『新东方在线托福阅读』为托福考生准备了ETS托福TPO/Official 36 Passage 1阅读练习：In paragraph 2, why does the author mention the activity of fungi in acidic soils?真题题目及答案解析，TPO/Official 36 Passage 1阅读原文范文音频翻译

托福TPO/Official 36 Passage 1阅读原文In paragraph 2, why does the author mention the activity of fungi in acidic soils?题目答案及解析-新东方托福官方网校手机版

活生物体在土壤形成中起着重要作用。

Living organisms play an essential role in soil formation.

生活在土壤中的大量动植物从土壤形成的母质中释放矿物质，提供有机质，帮助土壤的迁移（移动）和通气，并帮助保护土壤免受侵蚀。

The numerous plants and animals living in the soil release minerals from the parent material from which soil is formed, supply organic matter, aid in the translocation (movement) and aeration of the soil, and help protect the soil from erosion.

在土壤中生长或生活的生物体种类会极大地影响土壤的物理和化学特性。

The types of organisms growing or living in the soil greatly influence the soil’s physical and chemical characteristics.

实际上，对于世界许多地方的成熟土壤，人们认为自然植被的主要类型对土壤特性有着最重要的直接影响。

In fact, for mature soils in many parts of the world, the predominant type of natural vegetation is considered the most important direct influence on soil characteristics.

因此，土壤科学家只需知道土壤支持的植物种类，就可以在任何给定的区域中了解土壤的大部分特性。

For this reason, a soil scientist can tell a great deal about the attributes of the soil in any given area simply from knowing what kind of flora the soil supports.

因此，具有标志性植被的大草原和苔原地区也具有标志性的土壤。

Thus prairies and tundra regions, which have characteristic vegetations, also have characteristic soils.

土壤植物的数量和总重量通常超过土壤动物的数量和总重量。

The quantity and total weight of soil flora generally exceed that of soil fauna.

迄今为止，生活在土壤中的数量最多，最小的植物是细菌。

By far the most numerous and smallest of the plants living in soil are bacteria.

在有利的条件下，每立方厘米的土壤中可以栖息着一百万甚至更多的这些微小的单细胞植物。

Under favorable conditions, a million or more of these tiny, single-celled plants can inhabit each cubic centimeter of soil.

细菌比其他任何生物体都更能使岩石或其他母体物质逐渐转化为土壤。

It is the bacteria, more than any other organisms, that enable rock or other parent material to undergo the gradual transformation to soil.

一些细菌产生的有机酸会直接攻击母体物质，分解并释放出植物养分。

Some bacteria produce organic acids that directly attack parent material, breaking it down and releasing plant nutrients.

其他细菌分解有机垃圾（残渣），形成腐殖质（营养丰富的有机物）。

Others decompose organic litter (debris) to form humus (nutrient-rich organic matter).

第三类细菌栖息在称为豆类的植物的根系中。

A third group of bacteria inhabits the root systems of plants called legumes.

这些豆类包括许多重要的农作物，例如苜蓿、三叶草、大豆、豌豆和花生。

These include many important agricultural crops, such as alfalfa, clover, soybeans, peas, and peanuts.

豆类根瘤（根部的小肿块）中寄生的细菌将大气中的氮气转化为植物能够代谢的氮化合物，这一过程被称为固氮，使土壤更加肥沃。

The bacteria that legumes host within their root nodules (small swellings on the root) change nitrogen gas from the atmosphere into nitrogen compounds that plants are able to metabolize, a process, known as nitrogen fixation, that makes the soil more fertile.

其他微观植物在土壤发育中也很重要。

Other microscopic plants also are important in soil development.

例如，在酸性极高的土壤中，几乎没有细菌可以生存，真菌经常成为有机物的主要分解者。

For example, in highly acidic soils where few bacteria can survive, fungi frequently become the chief decomposers of organic matter.

相对于土壤，更复杂的植被形式起着至关重要的作用。

More complex forms of vegetation play several vital roles with respect to the soil.

树木，草和其他大型植物提供了土壤的大部分腐殖质。

Trees, grass, and other large plants supply the bulk of the soil’s humus.

这些植物在表面分解时释放的矿物质构成了后代植物以及其他土壤生物体的重要营养来源。

The minerals released as these plants decompose on the surface constitute an important nutrient source for succeeding generations of plants as well as for other soil organisms.

此外，树木可以将其根部延伸到土壤深处，并从地表以下吸收养分。

In addition, trees can extend their roots deep within the soil and bring up nutrients from far below the surface.

当树木掉落叶子或死亡和分解时，这些养分最终会丰富表层土壤。

These nutrients eventually enrich the surface soil when the tree drops its leaves or when it dies and decomposes.

最后，树木起着至关重要的作用：减缓了水的径流，并通过根系将土壤固定在适当的位置，从而抵抗了侵蚀。

Finally, trees perform the vital function of slowing water runoff and holding the soil in place with their root systems, thus combating erosion.

坡地的农业利用常常伴随着水土流失的加剧，这主要是由于坡地天然植被的保护层被破坏造成的。

The increased erosion that often accompanies agricultural use of sloping land is principally caused by the removal of its protective cover of natural vegetation.

和细菌相对应的动物类型是原生动物。

The faunal counterparts of bacteria are protozoa.

这些单细胞生物是动物王国中数量最多的代表，就像细菌一样，每一立方厘米的土壤中有时可以栖息100万或更多的细菌。

These single-celled organisms are the most numerous representatives of the animal kingdom, and, like bacteria, a million or more can sometimes inhabit each cubic centimeter of soil.

