Question

A student measured the amount of oxygen and carbon dioxide dissolved in an aquarium containing an aquatic plant and a snail. Why did the amount of dissolved oxygen decrease when the aquarium was kept in the dark for 10 hours?A . Because photosynthesis could not occur

  B. Because the plant died   C. Because the snail died   D. Because cellular respiration could not occur

Answer 1

The answer is A. Putting the aquarium in the dark means that the aquatic plants will not be able to photosynthesize. The process of photosynthesis produces oxygen as a by-product. The oxygen is used by the fishes in respiration and release carbon dioxide. The carbon dioxide is used by the aquatic plants in photosynthesis.