Introduction to Ecological Pyramid
An ecological pyramid is a graphical representation of the distribution of biomass or energy within an ecosystem. The biomass is distributed according to the number of individual organisms in each trophic level. Each step or level of the food chain forms a trophic level. The autotrophs or the producers are at the first trophic level. They fix up the solar energy and make it available for heterotrophs or the consumers. The herbivores or the primary consumers come at the second, small carnivores or the secondary consumers at the third, and larger carnivores or the tertiary consumers form the fourth trophic level. The different types of ecological pyramids are based on how much energy or biomass is available to each trophic level.
Ecological Pyramid :
The graphical representation of the relationship between various living beings at various trophic levels within a food chain is called an ecological pyramid. The pyramid is formed on the basis of the number of organisms, energy and biomass, and just like the name suggests, these are shaped in the form of a pyramid.
The theory of ecological pyramid was suggested by Raymond Linderman and G.Evylen Hutchinson. The ecological pyramid is also often known as the energy pyramid.
The bottom of the pyramid, which is also the broadest part is occupied by the ones at the first trophic level, that is the producers. The next level of the pyramid is occupied by primary consumers. This is followed by the next level in the pyramid, belonging to the secondary and tertiary consumers.
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The ecological pyramid is also used to explain how various organisms in an ecosystem are related to one another. The pyramid ideally shows who is consumed by whom, while also showing the order in which the energy flows.
The flow of energy in an ecological pyramid is from bottom to top, which means energy from the autotrophs, who are also the primary producers, goes to the primary consumers, meaning those who consume these plants. At the next step, the energy goes to the secondary consumers who eat the primary consumers. This hierarchical system completes the above diagram.
Types of Ecological Pyramid
Ecological pyramids can be of three kinds. These are as follows:
Pyramid of numbers
Pyramid of biomass
Pyramid of energy
Pyramid of Numbers
This ecological pyramid takes into account the number of organisms present at each trophic level, making up that level for the pyramid. The number of organisms decreases while going higher up the pyramid. The ones at the bottom are the producers who are present in the largest number and hence form the base of the ecological pyramid.
Pyramid of Biomass
This ecological pyramid takes into consideration the amount of biomass that is produced at each trophic level as it adds to the pyramid. This pyramid is usually upright except for exceptional cases like the marine ecosystem where the number of phytoplanktons is lesser than the number of zooplanktons that depend on them.
The producers or the autotrophs have the highest level of biomass in this pyramid. The next level of primary consumers have lesser biomass than the producers and similarly, the secondary consumers have lesser biomass than the primary consumers. As a result, the level of the pyramid that has the least biomass is at the top of the pyramid.
Pyramid of Energy
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This pyramid shows the flow of energy that is in the direction of the consumers and comes from the producers. This pyramid is always in an upright form since it signifies the flow of energy within a food chain, something that is always unidirectional. The typical energy pyramid has three levels: the producer level, the consumer level, and the decomposer level. The flow of energy in an ecological pyramid is from bottom to top, which means energy from the autotrophs, who are also the primary producers, goes to the primary consumers, meaning those who consume these plants.
At the next step, the energy goes to the secondary consumers who eat the primary consumers. The producer level is the bottom of the pyramid and contains the green plants that use photosynthesis to create their own food. The consumer level is made up of animals that eat the plants at the producer level. The decomposer level is the top of the pyramid and contains organisms that are responsible for breaking down dead matter.
The energy pyramid represents the energy flowing through each trophic level while also showing the amount of energy at each level and the energy that is lost during the transfer to another trophic level. In simpler terms, this pyramid helps to quantify the energy transfer within the food chain as it goes from one organism to another. The energy pyramid is always upright because the energy level only decreases as it moves in the upward direction, from one level to the next one.
Each trophic level contains about ten times less energy than the previous level because some of the energy is lost as heat.
Importance of the Ecological Pyramid
The ecological pyramid is highly significant in an ecosystem and the reasons are explained below-
An ecological pyramid shows how efficiently energy is transferred from one level to the other and also helps to quantify energy in a food chain.
This pyramid also shows how various organisms in various ecosystems feed on each other, highlights their food patterns and explains the relationship between the various levels within it.
The ecological pyramid also helps in monitoring the overall health and condition of an ecosystem, and helps in restoring balance. It also helps to understand how any further damage to an ecosystem can be prevented.
Limitations of the Ecological Pyramid
The ecological pyramid comes with its own set of limitations since it overlooks a couple of important aspects. These have been discussed below:
The ecological pyramid does not take saprophytes into consideration and assumes them as unimportant in the ecosystem, even though they play a highly important role in maintaining the balance of the environment.
There is no mention of diurnal or seasonal variations in this pyramid, the concept of climate or seasons is completely unassumed here.
