環(huán)境科學(xué)概論教學(xué)課件(第二講)

CHAPTERTWOInteractions:EnvironmentandOrganisms

1Beeandsunflower2Soybeanandrhizobium3FishandcoralFishandshrimp4paddygrasshopperfrogsnakeeagle56OBJECTIVESAfterreadingthischapter,youshouldbeableto:Identifytheabioticandbioticfactorsinanecosystem..Defineniche.Describetheprocessofnaturalselectionasitoperatestorefinethefitbetweenorganism,habitat,andniche.Describepredator-prey,parasite-host,competitive,mutualistic,andcommensalisticrelationships.Differentiatebetweenacommunityandanecosystem.Listsomeofthecomponentsofanecosystem.Definetherolesofproducer,herbivore,carnivore,omnivore,anddecomposer..Describeenergyflowinanecosystem.Relatetheconceptsoffoodwebsandfoodchainstotrophiclevels.Explainthecyclingofnutrientssuchasnitrogen,carbon,andphosphorusthroughanecosystem.71EcologicalConcepts

Environment:Everythingthataffectsanorganismduringitslifetimeiscollectivelyknownasitsenvironment.itisusefultosubdividetheconceptofenvironmentintoabiotic(nonliving)andbiotic(living)factors.Abioticfactorscanbeorganizedintoseveralbroadcategories:energy,nonlivingmatter,andprocessesthatinvolvetheinteractionofnonlivingmatterandenergy.Bioticfactorsincludeallformsoflifewithwhichitinteracts.LimitingFactors:Ashortageorabsenceofakeyfactorrestrictsthesuccessofthespecies;thusthefactorisknownasalimitingfactor.

Habitat:Thehabitatofanorganismisthespacethattheorganisminhabits,theplacewhereitlives(itsaddress)

Niche:isthefunctionalroleithasinitssurroundings(itsprofession).Ecology:isthestudyofthewaysorganismsinteractwitheachotherandwiththeirnonlivingsurroundings.8CompositionofanecosystemBioticenvironmentAbioticenvironment9Limitingfactor:A

shortageorabsenceofakeyfactorrestrictsthesuccessofthespecies;thusthefactorisknownasalimitingfactor.

10Habitat(生境）:Thehabitatofanorganismisthespacethattheorganisminhabits,theplacewhereitlives(itsaddress).Environmentisthehome.1112Niche:isthefunctionalroleithasinitssurroundings(itsprofession).132TheRoleofNaturalSelectionandEvolution

Population:agroupofindividualsofthesamespeciesinhabitingaparticularareaataspecifictime.Species:isapopulationoforganismsinwhichtheindividualsarepotentiallyabletointerbreedandproducefertileoffspring.Naturalselection:istheprocessthatdetermineswhichindividualswithinaspecieswillreproduceandpasstheirgenestothenextgeneration.Gene:isdistinctpiecesofDNAthatdeterminethecharacteristicsanindividaldisplays.Evolution:thechangesthatcanbeseeninthegenesandthecharacteristicdisplayedbysuccessivegenerationsofpopulationoforganismsovertime.Extinction:isthelossofanentirespecies.141.Individualswithinaspeciesshowedvariation;someofthevariationswereveryusefulandotherswerenot.Forexample,individualanimalsthatarepartofthesamespeciesshowcolorvariations.Somecolorsmaketheanimalmoreconspicuouswhileothersmakeitlessconspicuous.2.Organismswithinaspeciestypicallyproducemanymoreoffspringthancansurvive.Thismeansthatthereisnotenoughsuitablehabitatforalloftheoffspringtogrowtomaturity.Oneappletreemayproducehundredsofappleswithseveralseedsineachapple,orapairofrabbitsmayhavethreetofourlittersofoffspringeachsummer,withseveralyoungineachlitter.3.Theexcessnumberofindividualsresultsinastruggleforsurvival.Individualswithinthepopulationmustcompetewitheachotherforfood,space,mates,orotherrequirementsthatareinlimitedsupply.Ifyouplant100beanseedsinapot,manyofthemwillbegintogrow,buteventuallysomewillbecometallerandshadetheremainingplants.Greathomedowlstypicallyproducetwoyoungatatime,butiffoodisinshortsupply,thelargerofthetwoyoungwillgetthemajorityofthefood.4.Becauseofvariationamongindividuals,somehaveagreaterchanceofsurvivingandreproducingthanothers.Thecompetitionforresourcesoftenresultsinthelessfitindividualsdying;therefore,theydonotgetachancetoreproducethemselves.Eveniftheydonotdie,theymaymaturemoreslowlyandnotbeabletoreproduceasmanytimesasthemorefitmembersofthespecies.5.Astimepassesandeachgenerationissubjectedtothesameprocess,thepercentageofindividualsshowingfavorablevariationswillincreaseandthosehavingunfavorablevariationswilldecrease.Thus,thespecieswillbecomebetterandbetteradaptedtoitsenvironment.TheMechanismofNaturalSelection153KindsOfOrganismInteractionsPredation:Onecommonkindofinteractioncalledpredationoccurswhenoneanimal,knownasapredator,killsandeatsanother,knowastheprey.Competition:Asecondtypeofinteractionbetweenspeciesiscompetition,inwhichtwoorganismsstrivetoobtainthesamelimitedresource.Intheprocess,bothorganismsareharmedtosomeextent.SymbioticRelationships:symbiosisisaclose,long-lasting,physicalrelationshipbetweentwodifferentspecies.Inotherwords,thetwospeciesareusuallyinphysicalcontactandatleastoneofthemderivessomesortofbenefitfromthiscontact.

