The shape of the lesson
By the end of the lesson, learners can
- Parts of an insect-pollinated flower: In the lab one petal is removed and the ovary is see-through.
- Insect or wind?: Compare the two flowers in the lab, then press Blow the wind and watch pollen stream from the dangling anthers of the grass.
- Self- or cross-pollination: Extended.
- Stamen = anther + filament; carpel = stigma + style + ovary (with ovules).
- Pollination: pollen grains from an anther to a stigma.
- Insect: showy petals, scent, nectar, sticky stigma inside, larger sticky pollen. Wind: dangling anthers, feathery stigmas, small light pollen.
- Extended: self = same flower or same plant; cross = different plant, same species.
One picture every idea returns to
Pollination is the transfer of pollen grains from an anther to a stigma. Insect-pollinated flowers have large, coloured, scented petals and nectar, with anthers and a sticky stigma inside the flower; wind-pollinated flowers have small or no petals, anthers hanging outside on long filaments and large feathery stigmas. Extended: self-pollination moves pollen to a stigma on the same plant; cross-pollination moves it to a flower on a different plant of the same species.
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, Getting pollen from anther to stigma.. A flower is a reproductive organ. Put the figure on the board: it is the one picture every idea in the lesson returns to. | Whole class, then pairs |
| 5 to 13 min | Teach and check: Parts of an insect-pollinated flower | In the lab one petal is removed and the ovary is see-through. Project tab 2 of the lab (An insect-pollinated flower) and let a student drive it while the class predicts. | Whole class, then pairs |
| 13 to 21 min | Teach and check: Insect or wind? | Compare the two flowers in the lab, then press Blow the wind and watch pollen stream from the dangling anthers of the grass. Project tab 3 of the lab (Insect-pollinated and wind-pollinated flowers) and let a student drive it while the class predicts. | Pairs |
| 21 to 30 min | Teach and check: Self- or cross-pollination | Extended. Project tab 4 of the lab (Self- and cross-pollination) and let a student drive it while the class predicts. | Jigsaw |
| 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, 20 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 Self- or cross-pollination, 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.
Jigsaw
Split the content into expert pieces. Expert groups master one piece each, then regroup so every home team has one expert per piece, and each expert teaches their piece to the team.
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 |
|---|---|
| The stamen is the anther and filament together; the carpel is the stigma, style and ovary together. | Do not label the whole carpel as the "ovary" or the anther as the "stamen". |
| A wind-pollinated flower has large feathery stigmas but small pollen grains. | Students often swap these. A large surface catches pollen; small light grains travel far. |
| Two flowers on the same plant count as self-pollination, even though pollen has moved between flowers. | Cross-pollination needs a different plant of the same species. |
Flowers and pollination: worksheet
6 questions, 20 marks. Written in the style of the papers; no past paper question is reproduced.
State the function of each part of an insect-pollinated flower: (a) sepal, (b) anther, (c) stigma, (d) ovule.
Describe three ways in which the structure of a wind-pollinated grass flower differs from an insect-pollinated flower, and explain one of them.
Pollen grains from a wind-pollinated flower are small, smooth and light, and are produced in huge numbers. Explain why each feature is useful.
Define pollination.
Extended. Distinguish between self-pollination and cross-pollination, and describe the effect of each on variation in the population.
Extended. A population of wild plants is mostly self-pollinated. Discuss how this might affect the population if (a) pollinating insects become rare, and (b) the climate becomes much drier.
Answer key and marking notes
- (a) Sepal: protects the flower when it is a bud.
- (b) Anther: makes and releases pollen (containing male gametes).
- (c) Stigma: sticky surface that receives / catches pollen.
- (d) Ovule: contains the female gamete; becomes a seed after fertilisation.
- Grass has small, green petals (or none) with no scent and no nectar; insect flowers have large, coloured, scented petals and nectar.
- Grass anthers hang outside the flower on long filaments; insect flower anthers are inside.
- Grass stigmas are large and feathery and outside the flower; insect flower stigmas are inside and sticky.
- Explanation, e.g.: feathery stigmas have a large surface area to trap pollen grains carried in the air (or: hanging anthers let the wind shake pollen out).
