Shark General Knowledge Facts

The earliest known sharks date from more than 420 million years ago and have diversified into over 470 species.  The smallest shark species is dwarf lanternshark which is of only 17 centimetres (6.7 in) in length. The largest shark species is the whale shark (Rhincodon typus), which reaches to approximately 12 metres (39 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 survive in both seawater and freshwater Sharks living in frigid waters can heat their eyes using a special organ next to a muscle in their eye socket. This ability enables them to keep hunting their prey in extreme temperatures. Almost 50 different species of sharks have light-emitting organs called photospheres. Sharks use the light that comes from these organs for camouflage and to attract mates. The average shark lives to be 25 years old, but some can get as old as 100! They live so long because their chances of contracting a disease are low.  The teeth of sharks don’t have roots, because of this they usually fall out rapidly,but ,they have many teeth rows and a new one can move in within one day to take the old one’s place.  Sharks have five to 15 rows of teeth in each jaw, with most having five rows. Sharks have extremely sensitive hearing. They can identify much lower sounds than human ears can detect, and some can hear sounds more than 700 feet away. Depending on the species, a shark may give birth to one or to dozens of pups. Nurse sharks are nocturnal and will often rest on the sea floor during the day in groups of up to 40 sharks, sometimes piled on top of each other. The tiger shark's will swallow anything it finds, including garbage and hence has earned its nickname "wastebasket of the sea." Great whites can detect one drop of blood in 25 gal (100 L) of water and can sense even tiny amounts of blood in the water up to 3 mi (5 km) away. The phase of the moon can affect sharks' eating habits and draw them closer to shore which in turn, can lead to increased attacks on humans Sharks can see in murky water because of a special feature that makes their eyes more sensitive to light.  Baby sharks are called pups. All sharks are negatively buoyant which means that if they stop swimming they will sink to the bottom of the sea. Sharks' eyes are on the sides of their heads, so they have an amazingly wide sightline spanning nearly 360 degrees. Sharks can generate up to 40,000 pounds per square inch of pressure in a single bite. That's easily enough to chomp a meaty limb right off.  Sharks' skeletons are made entirely of cartilage, an elastic tissue that is much softer than bones. When a shark dies, salt from the ocean water completely dissolves its skeleton, leaving only the shark's teeth behind.