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The Mammals. Fred Searcy Zoology. Mammals. Kitti’s Hognosed Bat of Thailand 1.5 g Blue Whale 130 metric tons Ubiquitous 4600 species Compared to 9000 birds 24,600 fish 800,000 insects. Evolution. Evolution. Synapsid ancestor Excellent fossilization and preservation

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the mammals

The Mammals

Fred Searcy

Zoology

mammals
Mammals
  • Kitti’s Hognosed Bat of Thailand 1.5 g
  • Blue Whale 130 metric tons
  • Ubiquitous
  • 4600 species
    • Compared to
      • 9000 birds
      • 24,600 fish
      • 800,000 insects
evolution4
Evolution
  • Synapsid ancestor
  • Excellent fossilization and preservation
  • Herbivorous and carnivorous pelycosaurs
  • Lead to carnivorous therapsids
  • Lead to cynodonts (faster metabolic rate)
    • Musculature of jaw muscles for stronger bite
    • Facilitated capture of prey and feeding
    • Turbinate bones in nasal cavity retain body heat by warming air prior to entry
    • Secondary bony palate to breather while eating (and nursing young to feed and breathe)
    • More upright posture
    • Muscular diaphragm for breathing
characteristics
Characteristics
  • Hair
  • Integument with sweat, scent, sebaceous and mammary glands
  • Skull with 2 occipital condyles; secondary palate; turbinate bones; middle ear with incus, malleus, stapes; 7 cervical vertebrate; pelvic bones fused
  • Diphyodont dentition (2 sets of teeth); lower jaw a single, large bone
  • Moveable eyelids; fleshy external ears
  • 4 chambered heart; persistent left aorta, non-nucleated erythrocytes
  • Lungs with alveoli; larynx, secondary palate to separate food passage from respiratory passage; muscular diaphragm
  • Metanephric kidneys with ureters into bladder
  • Highly developed brain with well developed cerebral cortex; 12 pairs cranial nerves
  • Endothermic and homeothermic
  • Devolution of cloaca (found only in monotremes and marsupials)
  • Separate sexes with specific organs for fertilization; male determines sex
  • Embryo in utero with placenta (except monotremes); fetal membranes: amnion, chorion, allantois
  • Young nourished by milk from mammary glands
integument its derivatives
Integument & Its Derivatives
  • 1st line of defense against
    • Infections
    • Toxins
    • Retards water loss
    • Cools body
    • Weatherproofing chemicals (keratin, cellulose)
  • Thicker where no hair
  • Epidermis, dermis
epidermis
Epidermis
  • Mostly stratified squamous epithelia
  • Large amounts of keratin
  • Sloughed off as new formed
  • Non-keratinized cells may contain melanin
dermis
Dermis
  • 0.6 to 3mm in thickness
  • Irregular connections with epidermis via papillae (papillary layer). Underneath lies the:
    • Dermal layer composed mostly of dense connective tissue (reticular layer)
slide9
Hair
  • Originates in epidermis
  • Two forms:
    • Pelage (underhair – soft, dense, insulation)
    • Guard hair (coarse, wear and tear, coloration)
  • Composed of dead keratinized epidermal cells
  • From an epidermal follicle
  • Three layers:
    • Medulla
    • Cortex – may contain pigments
    • Cuticle – keratinized scales
hair continued
Hair Continued
  • Eventually stops growing
  • Replaced with new hair
  • Periodic molts
    • Humans molt year round
    • Foxes once a year
    • Some may molt up to 3 times
    • White coats in winter an example of leukemism (not albinism)
  • Types:
    • Sensory hairs on snout (vibrissae – cat’s whiskers)
    • Quills of porcupine are hair
horns antlers
Horns & Antlers
  • True horns
    • arise from a core of bone from the skull
    • Enveloped in sheath of epidermis
    • Not shed
    • Cattle and sheep
  • Antlers
    • Shed after each breeding season
    • Outgrowths from skull
    • Temporarily covered in epidermis (velvet stage)
    • Deer, antelope, caribou (except for caribou, only males produce antlers
  • Rhino “horn” is actually fused hair
glands
Glands
  • Methods of classification
    • Mode of secretion
    • Method of discharge
    • Unicellular or multicellular
    • Structural geometry
mode of secretion
Mode of Secretion
  • Exocrine – secrete their product to an internal or external surface
  • Endocrine – secrete their product into blood stream and lymph system
  • Mixed – combination of both
method of discharge
Method of Discharge
  • Merocrine – release product through their membrane and cell remains intact
  • Apocrine – material released also includes a portion of the cell’s cytoplasm
  • Holocrine – results in the destruction of the cell when product is released
composition and structural geometry
Composition and Structural Geometry
  • Single cells
  • Multicelluar
    • Ductless
    • Ducted
      • Tubular
      • Alveolar (acinar)
      • Tubulalveolar
      • Saccular
      • Other variations
categories
Categories
  • Sweat glands
  • Scent glands
  • Sebaceous Glands
  • Mammary Glands
sweat glands
Sweat Glands
  • Tubular, coiled
  • Located all over body
  • Specific to mammals
  • Produce fluid (mostly water) to cool the body (evaporation)
scent glands
Scent Glands
  • Various functions
    • Communication
    • Marking territories
    • Warning
    • Defense
sebaceous glands
Sebaceous Glands
  • Sebum (fatty material)
    • Keeps skin and hair pliable and glossy
    • Associated with hair follicles
    • Holocrine type
    • Usually doesn’t sour or turn rancid
mammary glands
Mammary Glands
  • Origin in epidermis of embryo
  • Two milk lines form along abdomen
  • Mammaries develop along milk lines
  • 10 mammary glands in mammals (including humans)
food and feeding
Food and Feeding
  • Variety of strategies
    • Herbivorous
    • Carnivorous
    • Omnivorous
  • Variations of these strategies
    • Coprophagy (rabbits)
    • Insectivorous
    • Herbivorous
      • browsers,
      • Grazers
      • Gnawers
  • Diet tied to physical structure and metabolism of animal
teeth
Teeth
  • Heterodont Dentition – differentiated according to function
    • Incisors – cutting & biting
    • Canines - piercing
    • Premolars – shearing, crushing, grinding
    • Molars – shearing, crushing, grinding
  • Diphyodont Dentition (two sets)
    • Baby or deciduous
    • permanent
dental formulas
Dental Formulas
  • Provides numbers of specific teeth for upper and lower half of the jaw
body weight food consumption
Body Weight & Food Consumption
  • Smaller the animal, faster the metabolic rate, the more the food required
migration
Migration
  • Not all migrate
  • Few seasonal migrations
  • Most migrations center around home ranges
    • Based on food abundance
  • Longest are marine mammals
    • Gray whale 18,000 km (11,2500 miles) from Alaska to Baja California and back
flight echo location
Flight & Echo Location
  • Bat – only flying mammal
    • Nocturnal and crepuscular (active at twilight)
    • Echolocation
      • Pulses emited 5-10 millisecs
      • Modulated at beginning with high frequency of 100,000 hz then down to 30,000 hz (ultrasonic range)
reproduction
Reproduction
  • Majority have estrous cycles
    • Monestrous vs polyestrous
    • Old World monkeys and humans have menstrual cycles
estrous cycles29
Estrous Cycles

