A variation is a reference to the differences or deviations, such as the structure and form, as for crossing over is the exchange of genetic material between the non-sister chromatids of the homologous chromosomes during meiosis.
I have a question are you asking what are the molecules of a shark or something
Cementation, Hope this helped.
Since an animal only becomes more complex, and not simpler, an ancestor to all organisms would have to be the most simple and primitive organism.
