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Exploring the structure of ecosystems

Find out what ecosystems are, how they work, and what the structure of ecosystems looks like. Learn more about ecosystems.

How ecosystems work

Our planet is made up of a range of complex ecosystems, consisting of a variety of organisms and environments. Each species plays a different role, and the structure of ecosystems themselves differ greatly. 

Have you ever wondered what ecosystems are made up of? Here, we explore what an ecosystem is, which types of ecosystems there are, and delve into the structure of ecosystems.

What does ecosystem mean? 

So, what is an ecosystem? An ecosystem is a community made up of living organisms and the physical environment within which they interact. These organisms include animals, plants, fungi, and bacteria. All of these complex ecosystems are interconnected to create what is known as the biosphere. 

The biosphere is the worldwide sum of all existing ecosystems, ranging from 8 kilometres above the planet to the deep-sea paths within oceans. Within the biosphere, we have hundreds of ecosystems, ranging in types and made up of wildly different ecological relationships.

What is ecology? 

Now that we know what an ecosystem is let’s find out what ecology means. Ecology is the study of how organisms interact with each other and their environment. Thus, ecologists undertake the important task of studying ecosystems and the organisms that live amongst them. 

Ecologists play an important role in the conservation of wildlife and the conservation of biodiversity, preventing endangerment and extinctions. We’ll discuss biodiversity a little later. To learn more about the world of ecology, check out our Ecology and Wildlife Conservation course.

What is a biome?

You may have heard the term biome if you’re already familiar with ecosystems. A biome is a group of ecosystems categorised by vegetation, wildlife, soil, and climate. A biome is typically a large region grouped by the similarities in its wildlife, climate, and other traits.

Are ecosystems at risk? 

Due to various environmental challenges, the survival of many ecosystems is at risk. With so many endangered species, the loss of one species could lead to an even larger impact. Ecosystems with the lowest diversity are the most vulnerable.

In our IUCN Red List of Ecosystems course, we explore where ecosystems are at greatest risk and discuss the global standard for ecosystem risk management. 

Types of ecosystems

There are two main types of ecosystems: terrestrial and aquatic. Terrestrial ecosystems include forests, grasslands, tundra, and desert. Aquatic ecosystems include both freshwater and marine. Let’s take a brief look at what some of these ecosystems encompass: 

Marine ecosystems 

These are the largest water-based ecosystems and are found in waters with very high salt levels. Since marine waters take up two-thirds of the planet’s surface, it makes up a large portion of our ecosystems. 

An example of a relationship within a marine ecosystem is the mutual bond between clownfish and anemone. Clownfish use anemones as shelter and protection from predators as they have developed immunity to an anemone’s sting. In return, the anemone feeds on the waste of a clownfish, so they are both benefiting each other’s survival. 

To learn more about this type of ecosystem, check out our Life Below Water: Conservation, Current Issues, Possible Solutions course. 

Freshwater ecosystems

This type of ecosystem encompasses ponds, lakes, rivers, streams, wetlands, and springs. Freshwater ecosystems only make up 1% of the Earth’s surface and provide habitats for over 10% of the species on Earth. 

These ecosystems not only provide habitats for a range of species, but also provide us with the vital resource that is freshwater. It’s vital for use as drinking water and growing crops among other things. 


As we discovered in our open step from Cardiff University, freshwater ecosystems are biologically rich and diverse. Some of the animals that call freshwater ecosystems home include alligators, toads, newts, and shrimp.

Grassland ecosystems

These ecosystems are largely dominated by grass and other green plants. Grassland ecosystems make up around 20% of the earth’s land surface. Typically, grazing species such as zebras live in grasslands. 

An example of an ecological relationship within grassland ecosystems is that between cattle and cattle egrets. The birds have learnt to feed on any insects disturbed by cattle grazing. Although the cattle do not benefit from this interaction, the cattle egrets benefit from the cattle. 

Forest ecosystems

A forest ecosystem is an environment dominated by trees. These ecosystems provide oxygen, timber, and a home to a huge variety of animals and plants. As well as providing homes for animals, forests also house indigenous communities of people. 

Forest ecosystems make up 31% of the Earth’s surface on land, with the largest being the Amazon forest. Forest ecosystems can be broken down into three different types: tropical, temperate and boreal. The Amazon is a tropical rainforest and is home to jaguars, ocelots, toucans and anacondas to name a few.

Tundra ecosystems

Completely unlike the forest ecosystems, tundra ecosystems are environments that are void of trees. Tundra ecosystems are the coldest of all biomes as they are found in the arctic and at the top of mountains. These ecosystems make up roughly 10% of the Earth’s surface, 

As well as being extremely cold, the tundra gets low amounts of precipitation, making it incredibly dry. Despite the harsh weather conditions, tundra ecosystems still house a few species, including arctic foxes, polar bears, and mountain goats.

Desert ecosystems 

These ecosystems are incredibly dry and see very little rainfall. Although these environments are dry, it is home to many well-adapted plants and animals. Some of the animals that can be found in deserts include meerkats, fennec foxes, and coyotes. 

