A graphical representation of the trophic levels that exist within an ecosystem is known as an ecological pyramid. It is called a pyramid because it is typically arranged with the base representing the primary producers, which are usually plants that use photosynthesis to convert sunlight into energy. The next level up consists of primary consumers, which are herbivores that eat the primary producers. The third level consists of secondary consumers, which are carnivores that eat the primary consumers. Each successive level up the pyramid consists of higher-level consumers that eat the organisms in the level below.
The pyramid shape illustrates the decreasing amount of energy available at each successive level, with the primary producers at the base representing the largest amount of energy. Ecological pyramids can be inverted, meaning that the producers are at the top of the pyramid and the top carnivores are at the bottom, which can occur in certain aquatic ecosystems.
The number of organisms, the amount of biomass, and the energy interactions among the various trophic levels of an ecosystem can all be used to construct an ecological pyramid.
The producers are shown at the bottom of the pyramid, while consumers are shown ascending the remainder of the rows as the pyramid moves up through its levels.
There are three distinct ecological pyramids that can be found.
- Number pyramid
- Biomass pyramid
- Energy pyramid
The number pyramid is a graphical representation of the number of organisms in different trophic levels. It is measured in terms of the number of organisms per square meter (1 m2).
The number of creatures in one trophic level may be larger or less than the number of species in the next trophic level. As a result, both upright and inverted number pyramids can be seen.
The biomass pyramid is a graphical representation of the total amount of organic matter present in different trophic levels. The dry mass of organisms is represented in grammes per square meter each year (g m-2 yr-1)
The biomass of consumers is typically lower than that of producers. As a result, the biomass pyramids are usually vertical. However, in an aquatic environment, the biomass of consumers is rarely more than that of producers. The biomass pyramid is then inverted.
The energy pyramid is a visual illustration that displays how much energy moves via different trophic levels. It is measured in kilojoules per square meter each year (kJ m-2 yr-1).
Only 10% of the energy in a trophic level is transferred to the next trophic level. 90% of the energy is lost to the atmosphere. As a result, the energy at the higher trophic levels is less than that in the lower trophic levels. As a result, the energy pyramids are always upright. Because of this energy waste, the number of links in a food chain is less than five.