Which of these observations gives the most support to the endosymbiotic theory for the origin of eukaryotic cells?
A) the existence of structural and molecular differences between the plasma membranes of prokaryotes and the internal membranes of mitochondria and chloroplasts
B) the similarity in size between the cytosolic ribosomes of prokaryotes and the ribosomes within mitochondria and chloroplasts
C) the size disparity between most prokaryotic cells and most eukaryotic cells
D) the observation that some eukaryotic cells lack mitochondria

Question

Quizplus · Accepted Answer

The similarity in size between the cytosolic ribosomes of prokaryotes and the ribosomes within mitochondria and chloroplasts supports the endosymbiotic theory, as it suggests that these organelles were once free-living prokaryotes that were engulfed by ancestral eukaryotic cells and eventually evolved into permanent endosymbionts. This is because prokaryotic and mitochondrial ribosomes are similar in size and composition, while eukaryotic ribosomes are larger and more complex. The other observations (A, C, and D) are not as directly related to the endosymbiotic theory.

Which of These Observations Gives the Most Support to the Endosymbiotic