托福预测是很多同学在考前必看的，这样既可以看看自己的水平怎么样，而且，说不定真的可以帮上忙，那么下面就和出国留学网来看看2020年2月16日托福阅读考试预测。

ModelsofEggDevelopment

Severaldifferenttheorieshavebeenputforwardtoexplainhowthehard-shelledeggsofland-dwellingreptiles（e.g.lizards）evolvedfromthesofteggsthatamphibians（e.g.frogsandtoads）layinwater.TheRomermodelofeggdevelopmentisnamedafterthelateAlfredRomer，apaleontologistwhoalsobecamedirectoroftheHarvardUniversityMuseumofComparativeZoology.Hisspecialtywasearlyreptilesbecause，hefelt，theywerethekeytounderstandingthegreatreptilediversificationseenintheLatePaleozoicandMesozoicEras（around230millionyearsago）.Romer＇shypothesiswasthatsomeaquaticamphibiansthatis，amphibianslivinginwatercalledanthracosaursbegantolaytheireggsonlandataboutthetimethattheywereevolvingreptile-likeskeletalfeatures.Indeed，someoftheseearlyamphibiansandearliestreptilesaresosimilarintheirskeletonsthattheexacttransitionpointfromonetotheotherisstilldifficulttodetermine.Eventually，though，thetransitionwasmade，buttheseearlyreptilesremainedaquatic.Theadvantageforlayingeggsonlandwasprimarilytoavoidtheaquaticlarval（pre-adult）stageduringwhichimmatureamphibiansliveexclusivelyinwaterwithitsinherentriskofpredatorsanddryingofponds.However，thelandhasitsownsetofdangers，notleastofwhichisthedryingeffectoftheatmosphere.Tocopewiththeseproblems，aseriesofprotectivemembranesdevelopedaroundtheegg，includingahardshell.Onlylaterdidthereptilescompletelyabandonanaquaticlifestyle.

AnotherhypothesiswasproposedbyGermanpaleontologistRolfKohring，whosespecialtyisfossileggs.

InKohring＇smodel，amphibiansduringtheMississippianepoch（360-320millionyearsago）spreadintonutrient-poororcoolerwater.Becauseoftheharsherconditions，eggswereproducedwithlargeryolks，thatis，morenutrientsfortheembryo.Withlargeryolks，theeggswerebigger，andfewerofthemcouldbeproducedbythefemalehundredsratherthanthousands.■Tokeepthelargereggintact，oneormoremembranesweredeveloped，includingonethatsurroundedandprotectedtheegg.■Thisoutermembraneprovidedaplacetosafelystorecalciumions，whicharepoisonous.■Accumulatingthecalciuminahardshellthenmadeitpossiblefortheeggtobelaidonland（itwaspre-adaptedtobelaidthere.）■

Oneothermodelweshouldconsideristheanti-predatorhypothesisproposedbyGaryandMaryPackardtoexplaintheevolutionofthehard-shelledegg.Theirmodelwasnotconcernedwiththedevelopmentofmembranessurroundingtheeggbutcontinuesthestoryafterthesemembranesappeared.ThePackardsassumethattheearliestreptileslaidleatheryshelledeggsonverywetgroundwheretheycouldabsorbwaterduringtheembryos＇growth.Butlifeonthegroundisnotwithouthazards，basedonstudiesofmodernreptileswithleatheryshelledeggs.Predatoryinsectsandmicrobescanbeamajorcauseofeggmortality.Tocounterthislossofeggs，someoftheearlyreptilesbegansecretingathincalcareous（containingcalciumcarbonate）layer.Thishardlayergavetheembryosabetterchanceofsurvivinguntilhatching.Andthesesurvivorsinturnwouldprobablyleavemoreprogenyonceafewofthemreachedreproductiveage.Intime，athicker，moreresistantshelldeveloped.However，athickereggshellmeantthatlesswatercouldbeabsorbedfortheneedsoftheembryo.Tocompensate，largereggswereproduced，containingagreatdealmorealbumen（eggwhite，awater-solubleprotein）.Atthispoint，therigideggshellhadreachedthebirdegglevelofcomplexity.

MaryPackardpresentedyetanothermodelwithhercolleagueRogerSeymour.Theynotethatamphibianeggscannevergetverylargebecausethegelatincoatsurroundingthedevelopinglarvaisnotverygoodattransmittingoxygen.Becauseofthisrestriction，wewillneverseefrogeggsthesizeofachicken＇s.ForPackardandSeymour，themajorevolutionarybreakthroughinreptileeggswastheeliminationofthethickgelatincoatandreplacingpartofitwithafibrousmembrane.Thischangeallowedlargereggstobedeveloped.

1.Whichofthesentencesbelowbestexpressestheessentialinformationinthehighlightedsentenceinthepassage.Incorrectchoiceschangethemeaninginimportantwaysorleaveoutessentialinformation.

A.Duringtheperiodthatearlyamphibianschangedintoreptiles，theirskeletonswereexactlythesame.

B.Itisdifficulttoidentifythetimethatearlyamphibianschangedtoreptilesbecausetheirskeletonslooksomuchalike.

