A salmon is a fish that lives in the sea but swims upstream into rivers to lay its eggs. Describe four characteristics of living organisms that a salmon demonstrates during its lifetime.

Cambridge International IGCSE Biology (0610) — 1.1 Characteristics of living organisms · Describe · 4 marks · View as Markdown

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

Model answer (4 marks)

1. Movement – the salmon swims upstream against the river current.
2. Sensitivity – it senses water chemistry and currents to find its spawning grounds.
3. Reproduction – it lays eggs and fertilises them, producing a new generation of salmon.
4. Nutrition – it feeds on plankton and small fish, taking in food to grow and develop.

Examiner tips

  • Use the exact words from the mark scheme (movement, sensitivity, reproduction, nutrition).
  • Give a clear example for each characteristic.
  • Keep each point short and to the point.
  • Show the salmon’s behaviour in the context of its life cycle.

Common mistakes

  • Writing a generic ‘breathing’ instead of a salmon‑specific example.
  • Using vague phrases like ‘it moves’ without specifying upstream swimming.
  • Mixing up the order of the characteristics and missing one of the required points.

Mark scheme (4 marks)

  1. Movement — the salmon moves all or part of itself (e.g. swimming upstream)
  2. Sensitivity — the salmon detects and responds to changes in its environment (e.g. detects river currents / water chemistry to navigate)
  3. Reproduction — the salmon produces more salmon of the same kind (lays eggs / fertilises eggs)
  4. Nutrition / Respiration / Excretion / Growth — any ONE further characteristic correctly described in the context of the salmon

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