Natural selection changes allele frequencies because some survive and reproduce more successfully than others.

One gene can influence trait(s). one trait can be determined by gene(s).

What function does the limb sever in each animal? how are the limb bones of the four animals similar? based on these similarities what can be inferred about the evolution of the four animals.

When listening the levels of orginization in orginisims from the smallest to most complex , which level is just below organs in complexity