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OFFICIAL40 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. Drag your answer choices to the spaces where they belong. To remove an answer choice, click on it. To review the passage, click VIEW TEXT.A number of factors may help account for the difference in biodiversity between low and high latitudes.

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Latitude and Biodiversity
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When we look at the way in which biodiversity (biological diversity) is distributed over the land surface of the planet, we find that it is far from even. The tropics contain many more species overall than an equivalent area at the higher latitudes. This seems to be true for many different groups of animals and plants.

Why is it that higher latitudes have lower diversities than the tropics? Perhaps it is simply a matter of land area. The tropics contain a larger surface area of land than higher latitudes - a fact that is not always evident when we examine commonly used projections of Earth’s curved surface, since this tends to exaggerate the areas of land in the higher latitudes - and some biogeographers regard the differences in diversity as a reflection of this effect. But an analysis of the data by biologist Klaus Rohde does not support this explanation. Although area may contribute to biodiversity, it is certainly not the whole story; otherwise, large landmasses would always be richer in species.

Productivity seems to be involved instead, though perhaps its influence is indirect. Where conditions are most suitable for plant growth - that is, where temperatures are relatively high and uniform and where there is an ample supply of water - one usually finds large masses of vegetation. This leads to a complex structure in the layers of plant material In a tropical rain forest, for example, a very large quantity of plant material builds up above the surface of the ground. There is also a large mass of material, developed below ground as root tissues, but this is less apparent. Careful analysis of the above ground material reveals that it is arranged in a series of layers, the precise number of layers varying with age and the nature of the forest. The arrangement of the biological mass ("biomass") of the vegetation into layered forms is termed its “structure” (as opposed to its “composition”, which refers to the species of organisms forming the community). Structure is essentially the architecture of vegetation, and as in the case of tropical forests, it can be extremely complicated. In a mature floodplain tropical forest in the Amazon River basin, the canopy (the uppermost layers of a forest, formed by the crowns of trees) takes on a stratified structure. There are three clear peaks in leaf cover at heights of approximately 3, 6, and 30 meters above the ground; and the very highest layer, at 50 meters, corresponds to the very tall trees that stand free of the main canopy and form an open layer of their own. So, such a forest contains essentially four layers of canopy. Forests in temperate lands often have just two canopy layers, so they have much less complex architecture.

Structure has a strong influence on the animal life inhabiting a site. It forms the spatial environment within which an animal feeds, moves around shelters, lives, and breeds. It even affects the climate on a very local level (the "microclimate") by influencing light intensity, humidity, and both the range and extremes of temperature. An area of grassland vegetation with very simple structure, for example, has a very different microclimate at the ground level from that experienced in the upper canopy. Wind speeds are lower, temperatures are lower during the day (but warmer at night), and the relative humidity is much greater near the ground. The complexity of the microclimate is closely related to the complexity of structure in vegetation, and generally speaking, the more complex the structure of vegetation, the more species of animal are able to make a living there. The high plant biomass of the tropics leads to a greater spatial complexity in the environment, and this leads to a higher potential for diversity in the living things that can occupy a region. The climates of the higher latitudes are generally less favorable for the accumulation of large quantities of biomass; hence, the structure of vegetation is simpler and the animal diversity is consequently lower.

14.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. Drag your answer choices to the spaces where they belong. To remove an answer choice, click on it. To review the passage, click VIEW TEXT.A number of factors may help account for the difference in biodiversity between low and high latitudes.

A.Though land area may be related to a region's biodiversity, it is not a primary determining factor

B.A structure of varying heights is found in both tropical and temperate forests.

C.The more complex the structure of the vegetation of a region, the more species it is able to support.

D.Regions possessing conditions that are favorable for plant growth tend to have abundant and diverse vegetation that supports a large number of species.

E.The difference in microclimate between a ground-level canopy and an upper-level canopy is responsible for the number of species that inhabit each canopy.

F.The temperature range of a region determines the number of animals that feed, move around, shelter themselves, live, and breed in that region.

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正确答案:ACD
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【题目翻译】说明:下面提供了一个简短总结文章的介绍性句子。通过选择三个答案选项来完成总结,这些选项表达了文章中最重要的观点。有些句子不属于摘要,因为它们表达的观点不是在文章中呈现的,或者是文章中的次要观点。 一些因素可能有助于解释低纬度和高纬度地区生物多样性的差异。 A:虽然土地面积可能与一个地区的生物多样性有关,但它不是一个主要决定因素。 B:热带和温带森林都有不同高度的结构。 C:一个地区的植被结构越复杂,它所能支持的物种就越多。 D:有利于植物生长条件的地区,往往有丰富多样的植被,支持大量物种。 E:地面树冠和上层树冠之间的小气候差异是每个树冠上栖息的物种数量的原因。 F:一个地区的温度范围决定了该地区的动物的数量,它们在该地区觅食、活动、栖息、生活和繁殖。 【判定题型】:根据问题的提问方式和6选3的作答方式可以确定该题目为概要小结题。 【选项定位及分析】 根据原文Although area may contribute to biodiversity, it is certainly not the whole story;其中it is certainly not the whole story对应A选项中的it is not a primary determining factor. 所以A选项正确。 文章并没有提及在热带雨林和温带森林都有不同高度的结构。所以B选项错误。 根据原文the more complex the structure of vegetation, the more species of animal are able to make a living there. 所以C选项正确。 根据原文The high plant biomass of the tropics leads to a greater spatial complexity in the environment, and this leads to a higher potential for diversity in the living things that can occupy a region. 其中a higher potential for diversity in the living things对应D选项中的a large number of species. 所以D选项正确。 根据关键词a ground-level canopy和an upper-level canopy定位至文章第四段第四句话An area of grassland vegetation with very simple structure, for example, has a very different microclimate at the ground level from that experienced in the upper canopy.并未发现有提及到地面树冠和上层树冠的微气候差别决定了每个树冠层中栖息的物种的数量。所以E选项错误。 根据原文The complexity of the microclimate is closely related to the complexity of structure in vegetation, and generally speaking, the more complex the structure of vegetation, the more species of animal are able to make a living there.可知并非是气温的变化导致动物的数量。所以F选项错误。

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