Krebs' Class Blogs

Genetics Simulation for Friday

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.

Here is a very short clip showing the peppered moth in its natural protective lichen surroundings.
ARKive video - Peppered moth camouflaged on lichen

Here is a clip of the darker form of the peppered moth.
ARKive video - Peppered moth

First, students were given a moth showing a light or dark phenotype. The genotype for the wing color allele was written on the back.

Genetic info (genotype) on back. Physical info (phenotype) on front in picture of moth.

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.

Do you have any more information about the peppered moth that we should know?