SHARKS :: essays research papers

Out of all the species walking, flying, slithering or swimming, there aren't many who have been around as long, survived as well, or come in so many shapes and kinds as the shark. The earliest evidences of sharks are isolated spines, teeth and scales that appeared about 430 million years ago in the Silurian Period, known as the "Age of Fishes". Sharks have a sleek, streamlined design which helps them swim without using up a lot of energy.They certainly need to conserve their energy because they never really sleep and most of them never stop swimming. Some sharks are fierce predators, and would be happy to eat you if they encountered you. Almost any shark six feet or longer is a potential danger, but three species have been identified repeatedly in attacks: the Great White Shark, the Tiger Shark and the Bull Shark . All three live world wide, reach large sizes and eat large prey such as marine mammals or sea turtles. But most sharks never grow longer than five feet and never even see anyone with legs and arms anyway. People kill thousands more sharks every year than sharks kill people. Sharks take about as long to mature as we do. Some of them become adults in their teens. A mother shark carries her babies inside her body while they develop, sometimes for more than a year. Even so, some sharks are born inside an egg which they have to crack open. They spend early portions of their lives in nursery grounds. Some of the advantages sharks have over people is that they keep growing new teeth, they don't have breakable bones, and they are not prone to get cancer. Sometimes sharks are referred to as swimming computers because of the six senses which they possess: vision, hearing, vibration, smell, taste and electro-perception. Sharks come in many shapes, sizes, and colors. They have different personalities, and they live in oceans all over the world. Not much you can say about sharks is true for all of them, but there are a few things you can say about the anatomy of most sharks. They breathe through gill slits, have rigid fins and they don't have a bladder. The Whale Shark is the biggest creature in the ocean, about eleven times taller than your Mom or Dad, and weighing in at about 2,000 pounds. A Whale Shark wouldn't be too interested in eating you, but you could offer him about half a ton of teeny fish, crustaceans and little drifting invertebrates and he would be very happy.