The Question is from neet-botany , and it was created by the author Mr. NARESH KUMAR K

Question

A sample of detritus undergoes decomposition under controlled conditions.  Initially, the C:N ratio is 40:1. After a significant period, the fungal biomass significantly increases. What is the MOST LIKELY change in the C:N ratio of the remaining detritus?

Mr. NARESH KUMAR K · Accepted Answer

## CORE INFORMATION
✓ **Answer**: A
## CONCEPT FRAMEWORK
	**Primary Concept**: Decomposition and Nutrient Cycling
	**Related Topics**: C:N Ratio, Fungal Growth, Detritus, Immobilization
	**Prerequisites**: Understanding of decomposition processes and the role of fungi.
## SOLUTION PATHWAY
**Given Information**:
		Initial C:N ratio of detritus: 40:1
		Significant increase in fungal biomass.
**Method & Steps**:
	1. **Fungal Growth and Nitrogen**: Fungi require nitrogen for growth.  A high C:N ratio in the detritus (like 40:1) indicates there is relatively little nitrogen compared to carbon.
		Reasoning: Fungi will absorb nitrogen from the surrounding environment (the detritus) to build their biomass.
	2. **Nitrogen Immobilization**: As fungi grow, they incorporate nitrogen into their own tissues. This process is called immobilization, effectively removing nitrogen from the detritus pool and locking it up in the fungal biomass.
		Working: As nitrogen is immobilized, the amount of nitrogen in the remaining detritus decreases.
		Key Point: While fungi also utilize carbon, the demand for nitrogen is proportionally higher for biomass production.
	3. **C:N Ratio Change**: With less nitrogen in the detritus and a relatively stable amount of carbon (though some is used by the fungi), the C:N ratio of the remaining detritus increases.
		Result: The C:N ratio increases.
		Verification:  The initial high C:N ratio suggests nitrogen limitation. Fungal growth exacerbates this limitation by further reducing available nitrogen, thus increasing the C:N ratio.
 ## OPTION ANALYSIS
[A] ✓: Increases: Correct. As fungi grow, they take up nitrogen, increasing the C:N ratio of the remaining detritus. 
[B] :x: Decreases: Incorrect. Fungal growth would not decrease the C:N ratio unless they were adding substantial amounts of nitrogen to the detritus, which is not the case.
[C] :x: Remains the same: Incorrect. Fungal growth and nitrogen immobilization actively change the nutrient balance of the detritus.
[D] :x: Fluctuates unpredictably: Incorrect. While some fluctuation is possible, the overall trend is a predictable increase in the C:N ratio due to fungal nitrogen uptake.
 ## LEARNING AIDS
	**Common Mistakes**:
		1. Focusing only on carbon decomposition: Remember that nitrogen is crucial for fungal growth and its dynamics influence the C:N ratio.
		2. Misunderstanding immobilization: Immobilization removes nitrogen from the detritus pool, unlike mineralization which releases nitrogen.
	**Quick Tips**:
		1. High C:N ratio indicates nitrogen limitation.
		2. Fungal growth in high C:N environments leads to increased C:N ratio.

Mr. NARESH KUMAR K · Answer

The correct Option is "Increases"

Mr. NARESH KUMAR K · Answer

Decreases

Mr. NARESH KUMAR K · Answer

Remains the same

Mr. NARESH KUMAR K · Answer

Fluctuates unpredictably

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