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智 课 网 雅 思 备 考 资 料 雅思阅读真题演练 熟悉文章结构与出题规律 雅思阅读的文章和题目都有一定的规律性，比如说雅思阅读文段一 般是总分总的格式，考生重点关注首段，尾段，转折句，开头句，基本 上就能找到主题句，从这个方面来说，练习雅思阅读真题，从中总结雅 思阅读考试经验是十分必要的。 雅思阅读的文章和题目都有一定的规律性，比如说雅思阅读文段一 般是总分总的格式，考生重点关注首段，尾段，转折句，开头句，基本 上就能找到主题句，从这个方面来说，练习雅思阅读真题，从中总结雅 思阅读考试经验是十分必要的，下面小编为大家整理一份“TPO雅思阅 读真题答案及解析”，希望对大家有所帮助。 雅思阅读真题： 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 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 c