Energy Flow in Ecosystem

Energy Flow in Ecosystem

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Energy flow in an ecosystem is all about how living things and their environment interact. An ecosystem is a group of living things that interact with each other and with the non-living parts of their environment. These non-living parts include things like the air, water, and soil. Ecosystems are crucial because they help regulate the climate and maintain the quality of the soil, water and air.

The sun primary source of energy in an ecosystem. This energy is transformed into chemical energy during photosynthesis. In the terrestrial environment, plants use the sun's energy to make food. In aquatic ecosystems, microalgae, macroalgae, and cyanobacteria also transform the sun's energy into food. Consumers eat the producers, which then gives them the energy they need to survive. This energy flow is important to maintain the balance of the ecosystem.

Energy transfer in the ecosystems

According to how they obtain nutrition, we can divide living organisms into three main groups: producers, consumers,  and saprobionts (decomposers).


Producers are living things that can produce their food, like glucose, through photosynthesis. Examples of producers include photosynthetic plants. These producers are also known as autotrophs.

An autotroph is any living thing that can use inorganic compounds, like carbon, to make organic molecules like glucose.

Some organisms can use both autotrophic and heterotrophic ways to obtain energy. Heterotrophs are organisms that consume organic matter made by producers. For instance, the pitcher plant both photosynthesizes and consumes insects.

Producers are not just photosynthetic organisms (photoautotrophs). Another group of producers you might encounter are chemoautotrophs. Chemoautotrophs use chemical energy to make food. These organisms usually live in harsh environments like sulfur-oxidizing bacteria in marine and freshwater anaerobic environments.

Let's explore the deep sea where sunlight cannot reach. This is the habitat of chemoautotrophs that live in deep-sea hot springs and hydrothermal vents. These producers create food for deep-sea creatures like deep-sea octopuses (Figure 1) and zombie worms. They look pretty bizarre! Besides, organic particles, living and non-living, sink to the bottom of the ocean, providing another food source. This includes tiny bacteria and sinking pellets produced by copepods and tunicates.

A dumbo octopus dwelling in the deep sea
A dumbo octopus dwelling in the deep sea


Consumers are organisms that obtain their energy for reproduction, movement and growth by consuming other organisms. We also refer to them as heterotrophs. There are three groups of consumers found in ecosystems:

Herbivores Carnivores Omnivores

Herbivores are living things that eat producers like plants or macroalgae. They are the first consumers in the food chain.

Carnivores are living things that consume herbivores, carnivores, and omnivores to get their nutrition. They are the second and third consumers (and so on). There are only a limited number of consumers in food chains because the transfer of energy decreases until it is not enough to sustain another level. Food chains usually stop after the third or fourth consumer.

Trophic levels are the different stages in a food chain.

Omnivores are living things that eat both producers and other consumers. They can thus be first consumers., humans are first consumers when we eat vegetables. When humans consume meat, they are usually second consumers (since they mainly eat herbivores). 


Saprobionts, also called decomposers, are living things that break down organic matter into inorganic compounds. To digest organic matter, saprobiotics release enzymes that break down the decaying organism's tissue. The primary groups of saprobionts include fungi and bacteria.

Saprobionts are incredibly important in nutrient cycles since they release inorganic nutrients like ammonium and phosphate ions back into the soil, which producers can access once again. This completes the entire nutrient cycle, and the process starts again.

Mycorrhizal fungi create symbiotic relationships with plants. They can live in the root networks of plants and provide them with essential nutrients. In exchange, the plant will provide sugars like glucose for the fungi.

Energy transfer and productivity

Plants can only capture a small percentage of solar energy, which is usually around 1-3%. This happens due to four primary factors:

Clouds and dust reflect over 90% of the solar energy, and the atmosphere absorbs it. Other limiting factors like carbon dioxide, water, and temperature can also limit the amount of solar energy that can be taken.The light may not reach the chlorophyll in the chloroplasts.The plant can absorb only certain wavelengths (700-400nm). Non-usable wavelengths will be reflected.

Chlorophyll refers to pigments located in plant chloroplasts. These pigments are necessary for photosynthesis.

Photosynthetic pigments can also be found in unicellular organisms like cyanobacteria. include β

Net primary production

Net primary production (NPP) represents the chemical energy stored by producers after accounting for what is lost during respiration, which is typically around 20-50%. This energy is available for plant growth and reproduction.

The equation below can be used to explain the NPP of producers:

NPP = GPP - respiration

Gross primary production (GPP) represents the total chemical energy stored in plant biomass. NPP and GPP are expressed in units of biomass per land area per time, such as g/m2/year. Respiration is the loss of energy. The difference between GPP and respiration is the NPP. Approximately 10% of the energy is available for primary consumers, while secondary and tertiary consumers can expect up to 20% of the energy from primary consumers.

This is due to several factors, including the fact that not all parts of the organism are consumed, certain parts cannot be digested, energy is lost in excreted materials like urine and feces, and energy is lost as heat during respiration.

Trophic levels refer to an organism's position within the food chain or pyramid, with each level having a different amount of available biomass, expressed as kJ/m3/year. Biomass is the organic material derived from organisms like plants.

The of energy transfer at each trophic level can be calculated using the following equation:

Energy transfer efficiency = (biomass at current trophic level / biomass at previous trophic level) x 100% 

Food chains

A food chain/pyramid is a simplified way to describe the feeding relationship between producers and consumers. When the energy moves up to higher trophic levels, a large amount will be lost as heat (about 80-90%).

Food webs

A food web is a more realistic representation of the energy flow within an ecosystem. Most organisms have multiple food sources, and food chains are linked together, resulting in highly complex food webs For example, humans consume a wide variety of foods.

Figure 2 is an example of an aquatic food web. The producers in this food web are coontail, cottontail, and algae. The algae are consumed by three different herbivores, such as bullfrog tadpole, which are then consumed by multiple secondary consumers. The apex predators in this food web are humans and the great blue heron. All waste, including faeces and dead organisms, will be broken down by decomposers, which in this particular food chain are bacteria.

Human impact on the food webs

Humans have had a significant impact on food webs, disrupting the energy flow between trophic levels. This has been caused by factors such as excessive consumption, removal of apex predators, introduction of non-native species, pollution, excessive land use, and climate change. The Deepwater Horizon oil spill in the Gulf of Mexico is an example of human activity that had a detrimental impact on marine wildlife, affecting over 8,000 species. Understanding the energy flow in ecosystems is crucial for maintaining a healthy and balanced environment. Ecosystems play a vital role in regulating climate, air, soil, and water quality. Autotrophs harvest energy from the sun/chemical energy sources, which is then transformed into organic compounds. Energy is transferred from producers to consumers, and then travels within the food web to different trophic levels.ers. 

Energy Flow in Ecosystem

How do energy and matter move through an ecosystem?

The autotrophs (producers) harvest energy from the sun or chemical sources. The energy moves through the trophic levels within the foodwebs when the producers are consumed.

What is the role of energy in the ecosystem?

Energy is transferred within the food web, and organisms use it to carry out complex tasks. Animals will use energy for growth, reproduction and life, in general.

What are the examples of energy in an ecosystem?

Sun’s energy and chemical energy.

How does the energy flow into the ecosystem?

The energy will be harvested from physical sources such as chemical compounds and the sun. The energy will enter the ecosystem through the autotrophs.

What is the role of an ecosystem?

The ecosystem is essential in regulating climate, air, water and soil quality.

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