Question

In fishes, .......... maximizes oxygen transfer from water into the gills.

• A. more permeability for solutes
• B. more thin membranes of gills
• C. more number of gills
• D. counter-current flow

Hint:

In aquatic respiration, understanding the role of counter-current flow is crucial for explaining how fish extract oxygen from water efficiently.

Answer 1

The Correct Option is D

Step 1: Understanding the concept.
In fishes, oxygen is extracted from water through the gills. For effective oxygen transfer, the movement of water across the gills should be maximized. The counter-current flow mechanism plays a critical role in this process. It ensures that water and blood flow in opposite directions, which maximizes the gradient for oxygen diffusion, allowing for more oxygen to enter the blood.
Step 2: Analyzing the options.
(A) more permeability for solutes: While permeability is important for nutrient and gas exchange, it is not the main factor in maximizing oxygen transfer in fishes.
(B) more thin membranes of gills: The thin membranes are important for diffusion, but the arrangement of the flow (counter-current) is more crucial for maximizing oxygen transfer.
(C) more number of gills: Although more gills would increase surface area for oxygen exchange, the key factor in maximizing oxygen transfer is the flow mechanism, not the number of gills.
(D) counter-current flow: Correct — Counter-current flow maximizes oxygen transfer from water to the blood in fish gills by maintaining a high concentration gradient for oxygen throughout the length of the gill.
Step 3: Conclusion.
The correct answer is (D) counter-current flow, as this flow mechanism ensures efficient oxygen extraction in fishes.