Describe how sexual reproduction in flowering plants produces a seed. Include in your answer the roles of the male and female gametes and explain why the seeds may show variation.

Edexcel A-Level Biology A: Salters-Nuffield (9BN0) — 2.3 Sexual reproduction in animals and plants · Describe · 5 marks · View as Markdown

Written & reviewed by James Millett — Biology (Imperial College London), PGCE Science (University of Cambridge).

Model answer (5 marks)

Pollen grain, containing the male gamete (haploid nucleus), is transferred to the stigma of a flower during pollination.
The male gamete travels down the pollen tube to reach the female gamete in the ovule (egg cell) for fertilisation.
Fertilisation occurs when the male and female gametes fuse to form a diploid zygote.
The zygote undergoes mitotic divisions to develop into an embryo, which becomes enclosed in a seed.
Seeds may show variation because each gamete is haploid and carries a different combination of alleles; when they fuse, the offspring inherit a unique combination of genetic material, different from either parent.

Examiner tips

  • Use the exact terms: pollen grain, stigma, pollen tube, ovule, egg cell, fertilisation, zygote, embryo, seed.
  • Show the sequence of events in order.
  • Explain variation in terms of haploid gametes and allele combinations.
  • Keep the answer concise – 5 marks only.

Common mistakes

  • Mixing up the roles of male and female gametes (e.g., calling the pollen grain the female gamete).
  • Omitting the step that the zygote develops into an embryo before becoming a seed.
  • Using vague language such as "some variation" without linking it to haploid gametes and allele combinations.

Mark scheme (5 marks)

  1. Pollen grain (containing the male gamete / haploid nucleus) is transferred to the stigma of a flower (pollination)
  2. The male gamete travels down the pollen tube to reach the female gamete (ovule / egg cell) for fertilisation
  3. Fertilisation — the male and female gametes fuse to form a diploid zygote
  4. The zygote develops (by mitosis / cell division) into an embryo, which becomes enclosed in a seed
  5. Seeds may show variation because each gamete is haploid and contains a different combination of genetic information / alleles, so when they fuse the offspring have a unique combination of genetic material different from either parent

Key terms in this question

gamete · variation

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