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1、智课网TOEFL备考资料托福阅读练习：SWIMMINGMACHINES(翻译)摘要：托福阅读考试中会碰到一些练习，例如本文为大家介绍的托福阅读练习：SWIMMINGMACHINES(翻译)。小编为大家搜集整理了托福阅读练习：SWIMMINGMACHINES(翻译)，希望给大家的考试带来帮助。下面我们一起来看看吧!托福阅读练习：SWIMMINGMACHINES(英文)Tunas,mackerels,andbillfishes(marlins,sailfishes,andswordfish)swimcontinuously.Feeding,courtship,reproduction,an
2、deven"rest"arecarriedoutwhileinconstantmotion.Asaresult,practicallyeveryaspectofthebodyformandfunctionoftheseswimming"machines"isadaptedtoenhancetheirabilitytoswim.Manyoftheadaptationsofthesefishesservetoreducewaterresistance(drag).Interestinglyenough,severalofthesehydrodynamicadaptationsresembl
3、efeaturesdesignedtoimprovetheaerodynamicsofhigh-speedaircraft.Thoughhumanengineersarenewtothegame,tunasandtheirrelativesevolvedtheir"high-tech"designslongago.Tunas,mackerels,andbillfisheshavemadestreamliningintoanartform.Theirbodiesaresleekandcompact.Thebodyshapesoftunas,infact,arenearlyidealfro
4、manengineeringpointofview.Mostspecieslackscalesovermostofthebody,makingitsmoothandslippery.Theeyeslieflushwiththebodyanddonotprotrudeatall.Theyarealsocoveredwithaslick,transparentlidthatreducesdrag.Thefinsarestiff,smooth,andnarrow,qualitiesthatalsohelpcutdrag.Whennotinuse,thefinsaretuckedintospe
5、cialgroovesordepressionssothattheylieflushwiththebodyanddonotbreakupitssmoothcontours.Airplanesretracttheirlandinggearwhileinflightforthesamereason.Tunas,mackerels,andbillfisheshaveevenmoresophisticatedadaptationsthanthesetoimprovetheirhydrodynamics.Thelongbillofmarlins,sailfishes,andswordfishpr
6、obablyhelpsthemslipthroughthewater.Manysupersonicaircrafthaveasimilarneedleatthenose.Mosttunasandbillfisheshaveaseriesofkeelsandfinletsnearthetail.Althoughmostoftheirscaleshavebeenlost,tunasandmackerelsretainapatchofcoarsescalesneartheheadcalledthecorselet.Thekeels,finlets,andcorselethelpdirectt
7、heflowofwateroverthebodysurfaceinsuchaswayastoreduceresistance(seethefigure).Again,supersonicjetshavesimilarfeatures.Becausetheyarealwaysswimming,tunassimplyhavetoopentheirmouthsandwaterisforcedinandovertheirgills.Accordingl
