Whales, as mammals, are vertebrates and have internal skeletons composed of bone. Whales live in all oceans and seas with the exception of the Caspian and Aral seas.The first whales are believed to have appeared approximately 50 million years ago, based on fossil records.
Whales are divided into two suborders: baleen whales and toothed whales. Baleen whales use keratinous plates, called baleen, that are housed within the mouth to filter food from the water. On the other hand, Toothed whales have teeth and feature more predatory behavior as they prey on animals such as fish, cephalopods and even other whales. A thick layer of tissue under the skin protects whales from hypothermia in colder waters, while sophisticated thermoregulation mechanisms prevent whales from overheating.