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54 lectures ppt
54 lectures ppt
54 lectures ppt
54 lectures ppt
54 lectures ppt
54 lectures ppt
54 lectures ppt
54 lectures ppt
54 lectures ppt
54 lectures ppt
54 lectures ppt
54 lectures ppt
54 lectures ppt
54 lectures ppt
54 lectures ppt
54 lectures ppt
54 lectures ppt
54 lectures ppt
54 lectures ppt
54 lectures ppt
54 lectures ppt
54 lectures ppt
54 lectures ppt
54 lectures ppt
54 lectures ppt
54 lectures ppt
54 lectures ppt
54 lectures ppt
54 lectures ppt
54 lectures ppt
54 lectures ppt
54 lectures ppt
54 lectures ppt
54 lectures ppt
54 lectures ppt
54 lectures ppt
54 lectures ppt
54 lectures ppt
54 lectures ppt
54 lectures ppt
54 lectures ppt
54 lectures ppt
54 lectures ppt
54 lectures ppt
54 lectures ppt
54 lectures ppt
54 lectures ppt
54 lectures ppt
54 lectures ppt
54 lectures ppt
54 lectures ppt
54 lectures ppt
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54 lectures ppt
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  • 1. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin CummingsPowerPoint Lectures forBiology, Seventh EditionNeil Campbell and Jane ReeceLectures by Chris RomeroChapter 55Ecosystems
  • 2. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin CummingsOverview: Ecosystems, Energy, and Matter• An ecosystem consists of all the organisms livingin a community, as well as the abiotic factors withwhich they interact• Ecosystems range from a microcosm, such as anaquarium, to a large area such as a lake or forest
  • 3. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
  • 4. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings• Regardless of an ecosystem’s size, its dynamicsinvolve two main processes: energy flow andchemical cycling• Energy flows through ecosystems while mattercycles within them
  • 5. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin CummingsEcosystem ecology emphasizes energy flow andchemical cycling• Ecologists view ecosystems as transformers ofenergy and processors of matter• Laws of physics and chemistry apply toecosystems, particularly energy flow• Energy is conserved but degraded to heat duringecosystem processes
  • 6. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin CummingsTrophic Relationships• Energy and nutrients pass from primary producers(autotrophs) to primary consumers (herbivores)and then to secondary consumers (carnivores)• In an ecosystem, energy conversions are notcompletely efficient, and some energy is alwayslost as heat• Energy flows through an ecosystem, entering aslight and exiting as heat• Nutrients cycle within an ecosystem
  • 7. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin CummingsEnergy, Mass, and Trophic Levels• Autotrophs build molecules themselves usingphotosynthesis or chemosynthesis as an energysource• Heterotrophs depend on the biosynthetic output ofother organisms© 2011 Pearson Education, Inc.
  • 8. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin CummingsDecomposition• Decomposition connects all trophic levels• Detritivores, mainly bacteria and fungi, recycleessential chemical elements by decomposingorganic material and returning elements toinorganic reservoirs
  • 9. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin CummingsFigure 55.3
  • 10. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin CummingsKeyChemical cyclingEnergy flowSunHeatPrimary producersPrimaryconsumersSecondary andtertiary consumersDetritusMicroorganismsand otherdetritivoresFigure 55.4
  • 11. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin CummingsEnergy and other limiting factors control primaryproduction in ecosystems• In most ecosystems, primary production is theamount of light energy converted to chemicalenergy by autotrophs during a given time period• In a few ecosystems, chemoautotrophs are theprimary producers• The extent of photosynthetic production sets thespending limit for an ecosystem’s energy budget© 2011 Pearson Education, Inc.
  • 12. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin CummingsThe Global Energy Budget• The amount of solar radiation reaching the Earth’ssurface limits photosynthetic output of ecosystems• Only a small fraction of solar energy actuallystrikes photosynthetic organisms– Only visible light can power photosynthesis(~400-700 nm wavelengths), and of that lightenergy, about 0.27% is utilized
  • 13. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin CummingsGross and Net Production• Total primary production is known as theecosystem’s gross primary production (GPP)• GPP is measured as the conversion of chemicalenergy from photosynthesis per unit time• Net primary production (NPP) is GPP minusenergy used by primary producers for respiration• NPP is expressed as− Energy per unit area per unit time (J/m2⋅yr), or− Biomass added per unit area per unit time(g/m2⋅yr)© 2011 Pearson Education, Inc.
  • 14. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings• NPP is the amount of new biomass added in agiven time period• Only NPP is available to consumers• Standing crop is the total biomass ofphotosynthetic autotrophs at a given time• Ecosystems vary greatly in NPP and contributionto the total NPP on Earth© 2011 Pearson Education, Inc.
