Answer:
An
ecological pyramid is a graphic representation of an ecological parameter, like
number of individuals present in various trophic levels of a food chain with
producers forming the base and top carnivores the tip. Ecological pyramids were
developed by Charles Eiton (1927) and are, therefore, also called Eitonian
pyramids.
There are three types
of ecological pyramids, namely,
- Pyramid of
numbers
- Pyramid of
biomass
- Pyramid of
energy
Pyramid of numbers: It
is a graphic representation of the number of individuals per unit area of
various trophic levels stepwise with producers at the base and top carnivores
at the tip. In a grassland the producers, which are mainly grasses, are always
maximum in number. This number then shows a decrease towards apex, as the
primary consumers (herbivores) like rabbits, mice etc. are lesser in number
than the grasses; the secondary consumers, snakes and lizards are lesser in
number than the rabbits and mice. Finally, the top (tertiary) consumers hawks
or other birds, are least in number. Thus, the pyramid becomes upright. A
pyramid of number in grassland ecosystem is drawn below:
Pyramid of biomass:
Here, different trophic level of the ecosystem are arranged according to the
biomass of the organisms. This pyramid shows the total amount of living matter
(fresh weight or dry weight) present in each level. In grassland and forest,
there is generally a gradual decrease in biomass of organisms at successive
levels from the producers to the top carnivores. Thus these pyramids are upright.
But in pond ecosystem, it is inverted because the biomass gradually increases
from the produces to carnivores. A pyramid of biomass for a forest ecosystem is
given below:
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