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1、智课网TOEFL备考资料托福阅读英文加翻译OG【Word文本】摘要：托福TPO和OG都是我们在备考托福阅读过程中一定会用到的精华资料，今天我们就将TPO全套和OG全套资料的阅读部分单独摘录出来为大家做详细的介绍，其中只包含译文和英文部分，托福TPO和OG阅读文章中考到的核心词汇是我们托福阅读考试必备的精华资料，随意大家在备考的同时也要注意词汇方面的积累。托福阅读英文加翻译OG：THEORIGINSOFCETACEANS(OG)Itshouldbeobviousthatcetaceans-whales,porpoises,
2、anddolphins-aremammals.Theybreathethroughlungs,notthroughgills,andgivebirthtoliveyoung.Theirstreamlinedbodies,theabsenceofhindlegs,andthepresenceofafluke1andblowhole2cannotdisguisetheiraffinitieswithlanddwellingmammals.However,unlikethecasesofseaottersandpinniped
3、s(seals,sealions,andwalruses,whoselimbsarefunctionalbothonlandandatsea),itisnoteasytoenvisionwhatthefirstwhaleslookedlike.Extinctbutalreadyfullymarinecetaceansareknownfromthefossilrecord.Howwasthegapbetweenawalkingmammalandaswimmingwhalebridged?Missinguntilrecent
4、lywerefossilsclearlyintermediate,ortransitional,betweenlandmammalsandcetaceans.Veryexcitingdiscoverieshavefinallyallowedscientiststoreconstructthemostlikelyoriginsofcetaceans.In1979,ateamlookingforfossilsinnorthernPakistanfoundwhatprovedtobetheoldestfossilwhale.T
5、hefossilwasofficiallynamedPakicetusinhonorofthecountrywherethediscoverywasmade.Pakicetuswasfoundembeddedinrocksformedfromriverdepositsthatwere52millionyearsold.TheriverthatformedthesedepositswasactuallynotfarfromanancientoceanknownastheTethysSea.Thefossilconsists
6、ofacompleteskullofanarchaeocyte,anextinctgroupofancestorsofmoderncetaceans.Althoughlimitedtoaskull,thePakicetusfossilprovidespreciousdetailsontheoriginsofcetaceans.Theskulliscetacean-likebutitsjawboneslacktheenlargedspacethatisfilledwithfatoroilandusedforreceivin
7、gunderwatersoundinmodernwhales.Pakicetusprobablydetectedsoundthroughtheearopeningasinlandmammals.Theskullalsolacksablowhole,anothercetaceanadaptationfordiving.Otherfeatures,however,showexpertsthatPakicetusisatransitionalformbetweenagroupofextinctflesh-eatingmamma
8、ls,themesonychids,andcetaceans.IthasbeensuggestedthatPakicetusfedonfishinshallowwaterandwasnotyetadaptedforlifeintheopenocean.Itprobablybredandgavebirthonland.
