Careful Jack...
There is no "calling upon" as if in response to a need. Evolution is entirely dependent upon random, yes random, mutation. Natural selection is the powerful, but unconscious, filter that lets some mutants live to reproduce and dooms others to die. Cetaceans got their flippers from ancestral paws because some terrestrial ancestor was a mutant who had a bit of extra skin between the toes. Not a big advantage, but over millions of years, the tiny things add up. The phrase "genomic plan" makes me nervous I suppose. There is no plan. Some accidents work. Most do not.