Biology / Unit 8 Bio 1647 short lesson, about 20 seconds
Three Premises of Natural Selection
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The idea
Darwin argued natural selection inevitably follows from three premises: traits are heritable, more offspring are produced than resources can support, and offspring vary.
In practice
Where heritable variation exists and resources limit survival, individuals whose variants best fit the environment leave disproportionately more offspring.
Where people slip
All three premises must hold together — heritability alone, without limited resources and variation, does not yield natural selection.
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