A researcher tracks the escape behavior of a population of squirrels on campus across two generations. When she plots the escape behavior of the offspring generation against the parental behavior, she notes that the offspring's behavior exactly matches the parental behavior. Nonetheless, the narrow-sense heritability equals zero. How can the heritability equal zero in this example?
A) The additive genetic variance equals one.
B) All the escape behavior alleles are fixed in the population.
C) Phenotypes vary widely between generations.
D) Escape behavior is controlled by a rare recessive allele.

Question

Quizplus · Accepted Answer

Heritability measures the proportion of variation in a trait that is due to genetic factors. If all the individuals in the population have the same genotype (i.e., fixed alleles), there is no genetic variation, and therefore, the heritability is zero. Therefore, even though the offspring's behavior matches the parental behavior, if there is no genetic variation, the heritability will still be zero.

A Researcher Tracks the Escape Behavior of a Population of Squirrels