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Encyclopedia > Natural selection
Part of the Biology series on
Evolution
Mechanisms and processes

Adaptation
Genetic drift
Gene flow
Mutation
Natural selection
Speciation Natural selection is the process by which individual organisms with favorable traits are more likely to survive and reproduce. ... For the song by Girls Aloud see Biology (song) Biology studies the variety of life (clockwise from top-left) E. coli, tree fern, gazelle, Goliath beetle Biology (from Greek: Βιολογία - βίος, bio, life; and λόγος, logos, speech lit. ... This article is about evolution in biology. ... Image File history File links Tree_of_life. ... For other uses, see Adaptation (disambiguation). ... In population genetics, genetic drift is the statistical effect that results from the influence that chance has on the success of alleles (variants of a gene). ... In population genetics, gene flow (also known as gene migration) is the transfer of alleles of genes from one population to another. ... For linguistic mutation, see Apophony. ... Charles Darwins first sketch of an evolutionary tree from his First Notebook on Transmutation of Species (1837) Speciation is the evolutionary process by which new biological species arise. ...

Research and history

Evidence
Evolutionary history of life
History
Modern synthesis
Social effect / Objections While on board HMS Beagle, Charles Darwin collected numerous specimens, many new to science, which supported his later theory of evolution by natural selection. ... The evolutionary history of life and the origin of life are fields of ongoing geological and biological research. ... Evolutionary thought has roots in antiquity as philosophical ideas conceived during the Ancient Greek and Roman eras, but until the 18th century, biological thought was dominated by essentialism, the idea that living forms are static and unchanging in time. ... The modern evolutionary synthesis refers to a set of ideas from several biological specialities that were brought together to form a unified theory of evolution accepted by the great majority of working biologists. ... The theory of transmutation had early origins in the speculations and hypotheses of Erasmus Darwin, and Jean-Baptiste Lamarck. ... There have been numerous objections to evolution since alternative evolutionary ideas came to be hotly debated around the start of the nineteenth century. ...

Evolutionary biology fields

Cladistics
Ecological genetics
Evolutionary development
Human evolution
Molecular evolution
Phylogenetics
Population genetics
It has been suggested that Clade be merged into this article or section. ... Ecological genetics is the study of genetics (itself a field of biology) from an ecological perspective. ... Evolutionary developmental biology (evolution of development or informally, evo-devo) is a field of biology that compares the developmental processes of different animals in an attempt to determine the ancestral relationship between organisms and how developmental processes evolved. ... For the history of humans on Earth, see History of the world. ... Molecular evolution is the process of the genetic material in populations of organisms changing over time. ... Phylogenetic groups, or taxa, can be monophyletic, paraphyletic, or polyphyletic. ... Population genetics is the study of the distribution of and change in allele frequencies under the influence of the four evolutionary forces: natural selection, genetic drift, mutation, and migration. ...

Biology Portal · v  d  e 

Natural selection is the process by which favorable heritable traits become more common in successive generations of a population of reproducing organisms, and unfavorable heritable traits become less common. Natural selection acts on the phenotype, or the observable characteristics of an organism, such that individuals with favorable phenotypes are more likely to survive and reproduce than those with less favorable phenotypes. The phenotype's genetic basis, genotype associated with the favorable phenotype, will increase in frequency over the following generations. Over time, this process can result in adaptations that specialize organisms for particular ecological niches and may eventually result in the emergence of new species. In other words, natural selection is the mechanism by which evolution may take place in a population of a specific organism. Heredity (the adjective is hereditary) is the transfer of characteristics from parent to offspring, either through their genes or through the social institution called inheritance (for example, a title of nobility is passed from individual to individual according to relevant customs and/or laws). ... In biology, a trait or character is a feature of an organism. ... // Traditionally, a generation has been defined as “the average interval of time between the birth of parents and the birth of their offspring. ... Domains and Kingdoms Nanobes Acytota Cytota Bacteria Neomura Archaea Eukaryota Bikonta Apusozoa Rhizaria Excavata Archaeplastida Rhodophyta Glaucophyta Plantae Heterokontophyta Haptophyta Cryptophyta Alveolata Unikonta Amoebozoa Opisthokonta Choanozoa Fungi Animalia An ericoid mycorrhizal fungus Life on Earth redirects here. ... Individuals in the mollusk species Donax variabilis show diverse coloration and patterning in their phenotypes. ... Biological reproduction is the biological process by which new individual organisms are produced. ... This article is about the general scientific term. ... This article does not cite any references or sources. ... Allele frequency is a measure of the relative frequency of an allele on a genetic locus in a population. ... For other uses, see Adaptation (disambiguation). ... Two lichens on a rock, in two different ecological niches In ecology, a niche; (pronounced nich, neesh or nish)[1] is a term describing the relational position of a species or population in its ecosystem[1]. The ecological niche; describes how an organism or population responds to the distribution of... Charles Darwins first sketch of an evolutionary tree from his First Notebook on Transmutation of Species (1837) Speciation is the evolutionary process by which new biological species arise. ...


Natural selection is one of the cornerstones of modern biology. The term was introduced by Charles Darwin in his groundbreaking 1859 book The Origin of Species[1] in which natural selection was described by analogy to artificial selection, a process by which animals with traits considered desirable by human breeders are systematically favored for reproduction. The concept of natural selection was originally developed in the absence of a valid theory of inheritance; at the time of Darwin's writing, nothing was known of modern genetics. Although Gregor Mendel, the father of modern genetics, was a contemporary of Darwin's, his work would lie in obscurity until the early 20th century. The union of traditional Darwinian evolution with subsequent discoveries in classical and molecular genetics is termed the modern evolutionary synthesis. Although other mechanisms of molecular evolution, such as the neutral theory advanced by Motoo Kimura, have been identified as important causes of genetic diversity, natural selection remains the single primary explanation for adaptive evolution. For the song by Girls Aloud see Biology (song) Biology studies the variety of life (clockwise from top-left) E. coli, tree fern, gazelle, Goliath beetle Biology (from Greek: Βιολογία - βίος, bio, life; and λόγος, logos, speech lit. ... For other people of the same surname, and places and things named after Charles Darwin, see Darwin. ... Charles Darwins Origin of Species (publ. ... This Chihuahua mix and Great Dane show the wide range of dog breed sizes created using artificial selection. ... This article or section does not adequately cite its references or sources. ... This article is about the general scientific term. ... “Mendel” redirects here. ... Charles Darwin Darwinism is a term for the underlying theory in those ideas of Charles Darwin concerning evolution and natural selection. ... Classical genetics consists of the techniques and methodologies of genetics that predate the advent of molecular biology. ... Molecular genetics is the field of biology which studies the structure and function of genes at a molecular level. ... The modern evolutionary synthesis refers to a set of ideas from several biological specialities that were brought together to form a unified theory of evolution accepted by the great majority of working biologists. ... The neutral theory of molecular evolution (also, simply the neutral theory of evolution) is an influential theory that was introduced with provocative effect by Motoo Kimura in the late 1960s and early 1970s. ... Motoo Kimura (木村資生, born on November 13, 1924 in Okazaki, Aichi Prefecture - November 13, 1994) was a highly influential Japanese mathematical biologist, working in the field of theoretical population genetics. ... Genetic diversity is a characteristic of ecosystems and gene pools that describes an attribute which is commonly held to be advantageous for survival -- that there are many different versions of otherwise similar organisms. ...

Contents

General principles

Darwin's illustrations of beak variation in the finches of the Galápagos Islands, which hold 13 closely related species that differ most markedly in the shape of their beaks. The beak of each species is suited to its preferred food, suggesting that beak shapes evolved by natural selection. See also character displacement, adaptive radiation, divergent evolution.
Darwin's illustrations of beak variation in the finches of the Galápagos Islands, which hold 13 closely related species that differ most markedly in the shape of their beaks. The beak of each species is suited to its preferred food, suggesting that beak shapes evolved by natural selection. See also character displacement, adaptive radiation, divergent evolution.
See also: Genotype-phenotype distinction.

Natural selection acts on an organism's phenotype, or physical characteristics. Phenotype is determined by an organism's genetic make-up (genotype) and the environment in which the organism lives. Often, natural selection acts on specific traits of an individual, and the terms phenotype and genotype are used narrowly to indicate these specific traits. Image File history File links Darwin's_finches. ... Image File history File links Darwin's_finches. ... For other people of the same surname, and places and things named after Charles Darwin, see Darwin. ... The beak, bill or rostrum is an external anatomical structure of birds which, in addition to eating, is used for grooming, manipulating objects, killing prey, probing for food, courtship, and feeding their young. ... Genera Geospiza Camarhynchus Certhidea Pinaroloxias demon hickes and darwin were on a boat for seven years smoking crack and drinking rum!!!! The birds are all about the same size (10–20 cm). ... Galápagos redirects here. ... For other uses, see Species (disambiguation). ... Character displacement refers to the phenomenon where differences among similar species whose distributions overlap geographically are accentuated in regions where the species co-occur but are minimized or lost where the species’ distributions do not overlap. ... Four of the 13 finch species found on the Galápagos Archipelago, and thought to have evolved by an adaptive radiation that diversified their beak shapes to adapt them to different food sources. ... Divergent evolution occurs when two or more biological characteristics have a common evolutionary origin but have diverged over evolutionary time. ... The genotype-phenotype distinction refers to the fact that while genotype and phenotype of an organism are related, they do not necessarily coincide. ... Individuals in the mollusk species Donax variabilis show diverse coloration and patterning in their phenotypes. ... This article does not cite any references or sources. ... In biology, a trait or character is a feature of an organism. ...


When different organisms in a population possess different versions of a gene for a certain trait, each of these versions is known as an allele. It is this genetic variation that underlies phenotypic traits. A typical example is that certain combinations of genes for eye color in humans which, for instance, give rise to the phenotype of blue eyes. (On the other hand, when all the organisms in a population share the same allele for a particular trait, and this state is stable over time, the allele is said to be fixed in that population.) For other uses, see Gene (disambiguation). ... An allele (pronounced , ) (from the Greek αλληλος, meaning each other) is one member of a pair or series of different forms of a gene. ... Hazel Eyes redirects here. ... In population genetics, fixation occurs when every individual within a population has the same allele at a particular locus. ...


