"Great white shark, or white shark (Carcharodon carcharias)." Gale Science in Context. Detroit: Gale, 2010. Science In Context. Web. 16 Mar. 2013.
Sharks date back to the time of the dinosaurs. They have a reputation as being the great killers of the ocean but this is not necessarily true. The largest shark is the Whale Shark which can be as long as 59 feet. This shark is extremely gentle and feeds on zooplankton. The smallest shark species is the Dwarf Lanternshark which can fit into a man's palm. According to the Science in Context Database: " in the year 2012 there were eighty confirmed unprovoked shark attacks on humans world-wide. This included fifty-three attacks in U.S. waters, mostly occurring off beaches in Florida."
All sharks are cartilaginous. This means their skeletons are made completely of cartilage. Unlike fish, sharks don’t have scales, but rather spiny projections known as denticles. Sharks also have a third eye, called a pineal eye, which is used to sense light.
Fish have air bladders that allow them to float in the water but sharks do not. Most sharks must be in constant motion to stay afloat. One thing that does help them stay afloat is their fatty liver.