Homeostasis in Homeostasis in Animals Animals Temperature Temperature
Homeostasis in AnimalsHomeostasis in AnimalsTemperatureTemperature
Processes of Heat TransferProcesses of Heat Transfer
Radiation = heat transfer through waves of Radiation = heat transfer through waves of energyenergy
Conduction = direct transfer of heat from one Conduction = direct transfer of heat from one object to anotherobject to another
Convection = heat transfer by circulation of a Convection = heat transfer by circulation of a fluid (gas or liquid)fluid (gas or liquid)
Evaporation = heat loss as water changes from Evaporation = heat loss as water changes from liquid to vaporliquid to vapor
RadiationRadiation
Animals gain radiant heat directly from the Animals gain radiant heat directly from the sun and reflected from the atmosphere sun and reflected from the atmosphere and objects in the environmentand objects in the environment
Animals also lose heat as they radiate it to Animals also lose heat as they radiate it to their environmenttheir environment
Net gain during daytime, net loss at nightNet gain during daytime, net loss at night
ConductionConduction
Animals can either gain or lose heat to the Animals can either gain or lose heat to the ground or other objects depending on their ground or other objects depending on their relative temperaturesrelative temperatures
lizardlizard
rockrock
30°C30°C
20°C20°C
30°C30°C
40°C40°C
Animal loses heat when it’sAnimal loses heat when it’swarmer than contacted objectwarmer than contacted object
Animal gains heat when it’sAnimal gains heat when it’scooler than contacted objectcooler than contacted object
ConvectionConvection
Animals can gain or lose heat depending Animals can gain or lose heat depending on relative temperature of animal and fluidon relative temperature of animal and fluid
Typically animals lose heat through Typically animals lose heat through convection because their body convection because their body temperature is higher than air temperaturetemperature is higher than air temperature
Insulation of fur or feathers reduces Insulation of fur or feathers reduces convective heat lossconvective heat loss
brr!
EvaporationEvaporation
Always results in heat loss from the animalAlways results in heat loss from the animal Sweating, panting, and bathing are Sweating, panting, and bathing are
adaptations to increase evaporative heat adaptations to increase evaporative heat loss to prevent overheatingloss to prevent overheating
Bergmann’s RuleBergmann’s Rule
Individuals of a given species are larger in Individuals of a given species are larger in cold climates than in warm climates cold climates than in warm climates
(generally speaking)(generally speaking)
White-tailed deer skulls
Source: http://www.mun.ca/biology/scarr/Source: http://www.mun.ca/biology/scarr/Bergmann's_rule_in_Odocoileus.htmBergmann's_rule_in_Odocoileus.htm
Allen’s RuleAllen’s Rule
Individuals of a given species have shorter Individuals of a given species have shorter extremities in cold climates than in warm climatesextremities in cold climates than in warm climates
Arctic hareArctic hare- Arctic - Arctic tundratundra
Snowshoe hareSnowshoe hare- boreal forest- boreal forest
Black-tailedBlack-tailedjackrabbitjackrabbit- prairies- prairies
AntelopeAntelopejackrabbitjackrabbit- deserts- deserts
Source: http://www.mun.ca/biology/scarr/Lepus_variation.htmSource: http://www.mun.ca/biology/scarr/Lepus_variation.htm
(generally speaking)(generally speaking)
HOW SIZE MATTERS IN HOW SIZE MATTERS IN REGULATING BODY REGULATING BODY
TEMPERATURETEMPERATURE
ConceptConcept
Small-bodied animals or plant parts (e.g., Small-bodied animals or plant parts (e.g., leaves) heat up and cool down faster; leaves) heat up and cool down faster; bigger and/or thicker bodies heat up and bigger and/or thicker bodies heat up and cool down slower.cool down slower.
ExplanationExplanation
Smaller/thinner bodies have a larger Smaller/thinner bodies have a larger surface area to volume ratio. surface area to volume ratio. Bodies gain and lose heat out of the surface Bodies gain and lose heat out of the surface
of their body; more surface area means of their body; more surface area means greater gains and losses. greater gains and losses.
