Evolution and Natural Selection

Evolution is the process by which the characteristics of different organisms gradually change over time. Life started on Earth around 3.5 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 better suited to the environment, making them more likely to survive, reproduce, and pass these traits to the next generation compared to those without these advantages. 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.

Example of Natural Selection

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 inherited alleles for dark fur, while others have alleles for white fur.

1. Initially, the population of white mice is greater than the population of dark mice.

2. In this scenario, the fox (predator) sees the white mice more easily on the dark floor. Therefore it eats more white mice than black mice.

3. The next generation of mice will contain more black mice than white mice.

  • This is because black mice, being better suited to this environment, had a survival advantage and passed on the alleles for black fur.
  • However, if the environment were to change and the floor became white, the population dynamics would shift over several generations. Eventually, there will be a higher number of 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.