Sharks can change their teeth all the time because there are many teeth in their mouths. An adult shark will have more than 6,000 teeth in its mouth. There are 3-6 rows of teeth in their mouths, and each row has almost more than 1,600 teeth. However, sharks only use the teeth in the front row when hunting, and even if the teeth in the back row are used, they are only used for auxiliary purposes.

In addition, only the teeth in the front row of sharks are upright, and the teeth in the back row are reclining. After their front teeth fall off, the back teeth will be filled immediately. In addition, there are many tooth germs in the mouth of sharks, so the differentiation and calcification of tooth germs are very fast, and it is easy to form new teeth, so sharks can keep changing teeth.

It is not particularly common for sharks to eat the same kind, although they are fierce in character and will eat large creatures as their own food. However, only some sharks that are too ferocious will eat the same kind, while others will not. They eat the same kind because they have low IQ and can't tell if other creatures are their own kind, so they will eat them directly. But sharks generally don't kill their own kind, and usually eat some carcasses of their own kind.