Some traits are governed by only a single gene, but most traits are influenced by the interactions of many genes. A variation in one of the many genes that contributes to a trait may have only a small effect on the phenotype; together, these genes can produce a continuum of possible phenotypic values.[2]


Nomenclature and usage

The term "natural selection" has slightly different definitions in different contexts. In simple terms, "natural selection" is most often defined to operate on heritable traits, but can sometimes refer to the differential reproductive success of phenotypes regardless of whether those phenotypes are heritable. Natural selection is "blind" in the sense that individuals' level of reproductive success is a function of the phenotype and not of whether or to what extent that phenotype is heritable. Following Darwin's primary usage[1] the term is often used to refer to both the consequence of blind selection and to its mechanisms.[3][4] It is sometimes helpful to explicitly distinguish between selection's mechanisms and its effects; when this distinction is important, scientists define "natural selection" specifically as "those mechanisms that contribute to the selection of individuals that reproduce," without regard to whether the basis of the selection is heritable. This is sometimes referred to as 'phenotypic natural selection.'[5]


Traits that cause greater reproductive success of an organism are said to be selected for whereas those that reduce success are selected against. Selection for a trait may also result in the selection of other correlated traits that do not themselves directly influence fitness. This may occur as a result of pleiotropy or gene linkage.[6] Pleiotropy occurs when a single gene influences multiple phenotypic traits. ... Genetic linkage occurs when particular alleles are inherited together. ...


Fitness

Main article: Fitness (biology)

The concept of fitness is central to natural selection. However, as with Natural selection above, there is serious divergence of opinion over the precise meaning of the term, and Richard Dawkins manages in his later books to avoid it entirely. (He devotes a chapter of his The Extended Phenotype to discussing the various senses in which the term is used.) Although fitness is sometimes colloquially understood as a quality that promotes survival of a particular individual - as illustrated in the well-known phrase survival of the fittest - modern evolutionary theory defines fitness in terms of individual reproduction. The basis of this approach is: if an organism lives half as long as others of its species, but has twice as many offspring surviving to productive adulthood, its genes will become more common in the adult population of the next generation. This is known as differential reproduction. Fitness (often denoted in population genetics models) is a central concept in evolutionary theory. ... Fitness (often denoted in population genetics models) is a central concept in evolutionary theory. ... For other uses, see Survival of the fittest (disambiguation). ...


Though natural selection acts on individuals, its average effect on all individuals with a particular genotype corresponds to the fitness of that genotype. Very low-fitness genotypes cause their bearers to have few or no offspring on average; examples include many human genetic disorders like cystic fibrosis. Conditions like sickle-cell anemia may have low fitness in the general human population, but because it confers immunity from malaria, it has high fitness value in populations which have high malaria infection rates. Broadly speaking, an organism's fitness is a function of its alleles' fitnesses. Since fitness is an averaged quantity, however, it is possible a favorable mutation may arise in an individual that does not survive to adulthood for unrelated reasons. A genetic disorder is a condition caused by abnormalities in genes or chromosomes. ... Sickle-shaped red blood cells Sickle-cell anemia or anaemia (also sickle-cell disease) is a genetic disorder in which red blood cells may change shape under certain circumstances. ...


Types of selection

Natural selection can act on any phenotypic trait, and selective pressure can be produced by any aspect of the environment, including mates and conspecifics, or members of the same species. However, this does not imply that natural selection is always directional and results in adaptive evolution; natural selection often results in the maintenance of the status quo by eliminating less fit variants. Illustration from The Descent of Man and Selection in Relation to Sex by Charles Darwin showing the Tufted Coquette Lophornis ornatus, female on left, ornamented male on right. ... Competition is the act of striving against others for the purpose of achieving gain, such as income, pride, amusement, or dominance. ...


The unit of selection can be the individual or it can be another level within the hierarchy of biological organisation, such as genes, cells, and kin groups. There is still debate about whether natural selection acts at the level of groups or species to produce adaptations that benefit a larger, non-kin group. Selection at a different level such as the gene can result in an increase in fitness for that gene, while at the same time reducing the fitness of the individuals carrying that gene, in a process called intragenomic conflict. Overall, the combined effect of all selection pressures at various levels determines the overall fitness of an individual, and hence the outcome of natural selection. This article does not cite any references or sources. ... In evolutionary biology, kin selection refers to changes in gene frequency across generations that are driven at least in part by interactions between related individuals, and this forms much of the conceptual basis of the theory of social evolution. ... In evolutionary biology, group selection refers to the idea that alleles can become fixed or spread in a population because of the benefits they bestow on groups, regardless of the fitness of individuals within that group. ... The selfish gene theory postulates that natural selection will increase the frequency of those genes whose phenotypic effects ensure their successful replication. ...

The life cycle of a sexually reproducing organism. Various components of natural selection are indicated for each life stage.
The life cycle of a sexually reproducing organism. Various components of natural selection are indicated for each life stage.[7]

Natural selection occurs at every life stage of an individual. An individual organism must survive until adulthood before it can reproduce, and selection of those that reach this stage is called viability selection. In many species, adults must compete with each other for mates via sexual selection, and success in this competition determines who will parent the next generation. When individuals can reproduce more than once, a longer survival in the reproductive phase increases the number of offspring, called survival selection. The fecundity of both females and males (for example, giant sperm in certain species of Drosophila[8]) can be limited via fecundity selection. The viability of produced gametes can differ, while intragenomic conflicts such as meiotic drive between the haploid gametes can result in gametic or genic selection. Finally, the union of some combinations of eggs and sperm might be more compatible than others; this is termed compatibility selection. Image File history File links This is a lossless scalable vector image. ... Image File history File links This is a lossless scalable vector image. ... Illustration from The Descent of Man and Selection in Relation to Sex by Charles Darwin showing the Tufted Coquette Lophornis ornatus, female on left, ornamented male on right. ... Fecundity is the potential reproductive capacity of an organism or population, measured by the number of gametes (e. ... A spermatozoon or spermatozoan ( spermatozoa), from the ancient Greek σπέρμα (seed) and (living being) and more commonly known as a sperm cell, is the haploid cell that is the male gamete. ... Type species Drosophila funebris (Fabricius, 1787) Drosophila is a genus of small flies, belonging to the family Drosophilidae, whose members are often called fruit flies, or more appropriately vinegar flies, wine flies, pomace flies, grape flies, and picked fruit-flies, a reference to the characteristic of many species to linger... A gamete (from Ancient Greek γαμετης; translated gamete = wife, gametes = husband) is a cell that fuses with another gamete during fertilization (conception) in organisms that reproduce sexually. ... The selfish gene theory postulates that natural selection will increase the frequency of those genes whose phenotypic effects ensure their successful replication. ... Haploid (meaning simple in Greek) cells have only one copy of each chromosome. ...


Sexual selection

Main article: Sexual selection

It is also useful to make a mechanistic distinction between ecological selection and the narrower term sexual selection. Ecological selection covers any mechanism of selection as a result of the environment (including relatives, e.g. kin selection, and conspecifics, e.g. competition, infanticide), while sexual selection refers specifically to competition between conspecifics for mates.[9] Sexual selection can be intrasexual, as in cases of competition among individuals of the same sex in a population, or intersexual, as in cases where one sex controls reproductive access by choosing among a population of available mates. Most commonly, intrasexual selection involves male-male competition and intersexual selection involves female choice of suitable males, due to the generally greater investment of resources for a female than a male in a single offspring organism. However, some species exhibit sex-role reversed behavior in which it is males that are most selective in mate choice; the best-known examples of this pattern occur in some fishes of the family Syngnathidae, though likely examples have also been found in amphibian and bird species.[10] Some features that are confined to one sex only of a particular species can be explained by selection exercised by the other sex in the choice of a mate, for example, the extravagant plumage of some male birds. Similarly, aggression between members of the same sex is sometimes associated with very distinctive features, such as the antlers of stags, which are used in combat with other stags. More generally, intrasexual selection is often associated with sexual dimorphism, including differences in body size between males and females of a species.[11] Illustration from The Descent of Man and Selection in Relation to Sex by Charles Darwin showing the Tufted Coquette Lophornis ornatus, female on left, ornamented male on right. ... Ecological selection (or environmental selection or survival selection or individual selection or asexual selection) refers to natural selection minus sexual selection, i. ... Illustration from The Descent of Man and Selection in Relation to Sex by Charles Darwin showing the Tufted Coquette Lophornis ornatus, female on left, ornamented male on right. ... In evolutionary biology, kin selection refers to changes in gene frequency across generations that are driven at least in part by interactions between related individuals, and this forms much of the conceptual basis of the theory of social evolution. ... Trees in this Bangladesh forest are in competition for light. ... In sociology and biology, infanticide is the practice of intentionally causing the death of an infant of a given species, by members of the same species - often by the mother. ... For other uses, see Fish (disambiguation). ... Syngnathidae is a family of fishes, including seahorses, pipehorse, pipefish and sea dragons, among others. ... ‹ The template below (Citations missing) is being considered for deletion. ... For other uses, see Bird (disambiguation). ... Genera About 15 in 4 subfamilies. ... Female (left) and male Common Pheasant, illustrating the dramatic difference in both color and size, between the sexes Sexual dimorphism is the systematic difference in form between individuals of different sex in the same species. ...


An example: antibiotic resistance

Schematic representation of how antibiotic resistance is enhanced by natural selection. The top section represents a population of bacteria before exposure to an antibiotic. The middle section shows the population directly after exposure, the phase in which selection took place. The last section shows the distribution of resistance in a new generation of bacteria. The legend indicates the resistance levels of individuals.
Schematic representation of how antibiotic resistance is enhanced by natural selection. The top section represents a population of bacteria before exposure to an antibiotic. The middle section shows the population directly after exposure, the phase in which selection took place. The last section shows the distribution of resistance in a new generation of bacteria. The legend indicates the resistance levels of individuals.

