Endosymbiotic theory

The Endosymbiotic Theory suggests that certain cellular structures, like mitochondria and chloroplasts, originated from free-living bacteria that were engulfed by a larger host cell. Instead of being destroyed, these bacteria formed a mutually beneficial relationship, eventually becoming permanent parts of the cell. This explains why mitochondria and chloroplasts have their own DNA and double membranes, indicating their bacterial origins. The theory helps us understand how complex cells evolved from simpler ancestors, highlighting a key example of cooperation and integration at the cellular level.