Sure, but if we're assuming there's life in two dimensions, the amoeba's digestive system is much simpler than zipper organs.
It seems so on a first glance, but if you think about how this 2D phagocyte can be formed (especially on a macroscopic scale) and how would it interact with other structures it becomes much less obvious.
It's easier for amoebas; they don't know about Euclidean geometry (do they know about topology, or can they have holes in their body?)