A flask containing an aquatic plant in water is placed next to a light. A sensor that detects the amount of dissolved oxygen (i.e. the amount of oxygen produced by the plant) is placed in the flask, and the light is set on a timer to run on a 12- hour-light, 12-hour-dark cycle for 48 hours. (a) Explain how the amount of dissolved oxygen will change in the flask during the 12-hour-light cycle if ONLY photosynthesis is taking place during the daytime (i.e. no respiration). Support your explanation using information about the processes that are occurring in the flask. (b) Explain how the amount of dissolved oxygen will change in the flask during the 12-hour-dark cycle. You can assume that respiration IS taking place at night Support your explanation using information about the processes that are occurring in the flask.

Photosynthesis is the process by which plants, algae, and cyanobacteria produce their own food. The process of photosynthesis involves the trapping of sunlight by a pigment known as chlorophyll and CO2 and water along with it to produce oxygen, energy, and glucose.The amount of dissolved oxygen (DO) will increase in the flask during the 12-hour light cycle because only the process of photosynthesis is taking place in this time period and oxygen is a product of photosynthesis. As is mentioned in the question that no respiration takes place during the light cycle, so no oxygen is utilized by the plant. Hence, the amount of oxygen that is dissolved will keep on increasing during the 12-hour light cycle when no respiration is taking place, contributed by the process of photosynthesis. During the process of photosynthesis, in its light phase, oxygen is produced by the splitting of water molecules, which occurs by the release of high-energy electrons by the photosystems after trapping light.The dissolved oxygen (DO) decreases during the 12-hour dark cycle because photosynthesis cannot occur in the dark and respiration takes place. Respiration utilizes oxygen and produces carbon dioxide as a by-product. So, during the dark phase, the amount of dissolved oxygen already present in the flask will be used, leading to its depletion because oxygen is not being produced by photosynthesis during this phase. During photosynthesis in its dark phase, CO2 is converted into carbohydrates and other biomolecules, and there is no production of oxygen. Respiration is the metabolic pathway by which the sugars are broken down with the help of oxygen and in turn, energy is generated.