Campbell Biology (11th Edition) Edit edition

This problem has been solved:

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An independent variable is a parameter whose outcome is not defined. It is dependent on either the presence or the absence of another variable or parameter. In this case, it can be seen that there are presence of two variables.

One of them is the presence of moonlight. Either, there can be moonlight equivalent to a full moon or there can be absence of moonlight denoting the absence of a moon. The second variable is the amount of mice caught by the owl.

(a)

Moonlight and Soil color are the independent variables. It is a natural phenomenon that is going to occur irrespective of the presence of absence of mice or owls. It is represented on the X-axis as either full moon light or no moon light, light colored soil or dark colored soil.

(b)

The number of mice caught by the owl clearly indicates the dependent variables. It can be seen from the graph that the number of mice that are caught is influenced by either the presence or absence of moonlight. This variable is expressed on the Y-axis, as number of mice caught according to either presence or absence of moonlight.