Air Pollution's Impact On Moth Populations: An Ecological Mystery

The Industrial Revolution in England brought about a stark increase in air pollution, with coal-burning factories blanketing the countryside in soot. This pollution had a notable impact on moth populations, particularly the peppered moth (Biston betularia), which is found in Europe, Asia, and North America. The once light-coloured lichens and tree bark that allowed the light-coloured peppered moths to blend in were now darkened, making them more visible to predators. As a result, the frequency of dark-coloured moths, which were better camouflaged in the polluted environment, increased significantly. This shift in moth populations due to air pollution provided early evidence for Charles Darwin's theory of natural selection.

Dark moths were better camouflaged against soot-covered trees

The Industrial Revolution in England brought about a stark change in the colour of the peppered moth (Biston betularia). This moth is found in two forms, or morphs: a dark morph and a light, speckled morph. Before the Industrial Revolution, the light-coloured moth was the predominant form, as it could blend in with the light-coloured lichens and tree bark, making it harder for predators to spot.

However, as the new coal-burning factories began to blanket the countryside in soot, the light-bodied lichens died, and the trees became darkened. This change in the environment meant that the dark-coloured moths, which had previously stood out against the lighter bark, were now better camouflaged. The light-coloured moths, on the other hand, stood out dramatically against the darkened tree trunks. This shift in the ecosystem led to an increase in the population of dark-coloured moths, as they were better able to hide from predators like birds.

The Gizmo simulation illustrates this change by showing how dark and light moths are affected by their environment. In the simulation, the user acts as a bird hunting moths on both light and dark trees. The dark moths are more easily captured on light trees, and the light moths are more easily captured on dark trees. This demonstrates how the colour of the moth's environment can impact their survival, with the better-camouflaged moths having a higher chance of evading predators and reproducing.

The Industrial Revolution's air pollution caused a directional colour change in the moth population, with the frequency of dark-coloured moths increasing. This provided early evidence for Charles Darwin's theory of natural selection, as it showed how genetic variations of traits in a population can increase an individual's probability of surviving and reproducing in a specific environment.

Light moths were easier to spot on darkened trees

The peppered moth (Biston betularia) is found in two forms, or morphs: a dark morph and a light, speckled morph. During the Industrial Revolution in England, air pollution from coal-burning factories darkened trees with soot. This made the light-coloured moths easier to spot, and they were therefore more likely to be eaten by birds.

Before the Industrial Revolution, the light-bodied moths were able to blend in with the light-coloured lichens and tree bark, making them much more effective at hiding from predators. As a result, the frequency of the dark allele was very low, at about 0.01%. However, as the trees became darkened with soot, light-coloured moths were no longer camouflaged and stood out against the colour of the bark.

Bernard Kettlewell investigated the evolutionary mechanism behind peppered moth adaptation between 1953 and 1956. He found that the dark colour was beneficial in a polluted environment, as birds easily caught the light-coloured moths on darkened trees. This selective survival was due to the birds, which were the predators of the moths. As a result, the population of dark-coloured moths rapidly increased, and by 1895, the percentage of dark-coloured moths in Manchester was reported at 98%.

The evolution of the peppered moth is a clear example of directional colour change in the moth population as a consequence of air pollution during the Industrial Revolution. This instance of industrial melanism provided early support for Charles Darwin's theory of natural selection.

Birds preyed on light moths more in polluted areas

The peppered moth (Biston betularia) is found in two forms: a dark morph and a light, speckled morph. Birds are a frequent predator of the peppered moth. During the Industrial Revolution in England, the air was polluted with black soot from coal-burning factories. This soot coated trees and killed lichens, causing tree trunks to become darker. As a result, dark-colored moths were better camouflaged and had a higher chance of survival, while light-colored moths became more visible to predators.

The Gizmo simulation illustrates the impact of air pollution on moth populations. In the simulation, the player assumes the role of a bird preying on peppered moths. The moths are scattered over tree trunks, and the player attempts to capture them. This activity demonstrates how the color of the moths affects their survival in polluted environments.

In the context of air pollution, the statement "Birds preyed on light moths more in polluted areas" can be supported by the following paragraphs:

Paragraph 1:

The Industrial Revolution in England during the 19th century significantly impacted the peppered moth population. As factories burned coal, the air became polluted with black soot. This soot coated the trees and surfaces in the environment, including the tree trunks that peppered moths rested on. The once light-colored tree trunks became darkened, affecting the camouflage of the moths.

