Some protists also undergo another type of asexual reproduction known as budding. While binary fission produces two daughter cells similar in size, budding produces daughter cells that are unequal in size (but genetically identical). After nuclear replication, the daughter nuclei are located at opposite ends of the cell. However, the partitioning of the cytoplasm occurs unevenly, so a small amount of cytoplasm surrounds one daughter more than the other. Eventually, the smaller daughter cell pinches away from the larger cell - it will enter a growth phase and become the same size as the other mature cells of the species. One disadvantage of binary fission is that both daughter cells must enter a growth phase before reproducing. However, in budding systems, the larger daughter cell can enter another reproduction cycle without a long growth phase (the smaller budded cell must grow before reproducing).

Sporulation in a protist - an unusual example of alternation between unicellularity and multicellularity

The protist Dictyostelium discoideum is an amoeboid protist. It is also called a slime mould. It feeds on soil bacteria and normally divides by mitosis. However, when food becomes scarce, this organism transforms into a multicellular organism! The multicellular stage, called a slug, crawls to new locations and forms a fruiting body. Each fruiting body contains numerous spores. When favourable conditions return, the spores disperse and germinate, forming new amoeba. Therefore, Dictyostelium alternates between unicellular and multicellular stages.