Outline20- What causes evolution

Outline20- What causes evolution - BSCI 106 Dr Sara Via...

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BSCI 106 Outline 20 Fall 2008 p. 1 Dr. Sara Via What causes evolution? Violation of Hardy_weinberg without evolution Non-random mating - a. assortative mating -- genotypes mate preferentially with particular genotypes effects depend on particular situation. b. selfing - mating to self (common in plants, snails) c. inbreeding - mating to same/similar genotype With selfing, Population becomes more and more dominated by homozygotes Changes genotype frequencies, but not gene frequencies! Evolution without selection Mutation Migration Random genetic drift But, only natural selection can produce adaptive evolution! Mutation - usually a small effect in one generation because mutation is rare Ex: In a population of 500, gene frequencies are p = q = 0.5 (1000 alleles, 500 A, 500 a) One copy of a mutates to a*--initial frequency is 0.001 Now there are 3 alleles (p + q + q* = 1) p = 0.5, q = 0.499, q* = 0.001 This is a small change in gene frequencies! Migration - if incoming migrants come from population with different gene frequency - if outgoing migrants are not a random sample of the population, Genetic Drift - Genetic Bottleneck
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