Practice question · Put in order
Arrange these events in the order they occurred in the history of life.
- Photosynthesis begins to oxygenate the atmosphere
- A bacterium is engulfed and becomes the mitochondrion
- A photosynthetic bacterium is engulfed and becomes the chloroplast
- The first prokaryotic cells appear
Hints
- Prokaryotes precede all eukaryotic events.
- Mitochondria came before chloroplasts, every photosynthetic eukaryote also has mitochondria.
Show the answer
- The first prokaryotic cells appear
- Photosynthesis begins to oxygenate the atmosphere
- A bacterium is engulfed and becomes the mitochondrion
- A photosynthetic bacterium is engulfed and becomes the chloroplast
Why
Prokaryotes come first, then oxygenic photosynthesis transforms the atmosphere, then the mitochondrial endosymbiosis, and only later the chloroplast. The order is fixed by the observation that every chloroplast-bearing cell also has mitochondria, but not the reverse.
Practise The First Cells and Endosymbiosis
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