上海交通大学2013年考博英语阅读送答案

博士考试

上海交通大学2013年考博英语阅读及答案

第一篇

Therearedesertplantswhichsurvivethedryseasonintheformofinactiveseeds.Therearealsodesertinsectswhichsurviveasinactivelarvae(幼虫).Inaddition,difficultasitistobelieve,therearedesertfishwhichcansurvivethroughyearsofdrought(干旱)intheformofinactiveeggs.Thesearetheshrimps(小虾)thatliveintheMojaveDesert,anintenselydryregioninthesouth-westoftheUnitedStateswhereshadetemperaturesofover50Careoftenrecorded.

TheeggsoftheMojaveshrimpsarethesizeandhavetheappearanceofgrainsofsand.Whensufficientspringrainfallstoformalake,onceeverytwotofiveyears,theseeggshatch(孵化).Thenthewaterissoonfilledwithmillionsoftinyshrimpsaboutamillimetrelongwhichfeedontinyplantandanimalorganismswhichalsogrowinthetemporarydesertlake.Withinaweek,theshrimpsgrowfromtheiroriginal1millimetretoalengthofabout1.5centimetres.

Throughoutthetimethattheshrimpsarerapidlymaturing,thewaterinthelakeequallyrapidlyevaporates.Therefore,fortheshrimpsitisaraceagainsttime.Bythetwelfthday,however,whentheyareabout3centimetrelong,hundredsoftinyeggsformontheunderbodiesofthefemales.Usuallybythistime,allthatremainsofthelakeisalarge,muddypatchofwetsoil.Onthethirteenthdayandthenext,duringthefinalhoursoftheirbrieflives,theshrimpslaytheireggsinthemud.Then,havingensuredthattheirspecieswillsurvive,theshrimpsdieasthelastofthewaterevaporates.

Ifsufficientrainfallsthenextyeartoformanotherlake,theeggshatch,andonceagaintheshrimpspassrapidlythroughtheircycleofgrowth,adulthood,egg-laying,anddeath.Someyearsthereisinsufficientraintoformalake:inthiscase,theeggswillremaindormantforanotheryears,orevenlongerifnecessary.Very,veryoccasionally,perhapstwiceinahundredyears,sufficientrainfallstoformadeeplakethatlastsamonthormore.Inthiscase,thespeciespassesthroughtwocyclesofgrowth,egg-laying,anddeath.Thus,onsuchoccasions,thespeciesmultipliesconsiderably,whichfurtherensuresitssurvival.

1.WhichofthefollowingistheMOSTdistinctivefeatureofMojaveshrimps?

A)Theirlivesarebrief.

B)Theyfeedonplantandanimalorganisms.