The overall purpose of the countercurrent exchange system in biological organisms is to:

• A. store excess glucose produced during photosynthesis
• B. increase the rate of ATP synthesis during photosynthesis
• C. maximize the efficiency of gas or heat exchange between two fluids flowing in opposite directions
• D. convert light energy directly into chemical energy without any loss

Answer: (C)

Verified step by step guidance

1. Understand the concept of countercurrent exchange: Countercurrent exchange is a biological mechanism where two fluids flow in opposite directions, allowing for efficient transfer of heat, gases, or substances between them.
2. Identify examples of countercurrent exchange in organisms: Common examples include the exchange of oxygen and carbon dioxide in fish gills, heat conservation in extremities of animals, and nutrient absorption in kidneys.
3. Analyze why countercurrent exchange maximizes efficiency: The opposing flow of fluids maintains a gradient across the entire length of the exchange surface, ensuring continuous transfer without equilibrium being reached prematurely.
4. Compare countercurrent exchange to other mechanisms: Unlike concurrent flow (where fluids move in the same direction), countercurrent exchange prevents the loss of efficiency that occurs when equilibrium is reached quickly.
5. Conclude the purpose: The primary goal of countercurrent exchange is to maximize the efficiency of gas or heat exchange, which is critical for survival in various biological systems.