In northern elephant seals, body size is determined by at least 8 genes. males compete for territories on the beach and larger males are more likely to win fights. in this example, inheritance of body size is intrasexual selection on male body size is which results in in mean male body size in subsequent generations. pleiotropic / directional / increasesepistatic / disruptive / decreasespolyallelic/ stabilizing/ no changepolygenic / directional / increasespolygenic / disruptive / decreases

polygenic / directional / increases

Explanation:

A trait that is regulated by more than one gene is said to exhibit polygenic inheritance. Body size in northern elephant seals is regulated by at least 8 genes and therefore, an example of a polygenic trait. Directional selection is a type of natural selection that favors one extreme phenotype of the trait due to its survival and reproductive success.

In the given example, larger body size (an extreme phenotype) is favored since the males with larger body sizes are able to win the fights for territories. Here, average and small body sizes are not favored. Directional selection of larger body size would make the males with larger body size to leave more progeny. Over the generations, the population would consist of males with larger body sizes.