Answer:
mitochondria
Step-by-step explanation:
Endosymbiosis occurs when a single celled organism resides in another in a mutually beneficial relation.
The the endosymbiosis theory states eukaryotic cells originated from prokaryotic cells.
The membrane bound organelles such as mitochondria that distinguishes eukaryotes evolved through endosymbiosis.
Since these organelles are semi-autonomous and they have their own DNA ,it strong evidence that this hypothesis is correct.