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 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 zero.

b) All the escape behavior alleles are fixed in the population.

Explanation:

The relationship between additive genetic variance and total phenotypic variance is called narrow-sense heritability. In the exercise there is no genetic variation and also the behavior of the offspring is equal to the behavior of the parents, the additive genetic variance is equal to zero, due to the constant escape behavior, which produces alleles in the population. No phenotypic variance is specified in the exercise.

1. All the escape behavior alleles are fixed in the population.

2. The additive genetic variance equals zero.

Explanation:

According to above scenario, The parental and offspring's escape behavior is constant or same behavior. It means, there behavior of offspring is equal to parent behavior and no genetic variation due to which additive genetic variance is equal to zero. Narrow sense heritability is used to determine the relationship between additive genetic variance with total phenotypic variance.

Narrow-sense heritability = total additive genetic variation / the total phenotypic variation.