energy flow in ecosystems assignment

• Biology Article
• Energy Flow In Ecosystem

Energy Flow in Ecosystem

Table of Contents

Energy Flow

• Trophic Level

The chemical energy of food is the main source of energy required by all living organisms. This energy is transmitted to different trophic levels along the food chain. This energy flow is based on two different laws of thermodynamics:

• First law of thermodynamics, that states that energy can neither be created nor destroyed, it can only change from one form to another.
• Second law of thermodynamics, that states that as energy is transferred more and more of it is wasted.

The energy flow in the ecosystem is one of the major factors that support the survival of such a great number of organisms. For almost all organisms on earth, the primary source of energy is solar energy. It is amusing to find that we receive less than 50 per cent of the sun’s effective radiation on earth. When we say effective radiation, we mean the radiation, which can be used by plants to carry out photosynthesis.

Also Read:  Difference between food web and food chain

Most of the sun’s radiation that falls on the earth is usually reflected back into space by the earth’s atmosphere. This effective radiation is termed as the Photosynthetically Active Radiation (PAR).

Overall, we receive about 40 to 50 percent of the energy having Photosynthetically Active Radiation and only around 2-10 percent of it is used by plants for the process of photosynthesis. Thus, this percent of PAR supports the entire world as plants are the producers in the ecosystem and all the other organisms are either directly or indirectly dependent on them for their survival.

The energy flow takes place via the food chain and food web. During the process of energy flow in the ecosystem, plants being the producers absorb sunlight with the help of the chloroplasts and a part of it is transformed into chemical energy in the process of photosynthesis .

This energy is stored in various organic products in the plants and passed on to the primary consumers in the food chain when the herbivores consume (primary consumers) the plants as food. Then conversion of chemical energy stored in plant products into kinetic energy occurs, degradation of energy will occur through its conversion into heat.

Then followed by the secondary consumers. When these herbivores are ingested by carnivores of the first order (secondary consumers) further degradation will occur. Finally, when tertiary consumers consume the carnivores, energy will again be degraded. Thus, the energy flow is unidirectional in nature.

Moreover, in a food chain, the energy flow follows the 10 percent law. According to this law, only 10 percent of energy is transferred from one trophic level to the other; rest is lost into the atmosphere. This is clearly explained in the following figure and is represented as an energy pyramid.

Trophic level

The producers and consumers in the ecosystem can be arranged into different feeding groups and are known as trophic level or the feeding level.

• The producers (plants) represent the first trophic level.
• Herbivores (primary consumers) present the second trophic level.
• Primary carnivores (secondary consumers) represent the third trophic level
• Top carnivores (tertiary consumers) represent the last level.

There are basically three different types of food chains in the ecosystem, namely –

• Grazing food chain (GFC) – This is the normal food chain that we observe in which plants are the producers and the energy flows from the producers to the herbivores (primary consumers), then to carnivores (secondary consumers) and so on.
• Saprophytic or Detritus food chain (DFC) – In this type of food chain, the dead organic matter occupies the lowermost level of the food chain, followed by the decomposers and so on.
• Parasitic food chain (PFC) – In this type of food chain, large organisms either the producer or the consumer is exploited and therefore the food passes to the smaller organism.

In nature, we mostly observe food web as there are many organisms which are omnivores. As a result, they occupy multiple trophic levels.

Law of Thermodynamics in the Ecosystem

The law of thermodynamics in the ecosystem explains the flow of energy at each trophic level. The first law states that energy is neither created, nor destroyed; it can only be converted from one form to another. This is true in energy flow in the ecocystem.

The second law states that there is loss of energy at each step of energy flow. This law also stands true in ecology as their is progressive decrease in energy at each trophic level.

Also Read:  Ecosystem

Frequently Asked Questions

What do you understand by the energy flow.

The energy flow is the amount of energy that moves along the food chain. This energy flow is also known as calorific flow.

Why is the energy flow in ecosystem important?

The energy flow in the ecosystem is important to maintain an ecological balance. The producers synthesise food by the process of photosynthesis. A part of the energy is stored within the plants. The remaining energy is utilised by the plants in their growth and development. This stored energy is transferred to the primary consumers when they feed on the producers. This energy is further passed on to the secondary consumers when they feed on the primary consumers, and so on.

