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1、http:/托福阅读原文分析TPO3 生态系统的长期稳定托福阅读原文分析TPO3 生态系统的长期稳定TPO 是托福备考圣经，但是并不是有“圣经”就能完全把握托福考试。还要看大家怎么去利用这份资料。关于 TPO 阅读TPO 阅读，托福小编希望最大限度地利用这些 ETS 提供的阅读文章。在文章中，找到那些生词，长难句；分析文章结构。真正把它作为一份备考资料，而不是做题工具。今天托福小编分享给大家的是对 TPO3 The Long-Term Stability of EcosystemsThe Long-Term Stability of Ecosystems 的文章详细分析。一起学习吧。The L
2、ong-Term Stability of EcosystemsThe Long-Term Stability of Ecosystems生态系统的长期稳定生态系统的长期稳定1.Plant communities assemble themselves flexibly, and their particular structuredepends on the specific history of the area. Ecologists use the term “succession” to referto the changes that happen in plant communi
3、ties and ecosystems over time. The first communityin a succession is called a pioneer community, while the long-lived community at the endof succession is called a climax community. Pioneer and successional plant communities aresaid to change over periods from 1 to 500 years. These changesin plant n
4、umbers and themix of speciesare cumulative. Climax communities themselves change but over periods oftime greater than about 500 years.植物群体可以自由地聚集，它们特殊的结构取决于聚集区域的具体历史。生态学家使用“演替”来诠释植物群落和生态系统随着时间推移所发生的变化。演替中的第一个群落被称作先锋群落，而处于演替最后那个长期生存的群落被称为顶极群落。先锋群落和紧接着的植物群落的变化周期是从1 到 500 年不等，植物数量和混合种类数量的变化是慢慢积累的。顶极群落本
5、身也改变，但其变化周期超过 500 年。引出演替、先锋群落和顶极群落的概念。2.An ecologist who studies a pond today may well find it relatively unchanged in a years time. Individual fish may be replaced, but the number of fish will tend to be the samefrom one year to the next. We can say that the properties of an ecosystem are more stab
6、lethan the individual organisms that compose the ecosystem.现代一个研究池塘的生态学会发现池塘在一年当中相对而言是不变的。个别鱼类可能被替换，但年复一年鱼的总数都趋于一致。也就是说，一个生态系统自身的属性要比由单一生物体组成的生http:/态系统更稳定。一个生态系统自身的属性要比由单一生物体组成的生态系统更稳定。3.At one time, ecologists believed that species diversity made ecosystems stable. Theybelieved that the greater th
7、e diversity the more stable the ecosystem. Support for thisidea came from the observation that long-lasting climax communities usually have morecomplex food webs and more species diversity than pioneer communities. Ecologists concludedthat the apparent stability of climax ecosystems depended on thei
8、r complexity. To take anextreme example, farmlands dominated by a single crop are so unstable that one year of badweather or the invasion of a single pest can destroy the entire crop. In contrast, a complexclimax community, such as a temperate forest, will tolerate considerable damage from weatherto
9、 pests.生态学家们一度认为物种的多样性使生态系统稳定，生态系统物种越多样则生态系统越稳定。通过观察得出的结论支持了这个观点，长期持久的顶极群落通常要比先锋群落具备更为复杂的食物网和更多的物种。生态学家家们得出的结论是：顶点生态系统的稳定性明显取决于他们的复杂化程度。举个极端的例子，在单一作物的农田中，一年的恶劣天气或单一害虫的入侵就可以摧毁所有作物。与此相反，在一个复杂的顶极群落里，如温带森林，他们便可以抵御来自气候和害虫的干扰和入侵。生态学家观点：物种的多样性使生态系统稳定，有证据。4.The question of ecosystem stability is complicated
10、, however. The first problem isthat ecologists do not all agree what “stability” means. Stability can be defined as simplylack 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 bedefine
11、d as the speed with which an ecosystem returns to a particular form following a majordisturbance, 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 requirehundreds of years to return to the
12、 climax state.不管怎样，生态系统稳定性的问题非常复杂。首先，不是所有的生态学家都赞同“稳定”的含义。稳定性可以简单地定义为缺乏变化。如果是这样的话，顶极群落将被视为最稳定的，因为根据定义，他们随着时间推移而变化得最少。另外，稳定性也可以界定为生态系统在经历了严重破坏之后回复原貌的速度，比如火灾。这种稳定性也被称作弹性。在这种情况下，顶极群落将是最脆弱和http:/最不稳定的，因为他们可能需要数百年时间才能恢复到顶点状态。5.Even the kind of stability defined as simple lack of change is not always assoc
13、iatedwith maximum diversity. At least in temperate zones, maximum diversity is often found inmid-successional stages, not in the climax community. Once a redwood forest matures, forexample, the kinds of species and the number of individuals growing on the forest floorare reduced. In general, diversi
14、ty, by itself, does not ensure stability. Mathematicalmodels of ecosystems likewise suggest that diversity does not guarantee ecosystem stabilityjust the opposite, in fact. A more complicated system is, in general, more likely thana simple system to break down. A fifteen-speed racing bicycle is more
15、 likely to break downthan a childs tricycle.即使是这种被定义为简单地缺乏变化的稳定性并非总是与最多样的物种联系起来。至少在温带地区，会经常在演替过程中发现最多物种，而不是在顶极群落中。例如，红杉树林一旦成熟，其中的物种数量以及单个物种的数量都会减少。一般来说，多样性本身并不能保证稳定性(事实上正相反)，生态系统的数学模型也可以得出同样的结论。一个更复杂的系统可能比一个简单的系统更容易被破坏(一个十五速的赛车比一个孩子的三轮车更容易损坏)。生态系统稳定性的问题非常复杂。6.Ecologists are especially interested to
16、know what factors contribute to theresilience of communities because climax communities all over the world are being severelydamaged or destroyed by human activities. The destruction caused by the volcanic explosionof Mount St. Helens, in the northwestern United States, for example, pales in comparisonto the destruction caused by humans. We need to know what aspects of a community are mostimportant to the communitys resistance to destruction, as wel
