ECOLOGICAL PYRAMID- DEFINITION & TYPES

ECOLOGICAL PYRAMID

DEFINITION

It is a graphical representation designed to show various trophic level and biomass at each trophic level of an ecosystem.

IMPORTANT POINTS

Since the graphical representation shows various trophic level, therefore ecological pyramid is also known as trophic pyramid.
It also shows, how much energy is retained in the form of new biomass at each trophic level and hence also called energy pyramid.
The concept of ecological pyramid was first developed by a British ecologist Charles Elton (1927).
The ecological parameters like number, biomass or accumulated energy are graphically shown at different trophic level in a food chain in an ecosystem.
Ecological pyramids start with primary producer (such as plants) and proceed through the various trophic levels (such as herbivores that eat plants, then carnivores that eat flesh, then omnivores that eat both plants and flesh, and so on). The highest level is the top of the food chain.

TYPES OF ECOLOGICAL PYRAMID

There are three types of ecological pyramid based on energy flow at different trophic level, number of organisms and biomass of organisms.

Pyramid of Energy

A pyramid of energy shows the production of biomass at each trophic level.
It refers to the total quantity of energy utilized by the trophic levels in a unit area on a particular time. It means, it shows the flow of energy through the food chain.
Since there is always a gradual decrease in the energy content at every successive trophic level from producer to top consumers, the pyramid of energy is always upright.

Pyramid of Number

It shows the population or number of individual organisms per unit area at each trophic level without any consideration for their individual sizes or biomass.
The shape of pyramid is not always upright, but varies from ecosystem to ecosystem.
For example, in a parasitic food chain, a single large tree support the large number of fruit eating birds and each herbivores support the large number of parasites. Hence, the pyramid of number is upright.
In case of grassland ecosystem, the producers are mainly grasses and maximum in number. This number shows a decrease towards primary consumers (herbivores), secondary and tertiary consumers (like hawk, lion) i.e. apex. Thus, upright pyramid is found here.
The same shape of pyramid is also found in aquatic ecosystem where producers are large in numbers per unit area due to their very small size.

Pyramid of Biomass

A pyramid of biomass how the relationship between biomass and trophic level by quantifying the biomass present at each trophic level at a particular time.
It shows graphical representation of total amount of living or organic matter in an ecosystem, i.e. biomass, present in unit area in different trophic levels.
Pyramid of biomass is of two types viz. upright and inverted in shape.

Upright pyramid of biomass is found in grassland & forest ecosystem, where larger weight of producers supports a smaller weight of consumers.

Inverted type of pyramid of biomass is found in aquatic ecosystem, where smaller weight of producers supports a larger weight of consumers.

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