OpenRevise

Exam questions · Biology · Evolution and Natural Selection

Antibiotic Resistance

  • 6 exam questions
  • 19 marks
  • 9 quick checks
  1. 1 State [1 mark]

    State what is meant by antibiotic resistance.

    Show answerHide answer

    Model answer

    The ability of bacteria to survive an antibiotic that would normally kill them.

    Mark scheme

    • Bacteria survive the antibiotic — 1 mark
  2. 2 Explain [2 marks]

    Explain why antibiotics should not be used to treat a cold.

    Show answerHide answer

    Model answer

    A cold is caused by a virus, and antibiotics do not kill viruses. Using them unnecessarily increases the chance that bacteria will become resistant.

    Mark scheme

    • Antibiotics do not kill viruses — 1 mark
    • Increases the chance of resistance — 1 mark
  3. 3 Calculate [3 marks]

    A bacterium divides every 30 minutes. Calculate the number of bacteria produced from one bacterium after 5 hours, assuming no cells die.

    Show answerHide answer

    Model answer

    5 hours is 300 minutes, so there are 300 ÷ 30 = 10 divisions. The number is 2 to the power 10, which is 1024 bacteria.

    Mark scheme

    • 10 divisions — 1 mark
    • \(2^{10}\) — 1 mark
    • 1024 — 1 mark
  4. 4 Explain [4 marks]

    Explain how the use of an antibiotic can lead to a population of bacteria becoming resistant.

    Show answerHide answer

    Model answer

    There is variation in the bacteria, and by mutation a few are resistant. The antibiotic kills the non-resistant bacteria, but the resistant ones survive. They reproduce, passing on the resistance allele to their offspring, so the proportion of resistant bacteria in the population increases.

    Mark scheme

    • Mutation gives a resistant bacterium — 1 mark
    • Non-resistant bacteria are killed — 1 mark
    • Resistant bacteria survive and reproduce — 1 mark
    • The proportion of resistant bacteria increases — 1 mark
  5. 5 Explain [3 marks]

    Explain why a patient should always finish a course of antibiotics.

    Show answerHide answer

    Model answer

    Stopping early may leave some bacteria alive, including the ones that are least susceptible. These can reproduce, and the infection can return, with a greater chance that the surviving bacteria are resistant.

    Mark scheme

    • Some bacteria may survive — 1 mark
    • They reproduce — 1 mark
    • More likely to be resistant — 1 mark
  6. 6 Evaluate [6 marks]

    Hospitals use a number of measures to control MRSA. Evaluate how antibiotic resistance supports Darwin's theory of evolution, and suggest the ways it can be controlled.

    Show answerHide answer

    Model answer

    Antibiotic resistance supports Darwin's theory because it shows all the steps of natural selection. There is variation, because a few bacteria have a mutation that makes them resistant. The antibiotic is the selection pressure, and the resistant bacteria are more likely to survive and reproduce. They pass on their resistance alleles, so the population changes over generations, and this can be seen in a short time because bacteria reproduce so quickly. It can be controlled by using antibiotics only when they are needed, and for the full course, so that fewer resistant bacteria are selected. Hospitals can also reduce the spread by handwashing and isolating infected patients. New antibiotics are also needed.

    Mark scheme

    • Variation from mutation — 1 mark
    • Antibiotic as selection pressure — 1 mark
    • Resistant survive and reproduce — 1 mark
    • Population changes, over a short time — 1 mark
    • Use antibiotics carefully / complete course — 1 mark
    • Hygiene or isolation — 1 mark

Quick check

  1. 1

    How do bacteria become resistant to an antibiotic?

    1. AThey choose to change
    2. BThe antibiotic changes their DNA
    3. CBy random mutation, and the resistant ones survive
    4. DBy getting used to the drug
    Show answerHide answer

    C: By random mutation, and the resistant ones survive

    A random mutation gives a bacterium resistance, and it then survives and reproduces.

  2. 2

    What is the selection pressure in antibiotic resistance?

    1. AThe antibiotic
    2. BThe temperature
    3. CThe patient
    4. DThe food
    Show answerHide answer

    A: The antibiotic

    The antibiotic kills non-resistant bacteria, so it selects for the resistant ones.

  3. 3

    Why do bacteria evolve so quickly?

    1. AThey have large genomes
    2. BThey reproduce very rapidly
    3. CThey do not mutate
    4. DThey are large cells
    Show answerHide answer

    B: They reproduce very rapidly

    They reproduce rapidly, so there are many generations in a short time.

  4. 4

    Why should antibiotics not be given for viral infections?

    1. AViruses are too large
    2. BViruses are not harmful
    3. CThey cure viruses too quickly
    4. DThey do not work on viruses and increase resistance
    Show answerHide answer

    D: They do not work on viruses and increase resistance

    Antibiotics do not kill viruses, and unnecessary use makes resistance more likely.

  5. 5

    What does MRSA stand for?

    1. AMycobacterium resistant to some antibiotics
    2. BMultiple resistant spore-forming agent
    3. CMethicillin-resistant Staphylococcus aureus
    4. DMutated resistant Staphylococcus antibiotic
    Show answerHide answer

    C: Methicillin-resistant Staphylococcus aureus

    MRSA is methicillin-resistant Staphylococcus aureus.

  6. 6

    What happens to non-resistant bacteria when an antibiotic is used?

    1. AThey are killed
    2. BThey become resistant
    3. CThey become viruses
    4. DThey stay the same
    Show answerHide answer

    A: They are killed

    They are killed or stopped from growing.

  7. 7

    A bacterium divides every 20 minutes. How many bacteria are there after 2 hours, from one cell?

    1. A6
    2. B12
    3. C36
    4. D64
    Show answerHide answer

    D: 64

    There are 6 divisions in 2 hours, so \(2^6 = 64\) bacteria.

  8. 8

    Which action helps to slow the development of antibiotic resistance?

    1. AStopping the course when you feel better
    2. BFinishing the course of antibiotics
    3. CTaking antibiotics for colds
    4. DUsing antibiotics on healthy animals
    Show answerHide answer

    B: Finishing the course of antibiotics

    Finishing the course makes sure that all the bacteria are killed, instead of leaving resistant ones.

  9. 9

    A student says that "antibiotics cause bacteria to mutate and become resistant". What is wrong with this?

    1. ANothing
    2. BBacteria cannot mutate
    3. CMutations occur at random, and the antibiotic selects resistant bacteria
    4. DResistance is not inherited
    Show answerHide answer

    C: Mutations occur at random, and the antibiotic selects resistant bacteria

    Mutations happen at random. The antibiotic does not cause them, it selects the bacteria that already have the resistance allele.