Biology 30 – Populations Practice Test

Gene flow is the movement of alleles between populations, brought by migrating individuals or dispersal of gametes. When new alleles enter a population, genetic variation within that population increases because there are more alleles for natural selection to act on. At the same time, gene flow tends to make populations more genetically similar to each other, reducing differences in allele frequencies between populations. This combination—increasing variation within populations and decreasing differences among populations—can influence adaptation by supplying new genetic material for selection and spreading advantageous alleles across populations. It can also limit local adaptation if migrants carry alleles that aren’t well suited to a particular environment. The other statements misstate the effects: gene flow does not typically reduce variation within a population; it can increase it. It does not only affect population size; it directly affects genetic variation. And it does not generally increase differences between populations; it tends to lessen those differences.