DESIGN LAB: Nitrogen (3 of 4)

3 teachers like this lesson
Print Lesson


Students will be able to engage in an engineering design thinking cycle to develop a functional nitrogen cycle prototype from unique model ecoystems.

Big Idea

A functional nitrogen cycle is an essential part of healthy agricultural systems. How might we use models to help us understand how the nitrogen cycle becomes disrupted and what might be done to prevent disruption?

FRAME: Designing with model ecosystems

In the previous two lessons, students developed a framework for materials recycling, developed proficiency with testing strips that measure nitrate, nitrite, and ammonia, made predictions about how the levels of these compounds would change over time in model ecosystems, developed familiarity with key terms used to describe the nitrogen cycle, and described how humans can impact the nitrogen cycle.  At this point of the DESIGN LAB sequence, students possess foundation knowledge, basic conceptual frameworks, and lab skills.  They are ready to apply their experiences to a design challenge: how might we design a functional nitrogen cycle with our model ecosystems to understand factors that disrupt the nitrogen cycle, and, by extension, apply insights to prevent future disruptions?  This is the heart of this DESIGN LAB.  It allow students to model problems and solutions that occur in modern agricultural systems, a topic explored in "Does McDonalds Have a Farm?"

For this lesson, students will engage in a guided engineering design thinking cycle.  This will include the following stages: empathize, define, ideate, and prototype.  Testing will not formally happen until the final lesson in this sequence. (See Unit 0 of this curriculum for a deeper exploration of each of these parts of the engineering design thinking process.) The goal for the lesson is for students to develop prototypes of functional nitrogen cycles using model ecosystems.  The teacher formatively assesses students proficiency in engineering design thinking and supports students in empathizing, defining, ideating, and prototyping.  Most importantly, students' design choices should reflect an understanding of the requirements for a functional nitrogen cycle and the teacher's assessment and feedback should align to the objectives.  Students that develop a prototype are not proficient if they cannot explain the reasoning for their design choices.

By the end of this DESIGN LAB sequence, successful students will have met the following objectives:

  1. explain the role of recycling in biogeochemical cycles
  2. use test strips to measure levels of ammonia, nitrate, and nitrite in various aquatic environments
  3. predict how levels of ammonia, nitrate, and nitrite will change over time.
  4. trace the movement of nitrogen through the nitrogen cycle
  5. define key vocabulary terms used to describe the nitrogen cycle
  6. describe how humans influence the nitrogen cycle
  7. engage in an engineering design thinking cycle to develop a functional nitrogen cycle prototype from unique model ecoystems.
  8. test nitrogen cycle prototypes through peer review
  9. iterate prototype designs
  10. develop an experimental design to assess the effective of design prototypes
  11. connect potential experimental outcomes to modern agricultural practices.

FEEDBACK NOTE: Teacher that want to provide feedback to groups about their engineering design thinking process might use this rubric from Unit 0 or this series of rubrics from the Henry Ford Learning Institute.


  • The materials for this lab were purchased from Carolina.  
  • The included prototype activity guide is a basic template that might be differentiated for a a group of diverse learners.

EMPATHY- Minnesota's water

8 minutes

What is the purpose of this section?

Students review the components of the EMPATHY stage of engineering design thinking and then examine a case study to draw conclusions about how disrupted nitrogen cycles impact humans. This work happens in the same groups as the first lesson is this DESIGN LAB sequence.  The teacher can use formative assessment data from students' process to corrects missteps.  Do students rightly identify needs that arise from the poor health of the environment?  By the end of this section students should be able to describe real need Minnesota residents have.  An example might be: "Minnesota residents need to reduce the nitrates in the water because they want their children to be healthy."

What will the students do?

Students first review the key elements of the empathize stage.  Next, students examine a recent environmental news story about water in Minnesota as a case study to understand the human need for functioning nitrogen cycles.  The story captures a common problem caused by runoff from agricultural systems and connects back to content studied in the "Does McDonalds Have a Farm" lesson sequence. Here is the clip:


As students watch, they should capture response to the following questions:

  1. What problems do Minnesota residence face?
  2. Why is this is a problem?  
  3. What is the need that Minnesota residents have that this problem does not allow to be met?

Students will share out ideas in small groups and then with the whole class.  Ideas about Minnesota residents' needs will be placed on the front whiteboard.

What will the teacher do?

During this activity, the key teacher move is to support students' framing of the human need.  Many students might identify the problem of nitrates.  The empathy stage challenges students to explain why the problem is the problem.  What need do Minnesota residents have that makes the problem a problem?  Nitrates, for instance, are a problem, but only because Minnesota residents have a need for healthy families.  Framing the problem from the perspective of human need is how this curriculum attempts to provide the motivation for understanding environmental science.  My students might not care about the nitrogen cycle; however they will care about having unhealthy children because of environmental problems caused by a disrupted nitrogen cycle.

DEFINE: What is the problem?

22 minutes

What is the purpose of this section?

Students build on the human needs they identified in the EMPATHIZE sections and define a problem to be solved.  In an ideal school environment, students could travel to the community in Minnesota featured and develop local, specific problem statements.  For this activity, however, students will develop more general problem statements.  These defined problems can be written as statements or how might we questions.  For example, how might we use our model ecosystems to understand how to decrease the levels of nitrates in the water? 

What will the students do?

