Gas exchange in the gills of a bony fish is maximized by which of the following?

• A. A tracheal system
• B. Negative pressure breathing
• C. Alveoli
• D. Positive pressure breathing
• E. Countercurrent exchange

Answer: (E)

Verified step by step guidance

1. Understand the concept of gas exchange in bony fish: Bony fish use gills to extract oxygen from water and expel carbon dioxide. The efficiency of this process is crucial for their survival.
2. Learn about countercurrent exchange: This mechanism involves the flow of water over the gills in one direction while blood flows in the opposite direction. This arrangement maximizes the gradient for oxygen diffusion.
3. Compare countercurrent exchange with other options: A tracheal system, negative pressure breathing, alveoli, and positive pressure breathing are mechanisms found in other organisms, such as insects and mammals, and are not applicable to fish gills.
4. Recognize why countercurrent exchange is effective: By maintaining a constant gradient, countercurrent exchange allows for more efficient oxygen uptake compared to concurrent flow, where the gradient would diminish quickly.
5. Conclude that countercurrent exchange is the correct answer: It is specifically adapted for aquatic environments and is the most effective method for maximizing gas exchange in the gills of bony fish.