The chloroplasts of green algae and land plants have two membranes.These chloroplasts were acquired through endocytosis of a cyanobacterium containing chlorophyll and possessing a double membrane.What two events would explain why the chloroplasts of euglenids (a unicellular clade) have three membranes yet contain the same photosynthetic pigments as both green algae and land plants?
A) Plants arose from green algae and engulfed a euglenid to acquire photosynthetic pigments.
B) The ancestral euglenid engulfed a green alga through secondary endosymbiosis, while a different green alga became the ancestor to plants.
C) Ancestral green algae engulfed a euglenid through secondary endosymbiosis and gave rise to green plants.
D) Ancestral green plants arose from euglenids and then engulfed photosynthetic green algae.
E) Green plants engulfed a photosynthetic euglenid and were ancestral to green algae.

Question

Quizplus · Accepted Answer

The presence of three membranes in euglenid chloroplasts suggests that they acquired their chloroplasts through secondary endosymbiosis of a green alga that had already acquired a cyanobacterium through primary endosymbiosis. This is consistent with the current understanding of the evolutionary history of eukaryotic chloroplasts.

The Chloroplasts of Green Algae and Land Plants Have Two