapidly in the short summer season when the temperature rises and the days are long. Light is very limited under their dense cover and there may be little plant life on the forest floor, although fungi may abound. Similar woodland is found on mountains where the altitude causes the average temperature to be lower thus reducing the length of the growing season. Where rainfall is relatively evenly spread across the seasons in temperate regions, temperate broadleaf and mixed forest typified by species like oak, beech, birch and maple is found. Temperate forest is also found in the southern hemisphere, as for example in the Eastern Australia temperate forest, characterised by Eucalyptus forest and open acacia woodland. In tropical regions with a monsoon or monsoon-like climate, where a drier part of the year alternates with a wet period as in the Amazon rainforest, different species of broad-leaved trees dominate the forest, some of them being deciduous. In tropical regions with a drier savanna climate and insufficient rainfall to support dense forests, the canopy is not closed, and plenty of sunshine reaches the ground which is covered with grass and scrub. Acacia and baobab are well adapted to living in such areas. Parts and function Roots A young red pine (Pinus resinosa) with spread of roots visible, as a result of soil erosion Main article: Root The roots of a tree serve to anchor it to the ground and gather water and nutrients to transfer to all parts of the tree. They are also used for reproduction, defence, survival, energy storage and many other purposes. The radicle or embryonic root is the first part of a seedling to emerge from the seed during the process of germination. This develops into a taproot which goes straight downwards. Within a few weeks lateral roots branch out of the side of this and grow horizontally through the upper layers of the soil. In most trees, the taproot eventually withers away and the wide-spreading laterals remain. Near the tip of the finer roots are single cell root hairs. These are in immediate contact with the soil particles and can absorb water and nutrients such as potassium in solution. The roots require oxygen to respire and only a few species such as mangroves and the pond cypress (Taxodium ascendens) can live in permanently waterlogged soil. In the soil, the roots encounter the hyphae of fungi. Many of these are known as mycorrhiza and form a mutualistic relationship with the tree roots. Some are specific to a single tree species, which will not flourish in the absence of its mycorrhizal associate. Others are generalists and associate with many species. The tree acquires minerals such as phosphorus from the fungus, while the fungus obtains the carbohydrate products of photosynthesis from the tree. The hyphae of the fungus can link different trees and a network is formed, transferring nutrients and signals from one place to another. The fungus promotes growth of the roots and helps protect the trees against predators and pathogens. It can also limit damage done to a tree by pollution as the fungus accumulate heavy metals within its tissues. Fossil evidence shows that roots have been associated with mycorrhizal fungi since the early Paleozoic, four hundred million years ago, when the first vascular plants colonised dry land. Buttress roots of the kapok tree (Ceiba pentandra) Some trees such as Alder (Alnus species) have a symbiotic relationship with Frankia species, a filamentous bacterium that can fix nitrogen from the air, converting it into ammonia. They have actinorhizal root nodules on their roots in which the bacteria live. This process enables the tree to live in low nitrogen habitats where they would otherwise be unable to thrive. The plant hormones called cytokinins initiate root nodule formation, in a process closely related to mycorrhizal association. It has been demonstrated that some trees are interconnected through their root system, forming a colony. The interconnections are made by the inosculation process, a kind of natural grafting or welding of vegetal tissues. The tests to demonstrate this networking are performed by injecting chemicals, sometimes radioactive, into a tree, and then checking for its presence in neighbouring trees. The roots are, generally, an underground part of the tree, but some tree species have evolved roots that are aerial. The common purposes for aerial roots may be of two kinds, to contribute to the mechanical stability of the tree, and to obtain oxygen from air. An instance of mechanical stability enhancement is the red mangrove that develops prop roots that loop out of the trunk and branches and descend vertically into the mud. A similar structure is developed by the Indian banyan. Many large trees have buttress roots which flare out from the lower part of the trunk. These brace the tree rather like angle brackets and provide stability, reducing sway in high winds. They are particularly prevalent in tropical rainforests where the soil is poor and the roots are close to the surface. Some tree species have developed root extensions that pop out of soil, in order to get oxygen, when it is not available in the soil because of excess water. These root extensions are called pneumatophores, and are present, among others, in black mangrove and pond cypress. Trunk Northern beech (Fagus sylvatica) trunk in autumn Main article: Trunk (botany) The main purpose of the trunk is to raise the leaves above the ground, enabling the tree to overtop other plants and outcompete them for light. It also transports water and nutrients from the roots to the aerial parts of the tree, and distributes the food produced by the leaves to all other parts, including the roots. In the case of angiosperms and gymnosperms, the outermost layer of the trunk is the bark, mostly composed of dead cells of phellem (cork). It provides a thick, waterproof covering to the living inner tissue. It protects the trunk against the elements, disease, animal attack and fire. It is perforated by a large number of fine breathing pores called lenticels, through which oxygen diffuses. Bark is continually replaced by a living layer of cells called the cork cambium or phellogen. The London plane (Platanus × acerifolia) periodically sheds its bark in large flakes. Similarly, the bark of the silver birch (Betula pendula) peels off in strips. As the tree's girth expands, newer layers of bark are larger in circumference, and the older layers develop fissures in many species. In some trees such as the pine (Pinus species) the bark exudes sticky resin which deters attackers whereas in rubber trees (Hevea brasiliensis) it is a milky latex that oozes out. The quinine bark tree (Cinchona officinalis) contains bitter substances to make the bark unpalatable. Large tree-like plants with lignified trunks in the Pteridophyta, Arecales, Cycadophyta and Poales such as the tree ferns, palms, cycads and bamboos have different structures and outer coverings. A section of yew (Taxus baccata) showing 27 annual growth rings, pale sapwood and dark heartwood Although the bark functions as a protective barrier, it is itself attacked by boring insects such as beetles. These lay their eggs in crevices and the larvae chew their way through the cellulose tissues leaving a gallery of tunnels. This may allow fungal spores to gain admittance and attack the tree. Dutch elm disease is caused by a fungus (Ophiostoma species) carried from one elm tree to another by various beetles. The tree reacts to the growth of the fungus by blocking off the xylem tissue carrying sap upwards and the branch above, and eventually the whole tree, is deprived of nourishment and dies. In Britain in the 1990s, 25 million elm trees were killed by this disease. The innermost layer of bark is known as the phloem and this is involved in the transport of the sap containing the sugars made by photosynthesis to other parts of the tree. It is a soft spongy layer of living cells, some of which are arranged end to end to form tubes. These are supported by parenchyma cells which provide padding and include fibres for strengthening the tissue. Inside the phloem is a layer of undifferentiated cells one cell thick called the vascular cambium layer. The cells are continually dividing, creating phloem cells on the outside and wood cells known as xylem on the inside. The newly created xylem is the sapwood. It is composed of water-conducting cells and associated cells which are often living, and is usually pale in colour. It transports water and minerals from the roots to the upper parts of the tree. The oldest, inner part of the sapwood is progressively converted into heartwood as new sapwood is formed at the cambium. The conductive cells of the heartwood are blocked in some species. Heartwood is usually darker in colour than the sapwood. It is the dense central core of the trunk giving it rigidity. Three quarters of the dry mass of the xylem is cellulose, a polysaccharide, and most of the remainder is lignin, a complex polymer. A transverse section through a tree trunk or a horizontal core will show concentric circles of lighter or darker wood – tree rings. These rings are the annual growth rings There may also be rays running at right angles to growth rings. These are vascular rays which are thin sheets of living tissue permeating the wood. Many older trees may become hollow but may still stand upright for many years. Buds and growth Buds, leaves, flowers and fruit of oak (Quercus robur) Buds, leaves and reproductive structures of white fir (Abies alba) Form, leaves and reproductive structures of queen sago (Cycas circinalis) Main article: Bud Dormant Magnolia bud Trees do not usually grow continuously throughout the year but mostly have spurts of active expansion followed by periods of rest. This pattern of growth is related to climatic conditions; growth normally ceases when conditions are either too cold or too dry. In readiness for the inactive period, trees form buds to protect the meristem, the zone of active growth. Before the period of dormancy, the last few leaves produced at the tip of a twig form scales. These are thick, small and closely wrapped and enclose the growing point in a waterproof sheath. Inside this bud there is a rudimentary stalk and neatly folded miniature leaves, ready to expand when the next growing season arrives. Buds also form in the axils of the leaves ready to produce new side shoots. A few trees, such as the eucalyptus, have "naked buds" with no protective scales and some conifers, such as the Lawson's cypress, have no buds but instead have little pockets of meristem concealed among the scale-like leaves. When growing conditions improve, such as the arrival of warmer weather and the longer days associated with spring in temperate regions, growth starts again. The expanding shoot pushes its way out, shedding the scales in the process. These leave behind scars on the surface of the twig. The whole year's growth may take place in just a few weeks. The new stem is unlignified at first and may be green and downy. The Arecaceae (palms) have their leaves spirally arranged on an unbranched trunk. In some tree species in temperate climates, a second spurt of growth, a Lammas growth may occur which is believed to be a strategy to compensate for loss of early foliage to insect predators. Primary growth is the elongation of the stems and roots. Secondary growth consists of a progressive thickening and strengthening of the tissues as the outer layer of the epidermis is converted into bark and the cambium layer creates new phloem and xylem cells. The bark is inelastic. Eventually the growth of a tree slows down and stops and it gets no taller. If damage occurs the tree may in time become hollow. Leaves Main article: Leaf Leaves are structures specialised for photosynthesis and are arranged on the tree in such a way as to maximise their exposure to light without shading each other. They are an important investment by the tree and may be thorny or contain phytoliths, lignins, tannins or poisons to discourage herbivory. Trees have evolved leaves in a wide range of shapes and sizes, in response to environmental pressures including climate and predation. They can be broad or needle-like, simple or compound, lobed or entire, smooth or hairy, delicate or tough, deciduous or evergreen. The needles of coniferous trees are compact but are structurally similar to those of broad-leaved trees. They are adapted for life in environments where resources are low or water is scarce. Frozen ground may limit water availability and conifers are often found in colder places at higher altitudes and higher latitudes than broad leaved trees. In conifers such as fir trees, the branches hang down at an angle to the trunk, enabling them to shed snow. In contrast, broad leaved trees in temperate regions deal with winter weather by shedding their leaves. When the days get shorter and the temperature begins to decrease, the leaves no longer make new chlorophyll and the red and yellow pigments already present in the blades become apparent. Synthesis in the leaf of a plant hormone called auxin also ceases. This causes the cells at the junction of the petiole and the twig to weaken until the joint breaks and the leaf floats to the ground. In tropical and subtropical regions, many trees keep their leaves all year round. Individual leaves may fall intermittently and be replaced by new growth but most leaves remain intact for some time. Other tropical species and those in arid regions may shed all their leaves annually, such as at the start of the dry season. Many deciduous trees flower before the new leaves emerge. A few trees do not have true leaves but instead have structures with similar external appearance such as Phylloclades – modified stem structures – as seen in the genus Phyllocladus. Reproduction Further information: Plant reproduction, Pollination, and Seed dispersal Trees can be pollinated either by wind or by animals, mostly insects. Many angiosperm trees are insect pollinated. Wind pollination may take advantage of increased wind speeds high above the ground. Trees use a variety of methods of seed dispersal. Some rely on wind, with winged or plumed seeds. Others rely on animals, for example with edible fruits. Others again eject their seeds (ballistic dispersal), or use gravity so that seeds fall and sometimes roll. Seeds Main article: Seed Seeds are the primary way that trees reproduce and their seeds vary greatly in size and shape. Some of the largest seeds come from trees, but the largest tree, Sequoiadendron giganteum, produces one of the smallest tree seeds. The great diversity in tree fruits and seeds reflects the many different ways that tree species have evolved to disperse their offspring. Wind dispersed seed of elm (Ulmus), ash (Fraxinus) and maple (Acer) For a tree seedling to grow into an adult tree it needs light. If seeds only fell straight to the ground, competition among the concentrated saplings and the shade of the parent would likely prevent it from flourishing. Many seeds such as birch are small and have papery wings to aid dispersal by the wind. Ash trees and maples have larger seeds with blade shaped wings which spiral down to the ground when released. The kapok tree has cottony threads to catch the breeze. The seeds of conifers, the largest group of gymnosperms, are enclosed in a cone and most species have seeds that are light and papery that can be blown considerable distances once free from the cone. Sometimes the seed remains in the cone for years waiting for a trigger event to liberate it. Fire stimulates release and germination of seeds of the jack pine, and also enriches the forest floor with wood ash and removes competing vegetation. Similarly, a number of angiosperms including Acacia cyclops and Acacia mangium have seeds that germinate better after exposure to high temperatures. The flame tree Delonix regia does not rely on fire but shoots its seeds through the air when the two sides of its long pods crack apart explosively on drying. The miniature cone-like catkins of alder trees produce seeds that contain small droplets of oil that help disperse the seeds on the surface of water. Mangroves often grow in water and some species have propagules, which are buoyant fruits with seeds that start germinating before becoming detached from the parent tree. These float on the water and may become lodged on emerging mudbanks and successfully take root. Cracked thorny skin of a Aesculus tree seed Other seeds, such as apple pips and plum stones, have fleshy receptacles and smaller fruits like hawthorns have seeds enclosed in edible tissue; animals including mammals and birds eat the fruits and either discard the seeds, or swallow them so they pass through the gut to be deposited in the animal's droppings well away from the parent tree. The germination of some seeds is improved when they are processed in this way. Nuts may be gathered by animals such as squirrels that cache any not immediately consumed. Many of these caches are never revisited, the nut-casing softens with rain and frost, and the seed germinates in the spring. Pine cones may similarly be hoarded by red squirrels, and grizzly bears may help to disperse the seed by raiding squirrel caches. The single extant species of Ginkgophyta (Ginkgo biloba) has fleshy seeds produced at the ends of short branches on female trees, and Gnetum, a tropical and subtropical group of gymnosperms produce seeds at the tip of a shoot axis. Evolutionary history Lepidodendron, an extinct lycophyte tree Palms and cycads as they might have appeared in the middle Tertiary Further information: Evolutionary history of plants The earliest trees were tree ferns, horsetails and lycophytes, which grew in forests in the Carboniferous period. The first tree may have been Wattieza, fossils of which have been found in New York state in 2007 dating back to the Middle Devonian (about 385 million years ago). Prior to this discovery, Archaeopteris was the earliest known tree. Both of these reproduced by spores rather than seeds and are considered to be links between ferns and the gymnosperms which evolved in the Triassic period. The gymnosperms include conifers, cycads, gnetales and ginkgos and these may have appeared as a result of a whole genome duplication event which took place about 319 million years ago. Ginkgophyta was once a widespread diverse group of which the only survivor is the maidenhair tree Ginkgo biloba. This is considered to be a living fossil because it is virtually unchanged from the fossilised specimens found in Triassic deposits. During the Mesozoic (245 to 66 million years ago) the conifers flourished and became adapted to live in all the major terrestrial habitats. Subsequently, the tree forms of flowering plants evolved during the Cretaceous period. These began to displace the conifers during the Tertiary era (66 to 2 million years ago) when forests covered the globe. When the climate cooled 1.5 million years ago and the first of four glacial periods occurred, the forests retreated as the ice advanced. In the interglacials, trees recolonised the land that had been covered by ice, only to be driven back again in the next glacial period. Ecology Further information: Forest Trees are an important part of the terrestrial ecosystem, providing essential habitats including many kinds of forest for communities of organisms. Epiphytic plants such as ferns, some mosses, liverworts, orchids and some species of parasitic plants (e.g., mistletoe) hang from branches; these along with arboreal lichens, algae, and fungi provide micro-habitats for themselves and for other organisms, including animals. Leaves, flowers and fruits are seasonally available. On the ground underneath trees there is shade, and often there is undergrowth, leaf litter, and decaying wood that provide other habitat. Trees stabilise the soil, prevent rapid run-off of rain water, help prevent desertification, have a role in climate control and help in the maintenance of biodiversity and ecosystem balance. Many species of tree support their own specialised invertebrates. In their natural habitats, 284 different species of insect have been found on the English oak (Quercus robur) and 306 species of invertebrate on the Tasmanian oak (Eucalyptus obliqua). Non-native tree species provide a less biodiverse community, for example in the United Kingdom the sycamore (Acer pseudoplatanus), which originates from southern Europe, has few associated invertebrate species, though its bark supports a wide range of lichens, bryophytes and other epiphytes. Trees differ ecologically in the ease with which they can be found by herbivores. Tree apparency varies with a tree's size and semiochemical content, and with the extent to which it is concealed by nonhost neighbours from its insect pests. In ecosystems such as mangrove swamps, trees play a role in developing the habitat, since the roots of the mangrove trees reduce the speed of flow of tidal currents and trap water-borne sediment, reducing the water depth and creating suitable conditions for further mangrove colonisation. Thus mangrove swamps tend to extend seawards in suitable locations. Mangrove swamps also provide an effective buffer against the more damaging effects of cyclones and tsunamis. Uses Food Further information: nut (fruit) and fruit Trees are the source of many of the world's best known fleshy fruits. Apples, pears, plums, cherries and citrus are all grown commercially in temperate climates and a wide range of edible fruits are found in the tropics. Other commercially important fruit include dates, figs and olives. Palm oil is obtained from the fruits of the oil palm (Elaeis guineensis). The fruits of the cocoa tree (Theobroma cacao) are used to make cocoa and chocolate and the berries of coffee trees, Coffea arabica and Coffea canephora, are processed to extract the coffee beans. In many rural areas of the world, fruit is gathered from forest trees for consumption. Many trees bear edible nuts which can loosely be described as being large, oily kernels found inside a hard shell. These include coconuts (Cocos nucifera), Brazil nuts (Bertholletia excelsa), pecans (Carya illinoinensis), hazel nuts (Corylus), almonds (Prunus dulcis), walnuts (Juglans regia), pistachios (Pistacia vera) and many others. They are high in nutritive value and contain high-quality protein, vitamins and minerals as well as dietary fibre. A variety of nut oils are extracted by pressing for culinary use; some such as walnut, pistachio and hazelnut oils are prized for their distinctive flavours, but they tend to spoil quickly. Sugar maple (Acer saccharum) tapped to collect sap for maple syrup In temperate climates there is a sudden movement of sap at the end of the winter as trees prepare to burst into growth. In North America, the sap of the sugar maple (Acer saccharum) is most often used in the production of a sweet liquid, maple syrup. About 90% of the sap is water, the remaining 10% being a mixture of various sugars and certain minerals. The sap is harvested by drilling holes in the trunks of the trees and collecting the liquid that flows out of the inserted spigots. It is piped to a sugarhouse where it is heated to concentrate it and improve its flavour. Similarly in northern Europe the spring rise in the sap of the silver birch (Betula pendula) is tapped and collected, either to be drunk fresh or fermented into an alcoholic drink. In Alaska, the sap of the sweet birch (Betula lenta) is made into a syrup with a sugar content of 67%. Sweet birch sap is more dilute than maple sap; a hundred litres are required to make one litre of birch syrup. Various parts of trees are used as spices. These include cinnamon, made from the bark of the cinnamon tree (Cinnamomum zeylanicum) and allspice, the dried small fruits of the pimento tree (Pimenta dioica). Nutmeg is a seed found in the fleshy fruit of the nutmeg tree (Myristica fragrans) and cloves are the unopened flower buds of the clove tree (Syzygium aromaticum). Many trees have flowers rich in nectar which are attractive to bees. The production of forest honey is an important industry in rural areas of the developing world where it is undertaken by small-scale beekeepers using traditional methods. The flowers of the elder (Sambucus) are used to make elderflower cordial and petals of the plum (Prunus spp.) can be candied. Sassafras oil is a flavouring obtained from distilling bark from the roots of the sassafras tree (Sassafras albidum). The leaves of trees are widely gathered as fodder for livestock and some can be eaten by humans but they tend to be high in tannins which makes them bitter. Leaves of the curry tree (Murraya koenigii) are eaten, those of kaffir lime (Citrus × hystrix) (in Thai food) and Ailanthus (in Korean dishes such as bugak) and those of the European bay tree (Laurus nobilis) and the California bay tree (Umbellularia californica) are used for flavouring food. Camellia sinensis, the source of tea, is a small tree but seldom reaches its full height, being heavily pruned to make picking the leaves easier. Wood smoke can be used to preserve food. In the hot smoking process the food is exposed to smoke and heat in a controlled environment. The food is ready to eat when the process is complete, having been tenderised and flavoured by the smoke it has absorbed. In the cold process, the temperature is not allowed to rise above 100 °F (38 °C). The flavour of the food is enhanced but raw food requires further cooking. If it is to be preserved, meat should be cured before cold smoking. Fuel Main article: Wood fuel Selling firewood at a market Wood has traditionally been used for fuel, especially in rural areas. In less developed nations it may be the only fuel available and collecting firewood is often a time-consuming task as it becomes necessary to travel further and further afield in the search for fuel. It is often burned inefficiently on an open fire. In more developed countries other fuels are available and burning wood is a choice rather than a necessity. Modern wood-burning stoves are very fuel efficient and new products such as wood pellets are available to burn. Charcoal can be made by slow pyrolysis of wood by heating it in the absence of air in a kiln. The carefully stacked branches, often oak, are burned with a very limited amount of air. The process of converting them into charcoal takes about fifteen hours. Charcoal is used as a fuel in barbecues and by blacksmiths and has many industrial and other uses. Timber Main articles: Wood and Timber Roof trusses made from softwood Timber, "trees that are grown in order to produce wood" is cut into lumber (sawn wood) for use in construction. Wood has been an important, easily available material for construction since humans started building shelters. Engineered wood products are available which bind the particles, fibres or veneers of wood together with adhesives to form composite materials. Plastics have taken over from wood for some traditional uses. Wood is used in the construction of buildings, bridges, trackways, piles, poles for power lines, masts for boats, pit props, railway sleepers, fencing, hurdles, shuttering for concrete, pipes, scaffolding and pallets. In housebuilding it is used in joinery, for making joists, roof trusses, roofing shingles, thatching, staircases, doors, window frames, floor boards, parquet flooring, panelling and cladding. Trees in art: Weeping Willow, Claude Monet, 1918 Wood is used to construct carts, farm implements, boats, dugout canoes and in shipbuilding. It is used for making furniture, tool handles, boxes, ladders, musical instruments, bows, weapons, matches, clothes pegs, brooms, shoes, baskets, turnery, carving, toys, pencils, rollers, cogs, wooden screws, barrels, coffins, skittles, veneers, artificial limbs, oars, skis, wooden spoons, sports equipment and wooden balls. Wood is pulped for paper and used in the manufacture of cardboard and made into engineered wood products for use in construction such as fibreboard, hardboard, chipboard and plywood. The wood of conifers is known as softwood while that of broad-leaved trees is hardwood. Art Besides inspiring artists down the centuries, trees have been used to create art. Living trees have been used in bonsai and in tree shaping, and both living and dead specimens have been sculpted into sometimes fantastic shapes. Bonsai Informal upright style of bonsai on a juniper tree Main article: Bonsai Bonsai (盆栽, lit. "Tray planting") is the practice of hòn non bộ originated in China and spread to Japan more than a thousand years ago, there are similar practices in other cultures like the living miniature landscapes of Vietnam hòn non bộ. The word bonsai is often used in English as an umbrella term for all miniature trees in containers or pots. The purposes of bonsai are primarily contemplation (for the viewer) and the pleasant exercise of effort and ingenuity (for the grower). Bonsai practice focuses on long-term cultivation and shaping of one or more small trees growing in a container, beginning with a cutting, seedling, or small tree of a species suitable for bonsai development. Bonsai can be created from nearly any perennial woody-stemmed tree or shrub species that produces true branches and can be cultivated to remain small through pot confinement with crown and root pruning. Some species are popular as bonsai material because they have characteristics, such as small leaves or needles, that make them appropriate for the compact visual scope of bonsai and a miniature deciduous forest can even be created using such species as Japanese maple, Japanese zelkova or hornbeam. Tree shaping Main article: Tree shaping People trees, by Pooktre Tree shaping is the practice of changing living trees and other woody plants into man made shapes for art and useful structures. There are a few different methods of shaping a tree. There is a gradual method and there is an instant method. The gradual method slowly guides the growing tip along predetermined pathways over time whereas the instant method bends and weaves saplings 2 to 3 m (6.6 to 9.8 ft) long into a shape that becomes more rigid as they thicken up. Most artists use grafting of living trunks, branches, and roots, for art or functional structures and there are plans to grow "living houses" with the branches of trees knitting together to give a solid, weatherproof exterior combined with an interior application of straw and clay to provide a stucco-like inner surface. Tree shaping has been practised for at least several hundred years, the oldest known examples being the living root bridges built and maintained by the Khasi people of Meghalaya, India using the roots of the rubber tree (Ficus elastica). Bark Recently stripped cork oak (Quercus suber) Further information: Bark (botany) Cork is produced from the thick bark of the cork oak (Quercus suber). It is harvested from the living trees about once every ten years in an environmentally sustainable industry. More than half the world's cork comes from Portugal and is largely used to make stoppers for wine bottles. Other uses include floor tiles, bulletin boards, balls, footwear, cigarette tips, packaging, insulation and joints in woodwind instruments. The bark of other varieties of oak has traditionally been used in Europe for the tanning of hides though bark from other species of tree has been used elsewhere. The active ingredient, tannin, is extracted and after various preliminary treatments, the skins are immersed in a series of vats containing solutions in increasing concentrations. The tannin causes the hide to become supple, less affected by water and more resistant to bacterial attack. At least 120 drugs come from plant sources, many of them from the bark of trees. Quinine originates from the cinchona tree (Cinchona) and was for a long time the remedy of choice for the treatment of malaria. Aspirin was synthesised to replace the sodium salicylate derived from the bark of willow trees (Salix) which had unpleasant side effects. The anti-cancer drug Paclitaxel is derived from taxol, a substance found in the bark of the Pacific yew (Taxus brevifolia). Other tree based drugs come from the paw-paw (Carica papaya), the cassia (Cassia spp.), the cocoa tree (Theobroma cacao), the tree of life (Camptotheca acuminata) and the downy birch (Betula pubescens). The papery bark of the white birch tree (Betula papyrifera) was used extensively by Native Americans. Wigwams were covered by it and canoes were constructed from it. Other uses included food containers, hunting and fishing equipment, musical instruments, toys and sledges. Nowadays, bark chips, a by-product of the timber industry, are used as a mulch and as a growing medium for epiphytic plants that need a soil-free compost. Alleé of London plane trees (Platanus × acerifolia) in garden Ornamental trees Main article: Ornamental trees Trees create a visual impact in the same way as do other landscape features and give a sense of maturity and permanence to park and garden. They are grown for the beauty of their forms, their foliage, flowers, fruit and bark and their siting is of major importance in creating a landscape. They can be grouped informally, often surrounded by plantings of bulbs, laid out in stately avenues or used as specimen trees. As living things, their appearance changes with the season and from year to year. Trees are often planted in town environments where they are known as street trees or amenity trees. They can provide shade and cooling through evapotranspiration, absorb greenhouse gases and pollutants, intercept rainfall, and reduce the risk of flooding. Scientific studies show that street trees help cities be more sustainable, and improve the physical and mental wellbeing of the citizens. It has been shown that they are beneficial to humans in creating a sense of well-being and reducing stress. Many towns have initiated tree-planting programmes. In London for example, there is an initiative to plant 20,000 new street trees and to have an increase in tree cover of 5% by 2025, equivalent to one tree for every resident. Other uses Latex collecting from a rubber tree (Hevea brasiliensis) Further information: Resin, Latex, and Camphor Latex is a sticky defensive secretion that protects plants against herbivores. Many trees produce it when injured but the main source of the latex used to make natural rubber is the Pará rubber tree (Hevea brasiliensis). Originally used to create bouncy balls and for the waterproofing of cloth, natural rubber is now mainly used in tyres for which synthetic materials have proved less durable. The latex exuded by the balatá tree (Manilkara bidentata) is used to make golf balls and is similar to gutta-percha, made from the latex of the "getah perca" tree Palaquium. This is also used as an insulator, particularly of undersea cables, and in dentistry, walking sticks and gun butts. It has now largely been replaced by synthetic materials. Resin is another plant exudate that may have a defensive purpose. It is a viscous liquid composed mainly of volatile terpenes and is produced mostly by coniferous trees. It is used in varnishes, for making small castings and in ten-pin bowling balls. When heated, the terpenes are driven off and the remaining product is called "rosin" and is used by stringed instrumentalists on their bows. Some resins contain essential oils and are used in incense and aromatherapy. Fossilised resin is known as amber and was mostly formed in the Cretaceous (145 to 66 million years ago) or more recently. The resin that oozed out of trees sometimes trapped insects or spiders and these are still visible in the interior of the amber. The camphor tree (Cinnamomum camphora) produces an essential oil and the eucalyptus tree (Eucalyptus globulus) is the main source of eucalyptus oil which is used in medicine, as a fragrance and in industry. Threats Individual trees Dead trees pose a safety risk, especially during high winds and severe storms, and removing dead trees involves a financial burden, whereas the presence of healthy trees can clean the air, increase property values, and reduce the temperature of the built environment and thereby reduce building cooling costs. During times of drought, trees can fall into water stress, which may cause a tree to become more susceptible to disease and insect problems, and ultimately may lead to a tree's death. Irrigating trees during dry periods can reduce the risk of water stress and death. Conservation About a third of all tree species, some twenty thousand, are included in the IUCN Red List of Threatened Species. Of those, over eight thousand are globally threatened, including at least 1400 which are classed as "critically endangered". Mythology Main article: Trees in mythology Yggdrasil, the World Ash of Norse mythology Trees have been venerated since time immemorial. To the ancient Celts, certain trees, especially the oak, ash and thorn, held special significance as providing fuel, building materials, ornamental objects and weaponry. Other cultures have similarly revered trees, often linking the lives and fortunes of individuals to them or using them as oracles. In Greek mythology, dryads were believed to be shy nymphs who inhabited trees. The Oubangui people of west Africa plant a tree when a child is born. As the tree flourishes, so does the child but if the tree fails to thrive, the health of the child is considered at risk. When it flowers it is time for marriage. Gifts are left at the tree periodically and when the individual dies, their spirit is believed to live on in the tree. Trees have their roots in the ground and their trunk and branches extended towards the sky. This concept is found in many of the world's religions as a tree which links the underworld and the earth and holds up the heavens. In Norse mythology, Yggdrasil is a central cosmic tree whose roots and branches extend to various worlds. Various creatures live on it. In India, Kalpavriksha is a wish-fulfilling tree, one of the nine jewels that emerged from the primitive ocean. Icons are placed beneath it to be worshipped, tree nymphs inhabit the branches and it grants favours to the devout who tie threads round the trunk. Democracy started in North America when the Great Peacemaker formed the Iroquois Confederacy, inspiring the warriors of the original five American nations to bury their weapons under the Tree of Peace, an eastern white pine (Pinus strobus). In the creation story in the Bible, the tree of life and the knowledge of good and evil was planted by God in the Garden of Eden. Sacred groves exist in China, India, Africa and elsewhere. They are places where the deities live and where all the living things are either sacred or are companions of the gods. Folklore lays down the supernatural penalties that will result if desecration takes place for example by the felling of trees. Because of their protected status, sacred groves may be the only relicts of ancient forest and have a biodiversity much greater than the surrounding area. Some Ancient Indian tree deities, such as Puliyidaivalaiyamman, the Tamil deity of the tamarind tree, or Kadambariyamman, associated with the cadamba tree, were seen as manifestations of a goddess who offers her blessings by giving fruits in abundance. Superlative trees The General Sherman Tree, thought to be the world's largest by volume Main article: List of superlative trees Trees have a theoretical maximum height of 130 m (430 ft), but the tallest known specimen on earth is believed to be a coast redwood (Sequoia sempervirens) at Redwood National Park, California. It has been named Hyperion and is 115.85 m (380.1 ft) tall. In 2006, it was reported to be 379.1 ft (115.5 m) tall. The tallest known broad-leaved tree is a mountain ash (Eucalyptus regnans) growing in Tasmania with a height of 99.8 m (327 ft). The largest tree by volume is believed to be a giant sequoia (Sequoiadendron giganteum) known as the General Sherman Tree in the Sequoia National Park in Tulare County, California. Only the trunk is used in the calculation and the volume is estimated to be 1,487 m (52,500 cu ft). The oldest living tree with a verified age is also in California. It is a Great Basin bristlecone pine (Pinus longaeva) growing in the White Mountains. It has been dated by drilling a core sample and counting the annual rings. It is estimated to currently be 5,078 years old. A little farther south, at Santa Maria del Tule, Oaxaca, Mexico, is the tree with the broadest trunk. It is a Montezuma cypress (Taxodium mucronatum) known as Árbol del Tule and its diameter at breast height is 11.62 m (38.1 ft) giving it a girth of 36.2 m (119 ft). The tree's trunk is far from round and the exact dimensions may be misleading as the circumference includes much empty space between the large buttress roots. See also Agroforestry Arboretum da Vinci branching rule Dendrology Dendrometry Exploding tree Five Trees Forest restoration Fruit tree Great Green Wall (Africa) i-Tree List of lists of trees Million Tree Initiative Multipurpose tree – a tree grown and managed for more than one output Reforestation Tree climbing Tree credits Tree house Tree planting bar Tree planting Trillion Tree Campaign Urban forest Urban forestry Urban reforestation Notes ^ That bristlecone pine is unnamed, its location secret. The previous record holder was named Methuselah, with an age of 4,789 years measured in 1957.	biology	1043555	https://da.wikipedia.org/wiki/Bytr%C3%A6	Bytræ	Bytræ betegner alle træer, der vokser i byerne, om det nu er som spontan vegetation, eller det skyldes bevidst indplantning. Den bymæssige træpleje beskæftiger sig snarest med det sidste, dvs. de plantede og vedligeholdte træer. Til forskel fra den selvgroede flora, som fornyer sig over en kort årrække, arver bystyrerne ofte, som det er med de arkitektoniske ejendomme, nogle gamle træer (her ser man bort fra nybyggede byområder), som man må forvalte over lang tid. (Under gode forhold kan en Eg for eksempel leve mere end 500-700 år og et Rødtræ endnu længere). Når det drejer sig om selvgroede træer hører de ofte til blandt pionertræerne (arter af Pil, Birk osv.), der udvikler sig naturligt på dårlige jorde: mure eller tage i Europa. De er derfor ofte ledsaget af buske af indførte og invasive arter som f.eks. Sommerfuglebusk eller Glansbladet Hæg. Disse arter etablerer sig villigt på ruderater, på brakjord eller på mure og tagdækninger. I byerne findes også bevidst plantede træer af talrige andre arter, der ofte er eksotiske, valgt på grund af deres hårdførhed og deres skønhedsværdi. De er mere eller mindre nyttige for biodiversiteten, afhængigt af omstændighederne, men de har i hvert fald talrige nyttevirkninger, f.eks. ved at forbedre luftkvaliteten i byerne. Bytrætyper Bytræet kan være • indført eller hjemmehørende • klippet eller beskåret • solitært og isoleret eller i selskab med andre træer • plantet på række eller i busket • sammen med eller uden urteflora og epifytter Træet står undertiden i en privathave eller en bypark, eller endog i en by- eller forstadsskov. Man kan finde det i naturtilstand langs visse linjer (søbredder, vandløb, floder, kanaler, jernbaner osv.), hvor træet kan være en del af et mere eller mindre brugbart system af spredningskorridorer tværs gennem byen. Træer kan tilsvarende installeres af mennesker på altaner eller tagterrasser på det vilkår, at underlaget kan bære træernes vægt. Visse prydtræer planter man i baljer, som stilles ud i den varme årstid og hentes ind i et væksthus om vinteren (eksempelvis palmer eller sydfrugttræer, der dyrkes i tempereret eller koldt klima). Bytræets historie Selv om træerne sandsynligvis hurtigt er blevet færre rundt om byerne på grund af folks behov for træ til bygninger, madlavning, opvarmning osv., blev visse arter alligevel knyttet til byen alt efter tidsalderen og byens placering. De befæstede byer havde ofte træer til rådighed (plantet ude på selve fæstningsværkerne med Vaubans værker som et eksempel). De skulle dække behovet for «bagertræ» og træ til nødvendige arbejder under belejring. Plantematerialet fra træerne skulle også tjene til . Antallet af gadetræer varierer meget fra by til by ifølge en optælling, der viser tal fra 50-80 gadetræer pr. 1.000 indbyggere i Centraleuropa ned til 20 træer pr. 1.000 indbyggere i Nice. Dertil kommer, at adskillige sygdomme og skadedyr angriber kastanjetræer og plataner, der regnes blandt de træarter, der anses for at være de mest hårdføre bedst tilpassede under europæiske byforhold. Værdier og funktioner tilskrevet bytræer Bytræet har længe været betragtet som et fælles gode og en kilde til økologisk nytte, dvs. som en almen, offentlig interesse bl.a. af sociologiske, psykologiske politiske og etiske grunde. Træet forbindes især med afslapning og børns leg, med kunst og natur og med opdragelse til miljøforståelse, sundhed, livskvalitet og bymæssig biodiversitet. Siden det 19. århundrede har bytræet spillet en vigtig rolle i driften af byområderne, (man taler endog om grøn urbanisme). I hvert fald siden 1970'erne er bytræer en uomgængelig del i byøkologien, og man tilskriver dem i dag stor betydning for byernes økosystemer og delvis også for deres biodiversitet (særligt for de skovagtige områder i forstæderne, og især hvis de er integreres i økologisk reservat). Symbolske funktioner Træer som afgrænsning og pryd er bærere af nutidens symbolske og sociale værdier, men det samme viste sig også for længe side, i det mindste i Antikken. Samtidig med at bytræerne er et dekorativt element og en del af byens vedligeholdelse, synes de også at være tæt forbundet med folks forhold til liv og død, jf. gårdtræer, træer på tingsteder, træer på kirkegårde og de såkaldte pesttræer. Velfærdsfunktioner Lindetræer har været værdsat siden Middelalderen for at være beroligende og rensende. Som kilde til helbredende drikke har de været plantet i Europa nær ved hospitaler og spedalskhedsasyler. Man har for nylig vist, at blandt unge japanske mænd medførte et ophold på 2½ døgn i en skov en betydelig nedsat hjerterytme og mængde af cortisol (stresshormon) i spyttet. Desuden blev aktiviteten i det parasympatiske nervesystem forøget samtidig med, at der opstod en hæmning af det sympatiske nervesystem (i forhold til situationen i bymiljø). Psykologiske tests, som blev foretaget sideløbende, viste, at disse betingelser forøgede antallet af positive følelser og formindskede antallet af negative følelser (i forhold til påvirkningerne fra bymiljø). Der findes en veldokumenteret forbindelse mellem en persons socialklasse og vedkommendes livslængde, men man har også påvist, at der er en sammenhæng under byforhold mellem livslængde og adgangen til grønne områder, og mellem eksistensen af grønne områder og en persons følelse af at have et godt helbred. Det er videnskabeligt bevist, at træbevoksede byområder bidrager til at mindske stress<ref>Konstantinos Tzoulas Kalevi Korpela, Stephen Venn, Vesa Yli-Pelkonen, Aleksandra Kaźmierczak, Jari Niemela og Philip James : Promoting ecosystem and human health in urban areas using Green Infrastructure: A literature review i Landscape and Urban Planning , 2007, 81, 3 side 167-178</ref> (hvor man forbedrer trivsel i samme grad som man øger naturindholdet ifølge en ny undersøgelse). Store, grønne områder ser ud til at være mest effektive i mindskning af stress. Under indtryk af en tendens til overvægt og i sammenhæng med befolkningens øgede alder FN opmuntrer via WHO til mere fysisk aktivitet og et forøgelse af de grønne områder. Sociale, rekreative eller æstetiske funktioner Træet er et vigtigt element i parker, på pladser, skråninger parker, pladser, grøftekanter og på andre udendørs steder, der er beregnet til afslapning, hvile og fornøjelse. Det er uundværligt for borgernes sundhed og deres psykiske og fysiske ligevægt, hvad der viser sig på steder, hvor man spadserer, lufter hund, dyrker jogging, stavgang eller motionscykling osv. De store træer og busketter, miljøer med skovkarakter eller naturpræg har en fredfyldt virkning, og de bliver betragtet som et positivt element i steder med livsudfoldelse. Deres skygge bliver foretrukket i de tørre og varme egne. Europarådet har opmuntret til, at man øger mængden af grønne områder pr. indbyggerr, samtidig med, at man åbner dem for mere naturindhold og mere biodiversitet. Der findes byarboreter, botaniske haver, træsamlinger og bymæssige frugthaver, som først og fremmest huser arter, der er blevet sjældne. De botaniske haver og byparkerne ufrivilligt været en kilde til spredning af invasive arter (deriblandt træer). Dette har en ny analyse af spredningen af plantearter i historisk tid konkluderet, især i årene mellem 1800 og 1950. St. Louis deklarationen om invasive plantearter fra 2002 er et engagement, som sigter mod at begrænse risikoen for en biologisk invasion fra de botaniske haver. Et kildent spørgsmål drejer sig om ansvaret overfor børnene. Det at kravle op i træerne, at lege på væltede træstammer… det er på samme tid styrkende og farligt, så der må findes et kompromis for ansvarlighedens skyld, f.eks. en skelnen mellem forskellige brugere, og indretning af målrettede løsninger (det kan være træer, der er gjort sikre på legepladser og steder med tæt trafik, oplysningstavler osv.). Publikums interesse ændrer sig: alle nye undersøgelser viser, at når det drejer sig om landskabet, så opstår der lidt efter lidt og med stor kraft en holdning baseret på respekten for kulturelt og æstetisk arvegods, specielt interesse for biodiversitet og naturindhold. Det gælder både i offentligt og privatejede skove og i de åbne grønområder. Dødt ved, tæt underskov, naturligt formsprog og muligheden for at iagttage vilde dyr bliver for tiden undersøgt og foretrukket - endog i byerne - i takt med at behovet for en kunstfærdig og ordnet natur bliver mindre påtrængende end tidligere. Dette skift i offentlighedens ønsker stiller krav til administrationen om at gentænke deres forvaltning for denne del af fællesarven med hensyn til naturindhold, genetisk diversitet og habitatfragmentering. Forskellige undersøgelser viser i øvrigt, at udbuddet af grønne områder, typen af disse områder og deres udvikling har en virkning på beboernes valg af hverdagens fysiske aktiviteter. Som en faktor i den sociale sammenhængskraft er træet også en anledning til at forny beboernes syn på deres kvarter, at fremme nye aktiviteter og til at støtte nye bekendtskaber og samværsformer. Træet bidrager i en renatureringsproces eller ved nyplantning til at omforme de negative opfattelser, der er forbundet med bestemte kvarterers historie og den økonomiske og sociale realitet. Den 1. januar 2015 trådte Europaparlamentets og Europarådets ”Forordning (EU Nr. 1143/2011 af 22. oktober 2014 om forebyggelse og håndtering af introduktion og spredning af invasive, ikke-hjemmehørende arter” i kraft. Økologiske funktioner Træet er først og fremmest et levende væsen og et vigtigt element i talrige økosystemer, og det er vedblivende i samvirke med talrige arter. Det er også et bosted og fødegrundlag for epifytter, svampe og klatrende planter. Endelig er bytræet habitat for mange arter af leddyr (insekter, mider, bænkebidere) og hvirveldyr (fugle, flagermus og små pattedyr) gennem hele dets liv og også medregnet rodzonen. Det gælder i lang tid efter træets død. Hule træer og dødt ved er nødvendige for talrige svampes og hvirvelløse dyrs overlevelse, men det skaber samtidig problemer med sikkerheden i byerne end andre steder. Skovdrift ”med dødt ved” i bred betydning har sigte på at bevare hule eller flækkede stammer uden for områder, hvor træet udsat for forurening med tungmetaller (især for at undgå, at det bliver en form for økologisk fælde), og det gør det muligt at bevare et levested for fugle, pattedyr, krybdyr og padder, som udnytter hulhederne til redebyggeri eller overvintring. Genskabelse af økologiske korridorer Som et led i en byplan med et grønt eller blåt islæt kan træet indgå i spredningskorridorer, stødpudezoner eller økologiske vadesteder. Byøkologi vil dog rumme risikoen for at falde i økologiske fælder (som ofte findes i bymiljøet). FN opmuntrer til en skovdrift i byerne via FAO og European Forum on Urban Forestry (EFUF), støttet af den internationale union af skovforskningsorganisationer (IUFRO), fordi der skal genskabes forbindelser mellem de økologiske refugier og andre ”grønne reservater”. I byernes miljømæsssige sammenhæng er det blandt træbevoksningernes mange funktioner ofte mindre vigtigt at satse på produktion af tømmer, og det kan være meget mere afgørende med velvære og grønne forbindelsesveje. I Tyskland gælder det f.eks. byparken i Mechtenberg, hvor landbrugsområder er sammenknyttet med frugtplantager, grønne boulevarder og vildtvoksende træbestande på tidligere brakmarker og grønne baneterræner i Ruhr. Parken forbinder 3 store byer (Essen, Gelsenkirchen og Bochum), hvor visse bydele bruger landskabsparken i dagligdagen samtidig med, at den spiller en rolle for en grøn infrastruktur, der forbinder landbrugsområder, renaturerede, forladte industrianlæg med steder, der er helliget natur og kunst, til gavn for byernes befolkning, som nu kan nyde mere end 230 km nye vandre- og cyklestier i netværket mellem Emscherparken og den industrielle fortids stisystemer. Træerne spiller en vigtig rolle i dette grønne islæt ved at regulere mikroklima et og vandets kredsløb. Mikroklima Evapotranspirationen fra planterne afkøler luften og dæmper opvarmningen af byen. Omvendt ændrer varmecentrene, partikelforureningen og den sure regn nedbørsmønstrene i snesevis af km afstand i luftlinje fra de store byer.Dale Fuchs: Spain goes hi-tech to beat drought i The Guardian 28.5.2005. Træet har en tamponvirkning på byklimaet, som er forudbestemt til at blive varmere, hvad der tvinger byerne til en tilpasning til klimaændringerne. Denne træets virkning viser sig på flere måder: Ved skyggevirkningen om sommeren, hvor et løvdække mellem solskinnet og en bygning afkøler denne. Om vinteren i den bladløse tid lader træet sollyset trænge igennem og opvarme huset. Efter den første oliekrise i 1973 har arkitekterne vist stor interesse for bioklimatisk arkitektur og for træers evne til at regulere byernes mikroklima betydeligt. D. Nowak taler om en bioteknologi i beskrivelsen af skovdrift i byerne (urban forestry) og om mulighederne for at fjerne forurening af vand, luft og jord, og at standse chockvirkningerne i klimaet. Produktion af ilt Ilt har desinficerende virkninger (man blegede førhen linnedet ved at lægge det i solen udredt på engenes urter). En voksen person har brug for ca. 700 g pr. dag (255 kg/år), hvilket er, hvad godt og vel 20 træer skaber på et år (20 x 30 kg pr. træ). Bytræer skaber derfor kun en ringe andel af de store mængder O2, som bliver forbrugt i de store byer, men den selvskabte iltmængde fra bladene kan godt spille en vigtig, rensende rolle for træerne selv og for deres omgiveler, især inde i kronen. Pr. m2 producerer et stort træ betydeligt mere ilt pr. m2 af drypzone, end en m2 af græsplæne eller busket. I kolde eller tempererede egne producerer vise arter (taks f.eks.) ikke større mængde, men alger, epifytter og visse lianer, som vokser på træernes stammer, kan godt producere en del. Rensning for luftforurening Bytræer renser betydelige mængder luft for talrige partikel- eller gasformige forureninger - alt sammen i forhold til kronens størrelse, bladdækning eller bladenes indskårethed.,. Beskæringsgraden i kronen og afstanden til forureningskilden er to nøglefaktorer, som har indflydelse på rensningsraten. (F.eks.: -9,1 % af partikelforureningen, - 5,3 % af SO2-forureningen, - 2,6 % af NO2-forureningen i en bypark i distriktet Pudong, Shangai, some r en stærkt orurenet by). Selv under forhold med canyoneffekt, hvor der er en tendens til at støv og gasser hvirvles gennem gaderne, renser træer og andre planter luften betydeligt, forudsat de fylder luftrummet tistrækkeligt. Virkningerne er tydelige i lineær afstand på 5 m fra vegetationen . Til overraskelse for modelprogrammørerne og af grunde, som man endnu ikke forstår, har bladenes hældning eller harpikskirtlernes stilling næsten ingen betydning for opfangningen af partikler på bladet (det er processer med enten inertimæssig bremsning og opfangning af partiker eller opløsning/fisering af aerosoler, specielt radioaktive kerner). De viste sig at være mere "effektive" i virkeligheden end det, der kunne forventes efter modeller for fluidmekanik som for øvrigt mest drejer sig om trækroner i skove og ikke om bytræers kroner (de fineste aerosoler (diameter i mikroner) bliver fikseret 4 gange bedre af naturlige bade end på kunstig vis).W. Clough: The deposit of particles on moss and grass surfaces i Atmospheric Environment, 1975, 9 side 1113–1119 Den reelle overførsel af partikelformet bly (dampe af bly 212) i ægte blade fra bønner var – under naturlige forhold - 25 % højere, end ventet i teorien, muligvis på grund af turbulens, bladenes hældning, deres form og struktur eller på grund af respirationen fra bladene. Der vil altid findes store variationer alt afhængig af bladets type og alder, dets overhud (dets større eller mindre grad af voksdækning, ruhed og hårbeklædning), årstiden, tid på dagen, luftfugtigheden osv. Vandrette nåle opfanger færre af de mindste partikler (op til 60 % mindre) end dem, som er hængende eller oprette. Selv grene og stilke spiller en rolle ved at opfange gennemsnitligt ca. 10 %, dvs. 15 % af den totale mængde opfangede blypartikler fra bilerne. Forskellige planter viser sig i øvrigt altid at kunne opfange og optage eller nedbryde meget forskellige partikler eller gasser. Endelig afgifter træet også luften indirekte via Jorden, som det beriger med bakterier og svampe, der kan nedbryde komplekse, organiske forureningsstoffer (visse pesticider, hydroxyapatit, klorerede kulbrinter, etc.). Reduktion af kvælstofilter (NO2) og andre ”NOx” Bytræet bidrager kraftigt til at mildne luftforurening (men de løvfældende træer bidrager væsentligst på den årstid, hvor de har skudvækst en saison de croissance pour les arbres à feuilles caduques de zones tempérées), fra forskellige forureningstyper så som NOX, men også andre kvælstofforureninger. Et japansk studie drejede sig om optagelse af NO2, der var radioaktivt mærket, i de 70 mest anvendte arter langs byveje for at finde frem til de mest effective over for en forurening med NO2. Det viste, at træerne har meget forskellig evne til at optage kvælstofdioxid (variationen havde en faktor på 122 mellem den mest effective art yoshinokirsebær (Prunus yedoensis) og den mindst effektive kryptomeria (Cryptomeria japonica)). Det ser ud til, at man kan klassificere bytræer i fire grupper ud fra denne synsvinkel: de som er gode til at både at optage NO2 og til at modstå denne gas, de som optager den godt, men kun svagt modstår den de som har en ringe optagelse af gassen, og som modstår den dårligt de som har en ringe optagelse af gassen, men som modstår den godt. Blandt de 70 undersøgte arter rummede de 4 grupper henholdsvis 13, 11, 35 og 11 arter. Halvdelen af de testede bytræer havde kun ringe evne til at optage gassen samtidigt med, at de tålte den dårligt. Studiet afslører ikke noget om virkningen af en langvarig belastning. Det viser derimod, at under kortvarig belastning med meget høje doser af NO2, er de fire bedste nogle, som alle har et tæt bladdække med brede blade, nemlig (almindelig robinie (Robinia pseudoacacia), pagodetræ (Styphnolobium japonicum), sortpoppel (Populus nigra) og Prunus lannesiana). Det kunne tyde på, at løvfældende træer med store blade har en konkurrencefordel på dette område, som kan skyldes en stor biomasseque og en hurtig vækst. Men de er ikke aktive om efteråret eller vinteren. Reduktion af kulilte (CO) Man har vist ved at følge kulilte (CO), mærket med radioaktivt kulstof (kulstof 14), at bladene hos vise arter let kan absorbere kulilte (some r mere giftigt for dyr end CO2). Kulilte bliver optaget i planterne i løbet af dagen, og bliver straks omdannet til sukrose og proteiner eller til CO2). Det mere overraskende er, at gassen også bliver optaget om natten og næsten lige så hurtigt, som det sker om dagen. Derpå og næsten med det samme bliver den omdannet til CO2 og frigivet til atmosfæren. I en luft, der var tilført 1 à 10 ppm CO optog de afprøvede planter, fra 0 til 0,25 μmol/dm²/time (med variationer fra art til art), dvs. stort set svarende til koncentrationen af CO i luften, men uden sammenhæng med arternes evne til at lave fotosyntese. Kulilte kan dog ikke frakendes giftighed for de træer, hvor gassen findes: den kan nemlig blokere bindingen af CO2 i bestemte blade. En vegetation kan ifølge beregninger, lavet af Bidwell og Fraser, optage 12 til 120 kg CO/km²/dag. Det er mængder, som næsten svarer til dem, man opnår i jord under brug af langt højere koncentrationer af CO. Filtrering af partikler På de 50 år mellem 1950 og 2000, mens verdens befolkning er fordoblet, er antallet af biler steget endnu mere, har bytræerne langs hovedgaderne været de mest udsatte for blyforureningen (som siden er mindsket efter overgangen til blyfri benzin) og en betydelig forurening med luftbårne partikler. Denne forurening er en er en notorisk årsag til dårligt helbred, og man har fastlagt grænseværdier i mange lande. Takket være deres løvmasse, som fylder et stort rumfang (en stor, færdigt udviklet overflade) mere eller mindre i forhold til de fysiske og biologiske egenskaber ved bladoverflader, træstruktur, og først og fremmest deres kronebygningset kan træerne fungere som: og andre fotokemiske iltforbindelser så som forskelle typer PAN (PeroxyAcetylNitrat, som skyldes en sekundær, fotokemisk forurening, der findes i byerne) i de nederste luftlag af byens skærm (hvis den da eksisterer). Ozonforureningen, som påvirker både menneskers og træers sundhed) er en af de sundhedsmæssige ulemper, som træplejerne må mindske, specielt hvis de vil leve op til FAOs opfordring til at genindføre en bymæssig skovdrift og en form for bymæssigt landbrug med sigte på en mere bæredygtig by: Det må ske samtidig med at de tager hensyn til risici for sundheden (se jordforurening, zoonoseer og ligegyldighed over for farerne fra mikrober Udsættelse for en luft, der er unormalt sur (data og modelberegninger om sanitet stammer ganske vist fra studiet af sur regns virkning på skovene, men bytræerne er udsat for den same stresspåvirkning) ; Rødderne er træernes usynlige del, og de blev ofte indesluttet og misdannet fra begyndelsen af deres liv gennem dyrkningsforløbet, for derpå at blive udplantet i bede, der ofte var for små, og hvor de led under mangel på plads og næringsstoffer i en jord uden kvalitet. Selv i skove vokser træer mindre, når de stammer fra planteskolekulturer, end dem, der kommer af naturligt udsåede frø. For eksempel sammenlignede et studie af 80 klitfyr (Pinus contorta var. contorta), udført 12 år efter at de var blevet udplantet som 1-årige småplanter og opvokset i planteskolebede, med 60 fyrretræer af samme art og alder, men fremkommet som naturlig opvækst. De førstes rodsystemer var stadigvæk misdannede, og træerne voksede mindre godt med færre siderødder af første orden, med større afstand mellem overfladen og de første hovedrødder, en overtykkelse i rodhalsen og en koncentration af siderødder 10 cm under jordoverfladen. De udplantede træer havde stadigvæk følger af indespærringen i containere med et vist antal af misdannede rødder (unormalt afskårne eller indrullede og/eller foldede). Dertil kommer, at de naturligt opvoksede træer havde skabt sig en pælerod og et antal selv-podede rødder (”self-grafted roots”), noget man ikke fandt hos de 12-årige, udplantede træer. Dyrkning af træer i potter ser altså ud til at påvirke de unge træers fremtidige rodsystem. I byerne kan rødderne blive generet eller ødelagt ved udgravninger gennem rodnettet. De forsøger ofte at udvikle sig hen mod vandførende ledninger for at finde vand med fare for, at de kan gennemhulle eller helt tilstoppe dem. De tvinges ofte til at gro i en jord, som har dårlig tekstur, som er uigennemtrængelig og som derfor fremkalder vækstændringer af mangel på vand; Trærødderne lider ofte under den saltlage, man bruger til snebekæmpelse. Flere end 700.000 træer dør hvert år på grund af salt, og endnu flere er forgiftet af saltet (uden at være døde); Vandalisme er årsag til bytræers død (op til 15% af de træer, der er plantet for nylig i Europa ) Stammen, grenene og rødderne bliver ramt ved mekaniske og kemiske skader, ved hård eller meget æstetisk bestemt beskæring (beskæring til stammehæk f.eks.) og ved forureninger i byerne. Plantefstande, markeringer og beskyttende foranstaltninger er ofte dårligt tilpassede, eller træernes nærmiljø har ændret sig, uden at man har taget det i betragtning, (f.eks. overskæring af rodsytemet); Uerfarne ejere eller visse firmaer, hvis folk er utilstrækkeligt uddannede, behandler træerne på en uhensigtsmæssig måde; Fjernelse af nedfaldent løv ændrer træernes normale livsbetingelser; I gaderne eller i kvarterer, som er omsluttet af høje bygninger, mangler kronerne ofte dagslys, mens de bliver udsat for lysforurening om natten (”canyon-effekten”); På grund af det overvarme bymiljø og lysforurening, sker løvspringet ofte for tidligt, og løvfaldet bliver forsinket (med adskillige måneder, især under gadelamper), men ifølge NASA, producerer de 20% mindre ilt, målt i forhold til tilsvarende træer i naturen. Ikke desto mindre ser et nyligt studie tilsyneladende ud til, at man har undervurderet træernes evne til at rense luften for bestemte forureninger (i særdeleshed Flygtige organiske forbindelser. Udsathed for en lysforurening, hvis virkninger på bytræet stadigvæk er dårligt undersøgt; Pligtmæssig beskæring: af sikkerhedsgrunde kan EDF {{Citat\|nedskære træer eller grene, som generer luftledninger, eller som kan fremkalde kortslutninger eller nedbrud på værkerne, når de befinder sig i nærheden af ledningsnettet}} ; Konsekvensen af ophobet stress, sygdomsudbrud eller eksotiske skadegørere giver en samlet virkning, så meget desto mere som det ofte er de samme arter, der kommer fra de samme planteskoler, der bliver plantet overalt, Forvaltning Det er meget dyrt at plante tilstrækkeligt store træer. Det er et langtrukket og besværligt arbejde, hvis man i stedet sår frø eller prikler ungplanter og beskytter dem, så de bedst muligt kan få fodfæste, for de er sårbare i mange år. Mange kultivarer, som bliver plantet i rækker af samme sort, er yderst sårbare overfor epidemier og forskellige skadegørere, og de bidrager knap nok til biodiversiteten inden for deres egen art. God pleje indebærer dataopsamlinger, som hyppigt bliver holdt à jour (for eksempel, den i Nancy med ca. 10000 træer, hvoraf to er mere end 2560 år gamle), og et meget omhyggeligt sundhedstilsyn. I byerne er beskæring ofte påkrævet, selv med en adgang, som ofte er besværlig. Det er ønskeligt at beskæringen udføres nænsomt og af veluddannede fagfolk, for den er en adgangsvej for talrige skadegørere. Hos visse arter må den udføres til rette tid. Det er nødvendigt med opmærksom pleje og med en afpasset videregivelse af oplysninger, hvis man skal opnå offentlighedens støtte eller aktive medvirken, og hvis bytræet skal blive værdsat af det størst mulige antal borgere for dets goder i samme omfang som dets besværligheder (visne blade …). Pleje Skal man Det var temaet for et referat fra 1. Samling af “Forum 2011”: Bytræforvaltningen bliver i praksis ofte stillet over for adskillige meninger og pres, som er hinanden modstridende vedrørende træet, fra byens borgere, fra forvaltningen og fra politikerne. Desuden er bytræet udsat for privat stress og for spørgsmål om ansvarlighed over for brugerne af det offentlige rum, og derfor har det et større behov for omhu end det åbne lands eller skovenes træer (tilsvarende træer langs landeveje og de spredte træer langs transportsystemerne). Træer på række i same sort giver et specielt problem, for hvis et enkelt træ dør, opstår der en visuel effekt, som øjeblikkelig påvirker opfattelsen af hele rækken, og talrige iagttagere interesserer sig for det. Der er behov for opmærksomhed fra mange sider. Inden for deres agenda 21ramme, klimaplaner og papirer vedrørende byudvikling kan kvartererne og indbyggerne forsøge at bruge juridiske midler til beskyttelse af træerne, sådan at de skærmer dette arvegods. Nogle af kvartererne stiller træer til rådighed eller giver mulighed for at indkøbe dem til en lav pris. De koncessionshavende for infrastrukturnetværk kan lave aftaler med beboerne og kvartererne om et bedre fællesskab om træernes forhold. De kan gå sammen om optællinger over naturen (herunder deltagelse i Atlas de la biodiversité des communes quand il existe)., hvis det findes. Det er nødvendigt indgå kompromis’er mellem bevaringsbiologiske og rekreative hensyn, hvis man vil beskytte biodiversitet og jordbund mod konsekvenserne af for megen færdsel omkring skovplantningerne i byerne. Det sker ofte, at byerne ofrer bestemte områder (picnicsteder) under udviklingen af strategier for ”kanalisering” af offentligheden i stopzoner, eller at man ”holder noget i reserve” ved styring af adgangsveje, skiltning og kortmaterialer. Byen Louvain (Belgien) har således to ringparker, som er rester af kulsvierskove. Man har åbnet den noget større (Heverleebos-skov) og har begrænset adgangen til de centrale dele, som kaldes ”biodiversitetskerner” af den anden (Meerdaalwoud). Disse to områder er ikke desto mindre medtaget det paneuropæiske økologinetværk. Med visse undtagelser (ofte i bymidten), ses der enøkologisk ulighed i talrige byer: de velhavende boligkvarterer har generelt fornøjelsen af flere træer og af et højere gennemsnitligt bladarealindeks. Dette fænomen er f.eks. blev undersøgt i Santiago de Chile. I visse lande samarbejder talrige NGO'er eller lokale sammenslutninger med hinanden eller undertiden med bystyret og dem, der administrerer infrastrukturen, til gavn for bytræet, avec par exemple aux États-Unis: Alliance for Community Trees: Alliance for Community Trees American Forests: Tree Equity in America’s Cities Casey Trees: Residential Trees Friends of the Urban Forest International Society of Arboriculture: Who we are ISA: Trees Are Good International Society of Arboriculture: Australia Chapter Our City Forest: Neighborhood Plantings & Granted Areas Society of Municipal Arborists: Home page Society of American Foresters: Home page The Tree Council UK: Who we are Tree City USA: What is Tree City USA? TREE Fund: About Canopy: About us Trees Atlanta: About Dansk Træplejeforening: Formål Nogle tal Antallet af bytræer varierer fra ganske få til hundredvis, mest på grund af klimaforholdene og bytypen. Byer i meget varme eller tørre områder tilbyder slet ikke eller kun få grønne pletter. Byerne i de tempererede egne har mange flere af dem. I Europa har en undersøgelse afRichard Fuller og Kevin Gaston: Access to green space in European cities de grønne områder i 386 byer med mere end 100.000 indbyggere i 31 europæiske lande (svarende til 170,6 millioner beboere og 34 % af den europæiske befolkning i 2001) vist følgende: Ifølge data fra begyndelsen af det 21. århundrede konstaterer Det Europæiske Miljøagentur, at antallet af grønne områder dækkede mellem 1,9 % af byområdet (Reggio Calabria) i Italien, og 46 % (Ferrol) i Spanien, på grundlag af definitioner, der er kendt af forfatterne (forskellige beregningsmetoder er mulige). Byerne i Nordeuropa har i gennemsnit bevaret et større areal af grønne områder i sammenligning med byerne mod syd. 45 millioner af de indbyggere, som bor i de europæiske byer, har stadig en meget begrænset adgang til grønne byområder, særligt i byer, som kun har 2-3 % grønne områder med en generel tendens til, at det tilgængelige areal pr. indbygger bliver formindsket på grund af den øgede befolkningstæthed Bortset fra undtagelser har byerne i det sydlige Europa meget få grønne områder, f.eks.: 3–4 m2 pr. person i Cadiz, Almería, Fuenlabrada (alle i Spanien) og i regionen Calabrien (i Italien), mens byerne i det nordlige Europa har op til 100 gange mere pr. person, f.eks.: 300 m2 pr. person i Liège (Belgien), Oulu (Finland) eller Valenciennes (Frankrig). Pollen og pollenallergi Paradoksalt nok er det i byerne og de industrialiserede miljøer, hvor planternes pollen er mere sjældne, at indbyggerne er mere plaget af pollenallergier (allergier overfor pollen var helt fraværende i den medicinske litteratur før den industrielle revolution). Disse allergier er siden i systematisk udvikling, og det i en grad, så en arbejdsgruppe om luftkvalitet har foreslået at optage pollen blandt forureningerne i byluften. De alvorligste, allergifremkaldende pollen kommer fra en række vindbestøvede træer og buske. Omkostninger Plantningsprisen er meget lav for de små træer, som man selv har lavet (f.eks. i kommunale planteskoler), som man gør i Genève på 4 ha i en integreret produktion(PI)), men i de tæt bebyggede byer, er de meget sårbare. Plantning af vejtræer med en omkreds på 20–30 cm er efterhånden mere almindelig. De bliver bestilt i planteskolerne med rødderne i en klump, som er pakket ind i noget nedbrydeligt jutelærred. Det koster pr plantning mellem 200 og 1500 euro pr. træ. I nogle lande planter man endnu træer med bare rødder eller træer med en omkreds mindre end 12 cm i diameter. Hertil kommer udgifterne til overvågning og pleje, som varierer meget efter forholdene, særligt hvad angår prisen på. Gode plejetiltag Den nyere speciallitteratur om en effektiv og mindre forurenende pleje af bytræerne: Vedligehold træerne og skovbiomassen, der findes i byerne, ved at plante og øge antallet af sunde træer (og altså plantet under gode forhold) for at sænke forureningen af luft, vand og jord. Foretræk træk træarter, der udsender færre organiske forbindelser (der kan bidrage til fotokemisk smog i storbyer og forurenede småbyer. Gør jorden løs og beplant den. Forsøg at skaffe store, sunde træer (større forureningsdæmpende effekt pr. træ), og forbered i god tid, når træerne skal fjernes, fordi de bliver for gamle. Bevar dødt træ og visne blade på grønne områder, så der genskabes højkvalitetshumus samtidig med, at holde kontrol med de ikkenedbrydelige, forurenende stoffer (bly, cadmium, salt), som muligvis kan være ophobet af træerne gennem deres lange liv. Foretræk træer med lang livslængde (færre udslip af forurening ved plantning og ved fældning). Foretræk træer, der har mindre behov for pleje (færre omkostninger og forurening forbundet med vedligeholdelse). Formindsk brugen af brændstoffer i vedligeholdelse, pleje og genopretning af byvegetation (mindre forurenende udslip). Læg vægt på træernes klimatiske vilkår (mindre opvarmning og brug af klimaanlæg, mindre træk på kraftcentraler og fossile brændstoffer). Skab skygge på p-pladserne ved plantning af træer og vedbend (mindre afgivelse af organiske stoffer og opsugning af benzin, som fordamper fra tankene), uden at skygge for eventuelle solceller. Vær opmærksom på, om planterne mangler vand (mindre forurening og temperatursænkning som følge af evapotranspiration). Plant træer på steder, hvor der er forurening, og hvor der er høj befolkningstæthed (maksimer fordelene ved at have træer som luftrensere). Bekæmp de forureninger, der skader træerne (når træernes sundhed øges, gør menneskenes det også). Anvend stedsegrønne træer af hensyn til reduktionen af partikler (fjernelse hele året rundt). Opbyg en blanding af træarter, gerne lokale arter, som er tilpasset jordtypen og lokalmiljøet, og begræns brugen af kloner (for at nå frem til en genetisk diversitet, der er mindre følsom over for epidemier) med en tilgang, der er i samklang med træernes økosystemer (træerne lever f.eks. normalt i symbiose med svampe, som har behov for en jord, der er luftig, og for næring fra døde grene eller visne blade). Foretræk en nænsom og velbegrundet beskæring, når det er nødvendigt at beskære. Noter Se også Video Natureparif: Friche urbaine et la biodiversité, 2011. Natureparif: Qu'est la biodiversité urbaine?, 2011. Bibliografi <div style="-moz-column-count:2; -moz-column-gap:10px;"> Chow, P., Rolfe, G.L., 1989. Carbon and hydrogen contents ofshort-rotation biomass of five hardwood species i Wood and Fiber Science, 1989, 21 (I), 30-36. Forest Products Laboratory: Chemical analyses of wood, Tech. Note 235, 1952. Hallé, Francis: Du bon usage des arbres: Un plaidoyer à l'attention des élus et des énarques, 2011, . Kenney. W.A. and Associates, The Role of Urban Forests in Greenhouse Gas Reduction, 2001. Lenschow, D.H. (Ed.): Probing the Atmospheric Boundary Layer i American Meteorological Society, 1986. Luley, C.J. og J. Bond: A plan to integrate management ofurban trees into air quality planning i Report to Northeast State Foresters Association, 2002. McPherson, E.G.: Atmospheric carbon dioxide reduction by Sacramento's urban forest i Journal of Arboriculture, 1998, 24, 41. McPherson, E. G. & J.R. Simpson: Reducing Air Pollution Through Urban Forestry i Proceedings of the 48th meeting of California Pest Council, 2000. (netartikel). McPherson, E. G., J.R. Simpson & K. Scott: Actualizing Microclimate and Air Quality Benefits with Parking Lot Shade Ordinances i Wetter und Leben, 2002, 4, 98 (netartikel). Thierry Moigneu: Gérer les forêts périurbaines , 2005. (Udgivet på CD-Rom, som kan hentes hos Office National des Forêts). Nowak, David. J.: Atmospheric carbon reduction by urban trees. Journal of Environmental Management, 1993, 37, 3. Nowak, D.J.: Atmospheric carbon dioxide reduction by Chicago's urban forest i McPherson, E.G., Nowak. D.J., og Rowntree, R.A. (udg.): Chicago's Urban Forest Ecosystem: Results of the Chicago Urban Forest Climate Project i USDA Forest Service General Technical Report, 1994 side 83-94. 1994 Nowak, D.J.: Trees pollute? A "TREE" explains it all. i Kollin, C., Barratt, M. (udg.), Proceedings of the Seventh National Urban Forestry Conference i AmericanForests, 1995 side 28-30. Nowak, D.J., McHale, P.J., Ibarra, M., Crane, D., Stevens, J., Luley, C.: Modeling the effects of urban vegetation on air pollution i Gryning. S.E., Chaumerliac, N. (udg.): Air Pollution Modeling and Its Application XII, 1998. Nowak, D.J., Civerolo, K.L.. Rao, S.T.. Sistia, S.. Luley, C.J., Crane. D.E.: A modeling study of the impact of urban trees on ozone i Atmospheric Environment, 2001, 34, Nowak, D.J., Pasek, J., Sequeira, R.. Crane, D.E., Mastro, V.: Potential effect of Anoplophora glabripennis (Coleoptera: Cerambycidae) on urban trees in the United States i Journal of Economic Entomology, 2001, 94, 1. Nowak, D.J., Crane, D.E.: The Urban Forest Effects (UFORE) Model: quantifying urban forest structure and functions i Hansen, M., Burk, T. (udg.): Proceedings: Integrated Tools for Natural Resources Inventories in the 21 st Century, 2000. Nowak, D.J., Dwyer, J.F., Understanding the benefits and costs of urban forest ecosystems i Kuser, J.E. (udg.): Urban and Community Forestry in the Northeast, 2000, Nowak. D.J., Crane, D.E., Dwyer, J.F: Compensatory value of urban trees in the United States i Journal of Arboriculture. 2002, 28, 4. Nowak, D.J., Crane, D.E., Stevens, J.C., Ibarra, M.: Brooklyn's urban forest i General Technical Reports (USDA), 2002. Nowak, D.J.: Strategic Tree Planting as an EPA Encouraged Pollutant Reduction Strategy: How Urban Trees can Obtain Credit in State Implementation Plans, 2005 Nowak, D.J. og Walton, J.T.: Projected urban growth (2000-2050) and its estimated impact on the US forest resource i Journal of Forestry, 2005, 103, 8. Nowak, D.J., Crane, D.E., Stevens, J.C. og Hoehn, R.. The Urban Forest Effects (UFORE) Model: Field DataCollection Procedures i USDA Forest Service, NortheasternResearch Station, Syracuse, 2005. Nowak, D.J., Walton. J.T., Dwyer, J.F., Kaya, L.G., Myeong, S.: The increasing influence of urban environments on US forest management i Journal of Forestry, 2005, 103, 8. Nowak, D.J., Crane, D.E. og Stevens, J.C.: Air pollution removal by urban trees and shrubs in the United States i Urban Forestry & Urban Greening, 2006, 4, 3-4. Porse, Sten & Jens Thejsen: Bytræer. Økologi, Biodiversitet & pleje, 2016, Marianne Rosenbak: Den urbane varmeø. Byens overflader og materialer. Taha, H.: Modeling impacts of increased urbanvegetation on ozone air quality in the South Coast Air Basin i Atmospheric Environment, 1996, 30, 20. Tenley M. Conway og Lisa Urbani: Variations in municipal urban forestry policies: A case study of Toronto, Canada i Urban Forestry & Urban Greening, 2007, 6, 3 United Nations Framework Convention on Climate Change: Kyoto Protocol Status of Ratification 2006. United Nations Framework Convention on Climate Change: Essential Background 2006. US EPA: 8-Hour Ground-level Ozone Designations US Environmental Protection Agency, 2006. US Environmental Protection Agency: Incorporating emerging and voluntary measures in a state implementation plan (SIP) US Environmental Protection Agency, 2006. Yang, J., McBride, J.. Zhou, J. og Sun, Z.,. The urban forest in Beijing and its role in air pollution reduction i Forest Hydrology 2005, 3, 2. Se også Arborist Byøkologi Dødt træ Renaturering Træ (organisme) Træpleje Skov Byplanlægning i Danmark Byplanlægning en:Urban tree	danish	0.567647
