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My understanding is that the possible mechanisms of evolution are:

  • Environmental changes
  • Cultural/mating preferences
  • Population Immigration
  • Genetic Mutation

Am I missing anything? I've heard that population shifts within a existing populaces will effect evolution, but imagining the most simplicity scenario, it's hard to see why the would make a difference.

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It's not really clear what 'factors of evolution' you are referring to... there are many factors that play a role in evolution - availability of nutrients, availability of reproductive partners, space,... Could you clarify a bit what kind of factors you mean? –  Armatus May 22 '12 at 20:13
    
@Armatus: "availability of nutrients" would be an environmental change. I'm not sure about "availability of reproductive partners", though I believe that if the availability partners was stable, it would not be a factor, and I already stated in the question that it is unclear to me if "population shifts" beyond population immigration play any significant role. –  blunders May 22 '12 at 20:21
    
@Armatus: My list is based on this video, the "Five Fingers of Evolution" - though I've edited it's meaning to make more sense to me; for example, "Environmental changes" I believe are called adaption, which to me is less clear the saying the changes are a result of the environment changing. If it's still not clear what I mean, please attempt to be more description on were exactly things are clear, and unclear. Thanks! –  blunders May 22 '12 at 20:35
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I've changed the question title slightly from active to passive phrasing. The reason being is that not all of these directly affect changes in the gene pool (ie, environmental factors). Furthermore, evolution can be semantically argued to have differing definitions. –  leonardo May 23 '12 at 0:06
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The first version of the question was vastly superior. In the current form, it’s much too long, needlessly detailed, contains errors, and no longer is a question. I’d suggest reverting to something much closer to the original form. –  Konrad Rudolph May 23 '12 at 9:22
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up vote 9 down vote accepted

Evolution is defined as a change in the allele frequency of population through time. The Hardy-Weinberg model predicts that the allele frequency of a population will not change (i.e., evolution will not occur) if the following conditions are met:

  • no natural selection

  • no gene flow (immigration or emigration from the population)

  • no mutatation

  • no genetic drift (changes in allele frequency due to random events)

  • random mating (all gametes are equally likely to combine)

So we can conclude that if any of the above conditions are not met then there is a change in allele frequency and thus evolution, and thus that factor is the cause of evolution.

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+1 @DQdlM: Awesome! Knowing now that Hardy-Weinberg appears to be the source of the logic was a huge help, and you're answers was within my range of plain-English. Taking a step back from "bio-lingo", would it be correct to say that the "inputs" for natural selection are only mutation(s) and/or statistically significant changes in the way the organism interacts with the environment? Also, assuming mating was completely random, why would emigration affect evolution? Meaning it would appear that other conditional changes would be the source of the evolutionary change, not emigration. Thanks! –  blunders May 23 '12 at 1:39
    
@blunders natural selection requires heritable variation and a survival or reproductive advantage based on that variation. The ultimate source of all variation is mutation but note that the thing that evolves is a population, so you can change the allele frequency by having individuals enter or leave a population. This would be an evolutionary event unto itself but would also potentially add more heritable variation that natural selection could act upon. –  KennyPeanuts May 23 '12 at 10:57
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