Q. With reference to the Nitrogen Cycle, consider the following statements:
1.Atmospheric nitrogen must be converted to usable forms like ammonia or nitrate before plants can absorb it.
2.Denitrifying bacteria help in converting nitrates and nitrites back into elemental nitrogen.
3.Human-induced nitrogen fixation has become a major source of nitrogen pollution.
Which of the statements given above are correct?
Answer: D
Notes:
Explanation:
- Plants cannot absorb elemental nitrogen (N₂) directly; it must first be converted into ammonia, nitrates, or nitrites through processes like biological or atmospheric nitrogen fixation.
- Denitrifying bacteria such as Pseudomonas convert nitrates and nitrites into elemental nitrogen (N₂), which escapes into the atmosphere, completing the nitrogen cycle.
- Human activity, especially industrial nitrogen fixation (e.g. fertilizers), has exceeded natural fixation and caused environmental issues like eutrophication, acid rain, and harmful algal blooms.
Source: Environment (NCERT)
