No food in the upper atmosphere and all the way to space. I can guarantee we'd have space "whales" (overlords) if there were some kind of food up there (maybe just frozen spiders and bacteria). If life can adapt to pressures of 500atm, it can adapt to 0atm, gradually...if there'd be a food chain there to support it...but lower densities and/or residence times make minerals hard to come by...

Hah...maybe kessler syndrome will give the biosphere a way to reach space organically with a mineral substrate :3