A well-known example of natural selection in action is the development of antibiotic resistance in microorganisms. Since the discovery of penicillin in 1928 by Alexander Fleming, antibiotics have been used to fight bacterial diseases. Natural populations of bacteria contain, among their vast numbers of individual members, considerable variation in their genetic material, primarily as the result of mutations. When exposed to antibiotics, most bacteria die quickly, but some may have mutations that make them slightly less susceptible. If the exposure to antibiotics is short, these individuals will survive the treatment. This selective elimination of maladapted individuals from a population is natural selection. Image File history File links This is a lossless scalable vector image. ... Image File history File links This is a lossless scalable vector image. ... Antibiotic resistance is the ability of a microorganism to withstand the effects of an antibiotic. ... A cluster of Escherichia coli bacteria magnified 10,000 times. ... Penicillin core structure Penicillin (abbreviated PCN) is a group of β-lactam antibiotics used in the treatment of bacterial infections caused by susceptible, usually Gram-positive, organisms. ... Sir Alexander Fleming (6 August 1881 – 11 March 1955) was a Scottish biologist and pharmacologist. ... Staphylococcus aureus - Antibiotics test plate. ... Phyla Actinobacteria Aquificae Chlamydiae Bacteroidetes/Chlorobi Chloroflexi Chrysiogenetes Cyanobacteria Deferribacteres Deinococcus-Thermus Dictyoglomi Fibrobacteres/Acidobacteria Firmicutes Fusobacteria Gemmatimonadetes Lentisphaerae Nitrospirae Planctomycetes Proteobacteria Spirochaetes Thermodesulfobacteria Thermomicrobia Thermotogae Verrucomicrobia Bacteria (singular: bacterium) are unicellular microorganisms. ... For linguistic mutation, see Apophony. ...


These surviving bacteria will then reproduce again, producing the next generation. Due to the elimination of the maladapted individuals in the past generation, this population contains more bacteria that have some resistance against the antibiotic. At the same time, new mutations occur, contributing new genetic variation to the existing genetic variation. Spontaneous mutations are very rare, and advantageous mutations are even rarer. However, populations of bacteria are large enough that a few individuals will have beneficial mutations. If a new mutation reduces their susceptibility to an antibiotic, these individuals are more likely to survive when next confronted with that antibiotic. Given enough time, and repeated exposure to the antibiotic, a population of antibiotic-resistant bacteria will emerge.


The widespread use and misuse of antibiotics has resulted in increased microbial resistance to antibiotics in clinical use, to the point that the methicillin-resistant Staphylococcus aureus (MRSA) has been described as a 'superbug' because of the threat it poses to health and its relative invulnerability to existing drugs.[12] Response strategies typically include the use of different, stronger antibiotics; however, new strains of MRSA have recently emerged that are resistant even to these drugs.[13] This is an example of what is known as an evolutionary arms race, in which bacteria continue to develop strains that are less susceptible to antibiotics, while medical researchers continue to develop new antibiotics that can kill them. A similar situation occurs with pesticide resistance in plants and insects. Arms races are not necessarily induced by man; a well-documented example involves the elaboration of the RNA interference pathway in plants as means of innate immunity against viruses.[14] MRSA redirects here. ... Antibiotic resistance is the ability of a microorganism to withstand the effects of an antibiotic. ... In biology, Strain can be used two ways. ... An evolutionary arms race is an evolutionary struggle between a predator species and its prey (including parasitism) that is said to resemble an arms race. ... the plane is spreading pesticide. ... Cells use dicer to trim double stranded RNA to form small interfering RNA or microRNA. An exogenous dsRNA or endogenous pre-miRNA can be processed by dicer and incorporated into the RNA-induced silencing complex (RISC), which targets single-stranded messenger RNA molecules and triggers translational repression;[1] incorporation into... Innate immunity is immunity that the body possesses naturally, as opposed to adaptive immunity. ... This article is about biological infectious particles. ...


Genetical theory of natural selection

Natural selection by itself is a simple concept, in which fitness differences between phenotypes play a crucial role. It is the union of natural selection as a mechanism with genetic material as a substrate that offers most of the theory's explanatory power


Directionality of selection

When some component of a trait is heritable, selection will alter the frequencies of the different alleles, or variants of the gene that produces the variants of the trait. Selection can be divided into three classes, on the basis of its effect on allele frequencies.[15] An allele (pronounced , ) (from the Greek αλληλος, meaning each other) is one member of a pair or series of different forms of a gene. ...


Directional selection occurs when a certain allele has a greater fitness than others, resulting in an increase in frequency of that allele. This process can continue until the allele is fixed and the entire population shares the fitter phenotype. It is directional selection that is illustrated in the antibiotic resistance example above. In population genetics, directional selection (sometimes referred to as positive selection) occurs when natural selection favors a single allele and therefore allele frequency continuously shifts in one direction. ... In population genetics, fixation occurs when every individual within a population has the same allele at a particular locus. ...


Far more common is stabilizing selection (also known as purifying selection), which lowers the frequency of alleles that have a deleterious effect on the phenotype - that is, produce organisms of lower fitness. This process can continue until the allele is eliminated from the population. Purifying selection results in functional genetic features, such as protein-coding genes or regulatory sequences, being conserved over time due to selective pressure against deleterious variants. A chart showing three types of selection Stabilizing selection, also referred to as purifying selection, is a type of natural selection in which genetic diversity decreases as the population stabilizes on a particular trait value. ... Protein biosynthesis (synthesis) is the process in which cells build proteins. ... A regulatory sequence (also called regulatory region or ~ element) is a promoter, enhancer or other segment of DNA where regulatory proteins such as transcription factors bind preferentially. ... Conservation is a high degree of similarity in the primary or higher structure of homologous proteins amongst various phyla. ...


Finally, a number of forms of balancing selection exist, which do not result in fixation, but maintain an allele at intermediate frequencies in a population. This can occur in diploid species (that is, those that have two pairs of chromosomes) when heterozygote individuals, who have different alleles on each chromosome at a single genetic locus, have a higher fitness than homozygote individuals that have two of the same alleles. This is called heterozygote advantage or overdominance, of which the best-known example is the malarial resistance observed in heterozygous humans who carry only one copy of the gene for sickle cell anemia. Maintenance of allelic variation can also occur through disruptive or diversifying selection, which favors genotypes that depart from the average in either direction (that is, the opposite of overdominance), and can result in a bimodal distribution of trait values. Finally, balancing selection can occur through frequency-dependent selection, where the fitness of one particular phenotype depends on the distribution of other phenotypes in the population. The principles of game theory have been applied to understand the fitness distributions in these situations, particularly in the study of kin selection and the evolution of reciprocal altruism.[16][17] Sickle-shaped red blood cells Balancing selection refers to forms of natural selection which work to maintain genetic polymorphisms (or multiple alleles) within a population. ... Diploid (meaning double in Greek) cells have two copies (homologs) of each chromosome (both sex- and non-sex determining chromosomes), usually one from the mother and one from the father. ... A scheme of a condensed (metaphase) chromosome. ... An organism is a heterozygote or heterozygous for a gene or trait if it has different alleles at the genes locus for each homologous chromosome. ... Short and long arms Chromosome. ... This article or section does not cite its references or sources. ... A heterozygote advantage (heterozygous advantage or overdominance) describes the case in which the heterozygote genotype has a higher relative fitness than either the homozygote dominant or homozygote recessive genotype. ... Malaria is a vector-borne infectious disease caused by protozoan parasites. ... Sickle-shaped red blood cells Sickle cell anemia (American English), sickle cell anaemia (British English) or sickle cell disease is a genetic disease in which red blood cells may change shape under certain circumstances. ... Disruptive selection is a type of evolution that simultaneously favors individuals at both extremes of the distribution. ... In statistics, a bimodal distribution is a distribution with two different peaks — that is, there are two distinct values that measurements tend to center around. ... Frequency dependent selection is the term given to an evolutionary process where the fitness of a phenotype is dependent on the relative frequency of other phenotypes in a given population. ... Game theory is a branch of applied mathematics that is often used in the context of economics. ... In evolutionary biology, kin selection refers to changes in gene frequency across generations that are driven at least in part by interactions between related individuals, and this forms much of the conceptual basis of the theory of social evolution. ... In evolutionary biology, reciprocal altruism is a form of altruism in which one organism provides a benefit to another in the expectation of future reciprocation. ...


Selection and genetic variation

A portion of all genetic variation is functionally neutral in that it produces no phenotypic effect or significant difference in fitness; the hypothesis that this variation accounts for a large fraction of observed genetic diversity is known as the neutral theory of molecular evolution and was originated by Motoo Kimura. Neutral variation was once thought to encompass most of the genetic variation in non-coding DNA, which was hypothesized to be composed of "junk DNA". However, more recently, the functional roles of non-coding DNA, such as the regulatory and developmental functions of RNA gene products, has been studied in depth;[18] large parts of non-protein-coding DNA sequences are highly conserved under strong purifying selection and thus do not vary much from individual to individual, indicating that mutations in these regions have deleterious consequences.[19][20] When genetic variation does not result in differences in fitness, selection cannot directly affect the frequency of such variation. As a result, the genetic variation at those sites will be higher than at sites where variation does influence fitness.[15] Genetic variation is the variation in the genetic material of a population, and includes the nuclear, mitochodrial, ribosomal genomes as well as the genomes of other organelles. ... Genetic diversity is a characteristic of ecosystems and gene pools that describes an attribute which is commonly held to be advantageous for survival -- that there are many different versions of otherwise similar organisms. ... The neutral theory of molecular evolution (also, simply the neutral theory of evolution) is an influential theory that was introduced with provocative effect by Motoo Kimura in the late 1960s and early 1970s. ... Motoo Kimura (木村資生, born on November 13, 1924 in Okazaki, Aichi Prefecture - November 13, 1994) was a highly influential Japanese mathematical biologist, working in the field of theoretical population genetics. ... In genetics, noncoding DNA describes DNA which does not contain instructions for making proteins (or other cell products such as RNAs). ... In molecular biology, junk DNA is a collective label for the portions of the DNA sequence of a chromosome or a genome for which no function has yet been identified. ... For other uses, see RNA (disambiguation). ... A gene product is the biochemical material, either RNA or protein, resulting from expression of a gene. ...


