2015职称英语考试用书理工类最全新增文章222

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1、AnEssentialScientificProcessAlllifeontheearthdependsupongreenplants.Usingsunlight,theplantsproducetheirownfood.Thenanimalsfeedupontheplants.Theytakeinthenutrientstheplantshavemadeandstored・Butthat'snotall.Sunlightalsohelpsaplantproduceoxygen.Someoftheox

2、ygenisusedbytheplant,butaplantusuallyproducesmoreoxygenthanituses・Theexcessoxygenisnecessaryforanimalsandotherorganismstolive・Theprocessofchanginglightintofoodandoxygeniscalledphotosynthesis・Besideslightenergyfromthesun,plantsalsousewaterandcarbondioxid

3、e・Thewatergetstotheplantthroughitsroots.Thecarbondioxideenterstheleavesthroughtinyopeningscalledstomata.Thecarbondioxidetravelstochloroplasts,specialcellsinthebodiesofgreenplants.Thisiswherephotosynthesistakesplace.Chloroplastscontainthechlorophyllsthat

4、giveplantstheirgreencolor.Thechlorophyllsarethemoleculesthattraplightenergy.Thetrappedlightenergychangeswaterandcarbondioxidetoproduceoxygenandasimplesugarcalledglucose.Carbondioxideandoxygenmoveintoandoutofthestomata・Watervaporalsomovesoutofthestomata.

5、Morethan90percentofwateraplanttakesinthroughitsrootsescapesthroughthestomata.Duringthedaytime,thestomataofmostplantsareopen.Thisallowscarbondioxidetoentertheleavesforphotosynthesis・Asnightfalls,carbondioxideisnotneeded・Thestomataofmostplantsclose.Waterl

6、ossstops.Ifphotosynthesisceased,therewouldbelittlefoodorotherorganicmatterontheearth.Mostorganismswoulddisappear.Theearth'satmospherewouldnolongercontainoxygen.Photosynthesisisessentialforlifeonourplanet・1.Thenanimalsfeedupontheplants.动物以植物为食。练习：1-Inthe

7、firstparagraphstheword"excess"meansAheavy.Bextra.Cgreen.Dliquid.2.Whichofthefollowingdoesnotmovethroughaplant'sstomata?ACarbondioxide.BWatervapor.COxygen.DFood.3.Inthetitle,thetermEssentialScientificProcessreferstoAphotosynthesis.Btheformationofglucose.

8、Cglobalwarming.Dwatergettingtotherootsofplants.4・ThispassageisprimarilydevelopedbyAexplainingaprocess.Btellingastory・Ccomparingandcontrasting.Dconvincingthereaderofplants'importance・5・AnothergoodtitleforthispassagewouldbeAOxygena