By Sara Amundson and Kitty Block
Sharks have been around for 450 million years, outliving the dinosaurs and surviving mass extinctions. But now, out of the 500 or so species (that we know of), a third of all sharks and shark-like species are threatened with extinction due to human activity. Some of these species include the unique scalloped hammerhead shark, the common thresher shark, which uses a long tail to stun prey and the bespeckled whale shark, the world’s largest living fish.