Surface Area to Volume Ratio

This lesson covers:

  1. What surface area (SA) to volume (V) ratio means 
  2. How SA : V changes as organisms get larger 
  3. Why large organisms need specialised exchange surfaces
Illustration comparing the surface area to volume ratio of a small microorganism and a large cow.

Which organisms have a larger surface area to volume ratio? 

Small organisms

Large organisms

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Diagram of a cube with dimensions 4 cm by 4 cm by 4 cm

The above cube is 4 cm x 4 cm x 4 cm.


What is the total surface area of the cube?

96

cm2

cm2

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Calculate the volume of the cube.

64

cm3

cm3

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Calculate the surface area : volume ratio of the cube.

3 : 2

5 : 2

2 : 3

3 : 1

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Which type of organism can rely on diffusion to exchange all of the nutrients and waste products it needs?

Bacteria 

Grasshopper

Leopard 

Oak tree

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Give two examples of exchange surfaces in humans and describe their function. 

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