Which processes are involved in nutrient cycling in a functioning ecosystem?

Step 1: Analyze the question The question asks which processes are involved in nutrient cycling in an ecosystem. Nutrient cycling means the movement of essential elements (nitrogen, carbon, phosphorus and others) between living organisms and the non-living environment so they can be reused.

Step 2: Explain the concept Nutrient cycles, also called biogeochemical cycles, rely largely on microorganisms and biological transformations that change nutrients from one usable form to another. The nitrogen cycle is the classic example:

• Nitrogen fixation: bacteria such as Rhizobium (in legume root nodules) and Azotobacter convert atmospheric N₂ into ammonia/nitrates that plants can use.
• Ammonification: decomposers break down dead organisms and waste, releasing ammonia.
• Nitrification: ammonia is converted to nitrites and then nitrates.
• Denitrification: bacteria convert nitrates back to N₂ gas, returning it to the atmosphere.

Step 3: Evaluate each option

• A. Erosion, weathering, sedimentation: these are geological processes. They move rock and soil material and play a part in the phosphorus cycle, but they are not the main biological nutrient-cycling processes.
• B. Decomposition, evaporation, precipitation: decomposition does recycle nutrients, but evaporation and precipitation belong to the water cycle, so this option is mixed.
• C. Nitrogen fixation, denitrification, ammonification: all three are steps in the nitrogen cycle, a major nutrient cycle. ✔
• D. Respiration, photosynthesis, transpiration: these are physiological processes of organisms. Respiration and photosynthesis relate to the carbon cycle and energy flow, and transpiration relates to water loss, so the set does not describe nutrient cycling as well as C does.

Step 4: Answer The correct option is C.

Tip: In JAMB Biology, when you see "nutrient cycling", think of the nitrogen cycle terms: fixation, nitrification, ammonification, denitrification. If all the processes in an option belong to one nutrient cycle, that option is usually correct. Watch out for options that mix in the water cycle (evaporation, precipitation), because they are common distractors.