Ecological Pyramids

 “An Ecological Pyramid is a graphic representation of an Ecological Parameter, like no. of   individuals present in various trophic levels of a food chain with producers forming the base & top   carnivores, the tip.”

Ecological Pyramids were developed by ‘Charles Eiton’ (1927) & are therefore, also called ‘Eiton Pyramids’. In a pyramid the various steps of food chain are represented sequence-wise.

An Ecological Pyramid can be upright, inverted & spindle shaped (narrow, both at base & tip with broader part in the middle). There are three types of Ecological Pyramid:-

      1) Pyramid of Numbers: -

     “It is graphic representation of the no. of individuals per unit area of various trophic levels stepwise   with producers being kept at the base & top carnivores kept at the tip.” In most cases pyramid of   Number is upright.

   

       2) Pyramid of Biomass: - The amount of living or organic matter present in an organism is called ‘Biomass’. It is measured, both as fresh and dry weight.

“Pyramid of Biomass is a graphic representation of biomass present sequence wise per unit area of   different trophic levels with producers at the base & top carnivores kept at the tip.”

 Pyramid of Biomass is more real than the Pyramid of Numbers because latter doesn’t take   consideration the size of individual. E.g. Mouse, Squirrel, Rabbit, Deer & Antelope.

Pyramid of Biomass is upright for terrestrial habitats. Inverted or Spindle-shaped pyramid for aquatic habitats. However, if total biomass produced per unit time is calculated, the pyramid of biomass shall always be upright.

 3)   Pyramid of Energy: -

“It is a graphic representation of amount of energy trapped per unit time & area in different trophic   levels of a food chain with producers forming the base & top carnivores the tip.”

Maximum energy content is present in producers. As the energy passes in to higher trophic levels      along with food, its amount decreases because of its dissipation as heat & use in overcoming  entropy as well as for performing various body activities.

Thus Pyramid of Energy is always upright. It is more accurate than the Pyramid of Biomass or  the  Pyramid of Numbers.