WAEC Biology 2023 Theory — Question 6

Model answer

Organisms involved in the nitrogen cycle and their roles: Animals — Excrete nitrogenous compounds/eat proteins in plant, die/decay to form ammonium compound. Plants — Absorb nitrate from soil/die/decay to form ammonium compound. Putrefying bacteria — Break down dead plants/animals. Azotobacter — Converts atmospheric nitrogen to nitrate. Rhizobium — Converts atmospheric nitrogen to nitrates. Nitrobacter — Converts nitrite to nitrates. Nitrosomonas — Converts ammonium compound to nitrite. Pseudomonas — Converts amino compound to ammonium compounds.