1.
Evolution
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Evolution is change in the heritable characteristics of biological populations over successive generations. Evolutionary processes give rise to biodiversity at every level of organisation, including the levels of species, individual organisms. In July 2016, scientists reported identifying a set of 355 genes from the LUCA of all living on Earth. The fossil record includes a progression from early biogenic graphite, to microbial mat fossils, existing patterns of biodiversity have been shaped both by speciation and by extinction. More than 99 percent of all species that lived on Earth are estimated to be extinct. Estimates of Earths current species range from 10 to 14 million, more recently, in May 2016, scientists reported that 1 trillion species are estimated to be on Earth currently with only one-thousandth of one percent described. In the mid-19th century, Charles Darwin formulated the theory of evolution by natural selection. This teleonomy is the quality whereby the process of natural selection creates and preserves traits that are fitted for the functional roles they perform. The processes by which the changes occur, from one generation to another, are called evolutionary processes or mechanisms, the four most widely recognized evolutionary processes are natural selection, genetic drift, mutation and gene migration. Natural selection and genetic drift sort variation, mutation and gene migration create variation, consequences of selection can include meiotic drive, nonrandom mating and genetic hitchhiking. In the early 20th century the modern evolutionary synthesis integrated classical genetics with Darwins theory of evolution by natural selection through the discipline of population genetics, the importance of natural selection as a cause of evolution was accepted into other branches of biology. Moreover, previously held notions about evolution, such as orthogenesis, evolutionism, evolutionary computation, a sub-field of artificial intelligence, involves the application of Darwinian principles to problems in computer science. 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, such proposals survived into Roman times. The poet and philosopher Lucretius followed Empedocles in his masterwork De rerum natura, in contrast to these materialistic views, Aristotelianism considered all natural things as actualisations of fixed natural possibilities, known as forms. This was part of a teleological understanding of nature in which all things have an intended role to play in a divine cosmic order. In the 17th century, the new method of modern science rejected the Aristotelian approach, however, this new approach was slow to take root in the biological sciences, the last bastion of the concept of fixed natural types. The biological classification introduced by Carl Linnaeus in 1735 explicitly recognized the nature of species relationships. Other naturalists of this time speculated on the change of species over time according to natural laws
2.
Thomas Henry Huxley
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Thomas Henry Huxley PC PRS FLS was an English biologist, known as Darwins Bulldog for his advocacy of Charles Darwins theory of evolution. Huxleys famous debate in 1860 with Samuel Wilberforce was a key moment in the acceptance of evolution. Huxley had been planning to leave Oxford on the day, but, after an encounter with Robert Chambers. Wilberforce was coached by Richard Owen, against whom Huxley also debated about whether humans were closely related to apes. Huxley was slow to accept some of Darwins ideas, such as gradualism, and was undecided about natural selection, instrumental in developing scientific education in Britain, he fought against the more extreme versions of religious tradition. Originally coining the term in 1869, Huxley elaborated on agnosticism in 1889 to frame the nature of claims in terms of what is knowable and what is not. Huxley states Agnosticism, in fact, is not a creed, but a method, the fundamental axiom of modern science. In matters of the intellect, follow your reason as far as it will take you, in matters of the intellect, do not pretend that conclusions are certain which are not demonstrated or demonstrable. Use of that term has continued to the present day, Huxley had little formal schooling and was virtually self-taught. He became perhaps the finest comparative anatomist of the latter 19th century and he worked on invertebrates, clarifying relationships between groups previously little understood. Later, he worked on vertebrates, especially on the relationship between apes and humans, after comparing Archaeopteryx with Compsognathus, he concluded that birds evolved from small carnivorous dinosaurs, a theory widely accepted today. Thomas Henry Huxley was born in Ealing, which was then a village in Middlesex and he was the second youngest of eight children of George Huxley and Rachel Withers. Like some other British scientists of the century such as Alfred Russel Wallace. His father was a teacher at Ealing School until it closed. As a result, Thomas left school at age 10, after two years of formal schooling. Despite this unenviable start, Huxley was determined to educate himself and he became one of the great autodidacts of the nineteenth century. At first he read Thomas Carlyle, James Huttons Geology, in his teens he taught himself German, eventually becoming fluent and used by Charles Darwin as a translator of scientific material in German. He learned Latin, and enough Greek to read Aristotle in the original, later on, as a young adult, he made himself an expert, first on invertebrates, and later on vertebrates, all self-taught
3.
