Lecture 18: Thermal Physiology Part 1

Question 1

A thermal niche is defined as:
a) The specific heat capacity of an environment.
b) The range of temperatures over which a species/population can persist.
c) The ability of an organism to regulate its internal temperature.
d) The constant temperatures of a specific habitat.

Answer 1

b)

Question 2

In high-altitude environments, animals face challenges due to:
a) High oxygen availability and moderate cold.
b) Low oxygen availability and extreme cold.
c) High heat variation during the day and low humidity.
d) Constant temperatures and abundant thermal refuges.

Answer 2

b)

Question 3

Conduction is best described as:
a) Transfer of heat through moving particles, such as wind.
b) Direct contact with motionless particles, such as soil.
c) Heat loss via water vapor, such as sweating.
d) Emission of energy from a warm object to cooler surroundings.

Answer 3

b)

Question 4

Which of the following is an example of radiant heat transfer?
a) A warm ground heating an animal resting on it.
b) Warm air circulating around a moving animal.
c) Heat from a bush radiating to a nearby animal.
d) Loss of heat through evaporation of sweat.

Answer 4

c)

Question 5

In animals, which of the following mechanisms is involved in heat loss via water vapor?
a) Radiation
b) Conduction
c) Convection
d) Evaporation

Answer 5

d) Evaporation

Question 6

. With respect to heat flow between animals and their environment, high conductance corresponds to:
a) High insulation and high resistance to heat loss.
b) High insulation and low resistance to heat loss.
c) Low insulation and high resistance to heat loss.
d) Low insulation and low resistance to heat loss.

Answer 6

d)

Question 7

With respect to heat flow between animals and their environments, low insulation corresponds to _______ heat retention and _______ heat loss.
a) High; high
b) High; low
c) Low; low
d) Low; high

Answer 7

d)

Question 8

A thick fur coat in mammals provides _______ thermal conductivity and _______ resistance to heat transfer.
a) High; low
b) High; high
c) Low; low
d) Low; high

Answer 8

d)

Question 9

In aquatic environments, animals with high surface area-to-volume ratios experience _______ rates of heat loss and _______ thermoregulatory efficiency.
a) High; high
b) High; low
c) Low; high
d) Low; low

Answer 9

b)

Question 10

Animals living in cold climates often have _______ conductance and _______ heat retention compared to those in warmer climates.
a) High; low
b) High; high
c) Low; low
d) Low; high

Answer 10

d)

Question 11

With respect to heat exchange, blubber in marine mammals reduces _______ and increases _______ to minimize heat loss.
a) Insulation; conductance
b) Conductance; insulation
c) Resistance; insulation
d) Conductance; resistance

Answer 11

b)

Question 12

Thin body structures in desert animals promote _______ heat dissipation and _______ resistance to heat flow.
a) High; high
b) High; low
c) Low; low
d) Low; high

Answer 12

b)

Question 13

Animals in tropical environments typically have _______ thermal insulation and _______ heat conductance to manage heat flow.
a) Low; high
b) Low; low
c) High; high
d) High; low

Answer 13

a)

Question 14

What does the Q10 value represent in physiological systems?
a) The constant temperature of a reaction
b) The rate of a chemical reaction at one temperature compared to 10 degrees lower
c) The maximum temperature at which enzymes function
d) The difference in temperature between two reactions

Answer 14

b)

Question 15

If a reaction has a Q10 of 1, this means:
a) The rate doubles every 10 degrees.
b) The rate stays constant regardless of temperature changes.
c) The rate triples every 10 degrees.
d) The rate decreases as temperature increases.

Answer 15

b)

Question 16

At 40°C, a reaction rate is 8. At 30°C (10°C lower), the reaction rate is 4. What is the Q10 value?
a) 1
b) 2
c) 3
d) 4

Answer 16

b) 2

Question 17

Which of the following is true regarding Q10 values in animals?
a) Most physiological systems have a Q10 between 1 and 2.
b) Most physiological systems have a Q10 between 2 and 3.
c) Q10 values remain constant across all systems.
d) A higher Q10 always indicates better thermal tolerance.

