2. The largest single source of nitrogen is in the atmosphere. Nitrogen makes up 78% of our air!
3. What happens to atmospheric nitrogen (N 2 ) in the nitrogen cycle? N N N N N N
3. Atmospheric nitrogen is converted to ammonia or nitrates. Ammonia (NH 3 ) Nitrates (NO 3 ) Atmospheric Nitrogen (N 2 ) N N N N
4. Why does atmospheric nitrogen need to be converted? N N N N N N
5. Nitrogen is an essential component of DNA, RNA, and proteins—the building blocks of life. Although the majority of the air we breathe is nitrogen, most living organisms are unable to use nitrogen as it exists in the atmosphere!
6. How does atmospheric nitrogen get changed into a form that can be used by most living organisms? N N
6. By traveling through one of the four processes in the Nitrogen Cycle! (A) Nitrogen Fixation (C) Nitrification (B) Ammonification (D) Denitrification Nitrogen Cycle
The first process in the nitrogen cycle is… Nitrogen Fixation! (1) Nitrogen Fixation Nitrogen Cycle
7. What is “nitrogen fixation” and what does it mean to say nitrogen gets “fixed”? N N
7. “Nitrogen Fixation” is when the nitrogen gets “fixed” and combines with oxygen or hydrogen. N N N N N Oxygen Hydrogen Oxygen Hydrogen N
There are three ways that nitrogen gets “fixed”! (a) Atmospheric Fixation (b) Industrial Fixation (c) Biological Fixation Bacteria
(A)Atmospheric Fixation (Only 5 to 8% of the Fixation Process) Lightning breaks nitrogen molecules apart and combines with oxygen forming nitrogen oxides (N 2 O). Nitrogen oxides dissolve in rain, forming nitrates. Nitrates (NO 3 ) are carried to the ground with the rain. Lightning “fixes” Nitrogen! Nitrogen combines with Oxygen Nitrogen oxides forms Nitrogen oxides dissolve in rain and change to nitrates Plants use nitrates to grow! (NO 3 ) N NO (N 2 O)
(B) Industrial Fixation Under great pressure, at a temperature of 600 degrees Celcius, and with the use of a catalyst, atmospheric nitrogen (N 2 ) and hydrogen are combined to form ammonia (NH 3 ). Ammonia can be used as a fertilizer. Industrial Plant combines nitrogen and hydrogen Ammonia is formed Ammonia is used a fertilizer in soil (NH 3 ) N N H N H3H3
( C) Biological Fixation (where MOST nitrogen fixing is completed) There are two types of “Nitrogen Fixing Bacteria” Free Living Bacteria (“fixes” 30% of N 2 ) Symbiotic Relationship Bacteria (“fixes” 70% of N 2 )
Most atmospheric nitrogen (N 2 ) is “fixed” and changed to ammonia (NH 3 ). Ammonia is highly toxic to many organisms. Can plants use ammonia?
Very few plants can use ammonia (NH 3 )… …but, fortunately the second process Ammonification can help! (1) Nitrogen Fixation (2) Ammonification
10. Microorganisms convert the organic nitrogen to ammonium. The ammonium is either taken up by the plants (only in a few types of plants) or is absorbed into the soil particles. Ammonium (NH 4 ) in the soil is stored up to later be changed into inorganic nitrogen, the kind of nitrogen that most plants can use. Ammonium (NH 4 ) is stored in soil. Bacteria converts organic nitrogen to ammonium (NH 4 ) Ammonium (NH 4 ) is used by some plants Bacteria
What happens to ammonium (NH 4 ) stored in the soil?
11. It travels through the third process of the nitrogen cycle called Nitrification! (1) Nitrogen Fixation (2) Ammonification(3) Nitrification
11. Nitrifying bacteria in the ground first combine ammonia with oxygen to form nitrites. Then another group of nitrifying bacteria convert nitrites to nitrates which green plants can absorb and use! Nitrifying bacteria in soil combine ammonia with oxygen Ammonia changes to nitrites Nitrifying bacteria in soil convert nitrites to nitrates Plants absorb nitrates and grow! AmmoniaNitritesNitrates (NH 3 )(NO 3 )(NO 2 )
12. How does nitrogen reenter the atmosphere in the nitrogen cycle?
12. Through the fourth process called denitrification! (1) Nitrogen Fixation (2) Nitrification (3) Ammonification (4) Denitrification
13. Denitrification converts nitrates (NO 3 ) in the soil to atmospheric nitrogen (N 2 ) replenishing the atmosphere. Nitrates (NO 3 ) in Soil Nitrogen in atmosphere (N 2 )
Other ways that nitrogen returns to the atmosphere… Emissions from industrial combustion and gasoline engines create nitrous oxides gas (N 2 O). Volcano eruptions emit nitrous oxides gas (N 2 O).
Can you fill in the following diagram with the parts of the nitrogen cycle? Word bank: denitrification, nitrification, nitrogen fixation, ammonification
(1) _____________ (3) ____________(2) _____________ (4) _____________ Nitrogen Cycle Nitrates in Soil Ammonia is converted to nitrites and nitrates. Organic nitrogen is converted to ammonium. (a) (b) (c) N2N2 NH 3 NO 3 N2ON2O
(1) Nitrogen Fixation (3) Nitrification(2) Ammonification (4) Denitrification Nitrogen Cycle Nitrates in Soil Ammonia is converted to nitrites and nitrates. Organic nitrogen is converted to ammonium. (a) (b) (c) N2N2 NH 3 NO 3 N2ON2O