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Transcript of Dafeng Hui Office: Harned Hall 320 Phone: 963-5777 Email: dhui@tnstate
BIOL 4120: Principles of EcologyBIOL 4120: Principles of Ecology
Lecture 3: Lecture 3: Adaptation to Adaptation to Physical Environment: Light, Physical Environment: Light,
Energy and HeatEnergy and Heat
Dafeng HuiDafeng Hui
Office: Harned Hall 320Office: Harned Hall 320
Phone: 963-5777Phone: 963-5777
Email: [email protected]: [email protected]
Topics (Chapter 3)Topics (Chapter 3) 3.1 Light is primary source of energy for the 3.1 Light is primary source of energy for the
biospherebiosphere 3.2 Plants capture the energy of sunlight by 3.2 Plants capture the energy of sunlight by
photosynthesisphotosynthesis 3.3 Plants modify photosynthesis in high water stress 3.3 Plants modify photosynthesis in high water stress
environmentsenvironments 3.4 Diffusion limits uptakes of dissolved gases from 3.4 Diffusion limits uptakes of dissolved gases from
waterwater 3.5 Temperature limits occurrence of life3.5 Temperature limits occurrence of life 3.6 Each organism functions best under certain 3.6 Each organism functions best under certain
temperaturetemperature 3.7 Homeothermy increases metabolic rate and 3.7 Homeothermy increases metabolic rate and
efficiencyefficiency
Earth provides highly diverse environments:Earth provides highly diverse environments:
1.7 million known species now1.7 million known species now
All species have three common All species have three common basic functionsbasic functions
Assimilation:Assimilation: acquire energy from external environment acquire energy from external environment Reproduction:Reproduction: to produce new individuals to produce new individuals Response to external stimuli:Response to external stimuli: able to respond to both able to respond to both
physical (light, temperature etc) and biotic (predator etc).physical (light, temperature etc) and biotic (predator etc).
All organisms acquire energyAll organisms acquire energy• Energy obtained directly from an energy source by a living Energy obtained directly from an energy source by a living
organism is called autotrophy (autotroph)organism is called autotrophy (autotroph) Plants are autotrophs, primary producersPlants are autotrophs, primary producers So are certain bacteria like So are certain bacteria like Thiobacullus ferrooxidansThiobacullus ferrooxidans
• Energy obtained indirectly from organic molecules by a living Energy obtained indirectly from organic molecules by a living organism is called heterotrophy (heterotroph)organism is called heterotrophy (heterotroph)
All animals are heterotrophs, secondary producersAll animals are heterotrophs, secondary producers Some organisms can be a mixture like lichens where you have an Some organisms can be a mixture like lichens where you have an
alga and a fungus living togetheralga and a fungus living together
Autotrophs obtain solar energy through photosynthesis.
All life requires energy to All life requires energy to sustain itselfsustain itself
With very few exceptions, With very few exceptions, all life on earth is all life on earth is dependent on solar dependent on solar energyenergy
Life on Earth exists Life on Earth exists because itbecause it’’s fitness is s fitness is optimal for the optimal for the environment created by environment created by solar energysolar energy
Shortwave Shortwave longwave radiationlongwave radiation
Earth is a balanced ecosystem in term of solar energy inputs and outputs
3.1 Light is the primary source of 3.1 Light is the primary source of energy for the biosphereenergy for the biosphere
Light is the primary source of Light is the primary source of energy for the biosphereenergy for the biosphere
PAR: photosynthetically active radiation400-700 nm
Light absorption spectra of plants
Light absorption spectra of algae
Ulva: sea lettuce, shallow water
Porphyra: red alga, deep-water
3.2 Plants capture energy of 3.2 Plants capture energy of sunlight by photosynthesissunlight by photosynthesis
Photosynthesis (review)Photosynthesis (review) All life is built on a framework of carbon All life is built on a framework of carbon
atomsatoms The ultimate source of carbon for The ultimate source of carbon for
organic molecules is COorganic molecules is CO22
COCO22 is transformed into organic is transformed into organic molecules by plants (photosynthesis).molecules by plants (photosynthesis).
