TEMPERATURE
350 oC
•Prokaryotes (bacteria, cyanobacteria)
span almost the entire range of Earth’s
Temperatures.
(662 F)
Deep sea
Hydrothermal
vents
•Vertebrates can tolerate only a small
portion of this range.
Few Species of Fish 44 oC
0 oC
(32 F)
Large Polar Mammals -60 oC
-89 oC
-128 F
Antarctica
Temperature
sets limits…
Environment
Physiology
Morphology
Behavior
performance
Darwinian fitness
Limits at the Cellular Level
Increased Temperature speeds up biochemical reactions…
…to a point
Biochemical structures (i.e.
Rate of reaction
enzymes) breakdown
Increasing T
… but limits are species-specific
Performance
Thermal performance curves:
specialist
generalist
Lower
lethal
temp
Upper
lethal
temp
Temperature
Temperature Outline
• Definitions:
– Heat Transfer
Example: Camels are cool!
– Physiological strategy: endo, ecto, etc.
– Temperature tolerance
• Extreme Temperature: HEAT
– Death?
– Avoidance strategies
– Tolerance strategies
• Extreme Temperature: COLD
– Death?
– Avoidance strategies
– Tolerance strategies
Temperature Basics
• Heat Transfer
• Thermal Strategies
• Thermal Tolerance
Heat transfer between
animals and environment
What’s the difference
between temperature & heat?
Measure of intensity of heat
(oC, oF, K)
Total KE
(calories or joules)
1 Calorie
= energy required to raise 1g of water 1o C
How many calories to heat 1g water from
25o C to 50o C?
= 25 calories
How many calories to heat 100g water from
25o C to 50o C?
= 2500 calories
Same temp,
Different heat content
Body temperature depends on
heat stored
Heat
production
(metabolism)
+
Heat in
-
Heat out
=
Heat stored
Gains > losses
4 Mechanisms of heat transfer
•
•
•
•
Conduction
Conduction + Convection
Radiation
Evaporation
“The Rules”
1. Heat flows from warmer
cooler
2. Greater temperature gradient, greater flux
3. Physical properties matter
1. Conduction
= heat transfer between bodies
in direct physical contact
• temperature differential
• area of contact
• conductivity of materials
2. Convection
= bulk movement of fluid
- Accelerates heat transfer between a solid and a fluid
Why?
CONDUCTION ONLY
Hot object
CONDUCTION AND
CONVECTION
Hot object
Boundary Layer is Removed
2. Convection
…All fluids come to rest at a solid surface
Air reaches full speed
Fluid speed
Air reaches full speed
= “boundary layer”
0
Distance from
solid surface
Thicker boundary layer, less
heat loss to conduction
Size of boundary layer is
influenced by:
• size (and shape) of animal
• surface roughness
• fluid speed (air, H2O)
3. Radiation
= transfer of heat between objects
without contact
Above absolute zero, all objects emit &
receive radiation
Short
wavelengths
Surface temperature is important:
-intensity
∞ T4
-hotter surface, shorter wavelengths
Area of radiative surface is, too
Long
wavelengths
4. Evaporation
=Extremely effective
method of losing heat
@ 35o C, it takes 580
cal to vaporize 1g of
H2O!
• exposure of moist surfaces
• moisture gradient
4. Evaporation
=Extremely effective
method of losing heat
@ 35o C, it takes 580
cal to vaporize 1g of
H2O!
• exposure of moist surfaces
• moisture gradient
Heat flux from different sources
is additive
Infrared thermal
radiation from
atmosphere
Infrared thermal
radiation from lizard
Direct sunlight
Heat
Production
(metabolism)
+
HEAT
IN
-
HEAT
OUT
=
Body
Temp
Evaporation
Conduction to air
+ Convection
by wind
Conduction from rock
Infrared thermal radiation from rock
Temperature Basics
• Heat Transfer
–
–
–
–
Conduction
Convection
Radiation
Evaporation
Example: CAMELS ARE COOL!!!