原生动物以有机物为食，并加速其分解。

Protozoa feed on organic matter and hasten its decomposition.

在其他栖居于土壤中的动物里，蚯蚓可能是最重要的。

Among other soil-dwelling animals, the earthworm is probably the most important.

在异常有利的条件下，多达一百万只蚯蚓（总体重超过450公斤）可能居住在一英亩的土壤上。

Under exceptionally favorable conditions, up to a million earthworms (with a total body weight exceeding 450 kilograms) may inhabit an acre of soil.

蚯蚓摄入大量土壤，对其进行化学上的改变，然后将其作为有机物（粪便）排泄出去。

Earthworms ingest large quantities of soil, chemically alter it, and excrete it as organic matter called casts.

The casts form a high-quality natural fertilizer.

此外，蚯蚓在垂直和水平方向搅拌土壤，改善了土壤的通风和排水性能。

In addition, earthworms mix soil both vertically and horizontally, improving aeration and drainage.

在有利的气候和土壤条件下，蚂蚁和白蚁等昆虫也可能数量众多。

Insects such as ants and termites also can be exceedingly numerous under favorable climatic and soil conditions.

此外，哺乳动物，如鼹鼠、田鼠、地鼠和土拨鼠有时数量充足，足以对土壤产生重大影响。

In addition, mammals such as moles, field mice, gophers, and prairie dogs sometimes are present in sufficient numbers to have significant impact on the soil.

这些动物主要是机械地耕作土壤。

These animals primarily work the soil mechanically.

结果，土壤被充气，打碎，施肥并被带到地表，加速了土壤的发育。

As a result, the soil is aerated, broken up, fertilized, and brought to the surface, hastening soil development.

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

According to paragraph 1, which of the following factors is the most important in determining the characteristics of a mature soil?

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 2, which of the following statements about soil creation is true?

In paragraph 2, why does the author mention the activity of fungi in acidic soils?

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

According to paragraph 3, how do trees benefit other plants?

Paragraph 3 supports which of the following inferences about the effect of vegetation on soil?

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

According to paragraph 4, earthworms do all of the following to help soils develop EXCEPT

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

According to paragraph 5, in which of the following ways do some mammals help soils develop?

Look at the four squares  that indicate where the following sentence could be added to the passage. Nutrients obtained by these deep roots nourish the trees and are preserved within them.  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.

Soil Formation Living organisms play an essential role in soil formation. The numerous plants and animals living in the soil release minerals from the parent material from which soil is formed, supply organic matter, aid in the translocation (movement) and aeration of the soil, and help protect the soil from erosion. The types of organisms growing or living in the soil greatly influence the soil’s physical and chemical characteristics. In fact, for mature soils in many parts of the world, the predominant type of natural vegetation is considered the most important direct influence on soil characteristics. For this reason, a soil scientist can tell a great deal about the attributes of the soil in any given area simply from knowing what kind of flora the soil supports. Thus prairies and tundra regions, which have characteristic vegetations, also have characteristic soils. The quantity and total weight of soil flora generally exceed that of soil fauna. By far the most numerous and smallest of the plants living in soil are bacteria. Under favorable conditions, a million or more of these tiny, single-celled plants can inhabit each cubic centimeter of soil. It is the bacteria, more than any other organisms, that enable rock or other parent material to undergo the gradual transformation to soil. Some bacteria produce organic acids that directly attack parent material, breaking it down and releasing plant nutrients. Others decompose organic litter (debris) to form humus (nutrient-rich organic matter). A third group of bacteria inhabits the root systems of plants called legumes. These include many important agricultural crops, such as alfalfa, clover, soybeans, peas, and peanuts. The bacteria that legumes host within their root nodules (small swellings on the root) change nitrogen gas from the atmosphere into nitrogen compounds that plants are able to metabolize, a process, known as nitrogen fixation, that makes the soil more fertile. Other microscopic plants also are important in soil development. For example, in highly acidic soils where few bacteria can survive, fungi frequently become the chief decomposers of organic matter. More complex forms of vegetation play several vital roles with respect to the soil.  Trees, grass, and other large plants supply the bulk of the soil’s humus.  The minerals released as these plants decompose on the surface constitute an important nutrient source for succeeding generations of plants as well as for other soil organisms.  In addition, trees can extend their roots deep within the soil and bring up nutrients from far below the surface.  These nutrients eventually enrich the surface soil when the tree drops its leaves or when it dies and decomposes. Finally, trees perform the vital function of slowing water runoff and holding the soil in place with their root systems, thus combating erosion. The increased erosion that often accompanies agricultural use of sloping land is principally caused by the removal of its protective cover of natural vegetation. Animals also influence soil composition. The faunal counterparts of bacteria are protozoa. These single-celled organisms are the most numerous representatives of the animal kingdom, and, like bacteria, a million or more can sometimes inhabit each cubic centimeter of soil. Protozoa feed on organic matter and hasten its decomposition. Among other soil-dwelling animals, the earthworm is probably the most important. Under exceptionally favorable conditions, up to a million earthworms (with a total body weight exceeding 450 kilograms) may inhabit an acre of soil. Earthworms ingest large quantities of soil, chemically alter it, and excrete it as organic matter called casts. The casts form a high-quality natural fertilizer. In addition, earthworms mix soil both vertically and horizontally, improving aeration and drainage. Insects such as ants and termites also can be exceedingly numerous under favorable climatic and soil conditions. In addition, mammals such as moles, field mice, gophers, and prairie dogs sometimes are present in sufficient numbers to have significant impact on the soil. These animals primarily work the soil mechanically. As a result, the soil is aerated, broken up, fertilized, and brought to the surface, hastening soil development.