What is the 10 percent law of energy flow?

The 10 percent law of energy flow states that when the energy is passed on from one trophic level to another, only 10 percent of the energy is passed on to the next trophic level.

Green plants occupy the following trophic level in an ecosystem (a)Complete food chain (b)First trophic level (c)Second trophic level (d)Third trophic level

The y shaped energy flow model was given by, what is the single channel energy flow model, what is the primary or main source of energy in the ecosystem.

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Energy Flow through Ecosystems

• Matter & Energy
• Graph Interpretation

Resource Type

• Click & Learn

Description

This Click & Learn traces the flow of energy from the Sun all the way to cells within organisms. The embedded questions and calculations guide students’ understanding of how energy is distributed through a variety of ecosystems. 

Most students are familiar with the concept of energy transfer within ecosystems. But how does energy enter an ecosystem, and what role does it play in the structure of the ecosystem? In this Click & Learn, students explore the source of Earth’s energy and the factors that control how much energy ends up in different trophic levels. 

This Click & Learn is an interdisciplinary overview of the movement of energy through ecosystems and could be used as an introduction to the concept or as a summative experience. 

Student Learning Targets

• Calculate the amounts of energy entering different ecosystems around the world.
• Explain factors that lead to variation in energy in different ecosystems.
• Explain how the movement and transfer of energy within an ecosystem influences the trophic structure.

Estimated Time

biomass, cellular respiration, consumer, electromagnetic radiation, food chain, photosynthesis, producer, productivity, solar energy, trophic level

Terms of Use

Please see the Terms of Use for information on how this resource can be used.

Accessibility Level (WCAG compliance)

Version history, curriculum connections.

HS-LS1-5, HS-LS1-7, HS-LS2-4; SEP5

AP Biology 2019

ENE-1.H, ENE-1.M, ENE-1.N, ENE-1.O; SP4

IB Biology 2016

Ap environmental science 2020.

Topic(s): 1.8, 1.9, 1.10, 1.11 Learning Objectives & Practices: ENG-1.A–D; SP5, SP6 

IB Environmental Systems and Societies 2017

Common core 2010.

Math.A-SSE.1

Vision and Change 2009

CC2, CC4, DP2

Explore Related Content

Other related resources.

The Beautiful Undammed

3.1 Energy Flow through Ecosystems

An  ecosystem  is a community of organisms and their abiotic (non-living) environment. Ecosystems can be small, such as the tide pools found near the rocky shores of many oceans, or large, such as those found in the tropical rainforest of the Amazon in Brazil (Figure 1).

There are three broad categories of ecosystems based on their general environment: freshwater, marine, and terrestrial. Within these three categories are individual ecosystem types based on the environmental habitat and organisms present.

Freshwater ecosystems are the least common, occurring on only 1.8 percent of Earth’s surface. These systems comprise lakes, rivers, streams, and springs; they are quite diverse and support a variety of animals, plants, fungi, protists and prokaryotes.

Marine ecosystems are the most common, comprising 75 percent of Earth’s surface and consisting of three basic types: shallow ocean, deep ocean water, and deep ocean bottom. Shallow ocean ecosystems include extremely biodiverse coral reef ecosystems. Small photosynthetic organisms suspended in ocean waters, collectively known as  phytoplankton, perform 40 percent of all photosynthesis on Earth. Deep ocean bottom ecosystems contain a wide variety of marine organisms. These ecosystems are so deep that light is unable to reach them.

Terrestrial ecosystems , also known for their diversity, are grouped into large categories called biomes. A  biome  is a large-scale community of organisms, primarily defined on land by the dominant plant types that exist in geographic regions of the planet with similar climatic conditions. Examples of biomes include tropical rainforests, savannas, deserts, grasslands, temperate forests, and tundras. Grouping these ecosystems into just a few biome categories obscures the great diversity of the individual ecosystems within them. For example, the saguaro cacti ( Carnegiea gigantean ) and other plant life in the Sonoran Desert, in the United States, are relatively diverse compared with the desolate rocky desert of Boa Vista, an island off the coast of Western Africa (Figure 2).

Food Chains and Food Webs

A  food chain  is a linear sequence of organisms through which nutrients and energy pass as one organism eats another. The levels in the food chain are producers, primary consumers, higher-level consumers, and finally decomposers. These levels are used to describe ecosystem structure and dynamics. There is a single path through a food chain. Each organism in a food chain occupies a specific trophic level (energy level), its position in the food chain or food web.

