Gene flow

-evens out genetic differences between populations
-increases genetic differences between populations
-happens when random events change the genotype of a population
-is the same as genetic drift

movement of alleles from one population to another, occurs when individuals leave one population, join another, and breed. usually has one outcome: equalizes gene frequencies between the source and recipient populations (homogenizes populations to be more alike). random w/ respect to fitness, but movement of alleles between populations always tends to reduce genetic differences between them. arrival or departure of alleles can increase of decrease average fitness, depending on the situation.