Endosymbiotic theory archaeal organism evolved a nuclear membrane before or after engulfing a bacterium organisms developed a symbiosis which became an obligate relationship considerable sharing of genetic material similar mechanisms let to engulfing of a cyanobacterium to evolve chloroplastsEndosymbiotic theory • archaeal organism evolved a nuclear membrane, before or after engulfing a bacterium • organisms developed a symbiosis which became an obligate relationship • considerable sharing of genetic material • similar mechanisms let to engulfing of a cyanobacterium to evolve chloroplasts