The Atmosphere: It's a Gas! (AIG IRP)

Stage 2: Elaborate

Using the student-created diagrams from Day One, review the current composition of Earth’s atmosphere.  State that students will be delving into more detail using prepared diagrams of the cycles that maintain the atmosphere’s current state.  Explain that today’s process is almost the opposite of yesterday’s work: Yesterday they organized information to create diagrams, whereas today they will interpret existing diagrams to create short statements that explain the processes presented.

Hand out the prepared diagrams.  The teacher may choose to explain to students that since the earlier activity has already established that bacteria were necessary to start the conversion of both CO2 and N2 into useful forms, and then plants as a life form evolved to also perform photosynthesis, it is not necessary to establish these points as the starting point of the nitrogen and carbon cycles when they are described.  The gases in question and the living organisms that contribute to these cycles are already in existence, so students may start anywhere on these cycles.  Likewise, the water cycle also does not have a defined starting point.  

As students work in pairs to interpret and record the flow of atmospheric gases through these cycles, the teacher should be prepared to ask similar questions to Day One’s activity, as well as some additional questions:  “What would need to happen before _______?”  “What could be the result of _______?” “Would that have happened before or after ________?” “Where does the arrow indicate the gas travels next?”  “If there is a choice where the gas goes next, how can you make subsequent choices so that the gas goes through the entire cycle?”  Does the gas have to repeat any steps before it can finally get to ________?”