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1、AnOverviewofEcosystemDynamicsA.Anecologicalsystem,orecosystem,isthehighestlevelofbiologicalorganization.Itconsistsof:1.thebiologicalcommunity:alltheorganismsinagivenareaplus2.thephysicalenvironment,includingsoil,water,andair.B.Twomajorprocessessustainallecosystems1.Energyflowisthepassage
2、ofenergythroughthecomponentsoftheecosystem.2.Chemicalcyclingistheuseandreuseofchemicalelements,suchascarbon,withintheecosystem.3.Energyflowscontinuouslythroughanecosystem.a.Energyentersmostecosystemsaslight.b.Producersconvertthelightenergytothechemicalenergyoffood.c.Otherorganismsfeedonp
3、lantsororganismsthateatplants.d.Decomposersconsumethedeadremainsoflife.e.Inusingtheirchemicalenergyforwork,allorganismsdissipateheatenergytotheirsurroundings.4.Unliketheflowofenergythroughanecosystem,chemicalelementscanberecycledbetweenanecosystem’slivingcommunityandtheabioticenvironment
4、.a.Plantsandotherproducers:(1)acquiretheircarbon,nitrogen,andotherchemicalelementsfromtheairandsoiland(2)converttheseinorganicelementsintoorganiccompounds(carbohydratesandproteins)usingphotosynthesis.b.Animalsfeedontheseorganiccompounds.c.Themetabolismofallorganismsreturnssomeofthechemic
5、alelementstotheabioticenvironmentininorganicform.d.Decomposersfinishrecycling.C.Energyflowandchemicalrecyclingdependontransferofsubstancesinthefeedingrelationships,ortrophicstructure,oftheecosystem.1.Trophicrelationshipsdetermineanecosystem’sroutesofenergyflowandchemicalcycling(Figures19
6、.21–19.22).2.Ecologistsdividethespeciesofanecosystemintodifferenttrophiclevelsbasedontheirmainsourcesofnutrition.D.TrophicLevelsandFoodChains(Figures19.21–19.22)1.Thesequenceoffoodtransferfromtrophicleveltotrophicleveliscalledafoodchain.2.Thetrophiclevelthatsupportsallothersconsistsofthe
7、producers,theautotrophicorganisms.a.Plantsarethemainproducersonland.b.Inaquaticecosystems,theproducersaremainlyphotosyntheticprotistsandbacteria,calledphytoplankton.3.Allorganismsintrophiclevelsabovetheproducersareconsumers.a.Herbivores,whicheatplants,algae,orautotrophicb
