AQA GCSE Biology Biology Paper 2 (Higher), June 2023: Question 2

✅ Correct Answer

Accommodation

💡 Key Knowledge

• Accommodation: The process of changing the shape of the lens to focus on near or distant objects.
• Myopia: Short-sightedness (corrected with concave lenses).
• Hyperopia: Long-sightedness (corrected with convex lenses).
• Adaptation: An evolutionary feature or behavioural change, not optical focusing.

✅ Correct Selections

• 02.2 (Image focused): B (Retina)
• 02.3 (Muscle that contracts for near focus): E (Ciliary muscle)

💡 Label Guide for Figure 3

• A: Sclera – tough outer protective layer.
• B: Retina – light-sensitive layer of receptor cells at the back where the image forms.
• C: Optic nerve – carries impulses to the brain.
• D: Cornea – transparent front layer that refracts light.
• E: Ciliary muscle – contracts or relaxes to alter lens shape.

❌ Common Errors

• Confusing B (retina) with A (sclera).
• Mistaking suspensory ligaments for ciliary muscles (E). Remember: ciliary muscles contract; suspensory ligaments are connective tissue fibers that loosen or tighten passively.

✅ Correct Answer

The lens becomes fatter / thicker / wider / more convex / curved.

🧠 Exam Technique

Always use precise anatomical descriptors. Examiners explicitly award marks for: fatter, thicker, wider, or more rounded/convex.

💡 Near Accommodation Mechanism

1. Ciliary muscles contract.
2. Suspensory ligaments loosen / slacken.
3. The lens becomes thicker and refracts light rays more strongly.

✅ Marking Points (Any Two)

• (Muscles in the iris) contract / shorten [1 mark]
• Reduces pupil size / constricts pupil [1 mark]
• Reduces the amount of light entering the eye [1 mark]

❌ Critical Pitfalls & Examiner Notes

• Do NOT confuse iris muscles with ciliary muscles! Saying "ciliary muscles contract" gets 0 marks for that point.
• Do not state that the iris muscles "relax". In bright light, circular iris muscles actively contract.
• Top responses mention both the mechanism (muscles contracting to constrict the pupil) and the purpose (preventing excess light from bleaching or damaging the retina).

✅ Model Plan (Ruler Drop Test)

1. Initial Baseline Test: Have Person A sit with their forearm resting on a table, hand open at the edge. Hold a metre ruler vertically so the 0 cm mark is level with the top of their thumb.
2. Drop & Measure: Drop the ruler without warning. Person A catches it as quickly as possible. Record the reading on the ruler in cm at the thumb.
3. Repeats: Repeat this drop at least 3 to 5 times and calculate a mean baseline reaction distance (discarding anomalies).
4. Independent Variable: Have Person A drink a specified volume of coffee (e.g. 200 cm³). Wait a set period of time (e.g. 15–30 minutes) for caffeine absorption.
5. Repeat Under Test Condition: Repeat the ruler drop test using the exact same procedure for at least 3–5 repeats and calculate a mean reaction distance after coffee.
6. Comparison & Repetition: Compare the two means. Repeat the entire experiment with other individuals (e.g. 2+ other students).

📐 Essential Control Variables (Validity)

State at least 2–3 control variables explicitly:

• Catching hand: Always use the dominant hand.
• Drop height: Ruler held at exactly 0 cm above thumb each time.
• Coffee dose: Same type, brand, concentration, and volume (cm³) of coffee.
• Time delay: Identical wait time between drinking and testing.
• Participant factors: Same age, same amount of sleep, no other caffeinated drinks consumed previously.