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Evolution Notes

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Biology 3466B
Yolanda Morbey

Evolution NotesOct 2011 Migration is the movement of alleles between populations and is the same thing as gene flow The oneisland model is when genes are moving from a large population to a small population from a continent to an island Alleles arriving on the island from the continent represent a large fraction of the island gene pool Migration occurs between the juvenile and adult stages before the individuals have reached maturity The final allele frequencies of the gene pool are different from the initial allele frequencies Evolution occurs in one generation Genotype frequencies are also inconsistent with HWE If there is random mating and no migration in the second generation however HWE for genotype frequencies will be restored Genetic drift is due to sampling error small gene pool Genetic drift depends on population size The bigger the population size the more likely the allele frequencies are going to match HWE expectations Due to random sampling of small populations allele frequencies differ a lot from HWE expectations Genetic drift has bigger effects in small populations Founder effect is when populations are small because a group of individuals has just moved to a new location The allele frequencies in the new population will by chance be different than what they were in the source population The founder effect is a direct result of sampling error There is a decline in allelic diversity due to sampling error each time and therefore a decline in genetic diversity due to genetic drift If founding events are sequential these small declines in diversity add up Genetic drift happens in populations of all sizes but is more important in small populations If genetic drift is the only evolutionary mechanism at work in a population then sampling error causes allele frequencies to wander between 0
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