Organisms that die would have a harder time decaying, or may not even break down at all! Decomposers and detritivores break down dead organisms so without them it won't take place.
Very simply, I think that they may block the sun's rays from reaching the Earth, cooling down the planet, or they may eventually end up being turned into acid rain and rain back down to the Earth.
D. to seperate the inside of the cell from it's environment
