Evolution

Organisms tend to change. This is known as evolution. This sometimes applies to things in general.

Methods

Mutation

This is when the DNA sequence of an organism is changed.

Gene flow

This is when genes are transferred from one population to another.

Genetic drift

Oh no! Something unlucky just happened, and that could change the course of evolution forever!

Natural selection

Survival of the fittest. For example, the fittest giraffes had longer necks. This led to basically all giraffes having long necks, because they can easily eat leaves from tree branches.