Unique Adaptations That Sharks Have to Survive

Sharks have several adaptations that help them swim without expending too much energy, and enable them to maneuver quickly and with agility. Their bodies taper to points at both the snout and the tail, reducing water resistance. Also decreasing drag -- and therefore noise -- are dermal denticles, sharp scales that cover the skin of most shark species. These denticles also provide protection, and, like teeth, they’re replaced throughout the shark’s life. Rather than bone, sharks have cartilage, which is much lighter and more flexible. In addition, their livers produce squalene, a fatty oil that helps them remain afloat. Their pectoral fins allow them to quickly change direction, dive and swim upward.

Sharks have several means of sensing prey. Their snouts are covered with ampullae of Lorenzini, sensory organs that pick up electrical signals from potential prey. Their inner ears perceive nearby movement, and lateral lines -- parallel rows of scales that run down the shark’s body -- note abnormal movements and currents that might signal the presence of potential food.

When sharks lose a tooth, a new one grows to replace it. The shape and sharpness of the teeth varies by species, though, depending on prey preferences. Those who dine on crabs, mollusks and other shellfish tend to have blunt, flat teeth. Sharks who feed on larger fish and mammals such as seals have sharp, serrated teeth.

Most sharks are dark with pale bellies. This helps conceal them: Seen from below, the undersides match the pale sky; seen from above, their brown, black or gray backs blend into the deeper water.