Sharks also feed on dead or dying animals. Sharks have the reputation of attacking human beings. But fewer than 100 shark attacks a year are reported throughout the world. Sharks differ from most other kinds of fish in a number of ways. For example, sharks have a boneless skeleton made of a tough, elastic substance called cartilage.
Most species of sharks have a rounded body, shaped somewhat like a torpedo.
This streamlined shape helps sharks to swim. Angel sharks, which live near the ocean bottom, have a flat body similar to that of skates and rays. Sharks have fewer young at a time than most fish do. Some species give birth to 60 or more pups in a litter, but most have far fewer. Shark eggs, unlike those of most fish, are fertilized inside the female's body.