This is a mutation.

This is an episode of sampling error when a new colony is founded from an established population.

Inbreeding does this to the frequency of heterozygotes in a population, even after one generation.

This is the new frequency of p and q in population 2 after one migratory event of individuals from population 1.

(assume 10% of the individuals in pop 2 will be immigrants after the migratory event)

Population 1: p=0.5   q=0.5

Population 2: p=0.1   q=0.9

This is a selection differential.