Final answer:
Animals that select mates similar to themselves will have more homozygotes compared with Hardy-Weinberg predictions. When heterozygote advantage occurs, the value of 2pq representing heterozygotes increases as these individuals are favored by selection. Natural selection directly influences phenotype, causing different selection patterns.
Step-by-step explanation:
Animals that select mates that are phenotypically similar will have more homozygotes when compared with Hardy-Weinberg predictions. This mating pattern, known as assortative mating, leads to an increase in the frequency of homozygous individuals for particular traits because there is a preference for mating with individuals that possess similar phenotypic traits. This can result in a deviation from the genotype frequencies expected under the Hardy-Weinberg equilibrium, which assumes random mating.
When a population is undergoing heterozygote advantage, where individuals with two different alleles (heterozygotes) are more fit than those with two copies of the same allele (homozygotes), the value of 2pq, which represents the frequency of the heterozygous genotype in the population, is likely to increase. This is because natural selection favors the enhanced survival and reproductive success of these heterozygotes.
Natural selection acts on the phenotype and can lead to various selection patterns. Stabilizing selection favors the average phenotype, decreasing genetic variance and potentially leading to fewer individuals with extreme phenotypes. Similarly, directional selection can favor one extreme phenotype, potentially altering the frequency balance between dominant and recessive alleles.