Modeling the Nitrogen Cycle

A Nitrogen Cycle Activity Lesson 
Lindsey Truxel 
Barbara Morgan Elementary – McCall, Idaho



Lesson Title: Bacteria and the Nitrogen Cycle

Goal: 1. To cause students to comprehend the role and processes of bacteria converting the compound elements ammonia to nitrites, nitrites to nitrates as the cycle relates to a trout tank.
2. To cause student to analyze cycles that exist on our planet. 3. To cause student to evaluate and compare the similarities and differences in the types of cycle that exist on our planet.

Objective: Student will analyze and demonstrate the nitrogen cycle, discuss the relevant elements and their function and composition, and describe the function of two bacteria pertinent to the nitrogen cycle. And make comparisons to other cycles like the rock cycle, water cycle, food chain, and life cycle.

Materials: Balloons (pink, blue, white), plastic chips, 100 feet of string, blow bubbles, plastic bags. The kids can be creative and make bacteria and fish for the activity.

Terms: Fixing (convert or change), Nitrosomonas (microorganism) , Nitrobacters (microorganism), Nitrogen Cycle, ammonia NHɜ, nitrite NO2, nitrate NOɜ (chemical compounds).

Assigned groups: Assign students to act out a role including Nitrosomonas, Nitrobacters, ammonia NHɜ, nitrite NO2, nitrate NOɜ.

• Using string make a fish tank for all the activity to happen in
• Nitrosomonas (they convert ammonia to nitrites)
• Nitrobacters (they convert nitrites to nitrates)
• Ammonia atomic structure pink (H x 3) and blue (N x 1) balloons
• Nitrites atomic structure (N x 1) and white (O x 2) balloons
• Nitrates atomic structure (N x 1) and white (O x 3) balloons
• Fish to sprinkle chips in the tank that represent feces
• Blow bubbles can be used outside to demonstrate oxygenating of the tank.

Procedures: (In order to help the students gain an understanding of the processes of the nitrogen cycle in the tank this lesson has been set up in steps. Once the students have a good understanding of the cycle have the students all come together in the tank and do the activity as a smooth flowing processes as the nitrogen cycle isn’t steps but a process that happens continuously.)

1. Assign roles.
2. Pass out the assigned material
3. Take rope and create a fish tank on the floor with the rope. An area 20 x 20 would be a good amount of space for the activity.
4. Begin the activity by having the fish swim around the fish tank sparely dropping the chips from their plastic bags.
5. Introduce the rod shaped bacteria Nitrosomonas and Nitrobacter into the fish tank.
6. Wait a few seconds and introduce the element ammonia NH3 into the fish tank by tossing in blue and pink balloons. The ratio of balloons being three pink to one blue. Send in students to collect the elements Nitrogen and Hydrogen to make the compound element ammonia, one blue and three pink gathered up in their arms. The compound elements now being created just float around the tank.
7. The Nitrosomonas begin their work first by gently gobbling (fixing) up the compound element ammonia NH3. As the Nitrosomonas gobble up the element ammonia NH3, the students drop their balloons and leave the tank.
8. As the students leave the tank, toss in the blue and white balloons for Nitrites, the ratio being one blue to two white balloons. New students come into the tank and make the compound element NO2 by gathering up the elements Nitrogen and Oxygen.
9. The NO2 float around the tank.
10. The Nitrobacter begin their work by gently gobbling up the compound element NO2. As the Nitrobacters gobble up the compound element NO2 the students drop their balloons and leave the tank.
11. Next toss in white and blue balloons for Nitrates the ratio being one blue to three white balloons.
12. Finally new students come into the tank and gather up the elements Nitrogen and Oxygen NO3 the ratio being one blue to three white balloons in their arms. This compound stays in the tank as is and is not changed by the two bacteria in the tank. NO3 is dangerous to a fish tank and the job of changing this compound is done by anaerobic bacteria. The nitrosomonas and nitrobacters are an aerobic bacterium which means they need oxygen.
*The process of the nitrogen cycle is continuous without steps. Now have the students all enter the tank and demonstrate this cycle as a free flowing cycle.

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