Choose incorrect option w.r.t. amount of living material present in different trophic levels at a given time

Options

A. Can be measured as number
B. Is equivalent to standing crop
C. Is always represented as dry weight only
D. Expressed both as biomass and number

Answer

To solve the question regarding the incorrect option related to the amount of living material present in different trophic levels, we can follow these steps:

### Step-by-Step Solution:

1. **Understand Trophic Levels**: Trophic levels refer to the different levels in a food chain, where each level represents a different group of organisms that share the same function in the ecosystem.

2. **Identify the Options**: The options provided are:
- Option 1: Can be measured as number.
- Option 2: Equivalent to standing crop.
- Option 3: Always represented as dry weight only.
- Option 4: Expressed both as biomass and number.

3. **Analyze Each Option**:
- **Option 1**: "Can be measured as number" - This is correct because the amount of living material can indeed be quantified in terms of the number of organisms present.
- **Option 2**: "Equivalent to standing crop" - This is also correct as the standing crop refers to the total biomass of living material at a given time.
- **Option 3**: "Always represented as dry weight only" - This is incorrect. While biomass can be measured as dry weight, it can also be represented as fresh weight. Therefore, this statement is misleading.
- **Option 4**: "Expressed both as biomass and number" - This is correct because living material can be quantified in terms of both biomass and the number of organisms.

4. **Determine the Incorrect Option**: Based on the analysis, Option 3 is the incorrect statement because it limits the representation of biomass to dry weight only.

### Conclusion:
The incorrect option with respect to the amount of living material present in different trophic levels at a given time is **Option 3: "Always represented as dry weight only."**

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