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1、 为了帮助大家高效备考托福， 为大家带来托福 TPO27 阅读 Passage3 原文文本+题目+答案 解析，希望对大家备考有所帮助。 Predator-Prey Cycles How do predators affect populations of the prey animals?The answer is not as simple as might be thought.Moose reached Isle Royale in Lake Superior by crossing over winter ice and multiplied freely there in isola
2、tion without predators.When wolves later reached the island,naturalists widely assumed that the wolves would play a key role in controlling the moose population.Careful studies have demonstrated,however,that this is not the case.The wolves eat mostly old or diseased animals that would not survive lo
3、ng anyway.In general,the moose population is controlled by food availability,disease and other factors rather than by wolves. 捕食者是怎样影响被捕食者的数量呢?答案并不是想象中那么简单。 麋鹿通过穿越冬天的 冰层到达了在苏必略湖的罗亚尔岛，并由于没有捕食者而自由繁殖。当狼在晚一点的时候到 达那座岛时，自然学家都认为，狼对控制麋鹿的数量将起到关键作用。但是，严密的研究说 明并不是这样。 狼吃掉的大部分是年老的， 或生病的动物， 他们本身就不会存活很久。 一般地， 麋鹿的数
4、量是由食物、疾病、和其它的一些条件，而不是狼控制的。 When experimental populations are set up under simple laboratory conditions,the predator often exterminates its pre and then becomes extinct itself,having nothing left to eat.However,if safe areas like those prey animals have in the wild are provided,the prey population dr
5、ops to low level but not extinction.Low prey population levels then provide inadequate food for the predators,causing the predator population to decrease.When this occurs,the prey population can rebound.In this situation the predator and prey population may continue in this cyclical pattern for some
6、 time. 在简单的实验条件下，捕食者经常吃掉了所有的实验设定的被捕食者，然后因为食物缺 乏而自己灭绝了。但是，如果能给被捕食动物提供如同在野外的安全的区域，被捕食动物的 数量会降低到很低的数值，但不会灭绝。被捕食者的数量的降低造成了捕食者的食物不足， 使捕食者的数量下降。此时，被捕食者的数量又会反弹。这样，一定时间内捕食者和被捕食 者的数量会持续地循环。 Population cycles are characteristic of small mammals,and they sometimes appear to be brought about by predators.Ecolog
7、ists studying hare populations have found that the North American snow shoe hare follows a roughlyten-year cycle.Its numbers fall tenfold to thirty in a typical cycle,and a hundredfold change can occur.Two factors appear to be generating the cycle:food plants and predators. 这种数量的循环是小型哺乳动物的特性，有时候这种循环
8、是由捕食者带来的。生态学家 对野兔数量的研究发现，北美白靴兔一直遵守着大约以十年为周期的循环。在一个典型的循 环中，其数量会以十倍到三十倍的减少，甚至会出现一百倍的改变。有两种因素会导致这种 循环：食物和捕食者。 The preferred foods of snowshoe hares are willow and birch twigs.As hare density increases,the quantity of these twigs decreases,forcing the hares to feed on low- quality high-fiber food.Lower
9、birth rates,low juvenile survivorship,and low growth rates follow,so there is a corresponding decline in hare abundance.Once the hare population has declined,it takes two to three year for the quantity of twigs to recover. 白靴兔比较喜欢的食物是柳木和桦树树枝。 野兔的密度增加时， 这些树枝的数量就减少， 迫使野兔去吃一些低质量的，高纤维食物。随之而来的是低生育率，低成活率，
10、低生长率， 所以野兔数量随之减少。一旦野兔数量减少，树枝的数量需要两到三年恢复。 A key predator of the snowshoe hare is the Canada lynx.The Canada lynx shows a ten-year cycle of abundance that parallels the abundance cycle of hares.As hare numbers fall,so do lynx numbers,as their food supply depleted. 白靴兔的主要捕食者是加拿大山猫。加拿大山猫的数量呈现了平行于野兔的十年为周
11、期 的循环。野兔数量下降时，山猫的食物供给减少，数量也随之减少。 What causes the predator-prey oscillations?Do increasing number of hares lead to overharvesting of plants,which in turn results in reduced hare populations,or do increasing numbers of lynx lead to overharvesting hares?Field experiments carried out by Charles Krebs an
