it also assists scientists in classifying organisms based on similar characteristics of their anatomical structures. a common example of comparative anatomy is the similar bone structures in forelimbs of cats, whales, bats, and humans. all of these appendages consist of the same basic parts; yet, they serve completely different functions. the skeletal parts which form a structure used for swimming, such as a fin, would not be ideal to form a wing, which is better-suited for flight. one explanation for the forelimbs' similar composition is descent with modification. through random mutations and natural selection, each organism's anatomical structures gradually adapted to suit their respective habitats. the rules for development of "special" characteristics which differ significantly from general homology were listed by karl ernst von baer as the laws now named after him.