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PEPPERED MOTH AND NATURAL SELECTION adapted from http://www.mothscount.org/text/63/peppered_moth_and_natural_selection.html The Peppered Moth is widespread in Britain and Ireland and frequently found in ordinary back gardens, yet its amazing story has made it famous all over the world. It is one of the best known examples of evolution by natural selection, Darwin's great discovery, and is often referred to as 'Darwin's moth'. lichen on a tree The Peppered Moth is normally white with black speckles across the wings. It looks as if it has been “peppered,” giving it its name. Its ideal environment has many trees covered by lichens. (lichens are the moss-like dry fungi that grows on rocks and trees.) The moth’s patterning makes it well camouflaged against lichencovered tree trunks when it rests on them during the day. Predators cannot see them easily (as you can see in the picture to the left). In the moth species, however there is also a naturally-occurring genetic mutation which causes some moths to have almost moth on lichen (on tree) black wings. These black forms (called 'melanic') are not as well camouflaged on the lichen as their relatives (the 'peppered' forms). They are more likely to be eaten by birds and other predators. Fewer black moths survive to breed and so the black moths are less common in the population than the paler peppered forms. There was a time, however, that this pattern was different. In the nineteenth century towns and cities were starting to find more and more black moths and fewer peppered moths. In the 1800’s industries and homes were using coal in large quantities for power. This created a large amount of soot in the air and polluted the air with black dust. This soot killed the lichens on trees and blackened the tree trunks and building walls. This made the pale peppered form of the moth more visible as the lichen were gone and the surfaces were dark. The pale form of the moth was more obvious to predators. The darker moth (the melanic one) was actually better camouflaged now. It was the one that was more likely to survive and produce offspring. As a result, during the industrial revolution time frame and over successive generations, the black moths came to outnumber the pale forms in the towns and cities where there was a lot of soot in the air. Since moths are short-lived, this evolution by natural selection happened quite quickly. For example, the first black Peppered Moth was recorded in Manchester in 1848 and by 1895 98% of Peppered Moths in the city were black. After the cities were beginning to become polluted with soot, there was an endeavor to clean up the towns. In the midtwentieth century laws and controls were introduced to reduce air pollution. As a result, the air quality improved, tree trunks became cleaner, and lichen growth increased again. The town was no longer black and sooty. The black moths were losing their camouflage advantage. They were being seen and picked off by predators once again. The pale Peppered Moths were once again camouflaged in the lighter lichen-covered trees and the black forms were more noticeable. Normal pale Peppered Moths became again far more common than the black forms. Natural selection worked in both directions, always favouring the moth that is best suited to the environmental conditions. Sadly though, this species is now declining overall. Between 1968 and 2002 numbers of the Peppered Moth in Britain fell by almost two thirds, although the causes are as yet unknown. Something else is affecting them. Will they survive? Will they adapt? Will they become extinct? Nature will decide. Assignment: Requirements: 10 points: at least 5 panels long (2 points per panel) 3 points creativity (be unique and make it worth reading) 3 points neatness (needs to be legible and easy to see pictures) 5 points accuracy with information o 2 points for including peppered moth o 2 points for including melanic moth o 1 point for including industrial pollution 10 points: on the back of your comic strip, draw a graph like the one below. Draw a line to represent the amount of pollution over time based on the reading. Then on the same graph, draw a line to represent the amount of the black (melanic) moths corresponding to your pollution line. Amounts increasing --> DON’T SKIP THIS STEP!!!! 20 points: Make a comic strip about the story of the peppered moths (including the ones that were melanic). Be creative! It doesn’t have to be colored. Legend: Amount of black moths Amount of pollution Time increasing -->