Final answer:
The independent variable in the experiment is the type of gel (gel A or gel B), and the dependent variable is the growth rate of bacteria, which is measured to see the effect of the type of gel.
Step-by-step explanation:
The correct identification of the independent and dependent variables in the experiment of growing bacteria in a lab is:
: The independent variable is the
type of gel
(gel A or gel B), and the dependent variable is the
growth rate
of the bacteria on those gels.
An experiment involves manipulating one variable to determine if it causes a change in another variable, thereby establishing a cause-and-effect relationship. The variable that the experimenter changes is known as the independent variable, and the one that changes as a result, which is observed and measured, is called the dependent variable. For instance, when examining the growth of bacteria on different types of gel, the type of gel used is what the scientist changes, hence, it is the independent variable. The outcome, which is the growth rate of the bacteria, depends on the type of gel and is therefore the dependent variable. In this example, all other conditions, such as temperature, light, and the amount of bacteria placed on each gel, should be kept constant to ensure that any differences in bacterial growth rates are due solely to the type of gel, thus making this a controlled experiment.