The pyramid of energy is a graphical representation that shows energy accumulation patterns at different tropical levels in an ecosystem.
- The energy flow moves from the bottom to up through the layers of the energy pyramid. Energy is higher at the bottom of the pyramid but gradually reduced as energy is used up by the organism at each level.
- It is one of the types of three ecological pyramids along with the pyramid of numbers and the pyramid of biomass.
- The pyramid of energy represents the energy flows in the ecosystem. It helps quantify energy transfer from one organism to another along a food chain.
- The number and weight of organisms at any level depending on the rate at which food is being produced rather than the amount of fixed energy present at any one time in the level just below.
- The pyramid shape is used due to how energy is utilized and lost at each tropic level when organisms use it up.
Levels of an energy pyramid
The energy pyramid is made up of several bars. The order of these bars is based on who feeds on whom. Each bar has a different level to represent the four main levels of the energy pyramid are follows:
Level 1: Producers
- Level 1 comprises producers and the energy available within them. They are found at the base of an energy pyramid.
- Most producers are autotrophs, organisms that synthesize their food from abiotic materials. Plant areas can manufacture their food by photosynthesis. Plants and algae are included in level 1.
- Plants and algae have chlorophyll pigment inside the chloroplasts. Chlorophyll can absorb light energy.
- Few autotrophs do not obtain their energy from the sun directly but from the soil, they get energy. Such autotrophs are earthworms and mushrooms.
Level 2: Primary Consumer
- The second level is comprised of primary consumers, which are those organisms or animals that feed on the producers.
- Primary consumers are usually herbivores (an animal that feeds on plant material). They depend only on the plant for their survival and nourishment.
- Plant get their energy from the sun then plants pass the energy to the primary consumers. This facilitates the transfer of solar energy from one tropic level to another.
- Primary consumers have physiological and anatomical features that make them adapt to a plant diet. For example, they have wide flat teeth for grinding and gut flora (bacteria and protozoans) that help cellulosic material digestion. Examples of herbivores are goats, cattle, horses, etc.
Level 3: Secondary Consumers
- Secondary consumers are located on the third level of the energy pyramid. Secondary consumers feed on primary consumers. They are commonly known as carnivores (organisms that eat another animal).
- Secondary consumers have anatomical and physiological features that make them adapt to an animal diet.
- Carnivores or secondary consumers depend on primary consumers. Without primary consumers, they wouldn’t have anything to eat and hence not exist.
- At this level, the energy that gets to the primary consumers from the producers is now transmitted to secondary consumers. This facilitates the smooth flow of energy for effective use.
- Examples of secondary consumer animals are foxes, spiders, etc.
Level 4: Tertiary Consumers
- The last level of the energy pyramid is comprised of tertiary consumers. Tertiary consumers are also known as secondary carnivores that feed on both primary and secondary consumers.
- The energy level of the ecosystem is finished at this level.
- Usually, the energy that the plant does not utilize goes back to the environment, which includes the atmosphere, soil, and water bodies.
- It is vitally important that all the different level of the energy pyramid get sufficient energy as required to ensure the earth remain stable.
- Tertiary consumers include leopards, hawks, etc.
Role of decomposer in the pyramid of energy
- Decomposer (which include bacteria, worm, and fungi) plays an essential role in the whole pyramid of energy. They break down the tissues and organic matter that have not been consumed by the organisms higher in the pyramid. They also use a little amount of energy that remains in the tissue of the dead organism. Decomposers recycle the nutrient and minerals back into the soil and help in the carbon cycle and nitrogen cycle.
- The energy released when decomposers break down tissue and organic matter is ultimately taken up by plants and used in photosynthesis. This mechanism ensures that energy is being cycled in the ecosystem.
Process of energy transfer through the food chain
- The initial energy is obtained from the sun, and plants produce metabolic energy by photosynthesis, wherein only 10% of energy is stored in their tissue that’s means approximately 10% of energy available for consumption by grazing herbivores. The plant, in its metabolism, uses the remaining solar energy, lost as heat or lost as waste.
- Of the 10% that herbivores eat, approximately 10% are stored in their tissue to be fed by carnivores. Herbivores use up the remaining 90% of their metabolic energy in functioning.
- This process continues up the pyramid, with each subsequent carnivore only inheriting 10% of the previous energy level.
- As time passes, about 0.1% of the solar energy that hits the top of the pyramid is consumed by the top predator, and the rest is lost in metabolic activities.
- Decomposers (bacteria, fungi, and worms) get the little amount of energy remaining in the tissues of dead plants and animals.
- The 10% rule state that “about 90% of energy from food is used for bodily processes or lost as heat, leaving 10% of the original energy available to feed the next consumer”.
Importance of pyramid of energy
- Based on the pyramid of energy, it is possible to characterize the nature of the relationship or interaction between different groups of organisms.
- The energy pyramid indicates the introduction of solar energy into the ecosystem by photosynthesis.
- The magnitude of energy in the various tropic level of the ecosystem can be compared by using an energy pyramid.
- The rate and effectiveness of production of the ecosystem can be assessed using the energy pyramid. It shows the efficiency of energy transfer.
Limitation of pyramid of energy
- It is still difficult to place organisms into a specific tropic level because of the complexity of their biology.
- There is an issue with assigning the decomposer and detritivores to a specific level within the food chain.
Example of the pyramid of energy
Grass obtains energy from the sun by photosynthesis. Grasshoppers feed grass for their energy. On the next level up the pyramid, the grasshopper gives their energy to the frog. The frog eats the grasshopper. Snake is the next level of the pyramid and get their energy from frogs and so on.
- Verma, P. S., & Agrawal, V. K. (2006). Cell Biology, Genetics, Molecular Biology, Evolution & Ecology (1 ed.). S .Chand and Company Ltd.
- Preisser,E. (2008). Encyclopedia of Ecology. Tropic Strucuture,3608-3616. https://doi.org/10.1016/b978-008045405-4.00558-9.