John Gould
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John Gould FRS was an English ornithologist and bird artist. He has been considered the father of study in Australia. His identification of the birds now nicknamed Darwins finches played a role in the inception of Darwins theory of evolution by natural selection, Goulds work is referenced in Charles Darwins book, On the Origin of Species. Gould was born in Lyme Regis, Dorset, the first son of a gardener and he and the boy probably had a scanty education. Shortly afterwards his father obtained a position on an estate near Guildford, Surrey and he was for some time under the care of J. T. Aiton, of the Royal Gardens of Windsor. The young Gould started training as a gardener, being employed under his father at Windsor from 1818 to 1824 and he became an expert in the art of taxidermy. In 1824 he set himself up in business in London as a taxidermist, Goulds position brought him into contact with the countrys leading naturalists. This meant that he was often the first to see new collections of birds given to the Zoological Society of London, in 1830 a collection of birds arrived from the Himalayas, many not previously described. Gould published these birds in A Century of Birds from the Himalaya Mountains, the text was by Nicholas Aylward Vigors and the illustrations were lithographed by Goulds wife Elizabeth, daughter of Nicholas Coxen, of Kent. Most of Goulds work were rough sketches on paper from which artists created the lithographic plates. This work was followed by four more in the seven years. It was completed in 1837, Gould wrote the text, and his clerk, Edwin Prince, some of the illustrations were made by Edward Lear as part of his Illustrations of the Family of Psittacidae in 1832. Lear, however, was in difficulty, and he sold the entire set of lithographs to Gould. The books were published in a large size, imperial folio. Eventually 41 of these volumes were published, with about 3000 plates and they appeared in parts at £3 3s. A number, subscribed for in advance, and in spite of the expense of preparing the plates, Gould succeeded in making his ventures pay. This was a period for Gould who also published Icones Avium in two parts containing 18 leaves of bird studies on 54 cm plates as a supplement to his previous works. No further monographs were published as in 1838 he and his moved to Australia to work on the Birds of Australia
4.
Homology (biology)
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In biology, homology is the existence of shared ancestry between a pair of structures, or genes, in different taxa. Evolutionary biology explains homologous structures adapted to different purposes as the result of descent with modification from a common ancestor, examples include the legs of a centipede, the maxillary palp and labial palp of an insect, and the spinous processes of successive vertebrae in a vertebral column. Sequence homology between protein or DNA sequences is defined in terms of shared ancestry. Two segments of DNA can have shared ancestry because of either an event or a duplication event. Homology among proteins or DNA is inferred from their sequence similarity, significant similarity is strong evidence that two sequences are related by divergent evolution from a common ancestor. Alignments of multiple sequences are used to discover the homologous regions, the word homology, coined in about 1656, derives from the Greek ὁμόλογος homologos from ὁμός homos same and λόγος logos relation. Homology is the relationship between biological structures or sequences that are derived from a common ancestor, for example, many insects possess two pairs of flying wings. In beetles, the first pair of wings has evolved into a pair of hard wing covers, the same major forearm bones are found in fossils of lobe-finned fish such as Eusthenopteron. The opposite of homologous organs are analogous organs which do similar jobs in two taxa that were not present in their last common ancestor but rather evolved separately. For example, the wings of insects and birds evolved independently in widely separated groups, similarly, the wings of a sycamore maple seed and the wings of a bird are analogous but not homologous, as they develop from quite different structures. A structure can be homologous at one level, but only analogous at another, for example, in the pterosaurs, the wing involves both the forelimb and the hindlimb. Analogy is called homoplasy in cladistics, and convergent or parallel evolution in evolutionary biology, specialised terms are used in taxonomic research. Primary homology is that initially conjectured by a researcher based on similar structure or anatomical connections, secondary homology is implied by parsimony analysis, where a character that only occurs once on a tree is taken to be homologous. As implied in this definition, many cladists consider homology to be synonymous with synapomorphy, homologies provide the fundamental basis for all biological classification, although some may be highly counter-intuitive. The homologies between these have been discovered by comparing genes in evolutionary developmental biology, among insects, the stinger of the female honey bee is a modified ovipositor, homologous with ovipositors in other insects such as the Orthoptera, Hemiptera, and those Hymenoptera without stingers. The three small bones in the ear of mammals including humans, the malleus, incus. The malleus and incus develop in the embryo from structures that form jaw bones in lizards, both lines of evidence show that these bones are homologous, sharing a common ancestor. Among the many homologies in mammal reproductive systems, ovaries and testicles are homologous, in many plants, defensive or storage structures are made by modifications of the development of primary leaves, stems, and roots
5.
