WHAT IS THE ECOLOGICAL PYRAMID? - BIOLOGY - 2025

The ecological pyramid or Eltonian pyramid graphically represent the structure of the ecosystem and trophic function of the communities of organisms (Universidad Nacional Autónoma de México, 2017).

Each transfer of energy from one level to the other loses around 90% of it (Mata & Quevedo, 1990). For this reason, individuals at the bottom receive the most energy.

It is also known by the name of the Eltonian pyramid because it was the zoologist and animal ecologist, Charles Elton, who created it (Corwin, 2017).

Each link in the food chain must conserve adequate amounts of the population of its constituent species to support itself and nurture the higher link.

The 3 types of pyramids that exist are numbers, biomass and energy.

Levels of the ecological pyramid

The ecological pyramid consists of 4 horizontal bars of the same thickness but in decreasing size, in which each section shows the energy transfer to the next level through food.

Each level of the chain is called a link.

Producers

The first link is the base of the pyramid (the widest area) is occupied by the producers, organisms that, using the energy obtained by photosynthesis, synthesize complex organic substances from a simple inorganic substance (Lindeman, 2017). Producers are autotrophic organisms such as plants, moners, and protists.

Producers capture solar energy through the leaves, equipped with chloroplasts that transform inorganic substances in the soil (such as water, minerals and carbon dioxide) into organic compounds (glucose) thanks to the mechanism of photosynthesis.

Primary consumers

In the second link appear the primary consumers, herbivorous individuals and heterotrophic plants that feed on the producers (plants, bacteria and fungi).

These types of consumers oxidize a considerable amount of the energy obtained in the form of kinetic energy for their metabolic functioning such as breathing, running, reproducing; and the rest is transformed into complex chemicals for your body (Lindeman, 2017).

Secondary consumers

In the third trophic link we find the secondary consumers that are the carnivorous animals that feed on the herbivores. Like the latter, its energy expenditure occurs in metabolic functioning.

Tertiary consumers

Approaching the dome of the pyramid, tertiary consumers appear that feed on secondary consumers or other carnivores.

Scavengers are one of its members but not the only ones. For example, an eagle eating a snake that in turn fed on a mouse.

Types of pyramids

1- Pyramids of numbers

It is the graphical representation in the form of a pyramid that shows the nutritional relationship of the number of individuals of each species or population, in each link.

The pyramid of numbers can be used to determine how much population of specific species can affect another (Corwin, 2017).

The pyramid of numbers of individuals in an ecosystem is almost always consistent with the 10% rule (Mata & Quevedo, 1990): the energy transfer from one level to another is approximately that percentage, as we explained it initially.

Two types of food chain are represented with this pyramid, depending on the type of ecosystem:

• Direct or from Suppliers: The number of Producers is greater than herbivores and carnivores. It is the traditional one and helps to maintain the ecosystem balance.
• Inverse or Parasites and Superparasites: The number of individuals in the upper links is greater than that of the lower ones. This representation could be of an ecosystem where the number of carnivores increases and herbivores are scarce due to lack of plants. In this situation a parasital relationship is created.

2- Biomass pyramids

It is the graphic representation of the energy flow through the biotrophic or food chain (Mata & Quevedo, 1990). In other words, the biomass pyramid represents the amount of mass or living matter in each trophic link.

To calculate this indicator, the weight of the individuals is taken into account as if they were dehydrated, without necessarily having to sacrifice them. It is expressed in units of mass / surface or volume units, that is, g / cm2, kg / m2, g / cm3, kg / m3 (Universidad Nacional Autónoma de México, 2017).

The shape of this pyramid can be direct or inverted, as with the Energy Pyramid.

The Direct Biomass Pyramid illustrates the cases where the amount of biomass of Producers is greater than that of Consumers.

The Inverted Biomass Pyramid is usual in aquatic ecosystems because the number of Producers (Phytoplankton) is much less than the number of Consumers.

Something important to note is that the pyramid of numbers and biomass only indicate the amount of material present during a short period.

The amount of matter present at any one time is known as harvestable biomass and does not give any indication of the total amount of material produced or the rate at which this material is being produced (Phillipson, 1966, p. 14).

3- Pyramids of energy

It is the graphic representation of the amount of total energy consumed at each trophic level. This graph shows the distribution of energy supplied by the sun in the food chain of an ecosystem. The units used are calories and / or joules (Universidad Nacional Autónoma de México, 2017).

Therefore, when a secondary consumer feeds from a primary consumer, the former obtains energy from the latter, but not the same amount but approximately 10%. What is not transferred to the next link becomes heat.

This pyramid always goes direct because the Producers will always have a greater amount of available energy by not losing part of it in the passage from one link to another.

References

1. College of Bachelors of the State of Sinaloa. (2008). 1.4 Ecosystems. In C. d. Sinaloa, Ecology and Environment (pp. 22-26). Hermosillo: College of Bachelors of the State of Sinaloa.
2. Corwin, A. (2017, 7 5). Ecological Pyramids. Taken from Gould Academy: gouldacademy.instructure.com.
3. Mata, A., & Quevedo, F. (1990). Biomass pyramids. In A. MAta, & F. Quevedo, Didactic Dictionary of Ecology (p. 354). Costa Rica: Editorial of the University of Costa Rica.
4. Phillipson, J. (1966). Ecological pyramids. In J. Phillipson, Ecological Energetics (pp. 12-15). London: Edward Arnold Ltd.
5. National Autonomous University of Mexico. (2017, 7 5). Ecological pyramids. Taken from from Academic Portal National Autonomous University of Mexico: portalacademico.cch.unam.mx.