Metabolism & Thermal Environment (W8b) Flashcards

1
Q

On what basis is warm-blooded & cold-blooded defined?

A

Temperature.

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2
Q

Terms describing stability of the body temperature (Tb)? (2)

A

• Poikilotherms.
• Homeotherms.

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3
Q

Poikilotherm?

A

= organism that has a variable body temperature.

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4
Q

Homeotherm?

A

= organism that has a constant body temperature.

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5
Q

Poikilotherm attributes? (2)

A

• Variable Tb.
• Dependent on Te.

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6
Q

Homeotherm attributes? (2)

A

• Constant Tb.
• Independent of Te.

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7
Q

Terms describing metabolic response to Te? (2)

A

• Endothermy.
• Ectothermy.

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8
Q

Endothermy attributes? (3)

A

• MR changes with varying Te.
• Explained by Scholander-Irving model.
• Most endotherms are homeotherms.

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9
Q

Explain the Scholander-Irving model?

A
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10
Q

Thermoneutral zone attributes? (3)

A

• Endotherms don’t have to adjust MR.
• Minimum MR needed to survive (BMR).
• Have Lct & Uct.

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11
Q

Sections of Scholander-Irving model? (3)

A

• Heat production section.
• Thermoneutral zone.
• Heat dissipation section.

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12
Q

Heat production section attributes? (4)

A

• At Te increases, MR decreases.
• Negative relationship between Te & MR.
• Shivering occurs.
• Endotherms increase MR in order to increase heat production against low Te.

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13
Q

Heat dissipation attributes? (4)

A

• As Te increases, MR increases.
• Positive relationship between Te & MR.
• Panting (in dogs) & sweating.
• Endotherms increase MR in order to increase heat loss against high Te.

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14
Q

Ectothermy attributes? (4)

A

• MR increases with Te.
• Shapes of MR vs Te graphs vary among ectotherms.
• Body heat is from the environment.
• Most ectotherms are poikilotherms.

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15
Q

Explain graph with both endothermic & ectothermic graphs?

A

Shows that endotherms & ectotherms have different metabolic rate scales as ectotherms tend to “go with the flow” while endotherms tend to “fight the system” in different situations, i.e., at T(fridge), T(room) & Tb.

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16
Q

Components of graph with both endotherms & ectotherms? (3)

A

• T(fridge).
• T(room).
• Tb.

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17
Q

Endotherms at T(fridge)?

A

Increase MR to increase heat production.

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18
Q

Ectotherms at T(fridge)?

A

Lower MR to adjust to low Te.

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19
Q

Endotherms at T(room)?

A

No adjustments of MR to Te.

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20
Q

Ectotherms at T(room)?

A

Increase MR to adjust to increasing Te.

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21
Q

Endotherms at Tb?

A

Increase MR to increase heat loss in increasing Te.

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22
Q

Ectotherms at Tb?

A

Increase MR to increasing Tb.

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23
Q

Costs of living for endotherms? (2)

A

• Require more food to sustain life.
• Higher costs than ectotherms.

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24
Q

Costs of living for ectotherms? (3)

A

• Have proportionally low maximum MR & thus can’t perform at the same high levels as endotherms.

• Require less food to sustain life.
• Lower costs than endotherms.

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25
Q

Organisms to explain in Classification slide? (5)

A

• Naked mole rats.
• A few marine fish (tuna).
• Some small birds (hummingbirds).
• Bees & some other insects.
• Snakes, amphibians… (brooding pythons).

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26
Q

Naked mole rats attributes in Classification slide? (2)

A

• Can become poikilothermic/ectothermic when on their own due to them having thin & furless skin underground.

• Can also be homeothermic/endothermic when in the company of other mole rats (cuddle up together).

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27
Q

Pro of endothermy?

A

Successful as they have maximized performance.

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28
Q

Pro of ectothermy?

A

Successful as they have maximized efficiency of energy use.

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29
Q

Con of ectothermy?

A

Have a proportionally low maximum MR & thus can’t perform at the same high levels as endotherms.

30
Q

A few marine fish (tuna) attribute in Classification slide?

A

Tend to be homeothermic/endothermic compared to most marine fish which are ectotherms.

31
Q

Some small birds (hummingbirds) attribute in Classification slide?

A

Tend to slightly lean towards poikilothermy when they undergo torpor several times during the day even though they are endothermic to limit energy use.

32
Q

Bees attribute in Classification slide?

A

Are homeothermic/endothermic but may slightly lean towards poikilothermy if environmental conditions compel them to.

33
Q

Snakes, amphibians…(brooding python) attribute in Classification slide?

A

Although snakes, amphibians, etc are ectotherms & poikilothermic an exception is seen in brooding pythons which become homeothermic/endothermic when tending to their eggs (only during this period).

