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Mammals Chapter 28. I. Diversity  Only 4600 living species but most highly differentiated of all animal groups  Many domesticated to use as food, clothing,

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Presentation on theme: "Mammals Chapter 28. I. Diversity  Only 4600 living species but most highly differentiated of all animal groups  Many domesticated to use as food, clothing,"— Presentation transcript:

1 Mammals Chapter 28

2 I. Diversity  Only 4600 living species but most highly differentiated of all animal groups  Many domesticated to use as food, clothing, pets, beasts of burden, and in research  Habitat destruction is the cause of 300 species and subspecies being listed as endangered

3 II. Origin A. Synapsids  First amniotes to radiate into fully terrestrial habitats  Pair of openings in skull roof  Over 150 million years small, hairless ectothermic ancestors evolved into today’s furry endotherms  Herbivorous and carnivorous pelycosaurs

4 B. Therapsids  Arose from carnivorous synapsid lineage  Only synapsid group to survive beyond Paleozoic  Efficient erect gait with limbs beneath body  Cerebellum expanded to coordinate more muscles  Most died out in Permian extinction

5 C. Cynodonts  Therapsid subgroup that survived into Mesozoic  Higher metabolic rate to support more active lifestyle  Skeletal changes improved flexibility, agility, and muscle attachment  Developed secondary palate that allowed animal to breathe while eating prey; important innovation that allowed later mammals to breathe while suckling

6 D. Diphyodonts  Early mammals evolved in Triassic, small and shrewlike and nocturnal  Diphyodonts means teeth replaced once with permanent teeth  Endothermic but cooler than placental mammals  Hair with sebaceous and sweat glands  Hatched from eggs and relied on mammary milk  Radiated in Eocene after extinction of many amniote groups at end of Cretaceous

7 III. General Characteristics  Hair; even in aquatic forms may be few but present  Mammary glands to nourish young  Most specialized placenta to feed embryo  More advanced nervous system

8 IV. Skin  Thick  Dermis much thicker than epidermis  Thin epidermis protected by hair

9 V. Hair A. Structure  Hair follicle sunk in dermis of skin  Cells divide in follicle; as they grow away from source of nourishment, they die, forming hair shaft  Made of protein keratin  Three layers: pith center surrounded by cortex of pigment, then outer cuticle made of scales

10 B. Function  Protection against wear or attack (quills)  Concealment—spots, stripes, salt-and- pepper disrupt coloration  Waterproofing  Buoyancy  Signaling & sensing--coarse long guard hairs and whiskers  Thermal insulation--dense soft underhair

11 Hair

12 C. Molting  Usually twice in spring and fall  Some have winter coat which is heavier and may be white for camouflage; condition called leukemism which also includes dark eyes, dark ear tips, noses, etc

13 VI. Horns & Antlers A. Horns  Found in ruminants such as sheep and cattle  Hollow sheaths of epidermis surrounding a core of bone from skull  Not shed or branched, but may be greatly curved  Found in both sexes and grow continuously

14 B. Antlers  Deer family, males only  When, mature composed of solid bone  Covered in spring by highly vascular skin called “velvet’  Before breeding velvet drops off; after breeding antlers drop off  New set bigger than last

15 VII. Glands A. Sweat  1. Eccrine  Watery fluid evaporates heat from surface of skin  Found in hairless areas  Absent in rodents, rabbits, and whales

16 2. Apocrine  Larger than eccrine and open onto hair follicle  Forms film on skin  Related to reproductive cycle  In humans, develop at puberty in armpits, groin, ear canals

17 B. Scent  Found in all mammals though vary in location  Used for communication, warning, defense, and marking territory  Stronger during breeding season to attract mates  Skunks, minks, and weasels have very strong glands near anus

18 C. Sebaceous  Associated with hair follicles but some open directly onto skin; all over body  Fats and oils that keep skin soft, and hair flexible and glossy

19 D. Mammary  Modified apocrine glands  Rudimentary in males; occur on all females  Swelling when pregnant or nursing  Humans, develop at puberty with fat; further development at pregnancy