Mutation selection balance

Natural selection results in the reduction of genetic variation through the elimination of maladapted individuals and consequently of the mutations that caused the maladaptation. At the same time, new mutations occur, resulting in a mutation-selection balance. The exact outcome of the two processes depends both on the rate at which new mutations occur and on the strength of the natural selection, which is a function of how unfavorable the mutation proves to be. Consequently, changes in the mutation rate or the selection pressure will result in a different mutation-selection balance. mutation-selection balance is a balance between mutation and selection. ...


Genetic linkage

Genetic linkage occurs when the loci of two alleles are linked, or in close proximity to each other on the chromosome. During the formation of gametes, recombination of the genetic material results in reshuffling of the alleles. However, the chance that such a reshuffle occurs between two alleles depends on the distance between those alleles; the closer the alleles are to each other, the less likely it is that such a reshuffle will occur. Consequently, when selection targets one allele, this automatically results in selection of the other allele as well; through this mechanism, selection can have a strong influence on patterns of variation in the genome. Genetic linkage occurs when particular alleles are inherited jointly. ... Short and long arms Chromosome. ... A scheme of a condensed (metaphase) chromosome. ... Gametes (in Greek: γαμέτες) —also known as sex cells, germ cells, or spores—are the specialized cells that come together during fertilization (conception) in organisms that reproduce sexually. ... Genetic recombination is the process by which a strand of the genetic material (usually DNA; but can also be RNA) is broken and then joined to the end of a different DNA molecule. ...


Selective sweeps occur when an allele becomes more common in a population as a result of positive selection. As the prevalence of one allele increases, linked alleles can also become more common, whether they are neutral or even slightly deleterious. This is called genetic hitchhiking. A strong selective sweep results in a region of the genome where the positively selected haplotype (the allele and its neighbours) are essentially the only ones that exist in the population. A selective sweep is the reduction or elimination of variation among the nucleotides in neighbouring DNA of a mutation as the result of recent and strong natural selection. ... The process by which an evolutionary neutral or in some cases deleterious allele or mutation may spread through the gene pool by virtue of being linked to a beneficial mutation. ... A haplotype is the genetic constitution of an individual chromosome. ...


Whether a selective sweep has occurred or not can be investigated by measuring linkage disequilibrium, or whether a given haplotype is overrepresented in the population. Normally, genetic recombination results in a reshuffling of the different alleles within a haplotype, and none of the haplotypes will dominate the population. However, during a selective sweep, selection for a specific allele will also result in selection of neighbouring alleles. Therefore, the presence of strong linkage disequilibrium might indicate that there has been a 'recent' selective sweep, and this can be used to identify sites recently under selection. Linkage disequilibrium (LD) is the non-random association of alleles at two or more loci on a chromosome. ... Genetic recombination is the process by which a strand of the genetic material (usually DNA; but can also be RNA) is broken and then joined to the end of a different DNA molecule. ...


Background selection is the opposite of a selective sweep. If a specific site experiences strong and persistent purifying selection, linked variation will tend to be weeded out along with it, producing a region in the genome of low overall variability. Because background selection is a result of deleterious new mutations, which can occur randomly in any haplotype, it produces no linkage disequilibrium. The term background selection refers to the reduction in genetic variation that occurs in the genomic area surrounding a gene that repeatedly mutates to a bad version. ...


Evolution by means of natural selection

Main articles: Evolution and Darwinism

A prerequisite for natural selection to result in adaptive evolution, novel traits and speciation, is the presence of heritable genetic variation that results in fitness differences. Genetic variation is the result of mutations, recombinations and alterations in the karyotype (the number, shape, size and internal arrangement of the chromosomes). Any of these changes might have an effect that is highly advantageous or highly disadvantageous, but large effects are very rare. In the past, most changes in the genetic material were considered neutral or close to neutral because they occurred in noncoding DNA or resulted in a synonymous substitution. However, recent research suggests that many mutations in non-coding DNA do have slight deleterious effects.[19][20] Although both mutation rates and average fitness effects of mutations are dependent on the organism, estimates from data in humans have found that a majority of mutations are slightly deleterious.[21] This article is about evolution in biology. ... Charles Darwin Darwinism is a term for the underlying theory in those ideas of Charles Darwin concerning evolution and natural selection. ... For other uses, see Adaptation (disambiguation). ... Charles Darwins first sketch of an evolutionary tree from his First Notebook on Transmutation of Species (1837) Speciation is the evolutionary process by which new biological species arise. ... Genetic variation is the variation in the genetic material of a population, and includes the nuclear, mitochodrial, ribosomal genomes as well as the genomes of other organelles. ... For linguistic mutation, see Apophony. ... Genetic recombination is the process by which a strand of the genetic material (usually DNA; but can also be RNA) is broken and then joined to the end of a different DNA molecule. ... Karyogram of human male using Giemsa staining. ... A scheme of a condensed (metaphase) chromosome. ... It has been suggested that junk DNA be merged into this article or section. ... A synonymous substitution (also called a silent substitution) is the evolutionary substitution of one base for another in an exon of a gene coding for a protein, such that the amino acid sequence produced is not modified. ... This article is about modern humans. ...

The exuberant tail of the peacock is thought to be the result of sexual selection by females. This peacock is an albino - it carries a mutation that makes it unable to produce melanin. Selection against albinos in nature is intense because they are easily spotted by predators or are unsuccessful in competition for mates, and so these mutations are usually rapidly eliminated by natural selection
The exuberant tail of the peacock is thought to be the result of sexual selection by females. This peacock is an albino - it carries a mutation that makes it unable to produce melanin. Selection against albinos in nature is intense because they are easily spotted by predators or are unsuccessful in competition for mates, and so these mutations are usually rapidly eliminated by natural selection

By the definition of fitness, individuals with greater fitness are more likely to contribute offspring to the next generation, while individuals with lesser fitness are more likely to die early or fail to reproduce. As a result, alleles which on average result in greater fitness become more abundant in the next generation, while alleles which generally reduce fitness become rarer. If the selection forces remain the same for many generations, beneficial alleles become more and more abundant, until they dominate the population, while alleles with a lesser fitness disappear. In every generation, new mutations and recombinations arise spontaneously, producing a new spectrum of phenotypes. Therefore, each new generation will be enriched by the increasing abundance of alleles that contribute to those traits that were favored by selection, enhancing these traits over successive generations. Image File history File linksMetadata Pavo_cristatus_albino001xx. ... Image File history File linksMetadata Pavo_cristatus_albino001xx. ... Peacock re-directs here; for alternate uses see Peacock (disambiguation). ... Albinism is a genetic condition resulting in a lack of pigmentation in the eyes, skin and hair. ... Broadly, melanin is any of the polyacetylene, polyaniline, and polypyrrole blacks and browns or their mixed copolymers. ...

X-ray of the left hand of a ten year old boy with polydactyly.
X-ray of the left hand of a ten year old boy with polydactyly.

Some mutations occur in so-called regulatory genes. Changes in these can have large effects on the phenotype of the individual because they regulate the function of many other genes. Most, but not all, mutations in regulatory genes result in non-viable zygotes. Examples of nonlethal regulatory mutations occur in HOX genes in humans, which can result in a cervical rib[22] or polydactyly, an increase in the number of fingers or toes.[23] When such mutations result in a higher fitness, natural selection will favor these phenotypes and the novel trait will spread in the population. Download high resolution version (891x1077, 119 KB)Conversion of a DICOM-format X-ray from a patient of User:Drgnu23, a ten year old male. ... Download high resolution version (891x1077, 119 KB)Conversion of a DICOM-format X-ray from a patient of User:Drgnu23, a ten year old male. ... This article is about the human congenital disorder (disease). ... A regulatory sequence (also called regulatory region or ~ element) is a promoter, enhancer or other segment of DNA where regulatory proteins such as transcription factors bind preferentially. ... For other meanings see Zygote (disambiguation). ... A homeobox is a DNA sequence found within genes that are involved in the regulation of development (morphogenesis) of animals, fungi and plants. ... A cervical rib is a supernumerary (extra) rib which arises from the seventh cervical vertebra. ... This article is about the human congenital disorder (disease). ...


Established traits are not immutable; traits that have high fitness in one environmental context may be much less fit if environmental conditions change. In the absence of natural selection to preserve such a trait, it will become more variable and deteriorate over time, possibly resulting in a vestigial manifestation of the trait. In many circumstances, the apparently vestigial structure may retain a limited functionality, or may be co-opted for other advantageous traits in a phenomenon known as preadaptation. A famous example of a vestigial structure, the eye of the blind mole rat, is believed to retain function in photoperiod perception.[24] The human vermiform appendix is a vestigial structure; it no longer retains its original function. ... In evolutionary biology, preadaptation describes a situation where an organism uses a preexisting anatomical structure inherited from an ancestor for a potentially unrelated purpose. ... For other uses, see Eye (disambiguation). ... Genera Nannospalax Spalax Blind mole rats are one of many types of rodents that are referred to as mole rats. ... Photoperiodism is the physiological reaction of organisms to the length of day or night. ...


