But the research by Crowder, an insect ecologist at Washington State University in Pullman, and his colleagues, shows the importance of 'evenness' - the relative abundance of different species.

但是华盛顿州立大学的昆虫生态学家克劳德的研究显示平衡的重要性——各种物种相对充盈。

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Three that appear critical include how competent a person feels, whether he or she feels they have some control or choice in the matter and, for many, whether the activity fosters social relatedness, says Sarah Ullrich-French, a professor in kinesiology at Washington State University in Pullman, Wash.

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