Asexual ReproductionCambridge IGCSE Biology: Revision notes
Section 1
What Is Asexual Reproduction?
Asexual reproduction is a process resulting in the production of genetically identical offspring from one parent. No gametes fuse and no fertilisation takes place — offspring are produced by mitosis, so they are genetically identical to the parent and to each other (they are clones).
If a question mentions 'one parent' and 'genetically identical offspring', it is describing asexual reproduction.
Section 2
How Does Asexual Reproduction Compare with Sexual Reproduction?
| Feature | Asexual reproduction | Sexual reproduction |
|---|---|---|
| Number of parents | One | Two |
| Gametes/fertilisation | None | Fusion of nuclei of two gametes forms a zygote |
| Offspring genetics | Genetically identical to parent | Genetically different from each other and from parents |
| Cell division involved | Mitosis | Meiosis (to form gametes) then fertilisation |
Sexual reproduction is defined as a process involving the fusion of the nuclei of two gametes to form a zygote, producing offspring that are genetically different from each other.
Section 3
Where Is Asexual Reproduction Seen?
Examples of asexual reproduction include:
- Runners in plants such as strawberries, where a horizontal stem grows out and produces a new identical plant at its tip
- Bulbs, such as in daffodils, which grow into a new genetically identical plant
- Budding in yeast and Hydra, where a new individual grows out from the parent and detaches
- Binary fission in bacteria, where a single cell divides into two identical daughter cells
Questions may show a diagram or a description of an organism reproducing this way and ask you to identify the type of reproduction and justify your answer using the definition.
A strawberry plant sends out a runner along the ground; a new plantlet forms at a node on the runner. This plantlet is genetically identical to the parent — an example of asexual reproduction.
Section 4
What Are the Advantages and Disadvantages of Asexual Reproduction?
In the wild:
- Advantage: only one parent is needed, so reproduction is possible without finding a mate, and it can happen rapidly to colonise an area quickly
- Disadvantage: no genetic variation is produced, so a population may be unable to survive a change in the environment or a new disease
In crop production:
- Advantage: all offspring have the same desirable characteristics as the parent, so quality is guaranteed and reproduction is fast and cheap
- Disadvantage: a lack of variation means the whole crop is equally vulnerable to a disease or a change in conditions
Don't just say 'no variation is bad' — always link it to the specific consequence being asked about, e.g. vulnerability to disease or inability to adapt to environmental change.
Must Know
- Asexual reproduction: one parent, no gametes, genetically identical offspring (clones)
- Sexual reproduction: two parents, fusion of gametes, genetically different offspring
- Examples: runners (strawberry), bulbs (daffodil), budding (yeast, Hydra), binary fission (bacteria)
- Wild advantage: rapid reproduction without a mate; wild disadvantage: no variation to cope with change
- Crop advantage: guaranteed desirable characteristics; crop disadvantage: whole crop vulnerable to disease
That's the notes covered.
Carry on to the next subtopic.