reddish_adapt_to_color/Color.txt	Colour (Commonwealth English) or color (American English) is the visual perception based on the electromagnetic spectrum. Though colour is not an inherent property of matter, colour perception is related to an object's light absorption, reflection, emission spectra and interference. For most humans, colours are perceived in the visible light spectrum with three types of cone cells (trichromacy). Other animals may have a different number of cone cell types or have eyes sensitive to different wavelength, such as bees that can distinguish ultraviolet, and thus have a different colour sensitivity range. Animal perception of colour originates from different light wavelength or spectral sensitivity in cone cell types, which is then processed by the brain. Colours have perceived properties such as hue, colourfulness (saturation) and luminance. Colours can also be additively mixed (commonly used for actual light) or subtractively mixed (commonly used for materials). If the colours are mixed in the right proportions, because of metamerism, they may look the same as a single-wavelength light. For convenience, colours can be organised in a colour space, which when being abstracted as a mathematical colour model can assign each region of colour with a corresponding set of numbers. As such, colour spaces are an essential tool for colour reproduction in print, photography, computer monitors and television. The most well-known colour models are RGB, CMYK, YUV, HSL and HSV. Because the perception of colour is an important aspect of human life, different colours have been associated with emotions, activity, and nationality. Names of colour regions in different cultures can have different, sometimes overlapping areas. In visual arts, colour theory is used to govern the use of colours in an aesthetically pleasing and harmonious way. The theory of colour includes the colour complements; colour balance; and classification of primary colours (traditionally red, yellow, blue), secondary colours (traditionally orange, green, purple) and tertiary colours. The study of colours in general is called colour science. Physical properties The visible spectrum perceived from 390 to 710 nm wavelength Electromagnetic radiation is characterised by its wavelength (or frequency) and its intensity. When the wavelength is within the visible spectrum (the range of wavelengths humans can perceive, approximately from 390 nm to 700 nm), it is known as "visible light". Most light sources emit light at many different wavelengths; a source's spectrum is a distribution giving its intensity at each wavelength. Although the spectrum of light arriving at the eye from a given direction determines the colour sensation in that direction, there are many more possible spectral combinations than colour sensations. In fact, one may formally define a colour as a class of spectra that give rise to the same colour sensation, although such classes would vary widely among different species, and to a lesser extent among individuals within the same species. In each such class, the members are called metamers of the colour in question. This effect can be visualised by comparing the light sources' spectral power distributions and the resulting colours. Spectral colours Main article: Spectral color The familiar colours of the rainbow in the spectrum—named using the Latin word for appearance or apparition by Isaac Newton in 1671—include all those colours that can be produced by visible light of a single wavelength only, the pure spectral or monochromatic colours. The spectrum above shows approximate wavelengths (in nm) for spectral colours in the visible range. Spectral colours have 100% purity, and are fully saturated. A complex mixture of spectral colours can be used to describe any colour, which is the definition of a light power spectrum. The spectral colours form a continuous spectrum, and how it is divided into distinct colours linguistically is a matter of culture and historical contingency. Despite the ubiquitous ROYGBIV mnemonic used to remember the spectral colours in English, the inclusion or exclusion of colours is contentious, with disagreement often focused on indigo and cyan. Even if the subset of colour terms is agreed, their wavelength ranges and borders between them may not be. The intensity of a spectral colour, relative to the context in which it is viewed, may alter its perception considerably according to the Bezold–Brücke shift; for example, a low-intensity orange-yellow is brown, and a low-intensity yellow-green is olive green. In colour models capable of representing spectral colours, such as CIELUV, a spectral colour has the maximal saturation. In Helmholtz coordinates, this is described as 100% purity. colour of objects The physical colour of an object depends on how it absorbs and scatters light. Most objects scatter light to some degree and do not reflect or transmit light specularly like glasses or mirrors. A transparent object allows almost all light to transmit or pass through, thus transparent objects are perceived as colourless. Conversely, an opaque object does not allow light to transmit through and instead absorbing or reflecting the light it receives. Like transparent objects, translucent objects allow light to transmit through, but translucent objects are seen coloured because they scatter or absorb certain wavelengths of light via internal scatterance. The absorbed light is often dissipated as heat. Colour vision Main article: Color vision Development of theories of colour vision Main article: Color theory The upper disk and the lower disk have exactly the same objective colour, and are in identical gray surroundings; based on context differences, humans perceive the squares as having different reflectances, and may interpret the colours as different colour categories; see checker shadow illusion. Although Aristotle and other ancient scientists had already written on the nature of light and colour vision, it was not until Newton that light was identified as the source of the colour sensation. In 1810, Goethe published his comprehensive Theory of colours in which he provided a rational description of colour experience, which 'tells us how it originates, not what it is'. (Schopenhauer) In 1801 Thomas Young proposed his trichromatic theory, based on the observation that any colour could be matched with a combination of three lights. This theory was later refined by James Clerk Maxwell and Hermann von Helmholtz. As Helmholtz puts it, "the principles of Newton's law of mixture were experimentally confirmed by Maxwell in 1856. Young's theory of colour sensations, like so much else that this marvelous investigator achieved in advance of his time, remained unnoticed until Maxwell directed attention to it." At the same time as Helmholtz, Ewald Hering developed the opponent process theory of colour, noting that colour blindness and afterimages typically come in opponent pairs (red-green, blue-orange, yellow-violet, and black-white). Ultimately these two theories were synthesised in 1957 by Hurvich and Jameson, who showed that retinal processing corresponds to the trichromatic theory, while processing at the level of the lateral geniculate nucleus corresponds to the opponent theory. In 1931, an international group of experts known as the Commission internationale de l'éclairage (CIE) developed a mathematical colour model, which mapped out the space of observable colours and assigned a set of three numbers to each. Colour in the eye Main article: Color vision § Cone cells in the human eye Normalised typical human cone cell responses (S, M, and L types) to monochromatic spectral stimuli The ability of the human eye to distinguish colours is based upon the varying sensitivity of different cells in the retina to light of different wavelengths. Humans are trichromatic—the retina contains three types of colour receptor cells, or cones. One type, relatively distinct from the other two, is most responsive to light that is perceived as blue or blue-violet, with wavelengths around 450 nm; cones of this type are sometimes called short-wavelength cones or S cones (or misleadingly, blue cones). The other two types are closely related genetically and chemically: middle-wavelength cones, M cones, or green cones are most sensitive to light perceived as green, with wavelengths around 540 nm, while the long-wavelength cones, L cones, or red cones, are most sensitive to light that is perceived as greenish yellow, with wavelengths around 570 nm. Light, no matter how complex its composition of wavelengths, is reduced to three colour components by the eye. Each cone type adheres to the principle of univariance, which is that each cone's output is determined by the amount of light that falls on it over all wavelengths. For each location in the visual field, the three types of cones yield three signals based on the extent to which each is stimulated. These amounts of stimulation are sometimes called tristimulus values. The response curve as a function of wavelength varies for each type of cone. Because the curves overlap, some tristimulus values do not occur for any incoming light combination. For example, it is not possible to stimulate only the mid-wavelength (so-called "green") cones; the other cones will inevitably be stimulated to some degree at the same time. The set of all possible tristimulus values determines the human colour space. It has been estimated that humans can distinguish roughly 10 million different colours. The other type of light-sensitive cell in the eye, the rod, has a different response curve. In normal situations, when light is bright enough to strongly stimulate the cones, rods play virtually no role in vision at all. On the other hand, in dim light, the cones are understimulated leaving only the signal from the rods, resulting in a colourless response. (Furthermore, the rods are barely sensitive to light in the "red" range.) In certain conditions of intermediate illumination, the rod response and a weak cone response can together result in colour discriminations not accounted for by cone responses alone. These effects, combined, are summarised also in the Kruithof curve, which describes the change of colour perception and pleasingness of light as a function of temperature and intensity. Colour in the brain Main article: Color vision § Color in the primate brain While the mechanisms of colour vision at the level of the retina are well-described in terms of tristimulus values, colour processing after that point is organised differently. A dominant theory of colour vision proposes that colour information is transmitted out of the eye by three opponent processes, or opponent channels, each constructed from the raw output of the cones: a red–green channel, a blue–yellow channel, and a black–white "luminance" channel. This theory has been supported by neurobiology, and accounts for the structure of our subjective colour experience. Specifically, it explains why humans cannot perceive a "reddish green" or "yellowish blue", and it predicts the colour wheel: it is the collection of colours for which at least one of the two colour channels measures a value at one of its extremes. The exact nature of colour perception beyond the processing already described, and indeed the status of colour as a feature of the perceived world or rather as a feature of our perception of the world—a type of qualia—is a matter of complex and continuing philosophical dispute. The visual dorsal stream (green) and ventral stream (purple) are shown. The ventral stream is responsible for colour perception. From the V1 blobs, colour information is sent to cells in the second visual area, V2. The cells in V2 that are most strongly colour tuned are clustered in the "thin stripes" that, like the blobs in V1, stain for the enzyme cytochrome oxidase (separating the thin stripes are interstripes and thick stripes, which seem to be concerned with other visual information like motion and high-resolution form). Neurones in V2 then synapse onto cells in the extended V4. This area includes not only V4, but two other areas in the posterior inferior temporal cortex, anterior to area V3, the dorsal posterior inferior temporal cortex, and posterior TEO. Area V4 was initially suggested by Semir Zeki to be exclusively dedicated to colour, and he later showed that V4 can be subdivided into subregions with very high concentrations of colour cells separated from each other by zones with lower concentration of such cells though even the latter cells respond better to some wavelengths than to others, a finding confirmed by subsequent studies. The presence in V4 of orientation-selective cells led to the view that V4 is involved in processing both colour and form associated with colour but it is worth noting that the orientation selective cells within V4 are more broadly tuned than their counterparts in V1, V2 and V3. colour processing in the extended V4 occurs in millimeter-sised colour modules called globs. This is the part of the brain in which colour is first processed into the full range of hues found in colour space. Nonstandard colour perception Colour vision deficiency Main article: Color blindness A colour vision deficiency causes an individual to perceive a smaller gamut of colours than the standard observer with normal colour vision. The effect can be mild, having lower "colour resolution" (i.e. anomalous trichromacy), moderate, lacking an entire dimension or channel of colour (e.g. dichromacy), or complete, lacking all colour perception (i.e. monochromacy). Most forms of colour blindness derive from one or more of the three classes of cone cells either being missing, having a shifted spectral sensitivity or having lower responsiveness to incoming light. In addition, cerebral achromatopsia is caused by neural anomalies in those parts of the brain where visual processing takes place. Some colours that appear distinct to an individual with normal colour vision will appear metameric to the colour blind. The most common form of colour blindness is congenital red–green colour blindness, affecting ~8% of males. Individuals with the strongest form of this condition (dichromacy) will experience blue and purple, green and yellow, teal and gray as colours of confusion, i.e. metamers. Tetrachromacy Main article: Tetrachromacy Outside of humans, which are mostly trichromatic (having three types of cones), most mammals are dichromatic, possessing only two cones. However, outside of mammals, most vertebrate are tetrachromatic, having four types of cones, and includes most, birds, reptiles, amphibians and bony fish. An extra dimension of colour vision means these vertebrates can see two distinct colours that a normal human would view as metamers. Some invertebrates, such as the mantis shrimp, have an even higher number of cones (12) that could lead to a richer colour gamut than even imaginable by humans. The existence of human tetrachromats is a contentious notion. As many as half of all human females have 4 distinct cone classes, which could enable tetrachromacy. However, a distinction must be made between retinal (or weak) tetrachromats, which express four cone classes in the retina, and functional (or strong) tetrachromats, which are able to make the enhanced colour discriminations expected of tetrachromats. In fact, there is only one peer-reviewed report of a functional tetrachromat. It is estimated that while the average person is able to see one million colours, someone with functional tetrachromacy could see a hundred million colours. Synesthesia Main article: Synesthesia In certain forms of synesthesia, perceiving letters and numbers (grapheme–colour synesthesia) or hearing sounds (chromesthesia) will evoke a perception of colour. Behavioral and functional neuroimaging experiments have demonstrated that these colour experiences lead to changes in behavioral tasks and lead to increased activation of brain regions involved in colour perception, thus demonstrating their reality, and similarity to real colour percepts, albeit evoked through a non-standard route. Synesthesia can occur genetically, with 4% of the population having variants associated with the condition. Synesthesia has also been known to occur with brain damage, drugs, and sensory deprivation. The philosopher Pythagoras experienced synesthesia and provided one of the first written accounts of the condition in approximately 550 BCE. He created mathematical equations for musical notes that could form part of a scale, such as an octave. Afterimages Main article: Afterimage After exposure to strong light in their sensitivity range, photoreceptors of a given type become desensitised. For a few seconds after the light ceases, they will continue to signal less strongly than they otherwise would. Colours observed during that period will appear to lack the colour component detected by the desensitised photoreceptors. This effect is responsible for the phenomenon of afterimages, in which the eye may continue to see a bright figure after looking away from it, but in a complementary colour. Afterimage effects have also been used by artists, including Vincent van Gogh. Colour constancy Main article: Color constancy When an artist uses a limited colour palette, the human eye tends to compensate by seeing any gray or neutral colour as the colour which is missing from the colour wheel. For example, in a limited palette consisting of red, yellow, black, and white, a mixture of yellow and black will appear as a variety of green, a mixture of red and black will appear as a variety of purple, and pure gray will appear bluish. The trichromatic theory is strictly true when the visual system is in a fixed state of adaptation. In reality, the visual system is constantly adapting to changes in the environment and compares the various colours in a scene to reduce the effects of the illumination. If a scene is illuminated with one light, and then with another, as long as the difference between the light sources stays within a reasonable range, the colours in the scene appear relatively constant to us. This was studied by Edwin H. Land in the 1970s and led to his retinex theory of colour constancy. Both phenomena are readily explained and mathematically modeled with modern theories of chromatic adaptation and colour appearance (e.g. CIECAM02, iCAM). There is no need to dismiss the trichromatic theory of vision, but rather it can be enhanced with an understanding of how the visual system adapts to changes in the viewing environment. Reproduction Main article: Color reproduction The CIE 1931 colour space xy chromaticity diagram with the visual locus plotted using the CIE (2006) physiologically relevant LMS fundamental colour matching functions transformed into the CIE 1931 xy colour space and converted into Adobe RGB. The triangle shows the gamut of Adobe RGB. The Planckian locus is shown with colour temperatures labeled in Kelvins. The outer curved boundary is the spectral (or monochromatic) locus, with wavelengths shown in nanometers. The colours in this file are being specified using Adobe RGB. Areas outside the triangle cannot be accurately rendered since they are outside the gamut of Adobe RGB, therefore they have been interpreted. The colours depicted depend on the gamut and colour accuracy of your display. Colour reproduction is the science of creating colours for the human eye that faithfully represent the desired colour. It focuses on how to construct a spectrum of wavelengths that will best evoke a certain colour in an observer. Most colours are not spectral colours, meaning they are mixtures of various wavelengths of light. However, these non-spectral colours are often described by their dominant wavelength, which identifies the single wavelength of light that produces a sensation most similar to the non-spectral colour. Dominant wavelength is roughly akin to hue. There are many colour perceptions that by definition cannot be pure spectral colours due to desaturation or because they are purples (mixtures of red and violet light, from opposite ends of the spectrum). Some examples of necessarily non-spectral colours are the achromatic colours (black, gray, and white) and colours such as pink, tan, and magenta. Two different light spectra that have the same effect on the three colour receptors in the human eye will be perceived as the same colour. They are metamers of that colour. This is exemplified by the white light emitted by fluorescent lamps, which typically has a spectrum of a few narrow bands, while daylight has a continuous spectrum. The human eye cannot tell the difference between such light spectra just by looking into the light source, although the colour rendering index of each light source may affect the colour of objects illuminated by these metameric light sources. Similarly, most human colour perceptions can be generated by a mixture of three colours called primaries. This is used to reproduce colour scenes in photography, printing, television, and other media. There are a number of methods or colour spaces for specifying a colour in terms of three particular primary colours. Each method has its advantages and disadvantages depending on the particular application. No mixture of colours, however, can produce a response truly identical to that of a spectral colour, although one can get close, especially for the longer wavelengths, where the CIE 1931 colour space chromaticity diagram has a nearly straight edge. For example, mixing green light (530 nm) and blue light (460 nm) produces cyan light that is slightly desaturated, because response of the red colour receptor would be greater to the green and blue light in the mixture than it would be to a pure cyan light at 485 nm that has the same intensity as the mixture of blue and green. Because of this, and because the primaries in colour printing systems generally are not pure themselves, the colours reproduced are never perfectly saturated spectral colours, and so spectral colours cannot be matched exactly. However, natural scenes rarely contain fully saturated colours, thus such scenes can usually be approximated well by these systems. The range of colours that can be reproduced with a given colour reproduction system is called the gamut. The CIE chromaticity diagram can be used to describe the gamut. Another problem with colour reproduction systems is connected with the initial measurement of colour, or colourimetry. The characteristics of the colour sensors in measurement devices (e.g. cameras, scanners) are often very far from the characteristics of the receptors in the human eye. A colour reproduction system "tuned" to a human with normal colour vision may give very inaccurate results for other observers, according to colour vision deviations to the standard observer. The different colour response of different devices can be problematic if not properly managed. For colour information stored and transferred in digital form, colour management techniques, such as those based on ICC profiles, can help to avoid distortions of the reproduced colours. Colour management does not circumvent the gamut limitations of particular output devices, but can assist in finding good mapping of input colours into the gamut that can be reproduced. Additive colouring Additive colour mixing: combining red and green yields yellow; combining all three primary colours together yields white. Additive colour is light created by mixing together light of two or more different colours. Red, green, and blue are the additive primary colours normally used in additive colour systems such as projectors, televisions, and computer terminals. Subtractive colouring Subtractive colour mixing: combining yellow and magenta yields red; combining all three primary colours together yields black. Twelve main pigment colours Subtractive colouring uses dyes, inks, pigments, or filters to absorb some wavelengths of light and not others. The colour that a surface displays comes from the parts of the visible spectrum that are not absorbed and therefore remain visible. Without pigments or dye, fabric fibers, paint base and paper are usually made of particles that scatter white light (all colours) well in all directions. When a pigment or ink is added, wavelengths are absorbed or "subtracted" from white light, so light of another colour reaches the eye. If the light is not a pure white source (the case of nearly all forms of artificial lighting), the resulting spectrum will appear a slightly different colour. Red paint, viewed under blue light, may appear black. Red paint is red because it scatters only the red components of the spectrum. If red paint is illuminated by blue light, it will be absorbed by the red paint, creating the appearance of a black object. The subtractive model also predicts the colour resulting from a mixture of paints, or similar medium such as fabric dye, whether applied in layers or mixed together prior to application. In the case of paint mixed before application, incident light interacts with many different pigment particles at various depths inside the paint layer before emerging. Structural colour Further information: Structural coloration and Animal coloration Structural colours are colours caused by interference effects rather than by pigments. Colour effects are produced when a material is scored with fine parallel lines, formed of one or more parallel thin layers, or otherwise composed of microstructures on the scale of the colour's wavelength. If the microstructures are spaced randomly, light of shorter wavelengths will be scattered preferentially to produce Tyndall effect colours: the blue of the sky (Rayleigh scattering, caused by structures much smaller than the wavelength of light, in this case, air molecules), the luster of opals, and the blue of human irises. If the microstructures are aligned in arrays, for example, the array of pits in a CD, they behave as a diffraction grating: the grating reflects different wavelengths in different directions due to interference phenomena, separating mixed "white" light into light of different wavelengths. If the structure is one or more thin layers then it will reflect some wavelengths and transmit others, depending on the layers' thickness. Structural colour is studied in the field of thin-film optics. The most ordered or the most changeable structural colours are iridescent. Structural colour is responsible for the blues and greens of the feathers of many birds (the blue jay, for example), as well as certain butterfly wings and beetle shells. Variations in the pattern's spacing often give rise to an iridescent effect, as seen in peacock feathers, soap bubbles, films of oil, and mother of pearl, because the reflected colour depends upon the viewing angle. Numerous scientists have carried out research in butterfly wings and beetle shells, including Isaac Newton and Robert Hooke. Since 1942, electron micrography has been used, advancing the development of products that exploit structural colour, such as "photonic" cosmetics. Cultural perspective Colours, their meanings and associations can play a major role in works of art, including literature. Associations Individual colours have a variety of cultural associations such as national colours (in general described in individual colour articles and colour symbolism). The field of colour psychology attempts to identify the effects of colour on human emotion and activity. Chromotherapy is a form of alternative medicine attributed to various Eastern traditions. Colours have different associations in different countries and cultures. Different colours have been demonstrated to have effects on cognition. For example, researchers at the University of Linz in Austria demonstrated that the colour red significantly decreases cognitive functioning in men. The combination of the colours red and yellow together can induce hunger, which has been capitalised on by a number of chain restaurants. colour plays a role in memory development too. A photograph that is in black and white is slightly less memorable than one in colour. Studies also show that wearing bright colours makes you more memorable to people you meet. Terminology Main article: Color term See also: Lists of colors and Web colors olours vary in several different ways, including hue (shades of red, orange, yellow, green, blue, and violet, etc), saturation, brightness. Some colour words are derived from the name of an object of that colour, such as "orange" or "salmon", while others are abstract, like "red". In the 1969 study Basic colour Terms: Their Universality and Evolution, Brent Berlin and Paul Kay describe a pattern in naming "basic" colours (like "red" but not "red-orange" or "dark red" or "blood red", which are "shades" of red). All languages that have two "basic" colour names distinguish dark/cool colours from bright/warm colours. The next colours to be distinguished are usually red and then yellow or green. All languages with six "basic" colours include black, white, red, green, blue, and yellow. The pattern holds up to a set of twelve: black, gray, white, pink, red, orange, yellow, green, blue, purple, brown, and azure (distinct from blue in Russian and Italian, but not English). See also Chromophore colour analysis colour in Chinese culture colour mapping Complementary colours Impossible colour International colour Consortium International Commission on Illumination Lists of colours (compact version) Neutral colour Pearlescent coating including Metal effect pigments Pseudocolour Primary, secondary and tertiary colours	biology	3298716	https://sv.wikipedia.org/wiki/Lampria%20bicolor	Lampria bicolor	Lampria bicolor är en tvåvingeart som först beskrevs av Christian Rudolph Wilhelm Wiedemann 1828. Lampria bicolor ingår i släktet Lampria och familjen rovflugor. Inga underarter finns listade i Catalogue of Life. Källor Rovflugor bicolor	swedish	1.211356
reddish_adapt_to_color/Red.txt	Red is the color at the long wavelength end of the visible spectrum of light, next to orange and opposite violet. It has a dominant wavelength of approximately 625–740 nanometres. It is a primary color in the RGB color model and a secondary color (made from magenta and yellow) in the CMYK color model, and is the complementary color of cyan. Reds range from the brilliant yellow-tinged scarlet and vermillion to bluish-red crimson, and vary in shade from the pale red pink to the dark red burgundy. Red pigment made from ochre was one of the first colors used in prehistoric art. The Ancient Egyptians and Mayans colored their faces red in ceremonies; Roman generals had their bodies colored red to celebrate victories. It was also an important color in China, where it was used to color early pottery and later the gates and walls of palaces. In the Renaissance, the brilliant red costumes for the nobility and wealthy were dyed with kermes and cochineal. The 19th century brought the introduction of the first synthetic red dyes, which replaced the traditional dyes. Red became a symbolic color of communism and socialism; Soviet Russia adopted a red flag following the Bolshevik Revolution in 1917. The Soviet red banner would subsequently be used throughout the entire history of the Soviet Union, starting from 1922 and ending with its 1991 dissolution. China adopted its own red flag following the Chinese Revolution of 1949. A red flag was also adopted by North Vietnam in 1954, and by all of Vietnam in 1975. Since red is the color of blood, it has historically been associated with sacrifice, danger, and courage. Modern surveys in Europe and the United States show red is also the color most commonly associated with heat, activity, passion, sexuality, anger, love, and joy. In China, India, and many other Asian countries it is the color symbolizing happiness and good fortune. Shades and variations Main article: Shades of red Varieties of the color red may differ in hue, chroma (also called saturation, intensity, or colorfulness), or lightness (or value, tone, or brightness), or in two or three of these qualities. Variations in value are also called tints and shades, a tint being a red or other hue mixed with white, a shade being mixed with black. Four examples are shown below. The cardinal takes its name from the color worn by Catholic cardinals.Pink is a pale shade of red. Cherry blossoms in the Tsutsujigaoka Park, Sendai, Miyagi, Japan.Vermilion is similar to scarlet, but slightly more orange. This is sindoor, a red cosmetic powder used in India; some Hindu women put a stripe of sindoor in their hair to show they are married.Ruby is the color of a cut and polished ruby gemstone. In science and nature Seeing red Bulls, like dogs and many other animals, have dichromacy, which means they cannot distinguish the color red. They charge the matador's cape because of its motion, not its color. The human eye sees red when it looks at light with a wavelength between approximately 625 and 740 nanometers. It is a primary color in the RGB color model and the light just past this range is called infrared, or below red, and cannot be seen by human eyes, although it can be sensed as heat. In the language of optics, red is the color evoked by light that stimulates neither the S or the M (short and medium wavelength) cone cells of the retina, combined with a fading stimulation of the L (long-wavelength) cone cells. Primates can distinguish the full range of the colors of the spectrum visible to humans, but many kinds of mammals, such as dogs and cattle, have dichromacy, which means they can see blues and yellows, but cannot distinguish red and green (both are seen as gray). Bulls, for instance, cannot see the red color of the cape of a bullfighter, but they are agitated by its movement. (See color vision). One theory for why primates developed sensitivity to red is that it allowed ripe fruit to be distinguished from unripe fruit and inedible vegetation. This may have driven further adaptations by species taking advantage of this new ability, such as the emergence of red faces. Red light is used to help adapt night vision in low-light or night time, as the rod cells in the human eye are not sensitive to red. In color theory and on a computer screen In the RYB color model, which is the basis of traditional color theory, red is one of the three primary colors, along with blue and yellow. Painters in the Renaissance mixed red and blue to make violet: Cennino Cennini, in his 15th-century manual on painting, wrote, "If you want to make a lovely violet colour, take fine lac (red lake), ultramarine blue (the same amount of the one as of the other) with a binder"; he noted that it could also be made by mixing blue indigo and red hematite. In the CMY and CMYK color models, red is a secondary color subtractively mixed from magenta and yellow. In the RGB color model, red, green and blue are additive primary colors. Red, green and blue light combined makes white light, and these three colors, combined in different mixtures, can produce nearly any other color. This principle is used to generate colors on such as computer monitors and televisions. For example, magenta on a computer screen is made by a similar formula to that used by Cennino Cennini in the Renaissance to make violet, but using additive colors and light instead of pigment: it is created by combining red and blue light at equal intensity on a black screen. Violet is made on a computer screen in a similar way, but with a greater amount of blue light and less red light. In a traditional color wheel from 1708, red, yellow and blue are primary colors. Red and yellow make orange; red and blue make violet. In modern color theory, red, green and blue are the additive primary colors, and together they make white. A combination of red, green and blue light in varying proportions makes all the colors on your computer screen and television screen. Tiny Red, green and blue sub-pixels (enlarged on left side of image) create the colors you see on your computer screen and TV. Color of sunset Main article: Sunset § Colors Sunsets and sunrises are often red because of an optical effect called Rayleigh scattering. As a ray of white sunlight travels through the atmosphere to the eye, some of the colors are scattered out of the beam by air molecules and airborne particles due to Rayleigh scattering, changing the final color of the beam that is seen. Colors with a shorter wavelength, such as blue and green, scatter more strongly, and are removed from the light that finally reaches the eye. At sunrise and sunset, when the path of the sunlight through the atmosphere to the eye is longest, the blue and green components are removed almost completely, leaving the longer wavelength orange and red light. The remaining reddened sunlight can also be scattered by cloud droplets and other relatively large particles, which give the sky above the horizon its red glow. Lasers Lasers emitting in the red region of the spectrum have been available since the invention of the ruby laser in 1960. In 1962 the red helium–neon laser was invented, and these two types of lasers were widely used in many scientific applications including holography, and in education. Red helium–neon lasers were used commercially in LaserDisc players. The use of red laser diodes became widespread with the commercial success of modern DVD players, which use a 660 nm laser diode technology. Today, red and red-orange laser diodes are widely available to the public in the form of extremely inexpensive laser pointers. Portable, high-powered versions are also available for various applications. More recently, 671 nm diode-pumped solid state (DPSS) lasers have been introduced to the market for all-DPSS laser display systems, particle image velocimetry, Raman spectroscopy, and holography. Red's wavelength has been an important factor in laser technologies; red lasers, used in early compact disc technologies, are being replaced by blue lasers, as red's longer wavelength causes the laser's recordings to take up more space on the disc than would blue-laser recordings. Astronomy Mars is called the Red Planet because of the reddish color imparted to its surface by the abundant iron oxide present there. Astronomical objects that are moving away from the observer exhibit a Doppler red shift. Jupiter's surface displays a Great Red Spot caused by an oval-shaped mega storm south of the planet's equator. Red giants are stars that have exhausted the supply of hydrogen in their cores and switched to thermonuclear fusion of hydrogen in a shell that surrounds its core. They have radii tens to hundreds of times larger than that of the Sun. However, their outer envelope is much lower in temperature, giving them an orange hue. Despite the lower energy density of their envelope, red giants are many times more luminous than the Sun due to their large size. Red supergiants like Betelgeuse, Antares, Mu Cephei, VV Cephei, and VY Canis Majoris one of the biggest stars in the Universe, are the biggest variety of red giants. They are huge in size, with radii 200 to 1700 times greater than the Sun, but relatively cool in temperature (3000–4500 K), causing their distinct red tint. Because they are shrinking rapidly in size, they are surrounded by an envelope or skin much bigger than the star itself. The envelope of Betelgeuse is 250 times bigger than the star inside. A red dwarf is a small and relatively cool star, which has a mass of less than half that of the Sun and a surface temperature of less than 4,000 K. Red dwarfs are by far the most common type of star in the Galaxy, but due to their low luminosity, from Earth, none are visible to the naked eye. Interstellar reddening is caused by the extinction of radiation by dust and gas Mars appears to be red because of iron oxide on its surface. Mira, a red giant Artist's impression of a red dwarf, a small, relatively cool star that appears red due to its temperature Pigments and dyes See also: Red pigments Red ochre cliffs near Roussillon in France. Red ochre is composed of clay tinted with hematite. Ochre was the first pigment used by man in prehistoric cave paintings. Vermilion pigment, made from cinnabar. This was the pigment used in the murals of Pompeii and to color Chinese lacquerware beginning in the Song dynasty. Red lead, also known as minium, has been used since the time of the ancient Greeks. Chemically it is known as lead tetroxide. The Romans prepared it by the roasting of lead white pigment. It was commonly used in the Middle Ages for the headings and decoration of illuminated manuscripts. The roots of the Rubia tinctorum, or madder plant, produced the most common red dye used from ancient times until the 19th century. Alizarin was the first synthetic red dye, created by German chemists in 1868. It duplicated the colorant in the madder plant, but was cheaper and longer lasting. After its introduction, the production of natural dyes from the madder plant virtually ceased. Food coloring The most common synthetic food coloring today is Allura Red AC, a red azo dye that goes by several names including: Allura Red, Food Red 17, C.I. 16035, FD&C Red 40, It was originally manufactured from coal tar, but now is mostly made from petroleum. In Europe, Allura Red AC is not recommended for consumption by children. It is banned in Denmark, Belgium, France and Switzerland, and was also banned in Sweden until the country joined the European Union in 1994. The European Union approves Allura Red AC as a food colorant, but EU countries' local laws banning food colorants are preserved. In the United States, Allura Red AC is approved by the Food and Drug Administration (FDA) for use in cosmetics, drugs, and food. It is used in some tattoo inks and is used in many products, such as soft drinks, children's medications, and cotton candy. On June 30, 2010, the Center for Science in the Public Interest (CSPI) called for the FDA to ban Red 40. Because of public concerns about possible health risks associated with synthetic dyes, many companies have switched to using natural pigments such as carmine, made from crushing the tiny female cochineal insect. This insect, originating in Mexico and Central America, was used to make the brilliant scarlet dyes of the European Renaissance. Autumn leaves This section needs additional citations for verification. Please help improve this article by adding citations to reliable sources in this section. Unsourced material may be challenged and removed.Find sources: "Red" – news · newspapers · books · scholar · JSTOR (July 2021) (Learn how and when to remove this template message) The red of autumn leaves is produced by pigments called anthocyanins. They are not present in the leaf throughout the growing season, but are actively produced towards the end of summer. They develop in late summer in the sap of the cells of the leaf, and this development is the result of complex interactions of many influences—both inside and outside the plant. Their formation depends on the breakdown of sugars in the presence of bright light as the level of phosphate in the leaf is reduced. During the summer growing season, phosphate is at a high level. It has a vital role in the breakdown of the sugars manufactured by chlorophyll. But in the fall, phosphate, along with the other chemicals and nutrients, moves out of the leaf into the stem of the plant. When this happens, the sugar-breakdown process changes, leading to the production of anthocyanin pigments. The brighter the light during this period, the greater the production of anthocyanins and the more brilliant the resulting color display. When the days of autumn are bright and cool, and the nights are chilly but not freezing, the brightest colorations usually develop. Anthocyanins temporarily color the edges of some of the very young leaves as they unfold from the buds in early spring. They also give the familiar color to such common fruits as cranberries, red apples, blueberries, cherries, raspberries, and plums. Anthocyanins are present in about 10% of tree species in temperate regions, although in certain areas—a famous example being New England—up to 70% of tree species may produce the pigment. In autumn forests they appear vivid in the maples, oaks, sourwood, sweetgums, dogwoods, tupelos, cherry trees and persimmons. These same pigments often combine with the carotenoids' colors to create the deeper orange, fiery reds, and bronzes typical of many hardwood species. (See Autumn leaf color). Blood and other reds in nature This section needs additional citations for verification. Please help improve this article by adding citations to reliable sources in this section. Unsourced material may be challenged and removed.Find sources: "Red" – news · newspapers · books · scholar · JSTOR (July 2021) (Learn how and when to remove this template message) Oxygenated blood is red due to the presence of oxygenated hemoglobin that contains iron molecules, with the iron components reflecting red light. Red meat gets its color from the iron found in the myoglobin and hemoglobin in the muscles and residual blood. Plants like apples, strawberries, cherries, tomatoes, peppers, and pomegranates are often colored by forms of carotenoids, red pigments that also assist photosynthesis. Red blood cell agar. Blood appears red due to the iron molecules in blood cells. A red setter or Irish setter A pair of European red foxes The European robin or robin redbreast Hair color Main article: Red hair Red hair only occurs in 1–2% of the human population. Red hair occurs naturally on approximately 1–2% of the human population. It occurs more frequently (2–6%) in people of northern or western European ancestry, and less frequently in other populations. Red hair appears in people with two copies of a recessive gene on chromosome 16 which causes a mutation in the MC1R protein. Red hair varies from a deep burgundy through burnt orange to bright copper. It is characterized by high levels of the reddish pigment pheomelanin (which also accounts for the red color of the lips) and relatively low levels of the dark pigment eumelanin. The term "redhead" (originally redd hede) has been in use since at least 1510. In animal and human behavior Red is associated with dominance in a number of animal species. For example, in mandrills, red coloration of the face is greatest in alpha males, increasingly less prominent in lower ranking subordinates, and directly correlated with levels of testosterone. Red can also affect the perception of dominance by others, leading to significant differences in mortality, reproductive success and parental investment between individuals displaying red and those not. In humans, wearing red has been linked with increased performance in competitions, including professional sport and multiplayer video games. Controlled tests have demonstrated that wearing red does not increase performance or levels of testosterone during exercise, so the effect is likely to be produced by perceived rather than actual performance. Judges of tae kwon do have been shown to favor competitors wearing red protective gear over blue, and, when asked, a significant majority of people say that red abstract shapes are more "dominant", "aggressive", and "likely to win a physical competition" than blue shapes. In contrast to its positive effect in physical competition and dominance behavior, exposure to red decreases performance in cognitive tasks and elicits aversion in psychological tests where subjects are placed in an "achievement" context (e.g. taking an IQ test). History and art See also: History of red In prehistory and the ancient world Bison in red ochre in the Cave of Altamira, Spain, from upper Paleolithic era (36,000 BC) Image of a human hand created with red ochre in Pech Merle cave, France (Gravettian era, 25,000 BC) The Prince of Lilies, from the Bronze Age Palace of Minos at Knossos on Crete Roman wall painting showing a dye shop, Pompeii (40 BC) Inside cave 13B at Pinnacle Point, an archeological site found on the coast of South Africa, paleoanthropologists in 2000 found evidence that, between 170,000 and 40,000 years ago, Late Stone Age people were scraping and grinding ochre, a clay colored red by iron oxide, probably with the intention of using it to color their bodies. Red hematite powder was also found scattered around the remains at a grave site in a Zhoukoudian cave complex near Beijing. The site has evidence of habitation as early as 700,000 years ago. The hematite might have been used to symbolize blood in an offering to the dead. Red, black and white were the first colors used by artists in the Upper Paleolithic age, probably because natural pigments such as red ochre and iron oxide were readily available where early people lived. Madder, a plant whose root could be made into a red dye, grew widely in Europe, Africa and Asia. The cave of Altamira in Spain has a painting of a bison colored with red ochre that dates to between 15,000 and 16,500 BC. A red dye called Kermes was made beginning in the Neolithic Period by drying and then crushing the bodies of the females of a tiny scale insect in the genus Kermes, primarily Kermes vermilio. The insects live on the sap of certain trees, especially Kermes oak trees near the Mediterranean region. Jars of kermes have been found in a Neolithic cave-burial at Adaoutse, Bouches-du-Rhône. Kermes from oak trees was later used by Romans, who imported it from Spain. A different variety of dye was made from Porphyrophora hamelii (Armenian cochineal) scale insects that lived on the roots and stems of certain herbs. It was mentioned in texts as early as the 8th century BC, and it was used by the ancient Assyrians and Persians. Red hematite powder was also found scattered around the remains at a grave site in a Zhoukoudian cave complex near Beijing. The site has evidence of habitation as early as 700,000 years ago. The hematite might have been used to symbolize blood in an offering to the dead. In ancient Egypt, red was associated with life, health, and victory. Egyptians would color themselves with red ochre during celebrations. Egyptian women used red ochre as a cosmetic to redden cheeks and lips and also used henna to color their hair and paint their nails. The ancient Romans wore togas with red stripes on holidays, and the bride at a wedding wore a red shawl, called a flammeum. Red was used to color statues and the skin of gladiators. Red was also the color associated with army; Roman soldiers wore red tunics, and officers wore a cloak called a paludamentum which, depending upon the quality of the dye, could be crimson, scarlet or purple. In Roman mythology red is associated with the god of war, Mars. The vexilloid of the Roman Empire had a red background with the letters SPQR in gold. A Roman general receiving a triumph had his entire body painted red in honor of his achievement. The Romans liked bright colors, and many Roman villas were decorated with vivid red murals. The pigment used for many of the murals was called vermilion, and it came from the mineral cinnabar, a common ore of mercury. It was one of the finest reds of ancient times – the paintings have retained their brightness for more than twenty centuries. The source of cinnabar for the Romans was a group of mines near Almadén, southwest of Madrid, in Spain. Working in the mines was extremely dangerous, since mercury is highly toxic; the miners were slaves or prisoners, and being sent to the cinnabar mines was a virtual death sentence. The Middle Ages Roman Catholic Popes wear red as the symbol of the blood of Christ. This is Pope Innocent III, in about 1219. Red was the traditional color of martyrs. A Russian icon of Saint George (14th c.). The colour of majesty - portrait of Charlemagne, King of the Franks and Holy Roman Emperor, Netherlands (14th c.) After the fall of the Western Roman Empire, red was adopted as a color of majesty and authority by the Byzantine Empire, and the princes of Europe. It also played an important part in the rituals of the Roman Catholic Church, symbolizing the blood of Christ and the Christian martyrs. In Western Europe, Emperor Charlemagne painted his palace red as a very visible symbol of his authority, and wore red shoes at his coronation. Kings, princes and, beginning in 1295, Roman Catholic cardinals began to wear red colored habitus. When Abbe Suger rebuilt Saint Denis Basilica outside Paris in the early 12th century, he added stained glass windows colored blue cobalt glass and red glass tinted with copper. Together they flooded the basilica with a mystical light. Soon stained glass windows were being added to cathedrals all across France, England and Germany. In medieval painting red was used to attract attention to the most important figures; both Christ and the Virgin Mary were commonly painted wearing red mantles. In western countries red is a symbol of martyrs and sacrifice, particularly because of its association with blood. Beginning in the Middle Ages, the Pope and Cardinals of the Roman Catholic Church wore red to symbolize the blood of Christ and the Christian martyrs. The banner of the Christian soldiers in the First Crusade was a red cross on a white field, the St. George's Cross. According to Christian tradition, Saint George was a Roman soldier who was a member of the guards of the Emperor Diocletian, who refused to renounce his Christian faith and was martyred. The Saint George's Cross became the Flag of England in the 16th century, and now is part of the Union Flag of the United Kingdom, as well as the Flag of the Republic of Georgia. Renaissance The young Queen Elizabeth I (here in about 1563) The Wedding Dance (1566), by Pieter Bruegel the Elder The Girl with the Wine Glass, by Johannes Vermeer (1659–60) Princess Anne of Denmark (later Queen Anne of Great Britain) (1685) In Renaissance painting, red was used to draw the attention of the viewer; it was often used as the color of the cloak or costume of Christ, the Virgin Mary, or another central figure. In Venice, Titian was the master of fine reds, particularly vermilion; he used many layers of pigment mixed with a semi-transparent glaze, which let the light pass through, to create a more luminous color. The figures of God, the Virgin Mary and two apostles are highlighted by their vermilion red costumes. Queen Elizabeth I of England liked to wear bright reds, before she adopted the more sober image of the "Virgin Queen". Red costumes were not limited to the upper classes. In Renaissance Flanders, people of all social classes wore red at celebrations. One such celebration was captured in The Wedding Dance (1566) by Pieter Bruegel the Elder. The painter Johannes Vermeer skilfully used different shades and tints of vermilion to paint the red skirt in The Girl with the Wine Glass, then glazed it with madder lake to make a more luminous color. Reds from the New World Textiles dyed red from the Paracas culture of Peru (about 200 BC), in the British Museum Feather headdress from the Aztec people of Mexico and Central America, dyed with cochineal A native of Central America collecting cochineal insects from a cactus to make red dye (1777) In Latin America, the Aztec people, the Paracas culture and other societies used cochineal, a vivid scarlet dye made from insects. From the 16th until the 19th century, cochineal became a highly profitable export from Spanish Mexico to Europe. 18th to 20th century King Joseph I of Portugal (1773) The Brazilian imperial family (1857) King Edward VII of the United Kingdom (1901) Red flag of the Bolsheviks, by Boris Kustodiev (1920) Chinese honour guard, Beijing, 2007 In the 18th century, red began to take on a new identity as the colour of resistance and revolution. It was already associated with blood, and with danger; a red flag hoisted before a battle meant that no prisoners would be taken. In 1793-94, red became the colour of the French Revolution. A red Phrygian cap, or "liberty cap", was part of the uniform of the sans-culottes, the most militant faction of the revolutionaries. In the late 18th century, during a strike English dock workers carried red flags, and it thereafter became closely associated with the new labour movement, and later with the Labour Party in the United Kingdom, founded in 1900. In Paris in 1832, a red flag was carried by working-class demonstrators in the failed June Rebellion, an event immortalised in Les Misérables), and later in the 1848 French Revolution. The red flag was proposed as the new national French flag during the 1848 revolution, but was rejected by at the urging of the poet and statesman Alphonse Lamartine in favour of the tricolour flag. It appeared again as the flag of the short-lived Paris Commune in 1871. It was then adopted by Karl Marx and the new European movements of socialism and communism. Soviet Russia adopted a red flag following the Bolshevik Revolution in 1917. Communist China adopted the red flag following the Chinese Revolution of 1949. It was adopted by North Vietnam in 1954, and by all of Vietnam in 1975. Symbolism Courage and sacrifice Surveys show that red is the color most associated with courage. In western countries red is a symbol of martyrs and sacrifice, particularly because of its association with blood. Beginning in the Middle Ages, the Pope and Cardinals of the Roman Catholic Church wore red to symbolize the blood of Christ and the Christian martyrs. The banner of the Christian soldiers in the First Crusade was a red cross on a white field, the St. George's Cross. According to Christian tradition, Saint George was a Roman soldier who was a member of the guards of the Emperor Diocletian, who refused to renounce his Christian faith and was martyred. The Saint George's Cross became the Flag of England in the 16th century, and now is part of the Union Flag of the United Kingdom, as well as the Flag of the Republic of Georgia. Robert Gibb's 1881 painting, The Thin Red Line, depicting The Thin Red Line at the Battle of Balaclava (1854), when a line of the Scottish Highland infantry repulsed a Russian cavalry charge. The name was given by the British press as a symbol of courage against the odds. The red poppy flower is worn on Remembrance Day in Commonwealth countries to honor soldiers who died in the First World War. Hatred, anger, aggression, passion, heat and war While red is the color most associated with love, it also the color most frequently associated with hatred, anger, aggression and war. People who are angry are said to "see red." Red is the color most commonly associated with passion and heat. In ancient Rome, red was the color of Mars, the god of war—the planet Mars was named for him because of its red color. Warning and danger Red is the traditional color of warning and danger, and is therefore often used on flags. In the Middle Ages up through the French Revolution, a red flag shown in warfare indicated the intent to take no prisoners. Similarly, a red flag hoisted by a pirate ship meant no mercy would be shown to their target. In Britain, in the early days of motoring, motor cars had to follow a man with a red flag who would warn horse-drawn vehicles, before the Locomotives on Highways Act 1896 abolished this law. In automobile races, the red flag is raised if there is danger to the drivers. In international football, a player who has made a serious violation of the rules is shown a red penalty card and ejected from the game. Several studies have indicated that red carries the strongest reaction of all the colors, with the level of reaction decreasing gradually with the colors orange, yellow, and white, respectively. For this reason, red is generally used as the highest level of warning, such as threat level of terrorist attack in the United States. In fact, teachers at a primary school in the UK have been told not to mark children's work in red ink because it encourages a "negative approach". Red is the international color of stop signs and stop lights on highways and intersections. It was standardized as the international color at the Vienna Convention on Road Signs and Signals of 1968. It was chosen partly because red is the brightest color in daytime (next to orange), though it is less visible at twilight, when green is the most visible color. Red also stands out more clearly against a cool natural backdrop of blue sky, green trees or gray buildings. But it was mostly chosen as the color for stoplights and stop signs because of its universal association with danger and warning. The 1968 Vienna Convention on Road Signs and Signals of 1968 uses red color also for the margin of danger warning sign, give way signs and prohibitory signs, following the previous German-type signage (established by Verordnung über Warnungstafeln für den Kraftfahrzeugverkehr in 1927). The standard international stop sign, following the Vienna Convention on Road Signs and Signals of 1968 A footballer is shown a red card and ejected from a soccer match. A red Chinese typhoon alert sign Red is the color of a severe terrorist threat level in the United States, under the Homeland Security Advisory System. Red is the color of extreme fire danger in Australia; new black/red stripes are an even more catastrophic hazard. The color that attracts attention Fashion model Magdalena Frackowiak at Paris Fashion Week (Fall 2011) Red is the color that most attracts attention. Surveys show it is the color most frequently associated with visibility, proximity, and extroverts. It is also the color most associated with dynamism and activity. Red is used in modern fashion much as it was used in Medieval painting; to attract the eyes of the viewer to the person who is supposed to be the center of attention. People wearing red seem to be closer than those dressed in other colors, even if they are actually the same distance away. Monarchs, wives of presidential candidates and other celebrities often wear red to be visible from a distance in a crowd. It is also commonly worn by lifeguards and others whose job requires them to be easily found. Because red attracts attention, it is frequently used in advertising, though studies show that people are less likely to read something printed in red because they know it is advertising, and because it is more difficult visually to read than black and white text. Seduction, sexuality and sin Red by a large margin is the color most commonly associated with seduction, sexuality, eroticism and immorality, possibly because of its close connection with passion and with danger. Red was long seen as having a dark side, particularly in Christian theology. It was associated with sexual passion, anger, sin, and the devil. In the Old Testament of the Bible, the Book of Isaiah said: "Though your sins be as scarlet, they shall be white as snow." In the New Testament, in the Book of Revelation, the Antichrist appears as a red monster, ridden by a woman dressed in scarlet, known as the Whore of Babylon. Satan is often depicted as colored red and/or wearing a red costume in both iconography and popular culture. By the 20th century, the devil in red had become a folk character in legends and stories. The devil in red appears more often in cartoons and movies than in religious art. In 17th-century New England, red was associated with adultery. In the 1850 novel by Nathaniel Hawthorne, The Scarlet Letter, set in a Puritan New England community, a woman is punished for adultery with ostracism, her sin represented by a red letter 'A' sewn onto her clothes. Red is still commonly associated with prostitution. At various points in history, prostitutes were required to wear red to announce their profession. Houses of prostitution displayed a red light. Beginning in the early 20th century, houses of prostitution were allowed only in certain specified neighborhoods, which became known as red-light districts. Large red-light districts are found today in Bangkok and Amsterdam. In the handkerchief code, the color red signifies interest in the sexual act of fisting. In both Christian and Hebrew tradition, red is also sometimes associated with murder or guilt, with "having blood on one's hands", or "being caught red-handed. The Whore of Babylon, depicted in a 14th-century French illuminated manuscript. The woman appears attractive, but is wearing red under her blue garment. Reine de joie, (Queen of Joy), a book cover illustration by Henri de Toulouse-Lautrec (1892) about a Paris prostitute Sheet music for "At the Devil's Ball", by Irving Berlin, United States, 1915 The red-light district in Amsterdam (2003). Red is the sex industry's preferred color in many cultures, due to being strongly associated with passion, love and sexuality. Red lipstick has been worn by women as a cosmetic since ancient times. It was worn by Cleopatra, Queen Elizabeth I, and film stars such as Elizabeth Taylor and Marilyn Monroe. In religion In Christianity, red is associated with the blood of Christ and the sacrifice of martyrs. In the Roman Catholic Church it is also associated with pentecost and the Holy Spirit. Since 1295, it is the color worn by Cardinals, the senior clergy of the Roman Catholic Church. Red is the liturgical color for the feasts of martyrs, representing the blood of those who suffered death for their faith. It is sometimes used as the liturgical color for Holy Week, including Palm Sunday and Good Friday, although this is a modern (20th-century) development. In Catholic practice, it is also the liturgical color used to commemorate the Holy Spirit (for this reason it is worn at Pentecost and during Confirmation masses). Because of its association with martyrdom and the Spirit, it is also the color used to commemorate saints who were martyred, such as St. George and all the Apostles (except for the Apostle St. John, who was not martyred, where white is used). As such, it is used to commemorate bishops, who are the successors of the Apostles (for this reason, when funeral masses are held for bishops, cardinals, or popes, red is used instead of the white that would ordinarily be used). In Buddhism, red is one of the five colors which are said to have emanated from the Buddha when he attained enlightenment, or nirvana. It is particularly associated with the benefits of the practice of Buddhism; achievement, wisdom, virtue, fortune and dignity. It was also believed to have the power to resist evil. In China red was commonly used for the walls, pillars, and gates of temples. In the Shinto religion of Japan, the gateways of temples, called torii, are traditionally painted vermilion red and black. The torii symbolizes the passage from the profane world to a sacred place. The bridges in the gardens of Japanese temples are also painted red (and usually only temple bridges are red, not bridges in ordinary gardens), since they are also passages to sacred places. Red was also considered a color which could expel evil and disease. In Taoism, red is sometimes used to symbolize yang. In Chinese folk religion, red is also sometimes used to symbolize yang in the context of the creator Pangu, who hatched out of a cosmic egg colored like a taijitu. Some art of Pangu colored yang as red. A Shinto torii at Itsukushima, Japan Cardinals of the Roman Catholic Church at the funeral of Pope John Paul II Buddhist monks in Tibet In Hinduism, red is associated with Lakshmi, the goddess of wealth and embodiment of beauty. Red flags in a celebration of Muharram in Iran Military uses Red uniform This section needs additional citations for verification. Please help improve this article by adding citations to reliable sources in this section. Unsourced material may be challenged and removed.Find sources: "Red" – news · newspapers · books · scholar · JSTOR (July 2021) (Learn how and when to remove this template message) The red military uniform was adopted by the English Parliament's New Model Army in 1645, and was still worn as a dress uniform by the British Army until the outbreak of the First World War in August 1914. Ordinary soldiers wore red coats dyed with madder, while officers wore scarlet coats dyed with the more expensive cochineal. This led to British soldiers being known as red coats. In the modern British army, scarlet is still worn by the Foot Guards, the Life Guards, and by some regimental bands or drummers for ceremonial purposes. Officers and NCOs of those regiments which previously wore red retain scarlet as the color of their "mess" or formal evening jackets. The Royal Gibraltar Regiment has a scarlet tunic in its winter dress. Scarlet is worn for some full dress, military band or mess uniforms in the modern armies of a number of the countries that made up the former British Empire. These include the Australian, Jamaican, New Zealand, Fijian, Canadian, Kenyan, Ghanaian, Indian, Singaporean, Sri Lankan and Pakistani armies. The musicians of the United States Marine Corps Band wear red, following an 18th-century military tradition that the uniforms of band members are the reverse of the uniforms of the other soldiers in their unit. Since the US Marine uniform is blue with red facings, the band wears the reverse. Red Serge is the uniform of the Royal Canadian Mounted Police, created in 1873 as the North-West Mounted Police, and given its present name in 1920. The uniform was adapted from the tunic of the British Army. Cadets at the Royal Military College of Canada also wear red dress uniforms. The Brazilian Marine Corps wears a red dress uniform. Officer and soldier of the British Army, 1815 The scarlet uniform of the National Guards Unit of Bulgaria Musicians of the United States Marine Corps Band Officer of the Royal Canadian Mounted Police The Brazilian Marine Corps wears a dress uniform called A Garança. Soldiers of the Rajput Regiment of the Indian Army NATO Military Symbols for Land Based Systems uses red to denote hostile forces, hence the terms "red team" and "Red Cell" to denote challengers during exercises. In sports This section needs additional citations for verification. Please help improve this article by adding citations to reliable sources in this section. Unsourced material may be challenged and removed.Find sources: "Red" – news · newspapers · books · scholar · JSTOR (July 2021) (Learn how and when to remove this template message) The first known team sport to feature red uniforms was chariot racing during the late Roman Empire. The earliest races were between two chariots, one driver wearing red, the other white. Later, the number of teams was increased to four, including drivers in light green and sky blue. Twenty-five races were run in a day, with a total of one hundred chariots participating. Today many sports teams throughout the world feature red on their uniforms. Along with blue, red is the most commonly used non-white color in sports. Numerous national sports teams wear red, often through association with their national flags. A few of these teams feature the color as part of their nickname such as Spain (with their association football (soccer) national team nicknamed La Furia Roja or "The Red Fury") and Belgium (whose football team bears the nickname Rode Duivels or "Red Devils"). In club association football (soccer), red is a commonly used color throughout the world. Among European notable club teams most often playing at home in red shirts include Bayern Munich, Benfica, Liverpool, Manchester United and Roma. Furthermore, many prominent teams play in partially red color schemes, involving different-colored sleeves or stripes. A number of teams' nicknames feature the color. A red penalty card is issued to a player who commits a serious infraction: the player is immediately disqualified from further play and his team must continue with one fewer player for the game's duration. Rosso Corsa is the red international motor racing color of cars entered by teams from Italy. Since the 1920s Italian race cars of Alfa Romeo, Maserati, Lancia, and later Ferrari and Abarth have been painted with a color known as rosso corsa ("racing red"). National colors were mostly replaced in Formula One by commercial sponsor liveries in 1968, but unlike most other teams, Ferrari always kept the traditional red, although the shade of the color varies. Ducati traditionally run red factory bikes in motorcycle World Championship racing. The color is commonly used for professional sports teams in Canada and the United States with eleven Major League Baseball teams, eleven National Hockey League teams, seven National Football League teams and eleven National Basketball Association teams prominently featuring some shade of the color. The color is also featured in the league logos of Major League Baseball, the National Football League and the National Basketball Association. In the National Football League, a red flag is thrown by the head coach to challenge a referee's decision during the game. During the 1950s when red was strongly associated with communism in the United States, the modern Cincinnati Reds team was known as the "Redlegs" and the term was used on baseball cards. After the red scare faded, the team was known as the "Reds" again. In boxing, red is often the color used on a fighter's gloves. George Foreman wore the same red trunks he used during his loss to Muhammad Ali when he defeated Michael Moorer 20 years later to regain the title he lost. Boxers named or nicknamed "red" include Red Burman, Ernie "Red" Lopez, and his brother Danny "Little Red" Lopez. Ancient Roman mosaic of the winner of a chariot race, wearing the colors of the red team Both the Cleveland Indians and the Boston Red Sox wear red. In martial arts, a red belt shows a high degree of proficiency, second only, in some schools, to the black belt. An Alfa Romeo Sports Racing car in 1977, painted Rosso Corsa ("racing red"), the traditional racing color of Italy from the 1920s until the late 1960s. On flags See also: Red flag (politics) This section needs additional citations for verification. Please help improve this article by adding citations to reliable sources in this section. Unsourced material may be challenged and removed.Find sources: "Red" – news · newspapers · books · scholar · JSTOR (July 2021) (Learn how and when to remove this template message) Countries with red on their flags; the shades of red correspond to those on their respective flags. Red is the most common color found in national flags, found on the flags of 77 percent of the 210 countries listed as independent in 2016; far ahead of white (58 percent); green (40 percent) and blue (37 percent). The British flag bears the colors red, white and blue; it includes the cross of Saint George, patron saint of England, and the saltire of Saint Patrick, patron saint of Ireland, both of which are red on white. The flag of the United States bears the colors of Britain, the colors of the French tricolore include red as part of the old Paris coat of arms, and other countries' flags, such as those of Australia, New Zealand, and Fiji, carry a small inset of the British flag in memory of their ties to that country. Many former colonies of Spain, such as Mexico, Colombia, Costa Rica, Cuba, Ecuador, Panama, Peru, Puerto Rico and Venezuela, also feature red-one of the colors of the Spanish flag-on their own banners. Red flags are also used to symbolize storms, bad water conditions, and many other dangers. The red on the flag of Nepal represents the floral emblem of the country, the rhododendron. Red, blue, and white are also the Pan-Slavic colors adopted by the Slavic solidarity movement of the late nineteenth century. Initially these were the colors of the Russian flag; as the Slavic movement grew, they were adopted by other Slavic peoples including Slovaks, Slovenes, and Serbs. The flags of the Czech Republic and Poland use red for historic heraldic reasons (see Coat of arms of Poland and Coat of arms of the Czech Republic) & not due to Pan-Slavic connotations. In 2004 Georgia adopted a new white flag, which consists of four small and one big red cross in the middle touching all four sides. Red, white, and black were the colors of the German Empire from 1870 to 1918, and as such they came to be associated with German nationalism. In the 1920s they were adopted as the colors of the Nazi flag. In Mein Kampf, Hitler explained that they were "revered colors expressive of our homage to the glorious past." The red part of the flag was also chosen to attract attention – Hitler wrote: "the new flag ... should prove effective as a large poster" because "in hundreds of thousands of cases a really striking emblem may be the first cause of awakening interest in a movement." The red also symbolized the social program of the Nazis, aimed at German workers. Several designs by a number of different authors were considered, but the one adopted in the end was Hitler's personal design. Red, white, green and black are the colors of Pan-Arabism and are used by many Arab countries. Red, gold, green, and black are the colors of Pan-Africanism. Several African countries thus use the color on their flags, including South Africa, Ghana, Senegal, Mali, Ethiopia, Togo, Guinea, Benin, and Zimbabwe. The Pan-African colors are borrowed from the flag of Ethiopia, one of the oldest independent African countries. Rwanda, notably, removed red from its flag after the Rwandan genocide because of red's association with blood. The flags of Japan and Bangladesh both have a red circle in the middle of different colored backgrounds. The flag of the Philippines has a red trapezoid on the bottom signifying blood, courage, and valor (also, if the flag is inverted so that the red trapezoid is on top and the blue at the bottom, it indicates a state of war). The flag of Singapore has a red rectangle on the top. The field of the flag of Portugal is green and red. The Ottoman Empire adopted several different red flags during the six centuries of its rule, with the successor Republic of Turkey continuing the 1844 Ottoman flag. The flag of the Byzantine Empire from 1260 to its fall in 1453 The St George's cross was the banner of the First Crusade, then, beginning in the 13th century, the flag of England. It is the red color (along with that of the Cross of Saint Patrick) in the flag of the United Kingdom, and, by adoption, of the red in the flag of the United States. The red stripes in the flag of the United States were adapted from the flag of the British East India Company. This is the Grand Union Flag, the first U.S. flag established by the Continental Congress. The Flag of Georgia also features the Saint George's Cross. It dates back to the banner of Medieval Georgia in the 5th century. The maple leaf flag of Canada, adopted in 1965. The red color comes from the Saint George's Cross of England. In politics This section needs additional citations for verification. Please help improve this article by adding citations to reliable sources in this section. Unsourced material may be challenged and removed.Find sources: "Red" – news · newspapers · books · scholar · JSTOR (July 2021) (Learn how and when to remove this template message) The red Phrygian cap worn by sans-culottes during the French Revolution Logo of the German Social Democratic Party In 18th-century Europe, red was usually associated with the monarchy and with those in power. The Pope wore red, as did the Swiss Guards of the Kings of France, the soldiers of the British Army and the Danish Army. In the Roman Empire, freed slaves were given a red Phrygian cap as an emblem of their liberation. Because of this symbolism, the red "Liberty cap" became a symbol of the American patriots fighting for independence from England. During the French Revolution, the Jacobins also adapted the red Phrygian cap, and forced the deposed King Louis XVI to wear one after his arrest. Socialism and communism In the 19th century, with the Industrial Revolution and the rise of worker's movements, red became the color of socialism (especially the Marxist variant), and, with the Paris Commune of 1871, of revolution. In the 20th century, red was the color first of the Russian Bolsheviks and then, after the success of the Russian Revolution of 1917, of communist parties around the world. However, after the fall of the Soviet Union in 1991, Russia went back to the pre-revolutionary blue, white and red flag. Red also became the color of many social democratic parties in Europe, including the Labour Party in Britain (founded 1900); the Social Democratic Party of Germany (whose roots went back to 1863) and the French Socialist Party, which dated back under different names, to 1879. The Socialist Party of America (1901–72) and the Communist Party USA (1919) both also chose red as their color. Members of the Christian-Social People's Party in Liechtenstein (founded 1918) advocated an expansion of democracy and progressive social policies, and were often referred to disparagingly as "Reds" for their social liberal leanings and party colors. The Chinese Communist Party, founded in 1920, adopted the red flag and hammer and sickle emblem of the Soviet Union, which became the national symbols when the Party took power in China in 1949. Under Party leader Mao Zedong, the Party anthem became "The East Is Red", and Mao Zedong himself was sometimes referred to as a "red sun". During the Cultural Revolution in China, Party ideology was enforced by the Red Guards, and the sayings of Mao Zedong were published as a little red book in hundreds of millions of copies. Today the Chinese Communist Party claims to be the largest political party in the world, with eighty million members. Beginning in the 1960s and the 1970s, paramilitary extremist groups such as the Red Army Faction in Germany, the Japanese Red Army and the Shining Path Maoist movement in Peru used red as their color. But in the 1980s, some European socialist and social democratic parties, such as the Labour Party in Britain and the Socialist Party in France, moved away from the symbolism of the far left, keeping the red color but changing their symbol to a less-threatening red rose. Red is used around the world by political parties of the left or center-left. In the United States, it is the color of the Communist Party USA, of the Social Democrats, USA, and in Puerto Rico, of the Popular Democratic Party. United States A map of the U.S. showing the blue states, which voted for the Democratic candidate in the 2008, 2012, 2016, and 2020 presidential elections, and the red states, which voted for the Republican Party In the United States, political commentators often refer to the "red states", which voted for Republican candidates in the last four presidential elections, and "blue states", which voted for Democrats. This convention is relatively recent: before the 2000 presidential election, media outlets assigned red and blue to both parties, sometimes alternating the allocation for each election. Fixed usage was established during the 39-day recount following the 2000 election, when the media began to discuss the contest in terms of "red states" versus "blue states". States which voted for different parties in two of the last four presidential elections are called "Swing States", and are usually coloured purple, a mix of red and blue. Social and special interest groups Such names as Red Club (a bar), Red Carpet (a discothèque) or Red Cottbus and Club Red (event locations) suggest liveliness and excitement. The Red Hat Society is a social group founded in 1998 for women 50 and over. Use of the color red to call attention to an emergency situation is evident in the names of such organizations as the Red Cross (humanitarian aid), Red Hot Organization (AIDS support), and the Red List of Threatened Species (of IUCN). In reference to humans, term "red" is often used in the West to describe the indigenous peoples of the Americas. Idioms Many idiomatic expressions exploit the various connotations of red: Expressing emotion "to see red" (to be angry or aggressive) "to have red ears / a red face" (to be embarrassed) "to paint the town red" (to have an enjoyable evening, usually with a generous amount of eating, drinking, dancing) Giving warning "to raise a red flag" (to signal that something is problematic) "like a red rag to a bull" (to cause someone to be enraged) "to be in the red" (to be losing money, from the accounting convention of writing deficits and losses in red ink) Calling attention "a red letter day" (a special or important event, from the medieval custom of printing the dates of saints' days and holy days in red ink.) "to roll out the red carpet" (to formally welcome an important guest) "to give red-carpet treatment" (to treat someone as important or special) "to catch someone red-handed" (to catch or discover someone doing something bad or wrong) Other idioms "to tie up in red tape". In England red tape was used by lawyers and government officials to identify important documents. It became a term for excessive bureaucratic regulation. It was popularized in the 19th century by the writer Thomas Carlyle, who complained about "red-tapism". "red herring". A false clue that leads investigators off the track. Refers to the practice of using a fragrant smoked fish to distract hunting or tracking dogs from the track they are meant to follow. "red ink" (to show a business loss) See also Blushing Lists of colors Little Red Riding Hood Red flag (politics) Red pigments	biology	13355	https://da.wikipedia.org/wiki/R%C3%B8d	Rød	Rød er en farve. Rødt lys har en bølgelængde på 647-723 nm. Symbolik Inden for kristendommen hentyder farven til Kristi lidelse og Helligåndens ild. I kirken bruges den som liturgisk farve i pinsen og anden juledag. Rødt i forbindelse med korset symboliserer Jesus blod. Rød kan også symbolisere Satan,Helvede, liderlighed og hovmod. Af Israels tolv stammer er rød tilknyttet Juda og Ruben. Det er kardinalernes farve i Vatikanet, og inden for den katolske kirke symboliserer rødt martyrernes blod. De indiske modergudinder repræsenteredes ved rødt. I Egypten blev rød sat i forbindelse med guden Seth (kaos) og den fjendtlige Apophis slange. Hos mayafolket forestillede den øst, hos højlandsfolket i det gamle Mexico. I Kina var det den hellige, livgivende farve. I alkymien forbindes rødt med hvidt som et modsætningspar, og symboliserer det materielle princip Sulphur, det brændende. Stjernetegnet vædderens farve er rød Uden kontekst Udsagn der mangler angivelse af kontekst, og derfor ikke kan tages alvorligt. Rød forbindes med blod, hjerte, liv, lidenskab, stærke følelser, varme, hede, ild, opofrelse og fare. Den står for aggressivitet og vitalitet. Det er kærlighedens farve, men også hadets og raseriets. Det er kampens, krigens og dermed også militærets farve. Romerne brugte rød som symbol for magten, kejseren, adelen og krigerne. Farven er tilknyttet krigsguden Mars. Den kan symbolisere revolution, socialisme, kommunisme (røde faner). I oldtiden mente man at rødt beskyttede mod farer. Rod-chakraets farve er rød, og står for jordforbindelsen, det fysiske fundament og den fysiske krop. I drømme kan den røde farve fortælle nogen om følelses-funktionen. Rød er også i naturens sammenhæng et udtryk for fare og advarsel. I kombination med gul og sort er dette især hos dyr et udtryk for giftighed. Anvendelse Fra starten på international motorsport og indtil 1960'erne blev grøn anvendt som international racingfarve på britiske biler. Nuancen kaldes British racing green. Inden for politik er rød farven for socialisme og kommunisme. I amerikansk politik er rød dog farven for det republikanske parti, der ikke er hverken socialistiske eller kommunistiske. I trafikken betyder det stop, røde lygter betyder optaget. Fodnoter Farver	danish	0.541227
reddish_adapt_to_color/Afterimage.txt	An afterimage is an image that continues to appear in the eyes after a period of exposure to the original image. An afterimage may be a normal phenomenon (physiological afterimage) or may be pathological (palinopsia). Illusory palinopsia may be a pathological exaggeration of physiological afterimages. Afterimages occur because photochemical activity in the retina continues even when the eyes are no longer experiencing the original stimulus. The remainder of this article refers to physiological afterimages. A common physiological afterimage is the dim area that seems to float before one's eyes after briefly looking into a light source, such as a camera flash. Palinopsia is a common symptom of visual snow. Negative afterimages[edit] Negative afterimages are generated in the retina but may be modified like other retinal signals by neural adaptation of the retinal ganglion cells that carry signals from the retina of the eye to the rest of the brain. Normally, any image is moved over the retina by small eye movements known as microsaccades before much adaptation can occur. However, if the image is very intense and brief, or if the image is large, or if the eye remains very steady, these small movements cannot keep the image on unadapted parts of the retina. Afterimages can be seen when moving from a bright environment to a dim one, like walking indoors on a bright snowy day. They are accompanied by neural adaptation in the occipital lobe of the brain that function similar to color balance adjustments in photography. These adaptations attempt to keep vision consistent in dynamic lighting. Viewing a uniform background while adaptation is still occurring will allow an individual to see the afterimage because localized areas of vision are still being processed by the brain using adaptations that are no longer needed. The Young-Helmholtz trichromatic theory of color vision postulated that there were three types of photoreceptors in the eye, each sensitive to a particular range of visible light: short-wavelength cones, medium-wavelength cones, and long-wavelength cones. Trichromatic theory, however, cannot explain all afterimage phenomena. Specifically, afterimages are the complementary hue of the adapting stimulus, and trichromatic theory fails to account for this fact. The failure of trichromatic theory to account for afterimages indicates the need for an opponent-process theory such as that articulated by Ewald Hering (1878) and further developed by Hurvich and Jameson (1957). The opponent process theory states that the human visual system interprets color information by processing signals from cones and rods in an antagonistic manner. The opponent color theory is that there are four opponent channels: red versus cyan, green vs magenta, blue versus yellow, and black versus white. Responses to one color of an opponent channel are antagonistic to those of the other color. Therefore, a green image will produce a magenta afterimage. The green color adapts the green channel, so they produce a weaker signal. Anything resulting in less green is interpreted as its paired primary color, which is magenta (an equal mixture of red and blue). Example video which produces a distorted illusion after one watches it and looks away. See motion aftereffect. Positive afterimages[edit] Positive afterimages, by contrast, appear the same color as the original image. They are often very brief, lasting less than half a second. The cause of positive afterimages is not well known, but possibly reflects persisting activity in the brain when the retinal photoreceptor cells continue to send neural impulses to the occipital lobe. A stimulus which elicits a positive image will usually trigger a negative afterimage quickly via the adaptation process. To experience this phenomenon, one can look at a bright source of light and then look away to a dark area, such as by closing the eyes. At first one should see a fading positive afterimage, likely followed by a negative afterimage that may last for much longer. It is also possible to see afterimages of random objects that are not bright, only these last for a split second and go unnoticed by most people. On empty shape[edit] An afterimage in general is an optical illusion that refers to an image continuing to appear after exposure to the original image has ceased. Prolonged viewing of the colored patch induces an afterimage of the complementary color (for example, yellow color induces a bluish afterimage). The "afterimage on empty shape" effect is related to a class of effects referred to as contrast effects. In this effect, an empty (white) shape is presented on a colored background for several seconds. When the background color disappears (becomes white), an illusionary color similar to the original background is perceived within the shape. The mechanism of the effect is still unclear, and may be produced by one or two of the following mechanisms: During the presentation of the empty shape on a colored background, the colored background induces an illusory complementary color ("induced color") inside the empty shape. After the disappearance of the colored background an afterimage of the "induced color" might appear inside the "empty shape". Thus, the expected color of the shape will be complementary to the "induced color", and therefore similar to the color of the original background. After the disappearance of the colored background, an afterimage of the background is induced. This induced color has a complementary color to that of the original background. It is possible that this background afterimage induces simultaneous contrast on the "empty shape". Simultaneous contrast is a psychophysical phenomenon of the change in the appearance of a color (or an achromatic stimulus) caused by the presence of a surrounding average color (or luminance). Gallery[edit] The U.S. flag inverted Stare at the middle stripe for around 25 to 30 seconds. If you look at a wall and blink rapidly, this image will appear in color. A white square The Italian flag inverted Stare at the middle of the flag. If you stare long enough and blink at a wall rapidly, this flag will appear in color. See also[edit] Book of Optics Emmert's law Lilac chaser McCollough effect Motion aftereffect Neural adaptation Palinopsia Persistence of vision Screen burn-in Spectropia Visual perception Notes[edit] ^ Bender, MB; Feldman, M; Sobin, AJ (Jun 1968). "Palinopsia". Brain: A Journal of Neurology. 91 (2): 321–38. doi:10.1093/brain/91.2.321. PMID 5721933. ^ Gersztenkorn, D; Lee, AG (Jul 2, 2014). "Palinopsia revamped: A systematic review of the literature". Survey of Ophthalmology. 60 (1): 1–35. doi:10.1016/j.survophthal.2014.06.003. PMID 25113609. ^ Zaidi, Q., Ennis, R., Cao, D., & Lee, B. (2012). "Neural locus of color afterimages. ". Current Biology. 22 (3): 220–224. doi:10.1016/j.cub.2011.12.021. hdl:11858/00-001M-0000-000F-4AA5-4. PMID 22264612. Retrieved 17 October 2022.{{cite journal}}: CS1 maint: multiple names: authors list (link) ^ Horner, David. T. (2013). "Demonstrations of Color Perception and the Importance of Colors". In Ware, Mark E.; Johnson, David E. (eds.). Handbook of Demonstrations and Activities in the Teaching of Psychology. Vol. II: Physiological-Comparative, Perception, Learning, Cognitive, and Developmental. Psychology Press. pp. 94–96. ISBN 978-1-134-99757-2. Retrieved 2019-12-06. Originally published as: Horner, David T. (1997). "Demonstrations of Color Perception and the Importance of Contours". Teaching of Psychology. 24 (4): 267–268. doi:10.1207/s15328023top2404_10. ISSN 0098-6283. S2CID 145364769. ^ "positiveafterimage". www.exo.net. External links[edit] Wikimedia Commons has media related to Afterimage illusions. The Palinopsia Foundation is dedicated to increasing awareness of palinopsia, to funding research into the causes, prevention and treatments for palinopsia, and to advocating for the needs of individuals with palinopsia and their families. Eye On Vision Foundation raises money and awareness for persistent visual conditions Afterimages, a small demonstration. afterimage examples Archived 2015-06-18 at the Wayback Machine The Color Dove Illusion vteOptical illusions (list)Illusions Afterimage Ambigram Ambiguous image Ames room Autostereogram Barberpole Bezold Café wall Checker shadow Chubb Cornsweet Delboeuf Ebbinghaus Ehrenstein Flash lag Fraser spiral Gravity hill Grid Hering Impossible trident Irradiation Jastrow Lilac chaser Mach bands McCollough Müller-Lyer Necker cube Oppel-Kundt Orbison Penrose stairs Penrose triangle Peripheral drift Poggendorff Ponzo Rubin vase Sander Schroeder stairs Shepard tables Spinning dancer Ternus Vertical–horizontal White's Wundt Zöllner Popular culture Op art Trompe-l'œil Spectropia (1864 book) Ascending and Descending (1960 drawing) Waterfall (1961 drawing) The dress (2015 photograph) Related Accidental viewpoint Auditory illusions Illusions Tactile illusions Temporal illusion vtePhenomena of the visual systemEntoptic phenomena Blind spot Phosphene Floater Afterimage Haidinger's brush Prisoner's cinema Blue field entoptic phenomenon Purkinje images Other phenomena Aura Form constant Scintillating scotoma Palinopsia Visual snow Afterimage on empty shape Cosmic ray visual phenomena Closed-eye hallucination	biology	4195582	https://sv.wikipedia.org/wiki/Oxystophyllum%20minutigibbum	Oxystophyllum minutigibbum	Oxystophyllum minutigibbum är en orkidéart som först beskrevs av Johannes Jacobus Smith, och fick sitt nu gällande namn av Mark Alwin Clements. Oxystophyllum minutigibbum ingår i släktet Oxystophyllum och familjen orkidéer. Artens utbredningsområde är Sumatera. Inga underarter finns listade i Catalogue of Life. Källor Orkidéer minutigibbum	swedish	1.421304
