您好,欢迎访问三七文档
当前位置:首页 > 电子/通信 > 综合/其它 > 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。
本文标题:托福TPO44阅读题目及答案
链接地址:https://www.777doc.com/doc-6197139 .html