There are different species of whales ranging from size to color- blue, white, gray, humpbacked, bottle-nosed, pilot whales and many others. All these whales are classified into two main groups- the toothed and baleen whales. Baleen is a fibrous material just like the finger nail that works as a strainer separating small bits of food from the water. They can grow up to even 95 feet long.
Whales are said to have blowholes instead of gills. Though they do not look like a typical mammal, they are indeed one. Instead of forelegs, they have flippers. Hind legs remain as vestiges inside the body. Hair lingers as bristles rather than heat-retaining fur; insulation is supplied by blubber.
Plenty of small plants and animals are food for even the largest of whales. A relative of shrimp called krill make their favorite food. In one single day, a whale can strain out a ton of food. Whales dive deep to hunt for food and can stay underwater for more than an hour. They must however come to the surface of water for air.
The biggest whale that has ever lived is the 100-foot blue whale. This mighty creature feeds on the smallest marine life that it traps on the curtain or baleen or whalebone that hangs from the roof of its mouth.
The killer whales are also called orcas grow only to about 30 feet long. They are known to be the fastest of all whales. They attack much bigger whales without any fear. More often their prey is smaller. They eat everything from other whales to fish, squid, seals, dolphins and porpoises.