Consider the following statements about the nitrogen cycle: 1. Nitrogen fixation converts N₂ to ammonia. 2. Nitrification converts ammonia to nitrates. 3. Denitrification returns nitrogen to the atmosphere. Which of the above is/are correct? MCQ with Answer and Explanation

Explanation:
Rhizobium is a symbiotic nitrogen-fixing bacterium that forms root nodules in the roots of leguminous plants (like peas, beans, clover). Inside these nodules, the bacterium converts atmospheric nitrogen (N2) into ammonia (NH3), which the plant can use. In return, the plant provides the bacteria with carbohydrates and a protected environment. It significantly reduces the need for chemical nitrogen fertilizers.

Explanation:
The nephron is the microscopic structural and functional unit that filters blood and forms urine. It consists of the renal corpuscle (glomerulus + Bowman's capsule) and tubules. Alveoli are lung units, neurons are nerve cells, hepatocytes are liver cells. Each kidney contains about one million nephrons.

Explanation:
Transformation is the uptake of free DNA from the surroundings and its incorporation into the bacterial genome. Conjugation requires cell-to-cell contact via pilus, transduction involves bacteriophage, translation is protein synthesis.