1. The Nitrogen Cycle Welcome! Please Do Now…
Prepare for class: iPad, journal
Do you know what room you are in tomorrow?
Hand in your homework.
Please take a webquest from the front. You may want a textbook and/or your cornell notes on the nitrogen cycle.
Use your notes, text, and iPad to answer the questions on the webquest. You have 20 minutes to complete this task.

2. What is nitrogen? Nitrogen is Nitrogen has two abiotic reservoirs:
Nitrogen is
an ingredient of proteins and nucleic acids
essential to the structure and functioning of all organisms
limiting plant nutrient
Nitrogen has two abiotic reservoirs:
1. the atmosphere (about 80% is nitrogen gas)
2. soil
Student Misconceptions and Concerns
Students are unlikely to have any prior knowledge of biogeochemical cycles. Although some transfers between the biotic and abiotic components of ecosystems, such as the use of fertilizer on plants, may be known to them, the broader fact that the biosphere is a self-cycling system is not appreciated by most students. Before you lecture, consider asking your students to explain how carbon, phosphorus, and nitrogen cycle through the atmosphere. Pre-testing your students on their knowledge can confirm both what they understand and what they may need explained to them in more detail.
Teaching Tips
The nitrogen-fixing bacteria living in the roots of soybeans add nitrogen to the soil. Corn does not enjoy this same relationship with bacteria. However, by rotating corn and soybean crops, farmers can allow corn crops to use some of the nitrogen fixed by the soybean crop in the previous year. Such rotation has other benefits. Since corn is a monocot and soybeans are dicots, few pests attack both corn and soybeans. Thus, crop rotation also helps to control the pest populations that target each type of plant, reducing the need for other pest-fighting strategies.
© 2012 Pearson Education, Inc. 2

3. The nitrogen cycle depends on bacteriaN2 N2
Vocab Word!
Nitrogen fixation
converts N2 to compounds of nitrogen that can be used by plants
carried out by bacteria
plants can’t absorb nitrogen in the form of N2
Student Misconceptions and Concerns
Students are unlikely to have any prior knowledge of biogeochemical cycles. Although some transfers between the biotic and abiotic components of ecosystems, such as the use of fertilizer on plants, may be known to them, the broader fact that the biosphere is a self-cycling system is not appreciated by most students. Before you lecture, consider asking your students to explain how carbon, phosphorus, and nitrogen cycle through the atmosphere. Pre-testing your students on their knowledge can confirm both what they understand and what they may need explained to them in more detail.
Teaching Tips
The nitrogen-fixing bacteria living in the roots of soybeans add nitrogen to the soil. Corn does not enjoy this same relationship with bacteria. However, by rotating corn and soybean crops, farmers can allow corn crops to use some of the nitrogen fixed by the soybean crop in the previous year. Such rotation has other benefits. Since corn is a monocot and soybeans are dicots, few pests attack both corn and soybeans. Thus, crop rotation also helps to control the pest populations that target each type of plant, reducing the need for other pest-fighting strategies.
© 2012 Pearson Education, Inc. 3

4. LEGUMES!
legumes have a mutualistic relationship with bacteria – the bacteria live in the roots of the plant and they supply their host with a direct source of usable nitrogen
convert N2 to ammonia (NH3), which picks up another H to become ammonium (NH4) – now the nitrogen is “fixed” and taken up by plants

5. Nitrogen (N2) in atmosphere
Figure 37.21
Nitrogen (N2) in atmosphere 8
Plant
Animal 6
Assimilation
by plants 1 5
Denitrifiers 3
Nitrogen-fixing
bacteria in
root modules
Nitrates
in soil
(NO3)
Detritus
Figure The nitrogen cycle
Decomposers
Free-living
nitrogen-fixing
bacteria
Nitrifying
bacteria 4 7
Ammonium (NH4)
in soil 2 5

6. Nitrogen Cycle Notes
What is nitrogen? The nitrogen cycle depends on ___________________________________________. How do legumes play a role in the nitrogen cycle?

7. Student handout