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Movement of Energy in Ecosystems
Lesson objectives•Understand how energy moves through an ecosystem•Describe different ways to measure productivity•Compare net productivity among different ecosystems•Understand how nutrients can affect productivity•Calculate trophic efficiencies
•Solar energy powersphotosynthesis of producers•Few ecosystems use chemicalenergy for chemosynthesis•Producers form base of food websThe sun is the ultimate source of energyfor most ecosystems1% of solar energy is captured
•Gross primary productivity(GPP)rate that energy is captured andassimilated by producers•Energy used for respiration,growth, reproduction•Net primary productivity(NPP)rate that energy is assimilatedinto producer biomass•Standing crop•NPP = GPP - respirationPrimary productivity is the rate at which energy isconverted into organic compounds in producersGPP = 2.5 kg C/m2/yrRespiration = 1.5 kg C/m2/yrNPP = 1 kg C/m2/yr
How can primary productivity be quantified?ProducerbiomassRemotesensingUptake/Release ofCO2or O2Light-dark bottle experimentsNPP = net CO2GPP = net CO2+ respired CO2Terrestrial vs AquaticNPP =net O2GPP = net O2+ respired O2NPP = GPP - respirationGPP-R+GPP-RGPP = NPP + respirationR