Ecology: Photosynthesis and Earth's Atmosphere

See real-time evidence that gaseous oxygen is produced during the light-dependent reactions of photosynthesis! Also see evidence that gaseous CO2 is used up by the plant during the light -- independent reactions of photosynthesis.

Motion Sensors

As oxygen is released during photosynthesis, pressure increases in the test tube. Challenge your students to understand why the pressure decreases when the light is turned off. Enlarge graph.

Lab Summary:

In this exploration, students will use a Barometer to observe the increasing pressure resulting from oxygen production by an aquatic plant that is exposed to light. This activity will help students understand the contribution of plants to the Earth’s atmospheric oxygen.

This activity will also help students understand that plants remove CO2 from the atmosphere during the light-independent reactions of photosynthesis. When students place the plant in darkness, they will see the pressure decreasing as the plant takes up CO2 to support the light-independent reactions of photosynthesis.

Download Free Lab  (PDF, 496 KB)

(student version)

Method:

Use the Barometer to observe the increasing pressure resulting from oxygen production by an aquatic plant that is exposed to light.

Here's What You Need:

Probeware

Other Materials

  • High intensity lamp, such as one with a 100-watt Fluorescent Bulb
  • Erlenmeyer Flask, 250-mL
  • Test Tube, large
  • Dark cloth, 1.0 m2
  • Protective Gear
  • Water, 250.0 mL
  • Healthy Elodea (Anacharis) plants

Lab Manual:

This activity is included in Explorations in Biology (PS-2807), complete with Teacher Information pages, student instructions and handouts, and sample data for a total of 25 probeware-based labs. For your convenience, we offer bundles which provide the probeware necessary for the activities in the manual. For more information on these resources and bundles, click here.