Introduction to evolution
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Evolution is the process of change in all forms of life over generations, and evolutionary biology is the study of how evolution occurs. Biological populations evolve through changes that correspond to changes in the organisms observable traits. Genetic changes include mutations, which are caused by damage or replication errors in an organisms DNA, the age of the Earth is about 4.54 billion years. There are microbial mat found in 3.48 billion-year-old sandstone discovered in Western Australia. According to one of the researchers, If life arose relatively quickly on Earth, then it could be common in the universe. More than 99 percent of all species, amounting to five billion species. Estimates on the number of Earths current species range from 10 million to 14 million, of which about 1.2 million have been documented and over 86 percent have not yet been described. More recently, in May 2016, scientists reported that 1 trillion species are estimated to be on Earth currently with only one-thousandth of one percent described. Evolution does not attempt to explain the origin of life, all individuals have hereditary material in the form of genes that are received from their parents, then passed on to any offspring. Among offspring there are variations of genes due to the introduction of new genes via random changes called mutations or via reshuffling of existing genes during sexual reproduction, the offspring differs from the parent in minor random ways. If those differences are helpful, the offspring is more likely to survive and this means that more offspring in the next generation will have that helpful difference and individuals will not have equal chances of reproductive success. In this way, traits that result in organisms being better adapted to their living conditions become more common in descendant populations and these differences accumulate resulting in changes within the population. This process is responsible for the diverse life forms in the world. The forces of evolution are most evident when populations become isolated, over time, isolated populations can branch off into new species. The majority of genetic mutations neither assist, change the appearance of, through the process of genetic drift, these mutated genes are neutrally sorted among populations and survive across generations by chance alone. In contrast to genetic drift, natural selection is not a process because it acts on traits that are necessary for survival. Natural selection and random genetic drift are constant and dynamic parts of life, the modern understanding of evolution began with the 1859 publication of Charles Darwins On the Origin of Species. In addition, Gregor Mendels work with plants helped to explain the patterns of genetics
6.
