A Level Biology Practice Exam

What is a key feature of exchange surfaces in organisms?

1. They are always found inside cells

2. They increase the surface area to enhance material exchange

3. They restrict the flow of nutrients

4. They are generally impermeable to substances

The correct answer is: They increase the surface area to enhance material exchange

A key feature of exchange surfaces in organisms is that they increase surface area to enhance material exchange. This feature is crucial because larger surface areas allow more efficient transfer of gases, nutrients, and wastes between the organism and its environment. For example, in the human lungs, the extensive branching of alveoli significantly boosts the surface area available for gas exchange, facilitating oxygen uptake and carbon dioxide removal. The design of exchange surfaces, such as those found in the lungs, gills, or roots of plants, emphasizes thinness and extensive surface area to maximize the rate of diffusion. Therefore, by increasing the surface area, these structures can meet the metabolic demands of the organism more effectively. In contrast, other options describe features that do not align with the function of exchange surfaces. Being always found inside cells is not accurate since exchange surfaces are typically located in the body tissues exposed to the external environment. Restricting the flow of nutrients contradicts the main purpose of exchange surfaces, which is to allow for the free movement of essential substances. Additionally, being impermeable to substances would prevent the very function of exchange, as these surfaces need to be selectively permeable to facilitate the exchange of materials effectively.