Features of mammals, external and internal.

The body structure of absolutely all mammals directly depends on the environment in which they live, on their lifestyle. Many body parts help mammals adapt to life in different conditions. For example, the large incisors of a beaver. With their help, the animal gnaws tree trunks, which helps it survive. The prehensile tails and limbs of the monkeys allow them to stay in the trees without much difficulty.
In almost all mammals, the body is covered with skin. Quite sturdy and flexible. Hair grows on the skin; in different species of animals, it differs in density and length.