Carbon dioxide levels affect the rate of photosynthesis and how much oxygen is produced in the process. In this interactive, the carbon dioxide levels can be manipulated. The resulting oxygen changes are followed with the help of an electrochemical gas sensor. Instructions: Drag the carbon dioxide slider to see how carbon dioxide affects the rate of photosynthesis of the water plant Elodea. Select the “Show oxygen” and "Show carbon dioxide" boxes to see the gases being released as bubbles in the tube.