Sharks are medium to large fish, usually grey in colour, that are active predators and can be dangerous to humans. There are nearly 400 different shark species, all with varying life cycles. While some sharks live an average of as little as 16 years others can live between 100 to 150 years.
It usually takes at least a decade for sharks to reach sexual maturity; however, it can vary depending on the shark species. In all species, a female and male shark must mate in order to reproduce. The mating process requires a male shark to insert one of his two claspers into the female's cloaca and sperm is transferred into the female.
When sharks reproduce, the babies are called pups. However, different species produce varying numbers of pups in their litter. The nurse shark typically has a litter of between 21 and 30, while the tiger shark can have between 10 and 82. In addition, different species of sharks can give birth in various ways. Sharks can lay eggs similar to birds or the mother can fertilise eggs through hatching eggs internally or holding pups in a placenta and then giving live birth. Pregnancy can last from 9 to 22 months depending on the species.
Different shark species have different feeding patterns through their life cycle. For example, the tiger shark is omnivorous and will eat turtles, mammals and even other sharks. Other species such as the nurse shark mostly stick to small fish and shell fish such as lobster, shrimp, snails and crabs. Sharks have keen senses of smell and sight, which allows them to find their prey. Sharks also live in oceans throughout the world in both cold and warm waters.
Lifespans of sharks can vary based on the species. For instance, species such as the smooth dogfish are the smallest sharks and typically live only about 16 years. Sharks such as the porbeagle can live up to 46 years. Whale sharks, the largest of the species, can live more than 150 years. Whale sharks average around 3 to 7 meters long, but many longer whale sharks have been recorded.