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350 oC(662 F)
-89 oC -128 F
0 oC(32 F)
Large Polar Mammals -60 oC
Few Species of Fish 44 oC
Deep sea Hydrothermal vents
Antarctica
• Prokaryotes (bacteria, cyanobacteria) span almost the entire range of Earth’s Temperatures.
• Vertebrates can tolerate only a small portion of this range.
Limits at the Cellular Level
Increased Temperature speeds up biochemical reactions……to a point
Rat
e of
rea
ctio
n
Increasing T
Biochemical structures (i.e. enzymes) breakdown
… but limits are species-specific
Temperature
Perf
orm
ance
Thermal performance curves:
generalist
specialist
Lower lethal temp
Upper lethal temp
Temperature Outline• Definitions:
– Heat Transfer– Physiological strategy: endo, ecto, etc.– Temperature tolerance
• Extreme Temperature: HEAT– Death?– Avoidance strategies– Tolerance strategies
• Extreme Temperature: COLD– Death?– Avoidance strategies– Tolerance strategies
• Example: Camels are cool!
What’s the difference between temperature &
heat?
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
Measure of intensity of heat(oC, oF, K)
Total KE(calories or joules)
Same temp,Different heat content
Body temperature depends on heat stored
Heat production
(metabolism)
- Heat out+ Heat in
=
Heat stored
Gains > losses
“The Rules”1. Heat flows from warmer cooler
2. Greater temperature gradient, greater flux3. Physical properties matter
4 Mechanisms of heat transfer • Conduction
• Conduction + Convection• Radiation• Evaporation
1. Conduction= heat transfer between bodies in direct physical contact
• temperature differential• area of contact
• conductivity of materials
2. Convection
- Accelerates heat transfer between a solid and a fluid
= bulk movement of fluid
Why?
Hot object
CONDUCTION ONLY
Hot object
CONDUCTION ANDCONVECTION
Boundary Layer is Removed
2. Convection…All fluids come to rest at a solid surface
Size of boundary layer is influenced by: • size (and shape) of animal Thicker boundary layer,
less heat loss to conduction
Flu
id
speed
Distance from solid surface
0
• fluid speed (air, H2O)
• surface roughness
Air reaches full speed
Air reaches full speed
= “boundary layer”
3. Radiation
= transfer of heat between objects without contact
Short wavelengths
Long wavelengths
Above absolute zero, all objects emit & receive radiation
∞-intensity T4
-hotter surface, shorter wavelengths
Area of radiative surface is, too
Surface temperature is important:
4. Evaporation
@ 35o C, it takes 580 cal to vaporize
1g of H2O!
• exposure of moist surfaces• moisture gradient
=Extremely effective method of losing heat
4. Evaporation
• exposure of moist surfaces• moisture gradient
=Extremely effective method of losing heat
@ 35o C, it takes 580 cal to vaporize
1g of H2O!
Infrared thermal radiation from lizard
Infrared thermal radiation from rock
Direct sunlight
Conduction from rock
Convection by wind
Evaporation
Infrared thermal radiation from atmosphere
Heat flux from different sources is additive
Temperature Basics• Heat Transfer
– Conduction– Convection– Radiation– Evaporation
• Thermal Strategies
• Thermal Tolerance
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
ENDOTHERMS
ECTOTHERMS
POIKILOTHERMY HOMEOTHERMY
Ta
TbMR
Ta
TbMR
Terrestrial Birds and Mammals
Most Marine Fish
Most Amphibians and Reptiles
PolarMarine Fish
A few fish
A few Amphand ReptFreshwater
Fish
Brooding Python
Some small birds and mammals
Temperature Basics
• Heat Transfer– Conduction– Convection– Radiation– Evaporation
• Thermal Strategies– Endotherm vs Ectotherm– Homeothermy vs Poikilothermy
• Thermal Tolerance
Temperature
Perf
orm
ance
Thermal performance curves:
Preferred Body Temp
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
Temperature also has major effects on cell membrane fluidity
If you live in hot climate, what sort of fatty acids should you have?
If you live in cold climate, what sort of fatty acids should you have?
Species Body Temperature oC
Ratio of sat. to unsat. fatty acids in phospholipid
Arctic Sculpin 0 0.59
Goldfish(acclimated to 2 temps)
525
0.660.82
Desert Pupfish 34 0.99
Rat 37 1.22
Temperature
Perf
orm
ance
Thermal performance curves:
Preferred Body Temp
Environmental Temperature shift?
Increase PUFA in diet!
Enzymes= different forms of particular enzymes with different temperature optima
isozymes
4 different forms of ATPase
Each with a separatethermal performance
curve
Heat Shock Proteins
Under High Temperatures, Proteins unfold (denature)
How can you protectCells during protein denaturation?
“Heat Shock Proteins” protect against heat damage
= proteins synthesized in response to cellular stress (including high temps)
function as “molecular chaperones”
Protein denatures from Heat
Heat increases
HSP expression increases (more HSP)
HSP binds up denatured protein
Heat decreases
HSP lets go, protein can refold
Cataglyphis Ants
http://www.youtube.com/watch?v=w9KDM4C1kVg&feature=related
Other insects stop foragingCataglyphis spend 10-15 minutesIn the tunnel to the nest, making heat shock proteins to protect their cells while they are out on the desert foraging
>50C on sand
45C in nest entrance
<30C inside nest
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
• Thermal Strategies– Endotherm vs Ectotherm– Homeothermy vs Poikilothermy
• Thermal Tolerance– Acclimatization of membranes and enzymes
Temperature Outline• Definitions:
– Heat Transfer– Physiological strategy: endo, ecto, etc.– Temperature tolerance
• Extreme Temperature: COLD– Death?– Avoidance strategies– Tolerance strategies
• Extreme Temperature: HEAT– 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
COLD• What causes death?
