Which of the following always has a “pyramidal” shape, that is, decreasing values at higher trophic levels?

Options

A. Pyramids of numbers
B. Pyramids of biomass
C. Pyramids of energy
D. Both b and c

Answer

To answer the question "Which of the following always has a ‘pyramidal’ shape, that is, decreasing values at higher trophic levels?", we can follow these steps:

### Step-by-Step Solution:

1. **Understand Trophic Levels**:
- The ecosystem consists of different trophic levels: producers (first level), primary consumers (second level), secondary consumers (third level), and tertiary consumers (fourth level). Each level represents a different stage in the food chain.

2. **Identify the Pyramidal Shape**:
- A pyramidal shape indicates that as you move up the trophic levels, the number of organisms, biomass, or energy decreases. This is typical for most ecosystems.

3. **Analyze Different Types of Pyramids**:
- **Pyramid of Numbers**: This can sometimes be inverted in certain ecosystems (like aquatic ecosystems) where a few large producers support many small consumers.
- **Pyramid of Biomass**: Similar to the pyramid of numbers, it can also be inverted in certain cases.
- **Pyramid of Energy**: This pyramid always has a decreasing shape because energy transfer between trophic levels is inefficient. Typically, only about 10% of the energy is passed on to the next level.

4. **Conclusion**:
- Among the options provided, the pyramid of energy is the one that consistently maintains a pyramidal shape with decreasing values at higher trophic levels. Therefore, the correct answer is the pyramid of energy.

### Final Answer:
The correct option is the **pyramid of energy**.

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