Explain how ex situ conservation methods can complement in situ conservation in efforts to prevent the extinction of an endangered species.
Written & reviewed by James Millett — Biology (Imperial College London), PGCE Science (University of Cambridge).
Model answer (4 marks)
Ex situ conservation, such as captive breeding, seed banks and botanic gardens, keeps individuals or genetic material outside the species’ natural habitat, creating a safety net when in‑situ populations are critically small.
By maintaining or increasing population size and genetic diversity ex situ programmes reduce the risk of in‑breeding depression that would otherwise threaten small in‑situ groups.
Individuals bred or propagated ex situ can later be reintroduced into restored or protected habitats, supplementing in‑situ populations and helping to restore ecological function.
Because ex situ methods can address immediate threats (disease, habitat loss, poaching) that in‑situ measures cannot always control, the two approaches together cover a wider range of extinction risks than either alone.
By maintaining or increasing population size and genetic diversity ex situ programmes reduce the risk of in‑breeding depression that would otherwise threaten small in‑situ groups.
Individuals bred or propagated ex situ can later be reintroduced into restored or protected habitats, supplementing in‑situ populations and helping to restore ecological function.
Because ex situ methods can address immediate threats (disease, habitat loss, poaching) that in‑situ measures cannot always control, the two approaches together cover a wider range of extinction risks than either alone.
Examiner tips
- Use the word ‘ex situ’ and give specific examples (captive breeding, seed banks).
- Show how ex situ reduces in‑breeding and increases numbers.
- Explain the reintroduction link to in‑situ.
- Mention the complementary threat coverage.
Common mistakes
- Confusing ex situ with in situ or vice versa.
- Failing to mention genetic diversity or reintroduction.
Mark scheme (4 marks)
- Ex situ conservation (e.g. captive breeding programmes, seed banks, botanic gardens) maintains individuals or genetic material outside their natural habitat, providing a safety net when in situ populations are critically small.
- Ex situ programmes can maintain or increase population size / genetic diversity when in situ populations are too small to sustain themselves, reducing the risk of inbreeding depression.
- Individuals bred or propagated ex situ can be reintroduced into restored or protected habitats, supplementing in situ populations and restoring ecological function.
- Ex situ methods address immediate threats (e.g. disease, habitat destruction, poaching) that in situ methods cannot always control, so the two approaches together cover a wider range of extinction risks than either alone.
Key terms in this question
ex situ conservation · in situ conservation
Related
- All IB DP Biology Higher Level (2023 syllabus) revision notes →
- How to answer a "Explain" question →
- Decode the mark scheme abbreviations →
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