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TEMPERATURE. 350 o C (662 F). Prokaryotes (bacteria, cyanobacteria) span almost the entire range of Earth’s Temperatures. Vertebrates can tolerate only a small portion of this range. Deep sea Hydrothermal vents. Few Species of Fish 44 o C. 0 o C (32 F). Large Polar Mammals -60 o C.

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slide2

350 oC

(662 F)

  • Prokaryotes (bacteria, cyanobacteria) span almost the entire range of Earth’s Temperatures.
  • Vertebrates can tolerate only a small portion of this range.

Deep sea Hydrothermal vents

Few Species of Fish 44 oC

0 oC

(32 F)

Large Polar Mammals -60 oC

-89 oC

-128 F

Antarctica

slide3

Temperature sets limits…

Physiology

Morphology

Behavior

performance

Darwinian fitness

Environment

slide4

Biochemical structures (i.e. enzymes) breakdown

Rate of reaction

Increasing T

Limits at the Cellular Level

Increased Temperature speeds up biochemical reactions…

…to a point

slide5

Thermal performance curves:

specialist

generalist

Performance

Lower lethal temp

Upper lethal temp

Temperature

… but limits are species-specific

temperature outline
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
Temperature Basics
  • Heat Transfer
  • Thermal Strategies
  • Thermal Tolerance
slide9

What’s the difference between temperature & heat?

Measure of intensity of heat

Total KE

(calories or joules)

(oC, oF, K)

Same temp,

Different heat content

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

slide10

Heat production

-

+

Heat in

Heat out

(metabolism)

=

Heat stored

Body temperature depends on heat stored

Gains > losses

slide11

Heat flows from warmer cooler

4 Mechanisms of heat transfer

  • Conduction
  • Conduction + Convection
  • Radiation
  • Evaporation

“The Rules”

Greater temperature gradient, greater flux

Physical properties matter

slide12

1. Conduction

= heat transfer between bodies in direct physical contact

  • temperature differential
  • area of contact

• conductivity of materials

slide13

2. Convection

CONDUCTION ONLY

CONDUCTION AND

CONVECTION

Hot object

Hot object

= bulk movement of fluid

- Accelerates heat transfer between a solid and a fluid

Why?

Boundary Layer is Removed

slide14

2. Convection

…All fluids come to rest at a solid surface

Air reaches full speed

Air reaches full speed

= “boundary layer”

Fluid speed

0

Distance from solid surface

Size of boundary layer is influenced by:

Thicker boundary layer, less heat loss to conduction

  • size (and shape) of animal
  • surface roughness
  • fluid speed (air, H2O)
slide15

3. Radiation

Short wavelengths

Surface temperature is important:

-intensity

T4

Long wavelengths

= transfer of heat between objects without contact

Above absolute zero, all objects emit & receive radiation

-hotter surface, shorter wavelengths

Area of radiative surface is, too

slide16

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
slide17

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
slide18

Heat flux from different sources is additive

Infrared thermal radiation from lizard

Infrared thermal radiation from atmosphere

Direct sunlight

Evaporation

Conduction from rock

Infrared thermal radiation from rock

+

-

Heat Production

(metabolism)

HEAT IN

HEAT OUT

=

Body Temp

Conduction to air

+ Convection by wind

temperature basics1
Temperature Basics
  • Heat Transfer
    • Conduction
    • Convection
    • Radiation
    • Evaporation

Example: CAMELS ARE COOL!!!

  • Thermal Strategies
  • Thermal Tolerance
slide20
BODY HEAT REGULATION

WATER

BRAIN FUNCTION

Ta (air temp) can exceed 50ºC (138 F)

Normal mammalian body temp = 37ºC

How do they cope????

CAMELS

slide21

How do camels manage to live in the desert heat?

1. Thick fur: prevents heat gain

slide22

How do camels manage to live in the desert heat?

  • Thick fur: prevents heat gain
  • 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
slide23

How do camels manage to live in the desert heat?

  • Thick fur: prevents heat gain
  • Body Heat can increase above 37ºC
  • Fat stored in Hump, not under skin

Why Helpful???

During cool nights, heat loss is not restricted

slide24
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????

