What are the key concepts in the evolution theory of Darwin?

(N/A) The essence of Darwinian theory about evolution is Natural selection.
$(i)$ Rapid multiplication: Organisms have a high reproductive potential.
$(ii)$ Limited food and space: Resources are finite,leading to competition.
$(iii)$ Struggle for existence: Individuals compete for limited resources.
$(iv)$ Variations: Individuals within a population exhibit variations.
$(v)$ Survival of the fittest: Individuals with advantageous variations are more likely to survive and reproduce.
$(vi)$ Natural selection: Nature selects those individuals that are better adapted to their environment.
$(vii)$ Speciation: Over time,these accumulated variations lead to the formation of new species.
Branching descent and natural selection are the two key concepts of the Darwinian Theory of Evolution.