What do Marsupials, Primates, Rodents, Whales, and humans have in common? They are all mammals. Hi, I'm Aubrey for About.com. Today I'm going to share a few distinctive characteristics of mammals, using information from animals.about.com.Mammals are vertebrates that have many varied adaptations, allowing them to survive in a diverse habitats. The majority of mammals are warm-blooded. They breath air. They give birth to live babies, they nurse their young with milk produced from their mammary glands.Let's take a closer look at a few of the traits common among mammals.Warm-blooded: All mammals are endothermic or warm-blooded. This simply means, regardless of the temperature around them, mammals generally regulate a consistent body temperature.Nursing: Mammals have mammary glands which they use to produce milk and nurse their young. The milk sustains their young with the nutrients that help them survive and grow.Single Lower Jaw: Mammals have a lower jaw, or dentary, that is comprised of one bone. It attaches to the skull and supports the bottom teeth. Other vertebrates have multiple lower jaw bones.Specialized Teeth & Tooth: ReplacementMammals have teeth that are adapted to their specific diets. Felines and canines have sharp incisors that allow them to tear meat, for example.Four-Chambered Heart: Mammals have four-chambered hearts. A four-chambered heart separates deoxygenated and oxygenated blood. This helps mammals to regulate their body temperature. It also increases their metabolisms, helps to support their muscular activity, and increases their endurance.3 Middle Ear Bones: Another characteristic of mammals is that they have a distinctive arrangement of 3, tiny bones in their middle ear. These bones transmit sound to the inner ear where it is converted into electrical impulses that are received by the brain and interpreted as sound.Hair: Another distinctive characteristic of mammals is that they grow hair at some point in their lives at least somewhere on their bodies. The hair can take many different forms, ranging from quills, to eye brows, eye lashes, fur and even whiskers.Thank you for watching, for more information on mammals or other animal groups, go to: education.about.com.