[Biology Class Notes] on Different Types of Ecological Pyramids Pdf

The ecological pyramid shows the relationship between various organisms in an ecosystem. The bars forming the pyramid represent different trophic levels and their order, which is decided by who is eaten by whom. It also represents the energy flow. In the pyramid, energy moves in the upward direction initiated by the primary producers or autotrophs which includes plants and algae. Primary producers are present at the bottom of the pyramid. On top of this are the primary consumers who eat the primary producers. On top of which we have the secondary consumers, who consume the primary consumers. This hierarchy goes on forming the pyramid. While the height of the bar measures equal, the width of the bar depends on the quantity of the aspect measured.

Types of Ecological Pyramids 

This pyramid shows the population present in each trophic level without taking into account their size. It is an upright pyramid with the producers being more in number than any other trophic level.

Unit: number of organisms

This pyramid depicts the total mass of organisms at each trophic level. Normally in this kind of pyramid, the bottom would be of the largest size, and it gets smaller travelling up. To attain the biomass of one trophic level we need to multiply the number of individuals in a trophic level by the average mass of one individual in a particular area. The pyramid of biomass solves some issues posed by the pyramid of numbers as the pyramid of biomass can give a more accurate image of the energy contained in each trophic level.

Eg: the duration when the data is procured is very important, the breeding time varies from species to species. Also one must take into account the fact that we cannot measure the ether mass of each organism. This sample is taken for this matter, which may lead to inaccuracies.

Unit: gm-2, Kg m-2

This pyramid looks at the maximum energy present at a trophic level and difference in the loss of energy in tropical levels. This pyramid takes into account the fact that the complete energy in one trophic level cannot be made available for the next. This is taken from Lindeman’s ten percent law which stated that “ only about 10% of the energy in a trophic level will go towards creating biomass ” this means that the making of tissues, leaves, stems only take up 10% of the energy in the next trophic level. The rest goes to the environment as heat or is used up in respiration etc. As we go up the ecological pyramid more and more toxins get accumulated in the organisms.This is known as biomagnification. 

This pyramid is not like the other two pyramids, it cannot be greater at the apex and smaller at the bottom. The energy flow in an ecosystem is determined by this pyramid.

Unit: J m-2 yr-1.

Example of a productivity pyramid can be demonstrated through this example

Taking an oak tree, which feeds millions of oak worms. The oak tree is the producer (one tree) will occupy smaller space in the pyramid than the primary consumer which are the worms (millions of insects). This is very unlikely in a biomass pyramid.

• Ecological Pyramid Examples

The productivity pyramid is also called the energy pyramid.

Sun is the primary source of energy. Fungi and bacteria are decomposers which can procure nutrients from any trophic level by breaking down dead and decaying organisms. These nutrients return to the soil and ate taken up by plants.

“Taking into consideration the total amount of energy that the primary producers contain, it is indicated by 100%, as we go up level one 90% of the energy is used up. The primary consumers end up with 10% of the starting energy. 10% of this 10% is lost while transferring it to the next level. As a result of which the apex, occupied by the predators will only reactive 0.01% of the initial energy. This inefficiency results in the productivity pyramid being upright.

The Function of the Ecological Pyramid

The ecological pyramid represents the inefficiency of energy transfer, the effects of how a change of numbers in one trophic level affects the trophic levels above and below it. It also shows the food patterns of various organisms in multiple ecosystems. The data that has been collected over the years can be compared giving us an idea of how the changing environment affects an organism, which will paint a vivid picture of how the ecological conditions are worsening and actions can be accordingly taken.

Related Biology Terms

Trophic Level: the position where an organism is placed in the ecological pyramid depending on what they feed on. Eg producers, primary consumers.

Species: a group of organism that has characteristics in common, and can repopulate among themselves.

Ecosystem: a group of living organisms living together with non-living entities surrounding them. Through the exchange of nutrients and energy living organisms interact with the physical environment.

Food Web: a system of the interdependent food chain. The difference between the food chain and the food web is that in a food web an organism can occupy any trophic level wherein a food chain they have specific positions.