Summary
Gene exchange among microbes makes their ancestry network-like rather than strictly tree-like.
In depth
The tree is better described as a web in prokaryotes; vertical descent is often inferred from core genes. Endosymbiosis merges lineages.
Network approaches visualise reticulate evolution. Core genes give a backbone. Endosymbiosis created eukaryote chimeras.
Key idea: not all genes follow the same history.
Horizontal gene transfer (HGT) is the movement of genetic material between organisms other than by descent, through transformation, transduction and conjugation. It is common in bacteria and archaea, spreading antibiotic resistance and metabolic genes.
Because genes in a genome can have different histories, the early evolution of microbes looks like a web or network, not a clean tree; Doolittle and others suggested a web of life. Eukaryotes also show transfers: mitochondrial and chloroplast genes moved to the nucleus, and some animals have bacterial genes (bdelloid rotifers, nematodes). However, a core of genes, such as ribosomal ones, still gives a tree-like signal of vertical descent.
Example: plasmids pass resistance among different bacterial species.
Frequently asked questions
What is Horizontal Transfer and the Tree of Life?
Gene exchange among microbes makes their ancestry network-like rather than strictly tree-like.
Which area of biology covers Horizontal Transfer and the Tree of Life, and how advanced is it?
Horizontal Transfer and the Tree of Life is one of the 52 topics in Taxonomy & Biodiversity. It is rated Advanced, so it suits learners who want specialist depth. Related topics in this area include Kingdoms, Molecular Systematics, Taxonomy.
Why does Horizontal Transfer and the Tree of Life matter?
It complicates classification and the idea of a single universal tree.
Can you give an example of Horizontal Transfer and the Tree of Life?
Some genes in bdelloid rotifers come from bacteria and fungi.
What should I learn before Horizontal Transfer and the Tree of Life?
Work through the Beginner topics in Taxonomy & Biodiversity first, such as Taxonomy, Binomial Nomenclature, Taxonomic Hierarchy, then return to Horizontal Transfer and the Tree of Life. Advanced topics assume the Intermediate vocabulary.
What topics are related to Horizontal Transfer and the Tree of Life?
The closest topics to Horizontal Transfer and the Tree of Life are Kingdoms, Molecular Systematics, Taxonomy, Phylogenetic Classification. Comparing them side by side is a good way to see how the ideas connect.
How can I check that I understand Horizontal Transfer and the Tree of Life?
Read the summary and the in-depth section, then use the quick check on the interactive lesson for Horizontal Transfer and the Tree of Life. To practise the whole of Taxonomy & Biodiversity, use the Taxonomy & Biodiversity quiz.
How is Horizontal Transfer and the Tree of Life different from Kingdoms?
Horizontal Transfer and the Tree of Life: Gene exchange among microbes makes their ancestry network-like rather than strictly tree-like. Kingdoms: Major groups of eukaryotes: animals, plants, fungi and protists, plus prokaryotes. Read both side by side and note what each one explains.
How should I study Horizontal Transfer and the Tree of Life step by step?
First, read the summary and write the definition in your own words. Second, read the in-depth section and note any example. Third, compare it with Kingdoms and explain the difference aloud. Finally, take the Taxonomy & Biodiversity quiz and come back to this page for any question you miss.