Why do sharks have so many different shapes and sizes?

There are more than 500 species of sharks, and they occupy an enormous range of habitats and feeding strategies. A slender reef shark is built for speed, while a nurse shark is adapted to life on the seafloor. The whale shark, the largest fish alive, filters plankton instead of hunting large prey. These differences come from millions of years of evolution shaping fins, teeth, body size, and swimming style. The diversity of sharks shows how one ancient group can adapt to very different ecological roles.