Final answer:
Directional selection leads to greater genetic variance by favoring one extreme phenotype and changing allele frequencies over time. High heritability intensifies this effect. Populations with these factors will exhibit more change across generations.
Step-by-step explanation:
The student's question revolves around understanding how different evolutionary mechanisms, such as directional selection, heritability, genetic drift, gene flow, and natural selection, affect allele frequencies and, consequently, the phenotype distribution of populations. To determine which population would exhibit the most change due to directional selection and heritability, it's essential to elucidate how these factors interact.
Directional selection refers to when environmental pressures favor one extreme phenotype, thus shifting the phenotype distribution over time. It typically results in greater genetic variance in the population because it moves the allele frequencies steadily in one direction. Populations with high heritability for the selected trait will respond more to this selection and thus change more across generations.
Genetic drift is a change in allele frequencies due to random events, primarily affecting smaller populations. Gene flow is the transfer of alleles into or out of the population due to migration of individuals or gametes. Natural selection is the process by which organisms better adapted to their environment tend to survive and produce more offspring, thus changing allele frequencies over time.