Some days ago, I was thinking (partially) about the complex balance that is needed for an ecosystem to exist. I got curious about the existence of some sort of critical point, something - that when taken out of the system - makes life vanish.
Is there a single species that when took out of one ecosystem destroys the life in it? Perhaps there's not a single species, perhaps there could be a minimal set of species in which this could happen.
Excuse me for the poorly formulated question. I'm not a biology student, I just get random curiosities from time to time.