托福閱讀真題第246篇AquaticDesertAnimals（答案文章最后）

托福閱讀真題第246篇AquaticDesertAnimals（答案文章最后）AquaticDesertAnimalsParagraph1：Itmayseemsurprising,butdesertanimalshavemadefewspecificbodilyadaptationstothedesertenvironment.Rather,theymanagetosurvivethroughpropertimingoftheirbiologicalactivities,andthisisbestillustratedbysemiaquaticandaquaticdesertanimals.

Paragraph2：Theaquaticnatureofamphibiansmakesthemseemunlikelydesertresidents.Reproductionrequiresopenwater,wherethefemaleandmaledeposittheeggsandsperm,respectively,andfertilizationoccurs.Developmentofthefertilizedeggsoccursinwater,andthegilledandleglessjuvenilesmustswimandfeedinwater.Itisonlytheadultthatcansurviveonland,butthepoorlydevelopedlungsandwater-permeableskinrestrictthemtomoisterhabitats.Amphibiansbeattheodds,notwithextremelyadaptivestructuresororganicprocessesbutwithalifehistoryinwhichtheiractivityandreproductionoccurduringbriefperiodsoffavorableconditions.AndnoamphibianbetterillustratesthisabilitythanthespadefoottoadofthesouthernUnitedStatesdeserts.

1.Whichofthesentencesbelowbestexpressestheessentialinformationinthehighlightedsentenceinthepassage?Incorrectchoiceschangethemeaninginimportantwaysorleaveoutessentialinformation.

A.Amphibianshavenotbeenabletodevelopthestructuresorprocessesneededtosurviveinthedesert.

B.Desertamphibianssurvivenotthroughphysicaladaptationsororganicprocessesbutbybeingactiveandreproducingduringfavorableconditions.C.Thelifehistoryofdesertamphibiansbeginswithreproductionfollowedbyshortperiodsofactivity.

D.Desertamphibiansrequirefavorableconditionsinordertodevelopthekindsofphysicaladaptationsneededtosurviveinthedesert.

Paragraph3：Duringthedrierwinterseasontheadultspadefootremainsdormantunderground,sometimesnearlyameterdeep.Nestedbelowthesurface,wherethetoadisprotectedfromdesiccatingairandtemperatureextremes,thespadefootisenvelopedbyun-shedskinthatformsacocoonofsorts.Waterstoredintissueandinthebladderisslowlylost,butthespadefootisabletolosesome50percentofitswaterandsurvive.Andsothetoadwaits,sometimesformorethantwoyears,untilheavyrainscomewithenoughmoisturetocreatetemporarypoolsinwhichitcanreproduce.

2.Accordingtoparagraph3,thespadefoottoadisabletosurvivethedrierwinterseasonforallofthefollowingseasonsEXCEPT:

A.Itremainsinactivedeepundergroundduringthewintermonths.

B.Itisprotectedfromharshconditionsbyalayerofun-shedskinthatsurroundsitsbody.

C.Itisabletosurvivelosinghalfofthewaterfromitsbody.

D.Itwarmsitselfduringperiodsoflessextremetemperatures.Paragraph4：Waterwillawakenspadefoottoads,butinsomecasessimplythethumpingofraindropsonthesurfaceisenoughtoarousethemfromtheirtorpor.Hasteningtoshallow,temporarypools,thespadefootsmate.Thefemaleslayseveralthousandeggsthatarelessthan2millimetersindiameter.Thefertilizedeggsdevelopquickly,andinwarmwaterthetadpolescanemergefromtheireggsshellsinlessthantwodays.Tadpoledevelopmentrequiresjustonetothreeweeks,andifpoolevaporationisoutpacingdevelopment,metamorphosis(theseriesofphysicalchangesoccurringafterhatchingorbirth)isaccelerated,resultinginsmallerspadefoots.Theomnivoroustadpolescanresorttocannibalism,thelargereatingthesmaller,andpredationbyotherspeciesisalsocommon.Mortalityishigh,andnotinfrequentlythepooldriesbeforeeventhelargesttadpoleshavefullymetamorphosedintoadults.Spadefoottadpolecanhelpprolongthelifeoftheiraquatichabitat,however.Beforefullmetamorphosistheycollectintosquirmingswarmsthatagitatethewaterandstirthemud,therebycreatingadeeperdepressionthatretainsthewater.Aftertheyarefullymetamorphosedandleavetheiraquaticnursery,adultspadefoottoadsfeedontheinsectsflourishinginthemoistpost-rainenvironmentbeforereturningundergroundtowaitoutthenextdrought.

3.Whydospadefoottadpoles“agitatethewaterandstirthemud”oftheiraquatichabitat?

