The correct option is
Both A and R are true and R is the correct explanation of A
.Explanation
Respiration involves the intake of oxygen from the environment for cellular metabolism. The rate of breathing in an organism is primarily determined by the metabolic requirement for oxygen and the concentration of oxygen available in the surrounding medium (air or water).
Analysis of Assertion and Reason:
- Assertion (A): Correct. Aquatic organisms, such as fish, exhibit a significantly faster rate of breathing compared to terrestrial organisms. They must constantly pump water over their respiratory surfaces (gills) to maintain adequate oxygen uptake.
- Reason (R): Correct. The amount of dissolved oxygen in water is fairly low compared to the amount of oxygen in the air. While air contains approximately 21% oxygen, the concentration of oxygen dissolved in water is much lower.
- Justification: Because the oxygen concentration in water is low, aquatic organisms must process a larger volume of the medium (water) in a shorter time to extract the necessary amount of oxygen. This necessitates a faster breathing rate. Therefore, the low availability of oxygen (Reason) is the direct cause of the faster breathing rate (Assertion).
Key Takeaway:
Aquatic organisms have a faster breathing rate than terrestrial organisms as a physiological adaptation to compensate for the low concentration of dissolved oxygen in water compared to the high oxygen content in air.