托福閱讀tpo3TheLongTermStabilityofEcosystems生態(tài)系統(tǒng)的長(zhǎng)期穩(wěn)定原題解析

1、閱讀原文：Plant communities assemble themselves flexibly, and their particular structure depends on the specific history of the area. Ecologists use the term “succession” to refer to the changes that happen in plant communities and ecosystems over time. The first community in a succession is called a pio

2、neer community, while the long-lived community at the end of succession is called a climax community. Pioneer and successional plant communities are said to change over periods from 1 to 500 years. These changesin plant numbers and the mix of speciesare cumulative. Climax communities themselves chan

3、ge but over periods of time greater than about 500 years.植物群體可以自由地聚集，它們特殊的結(jié)構(gòu)取決于聚集區(qū)域的具體歷史。生態(tài)學(xué)家使用“演替”來(lái)詮釋植物群落和生態(tài)系統(tǒng)隨著時(shí)間推移所發(fā)生的變化。演替中的第 一個(gè)群落被稱作先鋒群落，而處于演替最后那個(gè)長(zhǎng)期生存的群落被稱為頂極群落。先鋒群落和緊接著的植物群落的變化周期是從1到500年不等，植物數(shù)量和混合 種類數(shù)量的變化是慢慢積累的。頂極群落本身也改變，但其變化周期超過(guò)500年。An ecologist who studies a pond today may well find it relat

4、ively unchanged in a years time. Individual fish may be replaced, but the number of fish will tend to be the same from one year to the next. We can say that the properties of an ecosystem are more stable than the individual organisms that compose the ecosystem.現(xiàn)代一個(gè)研究池塘的生態(tài)學(xué)會(huì)發(fā)現(xiàn)池塘在一年當(dāng)中相對(duì)而言是不變的。個(gè)別魚類可能被替

5、換，但年復(fù)一年魚的總數(shù)都趨于一致。也就是說(shuō)，一個(gè)生態(tài)系統(tǒng)自身的屬性要比由單一生物體組成的生態(tài)系統(tǒng)更穩(wěn)定。At one time, ecologists believed that species diversity made ecosystems stable. They believed that the greater the diversity the more stable the ecosystem. Support for this idea came from the observation that long-lasting climax communities usually

6、 have more complex food webs and more species diversity than pioneer communities. Ecologists concluded that the apparent stability of climax ecosystems depended on their complexity. To take an extreme example, farmlands dominated by a single crop are so unstable that one year of bad weather or the i

7、nvasion of a single pest can destroy the entire crop. In contrast, a complex climax community, such as a temperate forest, will tolerate considerable damage from weather to pests.生態(tài)學(xué)家們一度認(rèn)為物種的多樣性使生態(tài)系統(tǒng)穩(wěn)定，生態(tài)系統(tǒng)物種越多樣則生態(tài)系統(tǒng)越穩(wěn)定。通過(guò)觀察得出的結(jié)論支持了這個(gè)觀點(diǎn)，長(zhǎng)期持久的頂極群落通常要比先 鋒群落具備更為復(fù)雜的食物網(wǎng)和更多的物種。生態(tài)學(xué)家家們得出的結(jié)論是：頂點(diǎn)生態(tài)系統(tǒng)的穩(wěn)定性明顯取決于

8、他們的復(fù)雜化程度。舉個(gè)極端的例子，在單一作物的農(nóng) 田中，一年的惡劣天氣或單一害蟲的入侵就可以摧毀所有作物。與此相反，在一個(gè)復(fù)雜的頂極群落里，如溫帶森林，他們便可以抵御來(lái)自氣候和害蟲的干擾和入侵。The question of ecosystem stability is complicated, however. The first problem is that ecologists do not all agree what “stability” means. Stability can be defined as simply lack of change. In that case,

9、 the climax community would be considered the most stable, since, by definition, it changes the least over time. Alternatively, stability can be defined as the speed with which an ecosystem returns to a particular form following a major disturbance, such as a fire. This kind of stability is also cal