C.Theskeletonsofsomeearlyamphibiansandreptilesaresosimilarthatitisdifficulttosaywhichareamphibiansandwhicharereptiles.

D.Earlyamphibiansandreptileshadthesamekindofskeletonatthesamepointintime.

2.Theword“exclusively”inthepassageisclosestinmeaningto

A.only

B.initially

C.primarily

D.temporarily

3.Accordingtoparagraph1，aquaticamphibianslaidtheireggsonlandinorderto

A.enableyoungamphibianstobenefitfromadryatmosphere

B.ensuretherapiddevelopmentofahardshell

C.enableyoungamphibianstoevolvefeaturesnecessaryforlivingonland

D.protectyoungamphibiansfromthedangersassociatedwithlifeinthewater

4.Theword“Accumulating”inthepassageisclosestinmeaningto

A.Forcing

B.Collecting

C.Distributing

D.Isolating

5.Inparagraph2，whydoestheauthormentiontheinformationaboutcalciumions

A.ToexplainKoherig＇stheorythatamphibianeggsdevelopedatleasttwoprotectiveoutermembranes

B.Toexplainthatthecalciuminahardshellisnotpoisonouswhentheeggislaidonland

C.Toexplainwhy，accordingtoKohring，ahardshellevolved

D.Toexplainwhyonlytheoutermembranestoredcalcium

6.Whichofthefollowingcanbeinferredfromparagraph2abouttherelationshipbetweeneggsandwater

temperature

A.Eggsneededadaptationstosurviveincoldwater.

B.Eggsneededwarmwatertosurvive.

C.Smallereggswereproducedincoldwater.

D.Fewereggswereproducedinwarmwater.

7.Accordingtoparagraph2，allofthefollowingaretrueoftheeggsofamphibiansduringtheMississippianepochEXCEPT：

A.Theyhadhardshellsmadefromcalciumions.

B.Theyhadlargeryolksthanpreviously.

C.Theyhadprotectivemembranes.

D.Theywereproducedinlargerquantitiesthanpreviously.

8.Theword“counter”inthepassageisclosestinmeaningto

A.escape

B.stop

C.combat

D.delay

9.Accordingtoparagraph3，earlyreptilesbegantodevelopathincalcareouslayeraroundtheeggsothat

A.theembryocouldsurviveattacksfrompredatoryinsectsandmicrobes

B.theembryocouldabsorbsufficientwaterduringitsgrowth

C.thesurvivingembryocouldreachreproductiveage

D.theeggcouldbelaidonland

10.Whichofthefollowingismentionedinparagraph3asadisadvantageofthehardeggshell

A.Itincreasedthehatchingperiod.

B.Itpreventedthedevelopmentoflarge-sizeeggs.

C.Itmadeitmoredifficultfortheembryotoobtainwater.

D.Itmadeitharderfortheembryotosurviveuntilhatching.

11.Theword“breakthrough”inthepassageisclosestinmeaningto

A.effect

B.development

C.requirement

D.goal

12.Whichofthefollowingcanbeinferredfromparagraph4aboutthefibrousmembrane

A.Itservedthesamefunctionasthegelatincoat.

B.Itwaslargerthanthegelatincoat.

C.Itallowedamphibianstoproduceeggsaslargeasthoseofreptiles.

D.Itallowedforbettertransmissionofoxygen.

13.Lookatthefoursquaresthatindicatewherethefollowingsentencecouldbeaddedtothepassage.

Andtherelativelyfewthatwereproducedhadtobeproperlyprotected.

Wherewouldthesentencebestfit？Clickonasquaretoaddthesentencetothepassage.

14.Directions：Anintroductorysentenceforabriefsummaryofthepassageisprovidedbelow.CompletethesummarybyselectingtheTHREEanswerchoicesthatexpressthemostimportantideasinthepassage.Someanswerchoicesdonotbelonginthesummarybecausetheyexpressideasthatarenotpresentedinthepassageorareminorideasinthepassage.Thisquestionisworth2points.

AnswerChoices

A.AlfredRomer＇shypothesiswasthatearlyamphibiansstartedevolvingreptilianskeletalfeatureslongbeforetheystartedlayingeggsonland.

B.AlfredRomertheorizedthatearlyreptilesdevelopedprotectivemembranesaroundtheegginresponsetothedangerstoyoungamphibiansinwaterandthreatstotheeggonland.

C.InRolfKohring＇sview，earlyreptilesdevelopedprotectivemembranesaroundthelargeeggsthatwereproducedinharshwaterconditions，makingitpossiblefortheeggtobelaidonland.

D.GaryandMaryPackardclaimedthatreptilesdevelopedthehard-shelledegginordertoreducetherateatwhicheggsweredestroyedbypredatoryinsectsandmicrobes.

E.RolfKohringarguedthateggdevelopmentwaspoorduringtheMississippianepochduetonutrient-poorwaters.

F.AccordingtoMaryPackardandRogerSeymour，reptilescouldnotsuccessivelydevelopverylargeeggsbecauseoftheeliminationofthegelatincoat.

参考答案

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