Chapter 5Chapter 5How Ecosystems WorkHow Ecosystems Work

Lake VictoriaLake Victoria Freshwater lake in AfricaFreshwater lake in Africa Formerly home to ≈ 400 species of cichlidsFormerly home to ≈ 400 species of cichlids 1960: Nile perch 1960: Nile perch

introducedintroduced 1990: water hyacinth 1990: water hyacinth

invadedinvaded Today, ecological Today, ecological

imbalance; why?imbalance; why?

What Is Ecology?What Is Ecology? Literally study of one’s “house”Literally study of one’s “house” InteractionsInteractions Two componentsTwo components

BioticBiotic AbioticAbiotic

Broadest biological field of studyBroadest biological field of study

Ecological OrganizationEcological Organization

OrganismOrganism PopulationPopulation CommunityCommunity EcosystemEcosystem LandscapeLandscape BiosphereBiosphere

Positive and Negative Positive and Negative Feedback LoopsFeedback Loops

Feedback LoopFeedback Loop circular processcircular process

Positive Feedback LoopPositive Feedback Loop change becomes more change becomes more

pronouncedpronounced Negative Feedback LoopNegative Feedback Loop

change is reduced or inhibitedchange is reduced or inhibited

Landscape EcologyLandscape Ecology Studies the connections Studies the connections

among ecosystemsamong ecosystems Ecosystem engineers Ecosystem engineers

Organisms that create Organisms that create or modify habitator modify habitat

How are grizzly bears How are grizzly bears ecosystem engineers?ecosystem engineers?

Goals Of EcologistsGoals Of Ecologists Understand how ecosystems functionUnderstand how ecosystems function Make connections: landscape ecologyMake connections: landscape ecology

Connections among ecosystemsConnections among ecosystems Grizzly BearsGrizzly Bears

EnergyEnergy Capacity or ability to do workCapacity or ability to do work Flows through ecosystemsFlows through ecosystems Why do organisms need energy?Why do organisms need energy? Different kindsDifferent kinds

Potential energyPotential energy Kinetic energyKinetic energy

First Law of First Law of ThermodynamicsThermodynamics

Energy cannot Energy cannot be created or be created or destroyeddestroyed

Energy can be Energy can be changed from changed from one form to one form to anotheranother

Second Law of Second Law of ThermodynamicsThermodynamics

When energy is changed from one When energy is changed from one form to another, some is degraded form to another, some is degraded into heatinto heat

Heat is a less usable form of energyHeat is a less usable form of energy Increases entropy in the universeIncreases entropy in the universe

Ecosystem CompositionEcosystem Composition

ProducersProducers ConsumersConsumers DecomposersDecomposers

ProducersProducers

Make their own foodMake their own food PhotosynthesisPhotosynthesis Examples?Examples?

6CO6CO22 + 6H + 6H22O + ------> CO + ------> C66HH1212OO66 + 6O + 6O22

Light energy

Light energy

ConsumersConsumers

Feed on other thingsFeed on other things HerbivoresHerbivores CarnivoresCarnivores OmnivoresOmnivores DetrivoresDetrivores

DecomposersDecomposers

Break down dead organisms and Break down dead organisms and waste productswaste products

Examples?Examples?

Energy FlowEnergy Flow Energy passes from one organism to Energy passes from one organism to

the nextthe next Trophic level: each step in this flow of Trophic level: each step in this flow of

energyenergy Food chain: straight pathFood chain: straight path Food webFood web

Interconnected food chainsInterconnected food chains More realistic than food chain; why?More realistic than food chain; why?

Food ChainFood Chain

Biological ProductionBiological Production Net Primary Production: amount of Net Primary Production: amount of

plant mass generated by plant mass generated by photosynthesis and that remains after photosynthesis and that remains after cellular respirationcellular respiration

Biomass: total amount of organic Biomass: total amount of organic mattermatter

NPP is measured by tracking the NPP is measured by tracking the changes in biomass over timechanges in biomass over time

(NPP = B2 –B1)(NPP = B2 –B1)

Food Food WebWeb

Biogeochemical CyclesBiogeochemical Cycles

Matter cycles through ecosystemsMatter cycles through ecosystems Five cyclesFive cycles

CarbonCarbon Hydrologic (water)Hydrologic (water) NitrogenNitrogen SulfurSulfur PhosphorusPhosphorus

Carbon CycleCarbon Cycle

Essential component for lifeEssential component for life Gas (COGas (CO22) in atmosphere) in atmosphere Several forms in oceanSeveral forms in ocean Can take a long time—think fossil fuelsCan take a long time—think fossil fuels

