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Trinity Term 1 > Mammalian structure and function: endothermy > Flashcards

Mammalian structure and function: endothermy Flashcards

1
Q

Describe Mammalia

A
  • group of animals with backbones, and bodies insulated by hair
  • nurse their infants with milk and share a unique jaw articulation
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2
Q

Give the characteristics of modern mammals

A
  • single bone in mandible
  • two occipital condyles
  • long bones with epiphyses (determinant growth)
  • four-chambered heart (with left aortic arch)
  • dentition (more on next lecture)
  • middle ear with three ossicles
  • epidermis with hair
  • viviparous (except monotremes)
  • mammary glands
  • endothermic (high metabolic rate)
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3
Q

Describe the smallest mammal

A
  • ~2g Kitti’s hog-nosed bat
  • Craseonycteris thonglongyai
  • bumblebee bat (smallest mammal)
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4
Q

Describe the largest mammal

A
  • blue whale
  • Balaenoptera musculus
  • 100 million times biggest
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5
Q

Describe long ranging mammals

A
  • African wild dog
  • Lycaon pictus
  • roam a home range of 2,500km2
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6
Q

Describe sedentary mammals

A
  • naked molerats
  • Heterocephalus glaber
  • never leave their burrow
  • up to 28 pups in one litter
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7
Q

Describe slow developing mammals

A
  • 22 months to gestate a calf
  • live up to 70 years
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8
Q

Describe short-lived developing mammals

A
  • male of the brown antechinus (Antechinus stuartii)
  • never sees a second season and dies before the first and only litter it has fathered
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9
Q

Subclass Protheria

A
  • Monotremes
  • Order Monotremata
  • 5 species in 3 genera and 2 families
  • Egg layers
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10
Q

Describe Subclass Theria

A
  • live bearers
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11
Q

Describe endothermy

A
  • cold environments or be active at night
  • high BMR (7-10 times higher than ectotherms)
  • high food requirements
  • high internal body temperature (28-42 °C)
  • constant internal body temperature (± 2 °C)
  • high aerobic metabolic scope (5-10 times higher)
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12
Q

Describe BMR

A

metabolic activity required for minimal resting lifestyle with no spontaneous activity, digestion and no stress (physical, thermal or psychological).

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13
Q

Heat exchanges with the environment IN

A
  • direct solar radiation
  • thermal radiation from atmosphere and socks
  • reflected light
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14
Q

Heat exchanges of endoderms OUT

A
  • thermal radiation to ground and sky
  • evaporation
  • conduction
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15
Q

Describe winter survival mechanisms

A

– avoidance (energy conservation)
- body size
- insulation
- appendages
- colouration
- migration (marine mammals)
- microclimate modification (communal nesting, elaborate nests)
- food hoarding
- reduction in activity
- reduction in body mass
- dormancy

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16
Q

Describe endotherm body size

A
  • allometry
  • Bergmann’s rule
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17
Q

allometry

A

as the size of an animal increases, volume and mass change more rapidly than area

18
Q

Bergmann’s rule (1987)

A

“on the whole…larger species further north and the smaller ones further south” (1987)

19
Q

Describe endotherm insulation

A
  • insulating values of pelts are proportion to length of hair
20
Q

Describe the Arctic fox

A
  • winter coat
  • lower critical Tb of -40 °C
  • Ta of -70°C
21
Q

Describe blubber

A
  • insulation in marine mammals
  • fat + collagene
  • up to 40% of body mass
22
Q

Describe behavioural thermoregulation of marine mammals

A
  • saving hind flippers (sweat glands)
  • panting
  • reduced activity
23
Q

Describe regional heterothermy

A
  • countercurrent heat exchange
  • circulation in limb of a mammal
24
Q

Describe thermoregulation in caribou

A
  • regulation of external body T
  • meshwork of veins and arteries keep T of limbs near that of environment so heat is not lost
25
Q

Allen’s rule (1877)

A
  • “…mammals (and birds) living in cold climates have shorter appendages than do close relatives in warmer climates”.
  • e.g. foxes and hares
26
Q

Describe microclimate modification

A
  • winter survival mechanisms
  • taiga vole: burrows, food cache chambers, nesting chambers
27
Q

Describe Gloger’s rule (1833)

A

“races in warm and humid areas are more heavily pigmented than those in cool and dry areas”

28
Q

Describe colouration in
Springbok

A
  • colouration and differential heating
  • white winter coat in Arctic mammals
29
Q

Describe the reduction of BMR for endotherms

A
  • reduction in activity (e.g. shrews)
  • Dehnel’s phenomenon
  • dormancy
  • torpour
  • hibernation
30
Q

Dehnel’s phenomenon

A
  • reduction in body mass
  • general overwinter mass decline (e.g. voles and shrews)
31
Q

Describe the dormancy

A
  • temporal abandonment of euthermia
  • reduced metabolic rate & lowering of body T
  • exhibited in seven orders: marsupials, insectivores, elephant shrews, bats, primates, carnivores
32
Q

Torpour

A
  • body T, heart rate & breathing are lowered
  • tolerable body T range 10-20 °C
  • daily torpor – response to an immediate energy emergency
33
Q

Describe winter torpour

A
  • profound dormancy
34
Q

List some mammals with particularly low BMRs

A
  • Marsupials, especially koalas
  • Tenrecs
  • Sloths
  • Echidnas
35
Q

Describe hibernation

A
  • animal remains at Tb of 2-5°C for weeks in winter
  • hedgehogs, ground squirrels, marmots (largest to undergo hypothermia)
36
Q

Describe adaptations to heat

A
  • majority nocturnal activity
  • avoid exposure to high temperatures
  • burrow during the day/patches of shades
37
Q

List some heat-adapted mammals

A
  • Fennec
  • Heath shield of Cape ground squirrel
38
Q

Describe thermoregulation in Dipodomys

A
  • burrowing during day
  • respiratory moisture
  • metabolic water derived from dry seeds
  • faeces dehydrated prior to defecation
  • urine concentration by countercurrent exchange in extra long loop of Henle
39
Q

Describe the relationship between evaporation and body mass

A
  • increases rapidly
  • assumes heat load is proportional to body surface
40
Q

Describe cranial thermoregulation

A
  • anatomic arrangement
    promotes cooling of the brain
  • arterial and (cool) venous vessels flow in intimate juxtaposition in the cavernous sinus
  • evaporation in nasal passages
41
Q

Describe resistance endothermy

A
  • increase in thermogenic capacity (BMR)
  • non-shivering thermogenesis
  • shivering
42
Q

Endothermy evolution

A
  • Nocturnalisation
    ▪ Aerobic capacity (Bennet and Ruben, 1979): higher metabolism
    ▪BUT larger need of food
    ▪ and increased metabolism on ectotherms - heat wasted if no insulation

Trinity Term 1 (38 decks)

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