Genetic drift

Random sampling error

sampling error is reduced with increased sample size genetic drift is rapid in small populations Over time 1. an allele can become fixed (contrast: [[selection]] drives fixation directionally; drift is random) 2. an allele can become lost 3. the frequency of homozygotes will decline The probability that a specific allele will be the one to drift to fixation = that allele's initial frequency.

Founder effect small founding populations have different allele frequency from the parent population related: [[migration models]] — continent-island and isolation-by-distance models build on founder dynamics