TPO 19-2 Succession Climax and Ecosystems（生命科学--生态系统）

字数：694

建议做题时间20分钟

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. 

Even less fortunate was the extension of this type of thinking to include animals as well as plants. This resulted in the "biome," a combination of coexisting flora and fauna. Though it is true that many animals are strictly associated with certain plants, it is misleading to speak of a "spruce-moose biome," for example, because there is no internal cohesion to their association as in an organism. The spruce community is not substantially affected by either the presence or absence of moose. Indeed, there are vast areas of spruce forest without moose. The opposition to the Clementsian concept of plant ecology was initiated by Herbert Gleason, soon joined by various other ecologists. Their major point was that the distribution of a given species was controlled by the habitat requirements of that species and that therefore the vegetation types were a simple consequence of the ecologies of individual plant species.

With "climax," "biome," "superorganism," and various other technical terms for the association of animals and plants at a given locality being criticized, the term "ecosystem" was more and more widely adopted for the whole system of associated organisms together with the physical factors of their environment. Eventually, the energy-transforming role of such a system was emphasized. Ecosystems thus involve the circulation, transformation, and accumulation of energy and matter through the medium of living things and their activities. The ecologist is concerned primarily with the quantities of matter and energy that pass through a given ecosystem, and with the rates at   which they do so.

Although the ecosystem concept was very popular in the 1950s and 1960s, it is no longer the dominant paradigm. Gleason's arguments against climax and biome are largely valid against ecosystems as well. Furthermore, the number of interactions is so great that they are difficult to analyze, even with the help of large computers. Finally, younger ecologists have found ecological problems involving behavior and life-history adaptations more attractive than measuring physical constants. Nevertheless, one still speaks of the ecosystem when referring to a local association of animals and plants, usually without paying much attention to the energy aspects.

题目

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答案解析

1. 事实信息题

解析：本段很短，快速看完，都在说C的观点。A原文无比较。B虽然是对的，但是答非所问，不是C的观点。C对应最后一句，对。D原文没说do not change.

2. 词汇题（but，上下文）

解析：这句话说C在order of succession中发现了什么，但是这个发现not substantiated，猜测是没有得到证实，选A。Substantiate证实

3. 词汇题（but，general trend, details)

解析：trend倾向，选D。

4. 词汇题

解析：likewise同样地，选B

5. 词汇题（词根）

解析：legitimate合法的、正当的、合理的，选D

6. 事实信息题

解析：根据引号词定位到最后一句，说作家更喜欢用association是为了强调互动的松弛，与A选项not tight network对应，选A

7. 事实信息题

解析：根据引号词定位到第2句，但这句话没有说明作家的反驳，继续往后看，后句就说这是misleading的，因为没有内聚力，选A

8. 修辞目的题

解析：这句话接前句递进说明moose不会影响spruce，而前句又是在说明Though it is true这句话后半部分的观点spruce-moose biome这种说法是misleading，所以选D

9. 词汇题

解析：initiate开启，选C

10. 事实信息题

解析：根据Gleason定位到倒数1-2句，说G不同于C的观点，G认为物种的分布是由该物种栖息地要求所控制的，而前文说物种之间是组合出现的，这些G的例子与前文相反，选B

11. 句子简化题

解析：原句结构为一些术语被批判，术语ecosystem运用广泛。A原文重点不是在强调两类术语所指内容的不同点，B原文不是在说一些比另一些术语更矛盾，C原文没有became too technical这层意思，选D

12. 事实信息题

解析：根据ecologist定位到最后一句，选D

13. 句子插入题

解析：插入句提到他们可能对研究适应力更有兴趣，说明前文应该会提到他们对什么不那么感兴趣。A前没有they可以指代的人群，直到C前才出现多人younger ecologists，选C

14. 段落小结题

解析：A对应第1段第3句，是细节且提供机会没讲，不选

B与第5段最后一句相反，不选

C与第7段第3句相反，且是细节，不选

D对应第2-3段首句，正确

E对应第4段第2句，正确

F对应第7段第1句，正确

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