Chapter 3 Communities,Biomes,and Ecosystems：3章群落生物群落和生态系统

Chapter3:Communities,Biomes,andEcosystemsBiology,BiologyR,andBiologyAcademicMrs.Fournier3.1CommunityEcologyMainidea-Alllivingorganismsarelimitedbyfactorsintheenvironment.Objectives-Recognizehowunfavorableabioticandbioticfactorsaffectaspecies.Describehowrangesoftoleranceaffectthedistributionoforganisms.Sequencethestagesofprimaryandsecondarysuccession.ReviewVocabularyAbioticfactor:thenonlivingpartofanorganism’senvironmentCommunitiesAbiologicalcommunityisagroupofinteractingpopulationsthatoccupythesameareaatthesametimeLimitingFactorsAnyabioticorbioticfactorthatrestrictsthenumbers,reproduction,ordistributionoforganismsiscalledalimitingfactor.Includessunlight,climate,temperature,water,nutrients,fire,soilchemistry,andspace,andotherlivingthings.RangeofToleranceAnupperlimitandlowerlimitthatdefinetheconditionsinwhichanorganismcansurviveTheabilityofanyorganismtosurvivewhensubjectedtoabioticfactorsorbioticfactorsiscalledtolerance.EcologicalSuccessionThechangeinanecosystemthathappenswhenonecommunityreplacesanotherasaresultofchangingabioticandbioticfactorsisecologicalsuccession.Therearetwotypesofecologicalsuccession–primarysuccessionandsecondarysuccession.PrimarySuccessionTheestablishmentofacommunityinanareaofexposedrockthatdoesnothaveanytopsoilisprimarysuccession.PioneerStagesPrimarysuccessionusuallyoccursslowlyatfirst:Usuallylichens,acombinationofafungusandalgae,begintogrowontherock.Becauselichensareamongthefirstorganismstoappeartheyarecalledpioneerspecies.Pioneerspecieshelptocreatesoilbysecretingacidsthathelptobreakdownrocks.PrimarySuccessionThen…Asthepioneerorganismsdie,theirdecayingorganicmaterials,alongwithbitsofsedimentfromtherocks,makeupthefirststageofsoildevelopment.Atthispoint,smallweedyplants,includingfernsandotherorganismssuchasfungiandinsects,becomeestablished.Astheseorganismsdie,additionalsoiliscreated.IntermediateStagesThen…Seeds,broughtinbyanimals,water,orwind,begintogrowinthenewlyformedsoil.Eventually,enoughsoilispresentsothatshrubsandtreescangrow.MatureCommunityAclimaxcommunityeventuallycandevelopfromthebarerock,lichens,smallannualplants,perennialherbsandgrassesinthepioneerstagestothegrasses,shrubsandshade-intoleranttreesintheintermediatestagestotheshadetoleranttreesofthematurecommunity.Thestable,maturecommunitythatresultswhenthereislittlechangeinthenumberofspeciesisaclimaxcommunity.SecondarySuccessionSecondarySuccessionoftenoccursasaresultofanaturaldisturbance,suchas,fire,flood,orawindstorm.Afteradisturbance,newspeciesofplantsandanimalsmightoccupythehabitat.Overtime,thereisanaturaltendencyforthespeciesbelongingtothematurecommunitytoreturn.Theorderlyandpredictablechangethattakesplaceafteracommunityoforganismshasbeenremovedbutthesoilhasremainedintactissecondarysuccession.SecondarySuccessionPioneerspecies–mainlyplantsthatbegintogrowinthedisturbedarea–arethefirstspeciestostartsecondarysuccession.3.2TerrestrialBiomesMainidea–Ecosystemsonlandaregroupedintobiomesprimarilybasedontheplantcommunitieswithinthem.Objectives–Relatelatitudeandthethreemajorclimatezones.Describethemajorabioticfactorsthatdeterminethelocationofaterrestrialbiome.Distinguishamongterrestrialbiomesbasedonclimateandbioticfactors.ReviewVocabularyBiome:alargegroupofecosystemsthatsharethesameclimateandhavesimilartypesofplantcommunities.

