Which piece of evidence best supports the endosymbiotic theory of organelle evolution?

Question

Quizplus · Accepted Answer

The fact that the outer membrane of a mitochondrion and chloroplast resembles a eukaryotic cell while the inner membrane resembles that of a bacterial cell is a strong indication that these organelles were once free-living bacteria that were engulfed by a eukaryotic cell and established a symbiotic relationship, leading to their evolution into organelles. This is a key piece of evidence supporting the endosymbiotic theory. B is incorrect because the inner membrane does not resemble that of a eukaryotic cell. C and D are also incorrect as they do not provide evidence that supports the endosymbiotic theory.

Which Piece of Evidence Best Supports the Endosymbiotic Theory of Organelle