托福阅读模考软件TPO19文本解析(精)

合集下载

相关主题

托福阅读tpo文本

1、下载文档前请自行甄别文档内容的完整性，平台不提供额外的编辑、内容补充、找答案等附加服务。
2、"仅部分预览"的文档,不可在线预览部分如存在完整性等问题,可反馈申请退款(可完整预览的文档不适用该条件!)。
3、如文档侵犯您的权益，请联系客服反馈,我们会尽快为您处理(人工客服工作时间：9:00-18:30)。

智课网TOEFL备考资料

托福阅读模考软件TPO19文本+解析

摘要:小马托福资料下载栏目为大家提供最完整的TPO资料和TPO模考软件,其中本次分享的托福阅读模考软件TPO19文本+解析是TPO阅读中的一套,包含三篇文章每篇文章14道题目,形式与真实考试一样,考生们在练习的时候一定要将原文内容完全掌握然后再去作答。

阅读是托福考试最容易复习的一项了,但是大家还是不能轻易的放松,今天小编为大家带来的资料是托福阅读模考软件TPO19文本+解析,大家一起来看看本资料的精彩内容吧。

Succession, Climax, and Ecosystems

In the late nineteenth century, ecology began to grow into an independent science from its roots in natural history and plant geography. The emphasis of this new "community ecology" was on the composition and structure of communities consisting of different species. In the early twentieth century, the American ecologist Frederic Clements pointed out that a succession of plant communities would develop after a disturbance such as a volcanic eruption, heavy flood, or forest fire. An abandoned field, for instance, will be invaded successively by herbaceous plants (plants with little or no woody tissue, shrubs, and trees, eventually becoming a forest. Light-loving species are always among the first invaders, while shade-tolerant species appear later in the succession.

Clements and other early ecologists saw almost lawlike regularity in the order of succession, but that has not been substantiated. A general trend can be recognized, but the details are usually unpredictable. Succession is influenced by many factors: the nature of the soil, exposure to sun and wind, regularity of precipitation, chance colonizations, and many other random processes.

The final stage of a succession, called the climax by Clements and early ecologists, is likewise not predictable or of uniform composition. There is usually a good deal of turnover in species composition, even in a mature community. The nature of the climax is influenced by the same factors that influenced succession. Nevertheless, mature natural environments are usually in equilibrium. They change relatively little through time unless the environment itself changes.

For Clements, the climax was a "superorganism," an organic entity. Even some authors who accepted the climax concept rejected Clements' characterization of it as a superorganism, and it is indeed a misleading metaphor. An ant colony may be legitimately called a superorganism because its communication system is so highly organized that the colony always works as a whole and appropriately according to the circumstances. But there is no evidence for such an interacting communicative network in a climax plant formation. Many authors prefer the term "association" to the term "community" in order to stress the looseness of the interaction.

上述内容就是小编为大家准备的托福阅读模考软件TPO19文本+解析的部分内容,但是仅仅只是部分内容,大家可以点击下载按钮进行免费的下载,希望本资料对大家的备考有帮助。