The mass of living material at a trophic level at a particular time is called

Options

A. standing state
B. Net primary productivity
C. standing crop
D. gross primary productivity

Explanation

To answer the question, "The mass of living material at a trophic level at a particular time is called," we will analyze the options provided and determine the correct term.

### Step-by-Step Solution:

1. **Understanding the Question**: The question asks for a term that describes the mass of living material at a specific trophic level at a particular time.

2. **Reviewing the Options**:
- **Standing State**: This refers to the total amount of living material in a specified population at a particular time, expressed in biomass. However, it does not specifically refer to a trophic level.
- **Net Primary Productivity (NPP)**: This is the rate at which plants incorporate atmospheric carbon through photosynthesis. It measures productivity over time, not the mass at a specific moment.
- **Standing Crop**: This term refers to the mass of living material present at a specific trophic level at a particular time. It can vary with seasons and is not fixed.
- **Gross Primary Productivity (GPP)**: This is the rate at which an ecosystem's producers capture and store energy as biomass over time. Like NPP, it does not refer to a specific mass at a moment.

3. **Identifying the Correct Answer**: Among the options, "Standing Crop" is the only term that specifically refers to the mass of living material at a trophic level at a particular time. It is variable and can change with seasons, which aligns with the question's requirement.

4. **Conclusion**: Therefore, the correct answer to the question is **Standing Crop**.

### Final Answer:
The mass of living material at a trophic level at a particular time is called **Standing Crop**.

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