Mammals

What’s a mammal? hair Mammary/milk glands (mamma = nipple) breathe air and have a diaphragm Most are Viviparous (except marsupials and monotremes) 4 chamber heart/ double loop circulation endotherms

3 Groups Placental Marsupial Monotreme About 90% of all mammals Over 4,000 species viviparous Marsupial Ovoviviparous About 334 species Have a pouch to nurse young Monotreme Only 5 living species oviparous

Evolution first mammals appeared 220 million years ago, very small creatures stayed small until dinosaurs died out, then underwent a burst of evolution and diversity First mammals were monotremes Marsupial family came next Placental is the most recent Very few monotremes and marsupials still exist – most evolved or died out

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

Circulation 4 chamber/ double loop

Excretion kidneys- extract nitrogenous waste from blood 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 3 groups are largely based on this