滚动题组23阅读理解+阅读表达+书面表达(时间:60分钟总分:80分分数:)滚动题组第28页Ⅰ.阅读理解A(2019·天津卷)Howdoesanecosystem(生态系统)work?Whatmakesthepopulationsofdifferentspeciesthewaytheyare?Whyaretheresomanyfliesandsofewwolves?Tofindananswer,scientistshavebuiltmathematicalmodelsoffoodwebs,notingwhoeatswhomandhowmucheachoneeats.Withsuchmodels,scientistshavefoundoutsomekeyprinciplesoperatinginfoodwebs.Mostfoodwebs,forinstance,consistofmanyweaklinksratherthanafewstrongones.Whenapredator(掠食动物)alwayseatshugenumbersofasingleprey(猎物),thetwospeciesarestronglylinked;whenapredatorlivesonvariousspecies,theyareweaklylinked.Foodwebsmaybedominatedbymanyweaklinksbecausethatarrangementismorestableoverthelongterm.Ifapredatorcaneatseveralspecies,itcansurvivetheextinction(灭绝)ofoneofthem.Andifapredatorcanmoveontoanotherspeciesthatiseasiertofindwhenapreyspeciesbecomesrare,theswitchallowstheoriginalpreytorecover.Theweaklinksmaythuskeepspeciesfromdrivingoneanothertoextinction.Mathematicalmodelshavealsorevealedthatfoodwebsmaybeunstable,wheresmallchangesoftoppredatorscanleadtobigeffectsthroughoutentireecosystems.Inthe1960s,scientistsproposedthatpredatorsatthetopofafoodwebhadasurprisingamountofcontroloverthesizeofpopulationsofotherspecies—includingspeciestheydidnotdirectlyattack.Andunplannedhumanactivitieshaveprovedtheideaoftop-downcontrolbytoppredatorstobetrue.Intheocean,wefishedfortoppredatorssuchascodonanindustrialscale,whileonland,wekilledofflargepredatorssuchaswolves.Theseactionshavegreatlyaffectedtheecologicalbalance.Scientistshavebuiltanearly-warningsystembasedonmathematicalmodels.Ideally,thesystemwouldtelluswhentoadapthumanactivitiesthatarepushinganecosystemtowardabreakdownorwouldevenallowustopullanecosystembackfromtheborderline.Preventioniskey,scientistssay,becauseonceecosystemspasstheirtippingpoint(临界点),itisremarkablydifficultforthemtoreturn.【语篇解读】本文是一篇说明文。主要讲述了科学家们利用建立的食物网数学模型,发现了食物网运行的基本原则以及人类活动对于生态系统的影响。1.Whathavescientistsdiscoveredwiththehelpofmathematicalmodelsoffoodwebs?A.Thelivinghabitsofspeciesinfoodwebs.B.Therulesgoverningfoodwebsoftheecosystems.C.Theapproachestostudyingthespeciesintheecosystems.D.Thedifferencesbetweenweakandstronglinksinfoodwebs.答案:B解析:细节理解题。根据文章第二段第一句中的“...scientistshavefoundout...infoodwebs.”得知科学家们发现了食物网运行的关键法则,即B项。2.Astronglinkisfoundbetweentwospecieswhenapredator.A.hasawidefoodchoiceB.caneasilyfindnewpreyC.stickstoonepreyspeciesD.canquicklymovetoanotherplace答案:C解析:细节理解题。根据第二段第三句中的“Whenapredator...arestronglylinked...”得出结论,只吃一种猎物是“stronglink”。3.Whatwillhappenifthepopulationsoftoppredatorsinafoodwebgreatlydecline?A.Thepreyspeciestheydirectlyattackwilldieout.B.Thespeciestheyindirectlyattackwillturnintotoppredators.C.Thelivingenvironmentofotherspecieswillremainunchanged.D.Thepopulationsofotherspecieswillexperienceunexpectedchanges.答案:D解析:推理判断题。根据第三段第一句“Mathematicalmodels...entireecosystems.”可知“食物链顶端掠食动物的变化可能会给整个生态系统带来大的影响”。故选D项。4.WhatconclusioncanbedrawnfromtheexamplesinParagraph4?A.Uncontrolledhumanactivitiesgreatlyupsetecosystems.B.Rapideconomicdevelopmentthreatensanimalhabitats.C.Speciesofcommercialvaluedominateotherspecies.D.Industrialactivi...
