Question 6 indicated that chloroplasts arose several distinct times in separate acts of endosymbiosis. If that is true, does the term “plastid” refer to a natural group of organelles that descended from a common ancestor? Would it be safer to use three separate names for these three separate structures?

Question 6

Why do we think that cyanobacteria rather than purple or green bacteria gave rise to chloroplasts in the primary endosymbiosis? Which cyanobacteria are most similar to chloroplasts? Which algae were involved in the secondary symbioses?