12、d coworkers in 1992 provide an answer.Krebs investigated experimental plots in Canada s Yukon territory that contained hare populations.When food was added to those plots(no food effect)and predators were excluded(no predator effect)from an experimental area,hare numbers increased tenfold and stayed
13、 therethe cycle was lost.However,the cycle was retained if either of the factors was allowed to operate alone:if predators were excluded but food was not added(food effect alone),or if food was added in the presence of predators(predator effect alone).Thus both factors can affect the cycle,which,in
14、practice,seems to be generated by conjunction of the two factors. 什么造成了捕食者和被捕食者的周期振动呢?是野兔数量的增长使得植物被过度采食， 随 之导致了野兔的减少还是山猫的增加导致了野兔被过度捕食?在 1992 年， Charles Krebs 和其 合作者的野外试验提供了答案。Krebs 研究了在加拿大 Yuhon 地区有野兔种群的试验田。当 食物被加到这片试验田(没有食品因素影响)并且将捕食者移去(也没有捕食者因素影响)。野 兔的数量增加了十倍并且保持稳定-不再循环。但是，在任意一个因素单独存在时，循环 都会出现 ： 不
15、管是捕食者被移除，食物不添加(也就是只有食物影响);还是食物在捕食者存在 的情况下被添加(也就是只有捕食者影响)。 因此， 两个因素都可以影响这个循环， 即在现实中， 循环是两个因素同时作用的结果。 Predators are an essential factor in maintaining communities that are rich and diverse in species.Without predators,the species that is the best competitor for food,shelter,nesting sites,and other env
16、ironmental resources tends to dominate and exclude the species with which it competes.This phenomenon is known as“competitor exclusion”.However,if the community contains a predator of the strongest competitor species,then the population of that competitor is controlled.Thus even the less competitive
17、 species are able to survive.For example,sea stars prey on a variety of bivalve mollusks and prevent these bivalves from monopolizing habitats on the sea floor.This opens up space for many other organisms.When sea stars are removed,species diversity falls sharply.Therefore,from the stand point of di
18、versity,it is usually a mistake to eliminate a major predator from a community 捕食者是保持群体多样性和数量的必要条件。没有捕食者时，那种在对食物、庇护所、 筑巢点和其它环境资源的争夺中胜出的竞争者， 趋向于统治， 并且灭绝与其竞争的其它物种。 这种现象被称作“驱逐竞争者” 。但是，如果种群中的具有最强竞争力的物种存在天敌，那这 一物种数量就被控制。因此，竞争力比较弱的物种都会得以生存。比如，海星捕食各种双壳 的软体动物，防止这些双壳动物垄断海底。这使得其它的很多生物有了生存空间。海星被移 除后，物种多样性大幅度降低
19、。因此，从多样性的角度说，从一个种群中消除一个主要捕食 者通常是错误的决定。 托福阅读试题 1.In paragraph 1,why does the author discussthe moose and wolves on Isle Royale? A.To provide an example of predators moving to newhabitats by following migrating prey. B.To show that the interactions between predator populations and prey populations are
20、 notalways might be expected. C.To suggest that prey populations are more influenced by predation than food availabilityand disease. D.To argue that studies of geographically isolated populations tend not to be useful tonaturalists. 1.对应文章的第四句， Careful studiesnot the case.这句话前面说人们觉得狼对控制 鹿的数量控制起到了重要作
21、用， 这句话对其进行了否定， 对应了 B 选项。 A 与原文没有关系。 C 与原文第一段最后一句话矛盾。D 也不对。 2.The word“rebound”in the passage(paragraph 2)is closest inmeaning to A.escape. B.recover. C.survive. D.resist. 2.原词汇是反弹的意思。A 是逃走，B 是恢复，C 是存活，D 是反抗。这里 B 最符合原文 意思。原文词汇可以通过词根词缀分析。Bound 本来就是跳跃的意思，加 re 前缀就是再次跳 跃，也就是反弹。 3.Paragraph 2 implies whic
22、h of the following about experimental environments inwhich predators become extinct? A.They may yield results that do not accurate predict changes of populations in the wild. B.In these environments,the prey species is better adapted than the predator species. C.These environments are appropriate on
23、ly for studying small populations of predators andprey. D.They are unrealistic because some predators are also the prey of other predators. 3.第一句说了 experimental environments 的结果， 但后面立刻出现了 however。 证明出 现了转折，后文在一定程度上否定了前面的观点。所以选 A。B 和原文主题没关系，C 虽然没 有明显错误，但没有表现出真正的主题，重点是在真实生活中的情况。D 原文也没提到。 4.Which of th
