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In a closed ecological system, any waste products produced by one species must be used by at least one other species. If the purpose is to maintain a life form, such as a mouse or a human, waste products such as carbon dioxide, feces and urine must eventually be converted into oxygen, food, and water.
1000 meters are in a kilometer
Answer:
D. It allows some molecules to pass through but prevents others from doing so.
Explanation:
Plasma membrane or cell membrane is a selective permeable membrane which allows light molecules to pass and prevents heavy molecules.
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