actually, if you look at nature, you can see that the competion between species helps to keep the ecosystem in balance. If animals didn't compete for terriory, then there would be too many in areas where there shouldn't be and not enough where there should. Without outside interferance and healthy populations of native animals within it, an ecosystem can keep itself balanced indefinatelly. Survival of the fittest is simplifying very complex and intricate relationships between species and individual life forms, and in actuallity recent observations and genetic testing is showing that it isn't always the fittest or "alpha" memebers of a species that breed, and that if that was always the case, gene pools would suffer. So yes, while the weak get eaten, the idea of "fittest" is changing and subjective.