It's straightforward to model the cells of organisms using cubes. By doing this we can easily see how the surface area to volume ratio changes as organisms increase in size.
We can investigate the effect of increasing size on surface area to volume ratios using models based on cubes:
So, as the volume increases, the surface area does not increase at the same rate.
If a graph is drawn:
What is the surface area to volume ratio of the highlighted mark?
This cube will have a surface area:volume ratio of 1.
The volume = 6 × 6 × 6 = 216
The surface area = 6 × (6 × 6) = 216
A stacked bar chart can be drawn to illustrate the proportions of surface area and volume.
In the below table scientists have estimated the surface area:volume ratios of various organisms.
|Organism||Surface area in square metres||Volume in cube metres||Surface area:volume|
|Bacterium||6 × 10−12||1 × 10−18||6,000,000:1|
|Blow fly||6 × 10−4||1 × 10−6||600:1|
|Whale||6 × 104||1 × 106||0.06|
Large organisms have:
Organisms living in harsh environmental conditions may reduce their surface area, for example cacti have adapted to have less surface area to lose water through.