• Thermal Strategies
• Thermal Tolerance
CAMELS
• Ta (air temp) can exceed
50ºC (138 F)
• Normal mammalian body temp
= 37ºC
• How do they cope????
• BODY HEAT REGULATION
• WATER
• BRAIN FUNCTION
How do camels manage to
live in the desert heat?
1. Thick fur: prevents heat gain
How do camels manage to
live in the desert heat?
1. Thick fur: prevents heat gain
2. Body Heat can increase above 37ºC
 Body temp can increase to 41ºC (106ºF)
 Heat can be lost at night, don’t need to lose
water through evaporative cooling
 Saves 5 L of water a day
 Lowers temp difference between air and
camel
How do camels manage to
live in the desert heat?
1. Thick fur: prevents heat gain
2. Body Heat can increase above 37ºC
3. Fat stored in Hump, not under skin
Why Helpful???
During cool nights, heat loss is not restricted
CAMELS
• Ta (air temp) can exceed 50ºC (138
F)
• Normal mammalian body temp =
37ºC
• How do they cope????
• BODY HEAT REGULATION
– Thick Fur
– Body Heat to 41ºC
– Fat stored in hump
• WATER
• BRAIN FUNCTION
How do camels manage to
live in the desert heat?
1. Can go for 3-4 days without water
When they reach water, they can drink
up to 100L in 10 minutes
How do camels manage to
live in the desert heat?
1. Can go for 3-4 days without water
2. Minimize water loss…
 Concentrate Urine
 Camel does not sweat (until body temp above 41)
 The NOSE:
 Main place for evaporative cooling
Our nasal passages 10 cm2
Camel Nasal Passages 1000 cm2
Called ‘nasal turbinate’
Can open and close to save water
Nasal Membranes are HYGROSCOPIC (very cool)
CAMELS
•
•
•
Ta (air temp) can exceed 50ºC (138 F)
Normal mammalian body temp = 37ºC
How do they cope????
• BODY HEAT REGULATION
– Thick Fur
– Body Heat to 41ºC
– Fat stored in hump
• WATER
–
–
–
–
Can go 3-4 days without water
Concentrate urine 9-fold over plasma
Doesn’t sweat (mostly)
THE NOSE
• Huge surface area—used for evaporative cooling
• Can close nostrils to save water
• HYGROSCOPIC
• BRAIN FUNCTION
How do camels manage to live in
the desert heat?
Body Temp can increase 6C…
But Brain can’t function at that temp …?
THEY KEEP THEIR BRAIN COOL!
Rete mirabile
Arterial vessel
Venous vessel
“wonderful net”
= Counter Current
Exchange
Heat exchange
Rete mirabile
“wonderful net”
Evaporative
cooling
Rete mirabile
• brain
temperature
remains lower
CAMELS
•
•
•
•
BODY HEAT REGULATION
•
WATER
•
Ta (air temp) can exceed 50ºC (138 F)
Normal mammalian body temp = 37ºC
How do they cope????
– Thick Fur
– Body Heat to 41ºC
– Fat stored in hump
–
–
–
–
Can go 3-4 days without water
Concentrate urine 9-fold over plasma
Doesn’t sweat (mostly)
THE NOSE
• Huge surface area—used for evaporative cooling
• Can close nostrils to save water
• HYGROSCOPIC
BRAIN FUNCTION
– Rete Mirabile
• Allows for brain cooling in spite of very high body temp
Thermal Strategies
• Ectotherms: a body temperature principally
dependent on external heat sources
• Endotherms: a body temperature
principally dependent on internally generated
metabolic heat
• Homeotherms: body temperature kept
constant
• Poikilotherms: body temperature varies
MR
T
b
Ta
ENDOTHERMS
Some small birds
and mammals
Terrestrial Birds
and Mammals
Brooding
Python
POIKILOTHERMY
Freshwater
Fish
A few fish
Most Amphibians
and Reptiles
HOMEOTHERMY
Polar
Marine Fish
A few Amph
and Rept
Most
Marine Fish
ECTOTHERMS
MR
T
b
Shivering Python
http://www.flickr.com/photos/smacdonald/2520515097/
Ta
Temperature Basics
• Heat Transfer
–
–
–
–
Conduction
Convection
Radiation
Evaporation
Example: Camels are cool!!!
