Human Energy Systems | Activity 4.3

Target Student Performance

Students investigate the relationship between pools and fluxes in a physical model of a tiny world, showing how changing photosynthesis, cellular respiration, and combustion fluxes can account for both an annual cycle and a long-term trend in the atmospheric CO2 pool.

Resources You Provide

  • Markers for Tiny World Pool and Flux Activity to be used on the placement (30 per pair of students)

Resources Provided

Recurring Resources


Print the 4.3 Tiny World Pool and Flux Placemat. You may want to laminate them first in order to make them last longer. Print one copy of 4.3 Tiny World Modeling Worksheet for each student. Prepare a computer and projector to display the 4.3 Tiny World Modeling PPT.


1. Use the instructional model to show students where they are in the course of the unit.

Show Slide 2 of the 4.3 Tiny World Modeling PPT.


Check to see if students are making the connection that photosynthesis causes the inorganic pool to shrink and the organic pool to grow, whereas cellular respiration causes the opposite trend. Students might also suggest that photosynthesis causes a “flux” to the biomass pool, and cellular respiration causes a “flux” to the atmosphere pool. In addition, check that students are understanding how combustion contributes to the atmosphere pool and is not balanced by a different flux.

  • Identify locations in the room as the two carbon pools, then have students play the role of carbon atoms moving between the two pools.
  • Project the graphs onto a white board and demonstrate how to fill them in after each move.
  • Have students work in pairs and fill out one worksheet for each pair.

Demonstrate how to use one scenario card with the class before dividing them into pairs or groups to discuss their cards. You may also want to draw circles on the board to represent the biomass (organic) and atmosphere (inorganic) pools that students can use to illustrate the results discussion or ask questions.

Extending the Learning