The chloroplasts of red algae retain certain pigments of the original cyanobacterial endosymbiont that are absent in green algal chloroplasts. The evolutionary significance of this is that a. red algae cannot photosynthesize, leading to heterotrophy. b. neither green algae nor red algae can be classified as protists. c. chloroplasts likely originated as free-living cyanobacteria. d. red algae are classified as cyanobacteria. e. red algae are classified as prokaryotes.
