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Prior to 1800 in England, the typical moth of the species Biston betularia (peppered moth) had a light pattern. Dark colored moths were rare. By the late 19th century, the light-colored moths were rare, and the moths with dark patterns were abundant. The cause of this change was hypothesized to be selective predation by birds (J.W. Tutt, 1896). During the industrial revolution, soot and other wastes from industrial processes killed tree lichens and darkened tree trunks. Thus, prior to the pollution of the industrial revolution, dark moths stood out on light-colored trees and were vulnerable to predators. With the rise of pollution, however, the coloring of moths vulnerable to predators changed to light. In the late 1900s, England cleaned up its air, and pollution decreased. The bark of trees went from dark to light. Which of the following outcomes to the populations of peppered moth would you expect given this environmental change? a. An increase in the number of dark moths and a decrease in the number of light moths b. an increase in the number of moths overall c. an approximately equal number of light moths and dark moths d. an increase in the number of light moths and a decrease in the number of dark moths

Step by step solution

01

- Understand the historical context

Initially, the predominant moth variety in England was the light-colored Biston betularia, with dark-colored moths being rare.

02

- Identify the environmental changes during the Industrial Revolution

Soot and pollution killed lichens and darkened tree trunks, making light-colored moths more visible to predators and thus leading to an increase in dark-colored moths as they could better camouflage.

03

- Examine the environmental change in the late 1900s

Pollution levels decreased, tree barks lightened again, reversing the conditions that had previously favored dark moths.

04

- Predict the outcome based on environmental changes

With the trees' bark turning lighter, which means dark moths would become more visible to predators while light moths would blend in better.

05

- Draw a conclusion

As the tree bark became lighter again due to decreased pollution, it would lead to an increase in the number of light moths and a decrease in the number of dark moths.

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Key Concepts

These are the key concepts you need to understand to accurately answer the question.

Industrial Melanism

Industrial melanism is a phenomenon where darker forms of a species become more common due to industrial pollution.
The classic example involves the peppered moth, Biston betularia, in England. Before the Industrial Revolution, the light-colored form of the moth was dominant because they could easily blend into the lichen-covered trees and avoid predators. However, during the Industrial Revolution, soot from factories darkened tree trunks and killed the lichens.
This environmental change gave a survival advantage to the dark-colored (melanic) moths because they were better camouflaged on the soot-darkened trees.
As a result, the population of dark moths increased significantly. This is a clear demonstration of how human activities can directly impact natural populations and lead to changes in species' physical characteristics.

Natural Selection

Natural selection is the process by which certain traits become more or less common in a population due to their impact on the survival and reproduction of organisms.
In the case of the peppered moth, natural selection favored the dark-colored moths during the Industrial Revolution. Predatory birds could easily spot and eat the light-colored moths against the darkened tree bark, while the dark moths were better hidden and less likely to be eaten.
Consequently, dark moths survived longer and reproduced more, passing on their dark coloration to their offspring. Over time, this led to a significant increase in the population of dark moths.
With cleaner air in the late 1900s and a return to lighter-colored tree bark, the process reversed. Now, light-colored moths had the survival advantage, and their numbers increased again.
This is a classic example of how environmental factors can influence which traits are advantageous and drive the process of natural selection.

Environmental Impact on Species

The environment plays a crucial role in shaping the traits of a species and determining which individuals survive and reproduce.
The story of the peppered moth illustrates how quickly environmental changes can impact species populations. Before industrial pollution, the light-colored moths were well-camouflaged on lichen-covered trees, making it difficult for predators to spot them.
When pollution darkened the trees, the survival dynamics shifted in favor of dark-colored moths. The industrial pollution did not only cause physical changes to the environment but also directly affected the biological aspects of the local species.
As pollution levels decreased and tree bark became lighter again, the environment once again favored light-colored moths.
Therefore, species must constantly adapt to changes in their environment to survive. This ongoing interaction between a species and its environment is a fundamental aspect of evolutionary biology and demonstrates the impact human activities can have on natural ecosystems.