Rodentia refers to the group of animals with teeth for gnawing, and members include mice, squirrels and beavers. They have two incisors (front teeth) each on the top and bottom, which are sharp like chisels and grow their entire lives, allowing them to gnaw hard plant skins and eat the delicious food inside.
There are a large number of species in this group, occupying close to 40% of mammals worldwide. They live in most land environments.