I'm designing a terrestrial planet with 1.15 times Earth's gravity and about 1% helium in its atmosphere, as well as 1.2% hydrogen sulfide. The rest is very earthlike.
A type of animal that has arisen, a photosynthetic beast known as the yellowjelly. It carries two photopigments, a red one and a green one. I'm wondering though, if they were to evolve to fly without the use of conventional wings, how much would they have to change from their jellyfish like ancestors? could they even evolve such an ability in a reasonable timeframe? would using flattened tentacles as pseudowings help?
They're meant to be as small as possible and I imagine they can store helium in their bodies to make them more or less buoyant.