KEY CHARACTERISTICS KEY CHARACTERISTICS OF MAMMALSOF MAMMALS

Zoology

CLASS MAMMALIACLASS 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

ENDOTHERMYENDOTHERMY• 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.

HAIRHAIR• 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 HEARTCOMPLETELY 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.

MILKMILK• 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 JAWBONESINGLE 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 TEETHSPECIALIZED 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 MAMMALSCLASSIFICATION 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 MAMMALSCLASSIFICATION 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 MAMMALSCLASSIFICATION OF MAMMALS

• Placenta MammalsPlacenta Mammals

• Offspring are nourished inside the mother by a placenta – are then born live.

CLASSIFICATION OF MAMMALSCLASSIFICATION OF MAMMALS• Order Rodentia

• Two pairs of incisors grow continuously

• Examples:– Squirrels– Beavers– Mice– Rats

CLASSIFICATION OF MAMMALSCLASSIFICATION OF MAMMALS

• Order Primates

• Have grasping hands, well-developed brains, forward-facing eyes

• Examples: – Monkeys– Apes– Humans

CLASSIFICATION OF MAMMALSCLASSIFICATION OF MAMMALS• Order Carnivora

• Claws, long canine teeth, and strong jaws – all for eating meat

• Examples:– Dogs– Cats – Bears– Sea lions

CLASSIFICATION OF MAMMALSCLASSIFICATION OF MAMMALS

• Order Cetacea

• Fish-shaped bodies with flippers, lack hind limbs, and have a flat tail

• Examples:– Whales– Dolphins– Porpoises

CLASSIFICATION OF MAMMALSCLASSIFICATION OF MAMMALS

• Order Proboscidea

• Long, boneless trunk

• Example:– Elephants