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. The S pined Pygmy Shark only grows to the size of a medium cucumber, and sleeps all day at the bottom of the ocean.

'Aren't you scared Harriet?' 'Can't you tell that that's a very well fed Florida Smooth hound Heming? She's not going to hurt me or you.'s ome sharks only like warm water, and some only like cold water. Some of them like to travel all over the world and some of them never leave the neighborhood they were born in. There are even sharks in freshwater rivers. Most sharks like to eat fish, but none of them have ever tasted any tartar sauce. Of course there are a few of them who would eat you in less than a minute if you went to pay them a visit, but it wouldn't be anything personal.

The majority of sharks feed on live fish. Most of them make their homes in very deep water. Scientists divide all the species of sharks into eight groups, or orders according to certain features which they have in common. The biggest group of sharks are the Ground Sharks. They are found all around the world in temperate and tropical waters. Saw Sharks all have long, blade like snouts.

Dogfish Sharks live on the bottom of the ocean, bear live young and are not considered dangerous to humans. Angel Sharks look a lot like Rays and are found most often on the continental shelves. Carpet Sharks like warm water and live on the bottom of the ocean. Mackerel Sharks grow up to be very big, and can be found anywhere between tropical waters and Arctic waters. Bullhead Sharks like rocky reefs, and have only been found in the Pacific and Indian Oceans. And finally, Frilled Sharks are the only ones with six or seven gill slits.

They like deep water and usually stay near the bottom. All the creatures living under water have certain characteristics in common. They all need a way to get oxygen. They all need to reproduce to make sure their species continues. They all need to eat to live.

But each species also has special features which are unique. Sharks have highly sensitive senses, a special liver which helps them to float, several rows of teeth, and eyes which aren't so different from yours. Like rays, shark skeletons are made of cartilage. The shape of a shark is specially designed to help it navigate long distances and maneuver around its prey with ease. Its several pairs of fins help it navigate through the water, kind of like our legs get us humans around, and our arms help us keep our balance. 'Look I got a shark's tooth'.

You should really see what it's like for yourself Heming. You can learn to swim. A shark has several pairs of gills on either side of its head, unlike other fish who only have one gill on each side. You probably breathe through your nose and mouth, but a shark only uses its nostrils for smelling. When per pale don't want to be seen by their enemies they sometimes wear fatigue suits. Sharks are born with their own special colors to protect them from predators above and below them in the water.