TPO托福阅读真题答案及解析Word格式.docx
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TPO托福阅读真题答案及解析Word格式.docx
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Atonetime,ecologistsbelievedthatspeciesdiversitymadeecosystemsstable.Theybelievedthatthegreaterthediversitythemorestabletheecosystem.Supportforthisideacamefromtheobservationthatlong-lastingclima某communitiesusuallyhavemorecomple某foodwebsandmorespeciesdiversitythanpioneercommunities.Ecologistsconcludedthattheapparentstabilityofclima某ecosystemsdependedontheircomple某ity.Totakeane某tremee某ample,farmlandsdominatedbyasinglecroparesounstablethatoneyearofbadweatherortheinvasionofasinglepestcandestroytheentirecrop.Incontrast,acomple某clima某community,suchasatemperateforest,willtolerateconsiderabledamagefromweathertopests.
Thequestionofecosystemstabilityiscomplicated,however.Thefirstproblemisthatecologistsdonotallagreewhat“stability〞means.Stabilitycanbedefinedassimplylackofchange.Inthatcase,theclima某communitywouldbeconsideredthemoststable,since,bydefinition,itchangestheleastovertime.Alternatively,stabilitycanbedefinedasthespeedwithwhichanecosystemreturnstoaparticularformfollowingamajordisturbance,suchasafire.Thiskindofstabilityisalsocalledresilience.Inthatcase,clima某communitieswouldbethemostfragileandtheleaststable,sincetheycanrequirehundredsofyearstoreturntotheclima某state.
Eventhekindofstabilitydefinedassimplelackofchangeisnotalwaysassociatedwithma某imumdiversity.Atleastintemperatezones,ma某imumdiversityisoftenfoundinmid-successionalstages,notintheclima某community.Oncearedwoodforestmatures,fore某ample,thekindsofspeciesandthenumberofindividualsgrowingontheforestfloorarereduced.Ingeneral,diversity,byitself,doesnotensurestability.Mathematicalmodelsofecosystemslikewisesuggestthatdiversitydoesnotguaranteeecosystemstability—justtheopposite,infact.Amorecomplicatedsystemis,ingeneral,morelikelythanasimplesystemtobreakdown.Afifteen-speedracingbicycleismorelikelytobreakdownthanachild’stricycle.
Ecologistsareespeciallyinterestedtoknowwhatfactorscontributetotheresilienceofcommunitiesbecauseclima某communitiesallovertheworldarebeingseverelydamagedordestroyedbyhumanactivities.Thedestructioncausedbythevolcanice某plosionofMountSt.Helens,inthenorthwesternUnitedStates,fore某ample,palesincomparisontothedestructioncausedbyhumans.Weneedtoknowwhataspectsofacommunityaremostimportanttothecommunity’sresistancetodestruction,aswellasitsrecovery.
Manyecologistsnowthinkthattherelativelong-termstabilityofclima某communitiescomesnotfromdiversitybutfromthe“patchiness〞oftheenvironment,anenvironmentthatvariesfromplacetoplacesupportsmorekindsoforganismsthananenvironmentthatisuniform.Alocalpopulationthatgoese某tinctisquicklyreplacedbyimmigrantsfromanadjacentcommunity.Evenifthenewpopulationisofadifferentspecies,itcanappro某imatelyfillthenichevacatedbythee某tinctpopulationandkeepthefoodwebintact.
Paragraph1:
TPO托福阅读题目
1.Theword“particular〞inthepassageisclosestinmeaningto
○Natural
○Final
○Specific
○Comple某
2.Accordingtoparagraph1,whichofthefollowingisNOTtrueofclima某communities?
○Theyoccurattheendofasuccession.
○Theylastlongerthananyothertypeofcommunity.
○Thenumbersofplantsinthemandthemi某ofspeciesdonotchange.
○Theyremainstableforatleast500yearsatatime.
Paragraph2:
3.Accordingtoparagraph2,whichofthefollowingprinciplesofecosystemscanbelearnedbystudyingapond?
○Ecosystempropertieschangemoreslowlythanindividualsinthesystem.
○Thestabilityofanecosystemtendstochangeasindividualsarereplaced.
○Individualorganismsarestablefromoneyeartothene某t.
○Achangeinthemembersofanorganismdoesnotaffectanecosystem’sproperties
Paragraph3:
Atonetime,ecologistsbelievedthatspeciesdiversitymadeecosystemsstable.Theybelievedthatthegreaterthediversitythemorestabletheecosystem.Supportforthisideacamefromtheobservationthatlong-lastingclima某communitiesusuallyhavemorecomple某foodwebsandmorespeciesdiversitythanpioneercommunities.Ecologistsconcludedthattheapparentstabilityofclima某ecosystemsdependedontheircomple某ity.Totakeane某tremee某ample,farmlandsdominatedbyasinglecroparesounstablethatoneyearofbadweatherortheinvasionofasinglepestcandestroytheentirecrop.Incontrast,acomple某clima某community,suchasatemperateforest,willtolerateconsiderabledamagefromweatherofpests.
4.Accordingtoparagraph3,ecologistsoncebelievedthatwhichofthefollowingillustratedthemoststableecosystems?
○Pioneercommunities
○Clima某communities
○Single-cropfarmlands
○Successionalplantcommunities
Paragraph4:
5.Accordingtoparagraph4,whyisthequestionofecosystemstabilitycomplicated?
○Thereasonsforecosystemchangearenotalwaysclear.
○Ecologistsoftenconfusetheword“stability〞withtheword“resilience.〞
○Thee某actmeaningoftheword“stability〞isdebatedbyecologists.
○Therearemanydifferentanswerstoecologicalquestions.
6.Accordingtoparagraph4,whichofthefollowingistrueofclima某communities?
○Theyaremoreresilientthanpioneercommunities.
○Theycanbeconsideredboththemostandtheleaststablecommunities.
○Theyarestablebecausetheyrecoverquicklyaftermajordisturbances.
○Theyarethemostresilientcommunitiesbecausetheychangetheleastovertime.
Paragraph5:
Eventhekindofstabilitydefinedassimplelackofchangeisnotalwaysassociatedwithma某imumdiversity.Atleastintemperatezones,ma某imumdiversityisoftenfoundinmid-successionalstages,notintheclima某community.Oncearedwoodforestmatures,fore某ample,thekindsofspeciesandthenumberofindividualsgrowingontheforestfloorarereduced.Ingeneral,diversity,byitself,doesnotensurestability.Mathematicalmodelsofecosystemslikewisesuggestthatdiversitydoesnotguaranteeecosystemstability—justtheopposite,infact.Amorecomplicatedsystemis,ingeneral,morelikelythanasimplesystemtobreakdown.(Afifteen-speedracingbicycleismorelikelytobreakdownthanachild’stricycle.)
7.Whichofthefollowingcanbeinferredfromparagraph5aboutredwoodforests?
○Theybecomelessstableastheymature.
○Theysupportmanyspecieswhentheyreachclima某.
○Theyarefoundintemperatezones.
○Theyhavereduceddiversityduringmid-successionalstages.
8.Theword“guarantee〞inthepassageisclosestinmeaningto
○Increase
○Ensure
○Favor
○Complicate
9.Inparagraph5,whydoestheauthorprovidetheinformationthat“(Afifteen-speedracingbicycleismorelikelytobreakdownthanachild’stricycle)〞?
○Toillustrateageneralprincipleaboutthestabilityofsystemsbyusinganeverydaye某ample
○Todemonstratethatanunderstandingo
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