Discuss potential variation after self and cross pollination
Connect successful sexual contributions with population variation without calling selfed offspring clones.
Exam scope and assessment notes
Extended only (Supplement) · Biology 0970, 2026–2028. Use the stated specimen features and evidence. Diagrams are schematic. Written practice is self-checked; human subject-teacher review, supervised practical competence and cumulative assessment remain pending. Cambridge states that IGCSE 0970 has the same subject content as IGCSE 0610, with 9–1 grading. This StudyForA pathway maps the 2026–2028 syllabus only. This 9–1 graded qualification is available only in a limited number of administrative zones. Confirm that your centre can enter you for this code and exam series with Cambridge International. Cambridge has published a separate syllabus for 2029. StudyForA has not reconciled that version yet; this page supports exams in 2026, 2027 and 2028 only.
Before you begin
- Recall gametes, nuclear fusion, cellular respiration and the distinction between reproduction and growth.
Work on paper. Try each question before revealing help, and explain why your method works.
Quick readiness check
Which statement is appropriately qualified?
What you will learn
- Distinguish pollen routes from genetic outcomes
- Explain potential variation using conditional contributions
Discuss potential variation after self and cross pollination
| Feature | Meaning |
|---|---|
| Selfing | Less opportunity for mixing between plants |
| Crossing | Can mix different same-species contributions |
| Not guaranteed | All selfed offspring identical; all crossed offspring superior |
| Evidence limit | Transfer records alone do not measure population variation |
Distinguish pollen routes from genetic outcomes
Discuss genetic effects only after recognising that pollination is a transfer event. Potential offspring variation concerns successful fertilisation and inheritance that follow under suitable conditions. A pollen-transfer arrow alone does not establish the genotype of an offspring or the degree of variation across a whole population.
Self-pollination can lead to fertilisation using reproductive contributions from the same plant. This limits the opportunity to mix contributions from different plants, and repeated selfing can reduce genetic variation within lineages. It is nevertheless sexual reproduction: gamete formation and fusion mean offspring are not automatically genetically identical clones. A parent can carry different inherited variants, so selfed offspring can differ.
Explain potential variation using conditional contributions
Cross-pollination can combine reproductive contributions from different plants of the same species. Where those contributions differ genetically, it can introduce or maintain more variation in the resulting population than repeated selfing. The potential benefit is conditional: two different plants may be genetically identical, and cross-pollination does not make every offspring possess every useful trait.
Avoid absolute claims that all selfed offspring are identical or all crossed offspring are superior. The population outcome depends on the parental contributions and subsequent reproductive success. The model compares potential opportunities for genetic mixing; it is not a measured allele-frequency survey, a guarantee of heterozygosity or a complete inheritance unit.
Pause and explain
Why can selfed offspring still vary?
Worked example
Why can cross-pollination increase opportunities for genetic mixing?
Show the worked solution
- The contributions come from different same-species plants.
- They may carry different inherited variants.
Answer It can combine genetically different reproductive contributions from different plants.
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Write your answer and reasoning first. Use a hint only if you are stuck. The model solution is for self-checking; your written work is not automatically marked.
Explain a potential variation disadvantage of repeated self-pollination compared with cross-pollination.
Give me a hint
Focus on mixing between plants.
Compare my reasoning
- Selfing uses contributions from one plant.
- Crossing can introduce genetically different contributions from another.
Repeated selfing limits mixing between plants and can reduce lineage variation; crossing can mix differing contributions from different plants.
Look for these in your work
- Explain the same-plant limitation
- Retain the conditional cross benefit
Correct “every selfed seed is a clone of its parent.”
Give me a hint
Self-fertilisation still uses a sexual pathway.
Compare my reasoning
- Gametes are formed and their nuclei fuse.
- Inherited variants can differ among offspring.
Selfed offspring are not automatically clones: successful self-fertilisation is sexual and can yield different inherited combinations.
Look for these in your work
- Correct the cloning claim
- Connect variation with the sexual pathway
Two separate same-species plants are genetically identical. Does cross-pollination guarantee more inherited variation than selfing?
Give me a hint
Physical identity does not establish genetic difference.
Compare my reasoning
- The route qualifies as cross-pollination.
- The assumed genetic difference is absent.
No. It is cross-pollination by plant identity, but an increase from mixing genetically different contributions is not guaranteed when those plants are genetically identical.
Look for these in your work
- Keep the correct route definition
- Qualify the genetic outcome
Common mistakes
- Calling all selfed offspring clones.
- Guaranteeing variation from any two separate plants.
What can you explain now?
Why can selfed offspring still vary?
Compare with the explanation
The sexual contributions may carry different inherited variants
Selfing does not make gamete formation and fusion copying.
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Make it stick
Discuss potential variation effects without equating selfing with cloning.
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