• Thermal Strategies
– Endotherm vs Ectotherm
– Homeothermy vs Poikilothermy
• Thermal Tolerance
Thermal performance curves:
Performance
Preferred Body Temp
Temperature
Thermal performance curves:
Performance
Preferred Body Temp
Temperature
Environmental Temperature shift?
ACCLIMITIZATION!!
Temperature Tolerance
• Acclimitization
– Biochemical
• Membrane dynamics
• Enzyme types and concentrations
• Heat Shock Proteins
• Behavioral
• Morphological
• Physiological
Will discuss in hot vs. cold
Membrane Dynamics
What are the kinks?
Polyunsaturated
Fatty Acid
(Omega 6)
Temperature also has major effects
on cell membrane fluidity
If you live in hot climate, what sort
of fatty acids should you have?
Species
If you live in cold climate, what sort
of fatty acids should you have?
Body Temperature
oC
Ratio of sat. to
unsat. fatty acids
in phospholipid
Arctic Sculpin
0
0.59
Goldfish
5
25
0.66
0.82
Desert Pupfish
34
0.99
Rat
37
1.22
(acclimated to 2 temps)
Cage Floor temperature
Normal Diet
Common Shingleback
Diet very high in unsaturated fats
Thermal performance curves:
Performance
Preferred Body Temp
Temperature
Environmental Temperature shift?
Increase PUFA in diet!
Enzymes
 isozymes
= different forms of
particular enzymes with
different temperature optima
4 different
forms of ATPase
Each with a separate
thermal performance
curve
Enzymes
 isozymes
Alligator lizard
Fence lizard
Desert Fringed Lizard
Desert Iguana
Heat Shock Proteins
 Under High Temperatures, Proteins unfold (denature)
How can you protect
Cells during protein denaturation?
“Heat Shock Proteins” protect against heat
damage
 = proteins synthesized in response to cellular stress
(including high temps)
 function as “molecular chaperones”
Heat increases
Protein denatures from Heat
HSP expression increases (more HSP)
HSP binds up denatured protein
Heat decreases
HSP lets go, protein can refold
Cataglyphis Ants
>50C on sand
45C in nest entrance
Cataglyphis spend 10-15 minutes
Other insects stop foraging
In the tunnel to the nest, making
heat shock proteins to protect their
cells while they are out on the desert
foraging
<30C inside nest
http://www.youtube.com/watch?v=w9KDM4C1kVg&feature=related
Temperature Acclimatization
• Biochemical
– Membrane dynamics
• Colder? Incoporate more PUFA
• Hotter? Use less PUFA
– Enzyme types and concentrations
• Colder or hotter? Change isozyme
Goldfish Swimming
Speed
Temperature Acclimatization
• Biochemical
– Membrane dynamics
• Colder? Incoporate more PUFA
• Hotter? Use less PUFA
– Enzyme types and concentrations
• Colder or hotter? Change isozyme
– Heat Shock Proteins
• Protect protein denaturation from killing cells
Temperature Basics
• Heat Transfer
–
–
–
–
Conduction
Convection
Radiation
Evaporation
Example: Camels are Cool!!!
• Thermal Strategies
– Endotherm vs Ectotherm
– Homeothermy vs Poikilothermy
• Thermal Tolerance
– Acclimatization of membranes and enzymes
Temperature Outline
• Definitions:
– Heat Transfer
Ex: Camels are Cool!!!
– Physiological strategy: endo, ecto, etc.
