Why are fungi so important to the carbon cycle?

• A. They perform oxygenic photosynthesis, removing CO2 from the atmosphere and producing most ecosystem biomass.
• B. They decompose complex organic matter (e.g., lignin and cellulose), releasing carbon as CO2 and returning nutrients to ecosystems.
• C. They convert atmospheric nitrogen into ammonia, directly increasing carbon fixation by plants.
• D. They prevent carbon from entering the atmosphere by converting CO2 into carbonate rock.

Answer: (B)

Verified step by step guidance

1. Understand the role of fungi in ecosystems, particularly their function in breaking down organic materials.
2. Recognize that fungi are decomposers, meaning they break down complex organic compounds such as lignin and cellulose found in dead plant material.
3. Know that through decomposition, fungi release carbon dioxide (CO2) back into the atmosphere, which is a key part of the carbon cycle.
4. Realize that this decomposition process also returns essential nutrients to the soil, supporting plant growth and maintaining ecosystem health.
5. Contrast fungi's role with other processes like photosynthesis or nitrogen fixation, which are performed by different organisms, to clarify why fungi are specifically important for carbon cycling through decomposition.