Teacher sheet · Ages 15–16 · about 45–50 minutes
Camouflage and natural selection
Lesson page: echoesof.science/school/camouflage/ages-15-16/ · Pupil worksheet: echoesof.science/school/camouflage/ages-15-16/print/
Learning aims
- Explain how predation by sight-hunting predators can drive natural selection for camouflage.
- Describe evidence from field experiments with artificial prey (peppered moth models, countershaded caterpillars).
- Distinguish colour change within a lifetime (chromatophores, moult) from evolution over generations.
- Calculate proportions and differences from predation data and discuss sample size and uncertainty.
Lesson plan
| Time | Activity |
|---|---|
| 5 min | Starter: peppered moth photos on lichen and on soot-covered bark. |
| 10 min | Read and discuss the text; draw the natural selection chain. |
| 20 min | Paper moth predation experiment; pool class data. |
| 5 min | Calculations and uncertainty discussion. |
| 5 min | One life or many generations? game and quiz. |
Materials for the experiment
- White paper and old newspaper
- Scissors
- Sticky tack
- Two large boards or sheets: one covered with newspaper, one plain white
- Stopwatch
- Calculator
Safety: Use scissors carefully. Predators remove moths with their fingers only, no pins. Keep the boards flat on a table so nothing falls.
Common misconceptions
| Pupils may think… | Actually… |
|---|---|
| The moths turned dark because the soot coloured them. | The dark form already existed; dark moths were eaten less on sooty bark, so more of them survived to breed. |
| Individual animals evolve. | Individuals can change colour (octopus, hare) but evolution is a change in a population over generations. |
| A 21% higher survival means 21 out of 100 more moths survive. | Without the full paper we do not know whether the figure is a relative or an absolute difference; always check how a percentage was calculated. |
| If camouflage fails, the animal will simply change its behaviour. | The USGS hare study found that mismatched hares did not readily change how they hid or fled. |
Worksheet answers
- 1) Moths vary in colour and the colour is inherited. 2) On dark bark, birds find pale moths more easily. 3) Dark moths survive and reproduce more often. 4) Over generations the dark form becomes more common.
- White: 15/50 = 0.30 (30%); newspaper: 40/50 = 0.80 (80%); difference = 80% − 30% = 50 percentage points in favour of the newspaper moths, which match the background.
- Any two: small sample; children are not birds and do not see ultraviolet; predators learn where moths are; boards differ from real bark; only a few repeats.
- Its coat turns white because of day length, not snow; if the snow arrives later or melts earlier, the white hare stands out on brown ground and predators catch more hares.
Quiz answers
- Why did dark peppered moths become common during the Industrial Revolution? Soot darkened the bark and lichen died, so dark moths were better hidden from birds. Birds found the pale moths more easily on dark bark.[4]
- In the 2018 study, why did researchers model bird vision? Birds, the moths' predators, can see ultraviolet light that humans cannot. Camouflage has to work against the predator's eyes, not ours.[4]
- What did the countershading experiment with paper caterpillars find? The best shading pattern depends on the lighting. A sharp change worked best in sun, a smooth one in shade.[3]
- What triggers the snowshoe hare's colour moult? Day length. That is why shorter snow seasons cause a mismatch.[7][6]
- How does a chromatophore change the colour of a squid's skin? Muscles controlled by nerves expand or contract an elastic sac of pigment. Expanding the sac shows more pigment.[5]
- Which change happens over generations rather than within one animal's life? The rise of the dark peppered moth form. The moth change is evolution by natural selection.[4][5][6]
Going further
Plot the class data as a bar chart with the range (lowest to highest predator) shown as error bars. Then read how the 2018 peppered moth study used museum specimens and bird-vision models, and discuss why modelling the predator's eyes matters.
Sources used in this lesson
- [3] Optimizing countershading camouflage (press release) (University of Bristol (news, 31 October 2016; paper in PNAS)): reliability High
- [4] Study confirms truth behind 'Darwin's moth' (University of Exeter (news, 17 August 2018; paper in Communications Biology)): reliability High
- [5] How octopuses and squids change color (Smithsonian Ocean (Smithsonian Institution)): reliability High
- [6] Snowshoe hare (U.S. National Park Service (Rocky Mountain National Park)): reliability High
- [7] Can camouflage keep up with climate change? Connecting climate projections to adaptation for the snowshoe hare (U.S. Geological Survey (Climate Adaptation Science Centers)): reliability High
Full list with links and a note on each source's reliability: echoesof.science/school/camouflage/sources/
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