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OFFICIAL40 According to paragraph 3, which of the following statements best describes the difference between structure and composition?

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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.

9.According to paragraph 3, which of the following statements best describes the difference between structure and composition?

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正确答案:C
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【题目翻译】根据第3段,以下哪项陈述最能说明结构和组成之间的差异? A:“结构”是指植物材料在地表以上的排列;“组成”是指植物根系在地表以下的排列。 B:“结构”是指森林的年龄;“组成”是指森林的性质。 C:“结构”是指一个区域内植物种类的排列;“组成”是指该区域内存在的植物种类。 D:“结构”是指森林树冠的形状;“组成”是指形成树冠的树冠数量。 【判定题型】:题目问的是文章中的具体细节信息,故根据题目问法可以判断本题为事实信息题。 【关键词定位】:根据关键词“difference”,定位到Passage 3,原句为“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). ”,意思是“将植被的生物量(“生物量”)排列成分层形式被称为“结构”(而不是其“组成”,即构成群落的生物物种)。”。 【逻辑分析】可知,结构指的就是在一个地区植物物种的分布,组成指的就是在这个地区有哪一个植物物种。 【选项分析】 A.结构不是指地表上的植物排列。故选项错误。 B.“结构”是指一个区域内植物种类的排列;“组成”是指该区域内存在的植物种类。故选项错误。 C.符合文意,正确。 D.“结构”是指一个区域内植物种类的排列;“组成”是指该区域内存在的植物种类。故选项错误。

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