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BIO3B: Physiology To Behaviour > W5: Vertebrate Physiology (Evolution Of Endothermy) [Dr. Matt] > Flashcards

W5: Vertebrate Physiology (Evolution Of Endothermy) [Dr. Matt] Flashcards

1
Q

Poikilotherm attributes? (2)

A
  • Variable body temperature (Tb).
  • Dependent on environmental temperature (Te).
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2
Q

Homeotherm attributes? (2)

A
  • Constant Tb.
  • Independent of Te.
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3
Q

How do Poikilotherms & Homeotherms differ, i.e., by what factor are they differentiated by?

A

Differentiated by their stability of body temperature.

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4
Q

Types of metabolic strategies? (2)

A
  • Ectothermy.
  • Endothermy.
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5
Q

Ectotherm attributes? (3)

A
  • MR increases with Te.
  • Most body heat from the environment.
  • Many are poikilothermic.
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6
Q

Egs of ectotherms? (4)

A
  • Fish.
  • Invertebrates.
  • Reptiles.
  • Amphibians.
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7
Q

Describe the graphs specific to Ectotherms regarding Te (x-axis) & MR (y-axis)? (4)

A

1) Positive linear graph.

2) Exponential increase.

3) Increase then stabilise then increase.

4) Hill-like increase.

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8
Q

Endotherm attributes? (4)

A
  • MR changes with Te.
  • Body heat produced internally.
  • Many are homeothermic.
  • Scholander-Irving model.
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9
Q

Egs of Endotherms? (2)

A
  • Birds.
  • Mammals.
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10
Q

Describe Endotherm graph? (5)

A
  • x-axis = Te.
  • y-axis = MR.
  • First: negative linear decrease = heat production.
  • Second: constant horizontal line = TNZ.
  • Third: positive linear increase = heat dissipation.
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11
Q

TNZ stands for?

A

Thermo-Neutral Zone.

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12
Q

TNZ?

A

=

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13
Q

Describe the graph of combined ectotherm & endotherm? (8)

A
  • x-axis = Te.
  • y-axis = MR.
  • Ectotherm at Tfridge: starts off with a low MR but slightly increases MR to match fridge temperature.
  • Endotherm at Tfridge: starts off with a very high MR at low Te but increases MR as Te increases to Tfridge.
  • Ectotherm at Troom: increases MR further to match an increased Te.
  • Endotherm at Troom: as Te increases it decreases MR, so when it gets to Troom MR is within the TNZ & is constant.
  • Ectotherm at Tb: MR continues to increase with increasing Te, so its Tb matches that of the Te.
  • Endotherm at Tb: MR increases at Tb, but overall MR changes with Te.
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14
Q

Cons of Endothermy/Why is endothermy extremely costly? (4)

A
  • At the same Tb, MR is much lower in ectotherms than in endotherms.
  • The differences in MR becomes greater as Tb decreases.
  • Same amount of food sustains ectotherms for much longer.
  • Ectotherms have a higher proportion of energy to growth & reproduction than endotherms.
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15
Q

Eg of Con 1 of Endothermy?

A

A reptile has 1/5 to 1/10 MR of a mammal.

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16
Q

Eg of Con 2 of Endothermy?

A

At low Te, MR of a reptile can be 1-2% of mammals.

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17
Q

Eg of Con 3 of Endothermy?

A

A 300g mammal needs 17x more food than a 300g reptile (same habitat/diet).

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18
Q

Pros/Benefits of Endothermy? (4)

A
  • Independent of Te.
  • Stable internal environments.
  • Higher maximum metabolic rates (= increased aerobic capacity).
  • Parental care.
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19
Q

Explain Pro 1 of Endothermy?

A

Independent of Te enables niche expansion.

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20
Q

Explain Pro 2 of Endothermy?

A

Stable internal environments, which maintain stable temperatures for enzyme activities.

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21
Q

Explain Pro 3 of Endothermy?

A

Higher maximum metabolic rates & increased aerobic capacity allows for locomotion & sustained activity.

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22
Q

Explain Pro 4 of Endothermy?

A

Parental care as endotherms are able to:

  • Optimise incubation.
  • Shorten gestation.
  • Have the ability to lactate.
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23
Q

Thing to note about parental care?

A

All placental mammals share a single placental ancestor that survived the K-Pg boundary & radiated into all placental mammals.

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24
Q

Evolution of Endothermy attributes? (3)

A
  • One of the most important developments in vertebrate evolution.
  • Evolved separately in mammals (synapsids) & birds (sauropsids) from ectothermic ancestors.
  • Recent developments are now allowing for the evaluation of hypotheses.
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25
Q

What are the recent developments that are now allowing for the evaluation of the hypotheses of the evolution of endothermy? (3)

A
  • Fossils from Jurassic & Cretaceous eras.
  • Methods for character-state reconstruction.
  • Biochemical techniques such as bone histology (growth rates) & C and O isotopes (clumping in minerals, Tb).
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26
Q

List the single-cause models? (4)

A
  • Aerobic capacity model.
  • Parental care model.
  • Niche expansion model.
  • Body miniaturisation model.
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27
Q

Aerobic capacity model attributes? (4)

A
  • NS favoured capacity for sustained activity & locomotion, which increased MMR.
  • Parallel increases in resting metabolic rates (RMR).
  • Can be tested to an extent in living mammals.
  • Bennett & Ruben.
28
Q

Explain Parallel increases in RMR? (2)

A
  • Became the basis for endothermic homeothermy.
  • By product of increased aerobic scope (MMR/RMR).
29
Q

Explain attribute 3 of Aerobic capacity model?