Speciation

Speciation requires selective mating, which result in a reduced gene flow. Selective mating can be the result of, for example, a change in the physical environment (physical isolation by an extrinsic barrier), or by sexual selection resulting in assortative mating. Over time, these subgroups might diverge radically to become different species, either because of differences in selection pressures on the different subgroups, or because different mutations arise spontaneously in the different populations, or because of founder effects - some potentially beneficial alleles may, by chance, be present in only one or other of two subgroups when they first become separated. A lesser-known mechanism of speciation occurs via hybridization, well-documented in plants and occasionally observed in species-rich groups of animals such as cichlid fishes.[25] Such mechanisms of rapid speciation can reflect a mechanism of evolutionary change known as punctuated equilibrium, which suggests that evolutionary change and particularly speciation typically happens quickly after interrupting long periods of stasis. Charles Darwins first sketch of an evolutionary tree from his First Notebook on Transmutation of Species (1837) Speciation is the evolutionary process by which new biological species arise. ... In population genetics, gene flow (also known as gene migration) is the transfer of alleles of genes from one population to another. ... Assortative mating (also called Assortative pairing) takes place when sexually reproducing organisms tend to mate with individuals that are like themselves in some respect (positive assortative mating) or dissimilar (negative assortative mating). ... Simple illustration of founder effect. ... This article is about a biological term. ... For other uses, see Plant (disambiguation). ... Subfamilies Astronotinae Cichlasomatinae Cichlinae Etroplinae Geophaginae Heterochromidinae Paratilapiinae Pseudocrenilabrinae Ptychochrominae Retroculinae For genera, see below. ... Punctuated equilibrium (or punctuated equilibria) is a theory in evolutionary biology which states that most sexually reproducing species will show little to no evolutionary change throughout their history. ...


Genetic changes within groups result in increasing incompatibility between the genomes of the two subgroups, thus reducing gene flow between the groups. Gene flow will effectively cease when the distinctive mutations characterizing each subgroup become fixed. As few as two mutations can result in speciation: if each mutation has a neutral or positive effect on fitness when they occur separately, but a negative effect when they occur together, then fixation of these genes in the respective subgroups will lead to two reproductively isolated populations. According to the biological species concept, these will be two different species.


Historical development

Main articles: History of evolutionary thought, Inception of Darwin's theory, and Development of Darwin's theory
The modern theory of natural selection derives from the work of Charles Darwin in the nineteenth century.
The modern theory of natural selection derives from the work of Charles Darwin in the nineteenth century.

Evolutionary thought has roots in antiquity as philosophical ideas conceived during the Ancient Greek and Roman eras, but until the 18th century, biological thought was dominated by essentialism, the idea that living forms are static and unchanging in time. ... The inception of Darwins theory began with a search for explanations of contradictions in current Creationist ideas, and led him to formulate his theory of evolution which was eventually published in his book On the Origin of Species. ... The Development of Darwins theory began with a search for explanations of contradictions in current faith based ideas, and led him to formulate his theory of evolution which was eventually published in his book On the Origin of Species, a turning point in the history of evolutionary thought. ... Wikipedia does not yet have an article with this exact name. ... Wikipedia does not yet have an article with this exact name. ... For other people of the same surname, and places and things named after Charles Darwin, see Darwin. ...

Pre-Darwinian theories

Several ancient philosophers expressed the idea that Nature produces a huge variety of creatures, apparently randomly, and that only those creatures survive that manage to provide for themselves and reproduce successfully; well-known examples include Empedocles[26] and his intellectual successor, Lucretius,[27] while related ideas were later refined by Aristotle.[28] The struggle for existence was later described by al-Jahiz in the 9th century.[29][30] Such classical arguments were reintroduced in the 18th century by Pierre Louis Maupertuis[31] and others, including Charles Darwin's grandfather Erasmus Darwin. While these forerunners had an influence on Darwinism, they later had little influence on the trajectory of evolutionary thought after Charles Darwin. This article is about the physical universe. ... Empedocles (Greek: , ca. ... Lucretius Titus Lucretius Carus (c. ... For other uses, see Aristotle (disambiguation). ... Al-Jahiz (in Arabic الجاحظ) (real name Abu Uthman Amr Ibn Bahr al-Kinani al-Fuqaimi al-Basri) (born in Basra, 776 - 869) was a famous Arab scholar probably of Abyssinian descent. ... Pierre Louis Maupertuis, here wearing lapmudes or a fur coat from his Lapland expedition. ... For other people of the same surname, and places and things named after Charles Darwin, see Darwin. ... This article is about Erasmus Darwin who lived 1731–1802; for his descendants with the same name see Erasmus Darwin (disambiguation). ... Charles Darwin Darwinism is a term for the underlying theory in those ideas of Charles Darwin concerning evolution and natural selection. ...


Until the early 19th century, the prevailing view in Western societies was that differences between individuals of a species were uninteresting departures from their Platonic ideal (or typus) of created kinds. However, the theory of uniformitarianism in geology promoted the idea that simple, weak forces could act continuously over long periods of time to produce radical changes in the Earth's landscape. The success of this theory raised awareness of the vast scale of geological time and made plausible the idea that tiny, virtually imperceptible changes in successive generations could produce consequences on the scale of differences between species. Early 19th century evolutionists such as Jean Baptiste Lamarck suggested the inheritance of acquired characteristics as a mechanism for evolutionary change; adaptive traits acquired by an organism during its lifetime could be inherited by that organism's progeny, eventually causing transmutation of species.[32] This theory has come to be known as Lamarckism and was an influence on the anti-genetic ideas of the Stalinist Soviet biologist Trofim Lysenko.[33] Evolutionary thought has roots in antiquity as philosophical ideas conceived during the Ancient Greek and Roman eras, but until the 18th century, biological thought was dominated by essentialism, the idea that living forms are static and unchanging in time. ... The history of creationism is tied to the history of religions. ... Platonic idealism is the theory that the substantive reality around us is only a reflection of a higher truth. ... In creation biology, created kinds are believed to be the original forms of life as they were created by God. ... Uniformitarianism, in the philosophy of science, is the assumption that the natural processes operating in the past are the same as those that can be observed operating in the present. ... This article includes a list of works cited but its sources remain unclear because it lacks in-text citations. ... The table and timeline of geologic periods presented here is in accordance with the dates and nomenclature proposed by the International Commission on Stratigraphy. ... This article does not cite any references or sources. ... Jean-Baptiste Pierre Antoine de Monet, Chevalier de Lamarck (August 1, 1744 - December 28, 1829) was a major 19th century naturalist, who was one of the first to use the term biology in its modern sense. ... The inheritance of acquired characters (or characteristics) is the hereditary mechanism by which changes in physiology acquired over the life of an organism (such as muscle enlarged through use) are transmitted to offspring. ... Transmutation of species refers to the altering of one species into another. ... Lamarckism or Lamarckian evolution refers to the once widely accepted idea that an organism can pass on characteristics that it acquired during its lifetime to its offspring (also known as based on heritability of acquired characteristics or soft inheritance). It is named for the French biologist Jean-Baptiste Lamarck, who... Stalinism is a brand of political theory, and the political and economic system implemented by Joseph Stalin in the Soviet Union. ... CCCP redirects here. ... Trofim Denisovich Lysenko (Russian: Трофи́м Дени́сович Лысе́нко) (September 29, 1898–November 20, 1976) was a Soviet politician who made pretense of being a biologist. ...


Darwin's hypothesis

Between 1842 and 1844, Charles Darwin outlined his theory of evolution by natural selection as an explanation for adaptation and speciation. He defined natural selection as the "principle by which each slight variation [of a trait], if useful, is preserved".[34] The concept was simple but powerful: individuals best adapted to their environments are more likely to survive and reproduce.[35] As long as there is some variation between them, there will be an inevitable selection of individuals with the most advantageous variations. If the variations are inherited, then differential reproductive success will lead to a progressive evolution of particular populations of a species, and populations that evolve to be sufficiently different might eventually become different species. For other people of the same surname, and places and things named after Charles Darwin, see Darwin. ...


Darwin's ideas were inspired by the observations that he had made on the Voyage of the Beagle, and by the work of two economists. The first was Thomas Malthus, who in An Essay on the Principle of Population, noted that population (if unchecked) increases exponentially whereas the food supply grows only arithmetically; thus inevitable limitations of resources would have demographic implications, leading to a "struggle for existence", in which only the fittest would survive. The second was Adam Smith who, in The Wealth of Nations, identified a regulating mechanism in free markets, which he referred to as the "invisible hand", which suggests that prices self-adjust according to supplies and demand.[36] Thus for Darwin, the disaster that was supposed to occur according to Malthus was kept in check and constantly improved by competition (or law of selection). A watercolour by HMS Beagles draughtsman, Conrad Martens. ... Thomas Robert Malthus FRS (13 February 1766 – 23 December 1834),[1] was a political economist and British demographer. ... An Essay on the Principle of Population was first published anonymously in 1798. ... In mathematics, exponential growth (or geometric growth) occurs when the growth rate of a function is always proportional to the functions current size. ... A linear function is a mathematical function term of the form: f(x) = m x + c where c is a constant. ... For other persons named Adam Smith, see Adam Smith (disambiguation). ... Adam Smiths first title page An Inquiry into the Nature and Causes of the Wealth of Nations is the magnum opus of the Scottish economist Adam Smith, published on March 9, 1776, during the Scottish Enlightenment. ... For other uses, see Invisible hand (disambiguation). ...


Once the theory had been formulated, Darwin was meticulous about gathering and refining evidence, sharing his ideas only with a few friends; he was inspired to publish after the young naturalist Alfred Russel Wallace independently conceived of the principle and described it in a letter to Darwin. The two men arranged to present two short papers to the Linnean Society announcing co-discovery of the principle in 1858;[37] Darwin published a more detailed account of his evidence and conclusions in The Origin of Species in 1859. In the 6th edition of The Origin of Species Darwin acknowledged that others — notably William Charles Wells in 1813, and Patrick Matthew in 1831 — had proposed similar theories, but had not presented them fully or in notable scientific publications. For the Cornish painter, see Alfred Wallis. ... The Linnean Society of London is the worlds premier society for the study and dissemination about taxonomy. ... Charles Darwins Origin of Species (publ. ... William Charles Wells (1757 — 1817) was Wells was born Charlestown, where? and was sent to school in Dumfries and later attended the University of Edinburgh. ... Patrick Matthew Patrick Matthew (20 October 1790 — 8 June 1874) was a Scottish fruit grower who had proposed the principle of natural selection as a mechanism of evolution over a quarter-century earlier than did Charles Darwin and Alfred Russel Wallace. ...


