Lecture 6 1) Causes of micro evolution, causes allele frequencies to change. Each cause is a departure from one of the assumptions of a H-W equilibrium. Genetic Drift and Natural Selection are the most important. a) Genetic Drift – Random changes in the gene pool of a small population due to chance alone (ex. A tornado). Stochastic (random) events have a much greater effect on small populations. i) Bottleneck – Extreme case, dramatic reduction on population size. ii) Founder effect – A bottleneck that happens during the colonization of a new habitat. b) Gene Flow – Migration of fertile individuals or the transfer of gametes, between populations. Gene flow causes populations to become more similar to each other. c) Mutation – The probability of mutation at any particular locus is small. Often referred to as a weak evolutionary force in terms of allele change from one generation to the next. But evolution cannot occur without mutation.
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