High-Altitude Life?

So here's the rough idea. I'm trying to figure out what kind of life could exist that spends basically its entire life in the air, for an alien world I'm working on. No sentient life, just wilderness. In my mind, it's not so much something that actively flies (like birds or planes), and lands in-between, but something that literally never stops flying. It is born, eats, breeds, lives, and eventually dies in the air. So my main questions are these:

• What would be necessary for there to be an actually functioning aerial ecosystem, and how complex would it be? Would it be similar to a ground ecosystem, or would it have to be completely different?
• What kind of life would it be? Plant, animal, fungi, single-celled, or maybe something else entirely? What is/would be best suited to life in the air?
• How would it fly? Would it be some sort of living gasbag, or something kind of like spiders ballooning, but on a much larger scale? Maybe something like a living glider? Or jellyfish-type propulsion? Is using magnets to float around in the geomagnetic field at all possible?
• How big would it be? Would it be one big organism, or a giant colony composed of millions of tiny ones?
• What would it eat? Would it have to go down near the ground to feed, catching low-flying/ground life, or would it catch other aerial life in midair? Could it maybe strain smaller forms of life out of the sky, like whales eating krill?
• How would it reproduce? Would it have a larval/seed stage on the ground, where it releases seeds/spores/polyps/eggs/larvae/whatever that fell to the ground, grew, then took off?
• How high would it be? It is confined to a certain altitude, or can it move around? Could there be life all the way up at the edge of space?
• What would be different about the planet itself that could help this happen? Would the atmosphere be composed of some heavier gas that could make it easier for other gasses to float? What about the planet itself having less gravity?
• What happens when the life dies? Does it go crashing down to earth, or just float around and decay, forming a place for new life to grow?

I think that's pretty much it. I'm also interested in what possible mechanisms would be needed for life like this. Also, if there's anything that just makes this whole thing blatantly impossible, then tell me so that I can hopefully handwave around it.

posted almost 9 years ago

possiblySerious‭

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