The process by which bacteria convert atmospheric nitrogen into ammonia is called:
A. Ammonification
B. Denitrification
C. Nitrogen fixation
D. Nitrification
Answer: Option C
Solution (By JKSSB Mock Tests)
Nitrogen fixation is the conversion of inert atmospheric N₂ into ammonia (NH₃) by free-living (e.g., Azotobacter) or symbiotic (e.g., Rhizobium) bacteria, or by industrial processes. Nitrification is the oxidation of ammonia to nitrites then nitrates. Denitrification converts nitrates to N₂ gas. Ammonification is the release of ammonia from organic nitrogen by decomposers. Fixed nitrogen is essential for plant growth.
Consider the following statements about the greenhouse effect:
1. Greenhouse gases trap heat in the atmosphere.
2. CO₂, methane, and water vapor are greenhouse gases.
3. The greenhouse effect is solely harmful.
Which of the above is/are correct?
Explanation:
The natural greenhouse effect keeps Earth warm enough for life; its enhancement causes global warming. Statement 3 is incorrect. 1 and 2 are correct.
Explanation:
Pellagra, characterized by dermatitis, diarrhea, and dementia (3 Ds), is due to deficiency of niacin (vitamin B₃) or its precursor tryptophan. Niacin is part of NAD and NADP coenzymes.
Explanation:
In roots, the protoxylem (first formed xylem) lies towards the periphery and metaxylem towards the centre; this arrangement is called exarch. In stems, protoxylem is towards the centre, called endarch. Exarch condition is typical of roots. Mesarch is found in ferns. This arrangement aids in understanding anatomical differences between root and stem.
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