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
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.
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).
Great White Shark
Great White Sharks are the largest predatory fish in the sea
Scientists estimate that after a big meal, a Great White Shark can last up to three months before needing another one.
A Great White Shark may use and lose more than one thousand teeth in its life time.
Dogfish Shark
The spiny dogfish is one of the most abundant species of shark in the world
The life span of a Dogfish is 25-80 years old
Due to its relatively large size, aggressive nature and poisonous spikes, the only real predators of the spiny dogfish are larger sharks, humans and the occasional killer whale.
Hammerhead Shark
There are nine different species of Hammerhead sharks
When fully grown, it gets to 6 meters in length (20ft) and weighs 170 kilograms (600 pounds)
The lifespan for most Hammerheads is between 25 and 35 years