The series of evolution depicted on Figure 1 is the about the Chlamydomonas species turning to a Volvox species. Aside from that interpretation, there are more theories that elaborate multicellularity in different descriptions. First is the symbiotic theory. In this theory, cells of different unicellular species derive mutual benefits from aggregation and evolve to become the first cell types of a multicellular organism (See Figure 2). Secondly, we have the coenocytial theory that denotes that a single cell with multiple nuclei evolves to partition each nucleus within a separate membrane thereby creating a multicellular organism. See Figure 3. Finally, we have the colonial theory. This is considered as the most plausible hypothesis. A single cell divides to produce two daughter cells, which fail, to separate and lead to the production of a colony of attached cells. Selective pressure then lead to specialization and segregation of germ and somatic cells. Alternatively, separate cells aggregate to form as a colony. (See Figure 4)
Outside the box, multicellularity itself has both advantages and disadvantages. Starting from the pros is intelligence and evolution. Being multicellular allows an organism to develop a higher level of adaptation to its surroundings. The organism is more complex hence, it can become more intelligent as it made a contact with the surroundings. This complexity can also be a key to its survival, adaptation, and reproduction in terms of natural selection that can be the aid to the population’s evolution. Another positive outlook is being bigger than some other organisms. When you are large in size, the risk of being a prey is low. Another pro is having a complex cell structure means that an organism will have multiple cells that perform many different functions. There will be less stress and longer lifespan in the fact that there will be no single structure that does everything on its own that may lead to weaknesses in some aspects. Next advantage, production and repair of damaged cells in a multicellular organism are achieved by employing other cell types that act as worker cells. These worker cells serve as shield to harmful impacts on the system and deteriorate some delicate forms. Notwithstanding, in some cases, being a multicellular organism is also somehow not that good. These kind of organism have the possibility to be infected. Many bacteria and viruses are single-celled and this