Dafeng Hui Office: Harned Hall 320 Phone: 963-5777 Email: dhui@tnstate

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BIOL 4120: Principles of Ecology BIOL 4120: Principles of Ecology Lecture 3: Lecture 3: Adaptation Adaptation to Physical Environment: to Physical Environment: Light, Energy and Heat Light, Energy and Heat Dafeng Hui Dafeng Hui Office: Harned Hall Office: Harned Hall 320 320 Phone: 963-5777 Phone: 963-5777 Email: Email: [email protected] [email protected]

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BIOL 4120: Principles of Ecology Lecture 3: Adaptation to Physical Environment: Light, Energy and Heat. Dafeng Hui Office: Harned Hall 320 Phone: 963-5777 Email: [email protected]. Topics (Chapter 3). 3.1 Light is primary source of energy for the biosphere - PowerPoint PPT Presentation

Transcript of Dafeng Hui Office: Harned Hall 320 Phone: 963-5777 Email: dhui@tnstate

Page 1: 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]

Page 2: Dafeng Hui Office:  Harned Hall 320 Phone: 963-5777 Email: dhui@tnstate

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

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Earth provides highly diverse environments:Earth provides highly diverse environments:

1.7 million known species now1.7 million known species now

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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.

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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

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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

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Light absorption spectra of plants

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Light absorption spectra of algae

Ulva: sea lettuce, shallow water

Porphyra: red alga, deep-water

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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).

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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

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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

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RuBP: Ribulose biphosphateRubisco: ribulose biphosphate (RuBP) carboxylase-oxygenase

3-PGA: phosphoglycerate

G3P: glyceraldehyde 3-phosphate

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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

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Cellular respirationCellular respiration

ATPOHCOOOHC 2226126 666

Net photosynthesis = (Gross) Photosynthesis - Respiration

2612622 666 OOHCOHCO

PhotosynthesisPhotosynthesis

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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]

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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

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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

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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).

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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.

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Comparison of three photosynthetic pathways

C3: Dovefoot geranium, C4: sorghum, CAM: Sierra sedium

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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.

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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

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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

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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.

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In dry grassland ecosystems, plants have long roots

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Allocation and environmental factors (such Allocation and environmental factors (such as temperature and precipitation)as temperature and precipitation)

Hui & Jackson 2006

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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

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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

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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

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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

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Shade tolerance and intoleranceShade tolerance and intolerance

Shade tolerance

Shade intolerance

Seedling survival and growth of two tree species over a year

Augspurger (1982)

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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]

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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

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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

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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

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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

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Big saltbush, C4

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Affinity is a good measure of enzyme function. Produce different forms of enzyme.

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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

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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

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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.

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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.

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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

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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

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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

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Negative feedback (thermoregulation)

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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

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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

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• 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.

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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

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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)

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Metabolic rate and body massMetabolic rate and body mass

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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

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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]

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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

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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

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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

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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

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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

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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!

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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.

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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

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To cool brain, reduce T by 2-3 oC

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The ENDThe END