Evidence of common descent
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Additionally, this evidence supports the modern evolutionary synthesis—the current scientific theory that explains how and why life changes over time. Evolutionary biologists document evidence of descent by developing testable predictions, testing hypotheses. Additional genetic information conclusively supports the relatedness of life and has allowed scientists to develop phylogenetic trees and it has also led to the development of molecular clock techniques to date taxon divergence times and to calibrate these with the fossil record. Fossils are important for estimating when various lineages developed in geologic time, vestigial structures and comparisons in embryonic development are largely a contributing factor in anatomical resemblance in concordance with common descent. Since metabolic processes do not leave fossils, research into the evolution of the cellular processes is done largely by comparison of existing organisms physiology. Many lineages diverged at different stages of development, so it is possible to determine when certain metabolic processes appeared by comparing the traits of the descendants of a common ancestor and this is especially obvious in the field of insular biogeography. The development and spread of resistant bacteria provides evidence that evolution due to natural selection is an ongoing process in the natural world. Natural selection is ubiquitous in all research pertaining to evolution, taking note of the fact all of the following examples in each section of the article document the process. Alongside this are observed instances of the separation of populations of species into sets of new species, speciation has been observed directly and indirectly in the lab and in nature. Multiple forms of such have been described and documented as examples for individual modes of speciation, one of the strongest evidences for common descent comes from the study of gene sequences. Comparative sequence analysis examines the relationship between the DNA sequences of different species, producing several lines of evidence that confirm Darwins original hypothesis of common descent. If the hypothesis of common descent is true, then species that share a common ancestor inherited that ancestors DNA sequence, more closely related species have a greater fraction of identical sequence and shared substitutions compared to more distantly related species. The simplest and most powerful evidence is provided by phylogenetic reconstruction, such reconstructions, especially when done using slowly evolving protein sequences, are often quite robust and can be used to reconstruct a great deal of the evolutionary history of modern organisms. These reconstructed phylogenies recapitulate the relationships established through morphological and biochemical studies, while a minority of these elements might later be found to harbor function, in aggregate they demonstrate that identity must be the product of common descent rather than common function. All known extant organisms are based on the biochemical processes, genetic information encoded as nucleic acid, transcribed into RNA. Perhaps most tellingly, the Genetic Code is the same for almost every organism, ATP is used as energy currency by all extant life. A deeper understanding of developmental biology shows that morphology is, in fact. Another noteworthy example is the vertebrate body plan, whose structure is controlled by the homeobox family of genes
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Population genetics
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Julian Huxley invented the term in his 1942 book, Evolution, The Modern Synthesis. The modern synthesis solved difficulties and confusions caused by the specialisation, at its heart was the question of whether Mendelian genetics could be reconciled with gradual evolution by means of natural selection. A second issue was whether the changes of macroevolution seen by palaeontologists could be explained by changes seen in the microevolution of local populations. The synthesis included evidence from geneticists who studied populations in the field and these studies were crucial to evolutionary theory. The synthesis drew together ideas from several branches of biology which had separated, particularly genetics, cytology, systematics, botany. The modern synthesis of the early 20th century bridged the gap between the work of geneticists and naturalists, and paleontologists. It states that, All evolutionary phenomena can be explained in a way consistent with known genetic mechanisms, Evolution is gradual, small genetic changes regulated by natural selection accumulate over long periods. Discontinuities amongst species are explained as originating gradually through geographical separation and extinction and this theory contrasts with the saltation theory of William Bateson. Natural selection is by far the main mechanism of change, even slight advantages are important when continued, the object of selection is the phenotype in its surrounding environment. The role of genetic drift is equivocal, though strongly supported initially by Dobzhansky, it was downgraded later as results from ecological genetics were obtained. Thinking in terms of populations, rather than individuals, is primary, in palaeontology, the ability to explain historical observations by extrapolation from microevolution to macroevolution is proposed. Historical contingency means explanations at different levels may exist, gradualism does not mean constant rate of change. The idea that speciation occurs after populations are reproductively isolated has been much debated, in plants, polyploidy must be included in any view of speciation. Formulations such as evolution consists primarily of changes in the frequencies of alleles between one generation and another were proposed rather later. The traditional view is that biology played little part in the synthesis. In the 19th and early 20th centuries, variations of Lamarckism, orthogenesis, also, Darwin did not offer a precise explanation of how new species arise. Weismann and Wallace rejected the Lamarckian idea of inheritance of acquired characteristics, weismann was translated into English, and though he was influential, it took many years for the full significance of his work to be appreciated. Gregor Mendels work was re-discovered by Hugo de Vries and Carl Correns in 1900, news of this reached William Bateson in England, who reported on the paper during a presentation to the Royal Horticultural Society in May 1900
8.
