Duh. It's algebra. Didn't you know that?!
3:1.<span> The physical appearance of the </span>offspring<span> will be 3 </span>organisms<span> that look like the </span>parents<span>: 1 individual that differs in appearance.</span>
I believe the answer is comparative anatomy. It is the study of the similarities and differences in the structures of different species. Similar body parts may be homologies or analogies, such that both provide evidence of evolution. Similarities in embryos are evidence of common ancestry. For example all vertebrates embryos have gill slits and tails.