Download Nitrogen Cycle - Year 10 Life Science

Nitrogen Cycle
Chapter 6 – Global Systems
The Nitrogen Cycle
Nitrogen is an element essential to life as it is found in
proteins, DNA and RNA and in chlorophyll molecules
which assist in photosynthesis.
Air contains 78% Nitrogen however most organisms
cannot absorb nitrogen in its gaseous state and rely on a
process called fixation to obtain nitrogen in a usable form.
The Nitrogen Cycle
 Nitrogen comes in the following different forms:
 N2  Atmospheric Nitrogen/Gaseous Nitrogen
 NO2  Nitrites
 NO3  Nitrates
 NH3  Ammonia
NO2
Nitrite
The Nitrogen Cycle
Nitrogen Cycle Interactive
Nitrogen Fixation
 This process converts atmospheric nitrogen to a usable form for
plants to use
 There are three ways in which this can happen:
 Lightning
 Nitrogen fixing bacteria living in the soil
 Nitrogen fixing bacteria living in the roots of legume plants
Why is lightning so important?
 During storms the energy of lightning breaks nitrogen molecules
(N2) in the atmosphere into nitrogen atoms.
 The nitrogen atoms combine with oxygen in the air, forming
nitrogen oxides.
 These dissolve in rain to form nitrates (NO3) that enter the soil with
the rain.
 The nitrates are then available for plants to use.
Nitrogen fixing Bacteria
 The bacteria live in nodules in
the roots of the leguminous
plant Rhizobium takes nitrogen
gas from air in the soil and
manufactures nitrates.
 Nitrogen fixing bacteria that live
in the soil converts nitrogen gas
into ammonia (NH3)
Decomposers
When an organism dies, bacteria in the soil cause
nitrogen to be released into the soil as Ammonia (NH3)
Nitrifying Bacteria
 A different group of bacteria (Nitrifying bacteria) get their energy
from ammonia, and in the process they release water-soluble
nitrates back into the soil.
NH3  NO2  NO3
 Plants take up both the ammonia and the nitrates through their
roots.
Denitrifying Bacteria
 Denitrifying bacteria obtain their energy from the nitrates and
convert them back into gaseous nitrogen (N2), which is then
released back into the atmosphere.
Activity
Your task is complete the Nitrogen Cycle Summary
Worksheet using your notes/textbook and the
websites provided
http://www.classzone.com/books/ml_science_share/vis_sim/em05_pg20_nitrogen/em05
_pg20_nitrogen.swf
http://www.pbslearningmedia.org/resource/lsps07.sci.life.eco.nitrogen/the-nitrogencycle/
Nitrogen Cycle Interactive
Summary
Bacteria
Process
Nitrogen fixing bacteria
Converts atmospheric nitrogen into ammonia
N2 (g)  NH4
Nitrifying bacteria
Converts ammonia into nitrates
NH4  NO3 or NO2
Denitrifying bacteria
Converts nitrogen compounds in the soil back into the atmosphere
NO3 or NO2  N2 (g)
Lightening
Converts atmospheric nitrogen into nitrates
N2 (g)  NO3 or NO2
Travelling Nitrogen Activity
Aim: To simulate the nitrogen cycle
Materials: Dice, Station Cards
Method:
1. Each student will start at a different station with their own dice.
2. Roll the dice and the number rolled will tell you your next destination.
3. Record the work station title and the sentence of the number rolled.
4. Go to your next destination and repeat steps 2 and 3
5. Repeat this process for 20 minutes
Travelling Nitrogen Activity
Results:
1. Record the path you have travelled throughout the nitrogen
cycle. (Eg:
2. Draw a diagram of the nitrogen cycle identifying the path you
have taken (use arrows to show the direction you have taken)
Travelling Nitrogen Activity
Discussion:
1. Was everyone's journey the same in this activity? Why not?
2. Explain why nitrogen is an essential element for both plants and animals.
3. Recall which forms of Nitrogen plants can absorb
4. Explain the process of Nitrogen Fixation and how this occurs
5. Contrast between nitrifying and denitrifying bacteria
Conclusion:
Explain why the recycling of materials is important to the continued
functioning of ecosystems