CAIE IGCSE Biology 20.4.9 Risks of Decreasing Population Size
Practise explaining how small populations lose genetic variation and face inbreeding, poor adaptation and extinction risk.
- Syllabus
- 2026–2028
- Course
- Biology 0610
Exam points
- link falling population size to a smaller gene pool and reduced genetic variation
- explain how inbreeding increases homozygosity and expression of harmful recessive alleles
- connect low variation to weaker adaptation, disease vulnerability and higher extinction risk
20.4.9—Risks to a species if its population question 1
[Maximum number: 3]
Phytoplankton are producers found in the ocean. Phytoplankton absorb microplastics into their cells.
Explain the risks to a population if its population size decreases.
any three from:
1 reduction in genetic variation ;
2 inbreeding ;
3 less chance of population adapting to a (named) change in the environment ;
4 increased chance of harmful recessive alleles being
expressed / increase in genetic disease ;
5 extinction ;
6 idea that more difficult to find a mate ;
7 AVP ;
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