reddish_adapt_to_color/Eye.txt	An eye is a sensory organ that allows an organism to perceive visual information. It detects light and converts it into electro-chemical impulses in neurons (neurones). It is part of an organism's visual system. In higher organisms, the eye is a complex optical system that collects light from the surrounding environment, regulates its intensity through a diaphragm, focuses it through an adjustable assembly of lenses to form an image, converts this image into a set of electrical signals, and transmits these signals to the brain through neural pathways that connect the eye via the optic nerve to the visual cortex and other areas of the brain. Eyes with resolving power have come in ten fundamentally different forms, classified into compound eyes and non-compound eyes. Compound eyes are made up of multiple small visual units, and are common on insects and crustaceans. Non-compound eyes have a single lens and focus light onto the retina to form a single image. This type of eye is common in mammals. The human eye is a non-compound eye. The simplest eyes are pit eyes. They are eye-spots which may be set into a pit to reduce the angle of light that enters and affects the eye-spot, to allow the organism to deduce the angle of incoming light. Eyes enable several photo response functions that are independent of vision. In an organism that has more complex eyes, retinal photosensitive ganglion cells send signals along the retinohypothalamic tract to the suprachiasmatic nuclei to effect circadian adjustment and to the pretectal area to control the pupillary light reflex. Overview Eye of a European bison Human eye, a refractive cornea type eye. Complex eyes distinguish shapes and colours. The visual fields of many organisms, especially predators, involve large areas of binocular vision for depth perception. In other organisms, particularly prey animals, eyes are located to maximise the field of view, such as in rabbits and horses, which have monocular vision. The first proto-eyes evolved among animals 600 million years ago about the time of the Cambrian explosion. The last common ancestor of animals possessed the biochemical toolkit necessary for vision, and more advanced eyes have evolved in 96% of animal species in six of the ~35 main phyla. In most vertebrates and some molluscs, the eye allows light to enter and project onto a light-sensitive layer of cells known as the retina. The cone cells (for colour) and the rod cells (for low-light contrasts) in the retina detect and convert light into neural signals which are transmitted to the brain via the optic nerve to produce vision. Such eyes are typically spheroid, filled with the transparent gel-like vitreous humour, possess a focusing lens, and often an iris. Muscles around the iris change the size of the pupil, regulating the amount of light that enters the eye and reducing aberrations when there is enough light. The eyes of most cephalopods, fish, amphibians and snakes have fixed lens shapes, and focusing is achieved by telescoping the lens in a similar manner to that of a camera. The compound eyes of the arthropods are composed of many simple facets which, depending on anatomical detail, may give either a single pixelated image or multiple images per eye. Each sensor has its own lens and photosensitive cell(s). Some eyes have up to 28,000 such sensors arranged hexagonally, which can give a full 360° field of vision. Compound eyes are very sensitive to motion. Some arthropods, including many Strepsiptera, have compound eyes of only a few facets, each with a retina capable of creating an image. With each eye producing a different image, a fused, high-resolution image is produced in the brain. The eyes of a mantis shrimp (here Odontodactylus scyllarus) are considered the most complex in the whole animal kingdom. The mantis shrimp has the world's most complex colour vision system. It has detailed hyperspectral colour vision. Trilobites, now extinct, had unique compound eyes. Clear calcite crystals formed the lenses of their eyes. They differ in this from most other arthropods, which have soft eyes. The number of lenses in such an eye varied widely; some trilobites had only one while others had thousands of lenses per eye. In contrast to compound eyes, simple eyes have a single lens. Jumping spiders have one pair of large simple eyes with a narrow field of view, augmented by an array of smaller eyes for peripheral vision. Some insect larvae, like caterpillars, have a type of simple eye (stemmata) which usually provides only a rough image, but (as in sawfly larvae) can possess resolving powers of 4 degrees of arc, be polarization-sensitive, and capable of increasing its absolute sensitivity at night by a factor of 1,000 or more. Ocelli, some of the simplest eyes, are found in animals such as some of the snails. They have photosensitive cells but no lens or other means of projecting an image onto those cells. They can distinguish between light and dark but no more, enabling them to avoid direct sunlight. In organisms dwelling near deep-sea vents, compound eyes are adapted to see the infra-red light produced by the hot vents, allowing the creatures to avoid being boiled alive. Types There are ten different eye layouts. Eye types can be categorised into "simple eyes", with one concave photoreceptive surface, and "compound eyes", which comprise a number of individual lenses laid out on a convex surface. "Simple" does not imply a reduced level of complexity or acuity. Indeed, any eye type can be adapted for almost any behaviour or environment. The only limitations specific to eye types are that of resolution—the physics of compound eyes prevents them from achieving a resolution better than 1°. Also, superposition eyes can achieve greater sensitivity than apposition eyes, so are better suited to dark-dwelling creatures. Eyes also fall into two groups on the basis of their photoreceptor's cellular construction, with the photoreceptor cells either being ciliated (as in the vertebrates) or rhabdomeric. These two groups are not monophyletic; the Cnidaria also possess ciliated cells, and some gastropods and annelids possess both. Some organisms have photosensitive cells that do nothing but detect whether the surroundings are light or dark, which is sufficient for the entrainment of circadian rhythms. These are not considered eyes because they lack enough structure to be considered an organ, and do not produce an image. Every technological method of capturing an optical image that humans commonly use occurs in nature, with the exception of zoom and Fresnel lenses. Non-compound eyes Simple eyes are rather ubiquitous, and lens-bearing eyes have evolved at least seven times in vertebrates, cephalopods, annelids, crustaceans and Cubozoa. Pit eyes Pit eyes, also known as stemma, are eye-spots which may be set into a pit to reduce the angles of light that enters and affects the eye-spot, to allow the organism to deduce the angle of incoming light. Found in about 85% of phyla, these basic forms were probably the precursors to more advanced types of "simple eyes". They are small, comprising up to about 100 cells covering about 100 µm. The directionality can be improved by reducing the size of the aperture, by incorporating a reflective layer behind the receptor cells, or by filling the pit with a refractile material. Pit vipers have developed pits that function as eyes by sensing thermal infra-red radiation, in addition to their optical wavelength eyes like those of other vertebrates (see infrared sensing in snakes). However, pit organs are fitted with receptors rather different from photoreceptors, namely a specific transient receptor potential channel (TRP channels) called TRPV1. The main difference is that photoreceptors are G-protein coupled receptors but TRP are ion channels. Spherical lens eye The resolution of pit eyes can be greatly improved by incorporating a material with a higher refractive index to form a lens, which may greatly reduce the blur radius encountered—hence increasing the resolution obtainable. The most basic form, seen in some gastropods and annelids, consists of a lens of one refractive index. A far sharper image can be obtained using materials with a high refractive index, decreasing to the edges; this decreases the focal length and thus allows a sharp image to form on the retina. This also allows a larger aperture for a given sharpness of image, allowing more light to enter the lens; and a flatter lens, reducing spherical aberration. Such a non-homogeneous lens is necessary for the focal length to drop from about 4 times the lens radius, to 2.5 radii. Heterogeneous eyes have evolved at least nine times: four or more times in gastropods, once in the copepods, once in the annelids, once in the cephalopods, and once in the chitons, which have aragonite lenses. No extant aquatic organisms possess homogeneous lenses; presumably the evolutionary pressure for a heterogeneous lens is great enough for this stage to be quickly "outgrown". This eye creates an image that is sharp enough that motion of the eye can cause significant blurring. To minimise the effect of eye motion while the animal moves, most such eyes have stabilising eye muscles. The ocelli of insects bear a simple lens, but their focal point usually lies behind the retina; consequently, those can not form a sharp image. Ocelli (pit-type eyes of arthropods) blur the image across the whole retina, and are consequently excellent at responding to rapid changes in light intensity across the whole visual field; this fast response is further accelerated by the large nerve bundles which rush the information to the brain. Focusing the image would also cause the sun's image to be focused on a few receptors, with the possibility of damage under the intense light; shielding the receptors would block out some light and thus reduce their sensitivity. This fast response has led to suggestions that the ocelli of insects are used mainly in flight, because they can be used to detect sudden changes in which way is up (because light, especially UV light which is absorbed by vegetation, usually comes from above). Multiple lenses Some marine organisms bear more than one lens; for instance the copepod Pontella has three. The outer has a parabolic surface, countering the effects of spherical aberration while allowing a sharp image to be formed. Another copepod, Copilia, has two lenses in each eye, arranged like those in a telescope. Such arrangements are rare and poorly understood, but represent an alternative construction. Multiple lenses are seen in some hunters such as eagles and jumping spiders, which have a refractive cornea: these have a negative lens, enlarging the observed image by up to 50% over the receptor cells, thus increasing their optical resolution. Refractive cornea A refractive cornea type eye of a human. The cornea is the clear domed part covering the anterior chamber of the eye. In the eyes of most mammals, birds, reptiles, and most other terrestrial vertebrates (along with spiders and some insect larvae) the vitreous fluid has a higher refractive index than the air. In general, the lens is not spherical. Spherical lenses produce spherical aberration. In refractive corneas, the lens tissue is corrected with inhomogeneous lens material (see Luneburg lens), or with an aspheric shape. Flattening the lens has a disadvantage; the quality of vision is diminished away from the main line of focus. Thus, animals that have evolved with a wide field-of-view often have eyes that make use of an inhomogeneous lens. As mentioned above, a refractive cornea is only useful out of water. In water, there is little difference in refractive index between the vitreous fluid and the surrounding water. Hence creatures that have returned to the water—penguins and seals, for example—lose their highly curved cornea and return to lens-based vision. An alternative solution, borne by some divers, is to have a very strongly focusing cornea. Reflector eyes An alternative to a lens is to line the inside of the eye with "mirrors", and reflect the image to focus at a central point. The nature of these eyes means that if one were to peer into the pupil of an eye, one would see the same image that the organism would see, reflected back out. Many small organisms such as rotifers, copepods and flatworms use such organs, but these are too small to produce usable images. Some larger organisms, such as scallops, also use reflector eyes. The scallop Pecten has up to 100 millimetre-scale reflector eyes fringing the edge of its shell. It detects moving objects as they pass successive lenses. There is at least one vertebrate, the spookfish, whose eyes include reflective optics for focusing of light. Each of the two eyes of a spookfish collects light from both above and below; the light coming from above is focused by a lens, while that coming from below, by a curved mirror composed of many layers of small reflective plates made of guanine crystals. Compound eyes Main article: Compound eye Further information: Arthropod eye An image of a house fly compound eye surface by using scanning electron microscope Anatomy of the compound eye of an insect Arthropods such as this blue bottle fly have compound eyes. A compound eye may consist of thousands of individual photoreceptor units or ommatidia (ommatidium, singular). The image perceived is a combination of inputs from the numerous ommatidia (individual "eye units"), which are located on a convex surface, thus pointing in slightly different directions. Compared with simple eyes, compound eyes possess a very large view angle, and can detect fast movement and, in some cases, the polarisation of light. Because the individual lenses are so small, the effects of diffraction impose a limit on the possible resolution that can be obtained (assuming that they do not function as phased arrays). This can only be countered by increasing lens size and number. To see with a resolution comparable to our simple eyes, humans would require very large compound eyes, around 11 metres (36 ft) in radius. Compound eyes fall into two groups: apposition eyes, which form multiple inverted images, and superposition eyes, which form a single erect image. Compound eyes are common in arthropods, annelids and some bivalved molluscs. Compound eyes in arthropods grow at their margins by the addition of new ommatidia. Apposition eyes Apposition eyes are the most common form of eyes and are presumably the ancestral form of compound eyes. They are found in all arthropod groups, although they may have evolved more than once within this phylum. Some annelids and bivalves also have apposition eyes. They are also possessed by Limulus, the horseshoe crab, and there are suggestions that other chelicerates developed their simple eyes by reduction from a compound starting point. (Some caterpillars appear to have evolved compound eyes from simple eyes in the opposite fashion.) Apposition eyes work by gathering a number of images, one from each eye, and combining them in the brain, with each eye typically contributing a single point of information. The typical apposition eye has a lens focusing light from one direction on the rhabdom, while light from other directions is absorbed by the dark wall of the ommatidium. Superposition eyes The second type is named the superposition eye. The superposition eye is divided into three types: refracting, reflecting and parabolic superposition The refracting superposition eye has a gap between the lens and the rhabdom, and no side wall. Each lens takes light at an angle to its axis and reflects it to the same angle on the other side. The result is an image at half the radius of the eye, which is where the tips of the rhabdoms are. This type of compound eye, for which a minimal size exists below which effective superposition cannot occur, is normally found in nocturnal insects, because it can create images up to 1000 times brighter than equivalent apposition eyes, though at the cost of reduced resolution. In the parabolic superposition compound eye type, seen in arthropods such as mayflies, the parabolic surfaces of the inside of each facet focus light from a reflector to a sensor array. Long-bodied decapod crustaceans such as shrimp, prawns, crayfish and lobsters are alone in having reflecting superposition eyes, which also have a transparent gap but use corner mirrors instead of lenses. Parabolic superposition This eye type functions by refracting light, then using a parabolic mirror to focus the image; it combines features of superposition and apposition eyes. Other Another kind of compound eye, found in males of Order Strepsiptera, employs a series of simple eyes—eyes having one opening that provides light for an entire image-forming retina. Several of these eyelets together form the strepsipteran compound eye, which is similar to the 'schizochroal' compound eyes of some trilobites. Because each eyelet is a simple eye, it produces an inverted image; those images are combined in the brain to form one unified image. Because the aperture of an eyelet is larger than the facets of a compound eye, this arrangement allows vision under low light levels. Good fliers such as flies or honey bees, or prey-catching insects such as praying mantis or dragonflies, have specialised zones of ommatidia organised into a fovea area which gives acute vision. In the acute zone, the eyes are flattened and the facets larger. The flattening allows more ommatidia to receive light from a spot and therefore higher resolution. The black spot that can be seen on the compound eyes of such insects, which always seems to look directly at the observer, is called a pseudopupil. This occurs because the ommatidia which one observes "head-on" (along their optical axes) absorb the incident light, while those to one side reflect it. There are some exceptions from the types mentioned above. Some insects have a so-called single lens compound eye, a transitional type which is something between a superposition type of the multi-lens compound eye and the single lens eye found in animals with simple eyes. Then there is the mysid shrimp, Dioptromysis paucispinosa. The shrimp has an eye of the refracting superposition type, in the rear behind this in each eye there is a single large facet that is three times in diameter the others in the eye and behind this is an enlarged crystalline cone. This projects an upright image on a specialised retina. The resulting eye is a mixture of a simple eye within a compound eye. Another version is a compound eye often referred to as "pseudofaceted", as seen in Scutigera. This type of eye consists of a cluster of numerous ommatidia on each side of the head, organised in a way that resembles a true compound eye. The body of Ophiocoma wendtii, a type of brittle star, is covered with ommatidia, turning its whole skin into a compound eye. The same is true of many chitons. The tube feet of sea urchins contain photoreceptor proteins, which together act as a compound eye; they lack screening pigments, but can detect the directionality of light by the shadow cast by its opaque body. Nutrients The ciliary body is triangular in horizontal section and is coated by a double layer, the ciliary epithelium. The inner layer is transparent and covers the vitreous body, and is continuous from the neural tissue of the retina. The outer layer is highly pigmented, continuous with the retinal pigment epithelium, and constitutes the cells of the dilator muscle. The vitreous is the transparent, colourless, gelatinous mass that fills the space between the lens of the eye and the retina lining the back of the eye. It is produced by certain retinal cells. It is of rather similar composition to the cornea, but contains very few cells (mostly phagocytes which remove unwanted cellular debris in the visual field, as well as the hyalocytes of Balazs of the surface of the vitreous, which reprocess the hyaluronic acid), no blood vessels, and 98–99% of its volume is water (as opposed to 75% in the cornea) with salts, sugars, vitrosin (a type of collagen), a network of collagen type II fibres with the mucopolysaccharide hyaluronic acid, and also a wide array of proteins in micro amounts. Amazingly, with so little solid matter, it tautly holds the eye. Evolution Main article: Evolution of the eye Evolution of the mollusc eye Photoreception is phylogenetically very old, with various theories of phylogenesis. The common origin (monophyly) of all animal eyes is now widely accepted as fact. This is based upon the shared genetic features of all eyes; that is, all modern eyes, varied as they are, have their origins in a proto-eye believed to have evolved some 650-600 million years ago, and the PAX6 gene is considered a key factor in this. The majority of the advancements in early eyes are believed to have taken only a few million years to develop, since the first predator to gain true imaging would have touched off an "arms race" among all species that did not flee the photopic environment. Prey animals and competing predators alike would be at a distinct disadvantage without such capabilities and would be less likely to survive and reproduce. Hence multiple eye types and subtypes developed in parallel (except those of groups, such as the vertebrates, that were only forced into the photopic environment at a late stage). Eyes in various animals show adaptation to their requirements. For example, the eye of a bird of prey has much greater visual acuity than a human eye, and in some cases can detect ultraviolet radiation. The different forms of eye in, for example, vertebrates and molluscs are examples of parallel evolution, despite their distant common ancestry. Phenotypic convergence of the geometry of cephalopod and most vertebrate eyes creates the impression that the vertebrate eye evolved from an imaging cephalopod eye, but this is not the case, as the reversed roles of their respective ciliary and rhabdomeric opsin classes and different lens crystallins show. The very earliest "eyes", called eye-spots, were simple patches of photoreceptor protein in unicellular animals. In multicellular beings, multicellular eyespots evolved, physically similar to the receptor patches for taste and smell. These eyespots could only sense ambient brightness: they could distinguish light and dark, but not the direction of the light source. Through gradual change, the eye-spots of species living in well-lit environments depressed into a shallow "cup" shape. The ability to slightly discriminate directional brightness was achieved by using the angle at which the light hit certain cells to identify the source. The pit deepened over time, the opening diminished in size, and the number of photoreceptor cells increased, forming an effective pinhole camera that was capable of dimly distinguishing shapes. However, the ancestors of modern hagfish, thought to be the protovertebrate, were evidently pushed to very deep, dark waters, where they were less vulnerable to sighted predators, and where it is advantageous to have a convex eye-spot, which gathers more light than a flat or concave one. This would have led to a somewhat different evolutionary trajectory for the vertebrate eye than for other animal eyes. The thin overgrowth of transparent cells over the eye's aperture, originally formed to prevent damage to the eyespot, allowed the segregated contents of the eye chamber to specialise into a transparent humour that optimised colour filtering, blocked harmful radiation, improved the eye's refractive index, and allowed functionality outside of water. The transparent protective cells eventually split into two layers, with circulatory fluid in between that allowed wider viewing angles and greater imaging resolution, and the thickness of the transparent layer gradually increased, in most species with the transparent crystallin protein. The gap between tissue layers naturally formed a biconvex shape, an optimally ideal structure for a normal refractive index. Independently, a transparent layer and a nontransparent layer split forward from the lens: the cornea and iris. Separation of the forward layer again formed a humour, the aqueous humour. This increased refractive power and again eased circulatory problems. Formation of a nontransparent ring allowed more blood vessels, more circulation, and larger eye sizes. Relationship to life requirements Eyes are generally adapted to the environment and life requirements of the organism which bears them. For instance, the distribution of photoreceptors tends to match the area in which the highest acuity is required, with horizon-scanning organisms, such as those that live on the African plains, having a horizontal line of high-density ganglia, while tree-dwelling creatures which require good all-round vision tend to have a symmetrical distribution of ganglia, with acuity decreasing outwards from the centre. Of course, for most eye types, it is impossible to diverge from a spherical form, so only the density of optical receptors can be altered. In organisms with compound eyes, it is the number of ommatidia rather than ganglia that reflects the region of highest data acquisition. Optical superposition eyes are constrained to a spherical shape, but other forms of compound eyes may deform to a shape where more ommatidia are aligned to, say, the horizon, without altering the size or density of individual ommatidia. Eyes of horizon-scanning organisms have stalks so they can be easily aligned to the horizon when this is inclined, for example, if the animal is on a slope. An extension of this concept is that the eyes of predators typically have a zone of very acute vision at their centre, to assist in the identification of prey. In deep water organisms, it may not be the centre of the eye that is enlarged. The hyperiid amphipods are deep water animals that feed on organisms above them. Their eyes are almost divided into two, with the upper region thought to be involved in detecting the silhouettes of potential prey—or predators—against the faint light of the sky above. Accordingly, deeper water hyperiids, where the light against which the silhouettes must be compared is dimmer, have larger "upper-eyes", and may lose the lower portion of their eyes altogether. In the giant Antarctic isopod Glyptonotus a small ventral compound eye is physically completely separated from the much larger dorsal compound eye. Depth perception can be enhanced by having eyes which are enlarged in one direction; distorting the eye slightly allows the distance to the object to be estimated with a high degree of accuracy. Acuity is higher among male organisms that mate in mid-air, as they need to be able to spot and assess potential mates against a very large backdrop. On the other hand, the eyes of organisms which operate in low light levels, such as around dawn and dusk or in deep water, tend to be larger to increase the amount of light that can be captured. It is not only the shape of the eye that may be affected by lifestyle. Eyes can be the most visible parts of organisms, and this can act as a pressure on organisms to have more transparent eyes at the cost of function. Eyes may be mounted on stalks to provide better all-round vision, by lifting them above an organism's carapace; this also allows them to track predators or prey without moving the head. Physiology Visual acuity The eye of a red-tailed hawk Visual acuity, or resolving power, is "the ability to distinguish fine detail" and is the property of cone cells. It is often measured in cycles per degree (CPD), which measures an angular resolution, or how much an eye can differentiate one object from another in terms of visual angles. Resolution in CPD can be measured by bar charts of different numbers of white/black stripe cycles. For example, if each pattern is 1.75 cm wide and is placed at 1 m distance from the eye, it will subtend an angle of 1 degree, so the number of white/black bar pairs on the pattern will be a measure of the cycles per degree of that pattern. The highest such number that the eye can resolve as stripes, or distinguish from a grey block, is then the measurement of visual acuity of the eye. For a human eye with excellent acuity, the maximum theoretical resolution is 50 CPD (1.2 arcminute per line pair, or a 0.35 mm line pair, at 1 m). A rat can resolve only about 1 to 2 CPD. A horse has higher acuity through most of the visual field of its eyes than a human has, but does not match the high acuity of the human eye's central fovea region. Spherical aberration limits the resolution of a 7 mm pupil to about 3 arcminutes per line pair. At a pupil diameter of 3 mm, the spherical aberration is greatly reduced, resulting in an improved resolution of approximately 1.7 arcminutes per line pair. A resolution of 2 arcminutes per line pair, equivalent to a 1 arcminute gap in an optotype, corresponds to 20/20 (normal vision) in humans. However, in the compound eye, the resolution is related to the size of individual ommatidia and the distance between neighbouring ommatidia. Physically these cannot be reduced in size to achieve the acuity seen with single lensed eyes as in mammals. Compound eyes have a much lower acuity than vertebrate eyes. Colour perception Main article: Colour vision "Colour vision is the faculty of the organism to distinguish lights of different spectral qualities." All organisms are restricted to a small range of electromagnetic spectrum; this varies from creature to creature, but is mainly between wavelengths of 400 and 700 nm. This is a rather small section of the electromagnetic spectrum, probably reflecting the submarine evolution of the organ: water blocks out all but two small windows of the EM spectrum, and there has been no evolutionary pressure among land animals to broaden this range. The most sensitive pigment, rhodopsin, has a peak response at 500 nm. Small changes to the genes coding for this protein can tweak the peak response by a few nm; pigments in the lens can also filter incoming light, changing the peak response. Many organisms are unable to discriminate between colours, seeing instead in shades of grey; colour vision necessitates a range of pigment cells which are primarily sensitive to smaller ranges of the spectrum. In primates, geckos, and other organisms, these take the form of cone cells, from which the more sensitive rod cells evolved. Even if organisms are physically capable of discriminating different colours, this does not necessarily mean that they can perceive the different colours; only with behavioural tests can this be deduced. Most organisms with colour vision can detect ultraviolet light. This high energy light can be damaging to receptor cells. With a few exceptions (snakes, placental mammals), most organisms avoid these effects by having absorbent oil droplets around their cone cells. The alternative, developed by organisms that had lost these oil droplets in the course of evolution, is to make the lens impervious to UV light—this precludes the possibility of any UV light being detected, as it does not even reach the retina. Rods and cones The retina contains two major types of light-sensitive photoreceptor cells used for vision: the rods and the cones. Rods cannot distinguish colours, but are responsible for low-light (scotopic) monochrome (black-and-white) vision; they work well in dim light as they contain a pigment, rhodopsin (visual purple), which is sensitive at low light intensity, but saturates at higher (photopic) intensities. Rods are distributed throughout the retina but there are none at the fovea and none at the blind spot. Rod density is greater in the peripheral retina than in the central retina. Cones are responsible for colour vision. They require brighter light to function than rods require. In humans, there are three types of cones, maximally sensitive to long-wavelength, medium-wavelength, and short-wavelength light (often referred to as red, green, and blue, respectively, though the sensitivity peaks are not actually at these colours). The colour seen is the combined effect of stimuli to, and responses from, these three types of cone cells. Cones are mostly concentrated in and near the fovea. Only a few are present at the sides of the retina. Objects are seen most sharply in focus when their images fall on the fovea, as when one looks at an object directly. Cone cells and rods are connected through intermediate cells in the retina to nerve fibres of the optic nerve. When rods and cones are stimulated by light, they connect through adjoining cells within the retina to send an electrical signal to the optic nerve fibres. The optic nerves send off impulses through these fibres to the brain. Pigmentation The pigment molecules used in the eye are various, but can be used to define the evolutionary distance between different groups, and can also be an aid in determining which are closely related—although problems of convergence do exist. Opsins are the pigments involved in photoreception. Other pigments, such as melanin, are used to shield the photoreceptor cells from light leaking in from the sides. The opsin protein group evolved long before the last common ancestor of animals, and has continued to diversify since. There are two types of opsin involved in vision; c-opsins, which are associated with ciliary-type photoreceptor cells, and r-opsins, associated with rhabdomeric photoreceptor cells. The eyes of vertebrates usually contain ciliary cells with c-opsins, and (bilaterian) invertebrates have rhabdomeric cells in the eye with r-opsins. However, some ganglion cells of vertebrates express r-opsins, suggesting that their ancestors used this pigment in vision, and that remnants survive in the eyes. Likewise, c-opsins have been found to be expressed in the brain of some invertebrates. They may have been expressed in ciliary cells of larval eyes, which were subsequently resorbed into the brain on metamorphosis to the adult form. C-opsins are also found in some derived bilaterian-invertebrate eyes, such as the pallial eyes of the bivalve molluscs; however, the lateral eyes (which were presumably the ancestral type for this group, if eyes evolved once there) always use r-opsins. Cnidaria, which are an outgroup to the taxa mentioned above, express c-opsins—but r-opsins are yet to be found in this group. Incidentally, the melanin produced in the cnidaria is produced in the same fashion as that in vertebrates, suggesting the common descent of this pigment. Additional images The structures of the eye labelled Another view of the eye and the structures of the eye labelled See also Accommodation (vertebrate eye) (focusing) Adaptation (eye) (night vision) Capsule of lens Cornea Emission theory (vision) Eye color Eye development Eye disease Eye injury Eye movement Eyelid Lens (vertebrate anatomy) Nictitating membrane Ophthalmology Orbit (anatomy) Simple eye in invertebrates Tapetum lucidum Tears Notes ^ There is no universal consensus on the precise total number of phyla Animalia; the stated figure varies slightly from author to author.	biology	51868	https://sv.wikipedia.org/wiki/%C3%96ga	Öga	Ett öga () är ett anatomiskt organ för att förnimma ljus. Olika typer av ljuskänsliga organ finns i nästan hela djurriket. De enklaste varianterna särskiljer bara om omgivningen är mörk eller ljus. Mer komplexa ögon används för att ge ett synsinne. Många komplexa organismer, såsom däggdjur, fåglar, reptiler och fiskar har två ögon som är placerade i samma plan och vars intryck tolkas som en enda, tredimensionell "bild", liksom hos människan. Andra djurarter, till exempel kaniner och kameleonter har ögonen i olika plan och får två separata bilder. Ögontyper Hos de flesta ryggradsdjur och vissa blötdjur fungerar ögat genom att projicera bilder på en ljuskänslig näthinna (retina). Signaler skickas därifrån till hjärnan via synnerven. Sådana ögon är ofta ungefär sfäriska och fyllda med en genomskinlig geleartad substans som kallas glaskropp, har en lins som fokuserar ljuset, och en iris som reglerar hur mycket ljus som kommer in i ögat. Ögon hos bläckfiskar, fiskar, amfibiska djur och ormar har ofta en fast linsform och fokuserar blicken genom att teleskopera ögat (på samma sätt som en kamera fokuserar). Arter som skiljer sig mycket åt kan ha väldigt olika typer av ögon, men de tenderar att likna varandra i funktion och utseende när de är fullt utvecklade. Blötdjurens ögon verkar till exempel ha utvecklats från andra organ än ryggradsdjurens ögon, och kan vara ett exempel på hur evolutionen lett till samma slutresultat. Ryggradsdjurens ögon utvecklades från hjärnceller under den embryoniska tiden, medan blötdjurens ögon växte in från hudceller. Ryggradsdjurens näthinnor har lager med neuroner framför de ljuskänsliga cellerna, medan blötdjurens näthinnor har de ljuskänsliga cellerna framför neuronerna, och har därför ingen blind fläck och möjligen skarpare syn, men också långsammare bildåterhämtning från näthinnan och därför sämre sinne för rörelser. Vissa huvudfotningar har ingen fysisk lins, utan en väldigt liten ljusöppning (ungefär som en camera obscura). Vissa blötdjur har en konkav spegel för att fokusera ljuset tillsammans med en lins. Fasettögon finns hos leddjur, och ger en pixel-baserad bild (inte flera bilder som många tror). Varje sensor har sin egen lins och ljuskänsliga celler. Vissa ögon har upp emot 28 000 sådana sensorer, arrangerade i ett hexagonalt nät, vilket kan ge ett 360-gradigt synfält. Fasettögon är väldigt känsliga för rörelser. Vissa leddjurs fasettögon har ett fåtal fasetter var med en näthinna som kan skapa en bild, vilket ger en syn baserad på flera bilder, alla ur olika vinklar, sammansmälta till en bild med mycket hög upplösning. Djurrikets troligen mest komplicerade ögon är fasettögonen hos stomatopoder, mantisräkor, en grupp bland kräftdjuren. Färgseendet är mycket avancerat med det största kända antalet färgreceptorer, och de kan se i 12 färgkanaler (jfr 3 hos människan), s.k. hyperspektralt seende. Varje enskilt öga har även djupseende. Vidare kan de se polariserat ljus och bedöma polarisationsplanet, och de kan också se ultraviolett och kanske infrarött ljus. Trilobiterna, som nu är utdöda, hade unika fasettögon med genomskinliga kalk-kristaller som linser. (De flesta andra leddjur har mjuka ögon.) Antalet linser i sådana ögon varierar - vissa hade bara en, andra hade flera tusen linser per öga. Några av de enklaste ögonen återfinns hos djur såsom sniglar, och kan inte se i den vardagliga betydelsen. De har ljuskänsliga celler, men ingen lins och inget annat sätt att projicera en bild på de cellerna. De kan särskilja mellan ljust och mörkt (dag och natt) men inte mer. Det gör att sniglar kan undvika direkt solljus. Ögats evolutionära utveckling Hur en så komplex struktur som ögats projicering skulle ha kunnat utvecklats av sig självt sägs ofta vara en svår fråga för evolutionsteorin. Darwin behandlade ämnet i sin Om arternas uppkomst genom att hävda att det inte var så konstigt om de mest primitiva varianterna också hade en funktion, och därefter muterade lite i taget. Forskarna Dan-Eric Nilsson och Susanne Pelger i Lund har visat genom teoretiska beräkningar att ett primitivt optiskt sinnesorgan skulle kunna ha utvecklats till ett komplext människolikt öga på en rimlig tid (mindre än en miljon år), enbart genom små mutationer och naturliga urvalsprocesser. Ögon i olika djurarter visar att de har anpassats till sina omgivningar. Till exempel har rovfåglar skarpare blick än människor, och vissa rovfåglar som jagar på dagen kan se ultraviolett ljus. Dessutom visar de parallella utvecklingarna av ryggradsdjursögon och blötdjursögon att det inte är konstigt att ögat har utvecklats genom evolution. Anatomi Hos en nyfödd människa är ögats diameter omkring 17 mm och hos en vuxen människa är ögongloben omkring 25 mm i diameter. Ögat slutar växa ungefär i 6–7-årsåldern. Däggdjursögon är konstruerade för att fokusera ljus på näthinnan. Alla delar som ljuset färdas genom innan det når näthinnan är glasklart genomskinliga för att förhindra en förlust i ljusstyrka innan det når näthinnan. Hornhinnan i kombination med linsen ser till att ljusstrålarna fokuseras på näthinnan. Ljuset orsakar kemiska förändringar i de ljuskänsliga cellerna i näthinnan, som aktiveras och skickar nervimpulser till hjärnan. Ljuset, som kommer in i ögat via ett yttre medium såsom luft eller vatten, passerar först hornhinnan och vidare in i den främre ögonkammaren. Hornhinnan, som är rundad, står för den huvudsakliga (2/3) brytningen av ljuset. Den främre ögonkammaren är fylld med kammarvätska, en helt klar vätska som till sin sammansättning liknar blodserum. Trycket från kammarvätskan spänner ut hornhinnan så att den blir helt konvex, vilket är nödvändigt för att ljuset ska samlas på linsen. Den främre ögonkammaren avgränsas bakåt av iris, en ring av i huvudsak lucker bindväv och stråk av glatt muskulatur. I iris finns gott om melanocyter, som producerar färgämnet melanin. Mängden melanin avgör ögonfärgen. Mitt i iris finns ett hål, pupillen. Pupillens storlek regleras av en ringmuskel (m. sphincter pupillae) och ett radialt muskelstråk (m. dilator pupillae). Pupillen fungerar som bländaren på en kamera, och ser till att ljusnivån i ögat hålls konstant. Om för mycket ljus släpps in skulle näthinnan skadas, och om för lite ljus släpps in ser ögat inget. Innanför irisen finns den bakre ögonkammaren. Denna begränsas bakåt av linsen, en konvex, fjädrande skiva som fokuserar ljuset på näthinnan. Innan ljuset når näthinnan måste det ta sig genom glaskroppen, en geléartad struktur som fyller ut ögats insida. Glaskroppens uppgift är framförallt att stadga upp ögat, men även att bryta ljuset. Linsen är via tunna trådar fäst vid utskott i corpus ciliare, som omsluter den ringformiga ciliarmuskeln. För att se ett föremål som befinner sig långt borta, slappnar ciliarmuskeln av och får större diameter, vilket leder till att linsen dras ut och blir plattare. När ciliarmuskeln drar ihop sig fjädrar linsen tillbaka till en tjockare, mer konvex form. När vi åldras, förlorar linsen gradvis sin förmåga att fjädra tillbaka, och det leder till att det blir svårt att fokusera på näraliggande föremål. Det finns flera brytningsfel som kommer av hornhinnan och linsens form, och från ögats längd, till exempel översynthet, närsynthet, och astigmatism. Omkring glaskroppen finns tre lager av vävnader: Ytterst finns tunica externa bulbi, som delas in i tre delar, senhinnan (sclera), gränsregionen (limbus) och hornhinnan (cornea). Senhinnan hjälper till att hålla ögats form och förhindrar oönskad ljusgenomträngning. Utseendemässigt är senhinnan normalt vit, tjockast kring synnerven och tunnast vid ögonmusklernas fästen och i området där synnerven passerar (lamina cribrosa). Senhinnan består av bindväv innehållande framför allt kollagen. I mitten finns tunica vasculosa bulbi eller uvea, som även den delas in i tre delar, regnbågshinnan (iris), strålkroppen (corpus ciliare, ciliarkroppen) och åderhinnan (choroidea, koroidea). Melanocyter i åderhinnan ger ögats inre dess mörka färg, som förhindrar att det bildas störande reflexer i ögat. Åderhinnan innehåller också kapillärer, som levererar syre och näring till näthinnans fem yttersta lager och fraktar bort restprodukter. Näthinnans fem innersta lager får näring från retinas centrala artär som kommer in i ögat tillsammans med synnerven och vars kärlförgreningar ligger i näthinnans nervfiberlager. Näthinnan innehåller även pigmentepitel (med melanin) och de ljuskänsliga tapparna och stavarna samt nerver. Innerst finns tunica interna bulbi, som delas in i näthinnans seende och inte seende del. Gränsen mellan dessa två heter ora serrata. För att maximera ljusabsorptionen är näthinnan slät. Den har dock två punkter som är annorlunda: blinda fläcken, den punkt där synnerven går in, och i centrum gula fläcken (macula lutea) med bäst synskärpa. I denna finns centralgropen (fovea centralis), som är en liten grop klädd enbart med tappar. Tappar och stavar Näthinnan innehåller två typer av ljuskänsliga celler: tappar och stavar. Trots att de har samma uppbyggnad och metabolism, har de väldigt olika funktioner. Stavarna är mycket ljuskänsliga, vilket gör att de fungerar även i mycket svagt ljus. Det är de här cellerna som gör att människor och djur kan se i exempelvis månljus. Dock kan de inte skilja mellan olika färger, och de har dålig synskärpa (det vill säga de har svårt att skilja på detaljer). Det är därför som saker verkar få mindre färg, ju mörkare omgivningen blir. Tapparna å andra sidan ger hög synskärpa under goda ljusförhållanden. Ju tätare tapparna sitter, desto högre blir synskärpan. Olika sorters tappceller reagerar också på olika färger (våglängder av ljus), vilket gör dessa ansvariga för en organisms färgseende. Tapparna har även en möjlighet att bli trötta efter ett intensivt synintryck. Om man till exempel tittar intensivt på ett rött streck på marken så ser man ett grönt streck om man tittar på en vit yta. Det beror på att tapparna blir trötta och de sänder inte lika mycket röda signaler längre, då verkar den delen av synfältet mer grön (alltså motsatsfärgen) än resten av synfältet och därför ser man då ett grönt streck. Hos däggdjur och fåglar med god syn finns det ofta ett eller flera områden i ögats näthinna med extra mycket tappar. Hos människan (och en del andra djur) finns denna i en rund, lite tunnare fördjupning av näthinnan. Denna grop kallas för gula fläcken eller fovea (fullständigt latinskt namn: fovea centralis, centrala gropen) och sitter rakt bakom linsen. En del djur har en horisontellt formad fovea vilket gör att deras detaljseende fungerar bra längs med hela horisonten. Många fåglar har två foveor som även innehåller mycket fler tappar än hos exempelvis människan och som därmed ger dem ytterligare skarpare syn. Eftersom tapparna behöver mycket ljus för att fungera optimalt blir det problem för exempelvis astronomer, då de inte kan se på ljussvaga stjärnor med ögats vanliga fokus, där ljuset inte är tillräckligt för att stimulera tapparna. Därför betraktar ofta astronomer stjärnorna genom "ögonvrån" (genom att titta lite bredvid), där andelen ljuskänsligare stavar är högre. Både tappar och stavar är alltså känsliga för ljus, men för ljus av olika frekvenser. De innehåller båda ett pigmenterat ljusreceptor-protein, som i stavarna heter rhodopsin, i tapparna iodopsin. Både tappar och stavars ljusreceptorprotein består av en proteindel (stavar: opsin, tappar: fotodopsin), som är associerad med retinal, som inte är ett protein utan syntetiseras från vitamin A i näthinnans pigmentepitel. Processen som ljusreceptorproteinerna genomgår är likartade - när proteinet utsätts för elektromagnetisk strålning av en särskild våglängd och intensitet (det vill säga ljus inom det synliga spektret) bryts retinalet ned från sin normala konfiguration (11-cis-retinal) till en isoform (transretinal). Retinalen släpper också från opsinet/fotodopsinet. Denna process startar en signalväg som stänger jonkanaler i cellmembranet vilket förorsakar en impuls som så småningom når hjärnans syncentrum. I närmare detalj fungerar rhodopsinet/iodopsinet i princip som en så kallad G-protein-kopplad receptor, vars aktivering leder till att ett enzym, cGMP-fosfodiesteras, börjar omvandla signalmolekylen cGMP till 5'-GMP. Då cGMP behövs för öppning av natriumkanalerna leder spjälkning till stängning vilket ger en hyperpolarisering av cellen. Denna hyperpolarisering leder till att utsöndringen av neurotransmittorer till synapsen avbryts. Detta kan verka bakvänt, men i näthinnans fotoreceptorer har neurotransmittorerna en inhiberande effekt på synapsen, och utsöndras normalt konstant. Att de slutar utsöndras leder på så sätt till aktivering av synapsen. Flera sensoriska celler är kopplade till samma bipolära nervcell, som sedan är kopplad till en enda ganglie (nervknut) som skickar informationen vidare till syncentrat. Men tapparna i fovea är ofta kopplade individuellt till de bipolära cellerna och behöver sällan dela ganglie. Ju flera sensoriska celler som delar ganglie desto mindre skarp blir bilden från den delen av näthinnan. Enligt den trikromatiska färgteorin uttyds färger genom att iodopsinet i tapparna finns i olika varianter. En typ bryts ner av den specifika ljusvåglängd som kommer från rött ljus, en från grönt ljus och en från blått ljus, medan den fjärde typen av tappar är känslig för ultraviolett ljus. Människan och andra högre utvecklade apor har tre typer av tappar som främst reagerar på blått, grönt och rött. De flesta andra däggdjur har två typer av tappar som främst regarera på blått och grönt medan fåglar har fyra typer av tappar så att de förutom blått, grönt och rött också kan se ultraviolett ljus. Sköldpaddor har sex olika typer av tappar. Om alla tre typer stimuleras lika mycket, ser man vitt, och om ingen stimuleras ser man svart. Oftast stimuleras de olika typerna olika mycket, vilket leder till att man ser olika färger. De tre färgerna kallas primärfärger. Om man blandar två av dem får man sekundärfärger, och blandar man två sekundärfärger får man tertiärfärger, och så vidare. Felfunktion hos någon av tapptyperna ledar till olika grad av färgblindhet. För rovfåglarna blir det mer komplicerat. Ögats rörelser Det finns sex yttre ögonmuskler med ursprung från ögonhålan som fäster på ögonbulbens sidor. Dessa styr rörelserna av ögat och håller det kvar i ögonhålan. Fyra av de sex musklerna är raka muskler (rectus), som något förenklat vrider ögat i varsin riktning. Musculus rectus lateralis vrider ögat lateralt, m. rectus medialis vrider ögat medialt, m. rectus superior och inferior vrider ögat uppåt respektive nedåt. De två kvarvarande musklerna är de sneda ögonmusklerna, m. obliquus superior och m. obliquus inferior. M. obliquus superior löper genom en ligamentring, trochlea, i anteromediala ögonhåletaket. Från denna går sedan muskeln bakåt och fäster på laterala och posteriora sidan av ögat. Vid kontraktion av muskeln kommer ögat då att vridas inåt och nedåt. M. obliquus inferior utgår från främre delen av ögonhålan och går bakåt för att fästa posterolateralt. Rörelsen blir då vridning utåt och uppåt. Tre av de raka ögonmusklerna, m. rectus superior, inferior och medialis) samt den undre sneda ögonmuskeln (m. obliquus inferior) innerveras av den tredje (III) kranialnerven, nervus oculomotorius, medan m. obliquus superior innerveras av fjärde kranialnerven (IV), nervus trochlearis, och m. rectus lateralis av sjätte kranialnerven (VI), nervus abducens. Bilden till höger visar även m. levator palpebrae superioris, som lyfter det övre ögonlocket, samt ganglion ciliare, som styr pupillkontraktion och ackommodation. Ögats skyddsmekanismer Ögat är omgivet av korta hårstrån som kallas ögonfransar. De är till för att skydda ögat mot vattendroppar, damm och andra partiklar som skulle kunna komma in i ögat. Varje öga har tårkörtlar. De sänder kontinuerligt ut vätska som sprids ut över ögat när man blinkar. Detta förhindrar att ögat torkar ut. Om ögonfransarna misslyckats med sin uppgift och släppt in smuts i ögat, producerar tårkörtlarna extra mycket vätska för att skölja rent och då blinkar man samtidigt för att pressa ut smutsen. Ögonproblem och -sjukdomar Se separat artikel om ögonsjukdomar samt sammanställningen i :Kategori:Ögonsjukdomar. Se även Kikare Oftalmologi Optiker Tårar Ögonfärg Ögonkontakt Ögonrörelser Källor Kandel, Schwartz, Jessell "Principles of Neural Science", 4/e, McGraw-Hill: Health Professions Division, 2000, Malm, Liedholm "Akut neurologi" (1986), 7:e upplagan 2004, Wikipedia:Basartiklar	swedish	0.502005
reddish_adapt_to_color/Lens_(vertebrate_anatomy).txt	The lens, or crystalline lens, is a transparent biconvex structure in most land vertebrate eyes. Along with the cornea, aqueous and vitreous humours it refracts light, focusing it onto the retina. In many land animals the shape of the lens can be altered, effectively changing the focal length of the eye, enabling them to focus on objects at various distances. This adjustment of the lens is known as accommodation (see also below). In many fully aquatic vertebrates such as fish other methods of accommodation are used such as changing the lens's position relative to the retina rather than changing lens shape. Accommodation is analogous to the focusing of a photographic camera via changing its lenses. In land vertebrates the lens is flatter on its anterior side than on its posterior side, while in fish the lens is often close to spherical. Accommodation in humans is well studied and allows artificial means of supplementing our focus such as glasses for correction of sight as we age. The refractive power of a younger human lens in its natural environment is approximately 18 dioptres, roughly one-third of the eye's total power of about 60 dioptres. By 25 years of age the ability of the lens to alter the light path has reduced to 10 dioptres and accommodation continues to decline with age. Structure[edit] Position in the eye[edit] The lens is located towards the front part of the vertebrate eye called the anterior segment which includes the cornea and iris positioned in front of the lens. The lens is held in place by the suspensory ligaments (Zonule of Zinn), attaching the lens at its equator to the rest of the eye through the ciliary body. Behind the lens is the jelly-like vitreous body which helps hold the lens in place. At the front of the lens is the liquid aqueous humor which bathes the lens with nutrients and other things. Land vertebrate lenses usually have an ellipsoid, biconvex shape. The front surface is less curved than the back. A human adult the lens is typically about 10mm in diameter and 4mm thick though changes shape with accommodation and size due to grow throughout a person's lifetime. Anatomy[edit] 3D lens model from sheep with parts labeled and images of cells from different parts overlayed Sheep eye lens para-formaldehyde fixed front view. Small lenses are about 1cm in diameter. Small bumps at edge are remnants of suspensory ligaments Sheep lens fixed side view. Note the largest lens has damaged capsule and iris attached Microscope image of lens cell types and capsule The lens has three main parts: the lens capsule, the lens epithelium, and the lens fibers. The lens capsule is a relatively thick basement membrane forming the outermost layer of the lens. Inside the capsule much thinner lens fibers form the bulk of the lens. The cells of the lens epithelium form a thin layer between the lens capsule and the outermost layer of lens fibers at the front of the lens but not the back. The lens itself lacks nerves, blood vessels, or connective tissue. Anatomists will often refer to positions of structures in the lens by describing it like a globe of the world. The front and back of the lens are referred to as the anterior and posterior "poles", like the North and South poles. The "equator" is the outer edge of the lens often hidden by the iris and is the area of most cell differentiation. As the equator is not generally in the light path of the eye the structures involved with metabolic activity avoid scattering light that would otherwise affect vision. Lens capsule[edit] Main article: Capsule of lens Sheep lens capsule removed. Decapsulation leads to a nearly formless blob. A foot on a mouse lens capsule suspensory ligament forming part of the Zonule of Zinn The lens capsule is a smooth, transparent basement membrane that completely surrounds the lens. The capsule is elastic and its main structural component is collagen. It is presumed to be synthesized by the lens epithelium and its main components in order of abundance are heparan sulfate proteoglycan (sulfated glycosaminoglycans (GAGs)), entactin, type IV collagen, laminin. The capsule is very elastic and so allows the lens to assume a more spherical shape when the tension of the suspensory ligaments is reduced. The human capsule varies from 2 to 28 micrometres in thickness, being thickest near the equator (peri-equatorial region) and generally thinner near the posterior pole. The photo from an electron microscope shows an area of the capsule near the equator where one of the thousands of suspensory ligaments attach. Lens showing feet attached to the eye lens capsule with smaller feet embedded in the capsule Attachment must be strong enough to stop the ligament being detached from the lens capsule. Forces are generated from holding the lens in place and added to when focusing. The anterior and posterior capsule is thinner. Lens epithelium[edit] The lens epithelium is a single layer of cells at the front of the lens between the lens capsule and the lens fibers. By providing the lens fibers with nutrients and removing waste the cells of the epithelium regulate maintain lens homeostasis. As ions, nutrients, and liquid enter the lens from the aqueous humor, Na/K-ATPase pumps in the lens epithelial cells pump ions out of the lens to maintain appropriate lens osmotic concentration and volume, with equatorially positioned lens epithelium cells contributing most to this current. The activity of the Na/K-ATPases keeps water and current flowing through the lens from the poles and exiting through the equatorial regions. The cells of the lens epithelium also divide into new lens fibers at the lens equator. The lens lays down fibers from when it first forms in embryo until death. Lens fibers[edit] The lens fibers form the bulk of the lens. They are long, thin, transparent cells, firmly packed, with diameters typically 4–7 micrometres and lengths of up to 12mm long in humans. The lens fibers stretch lengthwise from the posterior to the anterior poles and, when cut horizontally, are arranged in concentric layers rather like the layers of an onion. If cut along the equator, it appears as a honeycomb. The approximate middle of each fiber lies around the equator. These tightly packed layers of lens fibers are referred to as laminae. The lens fiber cytoplasms are linked together via gap junctions, intercellular bridges and interdigitations of the cells that resemble "ball and socket" forms. The lens is split into regions depending on the age of the lens fibers of a particular layer. Moving outwards from the central, oldest layer, the lens is split into an embryonic nucleus, the fetal nucleus, the adult nucleus, the inner and outer cortex. New lens fibers, generated from the lens epithelium, are added to the outer cortex. Mature lens fibers have no organelles or nuclei. Cell fusion, voids and vacuoles[edit] Cellular and supercellular structure in the mouse lens. Photos at increasing depth: A-Epithelium B-Broadening fiber ends C-Fiber ends lock together D-F- Voids G-Vacuoles I-Sutures Left to right we have a smooth capsule, a small patch of epithelium next to fused lens fibers or perhaps a void, straighter fibers, and finally wrinkled fibers With the advent of other ways of looking at cellular structures of lenses while still in the living animal it became apparent that regions of fiber cells, at least at the lens anterior, contain large voids and vacuoles. These are speculated to be involved in lens transport systems linking the surface of the lens to deeper regions. Very similar looking structures also indicate cell fusion in the lens. The cell fusion is shown by micro-injection to form a stratified syncytium in whole lens cultures. Development[edit] Similar to a human, this is a lens forming in a chicken eye Development of the vertebrate lens begins when the human embryo is about 4mm long. The accompanying picture shows the process in a more easily studied chicken embryo. Unlike the rest of the eye which is derived mostly from the inner embryo layers, the lens is derived from the skin around the embryo. The first stage of lens formation takes place when a sphere of cells formed by budding of the inner embryo layers comes close to the embyro's outer skin. The sphere of cells induces nearby outer skin to start changing into the lens placode. The lens placode is the first stage of transformation of a patch of skin into the lens. At this early stage, the lens placode is a single layer of cells. As development progresses, the lens placode begins to deepen and bow inwards. As the placode continues to deepen, the opening to the surface ectoderm constricts and the lens cells bud off from the embryo's skin to form a sphere of cells known as the "lens vesicle". When the embryo is about 10mm long the lens vesicle has completely separated from the skin of the embryo. The embryo then sends signals from the developing retina, inducing the cells closest to the posterior end of the lens vesicle to elongate toward the anterior end of the vesicle. These signals also induce the synthesis of proteins called crystallins. As the name suggests the crystallins can form a clear highly refractive jelly. These elongating cells eventually fill in the center of the vesicle with cells, that are long and thin like a strand of hair, called fibers. These primary fibers become the nucleus in the mature lens. The epithelial cells that do not form into fibers nearest the lens front give rise to the lens epithelium. Pattern of lens fibers (anterior and lateral aspect) Additional fibers are derived from lens epithelial cells located at the lens equator. These cells lengthen towards the front and back wrapping around fibers already laid down. The new fibers need to be longer to cover earlier fibers but as the lens gets larger the ends of the newer fibers no longer reach as far towards the front and back of the lens. The lens fibers that do not reach the poles form tight, interdigitating seams with neighboring fibers. These seams being less crystalline than the bulk of the lens are more visible and are termed "sutures". The suture patterns become more complex as more layers of lens fibers are added to the outer portion of the lens. The lens continues to grow after birth, with the new secondary fibers being added as outer layers. New lens fibers are generated from the equatorial cells of the lens epithelium, in a region referred to as the "germinative zone" and "bow region". The lens epithelial cells elongate, lose contact with the capsule and epithelium at the back and front of the lens, synthesize crystallin, and then finally lose their nuclei (enucleate) as they become mature lens fibers. In humans, as the lens grows by laying down more fibers through to early adulthood, the lens becomes more ellipsoid in shape. After about age 20 the lens grows rounder again and the iris is very important for this development. Several proteins control the embryonic development of the lens though PAX6 is considered the master regulator gene of this organ. Other effectors of proper lens development include the Wnt signaling components BCL9 and Pygo2. The whole process of differentiation of the epithelial cells into crystallin filled fiber cells without organelles occurs within the confines of the lens capsule. Older cells cannot be shed and are instead internalized towards the center of the lens. This process results in a complete temporally layered record of the differentiation process from the start at the lens surface to the end at the lens center. The lens is therefore valuable to scientists studying the process of cell differentiation. Variations in lens structure[edit] Bony fish eye. Note the spherical lens and muscle to pull the lens backward In many aquatic vertebrates, the lens is considerably thicker, almost spherical resulting in increased light refraction. This difference helps compensate for the smaller angle of refraction between the eye's cornea and the watery environment, as they have more similar refractive indices than cornea and air. The fiber cells of fish are generally considerably thinner than those of land vertebrates and it appears crystalin proteins are transported to the organelle free cells at the lens exterior to the inner cells through many layers of cells. Some vertebrates need to see well both above and below water at times. One example is diving birds which have the ability to change focus by 50 to 80 dioptres. Compared with animals adapted for only one environment diving birds have a somewhat altered lens and cornea structure with focus mechanisms to allow for both environments. Even among terrestrial animals the lens of primates such as humans is unusually flat going some way to explain why our vision, unlike diving birds, is particularly blurry under water. Function[edit] Focusing[edit] An image that is partially in focus, but mostly out of focus in varying degrees. Eye and detailed ray path including one intraocular lens layer In humans the widely quoted Helmholtz mechanism of focusing, also called accommodation, is often referred to as a "model". Direct experimental proof of any lens model is necessarily difficult as the vertebrate lens is transparent and only functions well in the living animals. When considering all vertebrates aspects of all models may play varying roles in lens focus. The shape changing lens of many land based vertebrates[edit] 3D reconstruction of lens in a living 20 year old human male focusing from 0 dioptres (infinity) to 4.85 dioptres (26mm) side & back views External forces[edit] Two horse lenses suspended on water by cling wrap with 4 approximately parallel lasers directed through them. The 1 cm spaced grid indicates an accommodated, i.e. relaxed, near focus, focal length of around 6cm The model of a shape changing lens of humans was proposed by Young in a lecture on the 27th Nov 1800. Others such as Helmholtz and Huxley refined the model in the mid 1800s explaining how the ciliary muscle contracts rounding the lens to focus near and this model was popularized by Helmholtz in 1909. The model may be summarized like this. Normally the lens is held under tension by its suspending ligaments being pulled tight by the pressure of the eyeball. At short focal distance the ciliary muscle contracts relieving some of the tension on the ligaments, allowing the lens to elastically round up a bit, increasing refractive power. Changing focus to an object at a greater distance requires a thinner less curved lens. This is achieved by relaxing some of the sphincter like ciliary muscles. While not referenced this presumably allows the pressure in the eyeball to again expand it outwards, pulling harder on the lens making it less curved and thinner, so increasing the focal distance. There is a problem with the Helmholtz model in that despite mathematical models being tried none has come close enough to working using only the Helmholtz mechanisms. Schachar model of lens focus Schachar has proposed a model for land based vertebrates that was not well received. The theory allows mathematical modeling to more accurately reflect the way the lens focuses while also taking into account the complexities in the suspensory ligaments and the presence of radial as well as circular muscles in the ciliary body. In this model the ligaments may pull to varying degrees on the lens at the equator using the radial muscles while the ligaments offset from the equator to the front and back are relaxed to varying degrees by contracting the circular muscles. These multiple actions operating on the elastic lens allows it to change lens shape at the front more subtly. Not only changing focus, but also correcting for lens aberrations that might otherwise result from the changing shape while better fitting mathematical modeling. The "catenary" model of lens focus proposed by Coleman demands less tension on the ligaments suspending the lens. Rather than the lens as a whole being stretched thinner for distance vision and allowed to relax for near focus, contraction of the circular ciliary muscles results in the lens having less hydrostatic pressure against its front. The lens front can then reform its shape between the suspensory ligaments in a similar way to a slack chain hanging between two poles might change it's curve when the poles are moved closer together. This model requires fluid movement of the lens front only rather than trying to change the shape of the lens as a whole. Internal forces[edit] Tracing of Scheimpflug photographs of 20 year old human lens being thicker focusing near and thinner when focusing far. Internal layering of the lens is also significant Wrinkled lens fibers in picture below compared to straight fibers above When Thomas Young proposed the changing of the human lens's shape as the mechanism for focal accommodation in 1801 he thought the lens may be a muscle capable of contraction. This type of model is termed intracapsular accommodation as it relies on activity within the lens. In a 1911 Nobel lecture Allvar Gullstrand spoke on "How I found the intracapsular mechanism of accommodation" and this aspect of lens focusing continues to be investigated. Young spent time searching for the nerves that could stimulate the lens to contract without success. Since that time it has become clear the lens is not a simple muscle stimulated by a nerve so the 1909 Helmholtz model took precedence. Pre-twentieth century investigators did not have the benefit of many later discoveries and techniques. Membrane proteins such as aquaporins which allow water to flow into and out of cells are the most abundant membrane protein in the lens. Connexins which allow electrical coupling of cells are also prevalent. Electron microscopy and immunofluorescent microscopy show fiber cells to be highly variable in structure and composition. Magnetic resonance imaging confirms a layering in the lens that may allow for different refractive plans within it. The refractive index of human lens varies from approximately 1.406 in the central layers down to 1.386 in less dense layers of the lens. This index gradient enhances the optical power of the lens. As more is learned about mammalian lens structure from in situ Scheimpflug photography, MRI and physiological investigations it is becoming apparent the lens itself is not responding entirely passively to the surrounding ciliary muscle but may be able to change its overall refractive index through mechanisms involving water dynamics in the lens still to be clarified. The accompanying micrograph shows wrinkled fibers from a relaxed sheep lens after it is removed from the animal indicating shortening of the lens fibers during near focus accommodation. The age related changes in the human lens may also be related to changes in the water dynamics in the lens. Lenses of birds, reptiles, amphibians, fish and others[edit] Diving bird (Cormorant) lens focusing can be up to 80 dioptres for clearer underwater vision. Bony fish eye. Note the spherical lens and muscle to pull the lens backward In reptiles and birds, the ciliary body which supports the lens via suspensory ligaments also touches the lens with a number of pads on its inner surface. These pads compress and release the lens to modify its shape while focusing on objects at different distances; the suspensory ligaments usually perform this function in mammals. With vision in fish and amphibians, the lens is fixed in shape, and focusing is instead achieved by moving the lens forwards or backwards within the eye using a muscle called the retractor lentus. In cartilaginous fish, the suspensory ligaments are replaced by a membrane, including a small muscle at the underside of the lens. This muscle pulls the lens forward from its relaxed position when focusing on nearby objects. In teleosts, by contrast, a muscle projects from a vascular structure in the floor of the eye, called the falciform process, and serves to pull the lens backwards from the relaxed position to focus on distant objects. While amphibians move the lens forward, as do cartilaginous fish, the muscles involved are not similar in either type of animal. In frogs, there are two muscles, one above and one below the lens, while other amphibians have only the lower muscle. In the simplest vertebrates, the lampreys and hagfish, the lens is not attached to the outer surface of the eyeball at all. There is no aqueous humor in these fish, and the vitreous body simply presses the lens against the surface of the cornea. To focus its eyes, a lamprey flattens the cornea using muscles outside of the eye and pushes the lens backwards. While not vertebrate, brief mention is made here of the convergent evolution of vertebrate and Molluscan eyes. The most complex Molluscan eye is the Cephalopod eye which is superficially similar structure and function to a vertebrate eye, including accommodation, while differing in basic ways such as having a two part lens and no cornea. The fundamental requirements of optics must be filled by all eyes with lenses using the tissues at their disposal so superficially eyes all tend to look similar. It is the way optical requirements are met using different cell types and structural mechanisms that varies among animals. Crystallins and transparency[edit] Graph showing optical density (OD) of the human crystalline lens for newborn, 30-year-old, and 65-year-old from wavelengths 300-1400 nm. Crystallins are water-soluble proteins that compose over 90% of the protein within the lens. The three main crystallin types found in the human eye are α-, β-, and γ-crystallins. Crystallins tend to form soluble, high-molecular weight aggregates that pack tightly in lens fibers, thus increasing the index of refraction of the lens while maintaining its transparency. β and γ crystallins are found primarily in the lens, while subunits of α -crystallin have been isolated from other parts of the eye and the body. α-crystallin proteins belong to a larger superfamily of molecular chaperone proteins, and so it is believed that the crystallin proteins were evolutionarily recruited from chaperone proteins for optical purposes. The chaperone functions of α-crystallin may also help maintain the lens proteins, which must last a human for their entire lifetime. Another important factor in maintaining the transparency of the lens is the absence of light-scattering organelles such as the nucleus, endoplasmic reticulum, and mitochondria within the mature lens fibers. Lens fibers also have a very extensive cytoskeleton that maintains the precise shape and packing of the lens fibers; disruptions/mutations in certain cytoskeletal elements can lead to the loss of transparency. The lens blocks most ultraviolet light in the wavelength range of 300–400 nm; shorter wavelengths are blocked by the cornea. The pigment responsible for blocking the light is 3-hydroxykynurenine glucoside, a product of tryptophan catabolism in the lens epithelium. High intensity ultraviolet light can harm the retina, and artificial intraocular lenses are therefore manufactured to also block ultraviolet light. People lacking a lens (a condition known as aphakia) perceive ultraviolet light as whitish blue or whitish-violet. Nourishment[edit] The lens is metabolically active and requires nourishment in order to maintain its growth and transparency. Compared to other tissues in the eye, however, the lens has considerably lower energy demands. By nine weeks into human development, the lens is surrounded and nourished by a net of vessels, the tunica vasculosa lentis, which is derived from the hyaloid artery. Beginning in the fourth month of development, the hyaloid artery and its related vasculature begin to atrophy and completely disappear by birth. In the postnatal eye, Cloquet's canal marks the former location of the hyaloid artery. Channels regulate lens transport. After regression of the hyaloid artery, the lens receives all its nourishment from the aqueous humor. Nutrients diffuse in and waste diffuses out through a constant flow of fluid from the anterior/posterior poles of the lens and out of the equatorial regions, a dynamic that is maintained by the Na/K-ATPase pumps located in the equatorially positioned cells of the lens epithelium. The interaction of these pumps with water channels into cells called aquaporins, molecules less than 100 daltons in size among cells via gap junctions, and calcium using transporters/regulators (TRPV channels) results in a flow of nutrients throughout the lens. Glucose is the primary energy source for the lens. As mature lens fibers do not have mitochondria, approximately 80% of the glucose is metabolized via anaerobic metabolism. The remaining fraction of glucose is shunted primarily down the pentose phosphate pathway. The lack of aerobic respiration means that the lens consumes very little oxygen. Clinical significance[edit] Cataracts are opacities of the lens. While some are small and do not require any treatment, others may be large enough to block light and obstruct vision. Cataracts usually develop as the aging lens becomes more and more opaque, but cataracts can also form congenitally or after injury to the lens. Nuclear sclerosis is a type of age-related cataract. Diabetes is another risk factor for cataract. Cataract surgery involves the removal of the lens and insertion of an artificial intraocular lens. Presbyopia is the age-related loss of accommodation, which is marked by the inability of the eye to focus on nearby objects. The exact mechanism is still unknown, but age-related changes in the hardness, shape, and size of the lens have all been linked to the condition. Ectopia lentis is the displacement of the lens from its normal position. Aphakia is the absence of the lens from the eye. Aphakia can be the result of surgery or injury, or it can be congenital. Additional images[edit] MRI scan of human eye showing lens. Interior of anterior chamber of eye. The crystalline lens, hardened and divided. Section through the margin of the lens, showing the transition of the epithelium into the lens fibers known as the bow region. The structures of the eye labeled Another view of the eye and the structures of the eye labeled This svg file was configured so that the rays, diaphragm and crystalline lens are easily modified See also[edit] Medical portal Accommodation reflex Crystallin Evolution of the eye, for how the lens evolved Intraocular lenses Iris Lens capsule Phacoemulsification Visual perception Zonules of Zinn	biology	937884	https://da.wikipedia.org/wiki/Linse%20%28anatomi%29	Linse (anatomi)	Linsen er en gennemsigtig, bikonveks struktur i øjet, der sammen med hornhinden bryder lyset, der fokuseres på nethinden. Ved at forandre form kan linsen ændre øjets fokallængde, så det kan fokusere over forskellige afstande; derved kan der dannes et klart billede på nethinden af den genstand, øjet er rettet imod. Linsens tilpasning kaldes akkommodation og svarer til, når et kamera fokuserer ved at bevæge sine linser. Linsens tilpasningsevne aftager med alderen, i takt med at linsen mister sin elasticitet. Dette kan gøre det nødvendigt at bruge briller. Øjets anatomi	danish	0.527985
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[ News & Insights ](/news) [ Community & Equity ](/community-equity) [ Contact Us ](/contact-us) [ __ 310-825-2631 ](tel:3108252631) Breadcrumb 1. [ __ Home ](/) __ 2. [ News & Insights ](/news) __ # New details on how immune cells ‘see’ and respond to mutations in cancer cells may lead to more targeted and effective immunotherapy Study suggests immune responses could be strengthened even in patients showing no apparent clinical response ![Graphic of T cells attacking cancer cells](/sites/default/files/styles/landscape_3x2_016000_640x427/public/images/a8/istock-1206920970.jpg?f=36f94068&itok=Qh4WMXdH) Credit: Getty Images/iStockphoto __ March 8, 2023 __ By [ David Sampson ](/news/david-sampson) __ 4 min read For the first time, a research team has identified and analyzed the steps by which immune cells “see” and respond to cancer cells, providing insights into reasons some treatments may be effective for certain patients but not others. The [ UCLA Jonsson Comprehensive Cancer Center ](https://www.uclahealth.org/locations/ucla-jonsson-comprehensive-cancer- center) scientists leading the research believe their findings will lead to better, more personalized immunotherapies – even for patients whose immune systems currently do not appear to respond to treatment. “This is an important step forward in our understanding of what the T-cell responses “see” in the tumor and how they change over time in the tumor and in circulation in the blood,” said [ Cristina Puig-Saus, PhD ](https://newsroom.ucla.edu/dept/faculty/cristina-puig-saus-gatien-moriceau- young-investigator-award-melanoma) , a UCLA Jonsson Comprehensive Cancer Center researcher, adjunct assistant professor of medicine at UCLA, and the first author of a [ study in Nature ](https://www.nature.com/articles/s41586-023-05787-1) . “The deeper understanding of how the T-cell responses clear metastatic tumor masses will help us design better treatments and engineer T cells in multiple ways to mimic them,” she said. The researchers adapted advanced gene-editing technology to make unprecedented observations about immune responses in patients with metastatic melanoma receiving anti-PD-1 “checkpoint inhibitor” immunotherapy. Although immune cells called T cells have the ability to detect mutations in cancer cells and eliminate them, leaving normal cells unharmed, cancer cells often evade the immune system. Checkpoint inhibitors are designed to improve the T cells’ ability to recognize and attack cancer cells. “With this work, we can know exactly what the immune system of a particular patient recognized in their cancer to differentiate it from normal cells and attack it,” said [ Antoni Ribas, MD, PhD ](https://www.pharmacology.ucla.edu/people/antoni-ribas-m-d-ph-d/) , a UCLA Jonsson Comprehensive Cancer Center researcher, professor of medicine at UCLA, a co-senior author of the study. The investigators showed that when the immunotherapy is effective, it directs a diverse repertoire of T cells against a small group of selected mutations in a tumor. These T-cell responses expand and evolve during the course of treatment, both within the tumor and in the bloodstream. Patients for whom the therapy fails also present a T-cell response against a similarly reduced number of mutations in the tumor, but those immune responses are less diverse, and they do not expand during treatment. “This study demonstrates that patients without response to therapy still induce a tumor-reactive T-cell response,” Puig-Saus said. “These T cells could potentially be isolated and their immune receptors used to genetically modify a larger number of T cells to redirect them against the patient’s tumor. These T cells could be expanded in culture and reinfused into the patients to treat their tumors.” In the 11 patients studied, seven had a response to PD-1 blockade; four did not. The number of mutations in the tumors ranged between 3,507 and 31. Despite this wide range, the number of mutations seen by tumor-reactive T cells ranged between 13 and one. In patients with clinical benefit from the therapy, the responses were diverse, with a range between 61 and seven different mutation-specific T cells isolated in the blood and the tumor. In contrast, in the patients lacking a response to therapy, the researchers only identified between 14 and two different T cells. Also, in patients responding to treatment, the researchers were able to isolate tumor-reactive T cells in blood and tumors throughout treatment, but in patients without a response, the T cells were not recurrently detected. Still, the study showed that immune receptors from the T cells isolated from all patients – regardless of response or not – redirected the specificity of immune cells against the tumor, producing antitumor activity. The work to characterize T-cell activity in patients with and without a clinical response was made possible through the creation of a new technique using sophisticated technology to isolate mutation-reactive T cells from blood and tumor samples. It builds on technology developed through a collaboration with Ribas, James Heath, PhD, president of the Institute for Systems Biology in Seattle, and David Baltimore, PhD, Nobel laureate, emeritus professor at Caltech and a member of the UCLA Jonsson Comprehensive Cancer Center. As previously published in Nature and presented at the Society for Immunotherapy of Cancer (SITC) 2022 last November, the technology was further developed by PACT Pharma, using CRISPR gene editing to insert genes into immune cells to efficiently redirect them to recognize mutations in a patient’s own cancer cells. “With this technique, we generated large numbers of T cells expressing the immune receptors from the mutation-reactive T cells isolated from each patient. We used these cells to characterize the reactivity of the immune receptors against the patient’s own cancer cells,” Ribas said. “The new technologies allow us to study these rare immune cells that are the mediators of immune responses to cancer.” [ _ Article _ ](https://www.nature.com/articles/s41586-023-05787-1) _ : Neoantigen-targeted CD8+ T cell responses with PD-1 blockade therapy. 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immune_system_detect_tumor/Major_histocompatibility_complex.txt	The major histocompatibility complex (MHC) is a large locus on vertebrate DNA containing a set of closely linked polymorphic genes that code for cell surface proteins essential for the adaptive immune system. These cell surface proteins are called MHC molecules. The name of this locus comes from its discovery through the study of transplanted tissue compatibility. Later studies revealed that tissue rejection due to incompatibility is only a facet of the full function of MHC molecules: binding an antigen derived from self-proteins, or from pathogens, and bringing the antigen presentation to the cell surface for recognition by the appropriate T-cells. MHC molecules mediate the interactions of leukocytes, also called white blood cells (WBCs), with other leukocytes or with body cells. The MHC determines donor compatibility for organ transplant, as well as one's susceptibility to autoimmune diseases. In a cell, protein molecules of the host's own phenotype or of other biologic entities are continually synthesized and degraded. Each MHC molecule on the cell surface displays a small peptide (a molecular fraction of a protein) called an epitope. The presented self-antigens prevent an organism's immune system from targeting its own cells. The presentation of pathogen-derived proteins results in the elimination of the infected cell by the immune system. Diversity of an individual's self-antigen presentation, mediated by MHC self-antigens, is attained in at least three ways: (1) an organism's MHC repertoire is polygenic (via multiple, interacting genes); (2) MHC expression is codominant (from both sets of inherited alleles); (3) MHC gene variants are highly polymorphic (diversely varying from organism to organism within a species). Sexual selection has been observed in male mice choosing to mate with females with different MHCs. Also, at least for MHC I presentation, there has been evidence of antigenic peptide splicing, which can combine peptides from different proteins, vastly increasing antigen diversity. Discovery[edit] The first descriptions of the MHC were made by British immunologist Peter Gorer in 1936. MHC genes were first identified in inbred mice strains. Clarence Little transplanted tumors across different strains and found rejection of transplanted tumors according to strains of host versus donor. George Snell selectively bred two mouse strains, attained a new strain nearly identical to one of the progenitor strains, but differing crucially in histocompatibility—that is, tissue compatibility upon transplantation—and thereupon identified an MHC locus. Later Jean Dausset demonstrated the existence of MHC genes in humans and described the first human leucocyte antigen, the protein which we call now HLA-A2. Some years later Baruj Benacerraf showed that polymorphic MHC genes not only determine an individual’s unique constitution of antigens but also regulate the interaction among the various cells of the immunological system. These three scientists have been awarded the 1980 Nobel Prize in Physiology or Medicine for their discoveries concerning “genetically determined structures on the cell surface that regulate immunological reactions”. The first fully sequenced and annotated MHC was published for humans in 1999 by a consortium of sequencing centers from the UK, USA and Japan in Nature. It was a "virtual MHC" since it was a mosaic from different individuals. A much shorter MHC locus from chickens was published in the same issue of Nature. Many other species have been sequenced and the evolution of the MHC was studied, e.g. in the gray short-tailed opossum (Monodelphis domestica), a marsupial, MHC spans 3.95 Mb, yielding 114 genes, 87 shared with humans. Marsupial MHC genotypic variation lies between eutherian mammals and birds, taken as the minimal MHC encoding, but is closer in organization to that of nonmammals. The IPD-MHC Database was created which provides a centralised repository for sequences of the Major Histocompatibility Complex (MHC) from a number of different species. The database contains 77 species for the release from 2019-12-19. Genes[edit] The MHC locus is present in all jawed vertebrates; it is assumed to have arisen about 450 million years ago. Despite the difference in the number of genes included in the MHC of different species, the overall organization of the locus is rather similar. Usual MHC contains about a hundred genes and pseudogenes, not all of them are involved in immunity. In humans, the MHC region occurs on chromosome 6, between the flanking genetic markers MOG and COL11A2 (from 6p22.1 to 6p21.3 about 29Mb to 33Mb on the hg38 assembly), and contains 224 genes spanning 3.6 megabase pairs (3 600 000 bases). About half have known immune functions. The human MHC is also called the HLA (human leukocyte antigen) complex (often just the HLA). Similarly, there is SLA (Swine leukocyte antigens), BoLA (Bovine leukocyte antigens), DLA for dogs, etc. However, historically, the MHC in mice is called the Histocompatibility system 2 or just the H-2, in rats – RT1, and in chicken – B-locus. The MHC gene family is divided into three subgroups: MHC class I, MHC class II, and MHC class III. Among all those genes present in MHC, there are two types of genes coding for the proteins MHC class I molecules and MHC class II molecules that are directly involved in the antigen presentation. These genes are highly polymorphic, 19031 alleles of class I HLA, and 7183 of class II HLA are deposited for human in the IMGT database. Class Encoding Expression I (1) peptide-binding proteins, which select short sequences of amino acids for antigen presentation, as well as (2) molecules aiding antigen-processing (such as TAP and tapasin). One chain, called α, whose ligands are the CD8 receptor—borne notably by cytotoxic T cells—and inhibitory receptors borne by NK cells II (1) peptide-binding proteins and (2) proteins assisting antigen loading onto MHC class II's peptide-binding proteins (such as MHC II DM, MHC II DQ, MHC II DR, and MHC II DP). Two chains, called α & β, whose ligands are the CD4 receptors borne by helper T cells. III Other immune proteins, outside antigen processing and presentation, such as components of the complement cascade (e.g., C2, C4, factor B), the cytokines of immune signaling (e.g., TNF-α), and heat shock proteins buffering cells from stresses Various Proteins[edit] T-cell receptor complexed with MHC-I and MHC-II MHC class I[edit] Main article: MHC class I MHC class I molecules are expressed in some nucleated cells and also in platelets—in essence all cells but red blood cells. It presents epitopes to killer T cells, also called cytotoxic T lymphocytes (CTLs). A CTL expresses CD8 receptors, in addition to T-cell receptors (TCR)s. When a CTL's CD8 receptor docks to a MHC class I molecule, if the CTL's TCR fits the epitope within the MHC class I molecule, the CTL triggers the cell to undergo programmed cell death by apoptosis. Thus, MHC class I helps mediate cellular immunity, a primary means to address intracellular pathogens, such as viruses and some bacteria, including bacterial L forms, bacterial genus Mycoplasma, and bacterial genus Rickettsia. In humans, MHC class I comprises HLA-A, HLA-B, and HLA-C molecules. The first crystal structure of Class I MHC molecule, human HLA-A2, was published in 1989. The structure revealed that MHC-I molecules are heterodimers, they have polymorphic heavy α-subunit whose gene occurs inside the MHC locus and small invariant β2 microglobulin subunit whose gene is located usually outside of it. Polymorphic heavy chain of MHC-I molecule contains N-terminal extra-cellular region composed by three domains, α1, α2, and α3, transmembrane helix to hold MHC-I molecule on the cell surface and short cytoplasmic tail. Two domains, α1 and α2 form deep peptide-binding groove between two long α-helices and the floor of the groove formed by eight β-strands. Immunoglobulin-like domain α3 involved in the interaction with CD8 co-receptor. β2 microglobulin provides stability of the complex and participates in the recognition of peptide-MHC class I complex by CD8 co-receptor. The peptide is non-covalently bound to MHC-I, it is held by the several pockets on the floor of the peptide-binding groove. Amino acid side-chains that are most polymorphic in human alleles fill up the central and widest portion of the binding groove, while conserved side-chains are clustered at the narrower ends of the groove. Schematic view of MHC class I and MHC class II molecules Classical MHC molecules present epitopes to the TCRs of CD8+ T lymphocytes. Nonclassical molecules (MHC class IB) exhibit limited polymorphism, expression patterns, and presented antigens; this group is subdivided into a group encoded within MHC loci (e.g., HLA-E, -F, -G), as well as those not (e.g., stress ligands such as ULBPs, Rae1, and H60); the antigen/ligand for many of these molecules remain unknown, but they can interact with each of CD8+ T cells, NKT cells, and NK cells. The evolutionary oldest nonclassical MHC class I lineage in human was deduced to be the lineage that includes the CD1 and PROCR (alias EPCR) molecules and this lineage may have been established before the origin of tetrapod species. However, the only nonclassical MHC class I lineage for which evidence exists that it was established before the evolutionary separation of Actinopterygii (ray-finned fish) and Sarcopterygii (lobe-finned fish plus tetrapods) is lineage Z of which members are found, together in each species with classical MHC class I, in lungfish and throughout ray-finned fishes; why the Z lineage was well conserved in ray-finned fish but lost in tetrapods is not understood. MHC class II[edit] Main article: MHC class II MHC class II can be conditionally expressed by all cell types, but normally occurs only on "professional" antigen-presenting cells (APCs): macrophages, B cells, and especially dendritic cells (DCs). An APC takes up an antigenic protein, performs antigen processing, and returns a molecular fraction of it—a fraction termed the epitope—and displays it on the APC's surface coupled within an MHC class II molecule (antigen presentation). On the cell's surface, the epitope can be recognized by immunologic structures like T-cell receptors (TCRs). The molecular region which binds to the epitope is the paratope. On surfaces of helper T cells are CD4 receptors, as well as TCRs. When a naive helper T cell's CD4 molecule docks to an APC's MHC class II molecule, its TCR can meet and bind the epitope coupled within the MHC class II. This event primes the naive T cell. According to the local milieu, that is, the balance of cytokines secreted by APCs in the microenvironment, the naive helper T cell (Th0) polarizes into either a memory Th cell or an effector Th cell of phenotype either type 1 (Th1), type 2 (Th2), type 17 (Th17), or regulatory/suppressor (Treg), as so far identified, the Th cell's terminal differentiation. MHC class II thus mediates immunization to—or, if APCs polarize Th0 cells principally to Treg cells, immune tolerance of—an antigen. The polarization during primary exposure to an antigen is key in determining a number of chronic diseases, such as inflammatory bowel diseases and asthma, by skewing the immune response that memory Th cells coordinate when their memory recall is triggered upon secondary exposure to similar antigens. B cells express MHC class II to present antigens to Th0, but when their B cell receptors bind matching epitopes, interactions which are not mediated by MHC, these activated B cells secrete soluble immunoglobulins: antibody molecules mediating humoral immunity. Class II MHC molecules are also heterodimers, genes for both α and β subunits are polymorphic and located within MHC class II subregion. Peptide-binding groove of MHC-II molecules is forms by N-terminal domains of both subunits of the heterodimer, α1 and β1, unlike MHC-I molecules, where two domains of the same chain are involved. In addition, both subunits of MHC-II contain transmembrane helix and immunoglobulin domains α2 or β2 that can be recognized by CD4 co-receptors. In this way MHC molecules chaperone which type of lymphocytes may bind to the given antigen with high affinity, since different lymphocytes express different T-Cell Receptor (TCR) co-receptors. MHC class II molecules in humans have five to six isotypes. Classical molecules present peptides to CD4+ lymphocytes. Nonclassical molecules, accessories, with intracellular functions, are not exposed on cell membranes, but in internal membranes, assisting with the loading of antigenic peptides onto classic MHC class II molecules. The important nonclassical MHC class II molecule DM is only found from the evolutionary level of lungfish, although also in more primitive fishes both classical and nonclassical MHC class II are found. Sr.No Feature Class I MHC Class II MHC 1 Constituting polypeptide chains α chain (45KDa in humans) β2 chain (12 KDa in humans) α chain (30–34 KDa in humans) β chain (26–29 KDa in humans) 2 Antigen binding domain α1and α2 domains α1 and β1 domains 3 Binds protein antigens of 8–10 amino acids residues 13–18 amino acids residues 4 Peptide bending cleft Floor formed by β sheets and sides by α helices, blocked at both the ends Floor formed by β sheets and sides by α helices, opened at both the ends 5 Antigenic peptide motifs involved in binding Anchor residues located at amino and carbon terminal ends Anchor residues located almost uniformly along the peptide 6 Presents antigenic peptide to CD8+ T cells CD4+ T cells MHC class III[edit] Main article: MHC class III Class III molecules have physiologic roles unlike classes I and II, but are encoded between them in the short arm of human chromosome 6. Class III molecules include several secreted proteins with immune functions: components of the complement system (such as C2, C4, and B factor), cytokines (such as TNF-α, LTA, and LTB), and heat shock proteins. Function[edit] MHC is the tissue-antigen that allows the immune system (more specifically T cells) to bind to, recognize, and tolerate itself (autorecognition). MHC is also the chaperone for intracellular peptides that are complexed with MHCs and presented to T cell receptors (TCRs) as potential foreign antigens. MHC interacts with TCR and its co-receptors to optimize binding conditions for the TCR-antigen interaction, in terms of antigen binding affinity and specificity, and signal transduction effectiveness. Essentially, the MHC-peptide complex is a complex of auto-antigen/allo-antigen. Upon binding, T cells should in principle tolerate the auto-antigen, but activate when exposed to the allo-antigen. Disease states occur when this principle is disrupted. Antigen presentation: MHC molecules bind to both T cell receptor and CD4/CD8 co-receptors on T lymphocytes, and the antigen epitope held in the peptide-binding groove of the MHC molecule interacts with the variable Ig-Like domain of the TCR to trigger T-cell activation Autoimmune reaction: Having some MHC molecules increases the risk of autoimmune diseases more than having others. HLA-B27 is an example. It is unclear how exactly having the HLA-B27 tissue type increases the risk of ankylosing spondylitis and other associated inflammatory diseases, but mechanisms involving aberrant antigen presentation or T cell activation have been hypothesized. Tissue allorecognition: MHC molecules in complex with peptide epitopes are essentially ligands for TCRs. T cells become activated by binding to the peptide-binding grooves of any MHC molecule that they were not trained to recognize during positive selection in the thymus. Antigen processing and presentation[edit] MHC class I pathway: Proteins in the cytosol are degraded by the proteasome, liberating peptides internalized by TAP channel in the endoplasmic reticulum, there associating with MHC-I molecules freshly synthesized. MHC-I/peptide complexes enter Golgi apparatus, are glycosylated, enter secretory vesicles, fuse with the cell membrane, and externalize on the cell membrane interacting with T lymphocytes. Peptides are processed and presented by two classical pathways: In MHC class II, phagocytes such as macrophages and immature dendritic cells take up entities by phagocytosis into phagosomes—though B cells exhibit the more general endocytosis into endosomes—which fuse with lysosomes whose acidic enzymes cleave the uptaken protein into many different peptides. Via physicochemical dynamics in molecular interaction with the particular MHC class II variants borne by the host, encoded in the host's genome, a particular peptide exhibits immunodominance and loads onto MHC class II molecules. These are trafficked to and externalized on the cell surface. In MHC class I, any nucleated cell normally presents cytosolic peptides, mostly self peptides derived from protein turnover and defective ribosomal products. During viral infection, intracellular microorganism infection, or cancerous transformation, such proteins degraded in the proteosome are as well loaded onto MHC class I molecules and displayed on the cell surface. T lymphocytes can detect a peptide displayed at 0.1–1% of the MHC molecules. Peptide binding for Class I and Class II MHC molecules, showing the binding of peptides between the alpha-helix walls, upon a beta-sheet base. The difference in binding positions is shown. Class I primarily makes contact with backbone residues at the Carboxy and amino terminal regions, while Class II primarily makes contacts along the length of the residue backbone. The precise location of binding residues is determined by the MHC allele. Table 2. Characteristics of the antigen processing pathways Characteristic MHC-I pathway MHC-II pathway Composition of the stable peptide-MHC complex Polymorphic chain α and β2 microglobulin, peptide bound to α chain Polymorphic chains α and β, peptide binds to both Types of antigen-presenting cells (APC) All nucleated cells Dendritic cells, mononuclear phagocytes, B lymphocytes, some endothelial cells, epithelium of thymus T lymphocytes able to respond Cytotoxic T lymphocytes (CD8+) Helper T lymphocytes (CD4+) Origin of antigenic proteins cytosolic proteins (mostly synthesized by the cell; may also enter from the extracellular medium via phagosomes) Proteins present in endosomes or lysosomes (mostly internalized from extracellular medium) Enzymes responsible for peptide generation Cytosolic proteasome Proteases from endosomes and lysosomes (for instance, cathepsin) Location of loading the peptide on the MHC molecule Endoplasmic reticulum Specialized vesicular compartment Molecules implicated in transporting the peptides and loading them on the MHC molecules TAP (transporter associated with antigen processing) DM, invariant chain T lymphocyte recognition restrictions[edit] Main article: MHC restriction In their development in the thymus, T lymphocytes are selected to recognize MHC molecules of the host, but not recognize other self antigens. Following selection, each T lymphocyte shows dual specificity: The TCR recognizes self MHC, but only non-self antigens. MHC restriction occurs during lymphocyte development in the thymus through a process known as positive selection. T cells that do not receive a positive survival signal — mediated mainly by thymic epithelial cells presenting self peptides bound to MHC molecules — to their TCR undergo apoptosis. Positive selection ensures that mature T cells can functionally recognize MHC molecules in the periphery (i.e. elsewhere in the body). The TCRs of T lymphocytes recognise only sequential epitopes, also called linear epitopes, of only peptides and only if coupled within an MHC molecule. (Antibody molecules secreted by activated B cells, though, recognize diverse epitopes—peptide, lipid, carbohydrate, and nucleic acid—and recognize conformational epitopes, which have three-dimensional structure.) In sexual mate selection[edit] Main article: Major histocompatibility complex and sexual selection See also: Interpersonal compatibility MHC molecules enable immune system surveillance of the population of protein molecules in a host cell, and greater MHC diversity permits greater diversity of antigen presentation. In 1976, Yamazaki et al demonstrated a sexual selection mate choice by male mice for females of a different MHC. Similar results have been obtained with fish. Some data find lower rates of early pregnancy loss in human couples of dissimilar MHC genes. MHC may be related to mate choice in some human populations, a theory that found support by studies by Ober and colleagues in 1997, as well as by Chaix and colleagues in 2008. However, the latter findings have been controversial. If it exists, the phenomenon might be mediated by olfaction, as MHC phenotype appears strongly involved in the strength and pleasantness of perceived odour of compounds from sweat. Fatty acid esters—such as methyl undecanoate, methyl decanoate, methyl nonanoate, methyl octanoate, and methyl hexanoate—show strong connection to MHC. In 1995, Claus Wedekind found that in a group of female college students who smelled T-shirts worn by male students for two nights (without deodorant, cologne, or scented soaps), by far most women chose shirts worn by men of dissimilar MHCs, a preference reversed if the women were on oral contraceptives. In 2005 in a group of 58 subjects, women were more indecisive when presented with MHCs like their own, although with oral contraceptives, the women showed no particular preference. No studies show the extent to which odor preference determines mate selection (or vice versa). Evolutionary diversity[edit] Most mammals have MHC variants similar to those of humans, who bear great allelic diversity, especially among the nine classical genes—seemingly due largely to gene duplication—though human MHC regions have many pseudogenes. The most diverse loci, namely HLA-A, HLA-B, and HLA-C, have roughly 6000, 7200, and 5800 known alleles, respectively. Many HLA alleles are ancient, sometimes of closer homology to a chimpanzee MHC alleles than to some other human alleles of the same gene. MHC allelic diversity has challenged evolutionary biologists for explanation. Most posit balancing selection (see polymorphism (biology)), which is any natural selection process whereby no single allele is absolutely most fit, such as frequency-dependent selection and heterozygote advantage. Pathogenic coevolution, as a type of balancing selection, posits that common alleles are under greatest pathogenic pressure, driving positive selection of uncommon alleles—moving targets, so to say, for pathogens. As pathogenic pressure on the previously common alleles decreases, their frequency in the population stabilizes, and remain circulating in a large population. Genetic drift is also a major driving force in some species. It is possible that the combined effects of some or all of these factors cause the genetic diversity. MHC diversity has also been suggested as a possible indicator for conservation, because large, stable populations tend to display greater MHC diversity, than smaller, isolated populations. Small, fragmented populations that have experienced a population bottleneck typically have lower MHC diversity. For example, relatively low MHC diversity has been observed in the cheetah (Acinonyx jubatus), Eurasian beaver (Castor fiber), and giant panda (Ailuropoda melanoleuca). In 2007 low MHC diversity was attributed a role in disease susceptibility in the Tasmanian devil (Sarcophilus harrisii), native to the isolated island of Tasmania, such that an antigen of a transmissible tumor, involved in devil facial tumour disease, appears to be recognized as a self antigen. To offset inbreeding, efforts to sustain genetic diversity in populations of endangered species and of captive animals have been suggested. In ray-finned fish like rainbow trout, allelic polymorphism in MHC class II is reminiscent of that in mammals and predominantly maps to the peptide binding groove. However, in MHC class I of many teleost fishes, the allelic polymorphism is much more extreme than in mammals in the sense that the sequence identity levels between alleles can be very low and the variation extends far beyond the peptide binding groove. It has been speculated that this type of MHC class I allelic variation contributes to allograft rejection, which may be especially important in fish to avoid grafting of cancer cells through their mucosal skin. The MHC locus (6p21.3) has 3 other paralogous loci in the human genome, namely 19pl3.1, 9q33–q34, and 1q21–q25. It is believed that the loci arouse from the two-round duplications in vertebrates of a single ProtoMHC locus, and the new domain organizations of the MHC genes were a result of later cis-duplication and exon shuffling in a process termed "the MHC Big Bang." Genes in this locus are apparently linked to intracellular intrinsic immunity in the basal Metazoan Trichoplax adhaerens. In transplant rejection[edit] In a transplant procedure, as of an organ or stem cells, MHC molecules themselves act as antigens and can provoke immune response in the recipient, thus causing transplant rejection. MHC molecules were identified and named after their role in transplant rejection between mice of different strains, though it took over 20 years to clarify MHC's role in presenting peptide antigens to cytotoxic T lymphocytes (CTLs). Each human cell expresses six MHC class I alleles (one HLA-A, -B, and -C allele from each parent) and six to eight MHC class II alleles (one HLA-DP and -DQ, and one or two HLA-DR from each parent, and combinations of these). The MHC variation in the human population is high, at least 350 alleles for HLA-A genes, 620 alleles for HLA-B, 400 alleles for DR, and 90 alleles for DQ. Any two individuals who are not identical twins, triplets, or higher order multiple births, will express differing MHC molecules. All MHC molecules can mediate transplant rejection, but HLA-C and HLA-DP, showing low polymorphism, seem least important. When maturing in the thymus, T lymphocytes are selected for their TCR incapacity to recognize self antigens, yet T lymphocytes can react against the donor MHC's peptide-binding groove, the variable region of MHC holding the presented antigen's epitope for recognition by TCR, the matching paratope. T lymphocytes of the recipient take the incompatible peptide-binding groove as nonself antigen. Transplant rejection has various types known to be mediated by MHC (HLA): Hyperacute rejection occurs when, before the transplantation, the recipient has preformed anti-HLA antibodies, perhaps by previous blood transfusions (donor tissue that includes lymphocytes expressing HLA molecules), by anti-HLA generated during pregnancy (directed at the father's HLA displayed by the fetus), or by previous transplantation; Acute cellular rejection occurs when the recipient's T lymphocytes are activated by the donor tissue, causing damage via mechanisms such as direct cytotoxicity from CD8 cells. Acute humoral rejection and chronic disfunction occurs when the recipient's anti-HLA antibodies form directed at HLA molecules present on endothelial cells of the transplanted tissue. In all of the above situations, immunity is directed at the transplanted organ, sustaining lesions. A cross-reaction test between potential donor cells and recipient serum seeks to detect presence of preformed anti-HLA antibodies in the potential recipient that recognize donor HLA molecules, so as to prevent hyperacute rejection. In normal circumstances, compatibility between HLA-A, -B, and -DR molecules is assessed. The higher the number of incompatibilities, the lower the five-year survival rate. Global databases of donor information enhance the search for compatible donors. The involvement in allogeneic transplant rejection appears to be an ancient feature of MHC molecules, because also in fish associations between transplant rejections and (mis-)matching of MHC class I and MHC class II were observed. HLA biology[edit] Codominant expression of HLA genes Main article: Human leukocyte antigen Human MHC class I and II are also called human leukocyte antigen (HLA). To clarify the usage, some of the biomedical literature uses HLA to refer specifically to the HLA protein molecules and reserves MHC for the region of the genome that encodes for this molecule, but this is not a consistent convention. The most studied HLA genes are the nine classical MHC genes: HLA-A, HLA-B, HLA-C, HLA-DPA1, HLA-DPB1, HLA-DQA1, HLA-DQB1, HLA-DRA, and HLA-DRB1. In humans, the MHC gene cluster is divided into three regions: classes I, II, and III. The A, B and C genes belong to MHC class I, whereas the six D genes belong to class II. MHC alleles are expressed in codominant fashion. This means the alleles (variants) inherited from both parents are expressed equally: Each person carries 2 alleles of each of the 3 class-I genes, (HLA-A, HLA-B and HLA-C), and so can express six different types of MHC-I (see figure). In the class-II locus, each person inherits a pair of HLA-DP genes (DPA1 and DPB1, which encode α and β chains), a couple of genes HLA-DQ (DQA1 and DQB1, for α and β chains), one gene HLA-DRα (DRA1), and one or more genes HLA-DRβ (DRB1 and DRB3, -4 or -5). That means that one heterozygous individual can inherit six or eight functioning class-II alleles, three or more from each parent. The role of DQA2 or DQB2 is not verified. The DRB2, DRB6, DRB7, DRB8 and DRB9 are pseudogenes. The set of alleles that is present in each chromosome is called the MHC haplotype. In humans, each HLA allele is named with a number. For instance, for a given individual, his haplotype might be HLA-A2, HLA-B5, HLA-DR3, etc... Each heterozygous individual will have two MHC haplotypes, one each from the paternal and maternal chromosomes. The MHC genes are highly polymorphic; many different alleles exist in the different individuals inside a population. The polymorphism is so high, in a mixed population (nonendogamic), no two individuals have exactly the same set of MHC molecules, with the exception of identical twins. The polymorphic regions in each allele are located in the region for peptide contact. Of all the peptides that could be displayed by MHC, only a subset will bind strongly enough to any given HLA allele, so by carrying two alleles for each gene, each encoding specificity for unique antigens, a much larger set of peptides can be presented. On the other hand, inside a population, the presence of many different alleles ensures there will always be an individual with a specific MHC molecule able to load the correct peptide to recognize a specific microbe. The evolution of the MHC polymorphism ensures that a population will not succumb to a new pathogen or a mutated one, because at least some individuals will be able to develop an adequate immune response to win over the pathogen. The variations in the MHC molecules (responsible for the polymorphism) are the result of the inheritance of different MHC molecules, and they are not induced by recombination, as it is the case for the antigen receptors. Because of the high levels of allelic diversity found within its genes, MHC has also attracted the attention of many evolutionary biologists. See also[edit] Cell-mediated immunity Disassortative sexual selection Humoral immunity MHC multimer Pheromone Streptamer Transplant rejection Notes and references[edit] ^ Hull P (August 1970). "Notes on Dr Snell's observations concerning the H-2 locus polymorphism". Heredity. 