Photosynthesis begins with Photosynthesis begins with light reactionslight reactions• Absorption of light energy by Absorption of light energy by chlorophyllchlorophyll (a (a
pigment molecule)pigment molecule)• Conversion of the light energy into ATP (adenosine Conversion of the light energy into ATP (adenosine
tri-Phosphate) and NADPH (Reduced form of tri-Phosphate) and NADPH (Reduced form of nicotinamide adenine dinucleotide phosphate)nicotinamide adenine dinucleotide phosphate)
Photosynthesis continues with the Photosynthesis continues with the dark reactionsdark reactions
• Incorporation of COIncorporation of CO22 into simple (organic) sugars into simple (organic) sugars using the energy provided by ATP and NADPHusing the energy provided by ATP and NADPH
• Carboxylation is catalyzed by the enzyme Carboxylation is catalyzed by the enzyme rubisco rubisco (ribulose biphosphate (RuBP) carboxylase-(ribulose biphosphate (RuBP) carboxylase-oxygenase)oxygenase)
Photosynthesis is the process by which the Sun’s energy (shortwave radiation) is used to fix CO2 into carbohydrates (simple sugars) and release O2
The The Calvin cycleCalvin cycle ( (CC33 cycle cycle) initially ) initially fixes COfixes CO22 into 3-PGA into 3-PGA (phosphoglycerate)(phosphoglycerate)
This cycle is called Calvin-Bensen This cycle is called Calvin-Bensen cycle, or Ccycle, or C33 cycle. Plants employing it cycle. Plants employing it are known as Care known as C33 plants plants
C3C3
RuBP: Ribulose biphosphateRubisco: ribulose biphosphate (RuBP) carboxylase-oxygenase
3-PGA: phosphoglycerate
G3P: glyceraldehyde 3-phosphate
One major drawback of C3 pathway:
Rubisco can catalyze both carbonxylation
And RuBP oxygenation
Reduce the efficiency of photosynthesis.
C3 cycle (Calvin cycle) C3 cycle (Calvin cycle)
PGARuBPCO 322
C3 plant: trees, forbs, some grasses
22 CORuBPO
Cellular respirationCellular respiration
ATPOHCOOOHC 2226126 666
Net photosynthesis = (Gross) Photosynthesis - Respiration
2612622 666 OOHCOHCO
PhotosynthesisPhotosynthesis
BIOL 4120: Principles of EcologyBIOL 4120: Principles of Ecology
Lecture 3: Lecture 3: Adaptation to Adaptation to Physical Environment: Light, Physical Environment: Light,
Energy and HeatEnergy and Heat
Dafeng HuiDafeng Hui
Office: Harned Hall 320Office: Harned Hall 320
Phone: 963-5777Phone: 963-5777
Email: [email protected]: [email protected]
RecapRecap
Water and salt balance by plants and Water and salt balance by plants and animalsanimals
Solar radiation is the energy source Solar radiation is the energy source for life, PAR, water absorptionfor life, PAR, water absorption
PhotosynthesisPhotosynthesis C3 photosynthetic pathwayC3 photosynthetic pathway
To increase water use To increase water use efficiency in a warm dry efficiency in a warm dry environment, plants have environment, plants have modified process of modified process of photosynthesisphotosynthesis
CC33
• Normal in mesophyll Normal in mesophyll with rubiscowith rubisco
CC44
• Warm dry environmentWarm dry environment• Additional step in Additional step in
fixation of COfixation of CO22
• Phosphoenolpyruvate Phosphoenolpyruvate synthasesynthase (PEP) does (PEP) does initial fixation into initial fixation into Malate and aspartate Malate and aspartate
• Malate and aspartate Malate and aspartate are transported to are transported to bundle sheath as an bundle sheath as an intermediate moleculeintermediate molecule
• Rubisco and CORubisco and CO22 convert there to convert there to sucrosesucrose
3.3 Other photosynthesis pathways: adaptation to water and temperature conditions
C4 pathway
Advantages over C3 pathway
1. PEP does not interact with O2 (RuBP react with O2 and reduce the photosynthesis efficiency)
2. Conversion of malic and aspartic acids into CO2 within bundle sheath cell acts to concentrate CO2, create a much higher CO2 concentration.
