講義tpo033the long-term stability of ecosystems題目解析

TheLong-TermStabilityofPlantcommunitiesassemblethemselvesflexibly,andtheirparticularstructuredependsonthespecifichistoryofthearea.Ecologistsusetheterm“succession”torefertothechangesthathappeninplantcommunitiesandecosystemsovertime.Thefirstcommunityinasuccessioniscalledapioneercommunity,whilethelong-livedcommunityattheendofsuccessioniscalledaclimaxcommunity.Pioneerandsuccessionalplantcommunitiesaresaidtochangeoverperiodsfrom1to500years.Thesechanges—inplantnumbersandthemixofspecies—arecumulative.Climaxcommunitiesthemselveschangebutoverperiodsoftimegreaterthanabout500years.Anecologistwhostudiesapondtodaymaywellfinditrelativelyunchangedinayear’stime.Individualfishmaybereplaced,butthenumberoffishwilltendtobethesamefromoneyeartothenext.Wecansaythatthepropertiesofanecosystemaremorestablethantheindividualorganismsthatcomposetheecosystem.Atonetime,ecologistsbelievedthatspeciesdiversitymadeecosystemsstable.Theybelievedthatthegreaterthediversitythemorestabletheecosystem.Supportforthisideacamefromtheobservationthatlong-lastingclimaxcommunitiesusuallyhavemorecomplexfoodwebsandmorespeciesdiversitythanpioneercommunities.Ecologistsconcludedthattheapparentstabilityofclimaxecosystemsdependedontheircomplexity.Totakeanextremeexample,farmlandsdominatedbyasinglecroparesounstablethatoneyearofbadweatherortheinvasionofasinglepestcandestroytheentirecrop.Incontrast,acomplexclimaxcommunity,suchasatemperateforest,willtolerateconsiderabledamagefromweathertopests.Thequestionofecosystemstabilityiscomplicated,however.Thefirstproblemisthatecologistsdonotallagreewhat“stability”means.Stabilitycanbedefinedassimplylackofchange.Inthatcase,theclimaxcommunitywouldbeconsideredthemoststable,since,bydefinition,itchangestheleastovertime.Alternatively,stabilitycanbedefinedasthespeedwithwhichanecosystemreturnstoaparticularformfollowingamajordisturbance,suchasafire.Thiskindofstabilityisalsocalledresilience.Inthatcase,climaxcommunitieswouldbethemostfragileandtheleaststable,sincetheycanrequirehundredsofyearstoreturntotheclimaxstate.Eventhekindofstabilitydefinedassimplelackofchangeisnotalwaysassociatedwithumdiversity.Atleastintemperatezones,umdiversityisoftenfoundinmid-successionalstages,notintheclimaxcommunity.Oncearedwoodforestmatures,forexample,thekindsofspeciesandthenumberofindividualsgrowingontheforestfloorarereduced.Ingeneral,diversity,byitself,doesnotensurestability.Mathematicalmodelsofecosystemslikewisesuggestthatdiversitydoesnotguaranteeecosystemstability—justtheopposite,infact.Amorecomplicatedsystemis,ingeneral,morelikelythanasimplesystemtobreakdown.Afifteen-speedracingbicycleismorelikelytobreakdownthanachild’sEcologistsareespeciallyinterestedtoknowwhatfactorscontributetotheresilienceofcommunitiesbecauseclimaxcommunitiesallovertheworldarebeingseverelydamagedordestroyedbyhumanactivities.ThedestructioncausedbythevolcanicexplosionofMountSt.Helens,inthenorthwesternUnitedStates,forexample,palesincomparisontothedestructioncausedbyhumans.Weneedtoknowwhataspectsofacommunityaremostimportanttothecommunity’s todestruction,aswellasitsrecovery.Manyecologistsnowthinkthattherelativelong-termstabilityofclimaxcommunitiescomesnotfromdiversitybutfromthe“patchiness”oftheenvironment,anenvironmentthatvariesfromplacetoplacesupportsmorekindsoforganismsthananenvironmentthatisuniform.Alocalpopulationthatgoesextinctisquicklyreplacedbyimmigrantsfromanadjacentcommunity.Evenifthenewpopulationisofadifferentspecies,itcanapproximayfillthenichevacatedbytheextinctpopulationandkeepthefoodwebintact.Paragraph1:Plantcommunitiesassemblethemselvesflexibly,andtheirparticularstructuredependsonthespecifichistoryofthearea.Ecologistsusetheterm“succession”torefertothechangesthathappeninplantcommunitiesandecosystemsovertime.Thefirstcommunityinasuccessioniscalledapioneercommunity,whilethelong-livedcommunityattheendofsuccessioniscalledaclimaxcommunity.Pioneerandsuccessionalplantcommunitiesaresaidtochangeoverperiodsfrom1to500years.Thesechanges—inplantnumbersandthemixofspecies—arecumulative.Climaxcommunitiesthemselveschangebutoverperiodsoftimegreaterthanabout500years.Theword“particular”inthepassageisclosestinmeaningAccordingtoparagraph1,whichofthefollowingisNOTtrueofclimaxTheyoccuratofaTheylastlongerthananyothertypeofThenumbersofplantsinthemandthemixofspeciesdonotTheyremainstableforatleast500yearsata題型：否定事實(shí)信息題（NOT）climaxcommunities，答案出在這四句。