Natural Selection and Antibiotic Resistance

IGCSE Edexcel Biology
3.34, 3.38-3.39 Evolution and Resistance
Key Concept: Mutations create variation, and natural selection can increase the frequency of useful alleles.

Section A: Mutation and Selection

1. Define mutation. [2]
2. Outline the main steps of natural selection. [4]

Section B: Antibiotic Resistance

3. Explain how antibiotic resistance can increase in a bacterial population. [4]
4. Explain why overuse of antibiotics speeds up resistance. [2]
Total marks: 12

Mark Scheme

1. A random change in genetic material/DNA that can be inherited [2]
2. Variation exists; some individuals have advantageous alleles; they survive and reproduce; allele frequency increases over generations [4]
3. Resistant mutants survive antibiotics, reproduce, and pass on resistance so the population becomes mostly resistant [4]
4. More exposure kills non-resistant bacteria and selects resistant ones more often [2]