AQA GCSE Combined Science: Trilogy Biology Paper 1 (Higher), 2024: Question 6

✅ Correct answer

A full-mark answer should include these stages in order:

• DNA replicates, so there are two copies of each chromosome.
• One set of chromosomes is pulled to each end of the cell.
• The nucleus divides, or two new nuclei form.
• The cytoplasm or cell membrane divides, forming two genetically identical cells.

💡 Key knowledge

• This is mitosis as part of the cell cycle.
• The new cells are genetically identical to the original cell.
• The mark scheme accepts DNA replicates or two copies of each chromosome form .
• The mark scheme says do not write “DNA reproduces”.
• Names of mitosis stages are not needed.

🧠 Exam technique

• Describe the stages you can see in the figure, in sequence.
• Use simple, precise biological terms: DNA replicates , chromosomes pulled apart , nucleus divides , cell divides .
• Examiner note: if the stages are out of order, a maximum of 3 marks can be awarded.
• If you are unsure, writing mitosis may gain 1 mark only if nothing better is given.

❌ Common errors

• Saying DNA reproduces instead of DNA replicates .
• Missing the final idea that two genetically identical cells form.
• Giving stages in the wrong order.
• Talking vaguely about “the cell splits” without mentioning chromosomes or nucleus.

✅ Correct answers

• It is caused by uncontrolled cell division or uncontrolled growth.
• The tumour invades neighbouring tissues.
• Tumour cells can spread to other parts of the body, for example in the blood or lymph.

💡 Key knowledge

• Malignant tumours are cancerous.
• They do not stay contained in one place.
• The spread of cancer cells to other parts of the body is called metastasis.
• The mark scheme allows wording such as tumour metastasises .

🧠 Exam technique

• For full marks, include both uncontrolled division and spread.
• A short definition like “a cancerous tumour” is not enough on its own for 3 marks.
• Link the ideas in a sequence: uncontrolled growth → invades tissues → spreads around body.

❌ Common errors

• Describing a benign tumour instead.
• Only saying “it grows fast” with no mention of invasion or spread.
• Forgetting that the cells spread in the blood or lymph.

✅ Correct answer points

• Person B needs to breathe faster or deeper to get more oxygen.
• This is because the smoker’s alveoli have a smaller surface area.
• So less oxygen gets into the blood, or there is less oxygenation of haemoglobin.
• So there is less oxygen available for respiration.

💡 Key knowledge

• Healthy alveoli have a large surface area for gas exchange.
• Smoking damages alveoli, reducing their surface area.
• Less surface area means less diffusion of oxygen into the blood.
• During exercise, muscles need more oxygen for aerobic respiration.
• The mark scheme also allows ideas such as more anaerobic respiration, lactic acid production, or oxygen debt if clearly linked.

🧠 Exam technique

• This is an explain question, so do not just describe the alveoli drawings.
• Use a because/so chain: smoking damages alveoli → smaller surface area → less oxygen enters blood → less oxygen for respiration → breathes faster
• Top answers clearly connect the diagram difference to exercise and respiration.
• The mark scheme allows the converse if clearly stated, but the safest route is to explain why person B gets less oxygen.

❌ Common errors

• Saying smoking makes “more energy” without explaining oxygen supply. The mark scheme does not accept “energy produced / made / created” on its own.
• Only saying person B has “damaged lungs” with no mention of smaller surface area.
• Forgetting to link to the blood or to respiration.
• Just stating that person B breathes faster because they smoke, with no biological explanation.

💡 What distinguished stronger answers

• They used exact mark scheme wording like DNA replicates , uncontrolled cell division , and smaller surface area .
• They wrote in a logical order, especially for the cell cycle and the smoking explanation.
• They linked structure to function: damaged alveoli → reduced gas exchange.

🧠 Best strategy in the exam

• Count the marks and aim for that many separate science points.
• For describe questions, give stages in order.
• For explain questions, build a cause-and-effect chain.
• Use terms from GCSE Biology specification rather than vague everyday language.

❌ Biggest mark-losers

• Vague wording that is scientifically weak.
• Missing the word identical in mitosis answers.
• Not mentioning spread when defining malignant tumours.
• Talking about “not enough energy” instead of “less oxygen for respiration”.