Bodies retain heat within their bodies; more Bodies retain heat within their bodies; more volume means more heat retention. When the volume means more heat retention. When the surface area is large compared to the volume surface area is large compared to the volume (small/thin things), heat is gained and lost (small/thin things), heat is gained and lost quickly.quickly.
Example: compare 1 cm x 1 cm x 1 cm Example: compare 1 cm x 1 cm x 1 cm cube with 10 cm x 10 cm x 10 cm cubecube with 10 cm x 10 cm x 10 cm cube
11
11
11
Surface area = 1x1x6 = 6 cmSurface area = 1x1x6 = 6 cm22
Volume = 1x1x1 = 1 cmVolume = 1x1x1 = 1 cm33
SA:V ratio = 6:1 = 6.0SA:V ratio = 6:1 = 6.0
10
1010
1010
Surface area = 10x10x6 = 600 cmSurface area = 10x10x6 = 600 cm22
Volume = 10x10x10 = 1000 cmVolume = 10x10x10 = 1000 cm33
SA:V ratio = 600:1000 = 0.6SA:V ratio = 600:1000 = 0.6
Small animalSmall animal
LargeLargeanimalanimal
SIZE MATTERSSIZE MATTERS
Small cookies cool down faster than larger Small cookies cool down faster than larger cookies after coming out of the oven. Also small cookies after coming out of the oven. Also small cookies burn faster. cookies burn faster.
Your hand has the same volume whether it is Your hand has the same volume whether it is balled up (fat) or spread out (thin). On a cold balled up (fat) or spread out (thin). On a cold day, your hand will get cold faster when spread day, your hand will get cold faster when spread out because balling up you hand into a fist out because balling up you hand into a fist effectively reduces surface area because now effectively reduces surface area because now the part of your hand within your fist is no longer the part of your hand within your fist is no longer "surface". "surface".
Advantages and Disadvantages to Advantages and Disadvantages to Being Large:Being Large:
Heat is gained and lost more slowly so, for Heat is gained and lost more slowly so, for example, on a hot summer day, the a large example, on a hot summer day, the a large animal may never reach lethal temperatures by animal may never reach lethal temperatures by the time the sun sets. the time the sun sets.
Because heat is lost more slowly, the animal Because heat is lost more slowly, the animal doesn't have to replace lost heat as quicklydoesn't have to replace lost heat as quickly Therefore, the animal doesn't have to eat as much Therefore, the animal doesn't have to eat as much
compared to its body weight (compared to its body weight (e.ge.g., only has to eat 1/4 ., only has to eat 1/4 its body weight). its body weight).
However, it usually does have to eat more total food However, it usually does have to eat more total food than a smaller animal. than a smaller animal.
Advantages and Disadvantages to Advantages and Disadvantages to Being Small:Being Small:
Heat is gained and lost faster so, for example, Heat is gained and lost faster so, for example, on a hot summer day, a small leaf (less than on a hot summer day, a small leaf (less than about 1 square centimeter) will shed heat as fast about 1 square centimeter) will shed heat as fast as it acquires heat as it acquires heat Therefore the leaf will never reach temperatures Therefore the leaf will never reach temperatures
higher than air temperature (compared to a large, higher than air temperature (compared to a large, thick leaf that acquires a heat load and can reach very thick leaf that acquires a heat load and can reach very high, lethal temperatures). high, lethal temperatures).
Because heat is lost faster, the animal has to eat Because heat is lost faster, the animal has to eat faster to replace the lost energy (e.g., very small faster to replace the lost energy (e.g., very small mammals may eat up to 4 times their body mammals may eat up to 4 times their body weight each day). weight each day).
Summary ExampleSummary Example
A plant can either have very small leaves A plant can either have very small leaves that never heat up higher than air that never heat up higher than air temperature or very large leaves that heat temperature or very large leaves that heat up so slowly that they never reach lethal up so slowly that they never reach lethal temperatures, but a plant doesn't want to temperatures, but a plant doesn't want to have leaves in the middle sizes if the have leaves in the middle sizes if the temperatures are going to be extremely temperatures are going to be extremely hot or cold.hot or cold.