Parasitism:parasitismisarelationshipinwhichoneorganism,knownastheparasite,livesinoronanotherorganism,knownasthehost,fromwhichitderivesnourishment.

Commensalism:oneorganismbenefitswhiletheotherisnotaffected,itiscalledcommensalism.

Mutualism:akindofrelationshipthatisactuallybeneficialtobothspeciesinvolved.Thiskindofarelationshipiscalledmutualism.161718Intraspecificcompetition:membersofthesamespeciescompeteforresources.Interspecificcompetition:competitionbetweenorganismsofdifferentspecies.Competitiveexclusionprinciple:notwospeciescanoccupythesameecologicalnicheinthesameplaceatthesametime.19SymbioticrelationshipsParasitism:parasitismisarelationshipinwhichoneorganism,knownastheparasite,livesinoronanotherorganism,knownasthehost,fromwhichitderivesnourishment.

20Commensalism:relationshipbetweenorganismsinwhichoneorganismbenefitswhiletheotherisnotaffected,itiscalledcommensalism.Commensalism21Mutualism:akindofrelationshipthatisactuallybeneficialtobothspeciesinvolved.Mutualism22Somerelationshipsaredifficulttocategorize234communityandecosysteminteractions

MajorRolesofOrganisms:

Producers:areabletomakenew,complex,organicmaterialfromtheatomsintheirenvironment.

Consumers:allotherorganismsrelyonproducersasasourceoffood,eitherdirectlyorindirectly.Theseotherorganismsarecalledconsumers.

Decomposer:usenonlivingorganicmatterasasourceoffood.EnergyFlowThroughEcosystems:

Anecosystemisastable,self-regulatingunit.Tomaintainitself,itmusthaveacontinuousinputofenergy.Theonlysignificantsourceofenergyformostecosystemsissunlightenergy.FoodChainsandFoodWebs:Thepassageofenergyfromonetrophicleveltothenextasaresultofoneorganismconsuminganotherisknownasafoodchain.Whenseveralfoodchainsoverlapandintersect,theymakeupafoodweb.

Community:isanassemblageofalltheinteractingpopulationsofdifferentspeciesoforganismsinanarea.24Keystonespecies:

isonethathasacriticalroletoplayinthemaintenanceofspecificecosystems.bisonTrophicLevels

Eachstepintheflowofenergythroughanecosystemisknownasatrophiclevel.Biomass

istheweightoflivingmaterialinatrophiclevel.255EnergyflowthroughecosystemsCarnivoreOmnivoreHerbivoreProducer26Foodchain27286NutrientCyclesinEcosystems

CarbonCycle29NitrogenCycle

30PhosphorusCycle

31SummaryEverythingthataffectsanorganismduringitslifetimeiscollectivelyknownasitsenvironment.Theenvironmentofanorganismcanbedividedintobiotic(living)andabiotic(nonliving)components.Thespaceanorganismoccupiesisknownasitshabitat,andtheroleitplaysinitsenvironmentisknownasitsniche.Thenicheofanorganismistheresultofnaturalselectiondirectingtheadaptationoftheorganismtoaspecificsetofenvironmentalconditions.Organismsinteractwithoneanotherinavarietyofways.Predatorskillandeatprey.Organismsthathavethesameneedscompetewithoneanotheranddomutualharm,butoneisusuallyharmedlessandsurvives.