Paragraph 2:

Before the Industrial Revolution, the light-bodied peppered moths were well-camouflaged against the light-colored lichens and tree bark. Their light coloration allowed them to blend in with their surroundings, making it difficult for predators to spot them. However, as pollution levels increased, the environment darkened, and the light-colored moths became more visible against the soot-covered trees.

Paragraph 3:

Birds, being frequent predators of peppered moths, now had an easier time spotting the light-colored moths on the darkened tree trunks. The contrast between the light moths and the dark environment made them stand out, making them easier prey for the birds. This led to an increase in predation of light-colored moths, as they were less able to hide from their avian hunters.

Paragraph 4:

The survival rates of the two moth variations differed significantly due to the change in their surroundings. The dark-colored moths, or the melanic form, benefited from the polluted environment as their coloration provided effective camouflage. On the other hand, the light-colored moths, or the typica morphs, became more vulnerable as their light bodies stood out against the darkened trees.

Paragraph 5:

The Gizmo simulation further illustrates this phenomenon. In the simulation, the player, as a bird, captures moths that are most easily visible against the tree surface. This activity demonstrates how the color of the moths directly impacts their chances of survival in a polluted environment. The darker moths are more challenging to spot and capture, while the lighter moths become easier targets for the bird.

Dark moths were more easily spotted on light trees

The peppered moth (Biston betularia) is found in two forms: a dark morph and a light, speckled morph. Birds are a frequent predator of the peppered moth, and the colour of the moth that is easiest to spot depends on the colour of the tree.

On light-coloured trees, the dark-coloured moths are more easily spotted by predators, and therefore, the light-coloured moths have a higher chance of survival. This is because the light-coloured moths are better camouflaged against the light tree trunks.

During the 19th century, the Industrial Revolution in England caused an increase in air pollution. Coal-burning factories emitted soot into the air, which coated trees and killed lichens, turning their trunks darker. As a result, dark-coloured moths were better camouflaged against the polluted, darker tree trunks, and their population increased.

This phenomenon, known as industrial melanism, provided early evidence for Charles Darwin's theory of natural selection. The increase in the frequency of dark-coloured moths due to air pollution during the Industrial Revolution demonstrated how genetic variations in a population can increase an individual's probability of surviving and reproducing in a specific environment.

The Gizmo activity on moth populations and air pollution aims to illustrate these concepts. By playing the role of a bird hunting moths on light trees, users can observe how the colour of the moth affects its survival. The activity predicts that over time, the population of light-coloured moths will increase as they are better camouflaged against the light trees.

Light moths were better camouflaged on light trees

The peppered moth (Biston betularia) is found in two forms: a dark morph and a light, speckled morph. Birds are a frequent predator of the peppered moth, and the moth's colouring and patterns help it to blend in with the background, making it more difficult for predators to spot.

Before the Industrial Revolution, the light-bodied moths were able to blend in with the light-coloured lichens and tree bark, making them much more effective at hiding from predators. As a result, the frequency of the dark allele was very low, at about 0.01%.

However, during the Industrial Revolution, new coal-burning factories blanketed the countryside between London and Manchester with soot. The light-bodied lichens died from sulphur dioxide emissions, and the trees became darkened. This meant that light-coloured moths no longer blended in with their ecosystem and stood out against the colour of the bark. In contrast, dark-coloured moths were now well-camouflaged by the blackened trees.

As a result of this, there was an increase in bird predation of light-coloured moths, as they were more easily visible on the darkened trees. The dark-coloured moths, on the other hand, were better camouflaged and so were more likely to survive and reproduce, passing on their colouring to their offspring. Over time, this led to a rapid increase in the population of dark-coloured moths. By 1895, the percentage of dark-coloured moths in Manchester was reported to be 98%, a dramatic change from before the Industrial Revolution.

This provides evidence for Charles Darwin's theory of natural selection, as it demonstrates how genetic variations of traits in a population can increase some individuals' probability of surviving and reproducing in a specific environment. In this case, the trait of dark colouring in peppered moths increased their chances of survival in an environment where pollution from factories darkened the trees, making light-coloured moths more visible to predators.

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