Use the mammalian and reptile ear and jawbones to describe an example of von baer's principles.

Von Baer's principle suggests some of the fundamental points associated with embryogenesis. That is, at the time of embryogenesis, the embryo evolves through the more usual characteristics of a phylum or group to the more unique characteristics of its own species. The majority of the unique parts are developed from the more usual form. The embryo of a given animal becomes distinguished rather than passing through the other forms. Eventually, the embryo of a higher category does not resemble any other, however, only its embryo.  

For example, mammalian ear bones are homologous to reptile jawbones. Homology is the prevalence of similar organ or feature in various species, which fulfills distinct activities. At the time of development, the mammals develop the two bones into ear bones and in reptiles, the same bones get develops into jawbones. This signifies that they share common ancestors, however, they get distinguished from each other at the time of evolution.