Mitochondria and chloroplasts display similarities with bacteria that led to the endosymbiont theory. This theory states that an early ancestor of eukaryotic cells engulfed an oxygen-using non-photosynthetic prokaryotic cell. Eventually, the engulfed cell formed a relationship with the host cell in which it was enclosed, becoming an endosymbiont, a cell living within another cell. Indeed, over the course of evolution, the host cell and its endosymbiont merged into a single organism, a eukaryotic cell with a mitochondrion. At least one of these cells may have then taken up a photosynthetic prokaryote, becoming the ancestor of eukaryotic cells that contain chloroplasts.
| Game | Time | WPM | Accuracy |
|---|---|---|---|
| 21803 | 2019-05-19 19:21:19 | 101.81 | 96% |
| 15811 | 2018-02-09 14:57:35 | 113.48 | 98% |
| 13339 | 2017-11-20 21:37:57 | 112.11 | 97% |
| 13338 | 2017-11-20 21:26:38 | 111.38 | 97% |
| 12265 | 2017-10-07 12:57:32 | 104.80 | 97% |