Sharks have been roaming the oceans for over 400 million years and there are about 500 different species that we know of.  They are a majestic and fascinating creature.  As apex predators, sharks play a key role in maintaining the health and the balance of the ocean.  Sharks control populations of various marine species that fall below them on the food web, keeping populations at a healthy size and removing weak and sick individuals. All of which supports a healthy marine ecosystem and biodiversity.  Focusses research continues to allow us to learn more about the characteristics and behaviour of various shark species to give us a better understanding of their important role in the marine environment. Sharks are present in all oceans, and a few species including the Bull shark are able to survive in fresh water. Unlike boney fish, the skeleton of sharks is made up from cartilage.  Sharks control their buoyancy by constant swimming. The perfectly shaped fins and tail provide lift, while the oily liver also helps with buoyancy. Most sharks, like …