What do the polar bears, reindeer, and shrubs that live in a single area makeup

They form an ecosystem.

Explanation:

Different organisms that thrive in a single region in combination form an ecosystem. On certain occasions, it is also illustrated as the composite association amongst all the constituents, that is, whether they are non-living or living present within a specific region.  

Within an ecosystem, one can witness a great degree of biodiversity, as all the constituents found within an ecosystem relies heavily upon each other for one thing or another. A healthy balance between all the components that form an ecosystem makes it a sustainable ecosystem.  

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jk but i am serious about the part that most people cant answer it beacuse you did not mention the section you are talking about. but it would if you added some detail and were a bit more specific.

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