Have you read Darwins book on the origina of species? An important part of his thinking on evolution was derived from observing finches on the Galopagus (sp?) Islands. He believed that one species of finch had been blown there from the mainland, and then the different forms had evolved over time to fill different biological niches. For example some finches were born with bigger and stronger beaks, and were able to eat bigger, harder seeds. Eventually, there were finches that had such large, strong beaks that they were a different species. He observed a number of different finch species, each of which had developed different characteristics to live in the various Islands and their varied living conditions. They had elso become different species. Read the book.
Another excellent book is Sean Carrol’s “Endless Forms Most Beautiful. One fascinating experiment described an eye gene with a genetic flaw in mice, fruitflies and humans. Scientists grafted eye genetic material from a mouse on to the leg of a fruitfly. Amazingly, the mouse material began to develop into insect compound eye structure. Apparently, the evolutionary process is able to reuse genetic material, but alter it in some amazing ways over time. For example, the segmented worm, segments of a lobster, and the human spine also have genetic material that has been reused and modified over time.
;-)