I have yet to see a snake change into a bird. And if that is the demand you place on evolution, you'll never see it. Of course, nowhere has anyone suggested that a "snake turns into a bird" before your eyes. Except creationists attempting to disparage what the theory actually says.
That is, at the core what the Theory of Evolution proposes, that one kind of animal can change into another, through intermediary forms, with the 'pressure' to do so provided by the environment or by mutation.
This would require a process that would go against entropy (The tendancy towards disorder) and would require the increasing or adding of genetic information, when mutations and breeding actually reduces the amount thereof.
Your Follow-on questions:
1. What caused the adaptation? This can be almost anything. Actually, Darwin described it well with the Finches of the Galopogos. Over several years, the climate varied, some years the seeds the Finches ate had thicker hulls. This 'selected' for survival, birds with bigger, heavier beaks. BUT, when the seeds returned to thinner hulls, so did the thinner beaks. Environment, mutations, predation, etc. Adaptation is not and should not be confused with 'evolution'.
2. Why the need to adapt at all? See above, but again, adaptation is not evolution.
3. What sometimes happens to individuals who do not adapt? They die. However, see the Darwinian example above.... the adaption was only around while needed.
4. If a population is geographically separated by, say, volcanic destruction and one population adapts to the new flora it must eat to survive - whereas the other population's food source remained unaffected... What then? Then you would have two populations of genetically related, like animals, both of which might adapt to new conditions. However, those two populations of, say for instance, gazelles, would STILL BE Gazelles.
5. Given sufficient time, assuming you accept a 5 billion yo earth, what process "stops" those accepted adaptations from continuing to adapt over long stretches of time? I am pleased to see you using the correct term 'adaptation, as it is NOT evolution. None of your questions would relate to the idea of how a fish would adapt to life as a frog. Oh, and I do not accept a 5 billion year old Earth. That should be better.
You seem like a perfect candidate for the HMS Creation ping list. If you’re interested, feel free to drop me a PM :o)
Yes. Evolution would (and does) indeed require such a process. Fortunately for us all, there is such a process. It's called "life".
Living organisms all concentrate massive amounts of negative entropy within themselves. This is absolutely intrinsic to the process of living. But, you say, "then they die." Yet they can reproduce from within themselves new individuals which can continue the process of concentrating negative entropy indefinitely.