In the master plate, there is no antibiotic. So, no selection
pressure.
Hence all bacteria can grow.
In the passaged plates, ampicillin is present. It serves as a
selection pressure.
So, only cells that can degrade ampicillin can survive.
Darwinian evolution:
Bacteria that evolved AMP resistance by mutations are selected by
the selection pressure (Ampicillin).
Lamarckian evolution:
Some bacteria in the original population was preexposed to
ampicillin and they could metabolize it.
Only these colonies grew on the selection plate.
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