A flask containing photosynthetic green algae and a control flask containing water with no algae are both placed under a bank of lights,which are set to cycle between 12 hours of light and 12 hours of dark.The dissolved oxygen concentrations in both flasks are monitored.Predict what the relative dissolved oxygen concentrations will be in the flask with algae compared to the control flask.
A)The concentration of dissolved oxygen in the flask with algae will always be higher.
B)The concentration of dissolved oxygen in the flask with algae will always be lower.
C)The concentration of dissolved oxygen in the flask with algae will be higher in the light but the same in the dark.
D)The concentration of dissolved oxygen in the flask with algae will be higher in the light but lower in the dark.
E)The concentration of dissolved oxygen in the flask with algae will be lower in the light but higher in the dark.

Question

Quizplus · Accepted Answer

During the day (light phase), photosynthesis will take place in the flask with algae resulting in an increase in dissolved oxygen concentration. At night (dark phase), photosynthesis will cease but respiration by the algae will continue, resulting in a decrease in dissolved oxygen concentration. Therefore, the concentration of dissolved oxygen in the flask with algae will be higher in the light but lower in the dark compared to the control flask without algae.

A Flask Containing Photosynthetic Green Algae and a Control Flask