They are the Right whales, the Gray whale and the Rorquals. Rorquals are identified by their throat-grooves or pleats, which allow their throats to expand and gulp huge amounts of water. A few examples of Rorquals are Blue, Fin, Humpback and Minke whales. Toothed whales have a single blowhole. Their main food is fish and squid.
Dolphins are also small toothed whales.
Whales are able to grow to such enormous sizes because their weight is supported by the water. Unlike land Mammals whose bones are hard and strong, the bones of whales are soft and porous, and are also used to help store food reserves in the form of oil. Underwater, whales do not have good vision. They have very good hearing, and use a system known as Echo location which utilizes a series of sounds and echoes to help them find their way and their food. Because whales travel in cold, icy waters, and can dive great depths, they need to keep warm.