Which one of the following types of organisms occupy more than one trophic level in a pond ecosystem?

Options

A. Zooplankton
B. Frog
C. Phytoplankton
D. Fish

Explanation

To solve the question of which type of organisms occupy more than one trophic level in a pond ecosystem, we can follow these steps:

### Step-by-Step Solution:

1. **Understanding Trophic Levels**:
- Trophic levels refer to the position an organism occupies in a food chain. The first level consists of producers (like plants), followed by primary consumers (herbivores), secondary consumers (carnivores that eat herbivores), and so on.

2. **Identifying Organisms in a Pond Ecosystem**:
- In a pond ecosystem, common organisms include phytoplankton (producers), zooplankton (primary consumers), small fish (secondary consumers), and larger fish (tertiary consumers).

3. **Analyzing the Options**:
- **Plankton**: This term generally refers to both phytoplankton (producers) and zooplankton (consumers). They occupy different trophic levels but not more than one level simultaneously.
- **Frogs**: Frogs can occupy multiple levels as they can eat insects (primary consumers) and can also be prey for larger animals (secondary consumers).
- **Phytoplankton**: These are producers and occupy only the first trophic level.
- **Fish**: Fish can occupy multiple trophic levels. Some fish eat phytoplankton, while others may eat smaller fish, placing them at both the second and third trophic levels.

4. **Conclusion**:
- Among the given options, **fish** are the organisms that occupy more than one trophic level in a pond ecosystem. They can be both primary consumers (when they eat plankton) and secondary consumers (when they eat smaller fish).

### Final Answer:
The correct option is **fish**.

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