Multicellulare

Multicellulare (from Latin multus 'many' and cellula 'cell') is a descriptive term in biology used to denote organisms composed of many cells that function as an integrated whole. It is not a formal taxonomic name; rather, it characterizes life forms in which cells coordinate through adhesion, signaling, and development to form tissues and organs.

Multicellularity has evolved independently several times in eukaryotes. It can arise via clonal development, in which daughter cells remain joined after cell division, or via aggregative processes, in which independent cells come together to form a functional unit. This transition enables larger size, cellular specialization, and new ecological strategies.

Key features of multicellular organisms include cell adhesion, intercellular communication, differentiation, a coordinated life cycle, and often an extracellular matrix that stabilizes tissues. The genetic toolkit for multicellularity often involves co-option of existing genes for cell adhesion, signaling, and pattern formation, followed by regulatory innovations that control development.

Major multicellular groups include animals (Metazoa), land plants (Embryophyta), fungi, and various algae such as green, red, and brown algae. Volvox carteri is a well-studied colonial alga illustrating early forms of multicellularity; other lineages show true, differentiated tissues and organs.

Multicellularity remains a central topic in biology, linking evolution, development, and ecology. It raises questions about how cooperation evolves among cells and how complex body plans are generated and maintained.