10、led resilience. In that case, climax communities would be the most fragile and the least stable, since they can require hundreds of years to return to the climax state.不管怎樣，生態(tài)系統(tǒng)穩(wěn)定性的問(wèn)題非常復(fù)雜。首先，不是所有的生態(tài)學(xué)家都贊同“穩(wěn)定”的含義。穩(wěn)定性可以簡(jiǎn)單地定義為缺乏變化。如果是這樣的話，頂極群落將 被視為最穩(wěn)定的，因?yàn)楦鶕?jù)定義，他們隨著時(shí)間推移而變化得最少。另外，穩(wěn)定性也可以界定為生態(tài)系統(tǒng)在經(jīng)歷了嚴(yán)重破壞之后回復(fù)原

11、貌的速度，比如火災(zāi)。這種穩(wěn) 定性也被稱作彈性。在這種情況下，頂極群落將是最脆弱和最不穩(wěn)定的，因?yàn)樗麄兛赡苄枰獢?shù)百年時(shí)間才能恢復(fù)到頂點(diǎn)狀態(tài)。Even the kind of stability defined as simple lack of change is not always associated with maximum diversity. At least in temperate zones, maximum diversity is often found in mid-successional stages, not in the climax community. Onc

12、e a redwood forest matures, for example, the kinds of species and the number of individuals growing on the forest floor are reduced. In general, diversity, by itself, does not ensure stability. Mathematical models of ecosystems likewise suggest that diversity does not guarantee ecosystem stabilityju

13、st the opposite, in fact. A more complicated system is, in general, more likely than a simple system to break down. A fifteen-speed racing bicycle is more likely to break down than a childs tricycle.即使是這種被定義為簡(jiǎn)單地缺乏變化的穩(wěn)定性并非總是與最多樣的物種聯(lián)系起來(lái)。至少在溫帶地區(qū)，會(huì)經(jīng)常在演替過(guò)程中發(fā)現(xiàn)最多物種，而不是在頂極群落中。例 如，紅杉樹林一旦成熟，其中的物種數(shù)量以及單個(gè)物種的數(shù)量都會(huì)

14、減少。一般來(lái)說(shuō)，多樣性本身并不能保證穩(wěn)定性（事實(shí)上正相反），生態(tài)系統(tǒng)的數(shù)學(xué)模型也可以得 出同樣的結(jié)論。一個(gè)更復(fù)雜的系統(tǒng)可能比一個(gè)簡(jiǎn)單的系統(tǒng)更容易被破壞（一個(gè)十五速的賽車比一個(gè)孩子的三輪車更容易損壞）。Ecologists are especially interested to know what factors contribute to the resilience of communities because climax communities all over the world are being severely damaged or destroyed by human act

15、ivities. The destruction caused by the volcanic explosion of Mount St. Helens, in the northwestern United States, for example, pales in comparison to the destruction caused by humans. We need to know what aspects of a community are most important to the communitys resistance to destruction, as well

16、as its recovery.生態(tài)學(xué)家們更想弄清楚到底哪些因素有助于促成群落的恢復(fù)，因?yàn)槭澜绺鞯氐捻敇O群落都因?yàn)槿祟惢顒?dòng)而遭受到嚴(yán)重的損壞或毀壞。就像美國(guó)西北部圣海倫火山的猛 烈噴發(fā)所造成的破壞，在人類活動(dòng)對(duì)環(huán)境造成的破壞面前也相形見絀。我們必須了解對(duì)群落抵抗、破壞和恢復(fù)來(lái)說(shuō)哪些是最重要的。Many ecologists now think that the relative long-term stability of climax communities comes not from diversity but from the “patchiness” of the environme

17、nt, an environment that varies from place to place supports more kinds of organisms than an environment that is uniform. A local population that goes extinct is quickly replaced by immigrants from an adjacent community. Even if the new population is of a different species, it can approximately fill

18、the niche vacated by the extinct population and keep the food web intact.現(xiàn)在的很多生態(tài)學(xué)家們認(rèn)為，頂極群落相對(duì)長(zhǎng)期的穩(wěn)定性并非來(lái)自于多樣性，而是來(lái)自環(huán)境的“補(bǔ)綴”，隨處變化的環(huán)境比始終如一的環(huán)境更有利于多種有機(jī)體的生 存。當(dāng)?shù)匚锓N滅亡后，馬上就會(huì)被相鄰群落的移民取代。即便是另一種不同的物種，他們也可以填補(bǔ)那些已滅絕生物的空缺，并保持食物網(wǎng)的完整。第1題：The word “particular” in the passage is closest in meaning toA：naturalB：finalC：specif

