The problem I have with the theory of evolution is that there is no proof. Now I know that proof and science don't seem to blend too well I have been told, but I personally take vaccinations and believe they help me and otheres to not get seriously ill from some diseases. I am not against science per se.
So while it is possible that different animals can interbreed and lose the essential dna needed to reproduce the same parentage from which they came, eventually removing the possibility they remain the same type of bird, bat, etc., I do not see any viable reason to think (beyond the theoretical possibilities posited by philosophical reasoners) that fish evolved by dna change to become landlubbers by natural selection. Thus, fish of different varieties remain fish, gorillas remain gorillas and of course, humans remain humans. Birds remain birds. I see no reason so far beyond philosophical ideas to think that fish evolved to become landlubbers, for exaample.