9. Endosymbiosis and the Origin of Eukaryotes

Search for the term “endosymbiosis” in the Web of Science or the Zoological Record, and you will find a long list of some of the most intriguing and intellectually stimulating articles being published these days. The phenomenon of cells living inside other cells has had an enormous impact on the evolution of life. This has occurred on the macroscale with the endosymbiotic origin of numerous phyla of eukaryotes including the primary photoendosymbiotic green and red algae, and the numerous photosynthetic lineages that evolved by incorporating these algae into their cells, including brown algae, diatoms, and dinoflagellates. This process not only introduced new genes to the eukaryotic genome, but also altered that genome in novel ways.