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Class Mammalia

Class Mammalia. Chapter 28. Characteristics. Most covered with hair 4 chambered heart Young nourished with milk from mammary glands Internal fertilization; separate sexes Endothermic. Facts. Smallest = Kitti’s hognosed bat in Thailand weighs 1.5 g

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Class Mammalia

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  1. Class Mammalia Chapter 28

  2. Characteristics • Most covered with hair • 4 chambered heart • Young nourished with milk from mammary glands • Internal fertilization; separate sexes • Endothermic

  3. Facts • Smallest = Kitti’s hognosed bat in Thailand weighs 1.5 g • Largest = Blue whale weighing 130 metric tons • Only about 4800 species

  4. Structural and Functional Adaptations • Hair: • Hair is reduced in cetaceans (whales, dophins) to sensory bristles at snout • Made of keratin (protein), also makes up nails, claws, hooves, and feathers • 2 types: • Pelage- dense and soft under hair for insulation • Guard hair- coarse and longer hair for protection against wear and to provide coloration

  5. Hair • American beaver • 2nd largest rodent (Order Rodentia) • Waterproof pelage consisting of long, tough guard hairs overlying the thick, silky underhair • In other aquatic animals, guard hairs become wet and mat down, forming a protective blanket over the underhair

  6. Hair • Most have 2 annual molts, one in spring and one in fall • Summer coats are thinner than winter and in some cases, a different color • Coloration: to blend into natural surroundings • “Salt & pepper” • Spots • Stripes

  7. Hair • Hair has become modified to serve many purposes • Examples: bristles of hogs, spines of porcupines and vibrissae (whiskers) on the snouts of most mammals • Whiskers are really sensory hairs that provide a tactile sense to mammals-especially long in burrowing or nocturnal animals

  8. Spiny armor • Porcupines, hedgehogs, echidnas • When cornered, a porcupine will turns its back toward attacker and lashes out with its barbed tail • The lightly attached quills break off at the base when they enter the skin • Backward-pointed hooks on the tips, which help work into skin

  9. Horns and Antlers • True horns: hollow sheaths of keratinized epidermis that embrace a core of bone arising from the skull • Not shed • Not branched (although they may be curved) • Grow continuously • Found in both sexes • Seen in family Bovidae (sheep, cattle)

  10. Horns and Antlers • Antlers: • Seen in deer family Cervidae • Branched and composed of solid bone when mature • During spring growth, develop velvet (a highly vascular soft skin) • Except for caribou, only makes of the species produce antlers • When growth is complete (just before fall breeding season), blood vessels constrict and velvet is removed by rubbing against trees • Shed after breeding season

  11. Buck deer antlers • A- begin to grow in late spring due to hormones • B- bone grows very rapidly until halted by a rapid rise in testosterone production • C- the velvet dies and sloughs off • D-Testosterone levels peak during the fall breeding season • Antlers shed in January as testosterone levels subside

  12. Horns and Antlers • Horns of pronghorn antelope are similar to true horns except keratinized portion is forked and shed annually • Giraffe horns are similar to antlers but retains their integumentary covering and are not shed • Rhino horns-valued in China as an agent for reducing fever, and for treating heart, liver, and skin disease

  13. Glands • Mammals have the greatest variety of integumentary glands • Most fall into 4 types: • Sweat • Scent • Sebaceous • Mammary

  14. Glands • Sweat glands: • Tubular, highly coiled that occur over much of the body surface • Not present in other vertebrates • 2 kinds: • Eccrine-secrete watery fluid that if evaporated on the skin’s surface, cools the body • Apocrine-armpits, pubic areas, breasts, scrtoum and external auditory canals; milky fluid that dry on skin to form a film

  15. Glands • Scent glands: • Used for communication with members of the same species, for marking territories, for warning, and defense • Located behind eyes & on cheeks in woodchucks, on penis in beavers & muskrats, base of tail in wolves and foxes, anal region of skunks, minks, and weasels • During mating season, strong scents are released for attracting opposite sex

  16. Glands • Sebaceous glands: • Associated with hair follicles • Glands accumulate fat, die, and expel a greasy mixture called sebum into the hair follicle • Serves as a dressing to keep skin and hair pliable and glossy

  17. Glands • Mammary glands: • Occur on all females and in rudimentary form in males • Develop by thickening of the epidermis to form a milk line along each side of the abdomen in the embryo • Increase in size at maturity, becoming considerably larger during pregnancy

  18. Food and Feeding • Teeth reveal the life habit of a mammal • With exception (monotremes, anteaters, and certain whales), all mammals have teeth • Heterodont- perform specialized functions such as cutting, seizing, knawing, tearing, grinding, and chewing • 4 types: • Incisors-sharp edges for snipping or biting • Canines- for piercing • Premolars/Molars- crushing and grinding

  19. Food and Feeding • Mammals do not continuously replace their teeth throughout their lives • 2 sets of teeth • Deciduous, or milk, teeth: temporary teeth • Permanent set-when skull has reached a size that can hold a full set • Molars are never replaced

  20. Feeding specializations • 5 categories: • Herbivorous- feed on grasses and other vegetation • Browsers/grazers (deer, horses, cattle): Ungulates • Gnawers (rodents and rabbits) • House bacteria in gut to break down cellulose • Give food a second pass for additional fermenting and nutrient absorption • Insectivorous-feed on insects as well as small inverts • Teeth with points to puncture the exoskeleton of prey • Shrews, moles, anteaters, and most bats

  21. Feeding specializations 3. Omnivorous: use both plants and animals for food • Pigs, raccoons, many rodents, bears, and most primates 4. Ruminants: have a 4 chambered stomach • Cattle, bison, buffalo, goats, giraffes • Grasses pass down the esophagus to the rumen, where it is broken down by microorganisms and formed into small balls of cud

  22. Feeding specializations 5. Carnivorous: feed mainly on herbivores • Foxes, dogs, weasels, lions • Biting and piercing teeth with large claws

  23. Reproduction • Have a definite mating season, usually in winter or spring • Female fertility is restricted to a specific time during the estrous cycle • Estrus: period of heat, during ovulation of egg • Monoestrous-only a single estrus during breeding season ( dogs, foxes, and bats) • Polyestrus-recurrnence of estrus during breeding season (mice and squirrels)

  24. Lions breed at any season, but predominantly in spring and summer. 3 or 4 cubs are born after gestation of 100 days. Cubs go through an 18-24 month apprenticeship learning how to hunt.

  25. Reproduction • 3 different patterns: • Oviparous: egg laying (monotremes) • Viviparous: marsupials • Viviparous: placentals

  26. Opossums, 15 days old, fastened to teats in mother’s pouch When born after only 12 days of gestation, they are the size of honey bees Remain attached to nipples for 50-60 days

  27. Classification • Order Monotremata- egg laying (oviparous) • Duck billed platypus and echidna

  28. Classification • Marsupials • Opossums, koalas, wombats, wallabies, kangaroos

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