The chloroplasts of photosynthetic protists
A) are structurally identical.
B) gave rise to mitochondria.
C) are all descended from a once free-living cyanobacterium.
D) all have exactly two surrounding membranes.
E) are all descended from a once free-living red alga.

Question

Quizplus · Accepted Answer

The endosymbiotic theory suggests that chloroplasts in photosynthetic protists were once free-living cyanobacteria that were engulfed by a larger host cell. Over time, the host cell and the cyanobacteria developed a symbiotic relationship, and the cyanobacteria evolved into chloroplasts within the host cell. This is supported by the fact that chloroplasts have their own DNA and ribosomes, similar to prokaryotes like cyanobacteria.

The Chloroplasts of Photosynthetic Protists