Chapter 32.1 By: Rose, Ashley, Katelyn, and Tony Mammals Chapter 32.1 By: Rose, Ashley, Katelyn, and Tony

Characteristics All mammals are characterized by two features; hair and mammary glands. Mammary glands: gland in mammals that produces milk to nourish the young. Other characteristics that help identify mammals are their lower jaw, consisting of a large, teeth-bearing bone connected by a joint directly to the skull. Mammals all breath air, have four-chambered hearts, and are endotherms that generate their body heat internally.

Body Temperature Control Mammals are endotherms, which means their bodies generate heat internally. Mammals have a high metabolism that helps them generate body heat. They also use subcutaneous fat. Which is a layer of fat located beneath the skin, that helps conserve body heat. They use sweat glands to cool the body when the body becomes too hot.

What do they eat? A mammal eats nearly 10 times as much food as a reptile that’s the same size as it so that it can maintain homeostasis. Homeostasis: the process by which organisms maintain a relatively stable internal environment. Mammals can be classified as herbivores (eats plants), carnivores (eats meat), and omnivores (eats both plants and meats). A mammal’s digestive tract is specialized to break down and absorb the type of food it eats. Cows have a stomach chamber called a Rumen. This is where the newly swallowed plant food is stored and processed.

Respiration and Circulation All mammals use lungs to breath, which are controlled by two sets of muscles. When they breath they also use their diaphragm, which pulls the bottom of the chest cavity downward which increases its volume. Their circulatory system is divided into two different loops with a four chambered heart. The right side gets oxygen-poor blood and the left side releases oxygen-rich blood. The two separate loops transports materials very well.

Picture Example of Heart :

Excretion Mammals have highly developed kidneys that control the amount of body fluids that come in. Kidneys help maintain homeostasis by filtering urea from the blood, as well as by excreting excess water or retaining needed water. Because kidneys are so efficient at controlling the amount of water in the body, they enable mammals to live in many habitats.

Response Mammals have highly developed brains which consist of 3 parts: the cerebrum, the cerebellum, and the medulla oblongata. The cerebrum makes possible such complicated behaviors as thinking and learning. The cerebrum contains a well-developed outer layer called the cerebral cortex, which is the center of thinking and other complex behaviors. The cerebellum controls muscular coordination. The medulla oblongata regulates involuntary body functions, or those that are not under conscious control, such as breathing and heart rate.

Movement Mammals evolved many adaptations, such as the backbone, which flexes both vertically and side to side, to aid them in movement. The shoulder and pelvic girdles are flexible and permit both front and hind limbs to move in a variety of ways. Mammals also use variations in the limb bones and muscles to move about.

Reproduction Mammals reproduce by internal fertilization. Fertilization occurs when the male puts sperm inside the reproductive tract of the female. Once the babies are born, the parents take care of them for a long time to help ensure that the young mammals will survive and reproduce. The duration and intensity of parental care varies among different species.