19、icD：complex題目解析particular特別的，特定的，答案specific。前文說(shuō)assemble them flexibly，多變的，就是每個(gè)群落都不一樣，強(qiáng)調(diào)特殊性。A自然B最終D復(fù)雜都與前文不搭，所以都不對(duì)。第2題：According to paragraph 1, which of the following is NOT true of climax communities?A：They occur at the end of a succession.B：They last longer than any other type of community.C：The nu

20、mbers of plants in them and the mix of species do not change.D：They remain stable for at least 500 years at a time.題目解析以climax communities做關(guān)鍵詞定位至原文第三句和最后一句，第三句說(shuō)明A對(duì)，不選；最后一句說(shuō)明D對(duì)，不選；B沒(méi)直說(shuō)，說(shuō)其他的communities變化周期在1-500年，climax最少是500年，說(shuō)明climax最長(zhǎng)，B對(duì)，不選。而且最后一句也說(shuō)了climax是變化的，C說(shuō)反了，選。第3題：According to paragraph 2, w

21、hich of the following principles of ecosystems can be learned by studying a pond?A：Ecosystem properties change more slowly than individuals in the system.B：The stability of an ecosystem tends to change as individuals are replaced.C：Individual organisms are stable from one year to the next.D：A change

22、 in the members of an organism does not affect an ecosystems properties.題目解析本段非常短，迅速看完之后發(fā)現(xiàn)最后一句是結(jié)論，說(shuō)生態(tài)系統(tǒng)比組成生態(tài)系統(tǒng)的任意單一物種都穩(wěn)定，A是答案。第4題：According to paragraph 3, ecologists once believed that which of the following illustrated the most stable ecosystems?A：Pioneer communitiesB：Climax communitiesC：Single-cr

23、op farmlandsD：Successional plant communities題目解析以ecologists做關(guān)鍵詞定位至本段第一句，說(shuō)生態(tài)學(xué)家認(rèn)為生態(tài)系統(tǒng)中物種越多越穩(wěn)定。接著在舉例子的時(shí)候作者舉到了climax communities，說(shuō)明生態(tài)學(xué)家認(rèn)為climax communities最穩(wěn)定，答案B。第5題：According to paragraph 4, why is the question of ecosystem stability complicated?A：The reasons for ecosystem change are not always clear.

24、B：Ecologists often confuse the word “stability” with the word “resilience.”C：The exact meaning of the word “stability” is debated by ecologists.D：There are many different answers to ecological questions.題目解析以question of ecosystem stability為關(guān)鍵詞定位至本段頭兩句，說(shuō)生態(tài)學(xué)家對(duì)于什么是生態(tài)系統(tǒng)的穩(wěn)定性依然存在爭(zhēng)議，C是原文的忠實(shí)改寫。第6題：According

25、 to paragraph 4, which of the following is true of climax communities?A：They are more resilient than pioneer communities.B：They can be considered both the most and the least stable communities.C：They are stable because they recover quickly after major disturbances.D：They are the most resilient commu

26、nities because they change the least over time.題目解析關(guān)于climax communities原文有兩個(gè)地方提到。因?yàn)樯鷳B(tài)學(xué)家對(duì)什么是穩(wěn)定這個(gè)問(wèn)題存在兩個(gè)觀點(diǎn)，以不變這種觀點(diǎn)看，climax是最穩(wěn)定的，以快速恢復(fù)這種觀點(diǎn)看，climax是最不穩(wěn)定的，所以climax既穩(wěn)定也不穩(wěn)定，B明確說(shuō)到兩個(gè)方面，其它選項(xiàng)都只說(shuō)到一個(gè)方面。第7題：Which of the following can be inferred from paragraph 5 about redwood forests?A：They become less stable as t

27、hey mature.B：They support many species when they reach climax.C：They are found in temperate zones.D：They have reduced diversity during mid-successional stages.題目解析以redwood forest做關(guān)鍵詞定位至原文第三句，事實(shí)上這個(gè)redwood是前句的一個(gè)具體例子，前面句說(shuō)至少在溫帶，mid是最穩(wěn)定的，不是climax，緊接著就舉了一個(gè)redwood的例子，可以推斷redwood是溫帶植物，C是答案。A/B/D都與原文意思相反，而且B

