What is a shark?

A shark is a fish and a cold-blooded vertebrate. A shark does not have fur, skin or hair, but fine scales called denticles. It breathes through gills rather than lungs, so therefore is a fish and not a mammal, bird or reptile.
Sharks are fish that have a cartilaginous skeleton, gills slits that they breath through, a prominent dorsal fin, and toothlike scales. There are over 470 species of sharks and have a large range in size. The smallest shark is the dwarf lanternshark with a max length of about 8.3 in. The largest is the whale shark (the largest fish in the world) which grows to about 39 feet in length.

Several popular sharks, such as the great white shark, tiger shark, blue shark, mako shark, and the hammerhead shark, are apex predators. They pretty much will eat anything that they come across including seals, fish, humans, and other smaller sharks.