Question

question 15.
a scientist is studying the changes in an ecosystem in a pond. she is taking measurements of oxygen and carbon dioxide over 36 hours. her findings are noted in the graph below.
based on the data collected, how might this scientist explain this data?
a. there is an imbalance in the ecosystem due to the constant changes in oxygen and carbon dioxide availability throughout this period.
b. during the day, animals are less active and thus produce less carbon dioxide.
c. carbon dioxide levels decrease while oxygen levels increase due to photosynthetic activity during the day.
d. plants perform peak photosynthesis at night due to the availability of carbon dioxide present in the atmosphere.

Explanation:

• Option A: The data shows a regular pattern of gas level changes (not an imbalance).
• Option B: During the day, animals are more active (not less), and plants perform photosynthesis, which affects gas levels.
• Option C: During the day, plants photosynthesize (using \(CO_2\) and producing \(O_2\)), so \(CO_2\) levels decrease and \(O_2\) levels increase. At night, photosynthesis stops (but respiration continues), so \(CO_2\) levels increase and \(O_2\) levels decrease. This matches the graph.
• Option D: Plants perform photosynthesis mainly during the day (when there is light), not at night.

Answer:

C. Carbon dioxide levels decrease while oxygen levels increase due to photosynthetic activity during the day.