Which cycle includes nitrogen fixation and decomposition as processes?

Which cycle includes nitrogen fixation and decomposition as processes?

• A. The Carbon cycle
• B. The Phosphorus cycle
• C. The Nitrogen cycle
• D. The Oxygen cycle

Answer: (C)

Understanding how nitrogen moves through ecosystems is what this question tests. Nitrogen fixation is the process that converts inert atmospheric N2 into usable forms like ammonium or nitrate, a key step carried out by certain bacteria (and in some plants’ roots). Decomposition, through ammonification, breaks down organic nitrogen from dead matter and waste to release ammonium back into the soil. Together, these processes are central to the nitrogen cycle, which also includes nitrification, assimilation, and denitrification to shuttle nitrogen among the atmosphere, soil, plants, and microbes. Other cycles don’t include nitrogen fixation as a part of their pathways, so the cycle that includes both nitrogen fixation and decomposition is the nitrogen cycle.

Understanding how nitrogen moves through ecosystems is what this question tests. Nitrogen fixation is the process that converts inert atmospheric N2 into usable forms like ammonium or nitrate, a key step carried out by certain bacteria (and in some plants’ roots). Decomposition, through ammonification, breaks down organic nitrogen from dead matter and waste to release ammonium back into the soil. Together, these processes are central to the nitrogen cycle, which also includes nitrification, assimilation, and denitrification to shuttle nitrogen among the atmosphere, soil, plants, and microbes. Other cycles don’t include nitrogen fixation as a part of their pathways, so the cycle that includes both nitrogen fixation and decomposition is the nitrogen cycle.