Teacher sheet · Ages 10–11 · about 45–50 minutes
Natural selection
Lesson page: echoesof.science/school/evolution/ages-10-11/ · Pupil worksheet: echoesof.science/school/evolution/ages-10-11/print/
Learning aims
- Name the three ingredients of natural selection.
- Explain the finch and peppered moth examples.
- Give two kinds of evidence for evolution.
- Plan and carry out a fair test.
Lesson plan
| Time | Activity |
|---|---|
| 5 min | Starter: why do different birds have different beaks? |
| 10 min | Read the text; build a 'variation → competition → survival → inheritance' chain on the board. |
| 15 min | Beak tools. |
| 5 min | Play Variation, inheritance or selection? |
| 10 min | Quiz and discussion. |
Materials for the experiment
- Three 'beaks': a clothes peg, a teaspoon and a pair of plastic tweezers
- Three 'foods' in shallow trays: large dried beans, rice grains, and short pieces of wool or string in a tray of water ('insects')
- A cup for each 'bird' (its stomach)
- A stopwatch
Safety: Do not eat any of the food. Point tweezers away from faces. Wipe up spilt water and rice so nobody slips. Check for food allergies before using beans.
Common misconceptions
| Pupils may think… | Actually… |
|---|---|
| Animals change because they need to or want to. | Variation already exists; individuals that happen to suit the environment survive and reproduce more. |
| A finch's bill grew bigger during the drought. | Each bird kept its bill; the population changed because large-billed birds survived and had young. |
| 'Survival of the fittest' means the strongest. | It means the best suited to the environment, which may be the best hidden or the best at cracking seeds. |
Worksheet answers
- Box 1: light and dark moths on pale trees; box 2: soot darkens the trees; box 3: birds eat more light moths; box 4: almost all moths are dark (99 to 1 by 1898).
- Answers vary, for example the peg for beans, the spoon for rice, the tweezers for wool; fair: same tray, same time, same person, only the beak changed.
- Small, soft seeds became scarce; large-billed finches could eat the large, hard seeds and survived better; bill size is inherited, so their young had larger bills on average.
- An individual keeps its features all its life; what changes is how common each feature is in the population over generations.
Quiz answers
- Who presented the idea of natural selection together in 1858? Darwin and Wallace. Each had worked it out independently.[1]
- Which is NOT one of the three ingredients of natural selection? Animals deciding to change. Living things cannot choose to evolve; selection works on existing variation.[1]
- In the 1977 drought, which finches survived better? Those with large bills. Large bills could crack the large, hard seeds that were left.[2]
- Why did the next generation of finches have larger bills? Bill size is inherited. Surviving large-billed birds passed on their bill size.[2]
- Why did dark peppered moths become common near Manchester? Birds found the light moths more easily on sooty trees. Birds ate more of the light moths.[3]
- What do a human arm, a bird wing and a whale flipper share? The same bone layout. Homologous structures point to a common ancestor.[1]
Going further
Find out about another island animal and how its features suit its home. What might happen if its food changed?
Sources used in this lesson
- [1] Biology 2e, 18.1 Understanding Evolution (OpenStax (Rice University), open textbook): reliability High
- [2] Concepts of Biology, 11.1 Discovering How Populations Change (OpenStax (Rice University), open textbook): reliability High
- [3] Peppered moth (Encyclopaedia Britannica): reliability High
Full list with links and a note on each source's reliability: echoesof.science/school/evolution/sources/
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