Mammals Chapter 32

What’s a mammal?

• hair• mammary glands• breathe air and have a diaphragm• 4 chamber heart/ double loop circulation• endotherms

Evolution

• -first mammals appeared 220 million years ago, very small creatures

• - stayed small until dinosaurs died out, then underwent a burst of adaptive radiation in Cenozoic era

Characteristics

• Body temp control- allows mammals to move at night and in dark

• -endotherms

• -sweat glands for cooling, dogs pant instead, pigs wallow in mud

• -subcutaneous fat- under skin, insulates

• -high metabolism to generate internal heat

Feeding • eats 10 times as much food as a reptile of same size• some whales are filter feeders• omnivores/carnivores/ herbivores• early mammals ate insects• stronger jaws to support teeth: molars, premolars,

canines, incisors• carnivores-short intestines, herbivores- long intestines• Cows and their relatives have a stomach chamber

called “rumen” that holds symbiotic bacteria that helps with digestion

Respiration

• breathe air using diaphragm and chest muscles/ribs

Wake up!!

Circulation

• 4 chamber/ double loop

Excretion

• kidneys- extract nitrogenous waste in the form of urea. Urea and other waste mixed with water to become urine. Urine moves to urinary bladder for storage. Kidneys retain sugars, salts, and other compounds. (urine test)

Response

• -“Most highly developed brains?” • -3 parts: cerebrum, cerebellum, medulla

oblongata• -cerebrum-complicated behaviors such as

thinking and learning• -cerebellum- muscular coordination• -medulla oblongata-involuntary controls such as

breathing and heart rate• -highly refined senses: bloodhounds’ sense of

smell, bats’ hearing, color vision,

Movement

• backbone that flexes in many dimensions

• shoulder and pelvic girdles

• run, walk, climb, burrow, hop, pounce, swing, fly, leap, swim, etc.

Reproduction • internal fertilization• Oviparous- “monotremes”- duck bill platypus and 2

species of spiny anteaters• Viviparous- 1) “marsupials”- young crawls into

pouch before full grown – 2) “placentals”- young develops full term in

uterus