TPO托福閱讀真題答案及解析
TPO是我們常用的托福模考工具，對我們的備考很有價值，下面小編給大家帶來TPO托福閱讀真題答案及解析。
TPO托福閱讀真題答案及解析
托福閱讀真題：
The Long-Term Stability of Ecosystems
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 pioneer 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 changes—in plant numbers and the mix of species—are cumulative. Climax communities themselves change but over periods of time greater than about 500 years.
An ecologist who studies a pond today may well find it relatively unchanged in a year’s 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.
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 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 invasion 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.
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, 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 called 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.
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. Once 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 stability—just 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 child’s tricycle.
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.
Many ecologists now think that the relative long-term stability of climax communities comes not from diversity but from the “patchiness” of the environment, 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 the niche vacated by the extinct population and keep the food web intact.
Paragraph 1: 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 pioneer 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 changes—in plant numbers and the mix of species—are cumulative. Climax communities themselves change but over periods of time greater than about 500 years.
TPO托福閱讀題目
1. The word “particular” in the passage is closest in meaning to
○Natural
○Final
○Specific
○Complex
2. According to paragraph 1, which of the following is NOT true of climax communities?
○They occur at the end of a succession.
○They last longer than any other type of community.
○The numbers of plants in them and the mix of species do not change.
○They remain stable for at least 500 years at a time.
Paragraph 2: An ecologist who studies a pond today may well find it relatively unchanged in a year’s 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.
3. According to paragraph 2, which of the following principles of ecosystems can be learned by studying a pond?
○Ecosystem properties change more slowly than individuals in the system.
○The stability of an ecosystem tends to change as individuals are replaced.
○Individual organisms are stable from one year to the next.
○A change in the members of an organism does not affect an ecosystem’s properties
Paragraph 3: 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 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 invasion 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 of pests.
4. According to paragraph 3, ecologists once believed that which of the following illustrated the most stable ecosystems?
○Pioneer communities
○Climax communities
○Single-crop farmlands
○Successional plant communities
Paragraph 4: 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, 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 called 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.
5. According to paragraph 4, why is the question of ecosystem stability complicated?
○The reasons for ecosystem change are not always clear.
○Ecologists often confuse the word “stability” with the word “resilience.”
○The exact meaning of the word “stability” is debated by ecologists.
○There are many different answers to ecological questions.
6. According to paragraph 4, which of the following is true of climax communities?
○They are more resilient than pioneer communities.
○They can be considered both the most and the least stable communities.
○They are stable because they recover quickly after major disturbances.
○They are the most resilient communities because they change the least over time.
Paragraph 5: 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. Once 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 stability—just 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 child’s tricycle.)
7. Which of the following can be inferred from paragraph 5 about redwood forests?
○They become less stable as they mature.
○They support many species when they reach climax.
○They are found in temperate zones.
○They have reduced diversity during mid-successional stages.
8. The word “guarantee” in the passage is closest in meaning to
○Increase
○Ensure
○Favor
○Complicate
9. In paragraph 5, why does the author provide the information that “(A fifteen-speed racing bicycle is more likely to break down than a child’s tricycle)”?
○To illustrate a general principle about the stability of systems by using an everyday example
○To demonstrate that an understanding of stability in ecosystems can be applied to help understand stability in other situations
○To make a comparison that supports the claim that, in general, stability increases with diversity
○To provide an example that contradicts mathematical models of ecosystems
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.
10. The word “pales” in the passage is closest in meaning to
○Increases proportionally
○Differs
○Loses significance
○Is common
Paragraph 7：Many ecologists now think that the relative long-term stability of climax communities comes not from diversity but from the “patchiness” of the environment, 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 the niche vacated by the extinct population and keep the food web intact.
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：
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托福閱讀真題譯文：
生態系統的長期穩定
植物群體可以自由地聚集，他們特殊的結構取決于聚集區域的具體歷史。生態學家使用“演替”來詮釋植物群落和生態系統隨著時間推移所發生的變化。演替中的第一個群落被稱作先鋒群落，而處于演替最后那個長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，植物數量和混合種類數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。
現代一個研究池塘的生態學會發現池塘在一年當中相對而言是不變的。個別魚類可能被替換，但一年一年魚的總數都趨于一致。也就是說，生態系統自身的性質比組成生態系統的單個生物體更為穩定。
生態學家們一度認為物種的多樣性使生態系統穩定，生態系統物種越多樣則生態系統越穩定。通過觀察得出的結論支持了這個觀點，長期持久的頂極群落通常要比先鋒群落具備更為復雜的食物網和更多的物種。生態學家家們得出的結論是：頂點生態系統的穩定性明顯取決于他們的復雜化程度。舉個極端的例子，在單一作物的農田中，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，在一個復雜的頂極群落里，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，生態系統穩定性的問題非常復雜。首先，不是所有的生態學家都贊同“穩定”的含義。穩定性可以簡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定的，因為根據定義，他們隨著時間推移而變化是最少。另外，穩定性也可以界定為生態系統在經歷了嚴重破壞之后回復原貌的速度，比如火災。這種穩定性也被稱作彈性。在這種情況下，頂極群落將是最脆弱和最不穩定的，因為他們可能需要數百年時間才能恢復到頂點狀態。
即使是這種被定義為簡單地缺乏變化的穩定性并非總是與最多樣的物種聯系起來。至少在溫帶地區，會經常在演替過程中發現最多物種，而不是在頂極群落中。例如，紅樹林一旦成熟，其中的物種數量以及單個物種的數量都會減少。總的來說，多樣性本身并不能保證穩定性，生態系統的數學模型也可以得出同樣的結論。一般來說，一個更復雜的系統可能比一個簡單的系統更容易被破壞(一個十五速的賽車比一個孩子的三輪車更容易損壞)。
生態學家們更想弄清楚到底哪些因素有助于促成群落的恢復，因為世界各地的頂極群落都因為人類活動而遭受到嚴重的損壞或毀壞。就像美國西北部圣海倫火山的猛烈噴發所造成的破壞，在人類活動對環境造成的的破壞面前也相形見絀。我們必須了解對群落抵抗破壞和恢復來說哪些是最重要的。
現在的很多生態學家們認為，頂極群落相對長期的穩定性并非來于自多樣性，而是來自環境的“補綴”，隨處變化的環境比統一的環境更有利于多種有機體的生存。當地物種滅亡后，馬上就會被相鄰群落的移民取代。即便是另一種不同的物種，他們也可以填補那些已滅絕生物的空缺，并保持食物網的完整。
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