Final answer:
Mobile elements, such as transposons, developed movement genes to transpose within genomes and can be spread across species through horizontal gene transfer, contributing significantly to genetic diversity and adaptation.
Step-by-step explanation:
Mobile Genetic Elements and Transposons
Over time, mobile elements, specifically transposable elements or transposons, have acquired movement genes which allow them to transpose, or move, within the genome. These mobile genetic elements have garnered much understanding since Barbara McClintock's pioneering work on transposons in maize. Two primary types of transposons have evolved: DNA transposons which can move within the genome by a cut-and-paste mechanism or a replicative pathway, and retrotransposons which move via an RNA intermediate.
Transposons are considered significant contributors to genetic diversity and have evolved the ability to be transferred not just vertically from parent to offspring but also horizontally across species through a process called horizontal gene transfer. This inter-species gene transfer was facilitated even further by the evolution of retroviruses, revealing an adaptive advantage these mobile elements may confer to organisms in generating genomic variety despite their potential disruptive effects.
The presence of similar transposons in diverse species implies that these genetic elements have deep evolutionary roots, and the conservation across species points to an early evolution of these transposition enzymes. Moreover, the mechanisms by which transposons move, and their prevalence in different kinds of organisms, highlights their integral role in the evolution and adaptation of life forms.