C4 plants have a much higher photosynthetic rate and greater water-use efficiency.
C4 plants are mostly grasses native to tropical and subtropical regions and some shrubs of arid and saline environments (Crop: corn, sorghum, sugar cane).
CAM pathway
CAM (Crassulacean acid metabolism) pathway
Hot desert area
Mostly succulents in the family of Cactaceae (cacti), Euphorbiaceae and Crassulaceae)
Similar to C4 pathway
Different times:
Night: open stomata, convert CO2 to malic acid using PEP
Day:close stomata, re-convert malic acid to CO2, C3 cycle.
Comparison of three photosynthetic pathways
C3: Dovefoot geranium, C4: sorghum, CAM: Sierra sedium
3.4 Plant adaptation to control water loss
In addition to photosynthetic pathway differences, heat and drought-adapted plants have anatomic and physiological modifications that reduce transpiration, heat load and enable plants to tolerate high temperature.
3.5 Photosynthesis of aquatic plants3.5 Photosynthesis of aquatic plants
Unique featuresUnique features• Lack of stomataLack of stomata• Direct diffusion of CO2 across cell membraneDirect diffusion of CO2 across cell membrane
Slow in water than in air (10^4 times slower)Slow in water than in air (10^4 times slower)
• Some plants: CO2 reacts with H2O first to produce Some plants: CO2 reacts with H2O first to produce biocarbonate, and Convert biocarbonate to CO2biocarbonate, and Convert biocarbonate to CO2
Transport HCOTransport HCO33-- into leaf then convert to CO2 into leaf then convert to CO2
Excretion of the enzyme into adjacent waters and Excretion of the enzyme into adjacent waters and subsequent uptake of converted CO2 across the subsequent uptake of converted CO2 across the membrane. membrane.
CO2 could be a constraint in dense sea-grass bedsCO2 could be a constraint in dense sea-grass beds
Oxygen concentration in aquatic Oxygen concentration in aquatic environmentenvironment
O2 is dissolved in water
O2 concentration in water is determined by solubility and diffusion.
Anaerobic conditions in the deep water
High O2 in the surface due to diffusion
3.6 Carbon gained in photosynthesis is allocated to production of plant tissues
Carbon allocation is an important issue and has not been well studied.
Difficult to measure, especially below ground.
Allocation to different parts has major influences on survival, growth, and reproduction.
Leaf: photosynthesis
Stem: support
Root: uptake of nutrient and water
Flower and seed: reproduction.
In dry grassland ecosystems, plants have long roots
Allocation and environmental factors (such Allocation and environmental factors (such as temperature and precipitation)as temperature and precipitation)
Hui & Jackson 2006
Plants must maintain a positive carbon Plants must maintain a positive carbon balance to survive, grow, and reproducebalance to survive, grow, and reproduce
Essential plant resources and conditions are Essential plant resources and conditions are interdependentinterdependent• Light (PAR)Light (PAR)
• COCO22
• HH22O and MineralsO and Minerals
• TemperatureTemperature
Constraints Imposed by the Physical Constraints Imposed by the Physical Environment Have Resulted in a Wide Environment Have Resulted in a Wide
Array of Plant AdaptationsArray of Plant Adaptations
3.7 Species of Plants are adapted 3.7 Species of Plants are adapted to light conditionsto light conditions
Plants adapted to a shady Plants adapted to a shady environmentenvironment• Lower levels of rubiscoLower levels of rubisco• Higher levels of Higher levels of
chlorophyll (increase chlorophyll (increase ability to capture light, as ability to capture light, as light is limiting)light is limiting)
• low light compensation low light compensation and saturation lightsand saturation lights
Plants adapted to a full sun Plants adapted to a full sun environmentenvironment• Higher levels of rubiscoHigher levels of rubisco• Lower levels of chlorophyllLower levels of chlorophyll• High compensation and High compensation and
saturation lightssaturation lights Changes in leaf structure Changes in leaf structure
evolveevolve
Red oak leaves at top and bottom of canopy
Light intensity
Stuart Davies of Harvard University studied the photosynthesis and respiration of seedlings of nine tree species under different light
Light affects photosynthesis and respirationLight affects photosynthesis and respiration
Shade tolerant (shade-Shade tolerant (shade-adapted) speciesadapted) species• Plant species adapted to Plant species adapted to
low-light environmentslow-light environments Shade intolerant (sun-Shade intolerant (sun-
adapted) speciesadapted) species• Plant species adapted to Plant species adapted to
high-light environmentshigh-light environments
Change of allocation to leaf of broadleaved peppermint (Reich et al.).
