What was significant to darwin about the fauna and flora of the galápagos islands?

the organisms there were similar to fossils found elsewhere, indicating that the galápagos chain held many ancient species.
the organisms there were the same as those seen on similar island environments around the world.
the species were similar to south american species, indicating common descent, but they had been extensively modified and were well-adapted to island life.
the species on the galápagos islands were not similar to those anywhere else, indicating that they had been created specifically to inhabit this environment.