Natural selection

selectionselectiveselectednaturalselective pressureselective advantageselective pressuresevolution by natural selectiontheory of natural selectionnaturally selected
Natural selection is the differential survival and reproduction of individuals due to differences in phenotype.wikipedia
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Evolution

evolvedtheory of evolutionevolutionary theory
It is a key mechanism of evolution, the change in the heritable traits characteristic of a population over generations.
Evolution occurs when evolutionary processes such as natural selection (including sexual selection) and genetic drift act on this variation, resulting in certain characteristics becoming more common or rare within a population.

Charles Darwin

DarwinDarwinianCharles
Charles Darwin popularised the term "natural selection", contrasting it with artificial selection, which is intentional, whereas natural selection is not.
In a joint publication with Alfred Russel Wallace, he introduced his scientific theory that this branching pattern of evolution resulted from a process that he called natural selection, in which the struggle for existence has a similar effect to the artificial selection involved in selective breeding.

Sexual selection

sexually selectedmale-male competitionsexual competition
Other factors affecting reproductive success include sexual selection (now often included in natural selection) and fecundity selection.
Sexual selection is a mode of natural selection where members of one biological sex choose mates of the other sex to mate with (intersexual selection), and compete with members of the same sex for access to members of the opposite sex (intrasexual selection).

Alfred Russel Wallace

WallaceAlfred WallaceAlfred R. Wallace
The concept, published by Darwin and Alfred Russel Wallace in a [[On the Tendency of Species to form Varieties; and on the Perpetuation of Varieties and Species by Natural Means of Selection|joint presentation of papers in 1858]], was elaborated in Darwin's influential 1859 book On the Origin of Species by Means of Natural Selection, or the Preservation of Favoured Races in the Struggle for Life.
He is best known for independently conceiving the theory of evolution through natural selection; his paper on the subject was jointly published with some of Charles Darwin's writings in 1858.

Microevolution

micro levelmicro-evolutionmicroevolutionary processes
Over time, this process can result in populations that specialise for particular ecological niches (microevolution) and may eventually result in speciation (the emergence of new species, macroevolution).
This change is due to four different processes: mutation, selection (natural and artificial), gene flow and genetic drift.

Modern synthesis (20th century)

modern synthesismodern evolutionary synthesisevolutionary synthesis
The union of traditional Darwinian evolution with subsequent discoveries in classical genetics formed the modern synthesis of the mid-20th century.
The 19th century ideas of natural selection and Mendelian genetics were put together with population genetics, early in the twentieth century.

Speciation

divergedspeciatedtrichotomy
Over time, this process can result in populations that specialise for particular ecological niches (microevolution) and may eventually result in speciation (the emergence of new species, macroevolution).
Charles Darwin was the first to describe the role of natural selection in speciation in his 1859 book The Origin of Species.

Adaptation

adaptedadaptationsadaptive
While genotypes can slowly change by random genetic drift, natural selection remains the primary explanation for adaptive evolution.
Thirdly, it is a phenotypic or adaptive trait, with a functional role in each individual organism, that is maintained and has been evolved by natural selection.

Darwinism

DarwinianDarwinistDarwinian evolution
The union of traditional Darwinian evolution with subsequent discoveries in classical genetics formed the modern synthesis of the mid-20th century.
Darwinism is a theory of biological evolution developed by the English naturalist Charles Darwin (1809–1882) and others, stating that all species of organisms arise and develop through the natural selection of small, inherited variations that increase the individual's ability to compete, survive, and reproduce.

On the Origin of Species

Origin of SpeciesThe Origin of SpeciesOn the Origin of Species by Means of Natural Selection, or the Preservation of Favoured Races in the Struggle for Life
The concept, published by Darwin and Alfred Russel Wallace in a [[On the Tendency of Species to form Varieties; and on the Perpetuation of Varieties and Species by Natural Means of Selection|joint presentation of papers in 1858]], was elaborated in Darwin's influential 1859 book On the Origin of Species by Means of Natural Selection, or the Preservation of Favoured Races in the Struggle for Life.
Darwin's book introduced the scientific theory that populations evolve over the course of generations through a process of natural selection.

Genetic drift

driftrandom genetic driftrandom drift
While genotypes can slowly change by random genetic drift, natural selection remains the primary explanation for adaptive evolution.
In the early 20th century, vigorous debates occurred over the relative importance of natural selection versus neutral processes, including genetic drift.

Transmutation of species

transmutationtransformismtransmutationism
The early 19th-century zoologist 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.
Transmutation of species and transformism are 19th-century evolutionary ideas for the altering of one species into another that preceded Charles Darwin's theory of natural selection.