Concepts Concepts Van't Hoff's RuleVan't Hoff's Rule: for every temperature rise of 10 degrees : for every temperature rise of 10 degrees
C, rate of biochemical reactions (most body functions) C, rate of biochemical reactions (most body functions) doubles, up to a point (when proteins break down). What is doubles, up to a point (when proteins break down). What is the other name of this law?the other name of this law?
Energy AllocationEnergy Allocation: all energy taken in by plants and animals : all energy taken in by plants and animals is portioned out (is portioned out (allocatedallocated) to the following areas) to the following areas GrowthGrowth ReproductionReproduction ActivityActivity MaintenanceMaintenance Storage.Storage.
Savings in one area (e.g., maintenance which includes Savings in one area (e.g., maintenance which includes thermoregulation) means more energy can be diverted to thermoregulation) means more energy can be diverted to other areas (e.g., storage for hard times later). other areas (e.g., storage for hard times later).
Types of Animals Based on Means Types of Animals Based on Means of Thermoregulation: of Thermoregulation:
EctothermsEctotherms: animals whose principal : animals whose principal source of body heat is the environment. source of body heat is the environment. Includes essentially all animals except Includes essentially all animals except birds and mammals. birds and mammals.
EndothermsEndotherms: animals whose principal : animals whose principal source of body heat is from their own body source of body heat is from their own body generating heat metabolically. Birds and generating heat metabolically. Birds and mammals are endotherms. mammals are endotherms.
Types of ThermoregulationTypes of Thermoregulation
Behavioral ThermoregulationBehavioral Thermoregulation: using posture, : using posture, orientation, and microclimate selection to orientation, and microclimate selection to regulate body temperature. For example, a lizard regulate body temperature. For example, a lizard that wants to heat up will spread eagle (posture) that wants to heat up will spread eagle (posture) on the top of a hot rock (microclimate) and turn on the top of a hot rock (microclimate) and turn its entire back to the sun (orientation). its entire back to the sun (orientation).
Physiological ThermoregulationPhysiological Thermoregulation: altering : altering metabolic generation of heat to regulate body metabolic generation of heat to regulate body temperature. temperature.
Poikilotherms (ectotherms)Poikilotherms (ectotherms)
No internal physiological mechanism for keeping No internal physiological mechanism for keeping body temp constantbody temp constant
Body temp matches environmental tempBody temp matches environmental temp As temp drops body processes slow downAs temp drops body processes slow down
Source of body heat is the environmentSource of body heat is the environment
PlantsPlants
ReptilesReptiles
AmphibiansAmphibians
MostMost fish fish
Most Most invertebratesinvertebrates
Coping with Temperature VariationCoping with Temperature VariationPoikilothermsPoikilotherms
BehaviorBehavior
When temp is low lizard sits broadside to sun and When temp is low lizard sits broadside to sun and presses belly against warm rockspresses belly against warm rocks
When temp is high lizard moves to shade, burrow, When temp is high lizard moves to shade, burrow, walks on tiptoewalks on tiptoe
When temp is too low lizard seeks protected habitat When temp is too low lizard seeks protected habitat and becomes inactive; outcome depends on how and becomes inactive; outcome depends on how cold it getscold it gets
ExampleExample
Desert IguanaDesert Iguana ( (Dipsosaurus dorsalisDipsosaurus dorsalis)) in the in the southwestern US desert. southwestern US desert.
In summer temperatures can exceed 45In summer temperatures can exceed 45ooC, and in C, and in winter temperatures are often below 0winter temperatures are often below 0oo
During mid-July the thermal environment changes During mid-July the thermal environment changes so rapidly that activity is limited to 45 minutes in so rapidly that activity is limited to 45 minutes in the morning, and 45 minutes in the afternoon. the morning, and 45 minutes in the afternoon.
