Which evolutionary mechanism does not change allele frequencies but changes genotype frequencies by increasing the proportion of homozygotes in the next generation?

The evolutionary mechanism that changes genotype frequencies without affecting allele frequencies, thus increasing homozygotes, is nonrandom mating. It disrupts the Hardy-Weinberg equilibrium by changing genotype frequencies due to preferential mating patterns.

Explanation:

The evolutionary mechanism that does not change allele frequencies, but instead changes genotype frequencies by increasing the proportion of homozygotes, is called nonrandom mating. This mechanism affects only genotype frequencies as it involves organisms choosing mates based on certain characteristics, leading to an increase in homozygous pairings. Meanwhile, the Hardy-Weinberg equilibrium is not maintained in this scenario as genotype frequencies shift away from the equilibrium expectations due to preferential mating patterns. It is essential to note that nonrandom mating itself does not cause evolution because the allele frequencies remain constant. However, it can lead to an increase in the frequency of certain genetic diseases if they are associated with the homozygous genotypes that are being selectively mated.