Passage IV

Photosynthesis is the process by which green plants convert light energy into chemical energy. The process is shown in the generalized reaction below.

To study photosynthesis in the plant Elodea, a scientist conducted three experiments using the apparatus shown in Figure 1 below. In each experiment, the cut end of a 5-inch length of Elodea was inserted into the opening of an inverted graduated cylinder in Beaker A. All tests were conducted using a 60-watt floodlamp in a room at constant temperature. The amount of oxygen (O2) produced in the graduated cylinder, in milliliters (mL), was used as an estimate of the photosynthetic activity. The results from all three experiments are reported in Table 1.

Experiment 1

In this experiment, the effect of light intensity was studied. The distance between the floodlamp and Beaker A was varied. In each test, the amount of O2 produced after 10 minutes was recorded.

Experiment 2

In this experiment, the effect of light duration was studied. The amount of O2 produced in the graduated cylinder after various durations of light exposure was recorded.

Experiment 3

In this experiment, the effect of light color was studied. Filters of different colors were placed between Beaker A and Beaker B. Only wavelengths of light the same color as each filter could pass through the filters.

22. Water temperature affects the photosynthetic activity of aquatic plants such as Elodea. Based on the information in the passage and in Figure 1, one would conclude that the temperature of the water in Beaker A was controlled in the experiments by:

Answer and Explanation

Your Answer is

Correct Answer is F

Explanation

Because light transmits energy, in order to prevent temperature changes, put a beaker B to let the water in B absorb part of the energy, so that the temperature change in beaker A will be relatively much smaller