Class Mammalia

Biology ~ Advanced Studies DOL 60 - 64

VI. Class MammaliaA. General characteristics

1. Hair on bodies2. Females have mammary glands

a. nourish young with milk3. Breathe air with lungs4. 4-chambered hearts5. Endothermic6. Tetrapods - 4 limbs7. Most are terrestrial, some aquatic8. Bilateral symmetry

B. Mammalian Evolution1. True mammals appeared in late Triassic,

220 million yrs agoa. flourished after dinosaur extinction

1) Cenozoic Era = “Age of Mammals”2. Mammalian fossils have lower jaws

connected to skull by a jointa. have complex teeth

Lower cheek teeth of the opossum-sized

Baioconodon denverensis from South Table

Mountain. Its teeth suggest a diet of plants,

or a mixture of plants and meat.

Skull and teeth of an earliest

Tertiary mammal named

Baioconodon denverensis,

found at South Table

Mountain in 1990. This

mammal was about the size of

today's North American

opossums.

C. Mammal Anatomy & Physiology1. Body temperature regulation

a. endothermic w/ high metabolism b. external hair insulates body c. subcutaneous layer conserves heat

1) layer of fat below dermis d. many can sweat to cool body

1) panting, rolling in mud helps those w/out sweat glands

2. Feeding a. require large amounts of food to keep up

metabolism b. herbivores, insectivores, carnivores,

omnivores, filter feeders, scavengers c. jaw & tooth structure determines feeding

habits1) specialized teeth incl. incisors, canines,

premolars & molarsa) incisors & canines – cut & tearb) premolars & molars – crush & grind

d. Diet helps determine length of digestive tract 1) longer in herbivores

a) may have special stomach chambers (rumens) to aid digestion of tough plant fibers

3. Respiration a. lungs throughout life

1) aquatic mammals must breathe air2) large lung capacity to stay underwater

b. diaphragm & chest muscles allow lungs to expand1) diaphragm separates chest from

abdomen

Diaphragm separates

thorax from abdomen

4. Excretion a. highly developed kidneys

1) combine urea, water, other wastes into urine for release from bodyb. digestive waste removal occurs in large

intestine & rectum

5. Response a. most highly developed animal brain

1) cerebrum = thinking, learning, senses2) cerebellum = muscle coordination3) medulla oblongata = involuntary

behaviors (ex: heart beat)

b. Highly developed sense organs 1) detect & respond to external stimuli 2) abilities differ w/ order

a) ex: smell & sight aid predatorsb) ex: bats are capable of echolocationc) color vision benefits diurnal animalsd) primates distinguish colors best

6. Chemical response a. endocrine glands secrete hormones to help

respond to stimuli b. travel through blood to organs they affect c. ex: adrenal glands → adrenaline,

ovaries → estrogen, testes → testosterone

7. Immunity a. developed to prevent & respond to

disease-causing pathogensb. skin = barrier to pathogen entry

c. white blood cells = produce antibodies & destroy invading cells

8. Movement a. skeletal structure aids movement

1) vertebrae flex sideways & vertically2) arms, legs are adapted for walking,

running, jumping, climbing, grasping b. shoulder & pelvic girdles support limbs &

assist their range of motion

9. Sexual reproduction a. internal fertilization

b. newborns feed on mother’s milk c. parents care for young

d. most are viviparous1) monotremes are oviparous

10. Mammalian Developmenta. monotremes = lay eggs

1) ex: spiny anteater, platypus2) cloaca present

b. marsupials = immature embryo is born, develops fully in mom’s pouch

1) ex: opossum, kangarooc. eutherians (placental mammals) = embryo fully

develops in mother’s uterus 1) ex: humans, dogs, cats

Opossum with

1-week old

babies

D. Orders of Eutherian Mammals1. Insectivora = feed on insects, may live

undergrounda. mole, shrew, hedgehog

2. Rodentia = teeth for gnawing that grow all of life

a. mice, rats, beavers, squirrels, hamsters, guinea pigs

1) largest placental mammal order

3. Lagomorpha = rabbits, hares and pikasa. hares – larger, faster, longer feet & ears, born w/ hair & vision, wilderb. rabbits – smaller, slower, smaller feet

& ears, born hairless & blind

4. Chiroptera = batsa. the only flying mammalsb. use echolaction to hunt

5. Xenarthra = small or no teeth, eat insectsa. anteaters, sloths, armadillos, pangolins

6. Proboscidea = long trunk, tusksa. African & Asian elephantsb. largest living land mammalsc. only living animals w/ trunks

7. Artiodactyla = hooves w/ even # of toes a. pigs, deer, antelope, sheep, cattle b. part of the ungulates (hoofed animals)

8. Perissodactyla = odd # of toes on hoovesa. horses, rhinos, tapirs, zebrasb. part of ungulates

9. Carnivora = meat eaters, intelligenta. bears, cats, dogs, skunks, ferretsb. many are more omnivorous

10. Pinnipedia = meat eaters, spend time on land & in water

a. walrus, seal, sea lion

11. Cetacea = aquatic, always in water a. whales, dolphins, porpoisesb. incl. largest living mammal

1) blue whale = 98 ft. long, 200 tons

12. Sirenia = aquatic, plant eatersa. manatees, dugongs

13. Primates = live on land, highly intelligent, have opposable thumbs, binocular vision

a. humans, monkeys, apes