This article from Biology Online explains the endosymbiotic theory, which proposes that organelles such as mitochondria and chloroplasts evolved from free-living prokaryotic cells that formed symbiotic relationships within larger cells. Students explore evidence supporting the theory, including similarities between organelles and bacteria, and examine how endosymbiosis contributed to the evolution of eukaryotic cells.

symbiosis evolution eukaryotic cells life science cell biology mitochondria Organelles microbiology chloroplast endosymbiosis endosymbiotic theory ancestral cells