Carbon: Transformations in Matter and Energy Environmental Literacy Project Michigan State University Ecosystems Unit Activity 4.4 Seasonal Changes and Ecosystem Disturbances Image Credit: Craig Douglas, Michigan State University

Unit map You are here Use the instructional model to show students where they are in the course of the unit. Show Slide 2 of the 4.3 How Fluxes Change and Carrying Capacity PPT.

Computer Model for Seasons and Disturbances Read the handout until Section A to review the Constant Flux and Changing Fluxes Simulations. What did you learn from the first two simulations? How is Model 3 different? Review the Constant Fluxes Model and introduce the Changing Fluxes Model. Show Slide 3. Pass out the 4.3 Computer Model for Changing Fluxes Handout to each student. In partners or as a whole class, have students read the handout. Discuss how the Constant Flux and Changing Fluxes Models are different. Review the idea of carrying capacity for Activity 2.4 and relate it to the photosynthesis flux.

The Seasons Model 3 without seasonal variation Carrying capacity = 90 kg/yr Atmospheric pool = 500 kg Organic carbon pool = 500 kg Show students how to use the simulation. Show Slide 4 and open the simulation. Show students how to move the sliders and run an example. Point out the graphs and how they can slide the line of the graph to get data for a particular point in time.

Question 1 Year 14.0 Year 16.0 Photosynthesis flux   Year 14.0 Year 16.0 Photosynthesis flux Cellular respiration flux Organic matter pool

The Seasons Model 3 with seasonal variation Carrying capacity = 90 kg/yr Atmospheric pool = 500 kg Organic carbon pool = 500 kg

Question 2

Question 3

Press and Pulse Disturbances

Disturbances in Real Ecosystems Read about disturbances in real ecosystems. What are some examples of press and pulse disturbances? Record your answer for Question 6 on your worksheet.

Discussion How do the pools and fluxes change during seasons? Why? How do disturbances affect ecosystems? Discuss the patterns. Show Slide 14 of 4.3 How Fluxes Change and Carrying Capacity PPT. Have students share and discuss their answers to questions.

Students answer the Stability and Change Question. Show Slide 14. Remind students of the Four Questions focusing on the fourth. Have students write their ideas about how they would answer the Stability and Change Question. Remind students to follow the rules and to think about the evidence to include. Then, allow students to share their ideas with a partner. Have a whole class discussion about the Stability and Change Question.