Exam Focus

Exam Focus

Plant hormones carry some of the highest mark allocations in GCSE Biology examinations. Edexcel 1BI0 Paper 2 (Topic 6: Plant Structures and Their Functions) tests plant hormones with stimulus-based questions — you may be given a diagram of a seedling experiment or data on shoot curvature and asked to explain the results using auxin. The "Suggest" command appears frequently when the context is an unfamiliar experimental setup. Ensure you can explain phototropism, gravitropism, and commercial applications of auxins, gibberellins, and ethylene. Common question formats:

• Explain phototropism using auxin (4-6 marks): Must include: auxin moves to shaded side, cells elongate more on shaded side, shoot bends towards light. For 6 marks, add: auxin produced at tip, lateral transport, reference to cell elongation mechanism.
• Compare shoot and root auxin responses (3-4 marks): Shoots — high auxin = more growth; Roots — high auxin = less growth. Roots are more sensitive. Use this to explain gravitropism.
• Commercial uses of plant hormones (3-4 marks): Auxin: rooting powder (promotes root growth on cuttings), selective weedkillers. Gibberellin: seed germination, fruit size. Ethylene: fruit ripening. One mark per use with mechanism.
• RPA8 (plant growth practical): Experimental design questions on measuring the effect of different light directions on seedling growth — include valid controls, how to measure bending angle, and reliability.

Most common error: Saying "auxin moves towards the light" — it moves AWAY from the light (to the shaded side). This reversal is one of the most common biology exam mistakes at GCSE.