Therma Biology Slides

Question 1

Thermal Biology: How organisms obtain and

control heat for optimum protein function

Answer 1

Organisms can be:
Ectotherms: obtain heat from the environment

Endotherms: obtain heat from their own high metabolism
Poikilotherms: exhibit little physiological control of heat gain or loss
Homeotherms: have maximum physiological control of heat gain or loss
Heterotherms: do both endothermy and ectothermy at different times

Question 2

Ectotherms

Answer 2

Most organisms are poikilothermic ectotherms
Sessile ectotherms are restricted to regions with favorable temperatures
Motile ectotherms will seek out an eccritic temperature
ambient temp close to optimum
Some ectotherms will attempt behavioral homeothermy
e.g. shuttling behavior in lizards

Question 3

Some Ectotherms Physiologically

Adjust to Ambient Temperatures

Answer 3

Acclimation: adjustment of internal temperature optimum; change in
eccritic temperature fish
and amphibians are the fastest acclimators
Some control of blood flow to skin to lessen heat loss
Localized thermogenesis: specific tissues produce heat

Non homeothermic types include large fishes
Homeothermic Endotherms include the Birds and Mammals

Question 4

Features of Endotherms

Answer 4

Insulation
High metabolic rate for heat production
Optimal body shape to affect surface area heat gain/loss
via behavior or architecture
Allen’s Rule: mammals in cold regions have short
appendages
Relatively large body for optimal surface to volume ratio
Bergmann’s Rule: endotherms tend to be largest
where it is cold

Question 5

Internal adjustments of Homeothermic Endotherms

If too cold:

Answer 5

Increased overall metabolic rate
Increased metabolism of special heat generating tissue
e.g. brown fat or shivering muscles
Decreased blood flow to skin plus countercurrent exchange

Heat transfer from artery to
adjacent vein in limb; keeps
heat in trunk

Question 6

Large marine fishes have a Rete Mirabile:

Answer 6

countercurrent exchange network in axial muscles

Keeps body core temperature slightly above ambient

Question 7

Internal adjustments of Homeothermic Endotherms

Answer 7

If too hot:
Decrease in overall metabolism
Increased blood flow to skin
Promotion of evaporative cooling     
panting or sweating 
Sweating or panting requires increased metabolism of panting 
muscles or sweat glands

Question 8

cost and benefits of Endo vs exto

Answer 8

Cost Benefit

Endotherm Risk of starvation Maximum activity
and distribution
Ectotherm Limited activity Energy efficiency
and distribution