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- AuthorAmanda Robb
Amanda has taught high school science for over 10 years. She has a Master's Degree in Cellular and Molecular Physiology from Tufts Medical School and a Master's of Teaching from Simmons College. She is also certified in secondary special education, biology, and physics in Massachusetts.
View bio - InstructorEbony Potts
Ebony has taught middle and high school physical science, life science & biology. She's also been an assistant principal and has a doctorate in educational administration.
View bio - Expert ContributorAmanda Robb
Amanda has taught high school science for over 10 years. She has a Master's Degree in Cellular and Molecular Physiology from Tufts Medical School and a Master's of Teaching from Simmons College. She is also certified in secondary special education, biology, and physics in Massachusetts.
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Understand what is the 10 percent rule of energy transfer is. See its pictorial representation. Learn about the energy pyramid and percentages of energy transferred.Updated: 11/21/2023
Table of Contents
- What is the 10 Percent Rule of Energy Transfer?
- Lesson Summary
- FAQs
- Activities
A Local Energy Pyramid
In this activity, students will be researching a local food chain and creating an energy pyramid for it. Students can create their energy pyramid using poster paper and colored pencils or markers, or they can use the internet to create a digital energy pyramid in programs such as Google Drawings or Powerpoint. To get students started, remind them of reliable sources for internet research, such as encyclopedias, universities, news outlets, or government sources.
Directions
Now that you know all about energy pyramids and the 10% rule, it's time to apply it to the ecosystem you live in. For this project, you will be creating a visual energy pyramid for a food chain in your local ecosystem. First, consider the environment you live in. Is it a desert, a deciduous forest, the tundra, or somewhere else? Next, use reliable internet sources to learn about a local food chain. Reliable sources include websites from the government, universities, encyclopedias, or from science organizations. Once you've learned about the food chain, it's time to create a visual representation of it in an energy pyramid. Be sure to include the relative percentage of energy at each level! To be sure your energy pyramid has everything it needs, check out the criteria for success below.
Criteria For Success
- Energy pyramid is colorful, attractive and well designed
- Energy pyramid includes organisms from a local food chain, with pictures of each
- Energy pyramid includes the relative energy percentages at each trophic level
What is the 10% rule in food chain?
The 10% rule in a food chain is a law that explains that each trophic level transfers 10% of its energy to the level above them in the food chain. The other 90% of their energy is lost as heat or used for growth and reproduction.
What happens to the other 90% in the 10% rule?
The other 90% of energy during the 10% rule is used by that trophic level. It is used to live, grow, reproduce and is lost as heat to the environment.
Table of Contents
- What is the 10 Percent Rule of Energy Transfer?
- Lesson Summary
According to the law of conservation of energy, also known as the first law of thermodynamics, energy is never created or destroyed, rather it is only converted from one form to another. This law also applies to ecosystems and living things. In living ecosystems, the first law of thermodynamics manifests as the 10 percent rule. What is the 10 rule? The ten percent rule of energy transfer states that each level in an ecosystem only gives 10% of its energy to the levels above it. This law explains much of the structural dynamics of ecosystems including why there are more organisms at the bottom of the ecosystem pyramid compared to the top. To understand this further, let's look at the structure of an ecosystem pyramid.
Ecosystem energy transfer can be understood in the terms of food webs. Food webs are diagrams that show who eats who in a food web, or the energy transfer between organisms. Food webs are divided into levels called trophic levels. These levels can be drawn as a pyramid because the levels at the bottom of the food web support the levels at the top. Producers are at the bottom of the food web. These are organisms that make their own food. Producers are usually plants, but can also be algae and even bacteria. They get 100% of their energy from the Sun. Next in the food web are the consumers, or organisms that must eat to get energy. Consumers can be divided into different types. Primary consumers only eat producers. Secondary consumers eat primary consumers, and tertiary consumers eat secondary consumers and are considered carnivores. The table below summarizes the types of organisms that might be in each trophic level in a forest ecosystem.
| Trophic Level | Definition | Organism Example |
|---|---|---|
| Producer | Organisms that make their own food | Plants, algae, some bacteria |
| Primary consumer | Organisms that eat producers | Grasshoppers, rabbits, deer |
| Secondary consumer | Organisms that eat primary consumers | Frog, fox, spider |
| Tertiary consumer | Organisms that eat secondary consumers | Snake, eagle |
Understanding 10% Rule of Energy Transfer
In the food web or energy pyramid, each trophic level only gets 10% of its energy from the level before it. The other 90% of the energy in the trophic level goes to many functions, such as:
- Living
- Growing
- Reproduction
- Heat lost to the environment
For example, in a forest ecosystem, the grass could get 100,00 Joules of energy from the Sun. The primary consumers that eat the plants can only get 10,000 Joules from the plants. The secondary consumers that eat the primary consumers can only get 1,000 Joules and finally the tertiary consumers only have 100 Joules available to them. This explains the structure of many ecosystems. If we go into a forest, there will be lots of plants. This is because energy is abundant for them from the Sun. But it's unlikely we will see many tertiary consumers, such as large snakes or eagles. This is because their population is smaller due to less energy being available.
 |
An example of a food web is shown below.
 |
The table below summarizes the trophic levels and energy available for organisms in each level according to the example above.
| Trophic Level | Organisms | Energy in Joules |
|---|---|---|
| Producers | Phytoplankton, submerged vegetation, vegetation | 100,000J |
| Primary consumers | Zooplankton, benthic invertebrates, small fish, herbivorous ducks, mute swans | 10,000J |
| Secondary consumers | Gulls, terns, wading birds, large fish, sea ducks, Tundra swan | 1,000J |
| Tertiary consumers | Osprey, bald eagle | 100J |
The energy transfer in ecosystems also applies to humans. Let's look at an example of a student Jamal. Jamal is a tertiary consumer in his ecosystem and is going fishing to get food for dinner. In the aquatic ecosystem, the aquatic plants and algae get 100% of their energy from the Sun. They in turn give 10% of that energy to the primary consumers, plankton and invertebrates in the river. The secondary consumers, fish and crabs, get 1% of that total energy. The tertiary consumers, like Jamal who are eating the fish, only get 0.1% of the total energy in the food web. Thus, Jamal had to expend a lot of energy to get a small amount of energy and food from the food chain. Although it didn't cost him anything, it was still an expensive meal.
