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A fish with fins moves against gravity in water,then why cant it evolve into a bird with wings and move against gravity in air ?

Because underwater it only has to deal with a fraction of gravity under water. Buoyancy takes most of it away, making swimming almost weightless. A land creature has more experience with gravity than a fish.

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but think of a modern PC...slowly built from the first PC by Babel(?)
into the PC ur typing away right now...now I know that a PC was "created" but I'm only talking about the idea of "change" of the PC over years to the current state


You're probably referring to Babbage (who didn't build it). Either way that's as bad an analogy as creationists speaking about evolution from rock to human.