Chapter 5:Chapter 5:Ecosystems: Concepts and Ecosystems: Concepts and FundamentalsFundamentals

OverviewOverview The Ecosystem: Sustaining Life on EarthThe Ecosystem: Sustaining Life on Earth Ecosystem Communities and Food ChainsEcosystem Communities and Food Chains Ecosystems as SystemsEcosystems as Systems Biological Production and Ecosystem Biological Production and Ecosystem Energy FlowEnergy Flow

Biological Production and BiomassBiological Production and Biomass Energy Efficiency and Transfer Energy Efficiency and Transfer EfficiencyEfficiency

Ecological Stability and SuccessionEcological Stability and Succession Chemical Cycling and SuccessionChemical Cycling and Succession How Species Change SuccessionHow Species Change Succession

The Ecosystem: The Ecosystem: Sustaining Life on EarthSustaining Life on Earth Sustaining life on Earth Sustaining life on Earth requires more than individualsrequires more than individuals

EcosystemEcosystem Interactions of many organisms Interactions of many organisms functioning together in ecosystemsfunctioning together in ecosystems

Physical and chemical environmentsPhysical and chemical environments

Basic Characteristics of Basic Characteristics of EcosystemsEcosystems

Ecosystems have several Ecosystems have several fundamental characteristicsfundamental characteristics

Grouped intoGrouped into StructureStructure ProcessesProcesses

Basic Characteristics of Basic Characteristics of EcosystemsEcosystems

StructureStructure Made up of two major partsMade up of two major parts

Living (ecological community)Living (ecological community) Non living (physical & chemical Non living (physical & chemical environment)environment)

ProcessesProcesses Cycling of chemical elementsCycling of chemical elements Flow of energyFlow of energy

Basic Characteristics of Basic Characteristics of EcosystemsEcosystems At its simplest a At its simplest a community will community will have:have: At least one species At least one species that is a producerthat is a producer

Another species that Another species that is a decomposeris a decomposer

Plus a fluid mediumPlus a fluid medium Never this simple Never this simple

Basic Characteristics of Basic Characteristics of EcosystemsEcosystems

Ecosystem chemical cyclingEcosystem chemical cycling For complete recycling of For complete recycling of chemical elements, several chemical elements, several species must interactspecies must interact

Photosynthetic organisms produce Photosynthetic organisms produce sugar from carbon dioxide and watersugar from carbon dioxide and water

From sugar and inorganic compound From sugar and inorganic compound they make other organic compounds they make other organic compounds (protein, woody tissue)(protein, woody tissue)

Need decomposers to get back to Need decomposers to get back to inorganic compoundsinorganic compounds

Ecological Communities and Ecological Communities and Food ChainsFood Chains

Ecological community definitionsEcological community definitions A set of A set of interactinginteracting species found species found in the same place and functioning in the same place and functioning together to maintain lifetogether to maintain life

In practice it is difficult to In practice it is difficult to identify the interacting speciesidentify the interacting species

All the species found in an area, All the species found in an area, whether or not they interactwhether or not they interact

Operational definitionOperational definition

Food ChainsFood Chains

Food chainFood chain Linkage of who feeds on whomLinkage of who feeds on whom Energy, chemicals and some Energy, chemicals and some compounds are transferred from compounds are transferred from creature to creature along food creature to creature along food chains or food webs (more complex)chains or food webs (more complex)

Grouped by trophic levelGrouped by trophic level Number of feeding levels away from Number of feeding levels away from original source of energyoriginal source of energy

Trophic LevelsTrophic Levels

First trophic levelFirst trophic level Use energy from the sun and carbon Use energy from the sun and carbon dioxide from the air to photosynthesizesdioxide from the air to photosynthesizes

Green plants, algae and certain bacteriaGreen plants, algae and certain bacteria Called autotrophsCalled autotrophs

Second trophic levelSecond trophic level Organisms that feed on autotrophsOrganisms that feed on autotrophs Called herbivoresCalled herbivores

Trophic LevelsTrophic Levels

Third trophic levelThird trophic level Feed directly on herbivoresFeed directly on herbivores Called carnivores (meat eaters)Called carnivores (meat eaters)

Forth trophic levelForth trophic level Carnivores that feed on third-level Carnivores that feed on third-level carnivorescarnivores

Decomposers- feed on waste and Decomposers- feed on waste and dead organisms of all trophic dead organisms of all trophic levelslevels

A Food Chain ExampleA Food Chain Example

Example: Yellowstone Hot Example: Yellowstone Hot SpringsSprings 11stst level - photosynthetic level - photosynthetic algae and bacteriaalgae and bacteria

22ndnd level - Ephydrid flies level - Ephydrid flies (larvae feed on the (larvae feed on the bacteria and algae)bacteria and algae)

33rdrd level - dolichopodid level - dolichopodid fly (larvae feed on fly (larvae feed on herbivorous flies)herbivorous flies)

44thth level - parasites and level - parasites and predators to the fliespredators to the flies

