Mammalia

Mammalia, or mammals, are a class of endothermic vertebrates characterized by the presence of hair or fur, mammary glands, and a four-chambered heart.

The most defining characteristic is the presence of mammary glands, which produce milk to nourish their young. Mammals also have a unique jaw joint and three bones in the middle ear. The majority of mammals are viviparous, meaning they give birth to live young. They are incredibly adaptable and can be found in almost every habitat on Earth, from the coldest polar regions to the hottest deserts and deep oceans. The class includes a wide range of animals, from tiny shrews and bats to massive whales and elephants. Humans are also a part of this diverse and successful group of animals.