A scientist observed that tobacco plants flower only at certain times of the year. After careful consideration of this phenomenon, the scientist conducted an experiment. She grew five tobacco plants and exposed each to light for a specific period of time each day. Study the diagrams below which show the results of this experiment. Then complete the sentences that follow. 1. Since only one variable was changed in this experiment, this is called a
experiment.

2. The independent variable in this experiment is .

3. The dependent variable in this experiment is .

4. List some of the controlled variables in the experiment. (Identify at least three.)