Concept
Natural selection
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 claim links to the studies behind it.
Multiple empirical papers in this library examine natural selection with mechanistic biological findings.
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
Where studies disagree
Open questions, not settled findings — worth knowing before you cite any one of these.
Systems and scales differ across natural selection studies (species, tissues, methods), so mechanisms should not be over-generalised.
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
- 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.
- 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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Flashcards
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