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题目材料：
Ecologists tend to focus on pristine environments and ignore urban areas. Human beings, and especially their cities, fail to fit neatly into ecological theory-they are seen as an exogenous, perturbing force in nature. Yet people are a global force capable of affecting every ecosystem on the planet. In cities, people mobilize some nutrients and deplete others, create habitats that never before existed, increase temperatures, and, by intent or by accident, manipulate the communities of other species found within city boundaries and beyond. If there is a laboratory where ecological change can be viewed at close hand, it is the city. The processes and dynamics within cities, however, largely elude understanding based on traditional ecological theories.
以上解析由 考满分老师提供。
