What term describes the process by which genes are exchanged between populations?

The process described in the question is best characterized by the term gene flow. Gene flow refers to the movement of genes between populations through mechanisms such as migration or reproduction. When individuals from one population mate with those from another, they introduce new alleles into the gene pool, which can increase genetic diversity and potentially change the evolutionary trajectory of both populations involved.

Natural selection, in contrast, is about the differential survival and reproduction of individuals due to variations in phenotype, which influences how certain traits become more or less common over generations. Genetic drift focuses on the random changes in allele frequencies within a population, particularly in small groups, and does not involve the exchange of genes between different populations. Adaptation refers to the process by which a species becomes better suited to its environment through evolutionary changes but does not directly involve the movement of genes between populations.