Principles of Animal Physiology, 3e (Moyes/Schulte)

Chapter 15 Thermal Physiology

1) Some fish have the ability to keep certain parts of their body warm by the use of retia.
Retia are
A) countercurrent heat exchangers.
B) found in locomotor muscles of certain species of large fish, such as tuna and lamnid
sharks.
C) special adipose cells that generate heat.
D) A and B
Answer: D
Page Ref: 635

2) At which of the following systems would environmental temperatures be the most variable?
A) hydrothermal vents
B) cave systems
C) bathypelagic systems of the world's oceans
D) alpine terrestrial systems
Answer: D
Page Ref: 636

3) The exchange of thermal energy between an animal and its environment can occur by
A) conduction and convection.
B) radiation.
C) evaporation.
D) all of the above
Answer: D
Page Ref: 637

4) Which one of the following has the highest thermal conductivity?

A) fat
B) air
C) water
D) rock
Answer: D
Page Ref: 638

5) Radiant heat from the body of an animal is described by

A) the Nernst equation.
B) the Stefan-Boltzmann equation.
C) Fourier's law.
D) Q10.
Answer: B
Page Ref: 638

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6) From among the following list of animals, which would lose heat at the fastest rate per unit
mass?
A) bear
B) mouse
C) rabbit
D) wolf
Answer: B
Page Ref: 639

7) According to Bergmann's and Allen's rules, brown bears living in temperate regions would
be __________ than those living in the arctic.
A) larger with shorter limbs
B) smaller with shorter limbs
C) larger with longer limbs
D) smaller with longer limbs
Answer: D
Page Ref: 639

8) In animals insulated with fur or feathers, __________ heat loss is reduced.

A) convective
B) conductive
C) radiant
D) more than one of the above
Answer: B
Page Ref: 640

9) Which of the following is most synonymous with the term ectotherm?

A) heterotherm
B) poikilotherm
C) endotherm
D) pseudotherm
Answer: B
Page Ref: 641

10) Which of the following animals would be classified as a homeotherm?

A) polar fish
B) Burmese python
C) marine iguana
D) more than one of the above
Answer: A
Page Ref: 641

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11) A __________ is an example of a temporal heterotherm.

A) python
B) swordfish
C) hummingbird
D) laminid shark
Answer: A
Page Ref: 642

12) Temporal heterothermy

A) benefits ectotherms by enabling them to reach the thermoneutral zone.
B) benefits ectotherms by allowing them to increase their metabolism, which speeds up
digestion, nutrient absorption, and biosynthesis.
C) benefits endotherms by enabling them to conserve energy when temperatures are
cold.
D) B and C
Answer: D
Page Ref: 642

13) A __________ heterotherm can retain heat in certain parts of its body.
A) temporal
B) spatial
C) positional
D) regional
Answer: D
Page Ref: 642

14) The __________ of a resting homeotherm is the range of ambient temperature where its
metabolic rate is minimal.
A) thermoneutral zone
B) preferred temperature
C) optimal temperature range
D) idealized thermal region
Answer: A
Page Ref: 643

15) If the body temperature of an endothermic homeotherm falls below the __________
temperature, the metabolic rate increases.
A) upper critical
B) lower critical
C) incipient upper lethal
D) incipient lower lethal
Answer: B
Page Ref: 643

16) A(n) __________ cannot tolerate a wide ambient temperature range.

A) ectotherm
B) poikilotherm

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 Principles of Animal Physiology, 3e (Moyes/Schulte)

C) eurytherm
D) stenotherm
Answer: D
Page Ref: 642

17) Of the major classes of macromolecules, only __________ are substantially affected by
temperature over the normal range experienced by animals.
A) proteins and lipids
B) carbohydrates
C) nucleic acids
D) all of the above
Answer: A
Page Ref: 645

18) In the process of homeoviscous adaptation, cells

A) alter rates of chemical reactions.
B) alter membrane fluidity.
C) alter isozyme ratios.
D) switch to alternative biochemical pathways.
Answer: B
Page Ref: 647

19) __________ is essentially the ratio between reaction rates of a process adjusted for a 10°C
temperature difference.
A) Q10
B) An Arrhenius plot
C) Km
D) Homeoviscous adaptation
Answer: A
Page Ref: 650

20) Membrane fluidity can be increased by __________ of the plasma membrane.

