Summary:
- Scientists think that protists are the oldest eukaryotes.
- If so, they must have evolved from prokaryotic cells.
- How did this happen?
- The endosymbiotic theory provides the most widely-accepted explanation.
- This theory is well-supported by evidence.
- The first eukarian cells evolved from a symbiotic relationship between two or more prokarian cells.
- Some of the small cells were cyanobacteria.
- They were specialized for photosynthesis.
- They evolved into the chloroplasts of eukaries.
- They also had DNA that is different from the DNA found in the cell nucleus.