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Question
Explain the following cycle in your own words with a suitable diagram.
Nitrogen cycle.
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Solution
Nitrogen cycle
The nitrogen cycle involves the conversion of nitrogen from its elemental form in the atmosphere into simpler molecules in the soil and water. These further get converted into more complex molecules in living beings. Finally, the complex molecules are reduced and released back into the atmosphere as simple nitrogen molecules.
Fixing atmospheric nitrogen involves the following steps:
- Nitrogen fixation: It is the process wherein atmospheric nitrogen is converted into water-soluble nitrates. This step is performed by organisms like Rhizobium, Azotobacter and blue-green algae.
\[\ce{N2 → NO3− or NH4}\] - Nitrification: It is the process in which ammonia is first converted into nitrites and then into nitrates. This step is performed by nitrifying bacteria like Nitrosomonas and Nitrobacter.
\[\ce{NH3 → NO2− → NO3−}\] - Assimilation: In this step, NH3 and NO3 are incorporated into the biological tissues.
- Ammonification: It is the process in which complex, dead organic matter is decomposed into ammonia. This step is performed by organisms like decay bacteria and fungi.
\[\ce{Organic nitrogen compounds → NH4+}\] - Denitrification: It is the process wherein the nitrates present in the soil are reduced to release nitrogen back into the atmosphere.
\[\ce{NO3− → N2}\]
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Long Answer Question:
Explain biological nitrogen fixation with example.
Which of the following is TRUE regarding Rhizobium?
Which free living microorganism helps in nitrogen fixation?
The process of nitrogen-fixation by bacteria does not take place in the presence of
The nitrogen molecules present in the air can be converted into nitrates and nitrites by
When we breathe in air, nitrogen also goes inside along with oxygen. What is the fate of this nitrogen?
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Give reason for the following.
Farmers prefer to grow beans and peas in nitrogen deficient soils.
Match Column - I with Column - II.
| Column - I | Column - II | ||
| (a) | Nitrococcus | (i) | Denitrification |
| (b) | Rhizobium | (ii) | Conversion of ammonia to nitrite |
| (c) | Thiobacillus | (iii) | Conversion of nitrite to nitrate |
| (d) | Nitrobacter | (iv) | Conversion of atmospheric nitrogen to ammonia |
Choose the correct answer from the options given below.
Match Column - I with Column - II.
| Column - I | Column - II | ||
| (a) | Nitrococcus | (i) | Denitrification |
| (b) | Rhizobium | (ii) | Conversion of ammonia to nitrite |
| (c) | Thiobacillus | (iii) | Conversion of nitrite to nitrate |
| (d) | Nitrobacter | (iv) | Conversion of atmospheric nitrogen to ammonia |
Choose the correct answer from the options given below.
The bacteria present in the root nodules of leguminous plants is ______.
In the Nitrification process, the ammonium compounds are oxidised to soluble ______.
The atmosphere is a rich source of ______.
Draw a neat flow chart of the Nitrogen cycle. Briefly explain the various processes involved in the nitrogen cycle.
How are organisms like Pseudomonas and Thiobacillus of great significance in nitrogen cycle?
Name the cell which is responsible for nitrogen fixation in cyanobacteria.
Name any two nitrifying bacteria in soil.
