I would like to know how genes control body plan. Such as shape and size. I think this is a big problem for conventional evolutionary theory.
You might be talking about convergent evolution, as opposed to divergent evolution.
Different species will converge on a shape.
One species of Lemurs, one species of marsupials, and cats have converged on the cat shape.
Birds(Penguins), mammals(seals, etc), and fish have converged on a fish shape
Sharks and dolphins have converged on a shape