Energy Flow Through Ecosystems An Introduction to Energy and Laws of Thermodynamics.

Energy Energy Flow Flow

Through Through EcosystemEcosystem

ss

An Introduction to Energy and An Introduction to Energy and Laws of ThermodynamicsLaws of Thermodynamics

Ecosystem EcologyEcosystem Ecology• Examines interactions between the living and non-living worldExamines interactions between the living and non-living world• Ecosystem- the sum of all the organisms living within its Ecosystem- the sum of all the organisms living within its

boundaries (biotic community) and all the abiotic factors with boundaries (biotic community) and all the abiotic factors with which they interactwhich they interact

Levels of OrganizationLevels of OrganizationBiosphereBiosphere

BiomeBiome

EcosystemEcosystem

CommunityCommunity

PopulationPopulation

OrganismOrganism

ThermodynamicsThermodynamics• Physical Laws that govern energy relationshipsPhysical Laws that govern energy relationships• Involves Two Processes:Involves Two Processes: • Energy FlowEnergy Flow

– – Energy cannot Energy cannot be recycled be recycled therefore there therefore there must be a constant must be a constant supplysupply

• Chemical Recycling Chemical Recycling – – Matter can be Matter can be recycledrecycled and and Nature does it with Nature does it with perfection.perfection.

• The study of energy The study of energy transformationtransformation– In short, the law of conservation In short, the law of conservation

of energy states that energy can of energy states that energy can not be created or destroyed, it not be created or destroyed, it can only be changed from one can only be changed from one form to another or transferred form to another or transferred from one body to another, but from one body to another, but the total amount of energy the total amount of energy remains constant (the same).remains constant (the same).

First law of thermodynamics: Energy can be transferred or transformed but Neither created nor destroyed. For example, the chemical (potential) energy in food will be converted to the kinetic energy of the cheetah’s movement in (b).

(a)

Chemicalenergy

First Law of ThermodynamicsFirst Law of ThermodynamicsConservation of EnergyConservation of Energy

• In any energy transformation, some energy is lost as unusable In any energy transformation, some energy is lost as unusable energy in the sense that work cannot be performed. This is energy in the sense that work cannot be performed. This is usually in the form of heat.usually in the form of heat.

Second law of thermodynamics: Every energy transfer or transformation increasesthe disorder (entropy) of the universe. For example, disorder is added to the cheetah’ssurroundings in the form of heat and the small molecules that are the by-productsof metabolism.

(b)

Heat co2

H2O+

Second Law of ThermodynamicsSecond Law of ThermodynamicsLaw of EntropyLaw of Entropy

Two Important QuestionsTwo Important Questions• Where does the energy needed for living Where does the energy needed for living

organisms originate?organisms originate?• How is energy used by these organisms?How is energy used by these organisms?

Flow of energy through life = MetabolismFlow of energy through life = Metabolism• The totality of an organism’s chemical reactionsThe totality of an organism’s chemical reactions– driving life processes by transforming energy from one driving life processes by transforming energy from one

form to anotherform to another

organic molecules ATP & organic molecules

organic molecules ATP & organic molecules

sun

solar energy ATP & organic molecules

MetabolismMetabolismChemical reactions of life Chemical reactions of life Oxidation – Reduction Oxidation – Reduction

Anabolic reactionsAnabolic reactions› Forming bonds between Forming bonds between

moleculesmolecules› Consume energyConsume energy

Catabolic reactionsCatabolic reactions› Breaking bonds between Breaking bonds between

moleculesmolecules› Release energyRelease energy

Living OrganismsLiving Organisms• Temporary Temporary

storage units for storage units for useful energy, useful energy, whereby one whereby one organism can be organism can be used by another used by another as a source of as a source of energy.energy.

The Source of High Quality EnergyThe Source of High Quality Energy• Most of the Most of the

Energy arrives as Energy arrives as electromagnetic electromagnetic radiation from the radiation from the sun sun

• Supports Supports photosynthesis photosynthesis (less than 2%)(less than 2%)

• Powers the cycling Powers the cycling of matterof matter

• Drives climate and Drives climate and weather that weather that distribute heat distribute heat and Hand H22OO

Solarradiation

Energy in = Energy out

Reflected byatmosphere (34%)

UV radiation

Absorbedby ozone

Absorbedby the earth

Visiblelight

Lower Stratosphere(ozone layer)

Troposphere

Heat

Greenhouseeffect

Radiated byatmosphere

as heat (66%)

Earth

Heat radiatedby the earth

• They capture energy and They capture energy and synthesize their own organic synthesize their own organic nutrients. nutrients.

• They can do this by They can do this by photosynthesisphotosynthesis or or chemosynthesischemosynthesis. .

• Chemosynthetic bacteria get Chemosynthetic bacteria get energy and raw materials energy and raw materials from vents called "smokers" from vents called "smokers" on the ocean floor. on the ocean floor.