COCO22 SugarSugar COCO22

PhotosynthesisPhotosynthesis Cellular respirationCellular respiration

Carbon CycleCarbon Cycle

Hydrologic CycleHydrologic CycleOceanOcean AtmosphereAtmosphere LandLand OceanOcean

Nitrogen CycleNitrogen Cycle Proteins, DNAProteins, DNA Atmosphere is 78% NAtmosphere is 78% N22

Five stepsFive steps Nitrogen fixationNitrogen fixation NitrificationNitrification AssimilationAssimilation AmmonificationAmmonification DenitrificationDenitrification

Nitrogen FixationNitrogen Fixation Specialized bacteriaSpecialized bacteria Split atmospheric nitrogen and Split atmospheric nitrogen and

combine it with hydrogencombine it with hydrogen

Nitrogen CycleNitrogen Cycle

Phosphorus CyclePhosphorus Cycle

No atmospheric componentNo atmospheric component Phosphates used in DNA and ATP Phosphates used in DNA and ATP

(chemical energy)(chemical energy) Phosphates move through the food chainPhosphates move through the food chain

LandLand OrganismOrganism LandLandOrganismOrganism

Phosphorus CyclePhosphorus Cycle

Ecological NicheEcological Niche Everything about an organismEverything about an organism

AdaptationsAdaptations Use of resourcesUse of resources LifestyleLifestyle HabitatHabitat

Ecological NicheEcological Niche

Two species cannot occupy the same Two species cannot occupy the same niche: why?niche: why?

Resource partitioningResource partitioning Reduces niche overlapReduces niche overlap Reduces competitionReduces competition

Resource Partitioning At Work!Resource Partitioning At Work!

Species InteractionsSpecies Interactions No species lives in complete isolationNo species lives in complete isolation SymbiosisSymbiosis

Intimate relationship between Intimate relationship between members of at least 2 speciesmembers of at least 2 species

Mutualism, commensalism, Mutualism, commensalism, parasitismparasitism

Result of coevolutionResult of coevolution Other interactionsOther interactions

Predation, competitionPredation, competition

MutualismMutualism Both species benefitBoth species benefit

CommensalismCommensalism One species benefits, other not affected One species benefits, other not affected

ParasitismParasitism Parasite benefits, host is “harmed”Parasite benefits, host is “harmed” Ectoparasites & endoparasitesEctoparasites & endoparasites

Species InteractionsSpecies Interactions Predation: consumption of one Predation: consumption of one

species by anotherspecies by another Coevolution: “arms race”Coevolution: “arms race”

Avoiding PredatorsAvoiding Predators Mechanical defensesMechanical defenses Social groupsSocial groups CamouflageCamouflage Protective chemicalsProtective chemicals

Species InteractionsSpecies Interactions Competition: two or more organisms Competition: two or more organisms

attempting to use the same resourceattempting to use the same resource Intraspecific vs. interspecificIntraspecific vs. interspecific

Keystone SpeciesKeystone Species Crucial to maintenance of an ecosystemCrucial to maintenance of an ecosystem Loss affects many other Loss affects many other

speciesspecies Examples?Examples? What are the differences What are the differences

between a keystone, between a keystone,

umbrella or flagship umbrella or flagship

species?species?

Adaptive EcosystemAdaptive EcosystemManagementManagement

Ecosystem Management: meeting the goals or Ecosystem Management: meeting the goals or objectives of the biotic community and their associated objectives of the biotic community and their associated abiotic componentsabiotic components

Adaptive Ecosystem Management:Adaptive Ecosystem Management: developed by C.S. Holling and Carl J. Walters, developed by C.S. Holling and Carl J. Walters,

University of B.C., 1970University of B.C., 1970 acknowledges the uncertainty and the need for acknowledges the uncertainty and the need for

managers to learn while they managemanagers to learn while they manage passive and activepassive and active

Eco Canada Career FocusEco Canada Career Focus

Consider a career Consider a career as an ecologistas an ecologist

Ecologists study Ecologists study the relationships the relationships between living between living things and their things and their environmentsenvironments

Case Study: Human Case Study: Human Appropriation of Net Primary Appropriation of Net Primary

Productivity (HANPP)Productivity (HANPP) HANPP : indicator of are of land an the HANPP : indicator of are of land an the

amount of biomass consumed by amount of biomass consumed by humanshumans

Valuable indicator of “human domination Valuable indicator of “human domination of ecosystems” on a global scaleof ecosystems” on a global scale

Many countries are consuming an excess Many countries are consuming an excess of 100% of locally available NPPof 100% of locally available NPP

Case Study: Human Case Study: Human Appropriation of Net Primary Appropriation of Net Primary

Productivity (HANPP)Productivity (HANPP)