A population of bacteria reproduces asexually during a period of ideal conditions, rapidly colonising a nutrient-rich environment. Explain why this same population is at greater risk of being entirely destroyed by a new pathogen compared with a population that reproduces sexually.

Cambridge International IGCSE Biology (0610) — 16.1 Asexual reproduction · Explain · 4 marks · View as Markdown

Written & reviewed by James Millett — Biology (Imperial College London), PGCE Science (University of Cambridge).

Model answer (4 marks)

Asexual reproduction produces genetically identical offspring (clones). Because all individuals are genetically identical, if a pathogen can infect or kill one organism it can infect or kill all of them. Sexual reproduction produces genetic variation; genetically different offspring mean some individuals may have resistance to the pathogen and survive, so the whole population is not destroyed.

Examiner tips

  • Use the word "genetically identical" for asexual and "genetic variation" for sexual. Show the link between identical genetics and uniform susceptibility. Mention that variation allows some resistance. Keep answer concise to fit 4 marks.

Common mistakes

  • Confusing asexual with sexual reproduction terms. Assuming asexual populations have some variation. Failing to explain the link between identical genetics and vulnerability.

Mark scheme (4 marks)

  1. Asexual reproduction produces genetically identical offspring (clones)
  2. Because all individuals are genetically identical, if a pathogen can infect or kill one organism it can infect or kill all of them
  3. Sexual reproduction produces genetic variation / genetically different offspring
  4. In a sexually reproducing population, some individuals may have resistance to the pathogen and survive, so the whole population is not destroyed

Key terms in this question

pathogen

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