Evolutionary change refers to the gradual process by which species of organisms develop and adapt over time through variations in their genetic traits. This process is driven by mechanisms such as natural selection, where individuals with advantageous traits are more likely to survive and reproduce, passing those traits to future generations. Over long periods, these small changes can lead to significant differences in species, resulting in the emergence of new species or the extinction of others. This concept is central to the study of biology and helps explain the diversity of life on Earth, as well as the relationships between different organisms.