- Small and light: carried easily and far by the wind.
- Smooth: does not need to cling to an insect, and does not clump together.
- Huge numbers: most pollen is lost because the wind blows in random directions, so many grains increase the chance that some reach a stigma.
The transfer of pollen grains from an anther to a stigma.
- Self-pollination: pollen from an anther reaches the stigma of the same flower or another flower on the same plant.
- Cross-pollination: pollen reaches the stigma of a flower on a different plant of the same species.
- Self-pollination produces offspring with less variation.
- Cross-pollination produces offspring with more variation.
- (a) Self-pollinated plants do not rely on pollinators, so they can still make seeds; the population is not badly affected.
- (A cross-pollinated population would make fewer seeds without insects.)
- (b) Self-pollination gives little variation, so few or no individuals may be suited to the drier conditions.
- The population is less able to respond to the change and could decline or die out.
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.
The diagram shows a half-flower. Which letter labels the part that catches pollen grains?
- AB
- BA
- CC
- DD
Which two parts together make up a stamen?
- Aanther and filament
- Bstigma and style
- Covary and ovule
- Dpetal and sepal
What is the function of the sepals?
- ATo protect the flower while it is a bud
- BTo attract insects with bright colours
- CTo make sugary nectar for insects
- DTo hold up the anthers
A flower has small green petals, no scent, anthers hanging outside on long filaments and large feathery stigmas. How is it pollinated?
- ABy the wind
- BBy insects
- CBy self-pollination only
- DBy birds feeding on nectar
A student compares pollen from two flowers under a microscope. Pollen X is 25 μm across, smooth and dry. Pollen Y is 90 μm across and covered in spikes. Which conclusion is best?
- AX is from a wind-pollinated flower; Y is from an insect-pollinated flower
- BX is from an insect-pollinated flower; Y is from a wind-pollinated flower
- CBoth are from wind-pollinated flowers
- DBoth are from insect-pollinated flowers
Extended: pollen is carried from the anther of a flower to the stigma of another flower on the same plant. What is this called?
- Aself-pollination
- Bcross-pollination
- Cfertilisation
- Dasexual reproduction
Extended: a crop variety is grown that can only be cross-pollinated. Which is the most likely effect on the crop population compared with a self-pollinating variety?
- AMore variation, but seed set depends on pollinators
- BLess variation, and no need for pollinators
- CMore variation, and no need for pollinators
- DLess variation, but seed set depends on pollinators
Extended: some plants have anthers that ripen and release pollen before the stigma of the same flower is ready. What is the effect of this?
- AIt encourages cross-pollination
- BIt ensures self-pollination
- CIt stops pollination completely
- DIt makes the pollen grains smaller
Quiz key
B is the stigma, at the top of the style, which catches pollen. A is an anther (makes pollen), C is the ovary (contains ovules) and D is a sepal (protects the bud).
The stamen is the anther (makes pollen) on its filament (stalk). Stigma, style and ovary form the carpel; the ovule is inside the ovary; petals and sepals are not reproductive parts.
Sepals enclose and protect the flower bud. Attracting insects is the role of the petals, nectar comes from nectaries, and filaments hold up the anthers.
Dangling anthers and feathery stigmas are adaptations for wind pollination. Insect and bird pollinated flowers have showy petals, scent or nectar; feathery stigmas trap pollen from the air, which suits wind, not self-pollination only.
Small, smooth, light pollen is carried by the wind; larger spiky pollen catches on the hairs of insects. The second option reverses them, and the two pollen types are clearly adapted for different methods.
Pollen moving to a flower on the same plant is self-pollination. Cross-pollination needs a different plant of the same species; fertilisation is fusion of nuclei; pollination is part of sexual, not asexual, reproduction.
Cross-pollination mixes genes from different plants (more variation) but relies on insects or wind to reach another plant. Self-pollination gives less variation and relies less on pollinators; the other combinations mix the two up.
The flower's own pollen has gone before its stigma is ready, so its stigma receives pollen from other plants: cross-pollination is favoured. It prevents (not ensures) self-pollination of that flower, pollination still happens, and timing does not change pollen size.
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.