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简介：
whale is the common name for various marine mammals of the order Cetacea. The term whale sometimes refers to all cetaceans, but more often it excludes dolphins and porpoises, which belong to suborder Odontoceti (toothed whales). This suborder also includes the sperm whale, killer whale, pilot whale, and beluga whale. The other Cetacean suborder Mysticeti (baleen whales), are filter feeders that eat small organisms caught by straining seawater through a comblike structure found in the mouth called baleen. This suborder includes the blue whale, the humpback whale, the bowhead whale and the minke whale. All Cetacea have forelimbs modified as fins, a tail with horizontal flukes, and nasal openings (blowholes) on top of the head.
种类：
Blue Whales
Blue whale is the type of whale more familiar to a lot of people since it often represents the largest mammal in the whole world. It can grow as long as 108 feet and can reach a weight of more than 172 metric tons. A blue whale has elongated and lean body. The dorsal area's color varies in shades of bluish grey and lighter shade underside the body.
Orca Whales
An orca whale is more known as the killer whale. It is a very violent type of whale but does not establish threat to humans. An orca whale that reaches adulthood can grow as long as 105 feet and can reach a weight of almost 200 metric tons. An orca whale has a black back and white sides and chest. Its eyes have white patches behind and above. A baby whale has a yellowish color in its skin. This fades away later on and becomes white as the whale matures. This type of whale is the largest of the dolphin family.
Humpback Whales
Humpback whale or the Baleen whale that reaches adulthood can grow as long as 50 feet and can reach a weight of 36,000 kilograms. Its significant features are the unique body shape, elongated pectoral fins, and a knobby head. A humpback whale loves to show off its acrobatic talents such as slapping and rupturing the water.
Beluga Whale
A beluga whale or the white whale that reaches adulthood can grow as long as 15 feet and can reach a weight of up to 1600 kilograms for male and up to 1200 for females. A newly born beluga whale has a brown or gray colored skin. This color fades and becomes whitish grey or white as the whale matures. This type of whale has a fatty and oily bump on the forehead's center.
Fin Whale
A fin whale or the finback whale that reaches adulthood can grow as long as 88 feet and can reach a weight of 70000 kilograms. Thus, letting it grab the second spot as the largest whale in the world. Its features are the brownish grey color of its top skin and a whitish color underneath, a pointed snout, a pair of blowholes, and a broad and flat rostrum. Fin whales are already endangered species.
Gray Whale
A gray whale is often called the Devil Fish because it fights really hard when hunted. An adult whale can grow as long as 52 feet and can reach a weight of 36 tons. Its significant feature is the dark slated grays color of the skin and gray and white patches spread all over the whale's body.
Sperm whale
A sperm whale has the largest tooth on all mammals on earth. It is called a sperm whale because of the white and waxy substance excreted in its head. It was mistaken that the substance was the whale's sperm. Although, everyone knows that it's not sperms, the name remains. An adult whale can grow as long as 67 feet and can reach a weight of up to 57000 kilograms.
历史：
Whales collectively inhabit all the world's oceans and number in the millions, with annual population growth rate estimates for various species ranging from 3-13%. For centuries, whales have been hunted for meat and as a source of raw materials. By the middle of the 20th century, however, industrial whaling had left many species seriously endangered, leading to the end of whaling in all but a few countries.
pictures of Humpback Whale
参考资料： http://en.wikipedia.org/wiki/Whale http://www.abc.net.au/oceans/whale/type.htm
Whale is the common name for various marine mammals of the order Cetacea. The term whale sometimes refers to all cetaceans, but more often it excludes dolphins and porpoises, which belong to suborder Odontoceti (toothed whales). This suborder also includes the sperm whale, killer whale, pilot whale, and beluga whale. The other Cetacean suborder Mysticeti (baleen whales), are filter feeders that eat small organisms caught by straining seawater through a comblike structure found in the mouth called baleen. This suborder includes the blue whale, the humpback whale, the bowhead whale and the minke whale. All Cetacea have forelimbs modified as fins, a tail with horizontal flukes, and nasal openings (blowholes) on top of the head.
Whales range in size from the blue whale, the largest animal known to have ever existed at 35 m and 136 tonnes, to various pygmy species, such as the pygmy sperm whale at 3.5 m.
History:
All cetaceans, including whales, dolphins and porpoises, are descendants of land-living mammals of the Artiodactyl order (even-toed ungulates). Both descended from a common ancestor, the Indohyus (an extinct semi-aquatic deer-like ungulate) from which they split around 54 million years ago. Primitive whales probably first took to the sea about 50 million years ago and became fully aquatic about 5-10 million years later.
