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In 1858, Charles Darwin and Alfred Russel Wallace, who had each worked out the idea on their own, presented the theory of evolution by natural selection. Darwin's book On the Origin of Species followed in 1859.

Natural selection needs three things. Inheritance: most features are passed from parents to offspring. Variation: offspring differ from each other. Competition: more young are born than can survive. So individuals whose features suit their surroundings are more likely to survive and have young.

Darwin noticed that the beaks of Galápagos finches match their food: seed-eaters have thick, strong beaks, insect-eaters have spear-like beaks.

Experiment: Beak tools: which beak suits which food?

1. Predict which beak will be best for each food.
2. Plan a fair test: what will you change, and what will you keep the same? (Change the beak; keep the same food tray, time and person.)
3. One pupil uses the clothes peg to move as many beans as possible into their cup in 20 seconds. Count them.
4. Repeat with the teaspoon and the tweezers, then with the other foods.
5. Do each test twice and record the mean.
6. Which beak is best for which food? What would happen to the birds with each beak if only one food were left?

Beak	Beans (mean)	Rice (mean)	Wool 'insects' (mean)
Clothes peg
Teaspoon
Tweezers

Questions

1. Draw a cartoon strip in four boxes showing what happened to the peppered moths near Manchester.

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2. Which beak tool was best for which food? How did you keep your test fair?

3. Explain in your own words how the 1977 drought changed the finches' bills.

4. Why do scientists say that populations evolve, not individuals?

Sources for every fact on this sheet: echoesof.science/school/evolution/sources/

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