Ecosystem

Ecological Pyramid and Ecological Succession

By now, you have learnt that there is a lot of interaction between all the components of an ecosystem. Did you know that we can represent this relationship between the energy and biomass of organisms through a simple diagram? An Ecological pyramid shows precisely this relationship in a diagrammatic format. The predictable changes that are seen in organisms are shown by ecological succession.

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Ecological Pyramid

It is a graphic representation of the relationship between organisms at various trophic levels in a food chain. The basis of an ecological pyramid is the biomass, energy, and number. Just as the name suggests ecological pyramids are in the shape of a pyramid. The concept was first introduced by Charles Elton, the pioneer British Ecologist.

The bottom of an ecological pyramid is the broadest and is occupied the producers, which form the first trophic level. Producers are at the lowest level. Just as in a food chain, the producers are consumed by the primary consumers, in an ecological pyramid; the next level is occupied by the primary consumers. The next level of the pyramid is occupied by the secondary consumers and the last, by the tertiary consumers.

Types of Ecological Pyramids

Depending on the factors that we use to represent an ecological pyramid, there are three types. They are:

  • Pyramid of numbers– Here the factor that is taken into account is the number of organisms in each trophic level.  As we go up the levels of the pyramid, the number of organisms decreases. The producers form the largest number and hence are at the bottom of the pyramid.
  • Pyramid of energy– This is an upright pyramid that represents the flow of energy from the producers to the final consumers.
  • Pyramid of biomass – This pyramid represents the amount of biomass of the organisms present at each trophic level. Biomass is nothing but the weight of the organisms.

In general, all ecological pyramids are upright, except in certain cases. For example, in a detritus food chain, the pyramid of numbers is not upright because many organisms feed on one dead plant or animal. The pyramid of biomass in an ocean is also inverted. But a point of note is that the pyramid of energy is always upright as the flow of energy is unidirectional.

Ecological Pyramid

(Source – Encyclopedia Britannica)

Ecological Succession

A characteristic feature of biological communities is that their structure and composition changes according to certain changes in environmental conditions. Some of these changes occur in a more predictable and orderly fashion. The phenomenon through which these changes occur in ecological communities is Ecological succession.

This is an important aspect of the study of ecology and forms the core of ecological science. This ecological succession can be triggered by some form of disturbance or even due to the formation of new habitats in the ecosystem.

When the changes create a community that is almost in equilibrium with the environment, it is what we call a climax community. In a given ecological area, the communities change successively. This sequence of communities is a sere. The transitional communities are called seral communities. As the seral communities progress, there is an increase in diversity of organisms, increased number, and an increased biomass.

The starting point of ecological succession can be traced back to millions and millions of year back, where living organisms never existed. Slowly, as environmental changes happened, over time, new organisms developed, and the diversity of the planet started showing changes.

Types of Ecological Succession

Ecological succession is mainly of two types- Primary succession and secondary succession. The primary succession is a slow process that initiates in areas where there are no living organisms. Secondary succession begins in areas that were once inhabited but destroyed due to environmental disturbances. This is generally faster, as most of the other factors are already present.

Learn more about Biogeochemical Cycles here.

Solved Questions for You

Q: Are there any species that live on rock and be the starting point of ecological succession?

Ans: Lichens are organisms that can live on a rock. They can form the pioneer species on a bare rock. This is due to the fact that they have the ability to dissolve rock and help in the weathering and soil formation.