Cells can be modelled using cubes.
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 cube with a length of 6?
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 (m2)||Volume (m3)||Surface area : volume|
|Bacterium||6 x 10-12||1 x 10-18||6 000 000 : 1|
|Blow fly||6 x 10-4||1 x 10-6||600 : 1|
|Whale||6 x 104||1 x 106||0.06 : 1|
Organisms living in harsh environmental conditions may reduce their surface area, eg cacti, to reduce loss of water.