The shape of the lesson
By the end of the lesson, learners can
- The pollen tube and fertilisation: Extended.
- Conditions for germination: Four tubes of seeds are set up, each missing one condition except the control A.
- Fertilisation: a pollen nucleus fuses with a nucleus in an ovule.
- Extended: pollen tube grows down the style, enters the ovule through the micropyle.
- Germination needs water, oxygen and a suitable temperature; not light.
- Experiments: remove one condition per tube; keep a control with all three.
One picture every idea returns to
Fertilisation occurs when a pollen nucleus fuses with a nucleus in an ovule. Extended: after pollination a pollen tube grows out of the pollen grain, down through the style to an ovule, and enters it through the micropyle, carrying the pollen nucleus. Seeds need water, oxygen and a suitable temperature to germinate.
Forty-five minutes, phase by phase
| Time | Phase | What happens in the room | Grouping |
|---|---|---|---|
| 0 to 5 min | Hook: predict | Open with the question in the title, From pollen grain to seedling.. Pollination only delivers the pollen to the stigma. Put the figure on the board: it is the one picture every idea in the lesson returns to. | Whole class, then pairs |
| 5 to 17 min | Teach and check: The pollen tube and fertilisation | Extended. Project tab 5 of the lab (The pollen tube and fertilisation) and let a student drive it while the class predicts. | Whole class, then pairs |
| 17 to 30 min | Teach and check: Conditions for germination | Four tubes of seeds are set up, each missing one condition except the control A. Project tab 6 of the lab (Conditions for germination) and let a student drive it while the class predicts. | Corners |
| 30 to 36 min | Check | The four Stage 1 questions from the student lesson, answered on mini whiteboards or by show of fingers. Re-teach the one most get wrong. | Individual, then whole class |
| 36 to 43 min | Plenary | The exam-style questions from Stage 2, one at a time: thirty seconds alone, then a random call. The feedback lines in the key give the examiner's wording. | Individual, random call |
| 43 to 45 min | Exit and homework | Set the worksheet below (6 questions, 18 marks). Learners self-assess against the objectives before they leave. | Individual |
Protect the parts that carry the learning
The sequence carries about fifty minutes of material, so the lab is driven by one student while the class predicts rather than explored freely. Times are a guide.
Protected: the check at 30 minutes. It is the only individual read on whether the key idea landed, and it is not cut.
Cut first if the build overruns: the last check in Conditions for germination, never the check or the plenary.
In a 60 minute block: run worksheet questions 1 to 3 in class as a Rally Coach set and model both the hardest worked example and its check live.
Corners
Put one answer or viewpoint in each corner of the room. Students move to the corner they agree with, justify the choice to a partner there, then hear one voice from each corner before the reveal.
The full structure, with its variations and the other twelve, is on the cooperative-learning page.
What to head off, and how
| Trap learners fall into | Teaching move that pre-empts it |
|---|---|
| Pollination and fertilisation are different events. | Pollination is pollen landing on the stigma; fertilisation happens later, inside the ovule, when the nuclei fuse. A pollen grain does not travel down the style: its tube grows down, carrying the nucleus. |
| Light is not one of the conditions needed for germination: the seed uses its food store, not photosynthesis. | Do not add light, carbon dioxide or soil to your list. |
Fertilisation and germination: worksheet
6 questions, 18 marks. Written in the style of the papers; no past paper question is reproduced.
State what is meant by fertilisation in a flowering plant and name the structure that develops into a seed.
Extended. Describe what happens after a pollen grain lands on the stigma, up to and including fertilisation.
Plan an experiment to show that seeds need oxygen to germinate. Include a control and how you would remove oxygen.
Seeds were kept on damp cotton wool at different temperatures for 5 days.
| Temperature / °C | 5 | 15 | 25 | 35 | 45 |
|---|---|---|---|---|---|
| Seeds germinated (out of 20) | 0 | 9 | 20 | 13 | 0 |
Describe and explain the results.
Explain why a seed needs water to germinate.
A student says that seeds need light to germinate. Describe how you could test this claim and the result you would expect.
Answer key and marking notes
- Fertilisation: a pollen nucleus (male gamete) fuses with a nucleus in an ovule (female gamete).
- The (fertilised) ovule develops into a seed.
- A pollen tube grows out of the pollen grain.
- It grows down through the style to the ovary, towards an ovule, carrying the pollen nucleus.
- It enters the ovule through the micropyle.
- The pollen nucleus fuses with the female nucleus in the ovule (fertilisation), forming a zygote.
- Set up two tubes, each with the same number and type of seeds on damp cotton wool, at the same temperature (e.g. 20 °C).
