What term describes the process of a population's genetic makeup changing over time?

The term that describes how a population's genetic makeup changes over time is evolution. Evolution is the result of genetic variation within a population, which is then subject to natural selection, genetic drift, mutation, and migration. Population genetics is the field of biology that studies the genetic makeup of populations and how it changes over time. Therefore, evolution is the correct answer as it explains the changes that occur within a population's genetic makeup over time.