Question

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? only photosynthesis occurred because the plant was in direct sunlight. only 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.

Explanation:

1. Analyze photosynthesis: Photosynthesis requires light, produces oxygen, and consumes carbon dioxide. If only photosynthesis occurred (in light), oxygen would increase and carbon dioxide decrease, so options with "only photosynthesis" (first, fourth) are wrong.
2. Analyze respiration: Respiration (aerobic) occurs in light and dark, consumes oxygen, produces carbon dioxide. Anaerobic respiration produces CO₂ but doesn't consume O₂ (or consumes other, not O₂ here). In the dark, photosynthesis stops, so only respiration (aerobic, as plants do aerobic respiration mainly) happens: O₂ decreases (consumed), CO₂ increases (produced). The option "Only respiration occurred because the plant was in the dark" matches. Anaerobic respiration isn't indicated (no info on no O₂), so third option is wrong.

Answer:

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