Within the animal kingdom, mammals hold a very distinct position. They are considered to be more advanced, being very different from others in the animal kingdom with the presence of the mammary glands. Mammals belong to the class of vertebrate animals. Though the distinguishing feature is the mammary glands, the mammals are also characterized by the presence of sweat glands, hair, middle ear bone which enables hearing and a region in the brain called neocortex.

From the time it evolved, the mammals have come a long way. Today there are about 5,400 species of mammals. All of them feed the young ones and nurture them till they are able to take care of themselves. The mammary glands produce milk and are used to feed the young.

The largest group of mammals is the placental mammals. They have the placenta which is used during the gestation period. The placenta aids in feeding the young one growing in the womb of the mother. At the end of the gestation period, they give birth to a live young one. However this is an exception in a class of mammals called monotremes. Monotremes lay eggs.

Most mammals are endothermic or warm blooded. This means that their body temperature remains the same irrespective of the outside temperature. Most mammals also have the neck bone or cervical vertebrae including the blue whales. They possess lungs which are used for breathing. Hair is a characteristic which is seen in most mammals. During evolution this feature probably helped because most mammals are endothermic and needed hair to keep them warm during the cold season. The cerebrum of the brain is larger than the rest of the brain indicating intelligence.

Lot of the characteristics that mammals’ posses can be seen is some others in the animal kingdom as well. What make them truly separate are only the mammary glands which form part of the sweat glands.