Which of the following statement is not true ?

Options

A. Food chains are generally short with a few trophic levels as only 10% of the energy is transferred to higher trophic level from lower one.
B. The pyramid of biomass in the sea is generally inverted as the biomass of fish for exceeds that phytoplankton.
C. Pyramid of energy is mostly upright but sometimes it may be inverted
D. Pyramid of numbers and biomass may be either upright or inverted

Answer

To solve the question "Which of the following statement is not true?", we need to analyze each statement provided in the options.

### Step-by-Step Solution:

1. **Understanding the First Statement**:
- The first statement mentions that food chains are generally short with few trophic levels, as 10% of the energy is transferred to higher trophic levels from the lower one.
- This statement is true. According to Lindeman's 10% energy law, only a small fraction of energy (approximately 10%) is transferred from one trophic level to the next, which limits the number of trophic levels in a food chain.

2. **Analyzing the Second Statement**:
- The second statement claims that the pyramid of biomass in the sea is generally inverted because the biomass of fish exceeds that of phytoplankton.
- This statement is also true. In aquatic ecosystems, the biomass of fish (higher trophic levels) can indeed exceed that of phytoplankton (lower trophic levels), leading to an inverted pyramid of biomass.

3. **Evaluating the Third Statement**:
- The third statement states that the pyramid of energy is mostly upright but sometimes may be inverted.
- This statement is false. The pyramid of energy is always upright due to the 10% energy transfer rule; energy decreases as it moves up the trophic levels, which means it cannot be inverted.

4. **Considering the Fourth Statement**:
- The fourth statement indicates that the pyramid of numbers and biomass may be either upright or inverted.
- This statement is true. The pyramid of numbers can vary based on the ecosystem (e.g., upright in forests, inverted in certain cases), and the pyramid of biomass can also be upright or inverted depending on the ecosystem type.

5. **Conclusion**:
- After analyzing all statements, the only statement that is not true is the third one, which claims that the pyramid of energy may be inverted.

### Final Answer:
The statement that is not true is: **"The pyramid of energy is mostly upright but sometimes may be inverted."**

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