20 VIII. Teeth A. General  Heterodont (diphodont) dentition— differentiation of teeth for cutting, seizing, gnawing etc  Structure reveals life habits of animals; some are specialists and others generalists  Primitive mammal arrangement—3 incisors, 1 canine, 4 premolars, 3 molars  1 baby set and 1 adult set of teeth; generally molars only appear in adult set

21 Primary Teeth

22 B. Types  Incisors—sharp edges for snipping, biting  Canines—piercing  Premolars—compressed crowns with 1-2 cusps for shearing, slicing  Molars—large bodies, variable cusp arrangements for crushing, grinding

23 IX.Feeding Specializations A. Insectivores  Shrews, moles, anteaters, bats  Short digestive tract because eat few plants  Other mammals may eat insects but not exclusively

24 B. Herbivores  Browsers, grazers-- horses, deer, antelope, cattle, sheep, goats, camelids; Gnawers– rabbits, rodents  Reduced or absent canines; molars broad and high crowned  Rodents have chisel-shaped incisors that growth throughout life  Long digestive tracts; ceca add additional absorptive area  Fermentation chambers in stomach to aid in digestion of cellulose  Ruminants 4-chambered stomachs; food regurgitated and passed back through  Rodents eat fecal pellets to add to fermentation  Some use size and defensive behaviors to avoid predation; others keen senses and escape behavior

25 C. Carnivores  Feed mainly on herbivores; some switch to fruits, berries when food scarce  Many specializations to kill prey; more intelligence, stealth, and cunning used  Short digestive tract  More leisure time because do not have to continuously graze  Humans have exterminated many carnivores from areas; led to more crop pests in these areas

26 D. Omnivores  Eat plant and animal tissue—pigs, raccoons, rats, bears, primates  Migration, hibernation, food caching used in temperate areas where food supplies become scarce during certain seasons

27 X. Metabolism  Smaller the animal, greater metabolic rate and more must eat per unit size  Small animals end up spending more time hunting and eating than larger animals  Small shrews weighing 2 g. must eat more than this each day; if deprived of food for a few hours will die  Mountain lions need to eat an average of 1 deer a week

28 XI. Migration  Most remain in a home range, but some migrate and most located in North America  Caribou migrate100- 700 miles; gray whales 11, 250 miles

29 XII. Flight  Bats fly; some mammals glide  All bats nocturnal so use echolacation to find food  Echolocation uses high frequency sounds in pulses that bounce off objects  Large ears help collect “echos and bat forms mental image of object  Some moths have coevolved to have ultrasonic detectors to avoid bats

30 XIII.Reproduction A. Cycles  Mating seasons timed to coincide with favorable time to rear young  Estrous Cycle—mating restricted to fertile period in females (estrous or heat) when ovulation occurs; 1 mating/year (monoestrous); multiple (polyestrous)  Sometimes blastocyst remains dormant for implantation until a more favorable season— delayed gestation  Menstrual Cycle—old world monkeys and humans; cycle terminated by menstruation when uterine lining is shed

31 B. Patterns  Egg-laying—montremes only; egg fertilization and formation similar to birds but eggs are leathery; laid once a year in burrow and incubated; young hatch and nursed from milk  Pouched—marsupials only; short gestation with early birth of embryos; mother usually immediately becomes pregnant with suckling young still in pouch but development of embryos arrested (embryonic diapause); long lactation period  Placental—long gestation, short lactation period; embryo in uterus nourished by placenta; humans slowest developing animal

32 Forms of Reproduction

33 XIV.Humans & Mammals A. Domestication  Dogs were probably first; derived from wolves  Cats from African wildcat  Subdued horses, oxen, reindeer, camels, elephants, and llamas  Wild versions of llamas and dromedary camels no longer exist  Traits have been modified through selective breeding

34 B. Pests  Rodents and rabbits major pests of crops; elimination of natural predators has heightened problem  Diseases such as Tularemia, Lyme disease, and Rocky Mountain spotted fever transmitted by ticks on animals such as rodents, dogs, and deer  Tapeworms and trachina worms transmitted by eating infected meat

