Final answer:
The response to selection is calculated by multiplying heritability by the selection differential, not relative fitness or selection gradient; therefore, the correct answer is C. heritability; selection differential, which integrates concepts of heritability and natural selection in population genetics.
Step-by-step explanation:
The response to selection can be calculated as the product of heritability; that is, the fraction of phenotype variation due to genetic differences, and the selection differential; which is the difference between the mean phenotype of selected individuals and the mean phenotype of the general population. Thus, the correct answer is C. heritability; selection differential. This fundamental concept in population genetics helps to understand how selective forces change allele frequencies in a population over time, leading to evolutionary change through natural selection.
Understanding the role of heritability in natural selection is important as it determines how much phenotypic variation can be passed on to the next generation. Consequently, the higher the heritability of a trait, the more likely it is that the trait will be subject to evolutionary changes based on environmental pressures and relative fitness.