Modern sharks first appeared and diversified during the Jurassic period.[1] Since then, sharks have diversified into over 500 species. They range in size from the small dwarf lanternshark (Etmopterus perryi), a deep sea species that is only 17 centimetres (6.7 in) in length, to the whale shark (Rhincodon typus), the largest fish in the world, which reaches approximately 12 metres (40 ft) in length.[2] Sharks are found in all seas and are common to depths up to 2,000 metres (6,600 ft). They generally do not live in freshwater, although there are a few known exceptions, such as the bull shark and the river shark, which can be found in both seawater and freshwater.[3] Sharks have a covering of dermal denticles that protects their skin from damage and parasites in addition to improving their fluid dynamics. They have numerous sets of replaceable teeth.[4]

Several species are apex predators, which are organisms that are at the top of their food chain. Select examples include the tiger shark, blue shark, great white shark, mako shark, thresher shark, and hammerhead shark.

Sharks are caught by humans for shark meat or shark fin soup. Many shark populations are threatened by human activities. Since 1970, shark populations have been reduced by 71%, mostly from overfishing.

About

Shark Night 3D - Official HD Trailer
2:07
4/10
IMDb
19%
Rotten Tomatoes
3.2/5
Vudu
72% liked this film
Google users
A group of seven friends go to the Louisiana Gulf on a weekend. However, things turn dangerous after blood-thirsty sharks attack them multiple times.
Release date: 2 September 2011 (USA)
Director: David R. Ellis
Box office: 4.14 crores USD
Art director: Craig Jackson
Casting director: Kelly Wagner
Budget: 2.5 crores USD, 2.8 crores USD