Why is "Saying the antibiotic causes the bacteria to mutate or to become resistant" a common mistake in Antibiotic Resistance?

Why it happens: Resistance appears after the antibiotic is used, so students assume the antibiotic must have created it. How to avoid it: Remember the **mutation is random and happens by chance before** the antibiotic is used. The antibiotic only **selects** the bacteria that are **already** resistant — it does not cause the resistance. Source: Edexcel Biology examiner reports

Why is "Thinking antibiotics kill viruses (e.g. that they cure colds or flu)" a common mistake in Antibiotic Resistance?

Why it happens: People take medicine when ill and assume one type works for everything. How to avoid it: State clearly that antibiotics kill **bacteria only** and have **no effect on viruses** — colds and flu are viral, so antibiotics do not help. Source: Edexcel Biology examiner reports

Why is "Saying an individual bacterium 'adapts' or 'gets used to' the antibiotic during its life" a common mistake in Antibiotic Resistance?

Why it happens: Students confuse a population changing over generations with a single bacterium changing. How to avoid it: It is the **population** that changes over many generations, not one bacterium adapting. Resistant bacteria already exist and are **selected**, then reproduce. Source: Edexcel Biology examiner reports

Why is "Forgetting to say the resistant bacteria reproduce and pass on the resistance allele" a common mistake in Antibiotic Resistance?

Why it happens: Students focus on the resistant bacteria surviving and stop there. How to avoid it: Always include that the survivors **reproduce** and **pass on the resistance allele**, so the **resistant population increases** — this is what makes it natural selection. Source: Edexcel Biology examiner reports 2022–2024

Why is "Describing the process correctly but not naming it as natural selection" a common mistake in Antibiotic Resistance?

Why it happens: Students learn the steps but do not connect them to the term in the specification. How to avoid it: Finish your answer by stating the process is **natural selection** — questions often award a mark specifically for naming it. Source: Edexcel Biology examiner reports

Why is "Saying MRSA is completely untreatable / immune to all antibiotics" a common mistake in Antibiotic Resistance?

Why it happens: MRSA is called a 'superbug', so students overstate it as impossible to treat. How to avoid it: Say MRSA is resistant to **many** antibiotics and is therefore **difficult to control/treat** — not that it is impossible. Avoid the word 'immune'; use 'resistant'. Source: Edexcel Biology examiner reports

InheritanceEdexcel IGCSE Science(Double Award)-Biology (4WSD0-1B)

Antibiotic Resistance

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Antibiotic Resistance — Edexcel International GCSE Science (Double Award) Biology (4WSD0-1B) Study Notes

Bacteria can become resistant to antibiotics, making infections hard to treat. Learn how a random mutation makes a few bacteria resistant, how using antibiotics kills the non-resistant bacteria but lets the resistant ones survive and reproduce, and how this natural selection lets the resistant population grow. Covers Double Award Biology spec 3.39, including MRSA and the overuse of antibiotics, assessed on Biology Paper 1 (4WSD0/1B).

What you’ll learn

Mapped to the Edexcel IGCSE 4SD0 syllabus (2026 onwards).

3.39 — Understand how resistance to antibiotics can increase in bacterial populations, and appreciate how such an increase can lead to infections being difficult to control (for example MRSA).

What antibiotics do (spec 3.39)

Antibiotics kill bacteria (or stop them growing) but do not work on viruses.

An antibiotic is a medicine that kills bacteria or stops them from growing and reproducing. Doctors prescribe antibiotics (such as penicillin) to treat bacterial infections.

A few important points to fix in your mind:

Antibiotics work against bacteria only. They do not kill viruses, so they cannot cure a cold or flu (which are caused by viruses).
When an antibiotic is taken, it kills the bacteria that are making you ill, so you recover.
But not every bacterium is the same — some may be able to survive the antibiotic. These are described as resistant.

The big idea of this topic is this: bacterial populations can change over time so that more and more of the bacteria are resistant to a particular antibiotic. When that happens, the antibiotic stops working and the infection becomes hard to control.

Exam tip. Be ready to state that antibiotics kill bacteria but have no effect on viruses — this is a frequent one-mark point.

Antibiotics kill bacteria (or stop them reproducing).
They have no effect on viruses (e.g. cold, flu).
Some bacteria are resistant and can survive the antibiotic.