24、e following can be inferred from paragraphs 2 and 3 about the smallmammals that experience population cycles? A.Their population cycles are not affected by predators. B.Their predatorspopulations periodically disappear. C.They typically undergo ten-year cycles. D.They have access to places safe from
25、 predators. 4.A 错误，对应第三段最后一句话;B 错误，对应第二段的第二句话后面，证明在正常情 况下捕食者不会消失。C 对应第三段第二句，出现了 ten-year cycle 但是仅仅是对野兔的描 写，并不适用与全部哺乳动物。D 对应第二段第二句，说被捕食者在现实生活中可以居于安 全的远离捕食者的地方。所以选 D。 5.The word“roughly”in the passage is closest in meaning to A.usually. B.repeating. C.approximately. D.observable. 5.roughly 是粗略地。A 是通常
26、的，B 是重复的，C 是大约的，D 是可观察的。根据词义 选 C。 6.The word“generating”in the passage is closest in meaning to A.producing. B.changing. C.speeding up. D.smoothing out. 6.generate 是导致，产生的意思。A 是产生，B 是改变，C 是加速，D 是渐出。根据意思 选择 A。通过原文分析，前面说有两个因素可以怎么样这个 cycle，那么应该是导致，产生的 意思。 7.According to paragraph 4,all of the following
27、 are true of the food of snowshoehares EXCEPT A.The preferred food fore hares consists of willow and birch twigs. B.High fiber food is the most nutritious for hares. C.Depletion of the supply of willow and birch twigs cause low birth and growth rates. D.The food supply takes two or three years to re
28、cover after a peak in hare populationdensity. 7.排除题， 选项 A 对应第一句， 正确。 选项 B 对应第二句， 原文说 high-fiber 意味着 low quality，所以 B 错误，选。C 对应第三句，正确，不选。D 对应最后一句，正确，不选。 提供者：请选择 8.The word“conjunction”in the passage(paragraph 6)is closest in meaning to A.determination B.combination C.alternation D.transformation 8.原文
29、说的是由于野兔是山猫的食物，所以野兔数量下降，山猫数量也会随之下降。所 以选择 A。B 的逻辑关系不对， 并非野兔跟着山猫变化。 C 更不对， 两者数量是同时增减的。 D 也不符合原文。 9.According to paragraph 5,which of the following statements bestcharacterizes theabundance cycle of the Canada lynx? A.It closely follows the cycle the snowshoe hare. B.When the numbers of lynx fall,the nu
30、mbers of snowshoe hares soon decrease. C.When hare numbers decrease,lynx numbers increase. D.It is not clearly related to the availability of lynx food. 9.这句话的前面一句话说的是两个因素都会影响这个循环，而在现实中，两个因素都存 在。所以这里应该是共同作用的意思。所以 B，结合。符合原义。A 是决定，C 是交替，D 是 转化。 10.According to paragraph 6,which of the following was tr
31、ue of the harepopulationcycle in Krebss experiment? A.The effects of providing food while at the same time introducing predators cancelled eachother,so there was no cycle. B.The cycle existed when either the food supply was limited or there were predators. C.There was a cycle when there were no pred
32、ators and food was supplied. D.If the hares had places to hide from the lynx,the hare population increased tenfold andthen remained at that level. 10.对应位置是红色部分。总结就是两个因素只要其中一个存在就会导致 cycle。两个同 时都没有的时候，就不存在 cycle 了。所以 A 说 no cycle，那么条件中就多出了 food effect，错误不选。B 正确，两因素都不存在，nocycle，选!C 说 cycle 存在，可是两因素都 不存
33、在。D 跟两个因素都没关系，不选。 11.According to paragraph 7,which ofthe following statements correctlycharacterizes the effect of sea stars on the ecosystem in which they are predators ofbivalves? A.Bivalve population are kept low,allowing species that compete with bivalves to survive. B.The numbers of most speci
34、es of bivalves are greatly reduced,leaving the bivalve speciesthat is the strongest competitor to dominate among the survivors. C.Biological diversity begins to decrease because many bivalve species disappear. D.Sea stars dominate at first but then die off because of the depleted food supply. 11.对应了