Darwin thought of natural selection by analogy to how farmers select crops or livestock for breeding, which he called artificial selection; in his early manuscripts he referred to a 'Nature' which would do the selection. At the time, other mechanisms of evolution such as evolution by genetic drift were not yet explicitly formulated, and Darwin realized that selection was likely only part of the story: "I am convinced that [it] has been the main, but not exclusive means of modification."[38] For Darwin and his contemporaries, natural selection was thus essentially synonymous with evolution by natural selection. After the publication of The Origin of Species, educated people generally accepted that evolution had occurred in some form. However, natural selection remained controversial as a mechanism, partly because it was perceived to be too weak to explain the range of observed characteristics of living organisms, and partly because even supporters of evolution balked at its 'unguided' and non-progressive nature,[39] a response that has been characterized as the single most significant impediment to the idea's acceptance.[40] However, some thinkers enthusiastically embraced natural selection; after reading Darwin, Herbert Spencer introduced the term survival of the fittest, which became a popular summary of the theory. Although the phrase is still often used by non-biologists, modern biologists avoid it because it is tautological if fittest is read to mean functionally superior and is applied to individuals rather than considered as an averaged quantity over populations.[41] In a letter to Charles Lyell in September 1860, Darwin regrets the use of the term 'Natural Selection', preferring the term 'Natural Preservation'.[42] This Chihuahua mix and Great Dane show the wide range of dog breed sizes created using artificial selection. ... In population genetics, genetic drift is the statistical effect that results from the influence that chance has on the success of alleles (variants of a gene). ... This article is about evolution in biology. ... For other persons named Herbert Spencer, see Herbert Spencer (disambiguation). ... For other uses, see Survival of the fittest (disambiguation). ... In rhetoric, a tautology is an unnecessary (and usually unintentional) repetition of meaning, often utilising words from different languages. ... Charles Lyell The frontispiece from Principles of Geology Sir Charles Lyell, 1st Baronet, KT, (November 14, 1797 – February 22, 1875) was a Scottish lawyer, geologist, and populariser of uniformitarianism. ...


Modern evolutionary synthesis

Only after the integration of a theory of evolution with a complex statistical appreciation of Austrian monk Gregor Mendel's 're-discovered' laws of inheritance did natural selection become generally accepted by scientists. The work of Ronald Fisher (who developed the language of mathematics and natural selection in terms of the underlying genetic processes),[3] J.B.S. Haldane (who introduced the concept of the 'cost' of natural selection),[43] Sewall Wright (who elucidated the nature of selection and adaptation),[44] Theodosius Dobzhansky (who established the idea that mutation, by creating genetic diversity, supplied the raw material for natural selection),[45] William Hamilton (who conceived of kin selection), Ernst Mayr (who recognised the key importance of reproductive isolation for speciation)[46] and many others formed the modern evolutionary synthesis. This synthesis cemented natural selection as the foundation of evolutionary theory, where it remains today. The modern evolutionary synthesis refers to a set of ideas from several biological specialities that were brought together to form a unified theory of evolution accepted by the great majority of working biologists. ... “Mendel” redirects here. ... This article or section does not adequately cite its references or sources. ... Sir Ronald Aylmer Fisher, FRS (17 February 1890 – 29 July 1962) was an English statistician, evolutionary biologist, and geneticist. ... The Genetical Theory of Natural Selection is a book by Ronald Fisher. ... John Burdon Sanderson Haldane (November 5, 1892 - December 1, 1964), who normally used J.B.S. as a first name, was a geneticist born in Scotland and educated at Eton and Oxford University. ... Sewall Green Wright ForMemRS (December 21, 1889 – March 3, 1988) was an American geneticist known for his influential work on evolutionary theory. ... Theodosius Dobzhansky, ca. ... Genetics and the Origin of Species (ISBN 0231054750) is a 1937 book by the Ukrainian-American evolutionary biologist Theodosius Dobzhansky and one of the important books of the modern evolutionary synthesis. ... W. D. Hamilton William Donald Bill Hamilton, F.R.S. (1 August 1936 — 7 March 2000) was a British evolutionary biologist, considered one of the greatest evolutionary theorists of the 20th century. ... Ernst Mayr Ernst Walter Mayr (July 5, 1904, Kempten, Germany – February 3, 2005, Bedford, Massachusetts U.S.), was one of the 20th centurys leading evolutionary biologists. ... Systematics and the Origin of Species is a book written by zoologist and evolutionary biologist Ernst Mayr that was first published in 1942. ... The modern evolutionary synthesis refers to a set of ideas from several biological specialities that were brought together to form a unified theory of evolution accepted by the great majority of working biologists. ...


Impact of the idea

Darwin's ideas, along with those of Adam Smith and Karl Marx, had a profound influence on 19th century thought. Perhaps the most radical claim of the theory of evolution through natural selection is that "elaborately constructed forms, so different from each other, and dependent on each other in so complex a manner" evolved from the simplest forms of life by a few simple principles. This claim inspired some of Darwin's most ardent supporters—and provoked the most profound opposition. The radicalism of natural selection, according to Stephen Jay Gould,[47] lay in its power to "dethrone some of the deepest and most traditional comforts of Western thought". In particular, it challenged long-standing beliefs in such concepts as a special and exalted place for humans in the natural world and a benevolent creator whose intentions were reflected in nature's order and design. For other people of the same surname, and places and things named after Charles Darwin, see Darwin. ... For other persons named Adam Smith, see Adam Smith (disambiguation). ... Karl Heinrich Marx (May 5, 1818 – March 14, 1883) was a 19th century philosopher, political economist, and revolutionary. ... Stephen Jay Gould (September 10, 1941 – May 20, 2002) was an American paleontologist, evolutionary biologist, and historian of science. ...


Social and psychological theory

The social implications of the theory of evolution by natural selection also became the source of continuing controversy. Friedrich Engels, a German political philosopher and co-originator of the ideology of communism, wrote in 1872 that "Darwin did not know what a bitter satire he wrote on mankind when he showed that free competition, the struggle for existence, which the economists celebrate as the highest historical achievement, is the normal state of the animal kingdom".[48] Interpretation of natural selection as necessarily 'progressive', leading to increasing 'advances' in intelligence and civilisation, was used as a justification for colonialism and policies of eugenics, as well as broader sociopolitical positions now described as Social Darwinism. Konrad Lorenz won the Nobel Prize in Physiology or Medicine in 1973 for his analysis of animal behavior in terms of the role of natural selection (particularly group selection). However, in Germany in 1940, in writings that he subsequently disowned, he used the theory as a justification for policies of the Nazi state. He wrote "... selection for toughness, heroism, and social utility...must be accomplished by some human institution, if mankind, in default of selective factors, is not to be ruined by domestication-induced degeneracy. The racial idea as the basis of our state has already accomplished much in this respect."[49] Others have developed ideas that human societies and culture evolve by mechanisms that are analogous to those that apply to evolution of species.[50] Engels redirects here. ... Political philosophy is the study of the fundamental questions about the state, government, politics, property, law and the enforcement of a legal code by authority: what they are, why they are needed, what makes a government legitimate, what rights and freedoms it should protect and why, what form it should... This article is about the form of society and political movement. ... It has been suggested that Benign colonialism be merged into this article or section. ... Eugenics is the self-direction of human evolution: Logo from the Second International Eugenics Conference [10], 1921, depicting it as a tree which unites a variety of different fields. ... Social Darwinism is the idea that Charles Darwins theory can be extended and applied to the social realm, i. ... Lorenz being followed by his imprinted geese Konrad Zacharias Lorenz (November 7, 1903 in Vienna – February 27, 1989 in Vienna) was an Austrian zoologist, animal psychologist, and ornithologist. ... Emil Adolf von Behring was the first person to receive the Nobel Prize in Physiology or Medicine, for his work on the treatment of diphtheria. ... National Socialism redirects here. ... Cultural evolution is the structural development (change) of a society over time. ...


More recently, work among anthropologists and psychologists has led to the development of sociobiology and later evolutionary psychology, a field that attempts to explain features of human psychology in terms of adaptation to the ancestral environment. The most prominent such example, notably advanced in the early work of Noam Chomsky and later by Steven Pinker, is the hypothesis that the human brain is adapted to acquire the grammatical rules of natural language.[51] Other aspects of human behavior and social structures, from specific cultural norms such as incest avoidance to broader patterns such as gender roles, have been hypothesized to have similar origins as adaptations to the early environment in which modern humans evolved. By analogy to the action of natural selection on genes, the concept of memes - "units of cultural transmission", or culture's equivalents of genes undergoing selection and recombination - has arisen, first described in this form by Richard Dawkins[52] and subsequently expanded upon by philosophers such as Daniel Dennett as explanations for complex cultural activities, including human consciousness.[53] Extensions of the theory of natural selection to such a wide range of cultural phenomena have been distinctly controversial and are not widely accepted.[54] This article or section includes a list of works cited or a list of external links, but its sources remain unclear because it lacks in-text citations. ... Evolutionary psychology (abbreviated EP) is a theoretical approach to psychology that attempts to explain mental and psychological traits—such as memory, perception, or language—as adaptations, i. ... Psychology (Gk: psyche, soul or mind + logos, speech) is an academic and applied field involving the study of the human mind, brain, and behavior. ... Avram Noam Chomsky (born December 7, 1928) is an American linguist, philosopher, political activist, author, and lecturer. ... Steven Pinker Steven Arthur Pinker (born September 18, 1954) is a prominent Canadian-born American experimental psychologist, cognitive scientist, and popular science writer known for his spirited and wide-ranging advocacy of evolutionary psychology and the computational theory of mind. ... For the academic journal, see Language Acquisition: A Journal of Developmental Linguistics. ... For the rules of the English language, see English grammar. ... In the philosophy of language, a natural language (or ordinary language) is a language that is spoken, written, or signed by humans for general-purpose communication, as distinguished from formal languages (such as computer-programming languages or the languages used in the study of formal logic, especially mathematical logic) and... This article is about the psychological term. ... A bagpiper in Scottish military clan-uniform. ... For other uses, see Meme (disambiguation). ... Clinton Richard Dawkins, FRS (born March 26, 1941) is a British ethologist, evolutionary biologist and popular science writer who holds the Charles Simonyi Chair for the Public Understanding of Science at the University of Oxford. ... Daniel Clement Dennett (born March 28, 1942 in Boston, Massachusetts) is a prominent American philosopher whose research centers on philosophy of mind, philosophy of science and philosophy of biology, particularly as those fields relate to evolutionary biology and cognitive science. ... Consciousness is a quality of the mind generally regarded to comprise qualities such as subjectivity, self-awareness, sentience, sapience, and the ability to perceive the relationship between oneself and ones environment. ...


