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IB Biology HL 3.2.14 Antibiotic resistance evidence Question Bank

Practise IB Biology HL 3.2.14 by analysing resistance data and mechanisms selected by antibiotic exposure.

Syllabus
First assessment 2025
Course
Biology HL
Level
HL

Exam points

  • Interpret bacterial-population graphs to compare resistance between strains.
  • Analyse how mutations, selection pressure and antibiotic overuse drive resistance.

C3.2.14—Antibiotic resistance evolution question 1

[Maximum number: 3]

Different strains of the bacterium Enterobacter cloacae were grown on a plate and identified according to their place on the plate (for example, the first strain top left is A1). They were then transferred to Petri dishes containing agar with varying concentrations of antibiotic (5,10,20,40,80,160μgml−1)\left(5,10,20,40,80,160 \mu \mathrm{gml}^{-1}\right).

Figure for Question C3.2.14—Antibiotic resistance evolution question 1 — IB Biology HL

The Petri dishes were left for 24 hours in an incubator at 25∘C25^{\circ} \mathrm{C} and the resulting plates are shown.

Figure for Question C3.2.14—Antibiotic resistance evolution question 1 — IB Biology HL

Question (a)

(a)

State the strain with the least resistance to antibiotic.

[ 1 ]

Question (b)

(b)

Suggest reasons for the presence of strains such as B2 in all of the plates.

[ 2 ]
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