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十九世纪末期，生态学逐渐从自然历史学和植物地理学中脱离出来，发展成为一门独立的科学。

In the late nineteenth century, ecology began to grow into an independent science from its roots in natural history and plant geography.

“群落生态学”这一新概念强调的是不同物种所构成的群落的组合方式与结构。

The emphasis of this new “community ecology” was on the composition and structure of communities consisting of different species.

二十世纪早期，美国生态学家弗雷德里克·克莱门茨指出，火山喷发、大洪水或森林火灾等动乱发生后，将会出现植物群落的演替现象。

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.

例如，一片弃耕田地会相继被草本植物（没有木质组织或木质组织很少的植物）、灌木和树木所占领，最终形成一片森林。

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.

喜光物种总是最先入侵，而耐荫物种在演替过程中出现得更晚些。

Light-loving species are always among the first invaders, while shade-tolerant species appear later in the succession.

克莱门茨和其他早期的生态学家发现演替的顺序呈定律般的规律，但这个规律还没有得到证实。

Clements and other early ecologists saw almost lawlike regularity in the order of succession, but that has not been substantiated.

人们能看出一个整体趋势，但是细节通常是不可预测的。

A general trend can be recognized, but the details are usually unpredictable.

演替的顺序会受到很多因素的影响：土壤类型、光照与风吹的程度，降水规律，植物偶然的建群以及很多其他随机的过程。

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.

演替的最终阶段被克莱门茨和其他早期的生态学家们称为顶级群落，顶级群落同样也是不可预测的，也没有统一的组合方式。

The final stage of a succession, called the climax by Clements and early ecologists, is likewise not predictable or of uniform composition.

物种的组合方式通常会发生很大的变动，即便是成熟的群落也是这样。

There is usually a good deal of turnover in species composition, even in a mature community.

影响演替顺序的因素同样会影响到顶级群落的类型。

The nature of the climax is influenced by the same factors that influenced succession.

不过，成熟的自然环境通常是处于平衡状态的。

Nevertheless, mature natural environments are usually in equilibrium.

它们随时间而发生的变化相对较小，除非环境本身发生变化。

They change relatively little through time unless the environment itself changes.

对于克莱门茨来说，顶级群落是一个“超有机体”，是一个有机实体。

For Clements, the climax was a “superorganism,” an organic entity.

即使是一些接受顶级群落概念的作者都反对克莱门茨将其称作超有机体，而这种称呼也确实是一个让人误解的比喻。

Even some authors who accepted the climax concept rejected Clements’ characterization of it as a superorganism, and it is indeed a misleading metaphor.

一个蚁群被叫做超有机体还比较恰当，因为蚁群的交流系统非常有条理，这让整个群体总是能够根据环境采取适当的集体工作模式。

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.

但是没有证据能够表明植物形成的顶级群落中也存在这种互相交流的系统。

But there is no evidence for such an interacting communicative network in a climax plant formation.

为了强调缺少交流的现象，很多作者更倾向于使用术语“群丛”而不是“群落”。

Many authors prefer the term “association” to the term “community” in order to stress the looseness of the interaction.

更不幸的是，这种观点从植物拓展到了动物。

Even less fortunate was the extension of this type of thinking to include animals as well as plants.

于是，便产生了“生物带”的概念，生物带是指动植物群落共存的结合体。

This resulted in the “biome,” a combination of coexisting flora and fauna.

虽然很多动物与某些植物有绝对的联系，但是，打个比方，取名“云杉驼鹿生物带”是具有误导性的，因为云杉和驼鹿的结合体并不像有机体一样存在内在的必然联系。

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.

云杉种群不会因为驼鹿的存在与否而受到很大影响。

The spruce community is not substantially affected by either the presence or absence of moose.

实际上，很多云杉林中都没有驼鹿。

Indeed, there are vast areas of spruce forest without moose.

赫伯特·格里森首先提出了对于克莱门茨学派植物生态学观点的反对，很快其他的生态学家也加入了反对的阵营。

The opposition to the Clementsian concept of plant ecology was initiated by Herbert Gleason, soon joined by various other ecologists.

他们的主要观点是，某个特定的物种的分布是由该物种所在栖息地的限制条件所决定的，因此，植物类型不同只是因为不同个体植物物种有不同生态环境而已。

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.

在“顶级群落”、“生物带”、“超有机体”和其他表示某个特定地区动植物结合而成的群体的专业术语都遭到了诟病的情况下，“生态系统”这一术语被越来越广泛地用来表示相互结合的有机体在它们所处环境的物理因素影响下所形成的整个系统。

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.

该系统最终强调的是其能量转换的功能。

Eventually, the energy-transforming role of such a system was emphasized.

因此，生态系统包含了通过生物和生物活动的媒介而进行的能量与物质间的循环、转换和积累。

Ecosystems thus involve the circulation, transformation, and accumulation of energy and matter through the medium of living things and their activities.

特定生态系统中物质和能量互相转换的量以及它们之间转换的速度，是生态学家最关心的问题。

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.

尽管生态系统的概念在二十世纪五六十年代期间非常流行，但它已经不是主流范式了。

Although the ecosystem concept was very popular in the 1950s and 1960s, it is no longer the dominant paradigm.

格里森反驳顶级群落和生物带的论点基本上也可以用来反驳生态系统。

Gleason’s arguments against climax and biome are largely valid against ecosystems as well.

此外，交互的次数很多，即便是借助大型电脑也难以分析。

Furthermore, the number of interactions is so great that they are difficult to analyze, even with the help of large computers.

最后，年轻的生态学家发现，行为和生命历史的适应性变化方面的生态学问题比测量物理常量更有吸引力。

Finally, younger ecologists have found ecological problems involving behavior and life-history adaptations more attractive than measuring physical constants.

不过，当人们还是会用生态系统来表示某个区域动植物的结合现象，而通常不会特别注意能量的方面了。

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.

According to paragraph 2, which of the following is a criticism of Clements’ view of succession?

The word “substantiated” in the passage is closest in meaning to

The word “trend” in the passage is closest in meaning to

The word “likewise” in the passage is closest in meaning to

The word “legitimately” in the passage is closest in meaning to

According to paragraph 4, why do many authors prefer the term “association” to “community” when describing a climax plant formation?

In paragraph 5, the author challenges the idea of a “biome” by noting that

Why does the author make the statement, “Indeed, there are vast areas of spruce forest without moose”?

The word “initiated” in the passage is closest in meaning to

According to paragraph 5, Gleason’s opposition to the Clementsian views of plant ecology was based on the claim that plant species grow in places where

Which of the sentences below best expresses the essential information in the highlighted sentence in the passage? Incorrect choices change the meaning in important ways or leave out essential information.

According to paragraph 6, what did ecologists mainly study when the ecosystem concept was the dominant paradigm?

Look at the four squares  that indicate where the following sentence could be added to the passage. They may be more interested in researching, for example, the adaptations that some aquatic animals undergo to survive in dry desert environments.  Where would the sentence best fit? Click on a square  to add the sentence to the passage.

Directions: An introductory sentence for a brief summary of the passage is provided below. Complete the summary by selecting the THREE answer choices that express the most important ideas in the passage. Some sentences do not belong in the summary because they express ideas that are not presented in the passage or are minor ideas in the passage. This question is worth 2 points.

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. 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.