See the full worked example for antibiotic resistance →

Resistance starts with a random mutation (spec 3.39)

A chance change in a bacterium's DNA can make it resistant before any antibiotic is used.

Where does resistance come from? It begins with a mutation.

A mutation is a random change in the DNA (genes) of an organism. Mutations happen by chance all the time. In a large population of bacteria, sometimes a mutation produces a bacterium that can survive an antibiotic — it is resistant.

Two ideas are essential here:

The mutation happens randomly and by chance — it is not caused by the antibiotic. The resistant bacterium already exists before the antibiotic is used.
Resistance is controlled by an allele (a version of a gene). Because bacteria pass on their genes when they reproduce, the resistance allele can be passed to offspring.

So at the start, a population of bacteria might contain mostly non-resistant bacteria and just a few resistant ones that arose by mutation.

Exam tip. Examiners want the word random (or 'by chance') and the word mutation. A very common error is to say the antibiotic causes the bacteria to become resistant — it does not. The mutation comes first, by chance.

Resistance begins with a random mutation in the bacterium's DNA.
The mutation happens by chance, not because of the antibiotic.
Resistance is carried by an allele that can be passed to offspring.

See the full worked example for antibiotic resistance →

Natural selection makes the resistant population grow (spec 3.39)

Antibiotics kill non-resistant bacteria; resistant ones survive, reproduce and spread.

Once a few resistant bacteria exist, using an antibiotic changes the population dramatically. This is a clear example of natural selection ('survival of the fittest').

Here is the sequence, step by step:

A bacterial population contains mostly non-resistant bacteria and a few resistant ones (from a random mutation).
The antibiotic is used.
The non-resistant bacteria die.
The resistant bacteria survive because the antibiotic does not kill them.
The surviving resistant bacteria reproduce, passing on the resistance allele to their offspring.
Over many generations, more and more of the population is resistant — the resistant bacteria have been selected for.

You can picture the change like this:

Natural selection: the antibiotic kills the non-resistant bacteria, so only the resistant bacteria survive and reproduce, until the whole population is resistant.

Exam tip. A full-mark answer names the steps in order: random mutation → resistant bacteria survive the antibiotic → non-resistant die → resistant reproduce and pass on the allele → resistant population increases (natural selection).

Antibiotic used → non-resistant bacteria die, resistant survive.
Survivors reproduce and pass on the resistance allele.
The resistant population increases — this is natural selection.

See the full worked example for antibiotic resistance →

MRSA, overuse and why it matters (spec 3.39)

Overusing antibiotics breeds 'superbugs' like MRSA that are hard to treat.

MRSA stands for methicillin-resistant Staphylococcus aureus. You do not need to remember the full name — what matters is that MRSA is a type of bacterium that has become resistant to many antibiotics, so it is very difficult to treat. It is sometimes called a 'superbug'.

Why is antibiotic resistance becoming more common? The main reason is the overuse and misuse of antibiotics, for example:

Doctors prescribing antibiotics for viral infections (where they do not help anyway).
Patients not finishing the full course — this can leave the more resistant bacteria alive to reproduce.
Heavy use of antibiotics in farming.

Every time antibiotics are used, natural selection acts in favour of any resistant bacteria. The more often this happens, the faster resistant strains spread.

Why does this matter? If a person is infected with resistant bacteria, the usual antibiotics will not kill them, so the infection is difficult to control. The person stays ill for longer, the infection can spread to others, and in serious cases it can be life-threatening.

This is why doctors try to use antibiotics only when necessary, and why patients are told to finish the whole course. Slowing down natural selection keeps antibiotics working for longer.

Exam tip. Link overuse of antibiotics → more natural selection → more resistant bacteria (e.g. MRSA) → infections hard to control. Naming MRSA as an example of a resistant 'superbug' scores well.

MRSA is a bacterium resistant to many antibiotics (a 'superbug').
Overuse/misuse of antibiotics speeds up the spread of resistance.
Resistant infections are difficult to control because antibiotics no longer work.

See the full worked example for antibiotic resistance →

How it’s examined

Assessed on Biology Paper 1 (4WSD0/1B), 2 hours, 110 marks, untiered (Double Award has no separate Biology Paper 2). Common question shapes: 'state what antibiotics act against' (1 mark), 'explain how a population of bacteria becomes resistant to an antibiotic' (3–4 marks, a natural-selection sequence), 'why is MRSA difficult to treat?' (1–2 marks), and 'suggest why doctors are told not to overuse antibiotics' (2–3 marks). Reliable marks come from the keywords random mutation, resistant bacteria survive, non-resistant die, reproduce / pass on the allele, resistant population increases, natural selection and MRSA / overuse.

