Week 9, Lecture 1, Microevolution

Week 9, Lecture 1, Microevolution - Evolution H-W is...

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1 Lajoie – MMMGN ‘09 Evolution Lajoie – MMMGN ‘09 H-W is disrupted by 1) Mutation 2) Migration 3) Mate selection 4) Genetic drift 5) Natural selection Lajoie – MMMGN ‘09 Disrupting H-W 1) Mutation • original source of all new alleles • rare – once every 10 6 to 10 8 DNA replications • usually harmful or neutral, rarely beneficial • slow if it is the only source of variation • allele is protected in the heterozygote - the rarer the allele, the more protected it is q = q 2 = q = q 2 = Lajoie – MMMGN ‘09 Disrupting H-W 2) Migration (gene flow) • genes/alleles exchanged between populations • loss or gain of alleles • not usually adaptive • keeps populations similar • counteracts natural selection Lajoie – MMMGN ‘09 Disrupting H-W 3) Mate selection (nonrandom mating) • changes genotype frequencies and allelic frequencies • assortative mating - like mates with like - promotes inbreeding -morehomozygotes • disassortative mating -rareinnature - more heterozygotes Lajoie – MMMGN ‘09 Disrupting H-W 4) Genetic Drift • chance loss of alleles • greater effect in small populations • rare alleles lost • not usually adaptive • Two effects of genetic drift i) Bottleneck effect ii) Founder effect
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2 Lajoie – MMMGN ‘09 Disrupting H-W i) Bottleneck effect • A population is drastically reduced • Who survives? It's pure chance • Which alleles survive? It's pure chance e.g. elephant seals in the 1890’s many thousands 20 30,000 but very little genetic variability Lajoie – MMMGN ‘09 Disrupting H-W ii) Founder effect • small colony starts in a new habitat • different allele frequency than parent group e.g. - Starlings in New York - Island populations
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This note was uploaded on 04/18/2010 for the course BIOLOGY 1223 taught by Professor Gardiner/lajoie during the Spring '09 term at UWO.

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Week 9, Lecture 1, Microevolution - Evolution H-W is...

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