AQA GCSE Biology Biology Paper 2 (Higher), June 2025: Question 6

✅ Correct Answers

06.1: Cell division 1 [1 mark]

06.2: A and C [1 mark]

💡 Key Knowledge

• Mitosis produces two genetically identical cells from one parent cell. All cells formed solely by mitosis from cell A (such as B and C) are identical clones.
• Meiosis involves two consecutive divisions (divisions 2 and 3) resulting in four non-identical haploid cells.

🧠 Exam Technique

Trace the lineage: Cell division 1 keeps duplicating cells without halving chromosome sets. Divisions 2 & 3 represent the two stages of meiosis because one cell (D) yields four gametes (G, H, I, J).

❌ Common Errors

Assuming all cell division in the testes is meiosis. Stem cells / spermatogonia divide by mitosis first to ensure the male never runs out of sperm-producing cells.

✅ Correct Answers

06.3: 23 (or twenty-three) [1 mark]

06.4: 5 (or 6) [1 mark]

📐 How 06.4 is Calculated

A normal human male body cell has sex chromosomes XY:

1. Cell C: Diploid spermatogonium = has Y (1)
2. Cell D: Diploid cell after DNA replication = has Y (1)
3. Meiosis I (Division 2): Homologous pair XY separates. One daughter cell (e.g. E or F) gets the Y chromosome, the other gets X. That adds 1 cell.
4. Meiosis II (Division 3): The cell with the replicated Y divides its chromatids into two sperm cells (e.g. G & H or I & J). That adds 2 cells.
5. Total containing Y: 1 (C) + 1 (D) + 1 (E or F) + 2 (two sperm) = 5 cells.

Note: The mark scheme also generously permits 6 if students considered both intermediate cells or alternative chromatid counting.

❌ Common Trap in 06.3

Writing "23 pairs" instead of "23". Sperm and egg cells are haploid—they have 23 single chromosomes, not pairs! The mark scheme explicitly states: "do not accept 23 pairs".

🧠 Exam Tip for 06.4

Remember that gametes are haploid: 50% of sperm receive an X chromosome, and 50% receive a Y chromosome.

✅ Model Answers

06.5 (Runners):

• Offspring are formed by (only) mitosis [1 mark].
• So all cells receive an identical copy of every gene / allele (or a full copy of all DNA) [1 mark].

06.6 (Flowers & Seeds):

• Gametes (pollen and ovules) are produced by meiosis [1 mark].
• Fertilisation leads to random combinations of alleles / genes from two gametes/parents [1 mark].

🧠 Two-Mark Structure

For questions asking why offspring are or are not identical, always structure your answer in two steps:

1. Name the type of cell division involved (mitosis for runners; meiosis for flowers/seeds).
2. State the genetic consequence (exact copies of alleles passed on vs mix/random assortment of alleles).

❌ Examiner Warning: Spelling Matters!

Do not write blended words like "meitosis" or "metosis". Examiners cannot give benefit of the doubt if it is unclear whether you mean mitosis or meiosis.

💡 Key Knowledge

Sexual reproduction always introduces variation because:

• Meiosis produces genetically non-identical gametes.
• Random fertilisation combines different alleles from two parents.

✅ 06.7: Advantages of Asexual Reproduction (Runners)

Any two from:

• Faster process than sexual reproduction [1 mark].
• Many offspring produced rapidly to colonise the local area / outcompete weeds [1 mark].
• Offspring are well-adapted to the existing stable environment [1 mark].
• Only one parent needed (no need for pollinators like bees) [1 mark].
• Offspring receive water, sugars, and minerals directly from the parent plant via the runner [1 mark].
• Saves energy/materials (no need to construct flowers, nectar, or large fruit) [1 mark].

✅ 06.8: Advantages of Sexual Reproduction (Seeds)

Any two from:

• Genetic variation: Produces new combinations of alleles, allowing the population to adapt to environmental change or disease (selective advantage / evolution) [1 mark].
• Seed dispersal: Seeds are carried away (by animals eating fruit), reducing competition with the parent for light, space, and water [1 mark].
• Less vulnerable to local habitat loss because seeds colonise new areas [1 mark].
• Can produce a large number of offspring ensuring survival of the species [1 mark].

❌ Common Misconceptions

• Vague answers: Saying just "it is easier" or "it is good for them" earns 0 marks. Use biological terms: energy-efficient, independent of pollinators, or genetic diversity.
• Confusing advantages: Claiming asexual reproduction creates variation—it produces clones!

🧠 Top Tip: Survival Context

Notice the question says "for the survival of strawberry plants". Relate benefits to real plant ecology: connecting runner roots share nutrients, while fruits attract birds to disperse seeds far away.