Final answer:
Assortative mating can have effects on the Hardy-Weinberg equilibrium, leading to deviations from expected frequencies of genotypes. Positive assortative mating increases the frequency of homozygotes, while negative assortative mating increases the frequency of heterozygotes.
Step-by-step explanation:
Assortative mating refers to individuals choosing mates that are phenotypically similar to themselves (option a). This can occur in two ways: positive assortative mating, where individuals mate with those who are similar to themselves, and negative assortative mating, where individuals mate with those who are dissimilar to themselves.
In terms of the Hardy-Weinberg equilibrium (HW), both types of assortative mating cause deviations from HW expectations. Positive assortative mating leads to an increase in homozygotes, while negative assortative mating leads to an increase in heterozygotes.