沙老师托福阅读包-豆柴文库

您所在位置：网站首页 / 沙老师托福阅读包.doc / 文档详情

免费试读已结束，剩余 7 页请下载文档后查看

16 金币

下载文档

/ 12

下载提示

如果您无法下载资料，请参考说明：

1、部分资料下载需要金币，请确保您的账户上有足够的金币

2、已购买过的文档，再次下载不重复扣费

3、资料包下载后请先用软件解压，在使用对应软件打开

文本预览

SectionThree:ReadingComprehension(2)


Question1-10

Mountaineershavenotedthatastheyclimb,forexample,uptothe12,633-footHumphreysPeakintheSanFranciscoPeaksinArizona,plantlifechangesradically.StartingamongthecactioftheSonoranDesert,oneclimbsintoapineforestat7,000feetandatreelessalpinetundraatthesummit.Itmayseemthatplantsatagivenaltitudeareassociatedinwhatcanbecalled“communities”–groupingsofinteractingspecies.Theideaisthatovertime,plantsthatrequireparticularclimateandsoilconditionscometoliveinthesameplaces,andhencearefrequentlytobefoundtogether.Scientistswhostudythehistoryofplantlifeareknownaspaleobotanists,orpaleobotsforshort.Theybuildupapictureofhowgroupsofplantshaverespondedtoclimatechangesandhowecosystemsdevelop.Butaretheseassociations,whicharerealinthepresent,permanent?
Agreatnaturalexperimenttookplaceonthisplanetbetween25,000and10,000yearsago,whensmallchangesintheearth’sorbitandaxisofrotationcausedgreatsheetsoficetospreadfromthepoles.TheseglacierscoveredmuchofNorthAmericaandEuropetodepthsofuptotwomiles,andthen,astheclimatewarmed,theyretreated.Duringthisretreat,theyleftbehindnewlyuncoveredlandforlivingthingstocolonize,andasthoselivingthingsmovedintheylaiddownarecordwecanreadnow.Astheiceretreatedandplantsstartedtogrownearalake,theywouldreleasepollen.Somewouldfallintothelake,sinktothebottom,andbeincorporatedintothesediment.Bydrillingintothelakebottomitispossibletoreadtherecordofsuccessiveplantlifearoundthelake.Thefossilrecordseemsclear;thereislittleornoevidencethatentiregroupsofplantsmovednorthtogether.Thingsthatlivedtogetherinthepastdon’tlivetogethernow,andthingsthatlivetogethernowdidn’tlivetogetherinthepast.Eachindividualorganismmovedatitsownpace.Thefossilrecordseemstobetellingusthatweshouldbethinkingaboutpreservingspeciesbygivingthemroomtomaneuver–torespondtoenvironmentalchanges.

Whatisthepassagemainlyabout?
Theeffectsoftheiceageonplants
Plantmigrationaftertheiceage
Theneedtodevelopanewapproachtoenvironmentalissues
Communitiesofplantsliveatdifferentaltitudes

Th