History:
Whales are descended from land-dwelling mammals that ventured into the sea around 50 million years ago. Whales can be divided into two categories: Mysticetes (baleen whales) that use sieve-like structures in their mouth called baleen to filter tiny organisms from the water for food, and Odontocetes (toothed whales) that hunt other animals to catch in their toothed jaws. Both types of whale breathe through the top of their head via nostrils called blowholes. Myscticetes have two blowholes, whereas Odontocetes have one.
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