Natural selection
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Natural selection is the differential survival and reproduction of individuals due to differences in phenotype. It is a key mechanism of evolution, the change in heritable traits of a population over time, Charles Darwin popularised the term natural selection, and compared it with artificial selection. Variation exists within all populations of organisms and this occurs partly because random mutations arise in the genome of an individual organism, and offspring can inherit such mutations. Throughout the lives of the individuals, their genomes interact with their environments to cause variations in traits, the environment of a genome includes the molecular biology in the cell, other cells, other individuals, populations, species, as well as the abiotic environment. Individuals with certain variants of the trait may survive and reproduce more than individuals with other, less successful, variants, therefore, factors that affect reproductive success are also important, including sexual selection and fecundity selection. Over time, this process can result in populations that specialise for particular ecological niches, in other words, natural selection is a key process in the evolution of a population. Natural selection can be contrasted with artificial selection, in which humans intentionally choose specific traits, Natural selection is one of the cornerstones of modern biology. The concept of natural selection originally developed in the absence of a theory of heredity, at the time of Darwins writing. The union of traditional Darwinian evolution with subsequent discoveries in classical genetics formed the synthesis of the mid-20th century. The addition of molecular genetics has led to developmental biology. While genotypes can slowly change by random genetic drift, natural selection remains the primary explanation for adaptive evolution, empedocles idea that organisms arose entirely by the incidental workings of causes such as heat and cold was criticised by Aristotle in Book II of Physics. He posited natural teleology in its place, and believed that form was achieved for a purpose, nevertheless, he accepted in his biology that new types of animals, monstrosities, can occur in very rare instances. And in like manner as to the parts in which there appears to exist an adaptation to an end. Yet it is impossible that this should be the true view, for teeth and all other natural things either invariably or normally come about in a given way, but of not one of the results of chance or spontaneity is this true. We do not ascribe to chance or mere coincidence the frequency of rain in winter, but frequent rain in summer we do, nor heat in the dog-days, therefore action for an end is present in things which come to be and are by nature. The struggle for existence was later described by the Islamic writer Al-Jahiz in the 9th century, the classical arguments were reintroduced in the 18th century by Pierre Louis Maupertuis and others, including Darwins grandfather, Erasmus Darwin. Until the early 19th century, the view in Western societies was that differences between individuals of a species were uninteresting departures from their Platonic ideals of created kinds. However, the theory of uniformitarianism in geology promoted the idea that simple and this theory, Lamarckism, was an influence on the Soviet biologist Trofim Lysenkos antagonism to mainstream genetic theory as late as the mid 20th century
9.
Adaptation
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In biology, an adaptation, also called an adaptive trait, is a trait with a current functional role in the life of an organism that is maintained and evolved by means of natural selection. Adaptation refers to both the current state of being adapted and to the evolutionary process that leads to the adaptation. Adaptations enhance the fitness and survival of individuals, organisms face a succession of environmental challenges as they grow and develop and are equipped with an adaptive plasticity as the phenotype of traits develop in response to the imposed conditions. The developmental norm of reaction for any given trait is essential to the correction of adaptation as it affords a kind of insurance or resilience to varying environments. Adaptation is, first of all, a process, to rather be with the animal, an internal parasite can illustrate the distinction, such a parasite may have a very simple bodily structure, but nevertheless the organism is highly adapted to its specific environment. From this we see that adaptation is not just a matter of visible traits, in such parasites critical adaptations take place in the life cycle, however, as a practical term, adaptation often refers to a product, those features of a species which result from the process. Many aspects of an animal or plant can be correctly called adaptations, by using the term adaptation for the evolutionary process, and adaptive trait for the bodily part or function, one may distinguish the two different senses of the word. Adaptation is one of the two processes that explain the diverse species found in biology, such as the different species of Darwins finches. The other process is speciation, caused by geographical isolation or some other mechanism, a favorite example used today to study the interplay of adaptation and speciation is the evolution of cichlid fish in African lakes, where the question of reproductive isolation is much more complex. Adaptation is not always a simple matter where the ideal phenotype evolves for an external environment. An organism must be viable at all stages of its development and this places constraints on the evolution of development, behavior and structure of organisms. However, it is not clear what relatively small should mean, the origin of eukaryotic symbiosis exemplifies a more dramatic example. All adaptations help organisms survive in their ecological niches, the adaptive traits may be structural, behavioral or physiological. Structural adaptations are features of an organism. Behavioral adaptations are composed of inherited behavior chains and/or the ability to learn, behaviors may be inherited in detail, examples, searching for food, mating, vocalizations. Adaptation, then, affects all aspects of the life of an organism, the following definitions are mainly due to Theodosius Dobzhansky. Adaptation is the 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, 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
10.
