SIMULATING ENVIRONMENTAL CHANGES
Minibiospheres also provide an opportunity to set up experiments to test the effects of simulated environmental changes on the system. To spur inquiry, ask your students to hypothesize what might happen if something in the environment stimulated changes in their school pond. What if we let a tree grow up and shade the pond? What if salt used to melt ice on the sidewalk, or fertilizer used on the playground turf washed into it? Have students use their imaginations to come up with their own ideas. Compile their ideas and ask how they would set up an experiment to test such changes in the pondwater biospheres.
Have small groups of students set up several minibiosphere jars. Be sure to keep one jar as the control and experiment with the others. Groups might each test the same variables, or different concentrations or degrees of a single variable. Here are some suggestions:
- 24 hours of light vs. natural (12-14 hours)
- low pH versus actual pond pH (simulated acid rainfall)
- no light (cover with black paper)
- addition of small quantities of fertilizer (simulated fertilizer runoff)
- cold versus warmer temperatures
- addition of salt (simulated road salt runoff)
- addition of commercial phosphate detergent (simulated pollution)
- colored cellophane around jars (growth under different light colors)
Once you've recorded results from some of these experiments, extend them into a discussion or study of how human activities stimulate analogous environmental changes in your region (e.g., eutrophication in local water bodies from nutrient pollution; sterilization of lakes and waterways due to acid rain; salinization of water supplies) and what is being done to help restore health to these bodies of water.