Final answer:
Gene flow refers to the migration of new individuals and alleles into a population, affecting its allele frequencies. Genetic drift, however, is a random change in allele frequencies due to chance events in small populations. Both processes lead to changes in a population's genetic structure.
Step-by-step explanation:
The random change defined by the migration of new individuals and alleles into a population is known as gene flow. This process can significantly affect allele frequencies within a population by introducing new genetic variations. An example of gene flow is when several white rabbits migrate into a population of mostly brown rabbits, which leads to an increase in the allele for white fur.
Alternatively, the random change in allele frequencies that occurs especially in small populations is called genetic drift. Genetic drift is influenced by chance events that can lead to significant variations in a population's allele and genotype frequencies, which may occur due to chance occurrences affecting reproduction, mortality, and mating success. Notable concepts associated with genetic drift include the founder effect and bottle-neck events, which cause rapid changes in a population's genetic structure without conferring any selective advantage.