Polymorphism (biology)
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Polymorphism in biology and zoology is the occurrence of two or more clearly different morphs or forms, also referred to as alternative phenotypes, in the population of a species. In order to be classified as such, morphs must occupy the same habitat at the same time, three mechanisms may cause polymorphism, Genetic polymorphism - where the phenotype of each individual is genetically determined. A conditional development strategy, where the phenotype of each individual is set by environmental cues, a mixed development strategy, where the phenotype is randomly assigned during development. Polymorphism as used in zoology and biology involves morphs of the phenotype, polymorphism is common in nature, it is related to biodiversity, genetic variation and adaptation, it usually functions to retain variety of form in a population living in a varied environment. The most common example is sexual dimorphism, which occurs in many organisms, other examples are mimetic forms of butterflies, and human hemoglobin and blood types. According to the theory of evolution, polymorphism results from evolutionary processes and it is heritable and is modified by natural selection. In polyphenism, an individuals genetic make-up allows for different morphs, in genetic polymorphism, the genetic make-up determines the morph. Ants exhibit both types in a single population, polymorphism also refers to the occurrence of structurally and functionally more than two different types of individuals, called zooids within the same organism. It is a feature of Cnidarians. Although in general use polymorphism is quite a broad term, in biology it has given a specific meaning, being distinguishable from monomorphism. A more specific term, when there are two forms, is dimorphism. The term omits characters showing continuous variation, even though this has a heritable component, polymorphism deals with forms in which the variation is discrete or strongly bimodal or polymodal. Morphs must occupy the same habitat at the time, this excludes geographical races. The use of the words morph or polymorphism for what is a different geographical race or variant is common. The significance of geographical variation is in that it may lead to allopatric speciation, the term was first used to describe visible forms, but nowadays it has been extended to include cryptic morphs, for instance blood types, which can be revealed by a test. Rare variations are not classified as polymorphisms, and mutations by themselves do not constitute polymorphisms, to qualify as a polymorphism there has to be some kind of balance between morphs underpinned by inheritance. The criterion is that the frequency of the least common morph is too high simply to be the result of new mutations or, as a rough guide, polymorphism crosses several discipline boundaries, including ecology and genetics, evolution theory, taxonomy, cytology and biochemistry. Different disciplines may give the same concept different names, and different concepts may be given the same name, for example, there are the terms established in ecological genetics by E. B
11.
Speciation
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Speciation is the evolutionary process by which biological populations evolve to become distinct species. The biologist Orator F. Cook coined the term speciation in 1906 for the splitting of lineages or cladogenesis, Charles Darwin was the first to describe the role of natural selection in speciation in his 1859 book The Origin of Species. He also identified sexual selection as a mechanism, but found it problematic. There are four modes of speciation in nature, based on the extent to which speciating populations are isolated from one another, allopatric, peripatric, parapatric. Speciation may also be induced artificially, through animal husbandry, agriculture, whether genetic drift is a minor or major contributor to speciation is the subject matter of much ongoing discussion. All forms of speciation have taken place over the course of evolution, however. During allopatric speciation, a population splits into two isolated populations. When the populations come back into contact, they have evolved such that they are isolated and are no longer capable of exchanging genes. Island genetics is the associated with the tendency of small. Examples include insular dwarfism and the changes among certain famous island chains. The Galápagos Islands are particularly famous for their influence on Charles Darwin, though the finches were less important for Darwin, more recent research has shown the birds now known as Darwins finches to be a classic case of adaptive evolutionary radiation. In peripatric speciation, a subform of allopatric speciation, new species are formed in isolated and it is related to the concept of a founder effect, since small populations often undergo bottlenecks. Genetic drift is often proposed to play a significant role in peripatric speciation, parapatric speciation may be associated with differential landscape-dependent selection. Even if there is a gene flow between two populations, strong differential selection may impede assimilation and different species may eventually develop, habitat differences may be more important in the development of reproductive isolation than the isolation time. Ecologists refer to parapatric and peripatric speciation in terms of ecological niches, a niche must be available in order for a new species to be successful. Ring species such as Larus gulls have been claimed to illustrate speciation in progress, the grass Anthoxanthum odoratum may be starting parapatric speciation in areas of mine contamination. Sympatric speciation refers to the formation of two or more descendant species from an ancestral species all occupying the same geographic location. Often-cited examples of sympatric speciation are found in insects that become dependent on different host plants in the same area, however, the existence of sympatric speciation as a mechanism of speciation remains highly debated
12.
