Students as Teachers 20 min

• I explain that the "carbon students" will have 8 minutes to explain their cycle to the "nitrogen student". They should talk about their cycle, the reservoirs they went to and how they got there. They should also mention any reservoirs they did not visit and discuss why that could have happened. I clarify that their share is not about, "I rolled a two...", which is information that they do not have in their sheets, but rather, "I went to ______ because _________." I also explain that during this time, the job of the nitrogen students is to listen intently, take notes about what is being said, ask questions regarding the carbon cycle. I tell students that the sharing time is important for what they will do next, so even if the carbon student says s/he is done, they must not move on, but rather keep the conversation about the carbon cycle going. I set a timer for 8 minutes and have students begin their conversations.

• During this time, the students are engaged in scientific discussions with peers (SP8) and developing conceptual models of each other's work (SP2). As the students are talking about the carbon cycle, I am walking around the room helping facilitate conversations as needed.

• After the 8 minutes are up, I repeat the process, only this time it is the nitrogen cycle students that are sharing (with the same rules and expectations) to the carbon students.

• Watch as a student explains the carbon cycle to a partner.

Comparing the Cycles 20 min

• Once the second round of conversations is done, I explain that they will now work together with the same student to compare/contrast the nitrogen and carbon cycle, and hand out a cycles comparison sheet to each partnership.

• Students working on the comparison continue to develop the conceptual models (SP2) that illustrate the cycling of matter through ecosystems (SW1, SW2, SW3) (CCC Systems and System Models, Energy and Matter).

• Energy and Matter - Matter is conserved because atoms are conserved in physical and chemical processes.

• Systems and System Models - Models can be used to represent systems and their interactions - such as inputs, processes and outputs - and energy, matter, and information flows within systems.

• Note to teachers: Students often ask for the game boards during the comparison activity. When they ask, I do not give them the boards, but rather I have on hand more detailed copies of both cycles, which are helpful to clarify the finer points of the cycles (nitrogen, carbon).

• Although not imperative that all students do this, students who complete their comparisons early are asked to create a poster of the comparison they made. The posters stay up as reference during the remainder of the unit. If no partnership finishes with enough time, I offer this poster activity as an extra credit opportunity.

• I asked a couple of students to talk about the comparisons. Did you notice how one student thought "both are cycles" is too obvious to even include it?

Closure 5 min• To close this lesson, I post an assignment on Edmodo. This assignment is the

assessment for these lessons. I display the prompt, and read through it to make sure that everyone understands it. The prompt is:

• "Grandma Johnson had very sentimental feelings toward Johnson Canyon, Utah, where she and her late husband had honeymooned long ago. Her feelings toward this spot were such that upon her death she requested to be buried under a creosote bush overlooking the canyon. Trace the path of a carbon or nitrogen atom (your choice) from Grandma Johnson’s remains to where it could become part of a hawk. Note: The hawk did not dig up and consume Grandma Johnson’s remains."

• Note to teachers: This prompt comes directly from Barbara Fleming's lesson "Nutrient Cycling". The student answers (Grandma Johnson CC, Grandma Johnson NC) reveal a firm understanding of both processes.

READ THE FOLLOWING PASSAGE, THEN USING A DIAGRAM AND WRITING TO EXPLAIN THE DIAGRAM,

TELL HOW THE NITROGEN OR CARBON ATOM BECOMES A PART OF THE HAWK.

"Grandma Johnson had very sentimental feelings toward Johnson Canyon, Utah, where she and her late husband had honeymooned long ago. Her feelings toward this spot were such that upon her death she requested to be buried under a creosote bush overlooking the canyon. Trace the path of a carbon or nitrogen atom (your choice) from Grandma Johnson’s remains to where it could become part of a hawk. Note: The hawk did not dig up and consume Grandma Johnson’s remains."