Locate fertilisation inside an ovule
Distinguish the transferred pollen grain from the male nucleus involved in fusion.
Cross-referenced to the 2028–2029 0653 section using original teaching from the related single-science courses. A 0653-specific objective-by-objective and Core/Supplement review is in progress. Written practice is self-checked and does not demonstrate supervised laboratory competence or award an official Cambridge grade.
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 location contains the female nucleus for this fusion?
What you will learn
- Name the two reproductive nuclei
- Locate their fusion within the ovule
Locate fertilisation inside an ovule
| Feature | Meaning |
|---|---|
| Male contribution | Nucleus derived from pollen |
| Female contribution | Reproductive nucleus in an ovule |
| Event | Fusion of the two nuclei |
| Location | Within an ovule, not on the stigma |
Name the two reproductive nuclei
In flowering plants, fertilisation involves fusion of a male nucleus from pollen with a female reproductive nucleus in an ovule. The ovule lies inside the ovary. Use that nested location carefully: the whole ovary is an organ containing ovules, rather than one enormous female cell, and the stigma is a receiving surface rather than the site of the required nuclear fusion.
The pollen grain transferred during pollination is not itself the female reproductive structure. A male reproductive nucleus derived from pollen reaches the female nucleus through the later reproductive route. Extended lessons follow pollen-tube growth and entry in detail; this Core lesson establishes the identities and the location of the fusion event.
Locate their fusion within the ovule
Pollination and fertilisation are linked but different. Pollen may be transferred to a stigma without subsequent successful fusion, for example when later conditions do not permit the route to complete. Conversely, the definition of fertilisation should state nuclear fusion rather than only the arrival of pollen on the flower. An observed pollen grain on a stigma records a possible early step, not the required internal event.
Use the original enlarged diagram as a conceptual model. Its circles represent the two named nuclei before fusion and the resulting combined nucleus; they are not photographs, measurements or claims that every ovule has been fertilised. The objective is to connect pollen-derived male contribution, female nucleus in the ovule and nuclear fusion without substituting whole organs or surface contact.
Sources for this lesson
Pause and explain
Does a grain on a stigma prove this internal fusion?
Worked example
A diagram shows a pollen-derived male nucleus fusing with a female nucleus inside an ovule. Name the event.
Show the worked solution
- The two reproductive nuclei fuse.
- That event is fertilisation.
Answer Fertilisation within the ovule.
Try a topic test
Choose Easy, Normal or Difficult. Save your answers and open worked review after finishing.
Test this topic →From guided practice to a new situation
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.
Define fertilisation in a flowering plant, including the origins of the nuclei.
Give me a hint
Name the pollen-derived male contribution and ovule location.
Compare my reasoning
- The male reproductive nucleus comes from pollen.
- It fuses with the female reproductive nucleus in an ovule.
Fusion of a male nucleus from pollen with a female reproductive nucleus in an ovule.
Look for these in your work
- State nuclear fusion
- Identify both contributions and location
Correct “the entire ovary fuses with the whole pollen grain on the stigma.”
Give me a hint
Separate organs, grains and nuclei.
Compare my reasoning
- The ovary contains ovules.
- The fusion involves a pollen-derived male nucleus and a female nucleus in an ovule.
Fertilisation is nuclear fusion within an ovule; it does not fuse the whole ovary with a whole grain on the stigma.
Look for these in your work
- Correct the scale of the event
- Locate fusion inside an ovule
A source records anther-to-stigma pollen transfer but gives no internal reproductive observations. Which event is established and which remains unproven?
Give me a hint
Use the evidence for each stage separately.
Compare my reasoning
- The complete pollen-transfer route establishes pollination.
- The source does not establish nuclear fusion.
Pollination is established; fertilisation remains unproven by that record.
Look for these in your work
- Name the established event
- State the missing internal event
Common mistakes
- Describing fusion of the whole anther and ovary.
- Locating fertilisation on a petal or stigma.
What can you explain now?
Does a grain on a stigma prove this internal fusion?
Compare with the explanation
No; pollination and fertilisation are different events
The later nuclear event needs separate evidence.
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Make it stick
Define and locate fertilisation without confusing nuclei, grains or whole organs.
If you needed the solution, close it and solve the problem again from a blank page. A correct answer is stronger when you can explain the reason for each step.