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Most fish are evolved from land-dwelling animals

I wanted to check your source for this proposition, because after I upvoted your comment on other grounds, I wasn't completely sure that this squares with what I have read about evolution.

For example, this link

http://dinosaurs.about.com/od/otherprehistoriclife/a/prehist...

is to the contrary, suggesting that most fish living today had ancestors that were aquatic.

AFTER EDIT: To acknowledge your kind reply, I wondered if that was what you were getting at. To me, "land dwelling" implies, among other key behaviors, breeding and laying eggs on land. By contrast, "air breathing" would be a term unambiguous for what you meant, and still surprising to most readers.




The swim bladder is a modified lung: http://en.wikipedia.org/wiki/Swim_bladder#Evolution

Wikipedia claims that this is thought to have evolved as a survival method in oxygen poor water. My understanding had been that this was because their ancestors, however briefly, were adapted to survive out of the water. If only as well as today's lungfish.

My understanding may be wrong. But still, most fishes today are descended from air-breathing ancestors.




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