35 XV.Human Evolution A. Evolutionary Groups  Primates—grasping fingers, flat fingernails, forward facing eyes; split into prosimians & simians  Prosimians—dental comb, more projecting face; lemurs, tarsiers, lorises  Simians—opposable thumb, some tool use, large cerebrum; split into monkeys and apes  Monkeys—Old World located in Africa & Asia, close set nostrils, advanced dentition (baboon, mandrill, colobus); New World located in South America, grasping tail  Apes--tailless  Hominids—bipedal, larger cranium, speech

36 Primates

37 B. First Hominids  Grasslands and drought appeared about 8 mya; thought to be selective pressure that pushed apes out of trees.  Ardipithecus ramidus —appears about 4.4 mya with combination of ape/hominid traits  Australopithecus afarensis —appears about 4 mya; short bipedal hominid; brain size and facial features similar to chimp  Australopithicus africanus —appears about 2.2 mya; maybe descendant of A. afarensis and ancestor to Homo

38 A. afarensis H. erectus H. habilis and A.africanus

39 C. Emergence of Homo  Found in Africa  Homo habilis —first fully erect hominid that used stone and bone tools; appeared 2 mya and disappeared 1.5 mya  Homo erectus – appeared 1.5 mya; larger head and height; spread throughout Africa, Europe, and Asia; complex culture;disappeared about 300,000 years ago

40 D. Homo sapiens  Homo erectus disappeared about 300,000 years ago  H. neanderthalensis —some consider it a subspecies; emerged about 130,000 years ago; proficient hunters and tool users; large nose, big brow ridges, sloping head; big bones; disappeared about 30,000 years ago  H. sapiens —appear about 100,000 years ago; more tool using culture; rounded head, finer features; current people today

41 H. Erectus and H. sapiens

42 Neanderthal Man

43 XIV. Class Mammalia

44 A. Order Monotremata  Egg laying mammals  Oviparous  Duck billed platypus, spiny anteater; Australia, New Guinea & Tasmania

45 B. Order Marsupiala  Viviparous  Pouched (marsupium)  Young nourished by yolk-sac placenta  Short gestation  Australia and North America  260 species

46 C. Order Insectivora  Insect eaters  Pointy snout  Live part of time underground  Shrews, hedgehogs, tenrecs, and moles  All over except Australia and New Zealand  419 species

47 D. Order Chiroptera  Flying with modified forelimbs with membrane between elongated fingers  Bats  Worldwide  925 species

48 E. Order Primates  Large cerebrum  Most arboreal  5 digits with flat nails on fore- and hindlimbs; fore- used for grasping  Prosimians, monkeys, apes, humans  Worldwide  223 species

49 F. Order Xenarthra  Toothless or simple peg teeth  Anteateaters, armadillos, sloths  South and Central America  29 species

50 G. Order Lagomorpha  Long constantly growing incisors  Additional pair of peglike incisors growing behind 1 st set  Herbivores  Hares, rabbits, pikas  Worldwide  80 species

51 H. Order Rodentia  2 pairs of incisors used for gnawing which also grow constantly  Extremely adaptable; fast reproduces  Comprise 40 % of all mammals  Squirrels, rats, mice, woodchucks, beavers, porcupines, gophers  1935 species

52 I. Order Cetacea  Forelimbs modified into broad flippers  Posterior limbs absent  Tail divided into flukes; dorsal fin sometimes present  Nostrils modified into blowhole on top  No hair except some hairs around mouth  Mammary glands only  Whales, dolphins, porpoises  78 species

53 J. Order Carnivora  Teeth modified for eating flesh  Dogs, cats, bears, weasels, seals  Worldwide except Australia  280 species

54 K. Order Proboscidea  Proboscis (long nose)  Elongated incisors forming tusks  Elephants  Asia and Africa  2 species

55 L. Order Perissodactyla  Odd-toed hoofed mammals (1 or 3)  Ungulate  Teeth adapted for chewing  Horses,asses, zebras, tapirs, rhinoceroses  18 species

56 M. Order Artiodactyla  Even-toed hoofed mammals (2 or 4)  Toe sheathed in hoof  Ruminants  Herbivorous  Swine, camels, deer, hippos, antelope, cattle, sheep, goats


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