There are many different species of shark, examples include great white shark, reef shark, bull shark, tiger shark and whale sharks. Most sharks have remained largely unchanged for millions of years.
Whale sharks are the largest fish on the planet, growing up to 15ft long.
Great white sharks are superbly adapted to slicing chunks of flesh off animals. Their jaw isnt connected to their head, as in all sharks, allowing it throw open its mouth. Also, they ca roll their eyes back in their sockets for protection during their powerful lunges.
Sharks have a huge, oil rich liver which helps them be buoyant in the water. This means that they dont have to waste precious energy constantly swimming to stay off the bottom.
Sharks have an extra sense; electroreception! Thousands of sensors called ampullae of Lorenzini line the head and allow them to detect electrical signals given off my twitching muscles of other animals. Like other fish, sharks also have a lateral line which runs down their flanks, which can detect motion in the water.
Like penguins and other marine animals, sharks have a countershaded white belly and darker back. This camouflages them from from underneath and above, allowing them to better sneak by undetected.
Basking sharks, like whale sharks, are mostly filter feeders. They cruise along with their mouths open, sieving small organisms from the water. They can be routinely seen off the coast of the UK and are in no way dangerous to humans.
Sharks have a very long digestion time. However, some indigestible items are regurgitated or sharks can turn their stomachs inside out to get rid of them. Tiger sharks are known to eat anything, including tyres, so this technique can prove very useful!
Shark egg-cases, colloquially called "mermaids purses", sometimes wash up on beaches. Keep an eye out for them!