Biological evolution is the process by which populations of organisms change over time. In this lab, you were able to observe how a population of peppered moths can change based on their environmental surroundings. Why do these types of changes/adaptations occur?
These types of changes or adaptations occur in populations of organisms due to natural selection. Natural selection is the result of genetic variation within a population, coupled with selective pressures from the environment. Organisms that possess traits or variations that give them a survival advantage in their environment are more likely to reproduce and pass on their advantageous traits to the next generation.
In the case of peppered moths, their coloration serves as camouflage against predators. Before the industrial revolution, the moths predominantly had lighter coloration, which helped them blend in with tree bark. However, with the onset of industrialization and pollution, tree trunks became darker due to the accumulation of soot and other pollutants. This change in the environment placed lighter-colored moths at a disadvantage as they became more visible to predators, while darker-colored moths had a better chance of survival.
Over time, through natural selection, the darker-colored moths became more predominant in the population as they had a higher likelihood of surviving and reproducing. This change in the population's coloration is an example of an adaptation to the new environmental conditions, driven by natural selection.