Sinh học - Chapter 55: Ecosystems

Ch. 55 Warm-UpDraw an energy pyramid and label the following trophic levels:Primary producerPrimary consumerSecondary consumerTertiary consumerWhat is an example of an organism at each level of the pyramid in #1?If 5000 J of energy is available in producers, how much of that energy would be available to tertiary consumers?Define Ch. 55 Terms:AutotrophHeterotrophDetritivoreGross primary production (GPP)Net primary production (NPP)Biogeochemical cycleNitrogen fixationChapter 55: EcosystemsYou Must Know:How energy flows through the ecosystem (food chains and food webs)The difference between gross primary productivity and net primary productivity.The carbon and nitrogen biogeochemical cycles.EcosystemsEcosystem = sum of all the organisms living within its boundaries (biotic community) + abiotic factors with which they interactInvolves two unique processes:Energy flowChemical cyclingOverview of energy & nutrient dynamicsEnergy Flow in an EcosystemEnergy cannot be recycled  must be constantly supplied to an ecosystem (mostly by SUN)The autotrophs (“self feeders”) are the primary producers, and are usually photosynthetic (plants or algae).They use light energy to synthesize sugars and other organic compounds.Heterotrophs (“other feeders”) – can’t make own foodHeterotrophs areat trophic levelsabove the primaryproducers anddepend on theirphotosyntheticoutput.Herbivores that eat primary producers are called primary consumers.Carnivores that eat herbivores are called secondary consumers.Carnivores that eat secondary consumers are called tertiary consumers.Another important group of heterotrophs is the detritivores, or decomposers.They get energy from detritus, nonliving organic material, and play an important role in material cycling.Main decomposers:fungi & prokaryotesPrimary ProductionPrimary production = amt. of light energy that is converted to chemical energyGross primary production (GPP): total primary production in an ecosystemNet primary production (NPP) = gross primary production minus the energy used by the primary producers for respiration (R):NPP = GPP – RNPP = storage of chemical energy available to consumers in an ecosystemOpen 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)TerrestrialMarineKeyPercentage of Earth’ssurface areaAverage net primaryproduction (g/m2/yr)60504030201002,5002,0001,5001,0005000Percentage of Earth’s netprimary production25201510501252,5003601,5005003.0909006008002,2006002501,6001,2001,3002,0007001400.37.99.19.65.43.50.67.14.93.82.324.45.61.20.90.10.040.922Net primary production of different ecosystemsPrimary production affected by:Light availability (↑ depth, ↓ photosynthesis)Nutrient availability (N, P in marine env.)Key factors controlling primary production:Temperature & moistureA nutrient-rich lake that supports algae growth is eutrophic.Energy transfer between trophic levels is typically only 10% efficientProduction efficiency: only fraction of E stored in foodEnergy used in respiration is lost as heatEnergy flows (not cycle!) within ecosystems10% transfer of energy from one level to nextEcological pyramids give insight to food chainsPyramid of NumbersPyramid of BiomassLoss of energy limits # of top-level carnivoresMost food webs only have 4 or 5 trophic levelsTrophic levelSecondary consumersPrimary consumersPrimary producersThe dynamics of energy through ecosystems have important implications for the human populationMatter Cycles in EcosystemBiogeochemical cycles: nutrient cycles that contain both biotic and abiotic componentsorganic  inorganic parts of an ecosystemNutrient Cycles: water, carbon, nitrogen, phosphorusWater CycleCarbon CycleCO2 removed by photosynthesis, added by burning fossil fuelsNitrogen CycleNitrogen fixation:N2  plants by bacteriaNitrification:ammonium  nitrite  nitrateAbsorbed by plantsDenitrification:Release N to atmospherePhosphorus CycleRestoration EcologyBioremediation: use of organisms (prokaryotes, fungi, plants) to detoxify polluted ecosystemsBioaugmentation: introduce desirable species (eg. nitrogen-fixers) to add essential nutrientsBioremediation of groundwater contaminated with uraniumRestoration ecology projects