Final answer:
Genetic drift causes a decrease in heterozygosity over time because of founder effects and bottlenecks.
Step-by-step explanation:
Genetic drift causes a decrease in heterozygosity over time because of D) Founder effects and bottlenecks.
Genetic drift is a random process that leads to changes in allele frequencies within a population. The bottleneck effect occurs when a large portion of a population is suddenly reduced, resulting in a loss of genetic variation. The founder effect occurs when a small group of individuals establishes a new population, leading to a reduction in genetic diversity.
For example, if a wildfire kills a large portion of a population, the surviving individuals will have different allele frequencies compared to the original population. This loss of genetic diversity can lead to a decrease in heterozygosity over time.