Answer:
they developed some structures or parts to survive
the terrestrial environment
All DNA is remarkably similar, but some more than others. Humans' DNA would be closer to other mammals' than it is to, say, a bird. Using DNA shows how varied an animal really is from another. Specific parts of the DNA code for different things, so you might see a similar structure for wings and flippers.
hmmm....i don't even know the answer to your question.