35、原文这段倒数第二句和第三句。 说海星的存在对双壳动物是一个限制， 使得别 的生物有了生存的空间。 符合 A。 B 不对， 双壳动物并不是 dominate;C 不对， bivalve 控制后， diversity 应该是上升的。D 也不对，海星并不是死了啊。 12.According to paragraph 7,which of the following is true of the phenomenon ofcompetitor exclusion? A.It results in more diverse communities. B.It requires the presence
36、of predators. C.It affects all competitions equally. D.It happens only when there is a dominant competitor. 12.根据 competitor exclusion 定位，这句话说 this phenomenon，那么对于现象描写应 该在前面。往前找可以看到这个现象是要在“best competitor”存在的情况，这个竞争者还 tend to dominate.符合 D。A 并不是这个现象的直接作用，其直接作用是对其他 competitor 的限制。B 虽然正确，但没指出其唯一性。C 没提
37、到。 13.Look at the four squaresthat indicate where the following sentence could beadded to the passage.Where would the sentence best fit?As a result,there are notenough of the strong competitions to monopolize the environments resources. Predators are an essential factorin maintaining communities tha
38、t are rich and diverse inspecies.Without predators,the species that is the best competitor for food,shelter,nestingsites,and other environmental resources tends to dominate and exclude the specieswith which it competes.【A】This phenomenon is known as “competitor exclusion”.【B】However,if the community
39、 contains a predator of the strongest competitor species,then the population of that competitor is controlled. 【 C】 Thus even the less competitivespecies are able to survive. 【 D】 For example,seastars prey on a variety of bivalvemollusks and prevent these bivalves from monopolizing habitats on the s
40、ea floor.This opens upspace for many other organisms.When sea stars are removed,species diversity falls sharply.Therefore,from the stand point of diversity,it is usually a mistake toeliminate a majorpredator from a community. 13.这里说 as a result，那么首先前面要对某个现象进行描写，后面要对 there are not enough of thestrong
41、 competitors to monopolize the environment s resources.进行递进。 C 符合。 14.Directions:An introductory sentence for a brief summary of the passage isprovided below.Complete the summary by selecting the THREE answer choices thatexpress the most important ideas in the passage.Some sentences do not belong in
42、the summary because they express ideas that are not presented in the passage or areminor ideas in the passage.This question is worth 2 points. The relationships between predatorsand prey are complex. A.Studies of the interactions between wolves and moose on Isle Royale in Lake Superior revealthat wo
43、lf predation is not the primary factor controlling the moose population. B.Predators help maintain biological diversity by limiting populations of a dominantcompetitor species,thereby preventing that species from excluding others. C.A speciespopulation tends to rise and falls in a cycle pattern if t
44、he food supply for thepopulation is limited,or if the population has a major predator. D.Ecologists are interested in studying predator-prey population cycles becauseunderstanding how predators and prey interact will allow better wildlife managementprograms. E.In predator-prey population cycles,pred
45、ator populations increase or decrease followingsimilar population changes in the species they prey on. F.The removal of sea stars reduces the diversity of the community in which they arepredators,and is therefore a bad idea. 14.A 对应原文 1-3 段，虽然到第二段为止，都是符合这个选项的，但是第三段已经对这 个进行了否定，错误，不选。B 虽然意思正确，但是原文没有提到生态学家要研究捕食者和 被捕食者的关系的目的，不选。C 正确，选，对应原文最后一段。D 正确，选，原文第二段已 经表达了这句话了，后面也不断地重复。E 正确，选，对应原文倒数第二段。F 选项缺少了一 环-双壳动物，语义表达不完整，不选。 以上是给大家整理的托福 TPO27 阅读 Passage3 原文文本+题目+答案解析， 希望对你有所 帮助!