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Ecological pyramid:
 
 

Charles Elton developed the concept of ecological pyramid. After his name these pyramids are also called as Eltonian pyramids. It is a graphical representation or pyramid shaped diagram which depicts the number of organisms, biomass and productivity at each trophic level. Ecological pyramids begin with the producers at the bottom and proceed through the different trophic level.

There are three types of ecological pyramids as follows:

1.       Pyramid of number

2.       Pyramid of biomass

3.       Pyramid of energy

1.       Pyramid of number:

When plotted the relationships among the number of producers, primary consumers (herbivores), secondary consumers (carnivore of order 1), tertiary consumers (carnivore of order 2) and so on in any ecosystem, it forms a pyramidal structure called the pyramid of number. The shape of this pyramid varies from ecosystem to ecosystem.

There are three types of pyramid of numbers

          Upright

          Partly upright

          Inverted

Upright Pyramid of Number

In aquatic and grassland ecosystem numerous small autotrophs support lesser herbivores which support further smaller number of carnivores and hence the pyramidal structure is upright.

 

Partly upright pyramid of Number

In forest ecosystem lesser number of producers support greater number of herbivores who in turn support a fewer number of carnivores.

 

Inverted Pyramid of Number

In parasitic food chain one primary producer support numerous parasites which support still more hyperparasites.

 2.   Pyramid of Biomass:

When we plot the biomass (net dry weight) of producers, herbivores, carnivores and so on we have a pyramid of biomass.

Two types of pyramid of biomass are found

          Upright

          Inverted

Upright Pyramid of Biomass: When larger weight of producers support a smaller weight of consumers an upright pyramid results. eg forest ecosystem

 

Inverted Pyramid of Biomass: When smaller weight of producers supports larger weight of consumers an inverted pyramid of biomass is formed eg aquatic ecosystem

3.   Pyramid of Energy:

The pyramid of energy is drawn after taking into consideration the total quantity of energy utilized by the trophic levels in an ecosystem over a period of time. As the quantity of energy available for utilization in successive trophic levels is always less because there is loss of energy in each transfer, the energy pyramid will always be upright.

Note: The pyramid of numbers and pyramid of biomass have their limitations because they provide information only on the quantity of organic matter available at a particular time but not on the productivity and turnover time.

 

 
   

 

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