28、和D基本上意思一樣，都不對(duì)。第8題：The word “guarantee” in the passage is closest in meaning toA：increaseB：ensureC：favorD：complicate題目解析本句中有個(gè)likewise，說(shuō)明它與前面句子構(gòu)成類比，前句說(shuō)diversity does not ensure stability, 后文的內(nèi)容幾乎和前句一模一樣，除了動(dòng)詞被替換，因此guarantee的意思就是ensure。第9題：In paragraph 5, why does the author provide the information that

29、 “A fifteen-speed racing bicycle is more likely to break down than a childs tricycle”?A：To illustrate a general principle about the stability of systems by using an everyday exampleB：To demonstrate that an understanding of stability in ecosystems can be applied to help understand stability in other

30、situationsC：To make a comparison that supports the claim that, in general, stability increases with diversityD：To provide an example that contradicts mathematical models of ecosystems題目解析括號(hào)的作用是解釋括號(hào)之前的文字，前文說(shuō)系統(tǒng)越復(fù)雜越容易壞，后面舉了十五速賽車和小孩子的三輪車的例子，三輪車明顯比賽車簡(jiǎn)單，所以就是支持前文，A正確，C正好說(shuō)反，其他都沒(méi)說(shuō)。第10題：The word “pales” in th

31、e passage is closest in meaning toA：increases proportionallyB：differsC：loses significanceD：is common題目解析pale蒼白，使什么什么蒼白之意。單詞所在句之前說(shuō)很多climax communities都被人類破壞了，也就是強(qiáng)調(diào)人的破話很嚴(yán)重。后面舉了個(gè)例子，說(shuō)圣海倫斯火山爆發(fā)造船的破壞還沒(méi)有人類活動(dòng)的破壞嚴(yán)重，所以C選項(xiàng)lose significance正確。第11題：Which of the sentences below best expresses the essential informa

32、tion in the highlighted sentence in the passage? Incurred choices change the meaning in important ways or leave out essential information.A：Ecologists now think that the stability of an environment is a result of diversity rather than patchiness.B：Patchy environments that vary from place to place do

33、 not often have high species diversity.C：Uniform environments cannot be climax communities because they do not support as many types of organisms as patchy environments.D：A patchy environment is thought to increase stability because it is able to support a wide variety of organisms.題目解析原文的結(jié)構(gòu)是生態(tài)系統(tǒng)的長(zhǎng)期

34、穩(wěn)定性不是因?yàn)閎lablabla，而是因?yàn)閎lablabla，又對(duì)這個(gè)進(jìn)行了解釋，說(shuō)物種多；A說(shuō)反；B錯(cuò)，因?yàn)樵臎](méi)有說(shuō)patchiness和diversity是矛盾的；C錯(cuò)，因?yàn)樵谋容^的是patchiness和uniform，而C直接將patchiness和climax進(jìn)行比較，偷換概念；D正確，注意原文貌似沒(méi)有明顯的因果關(guān)系，因此可能單看句子間關(guān)系的話會(huì)排除D，但原文后半句整個(gè)是對(duì)patchiness的一種解釋，所以存在不明顯的因果關(guān)系。第12題：The word “adjacent” in the passage is closest in meaning toA：foreignB：s

35、tableC：fluidD：neighboring題目解析adjacent是相鄰之意，原文說(shuō)本地的population滅絕的話會(huì)被哪里來(lái)的群落補(bǔ)充，可能的只有foreign和neighboring，這兩個(gè)選項(xiàng)代入原文都是可以的，除知道這個(gè)單詞的意思之外，還可以認(rèn)為相鄰的群落更有可能迅速補(bǔ)充，而外來(lái)的范圍太大，不對(duì)。第13題：Look at the four squares that indicate where the following sentence could be added to the passage. Where would the sentence best fit?In f

36、act, damage to the environment by humans is often much more severe than damage by natural events and processes. 題目解析根據(jù)待插入句中的human判斷，A/B/C是可能的，natural events and processes自然的過(guò)程，與第二句中的圣海倫斯火山爆發(fā)是同義替換，所以B/C可能正確，但按照先理論后實(shí)例的原則，正確答案是B不是C。第14題：Directions: An introductory sentence for a brief summary of the passage is provided below. Complete the summary by selecting the THREE answer choices