  • 15. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings• Tropical rain forests, estuaries, and coral reefs areamong the most productive ecosystems per unitarea• Marine ecosystems are relatively unproductive perunit area, but contribute much to global netprimary production because of their volume© 2011 Pearson Education, Inc.
  • 16. LE 54-4Open oceanContinental shelfUpwelling zonesExtreme desert, rock, sand, iceSwamp and marshLake and streamDesert and semidesert scrubTropical rain forestTemperate deciduous forestTemperate evergreen forestTropical seasonal forestSavannaCultivated landEstuaryAlgal beds and reefsBoreal forest (taiga)Temperate grasslandWoodland and shrublandTundra0.40.41.01.31.51.61.71.82.42.72.93.33.54.70.30.10.15.265.0Freshwater (on continents)TerrestrialMarineKey Percentage of Earth’ssurface areaAverage net primaryproduction (g/m2/yr)6050403020100 2,5002,0001,5001,0005000Percentage of Earth’s netprimary production25201510501252,5003601,5005003.0909006008002,2006002501,6001,2001,3002,0007001400.37.99.19.65.43.50.67.14.93.82.324.45.61.20.90.10.040.922
  • 17. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin CummingsFigure 55.6Net primary production(kg carbon/m2yr)3201
  • 18. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin CummingsPrimary Production in Marine and FreshwaterEcosystems• In marine and freshwater ecosystems, bothlight and nutrients control primary production• Depth of light penetration affects primaryproduction in the photic zone of an ocean orlake• More than light, nutrients limit primaryproduction in geographic regions of the oceanand in lakes
  • 19. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin CummingsNutrient Limitation• A limiting nutrient is the element that must beadded for production to increase in an area• Nitrogen and phosphorous are typically thenutrients that most often limit marine production• Nutrient enrichment experiments confirmed thatnitrogen was limiting phytoplankton growth offthe shore of Long Island, New York© 2011 Pearson Education, Inc.
  • 20. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin CummingsAmmoniumenrichedPhosphateenrichedUnenrichedcontrolRESULTSA B C GFEDCollection sitePhytoplanktondensity(millionsofcellspermL)3024181260Figure 55.8
  • 21. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings• Experiments in the Sargasso Sea in thesubtropical Atlantic Ocean showed that ironlimited primary production© 2011 Pearson Education, Inc.
  • 22. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin CummingsTable 55.1
  • 23. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings• In some areas, sewage runoff has causedeutrophication of lakes, which can lead to loss ofmost fish species• In lakes, phosphorus limits cyanobacterial growthmore often than nitrogen• This has led to the use of phosphate-freedetergents© 2011 Pearson Education, Inc.
  • 24. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
  • 25. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin CummingsPrimary Production in TerrestrialEcosystems• In terrestrial ecosystems, temperature andmoisture affect primary production on a largescale• Primary production increases with moisture© 2011 Pearson Education, Inc.
  • 26. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin CummingsMean annual precepitation (cm)0 20 200180160140120100806040Netannualprimaryproduction(aboveground,dryg/m2yr) 1,4001,2001,000800600400200Figure 55.9
  • 27. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings• Actual evapotranspiration is the water transpiredby plants and evaporated from a landscape• It is affected by precipitation, temperature, andsolar energy• It is related to net primary production© 2011 Pearson Education, Inc.
  • 28. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings• On a more local scale, a soil nutrient is often thelimiting factor in primary production• In terrestrial ecosystems, nitrogen is the mostcommon limiting nutrient• Phosphorus can also be a limiting nutrient,especially in older soils© 2011 Pearson Education, Inc.Nutrient Limitations and Adaptations That ReduceThem
  • 29. LE 54-9ControlAugust 1980JulyJune00100200300Live,above-groundbiomass(gdrywt/m2)50150250N + PN onlyP only
  • 30. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings• Various adaptations help plants access limitingnutrients from soil– Some plants form mutualisms with nitrogen-fixingbacteria– Many plants form mutualisms with mycorrhizalfungi; these fungi supply plants with phosphorusand other limiting elements– Roots have root hairs to increase surface area– Many plants release enzymes that increase theavailability of limiting nutrients© 2011 Pearson Education, Inc.
  • 31. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin CummingsConcept 55.3: Energy transfer between trophic levelsis typically only 10% efficient• Secondary production of an ecosystem is theamount of chemical energy in food converted tonew biomass during a given period of time© 2011 Pearson Education, Inc.