Source: University of Wyoming at http://www.uwyo.edu/wjm/repro/tab4-4.htm

reproductive patterns
Reproductive Patterns
  • Oviparous Mammals (Prototherians)
  • Viviparous Mammals with pouches (Metatherians)
  • Viviparous Mammals with Placenta (Eutherians)
prototherians the monotremes
Prototherians – The Monotremes
  • Gr monos = single, trema = hole)
  • Egg layers
    • Duck-billed platypus
    • Echidnas
  • After hatching, young feed on milk of mammary glands
  • No nipples
therians the marsupials
Therians – the Marsupials
  • Pouched animals who give live birth
  • Young crawl into pouch
    • 235 days in case of kangaroos
  • Not true placentals
    • Have an ephemeral choriovitelline placenta
  • While nursing, mother often becomes pregnant again
    • Undergo embryonic diapause where embryos don’t develop until first brood leave pouch
  • Not all have embryonic diapause – not all have pouches
  • O’possum is only North American marsupial – does have pouch
    • Birth occurs 13 days after fertilization
    • Young in pouch for 2-3 months
    • Remain on mother’s body for additional 1-3 months
eutherians the placental mammals
Eutherians – The Placental Mammals
  • Marsupials have prolonged lactation; placentals have prolonged gestation
  • Embryo remains in uterus and nourished until live birth in the placenta
    • From either choriovitelline placenta or a chorioallantoic placenta
growth
Growth
  • Some mammals are precocial
  • Human growth is slower than any other mammal
  • # of progeny tied to mortality rate – the higher the number of progeny, the higher the mortality rate
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