This isn't true. Prokaryotes do not have membrane-bound organelles resulting from an ancestral symbiotic relationship. (You might be able to found some weird e

This isn't true. Prokaryotes do not have membrane-bound organelles resulting from an ancestral symbiotic relationship. (You might be able to found some weird exception to the rule out here. This is a generalization -- nothing in biology shocks me anymore.) Even for unicellular eukaryotes, it would be incorrect to claim they're separate organisms from their membrane-bound organelles just because of the organelle's evolutionary origin. Unicellular organisms really are "unitary." Edit: A biologist should always be humble. I just thinking of lichens, which are "composite organisms" consisting of fungi, bacteria, and algae, which can be an instance of what you're getting at. Still, some organisms really are "unitary."