Final answer:
Genetic diversity in a population can be decreased through factors like small population size, inbreeding, and chance events like natural disasters.
Step-by-step explanation:
Genetic diversity in a population can be decreased through various factors. One way is through a small initial population size, which limits the number of different alleles present. Another factor is inbreeding, where closely related individuals mate and bring together deleterious mutations that can cause harmful phenotypic effects. Additionally, chance events like natural disasters can also cause genetic drift by eliminating certain alleles from the population.