Mammals Ch. 12.3

Characteristics of Mammals All mammals are endothermic vertebrates that have a four chambered heart and skin covered with fur or hair. Most mammals are born alive, and every young mammal is fed with milk produced by organs in its mother’s body called mammary glands.

Obtaining Food Most mammals have teeth. Their teeth are adapted to make chewing food easier. They will have specialized teeth, meaning they do not look like each other. (molars, canines, etc.) Their teeth reflect their diet.

Obtaining O2 To release energy, food must combine with oxygen inside cells. Mammals breathe in and out with a muscle called a diaphragm. Only mammals have diaphragms. It is located right below the lungs and ribs. Like birds, we have a 4 chambered heart, and 2 loops to our circulatory system.

Homeostasis Like birds, mammals are endotherms. In addition, all mammals have fur or hair at some point in their lives that keep our temperature stable. The amount of fur or hair that covers a mammal's skin varies greatly. Each strand of fur or hair is composed of dead cells strengthened with the same material that makes feathers. Fur is the only adaptation that allows mammals to live in cold environments.

Movement In addition to adaptations for living in cold environments, mammals have adaptations that allow them to move in more ways that members of any other group. Most mammals walk or run on 4 limbs. But some have specialized movement. Kangaroos hop, orangutans swing, and “flying” squirrels can glide.

Nervous System A mammal’s nervous system coordinates its movements. Mammals have very complex nervous systems that allow them to learn and problem solve. We are one of the smartest groups on Earth. Huge eyes (part of nervous system) allow for sight at night. Smell is also a strong sense for mammals.

Diversity of Mammals There are three main groups of mammals: Monotremes Marsupials And Placental Mammals.

Monotremes Egg-laying mammals are called Monotremes. There are just three types of species. 2 spinney anteaters Lays eggs into a pouch in her belly (like a kangaroo) Duck-billed platypus Lays eggs in an underground nest

Marsupials Marsupials are mammals whose young are born at an early stage of development and then stay in a pouch on the mothers body. Koalas (Australia) Kangaroos (Australia) Opossums (America)

Marsupials Marsupials have a very short gestation period. Gestation period is the length between fertilization and birth. This is because the babies are “born” and then stay in the pouch until they are ready to come out. Staying in the pouch can take up to a year.

Placental Mammals Placental mammals develop the baby in the females stomach. Gestation for placental mammals is usually longer. Humans: 10 months Elephant: 21 months Mouse: 20 days

Caring for Young Whether a Monotremes, a marsupial, or a placental mammal, young mammals are usually quite helpless for a long time after being born. Many are born with their eyes sealed shut. Yong mammals usually stay with their mother or both parents for an extended period of time. They learn to walk, eat, and take care of themselves. This can take up to 20 years!

20? Years old… still needs his Momma… to make his superhero outfit…? Don’t be this guy. You should be taking care of yourself by 18 years old!