托福TPO44阅读题目及答案

1、阅读⼀1-5BDACC6-10DAADB11-13CAA14AEFFromFishtoTerrestrialVertebratesOneofthemostsignificantevolutionaryeventsthatoccurredonEarthwasthetransitionofwater-dwellingfishtoterrestrialtetrapods(four-limbedorganismswithbackbones).Fishprobablyoriginatedintheoceans,andourfirstrecordsofthemareinmarinerocks.However,bytheDevonianPeriod(408millionto362millionyearsago),theyhadradiatedintoalmostallavailableaquatichabitats,includingfreshwatersettings.Oneofthegroupswhosefossilsareespeciallycommoninrocksdepositedinf。

2、reshwateristhelobe-finnedfish.ThefreshwaterDevonianlobe-finnedfishrhipidistiancrossopterygianisofparticularinteresttobiologistsstudyingtetrapodevolution.Thesefishlivedinriverchannelsandlakesonlargedeltas.Thedeltarocksinwhichthesefossilsarefoundarecommonlyredduetooxidizedironminerals,indicatingthatthedeltasformedinaclimatethathadalternatewetanddryperiods.Iftherewereperiodsofdrought,anyadaptationsallowingthefishtosurvivethedryconditionswouldhavebeenadvantageous.Intheserhipidistians,severalsuchadap。

3、tationsexisted.Itisknownthattheyhadlungsaswellasgillsforbreathing.Crosssectionscutthroughsomeofthefossilsrevealthatthemudfilingtheinteriorofthecarcassdifferedinconsistencyandtexturedependingonitslocationinsidethefish.Thesedifferencessuggestasaclikecavitybelowthefrontendofthegutthatcanonlybeinterpretedasalung.Gillswereundoubtedlythemainsourceofoxygenforthesefish,butthelungsservedasanauxiliarybreathingdeviceforgulpingairwhenthewaterbecameoxygendepleted,suchasduringextendedperiodsofdrought.So,these。

4、fishhadalreadyevolvedoneoftheprimerequisitesforlivingonland,theabilitytouseairasasourceofoxygen.Asecondadaptationofthesefishwasinthestructureofthelobefins.Thefinswerethick,fleshy,andquitesturdy,withamedianaxisofbonedownthecenter.Theycouldhavebeenusedasfeeblelocomotordevicesonland,perhapsgoodenoughtoallowafishtoflopitswayfromonepoolofwaterthatwasalmostdrytoanadjacentpondthathadenoughwaterandoxygenforsurvival.Thesefinseventuallychangedintoshort,stubbylegs.ThebonesofthefinsofaDevonianrhipidistianex。

5、actlymatchinnumberandpositionthelimbbonesoftheearliestknowntetrapods,theamphibians.Itshouldbeemphasizedthattheevolutionoflungsandlimbswasinnosenseananticipationoffuturelifeonland.Theseadaptationsdevelopedbecausetheyhelpedfishtosurviveintheirexistingaquaticenvironment.Whatecologicalpressuresmighthavecausedfishestograduallyabandontheirwateryhabitatandbecomeincreasinglyland-dwellingcreatures?ChangesinclimateduringtheDevonianmayhavehadsomethingtodowiththisiffreshwaterareasbecameprogressivelymorerest。

6、ricted.Anotherimpetusmayhavebeennewsourcesoffood.Theedgesofpondsandstreamssurelyhadscattereddeadfishandotherwater-dwellingcreatures.Inaddition,plantshademergedintoterrestrialhabitatsinareasnearstreamsandponds,andcrabsandotherarthropodswerealsomembersofthisearliestterrestrialcommunity.Thus,bytheDevonianthelandhabitatmarginaltofreshwaterwasprobablyarichsourceofproteinthatcouldbeexploitedbyananimalthatcouldeasilyclimboutofwater.Evidencefromteethsuggeststhattheseearliesttetrapodsdidnotutilizelandpla。

7、ntsasfood;theywerepresumablycarnivorousandhadnotdevelopedtheabilitytofeedonplants.Howdidthefirsttetrapodsmakethetransitiontoaterrestrialhabitat?Likeearlylandplantssuchasrhyniophytes,theymadeonlyapartialtransition,theywerestillquitetiedtowater.However,manyproblemsthatfacedearlylandplantswerenotapplicabletothefirsttetrapods.Theancestorsoftheseanimalsalreadyhadacirculationsystem,andtheyweremobile,sothattheycouldmovetowatertodrink.Furthermore,theyalreadyhadlungs,whichrhipidistianspresumablyusedforau。

8、xiliarybreathing.Theprincipalchangesfortheearliesttetrapodswereintheskeletalsystem-changesinthebonesofthefins,thevertebralcolumn,pelvicgirdle,andpectoralgirdle.Paragraph1OneofthemostsignificantevolutionaryeventsthatoccurredonEarthwasthetransitionofwater-dwellingfishtoterrestrialtetrapods(four-limbedorganismswithbackbones)Fishprobablyoriginatedintheoceans,andourfirstrecordsofthemareinmarinerocks.However,bytheDevonianPeriod(408millionto362millionyearsago),theyhadradiatedintoalmostallavailableaquat。

9、ichabitats,includingfreshwatersettingsOneofthegroupswhosefossilsareespeciallycommoninrocksdepositedinfreshwateristhelobe-finnedfish.1.Paragraph1supportswhichofthefollowingstatementsaboutfishevolution?A.Lobe-finnedfishwereamongtheearliesttypesoffishtoappear.B.Fishbeganlivinginfreshwaterhabitatsonlyafteroriginatingelsewhere.C.Lobe-finnedfishradiatedintoalmostallavailableaquatichabitats.D.DuringtheDevonian,lobe-finnedfishweremorecommoninmarinethaninfreshwaterhabitats.Paragraph2ThefreshwaterDevonian。

10、lobe-finnedfishrhipidistiancrossopterygianIsofparticularinteresttobiologistsstudyingtetrapodevolution.Thesefishlivedinriverchannelsandlakesonlargedeltas.Thedeltarocksinwhichthesefossilsarefoundarecommonlyredduetooxidizedironminerals,indicatingthatthedeltasformedinaclimatethathadalternatewetanddryperiods.Iftherewereperiodsofdrought,anyadaptationsallowingthefishtosurvivethedryconditionswouldhavebeenadvantageous.Intheserhipidistians,severalsuchadaptationsexisted.Itisknownthattheyhadlungsaswellasgill。