Sources: Pearson Edexcel International GCSE Science (Double Award) 4SD0 specification — Issue 4, September 2024 (valid for 2026 onwards); Pearson Edexcel International GCSE Biology 4BI1 specification — Issue 4 (shared Biology Paper 1 content); Pearson Edexcel 4SD0 / 4BI1 examiner reports 2022–2024. Last reviewed 2026-06-04.

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Step-by-step worked examples — Antibiotic Resistance

Step-by-step solutions to past-paper-style questions on antibiotic resistance, written exactly the way a tutor would explain them at the board.

1What antibiotics act against (Getting started)
Getting started• 4WSD0/1B style — short answer• antibiotics, bacteria, viruses, spec-3.39
Question
(a) What type of microorganism do antibiotics kill? (b) Explain why taking an antibiotic will not cure a cold. (2 marks)
Step-by-step solution
1. Step 1
  (a) (1). Antibiotics kill bacteria (or stop them growing/reproducing).
2. Step 2
  (b) (1). A cold is caused by a virus, and antibiotics have no effect on viruses.
Answer
(a) Bacteria. (b) A cold is caused by a virus, and antibiotics do not kill viruses, so the antibiotic will not work.
Examiner tip
Two simple marking points: antibiotics kill bacteria, and have no effect on viruses. Naming the cold as 'viral' secures part (b).
2Where resistance comes from (Getting started)
Getting started• 4WSD0/1B style — short answer• mutation, random, resistance, spec-3.39
Question
(a) What is the original cause of antibiotic resistance in a bacterium? (b) Is this caused by the antibiotic? Explain. (2 marks)
Step-by-step solution
1. Step 1
  (a) (1). A random mutation in the bacterium's DNA makes it resistant.
2. Step 2
  (b) (1). No — the mutation happens by chance; the resistant bacterium exists before the antibiotic is used, so the antibiotic does not cause it.
Answer
(a) A random mutation in the bacterium's DNA. (b) No — the mutation occurs by chance, not because of the antibiotic; the resistant bacterium already exists before the antibiotic is used.
Examiner tip
The key terms are 'random' and 'mutation'. Stating that the antibiotic does NOT cause resistance is the discriminating point.
3Order the natural-selection steps (Building confidence)
Building confidence• 4WSD0/1B style — structured• natural-selection, survive, reproduce, spec-3.39
Question
These steps describe how a resistant bacterial population develops, but they are in the wrong order: resistant bacteria reproduce; antibiotic is used; a random mutation makes one bacterium resistant; non-resistant bacteria die; resistant population increases. Write them in the correct order. (3 marks)
Step-by-step solution
1. Step 1
  Start (1). A random mutation makes one bacterium resistant, then the antibiotic is used.
2. Step 2
  Middle (1). The non-resistant bacteria die (the resistant ones survive).
3. Step 3
  End (1). The resistant bacteria reproduce, so the resistant population increases.
Answer
Random mutation makes one bacterium resistant → antibiotic is used → non-resistant bacteria die → resistant bacteria reproduce → resistant population increases.
Examiner tip
The marks reward the correct sequence. The mutation must come before the antibiotic is used — putting the mutation after the antibiotic is the most common ordering error.
4Why MRSA is hard to treat (Building confidence)
Building confidence• 4WSD0/1B style — structured• mrsa, superbug, difficult-to-control, spec-3.39
Question
MRSA is described as a 'superbug'. (a) What does it mean to call MRSA resistant? (b) Explain why an infection with MRSA is difficult to control. (3 marks)
Step-by-step solution
1. Step 1
  (a) (1). Resistant means the bacteria can survive the antibiotic — they are not killed by it.
2. Step 2
  (b) (1). Because MRSA is resistant to many antibiotics, the usual antibiotics do not kill it.
3. Step 3
  (b) (1). So the infection cannot be treated/controlled in the normal way and can spread or persist.
Answer
(a) Resistant means the bacteria survive the antibiotic and are not killed by it. (b) MRSA is resistant to many antibiotics, so the usual antibiotics do not kill it, making the infection difficult to treat or control.
Examiner tip
Link 'resistant to many antibiotics' to 'antibiotics do not kill it' to 'hard to control'. Stating it survives the antibiotic is the core idea.
5Explain how a resistant population develops (Stretch)
Stretch• 4WSD0/1B style — extended• natural-selection, allele, mutation, spec-3.39
Question
Explain how the regular use of an antibiotic can lead to a bacterial population becoming resistant to that antibiotic. Use the idea of natural selection. (4 marks)
Step-by-step solution
1. Step 1
  Mutation (1). A random mutation produces a few resistant bacteria in the population.
2. Step 2
  Selection (1). When the antibiotic is used, the non-resistant bacteria die but the resistant bacteria survive.
3. Step 3
  Reproduction (1). The surviving resistant bacteria reproduce and pass on the resistance allele to their offspring.
4. Step 4
  Result (1). Over many generations the proportion of resistant bacteria increases — this is natural selection.
Answer
A random mutation makes a few bacteria resistant. When the antibiotic is used, the non-resistant bacteria are killed but the resistant ones survive. These survivors reproduce and pass on the resistance allele to their offspring, so over many generations more and more of the population is resistant — this is natural selection.
Examiner tip
Four marking points: random mutation, non-resistant die / resistant survive, reproduce and pass on the allele, and resistant population increases. Naming the process as natural selection is expected.
6Why overuse of antibiotics matters (Stretch)
Stretch• 4WSD0/1B style — extended• overuse, natural-selection, evaluation, spec-3.39
Question
Doctors are advised to prescribe antibiotics only when truly needed, and patients are told to finish the whole course. Explain, using natural selection, why these measures help reduce antibiotic resistance. (5 marks)
Step-by-step solution
1. Step 1
  Each use selects (1). Every time an antibiotic is used it kills non-resistant bacteria but allows any resistant bacteria to survive.
2. Step 2
  Survivors spread (1). The resistant survivors reproduce and pass on the resistance allele, increasing the resistant population (natural selection).
3. Step 3
  Less use = less selection (1). Using antibiotics only when needed means natural selection acts less often, so resistance spreads more slowly.
4. Step 4
  Finishing the course (1). Finishing the full course kills all the bacteria, including the harder-to-kill ones, so resistant bacteria are not left to reproduce.
5. Step 5
  Outcome (1). This keeps antibiotics working for longer and reduces the spread of resistant strains such as MRSA.
Answer
Every time an antibiotic is used, it kills non-resistant bacteria but lets resistant ones survive, reproduce and pass on the resistance allele — natural selection. Using antibiotics only when needed means this selection happens less often, so resistance spreads more slowly. Finishing the full course kills all the bacteria so resistant ones are not left behind to reproduce. Together these measures slow the spread of resistant strains like MRSA and keep antibiotics effective for longer.
Examiner tip
Top answers connect 'less/correct antibiotic use' to 'less natural selection' to 'slower spread of resistance'. The link between overuse and the rate of natural selection is the high-tariff idea.

