Biology / Unit 1 Bio 0057 short lesson, about 20 seconds
"Organisms Evolve Because They Need To"
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The idea
The claim that an organism evolves a trait because it needs one reverses the mechanism: variation is filtered by survival and reproduction, not summoned by need.
In practice
A bacterial population did not evolve antibiotic resistance because it needed to; resistant individuals already present survived treatment and multiplied.
Where people slip
Need can explain why a trait would help, never how it first arose in the population.
Your place on the trail
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Builds on
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