A.Tohelpreducepredationbyotherspecies

B.Tospeedupmetamorphosis

C.Toescapefromtheiraquaticnurseryoncetheyhavefullymetamorphosed

D.Todeepentheirpoolofwatersoitdriesuplessquickly4.Paragraph4suggeststhatwhichofthefollowingaffectsthetimingofwhenspadefoottadpolesemergefromtheirshells?

A.Thenumberofspadefooteggsinthewater

B.Thenumberofeggslaidbythefemale

C.ThetemperatureofthesurroundingwaterD.Therateoftheirmetamorphosis

5.Accordingtoparagraph4,themetamorphosisofspadefoottadpolesisacceleratedif

A.thefertilizedeggshatchtoosoon

B.wateriswarmerandmoreplentifulthanaverage

C.waterisevaporatingmorequicklythandevelopmentisoccurringD.thetadpolesaretoosmalltoavoidpredation

6.Paragraph4mentionsallofthefollowingasreasonsforthehighmortalityrateamongspadefoottoadtadpolesEXCEPT

A.predationbyadultspadefootsB.cannibalismofsmalltadpolesbylargertadpoles

C.predationbyotherspecies

D.evaporationofpoolsbeforethetadpoleshavefullydevelopedintoadults

Paragraph5：Evenmoresurprisingaretheaquaticanimalsthatfindawaytosurviveinthedesert.Temporarybodiesofwater,includingflat-bottomedbasinsknownasplayas,canhoststrictlyaquaticspecies,themostprominentofwhicharecrustaceanssuchasfairyshrimp.

7.Indescribingsomespeciesas“strictly”aquatic,theauthormeansthatthesespecies

A.existinaquaticenvironmentsonlyB.requirespecifickindsofaquaticenvironments

C.spendpartbutnotalloftheirlivesinwater

D.normallyrequireaquaticenvironments

Paragraph6：Thefairyshrimpsurviveascysts,actuallyshelledembryos,inthedryplayasoftheMojaveDesert.Heretheymayresideforyears,possiblyevenseveraldecades,dehydrated,inactive,andinconspicuous.Undertherightconditions,rainwillbringthefairyshrimpoutofdormancy.Cooler,near-freezingtemperaturespromotehatching,forintheMojaveDesertheavyrainsandmorereliableplayafloodingoccurinwinter.Timelyhatchingisalsopromotedbydilute,non-salinewaterthatcomeswithinitialplayaflooding.Withtimetheplaya’ssaltspermeatethewater,andfurthercysthatchingisinhibitedasthelakedries.However,additionalrainsmaydilutethesalts,andhatchingisrenewedwiththepromisethatthelake'slifewillbeprolonged.

8.Accordingtoparagraph6,whymightfairyshrimpcystsintheMojaveDeserttendtohatchwhentemperaturesarenearfreezing?

A.Desertraincontainsthemostsaltsduringthewinter.

B.Theheaviestrainsinthatareagenerallyoccurduringthecoldesttimeoftheyear.C.Coldweatherpreventstheplaya’ssaltsfromenteringthewater.

D.Damagingplayafloodsarelesslikelytooccurwhentemperaturesarelow.

Paragraph7：Thecystshatchpromptlybutoftenfacealess-than-idealenvironment.Nevertheless,completedevelopmentmaytakeaslittleastendays.Withtime,moreandmorepredatorsarrive,includingwingedinsectsthatarrivefromafar.Thefairyshrimpsthatsurvivereadilyreproduce,andtheresultingcystssettletothebottomandarelefttosurvivethenextdrought.Thus,aslongaswaterpersiststhreeweeksorso,thefairyshrimphastimetocompleteitslifecycle.

9.Whatcanbeinferredfromparagraphs6and7aboutfairyshrimpsoftheMojaveDesert?

A.Theyspendonlyasmallpartoftheirlivesasadults.B.Cystshatchduringseveralseasonsoftheyear.

C.Cyststhattakemorethantendaystodeveloparemorelikelytosurvive.

D.Adultsusuallyreproducemultipletimesduringtheirlives.

10.Directions:Anintroductorysentenceforabriefsummaryofthepassageisprovidedbelow.CompletethesummarybyselectedTHREEanswerchoicesthatexpressthemostimportantideasinthepassage.Somesentencesdonotbelonginthesummaryexpressideasthatarenotpresentedinthepassageorareminorideasinthepassage.Thisquestionisworth2points.

Thepresenceofanimalsthataredependentonwaterinthedesertenvironmentmayseemsurprisingbutitdoesoccur.

AnswerChoices:

A.Semiaquaticandaquaticspeciessurviveinthedesertbyco