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地质对美国经济影响讲美国的各种地质特点促进农业发展，进而促进经济发展，包括：风的作用形成平原，使金属矿物得以挖掘，冰川回退留下肥沃土地等等，最终对全世界各地的农业及经济发展产生良好影响。解析：本文属于地质学和农业话题组合，但都是托福阅读常考话题。在TPO中只有分别考察农业、地质学等内容的文章，并不话题交叉，可分别复习。GreatPlainsThenorthernandsouthernGreatPlainsareabroadexpanseofflatland,muchofitcoveredinprairie,steppeandgrassland,whichlieswestoftheMississippiRiverandeastoftheRockyMountainsintheUnitedStatesandCanada.ThisareacoverspartsoftheU.S.statesofColorado,Kansas,Montana,Nebraska,NewMexico,NorthDakota,Oklahoma,SouthDakota,Texas,andWyoming,andtheCanadianprovincesofAlberta,ManitobaandSaskatchewan.TheCanadianportionofthePlainsisknownasthePrairies.SomegeographersincludesometerritoryofMexicointhePlains,butmanystopattheRioGrande.TheregionisknownforsupportingextensiveranchingandagricultureGeologyTheGreatPlainsarethewesternmostportionofthevastNorthAmericanInteriorPlains,whichextendeasttotheAppalachianPlateau.TheUnitedStatesGeologicalSurveydividestheGreatPlainsintheUnitedStatesintotenphysiographic(145-65millionyearsago),theGreatPlainswascoveredbyashallowinlandseacalledtheWesternInteriorSeaway.However,duringtheLateCretaceoustothePaleocene(65-55millionyearsago),theseawayhadbeguntorecede,leavingbehindthickmarinedepositsandarelativelyflatterrainwheretheseawayhadonceoccupied.Paleontologicalfindsintheareahaveyieldedbonesofwoollymammoths,sabertoothedtigersandotherancientanimals,aswellasdozensofothermegafauna(largeanimalsover100lb(45kg))–suchasgiantsloths,horses,mastodons,andAmericanlion–thatdominatedtheareaoftheancientGreatPlainsformillionsofyears.ThevastmajorityoftheseanimalswentextinctinNorthAmericaaround13,000yearsagoduringtheendofthePleistocene.第二篇TOPIC动物的迁徙主要讲动物如何迁徙，原因不同。先举了蝴蝶与鲸鱼的例子，表明动物靠环境信号。然后说动物还靠内部生物钟判定方向，但有的鸟不靠这个方法。最后还有一些动物靠磁场导航。解析：本文属生物学话题，考察动物迁徙。类似内容在过去的托福考试中曾多次出现，分别考察过包括蜜蜂、鸟、蚂蚁、海龟等多种动物的迁徙导航，可谓是经久不衰。本文与TPO中OrientationandNavigation一篇较为对应，可作为参考。AnimalnavigationAnimalnavigationistheabilityofmanyanimalstofindtheirwayaccuratelywithoutmapsorinstruments.BirdssuchastheArctictern,insectssuchasthemonarch(fromtheearth'smagneticfieldorfromthesky)toidentifywheretheyareandsotonavigate.Internal'maps'areoftenformedusingvision,butothersensesincludingolfactionandecholocationmayalsobeused.Theabilityofwildanimalstonavigatemaybeadverselyaffectedbyproductsofhumanactivity.Forexample,thereisevidencethatpesticidesmayinterferewithbeenavigation,andthatlightsmayharmturtlenavigation.抯,StephenEmlentookthisastepfurtherandidentifiedtheprecisestarpatternsthatIndigoBuntingsusewhennavigatingatnight.ItwasassumedthattheNorthStarwasimportantasitisfixedinthenightsky,butthesurprisingresultwasthatthebirdsinsteadusedstarpatternswithinabout35degreesoftheNorthStar.Interestingly,thereislittleevidencethatthemoonplaysaroleinnighttimenavigationbybirds.Infact,theevidenceseemstosuggestthatabrightmoonactuallyinterfereswithstellarnavigation.Thisbringsustothetopicofman-madelightpollutionthatblotsoutthestarsacrossmuchofNorthAmerica,especiallyaroundhighlypopulateareas.Whatactuallyistheimpactoflightpollutiononbirdmigrationandotherfloraandfauna,andonmanhimself?Wewilldealwiththistopicinafutureposting.第三篇TOPIC:金星和地球的对比讲金星Venus和地球对比，金星含较多CO2。最开始金星和地球性质相似，后来因为地球较太阳更近，温度高，逐渐蒸发，造成不同。解析：本文属天文学话题，考察行星之间的对比。话题与TPO中PlanetsinourSolarSystem一篇较为对应，可作为参考。下附金星与地球对比的相关文章。VenuscomparedwiththeEarth