Well explained (:Evolution takes place over 100's of years. What it means is that, when an animal develops a new characteristic that will help it survive for longer, it breeds longer and passes on the characteristic. Over millions of years, the animals with the survival characteristic will begin to dominate the population. Imagine there were two moths, one black and one white. Now imagine all of the trees had white bark. This means that the white moth would be camouflaged better than the black one, and would survive better. Now imagine all the white bark suddenly turned black; the population of black moths would increase and the white moth population would decrease. They will not get wiped out completely, but there will be more species with an advantageous characteristic than not, hence why there are close to 7 billion humans and only a couple hundred thousand apes (something like that).