Pollination Virtual Lab: Flower Tubes, Pollinators and Seeds

This pollination virtual lab turns the pollination-syndrome investigation of NGSS middle-school life science and KS3 biology into a one-lesson fair test. Students keep a red, scentless, nectar-rich flower the same and change one structure, the corolla tube, from 5 mm to 25 mm. They record the visitors, visits per day and seed set. The data show that visits and successful reproduction differ, leading into coevolution. Every value below was read from the simulation.

Curriculum links

• NGSS MS-LS1-4: how specialized plant structures affect the probability of successful reproduction.
• NGSS HS-LS4-4: natural selection leads to adaptation (the coevolution extension).
• England KS3 Science: reproduction in plants, including flower structure and insect pollination.
• Cambridge IGCSE Biology (0610): sexual reproduction in plants, insect-pollinated flowers.

Simulic is not affiliated with or endorsed by NGSS, the Department for Education or Cambridge International.

Before the lab (5 min)

Ask students to commit to a prediction, on paper or as question 1 of the class link:

"A red, scentless flower with plenty of nectar. Its corolla tube gets longer, from 5 mm to 25 mm. What happens to the number of pollinator visits?"

Many students expect a longer tube to attract more animals.

Method in the simulation

1. On the Flowers and pollinators tab (it opens first), set Flower colour Red, Scent No scent and Nectar per flower 10 µL. Keep Flowers open By day and Breeding system Outcrossing only (self-incompatible).
2. Set Corolla tube length to 5 mm. Record the visits: …% label under Bee, Butterfly and Hummingbird: the chance that one passing animal visits.
3. Press Run 10 days (mean). From the new row of the Results table, record Visits (per day) and Seed set.
4. Repeat steps 2–3 for 10, 15, 20 and 25 mm.
5. Calculate the percentage decrease in the hummingbird's visit chance from 15 mm to 25 mm.

Tube (mm)	Bee (%)	Butterfly (%)	Hummingbird (%)	Visits per day	Seed set (%)
5
10
15
20
25

Expected results

The visit chances are fixed by the flower's design. Visits and seed set are random: the table gives our run, then the middle 99% of 5,000 runs of the sim's model.

Tube (mm)	Bee	Butterfly	Hummingbird	Visits per day	Seed set
5	5%	42%	62%	53.8 (45–62)	10% (7–14)
10	3%	40%	62%	41.1 (41–57)	8% (7–13)
15	2%	21%	62%	40.3 (31–46)	11% (9–14)
20	2%	1%	49%	20.8 (18–30)	8% (7–13)
25	2%	0%	7%	5.1 (3–11)	3% (2–6)

• Visits fall as the tube passes each tongue length: butterflies (about 15 mm) drop out between 10 and 20 mm, hummingbirds (bill about 22 mm) between 20 and 25 mm.
• Seed set does not follow visits. From 5 to 20 mm, visits roughly halve but seed set stays near 10%. On a short tube, butterflies and hummingbirds touch little pollen. At 20 mm the tube fits the hummingbird's bill, so its head presses on the anthers and stigma and each visit moves more pollen.
• At 25 mm even hummingbirds rarely feed, and seed set falls to about 3%.

Questions for students

1. (Prediction, asked again after the lab) What happens to visits as the corolla tube gets longer?
2. Which variable must stay the same in this investigation?
3. What is the seed set at a 20 mm tube?
4. By what percentage does the hummingbird's visit chance fall from 15 mm to 25 mm?
5. Explain why seed set stays steady from 5 to 20 mm but collapses at 25 mm.

Answers for teachers: (1) Visits fall, until almost none at 25 mm. (2) Nectar per flower (also colour, scent, opening time). (3) Accept 6–15% (8% in our run). (4) Accept 86–91%: (62 − 7) ÷ 62 × 100 = 89%. (5) Butterflies stop visiting a 20 mm tube, but they moved little pollen; the hummingbird still feeds and, pressed against anthers and stigma, moves more pollen per visit. At 25 mm the tube is longer than its bill.

Common misconceptions

• "More visits means more seeds." What counts is pollen moved to stigmas of the same species.
• "Bees pollinate every flower." Here the bee's visit chance is only 2–5%. Switch to Blue-violet at 5 mm and it jumps to 52%: our run gave 105 visits per day, 84 by bees, and 60% seed set.
• "The flower grows a long tube to choose its pollinator." Plants don't choose. Flowers whose shape fits a pollinator set more seed, so the trait spreads.

Extension

• Coevolution tab: keep Flower tube – moth tongue, h² 0.50 and cost 0.20, and press +10 generations five times. Both means rose from 10 and 8 mm to about 27 mm by generation 50, and 36.5 mm by generation 100.
• Breeding system at 25 mm: choose Self-pollinates if visitors are scarce. Seed set jumped from about 4% to 49% in our model runs, but selfed seedlings survive half as well. Why does outcrossing still pay?

FAQ

Why do my students get different visits and seed set?

Each passing animal visits by chance, and no setting repeats a run; the visit chance labels never change. The range for question 3 held in all 20,000 model runs we tried.

Can I set the flower up for my students?

Yes. In the class link's starting values, set Flower colour Red, Scent No scent and Nectar per flower 10. Students then change only Corolla tube length.

Does this replace looking at real flowers?

No. Pair it with a dissection or the seed germination virtual lab, whose simulation dissects insect- and wind-pollinated flowers.

Related simulations and guides

Flowering plant reproduction lab – dissection, pollination, dispersal and germination Natural selection – rabbit population, mutations, wolves and food

For selection over generations, see the selective breeding virtual lab.