An energy pyramid, also known as an ecological pyramid or trophic pyramid, is a graphical way of representing energy flow at each trophic level within an ecosystem. It is similar to a food chain and establishes the predator-prey relationship.
The order of the bars representing each trophic level is based on which predator feeds on which prey. Energy flows from the bottom toward the top of the pyramid, decreasing as we move up. The height of the bars is the same. However, each bar has a different width based on the units of energy available.
Overall, the model represents the amount of energy at each trophic level. It also helps to quantify the energy transfer from one organism to another along the food chain. An energy pyramid follows the 10% rule, which says that about 10% of energy from each level reaches the level above it, and the rest remains unutilized.
Trophic Levels of Energy Pyramid
The four main trophic levels in an energy pyramid are:
Producers or autotrophs (grasses, green plants) occupy the first level or at the bottom of the energy pyramid. They prepare their food by utilizing the sun’s energy through photosynthesis. These are mainly green plants, although some microorganisms like bacteria and algae can also produce food.
Almost 10% of solar energy is trapped in plant tissues. Some are lost as heat or in producing waste products; the plant uses the rest in its metabolism.
2. Primary Consumers
The second trophic level is occupied by primary consumers or herbivores like grasshoppers that feed on primary producers for food and energy. Like the first trophic level, only 10% of the energy consumed is stored in their tissues. The rest 90% is dissipated as heat, excreted out, or used for doing some work.
3. Secondary Consumers
The organisms occupying the third trophic level are known as secondary consumers. These organisms include carnivorous animals like frogs that feed on grasshoppers.
However, an organism’s role may change depending on the context. For example, if a snake eats a rabbit that eats grass, the snake is a secondary consumer. However, if the same snake eats a frog that ate an insect that ate plants, the snake is considered a tertiary consumer.
Like other trophic levels, secondary consumers use only 10% of the energy in the previous trophic level.
4. Tertiary Consumers
It is the last level of the energy pyramid consisting of organisms like owls, hawks, and foxes that consume both primary and secondary consumers for food. Above, the tertiary consumers are quaternary consumers or apex predators that reside at the top of a food chain or an energy pyramid. Such organisms as humans, wolves, polar bears, lions, and tigers do not have natural predators of their own.
Only a mere 0.1% of the solar energy absorbed by producers reaches this level.
Finally, decomposers also play an essential role in the ecosystem. They decompose the dead organic matter, wastes, and faces, thus helping to clean the environment. The breaking of organic matter provides nutrients to the soil that primary producers use to prepare food. It is the process of recycling energy in the ecosystem.
Example of Energy Pyramid
Grass, the primary producer, utilizes solar energy to produce their food, which grasshoppers, the primary consumer, eat. The grasshopper then transfers its energy to frogs, the secondary consumers. Frogs are eaten by snakes, the tertiary consumer, which the hawk, the apex consumer, then consumes.
Upon death, the organic matter of the hawk is mineralized by decomposers, returning the nutrients to the soil. The producers can utilize the nutrients to continue the food chain.
Article was last reviewed on Tuesday, February 7, 2023