Pyramid of biomass in a sea is generally inverted because the primary producers (phytoplanktons) have a lower biomass than that of succeeding zooplanktons, which further have a lower biomass than that of succeeding small fishes and so on.

Pyramid of energy is the only pyramid that can never be inverted and is always upright. This is because some amount of energy in the form of heat is always lost to the environment at every trophic level of the food chain.

In a grassland ecosystem, the number of producers is always maximum, followed by reducing number of organisms at second trophic level, third trophic level and other higher level (if present). Thus, the pyramid of number in grassland is upright.