Explain control of invasive alien species
Explain why introduced species may need control and evaluate possible responses.
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
Why may an invasive predator be controlled?
What you will learn
- Explain ecological and economic reasons to control invasive alien species
- Relate control to evidence, impacts and unintended effects
Build the explanation
An introduced alien species can become invasive if it spreads and causes harm. It may outcompete native species, prey on them, introduce disease, alter habitats or disrupt ecosystem processes. Control can protect native biodiversity, agriculture, fisheries or human health when monitoring shows a significant impact.
Use evidence within scope
Not every alien species is invasive, and control methods can also harm non-target organisms. Compare prevention, physical removal, biological control or other context-appropriate actions with evidence of effectiveness, welfare, cost and ecological side effects.
Pause and explain
How could prevention reduce the need for later control?
Worked example
An introduced predator causes a documented decline in a native island bird. Give a reason for considering control.
Show the worked solution
- The predator is non-native and the impact is documented.
- Native population decline threatens biodiversity.
Answer Control may reduce predation pressure and protect the declining native bird, while monitoring should assess non-target effects and recovery.
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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.
An introduced plant spreads but no ecological harm has been measured. What should managers do before broad control?
Give me a hint
Identify the required evidence and sequence the reasoning.
Compare my reasoning
- Assess spread and ecological impact.
- Monitor native communities and potential effects.
Collect evidence on spread and impacts, and monitor native species before choosing control; being alien alone does not establish harm.
Look for these in your work
- Relevant evidence selected
- Reasoning linked to conclusion
A pesticide reduces an invasive insect but also kills native pollinators. What trade-off must be considered?
Give me a hint
Use the supplied example or data to justify a conclusion.
Compare my reasoning
- Target control has non-target effects.
- Compare net ecological benefit and alternatives.
The control may harm pollination and native biodiversity; evaluate alternatives and whether the net benefit outweighs non-target damage.
Look for these in your work
- Concept applied
- Limit or assumption stated
How could prevention reduce the need for later control?
Give me a hint
Apply the concept in a new context and qualify its limits.
Compare my reasoning
- Stop introduction before establishment.
- Use monitoring and biosecurity.
Biosecurity and early detection can prevent or limit establishment, reducing later costs and ecological disruption.
Look for these in your work
- New context handled
- Conclusion appropriately bounded
Common mistakes
- Treating every non-native species as harmful
- Proposing control without considering non-target effects
What can you explain now?
Why may an invasive predator be controlled?
Compare with the explanation
It can reduce native populations or disrupt ecosystems
Control aims to limit demonstrated harm.
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Make it stick
What makes an alien species invasive, and what should control planning consider?
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.