Pyramids of Energy, Biomass and Number

Ecological Pyramids were given by Charles Elton (1927), these are also known as Eltonian Pyramids  It refers to a graphical representation of relationships between individuals present in different trophic levels in a food chain with respect to number, biomass or energy. Producers represent the base of each pyramid, while tertiary or top level consumers are represented by the apex of the pyramid. Every organism at each trophic level must be included for any calculation of energy content, biomass or energy. Trophic level represents a functional level. A single species can occupy more than one trophic level in the same ecosystem at the same time, as for example- sparrow is a primary consumer when it eats seeds, fruits, peas and a secondary consumer when it eats insects and worms.

Types of Ecological Pyramids

Three different types of ecological pyramids are observed they are discussed as follows:

Pyramid of Number:

It represents the number of individual organisms in a unit area at each trophic level. The pyramid is usually upright. This type of pyramid is seen in grassland and pond ecosystems. This pyramid can be inverted shaped as seen in parasitic food chains. A parasitic food chain that operates in a tree ecosystem where a single plant supports the growth of many herbivores, in turn several parasites get nutrition from herbivores, further these parasites support many hyperparasites. Therefore, from producer towards consumers the number of organisms increases making the pyramid inverted. Forest ecosystem shows a spindle shaped pyramid of numbers.

Pyramid of Biomass:

It represents total biomass present in series per unit area at different trophic levels. This pyramid is generally upright for terrestrial habitats. Aquatic ecosystems have an inverted shaped pyramid of biomass. Since in aquatic ecosystems producers are generally small organisms they have very less biomass  and this value moderately increases towards the apex of the pyramid, thus the pyramid looks inverted in shape.

Pyramid of Energy:

It represents the rate of energy flow or productivity per unit time and area at successive trophic levels. The shape of this pyramid always remains upright, as there is a moderate decrease in the energy content in successive trophic levels from producers to different consumers.

Advantages of pyramids of energy

·   It provides a description on the rate of production over time.

·       Different life spans are observed between two species of similar biomass, therefore a direct contrast of their total biomass is wrong but their productivity is truly similar.

·       Pyramids of energy help in comparing relative energy chains within an ecosystem.

·       No inverted pyramids are observed.

·   Input of solar energy can be increased.

 Disadvantages of pyramid of energy

·   Measurement of growth and reproduction through time requires the estimation of biomass production of an organism.

·   The allocation of organisms to a particular trophic level is still very confusing.

·   There is a difficulty in assigning a particular trophic level to decomposers and detritivores.

Limitations of Ecological Pyramids

The limitations are as follows:

·   The species which belong to two or more different trophic levels are not taken into account.

·   It is applicable to simple food chains that do not occur naturally.

·   Saprophytes are not included.

·   These pyramids do not consider the possibility of existence of the same species at different trophic levels.

·   Ecological Pyramids takes into account a food chain but not a food web.

Importance of Ecological Pyramids

·   This pyramid displays the feeding process of different organisms in different ecosystems.

·   It helps in monitoring the condition of the ecosystem, so as to prevent any further damages.

·   Ecological pyramids show the regulation of energy transfer.

Conclusion

Ecological studies have proved that there is an ecological balance between biotic and abiotic components in the biosphere. This balance gets interrupted by deforestation and human activities, in order to maintain the ecosystem balance we need to control it.