托福阅读tpo45R-2原文+译文+题目+答案+背景知识.pdf

托福阅读tpo45R-2WindPollination

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译文4

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原文

WindPollination

①Pollen,apowderysubstance,whichisproducedbyfloweringplants

andcontainsmalereproductivecells,isusuallycarriedfromplantto

plantbyinsectsorbirds,butsomeplantsrelyonthewindtocarry

theirpollen.Windpollinationisoftenseenasbeingprimitiveand

wastefulincostlypollenandyetitissurprisinglycommon,especiallyin

higherlatitudes.Windisverygoodatmovingpollenalongway;pollen

canbeblownforhundredsofkilometers,andonlybirdscangetpollen

anywherenearasfar.Thedrawbackisthatwindisobviouslyunspecific

astowhereittakesthepollen.Itisliketryingtogetalettertoafriend

attheotherendofthevillagebyclimbingontotheroofandthrowing

anarmfuloflettersintotheairandhopingthatonewillendupinthe

friendsgarden.Fortherelativelyfewdominanttreespeciesthatmake

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uptemperateforests,wheretherearemanyindividualsofthesame

specieswithinpollenrange,thisisquiteasafegamble.Ifanumberof

peopleinthevillagewerethrowinglettersoffroofs,yourfriendwould

beboundtogetone.Bycontrast,inthetropics,whereeachtree

specieshasfew,widelyscatteredindividuals,thechanceofwind

blowingpollentoanotherindividualissufficientlyslimthatanimalsare

asaferbetastransportersofpollen.Eventalltreesinthetropicsare

usuallynotwindpollinateddespitebeinginwindyconditions.Ina

similarway,treesintemperateforeststhatareinsectpollinatedtend

togrowassolitary,widelyspreadindividuals.

②Sincewind-pollinatedflowershavenoneedtoattractinsectsor

otheranimals,theyhavedispensedwithbrightpetals,nectar,and

scent.Theseareatbestawasteandatworstanimpedimenttothe

transferofpolle