When the ecological pyramid of number is inverted ?

Explanation

**Step-by-Step Solution:**

1. **Understanding Ecological Pyramids**: Ecological pyramids represent the number, biomass, or energy at different trophic levels in an ecosystem. Typically, these pyramids have a broad base (producers) and a narrow top (top predators).

2. **Definition of Inverted Pyramid**: An inverted ecological pyramid occurs when the number of individuals at higher trophic levels exceeds the number of individuals at lower trophic levels. This is contrary to the usual pattern where producers (like plants) are more numerous than consumers (like herbivores).

3. **Example of Tree Ecosystem**: In a tree ecosystem, you may find a situation where a single tree (producer) supports a large number of herbivores (like insects) and even more predators. However, in some cases, the number of parasites on a single tree can be greater than the number of trees themselves, leading to an inverted pyramid.

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