Natural Selection is the pressure put on a specie in an environment to survive. Animals with traits that are beneficial to the environment can live longer and potentially contribute more to the gene pool. Animals with detrimental traits will live shorter lives and potentially contribute less to the gene pool. With these two influences, a specie's gene pool will, over time, be more beneficial to survival in that specific environment. It may not be enough to cause a deviation from specie (after all, look at the range of phenotype among humans), but it will be enough to increase the survival rate for that population.

I would be interested in hearing what he discussed. I'm trying to think of how one would discuss Natural Selection "philosophically", unless one is talking about cultural selection and natural selection in a society. Even then. I think that's more of a "borrowing" of the term than a true application.