Imagine mixing all living animals in North America up in a (very large) bag, identifying which species are in the mix, and then making educated guesses about how those animals live.  Do the fishes and birds share a niche?  How often do monarch butterflies and polar bears interact?  We know the answers to these questions are dependent on the North American habitat in which each animal lives.  Sometimes fishes and birds do interact, but only in particular habitats. 

This mental exercise may see...
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