In many ecosystems, the base, or foundation, of the food chain consists of photosynthetic organisms (plants or phytoplankton), which are called  producers . The organisms that consume the producers are herbivores called  primary consumers .  Secondary consumers  are usually carnivores that eat the primary consumers.  Tertiary consumers  are carnivores that eat other carnivores. Higher-level consumers feed on the next lower trophic levels, and so on, up to the organisms at the top of the food chain. In the Lake Ontario food chain, shown in Figure 3, the Chinook salmon is the apex consumer at the top of this food chain.

One major factor that limits the number of steps in a food chain is energy. Energy is lost at each trophic level and between trophic levels as heat and in the transfer to decomposers (Figure 4 below). Thus, after a limited number of trophic energy transfers, the amount of energy remaining in the food chain may not be great enough to support viable populations at higher trophic levels.

There is a one problem when using food chains to describe most ecosystems. Even when all organisms are grouped into appropriate trophic levels, some of these organisms can feed at more than one trophic level. In addition, species feed on and are eaten by more than one species. In other words, the linear model of ecosystems, the food chain, is a hypothetical and overly simplistic representation of ecosystem structure. A holistic model—which includes all the interactions between different species and their complex interconnected relationships with each other and with the environment—is a more accurate and descriptive model for ecosystems. A  food web  is a concept that accounts for the multiple trophic (feeding) interactions between each species (Figure 5 below).

Two general types of food webs are often shown interacting within a single ecosystem. A grazing food web has plants or other photosynthetic organisms at its base, followed by herbivores and various carnivores. A detrital food web consists of a base of organisms that feed on decaying organic matter (dead organisms), including decomposers (which break down dead and decaying organisms) and detritivores (which consume organic detritus). These organisms are usually bacteria, fungi, and invertebrate animals that recycle organic material back into the biotic part of the ecosystem as they themselves are consumed by other organisms.

How Organisms Acquire Energy in a Food Web

All living things require energy in one form or another. At the cellular level, energy is used in most metabolic pathways (usually in the form of ATP), especially those responsible for building large molecules from smaller compounds. Living organisms would not be able to assemble complex organic molecules (proteins, lipids, nucleic acids, and  carbohydrates) without a constant energy input.

Food-web diagrams illustrate how energy flows directionally through ecosystems. They can also indicate how efficiently organisms acquire energy, use it, and how much remains for use by other organisms of the food web. Energy is acquired by living things in two ways: autotrophs harness light or chemical energy and heterotrophs acquire energy through the consumption and digestion of other living or previously living organisms.

Photosynthetic and chemosynthetic organisms are autotrophs, which are organisms capable of synthesizing their own food (more specifically, capable of using inorganic carbon as a carbon source). Photosynthetic autotrophs ( photoautotrophs ) use sunlight as an energy source, and chemosynthetic autotrophs ( chemoautotrophs ) use inorganic molecules as an energy source. Autotrophs are critical for ecosystems because they occupy the trophic level containing producers. Without these organisms, energy would not be available to other living organisms, and life would not be possible.

Photoautotrophs, such as plants, algae, and photosynthetic bacteria, are the energy source for a majority of the world’s ecosystems. Photoautotrophs harness the Sun’s solar energy by converting it to chemical energy. The rate at which photosynthetic producers incorporate energy from the Sun is called  gross primary productivity . However, not all of the energy incorporated by producers is available to the other organisms in the food web because producers must also grow and reproduce, which consumes energy.  Net primary productivity  is the energy that remains in the producers after accounting for these organisms’ metabolism and heat loss. The net productivity is then available to the primary consumers at the next trophic level.

Chemoautotrophs are primarily bacteria and archaea that are found in rare ecosystems where sunlight is not available, such as those associated with dark caves or hydrothermal vents at the bottom of the ocean (Figure 6). Many chemoautotrophs in hydrothermal vents use hydrogen sulfide (H 2 S), which is released from the vents, as a source of chemical energy. This allows them to synthesize complex organic molecules, such as glucose, for their own energy and, in turn, supplies energy to the rest of the ecosystem.