A) increasing the lengths of fatty acid chains
B) decreasing the number of double bonds in the fatty acids
C) decreasing the phosphatidylcholine to phosphatidylethanolamine ratio
D) decreasing the cholesterol content
Answer: C
Page Ref: 647

21) If the catalytic activity of an enzyme doubles with a biologically relevant 10°C increase in
temperature, then Q10 would be near the value of
A) 2.
B) 5.
C) 10.
D) 20.
Answer: A
Page Ref650 and Box 15.2

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 Principles of Animal Physiology, 3e (Moyes/Schulte)

22) The observation that a given enzyme retains its kinetic properties in different species
adapted to different temperature regimes is a phenomenon known as
A) Arrhenius effect.
B) Q10.
C) conservation of Km.
D) homozyme stability.
Answer: C
Page Ref649

23) Temperature-dependent remodeling may involve qualitative strategies such as

A) changes in mitochondrial density of muscle fibers.
B) hypertrophic growth of the heart.
C) seasonal differential expression of myosin isoforms.
D) variable levels of myoglobin concentrations.
Answer: C
Page Ref: 649

24) Organisms that thrive in the extreme cold are known as

A) psychrotrophs.
B) cryomorphs.
C) mesotrophs.
D) picnomorphs.
Answer: A
Page Ref: 651

25) Cold-adapted enzymes are more efficient at low temperatures than their warm-adapted
counterparts due to their
A) increased stability.
B) reduction in weak bonds that stabilize the three-dimensional structures.
C) higher proportion of hydrogen bonds.
D) more than one of the above
Answer: B
Page Ref: 652

26) __________ are able to survive without expressing functional myoglobin.

A) Coral reef damsel fish
B) Salmon
C) Polar bears and other arctic mammals
D) Antarctic fish
Answer: D
Page Ref: 652

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27) During times of thermal stress, heat shock proteins act as

A) chaperones to assist in the refolding of proteins.
B) transcriptional activators that ultimately lead to altered membrane lipids.
C) intercellular cytokine messengers that trigger adaptive responses in adjoining cells.
D) more than one of the above
Answer: A
Page Ref: 652

28) __________ have lost the ability to mount a heat shock response.
A) Antarctic fish
B) Fruit flies
C) Reindeer
D) Bluefin tuna
Answer: A
Page Ref: 652

29) Ice crystals forming within tissues are detrimental due to the
A) piercing of cell membranes.
B) generation of hyperosmotic stress.
C) loss of membrane fluidity.
D) all of the above
Answer: D
Page Ref: 653

30) In some freeze-tolerant animals, intracellular ice crystal formation is prevented by the
presence of
A) proton pumps.
B) antifreeze proteins.
C) heat shock proteins.
D) hydration elements.
Answer: B
Page Ref: 654

31) To date, __________ classes of antifreeze proteins have been identified.

A) 2
B) 3
C) 4
D) 5
Answer: C
Page Ref: 654

32) The antifreeze glycoproteins (AFGPs) share a common ancestry with

A) heat shock proteins.
B) pancreatic trypsinogen.
C) cytoskeletal actin.
D) Ca2+-dependent lectin.
Answer: B
Page Ref: 655

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33) The ability to produce endogenous body heat is known as

A) metabolic hyperthermy.
B) mesothermy.
C) thermogenesis.
D) oxidative metabolism.
Answer: C
Page Ref: 655

34) Shivering thermogenesis of many birds and mammals is associated with

A) white adipose tissue.
B) cardiac muscle tissue.
C) brown adipose tissue.
D) skeletal muscle tissue.
Answer: D
Page Ref: 657

35) Most thermogenic pathways of futile cycling involve cycling between the hydrolysis and
synthesis of
A) heat shock proteins.
B) fatty acids.
C) glucose-6-phosphate.
D) ATP.
Answer: D
Page Ref: 656

36) The mechanism by which bumblebees and certain moths generate preflight heat in thoracic
muscles involves
A) a metabolic futile cycle in carbohydrate metabolism
B) the simultaneous contraction of antagonistic flight muscles.
C) rapid wing movement that avoids lift.
D) all of the above
Answer: D
Page Ref: 657

37) Typically,an endotherm has a resting metabolic rate that is __________ higher than that of an
ectotherm of equivalent size.
A) 2-fold
B) 5-fold
C) 10-fold
D) 20-fold
Answer: C
Page Ref658

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38) BAT growth and thermogenesis are under the control of the
A) central nervous system.
B) sympathetic nervous system.
C) parasympathetic nervous system.
D) all of the above
Answer: B
Page Ref: 658

