Physician, there is, as you say, no concrete proof of evolution. What can be said is that there is a heck of a lot of evidence tospport the claims. biogeography, biochemistry, comparitive embryology, comparitive anatopmy, paelentology, the list goes on...
Natural selection is the precursor to evolution. Over years and years and years, natural selection acts in such a way that it changes a certain species in numerous ways (the selecting pressures of the changing physical,chemical environment and other factors such as comp. for resources, being the causative agent), such that organisms will not be able to breed with each other to form viable young, thus forming a new species (correct if wrong)
THus natural selection eventuially leads to evolution.
yes and micro evolution is definitely happeining, with viralent strains of bacteria, such as stepheloccocus Auerus etc, appearing, that is hard to beat due to natural selection leading to evolution.