Pyramid of numbers is

Options

A. always upright
B. always inverted
C. either upright or inverted
D. niether upright nor inverted

Answer

### Step-by-Step Text Solution:

1. **Understanding the Pyramid of Numbers**: The pyramid of numbers represents the number of individual organisms at each trophic level in an ecosystem. It illustrates the relationship between different levels of producers and consumers.

2. **Structure of the Pyramid**: In a typical terrestrial ecosystem, the pyramid starts with the producers (like trees and plants) at the base. As we move up the pyramid, we encounter primary consumers (herbivores), followed by secondary consumers (carnivores that eat herbivores), and finally tertiary consumers (top predators).

3. **Characteristics of the Pyramid**:
- In a terrestrial ecosystem, the pyramid of numbers is usually upright. This means that there are more producers than primary consumers, more primary consumers than secondary consumers, and so forth.
- For example, in a forest ecosystem, there are many trees (producers), fewer herbivores (primary consumers), and even fewer carnivores (secondary consumers).

4. **Aquatic Ecosystems**: The pyramid of numbers can also be applied to aquatic ecosystems. For instance, in a lake:
- Phytoplankton (producers) are at the base, followed by zooplankton (primary consumers), then small fish (secondary consumers), and large fish (tertiary consumers).
- This structure is also typically upright, as the number of producers is greater than the number of consumers at higher trophic levels.

5. **Conclusion**: The pyramid of numbers is consistently upright in both terrestrial and aquatic ecosystems. Therefore, it is incorrect to say that it can be inverted or neither upright nor inverted.

### Final Answer:
The pyramid of numbers is always upright in both terrestrial and aquatic ecosystems.