Darwin's theory is a theory about the evolution of species. According to him, the animal and vegetable species had to change to survive, adapting to the variations of their environment. Only those who survive to have descendants, this is called natural selection.
So evolution is a scientific theory that focuses on these species and explains the mechanisms of their appearance from existing or past species.
The correct answer would be the last one: "evolved from past organisms." This theory basically just states that all living organisms evolved from a single common ancestor. Hope this helped! :)
