About Sharks

What is a Shark?

Sharks are a type of fish. Sharks are amazing fish that have been around since long before the dinosaurs existed. They live in waters all over the world, in every ocean, and even in some rivers and lakes. 


Unlike bony fish, sharks have no bones; their skeleton is made of cartilage, which is a tough, fibrous substance, not nearly as hard as bone. Sharks also have no swim bladder (unlike bony fish).

Size

The Whale Shark is the largest fish in the world; the Basking Shark is the second largest fish. There are many different species of sharks that range in size from the size of a person's hand to bigger than a bus. Fully-grown sharks range in size from 7 inches (18 cm) long (the Spined Pygmy Shark), up to 50 feet (15 m) long (the Whale Shark). Most sharks are intermediate in size, and are about the same size as people, 5-7 feet (1.5-2.1 m) long. Half of the 368 shark species are under 39 inches (1 m) long. 

Anatomy

Sharks have a variety of body shapes. Most sharks have streamlined, torpedo-shaped bodies that glide easily through the water. Some bottom-dwelling sharks (e.g. the Angelshark) have flattened bodies that allow them to hide in the sand of the ocean bed. Some sharks have an elongated body shape (e.g.,Cookiecutter Sharks and Wobbegongs). Sawsharks have elongated snouts, Thresher Sharks have a tremendously elongated upper tail fin which they use to stun prey, and Hammerheads have extraordinarily wide heads. The Goblin Shark has a large, pointed protuberance on its head; its purpose is unknown. 

Varieties Of Sharks

There are about 368 different species of sharks, which are divided into 30 families. These different families of sharks are very different in the way they look, live, and eat. They have different shapes, sizes, color, fins, teeth, habitat, diet, personality, method of reproduction, and other attributes. Some types of shark are very rare (like the Great White Shark and the Megamouth) and some are quite common (like the Dogfish Shark and Bull Shark). Sharks belong to the group of cartilagenous fish, the Elasmobranchii, that includes the sharks, rays, and skates.

Skeleton 

Sharks are a type of fish that have no bones, only cartilage. Some parts of their skeleton, like their vertebrae, are calcified. Cartilage, a strong fibrous substance, is softer than bone; our nose and ears are made of cartilage. 


Sharks belong to the group of fishes called Elasmobranchii, which also includes the rays, skates, and ratfish. The Elasmobranchii are all fish that have no bones, only cartilage. 

Teeth

Sharks may have up to 3,000 teeth at one time. Most sharks do not chew their food, but gulp it down whole it in large pieces. The teeth are arranged in rows; when one tooth is damaged or lost, it is replaced by another. Most sharks have about 5 rows of teeth at any time. The front set is the largest and does most of the work. 

Diet

Sharks vary greatly in their diets, but they are all carnivores.
Some (like the Great White Shark, Mako Shark, Tiger Shark, and Hammerhead Shark) are swift predators that eat fish, squid, other sharks, and marine mammals.
Some (like the Zebra Horn Shark, Angelshark, and Wobbegong) are slow-swimming predators that crush and eat shellfish (crabs and clams) from the ocean floor.
Others (like the Whale Shark, the Basking Shark, and the Megamouth) are filter feeders that sieve tiny bits of plankton and small animals from the water as they swim with open mouths. They eat huge amounts of these tiny animals and plants.