Mitochondria are found in most eukaryotic cells and contain their own DNA and ribosomes that are similar to those typical of many prokaryotic cells. Which of the following statements is justified by these observations?

The endosymbiotic theory proposes that mitochondria and chloroplasts were once independent prokaryotes. Evidence for this comes from the fact that both organelles have their own DNA and ribosomes for protein synthesis.

An ancestral cell formed a symbiotic relationship with these prokaryotes, ultimately evolving into the familiar eukaryotic cells we know today.