– Intracellular ice– Low enzymatic reactions– CNS control
• Avoidance Strategies– Hibernation/Torpor/Estivation
• Tolerance Strategies– Behavioral– Physiological– Extreme Cold adaptations
Countercurrent can be used to retain heat…
Countercurrent heat exchangers also help keep animals warm…
Tolerance Strategies: 2 (physiological)
But what happens below 0OC?
• occasional pulses of blood to feet
• prevent tissue damage
Countercurrent heat exchangers
Shivering• keep body temp elevated
5oC
• nearly 9X increase in MR!
Shivering Thermogenesis
• warm up flight muscles
Tolerance Strategies: 2 (physiological)
Non-shivering thermogenesis(mammals)
BAT = Brown adipose tissueOxidation of BAT produces heat,
but not ATP
• neonatal animals• some cold acclimated mammals • hibernators during arousal
- highly vascularized
- abundant mitochondria
Tolerance Strategies: 2 (physiological)
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
How do some ectotherms deal with extreme cold?
Avoid Freezing
Option 1: use antifreeze compounds
colligative antifreezes
= lower freezing point by colligative propertiese.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.
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
Tolerate Freezing
Option 3: promote extracellular ice formation…
How do some ectotherms deal with extreme cold?
Avoid Freezing
Option 1: use antifreeze compounds
Option 2: supercooling
animals must remain inactive
ice formation is restricted to extracellular fluid
As ECF freezes… Water drawn
from cell
Ice nucleating agents promote freezing
Promoting extracellular ice formation
(65% frozen) (70% frozen) (50% frozen)
Wood Frog: Freeze TolerantBecoming Frozen: Unfreezing:
Freeze from outside in Thaw evenly
Dark areas are frozen
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– Physiological strategy: endo, ecto, etc.– Temperature tolerance
• Extreme Temperature: COLD– Death?– Avoidance strategies– Tolerance strategies
• Extreme Temperature: HEAT– Death?– Avoidance strategies– Tolerance strategies
Disruption of membrane integrity
Exceeding optimal temp for enzyme function
What ultimately causes heat death?
temperature optima vary by species
Acetylcholinesterase
Disruption of membrane integrity
Exceeding optimal temp for enzyme function
What ultimately causes heat death?
Protein Denaturation
HEAT
• What causes death?– Membrane disruption– Enzyme function– Protein denaturation
• Avoidance Strategies
• Tolerance 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
Avoidance Strategies
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 (behavioral)
Tolerance Strategies: 2 (physiological)
Evaporative heat loss
Even cicadas “sweat”!• accelerated water loss for evaporative cooling at 41o C• replenish with plant juices
Vasodilation
Without rest, this rabbit will die of heat exhaustion, but the dog can keep on running…
HOW?
Tolerance Strategies: 2 (physiological)
Rete mirabile
• Countercurrent heat exchanger
Arterial vessel
Venous vesselHeat exchange
“wonderful net”
HEAT• What causes death?
– Membrane disruption– Enzyme function– Protein denaturation
• Avoidance Strategies– Estivation– Migration
• Tolerance Strategies1. Behavioral:
Alter heat transfer propertiesLocate appropriate microclimateChange colorChange foraging strategyChange effective surface area
2. Physiological:VasodilationSweatingRete mirabile
Temperature Outline• Definitions:
– Heat Transfer– Physiological strategy: endo, ecto, etc.– Temperature tolerance
• Extreme Temperature: COLD– Death?– Avoidance Strategies– Tolerance Strategies
• Extreme Temperature: HEAT– Death?– Avoidance Strategies– Tolerance Strategies
CAMELS
• BODY HEAT REGULATION
• WATER
• BRAIN FUNCTION
• Ta (air temp) can exceed 50ºC (138 F)
• Normal mammalian body temp = 37ºC
• How do they cope????
How do camels manage to live in the desert
heat?1.Thick fur: prevents heat gain2. 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 gain2. Body Heat can increase above 37ºC3. Fat stored in Hump, not under skin
Why Helpful???
During cool nights, heat loss is not restricted
CAMELS
• BODY HEAT REGULATION– Thick Fur– Body Heat to 41ºC– Fat stored in hump
• WATER
• BRAIN FUNCTION
• Ta (air temp) can exceed 50ºC (138 F)
• Normal mammalian body temp = 37ºC
• How do they cope????
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 water2. 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
• 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
• Ta (air temp) can exceed 50ºC (138 F)
• Normal mammalian body temp = 37ºC
• How do they cope????
How do camels manage to live in the desert heat?
Body Temp can increase 6C…But Brain can’t function at that temp
Arterial vessel
Venous vessel Heat exchange
Rete mirabile“wonderful net”
…?
= Counter CurrentExchange
THEY KEEP THEIR BRAIN COOL!
CAMELS
• 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– Rete Mirabile
• Allows for brain cooling in spite of very high body temp
• Ta (air temp) can exceed 50ºC (138 F)• Normal mammalian body temp = 37ºC• How do they cope????