【助力2014】高考英语 任务型阅读专项特训（5）.doc

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1、【助力2014】高考英语任务型阅读专项特训（5）(1)Zebrashavetheirownbugrepellent(驱虫剂)?Ewwbugs!Theyaresoannoying!Wehumansareluckythatwecanapplyrepellentstoavoidnastybites.Butwhat’sananimaltodo?Theyhavenochoicebuttospendtheirdaysshooingthemoffwiththeirtails,unless,ofcourse,theyarezebras,whoapparentlyhavetheir

2、ownautomaticrepellent---theirstripedskin!ScientistshadoriginallythoughtthatthereasonwhytheanimalhaddevelopedtheblackandwhitelineswastohelpprotectitselffrompredatorsintheAfricansavannah,becausethestripesmakeitdifficulttosingleoutonezebrathatistravelingwithaherd.Whilethatmaybetrue,theth

3、eoryhasneverbeentestedorproven.Nowtheexpertshaveanother---thatthestripeshaveevolvedtorepeltheannoyinghorsefliesthatnotonlyfeedofftheirblood,butalso,transmitdangerousgermsintothebodiesoftheseinnocentanimals.ThestudywasperformedbyateamofSwedishscientists.Oneofthecluesthatgotthemthinking

4、alongtheselineswasthefactthatdarkerhorsesgotbittenmoreoftenthanlight-coloredorwhiteones.Thefactthatzebrasarebornblackandonlydevelopstripsastheygrowoldermadethescientiststheorizethatthestripesmaybesomethingtheanimalshavedevelopedtomakethemselveslessattractivetoflies.Totestifthismaybeth

5、ecase,theypaintedsomeboardsatahorse-infestedhorsefarminBudapestwithpattensofblackandwhitestripesofvaryingwidthsandappliedalayerofglueonthem.Whattheynoticedwasthattheplaceswheretheblackandwhitestripeswereattheirnarrowest(similartowhatzebrashave)attractedthefewestflies.Theyachievedsimil

6、arresultswhentheypaintedhorseswithblackandwhitezebra-likestripes.Whiletheresearcharenotsurewhythismaybethecase,theybelieveitmaybesomethingtodowiththewayinsectsoperate---horsefliesareattractedtohorizontallypolarizedlight（偏振光）;sincewhitedoesnotreflectit,whitehorsesareluckierthanblackone

7、s.Butzebrasseemtobetheluckiestofall.Whentheresearchersmeasuredthepolarizedlightreflectedfromrealzebraskins,theyfoundthatitmatchedlightpattensthatweretheleastattractivetohorseflies.Whilethistheorydoesmakelogicalsense,nobodyis100percentsurethatitisreallytrue,giventhatithasneverbeenteste

8、donar