托福閱讀模擬試題及答案：生態(tài)系統(tǒng)的長(zhǎng)期穩(wěn)定

11.Which of the sentences below best expresses the essential information in the highlighted sentence in the passage? Incurred choices change the meaning in important ways or leave out essential information.

○Ecologists now think that the stability of an environment is a result of diversity rather than patchiness.

○Patchy environments that vary from place to place do not often have high species diversity.

○Uniform environments cannot be climax communities because they do not support as many types of organisms as patchy environments.

○A patchy environment is thought to increase stability because it is able to support a wide variety of organisms.

12.The word “adjacent” in the passage is closest in meaning to

○Foreign

○Stable

○Fluid

○Neighboring

Paragraph 6: 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 activities. 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 community’s resistance to destruction, as well as its recovery.

13.Look at the four squares [ ] that indicate where the following sentence could be added to the passage.

In fact, damage to the environment by humans is often much more severe than damage by natural events and processes.

Where would the sentence best fit? Click on a square to add the sentence to the passage.

14.Directions: An introductory sentence for a brief summary of the passage is provided below. Complete the summary by selecting the THREE answer choices that express the most important ideas in the passage. Some sentences do not belong in the summary because they express ideas that are not presented in the passage or are minor ideas in the passage. This question is worth 2 points.

The process of succession and the stability of a climax community can change over time.

Answer choices

○The changes that occur in an ecosystem from the pioneer to the climax community can be seen in one human generation.

○A high degree of species diversity does not always result in a stable ecosystem.

○The level of resilience in a plant community contributes to its long-term stability.

○Ecologists agree that climax communities are the most stable types of ecosystems.

○Disagreements over the meaning of the term “stability” make it difficult to identify the most stable ecosystems.

○The resilience of climax communities makes them resistant to destruction caused by humans.

托福閱讀真題參考答案：

1. ○32. ○33. ○14. ○25. ○36. ○27. ○38. ○29. ○110. ○311. ○412. ○413. ○214. ○2 3 5

托福閱讀真題譯文：

生態(tài)系統(tǒng)的長(zhǎng)期穩(wěn)定

植物群體可以自由地聚集，他們特殊的結(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500年。

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)別魚類可能被替換，但一年一年魚的總數(shù)都趨于一致。也就是說，生態(tài)系統(tǒng)自身的性質(zhì)比組成生態(tài)系統(tǒng)的單個(gè)生物體更為穩(wěn)定。

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，他們便可以抵御來自氣候和害蟲的入侵。

不管怎樣，生態(tài)系統(tǒng)穩(wěn)定性的問題非常復(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)間推移而變化是最少。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)。

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。至少在溫帶地區(qū)， 會(huì)經(jīng)常在演替過程中發(fā)現(xiàn)最多物種，而不是在頂極群落中。例如，紅樹林一旦成熟，其中的物種數(shù)量以及單個(gè)物種的數(shù)量都會(huì)減少。總的來說，多樣性本身并不能保 證穩(wěn)定性，生態(tài)系統(tǒng)的數(shù)學(xué)模型也可以得出同樣的結(jié)論。一般來說，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)。

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?動(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)來說哪些是最重要的。

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)定性并非來于自多樣性，而是來自環(huán)境的“補(bǔ) 綴”，隨處變化的環(huán)境比統(tǒng)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。 

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