A

Can be tested using the relationship between metabolic rate at rest & during exercise.

30
Q

Egs of the relationship between MR at rest & during exercise? (3)

A
  • Deer mice.
  • Rodents.
  • Dark-eyed juncos.
31
Q

Basal metabolic rate (BMR)?

A

= maintenance of energy requirements of the organs & tissues.

32
Q

Maximum metabolic rate (MMR)?

A

= energy used by skeletal muscles to produce physical work.

33
Q

Explain Deer mice?

34
Q

Explain Rodent species?

35
Q

Explain Dark-eyed juncos?

36
Q

Parental care model attributes? (3)

A
  • NS for increases in RMR.
  • Suggested mechanism is mediated by thyroid hormones in the breeding season.
  • Links endothermy to fitness more directly.
37
Q

Results of natural selection for increases in RMR? (2)

A
  • Enhanced capacity for incubation,
  • Enhanced parental care/food provisioning, which increases growth & decreases juvenile mortality.
38
Q

Egs of Parental care model? (2)

A
  • Diamond pythons.
  • Burmese pythons.
  • Greater hedgehog tenrec.
39
Q

Explain Diamond pythons?

40
Q

Explain Burmese pythons?

41
Q

Explain Greater hedgehog tenrec?

42
Q

Aerobic capacity model VS Parental care model?

A
  • Aerobic capacity model
    = increase in MMR.
  • Parental care model
    = increase in RMR.
43
Q

Body miniaturisation model?

A

= retain homeothermy.

44
Q

Three-phase iterative model?

A

= a phenology of the evolution of endothermy in birds & mammals.

45
Q

Three-phase iterative model attributes? (2)

A
  • “Correlates” of endothermy.
  • Is able to explain the correlates of endothermy.
46
Q

Can a single-cause model explain all these correlates? (3)

A
  • Evolution of endothermy “began” about 250mya.
  • Numerous benefits of endothermy, perhaps each was a driver at different times.
  • Proposed a three-phase iterative model.
47
Q

Name the three phases of the Three-phase iterative model?

A
  • Phase 1.
  • Phase 2.
  • Phase 3.
48
Q

Phase 1 of model?

A

= parental care & land conquering.

49
Q

Phase 2?

A

= miniaturisation, thermoregulation & ecomorphological diversification.

50
Q

Phase 3?

A

= locomotion & climate adaptation.

51
Q

Phase 1 attributes? (3)

A
  • Permian-Triassic.
  • Therapsids & archosaurs.
  • Initial endothermic pulses (RMR).
52
Q

Therapsids & archosaurs attributes? (3)

A
  • Earliest ancestors of birds & mammals to show endothermy.
  • Commonalities.
  • Lacked insulation: thermoregulation via metabolic heat production unlikely.
53
Q

Commonalities between therapsids & archosaurs? (3)

A
  • Large body size.
  • Homeothermy.
  • Oviparity.
54
Q

Initial endothermic pulses (RMR) attributes? (2)

A
  • Parental care during egg brooding.
  • Likely benefits for aerobic capacity, which enabled colonising of dry land (niche expansion).
55
Q

Phase 2 attributes? (3)

A
  • Late Triassic-Jurassic.
  • Common, concurrent innovations.
  • Parental care & locomotion selected for concurrently.
56
Q

Common, concurrent innovations in Phase 2? (5)

A
  • Body size miniaturisation (retention of homeothermy).
  • Encephalisation (causes high metabolic demands of neuronal tissue).
  • Nocturnalism in mammals.
  • Enhanced body insulation (fur & feathers).
  • Ecomorphological diversification.
57
Q

Encephalisation?

A

= increased brain size.

58
Q

Phase 3 attributes? (3)

A
  • Cretaceous & Cenozoic.
  • Locomotory specialisations.
  • Climate adaptation during the late Cenozoic era.
59
Q

Locomotory specialisations attributes? (2)

A
  • Cursoriality in mammals (improves skeleton muscle performance).
  • Flapping flight in birds (causes increased demands of pectoral muscles).
60
Q

Climate adaption during the late Cenozoic era attributes? (2)

A
  • Global cooling phases = highly seasonal, high-latitude cold habitats.
  • Birds & mammals developed advanced thermoregulatory abilities to colonise.
61
Q

Summarise the diagram that concerns the Three-phase iterative model?

62
Q

Explain Lovegrove, 2017?

63
Q

Explain Farmer, 2000?

64
Q

Recap: Endothermy vs Ectothermy? (4)

A
  • Metabolic strategies in endotherms & ectotherms.
  • Endothermy is more costly than ectothermy.
  • Benefits of endothermy.
  • Evolution of endothermy from ectothermic ancestors.
65
Q

Recap: Single-cause models? (4)

A
  • Aerobic capacity model = increase in maximum metabolic rates.
  • Parental care model = increase in resting metabolic rates.
  • Niche expansion model.
  • Body miniaturisation model = retain homeothermy.
66
Q

Recap: Three-phase iterative model? (3)

A
  • Phase 1:
    = Permian-Triassic.
    = Parental care & locomotion capacity.
  • Phase 2:
    = Late Triassic-Jurassic.
    = Miniaturisation, thermoregulation (insulation), ecomorphological diversification.
  • Phase 3:
    = Cretaceous & Cenozoic.
    = Locomotory specialisations & climate adaptation.

BIO3B: Physiology To Behaviour (36 decks)

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