• Tube worms rely upon the Tube worms rely upon the bacteria that coexist with bacteria that coexist with them to make food at the them to make food at the bottom of the ocean.bottom of the ocean.

Autotrophs are producersAutotrophs are producers

PhotoautotrophsPhotoautotrophs• Autotrophs (=self-nourishing) are calledAutotrophs (=self-nourishing) are called primary primary

producersproducers..• PhotoautotrophsPhotoautotrophs fix energy from the sun and store fix energy from the sun and store

it in complex organic compoundsit in complex organic compounds• green plantsgreen plants

• algaealgae

• some bacteria some bacteria

• some protistssome protists

photoautotrophssimpleinorganiccompounds

complexorganic compounds

light

• ChemosynthesisChemosynthesis. . • Chemosynthetic bacteria get energy and Chemosynthetic bacteria get energy and

raw materials from inorganic sourcesraw materials from inorganic sources• Oxidize reduced inorganic substances Oxidize reduced inorganic substances

(typically sulfur and ammonia compounds) (typically sulfur and ammonia compounds) and produce complex organic compounds.and produce complex organic compounds.

ChemoautotrophsChemoautotrophs

• Nitrifing bacteriaNitrifing bacteria

• Halophiles (found in highly concentrated Halophiles (found in highly concentrated salt lakes)salt lakes)

• Thermophiles (found in hot springs and Thermophiles (found in hot springs and geysers)geysers)

complexorganic compounds

reducedinorganiccompounds

chemoautotrophs

oxygen

Heterotrophs are ConsumersHeterotrophs are Consumers• HeterotrophsHeterotrophs are consumers, they must are consumers, they must

consume preformed organic nutrients consume preformed organic nutrients synthesized by other organisms. synthesized by other organisms.

HeterotrophsHeterotrophs• Heterotrophs (=other-nourishing) cannot produce their Heterotrophs (=other-nourishing) cannot produce their

own food directly from sunlight+ inorganic compounds.own food directly from sunlight+ inorganic compounds. They require energy previously stored in complex They require energy previously stored in complex molecules.molecules.

• Examples of heterotrophsExamples of heterotrophs– Herbivores – eat plantsHerbivores – eat plants– Carnivores – eat meatCarnivores – eat meat– Omnivores – eat both plants and meatOmnivores – eat both plants and meat– Scavengers – eat carrionScavengers – eat carrion– Saprophytes – eat dead or decaying materialSaprophytes – eat dead or decaying material

heterotrophssimpleinorganiccompounds

complexorganic compounds

this may include several steps, with several different types of organismsthis may include several steps, with several different types of organisms

heat

Components of EcosystemsComponents of Ecosystems

Heat

Heat Heat

Heat

Heat

Abiotic chemicalsAbiotic chemicals(carbon dioxide,(carbon dioxide,oxygen, nitrogen,oxygen, nitrogen,

minerals)minerals)

ProducersProducers(plants)(plants)

DecomposersDecomposers(bacteria, fungus)(bacteria, fungus)

ConsumersConsumers(herbivores, (herbivores, carnivores)carnivores)

Solarenergy

• Abiotic cyclesAbiotic cycles

• Producers (autotrophs)Producers (autotrophs)– Source of all foodSource of all food

• PhotosynthesisPhotosynthesis

• ChemosynthesisChemosynthesis

• Consumers (heterotrophs)Consumers (heterotrophs)

• Aerobic respiration Aerobic respiration – OxygenOxygen

• Anaerobic respirationAnaerobic respiration

– Methane, HMethane, H22SS

• DecomposersDecomposers– Matter recyclers…Matter recyclers…– Release organic compounds into Release organic compounds into

soil and water where they can soil and water where they can be used by producersbe used by producers

PHOTOSYNTHESISPHOTOSYNTHESIS

6CO6CO22 + + 6H6H22OO + + ENERGYENERGY

CC66HH1212OO66 + + 6O6O22 Carbon Dioxide WaterCarbon Dioxide Water

Glucose Oxygen

CELLULAR RESPIRATIONCELLULAR RESPIRATION

CC66HH1212OO66 + + 6O6O22

Carbon Dioxide Water ATP

6CO6CO22 + + 6H6H22OO + + LIGHTLIGHT

Glucose OxygenGlucose Oxygen

Primary ProductivityPrimary Productivity• Primary productivity determines Primary productivity determines

the amount of energy available the amount of energy available in an ecosystemin an ecosystem

• Primary productivity is affected Primary productivity is affected mostly by light in aquatic mostly by light in aquatic ecosystemsecosystems• Limiting nutrient is Limiting nutrient is

phosphorus or nitrogenphosphorus or nitrogen• Temperature and moisture are Temperature and moisture are

key control factors in terrestrial key control factors in terrestrial ecosystemsecosystems

• EvapotranspitationEvapotranspitation• Water transpirationWater transpiration

Primary ProductivityPrimary Productivity• Gross Primary productionGross Primary production

• Total primary production in Total primary production in an ecosysteman ecosystem

• Not the amount of energy Not the amount of energy available to consumers!available to consumers!

