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:
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.
Producers do not eat but rather get their energy from the Sun and are able to transfer ten percent of their energy to the next trophic level
An example of a food web is shown below.
The ten percent rule creates the dynamics in the food web
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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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
energy pyramids
An energy pyramid is a diagram that shows the flow and quantification of energy transfer in an ecosystem. Energy pyramids are based on the trophic levels of a food web in an ecosystem. The main trophic levels are: Producers: organisms that make their own food. Primary consumers: Organisms that eat producers.
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On average only 10 percent of energy available at one trophic level is passed on to the next. This is known as the 10 percent rule, and it limits the number of trophic levels an ecosystem can support.
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.
Students will learn that there are four levels that represent groups of organisms that might make up a food chain. From the bottom up, the levels are producers, primary consumers, secondary consumers, and tertiary consumers.
The amount of energy at each trophic level decreases as it moves through an ecosystem. As little as 10 percent of the energy at any trophic level is transferred to the next level; the rest is lost largely through metabolic processes as heat.
Lindemann gave the ten percent law in 1942. This law states that only 10 percent of energy in a food chain out of the total energy is transferred from one trophic level to another. The rest of the energy is utilized for other metabolic processes and some are released as heat.
10 Percent Rule: The 10 percent rule is used to approximate the independence of trials where sampling is taken without replacement. If the sample size is less than 10% of the population size, then the trials can be treated as if they are independent, even if they are not.
The 10% rule states that only 10% of energy from one trophic level is able to move up to the next. So, if producers have 10,000 J of energy stored through photosynthesis, then only 1000 J is passed on to primary consumers.
Step 1: Identify the population size, , and calculate 10% of the population size, . Step 2: Identify the sample size, . Step 3: Compare the sample size to 10% of the population size. If n ≤ 0.1 N then the 10% rule is satisfied.
Calculate the percent of energy that is transferred from the first trophic level to the second trophic level. Divide energy from trophic level one and multiply by 100. This amount is the percent of energy transferred. Remember to add a percent sign.
An energy pyramid, also known as a trophic or ecological pyramid, is a graphical representation of the energy found within the trophic levels of an ecosystem. The bottom and largest level of the pyramid is the producers and contains the largest amount of energy.
A pyramid of energy represents how much energy, initially from the sun, is retained or stored in the form of new biomass at each trophic level in an ecosystem. Typically, about 10% of the energy is transferred from one trophic level to the next, thus preventing a large number of trophic levels.
Encyclopædia Britannica, Inc. An energy pyramid is a model that shows the flow of energy from one trophic, or feeding, level to the next in an ecosystem. The model is a diagram that compares the energy used by organisms at each trophic level. The energy in an energy pyramid is measured in units of kilocalories (kcal).
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.
On average only 10 percent of energy available at one trophic level is passed on to the next. This is known as the 10 percent rule, and it limits the number of trophic levels an ecosystem can support.
Only about 10% of the energy in one trophic level is transferred to the next trophic level. This is because much energy is lost as heat during transfers between trophic levels or to decomposers due to the second law of thermodynamics.
An energy pyramid, also known as a trophic or ecological pyramid, is a graphical representation of the energy found within the trophic levels of an ecosystem. The bottom and largest level of the pyramid is the producers and contains the largest amount of energy.
The 10 percent rule in biology refers to the energy transfer in a food chain, where only about 10% of the energy from one trophic level is passed on to the next level.The rest is lost as heat or used by the organism.
Step 1: Identify the population size, , and calculate 10% of the population size, . Step 2: Identify the sample size, . Step 3: Compare the sample size to 10% of the population size. If n ≤ 0.1 N then the 10% rule is satisfied.
One major factor that limits the number of steps in a food chain is energy. Only about 10% of the energy in one trophic level is transferred to the next trophic level. This is because much energy is lost as heat during transfers between trophic levels or to decomposers due to the second law of thermodynamics.
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