2021-8-2 · They shared much the same body plan, however, and we group them together as prokaryotes (Fig. 3.1). A third domain of life, the Eukarya, contains all other living organisms, and has a distinctly more complex body structure (Fig. 3.2, Box 3.1). Eukaryotes evolved after the other two, so they must have had ancestors that were some form of prokaryote.