An Oceanic Food ChainAn Oceanic Food Chain

Tend to have more trophic levelsTend to have more trophic levels 11stst level - planktonic algae and level - planktonic algae and planktonic bacteriaplanktonic bacteria

22ndnd level - zooplankton and some fish level - zooplankton and some fish 33rdrd level - fish and invertebrates level - fish and invertebrates feed on herbivores, baleen whalesfeed on herbivores, baleen whales

44th+th+ levels - killer whales, levels - killer whales, predatory fishpredatory fish

Complex Food Web - Harp Complex Food Web - Harp SealSeal Most species feed on several Most species feed on several trophic levelstrophic levels

Harp seal (shown at 5Harp seal (shown at 5thth level) level) Feeds on flatfish (4Feeds on flatfish (4thth level) level) But also feed on foods from 2But also feed on foods from 2ndnd – 4 – 4thth A species that feeds on several A species that feeds on several levels placed in a category one levels placed in a category one above the highest level it feeds onabove the highest level it feeds on

Ecosystem as SystemsEcosystem as Systems

An ecosystem is the minimal entity An ecosystem is the minimal entity that has the properties required to that has the properties required to sustain lifesustain life

Vary greatly in:Vary greatly in: Structural complexity and clarity of Structural complexity and clarity of their boundariestheir boundaries

SizeSize CompositionComposition Proportion of non-biological Proportion of non-biological constituentsconstituents

Degree of variation in time and spaceDegree of variation in time and space

Sharp and Distinct Sharp and Distinct Transition - lake to Transition - lake to forestforest

WatershedWatershed

WatershedWatershed Commonly used Commonly used practical practical delineation of delineation of the boundary of the boundary of an ecosysteman ecosystem

Determined by Determined by topographytopography

United in terms United in terms of chemical of chemical cyclingcycling

Ecosystem Energy flowEcosystem Energy flow

All life requires energyAll life requires energy Ability to do workAbility to do work

Ecosystem energy flowEcosystem energy flow Movement of energy through an Movement of energy through an ecosystem from the external ecosystem from the external environment through a series of environment through a series of organisms and back to the external organisms and back to the external environmentenvironment

Energy FlowEnergy Flow

Energy enters an ecosystem by Energy enters an ecosystem by two pathways:two pathways:

1.1. Energy fixed by organismsEnergy fixed by organisms

2.2. Transfer of heat energy by air, Transfer of heat energy by air, water, soil and warm living water, soil and warm living thingsthings

Ecosystem Energy FlowEcosystem Energy Flow

Energy is difficult and Energy is difficult and abstract conceptabstract concept

Most of the time energy is Most of the time energy is invisible to usinvisible to us With infrared film we can see With infrared film we can see difference between warm and cold difference between warm and cold objectobject

Birch forest in New Hampshire

Regular film Infrared film

A nearby rocky outcrop

Regular film Infrared film

Laws of ThermodynamicsLaws of Thermodynamics

First Law of ThermodynamicsFirst Law of Thermodynamics Law of conservation of energyLaw of conservation of energy In any physical or chemical change, In any physical or chemical change, energy is neither created nor destroyedenergy is neither created nor destroyed

Energy merely changed from one form to Energy merely changed from one form to anotheranother

If this is true, why can’t we If this is true, why can’t we continually recycle energy within continually recycle energy within our bodies?our bodies?

Impossible ecosystem because of 2nd law of thermodynamics

Energy must continually be added Energy must continually be added to an ecological system in a to an ecological system in a usable formusable form Because inevitably degraded into heatBecause inevitably degraded into heat Net flow of energy is a one way flowNet flow of energy is a one way flow

Second Law of ThermodynamicsSecond Law of Thermodynamics No use of energy is ever 100% No use of energy is ever 100% efficientefficient

Energy is lost to heatEnergy is lost to heat

Laws of ThermodynamicsLaws of Thermodynamics

Energy EfficiencyEnergy Efficiency

As energy flows through a food As energy flows through a food web, it is degraded, and less web, it is degraded, and less and less is useableand less is useable EntropyEntropy

Energy must be continually Energy must be continually added to an ecosystem, in added to an ecosystem, in usable formusable form

Biological ProductionBiological Production

BiomassBiomass Total amount of organic matter on Total amount of organic matter on Earth or in any ecosystem or areaEarth or in any ecosystem or area

Measured as the amount per unit Measured as the amount per unit surface areasurface area

Biological productionBiological production Capture of usable energy from the Capture of usable energy from the environment to produce organic environment to produce organic compoundscompounds

Biological ProductionBiological Production

Gross ProductionGross Production Increase in stored energy before Increase in stored energy before any is usedany is used

Net ProductionNet Production Change in biomass over a given timeChange in biomass over a given time

Three measures used for Three measures used for biological productionbiological production BiomassBiomass Energy stored Energy stored Carbon storedCarbon stored

Two Kinds of Biological Two Kinds of Biological ProductionProduction

Primary ProductionPrimary Production Autotrophs (& chemoautotrophs)Autotrophs (& chemoautotrophs) Photosynthesize or chemosynthesizePhotosynthesize or chemosynthesize

