TEMPERATURE. 350 o C (662 F) -89 o C -128 F 0 o C (32 F) Large Polar Mammals -60 o C Few Species of...

TEMPERATURE

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.

Environment

PhysiologyMorphologyBehavior

Temperature sets limits…

performance

Darwinian fitness

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!

Temperature Basics

• Heat Transfer

• Thermal Strategies

• Thermal Tolerance

Heat transfer between animals and environment

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 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


Temperature

Perf

orm

ance


Preferred Body Temp

Temperature

Perf

orm

ance


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

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?

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

Diet very high in unsaturated fats

Common Shingleback

Cage Floor temperature

Normal Diet

Temperature

Perf

orm

ance


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

Enzymes

Alligator lizardFence lizard

Desert Fringed Lizard

Desert Iguana

isozymes

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

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

• Thermal Strategies– Endotherm vs Ectotherm– Homeothermy vs Poikilothermy

• Thermal Tolerance– Acclimatization of membranes and enzymes

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



AvoidanceHibernation/torpor

Significantly lowered TbAvoidanceHibernation/torpor

Bod

y T

em

pera

ture

Time of day

Daytime temp

COLD• What causes death?

– Intracellular ice– Low enzymatic reactions– CNS control

• Avoidance Strategies– Hibernation/Torpor/Estivation

• Tolerance Strategies– Behavioral– Physiological– Extreme Cold adaptations

• Change conduction, convection, evaporation and radiation

Tolerance Strategies: 1 (behavioral)

Countercurrent can be used to retain heat…

Countercurrent heat exchangers also help keep animals warm…

Tolerance Strategies: 2 (physiological)

Countercurrent heat exchangers

Or countercurrent can be bypassed to lose heat

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


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– 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 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.


Avoid Freezing


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…


Avoid Freezing


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?

http://www.exploratorium.edu/frogs/woodfrog/woodfrog_2.html




• 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

HEAT

• What causes death?



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



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


Locate appropriate microclimate

Burrowing High evaporation

FIND SHADE!


Change Color

Change Foraging strategy

Change Effective Surface Area

ants

Tolerance Strategies: 1


Vasodilation-promotes heat loss


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?


Rete mirabile

• Countercurrent heat exchanger

Arterial vessel

Venous vesselHeat exchange

“wonderful net”

Rete mirabile“wonderful net”

Evaporativecooling

Rete mirabile

Who has it?

Cat Sheep Dog Rat

• primates• (& rabbits!)

??

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



• 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 gain


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


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





heat?1.Can go for 3-4 days without water

When they reach water, they can drink up to 100L in 10 minutes

http://stoneywageslave.files.wordpress.com/2007/05/camel-bathroom.jpg



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


• 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

Arterial vessel

Venous vessel Heat exchange


…?

= Counter CurrentExchange

THEY KEEP THEIR BRAIN COOL!


Evaporativecooling

Rete mirabile

• brain temperature remains lower

CAMELS


• 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????

Migration Routes

TEMPERATURE. 350 o C (662 F) -89 o C -128 F 0 o C (32 F) Large Polar Mammals -60 o C Few Species of...

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