The shark is a meat-eating fish and one of the most feared animals in the sea. There are over 300 types of sharks that live in oceans all over the world. Most of them live in warm seas but some sharks prefer colder regions like the seas around Antarctica.
The first sharks lived in our oceans about 300 million years ago. They belong to the earth’s oldest animals.
Size and habitat
Sharks have different sizes and habits. The largest is the whale shark, which can grow up to 15 metres long and weigh twice as much as an elephant. The smallest sharks are only about 16 cm long and weigh about 28 grams. One of the strangest looking sharks is the hammerhead, with a flat head that looks like a hammer.
Some kinds of sharks live in the deepest parts of the ocean, others are found near the surface. Some stay close to the coast, while others swim far out at sea. A few types of sharks even live in rivers and lakes.
All sharks are meat eaters. Most of them eat other fish, either as a whole or by tearing off chunks of a bigger fish. They also eat dead animals, plankton, crabs, sea turtles, seals, sometimes even whales.
A shark’s body
Most sharks have a body that is shaped like a torpedo. The two side fins are stiff; the tail is often curved and it helps the shark swim. Small scales cover a shark’s body and make its skin very rough. The mouth of most sharks is at the bottom of the head. They have many rows of teeth, which are sharp and pointed. New teeth grow and replace the older ones, sometimes as often as every week. Behind the eyes, sharks have five to seven gills on each side of the head. They use them to breathe underwater.
Sharks have sharp senses. They can find a fish to eat by the sound that it makes. They also have good eyes and can see almost everything in dark areas. Sharks must swim fast and well, otherwise they will sink. Some types have been recorded to swim at speeds of up to 90 km an hour.
More than half of the sharks in the world are not dangerous to people and seldom attack them. Among the most dangerous is the white shark, a fish with sharp teeth that can rip off chunks of flesh from animals. They hunt for large animals, such as sea lions, tuna and other sharks. They have even attacked human beings, especially when they are hungry or worried. Movement, noises or blood in the water can provoke sharks and make them attack.
Importance of sharks
Fishermen catch sharks mostly for their skin and flesh. Shark skin is used to make leather goods. The Chinese use dry shark fins to make popular and expensive soup. The liver oil of sharks has a lot of vitamin A.
Swimmers should always be careful in areas known to have sharks. Here are some rules to follow.
- Never swim or dive alone.
- Never swim or dive if you have an open cut on your body.
- Leave the water immediately when you see a shark. Swim as smoothly as possible and avoid wild movements.
- avoid = not do something
- chunk = a large piece of something
- coast = place where the sea meets land
- crab = sea animal with a hard shell , five legs on each side and two large claws
- dive = to swim under water with tanks that help you breathe
- either =whichever, any
- especially =above all
- fear = to be afraid of
- fin = one of the thin body parts that a fish uses to swim
- flat =level, smooth
- flesh = the soft part of the body of a person or animal that is between the skin and the bones
- gill = one of the organs on the side of a fish through which it breathes
- goods = things that are produced in factories
- habit = things that you normally do
- habitat = the living area of animals or fish
- human being = a person
- immediately = at once, quickly
- liver =a large organ in your body that helps you digest food and cleans your blood
- movement =the way something moves
- open cut =skin injury ; when you see blood on your skin
- otherwise = or else
- pointed =sharp
- prefer = to like more than something else
- provoke = to make someone or something react suddenly
- record = information that is written down so that you can find it in the future
- replace =grow in something’s place
- rip off = tear off
- rough =not smooth, with an uneven surface
- rule =instruction, advice
- scales = small flat pieces of skin that cover the body of a fish
- seal = a large sea animal that eats fish and lives around coasts
- seldom = not very often
- senses = the five natural powers that humans and animals have - seeing, hearing, feeling, tasting and smelling
- shape = form
- smoothly =soft, not with wild movements
- snout = long nose of an animal or fish
- speed =how fast something is
- stiff =hard, not bendable
- surface =the top layer of something
- tear off =rip or cut off
- tuna = a large sea fish that is caught for food
- twice = two times
- weigh =how heavy something is
- whole =complete, all of it
- worried =nervous because you keep thinking about something