Evolution is the process by which the characteristics of different organisms gradually change over time. Life started on Earth more than 3 billion years ago. The simple organisms that existed have gradually evolved to form more complex life forms.
There is variation within any population, which is due to differences in genes. Some individuals have characteristics that are suited to the environment, which means they are more likely to survive and reproduce. So they will pass on these characteristics to the next generation at a higher rate than individuals who do not have these advantageous characteristics. This results in natural selection.
Charles Darwin was a famous naturalist who came up with the theory of natural selection to explain how evolution occurs.
Individual organisms that are not well adapted to their environment are less likely to survive and pass on their genes. For example, we can see this in a population of mice:
Every mouse has a slightly different combination of alleles that it inherited from its parents. Some mice will have alleles for dark fur and some will have alleles for white fur.
1. Initially, the population of white mice is greater than the population of dark mice.
2. The fox sees the white mice more easily on the dark floor, so it eats more white mice than black mice.
3. The next generation of mice will contain more black mice than white mice.
Over time, the small differences in features lead to the evolution of a species. And when enough time passes, the species may change so drastically that it becomes a new species. This new species will be unable to reproduce with the original species.