Question

Which one of the following statements is incorrect?

• A. The residual air in lungs slightly decreases the efficiency of respiration in mammals
• B. The presence of non-respiratory air sacs, increases the efficiency of respiration in birds
• C. In insects, circulating body fluids serve to distribute oxygen to tissues
• D. The principle of countercurrent flow facilitates efficient respiration in gills of fishes

Answer 1

The Correct Option is A

 To determine the incorrect statement concerning respiratory efficiency across different organisms, we'll analyze each option based on biological principles:

1. The residual air in lungs slightly decreases the efficiency of respiration in mammals: Residual air, or residual volume, is the air remaining in the lungs even after maximum exhalation. It plays a crucial role in maintaining lung inflation and ensuring efficient gas exchange by preventing alveolar collapse. While it does slightly dilute the incoming air, the chief function is to assist in continuous gas exchange even between breaths. Therefore, this statement is indeed incorrect as it suggests a negative effect on efficiency, which is not the primary role of residual air.
2. The presence of non-respiratory air sacs increases the efficiency of respiration in birds: Birds have a highly efficient respiratory system involving air sacs that ensure a unidirectional flow of air through the lungs, enhancing gas exchange efficiency. This adaptation aids in meeting their high metabolic demands during flight. Thus, this statement is correct.
3. In insects, circulating body fluids serve to distribute oxygen to tissues: Insects use a tracheal system for direct oxygen delivery to tissues, bypassing the need for respiration through circulatory fluids. Instead, their hemolymph distributes nutrients but not gases like oxygen. Therefore, this statement is correct since it accurately describes the respiratory mechanism of insects.
4. The principle of countercurrent flow facilitates efficient respiration in gills of fishes: Fish gills utilize the countercurrent exchange mechanism where blood and water flow in opposite directions, maximizing oxygen absorption and carbon dioxide release. This process is highly efficient and is a correct statement about respiratory physiology in fish.

Given these evaluations, the incorrect statement is:

The residual air in lungs slightly decreases the efficiency of respiration in mammals

because the role of residual air is primarily supportive for continuous gas exchange, not inefficiency.