Ecological Pyramid

Ecological Pyramid is the graphical representations of trophic levels in an ecosystem. The concept of ecological pyramid was proposed byCharles Elton. In this article, you will learn about ecological pyramids, various ecological pyramids, their definition, types, structures, significance, limitations providing key insights for GS Paper-III Environment and Ecology section of UPSC IAS Exam.

Table of Content

• What is Ecological Pyramid?       
• Basic terminologies
• Ecological Pyramid of number
• Ecological Pyramid of biomass
• Ecological Pyramid of energy
• Importance of the Ecological Pyramid
• Limitations of the Ecological Pyramid
• Conclusion         
• Frequently Asked Questions                 

What is Ecological Pyramid?

• It is the graphical representations of trophic levels in an ecosystem.
• The concept and term of ecological pyramid was first given by Charles Elton and hence it is known as Eltonian pyramid.
• The producers form the base of the pyramid and then the subsequent tiers of the pyramid represent herbivore, carnivore and top carnivore levels.
• The next level of a pyramid depends upon its immediate lower level of pyramid for its nutrition and energy.
• Types of Ecological Pyramid: Pyramid of number; Pyramid of biomass and Pyramid of energy.

Basic terminologies:

• Producers includes autotrophs such as plants in case of terrestrial ecosystem and phytoplankton in case of aquatic ecosystem.
  • They directly depend upon solar energy or soil in some cases in order to make food.
• Herbivores includes organisms that directly feeds on producers such as grasshoppers or deer in case of terrestrial ecosystem and zooplankton in case of aquatic ecosystem.
• Carnivores includes organisms that feeds on herbivores such as lion in case of terrestrial ecosystem and sharks in case of aquatic ecosystem.
• Top carnivore includes organisms that feeds on Carnivores or Herbivores such as Hawks or vultures in case of terrestrial ecosystem and whales in case of aquatic ecosystem.
• Biomass: represents the total dry weight of the living organisms of different species at each trophic level at a particular time.

Fig. Types of ecological pyramids:

Ecological Pyramid of number:

• It represents the number of organisms or amount of population at each trophic level in the form of pyramid.
• It can be either upright or inverted.
• Upright pyramid example: in a grassland ecosystem the number of grasses is more than the number of herbivores that feeds on them and the number of herbivores is more than the number of carnivores.
• Inverted pyramid indicates the situationwhen herbivores are more than primary producers such as many caterpillars and insects feed on a single tree.
  • It is generally formed for parasitic food chain.
• It does not take into account the sizes or biomass of the organisms.
• It helps to count the number of creatures, thus helps in evaluating the ecological damage of that particular habitat.
• In Inverted ecological pyramid, food wastage while eating, digesting, and food use during respiration and physical activity leads to the population reduction of higher tropic species.

Ecological Pyramid of biomass:

• It represents the total standingcrop biomass at each trophic level.
  • Standing crop biomass is the amount of the living matter at any given time expressed as gm/unit area or kilo cal/unit area.
• The total dry weight of all organisms at each trophic level at a given time is calculated.
• In the terrestrial ecosystems, most of the pyramid of biomass is upright.
• In the aquatic ecosystems, most of the pyramid of biomass is inverted.
• Example of inverted pyramid: in a pond, phytoplankton are the main producers but as they have short life cycles and a rapidturnover rate, this makes their total biomass at any given time being less than the biomass of herbivores supported by them.
  • Turnover rate means they are rapidly replaced by new plants.
• It helps to resolve the problem of size disparity.

Ecological Pyramid of energy:

• It represents the total amount of energy at each trophic level.
• Energy is expressed in terms of rate such as kcal/unit area /unit time or cal/unit area/unit time.
• It also represents how different creatures has a role in energy transmission. 
• As energy moves from one trophic level to the successive trophic level, the energy pyramids describe how much energy is required by the next level. 
• It uses the principle that the energy can’t be created or destroyed, but can only be changed from one form to another.
• It is never inverted, as most of the energy is present at the base of the pyramid and energy gets lost at each tropic level due to their daily activities.
• Relation of energy with Biomass: Even when some species have more mass, the total amount of energy they use and pass can be lesser than that of species with less mass.
  • Example: the carnivores animal such as lion has more mass then the herbivores animal such as deer, yet lion passes less energy than the deer.
• Lindemann’s ten per cent law: a gradual decline in the amount of energy available takes place as one moves from producer level to upper trophic level.
  • As a result, only 10% of energy is available to be used by the next trophic level.
  • It is caused due to the fact that the organisms use up the energy for other purposes such as respiration, daily activities etc.

Importance of the Ecological Pyramid:

• It provides information about the region’s biodiversity and any harm caused by the climate change on them.
• It provides clarity regarding the amount of energy transferred from one trophic level to the next in an ecosystem.
• It is built on the interaction between food producers and consumers.
• Even, if one level of the pyramid is affected, the upper level of the pyramid will suffer.
• It helps assessing the overall state of an ecosystem.

Limitations of the Ecological Pyramid:

• It doesn’t take into account saprophytes, even if they form important part of ecosystem.
• It doesn’t take into account changes in food patterns of an organisms caused by the seasons.
• Sources of energy like litter and humus are not calculated, even if they are significant for the environment.
• Similar species may at exist at various levels in a pyramid which is not looked after for.
• It is only relevant in the case of straightforward food chains.

Conclusion

Though ecological pyramid has some of the limitations, yet it provides important insights in case when an organism at one of the trophic levels is affected and the amount of impact it will have on the subsequent trophic levels. The information that it provides helps to maintain the balance in the ecosystem. Even though, saprophytes are an important part of food web and food chains yet saprophytes are not given any place in ecological pyramids.

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FAQs(Frequently Asked Questions)