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  3. An ecosystem is a group of animals and plants living in a specific region and interacting with one another and with their physic

An ecosystem is a group of animals and plants living in a specific region and interacting with one another and with their physic

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问题     An ecosystem is a group of animals and plants living in a specific region and interacting with one another and with their physical environment. Ecosystems include physical and chemical components, such as soils, water, and nutrients that support the organisms living there and the interactions among all organisms in a given habitat. People are part of the ecosystems where they live and work. Human activities can harm or destroy local ecosystems unless land development for housing or businesses is carefully planned to conserve and sustain the ecology of the area.
    The "natural succession" of plant and animal communities refers to the changes in animal and plant life of a region as a result of environmental changes. With changes in environment, the previous animal and plant life disappears and is succeeded by new types, adapted to new conditions. A knowledge of succession is very important in tackling the problem of conservation. For example, if a forest is destroyed, the mosses and ferns of that forest, requiring shade, and the forest animals, requiring protection and food, will disappear and be replaced by insects and other animals common to the grassland and shrub area that had preceded the forest.
    We need to use traditional methods of soil conservation. Planting of terracing to strip cropping, all bind the soil and absorb rain runoff, preventing land erosion. We currently over-rely on high yield farming that shows disregard for ecology. It is an understanding of succession that keeps nature in balance. When we manipulate the land in an unnatural way, using chemicals and indiscriminate logging we are showing our ignorance of natural succession.
What is the main idea of the third paragraph?
选项 A、An ecosystem is a community that includes animals, plants, and microscopic bacteria.
B、Local ecosystems depend on each other, so human activity should be cautiously planned.
C、In managing the ecology of an area, we should use natural succession to our advantage.
D、People should remember that they are a part of the ecosystems where they live and work.
答案C
解析 属主旨思想题，考查第三段的大意概括。本段谈到我们需要使用传统方法保持土壤，即我们应对自然演替加以有利的利用。
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