The theory of endosymbiosis suggests that chloroplasts and mitochondria were once free-living prokaryotes, that were engulfed by larger prokaryotic cells. eventually, this relationship lead to the development of eukaryotic cells with cellular organelles. these organelles included mitochondria, and in some cases, chloroplasts. which of these is not supported by the endosymbiosis theory concerning organelles? a) contain dna. b) contain ribosomes. c) are capable of living independently. d) are surrounded by a double membrane.