Figure describes the diurnal and seasonal Figure describes the diurnal and seasonal pattern of behavior: pattern of behavior:
Coping with Temperature VariationCoping with Temperature VariationPoikilothermsPoikilotherms
PhysiologyPhysiology
produce chemicals that lower the freezing produce chemicals that lower the freezing point of cytoplasmpoint of cytoplasm
freeze-tolerant species - have ice-nucleating freeze-tolerant species - have ice-nucleating agents (ECF freezes at lower temp than agents (ECF freezes at lower temp than cytoplasm; prevents ice crystals)cytoplasm; prevents ice crystals)
freeze-susceptible - produce glycerol etc; facilitate freeze-susceptible - produce glycerol etc; facilitate supercooling; lower freezing point to avoid ice supercooling; lower freezing point to avoid ice crystalscrystals
Advantages of being an Advantages of being an EctothermEctotherm
Greater efficiency: allocate 30%-90% of Greater efficiency: allocate 30%-90% of ingested energy towards growth (<5% in ingested energy towards growth (<5% in most endotherms)most endotherms)
Lower energy demands: can tolerate long Lower energy demands: can tolerate long periods with low food availabilityperiods with low food availability
Less energetic cost for small body size: Less energetic cost for small body size: able to occupy more niches for small-able to occupy more niches for small-bodied animalsbodied animals
Large Ectotherms?Large Ectotherms?
As body size increases, As body size increases, surface area-to-volume ratio surface area-to-volume ratio decreases, and large decreases, and large ectotherms are thus ectotherms are thus improbable.improbable.
This had led to speculation This had led to speculation that large dinosaurs may that large dinosaurs may have had some degree of have had some degree of endothermy.endothermy.
Homeotherms (endotherms)Homeotherms (endotherms) Physiological mechanisms for controlling body tempPhysiological mechanisms for controlling body temp
Keeping warmKeeping warm Metabolic heat: increased metabolism, shiveringMetabolic heat: increased metabolism, shivering Insulation (fat, fluffed fur or feathers) e.g. Birds, mammalsInsulation (fat, fluffed fur or feathers) e.g. Birds, mammals Body size and shapeBody size and shape
Keeping coolKeeping cool Lower metabolic heat productionLower metabolic heat production Evaporation: panting, sweatEvaporation: panting, sweat Body size and shapeBody size and shape
BirdsBirds MammalsMammals
Range and limits of homeothermyRange and limits of homeothermy
Thermoneutral zone = range of environmental Thermoneutral zone = range of environmental temperatures over which an animal can maintain temperatures over which an animal can maintain a constant body temperature without raising its a constant body temperature without raising its metabolic ratemetabolic rate
Lower and upper critical temperatures = Lower and upper critical temperatures = environmental temperatures at which animal environmental temperatures at which animal must raise its metabolic rate to maintain must raise its metabolic rate to maintain homeothermyhomeothermy
Lower and upper lethal temperatures = Lower and upper lethal temperatures = environmental temperatures at which animal can environmental temperatures at which animal can no longer raise its metabolic rate and diesno longer raise its metabolic rate and dies
BehaviorBehavior Burrows, dens, Burrows, dens,
shade during shade during hottest part of dayhottest part of day
Sled dog, arctic fox Sled dog, arctic fox wrap tail around wrap tail around faceface
Grouse burrows Grouse burrows under snowunder snow
Gular flutteringGular fluttering UrohydrosisUrohydrosis
Coping with Temperature Coping with Temperature Variation Variation HomoiothermsHomoiotherms
UrohydrosisUrohydrosis Excretion on the feet or legs Excretion on the feet or legs
which evaporates and then which evaporates and then cools the organism as the cools the organism as the excretion evaporates excretion evaporates
This is a common This is a common adaptation in birds such as adaptation in birds such as turkey vultures. turkey vultures.
A similar adaptation is seen A similar adaptation is seen in Kangaroos which lick their in Kangaroos which lick their forearms to wet them with forearms to wet them with saliva. saliva.
