Animal Energetics

Question 1

Metabolic Rates

Answer 1

• Overall rate of energy use can be measured as oxygen consumption
• This is affected by activity level, body size, body temp

Question 2

Metabolic rate increases with activity

Answer 2

• At the start of exercise, oxygen consumption rises and then levels off
• this creates an oxygen debt, rely on ATP to start exercise
• When exercise ends, oxygen consumption falls gradually to resting levels
• recovery metabolism, regenerates ATP lost in oxygen debt
• cells are resynthesizing ATP store; metabolizing lactic acid

Question 3

Metabolic rate increases with body size

Answer 3

• metabolism increases with m^3/4
• increase in mass does not result in a proportional metabolic rate increase
• dependent on resting rate (kcal/hr) and mass (g)

Question 4

metabolic rate linked with temperature

Answer 4

• Chemical reactions speed up or slow down with changing temperatures
• Animals have thermal strategies - combination of behavioral, biochemical and physiological responses

Question 5

Endotherm

Answer 5

• source of heat term
• generates internal heat to maintain body temp
• thermoneutral zone is a stable temp until needed to decrease
• metabolic rate increases due dissipate heat

Question 6

Ectotherm

Answer 6

• source of heat term
• environment determines body temp

Question 7

Homeotherm

Answer 7

• response to environmental temp change
• stable body temp, balance heat gain/loss
• humans

Question 8

Poikilotherm

Answer 8

• variable body temp
• fish, lizard

Question 9

Maintaining optimal body temp for endo and ectotherms

Answer 9

• orienting towards or away from the sun, or seeking shade
• controlling blood flow to the body surface

Question 10

Controlling blood flow for heat exchange

Answer 10

• Normal/cool temp - constriction of arterioles reduces blood flow to skin
• High body temp decreases constriction, blood directed to skin
• shunt below the skin allows blood to bypass the skin, maintaining warm temp
• in high heat, the shunt is constricted to get warm blood to the skin to remove the heat
• some animals loose heat from unexpected extremities, birds (specifically toucans) loose heat from highly vascularized bills

Question 11

Heat production: endotherms

Answer 11

• Shivering thermogenesis
  
  • skeletal muscles pull against each other
  • ATP converted to ADP
• Non-shivering thermogenesis
  
  • occurs in mammals and some birds
  • Brown adipose tissue (BAT), full of mitochondria which produces ATP, produces heat
• Blood flows out of BAT warmer because it is connected to vessels

Question 12

Heat conservation: endotherms

Answer 12

• Evolutionary adaptations
  
  • large body size
  • reduced extremities
• Insulation
  
  • fur and feathers
  • traps air (when dry)

Question 13

Avoiding overheating

Answer 13

• Evaporative cooling
  
  • direct contact with water
  • sweating or panting
• heat windows - rabbit ears (larger = more heat loss)
• survival is easier when the temperature is < the thermoneutral zone

Question 14

Endothermy v. Ectothermy

Answer 14

• Ectotherms benefit from lower metabolic rates
  
  • expend little on thermoregulation
  • invest in growth and reproduction
  • less time foraging
• the benefits are balanced by costs though
  
  • limited ability to regulated body temp
  • limits activity
  • limits geographic distribution
  • limited bursts of high activity

Question 15

Regulation

Answer 15

• usually at high temp metabolic rate decreases, and at low temps metabolic rate increases
• some instances at very high temps, metabolic rate may increase (panting
• negative feedback loop