Organisms living near hydrothermal vents are

Are you looking for their name?

They are called chemotrophs; this means that they obtain their energy from chemical reactions.

They are different from phototrops, which obtain their energy from the sun, mostly through the process called photosynthesis.

Let me know if you were looking for something else than a name and if there were options:)

This is all you, but i can give you some topics that you could try. if it rained when you want to do something outdoors, it 'limits' that human activity. maybe you want to do an experiment that goes throughout the whole year and you have to have above freezing the entire year. this 'limits' your activity. i thought of those just off of the top of my head. something that gets to me that might be getting to you is you are thinking too hard about what to do. think simply, and if it is too simple, then bump it up just a little bit.