Bio93 Lecture5

Bio93 Lecture5 - Bottleneck sudden decrease in population...

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Bio Lecture 5 1/14/09 Gene pool concept Hardy-Weinberg princple assuming random mating Patterns of natural selecton -Heterozygote advantage -directional selection Stabilizing Selection-Reduces amount of variation so it gets more common to one type (scrunch together) Disruptive Selection- extreme phenotypes are favored and increase fitness. Middle type isn’t good Genetic Drift- any change in allele frequency in a population due to chance (sampling error) Random with respect to fitness. Not adaptive. Small populations are very susceptible to genetic drift. It can occur by any event that involves sampling error.
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Unformatted text preview: Bottleneck- sudden decrease in population size (disease, nature, etc) Survivors then have smaller gene pool. Founder effect- if founding group is small the allele frequency differ from source populations (islands) Gene flow- movement of alleles from one population to another occurs when individuals leave a population, join another, and breed Mutation restores genetic diversity by introducing new alleles. ULTIMATE SOURCE OF ALL GENETIC INNOVATION.-random with respect to fitness-most mutation result in deleterious alleles-alleles that lower fitness, since its random...
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