Evolution, allowed birds to survive in various climates
rDNA is using genetic cloning to form DNA molecules from different species. in this example you can make the hormone insulin by getting some of the components from one organism and getting the remainder from another organism. Specifically, Insulin has 2 amine chains, so you can get 1 amine chain from one organism, and the other from a different one. Then you can combine them and you'll get insulin.
Biologists call those groups DOMAINS
