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.

21. Experiment 1 was repeated with a new Elodea under conditions identical to those used for Plant 1. The amount of O2 measured was 1.7 mL. Such a difference in results between repeated experiments using different plants is to be expected because:

Answer and Explanation

Your Answer is

Correct Answer is C

Explanation

It has been said in the title that all external conditions are the same, so the difference in the amount of photosynthesis, that is, the production of oxygen, may only be due to individual differences.