TEMPERATURE

ADAPTATION

CONCEPTS

Van’t Hoff’s Rule: for every temperature rise of 10o C, rate of biochemical reactions

double up to a point.This is why it is bad to get too hot or too cold

– Too cold = body functions slow due to Van’t Hoff’s Rule.– Too hot = proteins break down and body functions slow;

that’s why Van’t Hoff’s Rule only works up to a point.

Energy Pie: distribution of individual’s energy among:• Growth• Reproduction• Activity• Maintenance: includes body temp• Storage

How plants and animals gain and lose heat

• Radiation (+/-): to/from nearby objects– E.g., lizard gains heat from sun, or loses heat to

surroundings in shade

• Conduction (+/-): to/from touching objects– E.g. lizard gains heat laying on warm rock or loses

heat laying on surface of cool burrow

• Convection (+/-): into wind/moving water– E.g. body is warmed by hot wind or cooled by cold

wind

• Metabolism (+): from body’s generation of heat

• Evaporation (-): from moist body surfaces

Types of animals based on way body temp is

maintained• Poikilotherms – have a variable body

temperature• Homeotherms – have a stable body temp• Endotherms principal source of body heat is

body’s metabolism (erroneously called warm-blooded)– Birds & Mammals

• Ectotherms principal source of body heat is from environment (erroneously called cold-blooded)– Everything else (with a few exceptions)

Surface Area to Volume Ratio

• Small, thin things have a greater surface area to volume ratio thus gain/lose heat faster than large, thick things.

SA:V Ratio• However… larger endotherms also

generate more heat per unit volume as well – and have a harder time losing it.– Elephant & Kangaroo

Types of Thermoregulation

• Physiological thermoregulation: altering body’s metabolic generation of heat to regulate body temp.

• Behavioral thermoregulation: altering posture, orientation, and/or microclimate to regulate body temp.

Impact of Van’t Hoff’s Rule • Since rates of reaction double for every

10oC – this applies to cell respiration too.• Oxygen consumption doubles, and so

does ATP production.

Internal Temp = POWER

What happens to a lizard in a fur coat?

• Gets colder & dies of hypothermia• WHY?

– Can’t absorb the heat & doesn’t generate enough of its own heat.

Hot Blood = a short life spent eating long & dangerously

HOT ENVIRONMENT

Lizard Mammal

•Absorbs heat from enviro.• Metabolism at max.

•Generates body heat•Must cool down (sweat, slow metabolism)

COLD ENVIRONMENT

Lizard Mammal

•Metabolism slows (less food needed)•Sleep, curl-up, burrow

•Generates extra body heat•HOW? More ATP… means more FOOD req’d•Possible Hibernation or TORPOR

•More exposed to predators, more food req’d/indiv, less food for reprod, lifespan drops

Torpor: lowering of body temp below activity temperature.

• Daily Estivation: <24 hr torpor in response to heat and/or dryness

• Seasonal Estivation: seasonal torpor in response to heat and/or dryness

• Daily Torpor in Response to Cold: daily torpor in response to cold and insufficient energy uptake. Note: name and definition are same.

• Hibernation: seasonal torpor in response to cold and insufficient energy uptake

Torpor:Adaptive Values

• Reduces Energy Needs– 2 ways

• Reduces Water Needs– 3 ways

Torpor:Adaptive Values

• Reduces Energy Needs– Lowers temp gradient which is the

difference in temp between body and environment: this slows rate of heat loss

– Less tissue demand because lower body temp

34o 34o

99o 35o

Quick heat loss

High temp gradient

Low temp gradient

Slow heat loss

Torpor:Adaptive Values

Reduces Water Needs– Decreases cutaneous (outer surface such as

skin) water loss•Less evaporation

– Decreases excretory water loss•Less waste products produced

– Decreases respiratory water loss•Less breathing (colder body temp slows

metabolism) and less water lost per breath (colder exhaled air contains less water)

Advantages and Disadvantages of

Endothermy versus Ectothermy•Endothermy

– Advantage•Always

ready to go– Disadvantage

•Uses 10x more energy

•Ectothermy– Advantage

•Uses 10x less energy

– Disadvantage•Prisoner of

environment (cold and slow when no source of heat)

What are the gains of endothermy?

• Nocturnal Ability• Niche expansion

– Climate zones

• Larger body size– Bigger brain

Not enough to offset the cost of a population size reduction, higher & more consistent food needs, lower life span, and number of offspring... (FITNESS)

BUILD A MUSCLE RPG

What are the strengths of your muscle?What problems might it have?

• High # fibres– Powerful muscle– Less stamina

• High # Mito & Caps– Weaker muscle– More stamina

Trade-Offs

High Power/Low Staminavs

Low Power/High Stamina

Reptiles are built for speed bursts – SPRINTERSMammals are built for STAMINA

STAMINA IS THE MAIN ADVANTAGE ENDOTHERMS HAVE

High stamina =

Increased activity=

Increased Aerobic Capacity

=Increased Metabolic

Rate

Ability to outrun predators

More energy to eat longerCan be a TRUE

herbivore [N-issues]

More energy to reproduce/care for offspring

Increasing stamina• All mitochondria

created equal• Incr. # Mitochondria• Incr. organ size

– PGC1 gene– Oncogenes– Brown fat “baby fat”

• Bony Palate• 4 Chambered

Heart• Larger nasal

passages• Nasal Turbinates

Where’s the HEAT?

• Inner membrane not 100% impervious to H+ ‘leaky’

• THERMOGENIN allows H+ to leak & release PMF energy as heat

PMF = electrochemical gradient

Summary ofEndothermy versus Ectothermy

Endothermy– Advantage

•Stamina– Disadvantage

•Uses 10x more energy

Ectothermy– Advantage

•Uses 10x less energy

– Disadvantage•Prisoner of

environment

• One of animal biology’s most intriguing, but largely unanswered questions has to do with the relationship between body size and metabolic rate.– Physiologists have shown that the amount of

energy it takes to maintain each gram of body weight is inversely related to body size.

– For example, each gram of a mouse consumes about 20 times more calories than a gram of an elephant.

Metabolic rate per gram is inversely related to body size

among similar animals

• The higher metabolic rate of a smaller animal demands a proportionately greater delivery rate of oxygen.– A smaller animal also has a higher

breathing rate, blood volume (relative to size), and heart rate (pulse) and must eat much more food per unit of body mass.

Copyright © 2002 Pearson Education, Inc., publishing as Benjamin Cummings

• One hypothesis for the inverse relationship between metabolic rate and size is that the smaller the size of an endotherm, the greater the energy cost of maintaining a stable body temperature.– The smaller the animal, the greater its

surface to volume ratio, and thus the greater loss of heat to (or gain from) the surroundings.

• However, this hypothesis fails to explain the inverse relationship between metabolism and size in ectotherms.

• Nor is it supported by experimental tests.• Researchers continue to search for causes

underlying this inverse relationship.