Why did the peppered moths number change in the 1900s?

The number of peppered moths changed in the 1900s primarily due to industrial pollution during the Industrial Revolution in England. As soot darkened tree bark, the previously light-colored moths became more visible to predators, leading to a decline in their population. In contrast, the darker variant of the moth became more prevalent as it offered better camouflage against the polluted environment. This phenomenon is a classic example of natural selection in response to environmental changes.