25 (3): 461–5. doi:10.1038/hdy.1970.47. PMID 5275401. ^ Janeway Jr CA, Travers P, Walport M, et al. (2001). "The Major Histocompatibility Complex and Its Functions". Immunobiology: The Immune System in Health and Disease (5th ed.). New York: Garland Science. ^ Kimball JW (11 February 2011). "Histocompatibility Molecules". Kimball's Biology Pages. 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PMID 31380027. ^ Castro-Prieto A, Wachter B, Sommer S (April 2011). "Cheetah paradigm revisited: MHC diversity in the world's largest free-ranging population". Molecular Biology and Evolution. 28 (4): 1455–68. doi:10.1093/molbev/msq330. PMC 7187558. PMID 21183613. ^ Babik W, Durka W, Radwan J (December 2005). "Sequence diversity of the MHC DRB gene in the Eurasian beaver (Castor fiber)". Molecular Ecology. 14 (14): 4249–57. Bibcode:2005MolEc..14.4249B. doi:10.1111/j.1365-294X.2005.02751.x. PMID 16313590. S2CID 22260395. ^ Zhu L, Ruan XD, Ge YF, Wan QH, Fang SG (June 2007). "Low major histocompatibility complex class II DQA diversity in the Giant Panda (Ailuropoda melanoleuca)". BMC Genetics. 8: 29. doi:10.1186/1471-2156-8-29. PMC 1904234. PMID 17555583. ^ Siddle HV, Kreiss A, Eldridge MD, Noonan E, Clarke CJ, Pyecroft S, et al. (October 2007). "Transmission of a fatal clonal tumor by biting occurs due to depleted MHC diversity in a threatened carnivorous marsupial". Proceedings of the National Academy of Sciences of the United States of America. 104 (41): 16221–6. doi:10.1073/pnas.0704580104. PMC 1999395. PMID 17911263. ^ Shum BP, Guethlein L, Flodin LR, Adkison MA, Hedrick RP, Nehring RB, et al. (March 2001). "Modes of salmonid MHC class I and II evolution differ from the primate paradigm". Journal of Immunology. 166 (5): 3297–308. doi:10.4049/jimmunol.166.5.3297. PMID 11207285. S2CID 5725603. ^ Aoyagi K, Dijkstra JM, Xia C, Denda I, Ototake M, Hashimoto K, et al. (January 2002). "Classical MHC class I genes composed of highly divergent sequence lineages share a single locus in rainbow trout (Oncorhynchus mykiss)". Journal of Immunology. 168 (1): 260–73. doi:10.4049/jimmunol.168.1.260. PMID 11751970. S2CID 36838421. ^ Yamaguchi T, Dijkstra JM (April 2019). "Major Histocompatibility Complex (MHC) Genes and Disease Resistance in Fish". Cells. 8 (4): 378. doi:10.3390/cells8040378. PMC 6523485. PMID 31027287. ^ Abi Rached L, McDermott MF, Pontarotti P (February 1999). "The MHC big bang". Immunological Reviews. 167 (1): 33–44. doi:10.1111/j.1600-065X.1999.tb01380.x. PMID 10319249. S2CID 29886370. ^ Suurväli J, Jouneau L, Thépot D, Grusea S, Pontarotti P, Du Pasquier L, et al. (September 2014). "The proto-MHC of placozoans, a region specialized in cellular stress and ubiquitination/proteasome pathways". Journal of Immunology. 193 (6): 2891–901. doi:10.4049/jimmunol.1401177. PMID 25114105. ^ Abbas AB, Lichtman AH (2009). "Ch.10 Immune responses against tumors and transplant". Basic Immunology. Functions and disorders of the immune system (3rd ed.). Saunders (Elsevier). ISBN 978-1-4160-4688-2. ^ Sarder MR, Fischer U, Dijkstra JM, Kiryu I, Yoshiura Y, Azuma T, et al. (August 2003). "The MHC class I linkage group is a major determinant in the in vivo rejection of allogeneic erythrocytes in rainbow trout (Oncorhynchus mykiss)". Immunogenetics. 55 (5): 315–24. doi:10.1007/s00251-003-0587-4. PMID 12879308. S2CID 21437633. ^ Quiniou SM, Wilson M, Bengtén E, Waldbieser GC, Clem LW, Miller NW (2005). "MHC RFLP analyses in channel catfish full-sibling families: identification of the role of MHC molecules in spontaneous allogeneic cytotoxic responses". Developmental and Comparative Immunology. 29 (5): 457–67. doi:10.1016/j.dci.2004.08.008. PMID 15707666. ^ Cardwell TN, Sheffer RJ, Hedrick PW (August 2001). "MHC variation and tissue transplantation in fish". The Journal of Heredity. 92 (4): 305–8. doi:10.1093/jhered/92.4.305. PMID 11535641. ^ Abbas AB, Lichtman AH (2009). "Ch.3 Antigen capture and presentation to lymphocytes". Basic Immunology. Functions and disorders of the immune system (3rd ed.). Saunders (Elsevier). ISBN 978-1-4160-4688-2. ^ Spurgin LG, Richardson DS (April 2010). "How pathogens drive genetic diversity: MHC, mechanisms and misunderstandings". Proceedings. Biological Sciences. 277 (1684): 979–88. doi:10.1098/rspb.2009.2084. PMC 2842774. PMID 20071384. Bibliography[edit] Davis DN (2014). The Compatibility Gene. London: Penguin Books. ISBN 978-0-241-95675-5. External links[edit] Major+Histocompatibility+Complex at the U.S. National Library of Medicine Medical Subject Headings (MeSH) Molecular Individuality Archived 2013-01-29 at the Wayback Machine—German online book (2012) NetMHC 3.0 server—predicts binding of peptides to a number of different MHC (HLA) alleles T-cell Group—Cardiff University The story of 2YF6: A Chicken MHC RCSB Protein Data Bank: Molecule of the Month—Major Histocompatibility Complex dbMHC Home, NCBI's database of the Major Histocompatibility Complex vteLymphocytic adaptive immune system and complementLymphoidAntigens Antigen Superantigen Allergen Antigenic variation Hapten Epitope Linear Conformational Mimotope Antigen presentation/professional APCs: Dendritic cell Macrophage B cell Immunogen Antibodies Antibody Monoclonal antibodies Polyclonal antibodies Autoantibody Microantibody Polyclonal B cell response Allotype Isotype Idiotype Immune complex Paratope Immunity vs. tolerance Action: Immunity Autoimmunity Alloimmunity Allergy Hypersensitivity Inflammation Cross-reactivity Co-stimulation Inaction: Tolerance Central Peripheral Clonal anergy Clonal deletion Tolerance in pregnancy Immunodeficiency Immune privilege Immunogenetics Affinity maturation Somatic hypermutation Clonal selection V(D)J recombination Junctional diversity Immunoglobulin class switching MHC/HLA Lymphocytes Cellular T cell Humoral B cell NK cell Substances Cytokines Opsonin Cytolysin vteMajor histocompatibility complex classesMHC class I HLA-A HLA-B HLA-C HLA-E HLA-F HLA-G MHC class II HLA-DM α β HLA-DO α β HLA-DP α1 β1 HLA-DQ α1 α2 β1 β2 β3 HLA-DR α β1 β3 β4 β5 Other Human leukocyte antigen Minor histocompatibility antigen Blood transfusion Arrestin Calgranulin Human blood group systems Cell adhesion molecules Cluster of differentiation vteTransmembrane receptors: immunoglobulin superfamily immune receptorsAntibody receptor:Fc receptorEpsilon (ε) FcεRI (FcεRII is C-type lectin) Gamma (γ) FcγRI FcγRII FcγRIII Neonatal Alpha (α)/mu (μ) FcαRI Fcα/μR Secretory Polymeric immunoglobulin receptor Antigen receptorB cellsAntigen receptor BCR Co-receptorstimulate: CD21/CD19/CD81 inhibit: CD22 Accessory molecules Ig-α/Ig-β (CD79) T cellsLigands MHC MHC class I MHC class II Antigen receptor TCR: TRA@ TRB@ TRD@ TRG@ Co-receptors CD8 (with two glycoprotein chains CD8α and CD8β) CD4 Accessory molecules CD3 CD3γ CD3δ CD3ε ζ-chain (also called CD3ζ and TCRζ) Cytokine receptor see cytokine receptors Killer-cell IG-like receptors KIR2DL1 KIR2DL2 KIR2DL3 KIR2DL4 KIR2DL5A KIR2DL5B KIR2DS1 KIR2DS2 KIR2DS3 KIR2DS4 KIR2DS5 KIR3DL1 KIR3DL2 KIR3DL3 KIR3DS1 Leukocyte IG-like receptors LILRA1 LILRA2 LILRA3 LILRA4 LILRA5 LILRA6 LILRB1 LILRB2 LILRB3 LILRB4 LILRB5 Portals: Biology Medicine Authority control databases International FAST National France BnF data Germany Israel United States Other IdRef 2	biology	2485304	https://sv.wikipedia.org/wiki/Homoleptohyphes%20dimorphus	Homoleptohyphes dimorphus	Homoleptohyphes dimorphus är en dagsländeart som först beskrevs av Allen 1967. Homoleptohyphes dimorphus ingår i släktet Homoleptohyphes och familjen Leptohyphidae. Inga underarter finns listade i Catalogue of Life. Källor Dagsländor dimorphus	swedish	0.972233
immune_system_detect_tumor/whatimmunotherapy.txt	Skip to Content * [ Español ](/es/desplazarse-por-atenci%C3%B3n-del-c%C3%A1ncer/como-se-trata-el-c%C3%A1ncer/inmunoterapia-y-vacunas/que-es-la-inmunoterapia) * [ ASCO.org ](https://www.asco.org/) * [ Conquer Cancer ](https://www.conquer.org/) * [ ASCO Journals ](https://ascopubs.org/) * [ Donate ](https://support.conquer.org/page/57033/donate/1) [ ![Cancer.Net ® ASCO: Knowledge Conquers Cancer](/sites/cancer.net/themes/cancernet2/images/ASCO-CancerNet-Tagline- RGB-2021-11.svg) ](/) ![Cancer.Net ® ASCO: Knowledge Conquers Cancer](/sites/cancer.net/themes/cancernet2/images/ASCO-CancerNet-Tagline- RGB-2021-11.svg) [ eNews Signup ](/about-us/inside-cancernet) * [ f Cancer.net on Facebook ](https://www.facebook.com/CancerDotNet) * [ t Cancer.net on Twitter ](https://twitter.com/cancerdotnet) * [ q Cancer.net on YouTube ](https://www.youtube.com/user/cancerdotnet?sub_confirmation=1) Search Menu * [ Home ](/) * [ Types of Cancer ](/cancer-types) * [ Navigating Cancer Care ](/navigating-cancer-care) * [ Cancer Basics ](/navigating-cancer-care/cancer-basics) * [ Diagnosing Cancer ](/navigating-cancer-care/diagnosing-cancer) * [ Managing Your Care ](/navigating-cancer-care/managing-your-care) * [ Financial Considerations ](/navigating-cancer-care/financial-considerations) * [ How Cancer is Treated ](/navigating-cancer-care/how-cancer-treated) * [ Making Decisions About Cancer Treatment ](/navigating-cancer-care/how-cancer-treated/making-decisions-about-cancer-treatment) * [ Bone Marrow/Stem Cell Transplantation ](/navigating-cancer-care/how-cancer-treated/bone-marrowstem-cell-transplantation) * [ Chemotherapy ](/navigating-cancer-care/how-cancer-treated/chemotherapy) * [ Getting Treatment in a Clinical Trial ](/navigating-cancer-care/how-cancer-treated/getting-treatment-clinical-trial) * [ Hormone Therapy ](/navigating-cancer-care/how-cancer-treated/hormone-therapy) * [ Immunotherapy and Vaccines ](/navigating-cancer-care/how-cancer-treated/immunotherapy-and-vaccines) * [ What Is Immunotherapy? ](/navigating-cancer-care/how-cancer-treated/immunotherapy-and-vaccines/what-immunotherapy) * [ What are Cancer Vaccines? ](/navigating-cancer-care/how-cancer-treated/immunotherapy-and-vaccines/what-are-cancer-vaccines) * [ Side Effects of Immunotherapy ](/navigating-cancer-care/how-cancer-treated/immunotherapy-and-vaccines/side-effects-immunotherapy) * [ Personalized and Targeted Therapies ](/navigating-cancer-care/how-cancer-treated/personalized-and-targeted-therapies) * [ Radiation Therapy ](/navigating-cancer-care/how-cancer-treated/radiation-therapy) * [ Surgery ](/navigating-cancer-care/how-cancer-treated/surgery) * [ When to Call the Doctor During Cancer Treatment ](/navigating-cancer-care/how-cancer-treated/when-call-doctor-during-cancer-treatment) * [ What is Maintenance Therapy? ](/navigating-cancer-care/how-cancer-treated/what-maintenance-therapy) * [ Integrative Medicine ](/navigating-cancer-care/how-cancer-treated/integrative-medicine) * [ When the First Treatment Does Not Work ](/navigating-cancer-care/how-cancer-treated/when-first-treatment-does-not-work) * [ Drug Information Resources ](/navigating-cancer-care/how-cancer-treated/drug-information-resources) * [ Palliative and Supportive Care ](https://www.cancer.net/coping-with-cancer/palliative-and-supportive-care) * [ Dating, Sex, and Reproduction ](/navigating-cancer-care/dating-sex-and-reproduction) * [ Advanced Cancer ](/navigating-cancer-care/advanced-cancer) * [ When Cancer Is Not Your Only Health Concern ](/navigating-cancer-care/when-cancer-not-your-only-health-concern) * [ For Children ](/navigating-cancer-care/children) * [ For Young Adults and Teenagers ](/navigating-cancer-care/young-adults-and-teenagers) * [ For Adults 65+ ](/navigating-cancer-care/adults-65) * [ For U.S. Veterans ](/navigating-cancer-care/us-veterans) * [ Prevention and Healthy Living ](/navigating-cancer-care/prevention-and-healthy-living) * [ Cancer.Net Videos ](https://cancernet.gallery.video/collection) * [ Coping With Cancer ](/coping-with-cancer) * [ Research and Advocacy ](/research-and-advocacy) * [ Survivorship ](/surv%C4%B0vorsh%C4%B0p) * [ Blog ](/blog) * [ About Us ](/about-us) ## You are here 1. [ Home ](/) > 2. [ Navigating Cancer Care ](/navigating-cancer-care) > 3. [ How Cancer is Treated ](/navigating-cancer-care/how-cancer-treated) > 4. [ Immunotherapy and Vaccines ](/navigating-cancer-care/how-cancer-treated/immunotherapy-and-vaccines) > 5. What Is Immunotherapy? [ Request Permissions ](mailto:[email protected]?subject=Cancer.Net Permissions Request&body=I would like permission to republish: %0D%0AWhat Is Immunotherapy?%0D%0Ahttps://www.cancer.net/navigating-cancer-care/how-cancer- treated/immunotherapy-and-vaccines/what-immunotherapy%0D%0A%0D%0APlease contact me at:%0D%0A) ## What Is Immunotherapy? Approved by the [ Cancer.Net Editorial Board ](/about-us/cancernet-editorial- board) , 05/2022 Immunotherapy is a type of cancer treatment. It uses substances made by the body or in a laboratory to boost the immune system and help the body find and destroy cancer cells. Immunotherapy can treat many different types of cancer. It can be used alone or in combination with chemotherapy and/or other cancer treatments. This article will help you understand the basics of how immunotherapy works to treat cancer. Learn more about the [ side effects of immunotherapy ](/node/35996) . ### How does the immune system fight cancer? The immune system consists of a complex process that your body uses to fight cancer. This process involves cells, organs, and proteins. Cancer can commonly get around many of the immune system's natural defenses, allowing cancer cells to continue to grow. Different types of immunotherapy work in different ways. Some immunotherapy treatments help the immune system stop or slow the growth of cancer cells. Others help the immune system destroy cancer cells or stop the cancer from spreading to other parts of the body. The different types of immunotherapy include: * [ Monoclonal antibodies and immune checkpoint inhibitors ](https://www.cancer.net/navigating-cancer-care/how-cancer-treated/immunotherapy-and-vaccines/what-immunotherapy#monoclonal-antibodies-immune-checkpoint-inhibitors) * [ Non-specific immunotherapies ](https://www.cancer.net/navigating-cancer-care/how-cancer-treated/immunotherapy-and-vaccines/what-immunotherapy#non-specific) * [ Oncolytic virus therapy ](https://www.cancer.net/navigating-cancer-care/how-cancer-treated/immunotherapy-and-vaccines/what-immunotherapy#oncolytic-virus-therapy) * [ T-cell therapy ](https://www.cancer.net/navigating-cancer-care/how-cancer-treated/immunotherapy-and-vaccines/what-immunotherapy#t-cell-therapy) * [ Cancer vaccines ](https://www.cancer.net/navigating-cancer-care/how-cancer-treated/immunotherapy-and-vaccines/what-immunotherapy#cancer-vaccines) The type of immunotherapy, dose, and treatment schedule your doctor recommends will depend on many factors. These can include the type of cancer, size, location, and where it has spread. Your age, general health, [ body weight ](https://www.asco.org/practice-patients/guidelines/supportive-care-and- treatment-related-issues#/9976) , and the possible side effects are also important. Talk with your doctor about why a specific immunotherapy plan is being recommended for you. ### What are monoclonal antibodies and immune checkpoint inhibitors? When the immune system detects something harmful, it makes antibodies. Antibodies are proteins that fight infection by attaching to antigens. Antigens are molecules that start the immune response in your body. Monoclonal antibodies are made in a laboratory to boost the body's natural antibodies or act as antibodies themselves. Monoclonal antibodies can help fight cancer in different ways. For example, they can be used to block the activity of abnormal proteins in cancer cells. This is also considered a type of [ targeted therapy ](/node/24729) , which is a cancer treatment using medication that targets a cancer's specific genes, proteins, or the tissue environment that helps the tumor grow and survive. Other types of monoclonal antibodies boost your immune system by inhibiting or stopping immune checkpoints. Immune checkpoints are used by the body to naturally stop an immune system response and prevent the immune system from attacking healthy cells. Cancer cells can find ways to hide from the immune system by activating these checkpoints. Checkpoint inhibitors prevent cancer cells from blocking the immune system. Common checkpoints that these inhibitors affect are the PD-1/PD-L1 and CTLA-4 pathways. Examples of immune checkpoint inhibitors include: * Atezolizumab (Tecentriq) * Avelumab (Bavencio) * Dostarlizumab (Jemperli) * Durvalumab (Imfinzi) * Ipilimumab (Yervoy) * Nivolumab (Opdivo) * Pembrolizumab (Keytruda) Many checkpoint inhibitors are approved by the U.S. Food and Drug Administration (FDA) for specific cancers. There are also 2 checkpoint inhibitors that are used to treat tumors anywhere in the body if they have specific genetic changes. This kind of approach is called a "tumor-agnostic treatment." For instance, pembrolizumab (Keytruda) is approved to treat any tumors that have spread to distant parts of the body if they have a specific molecular change called microsatellite instability-high (MSI-H) or DNA mismatch repair deficiency (dMMR). Another example is that dostarlimab (Jemperli) can be used for advanced cancer or cancer that has come back if it has dMMR. Learn more about [ tumor-agnostic treatments ](/node/39106) . The side effects of monoclonal antibody treatment depend on the drug's purpose. For example, the side effects of monoclonal antibodies used for targeted therapy are not like those used for immunotherapy. The side effects of immune checkpoint inhibitors may include side effects similar to an allergic reaction. Learn more about [ side effects of immune checkpoint inhibitors ](/node/41856) . [ _Return to top_ ](https://www.cancer.net/navigating-cancer-care/how-cancer- treated/immunotherapy-and-vaccines/what-immunotherapy#main-content) ### What are non-specific immunotherapies? Non-specific immunotherapies, also called non-specific immunomodulating agents, help your immune system destroy cancer cells. There are several kinds of non-specific immunotherapies that work in different ways. Cytokines. Cytokines are a part of the immune system. They are proteins that send messages between cells to activate the immune system. There are two types of cytokines that are used to treat cancer: * Interferons. These proteins are produced by your immune system to alert your body that there is a pathogen, typically a virus, in your body. Interferons can be made in a laboratory to help your immune system fight cancer. They can also slow the growth of cancer cells. The most common type of interferon used in cancer treatment is called interferon alpha (Roferon-A [2a], Intron A [2b], Alferon [2a]). Interferon can be used to several many different types of cancer. Side effects of interferon treatment may include flu-like symptoms, an increased risk of infection, skin rashes, and hair thinning. * Interleukins. Interleukins are proteins that pass messages between cells. They also start an immune response. For example, the lab-made interleukin-2 (IL-2) or aldesleukin (Proleukin) can treat [ kidney cancer ](/node/18976) and [ melanoma ](/node/19258) . Common side effects of IL-2 treatment include weight gain and low blood pressure. Some people also experience flu-like symptoms. Bacillus Calmette-Guerin (BCG). This type of immunotherapy is similar to the bacteria that causes tuberculosis. It is used to treat [ bladder cancer ](/node/18527) . BCG is placed directly into the bladder through a catheter. It attaches to the inside lining of the bladder and activates the immune system to destroy tumor cells. BCG can cause flu-like symptoms. [ _Return to top_ ](https://www.cancer.net/navigating-cancer-care/how-cancer- treated/immunotherapy-and-vaccines/what-immunotherapy#main-content) ### What is oncolytic virus therapy? Oncolytic virus therapy, sometimes just called virus therapy, uses viruses that have been changed in a laboratory to destroy cancer cells. A genetically modified version of the virus is injected into the tumor. When the virus enters the cancer cells, it makes a copy of itself. As a result, the cancer cells burst and die. As the cells die, they release proteins that trigger your immune system to target any cancer cells in your body that have the same proteins as the dead cancer cells. The virus does not enter healthy cells. Currently, one type of oncolytic virus therapy is approved in the United States to treat cancer: Talimogene laherparepvec (Imlygic) or T-VEC. This oncolytic virus therapy is approved to treat advanced melanoma that cannot be treated with surgery. It is used most often for people who cannot or choose not to receive any other recommended treatments. T-VEC is a modified version of the herpes simplex virus, which causes cold sores. It is injected directly into 1 or more melanoma tumors. Side effects of oncolytic virus therapy include flu-like symptoms and pain at the injection site. [ Clinical trials ](/node/24863) are testing other oncolytic viruses for different cancers. They are also testing how the viruses work with other cancer treatments, such as chemotherapy. [ _Return to top_ ](https://www.cancer.net/navigating-cancer-care/how-cancer- treated/immunotherapy-and-vaccines/what-immunotherapy#main-content) ### What is T-cell therapy? T cells are immune cells that fight infection. In T-cell therapy, the doctor removes T cells from the blood. Then, a laboratory adds specific proteins called receptors to the cells. The receptor allows those T cells to recognize cancer cells. The changed T cells are put back into the body. Once there, they find and destroy cancer cells. This type of therapy is known as chimeric antigen receptor (CAR) T-cell therapy. Side effects include fevers, confusion, low blood pressure, and, in rare occasions, seizures. CAR T-cell therapy is used to treat certain blood cancers. Researchers are still studying this type of therapy and other ways of changing T cells to treat cancer. Learn more about [ the basics of CAR T-cell therapy ](/node/41721) . [ _Return to top_ ](https://www.cancer.net/navigating-cancer-care/how-cancer- treated/immunotherapy-and-vaccines/what-immunotherapy#main-content) ### What are cancer vaccines? A cancer vaccine can also help your body fight disease. A vaccine exposes your immune system to a foreign protein, called an antigen. This triggers the immune system to recognize and destroy that antigen or related substances. There are 2 types of cancer vaccine: prevention vaccines and treatment vaccines. One example of a cancer prevention vaccine is Gardasil, the vaccine to protect against the [ human papillomavirus (HPV) ](/node/24561) , a virus that can cause specific types of cancer. An example of a treatment vaccine includes [ spuleucel-T (Provenge) ](https://www.cancer.net/cancer-types/prostate- cancer/types-treatment) , which treats advanced prostate cancer that does not respond to hormone therapy. T-VEC (see above) is also considered a cancer treatment vaccine. Side effects for both of these cancer vaccines are flu-like symptoms. [ _Return to top_ ](https://www.cancer.net/navigating-cancer-care/how-cancer- treated/immunotherapy-and-vaccines/what-immunotherapy#main-content) In general, immunotherapy is an important approach as cancer researchers continue to look for new cancer treatments. The examples above do not include every type of immunotherapy treatment. Researchers are studying many new drugs. You can learn more about immunotherapy in each [ cancer-specific section on Cancer.Net ](https://www.cancer.net/cancer-types) . Look at the "Types of Treatment" and "Latest Research" pages for specific information about immunotherapy for that type of cancer. You can also learn about the latest [ immunotherapy research on the Cancer.Net Blog ](https://www.cancer.net/blog/tags/immunotherapy) . ### Questions to ask your health care team If immunotherapy is a cancer treatment option for you, consider asking your health care team these questions: * What type of immunotherapy do you recommend? Why? * What are the goals of this treatment? * What immunotherapy clinical trials are open to me? * Will immunotherapy be my only type of cancer treatment? If not, what other treatments will I need? When? * How will I receive immunotherapy treatment? * Where will I receive this treatment? * How long will each treatment take? How often will I need to get this treatment? * What are the possible short-term side effects of immunotherapy? How can these be managed? * Who should I talk with about any side effects I experience? How soon? * What side effects should I let you know about right away? * Whom should I call with questions or problems? * How can I reach them during regular business hours? After hours? * How will this treatment affect my daily life? Will I be able to work, exercise, and do my usual activities? * If I'm very worried or anxious about having this treatment, who can I talk with? * If I'm worried about managing the cost of this treatment, who can help me? * What are possible long-term side effects of this immunotherapy? How can these be managed? * How will we know if this immunotherapy is working? * Will I need any tests or scans before, during, or after immunotherapy? * Could the dose or duration of my immunotherapy change over time? ### Related Resources [ ASCO Answers Fact Sheet: Understanding Immunotherapy (PDF) ](https://www.cancer.net/sites/cancer.net/files/asco_answers_immunotherapy.pdf) [ Side Effects of Immunotherapy ](https://www.cancer.net/node/35996) ### More Information [ American Cancer Society: Cancer Immunotherapy ](https://www.cancer.org/treatment/treatments-and-side-effects/treatment- types/immunotherapy.html) [ National Cancer Institute: Biologic Therapies ](https://www.cancer.gov/about-cancer/treatment/types/immunotherapy/bio- therapies-fact-sheet?redirect=true) [ Español ](/es/desplazarse-por-atenci%C3%B3n-del-c%C3%A1ncer/como-se-trata- el-c%C3%A1ncer/inmunoterapia-y-vacunas/que-es-la-inmunoterapia "¿Qué es la inmunoterapia?") ![ASCO Answers: Understanding Immunotherapy](https://www.cancer.net/sites/cancer.net/files/fs_understanding_immunotherapy_2019_bookstore_500x500.jpg) Download a free fact sheet on [ Understanding Immunotherapy (PDF) ](https://www.cancer.net/sites/cancer.net/files/asco_answers_immunotherapy.pdf) . This 1-page (front and back) fact sheet provides an overview of the different types of immunotherapy, possible side effects, terms to know, and questions to ask the health care team. [ f ](https://facebook.com/sharer/sharer.php?u=https://www.cancer.net/navigating- cancer-care/how-cancer-treated/immunotherapy-and-vaccines/what-immunotherapy) [ t ](https://twitter.com/intent/tweet/?text=Immunotherapy is a type of cancer treatment. It uses substances made by the body or in a laboratory to boost t...&url=https://www.cancer.net/navigating-cancer-care/how-cancer- treated/immunotherapy-and-vaccines/what-immunotherapy) [ k ](https://www.linkedin.com/shareArticle?mini=true&url=https://www.cancer.net/navigating- cancer-care/how-cancer-treated/immunotherapy-and-vaccines/what- immunotherapy&title=What Is Immunotherapy?&summary=Immunotherapy is a type of cancer treatment. It uses substances made by the body or in a laboratory to boost the immune system and help the body find and destroy cancer cells.Immunotherapy can treat many different types of cancer. It can be used alone or in combination with chemotherapy and/or other cancer treatments.&source=https://www.cancer.net/navigating-cancer-care/how-cancer- treated/immunotherapy-and-vaccines/what-immunotherapy) [ e ](mailto:?subject=Sharing%20What Is Immunotherapy?&body=https://www.cancer.net/navigating-cancer-care/how-cancer- treated/immunotherapy-and-vaccines/what-immunotherapy%0D%0AImmunotherapy is a type of cancer treatment. It uses substances made by the body or in a laboratory to boost the immune system and help the body find and destroy cancer cells.Immunotherapy can treat many different types of cancer. It can be used alone or in combination with chemotherapy and/or other cancer treatments.) 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All rights reserved worldwide	biology	4081776	https://sv.wikipedia.org/wiki/Tofieldia%20coccinea	Tofieldia coccinea	Tofieldia coccinea är en kärrliljeväxtart som beskrevs av John Richardson. Tofieldia coccinea ingår i släktet kärrliljor, och familjen kärrliljeväxter. Underarter Arten delas in i följande underarter: T. c. coccinea T. c. sphaerocephala Bildgalleri Källor Externa länkar Kärrliljor coccinea	swedish	1.469349
immune_system_detect_tumor/immunotherapy.txt	Skip to main content An official website of the United States government [ Español ](/espanol/cancer/tratamiento/tipos/inmunoterapia) [ ![](/sites/g/files/xnrzdm211/files/ncids_header/logos/Logo_NCI_Mobile.svg) ](/) Menu Search Search * [ About Cancer ](/about-cancer) * [ Cancer Types ](/types) * [ Research ](/research) * [ Grants & Training ](/grants-training) * [ News & Events ](/news-events) * [ About NCI ](/about-nci) 1. [ Home ](/) 2. [ About Cancer ](/about-cancer) 3. [ Cancer Treatment ](/about-cancer/treatment) 4. [ Types of Cancer Treatment ](/about-cancer/treatment/types) 5. Immunotherapy to Treat Cancer Print [ Email ](mailto:?subject=Information from the National Cancer Institute Web Site &body=I found this information on www.cancer.gov and I'd like to share it with you: https://www.cancer.gov/about- cancer/treatment/types/immunotherapy %0D%0A%0D%0A NCI's Web site, www.cancer.gov, provides accurate, up-to-date, comprehensive cancer information from the U.S. government's principal agency for cancer research. If you have questions or need additional information, we invite you to contact NCI's LiveHelp instant messaging service at https://livehelp.cancer.gov, or call the NCI's Contact Center 1-800-4-CANCER $1-800-422-6237$ $toll-free from the United States$.) * [ Cancer Treatment ](/about-cancer/treatment) * [ Types of Cancer Treatment ](/about-cancer/treatment/types) * [ Biomarker Testing ](/about-cancer/treatment/types/biomarker-testing-cancer-treatment) * [ Chemotherapy ](/about-cancer/treatment/types/chemotherapy) * [ Hormone Therapy ](/about-cancer/treatment/types/hormone-therapy) * [ Hyperthermia ](/about-cancer/treatment/types/hyperthermia) * [ Immunotherapy ](/about-cancer/treatment/types/immunotherapy) * [ Cancer Treatment Vaccines ](/about-cancer/treatment/types/immunotherapy/cancer-treatment-vaccines) * [ Checkpoint Inhibitors ](/about-cancer/treatment/types/immunotherapy/checkpoint-inhibitors) * [ Immune System Modulators ](/about-cancer/treatment/types/immunotherapy/immune-system-modulators) * [ Monoclonal Antibodies ](/about-cancer/treatment/types/immunotherapy/monoclonal-antibodies) * [ Side Effects ](/about-cancer/treatment/types/immunotherapy/side-effects) * [ T-cell Transfer Therapy ](/about-cancer/treatment/types/immunotherapy/t-cell-transfer-therapy) * [ Photodynamic Therapy ](/about-cancer/treatment/types/photodynamic-therapy) * [ Radiation Therapy ](/about-cancer/treatment/types/radiation-therapy) * [ Stem Cell Transplant ](/about-cancer/treatment/types/stem-cell-transplant) * [ Surgery ](/about-cancer/treatment/types/surgery) * [ Targeted Therapy ](/about-cancer/treatment/types/targeted-therapies) * [ Side Effects of Cancer Treatment ](/about-cancer/treatment/side-effects) * [ A to Z List of Cancer Drugs ](/about-cancer/treatment/drugs) * [ Complementary & Alternative Medicine (CAM) ](/about-cancer/treatment/cam) * [ Questions to Ask about Your Treatment ](/about-cancer/treatment/questions) * [ NIH Clinical Center ](/about-cancer/treatment/clinical-center) * [ Research ](/about-cancer/treatment/research) # Immunotherapy to Treat Cancer Immunotherapy is a type of cancer treatment that helps your [ immune system ](/Common/PopUps/popDefinition.aspx?id=CDR0000046356&version=Patient&language=en) fight cancer. The immune system helps your body fight infections and other diseases. It is made up of white blood cells and [ organs ](/Common/PopUps/popDefinition.aspx?id=CDR0000257523&version=Patient&language=en) and [ tissues ](/Common/PopUps/popDefinition.aspx?id=CDR0000046683&version=Patient&language=en) of the [ lymph system ](/Common/PopUps/popDefinition.aspx?id=CDR0000045764&version=Patient&language=en) . Immunotherapy is a type of [ biological therapy ](/Common/PopUps/popDefinition.aspx?id=CDR0000045617&version=Patient&language=English) . Biological therapy is a type of treatment that uses substances made from living organisms to treat cancer. ###### On This Page * How does immunotherapy work against cancer? * What are the types of immunotherapy? * Which cancers are treated with immunotherapy? * What are the side effects of immunotherapy? * How is immunotherapy given? * Where do you go for immunotherapy? * How often do you receive immunotherapy? * How can you tell if immunotherapy is working? * What is the current research in immunotherapy? * How do you find clinical trials that are testing immunotherapy? ## How does immunotherapy work against cancer? As part of its normal function, the immune system detects and destroys abnormal cells and most likely prevents or curbs the growth of many cancers. For instance, immune cells are sometimes found in and around tumors. These cells, called tumor-infiltrating lymphocytes or TILs, are a sign that the immune system is responding to the tumor. People whose tumors contain TILs often do better than people whose tumors don’t contain them. Even though the immune system can prevent or slow cancer growth, cancer cells have ways to avoid destruction by the immune system. For example, cancer cells may: * Have genetic changes that make them less visible to the immune system. * Have proteins on their surface that turn off immune cells. * Change the normal cells around the tumor so they interfere with how the immune system responds to the cancer cells. Immunotherapy helps the immune system to better act against cancer. ## What are the types of immunotherapy? [ ![Chat, email or call NCI's Cancer Information Service](/sites/g/files/xnrzdm211/files/styles/cgov_featured/public/cgov_image/media_image/2023-07/CIS_promo_icons.jpg?h=0bf6a64e&itok=5XfhdaeD) ### Get Answers > Wondering if immunotherapy is an option for you? Connect with a Cancer Information Specialist. ](http://www.cancer.gov/contact?cid=wl_cgov_cis_icons_connect_imm) Several types of immunotherapy are used to treat cancer. These include: * Immune checkpoint inhibitors , which are drugs that block immune checkpoints. These checkpoints are a normal part of the immune system and keep immune responses from being too strong. By blocking them, these drugs allow immune cells to respond more strongly to cancer. Learn more about [ immune checkpoint inhibitors ](/about- cancer/treatment/types/immunotherapy/checkpoint-inhibitors) . * T-cell transfer therapy , which is a treatment that boosts the natural ability of your [ T cells ](/Common/PopUps/popDefinition.aspx?id=CDR0000044928&version=Patient&language=en) to fight cancer. In this treatment, immune cells are taken from your tumor. Those that are most active against your cancer are selected or changed in the lab to better attack your cancer cells, grown in large batches, and put back into your body through a needle in a vein. T-cell transfer therapy may also be called adoptive cell therapy, adoptive immunotherapy, or immune cell therapy. Learn more about [ T-cell transfer therapy ](/about- cancer/treatment/types/immunotherapy/t-cell-transfer-therapy) . * Monoclonal antibodies , which are immune system proteins created in the lab that are designed to bind to specific targets on cancer cells. Some monoclonal antibodies mark cancer cells so that they will be better seen and destroyed by the immune system. Such monoclonal antibodies are a type of immunotherapy. Monoclonal antibodies may also be called therapeutic antibodies. Learn more about [ monoclonal antibodies ](/about- cancer/treatment/types/immunotherapy/monoclonal-antibodies) . * Treatment vaccines , which work against cancer by boosting your immune system’s response to cancer cells. Treatment vaccines are different from the ones that help prevent disease. Learn more about [ cancer treatment vaccines ](/about- cancer/treatment/types/immunotherapy/cancer-treatment-vaccines) . * Immune system modulators , which enhance the body’s [ immune response ](/Common/PopUps/popDefinition.aspx?id=CDR0000045722&version=Patient&language=en) against cancer. Some of these agents affect specific parts of the immune system, whereas others affect the immune system in a more general way. Learn more about [ immune system modulators ](/about- cancer/treatment/types/immunotherapy/immune-system-modulators) . ## Which cancers are treated with immunotherapy? Immunotherapy drugs have been approved to treat many types of cancer. However, immunotherapy is not yet as widely used as [ surgery ](/Common/PopUps/popDefinition.aspx?id=CDR0000045570&version=Patient&language=en) , [ chemotherapy ](/Common/PopUps/popDefinition.aspx?id=CDR0000045214&version=Patient&language=en) , or [ radiation therapy ](/Common/PopUps/popDefinition.aspx?id=CDR0000044971&version=Patient&language=en) . To learn about whether immunotherapy may be used to treat your cancer, see the [ PDQ ](/Common/PopUps/popDefinition.aspx?id=CDR0000044271&version=Patient&language=en) ® [ adult cancer treatment summaries ](/publications/pdq/information- summaries/adult-treatment) and [ childhood cancer treatment summaries ](/publications/pdq/information-summaries/pediatric-treatment) . ## What are the side effects of immunotherapy? Immunotherapy can cause [ side effects ](/Common/PopUps/popDefinition.aspx?id=CDR0000046580&version=Patient&language=en) , many of which happen when the immune system that has been revved-up to act against the cancer also acts against healthy cells and tissues in your body. Learn more about [ immunotherapy side effects ](/about- cancer/treatment/types/immunotherapy/side-effects) . ## How is immunotherapy given? Different forms of immunotherapy may be given in different ways. These include: * intravenous (IV) The immunotherapy goes directly into a [ vein ](/Common/PopUps/popDefinition.aspx?id=CDR0000476471&version=Patient&language=English) . * oral The immunotherapy comes in pills or [ capsules ](/Common/PopUps/popDefinition.aspx?id=CDR0000455334&version=Patient&language=en) that you swallow. * topical The immunotherapy comes in a cream that you rub onto your skin. This type of immunotherapy can be used for very early skin cancer. * intravesical The immunotherapy goes directly into the bladder. ## Where do you go for immunotherapy? You may receive immunotherapy in a doctor’s office, clinic, or outpatient unit in a hospital. Outpatient means you do not spend the night in the hospital. ## How often do you receive immunotherapy? How often and how long you receive immunotherapy depends on: * your type of cancer and how advanced it is * the type of immunotherapy you get * how your body reacts to treatment You may have treatment every day, week, or month. Some types of immunotherapy given in cycles. A cycle is a period of treatment followed by a period of rest. The rest period gives your body a chance to recover, respond to immunotherapy, and build new healthy cells. ## How can you tell if immunotherapy is working? You will see your doctor often. He or she will give you [ physical exams ](/Common/PopUps/popDefinition.aspx?id=CDR0000270871&version=Patient&language=English) and ask you how you feel. You will have medical tests, such as blood tests and different types of [ scans ](/Common/PopUps/popDefinition.aspx?id=CDR0000046570&version=Patient&language=English) . These tests will measure the size of your tumor and look for changes in your blood work. ## What is the current research in immunotherapy? Researchers are focusing on several major areas to improve immunotherapy, including: * Finding solutions for resistance. Researchers are testing combinations of immune checkpoint inhibitors and other types of immunotherapy, targeted therapy, and radiation therapy to overcome resistance to immunotherapy. * Finding ways to predict responses to immunotherapy. Only a small portion of people who receive immunotherapy will respond to the treatment. Finding ways to predict which people will respond to treatment is a major area of research. * Learning more about how cancer cells evade or suppress immune responses against them. A better understanding of how cancer cells get around the immune system could lead to the development of new drugs that block those processes. * How to reduce the side effects of treatment with immunotherapy. ## How do you find clinical trials that are testing immunotherapy? To find clinical research studies that involve immunotherapy visit [ Find NCI- Supported Clinical Trials ](/research/participate/clinical-trials-search) or call the Cancer Information Service, NCI’s contact center, at 1-800-4-CANCER (1-800-422-6237). NCI’s list of cancer clinical trials includes all NCI-supported clinical trials that are taking place across the United States and Canada, including the NIH Clinical Center in Bethesda, MD. ###### Related Resources * [ New Drugs, New Side Effects: Complications of Cancer Immunotherapy ](/news-events/cancer-currents-blog/2019/cancer-immunotherapy-investigating-side-effects) * [ Targeted Therapy to Treat Cancer ](/about-cancer/treatment/types/targeted-therapies) * [ CAR T Cells: Engineering Patients’ Immune Cells to Treat Their Cancers ](/about-cancer/treatment/research/car-t-cells) * [ Can Immunotherapy Succeed in Glioblastoma? ](/news-events/cancer-currents-blog/2018/immunotherapy-glioblastoma) * Updated: September 24, 2019 _If you would like to reproduce some or all of this content, see[ Reuse of NCI Information ](/policies/copyright-reuse) for guidance about copyright and permissions. In the case of permitted digital reproduction, please credit the National Cancer Institute as the source and link to the original NCI product using the original product's title; e.g., “Immunotherapy to Treat Cancer was originally published by the National Cancer Institute.” _ Want to use this content on your website or other digital platform? Our [ syndication services page ](/syndication) shows you how. Print [ Email ](mailto:?subject=Information from the National Cancer Institute Web Site &body=I found this information on www.cancer.gov and I'd like to share it with you: https://www.cancer.gov/about- cancer/treatment/types/immunotherapy %0D%0A%0D%0A NCI's Web site, www.cancer.gov, provides accurate, up-to-date, comprehensive cancer information from the U.S. government's principal agency for cancer research. If you have questions or need additional information, we invite you to contact NCI's LiveHelp instant messaging service at https://livehelp.cancer.gov, or call the NCI's Contact Center 1-800-4-CANCER $1-800-422-6237$ $toll-free from the United States$.) 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Det er anvendelse af grundforskning af cancerimmunologi og det voksende underspeciale onkologi. Metoden udnytter at kræftceller ofte har molekyler på deres overflade, der kan blive opdaget af immunforsvaret, kendt som tumorantigener; de er ofte proteiner eller andre makromolekyler (eksempelvis kulhydrater). Immunterapi kan blive kategoriseret som som aktiv, passiv eller hybrid (aktiv og passiv). Aktiv immunterapi styrer immunsystemet til at angribe tumorceller med målrettede tumor-antigener. Passiv immunterapi forbedrer eksisterende anti-tumorreaktioner og inkluderer monoklonale antistoffer, lymfocyter og cytokin. I 2018 modtog James P. Allison og Tasuku Honjo nobelprisen i fysiologi eller medicin for deres forskning i dette felt. Se også immun-checkpoint Henvisninger Immunforsvar Kræftbehandling	danish	0.443907
immune_system_detect_tumor/11582immunotherapy.txt	Locations : [ Abu Dhabi ](https://www.clevelandclinicabudhabi.ae/) \| [ Canada ](https://my.clevelandclinic.org/canada) \| [ Florida ](https://my.clevelandclinic.org/florida) \| [ London ](https://clevelandcliniclondon.uk/) \| [ Nevada ](https://my.clevelandclinic.org/locations/nevada) \| [ Ohio ](https://my.clevelandclinic.org) \| ![Gray gradient](/health/_next/static/media/gray-gradient- left-16.59910877.svg?w=32&q=75) ![Gray gradient](/health/_next/static/media/gray-gradient- right-32.dd7ce4e5.svg?w=64&q=75) * [ 800.223.2273 ](tel:800.223.2273) * [ 100 Years of Cleveland Clinic ](https://my.clevelandclinic.org/about/history) * [ MyChart ](https://my.clevelandclinic.org/online-services/mychart) * [ Need Help? ](https://my.clevelandclinic.org/help) * [ Giving ](https://my.clevelandclinic.org/giving) * [ Careers ](https://jobs.clevelandclinic.org) * [ ![Search Icon Blue](/health/_next/static/media/search--blue.a23a2bb9.svg?w=32&q=75) Search ](https://my.clevelandclinic.org/search) [ ![Cleveland Clinic logo](/health/_next/static/media/logo- ccf.a7ea0118.svg?w=3840&q=75) ](https://my.clevelandclinic.org/) [ ![Search Icon](/health/_next/static/media/search-- gray.86f52a63.svg?w=48&q=75) ](https://my.clevelandclinic.org/search) * [ ClevelandClinic.org ](https://my.clevelandclinic.org) * [ Find A Doctor ](https://my.clevelandclinic.org/staff) * [ Locations & Directions ](https://my.clevelandclinic.org/locations) * [ Patients & Visitors ](https://my.clevelandclinic.org/patients) * [ Health Library ](https://my.clevelandclinic.org/health) * [ Institutes & Departments ](https://my.clevelandclinic.org/departments) * [ Appointments ](https://my.clevelandclinic.org/patients/information/access) ![](//zdbb.net/l/Dnl1wmWs8xCCpvWNCt9Egf/?w=16&q=75) [ Home ](https://my.clevelandclinic.org) / [ Health Library ](https://my.clevelandclinic.org/health) / [ Treatments & Procedures ](https://my.clevelandclinic.org/health/treatments) / Immunotherapy Advertisement Advertisement Advertisement # Immunotherapy Immunotherapy for cancer uses your body’s immune system to find and destroy cancerous cells. There are several different immunotherapy types, but all immunotherapy works by training your immune system so it can do more to fight cancer. Immunotherapy may help some people with cancer to live longer. Contents Arrow Down Overview Procedure Details Risks / Benefits Recovery and Outlook When To Call the Doctor Contents Arrow Down Overview Procedure Details Risks / Benefits Recovery and Outlook When To Call the Doctor ## Overview ![Immunotherapy is cancer treatment that helps your immune system fight cancer.](https://my.clevelandclinic.org/-/scassets/Images/org/health/articles/11582-immunotherapy) Immunotherapy is cancer treatment that helps your immune system fight cancer. Healthcare providers typically use immunotherapy to treat advanced cancer, cancer that hasn’t respond to other treatments and cancer that’s come back. There are five types of immunotherapy, including checkpoint inhibitors, adoptive cell therapy, cancer vaccines, monoclonal antibodies and immune system modulators. ### What is immunotherapy? Immunotherapy is a cancer treatment that uses your body’s immune system to find and destroy cancer cells. Your [ immune system ](https://my.clevelandclinic.org/health/articles/21196-immune-system) identifies and destroys intruders, including cancerous cells. Immunotherapy boosts your immune system so it can do more to find and kill cancer cells. Immunotherapy for cancer is a very effective treatment that may help some people with [ cancer ](https://my.clevelandclinic.org/health/diseases/12194-cancer) live longer. Medical researchers are developing new immunotherapy drugs to treat more types of cancer. #### How does immunotherapy work? Your immune system’s everyday job is to protect your body from intruders, from allergens and viruses to damaged cells that could become cancerous. It has special cells that constantly patrol your body for intruders. When they find a damaged or cancerous cell, they destroy it. That keeps cancerous tumors from growing and spreading. But cancer is a moving target. Cancerous cells constantly look for ways to dodge immune system defenses. Immunotherapy works by: * Training your immune system so it can do more to find and kill cancer cells. * Helping your body produce cancer-fighting immune cells that effectively locate and destroy cancer cells. #### What cancers does immunotherapy treat? Healthcare providers consider immunotherapy a first-line or initial treatment for many types of metastatic cancer, or cancer that’s spread. They may combine immunotherapy with [ chemotherapy ](https://my.clevelandclinic.org/health/treatments/16859-chemotherapy) , [ targeted ](https://my.clevelandclinic.org/health/treatments/22733-targeted- therapy) therapy or other cancer treatments. Providers use different types of immunotherapy to treat many kinds of cancer. Each immunotherapy type uses different elements of your immune system. Advertisement Cleveland Clinic is a non-profit academic medical center. Advertising on our site helps support our mission. We do not endorse non-Cleveland Clinic products or services. [ Policy ](https://health.clevelandclinic.org/advertising) ### What are types of immunotherapy? Immunotherapy types include: * Checkpoint inhibitors. * Adoptive cell therapy (T-cell transfer therapy). * Monoclonal antibodies. * Cancer vaccines. * Immune system modulators. #### Checkpoint inhibitors Your immune system is a powerful defense system — sometimes too powerful. Your body has checkpoints to keep your immune system from overreacting to intruders and damaging healthy cells. For example, your bone marrow makes white blood cells called T lymphocytes, or T-cells. T-cells protect your body from infection and tackle cancer cells. Immune checkpoints connect with proteins on the surface of T-cells. ##### How checkpoint inhibitors work Checkpoint proteins and other proteins manage the flow of signals to T-cells, telling the cells when to turn off and on. (Think traffic monitors that manage traffic flow by switching traffic lights off and on.) T-cells turn on to kill cancerous cells. They turn off so they don’t damage normal cells. Checkpoint inhibitors are immunotherapy drugs that work by breaking the connection between the checkpoint proteins and other proteins. Breaking the connection keeps protein cells from telling T-cells to turn off. That way, T-cells keep on killing cancerous cells. ###### What cancers are treated with checkpoint inhibitors? Healthcare providers typically use checkpoint inhibitors to treat many different types of cancer. In general, providers use checkpoint inhibitors to treat advanced cancer, cancer that’s spread, cancer that can’t be treated with surgery or cancer that hasn’t responded to other treatments. They may combine checkpoint inhibitor drugs with other treatments, including chemotherapy or targeted therapy. The list below is expected to grow as medical researchers find ways to use immunotherapy to treat many more kinds of cancer: * [ Bladder cancer ](https://my.clevelandclinic.org/health/diseases/14326-bladder-cancer) . * [ Cervical cancer ](https://my.clevelandclinic.org/health/diseases/12216-cervical-cancer) . * [ Esophageal cancer ](https://my.clevelandclinic.org/health/diseases/6137-esophageal-cancer) . * [ Head and neck cancer ](https://my.clevelandclinic.org/health/diseases/14458-head-and-neck-cancer) . * [ Hepatocellular carcinoma ](https://my.clevelandclinic.org/health/diseases/21709-hepatocellular-carcinoma-hcc) . * High-risk [ triple-negative breast cancer ](https://my.clevelandclinic.org/health/diseases/21756-triple-negative-breast-cancer-tnbc) . * [ Kidney cancer ](https://my.clevelandclinic.org/health/diseases/9409-kidney-cancer-overview) . * [ Melanoma ](https://my.clevelandclinic.org/health/diseases/14391-melanoma) . * [ Mesothelioma ](https://my.clevelandclinic.org/health/diseases/22432-mesothelioma) . * [ Non-small cell lung cancer ](https://my.clevelandclinic.org/health/articles/6203-non-small-cell-lung-cancer) . #### Adoptive cell therapy (T-cell transfer therapy) This treatment improves your immune system’s ability to destroy cancerous cells. Healthcare providers take your immune cells and grow them in a laboratory. Once your cells have grown, providers insert the cells back into your body so they can kill cancerous cells. [ CAR T-cell therapy ](https://my.clevelandclinic.org/health/treatments/17726-car-t-cell-therapy) and tumor-infiltrating lymphocyte therapy are the two main types of T-cell transfer therapy. ##### How CAR T-cell therapy works Chimeric antigen receptor (CAR) T-cell therapy works by turning your T lymphocytes, or T-cells, into more efficient cancer-fighting machines. Your T-cells are white blood cells in your immune system. Your immune system monitors your body for intruders, such as cancerous cells, by tracking proteins called antigens that are located on the surface of intruder cells. Your immune system relies on T-cells to track and kill intruders. Your T-cells have their own proteins called receptors. Receptors are like the anti-virus software on your computer. When your T-cell security team senses intruder antigens, they use their receptors to catch and block the intruders. More than that, your T-cells can kill the intruders. But antigens have their own form of protection. They can disguise themselves to hide from your T-cells. CAR T-cell therapy ensures your T-cells aren’t fooled by antigens in disguise. ###### Cancers treated with CAR T-cell therapy CAR T-cell therapy treats certain [ blood cancers ](https://my.clevelandclinic.org/health/diseases/22883-blood-cancer) , including some types of [ leukemia ](https://my.clevelandclinic.org/health/diseases/4365-leukemia) , [ lymphoma ](https://my.clevelandclinic.org/health/diseases/22225-lymphoma) and [ multiple myeloma ](https://my.clevelandclinic.org/health/articles/6178-multiple-myeloma) . Medical researchers are investigating CAR T-cell therapy as a way to treat [ breast cancer ](https://my.clevelandclinic.org/health/diseases/3986-breast- cancer) and [ brain cancer ](https://my.clevelandclinic.org/health/diseases/6149-brain-cancer-brain- tumor) . ##### How tumor-infiltrating lymphocytes (TIL) work Tumor-infiltrating lymphocytes (TIL) act like a small group of soldiers doing reconnaissance into enemy territory. TIL cells can sneak close to or into cancerous tumors, but they can’t put up an effective fight against the cells because they’re outnumbered. They can’t call for reinforcements because they can’t keep cancerous cells from sending signals that suppress your immune system. In TIL therapy, healthcare providers grow larger and stronger TIL cells. They take the cells from tumors and treat them with substances so the TIL cells will grow. When the new and improved TIL cells are returned to the cancerous tumors, they’re able to kill cancerous cells and disrupt signals suppressing your immune system. ###### Cancers treated by TIL The U.S. Food and Drug Administration (FDA) hasn’t approved TIL therapy as a standard cancer treatment. Medical researchers are studying TIL therapy as a way to treat [ melanoma ](https://my.clevelandclinic.org/health/diseases/14391-melanoma) , cervical squamous carcinoma and [ cholangiocarcinoma ](https://my.clevelandclinic.org/health/diseases/21524-cholangiocarcinoma#diagnosis- and-tests) (bile duct cancer). #### Monoclonal antibody therapy [ Antibodies ](https://my.clevelandclinic.org/health/body/22971-antibodies) are part of the first line of defense when your immune system detects intrudes. Antibodies are proteins that fight infection by marking intruders so your immune system will destroy them. [ Monoclonal antibody therapy for cancer ](https://my.clevelandclinic.org/health/treatments/22774-monoclonal-antibody- therapy) involves lab-made antibodies that can support your existing antibodies or become their own attack force. ##### How monoclonal antibodies work The lab-made antibodies may attack parts of a cancerous cell. For example, they may block abnormal proteins in cancerous cells. [ Monoclonal antibodies ](https://my.clevelandclinic.org/health/treatments/22246-monoclonal- antibodies) can also target cancerous cells for special delivery of drugs, toxins or radioactive material that can kill cancerous cells. (Healthcare providers consider monoclonal antibody therapy a form of targeted therapy. In targeted therapy, providers target a cancer’s specific genes, proteins or the tissues where tumors are growing.) ###### Cancers treated with monoclonal antibody therapy The FDA has approved more than 60 different monoclonal antibody drugs that treat a wide range of cancer. Common types of cancer treated by different monoclonal antibodies include: * Bladder cancer. * Breast cancer, including triple-negative breast cancer. * Colorectal cancer. * Lymphomas, including non-Hodgkin lymphoma, cutaneous T-cell lymphoma and B-cell lymphoma. * Leukemia, including acute lymphoblastic leukemia, hairy cell leukemia, acute myeloid leukemia and chronic lymphocytic leukemia. * [ Multiple myeloma ](https://my.clevelandclinic.org/health/articles/6178-multiple-myeloma) . * [ Non-small cell lung cancer. ](https://my.clevelandclinic.org/health/articles/6203-non-small-cell-lung-cancer) #### Cancer vaccines [ Vaccines ](https://my.clevelandclinic.org/health/treatments/24135-vaccines) protect your body against certain diseases. Some vaccines, such as the vaccine against human papillomavirus (HPV), protect against an infectious disease that’s linked to [ anal cancer ](https://my.clevelandclinic.org/health/treatments/24135-vaccines) , [ throat cancer ](https://my.clevelandclinic.org/health/diseases/23136-throat-cancer) and penile cancers. These vaccines prevent you from getting an infection that can later lead to cancer. Cancer vaccines don’t prevent cancer. But if you develop cancer, cancer vaccines train your body to fight it. ##### How cancer vaccines work Vaccines that protect against cancer work by helping your immune system identify antigens in cancerous cells. Just like other kinds of vaccines, cancer vaccines use all or part of cancerous cells to help your body identify a harmful tumor in your body. Medical researchers are evaluating different ways to make cancer vaccines. The FDA has approved a cancer vaccine that uses an immune cell that responds to specific antigens on prostate cancer cells. #### Immunomodulators/immune system modulators [ Immunomodulators ](https://my.clevelandclinic.org/health/drugs/24987-immunomodulators) are substances that boost your body’s response to cancer. Immune system modulators include cytokines, BCG and immunomodulatory drugs. ##### Cytokines [ Cytokines ](https://my.clevelandclinic.org/health/body/24585-cytokines) are proteins that manage your immune system’s response to intruders, including cancerous cells. They help manage immune cell and blood cell growth and activity. For example, cytokines signal your immune system when it’s time to take care of intruders such as cancerous cells. They drive communication between immune system cells so the cells can coordinate attacks on specific cancerous targets. Cytokines also help destroy cancerous cells by sending signals that may help healthy cells to live longer and cancerous cells to die. Healthcare providers treat cancer with two different cytokines: * Interferons : Interferons help your immune system fight cancer and slow cancer cell growth. Healthcare providers may use lab-made interferons to treat many different types of cancer. * Interleukins : These proteins start an immune response and help immune system cells to communicate. A specific interleukin, IL-2, increases the number of white blood cells in your body. This includes T-cells and B-cells, which help fight cancer. Like interferons, providers may use lab-made interleukins to treat cancer, specifically melanoma and kidney cancer. ##### Immunomodulatory drugs Immunomodulatory drugs, also called biologic response modifiers, are medications that boost your immune system. Some of these drugs keep cancerous [ tumors ](https://my.clevelandclinic.org/health/diseases/21881-tumor) from developing new blood vessels. Healthcare providers may use these drugs to treat people with advanced forms of certain kinds of [ lymphoma ](https://my.clevelandclinic.org/health/diseases/22225-lymphoma) . Immunomodulatory drugs include: * Thalidomide (Thalomid®). * Lenalidomide (Revlimid®). * Pomalidomide (Pomalyst®). * Imiquimod (Aldara®, Zyclara®). Thalidomide, lenalidomide and pomalidomide make cells release the cytokine IL-2. IL-2 helps your body make additional white blood cells to fight cancer. The three drugs also help stop cancerous tumors’ growth. They do that by preventing the tumors from developing the new blood vessels the tumors need to keep growing. Another immunomodulatory drug, imiquimod, makes cells release cytokines. Thalidomide, lenalidomide (Revlimid) and pomalidomide (Pomalyst) are classified as immunomodulatory drugs, which stimulate your immune system. These drugs also keep new blood vessels from forming and feeding myeloma cells. Thalidomide and lenalidomide are approved to treat people who are newly diagnosed. Lenalidomide and pomalidomide are also effective for treating recurrent myeloma. These drugs stimulate your immune system. Some drugs keep cancerous tumors from forming the new blood vessels the tumors need to grow. Healthcare providers often use these drugs to treat metastatic cancer. ### What are immunotherapy side effects? Like most cancer treatments, immunotherapy causes [ side effects ](https://my.clevelandclinic.org/health/articles/21096-immunotherapy-side- effects) that can affect your daily life. Your immune system protects your entire body. Immunotherapy modifies your immune system so it’s a more effective cancer-fighting process. But immune cells may attack healthy cells, causing inflammation in healthy tissue. This is an immune-related adverse effect, or irAE. About 20% of people receiving immunotherapy have severe irAE. Side effects include: * [ Fatigue ](https://my.clevelandclinic.org/health/symptoms/21206-fatigue) . * Itchy rash. * [ Diarrhea ](https://my.clevelandclinic.org/health/diseases/4108-diarrhea) . * [ Nausea and vomiting ](https://my.clevelandclinic.org/health/symptoms/8106-nausea--vomiting) . * Decreased [ thyroid hormone ](https://my.clevelandclinic.org/health/articles/22391-thyroid-hormone) levels. Advertisement ## Procedure Details ### How do people receive immunotherapy? People receive immunotherapy through an intravenous (IV) infusion. You may receive immunotherapy daily, weekly, monthly or in a cycle. With cyclic immunotherapy, you take a rest period after treatment. The break gives your body time to produce healthy cells. Treatment length depends on: * Cancer type and stage. * Type of immunotherapy drug. * Your body’s response to treatment. Care at Cleveland Clinic [ Immunotherapy for Cancer Treatment ](https://my.clevelandclinic.org/services/immunotherapy-cancer-treatment) [ Request an Appointment ](https://my.clevelandclinic.org/webappointment/what- to-expect) ## Risks / Benefits ### What are the benefits of immunotherapy treatment? Immunotherapy may be an effective treatment for cancers that haven’t responded to traditional treatment or that have come back after traditional treatment. Advertisement ### What are the risks or complications? Immunotherapy doesn’t work on all kinds of cancer and it may not work for every person who receives treatment. Most immunotherapy treatments cause side effects. If your healthcare provider recommends immunotherapy, they’ll explain specific treatment side effects and ways they’ll help you manage those side effects. ## Recovery and Outlook ### Can immunotherapy cure cancer? No, but immunotherapy can control cancer so people can live longer. In some cases, it slows down cancer’s growth. In other cases, it may shrink cancerous tumors. Unfortunately, not everyone who receives immunotherapy responds to treatment ### What questions should I ask my healthcare provider? Immunotherapy is a relatively new area of focus for cancer treatment. You may not know much about the treatment. If immunotherapy is an option for you, you may have the following questions for your healthcare provider: * What type of immunotherapy do you recommend? * Will I receive other cancer treatment? * What immunotherapy clinical trials are open to me? * How will I receive immunotherapy treatment? * How long will each treatment take? How often will I need to get this treatment? * What are the possible short-term side effects of immunotherapy? How can these be managed? * What are the possible long-term side effects of this immunotherapy? How can these be managed? * What side effects should I let you know about right away? * How will this treatment affect my daily life? Will I be able to work, exercise and do my usual activities? * How will we know if this immunotherapy is working? ## When To Call the Doctor ### When should I see my healthcare provider? Most of the time, immunotherapy side effects are mild, but some side effects require immediate medical treatment. You should contact your healthcare provider any time you have immunotherapy side effects that are more severe than usual. A note from Cleveland Clinic Immunotherapy for cancer helps your immune system do more to find and kill cancerous cells. Healthcare providers may recommend immunotherapy if you have certain kinds of advanced cancer or if traditional treatments have stopped working. Immunotherapy is an effective treatment for many kinds of cancer, but not all kinds of cancer. And not everyone with cancer responds to immunotherapy treatment. That said, medical researchers are finding new ways to use immunotherapy so it can do more to manage cancer and help people live longer. If you have cancer and wonder if immunotherapy might be effective, talk to your healthcare provider. They’re your best resource for information. [ ](mailto:?subject=Cleveland Clinic - Immunotherapy&body=https://my.clevelandclinic.org/health/treatments/11582-immunotherapy) Medically Reviewed Last reviewed by a Cleveland Clinic medical professional on 11/15/2022. Learn more about our [ editorial process ](https://my.clevelandclinic.org/about/website/editorial-policy) . #### References Advertisement Cleveland Clinic is a non-profit academic medical center. Advertising on our site helps support our mission. We do not endorse non-Cleveland Clinic products or services. 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All Rights Reserved.	biology	659067	https://sv.wikipedia.org/wiki/Immunterapi	Immunterapi	Immunoterapi är behandling av sjukdom med immunologiska metoder. Cancerbehandling En princip för cancerbehandling varvid man förstärker immunsystemets inneboende förmåga att angripa tumörceller. Forskning inom området medförde att Nobelpriset i fysiologi eller medicin 2018 tillföll James P. Allison och Tasuku Honjo. Sådan immunterapi mot cancer, med så kallade immunkontrollpunktshämmare (), handlar om antikroppar mot de bromsande cellyteproteinerna CTLA-4 och PD-1 på mördar-T-celler och positiva resultat har observeras i flera typer av cancer, såsom lungcancer, njurcancer, lymfom och melanom. CAR-T-cellsbehandling () är en immunterapi vid cancer. Vid CAR T-cellsterapi har T-celler från patienten själv eller en allogen donator inokulerats med en CAR. En CAR är en typ av fusionsprotein bestående av fyra delar: En antigenbindande extracellulär domän, en hinge-region, en transmembranös del och en intracellullär signaleringsdomän. Den antigenbindande domänen kan riktas mot i teorin vilket protein som helst som uttrycks på ytan av en cell. Om man skapar en antigenbindande domän som känner igen exempelvis ett antigen som uttrycks på tumörceller och sedan kopplar denna del till en intracellullär signamolekyl som CD28 eller 4-1BB kan man skapa ett immunsvar mot tumörcellerna. CAR-T-cellsterapierna Yescarta (axicabtagene ciloleucel) och Kymriah (tisagenlekleucel) är godkända för behandling vid blodcancer av typen storcelligt B-cellslymfom och akut lymfatisk leukemi. Specifik immunterapi Specifik immunterapi (mer allmänt känt som allergisprutor) är ett sätt att behandla patientens allergi mot pollen genom att öka toleransen genom att injicera ett utspätt extrakt med pollenallergen under huden. Behandlingen genomförs initialt en eller två gånger i veckan och man arbetar sig så småningom upp i högre doser. Behandlingen kan vara en längre tid, upp till flera månader. Se även Hyposensibilisering Immunmodulerande behandling Immunonkologi Immuntolerans Referenser Immunsystemet	swedish	0.587849
genetic_sequence_of_SARS-CoV-2/COVID-19.txt	Coronavirus disease 2019 (COVID-19) is a contagious disease caused by the virus SARS-CoV-2. The first known case was identified in Wuhan, China, in December 2019. The disease quickly spread worldwide, resulting in the COVID-19 pandemic. The symptoms of COVID‑19 are variable but often include fever, cough, headache, fatigue, breathing difficulties, loss of smell, and loss of taste. Symptoms may begin one to fourteen days after exposure to the virus. At least a third of people who are infected do not develop noticeable symptoms. Of those who develop symptoms noticeable enough to be classified as patients, most (81%) develop mild to moderate symptoms (up to mild pneumonia), while 14% develop severe symptoms (dyspnea, hypoxia, or more than 50% lung involvement on imaging), and 5% develop critical symptoms (respiratory failure, shock, or multiorgan dysfunction). Older people are at a higher risk of developing severe symptoms. Some people continue to experience a range of effects (long COVID) for months or years after infection, and damage to organs has been observed. Multi-year studies are underway to further investigate the long-term effects of the disease. COVID‑19 transmits when infectious particles are breathed in or come into contact with the eyes, nose, or mouth. The risk is highest when people are in close proximity, but small airborne particles containing the virus can remain suspended in the air and travel over longer distances, particularly indoors. Transmission can also occur when people touch their eyes, nose or mouth after touching surfaces or objects that have been contaminated by the virus. People remain contagious for up to 20 days and can spread the virus even if they do not develop symptoms. Testing methods for COVID-19 to detect the virus's nucleic acid include real-time reverse transcription polymerase chain reaction (RT‑PCR), transcription-mediated amplification, and reverse transcription loop-mediated isothermal amplification (RT‑LAMP) from a nasopharyngeal swab. Several COVID-19 vaccines have been approved and distributed in various countries, which have initiated mass vaccination campaigns. Other preventive measures include physical or social distancing, quarantining, ventilation of indoor spaces, use of face masks or coverings in public, covering coughs and sneezes, hand washing, and keeping unwashed hands away from the face. While work is underway to develop drugs that inhibit the virus, the primary treatment is symptomatic. Management involves the treatment of symptoms through supportive care, isolation, and experimental measures. During the initial outbreak in Wuhan, the virus and disease were commonly referred to as "coronavirus" and "Wuhan coronavirus", with the disease sometimes called "Wuhan pneumonia". In the past, many diseases have been named after geographical locations, such as the Spanish flu, Middle East respiratory syndrome, and Zika virus. In January 2020, the World Health Organization (WHO) recommended 2019-nCoV and 2019-nCoV acute respiratory disease as interim names for the virus and disease per 2015 guidance and international guidelines against using geographical locations or groups of people in disease and virus names to prevent social stigma. The official names COVID‑19 and SARS-CoV-2 were issued by the WHO on 11 February 2020 with COVID-19 being shorthand for "coronavirus disease 2019". The WHO additionally uses "the COVID‑19 virus" and "the virus responsible for COVID‑19" in public communications. Complications may include pneumonia, acute respiratory distress syndrome (ARDS), multi-organ failure, septic shock, and death. Cardiovascular complications may include heart failure, arrhythmias (including atrial fibrillation), heart inflammation, and thrombosis, particularly venous thromboembolism. Approximately 20–30% of people who present with COVID‑19 have elevated liver enzymes, reflecting liver injury. Neurologic manifestations include seizure, stroke, encephalitis, and Guillain–Barré syndrome (which includes loss of motor functions). Following the infection, children may develop paediatric multisystem inflammatory syndrome, which has symptoms similar to Kawasaki disease, which can be fatal. In very rare cases, acute encephalopathy can occur, and it can be considered in those who have been diagnosed with COVID‑19 and have an altered mental status. According to the US Centers for Disease Control and Prevention, pregnant women are at increased risk of becoming seriously ill from COVID‑19. This is because pregnant women with COVID‑19 appear to be more likely to develop respiratory and obstetric complications that can lead to miscarriage, premature delivery and intrauterine growth restriction. Fungal infections such as aspergillosis, candidiasis, cryptococcosis and mucormycosis have been recorded in patients recovering from COVID‑19. COVID‑19 is caused by infection with a strain of coronavirus known as "severe acute respiratory syndrome coronavirus 2" (SARS-CoV-2). Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) is a novel severe acute respiratory syndrome coronavirus. It was first isolated from three people with pneumonia connected to the cluster of acute respiratory illness cases in Wuhan. All structural features of the novel SARS-CoV-2 virus particle occur in related coronaviruses in nature, particularly in Rhinolophus sinicus aka Chinese horseshoe bats. Outside the human body, the virus is destroyed by household soap which bursts its protective bubble. Hospital disinfectants, alcohols, heat, povidone-iodine, and ultraviolet-C (UV-C) irradiation are also effective disinfection methods for surfaces. SARS-CoV-2 is closely related to the original SARS-CoV. It is thought to have an animal (zoonotic) origin. Genetic analysis has revealed that the coronavirus genetically clusters with the genus Betacoronavirus, in subgenus Sarbecovirus (lineage B) together with two bat-derived strains. It is 96% identical at the whole genome level to other bat coronavirus samples (BatCov RaTG13). The structural proteins of SARS-CoV-2 include membrane glycoprotein (M), envelope protein (E), nucleocapsid protein (N), and the spike protein (S). The M protein of SARS-CoV-2 is about 98% similar to the M protein of bat SARS-CoV, maintains around 98% homology with pangolin SARS-CoV, and has 90% homology with the M protein of SARS-CoV; whereas, the similarity is only around 38% with the M protein of MERS-CoV. The many thousands of SARS-CoV-2 variants are grouped into either clades or lineages. The WHO, in collaboration with partners, expert networks, national authorities, institutions and researchers, have established nomenclature systems for naming and tracking SARS-CoV-2 genetic lineages by GISAID, Nextstrain and Pango. The expert group convened by the WHO recommended the labelling of variants using letters of the Greek alphabet, for example, Alpha, Beta, Delta, and Gamma, giving the justification that they "will be easier and more practical to discussed by non-scientific audiences". Nextstrain divides the variants into five clades (19A, 19B, 20A, 20B, and 20C), while GISAID divides them into seven (L, O, V, S, G, GH, and GR). The Pango tool groups variants into lineages, with many circulating lineages being classed under the B.1 lineage. Several notable variants of SARS-CoV-2 emerged throughout 2020. Cluster 5 emerged among minks and mink farmers in Denmark. After strict quarantines and a mink euthanasia campaign, the cluster was assessed to no longer be circulating among humans in Denmark as of 1 February 2021. As of December 2021, there are five dominant variants of SARS-CoV-2 spreading among global populations: the Alpha variant (B.1.1.7, formerly called the UK variant), first found in London and Kent, the Beta variant (B.1.351, formerly called the South Africa variant), the Gamma variant (P.1, formerly called the Brazil variant), the Delta variant (B.1.617.2, formerly called the India variant), and the Omicron variant (B.1.1.529), which had spread to 57 countries as of 7 December. On December 19, 2023, the WHO declared that another distinctive variant, JN.1, had emerged as a "variant of interest". Though the WHO expects an increase in cases globally, particularly for countries entering winter, the current overall global health risk (as of December 21, 2023) remains low. The SARS-CoV-2 virus can infect a wide range of cells and systems of the body. COVID‑19 is most known for affecting the upper respiratory tract (sinuses, nose, and throat) and the lower respiratory tract (windpipe and lungs). The lungs are the organs most affected by COVID‑19 because the virus accesses host cells via the receptor for the enzyme angiotensin-converting enzyme 2 (ACE2), which is most abundant on the surface of type II alveolar cells of the lungs. The virus uses a special surface glycoprotein called a "spike" to connect to the ACE2 receptor and enter the host cell. Following viral entry, COVID‑19 infects the ciliated epithelium of the nasopharynx and upper airways. Autopsies of people who died of COVID‑19 have found diffuse alveolar damage, and lymphocyte-containing inflammatory infiltrates within the lung. One common symptom, loss of smell, results from infection of the support cells of the olfactory epithelium, with subsequent damage to the olfactory neurons. The involvement of both the central and peripheral nervous system in COVID‑19 has been reported in many medical publications. It is clear that many people with COVID-19 exhibit neurological or mental health issues. The virus is not detected in the central nervous system (CNS) of the majority of COVID-19 patients with neurological issues. However, SARS-CoV-2 has been detected at low levels in the brains of those who have died from COVID‑19, but these results need to be confirmed. While virus has been detected in cerebrospinal fluid of autopsies, the exact mechanism by which it invades the CNS remains unclear and may first involve invasion of peripheral nerves given the low levels of ACE2 in the brain. The virus may also enter the bloodstream from the lungs and cross the blood–brain barrier to gain access to the CNS, possibly within an infected white blood cell. Research conducted when Alpha was the dominant variant has suggested COVID-19 may cause brain damage. Later research showed that all variants studied (including Omicron) killed brain cells, but the exact cells killed varied by variant. It is unknown if such damage is temporary or permanent. Observed individuals infected with COVID-19 (most with mild cases) experienced an additional 0.2% to 2% of brain tissue lost in regions of the brain connected to the sense of smell compared with uninfected individuals, and the overall effect on the brain was equivalent on average to at least one extra year of normal ageing; infected individuals also scored lower on several cognitive tests. All effects were more pronounced among older ages. The virus also affects gastrointestinal organs as ACE2 is abundantly expressed in the glandular cells of gastric, duodenal and rectal epithelium as well as endothelial cells and enterocytes of the small intestine. The virus can cause acute myocardial injury and chronic damage to the cardiovascular system. An acute cardiac injury was found in 12% of infected people admitted to the hospital in Wuhan, China, and is more frequent in severe disease. Rates of cardiovascular symptoms are high, owing to the systemic inflammatory response and immune system disorders during disease progression, but acute myocardial injuries may also be related to ACE2 receptors in the heart. ACE2 receptors are highly expressed in the heart and are involved in heart function. A high incidence of thrombosis and venous thromboembolism occurs in people transferred to intensive care units with COVID‑19 infections, and may be related to poor prognosis. Blood vessel dysfunction and clot formation (as suggested by high D-dimer levels caused by blood clots) may have a significant role in mortality, incidents of clots leading to pulmonary embolisms, and ischaemic events (strokes) within the brain found as complications leading to death in people infected with COVID‑19. Infection may initiate a chain of vasoconstrictive responses within the body, including pulmonary vasoconstriction – a possible mechanism in which oxygenation decreases during pneumonia. Furthermore, damage of arterioles and capillaries was found in brain tissue samples of people who died from COVID‑19. COVID‑19 may also cause substantial structural changes to blood cells, sometimes persisting for months after hospital discharge. A low level of blood lymphocytes may result from the virus acting through ACE2-related entry into lymphocytes. Another common cause of death is complications related to the kidneys. Early reports show that up to 30% of hospitalised patients both in China and in New York have experienced some injury to their kidneys, including some persons with no previous kidney problems. Although SARS-CoV-2 has a tropism for ACE2-expressing epithelial cells of the respiratory tract, people with severe COVID‑19 have symptoms of systemic hyperinflammation. Clinical laboratory findings of elevated IL‑2, IL‑7, IL‑6, granulocyte-macrophage colony-stimulating factor (GM‑CSF), interferon gamma-induced protein 10 (IP‑10), monocyte chemoattractant protein 1 (MCP1), macrophage inflammatory protein 1‑alpha (MIP‑1‑alpha), and tumour necrosis factor (TNF‑α) indicative of cytokine release syndrome (CRS) suggest an underlying immunopathology. Interferon alpha plays a complex, Janus-faced role in the pathogenesis of COVID-19. Although it promotes the elimination of virus-infected cells, it also upregulates the expression of ACE-2, thereby facilitating the SARS-Cov2 virus to enter cells and to replicate. A competition of negative feedback loops (via protective effects of interferon alpha) and positive feedback loops (via upregulation of ACE-2) is assumed to determine the fate of patients suffering from COVID-19. Additionally, people with COVID‑19 and acute respiratory distress syndrome (ARDS) have classical serum biomarkers of CRS, including elevated C-reactive protein (CRP), lactate dehydrogenase (LDH), D-dimer, and ferritin. Systemic inflammation results in vasodilation, allowing inflammatory lymphocytic and monocytic infiltration of the lung and the heart. In particular, pathogenic GM-CSF-secreting T cells were shown to correlate with the recruitment of inflammatory IL-6-secreting monocytes and severe lung pathology in people with COVID‑19. Lymphocytic infiltrates have also been reported at autopsy. Multiple viral and host factors affect the pathogenesis of the virus. The S-protein, otherwise known as the spike protein, is the viral component that attaches to the host receptor via the ACE2 receptors. It includes two subunits: S1 and S2. S1 determines the virus-host range and cellular tropism via the receptor-binding domain. S2 mediates the membrane fusion of the virus to its potential cell host via the H1 and HR2, which are heptad repeat regions. Studies have shown that S1 domain induced IgG and IgA antibody levels at a much higher capacity. It is the focus spike proteins expression that are involved in many effective COVID‑19 vaccines. The M protein is the viral protein responsible for the transmembrane transport of nutrients. It is the cause of the bud release and the formation of the viral envelope. The N and E protein are accessory proteins that interfere with the host's immune response. Human angiotensin converting enzyme 2 (hACE2) is the host factor that SARS-CoV-2 virus targets causing COVID‑19. Theoretically, the usage of angiotensin receptor blockers (ARB) and ACE inhibitors upregulating ACE2 expression might increase morbidity with COVID‑19, though animal data suggest some potential protective effect of ARB; however no clinical studies have proven susceptibility or outcomes. Until further data is available, guidelines and recommendations for hypertensive patients remain. The effect of the virus on ACE2 cell surfaces leads to leukocytic infiltration, increased blood vessel permeability, alveolar wall permeability, as well as decreased secretion of lung surfactants. These effects cause the majority of the respiratory symptoms. However, the aggravation of local inflammation causes a cytokine storm eventually leading to a systemic inflammatory response syndrome. Among healthy adults not exposed to SARS-CoV-2, about 35% have CD4 T cells that recognise the SARS-CoV-2 S protein (particularly the S2 subunit) and about 50% react to other proteins of the virus, suggesting cross-reactivity from previous common colds caused by other coronaviruses. It is unknown whether different persons use similar antibody genes in response to COVID‑19. The severity of the inflammation can be attributed to the severity of what is known as the cytokine storm. Levels of interleukin 1B, interferon-gamma, interferon-inducible protein 10, and monocyte chemoattractant protein 1 were all associated with COVID‑19 disease severity. Treatment has been proposed to combat the cytokine storm as it remains to be one of the leading causes of morbidity and mortality in COVID‑19 disease. A cytokine storm is due to an acute hyperinflammatory response that is responsible for clinical illness in an array of diseases but in COVID‑19, it is related to worse prognosis and increased fatality. The storm causes acute respiratory distress syndrome, blood clotting events such as strokes, myocardial infarction, encephalitis, acute kidney injury, and vasculitis. The production of IL-1, IL-2, IL-6, TNF-alpha, and interferon-gamma, all crucial components of normal immune responses, inadvertently become the causes of a cytokine storm. The cells of the central nervous system, the microglia, neurons, and astrocytes, are also involved in the release of pro-inflammatory cytokines affecting the nervous system, and effects of cytokine storms toward the CNS are not uncommon. There are many unknowns for pregnant women during the COVID-19 pandemic. Given that they are prone to have complications and severe disease infection with other types of coronaviruses, they have been identified as a vulnerable group and advised to take supplementary preventive measures. Physiological responses to pregnancy can include: However, from the evidence base, it is difficult to conclude whether pregnant women are at increased risk of grave consequences of this virus. In addition to the above, other clinical studies have proved that SARS-CoV-2 can affect the period of pregnancy in different ways. On the one hand, there is little evidence of its impact up to 12 weeks gestation. On the other hand, COVID-19 infection may cause increased rates of unfavourable outcomes in the course of the pregnancy. Some examples of these could be foetal growth restriction, preterm birth, and perinatal mortality, which refers to the foetal death past 22 or 28 completed weeks of pregnancy as well as the death among live-born children up to seven completed days of life. For preterm birth, a 2023 review indicates that there appears to be a correlation with COVID-19. Unvaccinated women in later stages of pregnancy with COVID-19 are more likely than other patients to need very intensive care. Babies born to mothers with COVID-19 are more likely to have breathing problems. Pregnant women are strongly encouraged to get vaccinated. COVID‑19 can provisionally be diagnosed on the basis of symptoms and confirmed using reverse transcription polymerase chain reaction (RT-PCR) or other nucleic acid testing of infected secretions. Along with laboratory testing, chest CT scans may be helpful to diagnose COVID‑19 in individuals with a high clinical suspicion of infection. Detection of a past infection is possible with serological tests, which detect antibodies produced by the body in response to the infection. The standard methods of testing for presence of SARS-CoV-2 are nucleic acid tests, which detects the presence of viral RNA fragments. As these tests detect RNA but not infectious virus, its "ability to determine duration of infectivity of patients is limited". The test is typically done on respiratory samples obtained by a nasopharyngeal swab; however, a nasal swab or sputum sample may also be used. Results are generally available within hours. The WHO has published several testing protocols for the disease. Several laboratories and companies have developed serological tests, which detect antibodies produced by the body in response to infection. Several have been evaluated by Public Health England and approved for use in the UK. The University of Oxford's CEBM has pointed to mounting evidence that "a good proportion of 'new' mild cases and people re-testing positives after quarantine or discharge from hospital are not infectious, but are simply clearing harmless virus particles which their immune system has efficiently dealt with" and have called for "an international effort to standardize and periodically calibrate testing" In September 2020, the UK government issued "guidance for procedures to be implemented in laboratories to provide assurance of positive SARS-CoV-2 RNA results during periods of low prevalence, when there is a reduction in the predictive value of positive test results". Chest CT scans may be helpful to diagnose COVID‑19 in individuals with a high clinical suspicion of infection but are not recommended for routine screening. Bilateral multilobar ground-glass opacities with a peripheral, asymmetric, and posterior distribution are common in early infection. Subpleural dominance, crazy paving (lobular septal thickening with variable alveolar filling), and consolidation may appear as the disease progresses. Characteristic imaging features on chest radiographs and computed tomography (CT) of people who are symptomatic include asymmetric peripheral ground-glass opacities without pleural effusions. Many groups have created COVID‑19 datasets that include imagery such as the Italian Radiological Society which has compiled an international online database of imaging findings for confirmed cases. Due to overlap with other infections such as adenovirus, imaging without confirmation by rRT-PCR is of limited specificity in identifying COVID‑19. A large study in China compared chest CT results to PCR and demonstrated that though imaging is less specific for the infection, it is faster and more sensitive. In late 2019, the WHO assigned emergency ICD-10 disease codes U07.1 for deaths from lab-confirmed SARS-CoV-2 infection and U07.2 for deaths from clinically or epidemiologically diagnosed COVID‑19 without lab-confirmed SARS-CoV-2 infection. The main pathological findings at autopsy are: Preventive measures to reduce the chances of infection include getting vaccinated, staying at home, wearing a mask in public, avoiding crowded places, keeping distance from others, ventilating indoor spaces, managing potential exposure durations, washing hands with soap and water often and for at least twenty seconds, practising good respiratory hygiene, and avoiding touching the eyes, nose, or mouth with unwashed hands. Those diagnosed with COVID‑19 or who believe they may be infected are advised by the CDC to stay home except to get medical care, call ahead before visiting a healthcare provider, wear a face mask before entering the healthcare provider's office and when in any room or vehicle with another person, cover coughs and sneezes with a tissue, regularly wash hands with soap and water and avoid sharing personal household items. The first COVID‑19 vaccine was granted regulatory approval on 2 December 2020 by the UK medicines regulator MHRA. It was evaluated for emergency use authorisation (EUA) status by the US FDA, and in several other countries. Initially, the US National Institutes of Health guidelines do not recommend any medication for prevention of COVID‑19, before or after exposure to the SARS-CoV-2 virus, outside the setting of a clinical trial. Without a vaccine, other prophylactic measures, or effective treatments, a key part of managing COVID‑19 is trying to decrease and delay the epidemic peak, known as "flattening the curve". This is done by slowing the infection rate to decrease the risk of health services being overwhelmed, allowing for better treatment of active cases, and delaying additional cases until effective treatments or a vaccine become available. The CDC states that avoiding crowded indoor spaces reduces the risk of COVID-19 infection. When indoors, increasing the rate of air change, decreasing recirculation of air and increasing the use of outdoor air can reduce transmission. The WHO recommends ventilation and air filtration in public spaces to help clear out infectious aerosols. Exhaled respiratory particles can build-up within enclosed spaces with inadequate ventilation. The risk of COVID‑19 infection increases especially in spaces where people engage in physical exertion or raise their voice (e.g., exercising, shouting, singing) as this increases exhalation of respiratory droplets. Prolonged exposure to these conditions, typically more than 15 minutes, leads to higher risk of infection. Displacement ventilation with large natural inlets can move stale air directly to the exhaust in laminar flow while significantly reducing the concentration of droplets and particles. Passive ventilation reduces energy consumption and maintenance costs but may lack controllability and heat recovery. Displacement ventilation can also be achieved mechanically with higher energy and maintenance costs. The use of large ducts and openings helps to prevent mixing in closed environments. Recirculation and mixing should be avoided because recirculation prevents dilution of harmful particles and redistributes possibly contaminated air, and mixing increases the concentration and range of infectious particles and keeps larger particles in the air. Thorough hand hygiene after any cough or sneeze is required. The WHO also recommends that individuals wash hands often with soap and water for at least twenty seconds, especially after going to the toilet or when hands are visibly dirty, before eating and after blowing one's nose. When soap and water are not available, the CDC recommends using an alcohol-based hand sanitiser with at least 60% alcohol. For areas where commercial hand sanitisers are not readily available, the WHO provides two formulations for local production. In these formulations, the antimicrobial activity arises from ethanol or isopropanol. Hydrogen peroxide is used to help eliminate bacterial spores in the alcohol; it is "not an active substance for hand antisepsis". Glycerol is added as a humectant. Social distancing (also known as physical distancing) includes infection control actions intended to slow the spread of the disease by minimising close contact between individuals. Methods include quarantines; travel restrictions; and the closing of schools, workplaces, stadiums, theatres, or shopping centres. Individuals may apply social distancing methods by staying at home, limiting travel, avoiding crowded areas, using no-contact greetings, and physically distancing themselves from others. In 2020, outbreaks occurred in prisons due to crowding and an inability to enforce adequate social distancing. In the United States, the prisoner population is ageing and many of them are at high risk for poor outcomes from COVID‑19 due to high rates of coexisting heart and lung disease, and poor access to high-quality healthcare. After being expelled from the body, coronaviruses can survive on surfaces for hours to days. If a person touches the dirty surface, they may deposit the virus at the eyes, nose, or mouth where it can enter the body and cause infection. Evidence indicates that contact with infected surfaces is not the main driver of COVID‑19, leading to recommendations for optimised disinfection procedures to avoid issues such as the increase of antimicrobial resistance through the use of inappropriate cleaning products and processes. Deep cleaning and other surface sanitation has been criticised as hygiene theatre, giving a false sense of security against something primarily spread through the air. The amount of time that the virus can survive depends significantly on the type of surface, the temperature, and the humidity. Coronaviruses die very quickly when exposed to the UV light in sunlight. Like other enveloped viruses, SARS-CoV-2 survives longest when the temperature is at room temperature or lower, and when the relative humidity is low (<50%). On many surfaces, including glass, some types of plastic, stainless steel, and skin, the virus can remain infective for several days indoors at room temperature, or even about a week under ideal conditions. On some surfaces, including cotton fabric and copper, the virus usually dies after a few hours. The virus dies faster on porous surfaces than on non-porous surfaces due to capillary action within pores and faster aerosol droplet evaporation. However, of the many surfaces tested, two with the longest survival times are N95 respirator masks and surgical masks, both of which are considered porous surfaces. The CDC says that in most situations, cleaning surfaces with soap or detergent, not disinfecting, is enough to reduce risk of transmission. The CDC recommends that if a COVID‑19 case is suspected or confirmed at a facility such as an office or day care, all areas such as offices, bathrooms, common areas, shared electronic equipment like tablets, touch screens, keyboards, remote controls, and ATMs used by the ill persons should be disinfected. Surfaces may be decontaminated with 62–71 per cent ethanol, 50–100 per cent isopropanol, 0.1 per cent sodium hypochlorite, 0.5 per cent hydrogen peroxide, 0.2–7.5 per cent povidone-iodine, or 50–200 ppm hypochlorous acid. Other solutions, such as benzalkonium chloride and chlorhexidine gluconate, are less effective. Ultraviolet germicidal irradiation may also be used, although popular devices require 5–10 min exposure and may deteriorate some materials over time. A datasheet comprising the authorised substances to disinfection in the food industry (including suspension or surface tested, kind of surface, use dilution, disinfectant and inoculum volumes) can be seen in the supplementary material of. Self-isolation at home has been recommended for those diagnosed with COVID‑19 and those who suspect they have been infected. Health agencies have issued detailed instructions for proper self-isolation. Many governments have mandated or recommended self-quarantine for entire populations. The strongest self-quarantine instructions have been issued to those in high-risk groups. Those who may have been exposed to someone with COVID‑19 and those who have recently travelled to a country or region with the widespread transmission have been advised to self-quarantine for 14 days from the time of last possible exposure. A 2021 Cochrane rapid review found that based upon low-certainty evidence, international travel-related control measures such as restricting cross-border travel may help to contain the spread of COVID‑19. Additionally, symptom/exposure-based screening measures at borders may miss many positive cases. While test-based border screening measures may be more effective, it could also miss many positive cases if only conducted upon arrival without follow-up. The review concluded that a minimum 10-day quarantine may be beneficial in preventing the spread of COVID‑19 and may be more effective if combined with an additional control measure like border screening. The severity of COVID‑19 varies. The disease may take a mild course with few or no symptoms, resembling other common upper respiratory diseases such as the common cold. In 3–4% of cases (7.4% for those over age 65) symptoms are severe enough to cause hospitalisation. Mild cases typically recover within two weeks, while those with severe or critical diseases may take three to six weeks to recover. Among those who have died, the time from symptom onset to death has ranged from two to eight weeks. The Italian Istituto Superiore di Sanità reported that the median time between the onset of symptoms and death was twelve days, with seven being hospitalised. However, people transferred to an ICU had a median time of ten days between hospitalisation and death. Abnormal sodium levels during hospitalisation with COVID-19 are associated with poor prognoses: high sodium with a greater risk of death, and low sodium with an increased chance of needing ventilator support. Prolonged prothrombin time and elevated C-reactive protein levels on admission to the hospital are associated with severe course of COVID‑19 and with a transfer to ICU. Some early studies suggest 10% to 20% of people with COVID‑19 will experience symptoms lasting longer than a month. A majority of those who were admitted to hospital with severe disease report long-term problems including fatigue and shortness of breath. On 30 October 2020, WHO chief Tedros Adhanom warned that "to a significant number of people, the COVID virus poses a range of serious long-term effects". He has described the vast spectrum of COVID‑19 symptoms that fluctuate over time as "really concerning". They range from fatigue, a cough and shortness of breath, to inflammation and injury of major organs – including the lungs and heart, and also neurological and psychologic effects. Symptoms often overlap and can affect any system in the body. Infected people have reported cyclical bouts of fatigue, headaches, months of complete exhaustion, mood swings, and other symptoms. Tedros therefore concluded that a strategy of achieving herd immunity by infection, rather than vaccination, is "morally unconscionable and unfeasible". In terms of hospital readmissions about 9% of 106,000 individuals had to return for hospital treatment within two months of discharge. The average to readmit was eight days since first hospital visit. There are several risk factors that have been identified as being a cause of multiple admissions to a hospital facility. Among these are advanced age (above 65 years of age) and presence of a chronic condition such as diabetes, COPD, heart failure or chronic kidney disease. According to scientific reviews smokers are more likely to require intensive care or die compared to non-smokers. Acting on the same ACE2 pulmonary receptors affected by smoking, air pollution has been correlated with the disease. Short-term and chronic exposure to air pollution seems to enhance morbidity and mortality from COVID‑19. Pre-existing heart and lung diseases and also obesity, especially in conjunction with fatty liver disease, contributes to an increased health risk of COVID‑19. It is also assumed that those that are immunocompromised are at higher risk of getting severely sick from SARS-CoV-2. One research study that looked into the COVID‑19 infections in hospitalised kidney transplant recipients found a mortality rate of 11%. Men with untreated hypogonadism were 2.4 times more likely than men with eugonadism to be hospitalised if they contracted COVID-19; Hypogonad men treated with testosterone were less likely to be hospitalised for COVID-19 than men who were not treated for hypogonadism. Genetics plays an important role in the ability to fight off Covid. For instance, those that do not produce detectable type I interferons or produce auto-antibodies against these may get much sicker from COVID‑19. Genetic screening is able to detect interferon effector genes. Some genetic variants are risk factors in specific populations. For instance, an allele of the DOCK2 gene (dedicator of cytokinesis 2 gene) is a common risk factor in Asian populations but much less common in Europe. The mutation leads to lower expression of DOCK2 especially in younger patients with severe Covid. In fact, many other genes and genetic variants have been found that determine the outcome of SARS-CoV-2 infections. While very young children have experienced lower rates of infection, older children have a rate of infection that is similar to the population as a whole. Children are likely to have milder symptoms and are at lower risk of severe disease than adults. The CDC reports that in the US roughly a third of hospitalised children were admitted to the ICU, while a European multinational study of hospitalised children from June 2020, found that about 8% of children admitted to a hospital needed intensive care. Four of the 582 children (0.7%) in the European study died, but the actual mortality rate may be "substantially lower" since milder cases that did not seek medical help were not included in the study. Around 10% to 30% of non-hospitalised people with COVID-19 go on to develop long COVID. For those that do need hospitalisation, the incidence of long-term effects is over 50%. Long COVID is an often severe multisystem disease with a large set of symptoms. There are likely various, possibly coinciding, causes. Organ damage from the acute infection can explain a part of the symptoms, but long COVID is also observed in people where organ damage seems to be absent. By a variety of mechanisms, the lungs are the organs most affected in COVID‑19. In people requiring hospital admission, up to 98% of CT scans performed show lung abnormalities after 28 days of illness even if they had clinically improved. People with advanced age, severe disease, prolonged ICU stays, or who smoke are more likely to have long-lasting effects, including pulmonary fibrosis. Overall, approximately one-third of those investigated after four weeks will have findings of pulmonary fibrosis or reduced lung function as measured by DLCO, even in asymptomatic people, but with the suggestion of continuing improvement with the passing of more time. After severe disease, lung function can take anywhere from three months to a year or more to return to previous levels. The risks of cognitive deficit, dementia, psychotic disorders, and epilepsy or seizures persists at an increased level two years after infection. The immune response by humans to SARS-CoV-2 virus occurs as a combination of the cell-mediated immunity and antibody production, just as with most other infections. B cells interact with T cells and begin dividing before selection into the plasma cell, partly on the basis of their affinity for antigen. Since SARS-CoV-2 has been in the human population only since December 2019, it remains unknown if the immunity is long-lasting in people who recover from the disease. The presence of neutralising antibodies in blood strongly correlates with protection from infection, but the level of neutralising antibody declines with time. Those with asymptomatic or mild disease had undetectable levels of neutralising antibody two months after infection. In another study, the level of neutralising antibodies fell four-fold one to four months after the onset of symptoms. However, the lack of antibodies in the blood does not mean antibodies will not be rapidly produced upon reexposure to SARS-CoV-2. Memory B cells specific for the spike and nucleocapsid proteins of SARS-CoV-2 last for at least six months after the appearance of symptoms. As of August 2021, reinfection with COVID‑19 was possible but uncommon. The first case of reinfection was documented in August 2020. A systematic review found 17 cases of confirmed reinfection in medical literature as of May 2021. With the Omicron variant, as of 2022, reinfections have become common, albeit it is unclear how common. COVID-19 reinfections are thought to likely be less severe than primary infections, especially if one was previously infected by the same variant. Several measures are commonly used to quantify mortality. These numbers vary by region and over time and are influenced by the volume of testing, healthcare system quality, treatment options, time since the initial outbreak, and population characteristics such as age, sex, and overall health. The mortality rate reflects the number of deaths within a specific demographic group divided by the population of that demographic group. Consequently, the mortality rate reflects the prevalence as well as the severity of the disease within a given population. Mortality rates are highly correlated to age, with relatively low rates for young people and relatively high rates among the elderly. In fact, one relevant factor of mortality rates is the age structure of the countries' populations. For example, the case fatality rate for COVID‑19 is lower in India than in the US since India's younger population represents a larger percentage than in the US. The case fatality rate (CFR) reflects the number of deaths divided by the number of diagnosed cases within a given time interval. Based on Johns Hopkins University statistics, the global death-to-case ratio is 1.02% (6,881,955/676,609,955) as of 10 March 2023. The number varies by region. A key metric in gauging the severity of COVID‑19 is the infection fatality rate (IFR), also referred to as the infection fatality ratio or infection fatality risk. This metric is calculated by dividing the total number of deaths from the disease by the total number of infected individuals; hence, in contrast to the CFR, the IFR incorporates asymptomatic and undiagnosed infections as well as reported cases. A December 2020 systematic review and meta-analysis estimated that population IFR during the first wave of the pandemic was about 0.5% to 1% in many locations (including France, Netherlands, New Zealand, and Portugal), 1% to 2% in other locations (Australia, England, Lithuania, and Spain), and exceeded 2% in Italy. That study also found that most of these differences in IFR reflected corresponding differences in the age composition of the population and age-specific infection rates; in particular, the metaregression estimate of IFR is very low for children and younger adults (e.g., 0.002% at age 10 and 0.01% at age 25) but increases progressively to 0.4% at age 55, 1.4% at age 65, 4.6% at age 75, and 15% at age 85. These results were also highlighted in a December 2020 report issued by the WHO. An analysis of those IFR rates indicates that COVID‑19 is hazardous not only for the elderly but also for middle-aged adults, for whom the infection fatality rate of COVID-19 is two orders of magnitude greater than the annualised risk of a fatal automobile accident and far more dangerous than seasonal influenza. At an early stage of the pandemic, the World Health Organization reported estimates of IFR between 0.3% and 1%. On 2 July, The WHO's chief scientist reported that the average IFR estimate presented at a two-day WHO expert forum was about 0.6%. In August, the WHO found that studies incorporating data from broad serology testing in Europe showed IFR estimates converging at approximately 0.5–1%. Firm lower limits of IFRs have been established in a number of locations such as New York City and Bergamo in Italy since the IFR cannot be less than the population fatality rate. (After sufficient time however, people can get reinfected). As of 10 July, in New York City, with a population of 8.4 million, 23,377 individuals (18,758 confirmed and 4,619 probable) have died with COVID‑19 (0.3% of the population). Antibody testing in New York City suggested an IFR of ≈0.9%, and ≈1.4%. In Bergamo province, 0.6% of the population has died. In September 2020, the U.S. Centers for Disease Control and Prevention (CDC) reported preliminary estimates of age-specific IFRs for public health planning purposes. COVID‑19 case fatality rates are higher among men than women in most countries. However, in a few countries like India, Nepal, Vietnam, and Slovenia the fatality cases are higher in women than men. Globally, men are more likely to be admitted to the ICU and more likely to die. One meta-analysis found that globally, men were more likely to get COVID‑19 than women; there were approximately 55 men and 45 women per 100 infections (CI: 51.43–56.58). The Chinese Center for Disease Control and Prevention reported the death rate was 2.8% for men and 1.7% for women. Later reviews in June 2020 indicated that there is no significant difference in susceptibility or in CFR between genders. One review acknowledges the different mortality rates in Chinese men, suggesting that it may be attributable to lifestyle choices such as smoking and drinking alcohol rather than genetic factors. Smoking, which in some countries like China is mainly a male activity, is a habit that contributes to increasing significantly the case fatality rates among men. Sex-based immunological differences, lesser prevalence of smoking in women and men developing co-morbid conditions such as hypertension at a younger age than women could have contributed to the higher mortality in men. In Europe as of February 2020, 57% of the infected people were men and 72% of those died with COVID‑19 were men. As of April 2020, the US government is not tracking sex-related data of COVID‑19 infections. Research has shown that viral illnesses like Ebola, HIV, influenza and SARS affect men and women differently. In the US, a greater proportion of deaths due to COVID‑19 have occurred among African Americans and other minority groups. Structural factors that prevent them from practising social distancing include their concentration in crowded substandard housing and in "essential" occupations such as retail grocery workers, public transit employees, health-care workers and custodial staff. Greater prevalence of lacking health insurance and care of underlying conditions such as diabetes, hypertension, and heart disease also increase their risk of death. Similar issues affect Native American and Latino communities. On the one hand, in the Dominican Republic there is a clear example of both gender and ethnic inequality. In this Latin American territory, there is great inequality and precariousness that especially affects Dominican women, with greater emphasis on those of Haitian descent. According to a US health policy non-profit, 34% of American Indian and Alaska Native People (AIAN) non-elderly adults are at risk of serious illness compared to 21% of white non-elderly adults. The source attributes it to disproportionately high rates of many health conditions that may put them at higher risk as well as living conditions like lack of access to clean water. Leaders have called for efforts to research and address the disparities. In the UK, a greater proportion of deaths due to COVID‑19 have occurred in those of a Black, Asian, and other ethnic minority background. More severe impacts upon patients including the relative incidence of the necessity of hospitalisation requirements, and vulnerability to the disease has been associated via DNA analysis to be expressed in genetic variants at chromosomal region 3, features that are associated with European Neanderthal heritage. That structure imposes greater risks that those affected will develop a more severe form of the disease. The findings are from Professor Svante Pääbo and researchers he leads at the Max Planck Institute for Evolutionary Anthropology and the Karolinska Institutet. This admixture of modern human and Neanderthal genes is estimated to have occurred roughly between 50,000 and 60,000 years ago in Southern Europe. Biological factors (immune response) and the general behaviour (habits) can strongly determine the consequences of COVID‑19. Most of those who die of COVID‑19 have pre-existing (underlying) conditions, including hypertension, diabetes mellitus, and cardiovascular disease. According to March data from the United States, 89% of those hospitalised had preexisting conditions. The Italian Istituto Superiore di Sanità reported that out of 8.8% of deaths where medical charts were available, 96.1% of people had at least one comorbidity with the average person having 3.4 diseases. According to this report the most common comorbidities are hypertension (66% of deaths), type 2 diabetes (29.8% of deaths), ischaemic heart disease (27.6% of deaths), atrial fibrillation (23.1% of deaths) and chronic renal failure (20.2% of deaths). Most critical respiratory comorbidities according to the US Centers for Disease Control and Prevention (CDC), are: moderate or severe asthma, pre-existing COPD, pulmonary fibrosis, cystic fibrosis. Evidence stemming from meta-analysis of several smaller research papers also suggests that smoking can be associated with worse outcomes. When someone with existing respiratory problems is infected with COVID‑19, they might be at greater risk for severe symptoms. COVID‑19 also poses a greater risk to people who misuse opioids and amphetamines, insofar as their drug use may have caused lung damage. In August 2020, the CDC issued a caution that tuberculosis (TB) infections could increase the risk of severe illness or death. The WHO recommended that people with respiratory symptoms be screened for both diseases, as testing positive for COVID‑19 could not rule out co-infections. Some projections have estimated that reduced TB detection due to the pandemic could result in 6.3 million additional TB cases and 1.4 million TB-related deaths by 2025. The virus is thought to be of natural animal origin, most likely through spillover infection. A joint-study conducted in early 2021 by the People's Republic of China and the World Health Organization indicated that the virus descended from a coronavirus that infects wild bats, and likely spread to humans through an intermediary wildlife host. There are several theories about where the index case originated and investigations into the origin of the pandemic are ongoing. According to articles published in July 2022 in Science, virus transmission into humans occurred through two spillover events in November 2019 and was likely due to live wildlife trade on the Huanan wet market in the city of Wuhan (Hubei, China). Doubts about the conclusions have mostly centered on the precise site of spillover. Earlier phylogenetics estimated that SARS-CoV-2 arose in October or November 2019. A phylogenetic algorithm analysis suggested that the virus may have been circulating in Guangdong before Wuhan. Most scientists believe the virus spilled into human populations through natural zoonosis, similar to the SARS-CoV-1 and MERS-CoV outbreaks, and consistent with other pandemics in human history. According to the Intergovernmental Panel on Climate Change several social and environmental factors including climate change, natural ecosystem destruction and wildlife trade increased the likelihood of such zoonotic spillover. One study made with the support of the European Union found climate change increased the likelihood of the pandemic by influencing distribution of bat species. Available evidence suggests that the SARS-CoV-2 virus was originally harboured by bats, and spread to humans multiple times from infected wild animals at the Huanan Seafood Market in Wuhan in December 2019. A minority of scientists and some members of the U.S intelligence community believe the virus may have been unintentionally leaked from a laboratory such as the Wuhan Institute of Virology. The US intelligence community has mixed views on the issue, but overall agrees with the scientific consensus that the virus was not developed as a biological weapon and is unlikely to have been genetically engineered. There is no evidence SARS-CoV-2 existed in any laboratory prior to the pandemic. The first confirmed human infections were in Wuhan. A study of the first 41 cases of confirmed COVID‑19, published in January 2020 in The Lancet, reported the earliest date of onset of symptoms as 1 December 2019. Official publications from the WHO reported the earliest onset of symptoms as 8 December 2019. Human-to-human transmission was confirmed by the WHO and Chinese authorities by 20 January 2020. According to official Chinese sources, these were mostly linked to the Huanan Seafood Wholesale Market, which also sold live animals. In May 2020, George Gao, the director of the CDC, said animal samples collected from the seafood market had tested negative for the virus, indicating that the market was the site of an early superspreading event, but that it was not the site of the initial outbreak. Traces of the virus have been found in wastewater samples that were collected in Milan and Turin, Italy, on 18 December 2019. By December 2019, the spread of infection was almost entirely driven by human-to-human transmission. The number of COVID-19 cases in Hubei gradually increased, reaching sixty by 20 December, and at least 266 by 31 December. On 24 December, Wuhan Central Hospital sent a bronchoalveolar lavage fluid (BAL) sample from an unresolved clinical case to sequencing company Vision Medicals. On 27 and 28 December, Vision Medicals informed the Wuhan Central Hospital and the Chinese CDC of the results of the test, showing a new coronavirus. A pneumonia cluster of unknown cause was observed on 26 December and treated by the doctor Zhang Jixian in Hubei Provincial Hospital, who informed the Wuhan Jianghan CDC on 27 December. On 30 December, a test report addressed to Wuhan Central Hospital, from company CapitalBio Medlab, stated an erroneous positive result for SARS, causing a group of doctors at Wuhan Central Hospital to alert their colleagues and relevant hospital authorities of the result. The Wuhan Municipal Health Commission issued a notice to various medical institutions on "the treatment of pneumonia of unknown cause" that same evening. Eight of these doctors, including Li Wenliang (punished on 3 January), were later admonished by the police for spreading false rumours and another, Ai Fen, was reprimanded by her superiors for raising the alarm. The Wuhan Municipal Health Commission made the first public announcement of a pneumonia outbreak of unknown cause on 31 December, confirming 27 cases – enough to trigger an investigation. During the early stages of the outbreak, the number of cases doubled approximately every seven and a half days. In early and mid-January 2020, the virus spread to other Chinese provinces, helped by the Chinese New Year migration and Wuhan being a transport hub and major rail interchange. On 20 January, China reported nearly 140 new cases in one day, including two people in Beijing and one in Shenzhen. Later official data shows 6,174 people had already developed symptoms by then, and more may have been infected. A report in The Lancet on 24 January indicated human transmission, strongly recommended personal protective equipment for health workers, and said testing for the virus was essential due to its "pandemic potential". On 30 January, the WHO declared COVID-19 a Public Health Emergency of International Concern. By this time, the outbreak spread by a factor of 100 to 200 times. Italy had its first confirmed cases on 31 January 2020, two tourists from China. Italy overtook China as the country with the most deaths on 19 March 2020. By 26 March the United States had overtaken China and Italy with the highest number of confirmed cases in the world. Research on coronavirus genomes indicates the majority of COVID-19 cases in New York came from European travellers, rather than directly from China or any other Asian country. Retesting of prior samples found a person in France who had the virus on 27 December 2019, and a person in the United States who died from the disease on 6 February 2020. RT-PCR testing of untreated wastewater samples from Brazil and Italy have suggested detection of SARS-CoV-2 as early as November and December 2019, respectively, but the methods of such sewage studies have not been optimised, many have not been peer-reviewed, details are often missing, and there is a risk of false positives due to contamination or if only one gene target is detected. A September 2020 review journal article said, "The possibility that the COVID‑19 infection had already spread to Europe at the end of last year is now indicated by abundant, even if partially circumstantial, evidence", including pneumonia case numbers and radiology in France and Italy in November and December. As of 1 October 2021, Reuters reported that it had estimated the worldwide total number of deaths due to COVID‑19 to have exceeded five million. The Public Health Emergency of International Concern for COVID-19 ended on May 5, 2023. By this time, everyday life in most countries had returned to how it was before the pandemic. After the initial outbreak of COVID‑19, misinformation and disinformation regarding the origin, scale, prevention, treatment, and other aspects of the disease rapidly spread online. In September 2020, the US Centers for Disease Control and Prevention (CDC) published preliminary estimates of the risk of death by age groups in the United States, but those estimates were widely misreported and misunderstood. Humans appear to be capable of spreading the virus to some other animals, a type of disease transmission referred to as zooanthroponosis. Some pets, especially cats and ferrets, can catch this virus from infected humans. Symptoms in cats include respiratory (such as a cough) and digestive symptoms. Cats can spread the virus to other cats, and may be able to spread the virus to humans, but cat-to-human transmission of SARS-CoV-2 has not been proven. Compared to cats, dogs are less susceptible to this infection. Behaviours which increase the risk of transmission include kissing, licking, and petting the animal. The virus does not appear to be able to infect pigs, ducks, or chickens at all. Mice, rats, and rabbits, if they can be infected at all, are unlikely to be involved in spreading the virus. Tigers and lions in zoos have become infected as a result of contact with infected humans. As expected, monkeys and great ape species such as orangutans can also be infected with the COVID‑19 virus. Minks, which are in the same family as ferrets, have been infected. Minks may be asymptomatic, and can also spread the virus to humans. Multiple countries have identified infected animals in mink farms. Denmark, a major producer of mink pelts, ordered the slaughter of all minks over fears of viral mutations, following an outbreak referred to as Cluster 5. A vaccine for mink and other animals is being researched. International research on vaccines and medicines in COVID‑19 is underway by government organisations, academic groups, and industry researchers. The CDC has classified it to require a BSL3 grade laboratory. There has been a great deal of COVID‑19 research, involving accelerated research processes and publishing shortcuts to meet the global demand. As of December 2020, hundreds of clinical trials have been undertaken, with research happening on every continent except Antarctica. As of November 2020, more than 200 possible treatments have been studied in humans. Modelling research has been conducted with several objectives, including predictions of the dynamics of transmission, diagnosis and prognosis of infection, estimation of the impact of interventions, or allocation of resources. Modelling studies are mostly based on compartmental models in epidemiology, estimating the number of infected people over time under given conditions. Several other types of models have been developed and used during the COVID‑19 pandemic including computational fluid dynamics models to study the flow physics of COVID‑19, retrofits of crowd movement models to study occupant exposure, mobility-data based models to investigate transmission, or the use of macroeconomic models to assess the economic impact of the pandemic. Repurposed antiviral drugs make up most of the research into COVID‑19 treatments. Other candidates in trials include vasodilators, corticosteroids, immune therapies, lipoic acid, bevacizumab, and recombinant angiotensin-converting enzyme 2. In March 2020, the World Health Organization (WHO) initiated the Solidarity trial to assess the treatment effects of some promising drugs: an experimental drug called remdesivir; anti-malarial drugs chloroquine and hydroxychloroquine; two anti-HIV drugs, lopinavir/ritonavir; and interferon-beta. More than 300 active clinical trials are underway as of April 2020. Research on the antimalarial drugs hydroxychloroquine and chloroquine showed that they were ineffective at best, and that they may reduce the antiviral activity of remdesivir. By May 2020, France, Italy, and Belgium had banned the use of hydroxychloroquine as a COVID‑19 treatment. In June, initial results from the randomised RECOVERY Trial in the United Kingdom showed that dexamethasone reduced mortality by one third for people who are critically ill on ventilators and one fifth for those receiving supplemental oxygen. Because this is a well-tested and widely available treatment, it was welcomed by the WHO, which is in the process of updating treatment guidelines to include dexamethasone and other steroids. Based on those preliminary results, dexamethasone treatment has been recommended by the NIH for patients with COVID‑19 who are mechanically ventilated or who require supplemental oxygen but not in patients with COVID‑19 who do not require supplemental oxygen. In September 2020, the WHO released updated guidance on using corticosteroids for COVID‑19. The WHO recommends systemic corticosteroids rather than no systemic corticosteroids for the treatment of people with severe and critical COVID‑19 (strong recommendation, based on moderate certainty evidence). The WHO suggests not to use corticosteroids in the treatment of people with non-severe COVID‑19 (conditional recommendation, based on low certainty evidence). The updated guidance was based on a meta-analysis of clinical trials of critically ill COVID‑19 patients. In September 2020, the European Medicines Agency (EMA) endorsed the use of dexamethasone in adults and adolescents from twelve years of age and weighing at least 40 kilograms (88 lb) who require supplemental oxygen therapy. Dexamethasone can be taken by mouth or given as an injection or infusion (drip) into a vein. In November 2020, the US Food and Drug Administration (FDA) issued an emergency use authorisation for the investigational monoclonal antibody therapy bamlanivimab for the treatment of mild-to-moderate COVID‑19. Bamlanivimab is authorised for people with positive results of direct SARS-CoV-2 viral testing who are twelve years of age and older weighing at least 40 kilograms (88 lb), and who are at high risk for progressing to severe COVID‑19 or hospitalisation. This includes those who are 65 years of age or older, or who have chronic medical conditions. In February 2021, the FDA issued an emergency use authorisation (EUA) for bamlanivimab and etesevimab administered together for the treatment of mild to moderate COVID‑19 in people twelve years of age or older weighing at least 40 kilograms (88 lb) who test positive for SARS‑CoV‑2 and who are at high risk for progressing to severe COVID‑19. The authorised use includes treatment for those who are 65 years of age or older or who have certain chronic medical conditions. In April 2021, the FDA revoked the emergency use authorisation (EUA) that allowed for the investigational monoclonal antibody therapy bamlanivimab, when administered alone, to be used for the treatment of mild-to-moderate COVID‑19 in adults and certain paediatric patients. A cytokine storm can be a complication in the later stages of severe COVID‑19. A cytokine storm is a potentially deadly immune reaction where a large amount of pro-inflammatory cytokines and chemokines are released too quickly. A cytokine storm can lead to ARDS and multiple organ failure. Data collected from Jin Yin-tan Hospital in Wuhan, China indicates that patients who had more severe responses to COVID‑19 had greater amounts of pro-inflammatory cytokines and chemokines in their system than patients who had milder responses. These high levels of pro-inflammatory cytokines and chemokines indicate presence of a cytokine storm. Tocilizumab has been included in treatment guidelines by China's National Health Commission after a small study was completed. It is undergoing a Phase II non-randomised trial at the national level in Italy after showing positive results in people with severe disease. Combined with a serum ferritin blood test to identify a cytokine storm (also called cytokine storm syndrome, not to be confused with cytokine release syndrome), it is meant to counter such developments, which are thought to be the cause of death in some affected people. The interleukin-6 receptor (IL-6R) antagonist was approved by the FDA to undergo a Phase III clinical trial assessing its effectiveness on COVID‑19 based on retrospective case studies for the treatment of steroid-refractory cytokine release syndrome induced by a different cause, CAR T cell therapy, in 2017. There is no randomised, controlled evidence that tocilizumab is an efficacious treatment for CRS. Prophylactic tocilizumab has been shown to increase serum IL-6 levels by saturating the IL-6R, driving IL-6 across the blood–brain barrier, and exacerbating neurotoxicity while having no effect on the incidence of CRS. Lenzilumab, an anti-GM-CSF monoclonal antibody, is protective in murine models for CAR T cell-induced CRS and neurotoxicity and is a viable therapeutic option due to the observed increase of pathogenic GM-CSF secreting T cells in hospitalised patients with COVID‑19. Transferring purified and concentrated antibodies produced by the immune systems of those who have recovered from COVID‑19 to people who need them is being investigated as a non-vaccine method of passive immunisation. Viral neutralisation is the anticipated mechanism of action by which passive antibody therapy can mediate defence against SARS-CoV-2. The spike protein of SARS-CoV-2 is the primary target for neutralising antibodies. As of 8 August 2020, eight neutralising antibodies targeting the spike protein of SARS-CoV-2 have entered clinical studies. It has been proposed that selection of broad-neutralising antibodies against SARS-CoV-2 and SARS-CoV might be useful for treating not only COVID‑19 but also future SARS-related CoV infections. Other mechanisms, however, such as antibody-dependant cellular cytotoxicity or phagocytosis, may be possible. Other forms of passive antibody therapy, for example, using manufactured monoclonal antibodies, are in development. The use of passive antibodies to treat people with active COVID‑19 is also being studied. This involves the production of convalescent serum, which consists of the liquid portion of the blood from people who recovered from the infection and contains antibodies specific to this virus, which is then administered to active patients. This strategy was tried for SARS with inconclusive results. An updated Cochrane review in May 2023 found high certainty evidence that, for the treatment of people with moderate to severe COVID‑19, convalescent plasma did not reduce mortality or bring about symptom improvement. There continues to be uncertainty about the safety of convalescent plasma administration to people with COVID‑19 and differing outcomes measured in different studies limits their use in determining efficacy. Since the outbreak of the COVID‑19 pandemic, scholars have explored the bioethics, normative economics, and political theories of healthcare policies related to the public health crisis. Academics have pointed to the moral distress of healthcare workers, ethics of distributing scarce healthcare resources such as ventilators, and the global justice of vaccine diplomacies. The socio-economic inequalities between genders, races, groups with disabilities, communities, regions, countries, and continents have also drawn attention in academia and the general public. Nomenclature Main article: COVID-19 naming During the initial outbreak in Wuhan, the virus and disease were commonly referred to as "coronavirus" and "Wuhan coronavirus", with the disease sometimes called "Wuhan pneumonia". In the past, many diseases have been named after geographical locations, such as the Spanish flu, Middle East respiratory syndrome, and Zika virus. In January 2020, the World Health Organization (WHO) recommended 2019-nCoV and 2019-nCoV acute respiratory disease as interim names for the virus and disease per 2015 guidance and international guidelines against using geographical locations or groups of people in disease and virus names to prevent social stigma. The official names COVID‑19 and SARS-CoV-2 were issued by the WHO on 11 February 2020 with COVID-19 being shorthand for "coronavirus disease 2019". The WHO additionally uses "the COVID‑19 virus" and "the virus responsible for COVID‑19" in public communications. Symptoms and signs Main article: Symptoms of COVID-19 Symptoms of COVID-19 The symptoms of COVID-19 are variable depending on the type of variant contracted, ranging from mild symptoms to a potentially fatal illness. Common symptoms include coughing, fever, loss of smell (anosmia) and taste (ageusia), with less common ones including headaches, nasal congestion and runny nose, muscle pain, sore throat, diarrhea, eye irritation, and toes swelling or turning purple, and in moderate to severe cases, breathing difficulties. People with the COVID-19 infection may have different symptoms, and their symptoms may change over time. Three common clusters of symptoms have been identified: one respiratory symptom cluster with cough, sputum, shortness of breath, and fever; a musculoskeletal symptom cluster with muscle and joint pain, headache, and fatigue; and a cluster of digestive symptoms with abdominal pain, vomiting, and diarrhea. In people without prior ear, nose, or throat disorders, loss of taste combined with loss of smell is associated with COVID-19 and is reported in as many as 88% of symptomatic cases. Of people who show symptoms, 81% develop only mild to moderate symptoms (up to mild pneumonia), while 14% develop severe symptoms (dyspnea, hypoxia, or more than 50% lung involvement on imaging) that require hospitalization, and 5% of patients develop critical symptoms (respiratory failure, septic shock, or multiorgan dysfunction) requiring ICU admission. Proportion of asymptomatic SARS-CoV-2 infection by age. About 44% of those infected with SARS-CoV-2 remained asymptomatic throughout the infection. At least a third of the people who are infected with the virus do not develop noticeable symptoms at any point in time. These asymptomatic carriers tend not to get tested and can still spread the disease. Other infected people will develop symptoms later (called "pre-symptomatic") or have very mild symptoms and can also spread the virus. As is common with infections, there is a delay between the moment a person first becomes infected and the appearance of the first symptoms. The median delay for COVID-19 is four to five days possibly being infectious on 1-4 of those days. Most symptomatic people experience symptoms within two to seven days after exposure, and almost all will experience at least one symptom within 12 days. Most people recover from the acute phase of the disease. However, some people continue to experience a range of effects, such as fatigue, for months, even after recovery. This is the result of a condition called long COVID, which can be described as a range of persistent symptoms that continue for weeks or months at a time. Long-term damage to organs has also been observed after the onset of COVID-19. Multi-year studies are underway to further investigate the potential long-term effects of the disease. The Omicron variant became dominant in the U.S. in December 2021. Symptoms with the Omicron variant are less severe than they are with other variants. Complications Mechanisms of SARS-CoV-2 cytokine storm and complications Complications may include pneumonia, acute respiratory distress syndrome (ARDS), multi-organ failure, septic shock, and death. Cardiovascular complications may include heart failure, arrhythmias (including atrial fibrillation), heart inflammation, and thrombosis, particularly venous thromboembolism. Approximately 20–30% of people who present with COVID‑19 have elevated liver enzymes, reflecting liver injury. Neurologic manifestations include seizure, stroke, encephalitis, and Guillain–Barré syndrome (which includes loss of motor functions). Following the infection, children may develop paediatric multisystem inflammatory syndrome, which has symptoms similar to Kawasaki disease, which can be fatal. In very rare cases, acute encephalopathy can occur, and it can be considered in those who have been diagnosed with COVID‑19 and have an altered mental status. According to the US Centers for Disease Control and Prevention, pregnant women are at increased risk of becoming seriously ill from COVID‑19. This is because pregnant women with COVID‑19 appear to be more likely to develop respiratory and obstetric complications that can lead to miscarriage, premature delivery and intrauterine growth restriction. Fungal infections such as aspergillosis, candidiasis, cryptococcosis and mucormycosis have been recorded in patients recovering from COVID‑19. Cause COVID‑19 is caused by infection with a strain of coronavirus known as "severe acute respiratory syndrome coronavirus 2" (SARS-CoV-2). Transmission Main article: Transmission of COVID-19 Transmission of COVID‑19 COVID-19 is mainly transmitted when people breathe in air contaminated by droplets/aerosols and small airborne particles containing the virus. Infected people exhale those particles as they breathe, talk, cough, sneeze, or sing. Transmission is more likely the closer people are. However, infection can occur over longer distances, particularly indoors. The transmission of the virus is carried out through virus-laden fluid particles, or droplets, which are created in the respiratory tract, and they are expelled by the mouth and the nose. There are three types of transmission: “droplet” and “contact”, which are associated with large droplets, and “airborne”, which is associated with small droplets. If the droplets are above a certain critical size, they settle faster than they evaporate, and therefore they contaminate surfaces surrounding them. Droplets that are below a certain critical size, evaporate faster than they settle; due to that fact, they form nuclei that remain airborne for a long period of time over extensive distances. Infectivity can begin four to five days before the onset of symptoms. Infected people can spread the disease even if they are pre-symptomatic or asymptomatic. Most commonly, the peak viral load in upper respiratory tract samples occurs close to the time of symptom onset and declines after the first week after symptoms begin. Current evidence suggests a duration of viral shedding and the period of infectiousness of up to ten days following symptom onset for people with mild to moderate COVID-19, and up to 20 days for persons with severe COVID-19, including immunocompromised people. Infectious particles range in size from aerosols that remain suspended in the air for long periods of time to larger droplets that remain airborne briefly or fall to the ground. Additionally, COVID-19 research has redefined the traditional understanding of how respiratory viruses are transmitted. The largest droplets of respiratory fluid do not travel far, but can be inhaled or land on mucous membranes on the eyes, nose, or mouth to infect. Aerosols are highest in concentration when people are in close proximity, which leads to easier viral transmission when people are physically close, but airborne transmission can occur at longer distances, mainly in locations that are poorly ventilated; in those conditions small particles can remain suspended in the air for minutes to hours. Virology Main article: SARS-CoV-2 Illustration of SARSr-CoV virion Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) is a novel severe acute respiratory syndrome coronavirus. It was first isolated from three people with pneumonia connected to the cluster of acute respiratory illness cases in Wuhan. All structural features of the novel SARS-CoV-2 virus particle occur in related coronaviruses in nature, particularly in Rhinolophus sinicus aka Chinese horseshoe bats. Outside the human body, the virus is destroyed by household soap which bursts its protective bubble. Hospital disinfectants, alcohols, heat, povidone-iodine, and ultraviolet-C (UV-C) irradiation are also effective disinfection methods for surfaces. SARS-CoV-2 is closely related to the original SARS-CoV. It is thought to have an animal (zoonotic) origin. Genetic analysis has revealed that the coronavirus genetically clusters with the genus Betacoronavirus, in subgenus Sarbecovirus (lineage B) together with two bat-derived strains. It is 96% identical at the whole genome level to other bat coronavirus samples (BatCov RaTG13). The structural proteins of SARS-CoV-2 include membrane glycoprotein (M), envelope protein (E), nucleocapsid protein (N), and the spike protein (S). The M protein of SARS-CoV-2 is about 98% similar to the M protein of bat SARS-CoV, maintains around 98% homology with pangolin SARS-CoV, and has 90% homology with the M protein of SARS-CoV; whereas, the similarity is only around 38% with the M protein of MERS-CoV. SARS-CoV-2 variants Main article: Variants of SARS-CoV-2 The many thousands of SARS-CoV-2 variants are grouped into either clades or lineages. The WHO, in collaboration with partners, expert networks, national authorities, institutions and researchers, have established nomenclature systems for naming and tracking SARS-CoV-2 genetic lineages by GISAID, Nextstrain and Pango. The expert group convened by the WHO recommended the labelling of variants using letters of the Greek alphabet, for example, Alpha, Beta, Delta, and Gamma, giving the justification that they "will be easier and more practical to discussed by non-scientific audiences". Nextstrain divides the variants into five clades (19A, 19B, 20A, 20B, and 20C), while GISAID divides them into seven (L, O, V, S, G, GH, and GR). The Pango tool groups variants into lineages, with many circulating lineages being classed under the B.1 lineage. Several notable variants of SARS-CoV-2 emerged throughout 2020. Cluster 5 emerged among minks and mink farmers in Denmark. After strict quarantines and a mink euthanasia campaign, the cluster was assessed to no longer be circulating among humans in Denmark as of 1 February 2021. As of December 2021, there are five dominant variants of SARS-CoV-2 spreading among global populations: the Alpha variant (B.1.1.7, formerly called the UK variant), first found in London and Kent, the Beta variant (B.1.351, formerly called the South Africa variant), the Gamma variant (P.1, formerly called the Brazil variant), the Delta variant (B.1.617.2, formerly called the India variant), and the Omicron variant (B.1.1.529), which had spread to 57 countries as of 7 December. On December 19, 2023, the WHO declared that another distinctive variant, JN.1, had emerged as a "variant of interest". Though the WHO expects an increase in cases globally, particularly for countries entering winter, the current overall global health risk (as of December 21, 2023) remains low. Pathophysiology COVID‑19 pathogenesis The SARS-CoV-2 virus can infect a wide range of cells and systems of the body. COVID‑19 is most known for affecting the upper respiratory tract (sinuses, nose, and throat) and the lower respiratory tract (windpipe and lungs). The lungs are the organs most affected by COVID‑19 because the virus accesses host cells via the receptor for the enzyme angiotensin-converting enzyme 2 (ACE2), which is most abundant on the surface of type II alveolar cells of the lungs. The virus uses a special surface glycoprotein called a "spike" to connect to the ACE2 receptor and enter the host cell. Respiratory tract Following viral entry, COVID‑19 infects the ciliated epithelium of the nasopharynx and upper airways. Autopsies of people who died of COVID‑19 have found diffuse alveolar damage, and lymphocyte-containing inflammatory infiltrates within the lung. Nervous system One common symptom, loss of smell, results from infection of the support cells of the olfactory epithelium, with subsequent damage to the olfactory neurons. The involvement of both the central and peripheral nervous system in COVID‑19 has been reported in many medical publications. It is clear that many people with COVID-19 exhibit neurological or mental health issues. The virus is not detected in the central nervous system (CNS) of the majority of COVID-19 patients with neurological issues. However, SARS-CoV-2 has been detected at low levels in the brains of those who have died from COVID‑19, but these results need to be confirmed. While virus has been detected in cerebrospinal fluid of autopsies, the exact mechanism by which it invades the CNS remains unclear and may first involve invasion of peripheral nerves given the low levels of ACE2 in the brain. The virus may also enter the bloodstream from the lungs and cross the blood–brain barrier to gain access to the CNS, possibly within an infected white blood cell. Tropism and multiple organ injuries in SARS-CoV-2 infection Research conducted when Alpha was the dominant variant has suggested COVID-19 may cause brain damage. Later research showed that all variants studied (including Omicron) killed brain cells, but the exact cells killed varied by variant. It is unknown if such damage is temporary or permanent. Observed individuals infected with COVID-19 (most with mild cases) experienced an additional 0.2% to 2% of brain tissue lost in regions of the brain connected to the sense of smell compared with uninfected individuals, and the overall effect on the brain was equivalent on average to at least one extra year of normal ageing; infected individuals also scored lower on several cognitive tests. All effects were more pronounced among older ages. Gastrointestinal tract The virus also affects gastrointestinal organs as ACE2 is abundantly expressed in the glandular cells of gastric, duodenal and rectal epithelium as well as endothelial cells and enterocytes of the small intestine. Cardiovascular system The virus can cause acute myocardial injury and chronic damage to the cardiovascular system. An acute cardiac injury was found in 12% of infected people admitted to the hospital in Wuhan, China, and is more frequent in severe disease. Rates of cardiovascular symptoms are high, owing to the systemic inflammatory response and immune system disorders during disease progression, but acute myocardial injuries may also be related to ACE2 receptors in the heart. ACE2 receptors are highly expressed in the heart and are involved in heart function. A high incidence of thrombosis and venous thromboembolism occurs in people transferred to intensive care units with COVID‑19 infections, and may be related to poor prognosis. Blood vessel dysfunction and clot formation (as suggested by high D-dimer levels caused by blood clots) may have a significant role in mortality, incidents of clots leading to pulmonary embolisms, and ischaemic events (strokes) within the brain found as complications leading to death in people infected with COVID‑19. Infection may initiate a chain of vasoconstrictive responses within the body, including pulmonary vasoconstriction – a possible mechanism in which oxygenation decreases during pneumonia. Furthermore, damage of arterioles and capillaries was found in brain tissue samples of people who died from COVID‑19. COVID‑19 may also cause substantial structural changes to blood cells, sometimes persisting for months after hospital discharge. A low level of blood lymphocytes may result from the virus acting through ACE2-related entry into lymphocytes. Kidneys Another common cause of death is complications related to the kidneys. Early reports show that up to 30% of hospitalised patients both in China and in New York have experienced some injury to their kidneys, including some persons with no previous kidney problems. Immunopathology Key components of the adaptive immune response to SARS-CoV-2 Although SARS-CoV-2 has a tropism for ACE2-expressing epithelial cells of the respiratory tract, people with severe COVID‑19 have symptoms of systemic hyperinflammation. Clinical laboratory findings of elevated IL‑2, IL‑7, IL‑6, granulocyte-macrophage colony-stimulating factor (GM‑CSF), interferon gamma-induced protein 10 (IP‑10), monocyte chemoattractant protein 1 (MCP1), macrophage inflammatory protein 1‑alpha (MIP‑1‑alpha), and tumour necrosis factor (TNF‑α) indicative of cytokine release syndrome (CRS) suggest an underlying immunopathology. Interferon alpha plays a complex, Janus-faced role in the pathogenesis of COVID-19. Although it promotes the elimination of virus-infected cells, it also upregulates the expression of ACE-2, thereby facilitating the SARS-Cov2 virus to enter cells and to replicate. A competition of negative feedback loops (via protective effects of interferon alpha) and positive feedback loops (via upregulation of ACE-2) is assumed to determine the fate of patients suffering from COVID-19. Additionally, people with COVID‑19 and acute respiratory distress syndrome (ARDS) have classical serum biomarkers of CRS, including elevated C-reactive protein (CRP), lactate dehydrogenase (LDH), D-dimer, and ferritin. Systemic inflammation results in vasodilation, allowing inflammatory lymphocytic and monocytic infiltration of the lung and the heart. In particular, pathogenic GM-CSF-secreting T cells were shown to correlate with the recruitment of inflammatory IL-6-secreting monocytes and severe lung pathology in people with COVID‑19. Lymphocytic infiltrates have also been reported at autopsy. Viral and host factors Virus proteins The association between SARS-CoV-2 and the Renin-Angiotensin-Aldosterone System (RAAS) Multiple viral and host factors affect the pathogenesis of the virus. The S-protein, otherwise known as the spike protein, is the viral component that attaches to the host receptor via the ACE2 receptors. It includes two subunits: S1 and S2. S1 determines the virus-host range and cellular tropism via the receptor-binding domain. S2 mediates the membrane fusion of the virus to its potential cell host via the H1 and HR2, which are heptad repeat regions. Studies have shown that S1 domain induced IgG and IgA antibody levels at a much higher capacity. It is the focus spike proteins expression that are involved in many effective COVID‑19 vaccines. The M protein is the viral protein responsible for the transmembrane transport of nutrients. It is the cause of the bud release and the formation of the viral envelope. The N and E protein are accessory proteins that interfere with the host's immune response. Host factors Human angiotensin converting enzyme 2 (hACE2) is the host factor that SARS-CoV-2 virus targets causing COVID‑19. Theoretically, the usage of angiotensin receptor blockers (ARB) and ACE inhibitors upregulating ACE2 expression might increase morbidity with COVID‑19, though animal data suggest some potential protective effect of ARB; however no clinical studies have proven susceptibility or outcomes. Until further data is available, guidelines and recommendations for hypertensive patients remain. The effect of the virus on ACE2 cell surfaces leads to leukocytic infiltration, increased blood vessel permeability, alveolar wall permeability, as well as decreased secretion of lung surfactants. These effects cause the majority of the respiratory symptoms. However, the aggravation of local inflammation causes a cytokine storm eventually leading to a systemic inflammatory response syndrome. Among healthy adults not exposed to SARS-CoV-2, about 35% have CD4 T cells that recognise the SARS-CoV-2 S protein (particularly the S2 subunit) and about 50% react to other proteins of the virus, suggesting cross-reactivity from previous common colds caused by other coronaviruses. It is unknown whether different persons use similar antibody genes in response to COVID‑19. Host cytokine response Mild versus severe immune response during virus infection The severity of the inflammation can be attributed to the severity of what is known as the cytokine storm. Levels of interleukin 1B, interferon-gamma, interferon-inducible protein 10, and monocyte chemoattractant protein 1 were all associated with COVID‑19 disease severity. Treatment has been proposed to combat the cytokine storm as it remains to be one of the leading causes of morbidity and mortality in COVID‑19 disease. A cytokine storm is due to an acute hyperinflammatory response that is responsible for clinical illness in an array of diseases but in COVID‑19, it is related to worse prognosis and increased fatality. The storm causes acute respiratory distress syndrome, blood clotting events such as strokes, myocardial infarction, encephalitis, acute kidney injury, and vasculitis. The production of IL-1, IL-2, IL-6, TNF-alpha, and interferon-gamma, all crucial components of normal immune responses, inadvertently become the causes of a cytokine storm. The cells of the central nervous system, the microglia, neurons, and astrocytes, are also involved in the release of pro-inflammatory cytokines affecting the nervous system, and effects of cytokine storms toward the CNS are not uncommon. Pregnancy response There are many unknowns for pregnant women during the COVID-19 pandemic. Given that they are prone to have complications and severe disease infection with other types of coronaviruses, they have been identified as a vulnerable group and advised to take supplementary preventive measures. Physiological responses to pregnancy can include: Immunological: The immunological response to COVID-19, like other viruses, depends on a working immune system. It adapts during pregnancy to allow the development of the foetus whose genetic load is only partially shared with their mother, leading to a different immunological reaction to infections during the course of pregnancy. Respiratory: Many factors can make pregnant women more vulnerable to hard respiratory infections. One of them is the total reduction of the lungs' capacity and inability to clear secretions. Coagulation: During pregnancy, there are higher levels of circulating coagulation factors, and the pathogenesis of SARS-CoV-2 infection can be implicated. The thromboembolic events with associated mortality are a risk for pregnant women. However, from the evidence base, it is difficult to conclude whether pregnant women are at increased risk of grave consequences of this virus. In addition to the above, other clinical studies have proved that SARS-CoV-2 can affect the period of pregnancy in different ways. On the one hand, there is little evidence of its impact up to 12 weeks gestation. On the other hand, COVID-19 infection may cause increased rates of unfavourable outcomes in the course of the pregnancy. Some examples of these could be foetal growth restriction, preterm birth, and perinatal mortality, which refers to the foetal death past 22 or 28 completed weeks of pregnancy as well as the death among live-born children up to seven completed days of life. For preterm birth, a 2023 review indicates that there appears to be a correlation with COVID-19. Unvaccinated women in later stages of pregnancy with COVID-19 are more likely than other patients to need very intensive care. Babies born to mothers with COVID-19 are more likely to have breathing problems. Pregnant women are strongly encouraged to get vaccinated. Diagnosis Further information: COVID-19 testing COVID‑19 can provisionally be diagnosed on the basis of symptoms and confirmed using reverse transcription polymerase chain reaction (RT-PCR) or other nucleic acid testing of infected secretions. Along with laboratory testing, chest CT scans may be helpful to diagnose COVID‑19 in individuals with a high clinical suspicion of infection. Detection of a past infection is possible with serological tests, which detect antibodies produced by the body in response to the infection. Viral testing Main article: COVID-19 testing Demonstration of a nasopharyngeal swab for COVID‑19 testing The standard methods of testing for presence of SARS-CoV-2 are nucleic acid tests, which detects the presence of viral RNA fragments. As these tests detect RNA but not infectious virus, its "ability to determine duration of infectivity of patients is limited". The test is typically done on respiratory samples obtained by a nasopharyngeal swab; however, a nasal swab or sputum sample may also be used. Results are generally available within hours. The WHO has published several testing protocols for the disease. Several laboratories and companies have developed serological tests, which detect antibodies produced by the body in response to infection. Several have been evaluated by Public Health England and approved for use in the UK. The University of Oxford's CEBM has pointed to mounting evidence that "a good proportion of 'new' mild cases and people re-testing positives after quarantine or discharge from hospital are not infectious, but are simply clearing harmless virus particles which their immune system has efficiently dealt with" and have called for "an international effort to standardize and periodically calibrate testing" In September 2020, the UK government issued "guidance for procedures to be implemented in laboratories to provide assurance of positive SARS-CoV-2 RNA results during periods of low prevalence, when there is a reduction in the predictive value of positive test results". Imaging A CT scan of a person with COVID-19 shows lesions (bright regions) in the lungs CT scan of rapid progression stage of COVID-19 Chest X-ray showing COVID‑19 pneumonia Chest CT scans may be helpful to diagnose COVID‑19 in individuals with a high clinical suspicion of infection but are not recommended for routine screening. Bilateral multilobar ground-glass opacities with a peripheral, asymmetric, and posterior distribution are common in early infection. Subpleural dominance, crazy paving (lobular septal thickening with variable alveolar filling), and consolidation may appear as the disease progresses. Characteristic imaging features on chest radiographs and computed tomography (CT) of people who are symptomatic include asymmetric peripheral ground-glass opacities without pleural effusions. Many groups have created COVID‑19 datasets that include imagery such as the Italian Radiological Society which has compiled an international online database of imaging findings for confirmed cases. Due to overlap with other infections such as adenovirus, imaging without confirmation by rRT-PCR is of limited specificity in identifying COVID‑19. A large study in China compared chest CT results to PCR and demonstrated that though imaging is less specific for the infection, it is faster and more sensitive. Coding In late 2019, the WHO assigned emergency ICD-10 disease codes U07.1 for deaths from lab-confirmed SARS-CoV-2 infection and U07.2 for deaths from clinically or epidemiologically diagnosed COVID‑19 without lab-confirmed SARS-CoV-2 infection. Pathology The main pathological findings at autopsy are: Macroscopy: pericarditis, lung consolidation and pulmonary oedema Lung findings: minor serous exudation, minor fibrin exudation pulmonary oedema, pneumocyte hyperplasia, large atypical pneumocytes, interstitial inflammation with lymphocytic infiltration and multinucleated giant cell formation diffuse alveolar damage (DAD) with diffuse alveolar exudates. DAD is the cause of acute respiratory distress syndrome (ARDS) and severe hypoxaemia. organisation of exudates in alveolar cavities and pulmonary interstitial fibrosis plasmocytosis in bronchoalveolar lavage (BAL) Blood and vessels: disseminated intravascular coagulation (DIC); leukoerythroblastic reaction, endotheliitis, hemophagocytosis Heart: cardiac muscle cell necrosis Liver: microvesicular steatosis Nose: shedding of olfactory epithelium Brain: infarction Kidneys: acute tubular damage. Spleen: white pulp depletion. Prevention Further information: COVID-19 vaccine, Workplace hazard controls for COVID-19, Pandemic prevention, Non-pharmaceutical intervention, Preparations prior to COVID-19, COVID-19 surveillance, and COVID-19 apps Without pandemic containment measures – such as social distancing, vaccination, and face masks – pathogens can spread exponentially. This graphic shows how early adoption of containment measures tends to protect wider swaths of the population. Preventive measures to reduce the chances of infection include getting vaccinated, staying at home, wearing a mask in public, avoiding crowded places, keeping distance from others, ventilating indoor spaces, managing potential exposure durations, washing hands with soap and water often and for at least twenty seconds, practising good respiratory hygiene, and avoiding touching the eyes, nose, or mouth with unwashed hands. Those diagnosed with COVID‑19 or who believe they may be infected are advised by the CDC to stay home except to get medical care, call ahead before visiting a healthcare provider, wear a face mask before entering the healthcare provider's office and when in any room or vehicle with another person, cover coughs and sneezes with a tissue, regularly wash hands with soap and water and avoid sharing personal household items. The first COVID‑19 vaccine was granted regulatory approval on 2 December 2020 by the UK medicines regulator MHRA. It was evaluated for emergency use authorisation (EUA) status by the US FDA, and in several other countries. Initially, the US National Institutes of Health guidelines do not recommend any medication for prevention of COVID‑19, before or after exposure to the SARS-CoV-2 virus, outside the setting of a clinical trial. Without a vaccine, other prophylactic measures, or effective treatments, a key part of managing COVID‑19 is trying to decrease and delay the epidemic peak, known as "flattening the curve". This is done by slowing the infection rate to decrease the risk of health services being overwhelmed, allowing for better treatment of active cases, and delaying additional cases until effective treatments or a vaccine become available. Vaccine Main article: COVID-19 vaccine Different vaccine candidate types in development for SARS-CoV-2 Death rates for unvaccinated Americans substantially exceeded those who were vaccinated, with bivalent boosters further reducing the death rate. Prior to the COVID‑19 pandemic, an established body of knowledge existed about the structure and function of coronaviruses causing diseases like severe acute respiratory syndrome (SARS) and Middle East respiratory syndrome (MERS). This knowledge accelerated the development of various vaccine platforms in early 2020. The initial focus of SARS-CoV-2 vaccines was on preventing symptomatic, often severe, illness. In 2020, the first COVID‑19 vaccines were developed and made available to the public through emergency authorizations and conditional approvals. Initially, most COVID‑19 vaccines were two-dose vaccines, with the sole exception being the single-dose Janssen COVID‑19 vaccine. However, immunity from the vaccines has been found to wane over time, requiring people to get booster doses of the vaccine to maintain protection against COVID‑19. The COVID‑19 vaccines are widely credited for their role in reducing the spread of COVID‑19 and reducing the severity and death caused by COVID‑19. According to a June 2022 study, COVID‑19 vaccines prevented an additional 14.4 to 19.8 million deaths in 185 countries and territories from 8 December 2020 to 8 December 2021. Many countries implemented phased distribution plans that prioritized those at highest risk of complications, such as the elderly, and those at high risk of exposure and transmission, such as healthcare workers. Common side effects of COVID‑19 vaccines include soreness, redness, rash, inflammation at the injection site, fatigue, headache, myalgia (muscle pain), and arthralgia (joint pain), which resolve without medical treatment within a few days. COVID‑19 vaccination is safe for people who are pregnant or are breastfeeding. As of 1 February 2024, 13.57 billion doses of COVID‑19 vaccines have been administered worldwide, based on official reports from national public health agencies. By December 2020, more than 10 billion vaccine doses had been preordered by countries, with about half of the doses purchased by high-income countries comprising 14% of the world's population. Face masks and respiratory hygiene Main article: Face masks during the COVID-19 pandemic Masks with an exhalation valve. The valves are a weak point that can transmit the viruses outwards. US Ambassador to Indonesia Sung Kim accompanied by local officials at the Presidential Palace wearing face masks amid the COVID-19 pandemic In community and healthcare settings, the use of face masks is intended as source control to limit transmission of the virus and for personal protection to prevent infection. Properly worn masks both limit the respiratory droplets and aerosols spread by infected individuals and help protect healthy individuals from infection. Reviews of various kinds of scientific studies have concluded that masking is effective in protecting the individual against COVID-19. Various case-control and population-based studies have also shown that increased levels of masking in a community reduces the spread of SARS-CoV-2, though there is a paucity of evidence from randomized controlled trials (RCTs). Masks vary in how well they work, with N95 and surgical masks outperforming cloth masks, but even cloth masks, with their variability in fabric type and mask fit, provide wearers with substantial protection from particles carrying COVID-19. Among readily available fabrics, double-layered cotton, hybrid masks, and cotton flannel perform best, and filtration effectiveness generally improves with thread count. Healthcare workers, given their exposure, are recommended against using cloth masks. Indoor ventilation and avoiding crowded indoor spaces The CDC states that avoiding crowded indoor spaces reduces the risk of COVID-19 infection. When indoors, increasing the rate of air change, decreasing recirculation of air and increasing the use of outdoor air can reduce transmission. The WHO recommends ventilation and air filtration in public spaces to help clear out infectious aerosols. Exhaled respiratory particles can build-up within enclosed spaces with inadequate ventilation. The risk of COVID‑19 infection increases especially in spaces where people engage in physical exertion or raise their voice (e.g., exercising, shouting, singing) as this increases exhalation of respiratory droplets. Prolonged exposure to these conditions, typically more than 15 minutes, leads to higher risk of infection. Displacement ventilation with large natural inlets can move stale air directly to the exhaust in laminar flow while significantly reducing the concentration of droplets and particles. Passive ventilation reduces energy consumption and maintenance costs but may lack controllability and heat recovery. Displacement ventilation can also be achieved mechanically with higher energy and maintenance costs. The use of large ducts and openings helps to prevent mixing in closed environments. Recirculation and mixing should be avoided because recirculation prevents dilution of harmful particles and redistributes possibly contaminated air, and mixing increases the concentration and range of infectious particles and keeps larger particles in the air. Hand-washing and hygiene Main article: Hand washing Students in Rwanda hand washing and wearing face masks during the COVID‑19 pandemic in the country. Thorough hand hygiene after any cough or sneeze is required. The WHO also recommends that individuals wash hands often with soap and water for at least twenty seconds, especially after going to the toilet or when hands are visibly dirty, before eating and after blowing one's nose. When soap and water are not available, the CDC recommends using an alcohol-based hand sanitiser with at least 60% alcohol. For areas where commercial hand sanitisers are not readily available, the WHO provides two formulations for local production. In these formulations, the antimicrobial activity arises from ethanol or isopropanol. Hydrogen peroxide is used to help eliminate bacterial spores in the alcohol; it is "not an active substance for hand antisepsis". Glycerol is added as a humectant. Social distancing Main article: Social distancing measures related to the COVID-19 pandemic Social distancing (also known as physical distancing) includes infection control actions intended to slow the spread of the disease by minimising close contact between individuals. Methods include quarantines; travel restrictions; and the closing of schools, workplaces, stadiums, theatres, or shopping centres. Individuals may apply social distancing methods by staying at home, limiting travel, avoiding crowded areas, using no-contact greetings, and physically distancing themselves from others. In 2020, outbreaks occurred in prisons due to crowding and an inability to enforce adequate social distancing. In the United States, the prisoner population is ageing and many of them are at high risk for poor outcomes from COVID‑19 due to high rates of coexisting heart and lung disease, and poor access to high-quality healthcare. Surface cleaning After being expelled from the body, coronaviruses can survive on surfaces for hours to days. If a person touches the dirty surface, they may deposit the virus at the eyes, nose, or mouth where it can enter the body and cause infection. Evidence indicates that contact with infected surfaces is not the main driver of COVID‑19, leading to recommendations for optimised disinfection procedures to avoid issues such as the increase of antimicrobial resistance through the use of inappropriate cleaning products and processes. Deep cleaning and other surface sanitation has been criticised as hygiene theatre, giving a false sense of security against something primarily spread through the air. The amount of time that the virus can survive depends significantly on the type of surface, the temperature, and the humidity. Coronaviruses die very quickly when exposed to the UV light in sunlight. Like other enveloped viruses, SARS-CoV-2 survives longest when the temperature is at room temperature or lower, and when the relative humidity is low (<50%). On many surfaces, including glass, some types of plastic, stainless steel, and skin, the virus can remain infective for several days indoors at room temperature, or even about a week under ideal conditions. On some surfaces, including cotton fabric and copper, the virus usually dies after a few hours. The virus dies faster on porous surfaces than on non-porous surfaces due to capillary action within pores and faster aerosol droplet evaporation. However, of the many surfaces tested, two with the longest survival times are N95 respirator masks and surgical masks, both of which are considered porous surfaces. The CDC says that in most situations, cleaning surfaces with soap or detergent, not disinfecting, is enough to reduce risk of transmission. The CDC recommends that if a COVID‑19 case is suspected or confirmed at a facility such as an office or day care, all areas such as offices, bathrooms, common areas, shared electronic equipment like tablets, touch screens, keyboards, remote controls, and ATMs used by the ill persons should be disinfected. Surfaces may be decontaminated with 62–71 per cent ethanol, 50–100 per cent isopropanol, 0.1 per cent sodium hypochlorite, 0.5 per cent hydrogen peroxide, 0.2–7.5 per cent povidone-iodine, or 50–200 ppm hypochlorous acid. Other solutions, such as benzalkonium chloride and chlorhexidine gluconate, are less effective. Ultraviolet germicidal irradiation may also be used, although popular devices require 5–10 min exposure and may deteriorate some materials over time. A datasheet comprising the authorised substances to disinfection in the food industry (including suspension or surface tested, kind of surface, use dilution, disinfectant and inoculum volumes) can be seen in the supplementary material of. Self-isolation Self-isolation at home has been recommended for those diagnosed with COVID‑19 and those who suspect they have been infected. Health agencies have issued detailed instructions for proper self-isolation. Many governments have mandated or recommended self-quarantine for entire populations. The strongest self-quarantine instructions have been issued to those in high-risk groups. Those who may have been exposed to someone with COVID‑19 and those who have recently travelled to a country or region with the widespread transmission have been advised to self-quarantine for 14 days from the time of last possible exposure. International travel-related control measures A 2021 Cochrane rapid review found that based upon low-certainty evidence, international travel-related control measures such as restricting cross-border