Final answer:
The rat population is not in Hardy-Weinberg equilibrium primarily due to genetic drift and mutation.
Step-by-step explanation:
The rat population is not in Hardy-Weinberg equilibrium primarily due to genetic drift. Genetic drift is the change in allele frequencies in a population due to chance events, such as random mating, bottleneck effect, or founder effect. In the case of the rat population, genetic drift is likely occurring, causing certain alleles to become more prevalent than others.
Additionally, mutation can also contribute to the deviation from Hardy-Weinberg equilibrium. Mutations are spontaneous changes in the DNA sequence of genes, which can introduce new alleles into a population. If a new allele becomes established and increases in frequency, it can disrupt the equilibrium.