A population bottleneck occurs when a population becomes much smaller in a short period. This lesson explains how bottlenecks arise, how they affect genetic variation, and why the size of the surviving population matters.
A population bottleneck, also called a genetic bottleneck, is a sharp reduction in a population's size. Environmental events such as droughts, disease, fires, floods, famines, and earthquakes can cause one. Human activities—including habitat destruction, widespread violence, intentional culling, and other severe impacts—can also reduce populations.
All flashcards
What is a population bottleneck?
A sharp reduction in population size. Survivors may carry less genetic diversity and different allele frequencies than the original population.
Why is genetic drift strong in a small population?
Chance gains or losses of individuals can substantially change allele proportions, and some alleles may disappear.
What is gene flow?
The movement of alleles between populations, often when individuals migrate and reproduce. It can introduce variation into a population.
What is the founder effect?
A change in genetic composition when a small group establishes a new population with only a sample of the source population's alleles.
What does minimum viable population size help conservationists assess?
The population size that may be needed for persistence rather than facing a high risk of extinction.
Quiz questions
What does inbreeding depression describe?Answer: Reduced health or reproductive success associated with mating between relatives.
What is the popular sire effect?Answer: One male contributes offspring to a large share of the next generation.
Why might a population remain genetically vulnerable after its numbers increase?Answer: Its genetic diversity may remain low despite numerical recovery.
Why can genetic homogeneity in a widely grown crop threaten food security?Answer: Many plants may share vulnerabilities to the same disease or pest.
What is one potential benefit of translocating animals between populations?Answer: It can increase genetic diversity by enabling gene flow.