AP Biology: Founder Effect in Island Populations Practice Questions
Practice founder effect questions in island population contexts. These original AP Biology items focus on small colonizing groups, random allele sampling, genetic drift, and how isolated populations can diverge over time.
Free original practice questions for study purposes. Open Exam Prep is an independent study resource and is not affiliated with, endorsed by, or sponsored by the makers of AP Exams.
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1. A small group of mainland lizards is carried to an island during a storm. The island population starts with only some of the alleles found in the mainland population. Which process best explains this pattern?
Explanation. The founder effect occurs when a new population begins from a small, nonrepresentative sample of a larger source population. Allele frequencies can differ by chance from the mainland group.
2. Why can the founder effect quickly make an island population genetically different from its mainland source population?
Explanation. A few founders are a small sample. By random sampling, they may overrepresent some alleles and miss others, causing immediate allele frequency differences.
3. Ten birds colonize an isolated island. One rare allele is present in 4 of the founders even though it is present in only 2 percent of the mainland population. What is the best explanation?
Explanation. A small founding group can carry a rare mainland allele at a much higher frequency simply by chance. This is a founder effect example.
4. Which observation would most strongly support a founder effect in a newly formed island population?
Explanation. Founder effects often reduce genetic variation because only a subset of source alleles is carried by the founders, and the frequencies may differ from the original population.
5. An island population is founded by 6 insects from a mainland population of 60,000. Which statement best predicts the role of genetic drift in the island population?
Explanation. The island population begins with very few individuals, so random differences in survival and reproduction can strongly affect allele frequencies.
6. A neutral allele becomes fixed in an island population after many generations. The allele did not improve survival or reproduction. Which mechanism can explain fixation?
Explanation. Genetic drift can increase or decrease neutral allele frequencies by chance. In small isolated populations, a neutral allele can become fixed without improving fitness.
7. How is a founder effect different from a bottleneck effect?
Explanation. Both are forms of genetic drift. Founder effects involve colonization by a small group; bottlenecks involve survival after a large population reduction.
8. Several island populations are founded independently from the same mainland bird species. Why might the island populations develop different allele frequencies even if the islands have similar climates?
Explanation. Founder effects and later drift are random processes. Separate islands can diverge because each starts with a different sample and then experiences independent chance changes.
9. A mainland snail population has alleles A1 and A2 at equal frequencies. Four snails colonize an island, and all four carry A1 only. What is the likely immediate result?
Explanation. If none of the founders carry A2, the new island population lacks that allele at the start. Mutation or migration would be needed to reintroduce it.
10. Which study design would best test whether an island population experienced a founder effect?
Explanation. Founder effect evidence comes from comparing genetic patterns between the island population and possible source populations, especially reduced variation and shifted allele frequencies.
11. Why can a harmful recessive allele become more common in a small island population after founding?
Explanation. If founders happen to carry a recessive allele, its starting frequency can be high in the new population. Drift can then increase it further by chance.
12. Which action would most directly reduce future founder-effect-like loss of variation when conservationists establish a new island refuge population?
Explanation. A larger, more genetically diverse founding group is more likely to capture source population variation and reduce random allele loss.
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FAQ
What is the founder effect in AP Biology?
The founder effect is a form of genetic drift that happens when a new population is started by a small group whose allele frequencies differ by chance from the source population.
Why are island populations common founder effect examples?
Island populations often begin with a few colonists from a mainland source, so the new population may contain only a small, random subset of the original genetic variation.
Is the founder effect the same as natural selection?
No. The founder effect is caused by random sampling of alleles in a small founding group. Natural selection changes allele frequencies because traits affect survival or reproduction.