In: Biology
According to the hypothesis of serial endosymbiosis, which of the following was a key initial step in the origin of mitochondria?
| A. A eukaryotic host cell engulfed an aerobic, photosynthetic bacterium. |
| B. A prokaryotic host cell engulfed an aerobic, heterotrophic bacterium. |
| C. A eukaryotic host cell engulfed an aerobic, heterotrophic bacterium. |
| D. A prokaryotic host cell engulfed an aerobic, photosynthetic bacterium. |