Final answer:
Narrow sense heritability includes additive genetic variance, which is the part of genetic variance that directly affects traits in an additive way, excluding dominance and environmental variances. The correct option is c).
Step-by-step explanation:
The genetic component of variance for narrow sense heritability includes c) Additive genetic variance. Narrow sense heritability is the proportion of phenotypic variance that can be attributed to additive genetic factors.
These factors include alleles that contribute to the trait in an additive manner, meaning that the effect of these alleles can be summed up to determine the overarching effect on the trait.
This contrasts with dominance variance, which involves interactions between alleles at the same locus, and environmental variance, which involves the influence of the surrounding environment on the expression of the trait.
Populations are influenced by genetic structure, their environment, and diet composition, all of which can contribute to phenotypic variation. However, only genetic differences, such as differences in alleles and genotypes, can be inherited and therefore affected by natural selection to alter genetic variance within a population.