Among pro-monerans, two main structural types played important role in evolution. In one type, the genus aggregated together into thread like filaments and formed loose structures which remained embedded within the cell substance and in direct contact with it. Such group of organisms formed monera or prokaryota. The organisms of this category are still in existence even in today, such as bacteria and blue green algae. These early monera must have developed four of the five methods of nutrition, i.e. photosynthetic, chemosynthetic, parasitic or saprophytic (except holotrophic). In second type, the nucleic acids in each cell again condensed into thread like filaments involving protein as integral part of it, thus formed chromosomes.