Brey-Lecture 3 - The source of all new alleles is Mutation...

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The source of all new alleles is Mutation Natural selection o Stabilizing – averages selected for extremes are selected against o Directional – one of the extremes is selected against while other is selected for o Disruptive – averages selected against – two different species The proportion of alleles in a population does not change if there is (random mating) Variation is the raw material for evolution What is nearly powerless by itself to change populations, but immensely powerful when combined with natural selection: mutation 2 kinds of genetic drift and examples Founder effect – startlings in N.A. Genetic bottleneck –northern elephant seal Sexual Selection Tug of war between the sexes Each one wants to pass genes down to next generation Darwin – perplexed o Peacock Male elaborate plumage why? Seemingly draw predators More concerned with attracting female and passing genes down than survival o Not natural selection, Sexual Selection o Powerful form of natural selection that occurs all the time Differential investment in reproduction – females generally make greater investment o Sperm is made all the time o Eggs are made once o Male mates once makes 40, twice 60, etc o No benefit to mate more than once Female is choosy – wants to mate with most fit male
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