Sexual and asexual reproduction — AQA GCSE Biology
Test yourself on Sexual and asexual reproduction with AQA GCSE practice questions.
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Sexual and asexual reproduction explained
Meiosis and mitosis are both types of cell division but they produce different outcomes.
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Mitosis produces two genetically identical diploid cells, which is important for growth, repair and asexual reproduction. Meiosis produces four genetically non-identical haploid cells called gametes, which is essential for sexual reproduction. The non-identical cells arise because of processes such as crossing over and independent assortment during meiosis. Students should be able to compare the two processes, stating that mitosis leads to identical cells and meiosis leads to non-identical cells. They should also understand that meiosis halves the chromosome number, while mitosis maintains it. For example, in humans, mitosis produces identical body cells with 46 chromosomes, while meiosis produces gametes with 23 chromosomes that are genetically varied.
Sexual reproduction involves the joining (fusion) of male and female gametes: • sperm and egg cells in animals • pollen and egg cells in flowering plants.
Sexual reproduction requires the fusion of male and female gametes, which are specialised sex cells. In animals, the male gamete is the sperm cell and the female gamete is the egg cell. In flowering plants, the male gamete is contained within pollen and the female gamete is the egg cell found in the ovule. The fusion of gametes is called fertilisation and results in a zygote that develops into a new individual. Gametes are haploid, meaning they contain half the normal number of chromosomes, so that the offspring has the correct diploid number after fertilisation. Students should be able to name the gametes in animals and flowering plants and describe the process of fusion. For example, in humans, a sperm cell fuses with an egg cell to form a zygote with 46 chromosomes.
In sexual reproduction there is mixing of genetic information which leads to variety in the offspring. The formation of gametes involves meiosis.
Sexual reproduction involves the mixing of genetic information from two parents, which produces offspring that are genetically varied. This variation arises because gametes are formed by meiosis, a type of cell division that produces non-identical haploid cells. During meiosis, crossing over and independent assortment shuffle the genetic material, so each gamete is genetically unique. When two gametes fuse during fertilisation, the resulting offspring receives a random combination of alleles from both parents, leading to variety in the population. For example, in humans, siblings are genetically different because each sperm and egg cell is unique. Students should understand that meiosis is essential for sexual reproduction because it produces the haploid gametes and introduces genetic variation. They should be able to explain how mixing of genetic information leads to variety.
Asexual reproduction involves only one parent and no fusion of gametes.
Asexual reproduction is a form of reproduction in which a single organism produces offspring without a partner. Because only one parent is involved, there is no fusion of gametes: no sperm and egg, or pollen and egg cell, combine. Instead, the parent's cells divide by mitosis to produce new individuals. For example, a strawberry plant can send out runners that grow into new plants. The offspring inherit all their genetic information from the one parent, so they are genetically identical to it. This contrasts with sexual reproduction, which requires two parents and the fusion of gametes. Asexual reproduction is common in some plants and fungi, and it allows rapid population growth in stable environments.
There is no mixing of genetic information. This leads to genetically identical offspring (clones). Only mitosis is involved.
In asexual reproduction, genetic information is not mixed because there is no fusion of gametes from two parents. The single parent's cells divide by mitosis, which produces two genetically identical daughter cells. Each new cell receives an exact copy of the parent's chromosomes, so the offspring are genetically identical to the parent and to each other. These offspring are called clones. Mitosis is the only type of cell division involved: meiosis does not occur because gametes are not formed. For example, when a strawberry plant produces a runner, the new individual has the same alleles as the parent. This lack of genetic variation means a population of clones may all be vulnerable to the same disease or environmental change.
Your focus
- State that mitosis produces identical cells and meiosis produces non-identical cells.
- Describe the difference in chromosome number between mitosis and meiosis.
- Explain how meiosis leads to genetic variation.
Show all 15 objectives
- Identify the male and female gametes in animals and flowering plants.
- Describe the process of fertilisation as the fusion of gametes.
- Explain the importance of gametes being haploid.
- State that meiosis forms gametes and leads to genetic variation.
- Describe how mixing of genetic information in sexual reproduction causes variety.
- Explain the role of meiosis in producing non-identical gametes.
- State that asexual reproduction involves only one parent.
- Describe asexual reproduction as involving no fusion of gametes.
- Give a named example of a plant that reproduces asexually.
- State that no mixing of genetic information occurs in asexual reproduction.
- Describe offspring of asexual reproduction as genetically identical clones.
- Identify mitosis as the only cell division involved in asexual reproduction.
Sexual and asexual reproduction exam tips
Marking Points
- Mitosis produces two genetically identical cells.
