Sharks have as many as 5 to 15 rows of teeth behind their main row. Their teeth are usually in functional service for about a week, but can be lost as early as 24 hours. They can be lost so fast because their teeth are not attached with roots like ours. As the main row is lost, teeth from the next row move in.
I have always enjoyed looking for these teeth along the beach. I have been to the beaches of South Carolina about 8 times and usually find about 20-30 teeth each time I go that range in size and shape. In looking at the teeth I have collected , I wanted to learn how to identify what type of shark they came from. I found this key that was helpful in determining what shark the tooth came from. There are a number of other keys online.
I have found teeth from the great white, tiger, sand, lemon and bull sharks. Hopefully we will have some time to search the beaches for teeth as a class on our trip!