The liver stores fatty acids that provide energy when the shark cannot find food. A shark's liver also provides buoyancy, especially important because the shark does not have a swim bladder, which keeps most fish afloat. Sharks are long-lived. Although the average lifespan is less than 25 years, the maximum may be 75-100 years. Sharks have relatively few babies, between one and one hundred, and the baby sharks take up to 24 months to grow.
Some shark babies grow in eggs inside leathery cases.