– Temperature tolerance
• Extreme Temperature: COLD
– Death?
– Avoidance strategies
– Tolerance strategies
• Extreme Temperature: HEAT
– Death?
– Avoidance strategies
– Tolerance strategies
COLD
• What causes death?
• Avoidance Strategies
• Tolerance Strategies
What causes cold death?
 Intracellular ice formation
- 0.5o C terrestrial, -1.7o C marine
 Chemical reaction rates drop
 CNS control, integration reduced
COLD
• What causes death?
– Intracellular ice
– Low enzymatic reactions
– CNS control
• Avoidance Strategies
• Tolerance Strategies
Avoidance
Hibernation/torpor
Avoidance
Significantly lowered Tb
Body Temperature
Hibernation/torpor
Daytime temp
Time of day
COLD
• What causes death?
– Intracellular ice
– Low enzymatic reactions
– CNS control
• Avoidance Strategies
– Hibernation/Torpor
• Tolerance Strategies
– Behavioral
– Physiological
– Extreme Cold adaptations
Tolerance Strategies: 1
(behavioral)
• Change conduction, convection, evaporation
and radiation
Tolerance Strategies: 2
(physiological)
Countercurrent heat exchangers
also help keep animals warm…
Countercurrent can be
used to retain heat…
Countercurrent heat exchangers
Or countercurrent can be
bypassed to lose heat
Countercurrent heat exchangers
But what happens
below 0OC?
• occasional
pulses of
blood to feet
• prevent
tissue damage
Tolerance Strategies: 2
(physiological)
Shivering Thermogenesis
Shivering
• keep body temp elevated 5oC
• nearly 9X increase in MR!
• warm up flight muscles
Tolerance Strategies: 2
(physiological)
Non-shivering thermogenesis (mammals)
BAT = Brown adipose tissue
Oxidation of BAT
produces heat, but
not ATP
- highly vascularized
- abundant mitochondria
• neonatal animals
• some cold acclimated mammals
• hibernators during arousal
COLD
• What causes death?
– Intracellular ice
– Low enzymatic reactions
– CNS control
• Avoidance Strategies
– Hibernation/Torpor/Estivation
• Tolerance Strategies
– Behavioral: alter heat transfer properties
• Conduction, convection, radiation
– Physiological
• Counter-current exchange
• Shivering thermogenesis
• Non-shivering thermogenesis
– Extreme Cold adaptations
Extreme Cold! (ectotherms)
Avoid Freezing
Tolerate Freezing
How do some ectotherms deal with
extreme cold?
Avoid Freezing
Option 1: use antifreeze compounds
colligative antifreezes
= lower freezing point by colligative properties
e.g., glycerol, sorbitol, mannitol
Non-colligative antifreezes
= lower freezing point b/c of special chemical properties
Non-colligative antifreezes:
Glycoprotein - polar groups; bind to ice crystals &
prevent their growth
(lowers the temp at which ice crystals enlarge)
Non-colligative antifreezes:
expression of genes for
antifreeze protein
increase seasonally…
…and freezing point
decreases seasonally in
winter flounder.
Antifreeze—colligative and non-colligative
} non-colligative
} colligative
How do some ectotherms deal with
extreme cold?
Avoid Freezing
Option 1: use antifreeze compounds
Option 2: supercooling*
-with gradual cooling, a liquid may remain
unfrozen well below its freezing point…
-…in the absence of ice nucleating agents
* Lowers the temperature at which ice crystals form
How do some ectotherms deal with
extreme cold?
Avoid Freezing
Tolerate Freezing
Option 1: use antifreeze compounds
Option 2: supercooling
Option 3: promote
extracellular ice
formation…
Promoting extracellular ice formation
 animals must remain inactive
 ice formation is restricted to extracellular fluid
As ECF
freezes…
(65% frozen)
Water drawn
from cell
(70% frozen)
(50% frozen)
Ice
nucleating
agents
promote
freezing
Wood Frog: Freeze Tolerant
Becoming Frozen:
Unfreezing:
Dark areas are frozen
Freeze from outside in
Thaw evenly
Why?