Light also affects whether a plant allocates to Light also affects whether a plant allocates to leaves or to rootsleaves or to roots
Shade tolerance and intoleranceShade tolerance and intolerance
Shade tolerance
Shade intolerance
Seedling survival and growth of two tree species over a year
Augspurger (1982)
BIOL 4120: Principles of EcologyBIOL 4120: Principles of Ecology
Lecture 3: Lecture 3: Adaptation to Adaptation to Physical Environment: Light, Physical Environment: Light,
Energy and HeatEnergy and Heat
Dafeng HuiDafeng Hui
Office: Harned Hall 320Office: Harned Hall 320
Phone: 963-5777Phone: 963-5777
Email: [email protected]: [email protected]
RecapRecap
C4 and CAM pathwaysC4 and CAM pathways Aquatic plantsAquatic plants Photosynthesis and environmental Photosynthesis and environmental
factorsfactors• Light, response curve, adaptationLight, response curve, adaptation
Different responses of Different responses of photosynthesis and photosynthesis and respiration to temperature;respiration to temperature;
Three basic Temperature Three basic Temperature pointspoints• Min T, max T and optimal TMin T, max T and optimal T
3.9 Temperatures influence photosynthesis and respiration
Plants need to make serious evolutionary Plants need to make serious evolutionary adaptations to temperatureadaptations to temperature
Topt: CTopt: C3: 3: <30<30ooC; CC; C4: 4: 3030ooC to 40C to 40ooC; CAM, >40C; CAM, >40ooCC
Neuropogon: Arctic lichen (C3)
Ambrosia: cool coastal dune plant (C3)
Tidestromia: summer-active desert C4 perennial
Atriplx: everygreen desert C4 plant
C3
C4
C4
Photosyn. rate and Topt
Temperature responses are not fixedTemperature responses are not fixed When individuals of the same species are When individuals of the same species are
grown under different thermal conditions, a grown under different thermal conditions, a divergence in temperature response of net divergence in temperature response of net photosynthesis is often observedphotosynthesis is often observed
• The The TToptopt shifts in the direction of the shifts in the direction of the thermal conditions under which the plant is thermal conditions under which the plant is growngrown
A similar pattern is seen in individual plants A similar pattern is seen in individual plants in response to seasonal shifts in temperature in response to seasonal shifts in temperature (acclimation)(acclimation)
Plants Vary in Their Response to Plants Vary in Their Response to Environmental TemperaturesEnvironmental Temperatures
Big saltbush, C4
Affinity is a good measure of enzyme function. Produce different forms of enzyme.
Plants need nutrient for Plants need nutrient for metabolic processes and metabolic processes and synthesize new tissuessynthesize new tissues
According to amount of According to amount of nutrient required:nutrient required:• Macronutrients: needed in Macronutrients: needed in
large amountlarge amount N, P, K, Ca, Mg, SN, P, K, Ca, Mg, S
• Micronutrients: needed in Micronutrients: needed in lesser quantitieslesser quantities
Zn, B, Cu, Ni, Fe Zn, B, Cu, Ni, Fe
Some nutrients can be Some nutrients can be inhibitoryinhibitory
3.12 Plants exhibit adaptations to variations in nutrient availability
Uptake of a nutrient Uptake of a nutrient through the roots through the roots depends on its depends on its concentrationconcentration
However there is a However there is a maximum uptake maximum uptake raterate
Effect of nutrient Effect of nutrient availability can also availability can also reach a maximumreach a maximum
Plants exhibit adaptations to variations in nutrient availability
Photosynthesis and nutrientPhotosynthesis and nutrient
Nitrogen can limit Nitrogen can limit photosynthesisphotosynthesis
N in enzyme N in enzyme rubisco and rubisco and pigment pigment chlorophyll.chlorophyll.
