Carl Sagan wrote about possibilities for gas-giant life in Cosmos. He came up with the folowing idea: organic compounds in the atmosphere ar hit by lightning forming amino acids and eventually simple life. This stuff is all photosynthetic and just floats un up- and downdrafts. Kind of like little bits of paper. Even in the Earth's atmosphere if I throw a apaper airplane off the Empire State Building (wouldn't recommend this -- I got in trouble :-) ) it stays in the air a while. Something like confetti stays up even longer.

The lifeforms would be at the levels of the atmosphere where between the hydrogen you have huge clouds of other stuff-- these are the colorful clouds you see when you look at Jupiter or Saturn. They could even draw some energy from the heat of the planet, which can be pretty balmy at certain altitudes.

Anyhow, the photosynthesizers' job is to reproduce really fast, and do it before they fall too far down and get cooked.

Feeding on these are the big floaters -- these are the big gasbags that would have evolved from the confetti creatures, becoming larger to get more light. Some take on parachute like shapes, like parasails. Some enclose completely and fill with hydrogen, using a combination of heat from the sun and energy gathered by eating the confetti creatures. Eventually yuo get really efficient top predators that eat the gasbags and can actually fly.

None of these creatures would be very substantial, by the way. And they would be big.

As for intelligence, the relationship between that and tool use is far from clear -- it seems to me to be synergystic rather than chicken-and-egg. (You start tool use because you are a tad smarter -- more tool use encourages being smarter, which lets you make better tools, but how do the two interact?). We only have one example on earth of tool use leading to or being a complement to better brains. For whatever reason the chimps didn't make it to real smarts, and the other species that were smart enough to make tools all died out. So I would say the relationship is complicated at best.

(A bit OT, but this is why one could argue that hominids are not terribly successful as a species, since our diversity is very low, whereas rodents are everywhere, diverse, and fill many niches. Having little diversity can make you vulnerable to all kinds of environmental shocks. Humans are pretty adaptable but not infinitely so. But diversity is only one measure of success in any case, there are many others).

That said, there is no reason that gasbags might not develop ways to manipulate their environment. "Farming" the primary producers, for instance.

-J