Ecological Pyramids/Eltonian Pyramids (Elton, 1927) – Essay

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Ecological pyramid is the graphic representation of an ecological parameter (number, biomass, energy) sequence-wise in various trophic levels of a food chain. It can be upright, inverted or spindle-shaped.

(a) Pyramid of Numbers:

It is an ecological/ eltorian pyramid which employs (he numbers of individuals per unit area at various trophic levels sequence-wise with producers at the base and various consumers at successively higher levels. It is generally upright as maximum number of individuals occurs at the producer level, followed by smaller number of herbivores, fewer primary carnivores and stills fewer higher levels of carnivores. However, a single large-sized tree can provide food to several herbivores (e.g. birds, squirrels) which support a few carnivores.

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Such a pyramid of number is spindle shaped. When the herbivores support a large number, of ecotoparasites, which are further parasitised by still larger number of hyperparasites, the pyramid of numbers is inverted.

(b) Pyramid of Biomass:

Biomass: It is the amount of living matter present in the individual/ population/community/trophic level/ecosystem. Biomass is measured on both fresh and dry weight basis. It is ecological/electronian pyramid which represents the biomass in various trophic levels.

It is more real than the numbers at various trophic levels. Only 10-20% biomass is transferred from one trophic level to the next – 10% law. 1000 kg (one tonne) vegetation shall form only 100 kg of herbivore, 10 kg of primary carnivore, 1 kg of secondary carnivore and only 0.1 kg of tertiary carnivore.

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Therefore, with increasing dependence on animal diet (nonvegetarian), the human population will require higher amount of farm produces-total nonvegetarian 10 times, 50% non vegetarian 5 times, vegetarian with milk 1.5 times. Pyramid of biomass is upright, exception aquatic food chain involving short lived plankton (biomass at one time will be less than consumers at higher levels.

(c) Pyramid of Energy:

It is ecological/eltorian pyramid that gives graphic representation of amount of energy trapped by different traphic levels per unit area. It is always upright because during transfer of energy from one trophic level to the next, a lot of wastage occurs in feeding, digestion, assimilation and respiration.

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