Bio3400 1nd Edition Lecture 9 Outline of Current Lecture I Selection II Mutation III Gene flow IV Genetic drif V The Founder Effect VI The Bottleneck Effect Current Lecture I II Unit 3 Mechanisms of Evolution Hardy Weinberg Equilibrium a Allele and genotype frequencies will not change over time if no outside forces are acting on the population b 5 assumptions i No selection ii No mutation iii No migration iv Infinite population size v Random mating c H W is a null model default condition when no outside forces are acting on a population d Defining the exact conditions when we expect no change tells us what factors can cause change e Evolution is the natural state for populations f Selection is a major mechanism of evolution g Mutation is a weak mechanism of evolution i Even very high mutation rates do not produce substantial change ii Mutation alone changes allele frequencies very slowly h Gene flow can change allele frequencies in populations i Gene flow results from migration of individuals between populations of the same species ii Gene flow tends to homogenize populations i Genetic drif is a major mechanism of evolution i Genetic drif is the change of allele frequencies due to chance These notes represent a detailed interpretation of the professor s lecture GradeBuddy is best used as a supplement to your own notes not as a substitute 1 Sampling error inherent in the transmission of gametes by individuals in a finite population 2 The Founder Effect a Allele frequencies in founding populations will be different from source populations due to chance sampling error b Older Order Amish of Pennsylvania i Descended from 200 German immigrants ii Marry within their own community closed off form gene flow iii Ellis van Creveld Syndrome 1 Samuel King and his wife carried the allele for the syndrome 2 Causes dwarfism polydactyly dental abnormalities sometimes heart defect 3 World frequency 1 in 20 60 thousand 4 Pennsylvania Amish 5 in 1 000 c The Bottleneck Effect i Northern elephant seal populations were reduced to about 20 individuals in the 1890s ii Now back to 30 000 iii Northern populations still have reduced genetic variation compared to Southern populations
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