An example of a relationship in the desert ecosystem is that of the coyote and fruit. Coyotes feast on fruit and disperse the fruit seed through their faeces. This is an example of mutualism, which we’ll discuss later.

Functions of an ecosystem

We now know ecosystems are all around us – but what purpose do ecosystems serve? What are the functions of an ecosystem? To put it simply, ecosystems exist for the exchange of nutrients and energy amongst organisms. 

Ecological processes

Ecological processes within ecosystems are the processes by which organisms are linked to their environment. This could be in the form of chemical, physical, or biological processes. Let’s look at some examples of ecological processes. 

Water cycle

The water cycle is a key ecological process within ecosystems, as many organisms depend on water for survival. The water cycle is made up of evaporation, condensation, and precipitation. With this, water is continually cycled within an ecosystem as it passes through a series of pathways. 

Energy flow

Energy flows are the paths that energy can take within an ecosystem. More often than not, energy enters the ecosystem via the sun. This is a one-way relationship since the energy does not return to the sun. 

Food chains

A key part of ecosystems is the process of a food chain. Although they vary depending on the ecosystem, every organism needs sustenance to survive. The food chain is a process by which each organism feeds on the next and energy is passed on to the next organism. Each organism is dependent on the next part of the chain as a means of sustenance. 

Biodiversity

As we discovered in our open step from the University of York, biodiversity deals with the balance and diversity amongst living things within an ecosystem. It relates to the variety of life amongst animals, plants, and microorganisms and how they interact with each other.

Biodiversity is built on three features – ecosystem diversity, genetic diversity, and species diversity. Biodiversity is also crucial to producing food, air, and other natural resources. Not only does it benefit us, but it is key to keeping many other species alive and thriving. 

The structure of ecosystems

Now that we have a strong understanding of what ecosystems are and what functions they serve, let’s delve into the structure of ecosystems and why they matter.

What makes up an ecosystem?

There are three groups of organisms within ecosystems – producers, consumers, and decomposers. Producers make up the first link of the food chain, producing food and oxygen for other organisms and themselves. 

Consumers can’t produce their own food and instead depend on producers as a source of sustenance. This could be a carnivore consuming another animal or a herbivore eating a plant. 

Herbivores are considered primary consumers, and carnivores are secondary. Carnivores that prey on other carnivores are known as tertiary consumers – a lion is a great example of a tertiary consumer. 

Decomposers break down organisms in a decomposition process. These are bacteria and fungi, and play a pivotal role in the recycling of matter. 

Biotic factors of an ecosystem 

As we know, ecosystems are made up of both living and nonliving organisms. We can define these as biotic and abiotic organisms. The biotic (living) components of an ecosystem include: 

  • Plants
  • Animals
  • Fungi
  • Bacteria

Abiotic factors in an ecosystem 

The abiotic factors encompass all non-living things within an ecosystem. These make up the environment which biotic components interact with. Abiotic factors are crucial to the survival of biotic factors in an ecosystem. Some abiotic factors include: 

  • Rocks
  • Air
  • Sunlight
  • Wind
  • Minerals
  • Water

Ecological relationships within an ecosystem 

Ecological relationships are key within the structure of ecosystems – each part of the ecosystem interacts with another to create a fully functioning ecosystem. There are also some particularly important ecological relationships within an ecosystem.

We can break ecological relationships down into three types of relationships: mutualism, commensalism, and parasitism. With mutualism, both members of the relationship will benefit from their interactions. The clownfish and anemone example from above is an example of mutualism.

Commensalism is a little different – although one member will benefit from the relationship, the other is completely unaffected. The cattle and cattle egret relationship we described above is considered commensalism. 

Parasitism is a much harsher relationship, as one member will benefit whilst the other suffers at the expense of the relationship. An example of parasitism is a tapeworm that lives in the intestines of animals such as cattle and pigs. Tapeworms feed on any nutrients that pass through the intestines, depriving the host of any nutrients. 

Keystone species

This phenomenon is an interesting example of the importance of ecosystems and biodiversity. A keystone species is a species that has a disproportionate effect on the environment.

These species are critical to the survival of other species within their ecosystems. They hold ecosystems together and could have a huge impact on their ecosystems if they become extinct. 

An example of a keystone species is the sea otter. This species is known to feast on sea urchins, removing them from the environment where they would otherwise damage kelp forests. In the past, when sea otter numbers have dropped dangerously low, they were unable to control the numbers of sea urchins. 

With sea urchins running loose in the kelp forests, they managed to destroy the kelp forests to a level that many kelp forests were disappearing. Since kelp forests provide a home to a range of fish, invertebrates, mammals, and birds, this resulted in a decrease in the number of these organisms. 

For another interesting example of a keystone species, read our 6 ways to prevent animal extinction article. 

Final thoughts 

Ecosystems are complex and crucial aspects of our planet that each host a unique array of creatures and environments. We hope you’ve learnt something about the structure of ecosystems and how they work. 

If you’d like to expand your knowledge of environmental science even further, why not sign up to our Introduction to Environmental Science course? 

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