Once isolated, the groups become less and less alike via selection, but also via random events random mutation creates green phenotype Little or no interbreeding

‘Disasters’ also change a gene pool usually decrease the variation of a population Change to a population from random events is called genetic drift

Northern Elephant Seal large pop. again, but little variation 20 hunted population Northern Elephant Seal In a Caribbean hurricane, a few Green Iguanas are rafted from Guadeloupe to Anguilla, the founders of a new population Seals: of 24 genes studied no variation at all Green Iguana

Evolution includes gene flow between populations as well pollination spreads sperm from one population to another Migration introduces varations from formerly separate populations