Which of the following statements is not true ?

Options

A. A single organism can feed at several trophic levels
B. Detritivores feed at all trophic levels except the producer level
C. Primary consumers are herbivores
D. Energy pyramids of an ecosystem tend to diminish at higher trophic levels

Answer

To determine which statement is not true regarding food chains, we will analyze each statement provided in the question step by step.

### Step-by-Step Solution:

1. **Understanding Trophic Levels**:
- Trophic levels refer to the different levels in a food chain where organisms obtain their energy. These levels include producers, primary consumers, secondary consumers, tertiary consumers, and decomposers.

2. **Evaluating the First Statement**:
- The first statement claims that a single organism can feed at several trophic levels. This is true as some organisms, like omnivores, can consume food from different levels (e.g., plants and animals).

3. **Evaluating the Second Statement**:
- The second statement suggests that detritivores feed at all trophic levels except the producer level. This is incorrect because detritivores feed on dead organic matter, which includes materials from all trophic levels, including producers.

4. **Evaluating the Third Statement**:
- The third statement states that primary consumers are herbivores. This is true since primary consumers primarily feed on plants.

5. **Evaluating the Fourth Statement**:
- The fourth statement mentions that energy pyramids of an ecosystem tend to diminish at higher trophic levels. This is also true, as only about 10% of energy is transferred from one trophic level to the next, leading to a decrease in energy availability at higher levels.

6. **Identifying the False Statement**:
- From the analysis, the second statement is the only one that is not true. Therefore, the answer to the question is that the false statement is the second one.

### Final Answer:
The statement that is not true is: "Detritivores feed at all trophic levels except the producer level."

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