Define an ecosystem
An ecosystem contains a community of organisms and their environment interacting together.
Core and Extended; Biology 0610, 2026–2028. Use the stated specimen features and evidence. Diagrams are schematic. Written practice is self-checked
Before you begin
- Know population, community and ecosystem terms and read the axis labels on a graph.
Work on paper. Try each question before revealing help, and explain why your method works.
Quick readiness check
Which description best defines an ecosystem?
What you will learn
- Define an ecosystem using community, environment and interaction
- Distinguish living and non-living components within an ecosystem
Include the community and its environment
An ecosystem is a unit containing the community of organisms and their environment, interacting together. The community is the living populations; the environment includes physical and chemical conditions such as water, soil, light and temperature. The interactions connect organisms with one another and with their surroundings.
An ecosystem has a stated boundary, such as a pond or woodland study area. The boundary helps make a model manageable; ecosystems can exchange organisms and materials with surrounding areas. Do not define an ecosystem as only a list of animals or only the non-living habitat.
Connect scale and interaction
Food relationships, competition for resources and dependence on physical conditions are examples of interactions. The definition names the interacting unit; a particular question may ask you to identify only the components supplied in its diagram or description.
Use population for one species, community for the different living populations, and ecosystem for the community plus environment interacting.
Pause and explain
Which item is part of the environment rather than a population?
Worked example
A pond study includes algae, fish, bacteria, dissolved oxygen, water and light. Explain why this is an ecosystem description.
Show the worked solution
- The organisms make up the community.
- Water, oxygen and light are environmental components.
- They interact in the pond unit.
Answer It describes an ecosystem because it includes a community of organisms and environmental conditions interacting together.
Try a topic test
Choose Easy, Normal or Difficult. Save your answers and open worked review after finishing.
Test this topic →From guided practice to a new situation
Write your answer and reasoning first. Use a hint only if you are stuck. The model solution is for self-checking; your written work is not automatically marked.
A woodland study includes plants, animals, soil water and light. Use the ecosystem definition to classify the parts.
Give me a hint
Separate the community from environment, then include interactions.
Compare my reasoning
- Plants and animals belong to the community.
- Soil, water and light are environmental components.
- The ecosystem includes their interactions.
The plants and animals are populations in the community; soil, water and light are environmental components. Together, interacting, they form the woodland ecosystem.
Look for these in your work
- Living and non-living parts separated
- Interaction included
Why is “an ecosystem is all the animals in a forest” incomplete?
Give me a hint
Check for plants, other organisms and environment.
Compare my reasoning
- Animals are only some populations.
- The definition includes the community and its environment.
It omits other community populations, such as plants and microorganisms, and leaves out the environment and interactions; an ecosystem includes all of these parts.
Look for these in your work
- Omitted populations named
- Environment restored
A diagram shows a fish, algae, water, light and dissolved oxygen. Give one example of an interaction without claiming the diagram proves a growth effect.
Give me a hint
Name a relationship supported by the components.
Compare my reasoning
- Fish and algae share the pond water and light environment.
- Dissolved oxygen is an environmental condition organisms may use.
The organisms share the pond environment; for example, fish use dissolved oxygen in the water. The diagram alone does not show a measured effect on population growth.
Look for these in your work
- Interaction identified
- Evidence limit stated
Common mistakes
- Leaving the environment out
- Listing only non-living factors
- Treating community and ecosystem as synonyms
What can you explain now?
Which description best defines an ecosystem?
Compare with the explanation
The community and its environment interacting together
Both living populations and their environment are included.
After trying it yourself, choose your next review. This is your self-assessment.
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Make it stick
Define ecosystem and give one living and one environmental component.
If you needed the solution, close it and solve the problem again from a blank page. A correct answer is stronger when you can explain the reason for each step.