Protists

 There are over 100,000 described living species of protists. It is unclear how many undescribed species may actually exist. The cells of protist are among the most elaborate of all cells. Most protist are microscopic and unicellular, but some true multicellular forms do exist. A few protist live as colonies that behave in someway as a group of free living cells and in other ways as a multicellular organism. Protists reproduce by a variety of mechanisms. Most are capable of some form of asexual reproduction, such as binary fission to produce two daughter cells, or multiple fission to divide simultaneously into many daughter cells. Others produce tiny buds that go on to divide and grow to the size of the parental protists. Many protist species can switch from asexual to sexual reproduction when necessary.