AQA GCSE Combined Science: Trilogy Biology Paper 2 (Higher), 2022: Question 5

✅ Correct answer

Negative feedback (or negative feedback control).

💡 Key knowledge

• Negative feedback keeps conditions close to a normal level.
• If blood glucose goes too high or too low, the body responds to return it to normal.
• The pancreas detects the change and releases the correct hormone.

🧠 Exam technique

• Use the exact phrase negative feedback.
• The mark scheme says ignore homeostasis, so don’t rely on that alone.

❌ Common errors

• Saying just homeostasis instead of negative feedback.
• Giving a vague answer like “hormonal control” with no detail.

✅ Correct answers

A = glucagon

B = insulin

💡 Key knowledge

• Insulin lowers blood glucose when it is too high.
• Glucagon raises blood glucose when it is too low.
• Both are made by the pancreas.

🧠 Exam technique

• Use the diagram clues: the hormone linked to high glucose is insulin.
• The hormone linked to low glucose is glucagon.
• Phonetic spellings are accepted, but try to spell them accurately.

❌ Common errors

• Mixing up insulin and glucagon.
• Writing adrenaline instead of glucagon.
• Giving the right hormones but in the wrong labels.

✅ What a full-mark answer needs

You need a linked explanation showing:

1. blood glucose rises after a meal,
2. insulin is released and lowers it,
3. glucagon is released if glucose becomes too low,
4. the body returns blood glucose to normal.

🧠 Exam technique

• Write in a clear sequence: stimulus → hormone → target organ/cell → effect → back to normal.
• Use the word because or so to show cause and effect.
• You can score well by describing both directions of control, not just the “after a meal” part.

❌ Common errors

• Saying insulin “turns glucose into fat” — not the expected GCSE answer here.
• Forgetting that glucose is stored as glycogen.
• Not explaining how glucose returns to normal.
• Mixing up when glucagon acts.

✅ Correct answer points

• FSH causes several ova/eggs to mature in the ovary.
• LH causes ovulation / release of the egg.
• So there are more eggs available, which gives a higher chance of fertilisation.

💡 Key knowledge

• FSH = Follicle Stimulating Hormone.
• LH = Luteinising Hormone.
• These hormones are used when a woman has difficulty becoming pregnant naturally.

🧠 Exam technique

• Make sure you include the effect of each hormone, not just its name.
• Use the chain: FSH → egg matures → LH → ovulation → more chance of fertilisation.

❌ Common errors

• Saying FSH “causes fertilisation” — it does not.
• Forgetting that LH causes ovulation.
• Not linking the hormones to the increased chance of pregnancy.

✅ Correct answer

1. Eggs are collected from the ovary.
2. The eggs are fertilised in the laboratory.
3. The fertilised eggs develop into embryos in the laboratory.
4. The embryos are inserted into the uterus/womb.

💡 Key knowledge

• IVF stands for in vitro fertilisation.
• In vitro means outside the body, in a lab.
• The embryo is the early stage after fertilisation and division.

🧠 Exam technique

• Keep the steps in the correct order.
• Use the words fertilised, embryo, and uterus/womb.
• If asked to describe a process, give each stage as a separate point.

❌ Common errors

• Saying the egg is fertilised in the fallopian tube — the mark scheme says do not accept this here.
• Calling the embryo a foetus.
• Missing out the step where embryos are transferred into the uterus.

✅ Any three correct differences

• Meiosis forms sperm cells, while mitosis forms liver cells.
• Two cell divisions are needed to form sperm cells, but one cell division forms liver cells.
• Four genetically different sperm cells are produced, but two genetically identical liver cells are produced.
• Sperm cells have 23 chromosomes; liver cells have 46 chromosomes.

💡 Key knowledge

• Meiosis makes gametes and halves the chromosome number.
• Mitosis makes body cells and produces identical cells.
• Sperm are haploid and liver cells are diploid.

🧠 Exam technique

• Write each difference as a clear pair: meiosis vs mitosis, 4 vs 2 cells, different vs identical, 23 vs 46 chromosomes.
• You only need three differences, but they must be clearly different from each other.

❌ Common errors

• Talking about reproduction in general instead of cell division.
• Saying sperm cells have 23 pairs of chromosomes — they have 23 chromosomes.
• Claiming liver cells are haploid.
• Giving the same idea in different words twice.

💡 Blood glucose

Insulin lowers blood glucose. Glucagon raises it. The pancreas uses negative feedback to keep levels normal.

💡 Fertility treatment

FSH matures eggs, LH triggers ovulation, and IVF involves fertilising eggs in the lab and placing embryos into the uterus.

💡 Cell division

Meiosis makes gametes with half the chromosome number. Mitosis makes identical body cells with the full chromosome number.