Unicellular eukaryotes are single-celled organisms, all of which were traditionally classified in the kingdom Protista. The term "unicellular" denotes that these organisms have only one cell, while the term "eukaryote" means that each of these cells has a nucleus -- and other organelles -- held in place by membranes. While these protists can be both plant-like or animal-like, their taxonomy is still undecided.
Types of Unicellular Eukaryotes
Unicellular eukaryotes include protozoans, slime molds and some forms of algae, and are differentiated by one of four ways in which they acquire energy. Some protists are photosynthetic, using photosynthesis to transform light into glucose. Others are chemosynthetic, performing a similar process to break down chemicals into usable fuel. Some protists are heterotrophs that secrete enzymes that digest food externally, after which they absorb the digested nutrients into their bodies. Finally, there are heterotrophs that eat food and digest it within their bodies.