Cactus Wren: Daily behavior reflects the temperature of the microhabitats used. The orientation of the nest changes during the breeding season in order to maximize cooling in this desert environment.
Coping with Temperature VariationCoping with Temperature VariationHomoiothermsHomoiotherms
MorphologyMorphology Coloration is thought to be an important factor in the Coloration is thought to be an important factor in the
reduction of heat absorption. reduction of heat absorption. A lighter colored coat will reflect more light relative to A lighter colored coat will reflect more light relative to
a darker coat which will absorb more light. The result a darker coat which will absorb more light. The result is reduced body temperatures and more water is reduced body temperatures and more water conservation. conservation.
Insulation in the form of feathers, hair, or even body fat Insulation in the form of feathers, hair, or even body fat which protects tissues beneath by insulation.which protects tissues beneath by insulation.
Enlarged appendages (desert Jackrabbit’s ears) in Enlarged appendages (desert Jackrabbit’s ears) in order to increase surface area and hence promote heat order to increase surface area and hence promote heat loss. loss.
Desert Jackrabbit
Arabian oryx
Coping with Temperature VariationCoping with Temperature VariationHomoiothermsHomoiotherms
Physiology – keeping warm Physiology – keeping warm requires lots requires lots of foodof food Increased body fat for cold weather insulationIncreased body fat for cold weather insulation Increased metabolic rateIncreased metabolic rate Shivering (heat from muscle activity)Shivering (heat from muscle activity) Increase air spaces by fluffing feathers, furIncrease air spaces by fluffing feathers, fur Counter current mechanismsCounter current mechanisms
During the winter, the Willow Ptarmigan produces a denser coat of feathers and actually down-regulates its basal metabolism, which reduces the gradient between the internal body temperature and the external temperature. This is the same as keeping your house at a cooler temperature in order to reduce your heating bill. Both responses reduce the amount of energy necessary to stay warm.
Metabolic Heat ProductionMetabolic Heat Production
Endotherms produce heat by oxidizing energy-Endotherms produce heat by oxidizing energy-rich carbohydrate moleculesrich carbohydrate molecules
Some of the energy is stored but much is Some of the energy is stored but much is dissipated as heatdissipated as heat
Metabolic rate = rate at which energy-releasing Metabolic rate = rate at which energy-releasing chemical reactions occurchemical reactions occur
Basal (standard) metabolic rate = lowest rate of Basal (standard) metabolic rate = lowest rate of energy expenditure of resting, fasting animal in energy expenditure of resting, fasting animal in its comfortable temperature rangeits comfortable temperature range
CC66HH1212OO66 + 6 O + 6 O22 → 6 CO → 6 CO22 + 6 H + 6 H22O + energyO + energy
Counter current heat exchange
Mammalian Counter Current Example
Reduce Heat InputReduce Heat Input
Staying out of the sunStaying out of the sun Shading (e.g., spines/fur)Shading (e.g., spines/fur) Posture and orientation (e.g., orienting Posture and orientation (e.g., orienting
leaves vertically to minimize surface area leaves vertically to minimize surface area directly hit by sun)directly hit by sun)
InsulationInsulation Shiny surfaces that reflect sun, etc. Shiny surfaces that reflect sun, etc.
Dissipating HeatDissipating Heat
If heat reduction wasn't If heat reduction wasn't enough, then it is time to enough, then it is time to get rid of body heat byget rid of body heat by evaporation (costs water evaporation (costs water
though), though), long appendages (legs, long appendages (legs,
ears, etc.), or ears, etc.), or small "bodies" (e.g., small "bodies" (e.g.,
whole body, leaves, etc.) whole body, leaves, etc.) that radiate heat. that radiate heat.
Tolerate HyperthermiaTolerate Hyperthermia
Some plants and animals Some plants and animals can survive body can survive body temperatures that would temperatures that would be dangerous to humans be dangerous to humans (e.g., this antelope (e.g., this antelope ground squirrel tolerates ground squirrel tolerates body temperatures over body temperatures over 104 degrees F!). 104 degrees F!).
