1. Surface Area to Volume Ratios
Chapter 10: Cell Division

2. Surface Area
A measure of the number of square units needed to cover the faces or surfaces of a figure.
Surface Area = Length x Width x # of sides

3. Example of Surface Area
A cube has 6 equal sides, so the
Surface Area = 6 x L2
 Example: The length of one side of a cube is 0.5 cm. Calculate the Surface Area of the cube.
Surface Area = 6 x L 2 = 6 x (0.5)2 = 6 x 0.25 = 1.5 cm2

4. Volume The amount of space occupied by a three-dimensional object
Volume = Length x Width x Height

5. Example of Volume A cube has 6 equal sides, so the Volume = L3
Example: The length of one side of a cube is 0.5 cm. Calculate the volume of the cube.
Volume = L3= (0.5)3 = cm3

6. Example of Surface Area to Volume Ratio
0.5 x 0.5 x 6 =
1.5 cm 2
Volume
0.5 x 0.5 x 0.5 = cm 3
Ratio of Surface Area to Volume
1.5/0.125 = 12:1

7. Surface Area to Volume Ratios
Changes in the surface area to volume ratio are important in determining an organism’s size, and help explain some of the modifications seen in larger-bodied organisms.
Imagine a cell shaped like a cube. As the length of the sides of a cube increases, its volume increases faster than its surface area, decreasing the ratio of surface area to volume.
If a cell gets too large, its surface area is not large enough to get enough oxygen and nutrients in and waste out efficiently.