A graphical representation of biomass contained in a unit area at multiple trophic levels is called a biomass pyramid. It shows the link between biomass and trophic level, as well as the biomass available in each trophic level of an energy community at any given time. This article will explain to you about the Pyramid of Biomass which will be helpful in preparing the Environment syllabus for the UPSC Civil service exam.

Pyramid of Biomass - Concept

• At a certain trophic level, biomass is the amount of living material present in an individual or a group of individuals per unit area product.
• Each level of this form of ecological pyramid accounts for the amount of biomass present in each trophic level.
• The representation of the biomass pyramid is based on the law of thermodynamics.
• According to this law, energy can neither be created nor be destroyed but it can be transferred from one state to another.
• Specifically, energy is transmitted from producers to consumers and so on, and then converted into biomass.
• A biomass pyramid can be used to calculate the amount of biomass available as a result of organisms at various trophic levels.

Example of Biomass Pyramid

• Grass seeds is eaten by mice. The owl eats the mice, and the mice eat the owl.
• In this chain, grass has the most biomass.
• As a result, its biomass is toward the bottom of the pyramid.
• The owl, on the other hand, has the lowest biomass in the chain and hence resides at the apex of the pyramid.
• The best example of an inverted pyramid is the pond ecosystem. The mass of phytoplankton, the ecosystem's main producer, is smaller than that of the ecosystem's consumers, which are mostly fish and other insects.

Pyramid of Biomass - Features

• Individuals at each trophic level are weighed rather than counted in this method.
• This results in a biomass pyramid, which represents the total dry weight of all creatures at each trophic level at a given moment.
• The dry weight of all species in each trophic level is routinely collected and measured to determine the biomass pyramid.
• Because all trophic levels of organisms are weighed, the size difference problem is solved. Biomass is measured in grams per square meter.

Types of Biomass Pyramid

Upward Pyramid

• The biomass pyramid in most terrestrial ecosystems has a big base of primary producers with a smaller trophic level mounted on top.
• Producer biomass (autotrophs) is at an all-time high.
• The biomass of primary consumers, the next trophic level, is lower than that of producers.
• The biomass of secondary consumers, the next higher trophic level, is lower than that of primary consumers.
• There is relatively little biomass at the top, a high trophic level.

Inverted Pyramid

• In many aquatic habitats, however, the biomass pyramid may take on an inverted shape.
• This is because the producers are small phytoplankton that multiplies and reproduces quickly. (In contrast, a pyramid of numbers for the aquatic ecology is vertical.)
• The biomass pyramid has a narrow base here, with consumer biomass always exceeding producer biomass, and the pyramid takes on an inverted appearance.

Limitations of Pyramid of Biomass

• One of the most significant drawbacks of a biomass pyramid is that each trophic level appears to have more energy than it actually has.
• The consumption of another animal by humans is a good example of this.
• The bone mass of the animal is determined. The mass of the bones, on the other hand, is not utilized at the following level of the biomass pyramid.
• The mass that is not really transported to the next trophic level is counted in a biomass pyramid.
• Nonetheless, a biomass pyramid remains one of the most effective techniques to assess if an ecosystem is out of balance

Conclusion

The pyramid of biomass was actually introduced to overcome the shortcomings of the pyramid of numbers as it does not take into account the biomass. Besides, the pyramid of biomass has more accuracy in comparison to the number pyramid. An upright biomass pyramid represents almost all of the world's ecosystems and biomes. However, the biomass pyramid can sometimes represent energy worth, but it doesn't always reveal how much energy is trapped at each energy level.

FAQs

Q1: What is a Pyramid of Biomass?

Q2: How does the Pyramid of Biomass differ from the Pyramid of Numbers?

Q3: Why is the Pyramid of Biomass usually upright?

Q4: Can the Pyramid of Biomass ever be inverted?

Q5: How does energy transfer in the Pyramid of Biomass?

MCQs

1. Which of the following best describes the Pyramid of Biomass?

a) Representation of energy flow in an ecosystem

b) Representation of total mass of organisms at each trophic level

c) Representation of the number of individuals at each trophic level

d) Representation of the size of organisms in an ecosystem

2. In which type of ecosystem can the Pyramid of Biomass be inverted?

a) Grassland

b) Forest

c) Aquatic ecosystem

d) Desert

3. Which trophic level has the highest biomass in a typical terrestrial ecosystem?

a) Herbivores

b) Primary consumers

c) Producers

d) Carnivores

4. Why is the Pyramid of Biomass narrower at the top in most ecosystems?

a) Because energy is lost at each trophic level

b) Because producers consume more energy

c) Because the number of organisms increases

d) Because higher trophic levels have more organisms

5. What is a major limitation of the Pyramid of Biomass?

a) It does not represent energy flow

b) It does not account for the number of organisms

c) It does not reflect the actual energy transfer

d) It can be inverted in some ecosystems

GS Mains Questions and Model Answers

Q1: "The Pyramid of Biomass provides a clearer understanding of the energy flow in ecosystems compared to the Pyramid of Numbers." Critically analyze this statement.

