Final answer:
Option D is not evidence for endosymbiosis; mitochondrial and chloroplast ribosomes resemble bacterial ribosomes, differing from the eukaryotic cell's cytoplasmic ribosomes.
Step-by-step explanation:
The theory of endosymbiosis suggests that certain organelles within eukaryotic cells, such as mitochondria and chloroplasts, originated from primitive prokaryotic cells forming a symbiotic relationship inside a host eukaryotic cell. To answer the student's question, option D, the presence of ribosomes in the cytoplasm that are identical to those in mitochondria and chloroplasts, is NOT a piece of evidence for endosymbiosis. This is because mitochondrial and chloroplast ribosomes are similar to bacterial ribosomes and not to the cytoplasmic ribosomes found in their eukaryotic host cells.
Evidence supporting the endosymbiotic theory includes the presence of double membranes in mitochondria and chloroplasts (A), the similarities between the DNA of mitochondria/chloroplasts and bacteria (B), and the ability of mitochondria and chloroplasts to divide independently within a cell (C), all of which hint at a shared evolutionary history with prokaryotic bacteria.