39) In brown adipose tissue, thermogenin inserts into the inner mitochondrial membrane and
serves to
A) uncouple oxidation from phosphorylation.
B) enhance the proton motive force.
C) eliminate two of the steps of electron transport.
D) more than one of the above
Answer: A
Page Ref: 658

40) In mice, the overexpression of a transcription factor PRDM16, results in an increase in

BAT, which appears to be important
A) as an uncoupling protein.
B) in decreasing mitochondrial respiration.
C) in protection against metabolic dysfunctions, such as obesity.
D) in ATP production.
Answer: C
Page Ref: 659 (Box 15.3)

41) The central thermostat of birds appears to reside in the

A) atrial wall.
B) adrenal cortex.
C) hypothalamus.
D) spinal cord.
Answer: D
Page Ref661

42) The reduction of heat loss via piloerection is a phenomenon commonly observed in
A) birds and mammals.
B) heterothermic fish.
C) large flying insects.
D) marine reptiles.
Answer: A
Page Ref: 661

43) What do the red muscles of tuna, the optical systems of billfish, and the legs of birds have in
common?
A) higher proportions of glycolytic muscle fibers
B) brown adipose tissue
C) countercurrent heat exchangers
D) more than one of the above

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Answer: C
Page Ref: 662-663

44) What is the primary role of salt as a constituent of sweat in evaporative cooling systems?
A) boiling point elevation
B) water balance
C) blood pressure regulation
D) electrolyte adjustment
Answer: A
Page Ref: 663

45) Many animals exhibit a daily hypometabolic state known as

A) estivation.
B) endothermy.
C) hibernation.
D) torpor.
Answer: D
Page Ref: 665

46) As compared to cooler regions, in the warmer regions of their habitats, reindeer are able to
reduce body temperature more effectively by
A) breathing through their nostrils.
B) increasing the rates of evaporative cooling from their ears.
C) switching to glycolysis in their brain stems.
D) panting and increasing the breathing frequency.
Answer: D
Page Ref: 664

47) __________ is the ability to generate and maintain elevated body temperatures.
Answer: Endothermy
Page Ref: 634

48) The independent routes to endothermy of birds and mammals can be explained by the
________________evolution of insulation.
Answer: convergent
Page Ref: 635

49) In biological systems, radiant heat exchange occurs through electromagnetic radiation in the
__________ range.
Answer: infrared
Page Ref: 637

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50) A __________ is an animal with a body temperature that varies in response to environmental
conditions.
Answer: poikilotherm
Page Ref: 641

51) The relatively constant temperature of the deep, internal region of a homeotherm is known
as the __________ temperature.
Answer: core
Page Ref: 642

52) A __________ heterotherm can retain heat in certain parts of the body.
Answer: regional
Page Ref: 642

53) The range of __________ is the difference between the incipient upper and lower lethal
temperatures.
Answer: tolerance
Page Ref: 643

54) Cells can remodel their membranes to preserve fluidity in a process known as __________
adaptation.
Answer: homeoviscous
Page Ref: 647

55) In the natural world, the complex response of an animal to seasonal changes in temperature
is known as __________.
Answer: acclimatization
Page Ref: 649

56) __________ are animals that thrive in the extreme cold.

Answer: Psychrotrophs
Page Ref: 651

57) Thermogenic pathways rely on __________ cycling in which chemical potential energy is
spent to generate heat.
Answer: futile
Page Ref: 656

58) The use of skeletal muscles to generate heat in birds and mammals is referred to as
__________. (two words)
Answer: shivering thermogenesis
Page Ref: 656

59) Typically located near the backs and shoulders, __________ tissue is particularly important
for thermogenesis in small mammals and newborns of larger mammals.
Answer: brown adipose
Page Ref: 658

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60) In animals, regulating how much blood flows into the vasculature is referred to as the
_____________ response.
Answer: vasomotor
Page Ref: 661

61) The raising of individual hairs in mammals to increase the insulation capacity of the fur is a
process known as __________.
Answer: piloerection
Page Ref: 661

62) __________ is a cooling behavior seen in birds and is characterized by rapid contraction and
relaxation of throat muscles.
Answer: Gular fluttering
Page Ref: 663

63) Name and briefly define the four routes by which heat is transferred between an animal and
its environment.
Answer: Conduction is the transfer of thermal energy from one region of an object or fluid to
another. Convection is the transfer of thermal energy between an object and a moving
external fluid. Radiation, usually in the form of infrared radiation, is either absorbed
by or emitted from an animal. Lastly, evaporation of water molecules from the surface
of an object absorbs thermal energy from the object during the phase change.
Page Ref: 637

