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Whales are about 80 species of large, exclusively aquatic placental mammals, members of the order Cetacea, which also includes dolphins and porpoises. The term whale is ambiguous: it can refer to all cetaceans, just the largest ones, or only to members of particular families within the order Cetacea—which leads to difficulties, as the Killer Whale and the Pilot Whale[?] are members of the family Delphinidae[?] and technically dolphins. The cetaceans are divided into two suborders: Mysticeti, the baleen whales, and Odontoceti, the toothed whales[?].

Like all members of the order, whales evolved from land mammals which returned to the sea, probably in the Eocene, between 55 and 34 million years ago. The precise ancestry of whales is still obscure, as there is no commonly agreed succession, but they are thought to have evolved from a group of carnivorous artiodactyla (even-toed hoofed animals). In 2001, two important 47-million-year-old partial fossils, named Rodhocetus Balochistanensis and Artiocetus clavis[?], were discovered in Balochistan, Pakistan. These fossils represent intermediate forms between land-living ungulates and whales and are evidence that the whales' closest relatives on land might be hippos, which had been previously suggested by DNA studies.

Like all mammals, whales breathe air into lungs, are warm-blooded (to be precise, endothermic), breast-feed their young, and have some (very little) hair. Whales have two blowholes which they use for breathing. When breathing out after a dive, a "V" shaped spout can be seen from the right perspective. Whales have a four-chambered heart. Baleen, the sieve-like structures which baleen whales use to filter food out of the water, is made from keratin. Whales are broadly classed as predators, but their food ranges from microscopic plankton to very large fish. The male is called a bull; the female, a cow; and the young, a calf.

Especially noteworthy is the Blue Whale, the largest animal that has ever lived. It may be up to 30 meters long and weigh 150 tons.

Many species of whales were hunted nearly to extinction, for their meat, fat (used to make lamp oil), oil and ambergris (from Sperm Whales[?]), a perfume ingredient. International treaties now sharply restrict whaling. Canada, Iceland, Japan and Norway and other countries hunt not endangered whales, while small aboriginal groups in the United States and Pacific island nations hunt endangered whales on a small scale.

Order Cetacea

The hunting of whales is the subject of one of the classics of the English language literary canon, Herman Melville's Moby Dick.

References and external links:

  • Cetacea site: http://www.cetacea.org/
  • Greenpeace whale site: http://whales.greenpeace.org/
  • Kate Wong: "The Mammals that Conquered the Seas", Scientific American, Vol 286, No 5, May 2002
  • Probably the best introductory guide to cetaceans is the inexpensive but comprehensive Whales, Dolphins and Porpoises by Mark Carwardine, published by Dorling Kindersley, 2000. ISBN 0-7513-2781-6

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