Emerald Robinson: Hi, I'm Emerald Robinson, and in this What is video, we'll answer the question, What is a mammal?
Mammals are a group of warm-blooded animals that have hair or fur, and secrete milk to feed their young.
All mammals are classified in the Eukarya domain, since their cells have nuclei. They are in the class Mammalia in the Animal kingdom, and, because they have a backbone, are vertebrates. Mammals are the smallest group of vertebrates, with only about 5,000 identified species of mammals known to science.
All mammals grow hair or fur, even whales and other marine mammals. Mammals use hair to help regulate their body temperature, as camouflage, for protection, for sensing their environment, and for communication.
All female mammals have a specialized sweat gland called a mammary gland which produces milk through a process called lactation. This milk, rich in fat and protein for nourishment, also provides the young with immunity from bacteria and viruses.
Mammals are warm-blooded, or endothermic. This means that they keep a fairly constant body temperature by producing their own heat. A strong, four chambered heart, sweat glands in the skin, and lungs that house an efficient gas exchange system are all required to help keep this consistent warm body temperature.
Many mammals carry their children inside a uterus. The developing young get nutrients from the mother through a special organ called a placenta, and are born alive.
Although most mammals are placental, there are exceptions. Monotremes like the duck-billed platypus mammals lay shelled eggs. Marsupials like opossums, kangaroos, and koalas nourish and protect their tiny young in pouches.
Unfortunately, half of the total number of mammalian species are at decline species in decline due to pollution or destruction of habitat. Though scientists and conservationists are working day to day to protect these animals. Its estimated that 22% of all mammal species are threatened with extinction.