Human Energy Systems | Activity 4.3

Ask students to verbally share accounts of the Keeling Curve to activate their prior knowledge.

• Display Slide 3 of 4.3 Tiny World Modeling PPT, which shows an image of the Keeling Curve.
• Ask the students about patterns they notice on the graph.

Display Slide 4 of 4.3 Tiny World Modeling PPT. Share with students their three goals that they want to figure during this activity:

• what makes CO₂ concentrations in Hawaii go up every winter and down every summer,
• what makes CO₂ concentrations a little higher each year, and
• how to predict future CO₂ concentrations

Display Slide 5 of 4.3 Tiny World Modeling PPT. Use the animation to review and make connections between the image and the more abstract “box diagrams” we use to represent the carbon pools.

You may want to point out two interesting things about these pools:

• The biomass pool contains carbon found in the form of living things (including people) and recently living plants and animals. Most biomass on the earth is stored in the wood of trees and other plants.
• The soil organic carbon pool is a large pool of carbon (as large as the atmosphere and biomass pools combined). It contains carbon in the form of dead organisms (plants, animals, and decomposers) and living decomposers.

Display Slide 6. Review the atmospheric, organic carbon and fossil fuels pools. Recognize where carbon is in each pool.

Turn to Slide 7 of 4.3 Tiny World Modeling PPT. Use the figure to ask some more in-depth questions about its content, such as:

• Where is the organic matter pyramid on the figure?
• Why doesn’t energy cycle like matter? (answer: energy flows, matter can be recycled)
• Why is the photosynthesis arrow so wide? (answer: this is the only process that incorporates “new” carbon atoms into an ecosystem, converting inorganic carbon molecules to organic carbon molecules)
• What ultimately happens to most of the carbon that enters the ecosystem through photosynthesis? (answer: it is returned to the atmosphere through cellular respiration carried out by producers, herbivore, carnivores, and decomposers)

Use Slide 8 to define fluxes as rates (mass/time). Explain the terms, movements and fluxes. Turn to Slide 9 to further discuss fluxes and to ask some more in-depth questions about its content.

Display Slide 10. Hand out one 4.3 Tiny World Modeling Worksheet to each student along with a 4.3 Tiny World Pool and Flux Placemat and 30 markers. The game can be done by individual students or in pairs. Each student keeps his/her own data and graphs.

Use Slides 10-11 to explain the game and setup.

Show Slide 12. As a class, run through scenario 1 of Tiny World Modeling: a world with no seasons and balanced fluxes. In this scenario, we will have 15 carbon atoms in the organic pool and 5 in the atmospheric pool. Have students put the appropriate number of markers on placemat and starting points on the graph. Both the photosynthesis and cellular respiration rate are at 2 carbon atoms/year. Have class work through years by moving chips according to the fluxes and recording each year’s result in the chart and on the graph. Students should connect the dots for the organic (green) pool with a dashed line and use a solid line for the inorganic atmospheric pool.

Have students play through year 5, recording and graphing their data as they go.

Have students compare their results to Slide 12.

Tell students they can try scenarios 2, 3 and 4. Display Slides 13-15 of 4.3 Tiny World Modeling PPT when students are ready to check their completed graphs.

When finished with the Tiny World Modeling Activity, Use Slide 16 to have students summarize what they found about the relationship between pool size and fluxes as a whole class. Don’t show the bullets until they are done summarizing.

Display Slide 17. Have students compare the Keeling Curve graph from earlier to their results from scenario 4: Tiny World Model with seasons and combustion. Discuss patterns and rules from the modeling activity that can be seen in the Keeling Curve graph.

Students complete pages 6 and 7 (explaining the annual cycle and the long-term trend on the Keeling Curve) of 4.3 Tiny World Modeling Worksheet, using the Four Questions handout and checklist.

Using Slides 18-21, have students trade their explanations with a partner and check each other's explanations using a different color pen. You may choose to allow students to revise their own explanations in a different color after receiving feedback.

Show Slide 22 of the 4.3 Tiny World Modeling PPT.

• Have students take out theirLearning Tracking Tool for Human Energy Systems from the previous lesson.
• Have students write the activity name in the first column, "4.3 Tiny World Modeling."
• Have a class discussion about what students figured out during the activity that will help them in answering the lesson driving questions:
• What causes the annual cycle: CO₂ concentrations in Hawaii to go down every summer and up every winter?
• What causes the long-term trend: CO₂ concentrations to go up every year?
• How can we predict what will happen to CO₂ concentrations in the future?
• When you come to consensus as a class, have students record the answer in the second column of the tool.
• Have a class discussion about what students are wondering now that will help them move towards answering the unit driving question. Have students record the questions in the third column of the tool.
• Have students keep their Learning Tracking Tool for future activities.
• Example Learning Tracking Tool

• Show Slide 24 of the 4.3 Tiny World Modeling PPT.
• Conclusions: What fluxes change the size of the atmospheric CO₂ pool?
• Predictions: How are those fluxes affecting the Earth’s atmospheric CO₂ pool?
• On a sheet of paper or a sticky note, have students individually answer the exit ticket questions. Depending on time, you may have students answer both questions, assign students to answer a particular question, or let students choose one question to answer. Collect and review the answers.

The conclusions question will provide you with information about what your students are taking away from the activity. Student answers to the conclusions question can be used on the Driving Questions Board (if you are using one). The predictions question allows students to begin thinking about the next activity and allows you to assess their current ideas as you prepare for the next activity. Student answers to the predictions question can be used as a lead into the next activity.