『新东方在线托福阅读』为托福考生准备了ETS托福TPO/Official 32 Passage 1阅读练习：The word “viable” in the passage is closest in meaning to真题题目及答案解析，TPO/Official 32 Passage 1阅读原文范文音频翻译

托福TPO/Official 32 Passage 1阅读原文The word “viable” in the passage is closest in meaning to题目答案及解析-新东方托福官方网校手机版

定居是植物改变一个地点生态环境的一种方式。

Colonization is one way in which plants can change the ecology of a site.

定居是一个过程，它由两部分组成：入侵和生存。

Colonization is a process with two components: invasion and survival.

植物在某一地点的定居率既取决于个体有机体(种子、孢子、未成熟或成熟个体)到达该地点的比率，也取决于它们在定居和存活方面的成功率。

The rate at which a site is colonized by plants depends on both the rate at which individual organisms (seeds, spores, immature or mature individuals) arrive at the site and their success at becoming established and surviving.

一个可供定居的地点——一个安全的地点，在很大程度上决定了定居的成功，在这个地点，火灾或砍伐树木的干扰要么将竞争物种消除，要么将竞争和其他负面互动降低到入侵物种能够建立起来的水平。

Success in colonization depends to a great extent on there being a site available for colonization—a safe site where disturbance by fire or by cutting down of trees has either removed competing species or reduced levels of competition and other negative interactions to a level at which the invading species can become established.

在给定的入侵率下，植物在湿润、肥沃的地点的定居可能比干燥、贫瘠的地点快得多，这是因为后一种环境下的存活率很低。

For a given rate of invasion, colonization of a moist, fertile site is likely to be much more rapid than that of a dry, infertile site because of poor survival on the latter.

一块肥沃的犁地会迅速受到各种杂草的侵袭，而邻近的建筑工地，土壤被压实或移走，暴露出粗糙、贫瘠的母质，尽管收到了与犁地相同的种子输入，但实际上可能在几个月甚至几年内没有植被。

A fertile, plowed field is rapidly invaded by a large variety of weeds, whereas a neighboring construction site from which the soil has been compacted or removed to expose a coarse, infertile parent material may remain virtually free of vegetation for many months or even years despite receiving the same input of seeds as the plowed field.

不同植物的入侵率和灭绝速率都有很大差异。

Both the rate of invasion and the rate of extinction vary greatly among different plant species.

先锋物种——那些只出现在定居最早阶段的物种——往往有很高的入侵率，因为它们会产生数量非常多的生殖繁殖体(种子、孢子等)，并且它们有一种有效的传播方式(通常是风媒传播)。

Pioneer species—those that occur only in the earliest stages of colonization—tend to have high rates of invasion because they produce very large numbers of reproductive propagules (seeds, spores, and so on) and because they have an efficient means of dispersal (normally, wind).

如果定居植物产生短暂存活的生殖繁殖体，那么它们必须产生数量非常大的生殖繁殖体，除非它们有有效的方式扩散到合适的新栖息地。

If colonizers produce short-lived reproductive propagules, then they must produce very large numbers unless they have an efficient means of dispersal to suitable new habitats.

许多植物依靠风进行传播，并且还产生大量小的、相对短暂存活的种子，它们以此弥补一种现实情况，即风并不总是（种子）到达适当类型栖息地的可靠媒介。

Many plants depend on wind for dispersal and produce abundant quantities of small, relatively short-lived seeds to compensate for the fact that wind is not always a reliable means of reaching the appropriate type of habitat.

一些植物已经进化出了替代策略，例如那些产出较少但较大种子的植物，它们的种子被鸟类或小型哺乳动物扩散到合适的位置，或者产出长寿命种子的植物。

Alternative strategies have evolved in some plants, such as those that produce fewer but larger seeds that are dispersed to suitable sites by birds or small mammals or those that produce long-lived seeds.

许多森林植物似乎表现出后一种适应：在一些森林的地面上可以发现大量可自行发育的先锋物种的种子。

Many forest plants seem to exhibit the latter adaptation, and viable seeds of pioneer species can be found in large numbers on some forest floors.

例如，在不列颠哥伦比亚省沿海的一片百年道格拉斯冷杉/西部铁杉森林中，每平方米发现了多达1125个可存活的种子。

For example, as many as 1,125 viable seeds per square meter were found in a 100-year-old Douglas fir/western hemlock forest in coastal British Columbia.

几乎所有从这个种子库发芽的种子都来自先锋物种。

Nearly all the seeds that had germinated from this seed bank were from pioneer species.

这些地点在受到干扰后迅速发生定居，这无疑在一定程度上反映了森林地面上巨大的种子库（的情况）。

The rapid colonization of such sites after disturbance is undoubtedly in part a reflection of the large seed bank on the forest floor.

在定居物种中发展良好的一种适应性是发芽(种子开始生长)的高度差异。

An adaptation that is well developed in colonizing species is a high degree of variation in germination (the beginning of a seed’s growth).

特定物种的种子表现出广泛的发芽日期，从而增加了至少部分种子在有利的环境条件下发芽的可能性。

Seeds of a given species exhibit a wide range of germination dates, increasing the probability that at least some of the seeds will germinate during a period of favorable environmental conditions.

