--- title: Rodents: the biggest group of mammals and their ever-growing teeth — a lesson of Mova's school · trees and pragmatics description: «Rodents: the biggest group of mammals and their ever-growing teeth», a lesson of the biology course of Mova's primary school, sentence by sentence with dependency trees and pragmatics. It begins: Mice, rats, squirrels, hamsters, beavers and capybaras are all rodents, the biggest group of mammals: o --- [Mova](https://md.mova.elamur.ai/free/en/) · [this page in HTML](https://mova.elamur.ai/free/en/corpora/school/biology/316-rodents-the-biggest-group-of-mammals-and-their-ever-growing-teeth/) [home](https://md.mova.elamur.ai/free/en/) / [corpora](https://md.mova.elamur.ai/free/en/corpora/) / [school](https://md.mova.elamur.ai/free/en/corpora/school/) / [Biology](https://md.mova.elamur.ai/free/en/corpora/school/biology/) / Rodents: the biggest group of mammals… # Rodents: the biggest group of mammals and their ever-growing teeth Lesson 316 of the biology course of Mova's primary school: 19 sentences, each with its syntax tree and pragmatics. The lessons are written for Mova, and their agreed trees are part of Mova corpus 0.4 (CC BY-SA 4.0). How Mova does on its tests: [the lesson at school](https://md.mova.elamur.ai/free/en/school-run/biology/316-rodents-the-biggest-group-of-mammals-and-their-ever-growing-teeth/). - [0](https://md.mova.elamur.ai/free/en/corpora/school/biology/316-rodents-the-biggest-group-of-mammals-and-their-ever-growing-teeth/0/) — Mice, rats, squirrels, hamsters, beavers and capybaras are all rodents, the biggest group of mammals: over 2,000 kinds, about four in every ten mammal kinds. - [1](https://md.mova.elamur.ai/free/en/corpora/school/biology/316-rodents-the-biggest-group-of-mammals-and-their-ever-growing-teeth/1/) — What makes a rodent is its teeth: two upper and two lower front teeth that never stop growing, and no long pointed canines at all. - [2](https://md.mova.elamur.ai/free/en/corpora/school/biology/316-rodents-the-biggest-group-of-mammals-and-their-ever-growing-teeth/2/) — The word rodent comes from the Latin rodere, to gnaw. - [3](https://md.mova.elamur.ai/free/en/corpora/school/biology/316-rodents-the-biggest-group-of-mammals-and-their-ever-growing-teeth/3/) — Each front tooth is hard enamel at the front and softer at the back, so gnawing wears the back faster and keeps a sharp chisel edge, like a knife that sharpens itself. - [4](https://md.mova.elamur.ai/free/en/corpora/school/biology/316-rodents-the-biggest-group-of-mammals-and-their-ever-growing-teeth/4/) — Look at a squirrel's teeth when it cracks a hazelnut: they are orange. - [5](https://md.mova.elamur.ai/free/en/corpora/school/biology/316-rodents-the-biggest-group-of-mammals-and-their-ever-growing-teeth/5/) — The colour comes from iron in the enamel, which makes the tooth harder. - [6](https://md.mova.elamur.ai/free/en/corpora/school/biology/316-rodents-the-biggest-group-of-mammals-and-their-ever-growing-teeth/6/) — There are over 2,000 kinds of rodent, about four in ten mammal kinds, living on every continent except Antarctica, from tiny mice to the capybara. - [7](https://md.mova.elamur.ai/free/en/corpora/school/biology/316-rodents-the-biggest-group-of-mammals-and-their-ever-growing-teeth/7/) — Rodents have two upper and two lower front teeth that never stop growing and are worn down by gnawing, so they stay sharp and the right length. - [8](https://md.mova.elamur.ai/free/en/corpora/school/biology/316-rodents-the-biggest-group-of-mammals-and-their-ever-growing-teeth/8/) — The orange colour of many rodents' front teeth comes from iron in the enamel, which makes it harder. - [9](https://md.mova.elamur.ai/free/en/corpora/school/biology/316-rodents-the-biggest-group-of-mammals-and-their-ever-growing-teeth/9/) — Each front tooth has hard enamel at the front and softer stuff at the back, so gnawing wears the back faster and keeps a chisel edge. - [10](https://md.mova.elamur.ai/free/en/corpora/school/biology/316-rodents-the-biggest-group-of-mammals-and-their-ever-growing-teeth/10/) — A house mouse has 16 teeth: 4 front gnawing teeth and 12 back grinders, with a big gap between them and no canines. - [11](https://md.mova.elamur.ai/free/en/corpora/school/biology/316-rodents-the-biggest-group-of-mammals-and-their-ever-growing-teeth/11/) — The gap lets a rodent pull its cheeks in behind the front teeth, closing its mouth while gnawing so it does not swallow wood chips. - [12](https://md.mova.elamur.ai/free/en/corpora/school/biology/316-rodents-the-biggest-group-of-mammals-and-their-ever-growing-teeth/12/) — If a rodent's front teeth do not meet, they keep growing and can curl right round; wild rodents with bad teeth can starve, and pet rodents need things to gnaw and checks at the vet. - [13](https://md.mova.elamur.ai/free/en/corpora/school/biology/316-rodents-the-biggest-group-of-mammals-and-their-ever-growing-teeth/13/) — Rabbits and hares are not rodents but lagomorphs; they have four upper front teeth, a small pair hidden behind the big pair, while rodents have two. - [14](https://md.mova.elamur.ai/free/en/corpora/school/biology/316-rodents-the-biggest-group-of-mammals-and-their-ever-growing-teeth/14/) — Rats gnaw wires, pipes and wood and can chew through soft metals like lead and aluminium; some house fires have been blamed on chewed wires, reported. - [15](https://md.mova.elamur.ai/free/en/corpora/school/biology/316-rodents-the-biggest-group-of-mammals-and-their-ever-growing-teeth/15/) — Mice can have babies from about six weeks old, with litters of about 5 to 10 every few weeks, so numbers explode when food is plentiful; owls, foxes, weasels and cats help keep them down. - [16](https://md.mova.elamur.ai/free/en/corpora/school/biology/316-rodents-the-biggest-group-of-mammals-and-their-ever-growing-teeth/16/) — Hamsters have stretchy pouches inside their cheeks reaching back to their shoulders, for carrying food home to store; in German, hamstern means to hoard. - [17](https://md.mova.elamur.ai/free/en/corpora/school/biology/316-rodents-the-biggest-group-of-mammals-and-their-ever-growing-teeth/17/) — Wild mice eat mostly seeds, grains, other plant food and some insects; the idea that cheese is their favourite food comes more from cartoons than from mice. - [18](https://md.mova.elamur.ai/free/en/corpora/school/biology/316-rodents-the-biggest-group-of-mammals-and-their-ever-growing-teeth/18/) — Scientists found rats make high chirps when tickled, too high for us to hear without a detector, and chase the tickling hand for more; young rats also love to play fight. - ← previous: [Bats near home: pipistrelles, noctules, bat boxes and why never to pick one up](https://md.mova.elamur.ai/free/en/corpora/school/biology/315-bats-near-home-pipistrelles-noctules-bat-boxes-and-why-never-to-pick-one-up/) - next →: [Rodents of every kind: squirrels, marmots, prairie dogs, porcupines, chinchillas and dormice](https://md.mova.elamur.ai/free/en/corpora/school/biology/317-rodents-of-every-kind-squirrels-marmots-prairie-dogs-porcupines-chinchillas-and-dormice/) - ↑ back to [Biology](https://md.mova.elamur.ai/free/en/corpora/school/biology/)