1. 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

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

3. 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

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