Sharks (Super Selachimorpha order) are a type of fish filled with cartilaginous skeleton and a streamlined body. The earliest known sharks of more than 420 million years ago.
Since then, the Sharks have diversified into 440 species, ranging in size from the dwarf lanternshark, Etmopterus Perrier, deep-sea species of only 17 centimeters (6.7 inches) long, the whale shark, R. typus, the largest fish, which reaches about 12 meters (39 feet 4 inches) and feeds only on plankton, squid and small fish feed on the filter. Sharks are found in all oceans and are common at depths of 2000 meters (6600 feet). I usually do not live in fresh water, with some exceptions such as shark and bull shark river that can live in both salt water and breathe through gill slits freshwater.They five to seven Sharks have a covering of dermal denticles protect the skin against damage and noise and improves fluid dynamics, so the shark can move faster. They have several sets of replaceable teeth.
A well-known species like the white shark, tiger shark, blue shark, mako shark, and hammer are apex predators, at the top of the underwater food chain. Extraordinary ability beasts fascinated and frightened people, although their survival is seriously threatened by fishing and other human activities.