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Oceans cover 70 per cent of the earth surface and whole more that 20,000 species of fish. Of these some 370 species are sharks. Long before dinosaurs existed, sharks roll the waters. They first originated more than 400 million years ago and have changed very little in last 100 million years; today few other species on earth inspire so much respect and fear. These amazing predators sit at the top of the marine food chain by eating out weak and injured. They help maintain a balance equal system. Sharks are highly tuned hunting machines that rely on specialize senses to catch prey. Using their sharp sense of hearing they can detect sound vibration up to 3,000 feet away. They are especially sensitive to the low frequency pulses from struggling prey. The vibrations from the speaker sound like wounded fish and send these sharks to the frenzy. As a shark goes closer to the catch its sense of smell takes over. It can detect a single drop of blood in 25 gallons of water. Water flows through nostrils on the under side of its snail giving the shark a steady steam of all factory information. Near the snail, sharks also have tiny gelyfill pores they pick up electrical signals created when animals move. It's like extra sense that helps sharks find prey, even when it's hiding in the sand. When we think of sharks we can't help the think of their teeth. Sharks use and loose their teeth all the time. Some species shed as many as 30,000 during their lifetime but replacements always nearby. Rows of teeth make it possible for new teeth to rotate in when needed. Besides their repetition, one thing that distinguishes sharks from other fish is their skeleton. Its made of tuff flexible cartilage inside of bone, cartilage is lighter than bone, so the sharks uses less energy as its swings than a bony fish does, tuff skin covers its stream line body, tiny tiff like structures make the skin as tuff as a sand paper protect the shark from injury. These teeth point ba...

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Sharks. (1969, December 31). In Retrieved 23:25, August 28, 2014, from