Surface Area to Volume Ratio
Biology: Edexcel IGCSE, topic 3.3.1
Surface Area to Volume Ratio
The surface area to volume ratio influences how substances and heat energy can be transferred around multicellular organisms.
%202.4.1.1%20-%20Surface%20area%20to%20volume%20ratio,w_800.png)
Surface area
- The surface area of an organism is the total surface over which substances and heat can be exchanged.
- Surface area alone cannot influence the rate of exchange.
- The surface area of an organism relative to their volume is more important.
Volume
- The volume of an organism determines the number of substances that need to be taken in and transported out.
- As the volume increases, more materials are needed for metabolism because there are more cells.
Surface area to volume ratio
- When an organism increases in size, its volume increases because there are more cells.
- The increase in the number of cells means that there is less surface area for the exchange of materials because many cells are in contact with one another.
- The surface area to volume ratio (SA : V) decreases with increasing organism size.
- Unicellular organisms can rely on diffusion to obtain the substances they need because they have a high SA : V ratio.
Test yourself on Surface Area to Volume Ratio
Why does the surface area of cells decrease when the number of cells increases?
Which of the following statements about surface area to volume ratio are true?
Which of the following animals has the largest surface area to volume ratio?