Final answer:
The endosymbiotic theory suggests that mitochondria and chloroplasts in eukaryotic cells evolved from prokaryotic cells through symbiotic relationships. Lynn Margulis proposed this theory, which is supported by genetic evidence and similarities between organelles and prokaryotes.
Step-by-step explanation:
The endosymbiotic theory proposes that mitochondria and chloroplasts, organelles found in eukaryotic cells, evolved from ancient prokaryotic cells that established a symbiotic relationship with the host cell. These organelles have their own DNA and evolved in tandem with the host cell. The theory was developed by Lynn Margulis and is supported by evidence such as genetic sequencing and similarities between organelles and prokaryotic cells.