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1、2014年5月25日托福阅读真题智课网整理（1）人类的活动和动物的灭绝将overhunting，中间一个个科学家说不对，其实是climatechange导致了，讲人类人前北美很多大型动物，但是人类出现以后大型动物都挂了，主要原因是人类的过度捕猎。接着说气候也是一个潜在原因，而且一些大型动物挂了，认识rodent并没有灭绝。有举例，在人类出现以后很短的时间内动物数量急剧下降，虽然这个事实被捕鱼大丰收的情况所disguise，一个明显的证据就是一种特殊的鱼到了食物链底端。解析：本篇文章讲解了动物的灭绝的原因。相似的话题可以参考tpo中
2、文章massextiction，文章的理解重点是要把握好解释灭绝的原因，以及相对应所举的例子。按照不同的灭绝的原因梳理文章的结构。相应的背景请参考下文：Aslongasspecieshavebeenevolving,specieshavebeengoingextinct.Itisestimatedthatover99.9%ofallspeciesthateverlivedareextinct.Theaveragelife-spanofaspeciesis10millionyears[citationneeded],although
3、thisvarieswidelybetweentaxa.Thereareavarietyofcausesthatcancontributedirectlyorindirectlytotheextinctionofaspeciesorgroupofspecies."Justaseachspeciesisunique",writeBeverlyandStephenC.Stearns,"soiseachextinction...thecausesforeacharevaried—somesubtleandcomplex,othersob
4、viousandsimple".Mostsimply,anyspeciesthatcannotsurviveandreproduceinitsenvironmentandcannotmovetoanewenvironmentwhereitcandoso,diesoutandbecomesextinct.Extinctionofaspeciesmaycomesuddenlywhenanotherwisehealthyspeciesiswipedoutcompletely,aswhentoxicpollutionrendersitse
5、ntirehabitatunliveable;ormayoccurgraduallyoverthousandsormillionsofyears,suchaswhenaspeciesgraduallylosesoutincompetitionforfoodtobetteradaptedcompetitors.Extinctionmayoccuralongtimeaftertheeventsthatsetitinmotion,aphenomenonknownasextinctiondebt.HabitatdegradationHab
6、itatdegradationiscurrentlythemainanthropogeniccauseofspeciesextinctions.Themaincauseofhabitatdegradationworldwideisagriculture,withurbansprawl,logging,miningandsomefishingpracticesclosebehind.Thedegradationofaspecies'habitatmayalterthefitnesslandscapetosuchanextenttha
7、tthespeciesisnolongerabletosurviveandbecomesextinct.Thismayoccurbydirecteffects,suchastheenvironmentbecomingtoxic,orindirectly,bylimitingaspecies'abilitytocompeteeffectivelyfordiminishedresourcesoragainstnewcompetitorspecies.Habitatdegradationthroughtoxicitycankilloff
8、aspeciesveryrapidly,bykillingalllivingmembersthroughcontaminationorsterilizingthem.Itcanalsooccuroverlongerperiodsatlowertox
