You discover a fungus that contains a strange star-shaped organelle not found in any other eukaryotic cell you have seen. On further investigation, you find the following. 1. The organelle possesses a small genome in its interior. 2. The organelle is surrounded by two membranes. 3. Vesicles do not pinch off from the organelle membrane. 4. The interior of the organelle contains proteins similar to those of many bacteria. 5. The interior of the organelle contains ribosomes. How might this organelle have arisen?