Advantages of being an endothermAdvantages of being an endotherm
Tolerate a wider range of Tolerate a wider range of environmental conditionsenvironmental conditions
Can be active day or night, Can be active day or night, year roundyear round
Can sustain high levels of Can sustain high levels of activity for longer periods activity for longer periods because rely more on because rely more on aerobic metabolism aerobic metabolism (anaerabic in ectotherms)(anaerabic in ectotherms)
Disadvantages of HomeothermyDisadvantages of Homeothermy
Homoiotherms can’t shut down completely if food, Homoiotherms can’t shut down completely if food, water, or oxygen disappearwater, or oxygen disappear
Homeotherms can’t be as small as poikilotherms. Homeotherms can’t be as small as poikilotherms. Lose too much heat as SA/V increases and can’t eat enough Lose too much heat as SA/V increases and can’t eat enough
to keep warm. to keep warm.
Homeotherms can't be wormlike or snakelike in shape. Homeotherms can't be wormlike or snakelike in shape. High SA/V - lose too much heat.High SA/V - lose too much heat.
Aquatic env favors poikilotherms because of high rate Aquatic env favors poikilotherms because of high rate of convection.of convection.
Other AdaptationsOther Adaptations Partial homeothermyPartial homeothermy - - Swordfish, Tuna, GW SharksSwordfish, Tuna, GW Sharks
Hunts near surface during the day; goes deep at nightHunts near surface during the day; goes deep at night T may be as much as 19T may be as much as 19oocc Has brain-eye heater to keep these organs at stable temp Has brain-eye heater to keep these organs at stable temp
(needed for hunting)(needed for hunting) Tissue rich in mitochondria; countercurrent blood supply; Tissue rich in mitochondria; countercurrent blood supply;
thick layer of fat around brain and eyesthick layer of fat around brain and eyes
HeterothermsHeterotherms - - warm-blooded species that hibernate warm-blooded species that hibernate (temporary poikilothermy)(temporary poikilothermy)
Temporary homeothermyTemporary homeothermy during egg incubation by during egg incubation by some snakessome snakes
Heat stable enzymesHeat stable enzymes in thermophilic bacteria in thermophilic bacteria
Endothermy in insectsEndothermy in insects: : sphinx mothssphinx moths
active moths maintain active moths maintain constant metabolic rateconstant metabolic rate
regulate body temp by regulate body temp by modifying cooling ratemodifying cooling rate
heat produced by flight heat produced by flight muscles in thorax is muscles in thorax is transported via transported via circulatory system to circulatory system to abdomenabdomen
Ecology of BumblebeesEcology of Bumblebees
Bumblebees live in many cool Bumblebees live in many cool regions.regions. Bernd HeinrichBernd Heinrich estimated the estimated the
energy budgetenergy budget of individuals of individuals foraging on different flowers foraging on different flowers and under different and under different temperatures.temperatures.
Energy Gain / LossEnergy Gain / Loss
Energy Intake - Energy Energy Intake - Energy ExpenditureExpenditure..
How to Keep WarmHow to Keep WarmMore ExamplesMore Examples
BaskBask
Compact BodyCompact Body
ShiverShiver
HibernateHibernate
HibernateHibernate
The Grizzled Checkerspot butterfly also is The Grizzled Checkerspot butterfly also is very short lived as an adult. As a very short lived as an adult. As a caterpillar, it takes two summers of eating caterpillar, it takes two summers of eating before it is ready to pupate and before it is ready to pupate and metamorphose into an adult butterfly, so it metamorphose into an adult butterfly, so it has to hibernate twice. Since most of this has to hibernate twice. Since most of this species is on the same two-year cycle, species is on the same two-year cycle, you are only likely to see these butterflies you are only likely to see these butterflies in odd years!in odd years!
Burrow Below GroundBurrow Below Ground
"Gopher Eskers" "Gopher Eskers"
Burrow Below GroundBurrow Below Ground
Pocket GopherPocket Gopher
Stay Awake and Hoard FoodStay Awake and Hoard Food
MigrateMigrate