An ecological pyramid is a sort of graphical representation showing the relationship between the various tropic levels of a community. In food web energy flow is often represented by a diagram of quantitative relationship among various tropic levels.
Large amounts of energy and biomass are dissipated at every tropic level, .with each level retaining a much smaller amount than the proceeding level, and diagrams looks like a triangular pyramids. These are 03 types of ecological pyramids.
(i) Pyramids of Numbers:
In most of the food chains, the number of organism’s decreases in each tropic level, a large number of small animals occur at the base, a few large ones at the top.
The pyramid may be upright or inverted depending upon the size of producers in the community.
The base of the pyramid always represents the numbers of primary producers and the subsequent structure on the base are represented by the number of consumers of successive levels, the top representing the number of top carnivores in the ecosystem e.g. Ponds ecosystem.
(ii) Pyramid of Biomass:
Biomass means total dry weight of dry matter or caloric value present in the ecosystem at any one time. The pyramid of biomass means weight of organisms at different tropic level e.g. terrestrial, pond ecosystem.
(iii) Pyramid of energy:
The total amount of energy utilized by different tropic level organisms of an ecosystem in unit area over a set period of time.
The pyramid of energy depicts the amount of energy flow to each successive tropic level in community. Greater amount of energy is available at the producer level then the consumer level.
Energy pyramids are always slopping because less energy is transferred from each level than was paid into it. Energy pyramid indicates amount of energy flow at each level and also actual role the various organisms play in the transfer of energy.
Productivity: The relationship between the amount of energy accumulated and the amount of energy utilized within one tropic level of food chain clarify how much energy one tropic level passes to next tropic level.
The ratio of output of energy to input of energy is referred to as ecological efficiency. Different kinds of efficiencies can be measured by the following parameters (a) Ingestion (b) Assimilation (c) Respiration.
The portion of fixed energy a tropic level passes on to the next tropic level is called production. Green plants fix solar energy and accumulate it in organic forms as chemical energy. Since it is first and basic form of energy storage, the rate at which the energy accumulates in the green plants or producers is known as primary productivity.
The amount of organic matter present at a given time per unit area is called standing crop or biomass. The amount of energy based organic matter created per unit area and time is left after respiration of these plants is net primary production (NPP) or plant growth.