OCR General Certificate of Secondary Education (GCSE) Biology Practice Exam

What adaptation helps maximise the effectiveness of exchange surfaces in specialized organs?

1. Thick membranes

2. Large surface area

3. High blood pressure

4. Immobilization of cells

The correct answer is: Large surface area

The adaptation that helps maximize the effectiveness of exchange surfaces in specialized organs is a large surface area. This is crucial because a greater surface area allows for more molecules to pass through an exchange surface at any given time, facilitating efficient gas exchange, nutrient absorption, or waste removal. For example, in the lungs, the presence of alveoli increases the surface area, thereby enhancing the oxygen and carbon dioxide exchange between the air and blood. Similarly, in the intestines, the presence of villi and microvilli provides an extensive surface area, allowing for efficient absorption of nutrients from digested food. Other adaptations, such as thin membranes, also contribute to effective exchanges, but having a large surface area is fundamental as it directly relates to the capacity for exchange to occur. In contrast, thick membranes, high blood pressure, and immobilization of cells do not enhance the surface for exchange; they can actually impede efficiency or do not directly contribute to maximizing the exchange process.