Question

Mr. Miller's biology class is studying cellular respiration. To model cellular respiration, they set up an experiment containing four flasks. Each flask is the same size and are stoppered and placed under a floodlight. Each flask also contains 200 mL of H20 and 2 mL of bromothymol blue. Bromothymol blue is a chemical indicator solution that changes color from blue to yellow in the presence of CO2. The students then place a plant and/or fish into each flask (except for Flask #4 which is the control group) according to the table above. Which flask(s) will turn yellow and why? Responses A Flask 1 & 3 because these flasks contain plants that undergo photosynthesis.Flask 1 & 3 because these flasks contain plants that undergo photosynthesis. B Flask 3 (only) because this is the only flask in which photosynthesis and cellular respiration are both taking place.Flask 3 (only) because this is the only flask in which photosynthesis and cellular respiration are both taking place. C Flask 1 & 2 because there is only one process taking place in each of these flasks so the products do not get used up.Flask 1 & 2 because there is only one process taking place in each of these flasks so the products do not get used up. D Flask 2 (only) because the fish produce CO2 as products of cellular respiration and do not undergo photosynthesis therefore not consuming CO2.

Answer 1

To determine which flasks will turn yellow, we need to consider the processes occurring in each flask.

1. Flask 1 contains a plant. Plants perform photosynthesis, which consumes CO2 and produces O2, leading to a reduction in CO2 concentration. This means the bromothymol blue will likely remain blue due to the uptake of CO2 by the plant.

2. Flask 2 contains a fish. Fish engage in cellular respiration, which produces CO2 as a byproduct. Since there is no plant to consume this CO2, the CO2 will accumulate, causing the bromothymol blue to turn yellow.

3. Flask 3 contains both a plant and a fish. In this situation, the fish's cellular respiration will produce CO2, while the plant will consume CO2 through photosynthesis. The overall interaction between the two processes may lead to the accumulation of CO2 depending on the balance of photosynthesis and respiration. However, because both processes are occurring, it's uncertain if the plant will fully compensate for the CO2 produced by the fish, making it likely that the flask could turn yellow if the fish's respiration produces more CO2 than the plant consumes.

4. Flask 4 is a control and does not contain any plants or fish, so there won't be any CO2 production, and thus the bromothymol blue will remain blue.

Based on this analysis:

• Flask 2 will turn yellow due to the fish's cellular respiration producing CO2.
• Flask 3 may also turn yellow, depending on the balance between the CO2 produced by the fish and the CO2 consumed by the plant.

Thus, the most suitable answer to the question is D: Flask 2 (only) because the fish produce CO2 as products of cellular respiration and do not undergo photosynthesis therefore not consuming CO2. However, keep in mind that Flask 3 might also turn yellow depending on the specific conditions and balance of photosynthesis versus respiration. But based on the options given, D is the most direct and accurate statement regarding CO2 production.