|Students play the role of nitrogen atoms traveling through the nitrogen cycle to gain understanding of the varied pathways through the cycle and the relevance of nitrogen to living things.
| 15 minutes prep time
In class: 30-minute activity plus optional 20 minutes for assessment
Student Learning Outcomes:
|Non-competitive game and writing or drawing assessment
- Make large reservoir signs for: atmosphere, surface water, rainwater, groundwater, fertilizers, soils, ocean, animal waste, dead plants and animals, live plants, live animals.
- Print Dice Codes for each reservoir station.
- Set up stations around the classroom (or outside). For each station, supply the appropriate reservoir sign, dice codes, a die, inkpad, and stamp.
- Go around the room with the Key to Stamps sheet and stamp each reservoir so that you know which stamp corresponds with which reservoir.
- Copy Passport Worksheets for all students.
- Have students read the Windows to the Universe page entitled The Nitrogen Cycle.
- Introduce nitrogen. Survey student knowledge. Where is nitrogen found on Earth? Does it move from place to place or stay still? Why is it important? Explain that nitrogen travels with the help of bacteria, water, lightning, plants and animals and that the class is going to discover how nitrogen travels.
- Show the nitrogen reservoir signs around the room and explain that these are the places to which nitrogen can travel. These places are called reservoirs.
- Tell students that for this activity they are each playing the role of a nitrogen atom. They will travel through the nitrogen cycle (i.e., to different stations around the room) based on rolling dice. Tell students that they will each carry a nitrogen passport with them and stamp it each time they get to a nitrogen reservoir station. Then toss the die at the reservoir to find out what your next destination will be. Write a note in the passport to indicate how you are getting from one place to another based on what the die says.
- Spread students so that there are 2 or three at each station and allow them to start traveling with their passport worksheet.
- Discussion questions:
- How many stops can you make on your trip?
- Will your journey ever end?
- Was everyone's journey the same? Why not?
- What would happen if a farmer used too much fertilizer? (In this game, that would mean that everyone started from the fertilizer station at the same time.)
- What would happen if we burnt too many fossil fuels?
- Livestock farming creates a large amount of animal waste. How would this affect the nitrogen cycle?
- Students write a paragraph about their trip through the nitrogen cycle. Include information about (1) where they went, and (2) how they got to each destination.
- Show students a diagram of the nitrogen cycle. Ask them to create a similar diagram specifically documenting their journey through the nitrogen cycle.
Nitrogen is an element that is found in both the living portion of our planet and the inorganic parts of the Earth system. The nitrogen cycle is one of the biogeochemical cycles and is very important for ecosystems. Nitrogen moves slowly through the cycle and is stored in reservoirs such as the atmosphere, living organisms, soils, and oceans along its way.
Most of the nitrogen on Earth is in the atmosphere. Approximately 80% of the molecules in Earth's atmosphere are made of two nitrogen atoms bonded together (N2). All plants and animals need nitrogen to make amino acids, proteins and DNA, but the nitrogen in the atmosphere is not in a form that they can use. The molecules of nitrogen in the atmosphere can become usable for living things when they are broken apart during lightning strikes or fires, by certain types of bacteria, or by bacteria associated with legume plants. Other plants get the nitrogen they need from the soils or water in which they live mostly in the form of inorganic nitrate (NO3- ). Nitrogen is a limiting factor for plant growth. Animals get the nitrogen they need by consuming plants or other animals that contain organic molecules composed partially of nitrogen. When organisms die, their bodies decompose bringing the nitrogen into soil on land or into the oceans. As dead plants and animals decompose, nitrogen is converted into inorganic forms such as ammonium salts (NH4+ ) by a process called mineralization. The ammonium salts are absorbed onto clay in the soil and then chemically altered by bacteria into nitrite (NO2- ) and then nitrate (NO3- ). Nitrate is the form commonly used by plants. It is easily dissolved in water and leached from the soil system. Dissolved nitrate can be returned to the atmosphere by certain bacteria in a process called denitrification.
Certain actions of humans are causing changes to the nitrogen cycle and the amount of nitrogen that is stored in reservoirs. The use of nitrogen-rich fertilizers can cause nutrient leading in nearby waterways as nitrates from the fertilizer wash into streams and ponds. The increased nitrate levels cause plants to grow rapidly until they use up the nitrate supply and die. The number of herbivores will increase when the plant supply increases and then the herbivores are left without a food source when the plants die. In this way, changes in nutrient supply will affect the entire food chain. Additionally, humans are altering the nitrogen cycle by burning fossil fuels and forests, which releases various solid forms of nitrogen. Farming also affects the nitrogen cycle. The waste associated with livestock farming releases a large amount of nitrogen into soil and water. In the same way, sewage waste adds nitrogen to soils and water.
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