One of the most important consequences of ecosystem dynamics in terms of human impact is biomagnification.  Biomagnification  is the increasing concentration of persistent, toxic substances in organisms at each successive trophic level. These are substances that are lipid soluble and are stored in the fat reserves of each organism. Many substances have been shown to biomagnify, including classical studies with the pesticide dichlorodiphenyltrichloroethane (DDT), which were described in the 1960s bestseller  Silent Spring  by Rachel Carson. DDT was a commonly used pesticide before its dangers to apex consumers, such as the bald eagle, became known. DDT and other toxins are taken in by producers and passed on to successive levels of consumers at increasingly higher rates.  As bald eagles feed on contaminated  fish, their DDT levels rise. It was discovered that DDT caused the eggshells of birds to become fragile, which contributed to the bald eagle being listed as an endangered species under U.S. law. The use of DDT was banned in the United States in the 1970s.

Another substances that biomagnifies is polychlorinated biphenyl (PCB), which was used as coolant liquids in the United States until its use was banned in 1979. PCB was best studied in aquatic ecosystems where predatory fish species accumulated very high concentrations of the toxin that is otherwise exists at low concentrations in the environment. As illustrated in a study performed by the NOAA in the Saginaw Bay of Lake Huron of the North American Great Lakes (Figure 7 below), PCB concentrations increased from the producers of the ecosystem (phytoplankton) through the different trophic levels of fish species. The apex consumer, the walleye, has more than four times the amount of PCBs compared to phytoplankton. Also, research found that birds that eat these fish may have PCB levels that are at least ten times higher than those found in the lake fish.

Other concerns have been raised by the biomagnification of heavy metals, such as mercury and cadmium, in certain types of seafood. The United States Environmental Protection Agency recommends that pregnant women and young children should not consume any swordfish, shark, king mackerel, or tilefish because of their high mercury content. These individuals are advised to eat fish low in mercury: salmon, shrimp, pollock, and catfish. Biomagnification is a good example of how ecosystem dynamics can affect our everyday lives, even influencing the food we eat.

Suggested Supplementary Reading

Canales, M. et al. 2018. 6 Things that Make Like on Earth Possible [Infographic]. National Geographic . March.

Attribution

Energy Flow through Ecosystems  by OpenStax is licensed under CC BY 3.0. Modified from the original by Matthew R. Fisher.

Environmental Biology Copyright © 2017 by Matthew R. Fisher is licensed under a Creative Commons Attribution 4.0 International License , except where otherwise noted.

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Energy Flow (Ecosystem): Definition, Process & Examples

An _ ecosystem is defined as a community of various organisms interacting with each other and their environment in a particular area. It accounts for all interactions and relationships between both biotic (living) and abiotic_ (nonliving) factors.

Energy is what drives the ecosystem to thrive. And while all matter is conserved in an ecosystem, **energy flows ** through an ecosystem, meaning it is not conserved. Energy enters all ecosystems as sunlight and is gradually lost as heat back into the environment.

However, before energy flows out of the ecosystem as heat, it flows between organisms in a process called energy flow . It's this energy flow that comes from the sun and then goes from organism to organism that is the basis of all interactions and relationships within an ecosystem.

Energy Flow Definition and Trophic Levels

The definition of energy flow is the transfer of energy from the sun and up each subsequent level of the food chain in an environment.

Each level of energy flow on the food chain in an ecosystem is designated by a trophic level, which refers to the position a certain organism or group of organisms occupies on the food chain. The start of the chain, which would be at the bottom of the energy pyramid, is the **first trophic level **. The first trophic level includes producers and autotrophs that convert solar energy into usable chemical energy via photosynthesis.

The next level up in the food chain/energy pyramid would be considered the second trophic level , which is usually occupied by a type of primary consumer like an herbivore that eats plants or algae. Each subsequent step in the food chain is equivalent to a new trophic level.

Terms to Know for Energy Flow in Ecosystems

Besides trophic levels, there are a few more terms you need to know to understand energy flow.

Biomass: Biomass is organic material or organic matter. Biomass is the physical organic material that energy is stored in, like the mass that makes up plants and animals.

Productivity: Productivity is the rate at which energy is incorporated into the bodies of organisms as biomass. You can define productivity for any and all trophic levels. For example, primary productivity is the productivity of primary producers in an ecosystem.

