Different Kinds of Whales
The world's 70 species of whales are mainly divided into two groups deriving from their food and eating habits, and consequently, their anatomy.
Baleen Whale Species - Mysticeti
The first group is Baleen Whales - named after the massive baleen that they have in their mouths. It helps them to filter their food. They are passive hunters that simply open their mouth and wait for the food to swim into their mouth. Because a lot of water also enters their mouth, they push the water out again, and the baleen helps them to stop their food getting out with the water. Baleen whales are typically very large animals, much larger than the next group below. Blue whale - the largest animal that has ever lived on the Earth, belongs to baleen whales. Others include Right Whales, Gray Whales, and Humpback Whales.
Toothed Whale Species - Odontoceti
Toothed Whales in contrast are active hunters and meat eaters. They get their food by chasing and catching fish, and in case of some, larger animals, other marine mammals even of the size of seals and sea lions. Being active hunters, they need to move fast and their bodies are therefore much smaller than the filter feeders' above.
The whales in this group are commonly known as dolphins, even though some of them, such as killer whales, still bear the common name "whale". Different groups of toothed whales include oceanic dolphins, river dolphins and porpoises.