这对于定居在没有现有植被来改善极端气候影响，从而可能导致极大的气候差异的环境中的物种显得极其重要。

This is particularly important for species that colonize an environment where there is no existing vegetation to ameliorate climatic extremes and in which there may be great climatic diversity.

植物群落中的物种演替（即物种出现和消失的时间序列）取决于一个物种的生命史上不同阶段发生的事件。

Species succession in plant communities, i.e., the temporal sequence of appearance and disappearance of species, is dependent on events occurring at different stages in the life history of a species.

入侵率和生长率的变化在确定演替模式，特别是次生演替中起着重要作用。

Variation in rates of invasion and growth plays an important role in determining patterns of succession, especially secondary succession.

最先在一个地点定居的物种是那些产生大量种子的物种，这些种子成功地分布到新的地点。

The species that are first to colonize a site are those that produce abundant seed that is distributed successfully to new sites.

这类物种通常生长迅速，在新的地点迅速占据主导地位，阻止了其他入侵率和生长率较低的物种进入。

Such species generally grow rapidly and quickly dominate new sites, excluding other species with lower invasion and growth rates.

因此，占据受干扰区域的第一个群落可能由入侵速率最高的物种组成，而随后阶段的群落可能由存活率相近但入侵速率较低的植物组成。

The first community that occupies a disturbed area therefore may be composed of species with the highest rate of invasion, whereas the community of the subsequent stage may consist of plants with similar survival rates but lower invasion rates.

According to paragraph 1, how does disturbance of a site influence its colonization by a plant species?

Why does the author mention a plowed field and a construction site in the passage?

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.

What can be inferred from paragraph 3 about the reason that large seeds are dispersed by birds or small animals rather than by the wind?

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

The example of the 100-year-old Douglas fir/western hemlock forest in paragraph 3 illustrates which of the following ideas?

According to paragraph 4, how do plants manage to germinate in areas with great climatic diversity and climatic extremes?

According to paragraph 5, which of the following determines the sequence in which plant species will colonize a site?

Look at the four squares  that indicate where the following sentence could be added to the passage. They require relatively little protection or nutrients.  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.

Plant Colonization Colonization is one way in which plants can change the ecology of a site. Colonization is a process with two components: invasion and survival. The rate at which a site is colonized by plants depends on both the rate at which individual organisms (seeds, spores, immature or mature individuals) arrive at the site and their success at becoming established and surviving. Success in colonization depends to a great extent on there being a site available for colonization—a safe site where disturbance by fire or by cutting down of trees has either removed competing species or reduced levels of competition and other negative interactions to a level at which the invading species can become established. For a given rate of invasion, colonization of a moist, fertile site is likely to be much more rapid than that of a dry, infertile site because of poor survival on the latter. A fertile, plowed field is rapidly invaded by a large variety of weeds, whereas a neighboring construction site from which the soil has been compacted or removed to expose a coarse, infertile parent material may remain virtually free of vegetation for many months or even years despite receiving the same input of seeds as the plowed field. Both the rate of invasion and the rate of extinction vary greatly among different plant species. Pioneer species—those that occur only in the earliest stages of colonization—tend to have high rates of invasion because they produce very large numbers of reproductive propagules (seeds, spores, and so on) and because they have an efficient means of dispersal (normally, wind). If colonizers produce short-lived reproductive propagules, then they must produce very large numbers unless they have an efficient means of dispersal to suitable new habitats. Many plants depend on wind for dispersal and produce abundant quantities of small, relatively short-lived seeds to compensate for the fact that wind is not always a reliable means of reaching the appropriate type of habitat. Alternative strategies have evolved in some plants, such as those that produce fewer but larger seeds that are dispersed to suitable sites by birds or small mammals or those that produce long-lived seeds. Many forest plants seem to exhibit the latter adaptation, and viable seeds of pioneer species can be found in large numbers on some forest floors. For example, as many as 1,125 viable seeds per square meter were found in a 100-year-old Douglas fir/western hemlock forest in coastal British Columbia. Nearly all the seeds that had germinated from this seed bank were from pioneer species. The rapid colonization of such sites after disturbance is undoubtedly in part a reflection of the large seed bank on the forest floor. An adaptation that is well developed in colonizing species is a high degree of variation in germination (the beginning of a seed’s growth). Seeds of a given species exhibit a wide range of germination dates, increasing the probability that at least some of the seeds will germinate during a period of favorable environmental conditions. This is particularly important for species that colonize an environment where there is no existing vegetation to ameliorate climatic extremes and in which there may be great climatic diversity. Species succession in plant communities, i.e., the temporal sequence of appearance and disappearance of species, is dependent on events occurring at different stages in the life history of a species.  Variation in rates of invasion and growth plays an important role in determining patterns of succession, especially secondary succession.  The species that are first to colonize a site are those that produce abundant seed that is distributed successfully to new sites.  Such species generally grow rapidly and quickly dominate new sites, excluding other species with lower invasion and growth rates. The first community that occupies a disturbed area therefore may be composed of species with the highest rate of invasion, whereas the community of the subsequent stage may consist of plants with similar survival rates but lower invasion rates.