*There are variations among individual of a given species. Some are obvious, and you can see them if you look around a roomful of people – they differ in height, hair color, facial features, bodily structure and so forth. Other differences are less obvious and may not even be visible. They include differences in blood type, running speed, and eyesight or hearing. Darwin’s point was that variation occurs naturally among all the populations.
*As long as the environment is stable and there is enough food, most variation will not have much meaning for the survival of the individual. But when environmental pressures arise because of population growth, climate change, the disappearance of a major food source, or a number of other things, some of the variations in the population will become more important for the survival of individuals who have those qualities. For example, if we look at a population of birds of the same species, we will note that some have longer beaks than others.
Now, as long as there is enough food for all, the length of the beaks not important, but if food becomes scarce it is possible that those birds with longer beaks will be able to dig deeper into the ground or into the bark of the trees for food, and therefore will have a greater chance and therefore will have a greater chance of survival.
This notion is commonly called survival of the fittest, meaning not the strongest but those best suited to a particular environment. The key to natural selection is not just the fact that individuals with certain variations may survive at a greater rate than the rest of the population, but they will produce a larger proportion of the next generation.
Darwin Evolutionary Scheme
