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SAMPLE 15 [生态学] 题目序号 题型归类 第1题 中心主旨题型 第2题 细节推导题型 第3题 审题定位与中心主旨题型 第4题 归纳推导题型 第5题 写作手法题型 As Gilbert White, Darwin, and others observed long ago, all speciesappear to have the innate capacity to increase their numbers from generation togeneration. The task for ecologists is to untangle the environmental andbiological factors that hold this intrinsic capacity for population growth incheck over the long run. The great variety of dynamic behaviors exhibited bydifferent population makes this task more difficult: some populations remainroughly constant from year to year; others exhibit regular cycles of abundanceand scarcity; still others vary wildly, with outbreaks and crashes that are insome cases plainly correlated with the weather, and in other cases not. To impose some order on this kaleidoscope of patterns, one school ofthought proposes dividing populations into two groups. These ecologists positthat the relatively steady populations have density-dependent growth parameters; that is, ratesof birth, death, and migration which depend strongly on population density. Thehighly varying populations have density-independent growth parameters, with vital rates buffeted by environmental events;these rates fluctuate in a way that is wholly independent of populationdensity. | 
