The theory of evolution by natural selection is a fundamental concept in biology that explains how species change over time. This theory is based on the idea that organisms that are better adapted to their environment are more likely to survive and reproduce, while those that are less adapted are more likely to die off. Charles Darwin was the first scientist to propose this theory in his book “On the Origin of Species” published in 1859.

One example of the theory of evolution by natural selection can be seen in the case of the peppered moth (Biston betularia) which is found in England. Before the industrial revolution, most peppered moths had light-colored wings with dark speckles, which helped them blend into tree bark and avoid being eaten by birds.

However, as pollution from factories increased, so did the amount of soot and dirt on trees, making them darker. This change in environment made it easier for birds to spot light-colored moths on dark trees.

Over time, a mutation occurred that caused some peppered moths to have dark wings instead of light ones. These dark moths were better adapted to their environment and were less likely to be eaten by birds. As a result, they were able to reproduce more successfully than their lighter counterparts, passing on their genes for dark coloration.

This process continued over several generations until nearly all peppered moths in polluted areas had dark wings. However, as pollution levels decreased due to environmental regulations, soot and dirt on trees also decreased and tree bark became lighter again. This change made it harder for birds to spot dark moths on light trees, giving an advantage once again to lighter colored moths.

This example demonstrates how natural selection can lead to changes in a species over time as they adapt to changing environments. It also highlights the importance of genetic variation within a population as mutations can give some individuals an advantage over others.

In conclusion, the theory of evolution by natural selection is a powerful concept that helps us understand how species evolve over time. The example of the peppered moth is just one illustration of how this theory works in the natural world. By studying such examples, we can gain a greater appreciation for the complexity and beauty of life on Earth.