The class first reviews the components of the DESIGN stage.  Then groups from the first lesson collect ammonia, nitrate, and nitrate readings from their assigned model ecosystem.  Students next use the three data readings to help define what the problem might be for Minnesota residents. We know that nitrates are in the water.  Why might this be happening?  To start to figure this out, we will take one more data recording of our plant, fish, and bacteria stations from the previous week.  By sharing the results, maybe we will spot a pattern.  Do we need more plants?  Do we need the same amount of bacteria?  Will fish help us reduce nitrates?

This process is open-ended and collaborative.  Students groups will communicate with each other to make meaning of collected data.  The only "right" answers are the answers supported by the data.  Groups should not use outside information to develop problem statements without also consulting data.

What will the teacher do?

This is a lesson taking place near the end of the school year so students' habits of collaborative work are well-developed.  The key teacher move in this activity is to redirect students towards authentic problem definition that evidence supports.  Where in the collected data do you see a trend that supports your problem definition?  What evidence did you use to come up with the idea that bacteria really reduce nitrates?  

IDEATE: How might we create a model of the nitrogen cycle?

10 minutes

What is the purpose of this section?

Students continue their work from the DEFINE stage to develop ideas for building a prototype of the nitrogen cycle.  The teacher frames the IDEATE stage as a design challenge.  We know that the negate human health consequence of nitrates in the water are a problem.  What can we do about this problem?  We have seen from our DEFINE stage that our individual model ecosystems did not efficiently cycle nitrogen.  So we have a design challenge.  We need to build functional nitrogen cycles, cycles in which the levels of ammonia, nitrate, and nitrite do not steadily build over time.  By the end of this activity students groups should have generated a few potential prototype ideas based on an understanding of the requirements for a functional nitrogen cycle.

What will the students do?

Students first review the important aspects of the IDEATE stage and then choose a problem statement from those listed.  Once student groups have a problem statement, they ideate solutions.  These solutions ideas are constrained by the materials available, which include the bacteria, fish, and plant ecosystems, water pumps, tape, scissors, test strips, and plastic tubing. The prototype activity guide contains three resources curated by the teacher that will assist students' ideation process.  

Ideation can be a complex task, but students will follow a familiar format of first thinking divergently and then narrowing choices through convergent thinking.  Many students will want to start prototyping.  If students are silently drawing ideas or attempting to build with the available materials, they have skipped to the PROTOTYPE stage.  The IDEATE stage requires communicate among all group members.  It is a key moment in the engineering design thinking cycle that positions a group to develop a successful, purposeful prototype.

What will the teacher do?

The teacher is in a framing and support role for this activity.  Framing this activity as an ideation stage process is an important teacher move.  Students may need a reminder that this stage is about communication and brainstorming.  As students move through this process, the teacher may need to facilitate discussions with groups.  If most groups appear to skip communication, another important teacher move is to conduct a teacher-facilitated brainstorming session that allows groups to think divergently before converging on a single prototype idea.  If students teams are truly having difficulty with this process, the teacher should recommend that groups revisit material from the aquaponics farm tour for solution ideas.

PROTOTYPE (1 of 2): What we want to make is...

10 minutes

What is the purpose of this section?

Student teams build out physical prototypes of their solution ideas using materials available in class. The teacher supports the prototyping process through purposeful questioning of individual groups. Why did you make this design choice?  What else did you consider?  By the end of this activity, students should have an in-process physical prototype that incorporates the essential elements of the IDEATE activity.

What will the students do?

Students will first review the requirements of prototyping and then develop a physical prototype that meets the requirements of this prototype description:

You will be designing a system that allows nitrogen to cycle throughout the three tanks. In order to accomplish this task, water will need to flow from one tank to another. There are two methods by which water can flow from one method to another: 1) tubing with an air pump 2) water falling over the edge of one tank into another (use foam to create different levels) Sketch ideas for your prototype in the space below and then build your prototype.

What will the teacher do?

The teacher frames this activity and then essentially allows controlled chaos to ensue.  Now that we have developed potential solution ideas, we are going to build rapid prototypes.  Available materials are on the front station.  Guidelines for how to complete this task are included in the prototype activity guide.  We will present our prototypes to each other in a baby shark tank format to receive feedback for iteration.  Once we have feedback we will construct final prototypes.  Students will jump at the chance to make their ideas physical realities.  This process can seem crazy, but teachers should trust that what seems like a process of control is what a classroom looks like then student groups are actively trying to make prototypes in a short period of time.  There will be noise and movement-bus beneath this there will be deep focus and authentic collaboration.

EXIT: Our prototype focus area is...

5 minutes

What is the purpose of this EXIT?

This EXIT will feel rushed because students will not want to stop their work.  The teacher explains that during the next class prototypes will be further developed, tested, and then iterated.  The teacher also asks the class to consider this question for the next lesson: how might these nitrogen cycle prototypes help us address real problems with industrial agriculture?  Once this framing is done, a member from each group shares a brief summary of an in-process prototype. These summaries will be about 20 seconds.  Many students are likely to talk about using the aquaponics farm tour as a solution idea.  If this occurs, the teache must remind all groups that aquaponics is one solution idea, but should not be considered as the "correct" solution idea. The goal is for student groups to design, not simply adopt a previously encountered design modelFinally, all groups clean lab stations and store materials as the class end in a soft close.