Step-by-Step Lesson • Step 1 of 6
ARCH-B-13: Natural Selection, Antibiotic Resistance, Heterozygote Advantage & Speciation Sequence Foils
Step 1 of 6 • The Core Idea
ARCH-B-13: Why the 120s Classroom Method Fails Under the 90s Clock
Standard Classroom Method (Too Slow)~120s (Blows 90s Clock)
In Darwinian natural selection applied to antibiotic resistance:
1. Random mutation generates a resistance allele spontaneously (independent of whether the antibiotic is present) (1 is correct).
2. Selection pressure: Methicillin kills non-resistant cells, so resistant cells survive, reproduce, and pass the allele (via vertical binary fission or horizontal plasmid conjugation) to offspring (2 is correct).
3. Bacteria never mutate 'in order to' survive exposure (3 is incorrect).
1. Random mutation generates a resistance allele spontaneously (independent of whether the antibiotic is present) (1 is correct).
2. Selection pressure: Methicillin kills non-resistant cells, so resistant cells survive, reproduce, and pass the allele (via vertical binary fission or horizontal plasmid conjugation) to offspring (2 is correct).
3. Bacteria never mutate 'in order to' survive exposure (3 is incorrect).
The Fast ShortcutTarget: 30s (Saves 90s)
Mutations are random/pre-existing (1), antibiotic is the selection pressure (2), never Lamarckian 'mutate to survive' (eliminate 3) 1 and 2 only.
Where Students Lose Time: In 7 past UAT-UK questions (3% of Biology), candidates lose 90s by mutations occur randomly and spontaneously before exposure; the antibiotic acts purely as an environmental selection pressure that kills non-resistant individuals. Instead, apply B7 with Maths 1 skill M7.7.
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