资源描述：
《托福阅读练习：swimming machines(翻译)》由会员上传分享，免费在线阅读，更多相关内容在教育资源-天天文库。
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,reproduct
2、ion,andeven"rest"arecarriedoutwhileinconstantmotion.Asaresult,practicallyeveryaspectofthebodyformandfunctionoftheseswimming"machines"isadaptedtoenhancetheirabilitytoswim.Manyoftheadaptationsofthesefishesservetoreducewaterresistance(drag).Interestinglyenough,severalofthesehydrodynamicadapta
3、tionsresemblefeaturesdesignedtoimprovetheaerodynamicsofhigh-speedaircraft.Thoughhumanengineersarenewtothegame,tunasandtheirrelativesevolvedtheir"high-tech"designslongago.Tunas,mackerels,andbillfisheshavemadestreamliningintoanartform.Theirbodiesaresleekandcompact.Thebodyshapesoftunas,infact
4、,arenearlyidealfromanengineeringpointofview.Mostspecieslackscalesovermostofthebody,makingitsmoothandslippery.Theeyeslieflushwiththebodyanddonotprotrudeatall.Theyarealsocoveredwithaslick,transparentlidthatreducesdrag.Thefinsarestiff,smooth,andnarrow,qualitiesthatalsohelpcutdrag.Whennotinuse
5、,thefinsaretuckedintospecialgroovesordepressionssothattheylieflushwiththebodyanddonotbreakupitssmoothcontours.Airplanesretracttheirlandinggearwhileinflightforthesamereason.Tunas,mackerels,andbillfisheshaveevenmoresophisticatedadaptationsthanthesetoimprovetheirhydrodynamics.Thelongbillofmar
6、lins,sailfishes,andswordfishprobablyhelpsthemslipthroughthewater.Manysupersonicaircrafthaveasimilarneedleatthenose.Mosttunasandbillfisheshaveaseriesofkeelsandfinletsnearthetail.Althoughmostoftheirscaleshavebeenlost,tunasandmackerelsretainapatchofcoarsescalesneartheheadcalledthecorselet.The
7、keels,finlets,andcorselethelpdirecttheflowofwateroverthebodysurfaceinsuchaswayastoreduceresistance(seethefigure).Again,supersonicjetshavesimilarfeatures.Becausetheyarealwaysswimming,tunassimplyhavetoopentheirmouthsandwaterisforcedinandovertheirgills.Accordingl