CAMELS

slide25

How do camels manage to live in the desert heat?

  • Can go for 3-4 days without water

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

slide26

How do camels manage to live in the desert heat?

  • Can go for 3-4 days without water
  • 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)
slide27
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????

CAMELS

slide28

Rete mirabile

“wonderful net”

Arterial vessel

Venous vessel

Heat exchange

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!

= Counter Current

Exchange

slide29

Evaporative

cooling

Rete mirabile

“wonderful net”

slide30

Rete mirabile

• brain temperature remains lower

slide31
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????

CAMELS

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
slide33

Some small birds

and mammals

Brooding

Python

A few fish

MR

MR

Tb

Tb

Ta

Ta

ENDOTHERMS

Terrestrial Birds

and Mammals

POIKILOTHERMY

HOMEOTHERMY

Polar

Marine Fish

Most Amphibians

and Reptiles

A few Amph

and Rept

Freshwater

Fish

Most

Marine Fish

ECTOTHERMS

Shivering Python

http://www.flickr.com/photos/smacdonald/2520515097/

temperature basics2
Temperature Basics
  • Heat Transfer
    • Conduction
    • Convection
    • Radiation
    • Evaporation

Example: Camels are cool!!!

  • Thermal Strategies
    • EndothermvsEctotherm
    • HomeothermyvsPoikilothermy
  • Thermal Tolerance
slide35

Thermal performance curves:

Preferred Body Temp

Performance

Temperature

slide36

Thermal performance curves:

Preferred Body Temp

Performance

Temperature

Environmental Temperature shift?

ACCLIMITIZATION!!

temperature tolerance

Will discuss in hot vs. cold

Temperature Tolerance
  • Acclimitization
    • Biochemical
      • Membrane dynamics
      • Enzyme types and concentrations
      • Heat Shock Proteins
  • Behavioral
  • Morphological
  • Physiological
membrane dynamics
Membrane Dynamics

What are the kinks?

slide39

Polyunsaturated

Fatty Acid

(Omega 6)

slide40

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?

slide41

Cage Floor temperature

Diet very high in unsaturated fats

Normal Diet

Common Shingleback

slide42

Thermal performance curves:

Preferred Body Temp

Performance

Temperature

Environmental Temperature shift?

Increase PUFA in diet!

enzymes
Enzymes

= different forms of particular enzymes with different temperature optima

  • isozymes

4 different

forms of ATPase

Each with a separate

thermal performance

curve

enzymes1

Alligator lizard

Fence lizard

Desert Fringed Lizard

Desert Iguana

Enzymes
  • isozymes
slide45

Heat Shock Proteins

  • Under High Temperatures, Proteins unfold (denature)

How can you protect

Cells during protein denaturation?

slide46

“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
Cataglyphis Ants

>50C on sand

45C in nest entrance

Cataglyphis spend 10-15 minutes

In the tunnel to the nest, making heat shock proteins to protect their cells while they are out on the desert foraging

Other insects stop foraging

<30C inside nest

http://www.youtube.com/watch?v=w9KDM4C1kVg&feature=related

temperature acclimatization
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 acclimatization1
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 basics3
Temperature Basics
  • Heat Transfer
    • Conduction
    • Convection
    • Radiation
    • Evaporation

Example: Camels are Cool!!!

  • Thermal Strategies
    • Endotherm vsEctotherm
    • HomeothermyvsPoikilothermy
  • Thermal Tolerance
    • Acclimatization of membranes and enzymes
temperature outline1
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
slide52
COLD
  • What causes death?
  • Avoidance Strategies
  • Tolerance Strategies
slide53

What causes cold death?

