Endosymbiosis and the “Tree of Life”

The Tree of Life Eukarya Archaea Bacteria Animals Fungi Plants Other single cell eukaryotes Proteobacteria Other bacteria Crenarchaeota Euryarchaeota

Endosymbiotic Theory Evidence suggests that eukaryotes obtained their mitochondria and chloroplasts by engulfing bacterial cells. Eventually, the engulfed bacterium gave up its ability to live on its own after some of its genes were transferred to the nucleus of the host cell. Lynn Margulis

The Revised Tree of Life Three domains: Bacteria, Archaea, and Eukarya Because lateral gene transfer is thought to have been common among the earth’s earliest organisms, the revised tree of life has some “untreelike” cross-links between branches.

EUKARYA BACTERIA ARCHAEA Animals Fungi Plants Cyanobacteria Crenarchaeota Euryarchaeota Other bacteria Proteobacteria Algae Bacteria that gave rise to chloroplasts Other single-cell eukaryotes Hyper- thermophillic bacteria Bacteria that gave rise to mitochondria