托福阅读满分是一种怎样的体验？

　　托福阅读总结题考察考生抓取每个段落中心的能力。新东方在线托福网为大家带来托福阅读满分是一种怎样的体验，希望对大家托福备考有所帮助。更多精彩尽请关注新东方在线托福网!

　　托福阅读中的总结题是导致很多学生不能拿满分的原因，总结题考察考生抓取每个段落中心的能力。下面老师给各位考生写出了TPO3 The Long-Term Stability of Ecosystems每个段落的中心，如果你们在课下能够每个段落抓成这样，那就意味着你抓住了这个段落的中心，进而说明你能够做对托福阅读中让很多考生云山雾罩的托福最后一题总结题也就是6选3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.

　　第一段段落中心： 介绍了两个概念Pioneer community和Climax community。

　　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.

　　第二段段落中心：生态系统比组成它的单个生物体更稳定。

　　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 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.

　　第三段段落中心：生态学家曾经认为物种多样性使生态系统更稳定。

　　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.

　　第四段段落中心：根据稳定性的定义，climax community可以是最稳定也可以是最不稳定的。

　　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.

　　第五段段落中心：当稳定性被定义为缺乏变化的时候，也不总是与最大的多样性有关。

　　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.

　　第六段段落中心：生态学家想知道什么对顶级群落的恢复力有帮助。

　　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.

　　第七段段落中心：生态学家现在认为顶级群落的长期稳定不是来自于多样性而是因为环境的斑块分布。

　　以上就是新东方在线托福网为你带来的托福阅读满分是一种怎样的体验，更多精彩敬请关注新东方在线托福网。