Plants respond Plants respond differently to extra differently to extra nitrogen depending nitrogen depending on their natural on their natural environmentenvironment’’s level s level of nitrogen or other of nitrogen or other nutrientnutrient
Two grass species, carpet bent grass (A. stolonifera) in high N and velent bent grass (A. canina) in low N conditions.
Illustration of Illustration of tradeoffs of tradeoffs of
C4, C3 plants C4, C3 plants with COwith CO22
concentrationconcentration
Increase in CO2 will influence the competition of C3 and C4
Other factors: Impact of CO2 on photosynthesis
3.13 Regulation of internal conditions 3.13 Regulation of internal conditions involves homeostasis and feedbackinvolves homeostasis and feedback
Homeostasis:Homeostasis: The maintenance of a The maintenance of a relatively constant internal environment in relatively constant internal environment in a varying external environment.a varying external environment.
Homeostasis depends on negative feedbackHomeostasis depends on negative feedbackNegative feedback:Negative feedback: when a system when a system
deviates from the normal or desired state, deviates from the normal or desired state, mechanisms function to restore the mechanisms function to restore the system back to that state.system back to that state.
Example: room temperature settingExample: room temperature setting
HomeostasisHomeostasis To stay alive, animals To stay alive, animals
need to keep their body need to keep their body within certain limitswithin certain limits• TemperatureTemperature• Water balanceWater balance• pHpH• Salt balanceSalt balance
Feedback systems to Feedback systems to help to keep within help to keep within specific limitsspecific limits
Outside limits Outside limits –– • DehydrationDehydration• Heat shockHeat shock• Salt imbalanceSalt imbalance• DeathDeath
Negative feedback (thermoregulation)
Body structure influences the Body structure influences the T exchangeT exchange
Temperature (Tb, Ts, Ta)Temperature (Tb, Ts, Ta)
Tb<->Ts Tb<->Ts conductionconduction• Core temperature TbCore temperature Tb• Surface temperature TsSurface temperature Ts
EarsEars FingersFingers ToesToes
Ts<->Ta: Ts<->Ta: convection, convection, radiation, evaporationradiation, evaporation Boundary layerBoundary layer (a thin layer of air (a thin layer of air
surround the body)surround the body)
Insulation (air, body Insulation (air, body covering) influences energy covering) influences energy exchangesexchanges
Animals exchange energy with their surrounding environment
3.14 Animals have different methods of 3.14 Animals have different methods of maintaining their body temperaturesmaintaining their body temperaturesThree groups of animalsThree groups of animals Endothermy resulting in homeothermyEndothermy resulting in homeothermy
• Use of internal heat source (metabolically)Use of internal heat source (metabolically) Mammals and birdsMammals and birds Maintain a fairly constant temperature (warm-blooded)Maintain a fairly constant temperature (warm-blooded)
Ectothermy resulting in poikilothermyEctothermy resulting in poikilothermy• Use of external heat sourcesUse of external heat sources
Reptiles, amphibians, fish, insects and invertebratesReptiles, amphibians, fish, insects and invertebrates Results in a variable body temperature (cold-blooded)Results in a variable body temperature (cold-blooded)
HeterothermyHeterothermy• Uses both endothermy and ectothermyUses both endothermy and ectothermy
Bats, bees and hummingbirdsBats, bees and hummingbirds
• As the temperature As the temperature increases, so does the increases, so does the metabolic ratemetabolic rate
• Therefore these animals Therefore these animals are more active during the are more active during the dayday
• Every 10Every 10ooC doubles C doubles metabolic rate (Q10)metabolic rate (Q10)
• Natural condition: low Natural condition: low metabolic rate and high metabolic rate and high conductivityconductivity
• Activities also controlled by Activities also controlled by temperaturetemperature
• Upper and lower limits varyUpper and lower limits vary Lizards and snakes have a Lizards and snakes have a
55ooCC Amphibians have a 10Amphibians have a 10ooCC
Poikilotherms depend on Poikilotherms depend on environmental temperaturesenvironmental temperatures
Operative T range: range of body T at which poikilotherms can carry out their daily activities.