Make their own organic matter from Make their own organic matter from energy source and inorganic compoundsenergy source and inorganic compounds

Secondary productionSecondary production HeterotrophsHeterotrophs Cannot make their own organic Cannot make their own organic compounds and must feed on other compounds and must feed on other living thingsliving things

Biological ProductionBiological Production

RespirationRespiration Use of energy from organic matter Use of energy from organic matter by most heterotrophic and by most heterotrophic and autotrophic organismsautotrophic organisms

Organic matter combines with oxygenOrganic matter combines with oxygen Releases energy, carbon dioxide and Releases energy, carbon dioxide and waterwater

Use of biomass to release energy Use of biomass to release energy that can be used to do workthat can be used to do work

Energy Efficiency and Energy Efficiency and Transfer EfficiencyTransfer Efficiency Trophic-level efficiencyTrophic-level efficiency

Ratio of production of one trophic Ratio of production of one trophic level to the production of the level to the production of the next trophic levelnext trophic level

Never very highNever very high 1–3% in natural ecosystems1–3% in natural ecosystems 10% may be maximum10% may be maximum

90% of all energy lost as heat90% of all energy lost as heat

Ecological Stability and Ecological Stability and SuccessionSuccession

Ecosystems are dynamic- always Ecosystems are dynamic- always changingchanging

Primary successionPrimary succession Establishment and development of an Establishment and development of an ecosystem where one did not exist ecosystem where one did not exist previously (lava flow - left; edge of previously (lava flow - left; edge of retreating glacier - right)retreating glacier - right)

Ecological Stability and Ecological Stability and SuccessionSuccession Secondary successionSecondary succession

Reestablishment of an ecosystem Reestablishment of an ecosystem following disturbancefollowing disturbance

Remnants of previous biological Remnants of previous biological community (soil, seeds, organic community (soil, seeds, organic material, etc.)material, etc.)

ExamplesExamples Forests that develop on abandoned pasturesForests that develop on abandoned pastures Development after hurricanes, floods, Development after hurricanes, floods, firesfires

Dune SuccessionDune Succession

Sand dunes continually formed Sand dunes continually formed along sandy shoresalong sandy shores Breached and destroyed by stormsBreached and destroyed by storms

After dune forms After dune forms Grasses establishGrasses establish Grass runners Grass runners stabilize dunesstabilize dunes

Other species seeds Other species seeds may germinate and may germinate and become establishedbecome established

Bog SuccessionBog Succession Bog - Open body of water with Bog - Open body of water with surface inlets but no surface surface inlets but no surface outletsoutlets

Succession:Succession: Sedge puts out floating runnersSedge puts out floating runners Wind blows particles into the mat of Wind blows particles into the mat of runnersrunners

Seeds land on runners and germinate Seeds land on runners and germinate Mat becomes thicker and shrubs and Mat becomes thicker and shrubs and trees developtrees develop

Bog SuccessionBog Succession Bog also fills in from the Bog also fills in from the bottombottom At the shore, floating mat and At the shore, floating mat and sediment meet forming a solid sediment meet forming a solid surfacesurface

Farther from shore all the Farther from shore all the vegetation is still floatingvegetation is still floating

General Patterns of General Patterns of SuccessionSuccession Successional stagesSuccessional stages

Early (1 and 2), middle, and lateEarly (1 and 2), middle, and late Similar patterns seen with Similar patterns seen with animals and other life-forms at animals and other life-forms at each stageeach stage Pioneers - species characteristic of Pioneers - species characteristic of early stageearly stage

Late-successional species tend to be Late-successional species tend to be slower- growing and longer-livedslower- growing and longer-lived

General Patterns of General Patterns of SuccessionSuccession In early stages of successionIn early stages of succession

Biomass and biological diversity Biomass and biological diversity increaseincrease

In middle stages In middle stages Gross production increase and net Gross production increase and net production decreaseproduction decrease

Organic material in soil increases, Organic material in soil increases, as does chemical element storageas does chemical element storage

How Species Change How Species Change SuccessionSuccession Earlier succession species Earlier succession species affect what happens later in affect what happens later in succession through:succession through: Facilitation Facilitation InterferenceInterference Life history differencesLife history differences

FacilitationFacilitation

Facilitators in dune and bog Facilitators in dune and bog succession are dune grass and succession are dune grass and floating sedge, respectivelyfloating sedge, respectively They prepare the way for other They prepare the way for other speciesspecies

InterferenceInterference

Certain early species interfere Certain early species interfere with the entrance of other with the entrance of other speciesspecies Grasses may form dense mats Grasses may form dense mats blocking other seeds from blocking other seeds from germinatinggerminating

Chronic PatchinessChronic Patchiness

Common in desertsCommon in deserts Major shrub species Major shrub species grow in patches grow in patches

Patch persist for long Patch persist for long period of time until period of time until next disturbancenext disturbance

Life tends to build upLife tends to build up Non-biological Non-biological processes tend to processes tend to erode or degradeerode or degrade In harsh environments In harsh environments degrading dominates and degrading dominates and succession does not succession does not occuroccur