Model Answers — Antibiotic Resistance

High-scoring sample answers for antibiotic resistance on the Pearson Edexcel IGCSE Biology Paper 1 (4WSD0/1B) paper, with examiner-style notes mapping each response to the mark scheme and assessment objectives.

Question 1
4WSD0/1B style2 marks
State what antibiotics are used to treat and one type of microorganism they do not affect. (2 marks)
Model answer
Antibiotics are used to treat infections caused by bacteria (1). They have no effect on viruses (1).
Why this scores
Two single marking points: antibiotics act on bacteria, and do not affect viruses. 'Germs' is too vague — name bacteria and viruses.
Question 2
4WSD0/1B style3 marks
Explain what is meant by a bacterium being 'resistant' to an antibiotic, and state how resistance first arises. (3 marks)
Model answer
A resistant bacterium is one that is not killed by the antibiotic and can survive when the antibiotic is present (1).

Resistance first arises from a random mutation (1) in the bacterium's DNA / genes, which happens by chance and not because of the antibiotic (1).
Why this scores
Mark for 'survives / not killed by the antibiotic', plus 'random mutation' and the idea that it occurs by chance (not caused by the antibiotic).
Question 3
4WSD0/1B style5 marks
Describe how a population of bacteria can become resistant to an antibiotic. (5 marks)
Model answer
A random mutation in a bacterium's DNA makes it resistant to the antibiotic (1).

