[Jason Abbadon]

Yeah- the perfect exmple of such adaptation is the one that Darwin himself first noticed- Galapagos Finches- each tiny island in the Galapagos has it's own kind of finch- a small bird that was probably blown there by chance.
On each island, the basic fich adapted to suit it's locale- some growing long beaks to sip nectar, others short beaks for nut cracking, etc.
Their plumage also changed over generations, making them visually distinct...but they were still adaptations of the common finch.

Evolution is really a bitch to get your head around as an unguided force- that tiny adaptations (mutations) that add up over generations account for all the diversity in nature as the more successful members of a species, plus dumb luck, become dominant.
External stresses do shape species, but it's usually like water making a canyon. Major upheveals uually only cause mass extinctions (as we see happening from pollution and climate change, over-fishing/hunting, habitat loss, etc.).

Religious groups love to say that it's a theory that says "people come from monkeys" but tat's not the case at all- Darwin only speculated that humans and other primates share a common ancestor- making us as less apes than houscats are lions, but related.

Darwin was strictly religous for most of his life (personal tragedy doing more to change him than science) and almost did not publish at all after sitting on his work for a decade- but another scientist was coming up with some f his same conclusions and so he published, knowing what a shit-storm it would cause.