Ecological Pyramids
An ecological pyramid is a graphical representation of the relationship between different organisms in an ecosystem. Producers make the base of the Pyramid and subsequent tiers of the Pyramid represent herbivores, carnivores, top carnivores etc.
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Types of Ecological Pyramids:
There can be 3 types of representation of ecological pyramids
- Number pyramids
- Pyramid of biomass
- Pyramid of energy
Pyramid of numbers
The pyramid of Numbers is the graphic representation of the number of individuals per unit area of various trophic levels. In an upright pyramid of numbers, the number of individuals
Upright Pyramid of Numbers: decreases from the lower level to the higher level. This type of pyramid is usually found in the grassland ecosystem and the pond ecosystem. The grass in a grassland ecosystem occupies the lowest trophic level because of its abundance.
Inverted Pyramid of Numbers: Here, the number of individuals increases from the lower level to the higher trophic level. For example, the tree ecosystem. Thus, the Pyramid of Numbers can be both inverted and upright.
Pyramid of biomass
Pyramid of Biomass as the name suggests shows the amount of biomass (living or organic matter present in an organism) present per unit area at each trophic level.
Upright Pyramid of Biomass: Ecosystems found on land mostly have pyramids of biomass with large bases of primary producers with smaller trophic levels perched on top, hence the upright pyramid of biomass.
Inverted Pyramid of Biomass: A reverse pyramidal structure is found in most aquatic ecosystems. Here, the pyramid of biomass may assume an inverted pattern. This is because, in a water body, the producers are tiny phytoplankton that grow and reproduce rapidly. In this condition, the pyramid of biomass has a small base, with the producer biomass at the base providing support to consumer biomass of large weight. Hence, it assumes an inverted shape. The pyramid of Biomass can be inverted and Upright.
Pyramid of energy
The pyramid of Energy is a graphical structure representing the flow of energy through each trophic level of a food chain over a fixed part of the natural environment. An energy pyramid represents the amount of energy at each trophic level and the loss of energy at each is transferred to another trophic level.
The energy pyramid, sometimes called the trophic pyramid or ecological pyramid, is used in quantifying the energy transfer from one organism to another along the food chain. Energy decreases as one moves through the trophic levels from the bottom to the top of the pyramid. Thus, the energy pyramid is always upright.
Importance of ecological pyramid
The importance of ecological pyramid can be explained in the following points:
- They show the feeding of different organisms in different ecosystems.
- Sudden increase or decrease in population of any species can be checked and its impact on other trophic can also be assessed.
- It shows the efficiency of energy transfer.
- The condition of the ecosystem can be monitored, and any further damage can be prevented.
Lindemann’s ruleLindemann (1942) put forth 10 % law for the transfer of energy from one trophic level to others. ➢ According to the law, “during the transfer of organic matter/energy from one trophic level to the next, only about 10% of the energy is transferred. The remaining is lost during transfer or broken down in respiration”. ➢ Plants utilise the energy from sun for primary production & can store only 10% of the utilised energy as net production available for herbivores. When plants are consumed by animals, only about 10% energy gets fixed in them. ➢ So at each trophic level 80- 90% energy is dissipated as heat. |
Limitations of ecological pyramids
- They assume a simple food chain and don’t accommodate a food web.
- Saprophytes are not given any place in pyramids.
- The utility of these pyramids is confined to simple food chains that may not accurately represent the intricacies of natural ecosystems.
