Class Mammalia. Biology ~ Advanced Studies

Transcription

1 Class Mammalia Biology ~ Advanced Studies DOL VI. Class Mammalia A. General characteristics 1. Hair on bodies 2. Females have mammary glands a. nourish young with milk 3. Breathe air with lungs 4. 4-chambered hearts 5. Endothermic 6. Tetrapods - 4 limbs 7. Most are terrestrial, some aquatic 8. Bilateral symmetry B. Mammalian Evolution 1. True mammals appeared in late Triassic, 220 million yrs ago a. flourished after dinosaur extinction 1) Cenozoic Era = Age of Mammals 2. Mammalian fossils have lower jaws connected to skull by a joint a. have complex teeth

2 Lower cheek teeth of the opossum-sized Skull and teeth of an earliest Baioconodon denverensis from South Table Tertiary mammal named Mountain. Its teeth suggest a diet of plants, Baioconodon denverensis, or a mixture of plants and meat. found at South Table Mountain in This mammal was about the size of today's North American opossums. 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 habits 1) specialized teeth incl. incisors, canines, premolars & molars a) incisors & canines cut & tear b) premolars & molars crush & grind C. Mammal Anatomy & Physiology 1. 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

3 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 air 2) large lung capacity to stay underwater b. diaphragm & chest muscles allow lungs to expand 1) diaphragm separates chest from abdomen Diaphragm separates thorax from abdomen

4 4. Excretion a. highly developed kidneys 1) combine urea, water, other wastes into urine for release from body b. digestive waste removal occurs in large intestine & rectum 5. Response a. most highly developed animal brain 1) cerebrum = thinking, learning, senses 2) cerebellum = muscle coordination 3) 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 predators b) ex: bats are capable of echolocation c) color vision benefits diurnal animals d) primates distinguish colors best

5 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 8. Movement a. skeletal structure aids movement 1) vertebrae flex sideways & vertically 2) arms, legs are adapted for walking, running, jumping, climbing, grasping b. shoulder & pelvic girdles support limbs & assist their range of motion 7. Immunity a. developed to prevent & respond to disease-causing pathogens b. skin = barrier to pathogen entry c. white blood cells = produce antibodies & destroy invading cells 9. Sexual reproduction a. internal fertilization b. newborns feed on mother s milk c. parents care for young d. most are viviparous 1) monotremes are oviparous

6 10. Mammalian Development a. monotremes = lay eggs 1) ex: spiny anteater, platypus 2) cloaca present b. marsupials = immature embryo is born, develops fully in mom s pouch 1) ex: opossum, kangaroo c. 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 Mammals 1. Insectivora = feed on insects, may live underground a. mole, shrew, hedgehog

7 2. Rodentia = teeth for gnawing that grow all of life a. mice, rats, beavers, squirrels, hamsters, guinea pigs 1) largest placental mammal order 4. Chiroptera = bats a. the only flying mammals b. use echolaction to hunt 3. Lagomorpha = rabbits, hares and pikas a. hares larger, faster, longer feet & ears, born w/ hair & vision, wilder b. rabbits smaller, slower, smaller feet & ears, born hairless & blind 5. Xenarthra = small or no teeth, eat insects a. anteaters, sloths, armadillos, pangolins

8 6. Proboscidea = long trunk, tusks a. African & Asian elephants b. largest living land mammals c. 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 hooves a. horses, rhinos, tapirs, zebras b. part of ungulates

9 9. Carnivora = meat eaters, intelligent a. bears, cats, dogs, skunks, ferrets b. 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, porpoises b. incl. largest living mammal 1) blue whale = 98 ft. long, 200 tons

10 12. Sirenia = aquatic, plant eaters a. manatees, dugongs 13. Primates = live on land, highly intelligent, have opposable thumbs, binocular vision a. humans, monkeys, apes

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