Ch08
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Why isn’t selection eliminating such detrimental allele?
Because of random effects due to small population size
What is the effect of using a small sample size instead of a large one in population experiment?
realized frequencies are not always close to the expected frequencies
List the assumptions of the Wright-Fisher model
• No natural selection • Random mating • No mutation • No migration • small population size
Define genetic drift
the process of random fluctuations in allele frequencies due to sampling effects in a finite population
Is sampling error larger in small or large samples?
Small. The effect of genetic drift is stronger in small populations
List the consequences of random genetic drift
1) allele frequencies fluctuate over time, even in absence of selection 2) Some alleles may be fixed & others lost, & heterozygotes frequency usually decreases (reduce genetic variation & heterozygotes) 3) Separate populations diverge in allele frequencies, that is: they vary independently
Genetic diversity was positively correlated with island size. T or F?
True. • Larger island => larger population => higher genetic diversity • Smaller island => smaller population => lower genetic diversity
Define population bottleneck
A brief period when population size is reduced. Can result in loss of alleles
Define Founder effect
Sampling effect that occurs when a small number of individuals migrate & start a new population. Small probability that allele frequencies will be equal in mainland & island
Give one example of population bottleneck & founder effect
• strong bottleneck reduced heterozygosity in northern elephant seals • Glaciers disappeared from Hudson Bay