看選項(xiàng)。A說在演替的最后出現(xiàn)，對應(yīng)原文的ofsuccession，正確，不選。B說比他任何一種群落持續(xù)的時間都長。原文一共說了三種群落：pioneercommunities、500年以上。說最后一種比另兩種周期長，正確，不選。C說其中的植物和Paragraph2:Anecologistwhostudiesapondtodaymaywellfinditrelativelyunchangedinayear’stime.Individualfishmaybereplaced,butthenumberoffishwilltendtobethesamefromoneyeartothenext.Wecansaythatthepropertiesofanecosystemaremorestablethantheindividualorganismsthatcomposetheecosystem.Accordingtoparagraph2,whichofthefollowingprinciplesofecosystemscanbelearnedbystudyingapond?EcosystempropertieschangemoreslowlythanindividualsintheThestabilityofanecosystemtendstochangeasindividualsareIndividualorganismsarestablefromoneyeartotheAchangeinthemembersofanorganismdoesnotaffectan變。A說整體比變得慢，正確。Paragraph3:Atonetime,ecologistsbelievedthatspeciesdiversitymadeecosystemsstable.Theybelievedthatthegreaterthediversitythemorestabletheecosystem.Supportforthisideacamefromtheobservationthatlong-lastingclimaxcommunitiesusuallyhavemorecomplexfoodwebsandmorespeciesdiversitythanpioneercommunities.Ecologistsconcludedthattheapparentstabilityofclimaxecosystemsdependedoncomplexity.Totakeanextremeexample,farmlandsdominatedbyasinglecroparesounstablethatoneyearofbadweatherortheinvasionofasinglepestcandestroytheentirecrop.Incontrast,acomplexclimaxcommunity,suchasatemperateforest,willtolerateconsiderabledamagefromweathertopests.Accordingtoparagraph3,ecologistsoncebelievedthatwhichofthefollowingillustratedthemoststableecosystems?PioneerClimaxSingle-cropSuccessionalplantB。Paragraph4:Thequestionofecosystemstabilityiscomplicated,however.Thefirstproblemisthatecologistsdonotallagreewhat“stability”means.Stabilitycanbedefinedassimplylackofchange.Inthatcase,theclimaxcommunitywouldbeconsideredthemoststable,since,bydefinition,itchangestheleastovertime.Alternatively,stabilitycanbedefinedasthespeedwithwhichanecosystemreturnstoaparticularformfollowingamajordisturbance,suchasafire.Thiskindofstabilityisalsocalledresilience.Inthatcase,climaxcommunitieswouldbethemostfragileandtheleaststable,sincetheycanrequirehundredsofyearstoreturntotheclimaxstate.Accordingtoparagraph4,whyisthequestionofecosystemstabilityThereasonsforecosystemchangearenotalwaysEcologistsoftenconfusetheword“stability”withthewordTheexactmeaningoftheword“stability”isdebatedbyTherearemanydifferentanswerstoecologicalC選項(xiàng)。Accordingtoparagraph4,whichofthefollowingistrueofclimaxTheyaremoreresilientthanpioneerTheycanbeconsideredboththemostandtheleaststableTheyarestablebecausetheyrecoverquicklyaftermajorTheyarethemostresilientcommunitiesbecausetheychangetheleastover種定義，climaxcommunitiesB。Paragraph5:Eventhekindofstabilitydefinedassimplelackofchangeisnotalwaysassociatedwithumdiversity.Atleastintemperatezones,umdiversityisoftenfoundinmid-successionalstages,notintheclimaxcommunity.Oncearedwoodforestmatures,forexample,thekindsofspeciesandthenumberofindividualsgrowingontheforestfloorarereduced.Ingeneral,diversity,byitself,doesnotensurestability.Mathematicalmodelsofecosystemslikewisesuggestthatdiversitydoesnotguaranteeecosystemstability—justtheopposite,infact.Amorecomplicatedsystemis,ingeneral,morelikelythanasimplesystemtobreakdown.Afifteen-speedracingbicycleismorelikelytobreakdownthanachild’stricycle.Whichofthefollowingcanbeinferredfromparagraph5aboutredwood elessstableastheyTheysupportmanyspecieswhentheyreachTheyarefoundintemperateTheyhavereduceddiversityduringmid-successional題目分析：信息點(diǎn)：redwoodforestsredwoodforests無關(guān)了，所以答案出三句。