There are about 80 species of whale and these are divided into two main groups, based on their method of feeding:
Toothed whales: have sharp teeth lining their mouth with which they catch and eat other marine mammals and fish. Whales belonging to this group include the sperm whale, killer whales (orca).
Baleen whales: have a mouth lined with rows of keratin plates which act like a sieve, straining the sea water to extract the tiny sea creatures known as krill. This group includes the blue whale, the humpback whale and the minke whale.