We had a science simulation today about the peppered moth. It was a good way to study genetics, use Punnett squares, and learn about natural selection due to environmental changes.
First, students were given a moth showing a light or dark phenotype. The genotype for the wing color allele was written on the back.
They matched two moths together and used Punnett squares to show the possible offspring if those two genotypes reproduced.
Each generation of offspring would be placed on a light-colored background. A small proportion of moths had dark wings, the recessive gene. This dominance of the lighter wings stayed, as long as the lichen protected these moths from predators.
However, when the Industrial Revolution began polluting cities in Britain, the light-colored lichen died. The soot on the buildings and the lack of lichen cover began to give the dark moths an advantage, and they were then more protected from their predators.
Students swooped in (as birds) and picked off some of the moths. On the darker background, the lighter moths were easier to see. By the next generation, more of the moths were dark. Eventually, the dark wings became dominant in the polluted cities of Industrial Britain and in our simulation.
If you have Flash, you can do an online simulation about the peppered moth.
Today, the gathering of samples is much more accurate than it was a hundred years ago, but the conclusions seem to agree that the change in color is an example of natural selection. Now that air pollution is less prevalent, there has again been a rise in lighter-colored peppered moths in urban areas in Britain.
Peppered Moths PDF used above.