资源描述:
《TPO extra2 Passage 1》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、bailiedu.comTPO36Passage1阅读文章和题目为了方便大家学习,这是小编为大家从模考软件里整理出来的TPO36Passage1的阅读文章和题目,这是最新的TPO了,大家还在等什么?Habitatsandchipmunkspecies♦ThereareeightchipmunkspeciesintheSierraNevadamountainrange,andmostofthemlookprettymuchalike.Buteightdifferentspeciesofchipmunksscurryin
2、garoundapicnicareawillnotbefound.NowhereintheSierradoalleightspeciesoccurtogether.Eachspeciestendsstronglytooccupyaspecifichabitattype,withinanelevationalrange,andtheoverlapamongthemisminimal.♦TheeightchipmunkspeciesoftheSierraNevadarepresentbutafewofthe15speci
3、esfoundinwesternNorthAmerica,yetthewholeofeasternNorthAmericamakesdowithbutonespecies:theEasternchipmunk.WhyaretheresomanyverysimilarchipmunksintheWest?ThepresenceoftallmountainsinterspersedwithvastareasofariddesertandgrasslandmakestheWestecologicallyfardiffere
4、ntfromtheEast.TheWestaffordsmuchmoreopportunityforchipmunkpopulationstobecomegeographicallyisolatedfromoneanother,aconditionofspeciesformation.Also,therearemoreextremesinwesternhabitats.IntheSierraNevada,highelevationsareclosetolowelevations,atleastintermsofmil
5、eage,butecologicallytheyareverydifferent.♦Mostecologistsbelievethatancientpopulationsofchipmunksdivergedgeneticallywhenisolatedfromoneanotherbymountainsandunfavorableecologicalhabitat.These地址:北京市海淀区海淀北二街8号中关村SOHOA区2层电话:400-890-6000传真:010-82607462网址:bailiedu.com
6、邮编:100080bailiedu.comscatteredpopulationsfirstevolvedintoraces—adaptedtothelocalecologicalconditions—andthenintospecies,reproductivelyisolatedfromoneanother.Thisperiodofevolutionwasrelativelyrecent,asevidencedbythesimilarappearanceofallthewesternchipmunkspecies
7、.EcologistshavestudiedthefourchipmunkspeciesthatoccurontheeasternslopeoftheSierraandhavelearnedjusthowthesespeciesinteractwhileremainingseparate,eachoccupyingitsownelevationalzone.Thesagebrushchipmunkisfoundatthelowestelevation,amongthesagebrush.Theyellowpinech
8、ipmunkiscommoninlowtomid-elevationsandopenconiferforests,includingpinonandponderosaandJeffreypineforests.Thelodgepolechipmunkisfoundathigherelevations,amongthelodgepoles,fir