Can you then show some evidence when it was observed that an ape evolved into a man, or a fish into an amphibian?
No, since apes didn't evolve into men, nor fish into amphibians. Modern humans
are apes, as are gorillas, etc. All apes share a common ancestor that lived however long ago (100 million, off the top of my head). Likewise, modern fish and modern amphibians (and, indeed, reptiles and mammals) are all descendants a common ancestor species that we call
Gnathostomata - the infraphylum containing all jawed vertebrates. That species may have very well resembled modern fish, at least superficially.
But it's incorrect to say fish evolved into amphibians, since no species will evolve into another, pre-existing species. Moreover, all descendants of a species will forever be part of that taxon: if 'cow' split into many distinct species, they would all be cows, but in the same way all flies are flies, or all dogs are dogs, or all mammals are mammals. Eventually, those various cow species would be as varied as insects - they're still cows, but evolution has undoubtedly happened.
The evidence is in the fossil record, comparative anatomy, comparative genetics, geographic distribution, the molecular clock, ERV sequencing, etc. Indeed, evidence comes from every field of science: radiology, geology, geography, biology (anatomy, genetics, etc), chemistry, biochemistry, etc.
Anyway. What I think Tinker Grey meant* was that evolution, the biological phenomenon that scientists talk about, is observed in the lab. Obviously that doesn't mean we can see fish evolving into amphibians (not least because that never happened); that's like saying a chemist in his lab can see
all chemical reactions that ever happened in the entire universe. Likewise, demanding a scientist show you in his lab a gorilla evolving into a human just belies your lack of understanding, and will probably get you a clip round the ear.
*Yes, Tinker Grey, I'm arrogant enough to speak for you