Answer 17

b) Most physiological systems have a Q10 between 2 and 3.

Question 18

Q10 is calculated as the _______ of a reaction at one temperature divided by the rate at a temperature that is _______ degrees lower.

Answer 18

rate; 10

Question 19

Animals maintain their body temperature within a reasonable range to ensure proper functioning of _______ and _______.

Answer 19

cells; physiological processes

Question 20

What is a thermal strategy?
a) A purely behavioral response to environmental temperature changes
b) A combination of behavioral, biochemical, and physiological responses to maintain body temperature
c) The ability to survive in extreme temperatures without adaptation
d) An organism’s method of increasing body heat production

Answer 20

Answer: b) A combination of behavioral, biochemical, and physiological responses to maintain body temperature

Question 21

Which of the following is the most important physiological parameter in an animal’s thermal physiology?
a) Surface area-to-volume ratio
b) Heat absorption rate
c) Body temperature (T_B)
d) Evaporative cooling capacity

Answer 21

Answer: c) Body temperature (T_B)

Question 22

What describes an ectotherm?
a) An animal that generates internal heat to maintain body temperature
b) An animal whose body temperature is determined by the environment
c) An animal with a stable body temperature
d) An animal with a variable body temperature

Answer 22

b) an animal whode body temp is determined by the environement

Question 23

Which term describes an animal with a stable body temperature?
a) Poikilotherm
b) Ectotherm
c) Endotherm
d) Homeotherm

Answer 23

Answer: d) Homeotherm

Question 24

Ectotherms rely on ________ to determine their body temperature, while endotherms generate ________ to maintain their body temperature.

Answer 24

Answer: the environment; internal heat

Question 25

Poikilotherms have ________ body temperature, while homeotherms maintain a ________ body temperature.

Answer 25

Answer: variable; stable

Question 26

Which of the following animals is both ectothermic and poikilothermic?
a) Human
b) Frog
c) Penguin
d) Polar bear

Answer 26

Answer: b) Frog

Question 27

Which of the following animals is an endothermic homeotherm?
a) Snake
b) Shark
c) Wolf
d) Goldfish

Answer 27

Answer: c) Wolf

Question 28

Which animal would best be classified as an ectothermic homeotherm?
a) Icefish
b) Naked mole rat
c) Kangaroo rat
d) Torpid bird

Answer 28

Answer: a) Icefish

Question 29

A lizard basking in the sun to regulate its body temperature would be classified as:
a) Endothermic poikilotherm
b) Ectothermic poikilotherm
c) Endothermic homeotherm
d) Ectothermic homeotherm

Answer 29

Answer: b) Ectothermic poikilotherm

Question 30

Which of the following animals is an endothermic poikilotherm?
a) Naked mole rat
b) Frog
c) Penguin
d) Large aquatic fish

Answer 30

Answer: a) Naked mole rat

Question 31

What is temporal heterothermy?
a) Body temperature varies by region within the body.
b) Body temperature changes over time, depending on conditions such as hibernation or activity.
c) The ability of an animal to maintain a constant body temperature.
d) A trait seen exclusively in ectotherms.

Answer 31

Answer: b) Body temperature changes over time, depending on conditions such as hibernation or activity.

Question 32

Which of the following is an example of temporal heterothermy?
a) Tuna retaining heat in red muscles.
b) Billfish using heater organs near the eyes.
c) Pythons raising body temperature after a large meal.
d) Insects maintaining constant body temperature during flight.

Answer 32

Answer: c) Pythons raising body temperature after a large meal.

Question 33

What is regional heterothermy?
a) Variations in body temperature across different parts of the body.
b) Changes in body temperature based on the time of day.
c) Maintaining constant body temperature throughout the body.
d) A characteristic unique to mammals.

Answer 33

a)

Question 34

Which of the following animals displays regional heterothermy?
a) Groundhog during hibernation.
b) Tuna retaining heat in red muscle.
c) Python after a large meal.
d) Human maintaining constant core temperature.

Answer 34

Answer: b) Tuna retaining heat in red muscle.