• NPP=GPP-RNPP=GPP-R

• R= energy used for R= energy used for respirationrespiration

• Energy expendedEnergy expended: Plants : Plants use the energy captured use the energy captured in photosynthesis for in photosynthesis for maintenance and growth.maintenance and growth.

Trophic Levels – Energy PyramidsTrophic Levels – Energy Pyramids• An An energy pyramidenergy pyramid provides provides

a means of describing the a means of describing the feeding and energy feeding and energy relationships within a food relationships within a food chain or web.  chain or web.  

• Each organism in an Each organism in an ecosystem is assigned to a ecosystem is assigned to a feeding (feeding (TrophicTrophic) level ) level based on source of energy based on source of energy

• The greatest amount of The greatest amount of energy is found at the base energy is found at the base of the pyramid. of the pyramid.

• The least amount of energy The least amount of energy is found at top of the is found at top of the pyramid pyramid

ProducersProducers

Primary consumers

Secondary consumers

Tertiary consumers

Energy FlowEnergy Flow

Heat Heat Heat Heat

Heat

Heat

Heat

First TrophicLevel

Second TrophicLevel

Third TrophicLevel

Fourth TrophicLevel

Solarenergy

Producers(plants)

Primaryconsumers(herbivores)

Tertiaryconsumers

(top carnivores)

Secondaryconsumers(carnivores)

Detritvores

Energy PyramidEnergy Pyramid• Each step shows that some energy is Each step shows that some energy is stored or utilizedstored or utilized in the in the

organism which eats the preceding one. organism which eats the preceding one. • Shows that much of the Shows that much of the energy is lostenergy is lost when one organism in a when one organism in a

food chain eats another. Most of this energy which is lost goes food chain eats another. Most of this energy which is lost goes into the environment as into the environment as heatheat energy. energy.

• It is estimated that only 10% of the energy at each trophic level It is estimated that only 10% of the energy at each trophic level is available to organisms at the next higher level.is available to organisms at the next higher level.

BiomassBiomass Energy is sometimes considered in Energy is sometimes considered in terms of terms of biomass biomass = the dry weight = the dry weight of tissue of all the organisms and of tissue of all the organisms and organic material in an area.organic material in an area.

Producer organisms represent the Producer organisms represent the greatest amount of living tissue or greatest amount of living tissue or biomass at the bottom of the biomass at the bottom of the pyramid. pyramid. There are more plants on Earth There are more plants on Earth

than there are animals.than there are animals.

Bio=life Mass=weightBio=life Mass=weight

Bio + Mass = Weight Bio + Mass = Weight of living things of living things within an ecosystem.within an ecosystem.

Why we transform each species into Why we transform each species into biomass instead of absolute numbersbiomass instead of absolute numbers

Numbers PyramidNumbers Pyramid

Biomass PyramidBiomass Pyramid

Implications of Pyramids….Implications of Pyramids….

• Why could the earth support more people if Why could the earth support more people if the eat at lower trophic levels?the eat at lower trophic levels?

• Why are food chains and webs rarely more Why are food chains and webs rarely more than four or five trophic levels?than four or five trophic levels?

• Why are there so few top level carnivores?Why are there so few top level carnivores?

• Why are these species usually the first to Why are these species usually the first to suffer when the the ecosystems that suffer when the the ecosystems that support them are disrupted? support them are disrupted?

Num

ber

of

obse

rvati

ons

Number of links in food chain

10

8

6

4

2

01 2 3 4 5 6

Streams

Lakes

Terrestrial

Average number of links = 3.5

Food WebsFood Webs• A A food webfood web is a series of is a series of

interrelated food chains which interrelated food chains which provides a more accurate provides a more accurate picture of the feeding picture of the feeding relationships in an ecosystemrelationships in an ecosystem

• More than one thing will More than one thing will usually eat a particular species. usually eat a particular species.

• A species will many times feed A species will many times feed at multiple levels on the trophic at multiple levels on the trophic pyramid    pyramid   

Generalized Food Web of the Generalized Food Web of the

AntarcticAntarctic Humans

Blue whale Sperm whale

Crabeater seal

Killerwhale Elephant

seal

Leopardseal

Adéliepenguins Petrel

Fish

Squid

Carnivorous plankton

Krill

Phytoplankton

Herbivorouszooplankton

Emperorpenguin

Note: Note: ArrowsArrowsGo in Go in directiondirectionOf energy Of energy flow…flow…