A scientist observes a Venus flytrap plant. When an insect lands on one of its leaves, the leaf snaps shut rapidly, trapping the insect. The plant then secretes digestive enzymes onto the insect and absorbs the digested products. Explain how the behaviour of the Venus flytrap demonstrates four characteristics of living organisms.
Written & reviewed by James Millett — Biology (Imperial College London), PGCE Science (University of Cambridge).
Model answer (4 marks)
1. The rapid snapping of the leaf when an insect lands shows the plant’s sensitivity to a stimulus.
2. The secretion of digestive enzymes to break down the insect provides the plant with nutrients, demonstrating nutrition.
3. The enzymes are released outside the cells and the digested products are taken up, showing extracellular digestion (a form of saprotrophic nutrition) and the removal of waste products.
4. The plant requires energy to grow and function, which it obtains through photosynthesis and respiration, demonstrating growth and metabolic activity.
2. The secretion of digestive enzymes to break down the insect provides the plant with nutrients, demonstrating nutrition.
3. The enzymes are released outside the cells and the digested products are taken up, showing extracellular digestion (a form of saprotrophic nutrition) and the removal of waste products.
4. The plant requires energy to grow and function, which it obtains through photosynthesis and respiration, demonstrating growth and metabolic activity.
Examiner tips
- Use the exact phrases from the mark scheme (sensitivity, nutrition, extracellular digestion, growth/respiration).
- Show each characteristic clearly in a separate sentence or numbered point.
- Keep sentences concise and avoid unnecessary words.
Common mistakes
- Mixing up excretion with digestion – remember the plant is secreting enzymes, not excreting waste.
- Failing to mention that the plant’s growth is due to photosynthesis/respiration.
Mark scheme (4 marks)
- The leaf snapping shut in response to the insect landing demonstrates sensitivity / response to a stimulus
- Secreting digestive enzymes onto the insect and absorbing the products demonstrates nutrition
- The plant secreting digestive enzymes outside the cell and absorbing the digested products demonstrates excretion (of waste products of metabolism) OR can be credited as saprotrophic / extracellular nutrition
- The plant carrying out photosynthesis / requiring energy to grow and function demonstrates respiration OR growth (plant increases in size / biomass over time using absorbed nutrients)
Related
- All Pearson Edexcel International GCSE Biology (4BI1) revision notes →
- How to answer a "Explain" question →
- Decode the mark scheme abbreviations →