How is natural selection related to evolution?

Natural selection is the driving force for evolution. Evolution was not first proposed by Charles Darwin. There had been many observations found pointing to the idea long before Charles Darwin. His grandfather, Erasmus Darwin, had proposed evolution 75 years before Charles Darwin first Published his book, "On the Origin of Species by Means of Natural Selection or the Preservation of Favoured Races in the Struggle for Life". Before this, it has been thought evolution took place as a conscious effort by species to adapt to their environment. Charles Darwin gave us the driving force to evolution, "Natural Selection". Natural selection needs several things to occur. First, there must be a variation within each species. Second, there must be a high enough Death Rate to prevent the variations which are not well adapted to die before individuals pass their characteristics on to the next generation. A giraffe with a slightly longer neck will survive better and so its offspring will have a slightly longer neck and they will also survive better. Those with slightly shorter necks will find it harder to survive, or will even die, and will not breed so well. In this way, giraffes developed long necks to reach the food they need. The trouble is, there are problems with having really long necks. Blood pressure and supply is one of them so giraffes have evolved a special organ between the blood supply and brain to prevent this. A giraffe's neck has become the ideal length to survive on the plants they eat.