Migration reduces genetic differences between populations primarily by:

• A. Exchanging alleles between populations
• B. Increasing population size restriction
• C. Causing genetic drift to dominate
• D. Eliminating mutations

Answer: (A)

Movement of individuals between populations introduces alleles into new gene pools, a process called gene flow. When migrants carry their alleles into a population, those alleles change the recipient’s allele frequencies, and over time repeated migration makes the gene pools of different populations more similar. That mixing directly reduces genetic differences between populations.

The other options don’t describe this mixing of gene pools. Genetic drift randomizes allele frequencies and can actually increase differences between isolated populations. Eliminating mutations would reduce new variation but doesn’t actively erase existing differences. A term about increasing population size restriction isn’t about exchanging alleles between populations, so it doesn’t explain how migration lowers genetic differences.