Answer: The Pyramid of Biomass offers a clearer understanding of energy flow in ecosystems compared to the Pyramid of Numbers because it reflects the total mass of organisms at each trophic level, giving a more accurate representation of the energy available. While the Pyramid of Numbers only shows the number of organisms, it does not account for the size or mass of these organisms, which can vary significantly across trophic levels. For example, in a forest ecosystem, a few large trees (producers) may support a larger number of herbivores, but the biomass of the trees far exceeds that of the herbivores. The Pyramid of Biomass corrects this discrepancy by focusing on the mass and energy content, which provides a more accurate depiction of energy transfer through the ecosystem. However, in certain ecosystems like aquatic environments, the Pyramid of Biomass may be inverted, which limits its effectiveness in such cases.

Q2: Evaluate the importance of the Pyramid of Biomass in the study of ecosystem productivity and trophic dynamics.

Answer: The Pyramid of Biomass is crucial in studying ecosystem productivity and trophic dynamics as it helps illustrate how energy is distributed among different trophic levels. By representing the total biomass at each level, it provides insight into the efficiency of energy transfer within the food chain. Since energy is lost at each trophic level through metabolic processes, the Pyramid of Biomass typically shows a decrease in biomass from producers to higher trophic levels, which helps in understanding ecosystem productivity.
It also highlights the importance of primary producers in sustaining ecosystems, as they form the foundation of the energy pyramid. In ecosystems where the Pyramid of Biomass is inverted, such as aquatic systems, it draws attention to the rapid turnover of producers and the dynamic nature of energy flow. Overall, the Pyramid of Biomass is essential for understanding trophic interactions, ecosystem stability, and the flow of energy through different ecological levels.

Q3: Discuss how the Pyramid of Biomass can be used to assess the sustainability of an ecosystem. Provide examples to support your argument.

Answer: The Pyramid of Biomass can be an effective tool for assessing the sustainability of an ecosystem by illustrating how biomass and energy are distributed across different trophic levels. A healthy, sustainable ecosystem typically has a broad base of biomass at the producer level, which supports a smaller biomass of herbivores and even smaller biomass of carnivores. This structure ensures that there is enough energy at the lower levels to sustain higher trophic levels.
For example, in a terrestrial ecosystem like a grassland, the large biomass of grasses (producers) supports a smaller biomass of herbivores like deer, which in turn supports a smaller population of carnivores like lions. If this balance is disturbed, such as through overgrazing or habitat loss, the ecosystem may become unsustainable.
In contrast, in some aquatic ecosystems where the Pyramid of Biomass is inverted, the rapid turnover of primary producers like phytoplankton can still support a larger biomass of consumers. However, this may indicate that the system is more vulnerable to disturbances, such as overfishing or pollution, which can quickly disrupt the balance. The Pyramid of Biomass, therefore, helps in understanding how energy flow impacts ecosystem sustainability and resilience.

Previous Year Questions on  Pyramid of Biomass

1. UPSC CSE 2020

Q1: Explain how the Pyramid of Biomass can be inverted in aquatic ecosystems. 
Answer: In aquatic ecosystems, the Pyramid of Biomass can be inverted because the biomass of primary producers, such as phytoplankton, is relatively small compared to the biomass of primary consumers like zooplankton and fish. Phytoplankton have a rapid turnover rate and reproduce quickly, allowing them to sustain a higher biomass of consumers despite their own low mass. This results in an inverted pyramid, where the biomass of consumers exceeds that of producers.

2. UPSC CSE 2019

Q2: Discuss the significance of the Pyramid of Biomass in understanding energy flow in an ecosystem. 

Answer: The Pyramid of Biomass is a critical tool for understanding energy flow in an ecosystem. It represents the total mass of living organisms at each trophic level, indicating how energy is distributed across the ecosystem. As energy moves up the pyramid from producers to herbivores and carnivores, there is a significant loss of energy, with only about 10% being transferred to the next trophic level. This helps explain why biomass decreases at higher trophic levels and highlights the inefficiency of energy transfer in ecosystems.