When the antibiotic is used, the non-resistant bacteria are killed (1).

The resistant bacteria survive because the antibiotic does not kill them (1).

The surviving resistant bacteria reproduce and pass on the resistance allele to their offspring (1).

Over many generations the proportion of resistant bacteria increases — this is natural selection (1).
Why this scores
The five points map onto the natural-selection sequence: mutation, non-resistant die, resistant survive, reproduce/pass on allele, resistant population increases. The mutation must precede the antibiotic use.
Question 4
4WSD0/1B style5 marks
MRSA is a bacterium that has become resistant to many antibiotics. Explain why infections caused by MRSA are difficult to control. (5 marks)
Model answer
MRSA is resistant to many antibiotics (1).

This means the usual antibiotics do not kill the bacteria (1).

So the infection cannot be treated in the normal way / is difficult to control (1).

The resistant bacteria continue to reproduce and the infection persists or spreads (1).

Because each antibiotic used selects for the resistant bacteria, resistance can keep increasing, making treatment even harder (1).
Why this scores
Credit 'resistant to many antibiotics', 'antibiotics do not kill it', and the consequence 'hard to control / treat'. Linking continued reproduction and selection to persistent infection reaches the top of the mark range.
Question 5
4WSD0/1B style — extended open response8 marks
Antibiotic resistance is increasing around the world. Using your knowledge of natural selection, explain how resistance develops in a bacterial population and why the overuse of antibiotics makes the problem worse. (8 marks)
Model answer
How resistance develops (natural selection)

A random mutation in the DNA of a bacterium makes it resistant to an antibiotic — this happens by chance, before the antibiotic is used (1).

When the antibiotic is used, the non-resistant bacteria are killed (1).

The resistant bacteria survive because the antibiotic does not kill them (1).

The survivors reproduce and pass on the resistance allele to their offspring (1).

Over many generations the resistant population increases — this is natural selection (1).

Why overuse makes it worse

Every time an antibiotic is used, it selects for resistant bacteria, so the more often antibiotics are used the more often this selection happens (1).

Overuse includes prescribing antibiotics for viral infections (where they do not help) and patients not finishing the course, both of which leave resistant bacteria to reproduce (1).

This speeds up the spread of resistant strains (such as MRSA), so infections become harder to control (1).
Why this scores
Full marks need the complete natural-selection sequence (mutation → non-resistant die → resistant survive → reproduce/pass on allele → resistant population increases) PLUS the link that more frequent antibiotic use means more frequent selection, naming overuse examples and MRSA.
Question 6
4WSD0/1B style — extended open response9 marks
A student says: 'When bacteria are exposed to an antibiotic, the antibiotic makes them mutate so they become resistant.' Using your knowledge of mutation and natural selection, explain why this statement is wrong and describe what really happens. (9 marks)
Model answer
The statement is wrong because the antibiotic does not cause the bacteria to mutate or to become resistant:

Why the statement is wrong

A mutation is a random change in DNA that happens by chance (1).

The resistant bacteria arise from this random mutation before the antibiotic is used — the antibiotic does not create the resistance (1).

Most bacteria in the population are non-resistant; only a few carry the resistance allele to begin with (1).

What really happens (natural selection)

When the antibiotic is used, the non-resistant bacteria are killed (1).

The resistant bacteria survive because the antibiotic does not kill them (1).

The survivors reproduce and pass on the resistance allele to their offspring (1).

Over many generations the proportion of resistant bacteria increases (1).

This is natural selection: the antibiotic acts as a selection pressure that favours the already-resistant bacteria (1).

So the antibiotic selects the resistant bacteria, rather than causing the resistance — which is why the student's idea is incorrect (1).
Why this scores
The evaluative top band needs the correction (mutation is random and pre-exists the antibiotic) AND the full natural-selection mechanism, finishing with the distinction that the antibiotic SELECTS for resistance but does not CAUSE it.

Key Definitions and Keywords — Antibiotic Resistance

Definitions to memorise and the exact keywords mark schemes credit for antibiotic resistance answers — sharpened from recent examiner reports for the 2026 Pearson Edexcel IGCSE Biology Paper 1 (4WSD0/1B) sitting.

