What are the driving forces behind evolution?

Charles Darwin noted that the main driving forces of evolution are: Heredity, variability, the struggle for existence and natural selection.
Heredity is the transmission of traits from ancestors to descendants, usually only those traits are transmitted that helped the previous generation to survive, i.e. more useful genes.
Variability – the ability of the body to adapt to the environment, change under its influence. For example, there are no two identical representatives of the same species, since they all changed during life.
The struggle for existence and natural selection is a confrontation between living organisms, as a result of which only the strongest representative survives.