RE: "Survival of the fittest," which was coined by Herbert Spencer (not Darwin). Spencer was using the concept of "fitness" to mean "able to live long enough to successfully reproduce." That is Evolution by Natural Selection in a nutshell.
"The impossibility of conceiving that this grand and wondrous universe, with our conscious selves, arose through chance, seems to me the chief argument for the existence of God." ~ Charles Darwin - Romans 1 shows us that this evidence is so sound that it renders us without excuse. Romans 1:20 "For the invisible things of Him from the creation of the world are clearly seen, being understood by the things that are made, even His eternal power and Godhead; so that they are without excuse"