4Energy Flow in an Ecosystem Energy 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 food
5Heterotrophs are at trophic levels above the primary producers and depend on their photosynthetic output.
6Herbivores 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.
8Primary 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 ecosystem
9Net primary production of different ecosystems Open oceanContinental shelf65.012524.45.23605.6EstuaryAlgal beds and reefs0.30.11,5001.22,5000.9Upwelling zonesExtreme desert, rock, sand, ice5000.14.73.00.04Desert and semidesert scrubTropical rain forest3.5900.93.32,20022SavannaCultivated land2.99007.92.76009.1Boreal forest (taiga)Temperate grassland2.48009.61.86005.4Woodland and shrublandTundra1.77003.51.61400.6Tropical seasonal forest1.51,6007.1Temperate deciduous forestTemperate evergreen forest1.31,2004.91.01,3003.8Swamp and marshLake and stream0.42,0002.32500.31020304050605001,0001,5002,0002,500510152025KeyPercentage of Earth’ssurface areaAverage net primaryproduction (g/m2/yr)Percentage of Earth’s netprimary productionMarineTerrestrialFreshwater (on continents)
10Energy transfer between trophic levels is typically only 10% efficient Production efficiency: only fraction of E stored in foodEnergy used in respiration is lost as heatEnergy flows (not cycle!) within ecosystems
12Ecological pyramids give insight to food chains Loss of energy limits # of top-level carnivoresMost food webs only have 4 or 5 trophic levelsPyramid of NumbersPyramid of Biomass
13The dynamics of energy through ecosystems have important implications for the human population Trophic levelSecondaryconsumersPrimaryconsumersPrimaryproducers
14Matter Cycles in Ecosystem Biogeochemical cycles: nutrient cycles that contain both biotic and abiotic componentsorganic inorganic parts of an ecosystemNutrient Cycles: water, carbon, nitrogen, phosphorus
20Restoration EcologyBioremediation: use of organisms (prokaryotes, fungi, plants) to detoxify polluted ecosystemsBioaugmentation: introduce desirable species (eg. nitrogen-fixers) to add essential nutrients
21Restoration ecology projects Bioremediation of groundwater contaminated with uraniumRestoration ecology projects