A desert cactus lives in a hot, dry environment. During the day, temperatures rise sharply and the cactus receives intense sunlight. At night, temperatures drop rapidly. Describe four characteristics of living organisms that the cactus would carry out.

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. The cactus takes in water, minerals and light for photosynthesis, providing the materials needed for growth and energy.
2. It carries out cellular respiration, breaking down stored sugars to release energy.
3. It shows sensitivity by detecting light and temperature changes and adjusting its stomata and water use accordingly.
4. It removes waste products such as CO₂ and metabolic by‑products through excretion mechanisms.

Examiner tips

  • Use the exact terms: nutrition, respiration, sensitivity, excretion. Include a brief example for each (e.g. photosynthesis, stomatal control).

Common mistakes

  • Confusing nutrition with photosynthesis alone; forgetting to mention respiration. Using vague phrases like ‘responds to light’ without linking to sensitivity.

Mark scheme (4 marks)

  1. The cactus carries out nutrition / takes in materials needed for growth and energy
  2. The cactus carries out respiration — chemical reactions in cells that release energy from nutrient molecules
  3. The cactus shows sensitivity — detects changes in its environment and responds to them
  4. The cactus carries out excretion — removes waste products of metabolism from the organism

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