Everything Life Sciences Grade 10

Histograms are used when the independent variable (x-axis) represents information which is
continuous, such as numerical ranges, i.e. 0-9, 10-19, 20-29, etc.

Histograms have the following features:

• Unlike a bar graph, in a histogram the data are plotted as columns or bars that touch
  each other as they are related to each other in some way.


• The numerical categoriesmust not overlap, for example, 0-10, 10-20, 20-30, etc. The
  ranges must be exclusive so that there is no doubt as to where to put a reading, for
  example, 0-9, 10-19, 20-29, etc.


• The bars can be vertically or horizontally drawn.


• A histogram must have a descriptive heading with is written below the graph


• and the axes must be labelled.

Figure 1.5: A histogram showing the number of learners in a Grade 10 Life sciences class with a
particular percentage test score

Pie charts DUMMY

• 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:

1. Count the number of each species and record it in a table.


2. Work out the total number of species in the ecosystem.


3. Calculate the percentage of each species.


4. Use the following formula to work out the angle of each slice:

a=

v× 360 ◦

t

Chapter 1. Introduction to Life Sciences 17