Nitrogen Cycle url: http://www.teachersdomain.org/resource/lsps07.sci.life.eco.nitrogen/

Molecular Forms of Nitrogen Nitrogen gas N2 NH4+ NO3- NO2- Ammonium Nitrate Nitrite

Nitrogen Changing Processes The process by which nitrogen-fixing bacteria in the roots of legumes change atmospheric nitrogen to nitrates is called _______________________ The process by which N2 or organic nitrogen is changed to ammonium is called____________________ The two-step process of changing ammonium to nitrate is called _______________________ The process of changing nitrate into atmospheric nitrogen is called __________________ The process of changing nitrates into organic nitrogen is called ______________________ Nitrogen fixation Ammonification Nitrification Denitrification Assimilation

Background Information

Nitrogen Fixation by nitrogen-fixing bacteria in the roots of legumes

Ammonification by soil bacteria and fungi

Nitrification: Step 1

Nitrification: Step 2

Assimilation

Ammonification by Decomposers - decomposing bacteria and fungi

Denitrification

The Whole Cycle

Nitrogen Cycle Summary Process Bacteria N Changed from N changed to Nitrogen Fixation Ammonification Nitrification step 1 Nitrification step 2 Assimilation N/A Denitrification Nitrogen-fixing bacteria in legume roots Nitrogen in air Nitrate Nitrogen-fixing bacteria in soil Nitrogen in air Ammonium Organic nitrogen Decay bacteria and fungi Ammonium Nitrite Nitrifiying bacteria Nitrite Nitrate Organic nitrogen Nitrate Denitrifying bacteria Nitrogen in air Nitrate

Discussion Questions 1. The atmosphere is 78% nitrogen: why do you think plants and animals can't use nitrogen as it is found in the atmosphere? 2. Explain what is meant by nitrogen fixation. 3. What is the role of bacteria in the nitrogen cycle? 4. Why don't legumes need nitrogen-containing fertilizers? 5. Why is nitrogen so important for living things?

Nitrogen gas nitrates organic nitrogen gas Ammomium Ammonification Nitrogen fixation is the process that changes nitrogen from ______________ . The type of bacteria able to “fix” nitrogen are called ___________________________. Nitrogen fixing bacteria in legume roots allow for nitrogen to be used by legume plants and become ____________________ nitrogen. 2. Nitrogen fixing bacteria in the soil change nitrogen from _________________ to ____________________ by a process called _________________________. 3. The nitrifying bacteria in the first white circle change nitrogen from __________________________ to _____________________________ in a process called ________________________________. nitrates organic nitrogen gas Ammomium Ammonification Ammomium nitrite nitrification

nitrates nitrite assimilated organic decay bacteria fungi ammonium 4. This process is continued by a second group of nitrifying bacteria that change nitrogen from _________________________ to _________________________. 5. Nitrates can follow one of two paths. If it is taken into a plant, it will be _____________________________ into _____________________ nitrogen. The chipmunk gets the nitrogen it needs by eating plants. Nitrogen containing organic wastes from either plants or animals will be broken down by ___________________________ and ___________________________ into __________________________________. 6. Denitrifying bacteria change nitrogen from ______________________________ to _______________________________ returning it to the atmosphere. nitrates nitrite assimilated organic decay bacteria fungi ammonium nitrate nitrogen gas