In fact, in this part of the lecture, we're interested in the origin of multicellularity. In fact, the association of cells into multicellular groups represents a major transition in the history of life and the division of labor within an organism. This transition is both important and enigmatic. It has occurred on numerous occasions (algae, descendant land plants, fungi, animals, amoebae), but has not stabilized in all taxa.
Two mechanisms that may lead to multicellularity are discussed by specialists. The first consists in not separating after division. The second consists in bringing together dispersed elements. In the first case, the cells are genetically homogeneous, and heterogeneity can only arise from "accidental" modifications to the genome, such as somatic mutation or infection by a pathogen. As a result, differentiation into different cell types or groupings - a form of organogenesis - is mainly the result of epigenetic mechanisms.
