Plastids That are Surrounded by More Than Two Membranes Are

Question

Plastids that are surrounded by more than two membranes are evidence of
A) evolution from mitochondria.
B) fusion of plastids.
C) origin of the plastids from archaea.
D) secondary endosymbiosis.
E) budding of the plastids from the nuclear envelope.

Accepted Answer

Plastids that are surrounded by more than two membranes are evidence of secondary endosymbiosis, where a eukaryotic host cell engulfed another eukaryotic cell that had already undergone primary endosymbiosis (such as a red or green alga with its own chloroplast) and kept it as a permanent endosymbiont. The additional membranes are from the host's cell membrane and the endomembrane system that surrounded the engulfed cell.