Page 34 - General and Inorganic Chemistry for Advanced Secondary Schools Students Book Form Five and Six

Biology for Secondary Schools

Figure 2.27 shows an experimental set up that can be used to test if earthworms
prefer moist areas.

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Figure 2.27: Experiment to investigate the conditions preferred by earthworms

In set-up A: determines the direction of movement
(a) The direction in which the of earthworms.
earthworms move is the factor
under investigation. This is the Observation and data recording
dependent variable. The scientist observes what happens
(b) The moisture content of one of the from the time the experiment is set
paper towels is varied. This is the up to the time it ends. It is important
independent variable. to note all the changes made in the
(c) The amount of light allowed is kept
constant. This is the controlled independent variable and the resulting
variable. changes in the dependent variable. For
example, the results of the experiment
Set-up B: is the control experiment. in Figure 2.27 can be recorded in a
In this set-up, the paper towels are not table, as shown in Table 2.5 below. The
moistened. The independent variable is
not changed. The control experiment results in the first row are given as an
proves that the independent variable example.

28 Student’s Book Form One Student’s Book Form One

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