A flower is a reproductive organ. Its male parts make pollen, its female parts hold the ovules, and the whole design is about moving pollen from one to the other. Insect-pollinated and wind-pollinated flowers solve that problem in very different ways. Self- and cross-pollination and their effects on a population are Extended content.
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.
In the lab one petal is removed and the ovary is see-through. Click each part, or pick it from the list, and read its function. Notice which parts are grouped into the stamen and the carpel.
| Part | Function |
|---|---|
| Sepals | protect the flower while it is a bud |
| Petals | large and brightly coloured, often scented, to attract insects |
| Stamen: anther | makes and releases pollen grains, which contain the male gametes |
| Stamen: filament | stalk that holds up the anther |
| Carpel: stigma | sticky surface that catches pollen grains |
| Carpel: style | holds up the stigma; the pollen tube grows down through it |
| Carpel: ovary | contains the ovules; develops into the fruit after fertilisation |
| Ovules | contain the female gametes; each develops into a seed after fertilisation |
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".
Compare the two flowers in the lab, then press Blow the wind and watch pollen stream from the dangling anthers of the grass. Switch to pollen grains to see them much magnified.
| Feature | Insect-pollinated | Wind-pollinated (e.g. grass) |
|---|---|---|
| Petals | large, coloured, scented; nectar | small, green or absent; no scent or nectar |
| Anthers | inside the flower, where insects brush them | hang outside on long filaments, shaken by the wind |
| Stigmas | inside the flower, sticky | outside, large and feathery, to trap pollen from the air |
| Pollen grains | larger, sticky or spiky, to cling to insects; fewer made | small, smooth and light, carried far; huge numbers made |
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.
Four quick checks. Each correct answer earns XP and records this skill on your profile.
In the flower tab, which part makes and releases pollen grains?
According to the lab, what does the ovary develop into after fertilisation?
When you blow the wind in the lab, where does the pollen come from?
Extended: in the self-pollination run, where does the bee take the pollen?
Extended. Choose a mode in the lab and press Send the bee. Watch where the bee carries pollen, then look at the eight offspring and the offspring variation reading: little for self-pollination, a lot for cross-pollination.
| Effect on the population | Self-pollination | Cross-pollination |
|---|---|---|
| Variation | less variation in the offspring | more variation |
| Response to environmental change | less able to respond (fewer individuals may be suited to new conditions) | more able to respond; more likely that some survive and the population adapts |
| Reliance on pollinators | low; seeds can still form if pollinators are scarce | high; relies on insects (or wind) to reach another plant |
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.
Unlocks once the four checks above are done. Worth more XP, written to IGCSE Paper 2 and Paper 4 standard.
Which describes pollination?
Which feature is typical of a wind-pollinated flower?
Which parts together form the carpel?
Extended: a plant species can only be cross-pollinated. What is the main risk if its pollinating insect dies out?
This skill is now recorded on your profile. Keep the chain going.