Co-operation (evolution)
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Co-operation in evolution is the process where groups of organisms work or act together for common or mutual benefits. It is commonly defined as any adaptation that has evolved, at least in part, for example, territorial choruses by male lions discourage intruders and are likely to benefit all contributors. This process contrasts with intragroup competition where individuals work against each other for selfish reasons, cooperation exists not only in humans but in other animals as well. The diversity of taxa that exhibits cooperation is quite large, ranging from zebra herds to pied babblers to African elephants, many animal and plant species cooperate with both members of their own species and with members of other species. Cooperation in animals appears to occur mostly between relatives, spending time and resources assisting a related individual may at first seem destructive to an organisms chances of survival but is actually beneficial over the long-term. However, some researchers, such as ecology professor Tim Clutton-Brock and they state that helpers may receive more direct, and less indirect, gains from assisting others than is commonly reported. These gains include protection from predation and increased reproductive fitness, furthermore, they insist that cooperation may not solely be an interaction between two individuals but may be part of the broader goal of unifying populations. For example, when a ground squirrel sounds an alarm call to other group members of a nearby coyote, it draws attention to itself. There have been multiple hypotheses for the evolution of cooperation, all of which are rooted in Hamiltons models based on inclusive fitness and these models hypothesize that cooperation is favored by natural selection due to either direct fitness benefits or indirect fitness benefits. As explained below, direct benefits encompass by-product benefits and enforced reciprocity, while indirect benefits encompass limited dispersal, kin discrimination, one specific form of cooperation in animals is kin selection, which involves animals promoting the reproductive success of their kin, thereby promoting their own fitness. Different theories explaining kin selection have been proposed, including the pay-to-stay, the pay-to-stay theory suggests that individuals help others rear offspring in order to return the favor of the breeders allowing them to live on their land. The territory inheritance theory contends that individuals help in order to have improved access to breeding areas once the breeders depart, studies conducted on red wolves support previous researchers contention that helpers obtain both immediate and long-term gains from cooperative breeding. Researchers evaluated the consequences of red wolves decisions to stay with their packs for extended periods of time after birth, while delayed dispersal helped other wolves offspring, studies also found that it extended male helper wolves life spans. This suggests that kin selection may not only benefit an individual in the long-term through increased fitness, some research suggests that individuals provide more help to closer relatives. This phenomenon is known as kin discrimination and they found that different species exhibited varying degrees of kin discrimination, with the largest frequencies occurring among those who have the most to gain from cooperative interactions. Cooperation exists not only in animals but also in plants, in a greenhouse experiment with Ipomoea hederacea, a climbing plant, results show that kin groups have higher efficiency rates in growth than non-kin groups do. This is expected to rise out of reduced competition within the kin groups, the inclusive fitness theory provides a good overview of possible solutions to the fundamental problem of cooperation, its contradiction to natural selection. Direct benefits can result from simple by-product of cooperation or enforcement mechanisms and this is also called mutually beneficial cooperation as both actor and recipient depend on direct fitness benefits, which are broken down into two different types, by-product benefit and enforcement
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