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Food chains and food webs explain the flow of energy through ecosystems.
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Ecology is the study of interactions between organisms and their environment, including both living and non-living components.
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Learn about Darwin's theory of evolution and natural selection on Khan Academy.
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2017年1月24日 · Videos and video talk-throughs [producer if specified, by last name, first name.], [video name as it appears in the menu, in quotations marks], [performer if different from producer], [medium, in parentheses], [if appropriate, time in (hours):minutes: seconds at which the issue occurs followed by /][running time in (hours):minutes: seconds], [Producing organization or company in italics ...