They point backwards to smooth the water over the shark s body so it can swim faster. Some sharks deposit a fertilized egg sac on the ocean floor. It has a strong leathery case that protects the embryo until it is born. In most sharks the eggs hatch inside the mother and the shark gives birth to a live pup. Once born, all sharks are on their own, and are not cared for by their mothers.
Sharks are fish because they have gills and get their oxygen from the water.
They do not nurse their young. Whales, on the other hand, are mammals because they have lungs and must surface to breathe air. They also nurse their young with milk after they are born. Some species of whales live alone, but others live in families. A family of whales is called a pod and can have from five to 100 members.