A mutation is a change in the DNA sequence of an organism's genome. These changes can occur naturally during cell division or can be caused by environmental factors like radiation or chemicals. Mutations can affect a single DNA base pair or larger sections of chromosomes, leading to variations in traits. Mutations can be beneficial, harmful, or neutral. Beneficial mutations may provide an advantage in survival, while harmful mutations can lead to diseases. In some cases, mutations are a driving force in evolution, contributing to the diversity of species, such as in Darwin's finches that adapted to different environments.