- Meiosis produces four genetically non-identical cells.
- Mitosis maintains the chromosome number (diploid to diploid).
- Meiosis halves the chromosome number (diploid to haploid).
- Meiosis introduces genetic variation through crossing over and independent assortment.
- Mitosis is used for growth, repair and asexual reproduction; meiosis is used to produce gametes for sexual reproduction.
- Sexual reproduction involves the fusion of male and female gametes.
- In animals, the male gamete is the sperm cell and the female gamete is the egg cell.
- In flowering plants, the male gamete is in pollen and the female gamete is the egg cell.
- Fusion of gametes is called fertilisation.
- Gametes are haploid, so the offspring receives half its chromosomes from each parent.
- The fusion of gametes leads to the formation of a zygote.
- Sexual reproduction involves the mixing of genetic information from two parents.
- This mixing leads to variety in the offspring.
- Gametes are formed by meiosis.
- Meiosis produces non-identical haploid cells.
- Crossing over and independent assortment during meiosis create genetic variation in gametes.
- Fertilisation combines gametes from two parents, increasing genetic variety in offspring.
- Asexual reproduction involves only one parent organism, with no second parent contributing genetic material.
- No fusion of gametes occurs, so there is no joining of a male and female sex cell.
- The offspring are produced from the parent's cells by mitosis, not by fertilisation.
- Examples include runners in strawberry plants and bulb formation in daffodils.
- Because there is no fusion of gametes, the offspring are genetically identical to the parent, forming clones.
- No mixing of genetic information occurs because there is no fusion of gametes from two parents.
- Mitosis is the only cell division involved in asexual reproduction in eukaryotes.
- Mitosis produces genetically identical daughter cells, so the offspring are clones of the parent.
- The offspring inherit the same alleles as the parent, so there is no genetic variation between parent and offspring.
- A lack of genetic variation can make a population of clones vulnerable to the same environmental change or disease.
Examiner Tips
- 💡Use a table to compare mitosis and meiosis clearly.
- 💡Mention both the number of cells and their genetic similarity when comparing.
- 💡Link the type of division to its function, such as growth for mitosis and gamete formation for meiosis.
- 💡Name the specific gametes for animals and flowering plants.
- 💡Use the term 'fusion' when describing fertilisation.
- 💡State that gametes are haploid and the zygote is diploid.
- 💡Link meiosis to the formation of gametes and genetic variation.
- 💡Explain that mixing of genetic information occurs at fertilisation.
- 💡Use examples such as siblings to illustrate variety.
- 💡State clearly that one parent is involved and that gametes do not fuse, using both ideas in your answer.
- 💡Use a named example such as strawberry runners or daffodil bulbs to support your explanation.
- 💡Link asexual reproduction to genetically identical offspring, because this follows directly from the absence of gamete fusion.
- 💡Use the term clone when describing offspring produced asexually, and explain that they are genetically identical.
- 💡Contrast mitosis with meiosis by stating that meiosis is not involved in asexual reproduction.
- 💡If asked about variation, explain that asexual reproduction produces little or no genetic variation because there is no mixing of genetic information.
Common Mistakes
- Thinking mitosis produces non-identical cells; correction: mitosis produces identical cells.
- Confusing the number of cells produced: mitosis produces two cells, meiosis produces four; correction: state the correct number.
- Believing meiosis produces identical gametes; correction: meiosis produces genetically non-identical gametes due to crossing over and independent assortment.
- Confusing the male gamete in plants: pollen is the structure containing the male gamete, not the gamete itself; correction: the male gamete is inside pollen.
- Thinking gametes are diploid; correction: gametes are haploid.
- Believing fertilisation occurs without fusion; correction: fertilisation is the fusion of gametes.
- Thinking meiosis produces identical cells; correction: meiosis produces non-identical cells.
- Believing variation comes only from fertilisation; correction: meiosis also creates variation in gametes.
- Confusing meiosis with mitosis; correction: meiosis forms gametes and halves the chromosome number.
- Thinking that asexual reproduction involves two parents but no gametes; the correction is that only one parent is involved.
- Confusing asexual reproduction with mitosis itself; the correction is that mitosis is the cell division process used in eukaryotes, while asexual reproduction is the whole reproductive process.
- Believing that gametes are produced but simply do not fuse; the correction is that no gametes are involved at all in asexual reproduction.
- Saying that meiosis is involved in asexual reproduction; the correction is that only mitosis is involved.
- Describing offspring as similar rather than genetically identical; the correction is that they are clones with identical genetic information.
- Thinking that genetic information is mixed during mitosis; the correction is that mitosis copies genetic information exactly, with no mixing.