64) Citing two examples, explain how an animal can alter its surface area to volume ratio to
reduce heat loss?
Answer: Individual organisms can curl their bodies to effectively reduce their surface area to
volume ratios. When a python rolls itself into a ball, the exposed surface area is
reduced as much as 85%. Groups of organisms can attain similar results by huddling:
Colonies of naked mole rats can maintain a constant body temperature by huddling,
whereas an individual will experience a significant loss of body heat if the ambient
temperature drops.
Page Ref: 639-640

65) What are the four mechanisms by which cells can remodel membranes to preserve fluidity?
Answer: The length of fatty acid chains of phospholipids can be shortened, reducing the
number of intermolecular bonds and viscosity. Intermolecular bonds between fatty
acid chains can also be reduced through bends in the chains by introducing double
bonds. Changing the polar heads of phospholipids can reduce the polar interactions
between the membrane and its environment: decreasing the phosphatidylcholine to
phosphatidylethanolamine ratio reduces the viscosity. And lastly, increasing the
concentration of cholesterol increases membrane fluidity at lower temperatures.
Page Ref: 645, 647

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66) How have selective pressures altered the expression of the LDH-B gene among populations
of killifish living along the eastern coast of North America?
Answer: Different alleles for the LDH-B gene exist in the killifish populations with different
levels of expression. One allele predominates in northern populations; another
predominates in southern populations. Due to mutations in the promoter, the
northern allele is expressed at twofold higher levels to compensate for the effects of
temperature on enzyme activity.
Page Ref: 649

67) Describe the molecular events of the heat shock response involving Hsp70.
Answer: When temperatures are elevated, usually by just a few degrees, the complex of heat
shock protein 70 (Hsp70) and heat shock factor (HSF) monomers in the cytoplasm
dissociate and Hsp70 binds to denatured proteins to act as chaperones. The HSF
monomers assemble into trimers, migrate into the nucleus, and bind to the promoters
of genes with heat shock elements. Transcription of Hsp70 increases, ultimately
resulting in the formation of more Hsp70/HSF complexes and cessation of the
transcriptional cascade.
Page Ref: 652

68) Describe the three preflight mechanisms of regional heterothermy observed in bumblebees
and large flying moths.
Answer: First, a metabolic futile cycle involving two opposing enzymes results in ATP
hydrolysis and heat production in the thorax. Second, two sets of antagonistic flight
muscles can engage in a pattern of simultaneous contractions to generate heat without
producing movement. And third, rapid wing movement generates heat, but by
controlling the frequency and orientation of the wings, no lift is produced.
Page Ref: 657

69) What is BAT and what role does it play in animal physiology?
Answer: BAT is brown adipose tissue found along the back and shoulder regions of
small mammals. BAT plays an important role in thermogenesis, because it
generates heat in newborn mammals and small mammals that live in cold
environments. BAT heat is referred to as nonshivering thermogenesis and a
key feature of BAT is the protein thermogenin. In the mitochondrial
membrane, thermogenin stimulates the rate of mitochondrial respiration and
heat production. Normally, mitochondria produce ATP, but thermogenin
uncouples mitochondria, dissipating the proton gradient so ATP cannot be
produced, but instead heat is generated.
Page Ref: 658

70) Describe the vasomotor response observed in the skin of animals.

Answer: Heat is lost as blood travels through the vasculature of the skin. The pattern of flow
can be altered by arteriovenous shunts known as arteriovenous anastomoses. Under
warm environmental conditions, the shunts are constricted, forcing blood near the
surface to enhance heat loss; when dilated, the blood travels deeper beneath the skin
and heat loss is reduced.
Page Ref: 661-662

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71) Describe how birds and mammals lose heat through ventilation.
Answer: Birds and mammals have respiratory surfaces that are well adapted for gas
exchange, so in these animals we see high vascularity, moist surfaces, and
high airflow. Cooling through ventilation exemplifies a fine balance between
respiratory demands and thermoregulation. To increase cooling, animals
increase ventilation frequency. When birds are trying to cool off, we observe
gular fluttering, which is characterized by rapid contraction and relaxation of
throat muscles. Mammals pant in order to cool off. Both gular fluttering and
panting have a cooling effect because rapid ventilation enhances heat loss
across respiratory surfaces by convection, rapid ventilation causes
evaporation of water via the tongue, and well-vascularized respiratory
surfaces of mammals and birds are kept moist with secretions.
Page Ref: 663

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