Information and systems theory

In 1922, Alfred Lotka proposed that natural selection might be understood as a physical principle which could be energetically quantified,[55] a concept that was later developed by Howard Odum as the maximum power principle whereby evolutionary systems with selective advantage maximise the rate of useful energy transformation. Such concepts are sometimes relevant in the study of applied thermodynamics. Alfred James Lotka (March 2, 1880 - December 5, 1949) was a US mathematician and statistician, most famous for his work in population dynamics. ... Howard Thomas Odum (1924-2002), commonly known as H.T. Odum or Tom Odum, was an eminent American ecosystem ecologist and a professor at the University of Florida. ... This article or section may be confusing for some readers, and should be edited to be clearer. ... Thermodynamics (from the Greek θερμη, therme, meaning heat and δυναμις, dynamis, meaning power) is a branch of physics that studies the effects of changes in temperature, pressure, and volume on physical systems at the macroscopic scale by analyzing the collective motion of their particles using statistics. ...


The principles of natural selection have inspired a variety of computational techniques, such as "soft" artificial life, that simulate selective processes and can be highly efficient in 'adapting' entities to an environment defined by a specified fitness function.[56] For example, a class of heuristic optimization algorithms known as genetic algorithms, pioneered by John Holland in the 1970s and expanded upon by David Goldberg,[57] identify optimal solutions by simulated reproduction and mutation of a population of solutions defined by an initial probability distribution.[58] Such algorithms are particularly useful when applied to problems whose solution landscape is very rough or has many local minima. This article is about a field of research. ... A fitness function is a particular type of objective function that quantifies the optimality of a solution (that is, a chromosome) in a genetic algorithm so that that particular chromosome may be ranked against all the other chromosomes. ... For other uses, see Heuristic (disambiguation). ... In mathematics, the term optimization, or mathematical programming, refers to the study of problems in which one seeks to minimize or maximize a real function by systematically choosing the values of real or integer variables from within an allowed set. ... Flowcharts are often used to graphically represent algorithms. ... A genetic algorithm (GA) is a search technique used in computing to find exact or approximate solutions to optimization and search problems. ... Dr. John Henry Holland (February 2, 1929) is known as the father of genetic algorithms. ... David E. Goldberg is a professor at the department of Industrial and Enterprise Systems Engineering (IESE) at the University of Illinois at Urbana-Champaign and is most noted for his seminal works in the field of genetic algorithms. ... A probability distribution describes the values and probabilities that a random event can take place. ... It has been suggested that this article or section be merged into hypersurface. ...


See also

This Chihuahua mix and Great Dane show the wide range of dog breed sizes created using artificial selection. ... Bumblebees and the flowers they pollinate have co-evolved so that both have become dependent on each other for survival. ... The gene-centered view of evolution, gene selection theory or selfish gene theory holds that natural selection acts through differential survival of competing genes, increasing the frequency of those alleles whose phenotypic effects successfully promote their own propagation. ... A genetic algorithm (GA) is a search technique used in computing to find exact or approximate solutions to optimization and search problems. ... Koinophilia is a term used in biology, meaning that when sexual creatures seek a mate, they prefer that mate not to have any unusual, peculiar or deviant features. ... It has been suggested that this article or section be merged with Stabilizing selection. ... , the white-bodied peppered moth. ... In this diagram, interbreeding populations are represented by coloured blocks. ... This article does not cite any references or sources. ...

References

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  4. ^ Works employing or describing this usage:
    Endler JA (1986). Natural Selection in the Wild. Princeton, New Jersey: Princeton University Press. ISBN 0-691-00057-3. 
    Williams GC (1966). Adaptation and Natural Selection. Oxford University Press. 
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    Lande R & Arnold SJ (1983) The measurement of selection on correlated characters. Evolution 37:1210-26
    Futuyma DJ (2005) Evolution. Sinauer Associates, Inc., Sunderland, Massachusetts. ISBN 0-87893-187-2
    Haldane, J.B.S. 1953. The measurement of natural selection. Proceedings of the 9th International Congress of Genetics. 1: 480-487
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    Lotka AJ (1922b) Natural selection as a physical principle [PDF] Proc Natl Acad Sci USA 8:151–4
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Charles Darwins Origin of Species (publ. ... The Genetical Theory of Natural Selection is a book by Ronald Fisher. ... Nassau Street, Princetons main street. ... This article is about the U.S. state. ... The Princeton University Press is a publishing house, a division of Princeton University, that is highly respected in academic publishing. ... Cover of the 1996 edition. ... Evolution, the International Journal of Organic Evolution, is a bimonthly scientific journal that publishes significant new results of empirical or theoretical investigations concerning facts, processes, mechanics, or concepts of evolutionary phenomena and events. ... Douglas Joel Futuyma (born 1942 in New York) is an American biologist. ... Sunderland is a town located in Franklin County, Massachusetts, part of the Pioneer Valley. ... This article is about the U.S. state. ... Elliott Sober -- Hans Reichenbach Professor and William F. Vilas Research Professor in the Department of Philosophy at University of Wisconsin. ... The University of Chicago Press is the largest university press in the U.S. It is operated by the University of Chicago and publishes a wide variety of academic titles, including The Chicago Manual of Style, dozens of academic journals including Critical Inquiry, and a wide array of texts covering... Evolutionary ecology lies at the intersection ecology and evolutionary biology. ... Blackwell Publishing was formed in 2001 from two Oxford-based academic publishing companies, Blackwell Science and Blackwell Publishers and is the worlds leading society publisher, partnering with 665 academic and professional societies. ... This article is about the city of Oxford in England. ... The Proceedings of the National Academy of Sciences (USA), mostly commonly referred to as PNAS, is the official publication of the National Academy of Sciences of the United States of America. ... American Naturalist is a monthly scientific journal, founded in 1867, and associated with the University of Chicago. ... The Quarterly Review of Biology or QRB (ISSN: 0033-5770) is a scientific review of current and historical topics in biology as well as a source of book reviews. ... Year 2006 (MMVI) was a common year starting on Sunday of the Gregorian calendar. ... is the 126th day of the year (127th in leap years) in the Gregorian calendar. ... The EMBO Journal is a scientific journal focusing on full-length papers describing original research of general interest in molecular biology and related areas. ... Science is the academic journal of the American Association for the Advancement of Science and is considered one of the worlds most prestigious scientific journals. ... A diagram of a thoracic vertebra. ... The Proceedings of the National Academy of Sciences (USA), mostly commonly referred to as PNAS, is the official publication of the National Academy of Sciences of the United States of America. ... Empedocles (Greek: , ca. ... Lucretius Titus Lucretius Carus (c. ... This article is about the capital of England and the United Kingdom. ... Pierre Louis Maupertuis, here wearing lapmudes or a fur coat from his Lapland expedition. ... Portrait of Jean-Baptiste Lamarck Jean-Baptiste Pierre Antoine de Monet, Chevalier de Lamarck (August 1, 1744 – December 18, 1829) was a French soldier, naturalist, academic and an early proponent of the idea that evolution occurred and proceeded in accordance with natural laws. ... David Orrell is a mathematician and author born in Edmonton and living in Vancouver, British Columbia, Canada. ... For the Cornish painter, see Alfred Wallis. ... Year 2006 (MMVI) was a common year starting on Sunday of the Gregorian calendar. ... is the 130th day of the year (131st in leap years) in the Gregorian calendar. ... Cover of the 1990 Princeton University reprint The Causes of Evolution is a 1932 book on evolutionary biology by J.B.S. Haldane, and one of the important books of the modern evolutionary synthesis. ... The Journal of Genetics (not to be confused with another journal called Genetics) is a scientific journal concerning genetics. ... Genetics and the Origin of Species (ISBN 0231054750) is a 1937 book by the Ukrainian-American evolutionary biologist Theodosius Dobzhansky and one of the important books of the modern evolutionary synthesis. ... Systematics and the Origin of Species is a book written by zoologist and evolutionary biologist Ernst Mayr that was first published in 1942. ... The term Engels could refer to more than one thing: Friedrich Engels, German socialist Engels, Russia, formerly known as Pokrovsk This is a disambiguation page — a navigational aid which lists other pages that might otherwise share the same title. ... Stuart Alan Kauffman (born September 28, 1939) is a theoretical biologist and complex systems researcher, who has given much thought to the origin of life on Earth. ...

