Pl
1. explain what caused the existence of the dark-colored peppered moths.

2. explain what caused the dark-colored peppered moths to become more numerous than the light-colored peppered moths when their environment became covered in soot.

3. explain what happened to the populations of the light and dark-colored peppered moths once the soot disappeared.

4.is the coloring of the peppered moths an example of competition, differential reproductive success, or inherited variation? explain why.

5. predict what may happen to the population of pepper moths if they were relocated to a lush, green rainforest ecosystem. how would this impact natural selection and their struggle to survive?

during the 1800s in britain there was an increase in factories and production called the industrial revolution. the main fuel for these factories were wood and coal that created black smoke when burned. as the factories became busy, the air filled with soot and pollution, which would eventually settle on the surrounding buildings and trees, turning them to a dark black color. this affected the local environment and the organisms that lived there.

one example is the peppered moth. peppered moths (biston betularia) are white speckled moths that could easily camouflage themselves on the lichen-covered white bark of the birch trees found in this area. now that these trees were covered in dark soot, it was harder for the moths to still be camouflaged. due to this, birds could easily spot and eat the light-colored moths. this caused the population of light-colored peppered moths to decline rapidly.

during this time, a dark-colored peppered moth appeared. scientists called this variation of the peppered moth biston carbonaria, which means charcoal version. the darker peppered moths could blend in to the soot-covered environment. the birds were not able to spot them easily.

did the pollution cause the moths to turn black? not exactly—the cause for the color change was a random mutation of the gene that controls wing color in moths. this mutation allowed for a small section of the gene for wing color to transpose, or jump onto another section of dna during cellular division. this caused the wings of the new offspring to be a dark color.

peppered moths, black and speckled, on a light colored tree trunk
© 2017 kim taylor / nature picture library / universal images group
the dark color of the pollution gave the mutant form of the peppered moths an advantage for better survival by increasing their ability to camouflage themselves on the soot-covered trees. this allowed them to avoid predators, pass on the mutation to their offspring, and increase their population numbers. this didn't happen overnight. scientists estimated that the mutated gene was passed on to about 20 to 30 generations of moths over 30 years. this resulted in approximately 95% of the peppered moths being the darker type in the polluted areas. scientists call this phenomenon in adaptation industrial melanism.

many years later, the factories found better ways to decrease the amount of soot and pollution. the trees began returning to a lighter color. this allowed the light-colored peppered moths to begin to repopulate in larger numbers. areas that were not exposed to the pollution had higher numbers of light-colored moths and lower numbers of dark-colored moths. this shows how a small change in an organism's dna can affect survival as environmental conditions change.

source: hesman saey, t. (2016, june 23). how a moth went to the dark side. science news for students

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