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[[Image:Evolution2.jpg|left]]
[[Image:Darwin_tree_4.jpg|left]"Darwin's Tree of Life: the first-known sketch by Charles Darwin of an evolutionary tree describing the relationships among groups of organisms."]
In [[biology]], '''evolution''' is the change in the [[heritability|inherited]] [[trait (biology)|traits]] of a [[population]] from generation to generation. These traits are the [[gene expression|expression]] of [[gene]]s that are copied and passed on to offspring during [[biological reproduction|reproduction]]. [[Mutation]]s in these genes can produce new or altered traits, resulting in heritable differences ([[genetic variation]]) between organisms. New traits can also come from transfer of genes between populations, as in [[migration]], or between species, in [[horizontal gene transfer]]. Evolution occurs when these heritable differences become more common or rare in a population, either non-randomly through [[natural selection]] or randomly through [[genetic drift]].
In [[biology]], '''evolution''' is the change in the [[heritability|inherited]] [[trait (biology)|traits]] of a [[population]] from generation to generation. These traits are the [[gene expression|expression]] of [[gene]]s that are copied and passed on to offspring during [[biological reproduction|reproduction]]. [[Mutation]]s in these genes can produce new or altered traits, resulting in heritable differences ([[genetic variation]]) between organisms. New traits can also come from transfer of genes between populations, as in [[migration]], or between species, in [[horizontal gene transfer]]. Evolution occurs when these heritable differences become more common or rare in a population, either non-randomly through [[natural selection]] or randomly through [[genetic drift]].
One definition of a [[species]] is a group of organisms that can reproduce with one another and produce fertile offspring. However, when a species is separated into populations that are [[reproductive isolation|prevented from interbreeding]], mutations, genetic drift, and the selection of novel traits cause the accumulation of differences over generations and the emergence of [[speciation|new species]]. Stephen Gould, The Structure of Evolutionary Theory, Belknap Press, ISBN 0-674-00613-5 . The similarities between organisms suggest that all known species are [[common descent|descended from a common ancestor]] (or ancestral gene pool) through this process of gradual divergence. {Douglas J. Futuyma, Evolution, Sinauer Associates, Sunderland, Massachusetts, ISBN 0-87893-187-2 )
One definition of a [[species]] is a group of organisms that can reproduce with one another and produce fertile offspring. However, when a species is separated into populations that are [[reproductive isolation|prevented from interbreeding]], mutations, genetic drift, and the selection of novel traits cause the accumulation of differences over generations and the emergence of [[speciation|new species]]. Stephen Gould, The Structure of Evolutionary Theory, Belknap Press, ISBN 0-674-00613-5 . The similarities between organisms suggest that all known species are [[common descent|descended from a common ancestor]] (or ancestral gene pool) through this process of gradual divergence. {Douglas J. Futuyma, Evolution, Sinauer Associates, Sunderland, Massachusetts, ISBN 0-87893-187-2 )
The [[Theory#Science|theory]] of evolution by natural selection was first proposed by [[Charles Darwin]] and [[Alfred Russel Wallace]] and set out in detail in Darwin's 1859 book ''[[The Origin of Species|On the Origin of Species]]''. On the Origin of Species [http://darwin-online.org.uk/content/frameset?itemID=F373&viewtype=text&pageseq=16]. Related earlier ideas were acknowledged in http://darwin-online.org.uk/content/frameset?itemID=F381&viewtype=text&pageseq=20] In the 1930s, Darwinian natural selection was combined with [[Gregor Mendel|Mendelian]] [[Mendelian inheritance|inheritance]] to form the [[modern evolutionary synthesis]], "understanding evolution" in which the connection between the ''units'' of evolution ([[gene]]s) and the ''mechanism'' of evolution (natural selection) was made. This powerful explanatory and [[predictive power|predictive]] theory has become the central organizing principle of modern biology, providing a unifying explanation for the [[biodiversity|diversity of life]] on Earth. [http://www.interacademies.net/Object.File/Master/6/150/Evolution%20statement.pdf] Statement on the Teaching of Evolution, The Interacademy Panel on International Issues, [http://www.aaas.org/news/releases/2006/pdf/0219boardstatement.pdf] Statement on the Teaching of Evolution, American Association for the Advancement of Science.
The [[Theory#Science|theory]] of evolution by natural selection was first proposed by [[Charles Darwin]] and [[Alfred Russel Wallace]] and set out in detail in Darwin's 1859 book ''[[The Origin of Species|On the Origin of Species]]''. On the Origin of Species [http://darwin-online.org.uk/content/frameset?itemID=F373&viewtype=text&pageseq=16]. Related earlier ideas were acknowledged in http://darwin-online.org.uk/content/frameset?itemID=F381&viewtype=text&pageseq=20] In the 1930s, Darwinian natural selection was combined with [[Gregor Mendel|Mendelian]] [[Mendelian inheritance|inheritance]] to form the [[modern evolutionary synthesis]], "understanding evolution" in which the connection between the ''units'' of evolution ([[gene]]s) and the ''mechanism'' of evolution (natural selection) was made. This powerful explanatory and [[predictive power|predictive]] theory has become the central organizing principle of modern biology, providing a unifying explanation for the [[biodiversity|diversity of life]] on Earth. [http://www.interacademies.net/Object.File/Master/6/150/Evolution%20statement.pdf] Statement on the Teaching of Evolution, The Interacademy Panel on International Issues, [http://www.aaas.org/news/releases/2006/pdf/0219boardstatement.pdf] Statement on the Teaching of Evolution, American Association for the Advancement of Science.
==Heredity==
==Heredity==