Final answer:
Gene flow refers to the movement of alleles between populations due to the migration of individuals or gametes, introducing new genetic variation and potentially affecting allele frequencies. It's different from mutations, which are changes to DNA that can also introduce new traits to a population.
Step-by-step explanation:
Gene flow occurs when alleles are transformed from one population to another through the movement of individuals or gametes. It is a critical evolutionary mechanism that involves the introduction of new genetic variation into a population. For example, when animals migrate or plant pollen is carried to a new location, these can introduce new alleles to that population. If the rate of migration is significant, it can greatly affect allele frequencies, altering the genetic structure of both the population immigrants leave and the population they enter. Gene flow can also occur when human populations migrate and mix, as seen with the Founder Effect during human immigration.
Mutations, on the other hand, are changes to an organism's DNA and provide another way for new genetic characteristics to arise and subsequently influence evolution through genetic drift and natural selection.