Sharks (Selachimorpha) are a type of fish with a streamlined body and a skeleton made of cartilage, which is much softer and more flexible than bone. Sharks have existed for over 400 million years and come in many different species and sizes. The smallest, the spined pygmy shark is only about 7 inches long, whereas the whale shark – which is largest fish in the world, can be over 50 feet long!
Most sharks live in saltwater environments such as oceans and seas and are carnivorous. Though some species such as the tiger shark will eat pretty much anything they can find, the majority stick to a single type of prey whenever possible. When most people think of sharks they picture vicious predators such as the great white. However, not all sharks feed this way. Several species of shark feed much like whales, swimming through schools of fish or plankton with their mouths open sucking in the their prey. Sharks lose teeth on a regular basis and will continue to grow new teeth throughout their lives.
Depending on species, sharks can give birth several ways. Like other fish, most sharks simply lay eggs for their young to hatch from. However some species such as the hammerhead shark give birth to live young. Sharks usually live on average for about 20-30 years. However some species such as the giant whale shark and the spiny dogfish can live to be over 100 years old.
SHARK FACTS
- A shark may lose as many as 30,000 teeth in a lifetime.
- The spiny dogfish shark’s spinal cord controls its movement instead of its brain, so it can continue to swim while sleeping.
- The fastest shark, the shortfin mako can swim at speeds up to 31 miles per hour.
REFERENCES
Defenders of Wildlife
http://www.defenders.org/wildlife_and_habitat/wildlife/sharks.php
National Geographic
http://animals.nationalgeographic.com/animals/fish/great-white-shark/?source=A-to-Z#start
