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Science - Earth Science
Standard 4 Objective 2
1 class periods of 60 minutes each
Students will learn about the nitrogen cycle through discussion and the construction of a diagram. They will also measure the nitrate levels in various water samples and discuss how humans affect nitrate content in the water.
* For information on equipment for loan or for purchase, contact USU Water Quality Extension at (435) 797-2580 or www.extension.usu.edu/waterquality
To diagram the nitrogen cycle and provide examples of human actions that affect this cycle.
Nitrogen is all around us and is found in a variety of forms throughout the global environment. The nitrogen cycle demonstrates the many different paths nitrogen may follow around our earth and the different reservoirs in which nitrogen is stored.
Although nitrogen gas (N2) is an important component of proteins for both plants and animals, most plants cannot use the nitrogen gas directly. The process of converting nitrogen to a "biologically available" form in other words, converting nitrogen gas to a form that plants can use - is called nitrogen fixation. Only specialized bacteria in soil and certain types of algae in water can fix nitrogen. Lightning strikes also result in some nitrogen fixation.
Human activities have had a huge impact on global nitrogen cycles. The amount of biologically available nitrogen generated by human activities now far exceeds nitrogen fixed by bacteria, algae and lightning. Humans produce synthetic fertilizers, burn fossil fuels, grow legumes (which fix nitrogen) as a crop, and engage in various land clearing, burning and wetland draining activities, which all release nitrogen in forms that plants use. See the table on the Teacher Resource page for more details on the amount of fixed nitrogen humans produce.
See the Utah Stream Team Manual or the Further Discussion questions to learn more about the nitrogen cycle and how humans have affected it.
Lesson plan authors: Andree Walker and Nancy Mesner (Utah State University Water Quality Extension)
This curriculum was made possible through funding from the Environmental Protection Agency, the United States Department of Agriculture, Cooperative State Research, Education, and Extension Service, the Utah Division of Wildlife Resources, and Utah State University Extension.
Additional resources can be found on the USU Stream Side Science 9th Grade Curriculum web page.