Final answer:
Heritability is the fraction of phenotype variation that can be attributed to genetic differences, or genetic variance, among individuals in a population.
Step-by-step explanation:
Heritability is the fraction of phenotype variation that can be attributed to genetic differences, or genetic variance, among individuals in a population. The greater the heritability of a population's phenotypic variation, the more susceptible it is to the evolutionary forces that act on heritable variation.