Sharks – predators of the sea
When the first dinosaurs walked on Earth, sharks were already swimming in the sea. Today there are about 400 species of shark. Sharks are some of the most fascinating, well-adapted marine organisms.
Most sharks live in oceans in the mild or warm parts of Earth. But the Greenland shark lives in the cold Arctic waters. Sand sharks spend most of their time at the bottom of shallow water. The Portuguese shark lives in the deepest parts of the ocean.
Sharks are great swimmers. Most species can swim from 32 to 48 kilometers per hour. But the speed of mako sharks has been recorded at more than 97 kilometers per hour.
Sharks play a crucial role as predators in ocean ecosystems. To save their energy, many sharks eat old, sick, or otherwise damaged fish thus getting rid of the weaker populations and freeing up resources for the strong.
A shark’s teeth are sharp and triangular and grow throughout its life.
Most shark attacks take place in shallow water, where sharks sometimes go to hunt for fish. A hungry shark can easily mistake a human arm or leg for a tasty fish.
Sharks may eat plankton, shellfish, sea turtles, fish, seals, porpoises, squid, or whales.
Most fish lay eggs. But most sharks do not. Their babies are born alive and completely developed. They do not need parental care. A baby shark is called a pup. The pup of the Great White Shark is almost the size of a man. As soon as they are born the pups go their own way. It isn’t safe to stay near a hungry mother.
A shark has to keep swimming all the time. Its body is made in such a way that if it doesn’t swim, it will sink to the bottom of the sea. They lack a swim bladder, the air–filled balloon–like organ that keeps most fish upright. They even know how to sleep while they swim!
– The whale shark is the largest living fish. It can reach about 15 meters long and weigh nearly 20 tons. The smallest shark is the dwarf lantern shark, which is only about 19 centimeters long.
– Unlike most other fish, sharks don’t have hard bones. Instead, their skeletons are made of cartilage, the same material that human noses and ears are made of.
– Blue Sharks are called the wolves of the sea because they stay together in packs. Blue Sharks often follow ships for days. A long time ago sailors took it as a bad omen. Today we know that they follow ships because of the noise they make. When the garbage is thrown into the water the sharks stop and eat it.
– The most dangerous shark in the sea is the Great White Shark. It is so named after its white belly. The Great White shark may be more than 6 meters. It can sink a boat, it can bite a man in two, it can even swallow a man whole.
– The Borneo shark is a very rare species, little known to humans. It is not a large or dangerous shark. An adult measures about 70 centimeters. They are known to form strong male–female pairs.