COLD
• What causes death?
– Intracellular ice
– Low enzymatic reactions
– CNS control
• Avoidance Strategies
– Hibernation/Torpor/Estivation
• Tolerance Strategies
– Behavioral: alter heat transfer properties
• Conduction, convection, radiation
– Physiological
• Counter-current exchange
• Shivering thermogenesis
• Non-shivering thermogenesis
– Extreme Cold adaptations
• Freeze avoidance: antifreezes (colligative and non-colligative)
• Freeze Tolerance: promote extracellular ice formation
Temperature Outline
• Definitions:
– Heat Transfer
Ex: Camels are COOL!!!
– Physiological strategy: endo, ecto, etc.
– Temperature tolerance
• Extreme Temperature: COLD
– Death?
– Avoidance strategies
– Tolerance strategies
• Extreme Temperature: HEAT
– Death?
– Avoidance strategies
– Tolerance strategies
HEAT
• What causes death?
• Avoidance Strategies
• Tolerance Strategies
What ultimately causes heat death?
 Disruption of membrane integrity
 Exceeding optimal temp for enzyme function
Acetylcholinesterase
temperature optima
vary by species
What ultimately causes heat death?
 Disruption of membrane integrity
 Exceeding optimal temp for enzyme function
 Protein Denaturation
HEAT
• What causes death?
– Membrane disruption
– Enzyme function
– Protein denaturation
• Avoidance Strategies
• Tolerance Strategies
Avoidance Strategies
Estivation = ‘summer sleep’
•
•
•
•
Metabolic rates reduced
Thermal tolerance limits expanded
Growth and reproduction cease
Animal becomes relatively unresponsive to external stimuli
Migration
• Spend part of the year in different location
Tolerance Strategies: 1
(behavioral)
Alter Heat Transfer Properties
• Decrease conduction from warm
surfaces
• Increase Convection
• Increase Evaporation
• Decrease Radiation Intake
Tolerance Strategies: 1 (behavioral)
Locate appropriate microclimate
Burrowing
High evaporation
FIND SHADE!
Tolerance Strategies: 1
Change Foraging
strategy
ants
Change Color
Change Effective
Surface Area
Tolerance Strategies: 2
Vasodilation
(physiological)
-promotes heat loss
Tolerance Strategies: 2
(physiological)
Vasodilation
Evaporative heat loss
Even cicadas “sweat”!
• accelerated water loss for
evaporative cooling at 41o C
• replenish with plant juices
Tolerance Strategies: 2
Without rest, this rabbit will
die of heat exhaustion, but
the dog can keep on running…
HOW?
(physiological)
Rete mirabile
“wonderful net”
• Countercurrent heat exchanger
Arterial vessel
Venous vessel
Heat exchange
Rete mirabile
“wonderful net”
Evaporative
cooling
Rete mirabile
Who has it?
Cat
Sheep
• ungulates
Dog
??
Rat
• primates
• rabbits
HEAT
• What causes death?
– Membrane disruption
– Enzyme function
– Protein denaturation
• Avoidance Strategies
– Estivation
– Migration
• Tolerance Strategies
1. Behavioral:
Alter heat transfer properties
Locate appropriate microclimate
Change color
Change foraging strategy
Change effective surface area
2. Physiological:
Vasodilation
Sweating
Rete mirabile
Temperature Outline
• Definitions:
– Heat Transfer
Ex: Camels are COOL!!!
– Physiological strategy: endo, ecto, etc.
– Temperature tolerance
• Extreme Temperature: COLD
– Death?
– Avoidance Strategies
– Tolerance Strategies
• Extreme Temperature: HEAT
– Death?
– Avoidance Strategies
– Tolerance Strategies
Migration Routes