Sharks are a member of Class Chondrichthyes which includes the rays and skates. There are 368 recognized species of sharks.
Sharks can be characterized as large, marine predators with a cartilaginous skeleton, multiple (usually five) gill slits along the sides or bottom of the head, dermal denticles covering the body, and rows of replaceable teeth in the mouth.
- Dorsal fin - The dorsal fin is on the sharks back and keeps the shark from rolling over.
- Pectoral fins - are used to move up and down.
- Caudal fins - push the shark through the water.
Sharks have two senses that many animals do not have:
- Ampullae of Lorenzini - These small pits in the head detect electricity. The shark has the greatest electricity sensitivity known in all animals. This sense is used to find prey hidden in sand in bottom feeding sharks, by detecting nerve impulses.
- Lateral line - This system is found in most fishes, including sharks. It is used to detect motion or 'sound' in the water. Sharks uses this to detect other organisms moving, especially wounded fish.
Sharks are carnivores. They eat other fishes, crustaceans, molluscs, marine mammals, and other sharks. Hammerhead sharks prefer to eat stingrays. Bull sharks prefer crabs and lobster. Sharks hunt for prey alone and in schools.
Sharks mate to reproduce. Shark babies are called pups. They are born in three different ways:
- Some mothers carry their pups in a sac in their body until birth.
- Most pups hatch from eggs inside their mother's body.
- Some species lay eggs - a leathery egg case protects the eggs from predators.
Few animals eat sharks. Sharks have no trouble defending themselves. In addition to their mouths full of teeth, their skin is also dangerous. It is covered with tiny sharp scales that are like little teeth.
