Sharks

Sharks do not have a single bone in their bodies. Instead they have a skeleton made up of cartilage; the same type of tough, flexible tissue that makes up human ears and noses.

Some sharks remain on the move for their entire lives. This forces water over their gills, delivering oxygen to the blood stream. If the shark stops moving then it will suffocate and die.

Sharks have outstanding hearing. They can hear a fish thrashing in the water from as far as 500 metres away!

If a shark was put into a large swimming pool, it would be able to smell a single drop of blood in the water.

Although most species of shark are less than one metre long, there are some species such as the whale shark, which can be 14 metres long.

A pup (baby shark) is born ready to take care of itself. The mother shark leaves the pup to fend for itself and the pup usually makes a fast get away before the mother tries to eat it!

Not all species of shark give birth to live pups. Some species lay the egg case on the ocean floor and the pup hatches later on its own.

Great whites are the deadliest shark in the ocean. These powerful predators can race through the water at 30 km per hour.

Unlike other species of shark, the great white is warm-blooded. Although the great white does not keep a constant body temperature, it needs to eat a lot of meat in order to be able to regulate its temperature.

A shark always has a row of smaller teeth developing behind its front teeth. Eventually the smaller teeth move forward, like a conveyor belt, and the front teeth fall out.

The term "cartilaginous fish" means that the structure of the animal's body is formed of cartilage, instead of bone. Unlike the fins of bony fishes, the fins of cartilaginous fishes cannot change shape or fold alongside their body. Even though sharks don't have a bony skeleton like many other fish, they are still categorized with other vertebrates in the Phylum Chordata, Subphylum Vertebrata, and Class Elasmobranchii. This class is made up of about 1,000 species of sharks, skates and rays.

Sharks come in a wide variety of shapes, sizes and even colors. The largest shark and the largest fish in the world is the whale shark (Rhincodon typus), which is believed to reach a maximum length of 59 feet. The smallest shark is thought to be the dwarf lanternshark (Etmopterus perryi) which is about 6-8 inches long.

The teeth of sharks don't have roots, so they usually fall out after about a week. However, sharks have replacements arranged in rows and a new one can move in within one day to take the old one's place. Sharks have five to 15 rows of teeth in each jaw, with most having five rows.

A shark has tough skin that is covered by dermal denticles, which are small plates covered with enamel, similar to that found on our teeth.

Sharks have a lateral line system along their sides, which detects water movements. This helps the shark find prey and navigate around other objects at night or when water visibility is poor. The lateral line system is made up of a network of fluid-filled canals beneath the shark's skin. Pressure waves in the ocean water around the shark vibrate this liquid. This, in turn is transmitted to jelly in the system, which transmits to the shark's nerve endings and the message is relayed to the brain.