<em>No, these exceptions do not discredit natural selection.</em>
Explanation:
Natural selection tends to favour those organisms which are better adapted to live in an environment. But it does not completely remove the other organisms from the world that are less adapted to live in an environment. Usually, the number of these organisms that are not favoured by natural selection is very less as compared to the number of organisms which are favoured by natural selection. As we see, the number of albino animals is far lesser as compared to their wild-type animals.
They are saying that every theory can eventually be changed a bit due to further research. It does not mean the theory is bad, just that it can become better.