Question 35

An insect with a thorax temperature significantly higher than its abdomen temperature during flight is an example of:
a) Temporal heterothermy.
b) Regional heterothermy.
c) Homeothermy.
d) Ectothermy.

Answer 35

Answer: b) Regional heterothermy.

Question 36

Which of the following animals is likely to exhibit both poikilothermic and homeothermic traits?
a) Billfish with heater organs near the eyes.
b) Naked mole rat.
c) Squirrel in hibernation.
d) Tuna.

Answer 36

Answer: a) Billfish with heater organs near the eyes.

Question 37

Compare the physiological responses of mammals and ectotherms to changes in ambient temperature. Include mechanisms used by mammals to retain and dissipate heat and how these differ from ectotherms’ responses to environmental temperature changes.

Answer 37

Mammals (Endotherms):

Through internal metabolic processes, mammals maintain a relatively constant body temperature (~37°C) regardless of ambient temperature.
At low temperatures, they retain heat through:
Shivering thermogenesis: Muscle contractions generate heat.
Vasoconstriction: Narrowing of blood vessels reduces heat loss at the skin surface.
Insulation: Use of fur or fat layers (e.g., blubber) to trap heat.
At high temperatures, they dissipate heat through:
Sweating or panting: Evaporation of water from the skin or respiratory surfaces cools the body.
Vasodilation: Widening of blood vessels increases heat loss through the skin.

Ectotherms (e.g., Lizards):

Ectotherms rely on external temperatures to regulate body temperature.
As environmental temperature increases, their body temperature and metabolic rate also increase linearly.
They use behaviors, such as basking in the sun to warm up or seeking shade to cool down, rather than internal metabolic mechanisms.
Key Difference: Mammals actively regulate body temperature through physiological mechanisms, whereas ectotherms rely on environmental conditions and behavioral adjustments.

Question 38

Explain the differences between the responses of ectotherms and endotherms to changes in environmental temperature, as shown in the graph (Effects of ambient temp on body temp and metabolic rate).
Include an explanation of what happens in the thermal neutral zone for endotherms.

Answer 38

Ectotherms, such as lizards, rely entirely on the external environment to regulate their body temperature. In the graph, the blue line shows a direct relationship between environmental temperature and body temperature for ectotherms. As the environmental temperature increases, the body temperature of the ectotherm increases linearly. Similarly, the metabolic rate of the ectotherm also increases as the external temperature rises, because biochemical reactions become more efficient at higher temperatures.

Endotherms, such as mice, actively regulate their body temperature through internal metabolic processes. In the graph, the red line for the endotherm’s body temperature remains constant at approximately 37°C across a range of environmental temperatures. This ability to maintain a stable internal temperature, regardless of external conditions, is a hallmark of endotherms.

The metabolic rate of the endotherm (red line in the second graph) changes depending on the environmental temperature. At low environmental temperatures (below the thermal neutral zone), the metabolic rate is high because the mouse must generate heat to compensate for heat loss. Mechanisms such as shivering and increased metabolic activity help the mouse maintain its body temperature. At high environmental temperatures (above the thermal neutral zone), the metabolic rate also increases as the mouse actively dissipates heat through sweating or panting.

The thermal neutral zone (TNZ) is the range of environmental temperatures where an endotherm can maintain its body temperature with minimal metabolic effort. In this zone, heat loss and gain are balanced through passive processes, such as adjusting blood flow to the skin (vasodilation or vasoconstriction). The mouse does not need to expend extra energy for heat production or dissipation within this range.

In summary, ectotherms rely on the environment for temperature regulation and exhibit a linear relationship between body temperature, metabolic rate, and environmental temperature. In contrast, endotherms maintain a constant body temperature and regulate metabolic rate depending on whether they need to produce or dissipate heat, with minimal effort required within the thermal neutral zone.

Question 39

The environmental temperature is 25°C, a small lizard at 20°C will ______ the environment whereas a large dog at 37°C contains _________ heat than the lizard and will __________ the environment.

a) Lose heat to; more; lose heat to

b) Gain heat from; less; lose heat to

c) Gain heat from; more; lose heat to

d) Gain heat from; more; gain heat from

Answer 39

b)