CTET Paper II (Mathematics and Science) 20 Aug 2023 Solved Paper

Concept:Nitrogen fixation is the process of converting inert atmospheric nitrogen ($N_2$) into compounds that living organisms can use.Explanation:The air contains about 78% nitrogen gas, but most organisms cannot use it directly.In nitrogen fixation, $N_2$ is changed into ammonia ($NH_3$) or other usable forms like nitrates.This can happen through lightning, industrial processes, or by special bacteria (e.g., in legume root nodules).These bacteria use the enzyme nitrogenase to break the strong triple bond of $N_2$.The fixed nitrogen then becomes available for plants to make proteins and DNA.Thus, nitrogen fixation is essential for life and the nitrogen cycle.Answer:Conversion of atmospheric nitrogen to a more usable form for living organisms (Option D).