Gross primary productivity (GPP): GPP is the rate at which the energy from the sun is captured in glucose molecules. It essentially measures how much total chemical energy is generated by primary producers in an ecosystem.

Net primary productivity (NPP): NPP also measures how much chemical energy is generated by primary producers, but it also takes into account the energy lost due to metabolic needs by the producers themselves. So, NPP is the rate at which the energy from the sun is captured and stored as biomass matter, and it's equal to the amount available energy to the other organisms in the ecosystem. NPP is always a lower amount than GPP.

NPP varies depending on the ecosystem. It depends on variables such as:

• Available sunlight. • Nutrients in the ecosystem. • Soil quality. • Temperature. • Moisture. • CO 2 levels.

Energy Flow Process

Energy enters ecosystems as sunlight and is transformed into usable chemical energy by producers such as land plants, algae and photosynthetic bacteria. Once this energy enters the ecosystem via photosynthesis and is converted into biomass by those producers, energy flows through the food chain when organisms eat other organisms.

Grass uses photosynthesis, beetle eats grass, bird eats beetle and so on.

Energy Flow Is Not 100 Percent Efficient

As you move up trophic levels and continue along the food chain, energy flow is not 100 percent efficient. Only about 10 percent of the available energy makes it from one trophic level to the next trophic level, or from one organism to the next. The rest of that available energy (about 90 percent of that energy) is lost as heat.

The net productivity of each level decreases by a factor of 10 as you go up each trophic level.

Why isn't this transfer 100 percent efficient? There are three main reasons:

1\. Not all organisms from each trophic level are consumed: Think of it this way: the net primary productivity amounts to all of the available energy for organisms in an ecosystem that's provided by producers for those organisms in higher trophic levels. In order to have all of that energy flow from that level to the next, it means that all of those producers would need to be consumed. Every blade of grass, every microscopic piece of algae, every leaf, every flower and so on. That doesn't happen, which means that some of that energy doesn't flow from that level up to the higher trophic levels.

2. Not all energy is able to be transferred from one level to the next: The second reason why the flow of energy is inefficient is because some energy is incapable of being transferred and, thus, is lost. For example, humans cannot digest cellulose. Even though that cellulose contains energy, people cannot digest it and get energy from it, and it's lost as "waste" (a.k.a., feces).

This is true for all organisms: there are certain cells and pieces of matter that they cannot digest that will be excreted as waste/lost as heat. So even if the available energy that a piece of food has is one amount, it's impossible for an organism that eats it to obtain every unit of available energy within that food. Some of that energy will always be lost.

3. Metabolism uses energy: Lastly, organisms use up energy for metabolic processes like cellular respiration. This energy is used up and cannot then be transferred to the next trophic level.

How Energy Flow Affects the Food and Energy Pyramids

Energy flow can be described through food chains as the transfer of energy from one organism to the next, beginning with the producers and moving up the chain as organisms are consumed by one another. Another way to display this type of chain or simply to display the trophic levels is through food/energy pyramids.

Because energy flow is inefficient, the lowest level of the food chain is almost always the largest in terms of both energy and biomass. That's why it appears at the base of the pyramid; that's the level that's the largest. As you move up each trophic level or each level of the food pyramid, both energy and biomass decrease, which is why levels narrow in number and narrow visually as you move up the pyramid.

Think of it this way: You lose 90 percent of the available amount of energy as you move up each level. Only 10 percent of the energy flows along, which cannot support as many organisms as the previous level. This results in both less energy and less biomass at each level.

That explains why there's usually a greater number of organisms lower on the food chain (like grass, insects and small fish, for example) and a much smaller number of organisms at the top of the food chain (like bears, whales and lions, for example).