During the day, the snake During the day, the snake can maintain a fairly can maintain a fairly constant temperature by constant temperature by adjusting itadjusting it’’s environment s environment (bask in sun to raise T, (bask in sun to raise T, seek shade to cool, seek shade to cool, submerge in water etc)submerge in water etc)
During the night, it has During the night, it has few optionsfew options• Temperature drops 10-Temperature drops 10-
15 degrees15 degrees• Become torpid (slow Become torpid (slow
moving)moving)• Restricted by Restricted by
environmentenvironment• Maximum size due to Maximum size due to
need for surface area need for surface area to gather heatto gather heat
• No minimum sizeNo minimum size
3.15 Homeotherms escape the thermal 3.15 Homeotherms escape the thermal restraints of the environmentrestraints of the environment
Homeotherms can escape the thermal restraints of Homeotherms can escape the thermal restraints of the environments, thus the environments, thus can exploit a wide range of thermal environments
But needs energy to maintain relative constant TBut needs energy to maintain relative constant T Therefore homeotherms use large amounts of Therefore homeotherms use large amounts of
glucose etc to maintain temperature (aerobic glucose etc to maintain temperature (aerobic respiration)respiration)
O2 is consumed during respirationO2 is consumed during respiration Rate of O2 consumption is used to measure Rate of O2 consumption is used to measure
metabolic ratemetabolic rate Basal metabolic rate is considered as proportional Basal metabolic rate is considered as proportional
to their body mass (body mass to their body mass (body mass 0.750.75) (debate? See ) (debate? See Hui & Jackson 2007 and others)Hui & Jackson 2007 and others)
Metabolic rate and body massMetabolic rate and body mass
Resting metabolic rate and ambient Resting metabolic rate and ambient temperaturetemperature
Thermoneutral zone: a range of environmental temperatures within which the metabolic rates are minimal.
Critical T: lower and upper critical T
BIOL 4120: Principles of EcologyBIOL 4120: Principles of Ecology
Lecture 3: Lecture 3: Adaptation to Adaptation to Physical Environment: Light, Physical Environment: Light,
Energy and HeatEnergy and Heat
Dafeng HuiDafeng Hui
Office: Harned Hall 320Office: Harned Hall 320
Phone: 963-5777Phone: 963-5777
Email: [email protected]: [email protected]
RecapRecap
Photosynthesis and environmental Photosynthesis and environmental factorsfactors• (Light) Temperature(Light) Temperature• Nutrients (and Water)Nutrients (and Water)• CO2CO2
Homeostasis and negative feedbackHomeostasis and negative feedback
Endothermy and ecotothermy Endothermy and ecotothermy
Homeotherms can escape the thermal Homeotherms can escape the thermal constraints of the environmentsconstraints of the environments
Ways to keep body warm: Ways to keep body warm: 1. Insulation to reduce the convection: fur, feather, or body fat1. Insulation to reduce the convection: fur, feather, or body fat Mammals: fur, change fur in the winterMammals: fur, change fur in the winter
Fur can keep body heat in and the Fur can keep body heat in and the heat outheat out Birds: featherBirds: feather Insects: a dense fur-like coat (moths, bees)Insects: a dense fur-like coat (moths, bees)2. When insulation fails: shivering (a form of involuntary 2. When insulation fails: shivering (a form of involuntary
muscular activity that increase heat production.muscular activity that increase heat production.3. Small mammals: burn brown fat (bats) without shivering.3. Small mammals: burn brown fat (bats) without shivering.
Ways to keep body Cool:Ways to keep body Cool:1. birds and mammals: evaporation of moisture from skin1. birds and mammals: evaporation of moisture from skin2. mammals: sweat glands (horse, human), panting2. mammals: sweat glands (horse, human), panting3. birds: gular fluttering3. birds: gular fluttering
3.16 Endothermy and Ectothermy involve 3.16 Endothermy and Ectothermy involve trade-offstrade-offs
Endotherms can survive in large range of T, Endotherms can survive in large range of T, why not all animals are endotherms?why not all animals are endotherms?
