Ecological pyramids are diagrammatic illustrations of connection between different trophic levels in terms of energy, biomass and number of organisms.
Pyramid of biomass can be both upright and inverted. This can be understood from the examples given below:
(i) The pyramid of biomass in a pond ecosystem is inverted. Because, the sum total of the weight of phytoplankton (producer) is far less than a few fishes feeding on them, at higher trophic levels.
(ii) Pyramid of biomass in a forest ecosystem is upright because producers are more in biomass than primary consumers. Primary consumers are more than secondary consumers and secondary consumers are more than tertiary consumers (top).
Pyramid of energy is never inverted, (i.e. it is always upright). 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.