A scientist places a plant in an enclosed system. After five days, she determines that the amount of carbon dioxide has increased and the amount of oxygen has decreased. How can her findings be explained?

Question

Responses

Only photosynthesis occurred because the plant was in direct sunlight.
Only photosynthesis occurred because the plant was in direct sunlight.

Only respiration occurred because the plant was in the dark.
Only respiration occurred because the plant was in the dark.

Only anaerobic respiration occurred because the plant was in the dark.
Only anaerobic respiration occurred because the plant was in the dark.

Only glycolysis occurred because the plant was in direct sunlight.

Answer 1

The best explanation for the scientist's findings—that the amount of carbon dioxide has increased and the amount of oxygen has decreased—would be:

Only respiration occurred because the plant was in the dark.

In the absence of light, plants cannot perform photosynthesis, which uses carbon dioxide and produces oxygen. Instead, they would rely on cellular respiration, which consumes oxygen and releases carbon dioxide. Thus, the observed increase in carbon dioxide and decrease in oxygen can be attributed to respiration occurring in the plant in the dark.