Mammals have characteristics in their cells and bodies that help classify them as mammals. All mammals are vertebrates, are endothermic, have hair on their bodies and produce milk in order to feed their young.
Mammals, unlike other animals, have hair, mammary glands and give birth to live young. Mammals have a regular body temperature and a four-chambered heart.
Humans are classified as mammals. Like other mammals, humans have body hair, suckle their young with milk produced from special glands on their chests, possess differentiated teeth and a four-chambered heart, and become pregnant rather than lay eggs.
Dogs are mammals. They are warm-blooded, which means they generate the heat of their own bodies. They have fur, and mother dogs feed their young with milk produced by their bodies.
The food eaten by mammals varies based on the type of mammal, the season and the environment. Mammals can be classified as carnivores, herbivores and omnivores. Carnivores primarily eat meat, herbivores primarily eat plants and omnivores eat both.
A fish is not a mammal. Mammals are animals that are warm-blooded, breathe air, possess hair and give birth to live young that they feed milk from mammary glands. Fish are cold-blooded, extract oxygen from water, have scales and lay eggs.
Mammals live in almost every habitat on Earth. This includes habitats in polar regions, oceans and tropical forests. The survival of mammals in almost all environments is largely a result of their various adaptations.