What Is an Ecosystem?
A schoolyard, a creek, a patch of bush and even a pile of rotting logs are all ecosystems. This lesson explains what makes an ecosystem work and why living things cannot survive without the non-living parts around them.
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Use the PDF for classwork, homework or revision. It includes key ideas, activities, questions, an extend task and success-criteria proof.
Q1: When you look at a pond or a patch of bush, what counts as "alive" and what doesn't?
Many students think only animals count as living parts of an ecosystem. Write your best guess about what else might matter before reading on.
Q2: If you took all the animals out of a forest, would the forest still be an ecosystem?
Think about what else is in a forest besides animals. This prepares you for the real-world anchor later in the lesson.
Know
- an ecosystem includes both living and non-living things
- biotic factors are living and abiotic factors are non-living
- producers, consumers and decomposers each have a role
Understand
- living things depend on non-living factors in their environment
- organisms interact with each other and their surroundings
- removing one part of an ecosystem can affect the whole system
Do
- classify factors as biotic or abiotic
- identify producers, consumers and decomposers in an example
- explain why abiotic factors matter for survival
Ecosystems are communities of living and non-living things interacting
An ecosystem is not just a collection of plants and animals. It is a system where living and non-living parts interact and depend on each other.
When scientists study an ecosystem, they look at everything in an area and how it connects. A creek in your local park is an ecosystem. It contains water, rocks, sunlight and air — these are the non-living parts. It also contains algae, water bugs, fish, birds and bacteria — these are the living parts. All of these parts interact. The algae use sunlight to grow, the water bugs eat the algae, the fish eat the water bugs, and bacteria break down anything that dies.
Biotic vs abiotic factors
Scientists divide the parts of an ecosystem into two groups: biotic (living) and abiotic (non-living). Both groups shape what can survive there.
Biotic factors are all the living things in an ecosystem. This includes obvious organisms like kangaroos and gum trees, but also less obvious ones like fungi, bacteria and plankton. Abiotic factors are the non-living parts. These include sunlight, temperature, rainfall, soil type, pH, wind and the availability of water.
Abiotic factors determine which organisms can live in an ecosystem. A desert has little water and high temperatures, so only organisms that can survive those conditions live there. A rainforest has high rainfall and humidity, so it supports different plants and animals. Even in your local park, the amount of shade, the type of soil and how much it rains will affect which plants grow and which animals visit.
Producers, consumers, decomposers and their roles
Every organism in an ecosystem has a role. The three main roles are producers, consumers and decomposers.
Producers make their own food. Most producers are plants, algae or some bacteria that use photosynthesis to turn sunlight, carbon dioxide and water into glucose. They are the foundation of every ecosystem because they create the energy that everything else depends on.
Consumers cannot make their own food, so they eat other organisms. A grasshopper eating grass is a consumer. A kookaburra eating a lizard is also a consumer. Consumers can be herbivores, carnivores or omnivores, but they all rely on other organisms for energy.
Decomposers break down dead plants and animals. Bacteria and fungi are the main decomposers. They return nutrients to the soil so producers can use them again. Without decomposers, dead matter would pile up and nutrients would be locked away.
Misconceptions to Fix
Wrong: "An ecosystem is just the animals."
Right: An ecosystem includes plants, microorganisms, air, water, soil and temperature. All of these parts interact.
Wrong: "Abiotic factors don't matter."
Right: Abiotic factors determine which organisms can survive. Sunlight, water and soil type control what lives where.
Right: A producer is any organism that makes its own food. Most are plants, but algae and some bacteria are producers too.
Right: Decomposers recycle nutrients back into the soil. Without them, ecosystems would run out of the materials producers need to grow.
Diagram 2: Roles in an Ecosystem
Flow diagram showing producers making food through photosynthesis, consumers eating other organisms, and decomposers recycling nutrients back to the soil.
What is an ecosystem?
A community of living and non-living things that interact in a particular area.
Biotic vs abiotic
Biotic = living. Abiotic = non-living. Both shape what survives in an ecosystem.
Three roles
Producers make food. Consumers eat other organisms. Decomposers recycle nutrients.
Common error
Forgetting that abiotic factors like sunlight and water are essential parts of every ecosystem.
Activities
Activity 1: Classify Factors as Biotic or Abiotic
Look at the list below and classify each factor as biotic or abiotic. For each one, explain why you chose that classification.
List: sunlight, eucalyptus tree, earthworm, temperature, soil pH, magpie, rainfall, mushroom
Activity 2: Evaluate the Claim
A student says: "A rock pool isn't an ecosystem because it has no soil." Use the Claim-Evidence-Reasoning frame below to evaluate this claim.
Claim-Evidence-Reasoning Frame
Claim: State whether the student is correct or incorrect.
Evidence: Use facts from the lesson about what an ecosystem needs.
Reasoning: Explain how the evidence supports your claim.