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

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

Connections among ecosystemsConnections among ecosystems Great blue heronGreat blue heron

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 ThermodynamicsFirst Law of Thermodynamics Energy cannot be Energy cannot be

created or created or destroyeddestroyed

Energy can be Energy can be changed from one changed from one form to anotherform to another

Second Law of Second Law of ThermodynamicsThermodynamics

When energy is changed from one form When energy is changed from one form to another, some is degraded into heatto another, some is degraded into 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 waste Break down dead organisms and waste productsproducts

Examples?Examples?

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

nextnext 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

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 Cycle

OceanOcean 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 combine it Split atmospheric nitrogen and combine it

with hydrogenwith hydrogen

Nitrogen CycleNitrogen Cycle

Sulfur CycleSulfur Cycle

Underground sedimentary rocks and Underground sedimentary rocks and mineralsminerals

Erosion releases compounds to oceanErosion releases compounds to ocean VolcanoesVolcanoes Essential component of proteinsEssential component of proteins

Sulfur CycleSulfur 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 members Intimate relationship between members of at least 2 speciesof at least 2 species

Mutualism, commensalism, parasitismMutualism, commensalism, parasitism 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 species by Predation: consumption of one species by

anotheranother 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? This idea is being This idea is being challenged; why?challenged; why?

Case Study: Case Study: Global Climate ChangeGlobal Climate Change

Atmospheric COAtmospheric CO22 increased dramatically. increased dramatically. Why?Why?

10 warmest years have occurred since 199010 warmest years have occurred since 1990 2005 warmest2005 warmest 1998 second warmest1998 second warmest 2002 third warmest2002 third warmest

Earth’s temperatures may rise 1.8Earth’s temperatures may rise 1.8oo – 4.0 – 4.0oo C C (3.2(3.2o o – 7.2– 7.2oo F) by end of 21 F) by end of 21stst century century What could occur?What could occur?

Case Study: Case Study: Global Climate Change Global Climate Change

Kyoto Protocol – International climate change conference Kyoto Protocol – International climate change conference – Kyoto, Japan 1997– Kyoto, Japan 1997 Highly developed countries to cutHighly developed countries to cut COCO22 emissions ~ 5.2% by 2012 emissions ~ 5.2% by 2012

US Department of EnergyUS Department of Energy Automotive vehiclesAutomotive vehicles designed for better gasdesigned for better gas mileagemileage High efficiency windHigh efficiency wind turbinesturbines