travel may help to contain the spread of COVID‑19. Additionally, symptom/exposure-based screening measures at borders may miss many positive cases. While test-based border screening measures may be more effective, it could also miss many positive cases if only conducted upon arrival without follow-up. The review concluded that a minimum 10-day quarantine may be beneficial in preventing the spread of COVID‑19 and may be more effective if combined with an additional control measure like border screening. Treatment Main article: Treatment and management of COVID-19 An overview of COVID-19 therapeutics and drugs The treatment and management of COVID-19 combines both supportive care, which includes treatment to relieve symptoms, fluid therapy, oxygen support as needed, and a growing list of approved medications. Highly effective vaccines have reduced mortality related to SARS-CoV-2; however, for those awaiting vaccination, as well as for the estimated millions of immunocompromised persons who are unlikely to respond robustly to vaccination, treatment remains important. Some people may experience persistent symptoms or disability after recovery from the infection, known as long COVID, but there is still limited information on the best management and rehabilitation for this condition. Most cases of COVID-19 are mild. In these, supportive care includes medication such as paracetamol or NSAIDs to relieve symptoms (fever, body aches, cough), proper intake of fluids, rest, and nasal breathing. Good personal hygiene and a healthy diet are also recommended. As of April 2020 the U.S. Centers for Disease Control and Prevention (CDC) recommended that those who suspect they are carrying the virus isolate themselves at home and wear a face mask. As of November 2020 use of the glucocorticoid dexamethasone had been strongly recommended in those severe cases treated in hospital with low oxygen levels, to reduce the risk of death. Noninvasive ventilation and, ultimately, admission to an intensive care unit for mechanical ventilation may be required to support breathing. Extracorporeal membrane oxygenation (ECMO) has been used to address respiratory failure, but its benefits are still under consideration. Some of the cases of severe disease course are caused by systemic hyper-inflammation, the so-called cytokine storm. Although several medications have been approved in different countries as of April 2022, not all countries have these medications. Patients with mild to moderate symptoms who are in the risk groups can take nirmatrelvir/ritonavir (marketed as Paxlovid) or remdesivir, either of which reduces the risk of serious illness or hospitalization. In the US, the Biden Administration COVID-19 action plan includes the Test to Treat initiative, where people can go to a pharmacy, take a COVID test, and immediately receive free Paxlovid if they test positive. Several experimental treatments are being actively studied in clinical trials. These include the antivirals molnupiravir (developed by Merck), and nirmatrelvir/ritonavir (developed by Pfizer). Others were thought to be promising early in the pandemic, such as hydroxychloroquine and lopinavir/ritonavir, but later research found them to be ineffective or even harmful, like fluvoxamine, a cheap and widely available antidepressant; As of December 2020, there was not enough high-quality evidence to recommend so-called early treatment. In December 2020, two monoclonal antibody-based therapies were available in the United States, for early use in cases thought to be at high risk of progression to severe disease. The antiviral remdesivir has been available in the U.S., Canada, Australia, and several other countries, with varying restrictions; however, it is not recommended for people needing mechanical ventilation, and has been discouraged altogether by the World Health Organization (WHO), due to limited evidence of its efficacy. In November 2021, the UK approved the use of molnupiravir as a COVID treatment for vulnerable patients recently diagnosed with the disease. Prognosis and risk factors See also: COVID-19 pandemic death rates by country The severity of COVID‑19 varies. The disease may take a mild course with few or no symptoms, resembling other common upper respiratory diseases such as the common cold. In 3–4% of cases (7.4% for those over age 65) symptoms are severe enough to cause hospitalisation. Mild cases typically recover within two weeks, while those with severe or critical diseases may take three to six weeks to recover. Among those who have died, the time from symptom onset to death has ranged from two to eight weeks. The Italian Istituto Superiore di Sanità reported that the median time between the onset of symptoms and death was twelve days, with seven being hospitalised. However, people transferred to an ICU had a median time of ten days between hospitalisation and death. Abnormal sodium levels during hospitalisation with COVID-19 are associated with poor prognoses: high sodium with a greater risk of death, and low sodium with an increased chance of needing ventilator support. Prolonged prothrombin time and elevated C-reactive protein levels on admission to the hospital are associated with severe course of COVID‑19 and with a transfer to ICU. Some early studies suggest 10% to 20% of people with COVID‑19 will experience symptoms lasting longer than a month. A majority of those who were admitted to hospital with severe disease report long-term problems including fatigue and shortness of breath. On 30 October 2020, WHO chief Tedros Adhanom warned that "to a significant number of people, the COVID virus poses a range of serious long-term effects". He has described the vast spectrum of COVID‑19 symptoms that fluctuate over time as "really concerning". They range from fatigue, a cough and shortness of breath, to inflammation and injury of major organs – including the lungs and heart, and also neurological and psychologic effects. Symptoms often overlap and can affect any system in the body. Infected people have reported cyclical bouts of fatigue, headaches, months of complete exhaustion, mood swings, and other symptoms. Tedros therefore concluded that a strategy of achieving herd immunity by infection, rather than vaccination, is "morally unconscionable and unfeasible". In terms of hospital readmissions about 9% of 106,000 individuals had to return for hospital treatment within two months of discharge. The average to readmit was eight days since first hospital visit. There are several risk factors that have been identified as being a cause of multiple admissions to a hospital facility. Among these are advanced age (above 65 years of age) and presence of a chronic condition such as diabetes, COPD, heart failure or chronic kidney disease. According to scientific reviews smokers are more likely to require intensive care or die compared to non-smokers. Acting on the same ACE2 pulmonary receptors affected by smoking, air pollution has been correlated with the disease. Short-term and chronic exposure to air pollution seems to enhance morbidity and mortality from COVID‑19. Pre-existing heart and lung diseases and also obesity, especially in conjunction with fatty liver disease, contributes to an increased health risk of COVID‑19. It is also assumed that those that are immunocompromised are at higher risk of getting severely sick from SARS-CoV-2. One research study that looked into the COVID‑19 infections in hospitalised kidney transplant recipients found a mortality rate of 11%. Men with untreated hypogonadism were 2.4 times more likely than men with eugonadism to be hospitalised if they contracted COVID-19; Hypogonad men treated with testosterone were less likely to be hospitalised for COVID-19 than men who were not treated for hypogonadism. Genetic risk factors Genetics plays an important role in the ability to fight off Covid. For instance, those that do not produce detectable type I interferons or produce auto-antibodies against these may get much sicker from COVID‑19. Genetic screening is able to detect interferon effector genes. Some genetic variants are risk factors in specific populations. For instance, an allele of the DOCK2 gene (dedicator of cytokinesis 2 gene) is a common risk factor in Asian populations but much less common in Europe. The mutation leads to lower expression of DOCK2 especially in younger patients with severe Covid. In fact, many other genes and genetic variants have been found that determine the outcome of SARS-CoV-2 infections. Children See also: Impact of the COVID-19 pandemic on children While very young children have experienced lower rates of infection, older children have a rate of infection that is similar to the population as a whole. Children are likely to have milder symptoms and are at lower risk of severe disease than adults. The CDC reports that in the US roughly a third of hospitalised children were admitted to the ICU, while a European multinational study of hospitalised children from June 2020, found that about 8% of children admitted to a hospital needed intensive care. Four of the 582 children (0.7%) in the European study died, but the actual mortality rate may be "substantially lower" since milder cases that did not seek medical help were not included in the study. Long-term effects Further information: Long COVID Around 10% to 30% of non-hospitalised people with COVID-19 go on to develop long COVID. For those that do need hospitalisation, the incidence of long-term effects is over 50%. Long COVID is an often severe multisystem disease with a large set of symptoms. There are likely various, possibly coinciding, causes. Organ damage from the acute infection can explain a part of the symptoms, but long COVID is also observed in people where organ damage seems to be absent. By a variety of mechanisms, the lungs are the organs most affected in COVID‑19. In people requiring hospital admission, up to 98% of CT scans performed show lung abnormalities after 28 days of illness even if they had clinically improved. People with advanced age, severe disease, prolonged ICU stays, or who smoke are more likely to have long-lasting effects, including pulmonary fibrosis. Overall, approximately one-third of those investigated after four weeks will have findings of pulmonary fibrosis or reduced lung function as measured by DLCO, even in asymptomatic people, but with the suggestion of continuing improvement with the passing of more time. After severe disease, lung function can take anywhere from three months to a year or more to return to previous levels. The risks of cognitive deficit, dementia, psychotic disorders, and epilepsy or seizures persists at an increased level two years after infection. Immunity See also: COVID-19 vaccine Human antibody response to SARS-CoV-2 infection The immune response by humans to SARS-CoV-2 virus occurs as a combination of the cell-mediated immunity and antibody production, just as with most other infections. B cells interact with T cells and begin dividing before selection into the plasma cell, partly on the basis of their affinity for antigen. Since SARS-CoV-2 has been in the human population only since December 2019, it remains unknown if the immunity is long-lasting in people who recover from the disease. The presence of neutralising antibodies in blood strongly correlates with protection from infection, but the level of neutralising antibody declines with time. Those with asymptomatic or mild disease had undetectable levels of neutralising antibody two months after infection. In another study, the level of neutralising antibodies fell four-fold one to four months after the onset of symptoms. However, the lack of antibodies in the blood does not mean antibodies will not be rapidly produced upon reexposure to SARS-CoV-2. Memory B cells specific for the spike and nucleocapsid proteins of SARS-CoV-2 last for at least six months after the appearance of symptoms. As of August 2021, reinfection with COVID‑19 was possible but uncommon. The first case of reinfection was documented in August 2020. A systematic review found 17 cases of confirmed reinfection in medical literature as of May 2021. With the Omicron variant, as of 2022, reinfections have become common, albeit it is unclear how common. COVID-19 reinfections are thought to likely be less severe than primary infections, especially if one was previously infected by the same variant. Mortality Main articles: COVID-19 pandemic and COVID-19 pandemic death rates by country Several measures are commonly used to quantify mortality. These numbers vary by region and over time and are influenced by the volume of testing, healthcare system quality, treatment options, time since the initial outbreak, and population characteristics such as age, sex, and overall health. The mortality rate reflects the number of deaths within a specific demographic group divided by the population of that demographic group. Consequently, the mortality rate reflects the prevalence as well as the severity of the disease within a given population. Mortality rates are highly correlated to age, with relatively low rates for young people and relatively high rates among the elderly. In fact, one relevant factor of mortality rates is the age structure of the countries' populations. For example, the case fatality rate for COVID‑19 is lower in India than in the US since India's younger population represents a larger percentage than in the US. Case fatality rate The case fatality rate (CFR) reflects the number of deaths divided by the number of diagnosed cases within a given time interval. Based on Johns Hopkins University statistics, the global death-to-case ratio is 1.02% (6,881,955/676,609,955) as of 10 March 2023. The number varies by region. Total confirmed cases over time Total confirmed cases of COVID‑19 per million people Total confirmed deaths over time Total confirmed deaths due to COVID‑19 per million people Infection fatality rate A key metric in gauging the severity of COVID‑19 is the infection fatality rate (IFR), also referred to as the infection fatality ratio or infection fatality risk. This metric is calculated by dividing the total number of deaths from the disease by the total number of infected individuals; hence, in contrast to the CFR, the IFR incorporates asymptomatic and undiagnosed infections as well as reported cases. Estimates The red line shows the estimate of infection fatality rate (IFR), in percentage terms, as a function of age. The shaded region depicts the 95% confidence interval for that estimate. Markers denotes specific observations used in the meta-analysis. The same relationship plotted on a log scale A December 2020 systematic review and meta-analysis estimated that population IFR during the first wave of the pandemic was about 0.5% to 1% in many locations (including France, Netherlands, New Zealand, and Portugal), 1% to 2% in other locations (Australia, England, Lithuania, and Spain), and exceeded 2% in Italy. That study also found that most of these differences in IFR reflected corresponding differences in the age composition of the population and age-specific infection rates; in particular, the metaregression estimate of IFR is very low for children and younger adults (e.g., 0.002% at age 10 and 0.01% at age 25) but increases progressively to 0.4% at age 55, 1.4% at age 65, 4.6% at age 75, and 15% at age 85. These results were also highlighted in a December 2020 report issued by the WHO. IFR estimate per age group(to December 2020) Age group IFR 0–34 0.004% 35–44 0.068% 45–54 0.23% 55–64 0.75% 65–74 2.5% 75–84 8.5% 85 + 28.3% An analysis of those IFR rates indicates that COVID‑19 is hazardous not only for the elderly but also for middle-aged adults, for whom the infection fatality rate of COVID-19 is two orders of magnitude greater than the annualised risk of a fatal automobile accident and far more dangerous than seasonal influenza. Earlier estimates of IFR At an early stage of the pandemic, the World Health Organization reported estimates of IFR between 0.3% and 1%. On 2 July, The WHO's chief scientist reported that the average IFR estimate presented at a two-day WHO expert forum was about 0.6%. In August, the WHO found that studies incorporating data from broad serology testing in Europe showed IFR estimates converging at approximately 0.5–1%. Firm lower limits of IFRs have been established in a number of locations such as New York City and Bergamo in Italy since the IFR cannot be less than the population fatality rate. (After sufficient time however, people can get reinfected). As of 10 July, in New York City, with a population of 8.4 million, 23,377 individuals (18,758 confirmed and 4,619 probable) have died with COVID‑19 (0.3% of the population). Antibody testing in New York City suggested an IFR of ≈0.9%, and ≈1.4%. In Bergamo province, 0.6% of the population has died. In September 2020, the U.S. Centers for Disease Control and Prevention (CDC) reported preliminary estimates of age-specific IFRs for public health planning purposes. Sex differences Main article: Gendered impact of the COVID-19 pandemic Estimated prognosis by age and sexbased on cases from Franceand Diamond Princess ship Percentage of infected people who are hospitalised 0–19 20–29 30–39 40–49 50–59 60–69 70–79 80+ Total Female 0.1(0.07–0.2) 0.5(0.3–0.8) 0.9(0.5–1.5) 1.3(0.7–2.1) 2.6(1.5–4.2) 5.1(2.9–8.3) 7.8(4.4–12.8) 19.3(10.9–31.6) 2.6(1.5–4.3) Male 0.2(0.08–0.2) 0.6(0.3–0.9) 1.2(0.7–1.9) 1.6(0.9–2.6) 3.2(1.8–5.2) 6.7(3.7–10.9) 11.0(6.2–17.9) 37.6(21.1–61.3) 3.3(1.8–5.3) Total 0.1(0.08–0.2) 0.5(0.3–0.8) 1.1(0.6–1.7) 1.4(0.8–2.3) 2.9(1.6–4.7) 5.8(3.3–9.5) 9.3(5.2–15.1) 26.2(14.8–42.7) 2.9(1.7–4.8) Percentage of hospitalised people who go to Intensive Care Unit 0–19 20–29 30–39 40–49 50–59 60–69 70–79 80+ Total Female 16.7(14.3–19.3) 8.7(7.5–9.9) 11.9(10.9–13.0) 16.6(15.6–17.7) 20.7(19.8–21.6) 23.1(22.2–24.0) 18.7(18.0–19.5) 4.2(4.0–4.5) 14.3(13.9–14.7) Male 26.9(23.1–31.1) 14.0(12.2–16.0) 19.2(17.6–20.9) 26.9(25.4–28.4) 33.4(32.0–34.8) 37.3(36.0–38.6) 30.2(29.1–31.3) 6.8(6.5–7.2) 23.1(22.6–23.6) Total 22.2(19.1–25.7) 11.6(10.1–13.2) 15.9(14.5–17.3) 22.2(21.0–23.5) 27.6(26.5–28.7) 30.8(29.8–31.8) 24.9(24.1–25.8) 5.6(5.3–5.9) 19.0(18.7–19.44) Percent of hospitalised people who die 0–19 20–29 30–39 40–49 50–59 60–69 70–79 80+ Total Female 0.5(0.2–1.0) 0.9(0.5–1.3) 1.5(1.2–1.9) 2.6(2.3–3.0) 5.2(4.8–5.6) 10.1(9.5–10.6) 16.7(16.0–17.4) 25.2(24.4–26.0) 14.4(14.0–14.8) Male 0.7(0.3–1.5) 1.3(0.8–1.9) 2.2(1.7–2.7) 3.8(3.3–4.4) 7.6(7.0–8.2) 14.8(14.1–15.6) 24.6(23.7–25.6) 37.1(36.1–38.2) 21.2(20.8–21.7) Total 0.6(0.2–1.3) 1.1(0.7–1.6) 1.9(1.5–2.3) 3.3(2.9–3.8) 6.5(6.0–7.0) 12.6(12.0–13.2) 21.0(20.3–21.7) 31.6(30.9–32.4) 18.1(17.8–18.4) Percent of infected people who die – infection fatality rate (IFR) 0–19 20–29 30–39 40–49 50–59 60–69 70–79 80+ Total Female 0.001(<0.001–0.002) 0.004(0.002–0.007) 0.01(0.007–0.02) 0.03(0.02–0.06) 0.1(0.08–0.2) 0.5(0.3–0.8) 1.3(0.7–2.1) 4.9(2.7–8.0) 0.4(0.2–0.6) Male 0.001(<0.001–0.003) 0.007(0.003–0.01) 0.03(0.02–0.05) 0.06(0.03–0.1) 0.2(0.1–0.4) 1.0(0.6–1.6) 2.7(1.5–1.4) 14.0(7.9–22.7) 0.7(0.4–1.1) Total 0.001(<0.001–0.002) 0.005(0.003–0.01) 0.02(0.01–0.03) 0.05(0.03–0.08) 0.2(0.1–0.3) 0.7(0.4–1.2) 1.9(1.1–3.2) 8.3(4.7–13.5) 0.5(0.3–0.9) Numbers in parentheses are 95% credible intervals for the estimates. COVID‑19 case fatality rates are higher among men than women in most countries. However, in a few countries like India, Nepal, Vietnam, and Slovenia the fatality cases are higher in women than men. Globally, men are more likely to be admitted to the ICU and more likely to die. One meta-analysis found that globally, men were more likely to get COVID‑19 than women; there were approximately 55 men and 45 women per 100 infections (CI: 51.43–56.58). The Chinese Center for Disease Control and Prevention reported the death rate was 2.8% for men and 1.7% for women. Later reviews in June 2020 indicated that there is no significant difference in susceptibility or in CFR between genders. One review acknowledges the different mortality rates in Chinese men, suggesting that it may be attributable to lifestyle choices such as smoking and drinking alcohol rather than genetic factors. Smoking, which in some countries like China is mainly a male activity, is a habit that contributes to increasing significantly the case fatality rates among men. Sex-based immunological differences, lesser prevalence of smoking in women and men developing co-morbid conditions such as hypertension at a younger age than women could have contributed to the higher mortality in men. In Europe as of February 2020, 57% of the infected people were men and 72% of those died with COVID‑19 were men. As of April 2020, the US government is not tracking sex-related data of COVID‑19 infections. Research has shown that viral illnesses like Ebola, HIV, influenza and SARS affect men and women differently. Ethnic differences In the US, a greater proportion of deaths due to COVID‑19 have occurred among African Americans and other minority groups. Structural factors that prevent them from practising social distancing include their concentration in crowded substandard housing and in "essential" occupations such as retail grocery workers, public transit employees, health-care workers and custodial staff. Greater prevalence of lacking health insurance and care of underlying conditions such as diabetes, hypertension, and heart disease also increase their risk of death. Similar issues affect Native American and Latino communities. On the one hand, in the Dominican Republic there is a clear example of both gender and ethnic inequality. In this Latin American territory, there is great inequality and precariousness that especially affects Dominican women, with greater emphasis on those of Haitian descent. According to a US health policy non-profit, 34% of American Indian and Alaska Native People (AIAN) non-elderly adults are at risk of serious illness compared to 21% of white non-elderly adults. The source attributes it to disproportionately high rates of many health conditions that may put them at higher risk as well as living conditions like lack of access to clean water. Leaders have called for efforts to research and address the disparities. In the UK, a greater proportion of deaths due to COVID‑19 have occurred in those of a Black, Asian, and other ethnic minority background. More severe impacts upon patients including the relative incidence of the necessity of hospitalisation requirements, and vulnerability to the disease has been associated via DNA analysis to be expressed in genetic variants at chromosomal region 3, features that are associated with European Neanderthal heritage. That structure imposes greater risks that those affected will develop a more severe form of the disease. The findings are from Professor Svante Pääbo and researchers he leads at the Max Planck Institute for Evolutionary Anthropology and the Karolinska Institutet. This admixture of modern human and Neanderthal genes is estimated to have occurred roughly between 50,000 and 60,000 years ago in Southern Europe. Comorbidities Biological factors (immune response) and the general behaviour (habits) can strongly determine the consequences of COVID‑19. Most of those who die of COVID‑19 have pre-existing (underlying) conditions, including hypertension, diabetes mellitus, and cardiovascular disease. According to March data from the United States, 89% of those hospitalised had preexisting conditions. The Italian Istituto Superiore di Sanità reported that out of 8.8% of deaths where medical charts were available, 96.1% of people had at least one comorbidity with the average person having 3.4 diseases. According to this report the most common comorbidities are hypertension (66% of deaths), type 2 diabetes (29.8% of deaths), ischaemic heart disease (27.6% of deaths), atrial fibrillation (23.1% of deaths) and chronic renal failure (20.2% of deaths). Most critical respiratory comorbidities according to the US Centers for Disease Control and Prevention (CDC), are: moderate or severe asthma, pre-existing COPD, pulmonary fibrosis, cystic fibrosis. Evidence stemming from meta-analysis of several smaller research papers also suggests that smoking can be associated with worse outcomes. When someone with existing respiratory problems is infected with COVID‑19, they might be at greater risk for severe symptoms. COVID‑19 also poses a greater risk to people who misuse opioids and amphetamines, insofar as their drug use may have caused lung damage. In August 2020, the CDC issued a caution that tuberculosis (TB) infections could increase the risk of severe illness or death. The WHO recommended that people with respiratory symptoms be screened for both diseases, as testing positive for COVID‑19 could not rule out co-infections. Some projections have estimated that reduced TB detection due to the pandemic could result in 6.3 million additional TB cases and 1.4 million TB-related deaths by 2025. History This section needs to be updated. The reason given is: excessive detail about the very early pandemic while missing an overview of the later pandemic. Please help update this article to reflect recent events or newly available information. (July 2023) Main articles: Timeline of the COVID-19 pandemic and Investigations into the origin of COVID-19 Part of a series on theCOVID-19 pandemicScientifically accurate atomic model of the external structure of SARS-CoV-2. Each "ball" is an atom. COVID-19 (disease) SARS-CoV-2 (virus) Cases Deaths Timeline 2019 2020 January responses February responses March responses April responses May responses June responses July responses August responses September responses October responses November responses December responses 2021 January responses February responses March responses April responses May responses June responses July responses August responses September responses October responses November responses December responses 2022 January responses February responses March responses April responses May responses June responses July responses August responses September responses October responses November December 2023 2024 Locations By country and territory Africa Antarctica Asia Europe North America Oceania South America By conveyance Cruise ships Naval ships International response Endemic phase Evacuations Face masks International aid Origin Lockdowns by country Misinformation by governments Fake treatments Social distancing Software Travel United Nations World Health Organization WTO IP waiver Undercounting of deaths COVID-19 apps Zero-COVID National responses Africa China European Union Germany Ghana India Ireland Netherlands New Zealand Nigeria Philippines Russia Sweden UK government US federal government Vietnam Medical response Disease testing Breathalyzer Development Drug development Drug repurposing Public health mitigation Vaccines History Research VITT Deployment Authorizations Operation Warp Speed Misinformation and hesitancy US Vaccine card Vaccine passports Current vaccines CoronaVac Covaxin Convidecia Janssen Medigen Moderna Novavax Oxford–AstraZeneca Pfizer–BioNTech Sinopharm BIBP Sputnik V Variants Variants of concern Alpha Beta Gamma Delta Omicron Other variants Epsilon Zeta Eta Theta Iota Kappa Lambda Mu Cluster 5 Lineage B.1.617 Economic impact and recession Arts and culture Aviation Cannabis Cinema films Disney Fashion Financial markets Food industry Food security Journalism Music Performing arts Retail Shipping Television US sportscasting programs Tourism Video games By country Canada India Ireland Malaysia New Zealand Russia UK US By sport Association football Baseball Basketball Combat sports Cricket Disc golf Gaelic games Gridiron football Ice hockey Motorsport Rugby league Impacts Animals Alzheimer's disease patients Black people Crime Death rates by country Disability Domestic violence Emergency evacuations Education Female Environment Hospitals Language LGBT community Long-term care Media coverage Mental health symptoms Migration Military Notable deaths Other health issues Politics diplomacy Popular culture Protests Pregnancy Prisons Religion Catholic Church Hajj Science and technology Social media Strikes Suicides Telehealth Xenophobia and racism Society Ireland Malaysia New Zealand Russia UK US COVID-19 portalvte The virus is thought to be of natural animal origin, most likely through spillover infection. A joint-study conducted in early 2021 by the People's Republic of China and the World Health Organization indicated that the virus descended from a coronavirus that infects wild bats, and likely spread to humans through an intermediary wildlife host. There are several theories about where the index case originated and investigations into the origin of the pandemic are ongoing. According to articles published in July 2022 in Science, virus transmission into humans occurred through two spillover events in November 2019 and was likely due to live wildlife trade on the Huanan wet market in the city of Wuhan (Hubei, China). Doubts about the conclusions have mostly centered on the precise site of spillover. Earlier phylogenetics estimated that SARS-CoV-2 arose in October or November 2019. A phylogenetic algorithm analysis suggested that the virus may have been circulating in Guangdong before Wuhan. Most scientists believe the virus spilled into human populations through natural zoonosis, similar to the SARS-CoV-1 and MERS-CoV outbreaks, and consistent with other pandemics in human history. According to the Intergovernmental Panel on Climate Change several social and environmental factors including climate change, natural ecosystem destruction and wildlife trade increased the likelihood of such zoonotic spillover. One study made with the support of the European Union found climate change increased the likelihood of the pandemic by influencing distribution of bat species. Available evidence suggests that the SARS-CoV-2 virus was originally harboured by bats, and spread to humans multiple times from infected wild animals at the Huanan Seafood Market in Wuhan in December 2019. A minority of scientists and some members of the U.S intelligence community believe the virus may have been unintentionally leaked from a laboratory such as the Wuhan Institute of Virology. The US intelligence community has mixed views on the issue, but overall agrees with the scientific consensus that the virus was not developed as a biological weapon and is unlikely to have been genetically engineered. There is no evidence SARS-CoV-2 existed in any laboratory prior to the pandemic. The first confirmed human infections were in Wuhan. A study of the first 41 cases of confirmed COVID‑19, published in January 2020 in The Lancet, reported the earliest date of onset of symptoms as 1 December 2019. Official publications from the WHO reported the earliest onset of symptoms as 8 December 2019. Human-to-human transmission was confirmed by the WHO and Chinese authorities by 20 January 2020. According to official Chinese sources, these were mostly linked to the Huanan Seafood Wholesale Market, which also sold live animals. In May 2020, George Gao, the director of the CDC, said animal samples collected from the seafood market had tested negative for the virus, indicating that the market was the site of an early superspreading event, but that it was not the site of the initial outbreak. Traces of the virus have been found in wastewater samples that were collected in Milan and Turin, Italy, on 18 December 2019. By December 2019, the spread of infection was almost entirely driven by human-to-human transmission. The number of COVID-19 cases in Hubei gradually increased, reaching sixty by 20 December, and at least 266 by 31 December. On 24 December, Wuhan Central Hospital sent a bronchoalveolar lavage fluid (BAL) sample from an unresolved clinical case to sequencing company Vision Medicals. On 27 and 28 December, Vision Medicals informed the Wuhan Central Hospital and the Chinese CDC of the results of the test, showing a new coronavirus. A pneumonia cluster of unknown cause was observed on 26 December and treated by the doctor Zhang Jixian in Hubei Provincial Hospital, who informed the Wuhan Jianghan CDC on 27 December. On 30 December, a test report addressed to Wuhan Central Hospital, from company CapitalBio Medlab, stated an erroneous positive result for SARS, causing a group of doctors at Wuhan Central Hospital to alert their colleagues and relevant hospital authorities of the result. The Wuhan Municipal Health Commission issued a notice to various medical institutions on "the treatment of pneumonia of unknown cause" that same evening. Eight of these doctors, including Li Wenliang (punished on 3 January), were later admonished by the police for spreading false rumours and another, Ai Fen, was reprimanded by her superiors for raising the alarm. The Wuhan Municipal Health Commission made the first public announcement of a pneumonia outbreak of unknown cause on 31 December, confirming 27 cases – enough to trigger an investigation. During the early stages of the outbreak, the number of cases doubled approximately every seven and a half days. In early and mid-January 2020, the virus spread to other Chinese provinces, helped by the Chinese New Year migration and Wuhan being a transport hub and major rail interchange. On 20 January, China reported nearly 140 new cases in one day, including two people in Beijing and one in Shenzhen. Later official data shows 6,174 people had already developed symptoms by then, and more may have been infected. A report in The Lancet on 24 January indicated human transmission, strongly recommended personal protective equipment for health workers, and said testing for the virus was essential due to its "pandemic potential". On 30 January, the WHO declared COVID-19 a Public Health Emergency of International Concern. By this time, the outbreak spread by a factor of 100 to 200 times. Italy had its first confirmed cases on 31 January 2020, two tourists from China. Italy overtook China as the country with the most deaths on 19 March 2020. By 26 March the United States had overtaken China and Italy with the highest number of confirmed cases in the world. Research on coronavirus genomes indicates the majority of COVID-19 cases in New York came from European travellers, rather than directly from China or any other Asian country. Retesting of prior samples found a person in France who had the virus on 27 December 2019, and a person in the United States who died from the disease on 6 February 2020. RT-PCR testing of untreated wastewater samples from Brazil and Italy have suggested detection of SARS-CoV-2 as early as November and December 2019, respectively, but the methods of such sewage studies have not been optimised, many have not been peer-reviewed, details are often missing, and there is a risk of false positives due to contamination or if only one gene target is detected. A September 2020 review journal article said, "The possibility that the COVID‑19 infection had already spread to Europe at the end of last year is now indicated by abundant, even if partially circumstantial, evidence", including pneumonia case numbers and radiology in France and Italy in November and December. As of 1 October 2021, Reuters reported that it had estimated the worldwide total number of deaths due to COVID‑19 to have exceeded five million. The Public Health Emergency of International Concern for COVID-19 ended on May 5, 2023. By this time, everyday life in most countries had returned to how it was before the pandemic. Misinformation Main article: COVID-19 misinformation After the initial outbreak of COVID‑19, misinformation and disinformation regarding the origin, scale, prevention, treatment, and other aspects of the disease rapidly spread online. In September 2020, the US Centers for Disease Control and Prevention (CDC) published preliminary estimates of the risk of death by age groups in the United States, but those estimates were widely misreported and misunderstood. Other species See also: Impact of the COVID-19 pandemic on animals Humans appear to be capable of spreading the virus to some other animals, a type of disease transmission referred to as zooanthroponosis. Some pets, especially cats and ferrets, can catch this virus from infected humans. Symptoms in cats include respiratory (such as a cough) and digestive symptoms. Cats can spread the virus to other cats, and may be able to spread the virus to humans, but cat-to-human transmission of SARS-CoV-2 has not been proven. Compared to cats, dogs are less susceptible to this infection. Behaviours which increase the risk of transmission include kissing, licking, and petting the animal. The virus does not appear to be able to infect pigs, ducks, or chickens at all. Mice, rats, and rabbits, if they can be infected at all, are unlikely to be involved in spreading the virus. Tigers and lions in zoos have become infected as a result of contact with infected humans. As expected, monkeys and great ape species such as orangutans can also be infected with the COVID‑19 virus. Minks, which are in the same family as ferrets, have been infected. Minks may be asymptomatic, and can also spread the virus to humans. Multiple countries have identified infected animals in mink farms. Denmark, a major producer of mink pelts, ordered the slaughter of all minks over fears of viral mutations, following an outbreak referred to as Cluster 5. A vaccine for mink and other animals is being researched. Research Further information: COVID-19 drug development International research on vaccines and medicines in COVID‑19 is underway by government organisations, academic groups, and industry researchers. The CDC has classified it to require a BSL3 grade laboratory. There has been a great deal of COVID‑19 research, involving accelerated research processes and publishing shortcuts to meet the global demand. As of December 2020, hundreds of clinical trials have been undertaken, with research happening on every continent except Antarctica. As of November 2020, more than 200 possible treatments have been studied in humans. Transmission and prevention research Further information: COVID-19 vaccine Modelling research has been conducted with several objectives, including predictions of the dynamics of transmission, diagnosis and prognosis of infection, estimation of the impact of interventions, or allocation of resources. Modelling studies are mostly based on compartmental models in epidemiology, estimating the number of infected people over time under given conditions. Several other types of models have been developed and used during the COVID‑19 pandemic including computational fluid dynamics models to study the flow physics of COVID‑19, retrofits of crowd movement models to study occupant exposure, mobility-data based models to investigate transmission, or the use of macroeconomic models to assess the economic impact of the pandemic. Treatment-related research Main article: COVID-19 drug repurposing research Seven possible drug targets in viral replication process and drugs Repurposed antiviral drugs make up most of the research into COVID‑19 treatments. Other candidates in trials include vasodilators, corticosteroids, immune therapies, lipoic acid, bevacizumab, and recombinant angiotensin-converting enzyme 2. In March 2020, the World Health Organization (WHO) initiated the Solidarity trial to assess the treatment effects of some promising drugs: an experimental drug called remdesivir; anti-malarial drugs chloroquine and hydroxychloroquine; two anti-HIV drugs, lopinavir/ritonavir; and interferon-beta. More than 300 active clinical trials are underway as of April 2020. Research on the antimalarial drugs hydroxychloroquine and chloroquine showed that they were ineffective at best, and that they may reduce the antiviral activity of remdesivir. By May 2020, France, Italy, and Belgium had banned the use of hydroxychloroquine as a COVID‑19 treatment. In June, initial results from the randomised RECOVERY Trial in the United Kingdom showed that dexamethasone reduced mortality by one third for people who are critically ill on ventilators and one fifth for those receiving supplemental oxygen. Because this is a well-tested and widely available treatment, it was welcomed by the WHO, which is in the process of updating treatment guidelines to include dexamethasone and other steroids. Based on those preliminary results, dexamethasone treatment has been recommended by the NIH for patients with COVID‑19 who are mechanically ventilated or who require supplemental oxygen but not in patients with COVID‑19 who do not require supplemental oxygen. In September 2020, the WHO released updated guidance on using corticosteroids for COVID‑19. The WHO recommends systemic corticosteroids rather than no systemic corticosteroids for the treatment of people with severe and critical COVID‑19 (strong recommendation, based on moderate certainty evidence). The WHO suggests not to use corticosteroids in the treatment of people with non-severe COVID‑19 (conditional recommendation, based on low certainty evidence). The updated guidance was based on a meta-analysis of clinical trials of critically ill COVID‑19 patients. In September 2020, the European Medicines Agency (EMA) endorsed the use of dexamethasone in adults and adolescents from twelve years of age and weighing at least 40 kilograms (88 lb) who require supplemental oxygen therapy. Dexamethasone can be taken by mouth or given as an injection or infusion (drip) into a vein. In November 2020, the US Food and Drug Administration (FDA) issued an emergency use authorisation for the investigational monoclonal antibody therapy bamlanivimab for the treatment of mild-to-moderate COVID‑19. Bamlanivimab is authorised for people with positive results of direct SARS-CoV-2 viral testing who are twelve years of age and older weighing at least 40 kilograms (88 lb), and who are at high risk for progressing to severe COVID‑19 or hospitalisation. This includes those who are 65 years of age or older, or who have chronic medical conditions. In February 2021, the FDA issued an emergency use authorisation (EUA) for bamlanivimab and etesevimab administered together for the treatment of mild to moderate COVID‑19 in people twelve years of age or older weighing at least 40 kilograms (88 lb) who test positive for SARS‑CoV‑2 and who are at high risk for progressing to severe COVID‑19. The authorised use includes treatment for those who are 65 years of age or older or who have certain chronic medical conditions. In April 2021, the FDA revoked the emergency use authorisation (EUA) that allowed for the investigational monoclonal antibody therapy bamlanivimab, when administered alone, to be used for the treatment of mild-to-moderate COVID‑19 in adults and certain paediatric patients. Cytokine storm Various therapeutic strategies for targeting cytokine storm A cytokine storm can be a complication in the later stages of severe COVID‑19. A cytokine storm is a potentially deadly immune reaction where a large amount of pro-inflammatory cytokines and chemokines are released too quickly. A cytokine storm can lead to ARDS and multiple organ failure. Data collected from Jin Yin-tan Hospital in Wuhan, China indicates that patients who had more severe responses to COVID‑19 had greater amounts of pro-inflammatory cytokines and chemokines in their system than patients who had milder responses. These high levels of pro-inflammatory cytokines and chemokines indicate presence of a cytokine storm. Tocilizumab has been included in treatment guidelines by China's National Health Commission after a small study was completed. It is undergoing a Phase II non-randomised trial at the national level in Italy after showing positive results in people with severe disease. Combined with a serum ferritin blood test to identify a cytokine storm (also called cytokine storm syndrome, not to be confused with cytokine release syndrome), it is meant to counter such developments, which are thought to be the cause of death in some affected people. The interleukin-6 receptor (IL-6R) antagonist was approved by the FDA to undergo a Phase III clinical trial assessing its effectiveness on COVID‑19 based on retrospective case studies for the treatment of steroid-refractory cytokine release syndrome induced by a different cause, CAR T cell therapy, in 2017. There is no randomised, controlled evidence that tocilizumab is an efficacious treatment for CRS. Prophylactic tocilizumab has been shown to increase serum IL-6 levels by saturating the IL-6R, driving IL-6 across the blood–brain barrier, and exacerbating neurotoxicity while having no effect on the incidence of CRS. Lenzilumab, an anti-GM-CSF monoclonal antibody, is protective in murine models for CAR T cell-induced CRS and neurotoxicity and is a viable therapeutic option due to the observed increase of pathogenic GM-CSF secreting T cells in hospitalised patients with COVID‑19. Passive antibodies Overview of the application and use of convalescent plasma therapy Transferring purified and concentrated antibodies produced by the immune systems of those who have recovered from COVID‑19 to people who need them is being investigated as a non-vaccine method of passive immunisation. Viral neutralisation is the anticipated mechanism of action by which passive antibody therapy can mediate defence against SARS-CoV-2. The spike protein of SARS-CoV-2 is the primary target for neutralising antibodies. As of 8 August 2020, eight neutralising antibodies targeting the spike protein of SARS-CoV-2 have entered clinical studies. It has been proposed that selection of broad-neutralising antibodies against SARS-CoV-2 and SARS-CoV might be useful for treating not only COVID‑19 but also future SARS-related CoV infections. Other mechanisms, however, such as antibody-dependant cellular cytotoxicity or phagocytosis, may be possible. Other forms of passive antibody therapy, for example, using manufactured monoclonal antibodies, are in development. The use of passive antibodies to treat people with active COVID‑19 is also being studied. This involves the production of convalescent serum, which consists of the liquid portion of the blood from people who recovered from the infection and contains antibodies specific to this virus, which is then administered to active patients. This strategy was tried for SARS with inconclusive results. An updated Cochrane review in May 2023 found high certainty evidence that, for the treatment of people with moderate to severe COVID‑19, convalescent plasma did not reduce mortality or bring about symptom improvement. There continues to be uncertainty about the safety of convalescent plasma administration to people with COVID‑19 and differing outcomes measured in different studies limits their use in determining efficacy. Bioethics Since the outbreak of the COVID‑19 pandemic, scholars have explored the bioethics, normative economics, and political theories of healthcare policies related to the public health crisis. Academics have pointed to the moral distress of healthcare workers, ethics of distributing scarce healthcare resources such as ventilators, and the global justice of vaccine diplomacies. The socio-economic inequalities between genders, races, groups with disabilities, communities, regions, countries, and continents have also drawn attention in academia and the general public. See also Coronavirus diseases, a group of closely related syndromes Disease X, a WHO term Law of declining virulence – Disproved hypothesis of epidemiologist Theobald Smith Theory of virulence – Theory by biologist Paul W. Ewald	biology	1023054	https://da.wikipedia.org/wiki/COVID-19	COVID-19	COVID-19 (et akronym for coronavirus disease 2019), også kendt som 2019-nCoV acute respiratory disease (2019-nCoV ARD), og novel coronavirus pneumonia (NCP), er en viral luftvejsinfektion forårsaget af SARS-CoV-2. Sygdommen blev første gang registreret i november eller december 2019 i den kinesiske millionby Wuhan. Statens Seruminstitut har samlet alle oplysninger i en portal. Verdenssundhedsorganisationen (WHO) oplyste den 5. januar 2020 om et muligt udbrud af lungebetændelse med ukendt årsag i det centrale Kina. Udbruddet havde relation til et fiskemarked i den kinesiske millionby Wuhan i Hubei-provinsen. COVID-19 blev erklæret en global sundhedstrussel af WHO 30. januar 2020. Den 11. marts 2020 erklærede WHO COVID-19 for en pandemi. Den 2. marts 2023 meddelte Sundhedsstyrelsen, at Covid-19 skal ikke længere være en "alment farlig sygdom" i Danmark. Ændringen gælder fra 1. april. Sundhedsstyrelsen kan ændre kategoriseringen tilbage hvis der for eksempel kommer ny meget sygdomsfremkaldende variant, som vacciner ikke kan forebygge. Efter omkring 2½ år erklærede WHO truslen fra COVID-19 for ovre den 6. maj 2023. WHO i den forbindelse, at mindst 20 millioner mennesker havde mistet livet som følge af virus-sygdommen, hvilket var en markant opjustering af det hidtidige dødstal, der lød på knap syv millioner mennesker. Symptomer COVID-19 resulterer i influenza-lignende symptomer, inklusive feber, hoste, åndenød, muskelsmerter og træthed. COVID-19 kan resultere i blodpropper - selv i unge mennesker, lungebetændelse, akut lungesvigt (ARDS), sepsis og septisk shock - og muligvis død. Inkubationstiden er fundet til i middel at være 6,4 dage og 95% af tilfældene har inkubationstid mellem 2,1 dag til 11,1 dag. I forhold til de to andre alvorlige coronavirus-sygdomme, er det længere end SARS og lidt længere end MERS. Disse tal var fundet på baggrund af 88 personer i Kina der var uden for Hubei-provinsen. En anden beregning på baggrund af 181 personer har fundet median-inkubationstiden til at være 5,1 dage. Den individuelle variation synes at være så stor at 1% af infektionerne er 14 dage eller mere om at udvikle symptomer. Sygdommens varighed fra begyndelse på symptomer til helbredelse kan være fra 12 til 32 dage. Såkaldt viral shedding er set i en patient i op til 37 dage. Årsag Årsagen til sygdommen er infektion med coronavirussen SARS-CoV-2. Den spredes hovedsagligt fra person-til-person ved kontakt på under to meters afstand. Smitten foregår først og fremmest som en dråbeinfektion og overføres når en smittet person taler, hoster eller nyser og luftbårne dråber herfra kommer ind i munden eller næsen på den usmittede person. Sygdommen er en zoonose og startede med overførsel af virus fra flagermus, formentlig via mellemværten skældyr og kan også overføres via andre dyr som f.eks. fra mink til mennesker. Virus kan overleve på overflader i flere dage. På den måde kan man også smittes hvis man rører en overflade med virus og efterfølgende rører mund eller næse. Muligvis kan virussen også optages fra slimhinderne ved øjnene. Kontaktsmitte lader dog ikke til at være virussens primære smittevej. Virussen SARS-CoV-2 er en såkaldt coronavirus, der er en stor familie af forskellige virustyper. Familien rummer blandt andet helt almindelig forkølelsesvirus, men de mere dødelige virus som SARS- og MERS tilhører også coronavirus-familien. SARS-CoV-2 er en slags fætter til SARS. SARS-CoV-2 undergår til stadighed forandringer, men de forskellige variationer kan muligvis inddeles i en L-type og en S-type. Smitte fra mor til foster sker muligvis ikke. Diagnose Diagnose kan ske på en infektionsmedicinsk afdeling på et hospital ved podning med en vatpind og ved en sugeprøve fra luftvejene. Prøverne sendes til undersøgelse og inden for 72 timer skulle svaret komme. Personer mistænkt for virussen instrueres i ikke at møde fysisk op hos den praktiserende læge, akutmodtagelse eller hospital men i stedet kontakte lægen per telefon, der så træffer beslutning om henvisning til en infektionsmedicinsk afdeling. Personer mistænkt bliver også instrueret i ikke selv at gå ind i hospitalet. Personerne bliver hentet i ambulance, der skal desinficeres efter specielle regler. I det først-rapporterede danske tilfælde kørte familien der skulle til test i bil og holdt på hospitalets parkeringsplads hvor beskyttet sundhedspersonale hentede dem. Forebyggelse Undgå kontakt med syge personer, specielt hostende og nysende personer. Undgå steder hvor levende eller døde dyr håndteres. Håndvaskning ofte og grundigt med vand og sæbe i mindst 20 sekunder. Desinfektion med et alkohol-baseret desinfektionsmiddel før spisning, efter toiletbesøg og efter kontakt med dyr. Undgå at røre øjne, næse og mund med uvaskede hænder. Mundbind kan hjælpe med at undgå spredning. Ansigtsmaske kan hjælpe med at undgå spredning fra sygdomsramte, men ansigtsmasker synes ikke at være så effektive til at beskytte personer der ikke er ramt. Rengøring af overflader der røres ofte: bordplader, dørgreb, armaturer, toiletter, tastaturer, telefoner og tablets. Vask vasketøj ved minimum 60 °C. Tiltagene har ifølge læger også reduceret visse andre sygdomme som influenza og forkølelse m.fl. Ifølge de amerikanske sundhedsmyndigheder (CDC) er der kun en lille risiko, for at blive smittet via overflader. Den primære smittevej er via dråber mellem mennesker. Statsministeren foretog samfundsmæssige ændringer 11. marts 2020 for at mindske smittespredning. Den 12. marts behandlede Folketinget "Hastelovsforlag L 133", som udløb automatisk 1. marts 2021. Folketinget vedtog 15. marts 2020 (sammen med lønmodtagerne og arbejdsgiverne) en milliard-stor hjælpepakke til erhvervslivet. De første EU-godkendte COVID-19-vacciner var Pfizer/BioNTechs mRNA-vaccine den 21. december 2020 - og den 6. januar 2021 Modernas mRNA-vaccine. Den første COVID-19-vaccine ankom til Danmark den 25. december 2020 om natten. Vaccinekøen per januar 2021 kan ses i kilden. For højt prioriteret forebyggelse med håndsprit 20 danske eksperter slog fast i et indlæg i Ugeskrift for Læger, at SARS-CoV-2 er en luftbåren virus. Det betyder, at virussen smitter via mikroskopiske partikler i luften, som smittede ånder ud. Om COVID-19 er en luftbåren virus eller ej, var løbende genstand for diskussion siden den første patient blev smittet i 2019. Det nye paradigme betyder konkret, at de 20 eksperter opfordrer til øget opmærksomhed på luftkvaliteten inden døre i bekæmpelsen af COVID-19, i lighed med andre luftvejssygdomme som influenza. Rådet om flittig brug af håndsprit kom fra eksperter i landets øverste sundhedsmyndigheder, der fremhævede det, som et centralt skridt i at bremse COVID-19-smitte. Efterfølgende fortrød nogle af disse eksperter, at håndsprit blev prioriteret så højt. Behandling Hvis man efter diagnose på et hospital er tilstrækkelig rask bliver man sendt hjem. Er man ikke rask nok kan man blive på hospitalet hvor man eventuelt kan behandles med ilttilskud og i yderste tilfælde sættes i respiratorbehandling. Medicinsk behandling Per medio 2021 har det antivirale middel redemsivir været anvendt i Danmark til patienter med svær COVID-19. Dexamethasone har vist en effekt. Ligeledes har tocilizumab. Prognose Baseret på data fra kinesiske patienter indtil 11. februar 2020 der var bekræftede med SARS-CoV-2 er forholdet af milde tilfælde på 80,9%, mens letalitet (case fatality rate) på 2,3%. Ældre har meget større dødelighed end yngre og mænd lidt større dødelighed end kvinder. Kønsforskellen skal dog ses på baggrund af at der er betydelig forskel på kinesiske mænd og kvinders rygevaner. Estimering af letalitet er dog baseret på personer der er COVID-19-bekræftet, og et skyggetal kan betyde, at tallet er lavere eller muligvis højere. Under pandemien testede Island en forholdsvis stor del af deres befolkning, og per ultimo april 2020 var der 1.797 positive test og 10 døde. En dansk undersøgelse af bloddonorer estimerede infection fatality rate (IFR) til 0.089% blandt individer under 70 år. I maj 2020 forventede Lægehåndbogen, at dødelighed for sygdomstilfælde ville ligge mellem 0,3% og 1%. Andre medicinske tilstande der synes at have betydning for dødeligheden (case fatality rate) er blandt andet hjerte-kar-sygdomme og diabetes. COVID-19-tilfælde kategoriseres i klasserne mild, alvorlig og kritisk. Kinesiske data har vist andelene på henholdsvis 80.9%, 13.8% og 4.7%. For de kritisk tilfælde er dødeligheden fundet til 49%. Per marts 2020 er det uklart om en SARS-CoV-2-infektion skaber langtidsimmunitet hos dem der har være inficeret og kommet sig. Geninfektion er almindelig blandt coronavirusser. Der har været et japansk eksempel på geninfektion. Flokimmunitet synes kun at kunne opnås ved vaccination. Epidemiologi For sygdomme der ligner COVID-19 i symptombilledet, såsom influenza, ses en vis grad af sæsonvariabilitet. Om COVID-19 også vil have en sæsonvariabilitet vides per marts 2020 ikke. Normalt dør 1.000-2.000 danskere om året af influenza. Eksperter vurderer at epidemien kan blusse op igen når samfundsbegrænsningerne ophæves og folk igen får mere kontakt med hinanden. Forskning Da COVID-19-virussen hører til Betacoronavirus, der også inkluderede virusserne for SARS og MERS, har det fået forskere til undersøge om lægemidler benyttet i forbindelse med SARS og MERS kunne have en effekt til COVID-19. Et in vitro-studie undersøgte ribavirin, penciclovir, nitazoxanide, nafamostat, klorokin, remdesivir og favipiravir og fandt at remdesivir og klorokin var højst effektive til at kontrollere COVID-19-virussens infektion in vitro. De positive in vitro-resultater har ført til forsøg i sygdomsramte mennesker, og klorokinens mulige virkning bliver undersøgt i en række kinesiske kliniske forsøg. Per 25. februar 2020 var der også et kliniske forsøg i gang med remdesivir fra virksomheden Gilead Sciences. Resultater fra forsøget forventes i april 2020. Derudover er en længere række af kliniske forsøg i gang for andre lægemidler. Datasæt omkring diagnosticering af COVID-19 ud fra computertomografi af lungerne har ført til forskning omkring anvendelsen af deep learning. Vaccineforskning Lige siden starten af pandemien har der været gjort et globalt omfattende forsknings- og udviklingsarbejde med vaccineudvikling. Eksempelvis blev positive resultater fra et klinisk forsøg med mRNA-vaccinen BNT162 fra BioNtec offentliggjort i november 2020; forsøget var da i fase 3 og nået cirka halvvejs i undersøgelsen, og 94 tilfælde af COVID-19 var da opstået blandt de over 40.000 forsøgspersoner og man ville fortsætte forsøget indtil 164 tilfælde var detekteret. I marts 2021 er der 90 kandidater til en vaccine og i forskellige lande er 12 vacciner allerede godkendt til vaccination mod CoViD-19 inkl. både mRNA-vacciner, vektor-vacciner, subunit-vacciner og inaktiverede vacciner. Forskning i oprindelse I januar-februar 2021 var en ekspergruppe under WHO i Kina, for at forsøge at finde sygdommens oprindelse i byen Wuhan. Den mest sandsynlige konklusion er ifølge WHO, at coronavirussen stammer fra flagermus, og at den er overført til mennesker via et andet uidentificeret dyr, hvilket for eksempel kan være ræve, mink eller skældyr. Der er dog endnu ingen endelige konklusioner. Smitten er angiveligt eksploderet på markedet i Wuhan, hvorfor det kan være interessant at undersøge, hvor de vilde dyr, der blev solgt på markedet, kom fra. Desuden hvilke jægere eller farme, der havde at gøre med dyrene, og hvordan de blev transporteret til markedet. Kina blev kritiseret for, at være usamarbejdsvilling i undersøgelser, herunder også en anden teori om, at der har været en lækage fra et laboratorie i Wuhan, hvorfra COVID-19-virus stammer. I begyndelsen af februar 2023 skrev det videnskabelige tidsskrift Nature, at den manglende samarbejdsvilje fra Kina havde fået WHO til helt at droppe planerne om at finde sygdommens oprindelse. Dette korrigerede WHO efterfølgende, det fortsat organisationens plan, at opklare COVID-19-virus' oprindelse. I marts måned fik internationale forskere adgang til resultater af flere end 1.000 prøver udtaget i januar 2020 fra Huanan Seafood Wholesale Market i Wuhan. Prøverne viste, at der befandt sig levende dyr, som kunne være bærere af COVID-19-smitte. En af dyrearterne var mårhund, der tidligere har været under mistanke for, at være det ukendte mellemværtsdyr, som har bragt den oprindelige flagermusesmitte videre til mennesker. De amerikanske aviser The Wall Street Journal og New York Times nævnte tillige i slutningen af februar 2023 en klassificeret rapport fra det amerikanske energiministerium, at det højst sandsynligt var en læk fra et kinesisk laboratorium, som i slutningen af 2019 førte til udbruddet af COVID-19-pandemien. Udmeldingen var i kontrast til tidligere vurderinger fra ministeriet, der tidligere havde givet udtryk for, at det var uvist, hvordan virus opstod. New York Times tilføjede, at efterretningerne pegede i flere retninger om, hvordan pandemien begyndte. Ifølge FBI peger dets undersøgelser på, at et laboratorielæk er den mest sandsynlige forklaring på COVID-19-pandemien. I alt otte amerikanske regeringsinstitutioner undersøger pandemiens oprindelse, hvoraf fire peger i retning af, at pandemien er opstået på naturlig vis og to har ikke taget stilling. Ingen af dem er pr. 1. marts sikre i deres vurdering. Den amerikanske præsident, Joe Biden, underskrev et lovforslag den 20. marts, der skal sørge for, at offentligheden får så mange informationer om COVID-19s oprindelse fra den nationale efterretningstjeneste, som muligt. Spredning I marts 2020, hvor mange lande indførte restriktioner af vidtgående karakter i forhold til borgernes bevægelsesfrihed, den internationale luftfart blev stort set indstillet og en række brancher med borgerkontakt måtte indstille aktiviteten, var det blandt forskere alment antaget, at virus spredte sig eksponentielt.<ref name="WHO2">[https://www.who.int/health-topics/coronavirus#tab=tab_1 WHO: Coronavirus], hentet den 26. marts 2020</ref> Endvidere har WHO anbefalet, at landene så vidt muligt isolerer de syge for at undgå smittespredning. På denne baggrund kunne "knækket" på stigningen i antallet af rapporterede tilfælde forklares med myndighedernes indsats i de ramte lande. I april og maj viste flere af hinanden uafhængige analyser, at smitte primært udbredes af superspredere. Ca. 10% af de smittede bærer sygdommen videre til ca. 80% af den følgende smittekæde. Mutationer I efteråret 2020 skete der en bekymrende udvikling i Danmark centreret i Nordjylland med smittespredning fra mink til mennesker. Her havde Statens Serum Institut identificeret en ny mutation i SARS-CoV-2 virus, benævnt Cluster 5, som viste en lavere effektivitet, fra de vacciner der var under udvikling. Flere mutationer blev konstateret og navngivet i nyhedsmedierne efter det land, som mutationen først blev konstateret i, for eksempel den "britiske variant" (B.1.1.7) og senere blandt andre også en "sydafrikansk" (B.1.351), en "brasiliansk" og en "indisk" (B.1.617.2). Den Indiske regering beklagede i maj 2021, at mutationer fik landenavne. Den 31. maj besluttede WHO at mutationerne i stedet skulle benævnes med bogstaver fra det græske alfabet, således kom den "britiske variant" til af hedde "alpha", den "sydafrikanske variant" blev til "beta" og den "indiske variant" benævnt som "delta". I slutningen af november 2021 konstateres endnu en ny variant i Sydafrika, B.1.1.529, som WHO navngav "Omicron" (på dansk omikron) efter det 15. bogstav i det græske alfabet. Omikron viste et højt antal af mutationer, hvoraf nogle var bekymrende. Indledende undersøgelser viste en forhøjet risiko for geninfektion ved denne variant. I 2022 blev en ny kombinatiuonsvariant af Delta og Omikron, navngivet "Deltacron", opdaget på Filippinerne. Varianten forsvandt i en periode, men genopstod i sub-varianterne XBC, XAY, XBA og XAW. XBC-varianten havde flere end 130 mutationer. Deltacron er i stand til at angribe lungerne, ligesom Delta, og er lige så let overførbar som Omicron. Selv om der foreløbigt kun er få smittede (november 2022), holder forskere over hele verden nøje øje med en ny COVID-19-variant. I januar 2023 blev en ny variant, XBB.1.5, dominerende i USA, hvor den på landsplan udgjorde 40 procent af alle registrerede tilfælde og idet nordøstlige USA 75 procent. XBB.1.5 har en mutation (F486P), der medfører, at antistoffer og vacciner ikke virker lige så effektivt som mod Omikron-varianten, hvorved flere fra allerede sårbare grupper rammes. Varianten blev navngivet Kraken'' efter den nordiske mytologi, hvor Kraken er et havuhyre med mange tentakler, der ødelagde hele skibe og slæbte sømænd i døden. Den første variant, som fik et øgenavn, var BA.2.75 i sommeren 2022, den blev døbt Centaurus fra den græske mytologi. BA.2.75 mutterede til BM.1.1.1, der sammen med BJ.1-varianten blev til XBB-varianten, opdaget i Indien i august 2022. I midten af februar blev XBB.1.5-Kraken den dominerende coronavariant i Danmark. Kilder/referencer Se også Cluster 5 Coronaviruspandemien (2019-) COVID-19 og graviditet Eksterne links Globale smittetal, opdateres dagligt Opdateret dansk oversigt fra Videnskab.dk Kardiovaskulære sygdomme Luftvejssygdomme Virussygdomme Zoonoser	danish	0.321921
genetic_sequence_of_SARS-CoV-2/SARS-CoV-2.txt	Severe acute respiratory syndrome coronavirus 2 (SARS‑CoV‑2) is a strain of coronavirus that causes COVID-19, the respiratory illness responsible for the COVID-19 pandemic. The virus previously had the provisional name 2019 novel coronavirus (2019-nCoV), and has also been called human coronavirus 2019 (HCoV-19 or hCoV-19). First identified in the city of Wuhan, Hubei, China, the World Health Organization designated the outbreak a public health emergency of international concern from January 30, 2020, to May 5, 2023. SARS‑CoV‑2 is a positive-sense single-stranded RNA virus that is contagious in humans. SARS‑CoV‑2 is a strain of the species severe-acute-respiratory-syndrome-related coronavirus (SARSr-CoV), as is SARS-CoV-1, the virus that caused the 2002–2004 SARS outbreak. There are animal-borne coronavirus strains more closely related to SARS-CoV-2, the most closely related being bat coronaviruses, including BANAL-52 and RaTG13. The virus is of zoonotic origin; its close genetic similarity to bat coronaviruses suggests it emerged from a bat-borne virus. Research is ongoing as to whether SARS‑CoV‑2 came directly from bats or indirectly through any intermediate hosts. The virus shows little genetic diversity, indicating that the spillover event introducing SARS‑CoV‑2 to humans is likely to have occurred in late 2019. Epidemiological studies estimate that in the period between December 2019 and September 2020 each infection resulted in an average of 2.4–3.4 new infections when no members of the community were immune and no preventive measures were taken. However, some subsequent variants have become more infectious. The virus is airborne and primarily spreads between people through close contact and via aerosols and respiratory droplets that are exhaled when talking, breathing, or otherwise exhaling, as well as those produced from coughs and sneezes. It enters human cells by binding to angiotensin-converting enzyme 2 (ACE2), a membrane protein that regulates the renin–angiotensin system. Terminology Sign with provisional name "2019-nCoV" During the initial outbreak in Wuhan, China, various names were used for the virus; some names used by different sources included "the coronavirus" or "Wuhan coronavirus". In January 2020, the World Health Organization (WHO) recommended "2019 novel coronavirus" (2019-nCoV) as the provisional name for the virus. This was in accordance with WHO's 2015 guidance against using geographical locations, animal species, or groups of people in disease and virus names. On 11 February 2020, the International Committee on Taxonomy of Viruses adopted the official name "severe acute respiratory syndrome coronavirus 2" (SARS‑CoV‑2). To avoid confusion with the disease SARS, the WHO sometimes refers to SARS‑CoV‑2 as "the COVID-19 virus" in public health communications and the name HCoV-19 was included in some research articles. Referring to COVID-19 as the "Wuhan virus" has been described as dangerous by WHO officials, and as xenophobic by many journalists and academics. Infection and transmission Main article: Transmission of COVID-19 This section has multiple issues. Please help improve it or discuss these issues on the talk page. (Learn how and when to remove these template messages) This section needs to be updated. Please help update this article to reflect recent events or newly available information. (August 2021) This section needs more reliable medical references for verification or relies too heavily on primary sources. Please review the contents of the section and add the appropriate references if you can. Unsourced or poorly sourced material may be challenged and removed. Find sources: "SARS-CoV-2" – news · newspapers · books · scholar · JSTOR (August 2021) (Learn how and when to remove this template message) Human-to-human transmission of SARS‑CoV‑2 was confirmed on 20 January 2020 during the COVID-19 pandemic. Transmission was initially assumed to occur primarily via respiratory droplets from coughs and sneezes within a range of about 1.8 metres (6 ft). Laser light scattering experiments suggest that speaking is an additional mode of transmission and a far-reaching one, indoors, with little air flow. Other studies have suggested that the virus may be airborne as well, with aerosols potentially being able to transmit the virus. During human-to-human transmission, between 200 and 800 infectious SARS‑CoV‑2 virions are thought to initiate a new infection. If confirmed, aerosol transmission has biosafety implications because a major concern associated with the risk of working with emerging viruses in the laboratory is the generation of aerosols from various laboratory activities which are not immediately recognizable and may affect other scientific personnel. Indirect contact via contaminated surfaces is another possible cause of infection. Preliminary research indicates that the virus may remain viable on plastic (polypropylene) and stainless steel (AISI 304) for up to three days, but it does not survive on cardboard for more than one day or on copper for more than four hours. The virus is inactivated by soap, which destabilizes its lipid bilayer. Viral RNA has also been found in stool samples and semen from infected individuals. The degree to which the virus is infectious during the incubation period is uncertain, but research has indicated that the pharynx reaches peak viral load approximately four days after infection or in the first week of symptoms and declines thereafter. The duration of SARS-CoV-2 RNA shedding is generally between 3 and 46 days after symptom onset. A study by a team of researchers from the University of North Carolina found that the nasal cavity is seemingly the dominant initial site of infection, with subsequent aspiration-mediated virus-seeding into the lungs in SARS‑CoV‑2 pathogenesis. They found that there was an infection gradient from high in proximal towards low in distal pulmonary epithelial cultures, with a focal infection in ciliated cells and type 2 pneumocytes in the airway and alveolar regions respectively. Studies have identified a range of animals—such as cats, ferrets, hamsters, non-human primates, minks, tree shrews, raccoon dogs, fruit bats, and rabbits—that are susceptible and permissive to SARS-CoV-2 infection. Some institutions have advised that those infected with SARS‑CoV‑2 restrict their contact with animals. Asymptomatic and presymptomatic transmission On 1 February 2020, the World Health Organization (WHO) indicated that "transmission from asymptomatic cases is likely not a major driver of transmission". One meta-analysis found that 17% of infections are asymptomatic, and asymptomatic individuals were 42% less likely to transmit the virus. However, an epidemiological model of the beginning of the outbreak in China suggested that "pre-symptomatic shedding may be typical among documented infections" and that subclinical infections may have been the source of a majority of infections. That may explain how out of 217 on board a cruise liner that docked at Montevideo, only 24 of 128 who tested positive for viral RNA showed symptoms. Similarly, a study of ninety-four patients hospitalized in January and February 2020 estimated patients began shedding virus two to three days before symptoms appear and that "a substantial proportion of transmission probably occurred before first symptoms in the index case". The authors later published a correction that showed that shedding began earlier than first estimated, four to five days before symptoms appear. Reinfection There is uncertainty about reinfection and long-term immunity. It is not known how common reinfection is, but reports have indicated that it is occurring with variable severity. The first reported case of reinfection was a 33-year-old man from Hong Kong who first tested positive on 26 March 2020, was discharged on 15 April 2020 after two negative tests, and tested positive again on 15 August 2020 (142 days later), which was confirmed by whole-genome sequencing showing that the viral genomes between the episodes belong to different clades. The findings had the implications that herd immunity may not eliminate the virus if reinfection is not an uncommon occurrence and that vaccines may not be able to provide lifelong protection against the virus. Another case study described a 25-year-old man from Nevada who tested positive for SARS‑CoV‑2 on 18 April 2020 and on 5 June 2020 (separated by two negative tests). Since genomic analyses showed significant genetic differences between the SARS‑CoV‑2 variant sampled on those two dates, the case study authors determined this was a reinfection. The man's second infection was symptomatically more severe than the first infection, but the mechanisms that could account for this are not known. Reservoir and origin Further information: Investigations into the origin of COVID-19 Transmission of SARS-CoV-1 and SARS‑CoV‑2 from mammals as biological carriers to humans No natural reservoir for SARS-CoV-2 has been identified. Prior to the emergence of SARS-CoV-2 as a pathogen infecting humans, there had been two previous zoonosis-based coronavirus epidemics, those caused by SARS-CoV-1 and MERS-CoV. The first known infections from SARS‑CoV‑2 were discovered in Wuhan, China. The original source of viral transmission to humans remains unclear, as does whether the virus became pathogenic before or after the spillover event. Because many of the early infectees were workers at the Huanan Seafood Market, it has been suggested that the virus might have originated from the market. However, other research indicates that visitors may have introduced the virus to the market, which then facilitated rapid expansion of the infections. A March 2021 WHO-convened report stated that human spillover via an intermediate animal host was the most likely explanation, with direct spillover from bats next most likely. Introduction through the food supply chain and the Huanan Seafood Market was considered another possible, but less likely, explanation. An analysis in November 2021, however, said that the earliest-known case had been misidentified and that the preponderance of early cases linked to the Huanan Market argued for it being the source. For a virus recently acquired through a cross-species transmission, rapid evolution is expected. The mutation rate estimated from early cases of SARS-CoV-2 was of 6.54×10 per site per year. Coronaviruses in general have high genetic plasticity, but SARS-CoV-2's viral evolution is slowed by the RNA proofreading capability of its replication machinery. For comparison, the viral mutation rate in vivo of SARS-CoV-2 has been found to be lower than that of influenza. Research into the natural reservoir of the virus that caused the 2002–2004 SARS outbreak has resulted in the discovery of many SARS-like bat coronaviruses, most originating in horseshoe bats. The closest match by far, published in Nature (journal) in February 2022, were viruses BANAL-52 (96.8% resemblance to SARS‑CoV‑2), BANAL-103 and BANAL-236, collected in three different species of bats in Feuang, Laos. An earlier source published in February 2020 identified the virus RaTG13, collected in bats in Mojiang, Yunnan, China to be the closest to SARS‑CoV‑2, with 96.1% resemblance. None of the above are its direct ancestor. Samples taken from Rhinolophus sinicus, a species of horseshoe bats, show an 80% resemblance to SARS‑CoV‑2. Bats are considered the most likely natural reservoir of SARS‑CoV‑2. Differences between the bat coronavirus and SARS‑CoV‑2 suggest that humans may have been infected via an intermediate host; although the source of introduction into humans remains unknown. Although the role of pangolins as an intermediate host was initially posited (a study published in July 2020 suggested that pangolins are an intermediate host of SARS‑CoV‑2-like coronaviruses), subsequent studies have not substantiated their contribution to the spillover. Evidence against this hypothesis includes the fact that pangolin virus samples are too distant to SARS-CoV-2: isolates obtained from pangolins seized in Guangdong were only 92% identical in sequence to the SARS‑CoV‑2 genome (matches above 90 percent may sound high, but in genomic terms it is a wide evolutionary gap). In addition, despite similarities in a few critical amino acids, pangolin virus samples exhibit poor binding to the human ACE2 receptor. Phylogenetics and taxonomy Genomic informationGenomic organisation of isolate Wuhan-Hu-1, the earliest sequenced sample of SARS-CoV-2NCBI genome ID86693Genome size29,903 basesYear of completion2020Genome browser (UCSC) SARS‑CoV‑2 belongs to the broad family of viruses known as coronaviruses. It is a positive-sense single-stranded RNA (+ssRNA) virus, with a single linear RNA segment. Coronaviruses infect humans, other mammals, including livestock and companion animals, and avian species. Human coronaviruses are capable of causing illnesses ranging from the common cold to more severe diseases such as Middle East respiratory syndrome (MERS, fatality rate ~34%). SARS-CoV-2 is the seventh known coronavirus to infect people, after 229E, NL63, OC43, HKU1, MERS-CoV, and the original SARS-CoV. Like the SARS-related coronavirus implicated in the 2003 SARS outbreak, SARS‑CoV‑2 is a member of the subgenus Sarbecovirus (beta-CoV lineage B). Coronaviruses undergo frequent recombination. The mechanism of recombination in unsegmented RNA viruses such as SARS-CoV-2 is generally by copy-choice replication, in which gene material switches from one RNA template molecule to another during replication. The SARS-CoV-2 RNA sequence is approximately 30,000 bases in length, relatively long for a coronavirus—which in turn carry the largest genomes among all RNA families. Its genome consists nearly entirely of protein-coding sequences, a trait shared with other coronaviruses. Transmission electron micrograph of SARS‑CoV‑2 virions (red) isolated from a patient during the COVID-19 pandemic A distinguishing feature of SARS‑CoV‑2 is its incorporation of a polybasic site cleaved by furin, which appears to be an important element enhancing its virulence. It was suggested that the acquisition of the furin-cleavage site in the SARS-CoV-2 S protein was essential for zoonotic transfer to humans. The furin protease recognizes the canonical peptide sequence RX[R/K] R↓X where the cleavage site is indicated by a down arrow and X is any amino acid. In SARS-CoV-2 the recognition site is formed by the incorporated 12 codon nucleotide sequence CCT CGG CGG GCA which corresponds to the amino acid sequence P RR A. This sequence is upstream of an arginine and serine which forms the S1/S2 cleavage site (P RR A R↓S) of the spike protein. Although such sites are a common naturally-occurring feature of other viruses within the Subfamily Orthocoronavirinae, it appears in few other viruses from the Beta-CoV genus, and it is unique among members of its subgenus for such a site. The furin cleavage site PRRAR↓ is highly similar to that of the feline coronavirus, an alphacoronavirus 1 strain. Viral genetic sequence data can provide critical information about whether viruses separated by time and space are likely to be epidemiologically linked. With a sufficient number of sequenced genomes, it is possible to reconstruct a phylogenetic tree of the mutation history of a family of viruses. By 12 January 2020, five genomes of SARS‑CoV‑2 had been isolated from Wuhan and reported by the Chinese Center for Disease Control and Prevention (CCDC) and other institutions; the number of genomes increased to 42 by 30 January 2020. A phylogenetic analysis of those samples showed they were "highly related with at most seven mutations relative to a common ancestor", implying that the first human infection occurred in November or December 2019. Examination of the topology of the phylogenetic tree at the start of the pandemic also found high similarities between human isolates. As of 21 August 2021, 3,422 SARS‑CoV‑2 genomes, belonging to 19 strains, sampled on all continents except Antarctica were publicly available. On 11 February 2020, the International Committee on Taxonomy of Viruses announced that according to existing rules that compute hierarchical relationships among coronaviruses based on five conserved sequences of nucleic acids, the differences between what was then called 2019-nCoV and the virus from the 2003 SARS outbreak were insufficient to make them separate viral species. Therefore, they identified 2019-nCoV as a virus of Severe acute respiratory syndrome–related coronavirus. In July 2020, scientists reported that a more infectious SARS‑CoV‑2 variant with spike protein variant G614 has replaced D614 as the dominant form in the pandemic. Coronavirus genomes and subgenomes encode six open reading frames (ORFs). In October 2020, researchers discovered a possible overlapping gene named ORF3d, in the SARS‑CoV‑2 genome. It is unknown if the protein produced by ORF3d has any function, but it provokes a strong immune response. ORF3d has been identified before, in a variant of coronavirus that infects pangolins. Phylogenetic tree A phylogenetic tree based on whole-genome sequences of SARS-CoV-2 and related coronaviruses is: SARS‑CoV‑2 related coronavirus (Bat) Rc-o319, 81% to SARS-CoV-2, Rhinolophus cornutus, Iwate, Japan Bat SL-ZXC21, 88% to SARS-CoV-2, Rhinolophus pusillus, Zhoushan, Zhejiang Bat SL-ZC45, 88% to SARS-CoV-2, Rhinolophus pusillus, Zhoushan, Zhejiang Pangolin SARSr-CoV-GX, 85.3% to SARS-CoV-2, Manis javanica, smuggled from Southeast Asia Pangolin SARSr-CoV-GD, 90.1% to SARS-CoV-2, Manis javanica, smuggled from Southeast Asia Bat RshSTT182, 92.6% to SARS-CoV-2, Rhinolophus shameli, Steung Treng, Cambodia Bat RshSTT200, 92.6% to SARS-CoV-2, Rhinolophus shameli, Steung Treng, Cambodia (Bat) RacCS203, 91.5% to SARS-CoV-2, Rhinolophus acuminatus, Chachoengsao, Thailand (Bat) RmYN02, 93.3% to SARS-CoV-2, Rhinolophus malayanus, Mengla, Yunnan (Bat) RpYN06, 94.4% to SARS-CoV-2, Rhinolophus pusillus, Xishuangbanna, Yunnan (Bat) RaTG13, 96.1% to SARS-CoV-2, Rhinolophus affinis, Mojiang, Yunnan (Bat) BANAL-52, 96.8% to SARS-CoV-2, Rhinolophus malayanus, Vientiane, Laos SARS-CoV-2 SARS-CoV-1, 79% to SARS-CoV-2 Variants Main article: Variants of SARS-CoV-2 This section needs to be updated. Please help update this article to reflect recent events or newly available information. (April 2023) False-colour transmission electron micrograph of a B.1.1.7 variant coronavirus. The variant's increased transmissibility is believed to be due to changes in the structure of the spike proteins, shown here in green. There are many thousands of variants of SARS-CoV-2, which can be grouped into the much larger clades. Several different clade nomenclatures have been proposed. Nextstrain divides the variants into five clades (19A, 19B, 20A, 20B, and 20C), while GISAID divides them into seven (L, O, V, S, G, GH, and GR). Several notable variants of SARS-CoV-2 emerged in late 2020. The World Health Organization has currently declared five variants of concern, which are as follows: Alpha: Lineage B.1.1.7 emerged in the United Kingdom in September 2020, with evidence of increased transmissibility and virulence. Notable mutations include N501Y and P681H. An E484K mutation in some lineage B.1.1.7 virions has been noted and is also tracked by various public health agencies. Beta: Lineage B.1.351 emerged in South Africa in May 2020, with evidence of increased transmissibility and changes to antigenicity, with some public health officials raising alarms about its impact on the efficacy of some vaccines. Notable mutations include K417N, E484K and N501Y. Gamma: Lineage P.1 emerged in Brazil in November 2020, also with evidence of increased transmissibility and virulence, alongside changes to antigenicity. Similar concerns about vaccine efficacy have been raised. Notable mutations also include K417N, E484K and N501Y. Delta: Lineage B.1.617.2 emerged in India in October 2020. There is also evidence of increased transmissibility and changes to antigenicity. Omicron: Lineage B.1.1.529 emerged in Botswana in November 2021. Other notable variants include 6 other WHO-designated variants under investigation and Cluster 5, which emerged among mink in Denmark and resulted in a mink euthanasia campaign rendering it virtually extinct. Virology Virus structure Structure of a SARSr-CoV virion Each SARS-CoV-2 virion is 60–140 nanometres (2.4×10–5.5×10 in) in diameter; its mass within the global human populace has been estimated as being between 0.1 and 10 kilograms. Like other coronaviruses, SARS-CoV-2 has four structural proteins, known as the S (spike), E (envelope), M (membrane), and N (nucleocapsid) proteins; the N protein holds the RNA genome, and the S, E, and M proteins together create the viral envelope. Coronavirus S proteins are glycoproteins and also type I membrane proteins (membranes containing a single transmembrane domain oriented on the extracellular side). They are divided into two functional parts (S1 and S2). In SARS-CoV-2, the spike protein, which has been imaged at the atomic level using cryogenic electron microscopy, is the protein responsible for allowing the virus to attach to and fuse with the membrane of a host cell; specifically, its S1 subunit catalyzes attachment, the S2 subunit fusion. SARS‑CoV‑2 spike homotrimer with one protein subunit highlighted. The ACE2 binding domain is magenta. Genome As of early 2022, about 7 million SARS-CoV-2 genomes had been sequenced and deposited into public databases and another 800,000 or so were added each month. By September 2023, the GISAID EpiCoV database contained more than 16 million genome sequences. SARS-CoV-2 has a linear, positive-sense, single-stranded RNA genome about 30,000 bases long. Its genome has a bias against cytosine (C) and guanine (G) nucleotides, like other coronaviruses. The genome has the highest composition of U (32.2%), followed by A (29.9%), and a similar composition of G (19.6%) and C (18.3%). The nucleotide bias arises from the mutation of guanines and cytosines to adenosines and uracils, respectively. The mutation of CG dinucleotides is thought to arise to avoid the zinc finger antiviral protein related defense mechanism of cells, and to lower the energy to unbind the genome during replication and translation (adenosine and uracil base pair via two hydrogen bonds, cytosine and guanine via three). The depletion of CG dinucleotides in its genome has led the virus to have a noticeable codon usage bias. For instance, arginine's six different codons have a relative synonymous codon usage of AGA (2.67), CGU (1.46), AGG (.81), CGC (.58), CGA (.29), and CGG (.19). A similar codon usage bias trend is seen in other SARS–related coronaviruses. Replication cycle Virus infections start when viral particles bind to host surface cellular receptors. Protein modeling experiments on the spike protein of the virus soon suggested that SARS‑CoV‑2 has sufficient affinity to the receptor angiotensin converting enzyme 2 (ACE2) on human cells to use them as a mechanism of cell entry. By 22 January 2020, a group in China working with the full virus genome and a group in the United States using reverse genetics methods independently and experimentally demonstrated that ACE2 could act as the receptor for SARS‑CoV‑2. Studies have shown that SARS‑CoV‑2 has a higher affinity to human ACE2 than the original SARS virus. SARS‑CoV‑2 may also use basigin to assist in cell entry. Initial spike protein priming by transmembrane protease, serine 2 (TMPRSS2) is essential for entry of SARS‑CoV‑2. The host protein neuropilin 1 (NRP1) may aid the virus in host cell entry using ACE2. After a SARS‑CoV‑2 virion attaches to a target cell, the cell's TMPRSS2 cuts open the spike protein of the virus, exposing a fusion peptide in the S2 subunit, and the host receptor ACE2. After fusion, an endosome forms around the virion, separating it from the rest of the host cell. The virion escapes when the pH of the endosome drops or when cathepsin, a host cysteine protease, cleaves it. The virion then releases RNA into the cell and forces the cell to produce and disseminate copies of the virus, which infect more cells. SARS‑CoV‑2 produces at least three virulence factors that promote shedding of new virions from host cells and inhibit immune response. Whether they include downregulation of ACE2, as seen in similar coronaviruses, remains under investigation (as of May 2020). Digitally colourised scanning electron micrographs of SARS-CoV-2 virions (yellow) emerging from human cells cultured in a laboratory Treatment and drug development Very few drugs are known to effectively inhibit SARS‑CoV‑2. Masitinib is a clinically safe drug and was recently found to inhibit its main protease, 3CLpro and showed >200-fold reduction in viral titers in the lungs and nose in mice. However, it is not approved for the treatment of COVID-19 in humans as of August 2021. In December 2021, the United States granted emergency use authorization to Nirmatrelvir/ritonavir for the treatment of the virus; the European Union, United Kingdom, and Canada followed suit with full authorization soon after. One study found that Nirmatrelvir/ritonavir reduced the risk of hospitalization and death by 88%. COVID Moonshot is an international collaborative open-science project started in March 2020 with the goal of developing an un-patented oral antiviral drug for treatment of SARS-CoV-2. Epidemiology Main article: COVID-19 pandemic Retrospective tests collected within the Chinese surveillance system revealed no clear indication of substantial unrecognized circulation of SARS‑CoV‑2 in Wuhan during the latter part of 2019. A meta-analysis from November 2020 estimated the basic reproduction number ( R 0 {\displaystyle R_{0}} ) of the virus to be between 2.39 and 3.44. This means each infection from the virus is expected to result in 2.39 to 3.44 new infections when no members of the community are immune and no preventive measures are taken. The reproduction number may be higher in densely populated conditions such as those found on cruise ships. Human behavior affects the R0 value and hence estimates of R0 differ between different countries, cultures, and social norms. For instance, one study found relatively low R0 (~3.5) in Sweden, Belgium and the Netherlands, while Spain and the US had significantly higher R0 values (5.9 to 6.4, respectively). Reproductive value R0 of SARS-CoV-2 variants Variant R0 Source Reference/ancestral strain ~2.8 Alpha (B.1.1.7) (40-90% higher than previous variants) Delta (B.1.617.2) ~5 (3-8) There have been about 96,000 confirmed cases of infection in mainland China. While the proportion of infections that result in confirmed cases or progress to diagnosable disease remains unclear, one mathematical model estimated that 75,815 people were infected on 25 January 2020 in Wuhan alone, at a time when the number of confirmed cases worldwide was only 2,015. Before 24 February 2020, over 95% of all deaths from COVID-19 worldwide had occurred in Hubei province, where Wuhan is located. As of 10 March 2023, the percentage had decreased to 0.047%. As of 10 March 2023, there were 676,609,955 total confirmed cases of SARS‑CoV‑2 infection. The total number of deaths attributed to the virus was 6,881,955. See also 3C-like protease (NS5)	biology	8528045	https://sv.wikipedia.org/wiki/Phylogenetic%20Assignment%20of%20Named%20Global%20Outbreak%20Lineages	Phylogenetic Assignment of Named Global Outbreak Lineages	Phylogenetic Assignment of Named Global Outbreak Lineages (PANGOLIN) är ett mjukvaruprogram som utvecklats av medlemmar från COG-UK consortium. Programmet använder sekvenser från helgenomsekvensering av patientprover med viruset sars-cov-2 för att sortera in de olika virusen i "släktträd", samt namnge olika grenar av det. Förkortningen pangolin betyder på engelska myrkotte, vilket är ett av de djur som misstänkts ha varit värd för sars-cov-2 innan viruset kom till människan. Programmet har alltså namngivits för att ge en lämplig förkortning. Se även Varianter av SARS-CoV-2 Referenser Externa länkar PANGOLIN open source software at GitHub.com Hälsa Datorprogram	swedish	0.912502
