Many paleontologists are very interested in living groups, because the study of the living organisms can both unlock their evolutionary history and provide important keys towards interpreting their fossil record. Some living groups have ancient histories. Today, sharks and rays, also called elasmobranchs, are represented by over 600 species that show a remarkable range of ecological and morphological diversity. Unlike the true fishes, sharks do not have internal bone, but instead have a cartilaginous skeleton. Although many people are told that sharks are primitive in comparison to other groups, this is not true.
Many sharks are efficient and specialized hunters that have thrived for millions of years.
The Great White is a greedy and efficient predator. Its prey includes a wide variety of bony fishes, including salmon, hake, halibut, mackerel, and tunas, plus other sharks, sea turtles, seabirds. They also prey on marine mammals as seals, sea lions, sea otters, and porpoises. Traditionally, white sharks were thought to be driven into a frenzy by the scent of blood. Recent research, however, shows that the white shark is a methodical feeder, employing extremely sophisticated food-finding mechanisms.