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Science · 2023 · 2 marks
CBSE 2023 · Region 2 · Set 1 · Q26
We do not clean ponds or lakes but an aquarium needs to be cleaned regularly. Why?
We do not clean ponds or lakes but an aquarium needs to be cleaned regularly. Why ?
Marking-scheme solution
An aquarium is a man-made ecosystem in which natural cleansing agents like decomposers are not present, so needs periodic cleaning;
ponds and lakes are natural ecosystems which have natural cleansing agents. (Decomposers)
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