Lesson One: Nitrogen Cycling

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Title of Lesson: Nitrogen Cycling

Subject(s): Science

Grades: 6-12

Teacher: Tami Lunsford tami_lunsford@hotmail.com

To the teacher: This activity is designed to strengthen the students' understanding of the nitrogen cycle in aquatic systems, the roles of different biological organisms and communities, the terms used, and the complexity of an ecosystem. Before attempting this activity, students should be familiar with the nitrogen cycle and the terms and organisms associated with it.

I. Standards Addressed through the lesson:

Domain II: What we need to know about the world around us.

Content Standards:
#5. Students describe, analyze, and give examples of how organisms are dependent on one another and their environments.
#6. Students trace the cycling of matter and the flow of energy through systems of living things.

II. Goals of the Lesson:

The goal of the lesson is to cycle nitrogen through a mock ecosystem to re-enforce the understanding of the natural processes. At the end, students should understand the roles of the organisms within the cycle, the complexity of the cycle, and the processes that occur.

III. Content:

The lesson will further develop the concept of Nitrogen cycling as an example of matter flow through a system of living things. Your classroom becomes a mock ecosystem and the students function as the biological components to cycle nitrogen through as the ecosystem would.

IV. Student Learning Objectives:

Benchmarks (6-8):

- Illustrate and explain the relationships among producers, consumers, and decomposers in a food web.

- Identify and describe the biotic and abiotic factors that affect the carrying capacity of a specific niche.

Benchmarks (9-12):

- Analyze the factors that affect the carrying capacity of an ecosystem.

- Analyze the interdependence within and between terrestrial, aquatic, and atmospheric systems.

- Explain what happens to energy and matter (at the molecular level) as the chemical element flows through each level in a food web.

V. Resources and Materials:

Students should already possess a diagram of the nitrogen cycle and a list of the definitions of the compounds and the processes. Click here for the nitrogen cycle *** Click here for a list of definitions

Other resources that I used for information and may be helpful are:

Nixon, Scott. 1998. Enriching the sea to Death. Scientific American (August 1998).

Smil, Vaclav. 1997. Global population and the Nitrogen Cycle. Scientific American 277(1): 76-81.

Materials f or this activity:

- 6-8 grades should have pre-made paper signs for each of the nitrogen compounds: Ammonia, Ammonium, Nitrate, Nitrite, Nitrogen gas, Organic Nitrogen
- 9-12 grades should use chemistry molecule kits to make the nitrogen molecules and modify them as they pass through the cycle

VI. Instructional Procedures:

Focusing or Pre-reading Activity:
This activity should follow the starter activity (including reading the article "Humble Beginnings") and the Nitrogen fate and transformations game.

Develop a driving question or working hypothesis such as:
How can we best clean the waste of the fish in the aquaculture tanks?

VII. Student Learning Activities:

Your classroom becomes a mock aquatic ecosystem. Use a desk to represent the atmosphere and one to represent the water. One student acts as the "water" and performs the physical and chemical processes that occur. Other students act as the biological components in the system: farmer (teacher may do this if the class is small or if the teacher wishes to participate), fish, heterotrophic bacteria, Nitroso- nitrifying bacteria, Nitro- nitrifying bacteria, and denitrifying bacteria.

Nitrogen is cycled through the system. Younger students should use pre-made paper signs for each nitrogen compound; older students (10-12 grade) can use chemistry molecular kits and perform the actual transformations from one molecule to another.

Two different steps occur in this activity. The first step involves looking at the nitrogen cycle within a fish tank alone. This helps to show the students why you need to clean the water to keep the fish alive. The second step adds a "cleaning" tank or a "living machine."

There are detailed explanations and a set of instructions to hand the students attached to this lesson plan. Click here for the detailed teacher instructions *** Click here for student instructions

VIII. Assessment:

Form groups of students that each include several different organisms from the activity (one student that was a fish, one that was a Nitroso- nitrifier, one that was a denitrifier, etc.). Have the students work together in their groups to complete a worksheet on the complete nitrogen cycle.

Click here for the first Nitrogen Cycle diagram (just aquaculture)

Click here for the second Nitrogen Cycle diagram (with the Living Machine)

Click here for the worksheet used to assess the diagrams

Ensure that they understand the interactions that took place within their mock ecosystems and why the nitrogen is cycled as it is.

IX. Teacher and/or Student Evaluation of Lesson:

Teacher: Do you feel the students gained a better understanding of the nitrogen cycle? Any thoughts, comments, suggestions….

Students: What did you learn about the nitrogen cycle? What did you learn about ecosystems and their functioning and complexity? What do you want to know more about?