Section 38.5 (Exam 3)

Question 1

How is metabolic rate measured?

Answer 1

consumption of O2 or production of CO2

Question 2

Describe the metabolic rate of endotherms in the thermoneutral zone.

Answer 2

Metabolic rate of endotherms is low and independent of temperature

Question 3

What is the basal metabolic rate (BMR)?

Answer 3

Metabolic rate of a resting animal at a temperature in the thermoneutral zone

Question 4

What is BMR correlated with?

Answer 4

body size and environmental temperature; larger animals have a higher BMR

Question 5

How does BMR per gram of tissue change with body size?

Answer 5

increases as animals get smaller

Question 6

Why does BMR per gram of tissue increase as animals get smaller?

Answer 6

The larger SA:V ratio means that smaller animals lose heat quicker, and need to increase their metabolic rate to maintain body temperature

Question 7

What is the effect of bigger animals having a smaller surface area to volume ratio?

Answer 7

They have less capacity to dissipate heat

Question 8

Why may large animals have evolved to have a lower BMR?

Answer 8

To prevent overheating, their lack of surface area makes it difficult to lose heat

Question 9

Why do larger animals have more metabolically inactive support tissue like bone and skin?

Answer 9

Because if their support tissue was too metabolically active, they would overheat

Question 10

An endotherm’s thermoneutral zone is bounded by critical temperatures. What is the meaning of these temperatures?

Answer 10

Beyond these bounds, temperature regulation would require metabolic energy expenditure

Question 11

How do endotherms respond to the cold?

Answer 11

increasing metabolic heat production to compensate for heat loss

Question 12

What are two examples of endotherms increasing metabolic heat production in response to the cold?

Answer 12

Shivering (when these muscles contract, ATP is converted to ADP, producing heat) increases muscle tone
These body movements also contribute to heat production

Thermogenin in brown fat breaking down fat and glucose to create heat

Question 13

What is brown fat?

Answer 13

A type of fat in mammals that produces heat

Brown fat has abundant mitochondria and blood supply

Question 14

What is the function of the protein thermogenin?

Answer 14

heat release without any ATP production in the cells by breaking down fat and glucose

Question 15

Where is brown fat found?

Answer 15

Newborn mammals
Hibernating mammals

Adult humans have some, and its metabolic activity is stimulated by cold exposure

Question 16

What type of adult humans have more or less brown fat?

Answer 16

Obese people tend to have less brown fat than lean people

Question 17

What are 4 endotherm adaptations to reduce heat loss (for cold climates)?

Answer 17

Smaller surface area-to-volume ratio, e.g., round body shapes and short appendages

Thermal insulation—fur, feathers, and short appendages

Ability to decrease blood flow to non insulated skin by constricting blood vessels

Countercurrent heat exchange in blood flow to appendages

Question 18

What are 4 endotherm adaptations for hot climates?

Answer 18

• Increased blood flow to the skin(heat loss), shade-seeking, decreasing activity levels
• Increased surface area for heat dissipation (e.g., jackrabbit ears)
• Large mammals have little or no insulating fur and seek water to wallow in—water has heat absorbing capacity
• Evaporation of water by sweating or panting to dissipate heat

Question 19

What problem can panting or sweating lead to in hot and arid climates?

Answer 19

water loss

Question 20

Why does the metabolic rate increase when the upper critical temperature is exceeded?

Answer 20

panting and sweating are active processes that generate heat

Question 21

What is the main thermoregulatory center in mammals?

Answer 21

hypothalamus

Question 22

What does cooling the hypothalamus cause?

Answer 22

restriction of skin blood vessels and increases in metabolic heat production

Question 23

What is hypothermia?

Answer 23

below-normal body temperature

Question 24

What can unregulated hypothermia be caused by?

Answer 24

starvation, extreme cold, illness, or anesthesia

Question 25

Many birds and mammals use regulated hypothermia to survive cold periods and food scarcity. What are two examples of regulated hypothermia?

Answer 25

Daily torpor and hibernation

Question 26

What is daily torpor?

Answer 26

Daily bouts of regulated hypothermia

Small endotherms such as hummingbirds lower body temperature and metabolic rate during inactive periods to conserve energy

Question 27

What is hibernation?

Answer 27

lasts for days or weeks; metabolic rate drops and body temperature falls close to ambient (even near freezing) temperatures