Genetic drift
Chance can change allele frequencies independently of an adaptive advantage.
Key knowledge
Genetic drift is random change in allele frequencies due to chance in which genetic variants are transmitted to later generations. It can cause a variant to be lost or fixed without that outcome being caused by a reproductive advantage of the variant.
Conditions and scope
- Drift can act in all finite populations; its effects are often stronger in small populations.
- Drift and natural selection can operate together; an observed frequency change alone does not identify the mechanism.
Sources · 4
References
Sources retain their recorded scope. A source link alone does not establish verification of every statement.
- Talking Glossary: Genetic DriftNational Human Genome Research Institute (NHGRI), NIHReference guide
- Understanding Evolution: Genetic driftUniversity of California Museum of Paleontology, BerkeleyTeaching resource
- Biology 2e, 19.1 Population EvolutionMary Ann Clark, Matthew Douglas and Jung Choi — OpenStax, Rice UniversityTextbook chapter
- Biology XII: EvolutionNCERTTextbook chapter · PDF
Evidence and review
NHGRI and UCMP descriptions compared with the textbook's drift/selection distinction; no simulation or population analysis was performed.
2026-10-10 · English chance mechanism, loss/fixation scope and coexistence with selection checked against the cited direct pages.
Foundational review
2026-10-10 · Fresh primary-source inspection of the complete compact record, including every statement, equation, quantity and material condition, followed by independent AI editorial review. This check does not certify all linked lessons or every passage of every cited publication.
Sources from other places
Scope or convention differs
Chance changes in population allele frequencies.
This introductory comparison does not quantify finite-population drift.
NCERT
- Biology XII: Evolution IndiaEnglish
§6.3, printed pp113–115: homology and common ancestry; §6.5, printed p118: branching descent and heritable fitness; §6.7, printed pp120–121: allele-frequency changes and chance drift
- Biology XII: Evolution
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