How Energy Flows in an Ecosystem

Here's a general chain of how energy flows in an ecosystem:

1. Energy enters the ecosystem via sunlight as  ** solar energy .  2. Primary producers (a.k.a., the first trophic level) turn that solar energy into chemical energy via photosynthesis. Common examples are land plants, photosynthetic bacteria and algae. These producers are photosynthetic autotrophs, which means they create their own food/organic molecules with the sun's energy and carbon dioxide. 3. Some of that chemical energy that the producers create is then incorporated into the matter that makes up those producers. The rest is lost as heat and used in those organisms' metabolism. 4. They're then consumed by primary consumers (a.k.a., second trophic level). Common examples are herbivores and omnivores that eat plants. The energy that has been stored in those organisms' matter is transferred to that next trophic level. Some energy is lost as heat and as waste. 5. The next trophic level includes other consumers/predators that will eat the organisms on the second trophic level ( secondary consumers, tertiary consumers, and so on ). With each step you go up the food chain, some energy is lost. 6. When organisms die, decomposers ** like worms, bacteria and fungi break down the dead organisms and both recycle nutrients into the ecosystem and take energy for themselves. As always, some energy is still lost as heat.

Without producers, there would be no way for any amount of energy to enter the ecosystem in a usable form. Energy must continually enter the ecosystem via sunlight and those primary producers, or else the entire food web/chain in the ecosystem would collapse and cease to exist.

Example Ecosystem: Temperate Forest

Temperate forest ecosystems are a great example for displaying how energy flow works.

It all starts with the solar energy that enters the ecosystem. This sunlight plus carbon dioxide will be used by a number of primary producers in a forest environment, including:

• Trees (such as maple, oak, ash and pine). • Grasses. • Vines. • Algae in ponds/streams.

Next come the primary consumers. In the temperate forest, this would include herbivores like deer, various herbivorous insects, squirrels, chipmunks, rabbits and more. These organisms eat the primary producers and incorporate their energy into their own bodies. Some energy is lost as heat and waste.

Secondary and tertiary consumers then eat those other organisms. In a temperate forest, this includes animals like raccoons, predatory insects, foxes, coyotes, wolves, bears and birds of prey.

When any of these organisms die, decomposers break down the dead organisms' bodies, and the energy flows to the decomposers. In a temperate forest, this would include worms, fungi and various types of bacteria.

The pyramidal "flow of energy" concept can be demonstrated with this example, too. The most available energy and biomass is at the lowest level of the food/energy pyramid: the producers in the form of flowering plants, grasses, bushes and more. The level with the least energy/biomass is at the top of the pyramid/food chain in the form of high-level consumers like bears and wolves.

Example Ecosystem: Coral Reef

While marine ecosystems like a coral reef are very different from terrestrial ecosystems like temperate forests, you can see how the concept of energy flow works in the exact same way.

Primary producers in a coral reef environment are mostly microscopic plankton, microscopic plant-like organisms found in the coral and free-floating in the water around the coral reef. From there, various fish, mollusks and other herbivorous creatures, like sea urchins that live in the reef, consume those producers (mostly algae in this ecosystem) for energy.

Energy then flows to the next trophic level, which in this ecosystem would be larger predatory fish like sharks and barracuda along with the moray eel, snapper fish, sting rays, squid and more.

Decomposers exist in coral reefs, too. Some examples include:

• Sea cucumbers. • Bacterial species. • Shrimp. • Brittle starfish. • Various crab species (for example, the decorator crab).

You can also see the concept of the pyramid with this ecosystem. The most available energy and biomass exists at the first trophic level and the lowest level of the food pyramid: the producers in the form of algae and coral organisms. The level with the least energy and accumulated biomass is at the top in the form of high-level consumers like sharks.

• U.S. Energy Information Administration: Biomass Explained
• National Oceanic and Atmospheric Administration: Life in a Coral Reef
• PBS LearningMedia: Energy Flow in the Coral Reef Ecosystem
• Encyclopaedia Britannica: Ecosystem
• Britannica Kids: Energy Flow and Trophic Levels
• Open Oregon Educational Resources: Energy Flow Through Ecosystems

Cite This Article

Walsh, Elliot. "Energy Flow (Ecosystem): Definition, Process & Examples" sciencing.com , https://www.sciencing.com/energy-flow-ecosystem-definition-process-examples-with-diagram-13719231/. 24 June 2019.

Walsh, Elliot. (2019, June 24). Energy Flow (Ecosystem): Definition, Process & Examples. sciencing.com . Retrieved from https://www.sciencing.com/energy-flow-ecosystem-definition-process-examples-with-diagram-13719231/

Walsh, Elliot. Energy Flow (Ecosystem): Definition, Process & Examples last modified August 30, 2022. https://www.sciencing.com/energy-flow-ecosystem-definition-process-examples-with-diagram-13719231/

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