Ecological pyramid that is always upright depicts

Pyramid of energy is always upright, can never be inverted, because when energy flows from a particular trophic level to the next trophic level, some energy is always lost as heat at each step. Each bar in the energy pyramid indicates the amount of energy present at each trophic level in a given time or annually per unit area.

Pyramid of number (one tree ecosystem) and pyramid of biomass (aquatic ecosystem) can be inverted.

Age pyramid may be triangular (upright) or urn-shaped (inverted).