Question

In an aquarium why do the fish open and close their mouths at regular intervals.
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Answer 1

Answer:

The aquarium fish opens its mouth regularly to take in water along with dissolved oxygen and closes the mouth regularly to push this water to gills where dissolved oxygen is separated from it and supplied to body. ... In this way fish open and closes the mouth alternately for respiration

Answer 2

Answer:

In an aquarium, the fishes open and close their mouth at regular intervals so as to intake water and to absorb the dissolved oxygen from water through their Gill's

Explanation:

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