Would it be possible for a terrestrial protist to evolve into a multicellular organism, and if so, in what ways would it differ from an organism that became multicellular in water and then moved onto land?
I don’t think there’s any terrestrial single celled organisms (the ones that “live on land” actually live in droplets or films of water on land), so that’s maybe not a good question.
But it’s likely that a multicellular creature that lives in droplets would soon have to become fully terrestrial
But it still starts in water. Or acid, if your planet has acid rain.
It would start in water, but would very quickly need to become terrestrial in order to increase in size
Fair enough. That makes me wonder what the smallest terrestrial organism is. I’m not actually sure what the transition between terrestrial and “terrestrial” but in a film of water looks like
The smallest non-cell creature that I know of are Water Bears.
Yep, they are pretty small, but they live in water as the name suggests.
They live anywhere, water bear is not their scientific name its a name coined by normal people like us. You try saying Tardigrades 10 times fast. To quote from a quick Google search:
Tardigrades, often called water bears or moss piglets, are near-microscopic animals with long, plump bodies and scrunched-up heads. They have eight legs, and hands with four to eight claws on each. While strangely cute, these tiny animals are almost indestructible and can even survive in outer space
They live anywhere… in films of water. They can survive a much greater variety of conditions if they take a couple hours to go into their suspended animation “tun” state, but they need water at a reasonable temperature to actually move around and eat.
Unicellular creatures, like yeast, can be xerophilic, meaning that they could be fully terrestrial