An ecological pyramid shows the relationship of biomass, productivity or energy at different trophic levels. The primary producers are generally shown at the bottom and apex predators at the top. The pyramids are different for different ecosystems.
Biomass and Productivity Pyramid
For terrestrial ecosystems, the biomass generally decreases at each higher trophic level from plants via herbivores to carnivores. This is evident from the fact that the terrestrial producers’ viz. grasses, trees and shrubs have a much higher biomass than the animals that consume them, such as deer, zebras and insects. The level with the least biomass is the highest predators in the food chain, such as foxes and eagles.
In the aquatic system, the biomass can increase at higher trophic levels. For example, in Oceans, the food chain typically starts with phytoplankton and ends at predatory fish, which has largest biomass. Thus, the pyramid of biomass may be inverted in the aquatic systems.
Pyramid of Energy
Energy cannot be recycled and during the flow of energy from one trophic level to other, there is a considerable loss in the form of heat, respiration, mechanical energy etc. Thus, highest energy is available to primary producers and lowest to tertiary consumers. Thus, the pyramid of energy is always upright and vertical. In this pyramid, the energy is minimum as the highest trophic level and is maximum at the lowest trophic level.
Pyramid of Numbers
This Pyramid shows the numbers of the producers, herbivores and the carnivores at their successive trophic levels. This pyramid can be either upright, or inverted or partially upright.