Antibiotic
Examiner keyword
A medicine that kills bacteria or stops them from growing and reproducing; antibiotics have no effect on viruses.
Antibiotic resistance
Examiner keyword
The ability of bacteria to survive an antibiotic that would normally kill them, so the antibiotic no longer works against them.
Mutation
Examiner keyword
A random change in the DNA (genes) of an organism; mutations occur by chance and can produce a resistant bacterium.
Natural selection
Examiner keyword
The process by which organisms best suited to their environment (e.g. resistant bacteria) survive, reproduce and pass on their alleles, so the population changes over time.
Resistance allele
Examiner keyword
The version of a gene that makes a bacterium resistant to an antibiotic; it is passed on to offspring when the bacterium reproduces.
MRSA
Examiner keyword
A type of bacterium (methicillin-resistant Staphylococcus aureus) that is resistant to many antibiotics and is therefore difficult to treat — a 'superbug'.
Selection pressure
A factor in the environment (such as the use of an antibiotic) that determines which organisms survive and reproduce.
Overuse of antibiotics
Using antibiotics too often or incorrectly (e.g. for viral infections or not finishing the course), which speeds up the natural selection of resistant bacteria.

Common Mistakes and Misconceptions — Antibiotic Resistance

The traps other students keep falling into on antibiotic resistance questions — taken from recent Pearson Edexcel IGCSE Biology Paper 1 (4WSD0/1B) examiner reports and mark schemes — and how to avoid them.

✕Saying the antibiotic causes the bacteria to mutate or to become resistant
Edexcel Biology examiner reports
Why it happens
Resistance appears after the antibiotic is used, so students assume the antibiotic must have created it.
How to avoid it
Remember the mutation is random and happens by chance before the antibiotic is used. The antibiotic only selects the bacteria that are already resistant — it does not cause the resistance.
✕Thinking antibiotics kill viruses (e.g. that they cure colds or flu)
Edexcel Biology examiner reports
Why it happens
People take medicine when ill and assume one type works for everything.
How to avoid it
State clearly that antibiotics kill bacteria only and have no effect on viruses — colds and flu are viral, so antibiotics do not help.
✕Saying an individual bacterium 'adapts' or 'gets used to' the antibiotic during its life
Edexcel Biology examiner reports
Why it happens
Students confuse a population changing over generations with a single bacterium changing.
How to avoid it
It is the population that changes over many generations, not one bacterium adapting. Resistant bacteria already exist and are selected, then reproduce.
✕Forgetting to say the resistant bacteria reproduce and pass on the resistance allele
Edexcel Biology examiner reports 2022–2024
Why it happens
Students focus on the resistant bacteria surviving and stop there.
How to avoid it
Always include that the survivors reproduce and pass on the resistance allele, so the resistant population increases — this is what makes it natural selection.
✕Describing the process correctly but not naming it as natural selection
Edexcel Biology examiner reports
Why it happens
Students learn the steps but do not connect them to the term in the specification.
How to avoid it
Finish your answer by stating the process is natural selection — questions often award a mark specifically for naming it.
✕Saying MRSA is completely untreatable / immune to all antibiotics
Edexcel Biology examiner reports
Why it happens
MRSA is called a 'superbug', so students overstate it as impossible to treat.
How to avoid it
Say MRSA is resistant to many antibiotics and is therefore difficult to control/treat — not that it is impossible. Avoid the word 'immune'; use 'resistant'.

Past paper style quiz

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Antibiotic Resistance

Detailed Notes

What you’ll learn

How it’s examined

1What antibiotics act against (Getting started)

2Where resistance comes from (Getting started)

3Order the natural-selection steps (Building confidence)

4Why MRSA is hard to treat (Building confidence)

5Explain how a resistant population develops (Stretch)

6Why overuse of antibiotics matters (Stretch)

Antibiotic

Antibiotic resistance

Mutation

Natural selection

Resistance allele

MRSA

Selection pressure

Overuse of antibiotics

✕Saying the antibiotic causes the bacteria to mutate or to become resistant

✕Thinking antibiotics kill viruses (e.g. that they cure colds or flu)

✕Saying an individual bacterium 'adapts' or 'gets used to' the antibiotic during its life

✕Forgetting to say the resistant bacteria reproduce and pass on the resistance allele

✕Describing the process correctly but not naming it as natural selection

✕Saying MRSA is completely untreatable / immune to all antibiotics

Past paper style quiz