Mammals are a group of animals that share certain characteristics. Here are some key features of mammals:

• Breathing air: Mammals breathe air through lungs.

• Backbone: Mammals are vertebrates, which means they have a backbone.

• Hair: Mammals have hair or fur at some point during their life.

• Milk: Female mammals have glands that can produce milk to feed their young.

• Specialized teeth: Mammals have specialized teeth for cutting, grabbing and tearing, and crushing and grinding.

• Mobility: Mammals have a backbone with great leg mobility, making them an agile group of animals.

• Diversity: The class of Mammalia includes everything from mice to elephants, bats to whales, and humans.

Mammals are found in every major habitat around the world. Most mammals live on land, but some live in water, and others live in both land and water. Mammals eat a wide variety of foods, including other animals, plants, and both animals and plants.

There are more than 5,000 species of living mammals, and they are classified into two subclasses: Prototheria and Theria. The 19 current orders of placental mammals (Eutheria) include rodents, carnivores, herbivores, and primates, among others.

Examples of mammals include rats, cats, dogs, deer, monkeys, apes, bats, whales, dolphins, and humans.