All whales dolphins. And porpoises belong to an order or major scientific group called the Cetacea by scientists. They are all mammals (air-breathing animals which have hair in at least some stage of their development, maintain a constant body temperature, bear their young alive. And nurse them for a while) which have undergone extensive changes in body form (anatomy) and function (physiology) to cope _with a life spent entirely in the water. The breathing aperture(s), called a blowhole or blowholes. Has (have) migrated to the top of the head to facilitate breathing while swimming; the forward appendages have become flippers; the hind appendages have nearly disappeared, they remain only as small traces of bone deeply imbedded in the muscles. Propulsion is provided by fibrous, horizontally flattened tail flukes.

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