SHARKS

Sharks are a group of elasmobranch fish ,characterized by cartiliginous skeleton , pectoral fins that are not fused to the head ,and five to seven gills slits on the side of the head .
Sharks are said to have existed for about 420 million years ago ,making it one of the oldest life in the sea , since than sharks have been diversified into 500 different species . The smallest is the dwarf lantern shark , a specie just over (6.7 in) about 17 centimeters and also a deep sea diver while the whale shark is the biggest of all sharks ,reaching a length of (40 ft) 12 meters .
Sharks lives in all sea and goes down to about 2'000 meters deep . apart from river sharks and bull sharks ,generally sharks are not known to live around fresh water . most sharks are apex predators (great white sharks, tiger sharks, Mako sharks blue sharks etc .)  .