Fig. 2.

Two views of the evolution of the eukaryotic cell. The outside in model (left) posits that the archaeal and eukaryotic cell membranes (both shown in green) are homologous and that this membrane was invaginated to generate internal compartments that eventually fused to yield the endomembrane system and nuclear compartment. Inside-out model (right) suggests that the archaeal plasma membrane is homologous to the inner nuclear membrane (both shown in red) and that this membrane formed outward protrusions that eventually formed the outer nuclear membrane, endomembrane system, and cell membrane (modified from Baum D. American J. Botany 2015, 102: 1–12)