A certain mass of living material at a particular time in each trophic level is called

Options

A. Standing state
B. Stratification
C. Standing crop
D. Species composition

Answer

To solve the question "A certain mass of living material at a particular time in each trophic level is called," we will analyze the options provided and determine the correct answer step by step.

### Step-by-Step Solution:

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

2. **Analyzing the Options**:
- **Option 1: Standing State**: This term refers to the amount of inorganic nutrients in an ecosystem, not the mass of living material. Therefore, this option is not correct.

- **Option 2: Stratification**: This term generally refers to the arrangement or classification of something into different groups. It does not specifically pertain to the mass of living material in trophic levels. Thus, this option is also incorrect.

- **Option 3: Standing Crop**: This term specifically refers to the mass of living material (or biomass) present at a particular time in an ecosystem, particularly at different trophic levels. This matches the description given in the question, making it a strong candidate for the correct answer.

- **Option 4: Species Composition**: This term describes the variety of different organisms that make up a community. It does not refer to the mass of living material, so this option is not correct.

3. **Conclusion**: After analyzing all the options, the correct answer is **Option 3: Standing Crop**. This term accurately describes the mass of living material at a particular time in each trophic level.

### Final Answer:
**Standing Crop**

---