A Level Biology Practice Exam

What does the surface area to volume ratio express?

1. The relationship between organism size and warmth

2. The efficiency of nutrient absorption in cells

3. The surface area in relation to the organism's volume

4. The density of organisms in an environment

The correct answer is: The surface area in relation to the organism's volume

The surface area to volume ratio expresses the surface area in relation to the organism's volume. This ratio is significant in biological contexts because it influences how substances such as nutrients and gases move in and out of cells. A high surface area to volume ratio typically indicates that an organism or cell can exchange materials more efficiently, which is crucial for processes like respiration and nutrient uptake. As organisms increase in size, their volume grows faster than their surface area, which can limit their ability to transport materials quickly enough to meet their metabolic needs. Thus, understanding this ratio helps explain various biological phenomena, such as the design of organs and the adaptation of species to their environments.