EffectsofLatitudeandClimateWeatheristheconditionoftheatmosphereataspecificplaceandtime.Oneofthekeystounderstandingthesecommunitiesistobeawareoflatitudeandclimaticconditions.EffectsofLatitudeandClimateThedistanceofanypointonthesurfaceofEarthnorthorsouthfromtheequatorislatitude.Latituderangefrom0˚attheequatorto90˚atthepoles.Earth’ssurfaceisheateddifferentlyindifferentareas.Ecologistsrefertotheseareasaspolar,temperate,andtropicalzones.EffectsofLatitudeandClimateTheaverageweatherconditionsinanarea,includingtemperatureandprecipitation,describethearea’sclimate.Thegraphshowshowtemperatureandprecipitationinfluencethecommunities.Biomesareclassifiedprimarilyaccordingtothecharacteristicsoftheirplants.MajorBiomesarealsocharacterizedbytemperature,precipitation,andanimalspecies.TundraAtreelessbiomewithalayerofpermanentlyfrozensoilbelowthesurfacecalledpermafrost.Averageprecipitation:15–25cmperyearTemperaturerange:-34°C–12°CGeographiclocation:SouthofthepolaricecapsintheNorthernHemisphereAbioticfactors:soggysummers;permafrost;coldanddarkmuchoftheyearBorealForestSouthofthetundraisabroadbandofdenseevergreenforestalsocalledthenorthernconiferousforest,ortaiga.Averageprecipitation:30–84cmperyearTemperaturerange:-54°C–21°CGeographiclocation:northernpartofNorthAmerica,EuropeandAsia.Abioticfactors:summersareshortandmoist;wintersarelong,cold,anddryTemperateForestIscomposedmostlyofbroad-leaveddeciduoustrees–shedtheirleavesinautumn.Averageprecipitation:75–150cmperyearTemperaturerange:-30°C–30°CGeographiclocation:southoftheborealforestsineasternNorthAmerica,easternAsia,Australia,andEuropeAbioticfactors:well-definedseasons;summersarehot,wintersarecoldTemperateWoodlandandShrublandOpenwoodlandsandmixedshrubcommunitiesarefoundinareaswithlessannualrainfallthanintemperateforests.Areasthataredominatedbyshrubs,suchasinCaliforniaarecalledthechaparral.Averageprecipitation:38–100cmperyearTemperaturerange:10°C–40°CGeographiclocation:surroundstheMediterraneanSea,westerncoastofNorthandSouthAmerica,SouthAfrica,andAustraliaAbioticfactors:summersareveryhotanddry;wintersarecoolandwetTemperateGrasslandAbiomethatischaracterizedbyfertilesoilsthatareabletosupportthickcoverofgrassesiscalledgrasslandGrasslandsarecalledsteppesinAsia;prariesinNorthAmerica;pampas,llanos,andcerradosinsouthAmerica;savannahsandveldsinAfrica;andrangelandsinAustraliaAverageprecipitation:50–89cmperyearTemperaturerange:-40°C–38°CGeographiclocation:NorthAmerica,SouthAmerica,Asia,Africa,andAustraliaAbioticfactors:summersarehot;wintersarecold;moderaterainfall;firespossibleDesertAdesertisanyareainwhichtheannualrateofevaporationexceedstherateofprecipitationAverageprecipitation:2–26cmperyearTemperaturerange:high:20°C–49°C;low:-18°C–10°CGeographiclocation:everycontinentexceptEuropeAbioticfactors:varyingtemperatures;lowrainfallTropicalSavannaIscharacterizedbygrassesandscatteredtreesinclimatesthatreceivelessprecipitationthansomeothertropicalareas.Averageprecipitation:50–130cmperyearTemperaturerange:20°C–30°CGeographiclocation:Africa,SouthAmerica,andAustraliaAbioticfactors:summersarehotandrainy;wintersarecoolanddryTropicalSeasonalForestAverageprecipitation:>200cmperyearTemperaturerange:20°C–25°CGeographiclocation:Africa,Asia,Australia,andSouthandCentralAmerica

Abioticfactors:rainfallisseasonalTropicalRainForestAlsocalledtropicaldryforestsAverageprecipitation:200–1000cmperyearTemperaturerange:24°C–27°CGeographiclocation:CentralandSouthAmerica,southernAsia,westernAfrica,andnortheasternAustraliaAbioticfactors:humidallyear;hotandwetOtherTerrestrialAreasManyecologistsomitmountainsandpolarregionsfromthelistofterrestrialbiomes.Mountainsarefoundthroughouttheworldanddonotfitthedefinitionofabiomebecausetheirclimatecharacteristicsandplantandanimallifevarydependingonelevation.Polarregionsalsoarenotconsideredtruebiomesbecausetheyareicemassesandnottruelandareaswithsoil.MountainsIfyougoupamountain,youmightnoticethatabioticconditions,suchastemperatureandprecipitation,changewithincreasingelevation.PolarRegionsPolarRegionsborderthetundraathighaltitudesPolarregionsarecoldallyear3.3AquaticEcosystemsMainidea–Aquaticecosystemsaregroupedbasedonabioticfactorssuchaswaterflow,depth,distancefromtheshore,salinity,andlatitude.ObjectivesIdentifythemajorabioticfactorsthatdeterminetheaquaticecosystemsRecognizethatfreshwaterecosystemsarecharacterizedbydepthandwaterflowIdentifytransitionalaquaticecosystemsandtheirimportanceDistinguishthezonesofmarineecosystemsReviewVocabularySalinity:ameasureoftheamountofsaltinabodyofwaterFreshwaterEcosystemsThemajorfreshwaterecosystemsincludeponds,lakes,streams,rivers,andwetlands.Plantsandanimalsintheseecoystemsareadaptedtothelowsaltcontentinfreshwaterandareunabletosurviveinareasofhighsaltconcentration.Onlyabout2.5%ofthewateronEarthisfreshwater.Ofthat2.5%68.9%iscontainedinglaciers,30.8%isgroundwater,andonly0.3isfoundinlakes,ponds,rivers,streams,andwetlandsEarth’sWatervs.FreshwaterRiversandStreamsThecharacteristicsofriversandstreamschangeduringthejourneyfromthesourcetothemouth.CharacteristicsofRiversandStreamsThewaterinriversandstreamsflowinonedirection,beginningatasourcecalledaheadwaterandtravelingtothemouth,wheretheflowingwateremptiesintoalargerbodyofwater.Theslopeofthelandscapedeterminesthedirectionandspeedofthewaterflow.Whentheslopeissteep,waterflowsquickly,causingalotofsedimenttobepickedupandcarriedbythewater.Sedimentismaterialthatisdepositedbywater,wind,orglaciers.Astheslopelevels,thespeedofthewaterflowdecreasesandsedimentsaredepositedintheformofsilt,mud,andsand.CharacteristicsofRiversandStreamsInteractionsbetweenwindandthewaterstirupthewater’ssurface,whichaddsasignificantamountofoxygentothewater.Interactionsbetweenlandandwaterresultinerosion,changesinnutrientavailability,andchangestothepathoftheriverorstream.Animportantcharacteristicofalllifeinriversandstreamsistheabilitytowithstandtheconstantwatercurrent.Thecurrentsandturbulenceoffast-movingriversandstreamspreventmuchaccumulationoforganicmaterialsandsediment.Usually,therearefewerspecieslivingintherapidwaters.Inslow-movingwater,insectslarvaearetheprimaryfoodsourceformanyfish.LakesandPondsThesizeoflakesandpondscanrangefromafewsquaremeterstomanysquarekilometers.Manypondsareseasonallastingonlyacoupleweeksormonthseveryyear,whileotherlakesmightexistforhundredsorthousandsofyears.Thetemperatureoflakesandpondsvarydependingontheseason.Duringthespringandautumn,deepwaterreceivesoxygenfromthesurfacewaterandsurfacewaterreceivesinorganicnutrientsfromthedeepwater.LakesandPondsLakesandPondsNutrient-poorlakesarecalledoligotrophiclakes,oftenfoundhighinthemountainswithfewplantandanimalspecies.Nutrient-richlakesarecalledeutrophiclakes,usuallyfoundatloweraltitudeswithmanyplantandanimalspecies.LakesandPondsLakesandpondsaredividedintothreezonesbasedontheamountofsunlightthatpenetratesthewater.Theareaclosesttotheshoreisthelittoralzone.LittoralZoneConsistsofspeciesofalgae,rootedandfloatingaquaticplants,grazingsnails,clams,insects,crustaceans,fishes,andamphibians.Someinsectspecies,suchasdragonfliesandmidges,laytheireggsinthelittoralzoneandthelarvalstagesoftheirlifecyclecanbefoundthere.Turtles,snakes,andbirdsmightpreyontheanimalsthatinhabitthiszone.LimneticZoneThelimneticzoneistheopenwaterareathatiswelllitandisdominatedbyplankton.Planktonarefree-floatingphotosyntheticautotrophsthatliveinfreshwaterormarineecosystems.Manyspeciesoffreshwaterfishliveinthelimenticzonebecausefoodisreadilyavailable.ProfundalZoneTheprofundalzoneisthedeepestareasofthelakeItismuchcolderandlowerinoxygenthantheothertwozonesLittlelightisabletopenetratethelimneticzoneinordertoentertheprofundalzone,whichlimitsthenumberofspeciesthatareabletolivethere.TransitionalAquaticEcosystemsTheseareasarewherelandandwaterorsaltwaterandfreshwaterintermingle.Wetlandsandestuariesarecommonexamplesoftransitionalaquaticecosystems.WetlandsAreasoflandsuchasmarshes,swamps,andbogsthataresaturatedwithwater.andthatsupportaquaticplants.Wetlandshavehighlevelsofspeciesdiversity.Manyamphibians,reptiles,birdsandmammalsliveinwetlandsEstuariesAreamongthemostdiverseecosystems,rivaledonlybythetropicalrainforestsandcoralreefs.Anestuaryisanecosystemthatisformedwhereafreshwaterriverorstreammergeswiththeocean.Algae,seaweeds,andmarshgrassesarethedominantproducers.How