Which of the Following is Evidence for the Endosymbiotic Theory

Question

Which of the following is evidence for the endosymbiotic theory?
A) Mitochondria have circular DNA.
B) The nucleus is surrounded by a nuclear membrane.
C) Chloroplasts have thylakoids.
D) The rough endoplasmic reticulum has ribosomes.

Accepted Answer

Mitochondria having circular DNA is evidence for the endosymbiotic theory because it suggests that mitochondria were once independent prokaryotic organisms that were engulfed by ancestral eukaryotic cells. This characteristic is similar to the circular DNA found in present-day bacteria, supporting the idea that mitochondria originated from a symbiotic relationship with a prokaryotic organism.