作推斷題，要讀完文章后逐項(xiàng)排除。看A選項(xiàng)，說成熟后community的穩(wěn)定性應(yīng)該更高，這樣才能說明穩(wěn)定性和多樣性的不一致。另外，第一段其實(shí)已經(jīng)明確說了climaxcommunityAB說到達(dá)climaxcommunityC選項(xiàng)說redwoodforests在溫帶，這是可以推斷出的。第三句是第二句的例子，所以記斷題的正確答案完全可能看起來非?，嵥?，與文章主旨沒什么關(guān)系。D說在Theword“guarantee”inthepassageisclosestinmeaningInparagraph5,whydoestheauthorprovidetheinformationthat“Afifteen-racingbicycleismorelikelytobreakdownthanachild’sToillustrateageneralprincipleaboutthestabilityofsystemsbyusinganeverydayexampleTodemonstratethatanunderstandingofstabilityinecosystemscanbeappliedtohelpunderstandstabilityinothersituationsTomakeacomparisonthatsupportstheclaimthat,ingeneral,stabilityincreaseswithdiversityToprovideanexamplethatcontradictsmathematicalmodelsof證關(guān)系。選A。Bbeapplied錯。Cstabilityincreaseswithdiversity錯。D選項(xiàng)contradicts錯。Paragraph6:Ecologistsareespeciallyinterestedtoknowwhatfactorscontributetotheresilienceofcommunitiesbecauseclimaxcommunitiesallovertheworldarebeingseverelydamagedordestroyedbyhumanactivities.ThedestructioncausedbythevolcanicexplosionofMountSt.Helens,inthenorthwesternUnitedStates,forexample,palesincomparisontothedestructioncausedbyhumans.Weneedtoknowwhataspectsofacommunityaremostimportanttothecommunity’stodestruction,aswellasitsrecovery.Theword“pales”inthepassageisclosestinmeaningincreaseslosesisParagraph7:Manyecologistsnowthinkthattherelativelong-termstabilityofclimaxcommunitiescomesnotfromdiversitybutfromthe“patchiness”oftheenvironment,anenvironmentthatvariesfromplacetoplacesupportsmorekindsoforganismsthananenvironmentthatisuniform.Alocalpopulationthatgoesextinctisquicklyreplacedbyimmigrantsfromanadjacentcommunity.Evenifthenewpopulationisofadifferentspecies,itcanapproximayfillthenichevacatedbytheextinctpopulationandkeepthefoodwebintact.Whichofthesentencesbelowbestexpressestheessentialinformationinthehighlightedsentenceinthepassage?Incurredchoiceschangethemeaninginimportantwaysorleaveoutessentialinformation.Ecologistsnowthinkthatthestabilityofanenvironmentisaresultofdiversityratherthanpatchiness.PatchyenvironmentsthatvaryfromplacetoplacedonotoftenhavehighspeciesUniformenvironmentscannotbeclimaxcommunitiesbecausetheydonotsupportasmanytypesoforganismsaspatchyenvironments.Apatchyenvironmentisthoughttoincreasestabilitybecauseitisabletosupportawidevarietyoforganisms.題目分析：較復(fù)雜，建議畫圖。說了四件事：1.穩(wěn)定性不來自多樣性2.穩(wěn)定性來自 3.patchiness指各處環(huán)境不一樣4.patchy的環(huán)境比各處一樣的支持的生物多。看選項(xiàng)：A憤青，B說patchy的不一定有高物種多樣，原文只說patchy的物種比uniform的多，沒說highspeciesdiversity問題，錯。C選項(xiàng)說各處一樣的環(huán)境不可能是頂級群落，原文沒。Because以后便也不對。只有D選項(xiàng)無，選D。注意這個選項(xiàng)完全沒提Theword“adjacent”inthepassageisclosestinmeaningParagraph5:…Afifteen-speedracingbicycleismorelikelytobreakdownthanchild’sParagraph6:█Ecologistsareespeciallyinterestedtoknowwhatfactorscontributetotheresilienceofcommunitiesbecauseclimaxcommunitiesallovertheworldarebeingseverelydamagedordestroyedbyhumanactivities.█ThedestructioncausedbythevolcanicexplosionofMountSt.Helens,inthenorthwesternUnitedStates,forexample,palesincomparisontothedestructioncausedbyhumans.█Weneedtoknowwhataspectsofacommunityaremostimportanttothecommunity’s todestruction,aswellasitsrecovery.█Lookatthefoursquares[█]thatindicatewherethefollowingsentencecouldbeaddedtothepassage.Infact,damagetotheenvironmentbyhumansisoftenmuchmoreseverethandamagebynaturaleventsandprocesses.Wherewouldthesentencebestfit?ClickonasquaretoaddthesentencetotheB。Directions:Anintroductorysentenceforabriefsummaryofthepassageisprovidedbelow.CompletethesummarybyselectingtheTHREEanswerchoicesthatexpressthemostimportantideasinthepassage.Somesentencesdonotbelonginthesummarybecausetheyexpreeasthatarenotpresentedinthepassageorareminorideasinthepassage.Thisquestionisworth2points.Theprocessofsuccessionandthestabilityofaclimaxcommunitychangeover●●●AnswerThechangesthatoccurinanecosystemfromthepioneertotheclimaxcommunitycanbeseeninonehumangeneration.Ahighdegreeofspeciesdiversitydoesnotalwaysresul