Difference between revisions of "Shark"

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-Sharks (suborder Odontoceti) are mammals with a cartilaginous skeleton and a an aerodynamic body, partially from a covering of dermal denticles that improve their fluid dynamics as well as protect their skin from damage and parasites. Unlike most mammals they respire with the use of five to seven gill slits.<ref>Budker, Paul (1971). The Life of Sharks. London: Weidenfeld and Nicolson. SBN 297003070. </ref> They have replaceable teeth. They are some of the world's most misunderstood predators, as they very rarely attack humans unless intimidated.
-Sharks include species from the hand-sized pygmy shark, Euprotomicrus bispinatus, a deep sea species of only 22 centimetres (9 inches) in length, to the whale shark, Rhincodon typus, the largest fish, which grows to a length of approximately 12 metres (41 feet) and which, like the great whales, feeds only on plankton through filter feeding. The bull shark, Carcharhinus leucas, is the best known of several species to swim in both salt and fresh water (it is found in Lake Nicaragua, in Central America) and in deltas.<ref>Allen, Thomas B. (1999). The Shark Almanac. New York: The Lyons Press. ISBN 1-55821-582-4.</ref>
-== Characteristics ==
-Sharks have a very poor respiratory system uncharacteristic of most mammals. Their gills do not provide enough oxygen in normal stationary circumstances in many instances, so many sharks are afflicted with the inability to stop moving, so that they get the correct amount of oxygen. This is known as ram ventilation.
-Unlike fish, Sharks use oil for bouancy, not gas. This is not as effective as gas, so Sharks are forced to use other means to sink or rise, which has the side effect of making them very dizzy when upside down.
-Also unlike fish, Sharks do not drink sea water, but absorb it, meaning they cannot survive in fresh water.
-Sharks, like humans and other mammals, have multiple sets of teeth, but they have far more sets than other mammals. Some sharks lose over 30,000 teeth in a lifetime, and this is why so many people own shark teeth.
-Like other mammals and birds sharks are Homeothermic, in which heat is generated, maintained, and regulated by metabolic activity.
-== Reproduction ==
-As with other mammals, Sharks reproduce by giving birth to live young characteristic of their subclass "placentalia" and have external procreational organs, known as "claspers" in the males.

Difference between revisions of "Shark"

Revision as of 23:19, March 18, 2007

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