资源描述：
《（课标专用）天津市2020高考英语二轮复习滚动题组23阅读理解阅读表达书面表达.docx》由会员上传分享，免费在线阅读，更多相关内容在教育资源-天天文库。
1、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,notingwhoea
2、tswhomandhowmucheachoneeats.Withsuchmodels,scientistshavefoundoutsomekeyprinciplesoperatinginfoodwebs.Mostfoodwebs,forinstance,consistofmanyweaklinksratherthanafewstrongones.Whenapredator(掠食动物)alwayseatshugenumbersofasingleprey(猎物),thetwospeciesarestronglyli
3、nked;whenapredatorlivesonvariousspecies,theyareweaklylinked.Foodwebsmaybedominatedbymanyweaklinksbecausethatarrangementismorestableoverthelongterm.Ifapredatorcaneatseveralspecies,itcansurvivetheextinction(灭绝)ofoneofthem.Andifapredatorcanmoveontoanotherspecie
4、sthatiseasiertofindwhenapreyspeciesbecomesrare,theswitchallowstheoriginalpreytorecover.Theweaklinksmaythuskeepspeciesfromdrivingoneanothertoextinction.Mathematicalmodelshavealsorevealedthatfoodwebsmaybeunstable,wheresmallchangesoftoppredatorscanleadtobigeffe
5、ctsthroughoutentireecosystems.Inthe1960s,scientistsproposedthatpredatorsatthetopofafoodwebhadasurprisingamountofcontroloverthesizeofpopulationsofotherspecies—includingspeciestheydidnotdirectlyattack.Andunplannedhumanactivitieshaveprovedtheideaoftop-downcontr
6、olbytoppredatorstobetrue.Intheocean,wefishedfortoppredatorssuchascodonanindustrialscale,whileonland,wekilledofflargepredatorssuchaswolves.Theseactionshavegreatlyaffectedtheecologicalbalance.Scientistshavebuiltanearly-warningsystembasedonmathematicalmodels.Id
7、eally,thesystemwouldtelluswhentoadapthumanactivitiesthatarepushinganecosystemtowardabreakdownorwouldevenallowustopullanecosystembackfromtheborderline.Preventioniskey,scientistssay,becauseonceecosystemspasstheirtippingpoint(临界点),itisremarkablydifficultforthem
8、toreturn.【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.Therules
