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1、智课网TOEFL备考资料刘文勇ibt黄金阅读123版本：东非草食动物的饮食摘要：最新版刘文勇新托福黄金阅读12.3版本高清PDF格式支持免费下载，一共71篇，包括刘文勇黄金阅读原29篇，下面是刘文勇ibt黄金阅读12.3版本：东非草食动物的饮食，希望对大家备考托福阅读考试有所帮助。刘文勇ibt黄金阅读12.3版本：FEEDINGHABITSOFEASTAFRICANHERBIVORES东非草食动物的饮食Buffalo,zebras,wildebeests,topi,andThomson’sgazellesliveinhugegro
2、upsthattogethermakeupsome90percentofthetotalweightofmammalslivingontheSerengetiPlainofEastAfrica.Theyareallherbivores(plant-eatinganimals),andtheyallappeartobelivingonthesamedietofgrasses,herbs,andsmallbushes.Thisappearance,however,isillusory.WhenbiologistRichardBella
3、ndhiscolleaguesanalyzedthestomachcontentsoffourofthefivespecies(theydidnotstudybuffalo),theyfoundthateachspecieswaslivingonadifferentpartofthevegetation.Thedifferentvegetationalpartsdifferintheirfoodqualities:lowerdown,therearesucculent,nutritiousleaves;higheruparethe
4、harderstems.Therearealsosparselydistributed,highlynutritiousfruits,andBellfoundthatonlytheThomson’sgazelleseatmuchofthese.Theotherthreespeciesdifferintheproportionoflowerleavesandhigherstemsthattheyeat:zebraseatthemoststemmatter,wildebeestseatthemostleaves,andtopiarei
5、ntermediate.Howarewetounderstandtheirdifferentfeedingpreferences?Theanswerliesintwoassociateddifferencesamongthespecies,intheirdigestivesystemsandbodysizes.Accordingtotheirdigestivesystems,theseherbivorescanbedividedintotwocategories:thenonruminants(suchasthezebra,whi
6、chhasadigestivesystemlikeahorse)andtheruminants(suchasthewildebeest,topi,andgazelle,whicharelikethecow).Nonruminantscannotextractmuchenergyfromthehardpartsofaplant;however,thisismorethanmadeupforbythefastspeedatwhichfoodpassesthroughtheirguts.Thus,whenthereisonlyashor
7、tsupplyofpoor-qualityfood,thewildebeest,topi,andgazelleenjoyanadvantage.Theyareruminantsandhaveaspecialstructure(therumen)intheirstomachs,whichcontainsmicroorganismsthatcanbreakdownthehardpartsofplants.Foodpassesonlyslowlythroughtheruminant’sgutbecauseruminating—diges
8、tingthehardparts—takestime.Theruminantcontinuallyregurgitatesfoodfromitsstomachbacktoitsmouthtochewitupfurther(thatiswhataco