Trade-offs:Trade-offs:
EndothermyEndothermy EctothermsEctothermsActivity: under all environments limited to environmental TActivity: under all environments limited to environmental TEnergy: high lowEnergy: high lowFood: most for respiration, less less for respirationFood: most for respiration, less less for respiration to growth more to growthto growth more to growthLimits on size:Limits on size: limit on minimum size limit on maximum size limit on minimum size limit on maximum size
Limited in sizeLimited in size
Warm-blooded animals: body Warm-blooded animals: body mass (volume) produce mass (volume) produce heat, lost through surface heat, lost through surface area, the ratio of surface to area, the ratio of surface to volume is key factor too.volume is key factor too.• Small animals have Small animals have
larger ratio and greater larger ratio and greater relative heat loss to relative heat loss to environment, require environment, require higher mass-specific higher mass-specific metabolic rate to metabolic rate to maintain and consume maintain and consume more food energy per more food energy per unit body weight. unit body weight.
• Too smallToo small Need too much Need too much
energy to keep energy to keep temperature stabletemperature stable
2 gm limit2 gm limit Shrew (SolexShrew (Solex spp) spp)
eats own body eats own body weight in food every weight in food every day to maintain day to maintain temperaturetemperature
Cold-blooded animals absorb heat through surface, thus the surface area to volume is key factor. Large animals limited to warm areas.
S/V=6*1/L
3.17 Torpor and hibernation help some 3.17 Torpor and hibernation help some animals conserve energyanimals conserve energy
TorporSmall homeothemic animals become heterothermic
Body temperature drops to ambient at night
Inactive
Bats, Some mice, kangaroos
Torpor and hibernation help some Torpor and hibernation help some animals conserve energyanimals conserve energy
HibernationHibernation• Many poikilotherms and some mammals have winter Many poikilotherms and some mammals have winter
torpor to save energytorpor to save energy• Selective advantage when resources are fewSelective advantage when resources are few• MammalsMammals
Heart rate, respiration fallHeart rate, respiration fall Temperature drops to ambientTemperature drops to ambient Groundhogs, chipmonksGroundhogs, chipmonks Not all bearsNot all bears
• No temperature changeNo temperature change• Just long sleep with no eating, drinking, defecating Just long sleep with no eating, drinking, defecating
or urinatingor urinating• Females give birth and feed young in this periodFemales give birth and feed young in this period• Can wake up easilyCan wake up easily• Do not visit a bear cave in winter!Do not visit a bear cave in winter!
3.18 Some animals use unique physiological 3.18 Some animals use unique physiological means for thermal balancemeans for thermal balance
Storing body heat: Storing body heat:
Camel, oryx and some gazelles Camel, oryx and some gazelles
Body T change from 34oc to 41oC for camelBody T change from 34oc to 41oC for camel
Reduce need for evaporative cooling and save water and energyReduce need for evaporative cooling and save water and energy
Supercooling:Supercooling:
many ectothermic animals of temperate and Arctic regionsmany ectothermic animals of temperate and Arctic regions
When the body T below freezing points without actually freezingWhen the body T below freezing points without actually freezing
The presence of certain solute (glycerol) in the body lower the The presence of certain solute (glycerol) in the body lower the freezing pointsfreezing points
Wood frog, grey tree frog, spring peeperWood frog, grey tree frog, spring peeper
Countercurrent heat exchange:Countercurrent heat exchange:to conserve heat in a cold environment and to cool vital part of to conserve heat in a cold environment and to cool vital part of body during heat stress.body during heat stress.
Countcurrent heat exchange happens in Countcurrent heat exchange happens in homeotherms (porpoise, whale) as well as in certain homeotherms (porpoise, whale) as well as in certain poikilotherms (tuna, mackerel shark)poikilotherms (tuna, mackerel shark)
To preserve heat in cold water, and get ride of heat in warm water
To cool brain, reduce T by 2-3 oC
The ENDThe END