Most of the life we see, including plants and animals are classified in the domain eukaryota. eukaryotic cells are more complex than prokaryotes, they contain organelles, and the dna is linear and found within the nucleus. the complex eukaryotic cell enabled a whole new era of life on earth, because these cells eventually evolved into multicellular organisms. but how did the eukaryotic cell itself evolve from a simple prokaryotic cell? evidence supports the idea that eukaryotic cells are actually the descendents of separate prokaryotic cells that joined together in a symbiotic union - endosymbiosis. what evidence supports the theory of endosymbiosis?