Define ecosystems and niches
Distinguish an ecosystem from the role and conditions described by an ecological niche.
Section 18.2 · Biodiversity
A Level; Cambridge International Biology 9700, 2028–2030. Written responses are self-checked; this does not certify supervised fieldwork or practical competence.
Before you begin
- Classification compares shared characteristics; populations occupy environments and contain variation.
Work on paper. Try each question before revealing help, and explain why your method works.
Quick readiness check
What does a niche describe?
What you will learn
- Define ecosystem in terms of organisms and abiotic conditions
- Define niche in terms of a species’ role and resource use
Build the explanation
An ecosystem includes a community of organisms and the abiotic environment with which they interact. A niche describes the role of a species and the conditions and resources it uses, including interactions with other organisms. Habitat describes where an organism lives; niche describes how it lives and interacts there.
Use evidence within scope
A species can occupy a habitat without using every available resource. Avoid defining a niche only as a place, and avoid describing an ecosystem as only its organisms while ignoring abiotic factors.
Pause and explain
Two species live in the same forest but use different food and nesting resources. Explain how they can share a habitat but have different niches.
Worked example
A pond contains plants, fish, microbes, water, light and dissolved minerals. Which term describes the interacting system?
Show the worked solution
- Include both organisms and abiotic factors.
- The term is ecosystem.
Answer The pond ecosystem includes the community and its abiotic environment.
Try a topic test
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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 student lists only fish, plants and microbes. What is missing from a full ecosystem description?
Give me a hint
Identify the required evidence and sequence the reasoning.
Compare my reasoning
- Include the abiotic environment.
- Name a condition such as light, water chemistry or temperature.
The abiotic factors and their interactions with the community are missing.
Look for these in your work
- Relevant evidence selected
- Reasoning linked to conclusion
A bird feeds on insects in tree bark and nests in cavities. Which kind of description is this?
Give me a hint
Use the supplied example or data to justify a conclusion.
Compare my reasoning
- It describes resource use and role.
- That is part of its niche.
It describes aspects of the bird’s niche; the habitat would identify the place where it lives.
Look for these in your work
- Concept applied
- Limit or assumption stated
Two species live in the same forest but use different food and nesting resources. Explain how they can share a habitat but have different niches.
Give me a hint
Apply the concept in a new context and qualify its limits.
Compare my reasoning
- Habitat is the place.
- Niche includes resource use and role.
They occupy the same habitat, the forest, but differ in resource use and ecological role, so their niches differ.
Look for these in your work
- New context handled
- Conclusion appropriately bounded
Common mistakes
- Using habitat and niche as exact synonyms
- Leaving abiotic factors out of an ecosystem
What can you explain now?
What does a niche describe?
Compare with the explanation
A species’ role, conditions and resource use
It includes interactions and the way resources are used.
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Make it stick
How does a niche differ from a habitat?
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.