Activity 2.4: Organic Carbon Pools in Other in Ecosystems (40 min)

Use 2.4 Organic Carbon Pools in Other Ecosystems PPT to compare the Meadow Simulation to different ecosystems.

• Remind students that the Meadow Simulation was a simulation of one specific ecosystem: a meadow. Show students the biomass pyramid on Slide 3 and discuss how it represents the patterns observed in the simulation.

Use Slide 4 to introduce four different types of ecosystems. Have students consider two ecosystems at a time—prairie vs. desert and cornfield vs. forest—during Slides 5-13. Students should write down a prediction on a piece of paper. Ask: Which ecosystem will have the most organic carbon? They could also predict which pool they think will be the largest.

Many students will make reasonable predictions about the amount of living organic matter, but we expect that many students will be surprised when they see that in most terrestrial ecosystems the largest organic carbon pool is soil carbon.

Accommodation: Have students share their predictions to the class for the question “Which ecosystem will have the most organic carbon?” As students share their predictions, write down these predictions on a sheet of paper or the board.

Use Slide 14 to prompt students to write down as many observations as they can about how the four ecosystems are alike and different.

• The main thing they should notice is that the relative sizes of ecosystem pools is the same across ecosystems: the largest pool is the soil organic carbon, followed by producers, then herbivores, then carnivores.
• They may also notice that soil organic carbon is the largest pool in the prairie, but the forest has the most organic carbon in producers. You may use this opportunity to talk about how pool sizes are different because of the history of the site (lots of grasses growing and dying increase the soil organic carbon pool) and the size of the organisms that live there (trees versus corn).
• They should also notice that the total organic carbon differs across ecosystems.
• They may also notice that human management produces a somewhat different pattern for the corn field. Humans use fences, hunting, and pesticides to kill or keep out most herbivores (since we want to use the corn for ourselves), so the herbivore and carnivore populations are much smaller than for natural ecosystems.

Use Slide 15 to introduce the ideas differ in the total organic carbon that they can support Students will be explore this idea more deeply more in Lesson 4. Ecologists answer the last question (about why different ecosystems have different amounts of total organic carbon) by identifying limiting factors, including:

• Water (the primary limiting factor for deserts)
• Temperature (the primary limiting factor in Arctic and alpine ecosystems)
• Nutrient availability (the primary limiting factor in rain forests)

This is a good time elicit students’ ideas and questions about what limits organic carbon in different ecosystems. You do not need to teach about limiting factors at this point.

Accommodation: For the information on the final slide, as a class create organic matter pyramids or other bar graphs to show the size of the pools as visuals. Have students describe the organic matter pools in the four ecosystems (desert, forest, corn field, and prairie) including the herbivores, producers, and carnivores that live in each ecosystem.

If you decided to use the Big Idea Probe: Wolves and Deer, have students complete it and share their ideas for a second time. See Assessing Big Idea Probe: Wolves and Deer and Using Big Idea Probes

Show Slide 16 of the 2.4 Organic Carbon Pools in Other Ecosystems PPT.

• Pass out a Learning Tracking Tool for Ecosystems to each student.
• Have students write the activity chunk name in the first column, "The Meadow Simulation."
• Have a class discussion about what students did during the activity chunk. 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 figured out during the activity chunk that will help them in answering the unit driving question. When you come to consensus as a class, have students record the answer in the third 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 fourth column of the tool.
• Have students keep their Learning Tracking Tool for Ecosystems for future activities.
• Example Learning Tracking Tool