Question

For some parents, their offspring have larger beak depths; for others it's smaller. How does the concept of variation of traits help to explain this?

Answer 1

beak depth is a complex (quantitative) trait

Step-by-step explanation:

Additive effects refer to the resulting effects of two or more genes acting together. Beak depth is a quantitative trait whose variation is determined by the additive effects of many genes acting together and the environment. In quantitative traits, variation is continuous and produces a range of phenotypes. In consequence, in this case, some offspring will have a larger average beak depth compared to their parents, whereas others will have a smaller average beak depth compared to their parents. It is due to the combination of alleles or 'additive effects' inherited from different parents, and the interaction between these genes and the environment. Heritability refers to the proportion of quantitative trait variation due to additive genetic factors: a higher heritability is due to the predominance of additive genetic effects and less influenced by environmental effects.