AQA GCSE Biology Biology Paper 2 (Foundation), June 2025: Question 4

✅ Correct Answer & Criteria

• Bar 1 (Sweat): Height plotted precisely at 420 cm³ and labelled Sweat .
• Bar 2 (Breathing): Height plotted precisely at 340 cm³ and labelled Breathing .

📐 Reading the Grid Scale

Carefully check the y-axis before plotting:

• 100 cm³ = 5 small grid squares.
• Therefore, 1 small square = 20 cm³.
• Sweat (420 cm³): Plot 1 small square above 400 cm³.
• Breathing (340 cm³): Plot 2 small squares above 300 cm³.

❌ Common Errors

• Assuming each small grid square equals 10 cm³ instead of checking the scale (20 cm³ per square).
• Drawing bars without x-axis labels beneath them.
• Plotting freehand lines without a ruler, leading to inaccurate bar heights.

🧠 Exam Technique

• Use a sharp pencil and a ruler to ensure clean lines within the allowed ± ½ square tolerance.
• Bar widths do not need to match exactly, but keeping them identical to the existing bars looks neat and avoids confusion.

✅ Correct Answer

Tick the box next to:

[✓] Increase

💡 Key Knowledge

During a race, muscle contraction demands more energy from cellular respiration. Respiration is exothermic, releasing thermal energy and raising body temperature.

The thermoregulatory centre triggers increased sweating. As sweat evaporates from the skin surface, it removes latent heat, cooling the body down.

💡 Process Breakdown

• Filtration: High pressure forces small molecules (water, glucose, ions, urea) out of the blood into kidney tubules.
• Selective Reabsorption: Useful substances (all glucose, some ions, and necessary water) move back into the blood.
• Excretion: Unwanted waste and excess water leave the body as urine via the bladder.

❌ Common Errors

• Drawing multiple lines from one box: The mark scheme specifically states: "do not accept more than one line from a box on the left". If two lines emerge from one box, that mark is cancelled out.
• Confusing filtration (blood into tubule) with reabsorption (tubule back into blood).

💡 Advantages of a Kidney Transplant

• Lifestyle freedom: No need to spend 18–24 hours every week tied to a dialysis machine; freedom to work and travel.
• Dietary freedom: Patients do not have to strictly restrict salt, protein, and fluid intake as required on dialysis.
• Long-term cost: Cheaper for healthcare systems over time compared to ongoing lifelong dialysis sessions.
• Overall health: Provides a continuous, steady regulation of blood waste products rather than peaks and troughs.

💡 Disadvantages of a Kidney Transplant

• Organ rejection: The recipient's immune system may recognize donor antigens as foreign and attack the organ.
• Immunosuppressant drugs: Must be taken for life, which lowers immunity and leaves the patient vulnerable to other infections.
• Surgical risks: Involves major surgery, general anaesthetic risks, bleeding, and potential post-op infection.
• Donor shortage: Long waiting lists for an organ with matching tissue type.

🧠 Structuring an 'Evaluate' Answer (Level 2: 3–4 Marks)

To achieve full 4 marks on an evaluation question, you must provide:

1. At least one valid reason in favour of a transplant.
2. At least one valid reason against a transplant (or in favour of dialysis).
3. Use of own knowledge (e.g., mention of rejection, immunosuppressants, or dietary freedom).
4. A clear conclusion / judgement that directly weighs the evidence.

✅ Model Full-Mark Answer

"A kidney transplant offers a much better quality of life than dialysis because the patient does not need to visit a hospital three times a week for 6 to 8 hours at a time, and they can eat a normal diet without strict fluid controls. In the long term, transplants are also less expensive for the NHS.

However, a transplant requires major surgery with risks of infection and complications. There is also a shortage of donors, and the patient risks organ rejection, requiring lifelong immunosuppressant medication which increases their susceptibility to illnesses.

Conclusion: Overall, a transplant is the better long-term treatment because it restores normal lifestyle and constant water regulation, provided a suitably matched donor is found."