  • 32. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin CummingsProduction Efficiency• When a caterpillar feeds on a leaf, only aboutone-sixth of the leaf’s energy is used forsecondary production• An organism’s production efficiency is thefraction of energy stored in food that is not usedfor respiration© 2011 Pearson Education, Inc.ProductionefficiencyNet secondary production  100%Assimilation of primary production
  • 33. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin CummingsPlant materialeaten by caterpillarGrowth (new biomass;secondary production)CellularrespirationAssimilatedFecesNot assimilated100 J33 J67 J200 JFigure 55.10
  • 34. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin CummingsTrophic Efficiency and Ecological Pyramids• Trophic efficiency is the percentage of productiontransferred from one trophic level to the next• It usually ranges from 5% to 20%• A pyramid of net production represents the loss ofenergy with each transfer in a food chain
  • 35. An Idealized Pyramid of Net Production1,000,000 J of sunlight10,000 J1,000 J100 J10 JTertiaryconsumersSecondaryconsumersPrimaryconsumersPrimaryproducers
  • 36. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin CummingsPyramids of Biomass• In a biomass pyramid, each tier represents the dryweight of all organisms in one trophic level• Most biomass pyramids show a sharp decrease atsuccessively higher trophic levels
  • 37. LE 54-12aTrophic level Dry weight(g/m2)Tertiary consumersSecondary consumersPrimary consumersPrimary producers1.51137809Most biomass pyramids show a sharp decrease in biomass atsuccessively higher trophic levels, as illustrated by data from abog at Silver Springs, Florida.
  • 38. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings• Certain aquatic ecosystems have invertedbiomass pyramids: producers (phytoplankton) areconsumed so quickly that they are outweighed byprimary consumers• Turnover time is a ratio of the standing cropbiomass to production© 2011 Pearson Education, Inc.
  • 39. LE 54-12bTrophic level Dry weight(g/m2)Primary consumers (zooplankton)Primary producers (phytoplankton)214In some aquatic ecosystems, such as the English Channel, a smallstanding crop of primary producers (phytoplankton) supports a largerstanding crop of primary consumers (zooplankton).
  • 40. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin CummingsPyramids of Numbers• A pyramid of numbers represents the number ofindividual organisms in each trophic level
  • 41. In a bluegrass field in Michigan, only 3 top carnivores aresupported in an ecosystem based on production by nearly 6million plantsTrophic level Number ofindividual organismsTertiary consumersSecondary consumersPrimary consumersPrimary producers3354,904708,6245,842,424
  • 42. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings• Dynamics of energy flow in ecosystems haveimportant implications for the human population• Eating meat is a relatively inefficient way oftapping photosynthetic production• Worldwide agriculture could feed many morepeople if humans ate only plant material
  • 43. LE 54-14Trophic levelSecondaryconsumersPrimaryconsumersPrimaryproducers
  • 44. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin CummingsMost terrestrial ecosystems have large standingcrops despite the large numbers of herbivores
  • 45. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin CummingsBiological and geochemical processes cyclenutrients and water in ecosystems• Life depends on recycling chemical elements• Nutrient circuits in ecosystems involve biotic andabiotic components and are often calledbiogeochemical cycles© 2011 Pearson Education, Inc.
  • 46. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin CummingsBiogeochemical Cycles• Gaseous carbon, oxygen, sulfur, and nitrogenoccur in the atmosphere and cycle globally• Less mobile elements include phosphorus,potassium, and calcium• These elements cycle locally in terrestrialsystems, but more broadly when dissolved inaquatic systems© 2011 Pearson Education, Inc.
  • 47. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings• A model of nutrient cycling includes mainreservoirs of elements and processes that transferelements between reservoirs• All elements cycle between organic and inorganicreservoirs© 2011 Pearson Education, Inc.
  • 48. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin CummingsReservoir AOrganic materialsavailable asnutrientsLivingorganisms,detritusReservoir BOrganicmaterialsunavailableas nutrientsReservoir DInorganic materialsunavailableas nutrientsReservoir CInorganic materialsavailable asnutrientsFossilizationBurning offossil fuelsAssimilation,photosynthesisWeathering,erosionFormation ofsedimentaryrockRespiration,decomposition,excretionPeatCoalOilMineralsin rocksSoilAtmosphereWaterFigure 55.13
  • 49. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin CummingsBiogeochemical Cycles• In studying cycling of water, carbon, nitrogen, andphosphorus, ecologists focus on four factors:1. Each chemical’s biological importance2. Forms in which each chemical is available orused by organisms3. Major reservoirs for each chemical4. Key processes driving movement of eachchemical through its cycle
  • 50. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin CummingsThe Water Cycle• Water is essential to all organisms• Liquid water is the primary physical phase in whichwater is used• The oceans contain 97% of the biosphere’s water;2% is in glaciers and polar ice caps, and 1% is inlakes, rivers, and groundwater• Water moves by the processes of evaporation,transpiration, condensation, precipitation, andmovement through surface and groundwater© 2011 Pearson Education, Inc.
