Describe the teeth of a shark. Why might they be like this?

The immature shark's head expands rapidly. Twenty-six teeth are contained in the top row and twenty-four in the bottom row. Successive rows of additional teeth are poised behind the functional teeth, ready to replace them when they are discarded. Every two or three weeks, a new, serrated set of teeth replaces the current set. With teeth that can easily be replaced, it seems that the shark is made to bite, chew, and tear into thick flesh and bone.