  • Intracellular ice formation

- 0.5o C terrestrial, -1.7o C marine

  • Chemical reaction rates drop
  • CNS control, integration reduced
slide54
COLD
  • What causes death?
    • Intracellular ice
    • Low enzymatic reactions
    • CNS control
  • Avoidance Strategies
  • Tolerance Strategies
slide55

Avoidance

Hibernation/torpor

slide56

Body Temperature

Daytime temp

Time of day

Avoidance

Significantly lowered Tb

Hibernation/torpor

slide57
COLD
  • What causes death?
    • Intracellular ice
    • Low enzymatic reactions
    • CNS control
  • Avoidance Strategies
    • Hibernation/Torpor
  • Tolerance Strategies
    • Behavioral
    • Physiological
    • Extreme Cold adaptations
slide58

Tolerance Strategies: 1 (behavioral)

  • Change conduction, convection, evaporation and radiation
slide59

Tolerance Strategies: 2 (physiological)

Countercurrent heat exchangers

also help keep animals warm…

Countercurrent can be used to retain heat…

slide60

Countercurrent heat exchangers

Or countercurrent can be bypassed to lose heat

slide61

Countercurrent heat exchangers

But what happens below 0OC?

  • occasional pulses of blood to feet
  • prevent tissue damage
slide62

• warm up flight muscles

Tolerance Strategies: 2 (physiological)

Shivering Thermogenesis

Shivering

  • keep body temp elevated 5oC
  • nearly 9X increase in MR!
slide63

(mammals)

Non-shivering thermogenesis

Tolerance Strategies: 2 (physiological)

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

slide64
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
slide65

Extreme Cold! (ectotherms)

Avoid Freezing

Tolerate Freezing

slide66

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

slide67

Non-colligative antifreezes:

Glycoprotein- polar groups; bind to ice crystals & prevent their growth

(lowers the temp at which ice crystals enlarge)

slide68

Non-colligative antifreezes:

expression of genes for antifreeze protein increase seasonally…

…and freezing point decreases seasonally in winter flounder.

antifreeze colligative and non colligative
Antifreeze—colligative and non-colligative

} non-colligative

} colligative

slide70

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

slide71

Option 3: promote extracellular ice formation…

How do some ectotherms deal with extreme cold?

Avoid Freezing

Tolerate Freezing

Option 1: use antifreeze compounds

Option 2: supercooling

slide72

Water drawn from cell

(65% frozen)

(70% frozen)

(50% frozen)

Promoting extracellular ice formation

  • animals must remain inactive
  • ice formation is restricted to extracellular fluid

Ice nucleating agents promote freezing

As ECF freezes…

wood frog freeze tolerant

Becoming Frozen:

Unfreezing:

Wood Frog: Freeze Tolerant

Dark areas are frozen

Why?

Freeze from outside in

Thaw evenly

slide74
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 outline2
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
slide76
HEAT
  • What causes death?
  • Avoidance Strategies
  • Tolerance Strategies
slide77

Acetylcholinesterase

What ultimately causes heat death?

  • Disruption of membrane integrity
  • Exceeding optimal temp for enzyme function

temperature optima

vary by species

slide78

What ultimately causes heat death?

  • Disruption of membrane integrity
  • Exceeding optimal temp for enzyme function
  • Protein Denaturation
slide79
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

Estivation = ‘summer sleep’

Avoidance Strategies

Migration

  • Spend part of the year in different location
alter heat transfer properties

Tolerance Strategies: 1 (behavioral)

Alter Heat Transfer Properties
  • Decrease conduction from warm surfaces
  • Increase Convection
  • Increase Evaporation
  • Decrease Radiation Intake
change effective surface area

Tolerance Strategies: 1

Change Effective Surface Area

Change Foraging strategy

ants

Change Color

slide84

Tolerance Strategies: 2 (physiological)

Vasodilation

-promotes heat loss

slide85

Even cicadas “sweat”!

Tolerance Strategies: 2 (physiological)

Vasodilation

Evaporative heat loss

  • accelerated water loss for evaporative cooling at 41o C
  • replenish with plant juices
slide86

Tolerance Strategies: 2 (physiological)

Without rest, this rabbit will die of heat exhaustion, but the dog can keep on running…

HOW?

slide87

Arterial vessel

Venous vessel

Heat exchange

Rete mirabile

“wonderful net”

  • Countercurrent heat exchanger
slide88

Evaporative

cooling

Rete mirabile

“wonderful net”

slide89

Cat

Sheep

Dog

Rat

??

Rete mirabile

Who has it?

• primates

• (& rabbits!)

slide90
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

Retemirabile

temperature outline3
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
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