diplonttinen

Diplonttinen, or the diplontic life cycle, is a term in biology describing a developmental pattern in which the multicellular organism is predominantly diploid (2n). In this pattern, meiosis occurs within the diploid germline to produce haploid gametes, which then fuse during fertilization to form a diploid zygote that grows into the diploid adult. Consequently, the haploid phase is limited to the production of gametes and is usually not a multicellular organism.

In practical terms, diplontic life cycles are most common in the animal kingdom. Most animals, including vertebrates and many invertebrates, display gametic meiosis where the zygote is the only clearly diploid cell stage that gives rise to all tissues after fertilization. The haploid stage, when present as gametes, is typically short-lived and unicellular or confined to reproductive tissues.

In plants and some algae, life cycles more often show alternation of generations with sporic meiosis (sporophyte-dominated or haplodiplontic patterns) rather than a strict diplontic one. However, there are lineages in which diplontic patterns persist or evolve, illustrating the diversity of reproductive strategies across taxa.

When used, the term is contrasted with haplontic life cycles (zygotic meiosis) and sporic life cycles (sporic meiosis). These concepts help explain variations in development, reproduction, and evolution across different groups of organisms.