Shark can generally be termed as a type of fish that has a full cartilaginous skeleton and a highly streamlined body. Such types of Animals have a highly streamed body. The earliest known sharks dates from more than four hundred and twenty million years ago which is way before the period when dinosaurs were found. Sharks are found in all seas and are common down to depths of 2,000 metres which is about 6,600 ft, some live even deeper but they are entirely absent below 3,000 metres about 9,800 ft.
Since that time, sharks have diversified into four hundred and forty species that ranges in dimension from the small dwarf lantern shark, Etmopterus perryi, a deep sea species of only about seventeen centimetres which is about seven inches in length, to the whale shark, Rhincodon typus which is the largest fish and which is known to reach just about twelve metres which is about thirty nine feet and which feeds only on plankton, squid, and small fish through filter feeding. They generally do not live in freshwater, with a few exceptions such as the bull shark and the river shark which can live both in seawater and freshwater. They respire with the use of five to seven gill slits. It is also a matter of fact that the body of these animals is way different from the other types of fishes.
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Sharks have a covering of dermal denticles that are used to protect their skin from damage and parasites and improve fluid dynamics so the shark can move faster. They always have several sets of replaceable teeth. Well known species such as the great white and the hammerhead are apex predators at the all the most top of the underwater food chain. Their extraordinary skills as predators fascinate and frighten us even as their survival is under serious threat from fishing and other human activities.
Sharks have a covering of dermal denticles that are used to protect their skin from damage and parasites and improve fluid dynamics so the shark can move faster. They always have several sets of replaceable teeth. Well known species such as the great white and the hammerhead are apex predators at the all the most top of the underwater food chain. Their extraordinary skills as predators fascinate and frighten us even as their survival is under serious threat from fishing and other human activities.
