Is Evolution A Key Part Of Evolution Or Natural Selection?

A key part of evolution is species evolving from other organisms, either if that's speciation or natural selection. Natural selection is when Nature “selects” the organisms with the best fit characteristics that help them survive to their environment and continues to let them reproduce while killing off the organisms with traits that cannot adapt. This means that all of the organisms that were able to adapt, survive have common DNA with the organisms that previously lived before them proving they evolved from a common ancestor but are also considered a “new” species because of all the different adaptations that occurred over time, during their environment changes. Speciation begins with a common ancestor of a certain species before reproductive
isolation occurs. As the isolated groups begin to adapt to their new environments, they no longer have similar enough DNA to reproduce again with their old species. So because they all came from the same species in the beginning, they have similar DNA, and ancestor but they have different trait now because of their differential adaptations to their environment.