## Drawing Pie Charts in Biology

- You want to give a visual representation of percentages as a relative proportion of the total of a circle.
- They are a type of graph even though they do not have any axes.
- A pie chart is a circle divided into sectors (think of them as the slices of a cake).
- 100% represents the whole complete circle, 50% represents a half circle, 25% is a quarter circle, and so on.

**Example:**

- Count the number of each species and record it in a table.
- Work out the total number of species in the ecosystem.
- Calculate the percentage of each species.
- Use the following formula to work out the angle of each slice:

\(a = \cfrac{v × 360^{\circ}}{t}\)

## Species | ## No. of Types | ## % | ## Slice Angle |

Insects | 17 | \(\cfrac{17 × 100}{50} = 34\%\) | \(\cfrac{34 × 360}{100} = 122.4^\circ\) |

Plants | 16 | \(\cfrac{16 × 100}{50} = 32\%\) | \(\cfrac{32 × 360}{100} = 115.2^\circ\) |

Birds | 9 | \(\cfrac{9 × 100}{50} = 18\%\) | \(\cfrac{18 × 360}{100} = 65.0^\circ\) |

Amphibians | 8 | \(\cfrac{8 × 100}{50} = 16\%\) | \(\cfrac{16 × 360}{100} = 57.6^\circ\) |

- Use a compass to draw the circle and a protractor to measure accurate angles for each slice.
- Start with the largest angle/percentage starting at 12 o’ clock and measure in a clockwise direction.
- Shade each slice and write the percentage on the slice and provide a key.