Darwin and Natural Selection
The peppered moth, generation by generation.
To watch natural selection act on a population of peppered moths, Biston betularia, around Manchester before and after the industrial revolution.
Before 1850 the tree trunks near Manchester were covered in pale lichens. Then industrial soot killed the lichens and blackened the bark. The moths themselves were never touched.
Predict first
Soot has now blackened the tree trunks. Predict what happens to the moth population over the following generations.
Darwin observed four things: overproduction, a struggle for existence, variation between individuals, and survival of the fittest. This population shows all four — but notice that the variation comes FIRST, before the environment changes.
Free play — set the experiment up, choose its control, and commit to a prediction before anything is revealed. Switch to when you're ready to test yourself.
What this lesson covers
Predict first
Soot has now blackened the tree trunks. Predict what happens to the moth population over the following generations.
What you do
- Inspect a moth in the starting population, then keep inspecting it as generations pass. It never changes. That is the whole point.
Challenges to clear
- Predict what will happen before running a single generation.
- Run all six generations, then explain what actually happened.
The task
Before 1850 the tree trunks near Manchester were covered in pale lichens. Then industrial soot killed the lichens and blackened the bark. The moths themselves were never touched.
The experiment
To watch natural selection act on a population of peppered moths, Biston betularia, around Manchester before and after the industrial revolution.
Hint
Darwin observed four things: overproduction, a struggle for existence, variation between individuals, and survival of the fittest. This population shows all four — but notice that the variation comes FIRST, before the environment changes.