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When organisms eat other organisms, energy is transferred. An energy pyramid can be used to diagram this flow of metabolic energy. Here we will examine the definition of an energy pyramid, look at some examples, and finish with a brief quiz.

Definition of an Energy Pyramid

When we talk about the food chain or food web, we typically conjure to mind a lion chasing a gazelle, or perhaps a grazing cow. We imagine one organism being eaten by another and typically associate a large, carnivorous predator at the ‘top’ of the food chain. While this does show the ecological relationships between organisms, it doesn’t exactly show the flow of energy through the ecosystem.This is where an energy pyramid (sometimes called a trophic pyramid or ecological pyramid) is useful in quantifying the energy transfer from one organism to another along the food chain. Energy decreases as you move through the trophic levels from the bottom to the top of the pyramid.

Trophic Levels of an Energy Pyramid
Energy Pyramid

Energy Transfers

So, we have outlined that an energy pyramid diagrams a transfer of energy through the food chain, but what exactly is this ‘energy’ we are describing and where does it come from? The whole reason why organisms must eat is to obtain this metabolic energy, vital for their ability to function.

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  1. The energy starts with the sun!
  2. Plants produce metabolic energy via photosynthesis, wherein approximately 10% of their energy is stored in their tissues, available for consumption by a grazing herbivore. The rest of the solar energy was used by the plant in its own metabolism, lost as heat or lost as waste.
  3. Of that 10% that an herbivore eats, only 10% of that is stored in its tissues to be eaten by a carnivore. Just like the plant, the other 90% of its metabolic energy is used up by the herbivore in functioning, excreting waste, and heat loss.

  4. This continues up the pyramid with each subsequent carnivore only inheriting 10% of the previous level’s energy.
  5. By the time that the original solar energy hits the top of the pyramid, as little as 0.1% of the energy is consumed by the top predator; the rest is lost to metabolic activities.
  6. Decomposers, such as bacteria, worms, and fungi, obtain the little amount of energy remaining in the tissues of dead plants and animals.

The 10% rule states 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.Think of this process like a group of people standing in a line. The person at the front of the line is holding a handful of rice.

He then tosses the handful of rice to the next person, who tosses it to the next person, and so on. The person at the end of the line would be lucky to catch a couple of grains of rice, as the rest of it would be dropped in the process of playing catch! The rice is analogous to the energy being passed through the pyramid: A little bit is retained, but most is lost to the process.For this reason, consumers on each step up the energy pyramid must consume a very high quantity of their food source to get enough energy from it.

This diagram shows the energy equivalencies of organisms on different levels of the energy pyramid: 10,000 freshwater shrimp could feed 1,000 bleak, which could feed 100 perch, which in turn could feed 10 northern pike, which finally could feed just 1 osprey.

The equivalent quantities of organisms on each step of the energy pyramid.
trophic food

Lesson Summary

In ecology, an energy pyramid diagrams the flow of metabolic energy through the food chain.

While food chains and food webs show relationships between organisms, an energy pyramid quantifies the amount of energy transferred from one trophic level to the next, when one organism eats another, wherein approximately 10% of the energy available is retained and passed along. In the energy pyramid, the producers are on the bottom and the carnivores on top, and as you move up the pyramid, less energy is available.

Energy Pyramid Review

1. Energy pyramid – (trophic/ecological); quantifies the energy transfer from one organism to another in the food chain.2.

Energy begins at the sun and works its way through the plants, which give 10% of their energy stored to the carnivores who eat the plants.3. As you go up the energy pyramid, each consumer obtains 10% of the previous consumer’s energy, with the top predator only receiving 0.1% of the original solar energy.4. The 10% rule states that 90% of energy from food is retained for bodily processes, while the remaining 10% is left to feed for the next consumer.

Learning Outcome

After watching this lesson, you should be able to define energy pyramid and analyze the different energy transfers from one consumer to another.

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