Science





SHARKS


Sharks are one of the most feared carnivores in the sea. There are 365 species of of sharks in the sea as we know today. All sharks are carnivores. Most of them eat live fish, including other sharks. A shark\'s most common natural enemy is an another shark. Most sharks eat their prey whole, or they tear off large chunks of the bodies. Some sharks crush their prey. Others take out small pieces off flesh from large fish. Sharks also feed on dead or dying animals. Sharks have the reputation of attacking human beings. But less than 100 shark attacks a year are reported throughout the world. Sharks are most common in warm seas and oceans. Whale sharks, are the largest shark known to man. Sharks are classified in the order Selachii, which belongs to a larger class of fish called Elasmobranchi. The earliest shark-like vertebrate fossils are from the Devonian Period of the Paleozoic Era.

Some kinds of sharks live in the depths of the ocean. The smallest streamlined, black and white shark of the genus Squaliolus can grow to be up to 6 inches long and the female can grow to be up to 8 inches. They can grow up to 40 feet long. They are also known to weigh over 15 tons. The smallest sharks known at a full stage of growth may measure about 6 inches long and weigh about 1 ounce.

Sharks live in many places throughout the ocean. Some sharks are known to be found near the surface of the water because the temperature of the water is warmer. Yet, some sharks are known to dwell on the bottom of the ocean. These sharks are sometimes referred to as bottom dwellers. A few species of sharks enter rivers and lakes where they can move to the seas and oceans easily.

Sharks have a boneless skeleton made of a substance called cartilage. Most species of sharks have a rounded body, shaped somewhat like a torpedo. This type of flexible body makes their swimming in oceans and strong currents much easier. Their bodies are also shaped somewhat like a torpedo to give them a more streamlined affect in the in water. Yet, some types of sharks, the ocean dwellers have a flat body similar to that of skates and rays. Sharks can travel with great bursts of speed especially when attacking their prey or when excited. The fastest-swimming sharks have a moon-shaped tail that provides extra power and durability for swimming.
Sharks don\'t have a swim bladder. This is what helps regulate depth control. Sharks do not have this organ. Yet, they do have a oil organ that also acts as a gas bladder. This oil is less dense than water and acts as a gas bladder.

A shark has multiple rows of teeth. The mouth of sharks is in the front of the head. In some species, sharks teeth are replaced as much as once a week. Some sharks have teeth used to crush and grind. These are some what like what humans have. They also have sharp teeth. These can be compared to incisors that humans have. These types of teeth are very important to sharks because they are carnivores and depend on their teeth in order to eat their prey. A sharks body in covered by scales which cover their bodies. These scales make the skin of a shark very rough and strong.

Sharks have a very different breathing system than most animals that live in or on this earth. Sharks also receive oxygen from the water through gills, yet, unlike fish, sharks do not have a gill cover. This makes a sharks breathing system very unique. Instead of a gill cover, sharks have from five to seven slits in the skin on each side of the head. Water passes through of these slits after the shark\'s gills remove the oxygen. Most sharks cannot pump water over their gills, as do the majority of fish.

Sharks have special senses that allow them to compete for prey. They have excellent hearing, yet, can not hear many low pitched sounds. Sharks can find their prey the sounds that they make. Some scientists believe that the shark\'s lateral line through out their back bone detects the lowest-pitched sounds. Sharks