Class: Mammalia. All mammals : Mammary glands Hair A middle ear with 3 bones A jaw that lets them...

Class: Mammalia

All mammals :Mammary glandsHairA middle ear with 3 bonesA jaw that lets them chew food

3 Main groups:

1. Monotremes – Mammals that lay eggs

Example: Platypus

2. Marsupials – Give birth to immature,underdeveloped live young.Grow to maturity insidea pouch called the marsupium

Only marsupial in the USA

Opossum babies in pouch

3. Eutherian mammals – Give live birth to liveyoung that have completed fetal development.

Body temperature control:• EndothermsHair, subcutaneous fat (under the skin) helpto conserve body fat.• Many have sweat glands that help to cool thebody during warm periods. Mammals without sweat glands will pant to get rid of excess heat.(Example of homeostasis)

Feeding:• High metabolic rate – must eat about 10xthe amount of food as a reptile of the samesize to maintain homeostasis.• Specialized teeth and jaws to eat different diets.

CarnivoreHerbivore

Piercing, cutting,Tearing. Works like blades

of scissors to crush and grind food

Flattened for grinding tough plants

Cutting, gnawing, grooming

Carnivores have a shorter digestive tract thanherbivores.Cows have a rumen where food is stored andprocessed.

• The teeth of whales have been replaced bystiffened plates called baleen.These strain out plankton from the water it takes in.

Respiration:• Use lungs

Circulation:• 4 Chambered heart

Excretion:• Well developed kidneys that extract

nitrogenous wastes from the blood to form urine.

Response:• Most highly developed brain of any animals.• Well developed sense of smell • Ears – 3 small bones in the middle ear.

• Well developed eyes – many have color-sensing Structures in their eyes.

Movement:• Many adaptations of limb bones and muscles

to allow mammals to run, walk, climb, burrow, hop, pounce, swing, fly, leap, swim.

Reproduction:

• Internal fertilization• Monotremes lay eggs outside the female’s bodyand nourishes that young with milk from mammaryglands.• Marsupials – give live birth to immature young,develop further in pouch and drink milk from mother.• Eutherian mammals – have placenta. Get nutrients and oxygen from mother, give off wastes during development• Have varied gestation periods (mouse = few weeks,Elephants = 22 months!)• Parental care of young (varies among different species)