A unicellular organism is an organism consisting of a single cell that performs all the functions necessary for its survival.
A single cell in a unicellular organism carries out processes such as obtaining nutrients, producing energy, responding to its environment, and reproducing. Bacteria, many fungi, and many protozoa are unicellular organisms.
“Single-celled organism” is a plain-language expression with the same basic meaning. Unicellular is the preferred scientific term.
QUICK FACT
A single cell can be a complete organism; multicellular organisms, by contrast, consist of many specialized cells working together.
COMMONLY CONFUSED WITH
Multicellular organism: A unicellular organism consists of one cell, whereas a multicellular organism consists of many cells.
SEE ALSO
- Multicellular
- Protozoa
- Protozoan parasite
- Microorganism
- Cell