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.
All mammals are vertebrates, which means that they have a spine and a spinal cord. They are all also endothermic, or warm-blooded. This allows them to regulate their own body temperature and live in a wide variety of climates on Earth. Mammals also have hair covering their bodies. The hair may be thick or thin depending on the mammal. Finally, all mammals produce milk to feed their young. This provides their babies with nutrition and allows mothers to stay with their babies and teach them important life skills they need to survive.