  • 51. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin CummingsMovement overland by windPrecipitationover landPrecipitationover oceanEvaporationfrom oceanEvapotranspira-tion from landRunoff andgroundwaterPercolationthroughsoilFigure 55.14a
  • 52. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin CummingsThe Carbon Cycle• Carbon-based organic molecules are essential toall organisms• Photosynthetic organisms convert CO2 to organicmolecules that are used by heterotrophs• Carbon reservoirs include fossil fuels, soils andsediments, solutes in oceans, plant and animalbiomass, the atmosphere, and sedimentary rocks© 2011 Pearson Education, Inc.
  • 53. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings• CO2 is taken up and released throughphotosynthesis and respiration; additionally,volcanoes and the burning of fossil fuelscontribute CO2 to the atmosphere© 2011 Pearson Education, Inc.
  • 54. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin CummingsCO2 inatmospherePhoto-synthesisBurningof fossilfuels andwood Phyto-planktonPhotosynthesisCellularrespirationConsumersConsumersDecompositionFigure 55.14b
  • 55. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin CummingsThe Nitrogen Cycle• Nitrogen is a component of amino acids, proteins,and nucleic acids• The main reservoir of nitrogen is the atmosphere(N2), though this nitrogen must be converted toNH4+or NO3–for uptake by plants, via nitrogenfixation by bacteria© 2011 Pearson Education, Inc.
  • 56. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings• Organic nitrogen is decomposed to NH4+byammonification, and NH4+is decomposed to NO3–by nitrification• Denitrification converts NO3–back to N2© 2011 Pearson Education, Inc.
  • 57. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin CummingsFixationDenitrificationN2 inatmosphereReactive NgasesIndustrialfixationN fertilizersRunoffNO3–NO3–NH4+DecompositionandsedimentationAquaticcyclingDissolvedorganic N TerrestrialcyclingDecom-positionDenitri-ficationNO3–NO2–N2AssimilationFixationin root nodulesAmmonification NitrificationNH4+NH3Uptakeof aminoacidsFigure 55.14c
  • 58. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin CummingsThe Phosphorus Cycle• Phosphorus is a major constituent of nucleicacids, phospholipids, and ATP• Phosphate (PO43–) is the most important inorganicform of phosphorus• The largest reservoirs are sedimentary rocks ofmarine origin, the oceans, and organisms• Phosphate binds with soil particles, andmovement is often localized© 2011 Pearson Education, Inc.
  • 59. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin CummingsGeologicupliftWind-blowndustWeatheringof rocksConsumptionRunoffDecompositionDecompositionLeachingSedimentationPlantuptakeof PO43–DissolvedPO43–PlanktonUptakeFigure 55.14d
  • 60. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin CummingsDecomposition and Nutrient Cycling Rates• Decomposers (detritivores) play a key role in thegeneral pattern of chemical cycling• Rates at which nutrients cycle in differentecosystems vary greatly, mostly as a result ofdiffering rates of decomposition• The rate of decomposition is controlled bytemperature, moisture, and nutrient availability© 2011 Pearson Education, Inc.
  • 61. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings• Rapid decomposition results in relatively low levelsof nutrients in the soil– For example, in a tropical rain forest, materialdecomposes rapidly and most nutrients are tiedup in trees other living organisms• Cold and wet ecosystems store large amounts ofundecomposed organic matter as decompositionrates are low• Decomposition is slow in anaerobic muds© 2011 Pearson Education, Inc.
  • 62. LE 54-18Nutrientsavailableto producersDecomposersGeologicprocessesAbioticreservoirConsumersProducers
  • 63. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin CummingsCase Study: Nutrient Cycling in the HubbardBrook Experimental Forest• The Hubbard Brook Experimental Forest has beenused to study nutrient cycling in a forestecosystem since 1963• The research team constructed a dam on the siteto monitor loss of water and minerals• They found that 60% of the precipitation exitsthrough streams and 40% is lost byevapotranspiration© 2011 Pearson Education, Inc.
  • 64. LE 54-19Concrete dams and weirsbuilt across streams at thebottom of watershedsenabled researchers tomonitor the outflow ofwater and nutrients fromthe ecosystem.One watershed was clear cut to study the effects of the lossof vegetation on drainage and nutrient cycling.The concentration of nitrate in runoff from the deforested watershed was 60 times greaterthan in a control (unlogged) watershed.DeforestedControlCompletion oftree cuttingNitrateconcentrationinrunoff(mg/L)1965 19681966 196780.060.040.020.04.03.02.01.00

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