genetic_sequence_of_SARS-CoV-2/Polyadenylation.txt	Polyadenylation is the addition of a poly(A) tail to an RNA transcript, typically a messenger RNA (mRNA). The poly(A) tail consists of multiple adenosine monophosphates; in other words, it is a stretch of RNA that has only adenine bases. In eukaryotes, polyadenylation is part of the process that produces mature mRNA for translation. In many bacteria, the poly(A) tail promotes degradation of the mRNA. It, therefore, forms part of the larger process of gene expression. The process of polyadenylation begins as the transcription of a gene terminates. The 3′-most segment of the newly made pre-mRNA is first cleaved off by a set of proteins; these proteins then synthesize the poly(A) tail at the RNA's 3′ end. In some genes these proteins add a poly(A) tail at one of several possible sites. Therefore, polyadenylation can produce more than one transcript from a single gene (alternative polyadenylation), similar to alternative splicing. The poly(A) tail is important for the nuclear export, translation and stability of mRNA. The tail is shortened over time, and, when it is short enough, the mRNA is enzymatically degraded. However, in a few cell types, mRNAs with short poly(A) tails are stored for later activation by re-polyadenylation in the cytosol. In contrast, when polyadenylation occurs in bacteria, it promotes RNA degradation. This is also sometimes the case for eukaryotic non-coding RNAs. mRNA molecules in both prokaryotes and eukaryotes have polyadenylated 3′-ends, with the prokaryotic poly(A) tails generally shorter and fewer mRNA molecules polyadenylated. Background on RNA[edit] Further information: RNA and Messenger RNA Chemical structure of RNA. The sequence of bases differs between RNA molecules. RNAs are a type of large biological molecules, whose individual building blocks are called nucleotides. The name poly(A) tail (for polyadenylic acid tail) reflects the way RNA nucleotides are abbreviated, with a letter for the base the nucleotide contains (A for adenine, C for cytosine, G for guanine and U for uracil). RNAs are produced (transcribed) from a DNA template. By convention, RNA sequences are written in a 5′ to 3′ direction. The 5′ end is the part of the RNA molecule that is transcribed first, and the 3′ end is transcribed last. The 3′ end is also where the poly(A) tail is found on polyadenylated RNAs. Messenger RNA (mRNA) is RNA that has a coding region that acts as a template for protein synthesis (translation). The rest of the mRNA, the untranslated regions, tune how active the mRNA is. There are also many RNAs that are not translated, called non-coding RNAs. Like the untranslated regions, many of these non-coding RNAs have regulatory roles. Nuclear polyadenylation[edit] Function[edit] In nuclear polyadenylation, a poly(A) tail is added to an RNA at the end of transcription. On mRNAs, the poly(A) tail protects the mRNA molecule from enzymatic degradation in the cytoplasm and aids in transcription termination, export of the mRNA from the nucleus, and translation. Almost all eukaryotic mRNAs are polyadenylated, with the exception of animal replication-dependent histone mRNAs. These are the only mRNAs in eukaryotes that lack a poly(A) tail, ending instead in a stem-loop structure followed by a purine-rich sequence, termed histone downstream element, that directs where the RNA is cut so that the 3′ end of the histone mRNA is formed. Many eukaryotic non-coding RNAs are always polyadenylated at the end of transcription. There are small RNAs where the poly(A) tail is seen only in intermediary forms and not in the mature RNA as the ends are removed during processing, the notable ones being microRNAs. But, for many long noncoding RNAs – a seemingly large group of regulatory RNAs that, for example, includes the RNA Xist, which mediates X chromosome inactivation – a poly(A) tail is part of the mature RNA. Mechanism[edit] Proteins involved: CPSF: cleavage/polyadenylation specificity factor CstF: cleavage stimulation factor PAP: polyadenylate polymerase PABII: polyadenylate binding protein 2 CFI: cleavage factor I CFII: cleavage factor II The processive polyadenylation complex in the nucleus of eukaryotes works on products of RNA polymerase II, such as precursor mRNA. Here, a multi-protein complex (see components on the right) cleaves the 3′-most part of a newly produced RNA and polyadenylates the end produced by this cleavage. The cleavage is catalysed by the enzyme CPSF and occurs 10–30 nucleotides downstream of its binding site. This site often has the polyadenylation signal sequence AAUAAA on the RNA, but variants of it that bind more weakly to CPSF exist. Two other proteins add specificity to the binding to an RNA: CstF and CFI. CstF binds to a GU-rich region further downstream of CPSF's site. CFI recognises a third site on the RNA (a set of UGUAA sequences in mammals) and can recruit CPSF even if the AAUAAA sequence is missing. The polyadenylation signal – the sequence motif recognised by the RNA cleavage complex – varies between groups of eukaryotes. Most human polyadenylation sites contain the AAUAAA sequence, but this sequence is less common in plants and fungi. The RNA is typically cleaved before transcription termination, as CstF also binds to RNA polymerase II. Through a poorly understood mechanism (as of 2002), it signals for RNA polymerase II to slip off of the transcript. Cleavage also involves the protein CFII, though it is unknown how. The cleavage site associated with a polyadenylation signal can vary up to some 50 nucleotides. When the RNA is cleaved, polyadenylation starts, catalysed by polyadenylate polymerase. Polyadenylate polymerase builds the poly(A) tail by adding adenosine monophosphate units from adenosine triphosphate to the RNA, cleaving off pyrophosphate. Another protein, PAB2, binds to the new, short poly(A) tail and increases the affinity of polyadenylate polymerase for the RNA. When the poly(A) tail is approximately 250 nucleotides long the enzyme can no longer bind to CPSF and polyadenylation stops, thus determining the length of the poly(A) tail. CPSF is in contact with RNA polymerase II, allowing it to signal the polymerase to terminate transcription. When RNA polymerase II reaches a "termination sequence" (⁵'TTTATT' on the DNA template and ⁵'AAUAAA' on the primary transcript), the end of transcription is signaled. The polyadenylation machinery is also physically linked to the spliceosome, a complex that removes introns from RNAs. Downstream effects[edit] The poly(A) tail acts as the binding site for poly(A)-binding protein. Poly(A)-binding protein promotes export from the nucleus and translation, and inhibits degradation. This protein binds to the poly(A) tail prior to mRNA export from the nucleus and in yeast also recruits poly(A) nuclease, an enzyme that shortens the poly(A) tail and allows the export of the mRNA. Poly(A)-binding protein is exported to the cytoplasm with the RNA. mRNAs that are not exported are degraded by the exosome. Poly(A)-binding protein also can bind to, and thus recruit, several proteins that affect translation, one of these is initiation factor-4G, which in turn recruits the 40S ribosomal subunit. However, a poly(A) tail is not required for the translation of all mRNAs. Further, poly(A) tailing (oligo-adenylation) can determine the fate of RNA molecules that are usually not poly(A)-tailed (such as (small) non-coding (sn)RNAs etc.) and thereby induce their RNA decay. Deadenylation[edit] In eukaryotic somatic cells, the poly(A) tails of most mRNAs in the cytoplasm gradually get shorter, and mRNAs with shorter poly(A) tail are translated less and degraded sooner. However, it can take many hours before an mRNA is degraded. This deadenylation and degradation process can be accelerated by microRNAs complementary to the 3′ untranslated region of an mRNA. In immature egg cells, mRNAs with shortened poly(A) tails are not degraded, but are instead stored and translationally inactive. These short tailed mRNAs are activated by cytoplasmic polyadenylation after fertilisation, during egg activation. In animals, poly(A) ribonuclease (PARN) can bind to the 5′ cap and remove nucleotides from the poly(A) tail. The level of access to the 5′ cap and poly(A) tail is important in controlling how soon the mRNA is degraded. PARN deadenylates less if the RNA is bound by the initiation factors 4E (at the 5′ cap) and 4G (at the poly(A) tail), which is why translation reduces deadenylation. The rate of deadenylation may also be regulated by RNA-binding proteins. Additionally, RNA triple helix structures and RNA motifs such as the poly(A) tail 3’ end binding pocket retard deadenylation process and inhibit poly(A) tail removal. Once the poly(A) tail is removed, the decapping complex removes the 5′ cap, leading to a degradation of the RNA. Several other proteins are involved in deadenylation in budding yeast and human cells, most notably the CCR4-Not complex. Cytoplasmic polyadenylation[edit] There is polyadenylation in the cytosol of some animal cell types, namely in the germ line, during early embryogenesis and in post-synaptic sites of nerve cells. This lengthens the poly(A) tail of an mRNA with a shortened poly(A) tail, so that the mRNA will be translated. These shortened poly(A) tails are often less than 20 nucleotides, and are lengthened to around 80–150 nucleotides. In the early mouse embryo, cytoplasmic polyadenylation of maternal RNAs from the egg cell allows the cell to survive and grow even though transcription does not start until the middle of the 2-cell stage (4-cell stage in human). In the brain, cytoplasmic polyadenylation is active during learning and could play a role in long-term potentiation, which is the strengthening of the signal transmission from a nerve cell to another in response to nerve impulses and is important for learning and memory formation. Cytoplasmic polyadenylation requires the RNA-binding proteins CPSF and CPEB, and can involve other RNA-binding proteins like Pumilio. Depending on the cell type, the polymerase can be the same type of polyadenylate polymerase (PAP) that is used in the nuclear process, or the cytoplasmic polymerase GLD-2. Results of using different polyadenylation sites on the same gene Alternative polyadenylation[edit] Many protein-coding genes have more than one polyadenylation site, so a gene can code for several mRNAs that differ in their 3′ end. The 3’ region of a transcript contains many polyadenylation signals (PAS). When more proximal (closer towards 5’ end) PAS sites are utilized, this shortens the length of the 3’ untranslated region (3' UTR) of a transcript. Studies in both humans and flies have shown tissue specific APA. With neuronal tissues preferring distal PAS usage, leading to longer 3’ UTRs and testis tissues preferring proximal PAS leading to shorter 3’ UTRs. Studies have shown there is a correlation between a gene's conservation level and its tendency to do alternative polyadenylation, with highly conserved genes exhibiting more APA. Similarly, highly expressed genes follow this same pattern. Ribo-sequencing data (sequencing of only mRNAs inside ribosomes) has shown that mRNA isoforms with shorter 3’ UTRs are more likely to be translated. Since alternative polyadenylation changes the length of the 3' UTR, it can also change which binding sites are available for microRNAs in the 3′ UTR. MicroRNAs tend to repress translation and promote degradation of the mRNAs they bind to, although there are examples of microRNAs that stabilise transcripts. Alternative polyadenylation can also shorten the coding region, thus making the mRNA code for a different protein, but this is much less common than just shortening the 3′ untranslated region. The choice of poly(A) site can be influenced by extracellular stimuli and depends on the expression of the proteins that take part in polyadenylation. For example, the expression of CstF-64, a subunit of cleavage stimulatory factor (CstF), increases in macrophages in response to lipopolysaccharides (a group of bacterial compounds that trigger an immune response). This results in the selection of weak poly(A) sites and thus shorter transcripts. This removes regulatory elements in the 3′ untranslated regions of mRNAs for defense-related products like lysozyme and TNF-α. These mRNAs then have longer half-lives and produce more of these proteins. RNA-binding proteins other than those in the polyadenylation machinery can also affect whether a polyadenylation site is used, as can DNA methylation near the polyadenylation signal. In addition, numerous other components involved in transcription, splicing or other mechanisms regulating RNA biology can affect APA. Tagging for degradation in eukaryotes[edit] For many non-coding RNAs, including tRNA, rRNA, snRNA, and snoRNA, polyadenylation is a way of marking the RNA for degradation, at least in yeast. This polyadenylation is done in the nucleus by the TRAMP complex, which maintains a tail that is around 4 nucleotides long to the 3′ end. The RNA is then degraded by the exosome. Poly(A) tails have also been found on human rRNA fragments, both the form of homopolymeric (A only) and heterpolymeric (mostly A) tails. In prokaryotes and organelles[edit] Polyadenylation in bacteria helps polynucleotide phosphorylase degrade past secondary structure In many bacteria, both mRNAs and non-coding RNAs can be polyadenylated. This poly(A) tail promotes degradation by the degradosome, which contains two RNA-degrading enzymes: polynucleotide phosphorylase and RNase E. Polynucleotide phosphorylase binds to the 3′ end of RNAs and the 3′ extension provided by the poly(A) tail allows it to bind to the RNAs whose secondary structure would otherwise block the 3′ end. Successive rounds of polyadenylation and degradation of the 3′ end by polynucleotide phosphorylase allows the degradosome to overcome these secondary structures. The poly(A) tail can also recruit RNases that cut the RNA in two. These bacterial poly(A) tails are about 30 nucleotides long. In as different groups as animals and trypanosomes, the mitochondria contain both stabilising and destabilising poly(A) tails. Destabilising polyadenylation targets both mRNA and noncoding RNAs. The poly(A) tails are 43 nucleotides long on average. The stabilising ones start at the stop codon, and without them the stop codon (UAA) is not complete as the genome only encodes the U or UA part. Plant mitochondria have only destabilising polyadenylation. Mitochondrial polyadenylation has never been observed in either budding or fission yeast. While many bacteria and mitochondria have polyadenylate polymerases, they also have another type of polyadenylation, performed by polynucleotide phosphorylase itself. This enzyme is found in bacteria, mitochondria, plastids and as a constituent of the archaeal exosome (in those archaea that have an exosome). It can synthesise a 3′ extension where the vast majority of the bases are adenines. Like in bacteria, polyadenylation by polynucleotide phosphorylase promotes degradation of the RNA in plastids and likely also archaea. Evolution[edit] Although polyadenylation is seen in almost all organisms, it is not universal. However, the wide distribution of this modification and the fact that it is present in organisms from all three domains of life implies that the last universal common ancestor of all living organisms, it is presumed, had some form of polyadenylation system. A few organisms do not polyadenylate mRNA, which implies that they have lost their polyadenylation machineries during evolution. Although no examples of eukaryotes that lack polyadenylation are known, mRNAs from the bacterium Mycoplasma gallisepticum and the salt-tolerant archaean Haloferax volcanii lack this modification. The most ancient polyadenylating enzyme is polynucleotide phosphorylase. This enzyme is part of both the bacterial degradosome and the archaeal exosome, two closely related complexes that recycle RNA into nucleotides. This enzyme degrades RNA by attacking the bond between the 3′-most nucleotides with a phosphate, breaking off a diphosphate nucleotide. This reaction is reversible, and so the enzyme can also extend RNA with more nucleotides. The heteropolymeric tail added by polynucleotide phosphorylase is very rich in adenine. The choice of adenine is most likely the result of higher ADP concentrations than other nucleotides as a result of using ATP as an energy currency, making it more likely to be incorporated in this tail in early lifeforms. It has been suggested that the involvement of adenine-rich tails in RNA degradation prompted the later evolution of polyadenylate polymerases (the enzymes that produce poly(A) tails with no other nucleotides in them). Polyadenylate polymerases are not as ancient. They have separately evolved in both bacteria and eukaryotes from CCA-adding enzyme, which is the enzyme that completes the 3′ ends of tRNAs. Its catalytic domain is homologous to that of other polymerases. It is presumed that the horizontal transfer of bacterial CCA-adding enzyme to eukaryotes allowed the archaeal-like CCA-adding enzyme to switch function to a poly(A) polymerase. Some lineages, like archaea and cyanobacteria, never evolved a polyadenylate polymerase. Polyadenylate tails are observed in several RNA viruses, including Influenza A, Coronavirus, Alfalfa mosaic virus, and Duck Hepatitis A. Some viruses, such as HIV-1 and Poliovirus, inhibit the cell's poly-A binding protein (PABPC1) in order to emphasize their own genes' expression over the host cell's. History[edit] Poly(A)polymerase was first identified in 1960 as an enzymatic activity in extracts made from cell nuclei that could polymerise ATP, but not ADP, into polyadenine. Although identified in many types of cells, this activity had no known function until 1971, when poly(A) sequences were found in mRNAs. The only function of these sequences was thought at first to be protection of the 3′ end of the RNA from nucleases, but later the specific roles of polyadenylation in nuclear export and translation were identified. The polymerases responsible for polyadenylation were first purified and characterized in the 1960s and 1970s, but the large number of accessory proteins that control this process were discovered only in the early 1990s. See also[edit] SV40	biology	214295	https://da.wikipedia.org/wiki/RNA-polymerase	RNA-polymerase	RNA polymerase er et enzym, der katalyserer dannelsen af RNA ud fra en DNA-skabelon. RNA polymeraser findes i stort set alle levende celler samt visse virus, og består i alle tilfælde af flere polypeptider, der tilsammen udgør enzymet. Eukaryoter I eukaryoter opdeles RNA polymeraser i følgende tre typer: RNA polymerase I, der danner rRNA RNA polymerase II, der danner mRNA og snRNA RNA polymerase III, der danner tRNA Prokaryoter I prokaryote celler findes kun en enkelt RNA polymerase, der står for al transskription. Reaktionsmekanisme RNA polymeraser katalyserer påsættelsen af nukleotider (enten ATP, CTP, GTP eller UTP) på den voksende RNA-streng, ved en reaktion, der skematisk kan fremstilles således: (NMP)n + NTP → (NMP)n+1 + PPi I RNA polymerasens aktive site sidder to metalioner (normalt magnesium), der holdes i position af tre af enzymets aspartat-aminosyrer. Den ene metalion binder den inderste fosfatgruppe på det næste nukleotid der skal tilføjes, hvilket gør det muligt for 3'-OH-gruppen på RNA-kæden at lave et nukleofilt angreb på nukleotidet, hvorved kæden forlænges. Den anden metalion koordinerer nukleotidets andre to fosfatgrupper, der efter reaktionen frigøres som pyrofosfat. Pyrofosfat hydrolyseres meget hurtigt i cellen, hvilket sikrer at reaktionen ikke kan løbe baglæns. Enzymer	danish	0.406736
genetic_sequence_of_SARS-CoV-2/Virus.txt	A virus is a submicroscopic infectious agent that replicates only inside the living cells of an organism. Viruses infect all life forms, from animals and plants to microorganisms, including bacteria and archaea. Viruses are found in almost every ecosystem on Earth and are the most numerous type of biological entity. Since Dmitri Ivanovsky's 1892 article describing a non-bacterial pathogen infecting tobacco plants and the discovery of the tobacco mosaic virus by Martinus Beijerinck in 1898, more than 11,000 of the millions of virus species have been described in detail. The study of viruses is known as virology, a subspeciality of microbiology. When infected, a host cell is often forced to rapidly produce thousands of copies of the original virus. When not inside an infected cell or in the process of infecting a cell, viruses exist in the form of independent viral particles, or virions, consisting of (i) genetic material, i.e., long molecules of DNA or RNA that encode the structure of the proteins by which the virus acts; (ii) a protein coat, the capsid, which surrounds and protects the genetic material; and in some cases (iii) an outside envelope of lipids. The shapes of these virus particles range from simple helical and icosahedral forms to more complex structures. Most virus species have virions too small to be seen with an optical microscope and are one-hundredth the size of most bacteria. The origins of viruses in the evolutionary history of life are still unclear. Some viruses may have evolved from plasmids, which are pieces of DNA that can move between cells. Other viruses may have evolved from bacteria. In evolution, viruses are an important means of horizontal gene transfer, which increases genetic diversity in a way analogous to sexual reproduction. Viruses are considered by some biologists to be a life form, because they carry genetic material, reproduce, and evolve through natural selection, although they lack the key characteristics, such as cell structure, that are generally considered necessary criteria for defining life. Because they possess some but not all such qualities, viruses have been described as "organisms at the edge of life" and as replicators. Viruses spread in many ways. One transmission pathway is through disease-bearing organisms known as vectors: for example, viruses are often transmitted from plant to plant by insects that feed on plant sap, such as aphids; and viruses in animals can be carried by blood-sucking insects. Many viruses spread in the air by coughing and sneezing, including influenza viruses, SARS-CoV-2, chickenpox, smallpox, and measles. Norovirus and rotavirus, common causes of viral gastroenteritis, are transmitted by the faecal–oral route, passed by hand-to-mouth contact or in food or water. The infectious dose of norovirus required to produce infection in humans is fewer than 100 particles. HIV is one of several viruses transmitted through sexual contact and by exposure to infected blood. The variety of host cells that a virus can infect is called its host range: this is narrow for viruses specialized to infect only a few species, or broad for viruses capable of infecting many. Viral infections in animals provoke an immune response that usually eliminates the infecting virus. Immune responses can also be produced by vaccines, which confer an artificially acquired immunity to the specific viral infection. Some viruses, including those that cause HIV/AIDS, HPV infection, and viral hepatitis, evade these immune responses and result in chronic infections. Several classes of antiviral drugs have been developed. Etymology See also: Plural form of words ending in -us The English word "virus" comes from the Latin vīrus, which refers to poison and other noxious liquids. Vīrus comes from the same Indo-European root as Sanskrit viṣa, Avestan vīša, and Ancient Greek ἰός (iós), which all mean "poison". The first attested use of "virus" in English appeared in 1398 in John Trevisa's translation of Bartholomeus Anglicus's De Proprietatibus Rerum. Virulent, from Latin virulentus ('poisonous'), dates to c. 1400. A meaning of 'agent that causes infectious disease' is first recorded in 1728, long before the discovery of viruses by Dmitri Ivanovsky in 1892. The English plural is viruses (sometimes also vira), whereas the Latin word is a mass noun, which has no classically attested plural (vīra is used in Neo-Latin). The adjective viral dates to 1948. The term virion (plural virions), which dates from 1959, is also used to refer to a single viral particle that is released from the cell and is capable of infecting other cells of the same type. Origins See also: Viral evolution Viruses are found wherever there is life and have probably existed since living cells first evolved. The origin of viruses is unclear because they do not form fossils, so molecular techniques are used to infer how they arose. In addition, viral genetic material occasionally integrates into the germline of the host organisms, by which they can be passed on vertically to the offspring of the host for many generations. This provides an invaluable source of information for paleovirologists to trace back ancient viruses that existed as far back as millions of years ago. There are three main hypotheses that aim to explain the origins of viruses: Regressive hypothesis Viruses may have once been small cells that parasitised larger cells. Over time, genes not required by their parasitism were lost. The bacteria rickettsia and chlamydia are living cells that, like viruses, can reproduce only inside host cells. They lend support to this hypothesis, as their dependence on parasitism is likely to have caused the loss of genes that enabled them to survive outside a cell. This is also called the 'degeneracy hypothesis', or 'reduction hypothesis'. Cellular origin hypothesis Some viruses may have evolved from bits of DNA or RNA that "escaped" from the genes of a larger organism. The escaped DNA could have come from plasmids (pieces of naked DNA that can move between cells) or transposons (molecules of DNA that replicate and move around to different positions within the genes of the cell). Once called jumping genes, transposons are examples of mobile genetic elements and could be the origin of some viruses. They were discovered in maize by Barbara McClintock in 1950. This is sometimes called the 'vagrancy hypothesis', or the 'escape hypothesis'. Co-evolution hypothesis This is also called the 'virus-first hypothesis' and proposes that viruses may have evolved from complex molecules of protein and nucleic acid at the same time that cells first appeared on Earth and would have been dependent on cellular life for billions of years. Viroids are molecules of RNA that are not classified as viruses because they lack a protein coat. They have characteristics that are common to several viruses and are often called subviral agents. Viroids are important pathogens of plants. They do not code for proteins but interact with the host cell and use the host machinery for their replication. The hepatitis delta virus of humans has an RNA genome similar to viroids but has a protein coat derived from hepatitis B virus and cannot produce one of its own. It is, therefore, a defective virus. Although hepatitis delta virus genome may replicate independently once inside a host cell, it requires the help of hepatitis B virus to provide a protein coat so that it can be transmitted to new cells. In similar manner, the sputnik virophage is dependent on mimivirus, which infects the protozoan Acanthamoeba castellanii. These viruses, which are dependent on the presence of other virus species in the host cell, are called 'satellites' and may represent evolutionary intermediates of viroids and viruses. In the past, there were problems with all of these hypotheses: the regressive hypothesis did not explain why even the smallest of cellular parasites do not resemble viruses in any way. The escape hypothesis did not explain the complex capsids and other structures on virus particles. The virus-first hypothesis contravened the definition of viruses in that they require host cells. Viruses are now recognised as ancient and as having origins that pre-date the divergence of life into the three domains. This discovery has led modern virologists to reconsider and re-evaluate these three classical hypotheses. The evidence for an ancestral world of RNA cells and computer analysis of viral and host DNA sequences give a better understanding of the evolutionary relationships between different viruses and may help identify the ancestors of modern viruses. To date, such analyses have not proved which of these hypotheses is correct. It seems unlikely that all currently known viruses have a common ancestor, and viruses have probably arisen numerous times in the past by one or more mechanisms. Microbiology Life properties Scientific opinions differ on whether viruses are a form of life or organic structures that interact with living organisms. They have been described as "organisms at the edge of life", since they resemble organisms in that they possess genes, evolve by natural selection, and reproduce by creating multiple copies of themselves through self-assembly. Although they have genes, they do not have a cellular structure, which is often seen as the basic unit of life. Viruses do not have their own metabolism and require a host cell to make new products. They therefore cannot naturally reproduce outside a host cell—although some bacteria such as rickettsia and chlamydia are considered living organisms despite the same limitation. Accepted forms of life use cell division to reproduce, whereas viruses spontaneously assemble within cells. They differ from autonomous growth of crystals as they inherit genetic mutations while being subject to natural selection. Virus self-assembly within host cells has implications for the study of the origin of life, as it lends further credence to the hypothesis that life could have started as self-assembling organic molecules. Structure Virions of some of the most common human viruses with their relative size. The nucleic acids are not to scale.Diagram of how a virus capsid can be constructed using multiple copies of just two protein moleculesStructure of tobacco mosaic virus: RNA coiled in a helix of repeating protein sub-unitsStructure of icosahedral adenovirus. Electron micrograph with an illustration to show shapeStructure of chickenpox virus. They have a lipid envelope.Structure of an icosahedral cowpea mosaic virusBacteriophage Escherichia virus MS2 capsid. This spherical virus also has icosahedral symmetry. Viruses display a wide diversity of sizes and shapes, called 'morphologies'. In general, viruses are much smaller than bacteria and more than a thousand bacteriophage viruses would fit inside an Escherichia coli bacterium's cell. Many viruses that have been studied are spherical and have a diameter between 20 and 300 nanometres. Some filoviruses, which are filaments, have a total length of up to 1400 nm; their diameters are only about 80 nm. Most viruses cannot be seen with an optical microscope, so scanning and transmission electron microscopes are used to visualise them. To increase the contrast between viruses and the background, electron-dense "stains" are used. These are solutions of salts of heavy metals, such as tungsten, that scatter the electrons from regions covered with the stain. When virions are coated with stain (positive staining), fine detail is obscured. Negative staining overcomes this problem by staining the background only. A complete virus particle, known as a virion, consists of nucleic acid surrounded by a protective coat of protein called a capsid. These are formed from protein subunits called capsomeres. Viruses can have a lipid "envelope" derived from the host cell membrane. The capsid is made from proteins encoded by the viral genome and its shape serves as the basis for morphological distinction. Virally-coded protein subunits will self-assemble to form a capsid, in general requiring the presence of the virus genome. Complex viruses code for proteins that assist in the construction of their capsid. Proteins associated with nucleic acid are known as nucleoproteins, and the association of viral capsid proteins with viral nucleic acid is called a nucleocapsid. The capsid and entire virus structure can be mechanically (physically) probed through atomic force microscopy. In general, there are five main morphological virus types: Helical These viruses are composed of a single type of capsomere stacked around a central axis to form a helical structure, which may have a central cavity, or tube. This arrangement results in virions which can be short and highly rigid rods, or long and very flexible filaments. The genetic material (typically single-stranded RNA, but single-stranded DNA in some cases) is bound into the protein helix by interactions between the negatively charged nucleic acid and positive charges on the protein. Overall, the length of a helical capsid is related to the length of the nucleic acid contained within it, and the diameter is dependent on the size and arrangement of capsomeres. The well-studied tobacco mosaic virus and inovirus are examples of helical viruses. Icosahedral Most animal viruses are icosahedral or near-spherical with chiral icosahedral symmetry. A regular icosahedron is the optimum way of forming a closed shell from identical subunits. The minimum number of capsomeres required for each triangular face is 3, which gives 60 for the icosahedron. Many viruses, such as rotavirus, have more than 60 capsomers and appear spherical but they retain this symmetry. To achieve this, the capsomeres at the apices are surrounded by five other capsomeres and are called pentons. Capsomeres on the triangular faces are surrounded by six others and are called hexons. Hexons are in essence flat and pentons, which form the 12 vertices, are curved. The same protein may act as the subunit of both the pentamers and hexamers or they may be composed of different proteins. Prolate This is an icosahedron elongated along the fivefold axis and is a common arrangement of the heads of bacteriophages. This structure is composed of a cylinder with a cap at either end. Enveloped Some species of virus envelop themselves in a modified form of one of the cell membranes, either the outer membrane surrounding an infected host cell or internal membranes such as a nuclear membrane or endoplasmic reticulum, thus gaining an outer lipid bilayer known as a viral envelope. This membrane is studded with proteins coded for by the viral genome and host genome; the lipid membrane itself and any carbohydrates present originate entirely from the host. Influenza virus, HIV (which causes AIDS), and severe acute respiratory syndrome coronavirus 2 (which causes COVID-19) use this strategy. Most enveloped viruses are dependent on the envelope for their infectivity. Complex These viruses possess a capsid that is neither purely helical nor purely icosahedral, and that may possess extra structures such as protein tails or a complex outer wall. Some bacteriophages, such as Enterobacteria phage T4, have a complex structure consisting of an icosahedral head bound to a helical tail, which may have a hexagonal base plate with protruding protein tail fibres. This tail structure acts like a molecular syringe, attaching to the bacterial host and then injecting the viral genome into the cell. The poxviruses are large, complex viruses that have an unusual morphology. The viral genome is associated with proteins within a central disc structure known as a nucleoid. The nucleoid is surrounded by a membrane and two lateral bodies of unknown function. The virus has an outer envelope with a thick layer of protein studded over its surface. The whole virion is slightly pleomorphic, ranging from ovoid to brick-shaped. Giant viruses Main article: Giant virus Mimivirus is one of the largest characterised viruses, with a capsid diameter of 400 nm. Protein filaments measuring 100 nm project from the surface. The capsid appears hexagonal under an electron microscope, therefore the capsid is probably icosahedral. In 2011, researchers discovered the largest then known virus in samples of water collected from the ocean floor off the coast of Las Cruces, Chile. Provisionally named Megavirus chilensis, it can be seen with a basic optical microscope. In 2013, the Pandoravirus genus was discovered in Chile and Australia, and has genomes about twice as large as Megavirus and Mimivirus. All giant viruses have dsDNA genomes and they are classified into several families: Mimiviridae, Pithoviridae, Pandoraviridae, Phycodnaviridae, and the Mollivirus genus. Some viruses that infect Archaea have complex structures unrelated to any other form of virus, with a wide variety of unusual shapes, ranging from spindle-shaped structures to viruses that resemble hooked rods, teardrops or even bottles. Other archaeal viruses resemble the tailed bacteriophages, and can have multiple tail structures. Genome Genomic diversity among viruses Property Parameters Nucleic acid DNA RNA Both DNA and RNA (at different stages in the life cycle) Shape Linear Circular Segmented Strandedness Single-stranded (ss) Double-stranded (ds) Double-stranded with regions of single-strandedness Sense Positive sense (+) Negative sense (−) Ambisense (+/−) An enormous variety of genomic structures can be seen among viral species; as a group, they contain more structural genomic diversity than plants, animals, archaea, or bacteria. There are millions of different types of viruses, although fewer than 7,000 types have been described in detail. As of January 2021, the NCBI Virus genome database has more than 193,000 complete genome sequences, but there are doubtlessly many more to be discovered. A virus has either a DNA or an RNA genome and is called a DNA virus or an RNA virus, respectively. The vast majority of viruses have RNA genomes. Plant viruses tend to have single-stranded RNA genomes and bacteriophages tend to have double-stranded DNA genomes. Viral genomes are circular, as in the polyomaviruses, or linear, as in the adenoviruses. The type of nucleic acid is irrelevant to the shape of the genome. Among RNA viruses and certain DNA viruses, the genome is often divided into separate parts, in which case it is called segmented. For RNA viruses, each segment often codes for only one protein and they are usually found together in one capsid. All segments are not required to be in the same virion for the virus to be infectious, as demonstrated by brome mosaic virus and several other plant viruses. A viral genome, irrespective of nucleic acid type, is almost always either single-stranded (ss) or double-stranded (ds). Single-stranded genomes consist of an unpaired nucleic acid, analogous to one-half of a ladder split down the middle. Double-stranded genomes consist of two complementary paired nucleic acids, analogous to a ladder. The virus particles of some virus families, such as those belonging to the Hepadnaviridae, contain a genome that is partially double-stranded and partially single-stranded. For most viruses with RNA genomes and some with single-stranded DNA (ssDNA) genomes, the single strands are said to be either positive-sense (called the 'plus-strand') or negative-sense (called the 'minus-strand'), depending on if they are complementary to the viral messenger RNA (mRNA). Positive-sense viral RNA is in the same sense as viral mRNA and thus at least a part of it can be immediately translated by the host cell. Negative-sense viral RNA is complementary to mRNA and thus must be converted to positive-sense RNA by an RNA-dependent RNA polymerase before translation. DNA nomenclature for viruses with genomic ssDNA is similar to RNA nomenclature, in that positive-strand viral ssDNA is identical in sequence to the viral mRNA and is thus a coding strand, while negative-sense viral ssDNA is complementary to the viral mRNA and is thus a template strand. Several types of ssDNA and ssRNA viruses have genomes that are ambisense in that transcription can occur off both strands in a double-stranded replicative intermediate. Examples include geminiviruses, which are ssDNA plant viruses and arenaviruses, which are ssRNA viruses of animals. Genome size Genome size varies greatly between species. The smallest—the ssDNA circoviruses, family Circoviridae—code for only two proteins and have a genome size of only two kilobases; the largest—the pandoraviruses—have genome sizes of around two megabases which code for about 2500 proteins. Virus genes rarely have introns and often are arranged in the genome so that they overlap. In general, RNA viruses have smaller genome sizes than DNA viruses because of a higher error-rate when replicating, and have a maximum upper size limit. Beyond this, errors when replicating render the virus useless or uncompetitive. To compensate, RNA viruses often have segmented genomes—the genome is split into smaller molecules—thus reducing the chance that an error in a single-component genome will incapacitate the entire genome. In contrast, DNA viruses generally have larger genomes because of the high fidelity of their replication enzymes. Single-strand DNA viruses are an exception to this rule, as mutation rates for these genomes can approach the extreme of the ssRNA virus case. Genetic mutation and recombination Antigenic shift, or reassortment, can result in novel and highly pathogenic strains of human flu Viruses undergo genetic change by several mechanisms. These include a process called antigenic drift where individual bases in the DNA or RNA mutate to other bases. Most of these point mutations are "silent"—they do not change the protein that the gene encodes—but others can confer evolutionary advantages such as resistance to antiviral drugs. Antigenic shift occurs when there is a major change in the genome of the virus. This can be a result of recombination or reassortment. When this happens with influenza viruses, pandemics might result. RNA viruses often exist as quasispecies or swarms of viruses of the same species but with slightly different genome nucleoside sequences. Such quasispecies are a prime target for natural selection. Segmented genomes confer evolutionary advantages; different strains of a virus with a segmented genome can shuffle and combine genes and produce progeny viruses (or offspring) that have unique characteristics. This is called reassortment or 'viral sex'. Genetic recombination is a process by which a strand of DNA (or RNA) is broken and then joined to the end of a different DNA (or RNA) molecule. This can occur when viruses infect cells simultaneously and studies of viral evolution have shown that recombination has been rampant in the species studied. Recombination is common to both RNA and DNA viruses. Coronaviruses have a single-strand positive-sense RNA genome. Replication of the genome is catalyzed by an RNA-dependent RNA polymerase. The mechanism of recombination used by coronaviruses likely involves template switching by the polymerase during genome replication. This process appears to be an adaptation for coping with genome damage. Replication cycle A typical virus replication cycle Some bacteriophages inject their genomes into bacterial cells (not to scale) Viral populations do not grow through cell division, because they are acellular. Instead, they use the machinery and metabolism of a host cell to produce multiple copies of themselves, and they assemble in the cell. When infected, the host cell is forced to rapidly produce thousands of copies of the original virus. Their life cycle differs greatly between species, but there are six basic stages in their life cycle: Attachment is a specific binding between viral capsid proteins and specific receptors on the host cellular surface. This specificity determines the host range and type of host cell of a virus. For example, HIV infects a limited range of human leucocytes. This is because its surface protein, gp120, specifically interacts with the CD4 molecule—a chemokine receptor—which is most commonly found on the surface of CD4+ T-Cells. This mechanism has evolved to favour those viruses that infect only cells in which they are capable of replication. Attachment to the receptor can induce the viral envelope protein to undergo changes that result in the fusion of viral and cellular membranes, or changes of non-enveloped virus surface proteins that allow the virus to enter. Penetration or viral entry follows attachment: Virions enter the host cell through receptor-mediated endocytosis or membrane fusion. The infection of plant and fungal cells is different from that of animal cells. Plants have a rigid cell wall made of cellulose, and fungi one of chitin, so most viruses can get inside these cells only after trauma to the cell wall. Nearly all plant viruses (such as tobacco mosaic virus) can also move directly from cell to cell, in the form of single-stranded nucleoprotein complexes, through pores called plasmodesmata. Bacteria, like plants, have strong cell walls that a virus must breach to infect the cell. Given that bacterial cell walls are much thinner than plant cell walls due to their much smaller size, some viruses have evolved mechanisms that inject their genome into the bacterial cell across the cell wall, while the viral capsid remains outside. Uncoating is a process in which the viral capsid is removed: This may be by degradation by viral enzymes or host enzymes or by simple dissociation; the end-result is the releasing of the viral genomic nucleic acid. Replication of viruses involves primarily multiplication of the genome. Replication involves the synthesis of viral messenger RNA (mRNA) from "early" genes (with exceptions for positive-sense RNA viruses), viral protein synthesis, possible assembly of viral proteins, then viral genome replication mediated by early or regulatory protein expression. This may be followed, for complex viruses with larger genomes, by one or more further rounds of mRNA synthesis: "late" gene expression is, in general, of structural or virion proteins. Assembly – Following the structure-mediated self-assembly of the virus particles, some modification of the proteins often occurs. In viruses such as HIV, this modification (sometimes called maturation) occurs after the virus has been released from the host cell. Release – Viruses can be released from the host cell by lysis, a process that kills the cell by bursting its membrane and cell wall if present: this is a feature of many bacterial and some animal viruses. Some viruses undergo a lysogenic cycle where the viral genome is incorporated by genetic recombination into a specific place in the host's chromosome. The viral genome is then known as a "provirus" or, in the case of bacteriophages a "prophage". Whenever the host divides, the viral genome is also replicated. The viral genome is mostly silent within the host. At some point, the provirus or prophage may give rise to the active virus, which may lyse the host cells. Enveloped viruses (e.g., HIV) typically are released from the host cell by budding. During this process, the virus acquires its envelope, which is a modified piece of the host's plasma or other, internal membrane. Genome replication The genetic material within virus particles, and the method by which the material is replicated, varies considerably between different types of viruses. DNA viruses The genome replication of most DNA viruses takes place in the cell's nucleus. If the cell has the appropriate receptor on its surface, these viruses enter the cell either by direct fusion with the cell membrane (e.g., herpesviruses) or—more usually—by receptor-mediated endocytosis. Most DNA viruses are entirely dependent on the host cell's DNA and RNA synthesising machinery and RNA processing machinery. Viruses with larger genomes may encode much of this machinery themselves. In eukaryotes, the viral genome must cross the cell's nuclear membrane to access this machinery, while in bacteria it need only enter the cell. RNA viruses Replication of RNA viruses usually takes place in the cytoplasm. RNA viruses can be placed into four different groups depending on their modes of replication. The polarity (whether or not it can be used directly by ribosomes to make proteins) of single-stranded RNA viruses largely determines the replicative mechanism; the other major criterion is whether the genetic material is single-stranded or double-stranded. All RNA viruses use their own RNA replicase enzymes to create copies of their genomes. Reverse transcribing viruses Reverse transcribing viruses have ssRNA (Retroviridae, Metaviridae, Pseudoviridae) or dsDNA (Caulimoviridae, and Hepadnaviridae) in their particles. Reverse transcribing viruses with RNA genomes (retroviruses) use a DNA intermediate to replicate, whereas those with DNA genomes (pararetroviruses) use an RNA intermediate during genome replication. Both types use a reverse transcriptase, or RNA-dependent DNA polymerase enzyme, to carry out the nucleic acid conversion. Retroviruses integrate the DNA produced by reverse transcription into the host genome as a provirus as a part of the replication process; pararetroviruses do not, although integrated genome copies of especially plant pararetroviruses can give rise to infectious virus. They are susceptible to antiviral drugs that inhibit the reverse transcriptase enzyme, e.g. zidovudine and lamivudine. An example of the first type is HIV, which is a retrovirus. Examples of the second type are the Hepadnaviridae, which includes Hepatitis B virus. Cytopathic effects on the host cell The range of structural and biochemical effects that viruses have on the host cell is extensive. These are called 'cytopathic effects'. Most virus infections eventually result in the death of the host cell. The causes of death include cell lysis, alterations to the cell's surface membrane and apoptosis. Often cell death is caused by cessation of its normal activities because of suppression by virus-specific proteins, not all of which are components of the virus particle. The distinction between cytopathic and harmless is gradual. Some viruses, such as Epstein–Barr virus, can cause cells to proliferate without causing malignancy, while others, such as papillomaviruses, are established causes of cancer. Dormant and latent infections Some viruses cause no apparent changes to the infected cell. Cells in which the virus is latent and inactive show few signs of infection and often function normally. This causes persistent infections and the virus is often dormant for many months or years. This is often the case with herpes viruses. Host range Viruses are by far the most abundant biological entities on Earth and they outnumber all the others put together. They infect all types of cellular life including animals, plants, bacteria and fungi. Different types of viruses can infect only a limited range of hosts and many are species-specific. Some, such as smallpox virus for example, can infect only one species—in this case humans, and are said to have a narrow host range. Other viruses, such as rabies virus, can infect different species of mammals and are said to have a broad range. The viruses that infect plants are harmless to animals, and most viruses that infect other animals are harmless to humans. The host range of some bacteriophages is limited to a single strain of bacteria and they can be used to trace the source of outbreaks of infections by a method called phage typing. The complete set of viruses in an organism or habitat is called the virome; for example, all human viruses constitute the human virome. Novel viruses A novel virus is one that has not previously been recorded. It can be a virus that is isolated from its natural reservoir or isolated as the result of spread to an animal or human host where the virus had not been identified before. It can be an emergent virus, one that represents a new virus, but it can also be an extant virus that has not been previously identified. The SARS-CoV-2 coronavirus that caused the COVID-19 pandemic is an example of a novel virus. Classification Main article: Virus classification Classification seeks to describe the diversity of viruses by naming and grouping them on the basis of similarities. In 1962, André Lwoff, Robert Horne, and Paul Tournier were the first to develop a means of virus classification, based on the Linnaean hierarchical system. This system based classification on phylum, class, order, family, genus, and species. Viruses were grouped according to their shared properties (not those of their hosts) and the type of nucleic acid forming their genomes. In 1966, the International Committee on Taxonomy of Viruses (ICTV) was formed. The system proposed by Lwoff, Horne and Tournier was initially not accepted by the ICTV because the small genome size of viruses and their high rate of mutation made it difficult to determine their ancestry beyond order. As such, the Baltimore classification system has come to be used to supplement the more traditional hierarchy. Starting in 2018, the ICTV began to acknowledge deeper evolutionary relationships between viruses that have been discovered over time and adopted a 15-rank classification system ranging from realm to species. Additionally, some species within the same genus are grouped into a genogroup. ICTV classification The ICTV developed the current classification system and wrote guidelines that put a greater weight on certain virus properties to maintain family uniformity. A unified taxonomy (a universal system for classifying viruses) has been established. Only a small part of the total diversity of viruses has been studied. As of 2022, 6 realms, 10 kingdoms, 17 phyla, 2 subphyla, 40 classes, 72 orders, 8 suborders, 264 families, 182 subfamilies, 2,818 genera, 84 subgenera, and 11,273 species of viruses have been defined by the ICTV. The general taxonomic structure of taxon ranges and the suffixes used in taxonomic names are shown hereafter. As of 2022, the ranks of subrealm, subkingdom, and subclass are unused, whereas all other ranks are in use. Realm (-viria) Subrealm (-vira) Kingdom (-virae) Subkingdom (-virites) Phylum (-viricota) Subphylum (-viricotina) Class (-viricetes) Subclass (-viricetidae) Order (-virales) Suborder (-virineae) Family (-viridae) Subfamily (-virinae) Genus (-virus) Subgenus (-virus) Species Baltimore classification Main article: Baltimore classification The Baltimore Classification of viruses is based on the method of viral mRNA synthesis The Nobel Prize-winning biologist David Baltimore devised the Baltimore classification system. The ICTV classification system is used in conjunction with the Baltimore classification system in modern virus classification. The Baltimore classification of viruses is based on the mechanism of mRNA production. Viruses must generate mRNAs from their genomes to produce proteins and replicate themselves, but different mechanisms are used to achieve this in each virus family. Viral genomes may be single-stranded (ss) or double-stranded (ds), RNA or DNA, and may or may not use reverse transcriptase (RT). In addition, ssRNA viruses may be either sense (+) or antisense (−). This classification places viruses into seven groups: I: dsDNA viruses (e.g. Adenoviruses, Herpesviruses, Poxviruses) II: ssDNA viruses (+ strand or "sense") DNA (e.g. Parvoviruses) III: dsRNA viruses (e.g. Reoviruses) IV:(+)ssRNA viruses (+ strand or sense) RNA (e.g. Coronaviruses, Picornaviruses, Togaviruses) V: (−)ssRNA viruses (− strand or antisense) RNA (e.g. Orthomyxoviruses, Rhabdoviruses) VI: ssRNA-RT viruses (+ strand or sense) RNA with DNA intermediate in life-cycle (e.g. Retroviruses) VII: dsDNA-RT viruses DNA with RNA intermediate in life-cycle (e.g. Hepadnaviruses) Role in human disease See also: Viral disease Overview of the main types of viral infection and the most notable species involved Examples of common human diseases caused by viruses include the common cold, influenza, chickenpox, and cold sores. Many serious diseases such as rabies, Ebola virus disease, AIDS (HIV), avian influenza, and SARS are caused by viruses. The relative ability of viruses to cause disease is described in terms of virulence. Other diseases are under investigation to discover if they have a virus as the causative agent, such as the possible connection between human herpesvirus 6 (HHV6) and neurological diseases such as multiple sclerosis and chronic fatigue syndrome. There is controversy over whether the bornavirus, previously thought to cause neurological diseases in horses, could be responsible for psychiatric illnesses in humans. Viruses have different mechanisms by which they produce disease in an organism, which depends largely on the viral species. Mechanisms at the cellular level primarily include cell lysis, the breaking open and subsequent death of the cell. In multicellular organisms, if enough cells die, the whole organism will start to suffer the effects. Although viruses cause disruption of healthy homeostasis, resulting in disease, they may exist relatively harmlessly within an organism. An example would include the ability of the herpes simplex virus, which causes cold sores, to remain in a dormant state within the human body. This is called latency and is a characteristic of the herpes viruses, including Epstein–Barr virus, which causes glandular fever, and varicella zoster virus, which causes chickenpox and shingles. Most people have been infected with at least one of these types of herpes virus. These latent viruses might sometimes be beneficial, as the presence of the virus can increase immunity against bacterial pathogens, such as Yersinia pestis. Some viruses can cause lifelong or chronic infections, where the viruses continue to replicate in the body despite the host's defence mechanisms. This is common in hepatitis B virus and hepatitis C virus infections. People chronically infected are known as carriers, as they serve as reservoirs of infectious virus. In populations with a high proportion of carriers, the disease is said to be endemic. Epidemiology Viral epidemiology is the branch of medical science that deals with the transmission and control of virus infections in humans. Transmission of viruses can be vertical, which means from mother to child, or horizontal, which means from person to person. Examples of vertical transmission include hepatitis B virus and HIV, where the baby is born already infected with the virus. Another, more rare, example is the varicella zoster virus, which, although causing relatively mild infections in children and adults, can be fatal to the foetus and newborn baby. Horizontal transmission is the most common mechanism of spread of viruses in populations. Horizontal transmission can occur when body fluids are exchanged during sexual activity, by exchange of saliva or when contaminated food or water is ingested. It can also occur when aerosols containing viruses are inhaled or by insect vectors such as when infected mosquitoes penetrate the skin of a host. Most types of viruses are restricted to just one or two of these mechanisms and they are referred to as "respiratory viruses" or "enteric viruses" and so forth. The rate or speed of transmission of viral infections depends on factors that include population density, the number of susceptible individuals, (i.e., those not immune), the quality of healthcare and the weather. Epidemiology is used to break the chain of infection in populations during outbreaks of viral diseases. Control measures are used that are based on knowledge of how the virus is transmitted. It is important to find the source, or sources, of the outbreak and to identify the virus. Once the virus has been identified, the chain of transmission can sometimes be broken by vaccines. When vaccines are not available, sanitation and disinfection can be effective. Often, infected people are isolated from the rest of the community, and those that have been exposed to the virus are placed in quarantine. To control the outbreak of foot-and-mouth disease in cattle in Britain in 2001, thousands of cattle were slaughtered. Most viral infections of humans and other animals have incubation periods during which the infection causes no signs or symptoms. Incubation periods for viral diseases range from a few days to weeks, but are known for most infections. Somewhat overlapping, but mainly following the incubation period, there is a period of communicability—a time when an infected individual or animal is contagious and can infect another person or animal. This, too, is known for many viral infections, and knowledge of the length of both periods is important in the control of outbreaks. When outbreaks cause an unusually high proportion of cases in a population, community, or region, they are called epidemics. If outbreaks spread worldwide, they are called pandemics. Epidemics and pandemics See also: 1918 flu pandemic, AIDS, Ebola virus disease, and COVID-19 pandemic Further information: List of epidemics Transmission electron microscope image of a recreated 1918 influenza virus A pandemic is a worldwide epidemic. The 1918 flu pandemic, which lasted until 1919, was a category 5 influenza pandemic caused by an unusually severe and deadly influenza A virus. The victims were often healthy young adults, in contrast to most influenza outbreaks, which predominantly affect juvenile, elderly, or otherwise-weakened patients. Older estimates say it killed 40–50 million people, while more recent research suggests that it may have killed as many as 100 million people, or 5% of the world's population in 1918. Although viral pandemics are rare events, HIV—which evolved from viruses found in monkeys and chimpanzees—has been pandemic since at least the 1980s. During the 20th century there were four pandemics caused by influenza virus and those that occurred in 1918, 1957 and 1968 were severe. Most researchers believe that HIV originated in sub-Saharan Africa during the 20th century; it is now a pandemic, with an estimated 37.9 million people now living with the disease worldwide. There were about 770,000 deaths from AIDS in 2018. The Joint United Nations Programme on HIV/AIDS (UNAIDS) and the World Health Organization (WHO) estimate that AIDS has killed more than 25 million people since it was first recognised on 5 June 1981, making it one of the most destructive epidemics in recorded history. In 2007 there were 2.7 million new HIV infections and 2 million HIV-related deaths. Ebola (top) and Marburg viruses (bottom) Several highly lethal viral pathogens are members of the Filoviridae. Filoviruses are filament-like viruses that cause viral hemorrhagic fever, and include ebolaviruses and marburgviruses. Marburg virus, first discovered in 1967, attracted widespread press attention in April 2005 for an outbreak in Angola. Ebola virus disease has also caused intermittent outbreaks with high mortality rates since 1976 when it was first identified. The worst and most recent one is the 2013–2016 West Africa epidemic. Except for smallpox, most pandemics are caused by newly evolved viruses. These "emergent" viruses are usually mutants of less harmful viruses that have circulated previously either in humans or other animals. Severe acute respiratory syndrome (SARS) and Middle East respiratory syndrome (MERS) are caused by new types of coronaviruses. Other coronaviruses are known to cause mild infections in humans, so the virulence and rapid spread of SARS infections—that by July 2003 had caused around 8,000 cases and 800 deaths—was unexpected and most countries were not prepared. A related coronavirus, severe acute respiratory syndrome coronavirus 2 (SARS-Cov-2), thought to have originated in bats, emerged in Wuhan, China in November 2019 and spread rapidly around the world. Infections with the virus caused the COVID-19 pandemic that started in 2020. Unprecedented restrictions in peacetime were placed on international travel, and curfews were imposed in several major cities worldwide in response to the pandemic. Cancer Further information: Oncovirus Viruses are an established cause of cancer in humans and other species. Viral cancers occur only in a minority of infected persons (or animals). Cancer viruses come from a range of virus families, including both RNA and DNA viruses, and so there is no single type of "oncovirus" (an obsolete term originally used for acutely transforming retroviruses). The development of cancer is determined by a variety of factors such as host immunity and mutations in the host. Viruses accepted to cause human cancers include some genotypes of human papillomavirus, hepatitis B virus, hepatitis C virus, Epstein–Barr virus, Kaposi's sarcoma-associated herpesvirus and human T-lymphotropic virus. The most recently discovered human cancer virus is a polyomavirus (Merkel cell polyomavirus) that causes most cases of a rare form of skin cancer called Merkel cell carcinoma. Hepatitis viruses can develop into a chronic viral infection that leads to liver cancer. Infection by human T-lymphotropic virus can lead to tropical spastic paraparesis and adult T-cell leukaemia. Human papillomaviruses are an established cause of cancers of cervix, skin, anus, and penis. Within the Herpesviridae, Kaposi's sarcoma-associated herpesvirus causes Kaposi's sarcoma and body-cavity lymphoma, and Epstein–Barr virus causes Burkitt's lymphoma, Hodgkin's lymphoma, B lymphoproliferative disorder, and nasopharyngeal carcinoma. Merkel cell polyomavirus closely related to SV40 and mouse polyomaviruses that have been used as animal models for cancer viruses for over 50 years. Host defence mechanisms See also: Immune system The body's first line of defence against viruses is the innate immune system. This comprises cells and other mechanisms that defend the host from infection in a non-specific manner. This means that the cells of the innate system recognise, and respond to, pathogens in a generic way, but, unlike the adaptive immune system, it does not confer long-lasting or protective immunity to the host. RNA interference is an important innate defence against viruses. Many viruses have a replication strategy that involves double-stranded RNA (dsRNA). When such a virus infects a cell, it releases its RNA molecule or molecules, which immediately bind to a protein complex called a dicer that cuts the RNA into smaller pieces. A biochemical pathway—the RISC complex—is activated, which ensures cell survival by degrading the viral mRNA. Rotaviruses have evolved to avoid this defence mechanism by not uncoating fully inside the cell, and releasing newly produced mRNA through pores in the particle's inner capsid. Their genomic dsRNA remains protected inside the core of the virion. When the adaptive immune system of a vertebrate encounters a virus, it produces specific antibodies that bind to the virus and often render it non-infectious. This is called humoral immunity. Two types of antibodies are important. The first, called IgM, is highly effective at neutralising viruses but is produced by the cells of the immune system only for a few weeks. The second, called IgG, is produced indefinitely. The presence of IgM in the blood of the host is used to test for acute infection, whereas IgG indicates an infection sometime in the past. IgG antibody is measured when tests for immunity are carried out. Antibodies can continue to be an effective defence mechanism even after viruses have managed to gain entry to the host cell. A protein that is in cells, called TRIM21, can attach to the antibodies on the surface of the virus particle. This primes the subsequent destruction of the virus by the enzymes of the cell's proteosome system. Two rotaviruses: the one on the right is coated with antibodies that prevent its attachment to cells and infecting them. A second defence of vertebrates against viruses is called cell-mediated immunity and involves immune cells known as T cells. The body's cells constantly display short fragments of their proteins on the cell's surface, and, if a T cell recognises a suspicious viral fragment there, the host cell is destroyed by 'killer T' cells and the virus-specific T-cells proliferate. Cells such as the macrophage are specialists at this antigen presentation. The production of interferon is an important host defence mechanism. This is a hormone produced by the body when viruses are present. Its role in immunity is complex; it eventually stops the viruses from reproducing by killing the infected cell and its close neighbours. Not all virus infections produce a protective immune response in this way. HIV evades the immune system by constantly changing the amino acid sequence of the proteins on the surface of the virion. This is known as "escape mutation" as the viral epitopes escape recognition by the host immune response. These persistent viruses evade immune control by sequestration, blockade of antigen presentation, cytokine resistance, evasion of natural killer cell activities, escape from apoptosis, and antigenic shift. Other viruses, called 'neurotropic viruses', are disseminated by neural spread where the immune system may be unable to reach them due to immune privilege. Prevention and treatment Because viruses use vital metabolic pathways within host cells to replicate, they are difficult to eliminate without using drugs that cause toxic effects to host cells in general. The most effective medical approaches to viral diseases are vaccinations to provide immunity to infection, and antiviral drugs that selectively interfere with viral replication. Vaccines Further information: Vaccination Vaccination is a cheap and effective way of preventing infections by viruses. Vaccines were used to prevent viral infections long before the discovery of the actual viruses. Their use has resulted in a dramatic decline in morbidity (illness) and mortality (death) associated with viral infections such as polio, measles, mumps and rubella. Smallpox infections have been eradicated. Vaccines are available to prevent over thirteen viral infections of humans, and more are used to prevent viral infections of animals. Vaccines can consist of live-attenuated or killed viruses, viral proteins (antigens), or RNA. Live vaccines contain weakened forms of the virus, which do not cause the disease but, nonetheless, confer immunity. Such viruses are called attenuated. Live vaccines can be dangerous when given to people with a weak immunity (who are described as immunocompromised), because in these people, the weakened virus can cause the original disease. Biotechnology and genetic engineering techniques are used to produce subunit vaccines. These vaccines use only the capsid proteins of the virus. Hepatitis B vaccine is an example of this type of vaccine. Subunit vaccines are safe for immunocompromised patients because they cannot cause the disease. The yellow fever virus vaccine, a live-attenuated strain called 17D, is probably the safest and most effective vaccine ever generated. Antiviral drugs Further information: Antiviral drug The structure of the DNA base guanosine and the antiviral drug acyclovir Antiviral drugs are often nucleoside analogues (fake DNA building-blocks), which viruses mistakenly incorporate into their genomes during replication. The life-cycle of the virus is then halted because the newly synthesised DNA is inactive. This is because these analogues lack the hydroxyl groups, which, along with phosphorus atoms, link together to form the strong "backbone" of the DNA molecule. This is called DNA chain termination. Examples of nucleoside analogues are aciclovir for Herpes simplex virus infections and lamivudine for HIV and hepatitis B virus infections. Aciclovir is one of the oldest and most frequently prescribed antiviral drugs. Other antiviral drugs in use target different stages of the viral life cycle. HIV is dependent on a proteolytic enzyme called the HIV-1 protease for it to become fully infectious. There is a large class of drugs called protease inhibitors that inactivate this enzyme. There are around thirteen classes of antiviral drugs each targeting different viruses or stages of viral replication. Hepatitis C is caused by an RNA virus. In 80% of people infected, the disease is chronic, and without treatment, they are infected for the remainder of their lives. There are effective treatments that use direct-acting antivirals. The treatment of chronic carriers of the hepatitis B virus has also been developed by using similar strategies that include lamivudine and other anti-viral drugs. Infection in other species Viruses infect all cellular life and, although viruses occur universally, each cellular species has its own specific range that often infects only that species. Some viruses, called satellites, can replicate only within cells that have already been infected by another virus. Animal viruses Main articles: Animal virus and Veterinary virology Viruses are important pathogens of livestock. Diseases such as foot-and-mouth disease and bluetongue are caused by viruses. Companion animals such as cats, dogs, and horses, if not vaccinated, are susceptible to serious viral infections. Canine parvovirus is caused by a small DNA virus and infections are often fatal in pups. Like all invertebrates, the honey bee is susceptible to many viral infections. Most viruses co-exist harmlessly in their host and cause no signs or symptoms of disease. Plant viruses Main article: Plant virus Peppers infected by mild mottle virus There are many types of plant viruses, but often they cause only a loss of yield, and it is not economically viable to try to control them. Plant viruses are often spread from plant to plant by organisms, known as vectors. These are usually insects, but some fungi, nematode worms, single-celled organisms, and parasitic plants are vectors. When control of plant virus infections is considered economical, for perennial fruits, for example, efforts are concentrated on killing the vectors and removing alternate hosts such as weeds. Plant viruses cannot infect humans and other animals because they can reproduce only in living plant cells. Originally from Peru, the potato has become a staple crop worldwide. The potato virus Y causes disease in potatoes and related species including tomatoes and peppers. In the 1980s, this virus acquired economical importance when it proved difficult to control in seed potato crops. Transmitted by aphids, this virus can reduce crop yields by up to 80 per cent, causing significant losses to potato yields. Plants have elaborate and effective defence mechanisms against viruses. One of the most effective is the presence of so-called resistance (R) genes. Each R gene confers resistance to a particular virus by triggering localised areas of cell death around the infected cell, which can often be seen with the unaided eye as large spots. This stops the infection from spreading. RNA interference is also an effective defence in plants. When they are infected, plants often produce natural disinfectants that kill viruses, such as salicylic acid, nitric oxide, and reactive oxygen molecules. Plant virus particles or virus-like particles (VLPs) have applications in both biotechnology and nanotechnology. The capsids of most plant viruses are simple and robust structures and can be produced in large quantities either by the infection of plants or by expression in a variety of heterologous systems. Plant virus particles can be modified genetically and chemically to encapsulate foreign material and can be incorporated into supramolecular structures for use in biotechnology. Bacterial viruses Main article: Bacteriophage Transmission electron micrograph of multiple bacteriophages attached to a bacterial cell wall Bacteriophages are a common and diverse group of viruses and are the most abundant biological entity in aquatic environments—there are up to ten times more of these viruses in the oceans than there are bacteria, reaching levels of 250,000,000 bacteriophages per millilitre of seawater. These viruses infect specific bacteria by binding to surface receptor molecules and then entering the cell. Within a short amount of time, in some cases, just minutes, bacterial polymerase starts translating viral mRNA into protein. These proteins go on to become either new virions within the cell, helper proteins, which help assembly of new virions, or proteins involved in cell lysis. Viral enzymes aid in the breakdown of the cell membrane, and, in the case of the T4 phage, in just over twenty minutes after injection over three hundred phages could be released. The major way bacteria defend themselves from bacteriophages is by producing enzymes that destroy foreign DNA. These enzymes, called restriction endonucleases, cut up the viral DNA that bacteriophages inject into bacterial cells. Bacteria also contain a system that uses CRISPR sequences to retain fragments of the genomes of viruses that the bacteria have come into contact with in the past, which allows them to block the virus's replication through a form of RNA interference. This genetic system provides bacteria with acquired immunity to infection. Some bacteriophages are called "temperate" because they cause latent infections and do not immediately destroy their host cells. Instead, their DNA is incorporated with the host cell's as a prophage. These latent infections become productive when the prophage DNA is activated by stimuli such as changes in the environment. The intestines of animals, including humans, contain temperate bacteriophages, which are activated by various stimuli including changes in diet and antibiotics. Although first observed in bacteriophages, many other viruses are known to form proviruses including HIV. Archaeal viruses Main article: Archaeal virus Some viruses replicate within archaea: these are DNA viruses with unusual and sometimes unique shapes. These viruses have been studied in most detail in the thermophilic archaea, particularly the orders Sulfolobales and Thermoproteales. Defences against these viruses involve RNA interference from repetitive DNA sequences within archaean genomes that are related to the genes of the viruses. Most archaea have CRISPR–Cas systems as an adaptive defence against viruses. These enable archaea to retain sections of viral DNA, which are then used to target and eliminate subsequent infections by the virus using a process similar to RNA interference. Role in aquatic ecosystems Main article: Marine virus Viruses are the most abundant biological entity in aquatic environments. There are about ten million of them in a teaspoon of seawater. Most of these viruses are bacteriophages infecting heterotrophic bacteria and cyanophages infecting cyanobacteria and they are essential to the regulation of saltwater and freshwater ecosystems. Bacteriophages are harmless to plants and animals, and are essential to the regulation of marine and freshwater ecosystems are important mortality agents of phytoplankton, the base of the foodchain in aquatic environments. They infect and destroy bacteria in aquatic microbial communities, and are one of the most important mechanisms of recycling carbon and nutrient cycling in marine environments. The organic molecules released from the dead bacterial cells stimulate fresh bacterial and algal growth, in a process known as the viral shunt. In particular, lysis of bacteria by viruses has been shown to enhance nitrogen cycling and stimulate phytoplankton growth. Viral activity may also affect the biological pump, the process whereby carbon is sequestered in the deep ocean. Microorganisms constitute more than 90% of the biomass in the sea. It is estimated that viruses kill approximately 20% of this biomass each day and that there are 10 to 15 times as many viruses in the oceans as there are bacteria and archaea. Viruses are also major agents responsible for the destruction of phytoplankton including harmful algal blooms, The number of viruses in the oceans decreases further offshore and deeper into the water, where there are fewer host organisms. In January 2018, scientists reported that 800 million viruses, mainly of marine origin, are deposited daily from the Earth's atmosphere onto every square meter of the planet's surface, as the result of a global atmospheric stream of viruses, circulating above the weather system but below the altitude of usual airline travel, distributing viruses around the planet. Like any organism, marine mammals are susceptible to viral infections. In 1988 and 2002, thousands of harbour seals were killed in Europe by phocine distemper virus. Many other viruses, including caliciviruses, herpesviruses, adenoviruses and parvoviruses, circulate in marine mammal populations. In December 2022, scientists reported the first observation of virovory via an experiment on pond water containing chlorovirus, which commonly infects green algae in freshwater environments. When all other microbial food sources were removed from the water, the ciliate Halteria was observed to have increased in number due to the active consumption of chlorovirus as a food source instead of its typical bacterivore diet. Role in evolution Main article: Horizontal gene transfer Viruses are an important natural means of transferring genes between different species, which increases genetic diversity and drives evolution. It is thought that viruses played a central role in early evolution, before the diversification of the last universal common ancestor into bacteria, archaea and eukaryotes. Viruses are still one of the largest reservoirs of unexplored genetic diversity on Earth. Applications Life sciences and medicine Scientist studying the H5N1 influenza virus Viruses are important to the study of molecular and cell biology as they provide simple systems that can be used to manipulate and investigate the functions of cells. The study and use of viruses have provided valuable information about aspects of cell biology. For example, viruses have been useful in the study of genetics and helped our understanding of the basic mechanisms of molecular genetics, such as DNA replication, transcription, RNA processing, translation, protein transport, and immunology. Geneticists often use viruses as vectors to introduce genes into cells that they are studying. This is useful for making the cell produce a foreign substance, or to study the effect of introducing a new gene into the genome. Similarly, virotherapy uses viruses as vectors to treat various diseases, as they can specifically target cells and DNA. It shows promising use in the treatment of cancer and in gene therapy. Eastern European scientists have used phage therapy as an alternative to antibiotics for some time, and interest in this approach is increasing, because of the high level of antibiotic resistance now found in some pathogenic bacteria. The expression of heterologous proteins by viruses is the basis of several manufacturing processes that are currently being used for the production of various proteins such as vaccine antigens and antibodies. Industrial processes have been recently developed using viral vectors and several pharmaceutical proteins are currently in pre-clinical and clinical trials. Virotherapy Main article: Virotherapy Virotherapy involves the use of genetically modified viruses to treat diseases. Viruses have been modified by scientists to reproduce in cancer cells and destroy them but not infect healthy cells. Talimogene laherparepvec (T-VEC), for example, is a modified herpes simplex virus that has had a gene, which is required for viruses to replicate in healthy cells, deleted and replaced with a human gene (GM-CSF) that stimulates immunity. When this virus infects cancer cells, it destroys them and in doing so the presence the GM-CSF gene attracts dendritic cells from the surrounding tissues of the body. The dendritic cells process the dead cancer cells and present components of them to other cells of the immune system. Having completed successful clinical trials, the virus gained approval for the treatment of melanoma in late 2015. Viruses that have been reprogrammed to kill cancer cells are called oncolytic viruses. Materials science and nanotechnology From the viewpoint of a materials scientist, viruses can be regarded as organic nanoparticles. Their surface carries specific tools that enable them to cross the barriers of their host cells. The size and shape of viruses and the number and nature of the functional groups on their surface are precisely defined. As such, viruses are commonly used in materials science as scaffolds for covalently linked surface modifications. A particular quality of viruses is that they can be tailored by directed evolution. The powerful techniques developed by life sciences are becoming the basis of engineering approaches towards nanomaterials, opening a wide range of applications far beyond biology and medicine. Because of their size, shape, and well-defined chemical structures, viruses have been used as templates for organising materials on the nanoscale. Examples include the work at the Naval Research Laboratory in Washington, D.C., using Cowpea mosaic virus (CPMV) particles to amplify signals in DNA microarray based sensors. In this application, the virus particles separate the fluorescent dyes used for signalling to prevent the formation of non-fluorescent dimers that act as quenchers. Another example is the use of CPMV as a nanoscale breadboard for molecular electronics. Synthetic viruses Many viruses can be synthesised de novo ("from scratch"). The first synthetic virus was created in 2002. Although somewhat of a misconception, it is not the actual virus that is synthesised, but rather its DNA genome (in case of a DNA virus), or a cDNA copy of its genome (in case of RNA viruses). For many virus families the naked synthetic DNA or RNA (once enzymatically converted back from the synthetic cDNA) is infectious when introduced into a cell. That is, they contain all the necessary information to produce new viruses. This technology is now being used to investigate novel vaccine strategies. The ability to synthesise viruses has far-reaching consequences, since viruses can no longer be regarded as extinct, as long as the information of their genome sequence is known and permissive cells are available. As of June 2021, the full-length genome sequences of 11,464 different viruses, including smallpox, are publicly available in an online database maintained by the National Institutes of Health. Weapons Further information: Biological warfare The ability of viruses to cause devastating epidemics in human societies has led to the concern that viruses could be weaponised for biological warfare. Further concern was raised by the successful recreation of the infamous 1918 influenza virus in a laboratory. The smallpox virus devastated numerous societies throughout history before its eradication. There are only two centres in the world authorised by the WHO to keep stocks of smallpox virus: the State Research Center of Virology and Biotechnology VECTOR in Russia and the Centers for Disease Control and Prevention in the United States. It may be used as a weapon, as the vaccine for smallpox sometimes had severe side-effects, it is no longer used routinely in any country. Thus, much of the modern human population has almost no established resistance to smallpox and would be vulnerable to the virus. See also Cross-species transmission Glossary of virology Law of declining virulence – Disproved hypothesis of epidemiologist Theobald Smith Non-cellular life Retrozyme Smallest organisms Theory of virulence – Theory by biologist Paul W. Ewald Viral metagenomics Viroplasm Zoonosis	biology	879883	https://da.wikipedia.org/wiki/Bunyaviridae	Bunyaviridae	Bunyaviridae er en familie af negativt polariserede enkeltstrengede RNA-virus. Tiltrods for at disse virus primært findes i leddyr eller gnavere, så kan bestemte virus i denne familie også lejlighedsvist inficere mennesker. Nogle af dem inficerer også planter. Bunyaviridae er vektor-bårne vira. Med undtagelse af hantavira, så er alle vira i Bunyaviridae-familien overført af leddyr (myg, mider eller sandfluer). Hantavira overføres via kontakt med gnaver-fæces. Antallet af infektioner er direkte forbundet til vektor-aktiviteten. Menneskeinfektioner med bestemte Bunyaviridae, såsom Krim-Congo hæmoragisk feber virus, er associeret med høj risiko for sygdomme og dødelighed og håndtering af disse vira må foregå på biologisk sikkerhedsniveau 4 laboratorier. De er også årsag til forekomsten af alvorlig feber med trombocytopeni syndrom. Virologi Klassifikation Der er i dag omkring 330 virus i Bunyaviridae-familien. Familien Bunyaviridae indeholder de følgende slægter: Slægt Hantavirus Slægt Nairovirus Slægt Orthobunyavirus Slægt Phlebovirus Slægt Tospovirus Der er et antal vira som endnu ikke er blevet indplaceret i en slægt: disse inkluderer Gan Gan virus, Maprik virus, Mapputta virus og Trubanaman virus. En ny slægt - endnu unavngiven - er blevet foreslået på basis af isolation af Chaoboridae. Yderligere to vira kan være placeret udenfor den tidligere definerede taksonomi: Ferak virus (FERV) og Jonchet virus (JONV). Struktur Bunyavirus morfologi minder i nogen grad om den, der kendetegner Paramyxoviridae-familien; Bunyaviridae etablerer kuvert, sfæriske virioner med diametre på 90–100 nm. Disse vira indeholder ingen matrix-proteiner. Arvemasse Bunyaviridae har tripartiere genomer, der består af et large (L), medium (M) og small (S) RNA-segment. Disse RNA-segmenter er enkeltstrengede og har en spiralformet formation inden i virionet. Ved siden af det har de en pseudo-circulær struktur pga. hvert segments komplementære ender. L-segmentet koder den RNA-afhængige RNA-polymerase, som er nødvendig for viral RNA-replikation og mRNA-syntese. M-segmentet koder de virale glycoproteiner, som er projekteret fra den virale overflade og hjælper virus med at vedhæfte sig og indtræge i værtscellen. S-segmentet koder nukleocapsidprotein (N). L- og M-segmentet er negativt polariset. For slægterne Phlebovirus og Tospovirus, er S-segmentet ambisense. Ambisense betyder at nogle af generne på RNA-strengen er negativt polariseret og andre er positivt polariseret. S-segmentets koder for det virale nucleoprotein (N) er negativt polariseret og et nonstruktural (NSs) protein er ambisense. Den totale genom-størrelse varierer fra 10,5 til 22,7 kbp. Menneskesygdomme Bunyavira som kan forårsage sygdomme i mennesker inkluderer: Californisk hjernebetændelse virus Hantavirus Krim-Congo hæmoragisk feber Rift Valley feber Bwamba feber Alvorlig feber med trombocytopeni syndrom Bunyavira har segmenterede genomer, som gør dem istand til hurtig rekombination og dermed en forøget risiko for sygdomsudbrud. Bunyaviridae overføres af leddyr som stikmyg, mider og sandfluer. Den virale inkubationstid er omkring 48 timer. Symptomatiske infektioner forårsager typisk ikke-specifikke influenza-lignende symptomer med feber i omkring tre dage. Pga. deres ikke-specifikke symptomer så forveksles de ofte med andre sygdomme. Bwamba feber forveksles for eksempel ofte med malaria. Referencer Eksterne henvisninger Viralzone: Bunyaviridae ICTVdb Index of Viruses—Bunyaviridae The Big Picture Book of Viruses: Bunyaviridae Bunyaviridae Genomes —database search results from the Viral Bioinformatics Resource Center Virus Pathogen Database and Analysis Resource (ViPR): Bunyaviridae	danish	0.449917