- Remove oxygen from one tube, for example by using boiled (cooled) water covered with oil, or by sealing it with a chemical that absorbs oxygen.
- The control tube has air (oxygen); keep water and temperature the same.
- Leave for several days and count how many seeds germinate in each tube.
- Germination increases from 5 to 25 °C (maximum, all 20) and then decreases, with none at 45 °C.
- At low temperature the enzymes in the seed work slowly (molecules have less kinetic energy), so few or no seeds germinate in 5 days.
- At high temperature the enzymes are denatured, so seeds cannot break down their food store and do not germinate.
- Water is absorbed so the seed swells and the seed coat splits.
- Water activates enzymes, which break down stored food (e.g. starch to sugar).
- The soluble products are transported to the growing embryo, which uses them for respiration and growth.
- Put seeds on damp cotton wool at the same suitable temperature, one tube in the light and one in a dark cupboard.
- Expected: seeds in both tubes germinate, showing light is not needed (the seed uses its food store, not photosynthesis).
8 multiple-choice questions on this lesson
From the topic question bank. Assign them in the app for a marked score in your gradebook, or run the topic as a class game.
Where does fertilisation take place in a flowering plant?
- AInside an ovule
- BOn the stigma
- CInside the anther
- DOn the petals
The table shows the results of a germination experiment. Which conclusion is fully supported by the results?
- ASeeds need water, air and a suitable temperature
- BSeeds need water and air but not warmth
- CSeeds need warmth and air but not water
- DSeeds need light, water and air
In a germination experiment, why is the water for the no-oxygen tube boiled and then covered with a layer of oil?
- ABoiling removes dissolved oxygen and oil stops it dissolving again
- BBoiling kills bacteria and oil keeps the seeds warm
- CBoiling softens the seed coat and oil feeds the seed
- DBoiling adds carbon dioxide and oil keeps out light
Why does a germinating seed need water?
- ATo activate enzymes that break down its food store
- BTo carry out photosynthesis in its first leaves
- CTo provide oxygen for respiration
- DTo keep the temperature of the seed constant
Seeds were placed on damp cotton wool at 5, 25 and 60 °C with air. Most germinated at 25 °C, none at 5 or 60 °C. Why did none germinate at 60 °C?
- ATheir enzymes were denatured
- BTheir enzymes worked too slowly
- CThere was no oxygen at 60 °C
- DThe water evaporated instantly
Extended: through which structure does the pollen tube grow on its way from the stigma to the ovary?
- Astyle
- Bfilament
- Csepal
- Danther
Extended: what does the pollen tube carry to the ovule?
- AThe pollen nucleus (male gamete)
- BSugar made in the anther
- CThe female nucleus
- DWater for the developing seed
Extended: a chemical stops pollen tubes growing but does not affect pollination. What would happen to a flower treated with it?
- APollen lands on the stigma, but no seeds form
- BNo pollen reaches the stigma, and no seeds form
- CSeeds form normally because pollination occurred
- DSeeds form but contain no female nucleus
Quiz key
Fertilisation happens when a pollen nucleus fuses with a nucleus in an ovule. The stigma is where pollen lands (pollination), the anther makes pollen and petals attract insects.
Only dish 1 (water, air, 25 °C) germinated; removing warmth (dish 2), water (dish 3) or air (dish 4) stopped germination. The other options ignore one of the failed dishes, and light was not tested.
Boiled water has had its dissolved oxygen driven off, and the oil layer stops oxygen from the air dissolving back in. The other reasons do not remove oxygen, and oil does not warm, feed or darken the seeds.
Water lets the seed swell and activates enzymes that digest stored food for growth. The seed does not photosynthesise until leaves appear; oxygen comes from air, not water; water is not needed to control temperature.
At 60 °C the enzymes in the seed are denatured, so stored food cannot be broken down. Enzymes working too slowly explains the result at 5 °C, not 60 °C; oxygen was present; the cotton wool was kept damp.
The pollen tube grows down through the style to the ovary. The filament supports the anther, the sepal protects the bud and the anther makes pollen; none links the stigma to the ovary.
The tube carries the pollen nucleus to the ovule, entering through the micropyle. It does not carry food or water for the seed, and the female nucleus is already inside the ovule.
Pollination still happens, but without a tube the pollen nucleus cannot reach the ovule, so there is no fertilisation and no seeds. Pollen still reaches the stigma; pollination alone does not make seeds; seeds do not form at all.
What to project
The student lesson embeds these tabs. Open them full screen on the projector; every slider has a drag handle on the stage.
Slides for this lesson
A projectable deck for every pack is on the way. Until then, present the student lesson full screen: its sections, figure and lab tabs follow the same order as the plan above.