Activity 2.2: The Meadow Simulation (50 min)

Use slides 3 – 5 to review the features of the online Meadow Simulation.

Give each student a copy of the 2.2 Meadow Simulation Worksheet. Students should work in pairs at a computer. Use slide 6 to give the following directions:

• With a partner complete trials 1 & 2 (questions 1 – 5) on the Meadow Simulation Worksheet.
• Tell students: "Be ready to explain your results and your answers to the class. Do not go on until we have discussed our results as a class."

Use Slide 7 and 8 to discuss the results of trial 1.

• Use Slide 7 to show the results of trial 1 (initial mass = 500 for foxes, rabbits, and grasses). Ask students: What happened when we started with populations of equal mass? Listen for students' responses to recognize that the fox population quickly declined, the rabbit population initially declined but then returned to somewhat higher levels, and the grass population increased and then leveled off (the line graph captures this information, but students also saw it happening on real time through the “camera” image of the organisms).
• Ask students: What are the relationships between the four different representations (line graph, organic mass diagram, table, picture)? Make sure that they realize that all four representations are different ways to represent the amount of organic matter in each of the three populations. The “camera” shows the populations in “real-time,” the line graph shows the mass of each population at each time point, and the organic matter diagram and table show the mass of each population at selected time points. Help students connect the more concrete representation of the organisms through the camera viewer with the more abstract representations (especially the line graph and the organic matter diagram).
• Note to teachers: you may know the organic matter diagram as the “biomass pyramid” or “organic matter pyramid.” In the next activity students will identify this pattern, so try to refrain from calling it a pyramid at this point. Subsequent lessons will help students to develop an explanation for the organic matter pyramid.
• Use Slide 8 to show the initial and final organic mass diagrams. Ask students: How do we explain the changes in the organic mass diagram? Listen for them to explain that rabbits eat grasses and foxes eat rabbits. Probe their ideas by asking When a rabbit eats 10 pounds of grass do all 10 pounds end up as rabbit organic matter? Where does the rest go? Listen to see if students remember that some of the mass of food that rabbits eat is lost as carbon dioxide and water through the process of cellular respiration. A full explanation of the organic matter diagram will be the focus of lesson 3.

Use Slides 9 and 10 to discuss the results of trial 2.

• Use Slide 9 to show the results of trial 2 (initial mass = 1000 for foxes, 500 for rabbits, and 100 for grasses). Ask students: What happened when we started with the greatest mass in the carnivore population, less in the herbivores, and the least mass in the producer population? Listen for students’ responses to recognize that the foxes quickly ate all of the rabbits, so both populations died out leaving only grasses.
• Use Slide 10 to ask, “How do we explain the changes in the organic matter diagram?” Listen for students to explain that only grasses remained and there were no herbivores, so the grass population increased.

Use Slide 11 to explain the challenge and how they should record their data on the worksheet. Students will use this data to complete the Evidence-Based Arguments Tool in Activity 2.3.

Show Slide 12 of the 2.2 Meadow Simulation PPT.

• Conclusions: What patterns did you find in the organic mass of the grass, rabbit, and fox populations?
• Predictions: Why is the fox population always small after 100 years?
• 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.