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Chapter 50An Introduction to Ecology andThe BiosphereI.ScopeofecologyA.Interactionsbetweenorganismsandtheirenvironment1.Ecologyisthescientificstudyoftheinteractionsbetweenorganismsandtheirenvironment.a.Interactionsdeterminedistributionandabundanceoforganisms.b.Twomainthemesinecologyare:-Wheredoorganismslive?&Why?-Howmanyorganismsarepresent?&Why?c.Ecologywashistoricallyanobservationalscience,oftendescriptive naturalhistory.d.Anorganismsenvironmenthasbothabioticandbioticcomponents.-Abioticcomponentsarenonlivingchemicalandphysicalfactorssuchastemperature,light,water,andnutrients.-Bioticcomponentsarelivingfactorssuchasotherorganisms.2.Ecologyandevolutionarybiologyarecloselyrelatedsciencesa.Eventsthatoccurintheframeworkofecologicaltime(minutes,days,years)translateintoeffectsoverevolutionarytime(decades,millennia).Example:Hawksfeedingonmiceimpactmousepopulationandmayeventuallyleadtoselectionformicewithfurascamouflage.3.Ecologicalresearchscalerangesfromindividualstothebiospherea.Organismalecologyisconcernedaboutthewayinwhichanindividualinteractswithitsenvironment.b.Populationecologyisthestudyofagroupofindividualsofthesamespecies.c.Communityecologydealswithallinteractingspecieswithinaparticulararea.d.Anecosystemconsistsofallabioticfactorsplusallorganismsthatexistinacertainarea Ecosystemecology.Landscapeecology-interactionsamongecosystems.e.Thebiosphereistheglobalecosystem.Globalclimateresearchisanexampleofecologyatthebiospherescale.II.Factorsaffectingthedistributionoforganisms-Biogeographyisthestudyofpastandpresentdistributionofindividualspecies.A.SpeciesdispersalcontributestothedistributionoforganismsDispersalreferstotheprocessofdistributionofindividualswithingeographicpopulationboundaries.Question:Isthedistributionofaspecieslimitedbydispersal,i.e.bymovementoftheorganisms?Answercanbeobtainedbytransplantexperiments.Ifthetransplantissuccessful,thentheorganismsjusthaventreachedthetargetarea.Ifthetransplantisnotsuccessful,thenotherfactorslimitthedistributionoftheorganisms,suchascompetitors,lackofafoodsource,etc.a.Introducedspeciessometimeshavedisasterousimpacts:-Africanhoneybee,ZebramusselsManyintroductionsintentional.The“Lawsof10”.Whydothesuccessfulinvaderssucceed?Invasionalmeltdowns?Climatechangeeffects?B.Behaviorandhabitatselectioncontributetothedistributionoforganisms1.Organismsmaynotoccupyallpotentiallysuitablehabitat.Why?a.Evolutiondoesntleadtoperfectorganisms.b.Evolutionisanongoingprocess.Environmentschange,butittakesawhilefororganismstorespond.C.Bioticfactorsaffectdistribution1.Organismsrequiredforpotentialcommunitymemberstocolonizemaybelacking.-Pollinators,prey,predatorsthatlimitcompetitionD.Abioticfactorsaffectdistribution1.Abioticfactorsofinterestinclude:-Temperature(rangefrom0to45C)-Water-Sunlight-Wind(increasesheat&waterloss)-RocksandsoilFig.50.13Copyright 2002 Pearson Education,Inc.,publishing as Benjamin CummingsLocal and seasonal effects on climate.Bodies of water and topographic features such as mountain ranges can affect local climates.Ocean currents can influence climate in coastal areas.Mountains affect rainfall greatly.Fig.50.14Copyright 2002 Pearson Education,Inc.,publishing as Benjamin Cummingsb.Lakestratificationandmixingaltersoxygenandnutrientlevels.Dependentontemperaturechangesandeffectonwaterdensity.Aquaticandterrestrialbiomes(Biome=majorecosystemtype)A.Aquaticbiomescoverabout75%oftheearthssurface-Wetlands-Lakes-Rivers,streams-Intertidalzones-Oceanicpelagicbiome-Coralreefs-BenthosOligotrophicLake:Nutrientpoor,waterisclear,oxygenrich;littleproductivitybyalgae,relativelydeepwithlittlesurfacearea.Eutrophiclake:nutrientrich,lotsofalgalproductivitysoitsoxygenpoorattimes,waterismurkieroftenaresultofinputofagriculturalfertilizersRiversandStreams:Organismsneedadaptationssothattheyarenotsweptawaybymovingwater;heavilyaffectedbymanchangingthecourseofflow(E.g.damsandchannel-straightening)andbyusingriverstodisposeofwaste.Wetlands:includesmarshes,bogs,swamps,seasonalponds.Amongrichestbiomeswithrespecttobiodiversityandproductivity.Veryfewnowexistastheyarethoughtofoftenaswastelands.Estuary:Placewherefreshwaterstreamorrivermergeswiththeocean.Highlyproductivebiome;importantforfisheriesandfeedingplacesforwaterfowl.Oftenheavilypollutedfromriverinputsomanyfisheriesarenowlost.Marineenvironmentwithzonation.IntertidalZone:Alternatelysubmergedandexposedbydailycycleoftides.Oftenpollutedbyoilthatdecreasesbiodiversity.CoralReefs:occurinneriticzonesofwarm,tropicalwater,dominatedbycnidarians(corals);veryproductive,protectlandfromstorms;mostarenowdyingfromriseinglobaltemperaturesDeep-seavent:Occursinbenthiczone;diverse,unusualorganisms;energycomesnotfromlightbutfromchemicalsreleasedfromthemagma.B.Terrestrialbiomes-Tropicalforest-Savanna-Desert-Chaparral-Temperategrassland-Temperatedeciduousforest-Coniferousforest-TundraTropicalForest:Verticalstratificationwithtreesincanopyblockinglighttobottomstrata.Manytreescoveredbyepiphytes(plantsthatgrowonotherplants).ExampleofTropical,DryForestDesert:Sparserainfall(30cmperyear),plantsandanimalsadaptedforwaterstorageandconservation.Canbeeithervery,veryhot,orverycold(e.g.Antarctica)Chaparral:Dense,spiny,evergreenshrubs,mildrainywinters;long,hot,drysummers.Periodicfires,someplantsrequirefireforseedstogerminate.TemperateGrassland:Markedbyseasonaldroughtandfires,andgrazingbylargeanimals.Richhabitatforagriculture,verylittleprairieexistsinUStoday.TemperateDeciduousForest:Mid-latitudeswithmoderateamountsofmoisture,distinctverticalstrata:trees,understoryshrubs,herbaceoussub-stratum.Lossofleavesincold,manyanimalshibernateormigratethen.OriginalforestslostfromNorthAmericabyloggingandclearing.Coniferousforest:Largestterrestialbiomeonearth,oldgrowthforestsrapidlydisappearing,usuallyreceiveslotsofmoistureasrainorsnow.Tundra:Permafrost(Permanentfrozenground),bittercold,highwindsandthusnotrees.Has20%oflandsurfaceonearth.
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