34
Q

Thermoregulation?

A

= regulation of body temperature.

35
Q

Thermoregulation types? (2)

A

• Autonomic thermoregulation.
• Behavioural thermoregulation.

36
Q

Autonomic thermoregulation?

A

= thermoregulation that involves the afferent nervous system (autonomic nervous system).

37
Q

Hypothalamus?

A

= central control of body temperature.

38
Q

Hypothalamus attributes? (3)

A

• Thermo-sensitive.
• Integrates inputs from afferent nerves.
• Uses a dual threshold system to thermoregulate.

39
Q

Explain the 1st graph?

A

Shows that to trigger cooling responses the hypothalamus temperature begins with a minimum threshold temperature (Tset) & increases after this has been reached with the firing rate of neuron increase.

40
Q

Explain the 2nd graph?

A

Shows that to trigger warming responses the hypothalamus temperature starts off low with increasing firing rates of neurons then decreases to a Tset.

41
Q

Set point range (Tset)?

A

= temperature range between which body temperature is maintained for an organism’s optimal performance.

42
Q

Explain heating & cooling in ectotherms? (2)

A

• Ectotherms attempt to keep Tb near Tset to either minimize or maximize heat exchange.

• So in order to determine whether an ectotherm will minimize or maximize heat exchange, always check what will get Tb near to Tset & in what environment (hot or cold).

43
Q

Autonomic thermoregulation functions/attributes? (2)

A

• Controls the circulatory system.
• Controls metabolic heat generation (particularly in endotherms).

44
Q

Egs of autonomic thermoregulation? (3)

A

• Sweating.
• Piloerection.
• Metabolic thermogenesis.

45
Q

Circulatory system?

A

= involves the vasomotor control of peripheral blood flow.

46
Q

Circulatory system vasomotor control “components”? (2)

A

• Vasoconstriction.
• Vasodilation.

47
Q

Effect of vasoconstriction?

A

Reduces heat loss to cold environment.

48
Q

Effect of vasodilation?

A

Increases heat loss to hot environment.

49
Q

Vasoconstriction is applied in which environment?

A

Cold environments.

50
Q

Vasodilation is applied in which environments?

A

Hot environments.

51
Q

Thermal windows?

A

= regions of an animal’s body surface that vary heat exchange in response to the environment.

52
Q

Egs of thermal windows? (3)

A

• Large ears of elephants.
• Ears of hares & rabbits.
• Beaks of some birds (Toco Toucan).

53
Q

Egs of evaporative cooling? (2)

A

• Sweating.
• Panting.

54
Q

Only way heat can be dissipated up a thermal gradient?

A

Via Evaporative cooling.

55
Q

Piloerection?

A

= elevation of hair follicles to trap heat.

56
Q

Piloerection attributes? (2)

A

• Increases the extent of “fluffing” of fur/feathers.
• Increases insulation.

57
Q

Piloerection is applied in which environments?

A

Cold environments.

58
Q

Metabolic thermogenesis types? (2)

A

• Non-shivering thermogenesis.
• Shivering thermogenesis.

59
Q

Non-shivering thermogenesis attributes? (2)

A

• Not associated with muscle activity.
• Occurs mainly in brown fat.

60
Q

Shivering thermogenesis?

A

= rhythmic oscillatory muscle contractions.

61
Q

Non-shivering thermogenesis is often seen in which organisms?

A

Babies of less than 6 months.

62
Q

Behavioural thermoregulation?

A

= diverse range of responses to adjust heat exchange with the environment.

63
Q

Endotherm?

A

= organism that adjusts its MR to maintain a stable Tb.

64
Q

Ectotherm?

A

= organism that attempts to keep Tb near Tset.

65
Q

Thermal window attributes? (3)

A

• Large surface area.
• Poor insulation.
• Rich vascular bed (High vascularization).

66
Q

Eg of Behavioural thermoregulation?

A

Basking in the sun.

67
Q

Explain behavioural thermoregulation in a lizard? (5)

A

● At sunrise as a lizard basks in the sun, its Tb increases and reaches its maximum.

● Once the maximum Tb is reached, the lizard shuttles between sun & shade to maintain the Tset.

● When the air temperature near the ground surface is at its highest, the lizard is mostly in the shade still maintaining Tset.

● As sunset approaches (less solar radiation) the lizard is in the sun getting as much heat as it can get.

● At sunset, the lizard returns to its burrow & its temperature decreases to the constant burrow’s temperature.

68
Q

Components of set point range? (2)

A

• Upper set point.
• Lower set point.

69
Q

Con of endothermy?

A

You have to constantly eat to regulate & maintain efficient metabolic function.

70
Q

What does the width of the TNZ depend on?

A

Small body mass animals = narrow/shorter TNZs.