An Essay on the Principle of Population

Essay on the Principle of PopulationPrinciple of PopulationMalthus's theory of population
Darwin's ideas were inspired by the observations that he had made on the second voyage of HMS Beagle (1831–1836), and by the work of a political economist, Thomas Robert Malthus, who, in An Essay on the Principle of Population (1798), 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".
The book's 6th edition (1826) was independently cited as a key influence by both Charles Darwin and Alfred Russel Wallace in developing the theory of natural selection.

Second voyage of HMS Beagle

second voyage of HMS ''Beaglevoyage of the ''BeagleBeagle'' voyage
Darwin's ideas were inspired by the observations that he had made on the second voyage of HMS Beagle (1831–1836), and by the work of a political economist, Thomas Robert Malthus, who, in An Essay on the Principle of Population (1798), 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".
He ably collected and made detailed observations of plants and animals, with results that shook his belief that species were fixed and provided the basis for ideas which came to him when back in England, and led to his theory of evolution by natural selection.

Selective breeding

artificial selectionselectively bredbreeding
Charles Darwin popularised the term "natural selection", contrasting it with artificial selection, which is intentional, whereas natural selection is not.
Selective breeding (also called artificial selection) is the process by which humans use animal breeding and plant breeding to selectively develop particular phenotypic traits (characteristics) by choosing which typically animal or plant males and females will sexually reproduce and have offspring together.

Evolutionary developmental biology

evo-devoevolutionary developmental biologistevolutionary development
The addition of molecular genetics has led to evolutionary developmental biology, which explains evolution at the molecular level.
This multiple pleiotropic reuse explains why these genes are highly conserved, as any change would have many adverse consequences which natural selection would oppose.

Survival of the fittest

survivalstruggle for existencedifferential survival
However, some thinkers enthusiastically embraced natural selection; after reading Darwin, Herbert Spencer introduced the phrase survival of the fittest, which became a popular summary of the theory.
"Survival of the fittest" is a phrase that originated from Darwinian evolutionary theory as a way of describing the mechanism of natural selection.

Fecundity selection

fecundityecundity
Other factors affecting reproductive success include sexual selection (now often included in natural selection) and fecundity selection.
Along with the theories of natural selection and sexual selection, fecundity selection is a fundamental component of the modern theory of Darwinian selection.

Patrick Matthew

appendicesMatthew
In the 3rd edition of 1861 Darwin acknowledged that others—like William Charles Wells in 1813, and Patrick Matthew in 1831—had proposed similar ideas, but had neither developed them nor presented them in notable scientific publications.
He published the basic concept of natural selection as a mechanism in evolutionary adaptation and speciation in 1831 (i.e. resulting from positive natural selection, in contrast to its already, widely known, negative role in removal of individuals in the Struggle for Survival), but failed to develop or publicise his ideas.

Mutation

mutationsgenetic mutationmutated
This occurs partly because random mutations arise in the genome of an individual organism, and offspring can inherit such mutations.
The abundance of some genetic changes within the gene pool can be reduced by natural selection, while other "more favorable" mutations may accumulate and result in adaptive changes.

Species

specificspecific namespecific epithet
The environment of a genome includes the molecular biology in the cell, other cells, other individuals, populations, species, as well as the abiotic environment.
Charles Darwin's 1859 book The Origin of Species explained how species could arise by natural selection.

Herbert Spencer

SpencerSpencerianSpencer, Herbert
However, some thinkers enthusiastically embraced natural selection; after reading Darwin, Herbert Spencer introduced the phrase survival of the fittest, which became a popular summary of the theory.
This term strongly suggests natural selection, yet as Spencer extended evolution into realms of sociology and ethics, he also made use of Lamarckism.

Struggle for existence

Struggle for SurvivalThe struggle for existence
The struggle for existence was later described by the Islamic writer Al-Jahiz in the 9th century.
For more technical information on how the struggle for existence is meshed with the theory of natural selection see the main article for natural selection.

Orthogenesis

orthogeneticprogressive evolutionevolutionary progress
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, a response that has been characterised as the single most significant impediment to the idea's acceptance.
Proponents of orthogenesis had rejected the theory of natural selection as the organizing mechanism in evolution for a rectilinear model of directed evolution.

The Genetical Theory of Natural Selection

Ronald Fisher developed the required mathematical language and wrote The Genetical Theory of Natural Selection (1930).
The Genetical Theory of Natural Selection is a book by Ronald Fisher which combines Mendelian genetics with Charles Darwin's theory of natural selection, with Fisher being the first to argue that "Mendelism therefore validates Darwinism" and stating with regard to mutations that "The vast majority of large mutations are deleterious; small mutations are both far more frequent and more likely to be useful", thus refuting orthogenesis.