THE OCEAN DEEP

Whales are marine mammals of order Cetacea which are neither dolphins – members, in other words, of the families Delphinidae or Platanistoidae – nor porpoises. They include the blue whale, the largest living animal. Orcas, colloquially referred to as "killer whales", and pilot whales have whale in their name but for the purpose of classification they are actually dolphins. For centuries whales have been hunted for meat and as a source of valuable raw materials. By the middle of the 20th century, large-scale industrial whaling had left many species seriously endangered. All cetaceans, including whales, dolphins and porpoises, are descendants of land-living mammals of the Artiodactyl order (even-toed ungulate animals). Both cetaceans and artiodactyl are now classified under the super-order Cetartiodactyla which includes both whales and hippopotamuses. In fact, whales are the closest living relatives of hippos; they evolved from a common ancestor at around 54 million years ago.[1][2] Whales entered the water roughly 50 million years ago.[3] Cetaceans are divided into two suborders:
• The baleen whales are characterized by baleen, a sieve-like structure in the upper jaw made of keratin, which they use to filter plankton from the water. They are the largest suborder of whale.
• The toothed whales have teeth and prey on fish, squid, or both. An outstanding ability of this group is to sense their surrounding environment through echolocation.
Whales are large, magnificent, intelligent, aquatic mammals. They breathe air through blowhole(s) into lungs (unlike fish who breathe using gills). Whales have sleek, streamlined bodies that move easily through the water. They are the only mammals, other than manatees (seacows), that live their entire lives in the water, and the only mammals that have adapted to life in the open oceans. Like all mammals:
• Whales breathe air into lungs,
• Whales have hair (although they have a lot less than land mammals, and have almost none as adults),
• Whales are warm-blooded (they maintain a high body temperature),
• Whales have mammary glands with which they nourish their young,
• Whales have a four-chambered heart.
The biggest whale is the blue whale, which grows to be about 94 feet (29 m) long - the height of a 9-story building. These enormous animals eat about 4 tons of tiny krill each day, obtained by filter feeding through baleen. Adult blue whales have no predators except man. The smallest whale is the dwarf sperm whale which as an adult is only 8.5 feet (2.6 m) long.