Evolution: Difference between revisions

Revision as of 02:50, 26 February 2004

Revision as of 13:06, 26 February 2004

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''Main articles:'' [[Microevolution]], [[Macroevolution]]

[[Microevolution]] refers to small-scale changes in gene-frequencies in a population over a few generations ([[population genetics]] is the branch of biology that provides the mathematical structure for the study of the process of microevolution). These changes may be due to a number of processes: [[mutation]], [[gene flow]], [[genetic drift]], as well as [[natural selection]]. [[Macroevolution]] refers to large-scale changes in gene-frequencies in a population over a long period of time (and may culminate in the evolution of new [[species]]). The difference between the two is hard to distinguish because, over time, successive tiny mutations like those evidenced in microevolution could build up in isolated populations and eventually create entirely new species, which is known as macroevolution. While microevolution has been demostrated in the laboratory to the satisfaction of most observers, macroevolution has to be inferred from the [[fossil record]], and its precise mechanisms are an active topic of discussion amongst scientists.

===Differential survival of traits===

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====Natural selection====

''Main article:'' [[Natural selection]]

Darwinism, and its descendant theories, state that biological evolution results through [[natural selection]]. Since natural selection is so important to Darwinism and modern theories of evolution, a very short summary of its main points follows:

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====Genetic drift====

''Main article:'' [[Genetic drift]]

Genetic drift describes changes in gene frequency that cannot be ascribed to selective pressures, but are due instead to events that are unrelated to inherited traits. This is especially important in

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==Creationism and evolution==

''Main article:'' [[Creationism]]

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===Status of evolution as a theory===

''Main article:'' [[Theory of evolution]]

When talking about ''biological evolution'', there is often a confusion the question of whether or not modern organisms have evolved (and are continuing to change) from older ancestral organisms and there are questions about the mechanism of the observed changes.

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===Symbiogenesis===

''Main article:'' [[Symbiogenesis]]

Another extension to the standard modern synthesis, advocated by [[Lynn Margulis]], is [[symbiogenesis]]. Symbiogenesis argues that acquisition and accumulation of random [[mutation]]s or [[genetic drift]] are not sufficient to explain how new inherited variations occur in [[evolution]]. This theory states that species arise from the merger of independent organisms through [[symbiosis]]. Symbiogenesis emphasizes the impact of [[cooperation]] rather than Darwinian competition. This commonly occurs in [[multigenomic organism]]s throughout nature.

Another extension to the standard modern synthesis, advocated by [[Lynn Margulis]], is [[symbiogenesis]]. Symbiogenesis argues that acquisition and accumulation of random [[mutation]]s or [[genetic drift]] are not sufficient to explain how new inherited variations occur in [[evolution]]. This theory states that species arise from the merger of independent organisms through [[symbiosis]]. Symbiogenesis emphasizes the impact of [[cooperation]] rather than Darwinian competition. This commonly occurs in [[multigenomic organism]]s throughout nature.

===Neo-structuralist themes in evolutionary theory===