Summary
The phylogenetic tree, first used by Darwin, is the classic “tree of life” model describing phylogenetic relationships among species, and the most common model used today. New ideas about HGT and genome fusion have caused some to suggest revising the model to resemble webs or rings.
Glossary
eukaryote-first hypothesis
proposal that prokaryotes evolved from eukaryotes
gene transfer agent (GTA)
bacteriophage-like particle that transfers random genomic segments from one species of prokaryote to another
genome fusion
fusion of two prokaryotic genomes, presumably by endosymbiosis
horizontal gene transfer (HGT)
(also, lateral gene transfer) transfer of genes between unrelated species
mitochondria-first hypothesis
proposal that prokaryotes acquired a mitochondrion first, followed by nuclear development
nucleus-first hypothesis
proposal that prokaryotes acquired a nucleus first, and then the mitochondrion
ring of life
phylogenetic model where all three domains of life evolved from a pool of primitive prokaryotes
web of life
phylogenetic model that attempts to incorporate the effects of horizontal gene transfer on evolution