Fig. 1. Evolution of multicellularity in eukaryotes.

Multicellular organisms can be subdivided into two types. Type I – cohesive multicellularity -starts off from a spore or fertilized egg that undergoes repeated divisions and morphogenesis, with cells remaining together and feeding in the multicellular stage. In Type II – aggregative multicellularity – cells feed and proliferate as single cells and only come together when stressed, usually by starvation. The aggregates next transform into a fruiting body where the cells enter dormancy and encapsulate into either cysts or spores. Aggregative multicellularity evolved independently in most major eukaryotic divisions. Phylogeny (grey lines) after He, et al. (2014).