How do sexual and asexual reproduction differ, and what does meiosis do?
Explain the advantages and disadvantages of asexual and sexual reproduction, and the role of meiotic cell division in producing four genetically different haploid daughter cells.
A focused answer to Edexcel GCSE Biology 3.1B to 3.3, covering the advantages and disadvantages of asexual and sexual reproduction and the role of meiosis in producing four genetically different haploid gametes.
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What this dot point is asking
Edexcel statements 3.1B to 3.3 want you to weigh up the advantages and disadvantages of asexual and sexual reproduction (3.1B and 3.2B are Biology only) and explain the role of meiosis in producing four genetically different haploid gametes. The contrast with mitosis is central.
Asexual reproduction
The advantages are that no mate is needed, reproduction is fast, and many offspring can be produced quickly when conditions are good. The disadvantage is that there is no genetic variation, so if the environment changes or a disease appears, the whole population may be affected equally.
Sexual reproduction
The advantage is the variation, which means some offspring may have features that help them survive a changing environment or a new disease, and this variation is also what selective breeding and natural selection act on. The disadvantages are that it is slower and requires finding a mate.
Meiosis
Because gametes are haploid, when two of them join at fertilisation the chromosome number is restored to the full diploid number (46 in humans). This keeps the chromosome number constant from one generation to the next. The mixing of chromosomes during meiosis, and the random combination of gametes at fertilisation, are the sources of genetic variation in sexually reproducing species.
Try this
Q1. State one advantage and one disadvantage of asexual reproduction. [2 marks]
- Cue. Advantage: only one parent needed and it is fast. Disadvantage: no variation, so the whole population is vulnerable to the same threat.
Q2. State two ways the cells produced by meiosis differ from those produced by mitosis. [2 marks]
- Cue. Meiosis makes four cells (mitosis makes two), they are genetically different (mitosis identical), and they are haploid with half the chromosomes (mitosis keeps the full number).
Exam-style practice questions
Practice questions written in the style of Pearson Edexcel exam questions on this dot point, with worked answer explainers. The year tag is the paper they imitate, not the source.
Edexcel 20184 marksCompare sexual and asexual reproduction. Give two advantages of sexual reproduction and two advantages of asexual reproduction.Show worked answer →
A 4-mark compare question rewards two clear advantages on each side.
Advantages of sexual reproduction: it produces variation in the offspring, which helps a species survive environmental change or disease, and this variation is the raw material for natural selection and selective breeding.
Advantages of asexual reproduction: only one parent is needed, so there is no need to find a mate, and reproduction is fast, producing many genetically identical offspring quickly when conditions are favourable.
Markers reward variation and survival of change for sexual, and no mate needed plus speed for asexual. Listing the same idea twice, or muddling which method gives variation, loses marks.
Edexcel 20213 marksA human body cell has 46 chromosomes. Explain why gametes produced by meiosis have 23 chromosomes and why this is important.Show worked answer →
A 3-mark explain question rewards halving plus the reason.
Meiosis halves the chromosome number, so each gamete (sperm or egg) has 23 chromosomes (one of each pair).
This is important because at fertilisation two gametes join, so , restoring the full chromosome number in the zygote. If gametes had 46, fertilisation would double the number each generation.
Markers reward the halving to 23 and the restoration to 46 at fertilisation. Saying meiosis makes identical cells is wrong; that is mitosis.
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Sources & how we know this
- Pearson Edexcel GCSE (9-1) Biology (1BI0) specification — Pearson (2016)