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How is Nitrogen cycled?Starter Questions
1. What is nitrogen used for in the body?
2. How is it related to growth and repair and why?
3. Around 78% of the Earth’s atmosphere is nitrogen – can organisms use it directly?
Key terms: Fixation, decomposition, nitrification, denitrification.
How is Nitrogen cycled?Objectives
Explore how nitrogen is cycled in our atmosphere.
Outcomes(3) Describe the ways nitrogen can be lost from soil.
(5) Explain each step of the nitrogen cycle and its relation to fertilisers.
(7) Analyse adaptations of plants for low nitrogen conditions.
Key terms: Fixation, decomposition, nitrification, denitrification.
Some chemicals to remember…
Nitrogen in the atmosphere is N2.
Plants take up nitrogen in the form of nitrates ( NO3-)
Ammonia ( NH3+) is released by decomposers.
Nitrite is a highly toxic substance that is produced by the oxidation of ammonia by some bacteria (NO2
-)
Where do these bacteria fit into the cycle?!
Nitrifying bacteria: These change ammonia in the soil into nitrates. (A Good Thing)
Denitrifying bacteria: These change nitrates into atmospheric nitrogen. ( A Bad Thing)
Nitrogen fixing bacteria: These live in the roots of some plants and change atmospheric nitrogen into nitrates. (A Good Thing)
Saprotrophic bacteria: Feed on decaying matter. Release ammonia into the soil.
Grade E – recall the nitrogen cycle.Grade C – explain each element of the nitrogen cycle.Grade A – explain using all key words and apply to a context.
This is Rhizobium, a nitrogen fixing bacteria. It is an obligate anaerobe. Anaerobic conditions are provided in the root nodules.
These are the root nodules on a pea plant. The plant and bacteria live together. Both benefit from the interaction. This is called symbiosis.
How is Nitrogen cycled?Task
Complete the blank cycle.
Outcomes(3) Describe the ways nitrogen can be lost from soil.
(5) Explain each step of the nitrogen cycle and its relation to fertilisers.
(7) Analyse adaptations of plants for low nitrogen conditions.
Key terms: Fixation, decomposition, nitrification, denitrification.
How is Nitrogen cycled?Outcomes
(3) Describe the ways nitrogen can be lost from soil.
(5) Explain each step of the nitrogen cycle and its relation to fertilisers.
(7) Analyse adaptations of plants for low nitrogen conditions.
Key terms: Fixation, decomposition, nitrification, denitrification.
How is Nitrogen cycled?What effect would water logged soils have on the
nitrogen cycle?
Outcomes(3) Describe the ways nitrogen can be lost from soil.
(5) Explain each step of the nitrogen cycle and its relation to fertilisers.
(7) Analyse adaptations of plants for low nitrogen conditions.
Key terms: Fixation, decomposition, nitrification, denitrification.
In some conditions denitrifying bacteria in the soil break down nitrates and return nitrogen to the air. This is usually in waterlogged soil.
How is Nitrogen cycled?How can plants overcome
the problem of low nitrates?Outcomes
(3) Describe the ways nitrogen can be lost from soil.
(5) Explain each step of the nitrogen cycle and its relation to fertilisers.
(7) Analyse adaptations of plants for low nitrogen conditions.
Key terms: Fixation, decomposition, nitrification, denitrification.
How is Nitrogen cycled?What Sort of adaptations do
these plants have?Outcomes
(3) Describe the ways nitrogen can be lost from soil.
(5) Explain each step of the nitrogen cycle and its relation to fertilisers.
(7) Analyse adaptations of plants for low nitrogen conditions.
Key terms: Fixation, decomposition, nitrification, denitrification.
How is Nitrogen cycled?Task
Answer the exam style questions.
Outcomes(3) Describe the ways nitrogen can be lost from soil.
(5) Explain each step of the nitrogen cycle and its relation to fertilisers.
(7) Analyse adaptations of plants for low nitrogen conditions.
Key terms: Fixation, decomposition, nitrification, denitrification.
How is Nitrogen cycled?Task
Put the cards into a cycle.
Outcomes(3) Describe the ways nitrogen can be lost from soil.
(5) Explain each step of the nitrogen cycle and its relation to fertilisers.
(7) Analyse adaptations of plants for low nitrogen conditions.
Key terms: Fixation, decomposition, nitrification, denitrification.
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