The ecological pyramid is only applicable in case of simple food chains, something that in itself is a rarity.
Neither does the ecological pyramid explain the concept of a food web.
This pyramid does not mention anything about the rate of energy transfer that occurs from one trophic level to the other trophic level.
Important sources of energy like litter and humus are completely ignored in the ecological pyramid even though their importance in the ecosystem is unparalleled.
The same species existing at different levels in a pyramid is not taken into consideration.
Conclusion
Understanding different aspects of the Ecological Pyramid with the Vedantu website can really help in preparing for the further study.
FAQs on Ecological Pyramid and Its Types
1. What is an ecological pyramid and what are its main types as per the CBSE Class 12 syllabus for 2025-26?
An ecological pyramid is a graphical representation designed to show the relationship between different organisms in an ecosystem at successive trophic levels. It illustrates the flow of energy, biomass, or the number of individuals. The base of the pyramid represents the producers (first trophic level), and the apex represents the top-level consumers. The three main types are:
- Pyramid of Numbers: Represents the total number of individual organisms at each trophic level.
- Pyramid of Biomass: Represents the total dry weight (biomass) of all organisms at each trophic level.
- Pyramid of Energy: Represents the total amount of energy present at each trophic level and the loss of energy at each transfer to another trophic level.
2. What does a pyramid of numbers illustrate with an example?
A pyramid of numbers illustrates the total count of individual organisms at each successive trophic level in an ecosystem. In most ecosystems, like a grassland, the pyramid is upright. For example, a large number of grass plants (producers) support a smaller number of grasshoppers (primary consumers), which in turn support an even smaller number of frogs (secondary consumers), and finally, very few snakes (tertiary consumers). However, it can be inverted, for instance, where a single large tree (producer) supports thousands of insects (primary consumers).
3. Explain the concept of a pyramid of biomass and mention an exception to its typical shape.
A pyramid of biomass represents the total amount of living organic matter, or biomass (usually measured in dry weight per unit area), at different trophic levels in an ecosystem. It shows the total mass of organisms at each stage. Typically, this pyramid is upright, as the total biomass of producers (like plants) is greater than that of primary consumers, and so on. A major exception is the aquatic ecosystem, where the pyramid of biomass can be inverted. Here, the biomass of phytoplankton (producers) at any given time is much smaller than the biomass of zooplankton (primary consumers) that feed on them.
4. Why is the pyramid of energy always upright and never inverted?
The pyramid of energy is always upright because the flow of energy in an ecosystem is unidirectional, moving from producers to consumers. According to the 10% Law of Energy Transfer, only about 10% of the energy from one trophic level is transferred to the next. The remaining 90% is lost, primarily as heat during metabolic processes. This continuous energy loss at each step means that the energy available at the highest trophic level is always significantly less than at the level below it, resulting in an upright pyramid shape that can never be inverted.
5. What is the overall significance of studying ecological pyramids?
Studying ecological pyramids is significant for several reasons:
- Shows Trophic Structure: It provides a clear visual of the feeding relationships and trophic structure of an ecosystem, showing who eats whom.
- Illustrates Energy Inefficiency: It highlights the progressive decrease in energy, biomass, and numbers at successive trophic levels, demonstrating the inefficiency of energy transfer.
- Ecosystem Health Monitoring: It can be used to monitor the health of an ecosystem. Any sudden change in the pyramid's shape can indicate an environmental disturbance or a decline in a particular species.
- Bioaccumulation and Biomagnification: The structure helps in understanding concepts like biomagnification, where toxins get concentrated at higher trophic levels.
6. What are the key limitations of using ecological pyramids to represent an ecosystem?
Ecological pyramids, while useful, have several key limitations:
- They do not account for species that feed at more than one trophic level (e.g., omnivores).
- They represent simple food chains, whereas nature consists of complex, interconnected food webs.
- Decomposers and saprophytes, which play a vital role in nutrient cycling, are not given any place in ecological pyramids.
- They do not account for seasonal or diurnal variations in trophic structures.
- They provide a static snapshot of an ecosystem at a particular moment and do not represent the rate of biomass or energy production over time.
7. How is it possible for a pyramid of numbers in a forest ecosystem to be spindle-shaped or inverted?
A pyramid of numbers in a forest ecosystem can be spindle-shaped or partially inverted due to the size of the organisms at different trophic levels. For example, a single large producer (like an oak tree) has a very small count (one organism) but supports a very large number of primary consumers (thousands of herbivorous insects). These insects, in turn, are consumed by a smaller number of secondary consumers (like woodpeckers). This results in a pyramid with a narrow base (one tree), a very wide middle section (insects), and a narrower top (birds), creating a spindle shape. This contrasts with a typical grassland pyramid, which is always upright.
