Though ecosystems might appear straightforward to us, they rarely are. A case in point is the roots of plants… while it might appear that they are simply taps to pull water and nutrients out of the ground, they rely on microorganisms to break down those nutrients to the point that they can ingest and utilize them for their own needs and worms to help counteract the natural tendency of soil to compactify over time. Every species occupies its own ecological niche, some of which we’re aware of, and some of which we’re not, and some, like these organisms, are the only niche in their ecosystem. (Also keep in mind that, in a closed system, mass has to be recycled in order for life to exist.) Some common roles are scavenger, producer, and detritovore, and these roles recur in (most) every ecosystem we’ve observed, though the particulars of how these functions are accomplished may change.