Over time, a species can change through a process called evolution. Evolution occurs through a combination of genetic variation and natural selection. Genetic variation happens when individuals within a species have differences in their genetic makeup. Natural selection occurs when certain traits make individuals better suited to survive and reproduce in their environment. These individuals are more likely to pass on their advantageous traits to their offspring. Over generations, the frequency of these advantageous traits increases, leading to changes in the species' characteristics. This gradual accumulation of changes can eventually result in the formation of new species altogether.