The ecological pyramid that is always upright is

Solution:

Ecological pyramids represent the relationship between different trophic levels in an ecosystem. There are three types of ecological pyramids: pyramid of number, pyramid of biomass, and pyramid of energy.

1. Pyramid of biomass in pond ecosystem: This pyramid is typically inverted because the biomass of producers (phytoplankton) at the base is less than the biomass of primary consumers (zooplankton) that feed on them, which in turn is less than the biomass of secondary consumers.

2. Pyramid of number in tree ecosystem: This pyramid is also inverted. A single large producer (tree) supports a large number of primary consumers (e.g., insects), which in turn support a smaller number of secondary consumers (e.g., birds).

3. Pyramid of energy: This pyramid is always upright, regardless of the ecosystem. This is because energy flow is unidirectional, from producers to consumers, and there is a significant loss of energy (approximately 90%) as heat at each successive trophic level according to the 10% law of energy transfer. Therefore, the amount of energy available at each higher trophic level is always less than that at the preceding lower level.

Thus, the pyramid of energy is the only ecological pyramid that is always upright.