What evolutionary process transfers DNA directly between unrelated organisms instead of from parent to offspring?

Horizontal gene transfer transfers DNA directly between unrelated organisms instead of from parent to offspring.

The process is especially important in bacteria and archaea. DNA can move through transformation, when cells take up free genetic material; transduction, when viruses carry DNA between cells; or conjugation, when cells transfer DNA through direct contact. Plasmids commonly carry genes involved in antibiotic resistance.

Horizontal transfer complicates the idea that evolution always follows a simple branching family tree. A gene may have a history different from that of the organism carrying it, producing a network-like pattern of relationships.

Vertical gene transfer is the ordinary inheritance of genetic material from ancestors. Horizontal transfer is also documented in eukaryotes, including some plants and animals, but it is generally most conspicuous and evolutionarily consequential among microbes.