对于托福阅读的备考，同学们最重要就是要多练习，除了了解托福阅读考试的特点和适应托福阅读考试的考试形式，还可以增强做题语感，因为阅读题目最重要的就是语感。下面新航道托福小编跟大家分享托福阅读TPO3真题及答案：The Long-Term Stability of Ecosystems ，供大家练习参考：

　　托福阅读TPO3真题：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 thatcompose 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.

　　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.

　　Paragraph 1:

　　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:

　　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:

　　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:

　　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:

　　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:

　　10. The word “pales” in the passage is　closest in meaning to

　　○Increases proportionally

　　○Differs

　　○Loses significance

　　○Is common

　　Paragraph 7：

　　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:

　　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.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TPO03 The Long-Term Stability of Ecosystems参考答案：

　　1. ○3 2. ○3 3. ○1 4. ○2 5. ○3

　　6. ○2 7. ○3 8. ○2 9. ○1 10. ○3

　　11. ○4 12. ○4 13. ○2 14. ○2 3 5

　　以上就是我跟大家分享的关于一篇托福阅读TOP及答案，希望对大家有所帮助！最后预祝大家在托福考试中取得好成绩！