1. Mammals are animals that have hair or fur on their bodies and feed milk to their young. Adult female mammals produce milk from mammary glands. Mammals have well-developed lungs for breathing and four-chambered hearts that pump blood through a closed circulatory system. Mammals are endotherms, which means they can maintain a constant internal body temperature. This helps them adapt to a wide range of biomes, from deserts to polar regions and even oceans. It should come as no surprise that mammals are found on every continent on Earth.
2. Rodents are a major mammal group that includes mice, rats, squirrels, beavers, and many others. Rodents are adapted for a vegetable-based diet. They have strong, sharp incisors in the fronts of their
hair. The sharp incisors of mice, rats, and squirrels enable them to bite through the tough shells that cover seeds and nuts. The incisors of a beaver are especially large and strong, an adaptation that enables these animals to chew wood for building dams and dens.
3. The hoofed mammals make up a large and highly diverse group of mammals. The hoofs of these animals are actually modified toes. They are very strong and are covered with a thick layer of homlike material that is similar to your fingernails. Walking on their toes gives these animals an advantage when escaping predators, because hoofs allow them to run very fast.