KEY CHARACTERISTICS OF MAMMALS Zoology

CLASS MAMMALIA 4,400 species Mammals Classified into more than 20 orders, one of which includes humans. Live on every continent and in every ocean Some can fly Some are exclusively aquatic

ENDOTHERMY Like birds, mammals produce body heat internally through metabolism. Keep their body temperature high and nearly constant by controlling their metabolism and regulating the loss of heat through the body surface.

HAIR All mammals have hair. Insulates the body against heat loss. Most mammals (humans and whales are obvious exceptions) are covered with a thick coat of hair. Hair color also serves to camouflage a mammal from predators or a predator from being seen by its prey.

COMPLETELY DIVIDED HEART Like crocodiles and birds, mammals have a four- chambered heart with two completely separate ventricles. Separate ventricles –keep deoxygenated blood from diluting oxygenated blood –allow more efficient pumping of blood through both circuits of the circulatory system.

MILK Female mammals produce milk to feed their offspring. Milk is a nutritious fluid that contains fats, protein, and sugars. It is produced by the mammary glands, which are modified sweat glands located on the thorax or abdomen.

SINGLE JAWBONE The lower jaw of a reptile is composed of several bones, but the lower jaw of a mammal is composed of a single bone. This characteristic is particularly important for identifying mammalian fossils because many of the other characteristics of mammals, such as hair and mammary glands, do not fossilize or leave traces on the skeleton.

SPECIALIZED TEETH Teeth in different parts of a mammal’s jaws are modified for different functions. Front –biting, cutting, or seizing prey, Along the sides –crushing, grinding, or slicing

CLASSIFICATION OF MAMMALS Order MonotremataOrder Monotremata Lay eggs 2 examples: –Duckbill platypus (beaver x duck) –Echidna (anteater x porcupine) Live in –Australia –New Guinea

CLASSIFICATION OF MAMMALS Order MarsupialaOrder Marsupiala Babies mature in a pouch Examples: –Kangaroo –Opossum (only one in the U.S.) Live in –Australia –New Guinea –North America

CLASSIFICATION OF MAMMALS Placenta MammalsPlacenta Mammals Offspring are nourished inside the mother by a placenta – are then born live.

CLASSIFICATION OF MAMMALS Order Rodentia Two pairs of incisors grow continuously Examples: –Squirrels –Beavers –Mice –Rats

CLASSIFICATION OF MAMMALS Order Primates Have grasping hands, well-developed brains, forward-facing eyes Examples: –Monkeys –Apes –Humans

CLASSIFICATION OF MAMMALS Order Carnivora Claws, long canine teeth, and strong jaws – all for eating meat Examples: –Dogs –Cats –Bears –Sea lions

CLASSIFICATION OF MAMMALS Order Cetacea Fish-shaped bodies with flippers, lack hind limbs, and have a flat tail Examples: –Whales –Dolphins –Porpoises

CLASSIFICATION OF MAMMALS Order Proboscidea Long, boneless trunk Example: –Elephants