Selection on traits does change allele frequencies
- The idea
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- Why
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The idea
“Selection only acts on what an organism looks like, so allele frequencies stay the same.”
An owl sees fur, not DNA, so the genes seem to come through untouched. The alleles ride inside the mice it catches.
The short version
The mistake: Selection only acts on what an organism looks like, so allele frequencies stay the same.
What's actually true: Selection acts on phenotypes, and individuals it removes take their alleles out of the gene pool, so allele frequencies change.
- Natural selection acts on phenotypes, the traits an organism shows.
- Every individual carries its alleles. When individuals with one phenotype die or fail to breed, their alleles don't reach the next generation.
- That's why selection breaks Hardy-Weinberg equilibrium. It shifts allele frequencies with no new mutation needed.
On the exam: Selection picks individuals by phenotype, and their alleles go with them.