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Question
Gas exchange in the gills of a fish is enhanced by having the blood flow in a direction opposite to the direction of water flow, a process known as
Gas exchange in the gills of a fish is enhanced by having the blood flow in a direction opposite to the direction of water flow, a process known as
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Solution
The correct option is A Counter current exchange
The principle of counter current exchange can be illustrated using fish gills. In the gills, oxygen diffuses from an area of high concentration, the water, into an area of lower concentration, the fish’s bloodstream. First, consider what would happen under same or concurrent exchange. If oxygen-rich water and oxygen-deficient blood flow in the same direction, diffusion occurs into the bloodstream until equilibrium is reached. Thus, the maximum amount of oxygen that can enter the blood at any given time is only 50% of the total oxygen. On the other hand, if oxygen-rich water and oxygen-deficient blood flow in opposite directions, oxygen diffusion is continuous. This is because even though the oxygen concentration may decrease, the amount of oxygen in the water is always slightly greater than that in the blood, allowing diffusion to continue, and equilibrium to be avoided. In this case, the maximum amount of oxygen that can enter the blood is 90%, much greater than the amount which entered via concurrent exchange.
Therefore, the correct answer is option A.
The principle of counter current exchange can be illustrated using fish gills. In the gills, oxygen diffuses from an area of high concentration, the water, into an area of lower concentration, the fish’s bloodstream. First, consider what would happen under same or concurrent exchange. If oxygen-rich water and oxygen-deficient blood flow in the same direction, diffusion occurs into the bloodstream until equilibrium is reached. Thus, the maximum amount of oxygen that can enter the blood at any given time is only 50% of the total oxygen. On the other hand, if oxygen-rich water and oxygen-deficient blood flow in opposite directions, oxygen diffusion is continuous. This is because even though the oxygen concentration may decrease, the amount of oxygen in the water is always slightly greater than that in the blood, allowing diffusion to continue, and equilibrium to be avoided. In this case, the maximum amount of oxygen that can enter the blood is 90%, much greater than the amount which entered via concurrent exchange.
Therefore, the correct answer is option A.
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