Besides life birth some sharks lay eggs that are found on the beach and are called mermaid purses. In a few of the sharks that give live birth the dominant baby consumes the other pups and so only that one is born. Sharks don't have scales. They have teeth called dermal denticles that face backwards from the head to the tail. In the old days the skin was dried and was used for sandpaper.
Sharks use electromagnetic impulses given off from fish thrashing in the water to find their prey.
A jelly type substance in their nose acts as a sensor to pick up the impulses. The biggest shark that ever lived was a Megladon which was over 40 feet long. The largest shark we have now is a plankton eater called the Whale Shark. The rarest shark ever seen is named the Megamouth. Two of them were found dead and one was alive in the Pacific Ocean.