Energy Pyramid Percentages
An energy pyramid is a diagram that combines the food web with the ten percent rule. An energy pyramid is drawn as a pyramid because the bottom levels of the food web tend to have more energy than the upper levels. The energy pyramid specifically shows how the different trophic levels are related through energy availability. A food web focuses on the energetic relationships between different species.
Energy pyramids start with the Sun and have producers at the base. The producers are followed by primary consumers, secondary consumers and finally tertiary consumers at the top.
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Food webs are diagrams that show the transfer of energy between species in an ecosystem. Food webs include the following trophic levels:
- Producers: Organisms that make their own food
- Primary consumers: Organisms that eat producers
- Secondary consumers: Organisms that eat primary consumers
- Tertiary consumers: Organisms that eat secondary consumers
Trophic levels can be organized into an energy pyramid, which demonstrates the 10% rule. The ten percent rule states that each trophic level can only give 10% of its energy to the next level. The other 90% is used to live, grow, reproduce and is lost to the environment as heat. All energy pyramids start with energy from the Sun which is transferred to the first trophic level of producers. Producers give their energy to organisms that eat others, called consumers such as carnivores. Humans are consumes too, like Jamal who spent energy fishing to become a tertiary consumer in the river ecosystem.
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Video Transcript
The 10% Rule
The day Jamal has been dreading has arrived. The annual family fishing trip. Jamal loves his family, but he absolutely hates fishing! There is so much preparation. He has to help his dad secure the boat to the truck. Then Jamal and his siblings have to pack gear, life jackets, waterproof goulashes, fishing rods, and bait. Then he has to get up really early in the morning, help load up the car and ride out to the lake. All that preparation, all that energy just to maybe, possibly, catch a few fish. Then Jamal has to go home and help unload the car, all before helping his dad clean, prepare, and cook the fish. Jamal wants to spend time with his family just as much as the next person, but fishing just seems like an incredible waste of energy to him!
What Jamal doesn't realize is that anytime a source of energy is obtained via natural means, the 10% Rule will apply. The 10% Rule means that when energy is passed in an ecosystem from one trophic level to the next, only ten percent of the energy will be passed on. A trophic level is the position of an organism in a food chain or energy pyramid.
For example, let's think about Jamal and his fishing trip. Let's say that Jamal caught a bass on his trip. The bass did not know he was going to end up on Jamal's plate for dinner that day, so he ate, swam and went about his normal routine. While completing his routine, the bass was expending energy. So, all of the energy that the bass could have given Jamal will not be transferred to him because some of it was used by the fish.
Now, to get the fish, Jamal has to expend energy. He has to catch the fish, clean it, prepare it, and cook it. Then when the fish ends up on his plate, he will cut it, chew it, and then begin to digest it. All of this takes place before Jamal has used any of the energy locked in the molecules of the fish to help his body power itself. In the end, Jamal will only end up with a ten percent energy transfer from his fish meal.
Energy Pyramids and Food Chains
An energy pyramid shows the feeding levels of organisms in an ecosystem and gives a visual representation of energy loss at each level. An energy pyramid demonstrates exactly what we just discussed about the 10% Rule. All energy pyramids start with the sun as the source of all energy, followed by the trophic levels: producers (plants) at the bottom, herbivores (Plant eaters) at the next level up, then omnivores (which eat both plants and meat) and then carnivores (or meat eaters) at the top. Again, as you move from the sun through each trophic level, only ten percent of the energy will be carried to the next level. Each organism uses some of what it obtains for its life processes, so the organism that eats it, can only use the energy that is left over. The organism that eats the one at the level below it also has to expend some energy to get the food, thus continuing the pattern.
Food chains show a very similar pattern. A food chain is a linear demonstration of the feeding pattern of organisms in an ecosystem. A food chain also follows the same pattern of an energy pyramid. Starting with a producer, then an herbivore, followed by an omnivore, and then a carnivore. Only ten percent of the energy possessed is passed onto the next level or organism. The biggest difference between an energy pyramid and a food chain is that the food chain names specific organisms. It does not just label them as a producer, a plant, or a consumer, an organism that eats others to obtain energy.
Lesson Summary
The 10% Rule means that when energy is passed in an ecosystem from one trophic level to the next, only ten percent of the energy will be passed on. An energy pyramid shows the feeding levels of organisms in an ecosystem and gives a visual representation of energy loss at each level. Energy pyramids start with the sun as the source of all energy, followed by the trophic levels: producers (plants), herbivores (Plant eaters), omnivores (eaters both plants and meat), and finally carnivores(or meat eaters). As you move from the sun through each trophic level, only ten percent of the energy will be carried to the next level.
A food chain is a linear demonstration of the feeding pattern of organisms in an ecosystem. The difference between an energy pyramid and a food chain is that the food chain names specific organisms. It doesn't just label them as producers, which plants, or consumers, organism that eat others to obtain energy.
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