AI-generated practice question — model-generated for extra practice, not a previous-year CBSE board question.
Aquatic organisms like fish must breathe much faster because the amount of dissolved oxygen in water is very low compared to the oxygen available in air. Since water contains less oxygen per unit volume, aquatic organisms need to process a much larger volume of water to obtain the required amount of oxygen, resulting in a faster breathing rate.
Examiners look for two key points: (1) dissolved oxygen in water is low/less than in air, and (2) therefore more water must be processed rapidly to meet oxygen needs. Both points are needed for full 2 marks. Keep the answer concise — one cause, one consequence.