Connect pollen-tube entry into an ovule with fertilisation
Put the transfer, tube and nuclear-fusion events in their correct order.
Section 16.3 · Sexual reproduction in plants
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
What follows tube entry in the required compatible sequence?
What you will learn
- Trace entry after growth through the style
- Name the fusion event after the male contribution reaches the ovule
Connect pollen-tube entry into an ovule with fertilisation
| Feature | Meaning |
|---|---|
| 1 · Sepals | Protect the developing bud |
| 2 · Petals | Can attract insect visitors |
| 3 · Anther | Produces pollen grains |
| 4 · Filament | Supports and positions anther |
| 5 · Stigma | Receives pollen |
| 6 · Style | Connection and pollen-tube route |
| 7 · Ovary | Contains ovules |
| 8 · Ovules | Contain female reproductive cells |
| 9 · Stamen | Complete anther + filament unit (3 + 4) |
| 10 · Carpel | Includes stigma, style and ovary (5 + 6 + 7) |
| Feature | Meaning |
|---|---|
| Pollination | Pollen transfer to stigma |
| Tube | Growth through style and entry into ovule |
| Fertilisation | Male and female reproductive nuclei fuse within ovule |
| Boundary | No complete life-cycle or endosperm-development claim |
Trace entry after growth through the style
The supplied compatible sequence begins with pollen transfer from anther to stigma. A tube grows from a grain through the style toward the ovary and enters an ovule. The male reproductive nucleus then reaches the female reproductive nucleus within the ovule. Entry and delivery connect the earlier surface transfer with the later internal fusion.
Fertilisation occurs when the pollen-derived male nucleus fuses with the female reproductive nucleus. The event is inside the ovule, which is enclosed by the ovary. Do not describe the stigma as the fusion site, the whole ovary as the female nucleus, or entry of a tube alone as proof that fusion has already occurred.
Name the fusion event after the male contribution reaches the ovule
The original diagram enlarges the ovule and nuclei conceptually and uses a stated sequence, not a photograph of every event. It shows one target ovule for clarity. It does not mean all the ovules in every flower have received tubes or completed fertilisation. The route can be discussed conditionally when the evidence records only an earlier stage.
Keep the syllabus boundary explicit: describe pollen-tube growth, entry into an ovule and subsequent fertilisation. Details of endosperm production and development are not required for this lesson and are not inferred from the model. Germination investigations concern later seeds under water, oxygen and suitable-temperature conditions; they are not a substitute for showing the preceding nuclear-fusion event.
Pause and explain
Does a diagram of one target ovule establish successful fusion in every ovule?
Worked example
Order these events: nuclear fusion in ovule; tube through style; anther-to-stigma transfer; tube enters ovule.
Show the worked solution
- Surface transfer comes first, followed by tube growth.
- Ovule entry precedes the supplied fusion event.
Answer Transfer → tube through style → entry into ovule → nuclear fusion.
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.
Put the four required route events in order and locate the final event.
Give me a hint
Begin with surface pollen transfer.
Compare my reasoning
- Pollination precedes tube growth through style.
- Entry into an ovule precedes fusion there.
Anther-to-stigma pollen transfer → tube growth through style → entry into an ovule → male and female nuclear fusion within the ovule.
Look for these in your work
- Order all four events
- Locate fusion within the ovule
Explain why a tube touching or entering an ovule does not alone prove completed fertilisation.
Give me a hint
Entry and fusion are separate stages.
Compare my reasoning
- Entry supplies the route for the male contribution.
- The later fusion must still occur and needs its own evidence.
Tube entry is a route stage; fertilisation requires actual fusion of the pollen-derived male nucleus with the female nucleus inside that ovule.
Look for these in your work
- Distinguish entry from fusion
- Name the required fusion event
A learner adds guaranteed fertilisation of every ovule and complete endosperm development to the diagram’s claim. What should be corrected?
Give me a hint
Check both the model scope and syllabus boundary.
Compare my reasoning
- Only one compatible teaching sequence is shown.
- Endosperm production and development details are outside this requirement.
The model does not establish outcomes for every ovule. It teaches tube growth, ovule entry and subsequent nuclear fusion; endosperm detail is not required or verified by this diagram.
Look for these in your work
- Retain the one-sequence limit
- State the endosperm scope boundary
Common mistakes
- Calling tube entry alone completed nuclear fusion.
- Claiming a model of one ovule proves all ovules are fertilised.
What can you explain now?
Does a diagram of one target ovule establish successful fusion in every ovule?
Compare with the explanation
No; its scope is the one stated teaching sequence
Other ovules and actual outcomes need evidence.
After trying it yourself, choose your next review. This is your self-assessment.
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Make it stick
Trace the complete required sequence and keep tube entry distinct from nuclear fusion.
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.