Further reading

  • Historical
    • Zirkle C (1941). Natural Selection before the "Origin of Species", Proceedings of the American Philosophical Society 84 (1), p. 71-123.
    • Kohm M (2004) A Reason for Everything: Natural Selection and the English Imagination. London: Faber and Faber. ISBN 0-571-22392-3. For review, see [8] van Wyhe J (2005) Human Nature Review 5:1-4

Stephen Jay Gould (September 10, 1941 – May 20, 2002) was an American paleontologist, evolutionary biologist, and historian of science. ... Professor John Maynard Smith[1], F.R.S. (6 January 1920 – 19 April 2004) was a British evolutionary biologist and geneticist. ... Sir Karl Raimund Popper (July 28, 1902 â€“ September 17, 1994) was an Austrian and British[1] philosopher and a professor at the London School of Economics. ... Elliott Sober -- Hans Reichenbach Professor and William F. Vilas Research Professor in the Department of Philosophy at University of Wisconsin. ... George Williams Professor George Christopher Williams (b. ... Cover of the 1996 edition. ... George Williams Professor George Christopher Williams (b. ... Clinton Richard Dawkins, FRS (born March 26, 1941) is a British ethologist, evolutionary biologist and popular science writer who holds the Charles Simonyi Chair for the Public Understanding of Science at the University of Oxford. ... Climbing Mount Improbable cover Climbing Mount Improbable is a 1996 popular science book by Richard Dawkins. ... Daniel Clement Dennett (born March 28, 1942 in Boston, Massachusetts) is a prominent American philosopher whose research centers on philosophy of mind, philosophy of science and philosophy of biology, particularly as those fields relate to evolutionary biology and cognitive science. ... cover Darwins Dangerous Idea: Evolution and the Meanings of Life (1995) is a controversial book by Daniel Dennett that argues that Darwinian processes are the central organising force not only in biology (which is not controversial), but also in most other aspects of the Universe, including the human mind... Stephen Jay Gould (September 10, 1941 – May 20, 2002) was an American paleontologist, evolutionary biologist, and historian of science. ... Steve Jones This article is about the evolutionary biologist. ... Richard Lewontin Richard Charles Dick Lewontin (born March 29, 1929) is an American evolutionary biologist, geneticist and social commentator. ... Jonathan Weiner is a Pulitzer Winning author of non-fiction books on his biology observations, in particular evolution in the Galápagos Islands, genetics, and the environment. ... The Beak of the Finch: A Story of Evolution in Our Time ISBN 067973337X is a book on evolution written for the layperson by Jonathan Weiner. ...

External links

While on board HMS Beagle, Charles Darwin collected numerous specimens, many new to science, which supported his later theory of evolution by natural selection. ... For other uses, see Adaptation (disambiguation). ... Macroevolution refers to evolution that occurs at or above the level of species, in contrast with microevolution, which refers to smaller evolutionary changes (typically described as changes in allele frequencies) within a species or population. ... Microevolution is the occurrence of small-scale changes in allele frequencies in a population, over a few generations, also known as change at or below the species level. ... Charles Darwins first sketch of an evolutionary tree from his First Notebook on Transmutation of Species (1837) Speciation is the evolutionary process by which new biological species arise. ... Population genetics is the study of the distribution of and change in allele frequencies under the influence of the four evolutionary forces: natural selection, genetic drift, mutation, and migration. ... In population genetics, genetic drift is the statistical effect that results from the influence that chance has on the success of alleles (variants of a gene). ... In population genetics, gene flow (also known as gene migration) is the transfer of alleles of genes from one population to another. ... For linguistic mutation, see Apophony. ... Evolutionary developmental biology (evolution of development or informally, evo-devo) is a field of biology that compares the developmental processes of different animals in an attempt to determine the ancestral relationship between organisms and how developmental processes evolved. ... We dont have an article called Phenotypic plasticity Start this article Search for Phenotypic plasticity in. ... Norms of reaction for two genotypes. ... Many organisms consist of modules, both anatomically and in their metabolism. ... A number of different Markov models of DNA sequence evolution have been proposed. ... The evolution of sex is a major puzzle in modern evolutionary biology. ... Enquiry into the evolution of ageing aims to explain why almost all living things weaken and die with age. ... The nature and origins of hominid intelligence is a much-studied and much-debated topic, of natural interest to humans as the most successful and intelligent hominid species. ... Diagram of major stages in the eyes evolution. ... Plant evolution is an aspect of the study of biological evolution, involving predominantly the evolution of plants suited to live on land, the greening of the various land masses by the filling of their niches with land plants, and the diversification of the groups of land plants. ... The evolutionary history of life and the origin of life are fields of ongoing geological and biological research. ... For the history of humans on Earth, see History of the world. ... Anagenesis is the progressive evolution of species involving a change in gene frequency in an entire population rather than a cladogenetic branching event. ... Catagenesis is an archaic term from evolutionary biology referring to evolutionary directions that were considered retrogressive. ... Cladogenesis is an evolutionary splitting event in which each branch and its smaller branches is a clade; an evolutionary mechanism and a process of adaptive evolution that leads to the development of a greater variety of animals or plants. ... Evolutionary thought has roots in antiquity as philosophical ideas conceived during the Ancient Greek and Roman eras, but until the 18th century, biological thought was dominated by essentialism, the idea that living forms are static and unchanging in time. ... For other people of the same surname, and places and things named after Charles Darwin, see Darwin. ... The 1859 edition of On the Origin of Species First published in 1859, The Origin of Species (full title On the Origin of Species by Means of Natural Selection, or the Preservation of Favoured Races in the Struggle for Life) by British naturalist Charles Darwin is one of the pivotal... The modern evolutionary synthesis refers to a set of ideas from several biological specialities that were brought together to form a unified theory of evolution accepted by the great majority of working biologists. ... The gene-centered view of evolution, gene selection theory or selfish gene theory holds that natural selection acts through differential survival of competing genes, increasing the frequency of those alleles whose phenotypic effects successfully promote their own propagation. ... This article is about life in general. ... Ecological genetics is the study of genetics (itself a field of biology) from an ecological perspective. ... Molecular evolution is the process of the genetic material in populations of organisms changing over time. ... Phylogenetic groups, or taxa, can be monophyletic, paraphyletic, or polyphyletic. ... Biological systematics is the study of the diversity of life on the planet earth, both past and present, and the relationships among living things through time. ... This is a list of topics in evolutionary biology and evolution. ... Life on Earth  â€¢  â€¢  | Axis scale: millions of years ago. ... Population genetics is the study of the distribution of and change in allele frequencies under the influence of the four evolutionary forces: natural selection, genetic drift, mutation, and migration. ... Hardy–Weinberg principle for two alleles: the horizontal axis shows the two allele frequencies p and q, the vertical axis shows the genotype frequencies and the three possible genotypes are represented by the different glyphs In population genetics, the Hardy–Weinberg principle is a relationship between the frequencies of alleles... Genetic linkage occurs when particular alleles are inherited jointly. ... Linkage disequilibrium (LD) is the non-random association of alleles at two or more loci on a chromosome. ... In population genetics, Ronald Fishers fundamental theorem of natural selection was originally stated as: The rate of increase in fitness of any organism at any time is equal to its genetic variance in fitness at that time. ... The neutral theory of molecular evolution (also, simply the neutral theory of evolution) is an influential theory that was introduced with provocative effect by Motoo Kimura in the late 1960s and early 1970s. ... The Price equation (also known as Prices equation) is a covariance equation which is a mathematical description of evolution and natural selection. ... For other uses, see Selection (disambiguation). ... Illustration from The Descent of Man and Selection in Relation to Sex by Charles Darwin showing the Tufted Coquette Lophornis ornatus, female on left, ornamented male on right. ... This Chihuahua mix and Great Dane show the wide range of dog breed sizes created using artificial selection. ... Ecological selection (or environmental selection or survival selection or individual selection or asexual selection) refers to natural selection minus sexual selection, i. ... The process by which an evolutionary neutral or in some cases deleterious allele or mutation may spread through the gene pool by virtue of being linked to a beneficial mutation. ... It has been suggested that this article or section be merged with Stabilizing selection. ... In population genetics, genetic drift is the statistical effect that results from the influence that chance has on the success of alleles (variants of a gene). ... Species with a small population size are subject to a higher chance of extinction because their small population size makes them more vulnerable to genetic drift, resulting in stochastic variation in their gene pool, their demography and their environment. ... A population bottleneck (or genetic bottleneck) is an evolutionary event in which a significant percentage of a population or species is killed or otherwise prevented from reproducing, and the population is reduced by 50% or more, often by several orders of magnitude. ... Simple illustration of founder effect. ... In genetics, coalescent theory is a retrospective model of population genetics that traces all alleles of a gene in a sample from a population to a single ancestral copy shared by all members of the population, known as the most recent common ancestor (MRCA; sometimes also termed the coancestor to... Sir Ronald Aylmer Fisher, FRS (17 February 1890 – 29 July 1962) was an English statistician, evolutionary biologist, and geneticist. ... John Burdon Sanderson Haldane (November 5, 1892 – December 1, 1964), who normally used J.B.S. as a first name, was a British geneticist and evolutionary biologist. ... Sewall Green Wright ForMemRS (December 21, 1889 – March 3, 1988) was an American geneticist known for his influential work on evolutionary theory. ... This article is about evolution in biology. ... Microevolution is the occurrence of small-scale changes in allele frequencies in a population, over a few generations, also known as change at or below the species level. ... Evolutionary game theory (EGT) is the application of population genetics-inspired models of change in gene frequency in populations to game theory. ... In evolutionary biology, fitness landscapes or adaptive landscapes are used to visualize the relationship between genotypes (or phenotypes) and replicatory success. ... Genetic genealogy is the application of genetics to traditional genealogy. ... This is a list of topics in evolutionary biology and evolution. ...

  Results from FactBites:
 
Natural selection - Wikipedia, the free encyclopedia (3939 words)
Natural Selection is the phrase Charles Darwin used in 1859 in his book The Origin of Species to name the natural process he proposed to be responsible for the origin of new species and the adaptation of organisms to their environments.
Natural selection occurs when individuals differ in reproductive output for functional reasons, i.e., when differences in reproduction follow from the fact that individuals differ from each other in their ability to tackle the challenges posed by their internal biology and by the biological and physical environment.
Natural selection is different from artificial selection which refers to the evolution of domesticated species as a result of human culling rather than culling by the "natural environment".
Natural selection - definition of Natural selection in Encyclopedia (1425 words)
Natural selection is the primary mechanism within the scientific theory of evolution, i.e.
Natural selection is distinguished from artificial selection by humans.
The basic concept of natural selection is that conditions (or "nature") determine (or "select") how well particular traits of organisms can serve the survival and reproduction of the organism; organisms lacking these traits might die before reproducing, or be less prolific.
  More results at FactBites »

 
 

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