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Ch 23 - The Evolution of Populations (1 slide per page)-1

causing random loss of individuals alleles shifting

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Unformatted text preview: lation Bottleneck can cause genetic drift Severe reduction in population size (disaster, disease, hunting, etc.) causing random loss of individuals & alleles & shifting allele frequencies • Survival not improved by any particular genetic advantage • Bad alleles just as likely to survive as good alleles 29 29 Population Bottlenecks Read prairie chicken example in your text Figure 23.11 (Campbell 9th ed) 30 30 Gene Flow can alter allele frequencies Movement of alleles btwn populations via migration of individuals btwn those populations • Can ↑ frequency of alleles already in the population • Can increase genetic diversity by introducing a novel allele from another population 31 31 Does sexual reproduction change allele frequencies? 32 32 Mutation could alter allele frequencies Before: 100% green After: 67% green, 33% brown 33 33 Out of all of the evolutionary mechanisms ONLY natural selection… always increases advantageous allele frequencies and decreases disadvantageous allele frequencies • Genetic drift • Gene flow • Mutation ? ?...
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