Concept · biology
Natural selection
Follow Natural selection — see important new research and changes in evidence.Change log
What changed
Dated edits to this page's evidence: studies added or removed from a claim, claims added or withdrawn, and new explanations tagged here. Rewordings are not listed.
- Concept page published
Natural selection is differential reproductive success of heritable variants, producing adaptation over generations.
Selection is biology’s core process; empirical tests keep the concept from becoming a slogan.
Evidence
What the evidence shows
Drawn from 9 studies in this library. Each finding starts with a plain-language takeaway, then the denser detail. Supports means evidence for a finding; Challenges means evidence against a stated position; Qualifies marks scope with a short note on each study’s contribution. Challenged positions are labeled — they are not findings.
Multiple empirical papers in this library examine natural selection with mechanistic biological findings.
- Hybrid necrosis as plant autoimmunity
- Can leaky vaccines favor nastier viruses?
- Why is CCR5-Δ32 common only in Europe?
Study Role Design N Population Outcome Hybrid necrosis as plant autoimmunity Supports Animal / in-vitroGenetic mapping of necrotic Uk-1×Uk-3 Arabidopsis hybrids to NB-LRR mismatch loci Plant hybrid incompatibility genetics; penetrance temperature-dependent — no single sample N Arabidopsis thaliana hybrid and introgression lines (Uk-1×Uk-3) DM1/DM2 necessity for autoimmune hybrid necrosis Can leaky vaccines favor nastier viruses? Supports Animal / in-vitroExperimental MDV infection of vaccinated vs unvaccinated chicks with shedding and sentinel transmission assays Multiple experiments (e.g., n=200, 120, 60 vaccinated + 60 maternal-Ab groups) — no single primary N One-day-old chicks infected with Marek's disease virus strains Infectious period, shedding, and sentinel infection under imperfect vaccination Why is CCR5-Δ32 common only in Europe? Supports Computational / modellingSpatially explicit wave-of-advance model of CCR5-Δ32 frequency clines and allele age Population-genetic modeling of allele frequencies — no single sample N Geographic CCR5-Δ32 allele-frequency data Selection and dispersal parameters explaining Δ32 geographic spread DM1 (Chr5, Uk-3) and DM2 (Chr3, Uk-1) are necessary and sufficient; phenotype fully penetrant at 16°C and suppressed at 23°C.
Vaccination prolongs infectious periods (~2 weeks), speeds sentinel infection (~9 days earlier), and can maintain hyperpathogenic strains that kill unvaccinated birds at up to 100%.
Strong selection (s≥0.1) and rapid long-range dispersal are needed; geographic restriction fits limited dispersal time better than purely local selection; origin may be outside northern Europe.
Maternal genetic variance and selection differentials both depend on environment and covary negatively.
Open questions
Tensions and limits
Some items are genuine disagreements on the same question. Others mark different assays, populations, or outcomes — limits on how far one study travels — not a forced fight between papers.
Systems and scales differ across natural selection studies (species, tissues, methods), so mechanisms should not be over-generalised.
- Hybrid necrosis as plant autoimmunity
- Can leaky vaccines favor nastier viruses?
- Why is CCR5-Δ32 common only in Europe?
Study Role Design N Population Outcome Hybrid necrosis as plant autoimmunity Supports Animal / in-vitroGenetic mapping of necrotic Uk-1×Uk-3 Arabidopsis hybrids to NB-LRR mismatch loci Plant hybrid incompatibility genetics; penetrance temperature-dependent — no single sample N Arabidopsis thaliana hybrid and introgression lines (Uk-1×Uk-3) DM1/DM2 necessity for autoimmune hybrid necrosis Can leaky vaccines favor nastier viruses? Supports Animal / in-vitroExperimental MDV infection of vaccinated vs unvaccinated chicks with shedding and sentinel transmission assays Multiple experiments (e.g., n=200, 120, 60 vaccinated + 60 maternal-Ab groups) — no single primary N One-day-old chicks infected with Marek's disease virus strains Infectious period, shedding, and sentinel infection under imperfect vaccination Why is CCR5-Δ32 common only in Europe? Supports Computational / modellingSpatially explicit wave-of-advance model of CCR5-Δ32 frequency clines and allele age Population-genetic modeling of allele frequencies — no single sample N Geographic CCR5-Δ32 allele-frequency data Selection and dispersal parameters explaining Δ32 geographic spread
Common misconceptions
Natural selection findings from one model organism always transfer to humans.
Model systems teach mechanism; transfer to other species is a separate empirical claim.
Exam-style questions
Short-answer questions that ask you to explain or compare, not recall.
What is Natural selection?
Natural selection is differential reproductive success of heritable variants, producing adaptation over generations.
Why does Natural selection matter for biology undergraduates?
Selection is biology’s core process; empirical tests keep the concept from becoming a slogan.
The studies
9 studies in this library bear on Natural selection, ordered by citations. The first 8 are shown.
- What does Arabidopsis polymorphism look like genome-wide?
A. thaliana shows clear global population structure and isolation by distance; demography can mimic selection in standard tests.
- Hybrid necrosis as plant autoimmunity
Arabidopsis hybrid necrosis is a Dobzhansky–Muller incompatibility driven by autoimmune NB-LRR conflict.
- Can leaky vaccines favor nastier viruses?
Imperfect Marek’s disease vaccination keeps infected chickens alive longer, boosting transmission of strains too lethal to persist without vaccines.
- Why isn’t diversity proportional to population size?
Natural selection via hitchhiking and background selection constrains neutral diversity, especially in species with larger census sizes.
- How do Sinocyclocheilus genomes record cave life?
Sinocyclocheilus cavefish genomes reveal troglomorphic adaptations such as eye degeneration and albinism, paralleling and differing from Astyanax.
- Environment couples selection and heritability
In Soay sheep, strong selection on birthweight occurs when heritability is lowest, limiting evolutionary response.
- Why is CCR5-Δ32 common only in Europe?
CCR5-Δ32 likely rose under strong selection and spread fast by long-range dispersal; its range is limited more by time than by southern selection barriers.
- Can one gene affect butterfly population growth?
Allelic variation at Pgi (or tightly linked loci) predicts population growth in the Glanville fritillary metapopulation.
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- Why do immune genes keep evolving across tetrapods?
Shared positive selection in birds and mammals concentrates on immune—especially antiviral—genes, implicating pathogens as a consistent selective pressure.
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