IGCSE Biology glossary
Antibiotic resistance
Biology editorial review is supported by the named review panel. Reviewer participation may vary by guide. Checked against Cambridge IGCSE Biology 0610 (2026–2028); last reviewed August 2026.
Definition
The ability of a strain of bacteria to survive and reproduce in the presence of an antibiotic that would normally kill or inhibit it. Resistance arises through random mutations and spreads by natural selection: resistant bacteria survive, reproduce and pass on the resistance gene.
What to include in an exam answer
This is a key natural selection application. Explain: random mutation gives resistance, antibiotic kills non-resistant bacteria, resistant bacteria survive and reproduce, resistance gene is passed on. Never say bacteria 'develop' resistance in response to the antibiotic.
Example in context
Explain how antibiotic resistance develops in a bacterial population (4 marks): A random mutation occurs in a bacterium, giving it resistance to the antibiotic. When the antibiotic is used, non-resistant bacteria are killed. The resistant bacterium survives, reproduces, and passes the resistance gene to offspring. Over time, the proportion of resistant bacteria in the population increases.
Related syllabus topic
Drugs