Biology / Unit 8 Bio 1783 short lesson, about 20 seconds
Selection's Limits: No Perfect Organism, Not All Evolution Adaptive
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The idea
Selection acts only on existing variation and cannot produce a perfect organism; other forces, especially drift per Bio 1757, can change fit without improving.
In practice
Genes close together on a chromosome are inherited together, so a beneficial allele can drag along a harmful linked allele.
Where people slip
Evolution has no goal — several forces change allele frequencies, and only natural selection consistently produces adaptation.
Your place on the trail
Every lesson rests on earlier ones and opens later ones. Tap any to jump.
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