Final answer:
Genetic drift is a random change in allele frequencies that occurs in small populations. Due to chance events, small populations are at a higher risk of losing all copies of an allele, causing a change in allele frequencies.
Step-by-step explanation:
Genetic drift is a random change in allele frequencies that occurs in a small population due to chance events. In small populations, the chance of the frequency of alleles going to 1 or 0 is higher because there is a greater likelihood of losing all copies of an allele. For example, if one individual in a population of ten individuals dies before reproducing, all of the genes associated with that individual's alleles will be lost, causing a change in the allele frequencies.