The evolutionary origin of which of the following is explained by the theory of endosymbiosis?

• A. Ribosomes
• B. Nucleus
• C. Golgi apparatus
• D. Mitochondria

Answer: (D)

Verified step by step guidance

1. Understand the theory of endosymbiosis: This theory explains how certain organelles in eukaryotic cells, such as mitochondria and chloroplasts, originated from free-living prokaryotic cells that were engulfed by an ancestral eukaryotic cell. These prokaryotes formed a symbiotic relationship with the host cell.
2. Identify the key features of mitochondria that support the theory of endosymbiosis: Mitochondria have their own circular DNA, similar to bacterial DNA, and they replicate independently of the host cell's nucleus. They also have double membranes, which is consistent with the engulfing process.
3. Compare the other options: Ribosomes are present in all cells and are not explained by endosymbiosis. The nucleus is a defining feature of eukaryotic cells but is not thought to have originated through endosymbiosis. The Golgi apparatus is part of the endomembrane system and also not explained by this theory.
4. Focus on mitochondria: Mitochondria are the organelles responsible for energy production (via cellular respiration) in eukaryotic cells, and their origin is directly explained by the theory of endosymbiosis.
5. Conclude that the correct answer is mitochondria, as it is the only organelle in the list whose evolutionary origin aligns with the theory of endosymbiosis.