genetic_sequence_of_SARS-CoV-2/Genome.txt	In the fields of molecular biology and genetics, a genome is all the genetic information of an organism. It consists of nucleotide sequences of DNA (or RNA in RNA viruses). The nuclear genome includes protein-coding genes and non-coding genes, other functional regions of the genome such as regulatory sequences (see non-coding DNA), and often a substantial fraction of junk DNA with no evident function. Almost all eukaryotes have mitochondria and a small mitochondrial genome. Algae and plants also contain chloroplasts with a chloroplast genome. The study of the genome is called genomics. The genomes of many organisms have been sequenced and various regions have been annotated. The Human Genome Project was started in October 1990, and then reported the sequence of the human genome in April 2003, although the initial "finished" sequence was missing 8% of the genome consisting mostly of repetitive sequences. With advancements in technology that could handle sequencing of the many repetitive sequences found in human DNA that were not fully uncovered by the original Human Genome Project study, scientists reported the first end-to-end human genome sequence in March 2022. Origin of the term[edit] Look up genome in Wiktionary, the free dictionary. The term genome was created in 1920 by Hans Winkler, professor of botany at the University of Hamburg, Germany. The website Oxford Dictionaries and the Online Etymology Dictionary suggest the name is a blend of the words gene and chromosome. However, see omics for a more thorough discussion. A few related -ome words already existed, such as biome and rhizome, forming a vocabulary into which genome fits systematically. Definition[edit] It's very difficult to come up with a precise definition of "genome." It usually refers to the DNA (or sometimes RNA) molecules that carry the genetic information in an organism but sometimes it is difficult to decide which molecules to include in the definition; for example, bacteria usually have one or two large DNA molecules (chromosomes) that contain all of the essential genetic material but they also contain smaller extrachromosomal plasmid molecules that carry important genetic information. The definition of 'genome' that's commonly used in the scientific literature is usually restricted to the large chromosomal DNA molecules in bacteria. Nuclear genome[edit] Eukaryotic genomes are even more difficult to define because almost all eukaryotic species contain nuclear chromosomes plus extra DNA molecules in the mitochondria. In addition, algae and plants have chloroplast DNA. Most textbooks make a distinction between the nuclear genome and the organelle (mitochondria and chloroplast) genomes so when they speak of, say, the human genome, they are only referring to the genetic material in the nucleus. This is the most common use of 'genome' in the scientific literature. Ploidy[edit] Most eukaryotes are diploid, meaning that there are two of each chromosome in the nucleus but the 'genome' refers to only one copy of each chromosome. Some eukaryotes have distinctive sex chromosomes, such as the X and Y chromosomes of mammals, so the technical definition of the genome must include both copies of the sex chromosomes. For example, the standard reference genome of humans consists of one copy of each of the 22 autosomes plus one X chromosome and one Y chromosome. Sequencing and mapping[edit] Further information: Whole genome sequencing and Genome project A genome sequence is the complete list of the nucleotides (A, C, G, and T for DNA genomes) that make up all the chromosomes of an individual or a species. Within a species, the vast majority of nucleotides are identical between individuals, but sequencing multiple individuals is necessary to understand the genetic diversity. Part of DNA sequence – prototypification of complete genome of virus In 1976, Walter Fiers at the University of Ghent (Belgium) was the first to establish the complete nucleotide sequence of a viral RNA-genome (Bacteriophage MS2). The next year, Fred Sanger completed the first DNA-genome sequence: Phage Φ-X174, of 5386 base pairs. The first bacterial genome to be sequenced was that of Haemophilus influenzae, completed by a team at The Institute for Genomic Research in 1995. A few months later, the first eukaryotic genome was completed, with sequences of the 16 chromosomes of budding yeast Saccharomyces cerevisiae published as the result of a European-led effort begun in the mid-1980s. The first genome sequence for an archaeon, Methanococcus jannaschii, was completed in 1996, again by The Institute for Genomic Research. The development of new technologies has made genome sequencing dramatically cheaper and easier, and the number of complete genome sequences is growing rapidly. The US National Institutes of Health maintains one of several comprehensive databases of genomic information. Among the thousands of completed genome sequencing projects include those for rice, a mouse, the plant Arabidopsis thaliana, the puffer fish, and the bacteria E. coli. In December 2013, scientists first sequenced the entire genome of a Neanderthal, an extinct species of humans. The genome was extracted from the toe bone of a 130,000-year-old Neanderthal found in a Siberian cave. New sequencing technologies, such as massive parallel sequencing have also opened up the prospect of personal genome sequencing as a diagnostic tool, as pioneered by Manteia Predictive Medicine. A major step toward that goal was the completion in 2007 of the full genome of James D. Watson, one of the co-discoverers of the structure of DNA. Whereas a genome sequence lists the order of every DNA base in a genome, a genome map identifies the landmarks. A genome map is less detailed than a genome sequence and aids in navigating around the genome. The Human Genome Project was organized to map and to sequence the human genome. A fundamental step in the project was the release of a detailed genomic map by Jean Weissenbach and his team at the Genoscope in Paris. Reference genome sequences and maps continue to be updated, removing errors and clarifying regions of high allelic complexity. The decreasing cost of genomic mapping has permitted genealogical sites to offer it as a service, to the extent that one may submit one's genome to crowdsourced scientific endeavours such as DNA.LAND at the New York Genome Center, an example both of the economies of scale and of citizen science. Viral genomes[edit] Viral genomes can be composed of either RNA or DNA. The genomes of RNA viruses can be either single-stranded RNA or double-stranded RNA, and may contain one or more separate RNA molecules (segments: monopartit or multipartit genome). DNA viruses can have either single-stranded or double-stranded genomes. Most DNA virus genomes are composed of a single, linear molecule of DNA, but some are made up of a circular DNA molecule. Prokaryotic genomes[edit] Prokaryotes and eukaryotes have DNA genomes. Archaea and most bacteria have a single circular chromosome, however, some bacterial species have linear or multiple chromosomes. If the DNA is replicated faster than the bacterial cells divide, multiple copies of the chromosome can be present in a single cell, and if the cells divide faster than the DNA can be replicated, multiple replication of the chromosome is initiated before the division occurs, allowing daughter cells to inherit complete genomes and already partially replicated chromosomes. Most prokaryotes have very little repetitive DNA in their genomes. However, some symbiotic bacteria (e.g. Serratia symbiotica) have reduced genomes and a high fraction of pseudogenes: only ~40% of their DNA encodes proteins. Some bacteria have auxiliary genetic material, also part of their genome, which is carried in plasmids. For this, the word genome should not be used as a synonym of chromosome. Eukaryotic genomes[edit] See also: Eukaryotic chromosome fine structure In a typical human cell, the genome is contained in 22 pairs of autosomes, two sex chromosomes (the female and male variants shown at bottom right), as well as the mitochondrial genome (shown to scale as "MT" at bottom left). Further information: Karyotype Eukaryotic genomes are composed of one or more linear DNA chromosomes. The number of chromosomes varies widely from Jack jumper ants and an asexual nemotode, which each have only one pair, to a fern species that has 720 pairs. It is surprising the amount of DNA that eukaryotic genomes contain compared to other genomes. The amount is even more than what is necessary for DNA protein-coding and noncoding genes due to the fact that eukaryotic genomes show as much as 64,000-fold variation in their sizes. However, this special characteristic is caused by the presence of repetitive DNA, and transposable elements (TEs). A typical human cell has two copies of each of 22 autosomes, one inherited from each parent, plus two sex chromosomes, making it diploid. Gametes, such as ova, sperm, spores, and pollen, are haploid, meaning they carry only one copy of each chromosome. In addition to the chromosomes in the nucleus, organelles such as the chloroplasts and mitochondria have their own DNA. Mitochondria are sometimes said to have their own genome often referred to as the "mitochondrial genome". The DNA found within the chloroplast may be referred to as the "plastome". Like the bacteria they originated from, mitochondria and chloroplasts have a circular chromosome. Unlike prokaryotes where exon-intron organization of protein coding genes exists but is rather exceptional, eukaryotes generally have these features in their genes and their genomes contain variable amounts of repetitive DNA. In mammals and plants, the majority of the genome is composed of repetitive DNA. Genes in eukaryotic genomes can be annotated using FINDER. DNA sequencing[edit] High-throughput technology makes sequencing to assemble new genomes accessible to everyone. Sequence polymorphisms are typically discovered by comparing resequenced isolates to a reference, whereas analyses of coverage depth and mapping topology can provide details regarding structural variations such as chromosomal translocations and segmental duplications. Coding sequences[edit] DNA sequences that carry the instructions to make proteins are referred to as coding sequences. The proportion of the genome occupied by coding sequences varies widely. A larger genome does not necessarily contain more genes, and the proportion of non-repetitive DNA decreases along with increasing genome size in complex eukaryotes. Composition of the human genome Noncoding sequences[edit] Main article: Non-coding DNA See also: Intergenic region Noncoding sequences include introns, sequences for non-coding RNAs, regulatory regions, and repetitive DNA. Noncoding sequences make up 98% of the human genome. There are two categories of repetitive DNA in the genome: tandem repeats and interspersed repeats. Tandem repeats[edit] Short, non-coding sequences that are repeated head-to-tail are called tandem repeats. Microsatellites consisting of 2–5 basepair repeats, while minisatellite repeats are 30–35 bp. Tandem repeats make up about 4% of the human genome and 9% of the fruit fly genome. Tandem repeats can be functional. For example, telomeres are composed of the tandem repeat TTAGGG in mammals, and they play an important role in protecting the ends of the chromosome. In other cases, expansions in the number of tandem repeats in exons or introns can cause disease. For example, the human gene huntingtin (Htt) typically contains 6–29 tandem repeats of the nucleotides CAG (encoding a polyglutamine tract). An expansion to over 36 repeats results in Huntington's disease, a neurodegenerative disease. Twenty human disorders are known to result from similar tandem repeat expansions in various genes. The mechanism by which proteins with expanded polygulatamine tracts cause death of neurons is not fully understood. One possibility is that the proteins fail to fold properly and avoid degradation, instead accumulating in aggregates that also sequester important transcription factors, thereby altering gene expression. Tandem repeats are usually caused by slippage during replication, unequal crossing-over and gene conversion. Transposable elements[edit] Transposable elements (TEs) are sequences of DNA with a defined structure that are able to change their location in the genome. TEs are categorized as either as a mechanism that replicates by copy-and-paste or as a mechanism that can be excised from the genome and inserted at a new location. In the human genome, there are three important classes of TEs that make up more than 45% of the human DNA; these classes are The long interspersed nuclear elements (LINEs), The interspersed nuclear elements (SINEs), and endogenous retroviruses. These elements have a big potential to modify the genetic control in a host organism. The movement of TEs is a driving force of genome evolution in eukaryotes because their insertion can disrupt gene functions, homologous recombination between TEs can produce duplications, and TE can shuffle exons and regulatory sequences to new locations. Retrotransposons[edit] Retrotransposons are found mostly in eukaryotes but not found in prokaryotes. Retrotransposons form a large portion of the genomes of many eukaryotes. A retrotransposon is a transposable element that transposes through an RNA intermediate. Retrotransposons are composed of DNA, but are transcribed into RNA for transposition, then the RNA transcript is copied back to DNA formation with the help of a specific enzyme called reverse transcriptase. A retrotransposon that carries reverse transcriptase in its sequence can trigger its own transposition but retrotransposons that lack a reverse transcriptase must use reverse transcriptase synthesized by another retrotransposon. Retrotransposons can be transcribed into RNA, which are then duplicated at another site into the genome. Retrotransposons can be divided into long terminal repeats (LTRs) and non-long terminal repeats (Non-LTRs). Long terminal repeats (LTRs) are derived from ancient retroviral infections, so they encode proteins related to retroviral proteins including gag (structural proteins of the virus), pol (reverse transcriptase and integrase), pro (protease), and in some cases env (envelope) genes. These genes are flanked by long repeats at both 5' and 3' ends. It has been reported that LTRs consist of the largest fraction in most plant genome and might account for the huge variation in genome size. Non-long terminal repeats (Non-LTRs) are classified as long interspersed nuclear elements (LINEs), short interspersed nuclear elements (SINEs), and Penelope-like elements (PLEs). In Dictyostelium discoideum, there is another DIRS-like elements belong to Non-LTRs. Non-LTRs are widely spread in eukaryotic genomes. Long interspersed elements (LINEs) encode genes for reverse transcriptase and endonuclease, making them autonomous transposable elements. The human genome has around 500,000 LINEs, taking around 17% of the genome. Short interspersed elements (SINEs) are usually less than 500 base pairs and are non-autonomous, so they rely on the proteins encoded by LINEs for transposition. The Alu element is the most common SINE found in primates. It is about 350 base pairs and occupies about 11% of the human genome with around 1,500,000 copies. DNA transposons[edit] DNA transposons encode a transposase enzyme between inverted terminal repeats. When expressed, the transposase recognizes the terminal inverted repeats that flank the transposon and catalyzes its excision and reinsertion in a new site. This cut-and-paste mechanism typically reinserts transposons near their original location (within 100kb). DNA transposons are found in bacteria and make up 3% of the human genome and 12% of the genome of the roundworm C. elegans. Genome size[edit] Log–log plot of the total number of annotated proteins in genomes submitted to GenBank as a function of genome size Genome size is the total number of the DNA base pairs in one copy of a haploid genome. Genome size varies widely across species. Invertebrates have small genomes, this is also correlated to a small number of transposable elements. Fish and Amphibians have intermediate-size genomes, and birds have relatively small genomes but it has been suggested that birds lost a substantial portion of their genomes during the phase of transition to flight. Before this loss, DNA methylation allows the adequate expansion of the genome. In humans, the nuclear genome comprises approximately 3.1 billion nucleotides of DNA, divided into 24 linear molecules, the shortest 45 000 000 nucleotides in length and the longest 248 000 000 nucleotides, each contained in a different chromosome. There is no clear and consistent correlation between morphological complexity and genome size in either prokaryotes or lower eukaryotes. Genome size is largely a function of the expansion and contraction of repetitive DNA elements. Since genomes are very complex, one research strategy is to reduce the number of genes in a genome to the bare minimum and still have the organism in question survive. There is experimental work being done on minimal genomes for single cell organisms as well as minimal genomes for multi-cellular organisms (see developmental biology). The work is both in vivo and in silico. Genome size differences due to transposable elements[edit] Comparison among genome sizes There are many enormous differences in size in genomes, specially mentioned before in the multicellular eukaryotic genomes. Much of this is due to the differing abundances of transposable elements, which evolve by creating new copies of themselves in the chromosomes. Eukaryote genomes often contain many thousands of copies of these elements, most of which have acquired mutations that make them defective. Here is a table of some significant or representative genomes. See #See also for lists of sequenced genomes. Organism type Organism Genome size (base pairs) Approx. no. of genes Note Virus Porcine circovirus type 1 1,759 1.8 kB Smallest viruses replicating autonomously in eukaryotic cells Virus Bacteriophage MS2 3,569 3.6 kB First sequenced RNA-genome Virus SV40 5,224 5.2 kB Virus Phage Φ-X174 5,386 5.4 kB First sequenced DNA-genome Virus HIV 9,749 9.7 kB Virus Phage λ 48,502 48.5 kB Often used as a vector for the cloning of recombinant DNA Virus Megavirus 1,259,197 1.3 MB Until 2013 the largest known viral genome Virus Pandoravirus salinus 2,470,000 2.47 MB Largest known viral genome. Eukaryotic organelle Human mitochondrion 16,569 16.6 kB Bacterium Nasuia deltocephalinicola (strain NAS-ALF) 112,091 112 kB 137 Smallest known non-viral genome. Symbiont of leafhoppers. Bacterium Carsonella ruddii 159,662 160 kB An endosymbiont of psyllid insects Bacterium Buchnera aphidicola 600,000 600 kB An endosymbiont of aphids Bacterium Wigglesworthia glossinidia 700,000 700 kB A symbiont in the gut of the tsetse fly Bacterium – cyanobacterium Prochlorococcus spp. (1.7 Mb) 1,700,000 1.7 MB 1,884 Smallest known cyanobacterium genome. One of the primary photosynthesizers on Earth. Bacterium Haemophilus influenzae 1,830,000 1.8 MB First genome of a living organism sequenced, July 1995 Bacterium Escherichia coli 4,600,000 4.6 MB 4,288 Bacterium – cyanobacterium Nostoc punctiforme 9,000,000 9 MB 7,432 7432 open reading frames Bacterium Solibacter usitatus (strain Ellin 6076) 9,970,000 10 MB Amoeboid Polychaos dubium ("Amoeba" dubia) 670,000,000,000 670 GB Largest known genome. (Disputed) Plant Genlisea tuberosa 61,000,000 61 MB Smallest recorded flowering plant genome, 2014 Plant Arabidopsis thaliana 135,000,000 135 MB 27,655 First plant genome sequenced, December 2000 Plant Populus trichocarpa 480,000,000 480 MB 73,013 First tree genome sequenced, September 2006 Plant Pinus taeda (Loblolly pine) 22,180,000,000 22.18 GB 50,172 Gymnosperms generally have much larger genomes than angiosperms Plant Fritillaria assyriaca 130,000,000,000 130 GB Plant Paris japonica (Japanese-native, order Liliales) 150,000,000,000 150 GB Largest plant genome known Plant – moss Physcomitrella patens 480,000,000 480 MB First genome of a bryophyte sequenced, January 2008 Fungus – yeast Saccharomyces cerevisiae 12,100,000 12.1 MB 6,294 First eukaryotic genome sequenced, 1996 Fungus Aspergillus nidulans 30,000,000 30 MB 9,541 Nematode Pratylenchus coffeae 20,000,000 20 MB Smallest animal genome known Nematode Caenorhabditis elegans 100,300,000 100 MB 19,000 First multicellular animal genome sequenced, December 1998 Insect Belgica antarctica (Antarctic midge) 99,000,000 99 MB Smallest insect genome sequenced thus far, likely an adaptation to an extreme environment Insect Drosophila melanogaster (fruit fly) 175,000,000 175 MB 13,600 Size variation based on strain (175–180 Mb; standard y w strain is 175 Mb) Insect Apis mellifera (honey bee) 236,000,000 236 MB 10,157 Insect Bombyx mori (silk moth) 432,000,000 432 MB 14,623 14,623 predicted genes Insect Solenopsis invicta (fire ant) 480,000,000 480 MB 16,569 Crustacean Antarctic krill 48,010,000,000 48 GB 23,000 70-92% repetitive DNA Amphibian Neuse River waterdog 118,000,000,000 118 GB Largest tetrapod genome sequenced as of 2022 Amphibian Ornate burrowing frog 1,060,000,000 1.06 GB Smallest known frog genome Mammal Mus musculus 2,700,000,000 2.7 GB 20,210 Mammal Pan paniscus 3,286,640,000 3.3 GB 20,000 Bonobo – estimated genome size 3.29 billion bp Mammal Homo sapiens 3,117,000,000 3.1 GB 20,000 Homo sapiens genome size estimated at 3.12 Gbp in 2022 Initial sequencing and analysis of the human genome Bird Gallus gallus 1,043,000,000 1.0 GB 20,000 Fish Tetraodon nigroviridis (type of puffer fish) 385,000,000 390 MB Smallest vertebrate genome known, estimated to be 340 Mb – 385 Mb Fish Protopterus aethiopicus (marbled lungfish) 130,000,000,000 130 GB Largest vertebrate genome known Genomic alterations[edit] All the cells of an organism originate from a single cell, so they are expected to have identical genomes; however, in some cases, differences arise. Both the process of copying DNA during cell division and exposure to environmental mutagens can result in mutations in somatic cells. In some cases, such mutations lead to cancer because they cause cells to divide more quickly and invade surrounding tissues. In certain lymphocytes in the human immune system, V(D)J recombination generates different genomic sequences such that each cell produces a unique antibody or T cell receptors. During meiosis, diploid cells divide twice to produce haploid germ cells. During this process, recombination results in a reshuffling of the genetic material from homologous chromosomes so each gamete has a unique genome. Genome-wide reprogramming[edit] Genome-wide reprogramming in mouse primordial germ cells involves epigenetic imprint erasure leading to totipotency. Reprogramming is facilitated by active DNA demethylation, a process that entails the DNA base excision repair pathway. This pathway is employed in the erasure of CpG methylation (5mC) in primordial germ cells. The erasure of 5mC occurs via its conversion to 5-hydroxymethylcytosine (5hmC) driven by high levels of the ten-eleven dioxygenase enzymes TET1 and TET2. Genome evolution[edit] Genomes are more than the sum of an organism's genes and have traits that may be measured and studied without reference to the details of any particular genes and their products. Researchers compare traits such as karyotype (chromosome number), genome size, gene order, codon usage bias, and GC-content to determine what mechanisms could have produced the great variety of genomes that exist today (for recent overviews, see Brown 2002; Saccone and Pesole 2003; Benfey and Protopapas 2004; Gibson and Muse 2004; Reese 2004; Gregory 2005). Duplications play a major role in shaping the genome. Duplication may range from extension of short tandem repeats, to duplication of a cluster of genes, and all the way to duplication of entire chromosomes or even entire genomes. Such duplications are probably fundamental to the creation of genetic novelty. Horizontal gene transfer is invoked to explain how there is often an extreme similarity between small portions of the genomes of two organisms that are otherwise very distantly related. Horizontal gene transfer seems to be common among many microbes. Also, eukaryotic cells seem to have experienced a transfer of some genetic material from their chloroplast and mitochondrial genomes to their nuclear chromosomes. Recent empirical data suggest an important role of viruses and sub-viral RNA-networks to represent a main driving role to generate genetic novelty and natural genome editing. In fiction[edit] Works of science fiction illustrate concerns about the availability of genome sequences. Michael Crichton's 1990 novel Jurassic Park and the subsequent film tell the story of a billionaire who creates a theme park of cloned dinosaurs on a remote island, with disastrous outcomes. A geneticist extracts dinosaur DNA from the blood of ancient mosquitoes and fills in the gaps with DNA from modern species to create several species of dinosaurs. A chaos theorist is asked to give his expert opinion on the safety of engineering an ecosystem with the dinosaurs, and he repeatedly warns that the outcomes of the project will be unpredictable and ultimately uncontrollable. These warnings about the perils of using genomic information are a major theme of the book. The 1997 film Gattaca is set in a futurist society where genomes of children are engineered to contain the most ideal combination of their parents' traits, and metrics such as risk of heart disease and predicted life expectancy are documented for each person based on their genome. People conceived outside of the eugenics program, known as "In-Valids" suffer discrimination and are relegated to menial occupations. The protagonist of the film is an In-Valid who works to defy the supposed genetic odds and achieve his dream of working as a space navigator. The film warns against a future where genomic information fuels prejudice and extreme class differences between those who can and cannot afford genetically engineered children. See also[edit] Bacterial genome size Cryoconservation of animal genetic resources Genome Browser Genome Compiler Genome topology Genome-wide association study List of sequenced animal genomes List of sequenced archaeal genomes List of sequenced bacterial genomes List of sequenced eukaryotic genomes List of sequenced fungi genomes List of sequenced plant genomes List of sequenced plastomes List of sequenced protist genomes Metagenomics Microbiome Molecular epidemiology Molecular pathological epidemiology Molecular pathology Nucleic acid sequence Pan-genome Precision medicine Regulator gene Whole genome sequencing	biology	5284	https://da.wikipedia.org/wiki/Gen	Gen	Et gen er en biologisk enhed for information kodet i DNA om dannelse af et biologisk molekyle. Et individs gener kaldes arvemassen eller genomet. Ordet gen indførtes i 1909 af den danske biolog Wilhelm Johannsen. Den klassiske genetik omhandler hvordan gener nedarves, se Gregor Mendel. Gener indeholder informationen til proteinsyntese i form af sekvensen af baser i DNA. Det kan f.eks. være informationen til fremstilling af et enzym, som f.eks. indgår i nedbrydningen af føden. Andre gener koder for andre proteiner som antistoffer og visse hormoner, transportmolekyler, enzymhæmmere, adhæsionsmolekyler, toksiner, receptorer, lectiner og mikroproteiner. Atter andre gener koder for rRNA, tRNA og andre RNA-molekyler med forskellige regulerende funktioner. Forskellige organismer har ikke det samme antal gener. Encellede bakteriers arvemasse har cirka 4.000 gener, en gærcelle har 6.000 gener, planter har et meget varierende antal gener, og dyr har typisk 10-100.000 gener. Mennesket har 20.344 gener der koder for proteiner. Generne består af DNA og udgør (sammen med proteiner, bl.a. histoner) cellens kromosomer. Det sted, som et gen sidder på et kromosom, kaldes genets locus. Hvert diploid individ har to kopier af hvert gen. En kopi er arvet fra faren og en fra moren. Grundlaget for genetisk variation er, at gener forekommer i funktionelt forskellige former, som betegnes alleler. Forskelle mellem alleler reflekterer forskelle i den DNA-sekvens, som udgør genet. Ændringer i et gen kaldes mutationer, f.eks. rækkefølgen af basene i DNAet, se f.eks. ændringen af CFTR hvor f.eks. en mangel på tre baser forårsager cystisk fibrose. Se også CRISPR Genetik Allel Genteknologi Arv (genetisk) Onkogen Eksterne henvisninger DR's tema om gener	danish	0.441212
snake_dizzy/Vertigo.txt	Vertigo is a condition in which a person has the sensation of movement or of surrounding objects moving when they are not. Often it feels like a spinning or swaying movement. It may be associated with nausea, vomiting, perspiration, or difficulties walking. It is typically worse when the head is moved. Vertigo is the most common type of dizziness. The most common disorders that result in vertigo are benign paroxysmal positional vertigo (BPPV), Ménière's disease, and vestibular neuritis. Less common causes include stroke, brain tumors, brain injury, multiple sclerosis, migraines, trauma, and uneven pressures between the middle ears. Physiologic vertigo may occur following being exposed to motion for a prolonged period such as when on a ship or simply following spinning with the eyes closed. Other causes may include toxin exposures such as to carbon monoxide, alcohol, or aspirin. Vertigo typically indicates a problem in a part of the vestibular system. Other causes of dizziness include presyncope, disequilibrium, and non-specific dizziness. Benign paroxysmal positional vertigo is more likely in someone who gets repeated episodes of vertigo with movement and is otherwise normal between these episodes. Benign vertigo episodes generally last less than one minute. The Dix-Hallpike test typically produces a period of rapid eye movements known as nystagmus in this condition. In Ménière's disease there is often ringing in the ears, hearing loss, and the attacks of vertigo last more than twenty minutes. In vestibular neuritis the onset of vertigo is sudden, and the nystagmus occurs even when the person has not been moving. In this condition vertigo can last for days. More severe causes should also be considered, especially if other problems such as weakness, headache, double vision, or numbness occur. Dizziness affects approximately 20–40% of people at some point in time, while about 7.5–10% have vertigo. About 5% have vertigo in a given year. It becomes more common with age and affects women two to three times more often than men. Vertigo accounts for about 2–3% of emergency department visits in the developed world. Classification[edit] Vertigo is classified into either peripheral or central depending on the location of the dysfunction of the vestibular pathway, although it can also be caused by psychological factors. Vertigo can also be classified into objective, subjective, and pseudovertigo. Objective vertigo describes when the person has the sensation that stationary objects in the environment are moving. Subjective vertigo refers to when the person feels as if they are moving. The third type is known as pseudovertigo, an intensive sensation of rotation inside the person's head. While this classification appears in textbooks, it is unclear what relation it has to the pathophysiology or treatment of vertigo. Peripheral[edit] Vertigo that is caused by problems with the inner ear or vestibular system, which is composed of the semicircular canals, the vestibule (utricle and saccule), and the vestibular nerve is called "peripheral", "otologic", or "vestibular" vertigo. The most common cause is benign paroxysmal positional vertigo (BPPV), which accounts for 32% of all peripheral vertigo. Other causes include Ménière's disease (12%), superior canal dehiscence syndrome, vestibular neuritis, and visual vertigo. Any cause of inflammation such as common cold, influenza, and bacterial infections may cause transient vertigo if it involves the inner ear, as may chemical insults (e.g., aminoglycosides) or physical trauma (e.g., skull fractures). Motion sickness is sometimes classified as a cause of peripheral vertigo. People with peripheral vertigo typically present with mild to moderate imbalance, nausea, vomiting, hearing loss, tinnitus, fullness, and pain in the ear. In addition, lesions of the internal auditory canal may be associated with facial weakness on the same side. Due to a rapid compensation process, acute vertigo as a result of a peripheral lesion tends to improve in a short period of time (days to weeks). Central[edit] Vertigo that arises from injury to the balance centers of the central nervous system (CNS), often from a lesion in the brainstem or cerebellum, is called "central" vertigo and is generally associated with less prominent movement illusion and nausea than vertigo of peripheral origin. Central vertigo may have accompanying neurologic deficits (such as slurred speech and double vision), and pathologic nystagmus (which is pure vertical/torsional). Central pathology can cause disequilibrium, which is the sensation of being off balance. The balance disorder associated with central lesions causing vertigo is often so severe that many people are unable to stand or walk. A number of conditions that involve the central nervous system may lead to vertigo including: lesions caused by infarctions or hemorrhage, tumors present in the cerebellopontine angle such as a vestibular schwannoma or cerebellar tumors, epilepsy, cervical spine disorders such as cervical spondylosis, degenerative ataxia disorders, migraine headaches, lateral medullary syndrome, Chiari malformation, multiple sclerosis, parkinsonism, as well as cerebral dysfunction. Central vertigo may not improve or may do so more slowly than vertigo caused by disturbance to peripheral structures. Alcohol can result in positional alcohol nystagmus (PAN). Signs and symptoms[edit] A drawing showing the sensation of vertigo Vertigo is a sensation of spinning while stationary. It is commonly associated with nausea or vomiting, unsteadiness (postural instability), falls, changes to a person's thoughts, and difficulties in walking. Recurrent episodes in those with vertigo are common and frequently impair the quality of life. Blurred vision, difficulty in speaking, a lowered level of consciousness, and hearing loss may also occur. The signs and symptoms of vertigo can present as a persistent (insidious) onset or an episodic (sudden) onset. Persistent onset vertigo is characterized by symptoms lasting for longer than one day and is caused by degenerative changes that affect balance as people age. Nerve conduction slows with aging, and a decreased vibratory sensation is common as a result. Additionally, there is a degeneration of the ampulla and otolith organs with an increase in age. Persistent onset is commonly paired with central vertigo signs and symptoms. The characteristics of an episodic onset vertigo are indicated by symptoms lasting for a smaller, more memorable amount of time, typically lasting for only seconds to minutes. Pathophysiology[edit] The neurochemistry of vertigo includes six primary neurotransmitters that have been identified between the three-neuron arc that drives the vestibulo-ocular reflex (VOR). Glutamate maintains the resting discharge of the central vestibular neurons and may modulate synaptic transmission in all three neurons of the VOR arc. Acetylcholine appears to function as an excitatory neurotransmitter in both the peripheral and central synapses. Gamma-Aminobutyric acid (GABA) is thought to be inhibitory for the commissures of the medial vestibular nucleus, the connections among the cerebellar Purkinje cells, the lateral vestibular nucleus, and the vertical VOR. Three other neurotransmitters work centrally. Dopamine may accelerate vestibular compensation. Norepinephrine modulates the intensity of central reactions to vestibular stimulation and facilitates compensation. Histamine is present only centrally, but its role is unclear. Dopamine, histamine, serotonin, and acetylcholine are neurotransmitters thought to produce vomiting. It is known that centrally acting antihistamines modulate the symptoms of acute symptomatic vertigo. Diagnosis[edit] Tests for vertigo often attempt to elicit nystagmus and to differentiate vertigo from other causes of dizziness such as presyncope, hyperventilation syndrome, disequilibrium, or psychiatric causes of lightheadedness. Tests of vestibular system (balance) function include electronystagmography (ENG), Dix-Hallpike maneuver, rotation tests, head-thrust test, caloric reflex test, and computerized dynamic posturography (CDP). The HINTS test, which is a combination of three physical examination tests that may be performed by physicians at the bedside, has been deemed helpful in differentiating between central and peripheral causes of vertigo. The HINTS test involves the horizontal head impulse test, observation of nystagmus on primary gaze, and the test of skew. CT scans or MRIs are sometimes used by physicians when diagnosing vertigo. Tests of auditory system (hearing) function include pure tone audiometry, speech audiometry, acoustic reflex, electrocochleography (ECoG), otoacoustic emissions (OAE), and the auditory brainstem response test. A number of specific conditions can cause vertigo. In the elderly, however, the condition is often multifactorial. A recent history of underwater diving can indicate a possibility of barotrauma or decompression sickness involvement, but does not exclude all other possibilities. The dive profile (which is frequently recorded by dive computer) can be useful to assess a probability for decompression sickness, which can be confirmed by therapeutic recompression. Benign paroxysmal positional vertigo[edit] Benign paroxysmal positional vertigo (BPPV) is the most common vestibular disorder and occurs when loose calcium carbonate debris has broken off of the otoconial membrane and enters a semicircular canal thereby creating the sensation of motion. People with BPPV may experience brief periods of vertigo, usually under a minute, which occur with change in the position. This is the most common cause of vertigo. It occurs in 0.6% of the population yearly with 10% having an attack during their lifetime. It is believed to be due to a mechanical malfunction of the inner ear. BPPV may be diagnosed with the Dix-Hallpike test and can be effectively treated with repositioning movements such as the Epley maneuver. Ménière's disease[edit] Further information: Ménière's disease Ménière's disease is an inner ear disorder of unknown origin, but is thought to be caused by an increase in the amount of endolymphatic fluid present in the inner ear (endolymphatic hydrops). However, this idea has not been directly confirmed with histopathologic studies, but electrophysiologic studies have been suggestive of this mechanism. Ménière's disease frequently presents with recurrent, spontaneous attacks of severe vertigo in combination with ringing in the ears (tinnitus), a feeling of pressure or fullness in the ear (aural fullness), severe nausea or vomiting, imbalance, and hearing loss. As the disease worsens, hearing loss will progress. Vestibular neuritis[edit] Vestibular neuritis presents with severe vertigo with associated nausea, vomiting, and generalized imbalance and is believed to be caused by a viral infection of the inner ear, although several theories have been put forward and the cause remains uncertain. Individuals with vestibular neuritis do not typically have auditory symptoms, but may experience a sensation of aural fullness or tinnitus. Persisting balance problems may remain in 30% of people affected. Vestibular migraine[edit] Vestibular migraine is the association of vertigo and migraines and is one of the most common causes of recurrent, spontaneous episodes of vertigo. The cause of vestibular migraines is currently unclear; however, one hypothesized cause is that the stimulation of the trigeminal nerve leads to nystagmus in individuals with migraines. Approximately 40% of all migraine patients will have an accompanying vestibular syndrome, such as vertigo, dizziness, or disruption of the balance system. Other suggested causes of vestibular migraines include the following: unilateral neuronal instability of the vestibular nerve, idiopathic asymmetric activation of the vestibular nuclei in the brainstem, and vasospasm of the blood vessels supplying the labyrinth or central vestibular pathways resulting in ischemia to these structures. Vestibular migraines are estimated to affect 1–3% of the general population and may affect 10% of people with migraine . Additionally, vestibular migraines tend to occur more often in women and rarely affect individuals after the sixth decade of life. Motion sickness[edit] Motion sickness is common and is related to vestibular migraine. It is nausea and vomiting in response to motion and is typically worse if the journey is on a winding road or involves many stops and starts, or if the person is reading in a moving car. It is caused by a mismatch between visual input and vestibular sensation. For example, the person is reading a book that is stationary in relation to the body, but the vestibular system senses that the car, and thus the body, is moving. Alternobaric vertigo[edit] Main article: Alternobaric vertigo Alternobaric vertigo is caused by a pressure difference between the middle ear cavities, usually due to blockage or partial blockage of one eustachian tube, usually when flying or diving underwater. It is most pronounced when the diver is in the vertical position; the spinning is toward the ear with the higher pressure and tends to develop when the pressures differ by 60 cm of water or more. Decompression sickness[edit] Further information: Decompression sickness Vertigo is recorded as a symptom of decompression sickness in 5.3% of cases by the U.S. Navy as reported by Powell, 2008 including isobaric decompression sickness. Decompression sickness can also be caused at a constant ambient pressure when switching between gas mixtures containing different proportions of different inert gases. This is known as isobaric counterdiffusion, and presents a problem for very deep dives. For example, after using a very helium-rich trimix at the deepest part of the dive, a diver will switch to mixtures containing progressively less helium and more oxygen and nitrogen during the ascent. Nitrogen diffuses into tissues 2.65 times slower than helium, but is about 4.5 times more soluble. Switching between gas mixtures that have very different fractions of nitrogen and helium can result in "fast" tissues (those tissues that have a good blood supply) increasing their total inert gas loading. This is often found to provoke inner ear decompression sickness, as the ear seems particularly sensitive to this effect. Stroke[edit] A stroke (either ischemic or hemorrhagic) involving the posterior fossa is a cause of central vertigo. Risk factors for a stroke as a cause of vertigo include increasing age and known vascular risk factors. Presentation may more often involve headache or neck pain, additionally, those who have had multiple episodes of dizziness in the months leading up to presentation are suggestive of stroke with prodromal TIAs. The HINTS exam as well as imaging studies of the brain (CT, CT angiogram, MRI) are helpful in diagnosis of posterior fossa stroke. Vertebrobasilar insufficiency[edit] Vertebrobasilar insufficiency, notably Bow Hunter's syndrome, is a rare cause of positional vertigo, especially when vertigo is triggered by rotation of the head. Management[edit] Definitive treatment depends on the underlying cause of vertigo. People with Ménière's disease have a variety of treatment options to consider when receiving treatment for vertigo and tinnitus including: a low-salt diet and intratympanic injections of the antibiotic gentamicin or surgical measures such as a shunt or ablation of the labyrinth in refractory cases. Common drug treatment options for vertigo may include the following: Anticholinergics such as hyoscine hydrobromide (scopolamine) Anticonvulsants such as topiramate or valproic acid for vestibular migraines Antihistamines such as betahistine, dimenhydrinate, or meclizine, which may have antiemetic properties Beta blockers such as metoprolol for vestibular migraine Corticosteroids such as methylprednisolone for inflammatory conditions such as vestibular neuritis or dexamethasone as a second-line agent for Ménière's disease All cases of decompression sickness should be treated initially with 100% oxygen until hyperbaric oxygen therapy (100% oxygen delivered in a high-pressure chamber) can be provided. Several treatments may be necessary, and treatment will generally be repeated until either all symptoms resolve, or no further improvement is apparent. Etymology[edit] Vertigo is from the Latin word, vertō, which means "a whirling or spinning movement". See also[edit] Acrophobia – Extreme fear of heights Broken escalator phenomenon – Illusion when stepping onto a broken escalator Chronic subjective dizziness – Type of dizziness (chronic functional vestibular disorder)Pages displaying wikidata descriptions as a fallback Fear of falling – Natural fear typical of most mammals Head for heights Ideomotor phenomenon – Concept in hypnosis and psychological research Illusions of self-motion – Misperception of one's location or movement Proprioception – Sense of self-movement, force, and body position Motion sickness – Nausea caused by motion or perceived motion Sense of balance, also known as Equilibrioception – Physiological sense regarding posture Spatial disorientation – Inability of a person to correctly determine their body position in space	biology	91826	https://da.wikipedia.org/wiki/Apopleksi	Apopleksi	Apopleksi (apoplexia cerebri, også kendt som slagtilfælde, hjerneblødning, blodprop i hjernen og stroke) er en pludseligt opstået neurologisk skade eller udfald på baggrund af iskæmi (nedsat blodforsyning) i hjernen. Den kan enten skyldes en blodprop i et forsynende blodkar (85%) eller en bristning af et blodkar, der medfører en blødning i hjernens væv (15%). Ved apopleksi er hurtig reaktion og behandling vigtig for at undgå død og skadelige følger. Symptomerne i den akutte fase afhænger af hvilket hjerneområde, der er ramt. Hyppigt drejer det sig om nedsat bevidsthed, nedsat kraft og følelse i den ene side af kroppen og kognitive forstyrrelser, der påvirker sprog, rumfornemmelse og hverdagsfunktioner. Psykiske forandringer og depressioner er ligeledes almindelige. Diagnosen stilles ud fra en klinisk undersøgelse, men det er ikke muligt at skelne mellem en blodprop og en blødning på baggrund af denne. Som supplement til den kliniske undersøgelse vil der næsten altid udføres en CT-scanning eller MR-scanning. Formålet med disse scanninger er at understøtte diagnosen, vurdere prognosen og udelukke differentialdiagnoser, f.eks. tumor/metastaser, subaraknoidal blødning (SAH) og subduralt hæmatom (SDH).I praksis skelnes der mellem apopleksi, hvor symptomerne har en varighed på over 24 timer og TCI (transitorisk cerebral iskæmi), hvor symptomerne forsvinder inden for 24 timer. Der ses årligt mellem 10.000-12.000 nye tilfælde af apopleksi i Danmark og det er derved en af de største folkesygdomme. Op imod 10 % af patienterne dør inden for den første måned, og hos de overlevende medfører sygdommen ofte en betydelig invalidering. Symptomer De forskellige dele af hjernen har forskellige arbejdsopgaver og symptomerne vil derfor også være forskellige alt efter hvor i hjernen skaden er sket. Er der f.eks. et infarkt i det område der styrer venstre ben, vil patienten have en lammelse i venstre ben. Dertil kan der være nogle mere generelle symptomer, fx hovedpine, træthed og epileptiske kramper. Symptomerne opstår enten fordi det område, som styrer den specifikke funktion, bliver ødelagt, eller fordi projektionsbanerne mellem det styrende område og kroppen bliver afskåret. Lammelser, føleforstyrrelser og bevægeforstyrrelser En stor del af vores hjerne beskæftiger sig med at bevæge forskellige dele af kroppen. Bevægelserne blive igangsat i det motoriske cortex, mens tilstødende områder har "programmer" for hvordan bevægelserne skal laves. Dertil er der en række områder dybere i hjerne, der, sammen med cerebellum, er vigtige for koordination og balance. Alle disse områder er forbundet med hinanden og samarbejder om at lave præcise og glidende bevægelser. De motoriske nervebaner, der løber fra cortex og ned igennem ryggen, krydser nede i hjernestammen. Det betyder, at bevægelser i venstre side af kroppen styres af højre hjernehalvdel. Der kan ses en række forskellige motoriske symptomer: Parese: er nedsat kraft i en kropsdel. Der er bevægelse, men med mindre styrke end normalt. Hvis det er hele den ene side af kroppen kaldes det hemiparese. Paralyse: betyder at al bevægelse er væk. Kropsdelen er altså hel lammet. Styringsbesvær/ataksi: Betyder, at patienten har problemer med at styre en kropsdel eller hele kroppen. Beder man f.eks. patienten om at sætte en finger på næsen, kan man se, at armen ikke bevæges i en blød bue, men i en hakket og ujævn bue og ofte vil fingeren ramme forbi næsen. Facialisparese En facialisparese er en lammelse af ansigtets muskler (de muskler der enerveres af nervus facialis). Ved apopleksi er det næsten altid en central facialisparese hvor patienten har hængende mundvig og ikke kan puste kinden op. Derimod vil de ikke have hængende øjenlåg eller problemer med at rynke panden. Dette er til forskel for en perifer facialis parese, som f.eks. ses ved borrelia. Dysfagi Hvis musklerne i munden og svælget er blevet lammet, kan det påvirke patientens evne til at synke normalt. I svære tilfælde udebliver synkebevægelsen helt, mens den i lettere tilfælde kommer med sekunders forsinkelse. Ved dysfagi lukkes der ikke ordentligt af til luftvejene og der er derfor risiko for, at der kommer vand, mad og sekreter ned i luftvejene (aspiration), hvilket kan medføre lungebetændelse. Føleforstyrrelser Ligesom der er motoriske områder, der styre bevægelser, er der sensoriske områder, der modtager beskeder fra kroppen. Beskederne kan groft deles i følesansen og proprioception. Følesansen modtager besked om berøring, smerte, temperatur og tryk, og proprioception modtager besked fra muskler, sener og led om hvor de forskellige dele af kroppen befinder sig og om bevægelse. Hvis følesansen bliver påvirket, bliver patientens evne til at føle berøring, smerte etc. nedsat. Mange beskriver det også som en summende eller stikkende fornemmelse. Det kan blive et problem, fordi patienten ikke kan mærke hvis de fx støder foden ind i noget, en hånd sidder i klemme eller de er ved at få trykssår. Hvis proprioceptionen er påvirket, får hjernen ikke be-sked om hvor kropsdelene befinder sig i forhold til krop-pen. Det gør det meget svært at styre og koordinere bevægelserne rigtigt og gøre at patienten fremstår klodset og kluntet. De sensoriske og motoriske baner hænger tæt sammen og derfor vil patienter med parese næsten altid også have føleforstyrrelser, og omvendt. Taleproblemer Det at tale er en kompliceret opgave, der involverer flere dele af hjernen. Der er dels en række ’talecentre’ der hos de fleste mennesker sidder i venstre hjernehalvdel, dels de motoriske områder, der laver bevægelserne i munden, tungen og svælget. Der findes flere måder at opdele taleproblemer, men den opdeling vi bruger i hverdagen er: Afasi: Omfatter både problemer med forståelsen og produktionen af sprog. Det kan altså både være et problem med at finde de rigtige ord, udtale ordene rigtigt og opbygge sætninger (ekspressiv afasi) og med at forstå det der bliver sagt til dem (impressiv afasi). De fleste patienter med afasi har dog både ekspressive og impressive problemer, og de kan samtidig have problemer med at læse og skrive. Dysartri: Ved dysartri er der udelukkende et problem med at udtale ordene pga. lammelse i de muskler i mund, tunge og svælg man bruger til at tale. Der er ikke problemer med sætningsopbygning og forståelse. (Dog kan man godt have afasi og dysartri samtidig). Patienter der har taleproblemer vurderes af en logopæd (talepædagog). Kognitive problemer Dette er en bred samlebetegnelse for problemer, der har med tankevirksomhed at gøre, herunder hukommelse, indlæring, indsigt, koncentration og hverdagsfærdigheder at gøre. Disse problemer er mindre synlige end f.eks. en lammelse og det kan være svært for patienten at beskrive dem. Det kræver derfor tæt observation og undersøgelse, før man finder ud af det præcise problem. Nedsat sygdomsindsigt (Anosognosi): Betyder, at patienten ikke oplever eller erkender sin sygdom. Der er et område i parietallappen, som har med kropsopfattelse og sygdomsfornemmelse at gøre. Hvis dette område skades, får resten af hjernen ikke besked om at der er noget galt med kroppen. Patienten er derfor ikke bevidst om, at han/hun er syg og kan i nogle tilfælde benægte, at der skulle være noget galt. Den manglende sygdomserkendelse kan både give problemer i forhold til genoptræningen, fordi patienten ikke er motiveret til træning, og i forhold til patientens sikkerhed, idet patienten ikke kan se sine egne begrænsninger. Neglect & nedsat opmærksomhed: Betyder, at patienten retter det meste eller al sin opmærksomhed væk fra den syge side. Det kan både være i forhold til selve kroppen, at patienten ’glemmer’ den lammede arm eller ben. Det kan også være i forhold til omgivelserne, at patienten slet ikke oplever hvad der foregår på den lammede side og f.eks. ikke høre når der bliver talt fra den side og ikke ser hvad der foregår. Pushing: Betyder, at patientens opfattelse af kroppens midtlinje er forstyrret. Derfor vil patienten spontant læne sig over mod den lammede side og bruge de raske ekstremiteter til aktivt at skubbe sig væk fra den raske side (deraf betegnelsen pushing). Patienten vil ofte insistere på at kroppen er lige, og ved forsøg på at rette den op, vil patienten arbejde imod. Apraksi: Betyder nedsat evne til at planlægge og udføre hverdagsaktiviteter. Det kan være fra at patienten ikke kan finde ud af at bruge redskaberne rigtigt (prøver at rede hår med tandbørsten) eller at udføre de enkelte delaktiviteter i en forkert rækkefølge (begynder at tørre hår inden de har skyllet sæben ud). Agnosi: betyder problemer med genkendelse, f.eks. af genstande eller ansigter. Hvis man f.eks. viser patienten en tandbørste, kan han ikke se hvad det er (visuel agnosi), men når patienten får den i hånden er han ikke i tvivl. Der kan også være problemer med genkendelse ved berøring af genstande (taktil agnosi). Et andet typisk fænomen er ansigtsagnosi, hvor patienten ikke kan genkende ansigter. Når patienten ser sine pårørende virker de ikke bekendte, men lige så snart de pårørende snakker, kan patienten genkende stemmerne. Hukommelsesproblemer: Det kan f.eks. være problemer med at huske sin fødselsdato eller huske informationerne fra personalet. Gråd- og latterlabilitet: Det kaldes også for tvangs-gråd eller tvangslatter, hvor patienten umotiveret og ude af sammenhæng enten græder eller griner vold-somt, uden at patienten kan fortælle hvorfor. Det kan være meget ubehageligt for patienten, fordi deres opførsel virker upassende overfor andre. Synsproblemer Synet kan blive påvirket på flere måder. Hvis synscortex bagerst i occipitallappen eller nervebanerne mellem synscortex og øjnene bliver skadet, kan dele af synet forsvinde. Ofte sker det ved, at enten halvdelen eller det kvarte af synet på begge øjne forsvinder, det kaldes henholdsvis for hemianopsi og kvadrantanopsi. Det er ikke altid, at patienten selv oplever det manglende synsfelt. Her kan det f.eks. observeres ved, at patienten støder ind i ting på den ene side. Dette adskiller sig fra neglect ved at patienten ellers reagere normalt på stimuli fra den påvirkede side. Dobbeltsyn er også et hyppigt symptom. Det kan opstå hvis koordinationen af øjnene bliver forstyrret eller hvis øjnenes muskler bliver lammet. Andre symptomer ved apopleksi Nedsat bevidsthed Ved store skader i hjernen kan bevidstheden være påvirket på forskellige måder. Man kan tale om enten bevidsthedsindhold eller bevidsthedsniveau. Bevidsthedsindhold beskriver om patienten er orienteret og relevant. Kan patienten fortælle sit navn og cpr-nummer, hvor han/hun er og hvilken dag det f.eks. er? Ved patienten om det er dag eller nat? Bevidsthedsniveau beskriver hvor vågen patienten er. Ligger patienten med åbne øjne og følger med i hvad der foregår? Ligger patienten med lukkede øjne, men åbner dem ved tiltale eller smertestimuli? Er patienten ukontaktbar og uden reaktion? Somnolens betyder at patienten er sovende, men kan vækkes til vågen tilstand Ukontaktbar bruges om patienter, som er bevidstløse og ikke kan vækkes ved smertestimuli. Her bør dog uddybes med en beskrivelse af patienten og en Glasgow Coma Scale. Hovedpine Mange patienter, selv ved mindre apopleksier, klager over hovedpine. Den kan både være konstant, trykkende eller dunkende. Hos nogle er den værst om morgenen og hos andre er den lige kraftig igennem døgnet. Patienter, der er bevidsthedssvækkede eller har afasi, kan ikke altid give udtryk for smerter. Her kan smerterne komme til udtryk som motorisk uro, grimasser eller øget puls og respirationsfrekvens. Feber Som en del af kroppens reaktion på den skade der er sket i hjernen, kan patienten godt få forhøjet temperatur. Det betyder ikke nødvendigvis, at patienten har en infektion, men kan bare være et tegn på at kroppen reagere. Temperatur forhøjelsen er imidlertid skadelig for hjernen og derfor forsøger man altid at sænke en temperatur over 37,5 °C ved at give Paracetamol. Svimmelhed og balanceproblemer Særligt hos patienter med skader i hjernestammen og cerebellum kan der være problemer med svimmelhed og med at holde balancen. Kramper Det skadede område i hjernen kan nogle gange være så irriteret, at det udløser et krampeanfald. I den akutte fase er det oftest patienter med blødning, der får krampeanfald. Men i det senere forløb kan både patienter med blødning og infarkt udvikle regelret epilepsi. Træthed Træthed (eller fatigue) er en af de hyppigste følger af apopleksi. Nogle patienter oplever, at de er trætte hele tiden eller hurtigt udtrættes ved aktivitet og måske sover meget. Andre oplever at de mangler energi, er uoplagte eller har svært ved at komme i gang. Mens nogle oplever, at de bliver meget følsomme over for for mange mennesker, støj og lignende. Vigtigste symptomer og kliniske fund efter lokalitet Ætiologi De hyppigste årsager til apopleksi er: Aterosclerose, som forårsager tilstopning af arterier inde i hjernen eller forkalkninger i større arterier uden for hjernen. Kardielle embolier, blodpropper kan dannes andre steder i kroppen og føres til hjernen via blodstrømmen. Emboliske blodpropper kan stamme fra hjertet, hvor atrieflimmer eller skader på hjertevæggen, kan få blodet til at størkne og danne blodpropper, eller fra halspulsårene. Intracranielle blødninger, ofte pga. kronisk forhøjet blodtryk, der har været ubehandlet eller dårligt reguleret, men kan også skyldes andre årsager, som blodfortyndende medicin, cancer, leversygdomme eller blodsygdomme. Småkarstilstopning, hos patienter med kronisk forhøjet blodtryk kommer der små skader på arterierne, der får karvæggen til at hæve op. I de små kar kan hævelse få karet til at lukke helt af så blodstrømmen stopper. Dette giver nogle karakteristiske tynde langstrakte infarkter (lakunære infarkter) dybt i hjernen Karsygdomme, som både kan være medfødte (f.eks. CADASIL) eller på grund af inflammation af kar-væggen, som kan komme af infektioner eller reumatiske sygdomme. Risikofaktorer Der findes over hundrede risikofaktorer for apopleksi. De mest betydningsfulde er disse: Høj alder. Forhøjet blodtryk, er en vigtig risikofaktor for både iskæmiske og hæmorrhagiske apopleksi. Diabetes, fordobler risikoen for iskæmisk apopleksi. Specielt patienter med meget svingende blodsukker er i risiko. Mange ved ikke selv, at de har type-2 diabetes, og derfor skal alle patienter, som indlægges for apopleksi screenes for diabetes med faste blodsukker. Hjertesygdomme, en hyppig årsag til apopleksi er atrieflimmer. Også andre hjertesygdomme, som fx myocardiopati, arytmi og hjerteklapsygdomme er risikofaktorer. Dyslipidæmi, for meget kolesterol og triglycerid i blodet øger risikoen for blodpropper. Rygning. Alkoholoverforbrug, mere end henholdsvis 7 og 14 genstande for kvinder og mænd om ugen. Familiær disponering, altså hvis andre i familien har haft blodpropper i hjernen eller hjertet. Tidligere apopleksi eller TCI. Forsnævring af halspulsårerne. Overvægt og nedsat fysisk aktivitet. Behandling Inden man begynder behandlingen, skal man have afklaret om apopleksien skyldes en blodprop eller en hjerneblødning. Dette kan gøres ved en CT-scanning eller en MR-scanning. Ved en CT-scanning kan man i begyndelsen kun se forandringer, hvis der er tale om en blødning, mens man ved en MR-scanning kan se forandringerne i alle tilfælde. Det evidensbaserede grundlag for behandlingen af patienter med apopleksi i Danmark er samlet i Referenceprogrammet for behandling af patienter med apopleksi og TCI. De fleste større sygehuse i Danmark har i løbet af de sidste 20 år oprettet specialiserede apopleksiafdelinger, til modtagelse og udredning af apopleksipatienter, i den akutte del af forløbet. I Referenceprogrammet bliver en apopleksiafdeling defineret som: en sygehusafdeling, der udelukkende eller næsten udelukkende beskæftiger sig med udredning og behandling af patienter med apopleksi, og som er karakteriseret ved tværfaglige team, et personale med særlig interesse for apopleksi, medinddragelse af pårørende og stadig kompetenceudvikling af personalet. Patienter, som bliver indlagt på disse afdelinger, bliver undersøgt og udredt efter standardiserede forløbsprogrammer. Disse programmer har til formål at sikre ensartede patientforløb af en høj kvalitet og med høj patienttilfredshed. Standardprogrammet vil på de fleste apopleksiafdelinger indbefatte: Klinisk undersøgelse af en reservelæge ved modtagelsen og en speciallæge på andendagen CT-scanning inden for 24 timer Monitorering af vitalværdier: blodtryk, puls, saturation (iltmætning), respirationsfrekvens og temperatur Undersøgelse for hjertesygdomme med EKG og telemetri Blodprøver: Blodbillede, infektionsparametre, blodsukker, lever-/galde-/pancreastal, blodlipider Antitrombotisk behandling: Ved modtagelsen gives 300 mg Acetylsalicylsyre og herefter tablet clopidogrel 75 mg dagligt Vurdering af ergoterapeut, fysioterapeut og evt. logopæd Patienten vil forblive indlagt til observation de første 48 timer efter symptomdebut, fordi risikoen for nye blodpropper er størst i denne periode. Trombolyse Hvis apopleksien skyldes en blodprop i hjernen har enkelte afdelinger i Danmark de senere år haft mulighed for at give blodpropsopløsende medicin, trombolysebehandling. Ved trombolyse gives der en kraftig blodfortyndende medicin intravenøst. Medicinen kan i en del tilfælde opløse blodproppen og derved forhindre yderligere skade på nervevævet. Behandlingen kan derfor kun bruges hvis der er tale om en blodprop, og derfor skal der først laves en CT-scanning for at udelukke en blødning. Hvis man giver trombolyse til en patient med en hjerneblødning, vil det få katastrofale følger, idet trombolysen vil modvirke blodets naturlige evne til at koagulere, og dermed vil blødningen være meget længere om at standse og dermed forrette større skade. Behandling med trombolyse skal, af hensyn til effekt og sikkerhed, gives så hurtigt som muligt. Dels er sandsynligheden for at behandlingen har god effekt større, jo hurtigere den startes. Patienter der behandles efter 4½ time har ingen effekt af behandlingen. Derudover stiger risikoen for bivirkninger, fx blødning, jo længere tid der går fra symptomerne starter. Indenfor 3 timer er der ikke forskel i risikoen for blødning mellem behandling og placebo. Efter 3 timer er risikoen marginalt større i behandlingsgruppen, mens risikoen stiger betydeligt efter 4½ time. Derfor gives trombolysebehandling normalt ikke til patienter med apopleksi efter 4½ time. Behandlingen er stadig ny og noget kontroversiel. Diskussionen bygger på, at behandlingen er meget omkostningsfuld (10-15.000 kr.) og at der har været tvivl om den egentlige effekt af den. Dertil kommer at behandlingen skal iværksættes meget hurtigt; inden for 4½ time efter symptomerne er startet, hvilket i mange tilfælde kan være svært at efterkomme. Trombolyse tilbydes i Aalborg, Holstebro, Århus, Esbjerg, Odense, Roskilde, Glostrup (på ulige datoer) og Bisbebjerg (lige datoer). Hvis det ikke lykkedes at fjerne blodproppen med trombolyse har man mulighed for at fjerne blodproppen med et kateter gennem lysken (thrombektomi). Dette foregår i Århus, Odense og på Rigshospitalet. Det skal foregå hurtigst muligt. Hvis apopleksien skyldes en blødning, vil man kun i sjældne tilfælde tilbyde en operation. Hvis patienten får følger efter apopleksien, vil der tilbydes genoptræning, enten under indlæggelse eller ambulant. Kørselsforbud Efter en blodprop i hjernen er der øget risiko for at udvikle en ny blodprop, også selv om der behandles forebyggende. Tidligere fik alle patienter kørselsforbud efter en blodprop i hjernen i minimum tre måneder, men i dag er det kun patienter med særligt forhøjet risiko, som ikke må køre bil. Man vurderer denne risiko ud fra en standardiseret skala, hvor hver risikofaktor gives point. Det er derved den samlede pointscore, som er afgørende for, om der nedlægges kørselsforbud eller ej. Se også Hjerneskadeforeningen Referencer Neurologiske sygdomme Dødsårsager	danish	0.596077
snake_dizzy/syc20371787.txt	This content does not have an English version. This content does not have an Arabic version. 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Overview Dizziness is a term used to describe a range of sensations, such as feeling faint, woozy, weak or unsteady. Dizziness that creates the false sense that you or your surroundings are spinning or moving is called vertigo. Dizziness is one of the more common reasons adults visit their doctors. Frequent dizzy spells or constant dizziness can significantly affect your life. But dizziness rarely signals a life-threatening condition. Treatment of dizziness depends on the cause and your symptoms. It's usually effective, but the problem may recur. ### Products & Services * [ A Book: Mayo Clinic Book of Home Remedies ](https://order.store.mayoclinic.com/books/gnweb44?utm_source=MC-DotOrg-PS&utm_medium=Link&utm_campaign=HomeRemedies-Book&utm_content=HOM) * [ A Book: Mayo Clinic on Hearing and Balance ](https://order.store.mayoclinic.com/flex/mmv/hrbal02?utm_source=MC-DotOrg-PS&utm_medium=Link&utm_campaign=Hearing-Book&utm_content=HEAR) Show more products from Mayo Clinic ## Symptoms People experiencing dizziness may describe it as any of a number of sensations, such as: * A false sense of motion or spinning (vertigo) * Lightheadedness or feeling faint * Unsteadiness or a loss of balance * A feeling of floating, wooziness or heavy-headedness These feelings may be triggered or worsened by walking, standing up or moving your head. Your dizziness may be accompanied by nausea or be so sudden or severe that you need to sit or lie down. The episode may last seconds or days and may recur. ### When to see a doctor Generally, see your doctor if you experience any recurrent, sudden, severe, or prolonged and unexplained dizziness or vertigo. Get emergency medical care if you experience new, severe dizziness or vertigo along with any of the following: * Sudden, severe headache * Chest pain * Difficulty breathing * Numbness or paralysis of arms or legs * Fainting * Double vision * Rapid or irregular heartbeat * Confusion or slurred speech * Stumbling or difficulty walking * Ongoing vomiting * Seizures * A sudden change in hearing * Facial numbness or weakness [ Request an appointment ](/appointments) There is a problem with information submitted for this request. Review/update the information highlighted below and resubmit the form. ## From Mayo Clinic to your inbox Sign up for free and stay up to date on research advancements, health tips, current health topics, and expertise on managing health. 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You'll soon start receiving the latest Mayo Clinic health information you requested in your inbox. ### Sorry something went wrong with your subscription Please, try again in a couple of minutes Retry ## ## Causes ![Inner ear](/-/media/kcms/gbs/patient- consumer/images/2013/08/26/10/11/ds00435_im00094_ha7_earanatomythu_jpg.jpg) Inner ear and balance Enlarge image Close ### Inner ear and balance ![Inner ear](/-/media/kcms/gbs/patient- consumer/images/2013/08/26/10/11/ds00435_im00094_ha7_earanatomythu_jpg.jpg) ### Inner ear and balance Loop-shaped canals in your inner ear contain fluid and fine, hairlike sensors that help you keep your balance. At the base of the canals are the utricle and saccule, each containing a patch of sensory hair cells. Within these cells are tiny particles (otoconia) that help monitor the position of your head in relation to gravity and linear motion, such as going up and down in an elevator or moving forward and backward in a car. Dizziness has many possible causes, including inner ear disturbance, motion sickness and medication effects. Sometimes it's caused by an underlying health condition, such as poor circulation, infection or injury. The way dizziness makes you feel and your triggers provide clues for possible causes. How long the dizziness lasts and any other symptoms you have also help pinpoint the cause. ### Inner ear problems that cause dizziness (vertigo) Your sense of balance depends on the combined input from the various parts of your sensory system. These include your: * Eyes, which help you determine where your body is in space and how it's moving * Sensory nerves, which send messages to your brain about body movements and positions * Inner ear, which houses sensors that help detect gravity and back-and-forth motion Vertigo is the false sense that your surroundings are spinning or moving. With inner ear disorders, your brain receives signals from the inner ear that aren't consistent with what your eyes and sensory nerves are receiving. Vertigo is what results as your brain works to sort out the confusion. * Benign paroxysmal positional vertigo (BPPV). This condition causes an intense and brief but false sense that you're spinning or moving. These episodes are triggered by a rapid change in head movement, such as when you turn over in bed, sit up or experience a blow to the head. BPPV is the most common cause of vertigo. * Infection. A viral infection of the vestibular nerve, called vestibular neuritis, can cause intense, constant vertigo. If you also have sudden hearing loss, you may have labyrinthitis. * Meniere's disease. This disease involves the excessive buildup of fluid in your inner ear. It's characterized by sudden episodes of vertigo lasting as long as several hours. You may also experience fluctuating hearing loss, ringing in the ear and the feeling of a plugged ear. * Migraine. People who experience migraines may have episodes of vertigo or other types of dizziness even when they're not having a severe headache. Such vertigo episodes can last minutes to hours and may be associated with headache as well as light and noise sensitivity. ### Circulation problems that cause dizziness You may feel dizzy, faint or off balance if your heart isn't pumping enough blood to your brain. Causes include: * Drop in blood pressure. A dramatic drop in your systolic blood pressure — the higher number in your blood pressure reading — may result in brief lightheadedness or a feeling of faintness. It can occur after sitting up or standing too quickly. This condition is also called orthostatic hypotension. * Poor blood circulation. Conditions such as cardiomyopathy, heart attack, heart arrhythmia and transient ischemic attack could cause dizziness. And a decrease in blood volume may cause inadequate blood flow to your brain or inner ear. ### Other causes of dizziness * Neurological conditions. Some neurological disorders — such as Parkinson's disease and multiple sclerosis — can lead to progressive loss of balance. * Medications. Dizziness can be a side effect of certain medications — such as anti-seizure drugs, antidepressants, sedatives and tranquilizers. In particular, blood pressure lowering medications may cause faintness if they lower your blood pressure too much. * Anxiety disorders. Certain anxiety disorders may cause lightheadedness or a woozy feeling often referred to as dizziness. These include panic attacks and a fear of leaving home or being in large, open spaces (agoraphobia). * Low iron levels (anemia). Other signs and symptoms that may occur along with dizziness if you have anemia include fatigue, weakness and pale skin. * Low blood sugar (hypoglycemia). This condition generally occurs in people with diabetes who use insulin. Dizziness (lightheadedness) may be accompanied by sweating and anxiety. * Carbon monoxide poisoning. Symptoms of carbon monoxide poisoning are often described as "flu-like" and include headache, dizziness, weakness, upset stomach, vomiting, chest pain and confusion. * Overheating and dehydration. If you're active in hot weather or if you don't drink enough fluids, you may feel dizzy from overheating (hyperthermia) or from dehydration. This is especially true if you take certain heart medications. ## Risk factors Factors that may increase your risk of getting dizzy include: * Age. Older adults are more likely to have medical conditions that cause dizziness, especially a sense of imbalance. They're also more likely to take medications that can cause dizziness. * A past episode of dizziness. If you've experienced dizziness before, you're more likely to get dizzy in the future. ## Complications Dizziness can increase your risk of falling and injuring yourself. Experiencing dizziness while driving a car or operating heavy machinery can increase the likelihood of an accident. You may also experience long-term consequences if an existing health condition that may be causing your dizziness goes untreated. ## [ By Mayo Clinic Staff ](/about-this-site/meet-our-medical-editors) [ Request an appointment ](/appointments) [ Diagnosis & treatment ](/diseases-conditions/dizziness/diagnosis- treatment/drc-20371792) Dec. 03, 2022 [ Print ](/diseases-conditions/dizziness/symptoms-causes/syc-20371787?p=1) Show references 1. Walls RM, et al., eds. Dizziness and vertigo. In: Rosen's Emergency Medicine: Concepts and Clinical Practice. 9th ed. Philadelphia, Pa.: Elsevier; 2018. https://www.clinicalkey.com. Accessed Aug. 5, 2018. 2. Dizziness and vertigo. Merck Manual Professional Version. https://www.merckmanuals.com/professional/ear-nose-and-throat-disorders/approach-to-the-patient-with-ear-problems/dizziness-and-vertigo. Accessed Aug. 5, 2018. 3. Dizziness and motion sickness. American Academy of Otolaryngology — Head and Neck Surgery. https://www.entnet.org//content/dizziness-and-motion-sickness. Accessed Aug. 5, 2018. 4. Flint PW, et al. Peripheral vestibular disorders. In: Cummings Otolaryngology: Head & Neck Surgery. 6th ed. Philadelphia, Pa.: Saunders Elsevier; 2015. https://www.clinicalkey.com. Accessed Aug. 8, 2018. 5. Bope ET, et al. Dizziness and vertigo. In: Conn's Current Therapy 2018. Philadelphia, Pa.: Elsevier; 2018. https://www.clinicalkey.com. Accessed Aug. 8, 2018. 6. Branch WT, et al. Approach to the patient with dizziness. https://www.uptodate.com/contents/search. Accessed Aug. 5, 2018. 7. Heat injury and heat exhaustion. American Academy of Orthopaedic Surgeons. http://orthoinfo.aaos.org/topic.cfm?topic=A00319. Accessed Aug. 5, 2018. 8. Muncie HL, et al. Dizziness: Approach to evaluation and management. American Family Physician. 2017;95:154. 9. Moskowitz HS, et al. Meniere disease. https://www.uptodate.com/contents/search. Accessed Aug. 5, 2018. 10. Migraine information page. National Institute of Neurological Disorders and Stroke. https://www.ninds.nih.gov/Disorders/All-Disorders/Migraine-Information-Page. Accessed Aug. 5, 2018. 11. Shepard NT (expert opinion). Mayo Clinic, Rochester, Minn. June 4, 2018. 12. Rohren CH (expert opinion). Mayo Clinic, Rochester, Minn. July 4, 2018. 13. Important facts about falls. Centers for Disease Control and Prevention. https://www.cdc.gov/homeandrecreationalsafety/falls/adultfalls.html. Accessed Aug. 5, 2018. 14. Carbon monoxide poisoning FAQs. Centers for Disease Control and Prevention. https://www.cdc.gov/co/faqs.htm. 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snake_dizzy/6422dizziness.txt	Locations : [ Abu Dhabi ](https://www.clevelandclinicabudhabi.ae/) \| [ Canada ](https://my.clevelandclinic.org/canada) \| [ Florida ](https://my.clevelandclinic.org/florida) \| [ London ](https://clevelandcliniclondon.uk/) \| [ Nevada ](https://my.clevelandclinic.org/locations/nevada) \| [ Ohio ](https://my.clevelandclinic.org) \| ![Gray gradient](/health/_next/static/media/gray-gradient- left-16.59910877.svg?w=32&q=75) ![Gray gradient](/health/_next/static/media/gray-gradient- right-32.dd7ce4e5.svg?w=64&q=75) * [ 800.223.2273 ](tel:800.223.2273) * [ 100 Years of Cleveland Clinic ](https://my.clevelandclinic.org/about/history) * [ MyChart ](https://my.clevelandclinic.org/online-services/mychart) * [ Need Help? ](https://my.clevelandclinic.org/help) * [ Giving ](https://my.clevelandclinic.org/giving) * [ Careers ](https://jobs.clevelandclinic.org) * [ ![Search Icon Blue](/health/_next/static/media/search--blue.a23a2bb9.svg?w=32&q=75) Search ](https://my.clevelandclinic.org/search) [ ![Cleveland Clinic logo](/health/_next/static/media/logo- ccf.a7ea0118.svg?w=3840&q=75) ](https://my.clevelandclinic.org/) [ ![Search Icon](/health/_next/static/media/search-- gray.86f52a63.svg?w=48&q=75) ](https://my.clevelandclinic.org/search) * [ ClevelandClinic.org ](https://my.clevelandclinic.org) * [ Find A Doctor ](https://my.clevelandclinic.org/staff) * [ Locations & Directions ](https://my.clevelandclinic.org/locations) * [ Patients & Visitors ](https://my.clevelandclinic.org/patients) * [ Health Library ](https://my.clevelandclinic.org/health) * [ Institutes & Departments ](https://my.clevelandclinic.org/departments) * [ Appointments ](https://my.clevelandclinic.org/patients/information/access) ![](//zdbb.net/l/Dnl1wmWs8xCCpvWNCt9Egf/?w=16&q=75) [ Home ](https://my.clevelandclinic.org) / [ Health Library ](https://my.clevelandclinic.org/health) / [ Symptoms ](https://my.clevelandclinic.org/health/symptoms) / Dizziness Advertisement Advertisement Advertisement # Dizziness Dizziness is a common issue. If you have dizziness, you may feel woozy and disoriented. You may feel as if you’re about to lose your balance. Many things may make you dizzy, such as anxiety or a reaction to medication. But dizziness may be a symptom of an underlying medical issue. Talk to your healthcare provider if you’re having frequent or serious dizzy spells. Contents Arrow Down Overview Possible Causes Care and Treatment When To Call the Doctor Additional Common Questions Contents Arrow Down Overview Possible Causes Care and Treatment When To Call the Doctor Additional Common Questions ## Overview ![Dizziness is commonly caused by inner ear infections $top right$, labyrinthitis $center$ and vestibular neuritis $far right$.](https://my.clevelandclinic.org/-/scassets/Images/org/health/articles/6422-dizziness) Dizziness is feeling woozy or unsteady. Many things can make you feel dizzy. Inner ear disorders are a common cause. Inner ear disorders include inner ear infections (top right), labyrinthitis (center) and vestibular neuritis (far right). ### What is dizziness? Healthcare providers describe dizziness as having impaired or disturbed spatial orientation. You might describe dizziness as feeling woozy or light headed. You may feel as if you need to sit down before you fall down. Frequent or severe dizziness may affect your quality of life. People experience dizziness in different ways, including: * Feeling [ faint. ](https://my.clevelandclinic.org/health/symptoms/21699-fainting) * Feeling [ nauseous ](https://my.clevelandclinic.org/health/symptoms/8106-nausea--vomiting) . * Feeling unsteady on their feet, as if they lost their sense of [ balance ](https://my.clevelandclinic.org/health/symptoms/21021-balance-problems) . * Feeling disoriented or confused . Advertisement Cleveland Clinic is a non-profit academic medical center. Advertising on our site helps support our mission. We do not endorse non-Cleveland Clinic products or services. [ Policy ](https://health.clevelandclinic.org/advertising) ## Possible Causes ### What causes dizziness? Dizziness happens when something affects your sense of balance. A stable sense of balance requires a steady flow of information from your ears, eyes, tissues and central nervous system. Your central nervous system uses this information to tell your body how to maintain balance. When something disrupts the flow, your central nervous system can process information incorrectly and you can feel unsteady and dizzy. Inner ear disorders, neurological conditions, medications and even stress may make you feel dizzy. #### Inner ear disorders * [ Benign paroxysmal positional vertigo ](https://my.clevelandclinic.org/health/diseases/11858-benign-paroxysmal-positional-vertigo-bppv) (BPPV). People with BPPV feel a spinning sensation when they move their heads. * Labyrinthitis. Inflammation in your labyrinth, the [ inner ear ](https://my.clevelandclinic.org/health/body/24340-inner-ear) system that’s responsible for hearing and balance. * [ Vestibular neuritis ](https://my.clevelandclinic.org/health/diseases/15227-vestibular-neuritis) . This disorder affects the vestibulocochlear nerve of your inner ear. * [ Persistent postural perceptual dizziness (PPPD) ](https://my.clevelandclinic.org/health/diseases/persistent-postural-perceptual-dizziness) . Dizziness that’s triggered by things or activities going on around you, like being around crowds. PPPD symptoms come and go. * [ Inner ear infections ](https://my.clevelandclinic.org/health/diseases/24240-inner-ear-infection-otitis-interna) . Inflammation in your inner ear from viral or bacterial ear infections may interfere with the messages your inner ear sends to your brain. #### Other medical conditions * [ Anemia ](https://my.clevelandclinic.org/health/diseases/3929-anemia) . Anemia is not having enough red blood cells. Dizziness is a common anemia symptom. * [ Acoustic neuroma ](https://my.clevelandclinic.org/health/diseases/16400-acoustic-neuroma) . Noncancerous tumors in your inner ear may affect your balance and make you feel dizzy. * Cardiovascular issues. Issues that affect the flow of blood to your brain such as irregular heartbeat ( [ atrial fibrillation ](https://my.clevelandclinic.org/health/diseases/16765-atrial-fibrillation-afib) ), low blood pressure, ( [ hypotension ](https://my.clevelandclinic.org/health/diseases/21156-low-blood-pressure-hypotension) ) or narrowed arteries ( [ atherosclerosis ](https://my.clevelandclinic.org/health/diseases/16753-atherosclerosis-arterial-disease) ) may make you feel dizzy. * [ Concussion. ](https://my.clevelandclinic.org/health/diseases/24240-inner-ear-infection-otitis-interna) This head injury damages your brain and causes dizziness, among other symptoms. * Neurological diseases or disorders [ . Migraine headaches ](https://my.clevelandclinic.org/health/diseases/5005-migraine-headaches) , [ multiple sclerosis ](https://my.clevelandclinic.org/health/diseases/17248-multiple-sclerosis) and [ Parkinson’s disease ](https://my.clevelandclinic.org/health/diseases/8525-parkinsons-disease-an-overview) are examples of neurological disorders that affect your sense of balance and make you feel dizzy. #### Other common causes Medical conditions and other issues that may cause dizziness include: * [ Anxiety ](https://my.clevelandclinic.org/health/diseases/9536-anxiety-disorders) and [ stress ](https://my.clevelandclinic.org/health/articles/11874-stress) . You may feel dizzy if you hyperventilate because you’re anxious or under stress. * [ Carbon monoxide poisoning ](https://my.clevelandclinic.org/health/diseases/15663-carbon-monoxide-poisoning) . Breathing in carbon monoxide causes dizziness. * [ Dehydration ](https://my.clevelandclinic.org/health/treatments/9013-dehydration) . Dizziness is a symptom of severe dehydration. * Low blood sugar ([ hypoglycemia ](https://my.clevelandclinic.org/health/diseases/11647-hypoglycemia-low-blood-sugar) ). Sudden dizziness is a hypoglycemia symptom. * Medications. [ Blood pressure medications ](https://my.clevelandclinic.org/health/treatments/21811-antihypertensives) often cause dizziness. * [ Motion sickness ](https://my.clevelandclinic.org/health/articles/12782-motion-sickness) . Motion sickness may make you feel dizzy and affect your balance. ## Care and Treatment ### How is dizziness treated? Dizziness treatment depends on the cause. For example, if you’re dizzy because you have an inner ear infection, your healthcare provider will treat the infection. If you’re taking medications that make you feel dizzy, your provider may recommend you limit activities until your body adjusts to the medication. Some people benefit from a [ vestibular test battery ](https://my.clevelandclinic.org/health/diagnostics/21518-vestibular-test- battery) to help determine if dizziness is due to an inner ear problem and [ vestibular rehabilitation therapy ](https://my.clevelandclinic.org/health/treatments/15298-vestibular- rehabilitation) (VRT) to help treat the dizziness. Vestibular rehabilitation therapy involves exercises to manage dizziness symptoms. #### Can I treat dizziness at home? No, but you can manage dizziness. If you’re feeling dizzy, lie down until dizziness passes. When you get up, be sure to move slowly and carefully. #### What are the possible complications or risks of not treating dizziness? Dizziness may not seem as if it’s a symptom of a serious issue, but you should still talk to a healthcare provider if you’re frequently dizzy: * Dizziness may be a symptom of medical conditions that could get worse if left untreated. * Dizziness is a balance issue, increasing your risk of falling and possibly being injured. * Dizziness may make it unsafe for you to drive vehicles. * Sometimes, dizziness may make it hard for you to work or manage your daily tasks and responsibilities. Advertisement ### Can dizziness be prevented? The best way to prevent dizziness is to find out why you’re dizzy. For example, if you become dizzy when you’re dehydrated, you may prevent dizziness by drinking enough water. If you take blood pressure medication that makes you dizzy, your healthcare provider may prescribe a different medication or dosage. Unfortunately, you can’t predict or prevent all things that cause dizziness, such as a neurological disorder. Care at Cleveland Clinic [ Find a Primary Care Provider ](https://my.clevelandclinic.org/services/primary-care) [ Schedule an Appointment ](https://my.clevelandclinic.org/services/primary- care#call-to-action-panel) ## When To Call the Doctor ### When should a healthcare provider treat dizziness? Talk to your provider if: * Dizziness affects your ability to go about your day. * Dizziness doesn’t go away or keeps coming back. Advertisement ## Additional Common Questions ### What’s the difference between dizziness and vertigo? With [ vertigo ](https://my.clevelandclinic.org/health/diseases/21769-vertigo) , you have a sensation that you’re moving through space or your surroundings are spinning. Dizziness is an overall feeling of being unbalanced. A note from Cleveland Clinic Everyone has dizzy spells — a sudden wooziness that comes and goes. But some people have severe or frequent dizziness that disrupts their daily lives. Talk to a healthcare provider if you often feel very dizzy. That way, you’ll know why you’re dizzy and what you can do to manage dizziness. [ ](mailto:?subject=Cleveland Clinic - Dizziness&body=https://my.clevelandclinic.org/health/symptoms/6422-dizziness) Medically Reviewed Last reviewed by a Cleveland Clinic medical professional on 04/03/2023. Learn more about our [ editorial process ](https://my.clevelandclinic.org/about/website/editorial-policy) . #### References Advertisement Cleveland Clinic is a non-profit academic medical center. Advertising on our site helps support our mission. We do not endorse non-Cleveland Clinic products or services. 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All Rights Reserved.	biology	2826409	https://sv.wikipedia.org/wiki/Theclinesthes%20albocincta	Theclinesthes albocincta	Theclinesthes albocincta är en fjärilsart som beskrevs av Waterhouse 1903. Theclinesthes albocincta ingår i släktet Theclinesthes och familjen juvelvingar. Inga underarter finns listade i Catalogue of Life. Källor Externa länkar Juvelvingar albocincta	swedish	1.353571
snake_dizzy/snakecatchhtml.txt	[ ![wildlifeanimalcontrol.com](images/bannerWAC.jpg) ](index.html) * __ [ [email protected] ](mailto:[email protected]) __ Call us for help in your town __ Wildlife Control Education * [ Home ](index.html) * [ Services ](services.html) * [ Photos ](photos.html) * [ Pest Info ](pestinformation.html) * [ About Us ](about.html) * [ FAQ ](faq.html) * [ Prices ](prices.html) * [ Locations ](locations.html) * [ Contact Us ](contact.html) # How to Catch a Snake in Your House ![](images/infosnake.jpg) Need snake removal in your hometown? We service over 500 USA locations! [ Click here to hire us in your town and check prices ](index.html) \- updated for year 2020. If you have a pesky snake in your garden, or are just interested in learning how to catch a snake, there are numerous things that you are able to do to safely and humanely capture the reptile. Identify It First The first thing you want to do is examine the snake. Take into consideration the length, size and color of the reptile, as well as other distinguishing characteristics. Once you have examined the snake, you may want to place the characteristics into a search engine to determine if the snake is venomous. If there is any question if it is poisonous, you should contact your local animal shelter and inquire with them. If the snake you are trying to catch is venomous, you should contact a local animal shelter or wildlife rescue, you should usually not attempt to catch a venomous snake. By Hand Before you begin handling the reptile, you should always wear protective gloves. Some snakes can carry bacteria that can be harmful for humans. Once you have protected your hands, you can use a long stick or other slender object that is long. You should use the stick to distract the reptile. Once the snake is distracted, you can firmly grasp the snakeâs tail and lift up. Make sure that you are leaving the top half of the snakeâs body on the ground and as far away from you as possible. Once you have a firm grasp on the tail of the snake, you can use your stick to lift the rest of the animal. You are able to do so by placing the stick underneath the top portion of the snake. Remember not to make sudden movements or startle the snake. Reptiles are more likely to bite when they are startled or scared. When you have a firm hold on the snake you are able to transition his location. Put it in a snake sack or pillow case. You will usually want to relocate the snake to a location that offers it many places to hide such as a stone wall or bushes. If you are able to walk your snake to his new area, you will just need to release the snake by aiming his head at the location where you would like it to go, and release the tail. The reptile will usually seek shelter to get away from you. Learn more: [ Does rope act as a snake repellent? ](snakerope.html) If you are unable to relocate the snake to a location that is within walking distance, you will need to place the snake into a cage. The snake can be placed into the cage in a similar fashion to the above instructions for releasing it into a bush. Once you have transported the reptile to his new home, simply lay the cage on its side and allow for the reptile to slither into his new environment. With Tools - Broom, Snake Tongs, Snake Hook Snake tongs are a good tool to grab a snake from a distance. You probably don't own a pair, but the pros do. A snake hook is good for larger heavier snakes - the snake drapes over the hook. Put it in a snake sack or pillow case. Find out more: [ Types of Florida Water Snakes ](snakesflorida.html) If you do not wish to touch the snake, you can always just sweep it out the door with a push broom. Or you can use a garbage can or cage. Lay the garbage can or cage on its side and use a broom and shovel to push the snake into the unit. Once you have captured the reptile, you will be able to safely transport and humanely relocate the snake to a new area. A thin snake like a garter snake is usually too small to capture with a snake stick or tongs. If you are attempting to catch a garden snake, you may be more successful to use your hands, with gloves of course. Approach the snake slowly so that you do not scare him into a bush or somewhere close by for him to hide. Once you have approached the snake, you can grab the tail and use a stick or similar object to hold his head into place. Make sure that you are not choking the snake. Once you have the snake pinned down you are able to grab the snake as firmly as possible by the neck as close to his head as you are able to grab. You can use your other hand the support the body of the snake to prevent it from moving around. Once you have captured the reptile, you are able to humanely relocate him. If you spot the snake that you are trying to capture you should not run over to it. This will startle the snake and cause it to move away quickly or bite. You should always approach the snake very carefully and slowly. ### More in-detail how-to snake removal articles: Information about [ snake trapping ](snaketrapping.html) \- analysis and methods for how to trap. Information about [ how to kill a snake ](snakekill.html) \- with fumigants or poison. Information about [ how to keep snakes away ](snakekeepaway.html) \- prevention techniques. Information about [ snake repellent ](snakerepellent.html) \- analysis of types and effectiveness. Learn how to get snakes out from [ under a shed or porch ](snakeporch.html) , what [ snake feces look like ](snakepoop.html) , and if snakes make [ good pets ](snakepet.html) . Find out if a [ pest control company ](snakepest.html) will remove a snake, or if the [ city or county animal services ](snakeissue.html) will help with a snake issue. Memorize the [ snake poem ](snakepoem.html) that can save a life, and learn all about [ The Northern Water Snake ](snakenorthern.html) . I can show you what to do if you [ find a nest of snakes ](snakenest.html) , and tactics to [ find a lost snake in your house ](snakelost.html) . Learn about [ Snake mating habits ](snakemating.html) , what animals [ catch and kill snakes ](snakekills.html) and if snakes [ have ears ](snakehear.html) . Read about [ The Garter Snake ](snakegarter.html) and the [ problem of Burmese Pythons in south Florida ](snakeflorida.html) . I can show you how to keep snakes [ out of the garden ](snakegarden.html) , if [ snake feces are dangerous ](snakefeces.html) , if snakes [ lay eggs ](snakeegg.html) , and if a [ high pitch sound deterrent machine ](snakedeterrent.html) will work against snakes. You are here to learn how to catch a snake in your house or yard. This site is intended to provide snake education and information, so that you can make an informed decision if you need to deal with a snake problem. This site provides many snake control articles and strategies, if you wish to attempt to solve the problem yourself. If you are unable to do so, which is likely with many cases of snake removal, please go to the home page and click the USA map, where I have wildlife removal experts listed in over 500 cites and towns, who can properly help you with your nuisance snake. Click here to read more about [ how to get rid of snakes ](snakes.html) . #### Select Your Animal [ ![](images/bar_raccoon2.jpg) ](raccoons.html) [ Raccoons ](raccoons.html) Raccoon Control Education and Services [ ![](images/bar_squirrel2.jpg) ](squirrels.html) [ Squirrels ](squirrels.html) Squirrel Control Education and Services [ ![](images/bar_opossum2.jpg) ](opossums.html) [ Opossum ](opossums.html) Opossum Control Education and Services [ ![](images/bar_skunk2.jpg) ](skunks.html) [ Skunks ](skunks.html) Skunk Control Education and Services [ ![](images/bar_rat2.jpg) ](rats.html) [ Rats ](rats.html) Rat Control Education and Services [ ![](images/bar_mouse2.jpg) ](mice.html) [ Mice ](mice.html) Mouse Control Education and Services [ ![](images/bar_mole2.jpg) ](moles.html) [ Moles ](moles.html) Mole Control Education and Services [ ![](images/bar_groundhog2.jpg) ](groundhogs.html) [ Groundhog ](groundhogs.html) Groundhog Control Education and Services [ ![](images/bar_armadillo2.jpg) ](armadillos.html) [ Armadillos ](armadillos.html) Armadillo Control Education and Services [ ![](images/bar_beaver2.jpg) ](beavers.html) [ Beaver ](beavers.html) Beaver Control Education and Services [ ![](images/bar_fox2.jpg) ](fox.html) [ Fox ](fox.html) Fox Control Education and Services [ ![](images/bar_coyote2.jpg) ](coyotes.html) [ Coyotes ](coyotes.html) Coyote Control Education and Services [ ![](images/bar_bird2.jpg) ](birds.html) [ Birds ](birds.html) Bird Control Education and Services [ ![](images/bar_bat2.jpg) ](bats.html) [ Bats ](bats.html) Bat Control Education and Services [ ![](images/bar_snake2.jpg) ](snakes.html) [ Snakes ](snakes.html) Snake Control Education and Services [ ![](images/bar_dead2.jpg) ](deadanimals.html) [ Dead ](deadanimals.html) Dead Animal Control Education and Services #### About Us Wildlife Animal Control is an educational resource for nuisance animal issues. We also provide professional service in over 600 locations. Call us today! #### Useful Links * [ Click to learn about our services ](services.html) * [ Click to see our prices for year 2020 ](prices.html) * [ Click to see our 600+ locations ](locations.html) * [ Frequently Asked Questions ](faq.html) #### Our Wildlife Experts ![](images/WACtechs.jpg) #### Our Services * Animal Education & Tips * Humane Trapping & Relocation * Critter Prevention & Repairs * Removal of Wildlife in Attic * Emergency Animal Services Â© Copyright 2020 by Wildlife Animal Control. Email us at [email protected] - Animal Education - Wildlife Control in Over 600 Locations	biology	8481883	https://sv.wikipedia.org/wiki/Sphaerotheca	Sphaerotheca	Sphaerotheca kan syfta på: ett släkte svampar, se Sphaerotheca (svampar) ett släkte groddjur, se Sphaerotheca (groddjur)	swedish	1.148364

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