Written by the Fiveable Content Team • Last updated August 2025
Written by the Fiveable Content Team • Last updated August 2025
Definition
Paramecium is a genus of unicellular ciliated protozoa commonly found in freshwater environments. They are characterized by their slipper-like shape and numerous hair-like structures called cilia.
Paramecia use cilia for locomotion and to sweep food particles into their oral groove.
They reproduce asexually through binary fission but can also engage in conjugation, a form of sexual reproduction.
The cell structure includes a macronucleus that controls non-reproductive cell functions and one or more micronuclei involved in reproductive processes.
They have specialized vacuoles: contractile vacuoles for expelling excess water and food vacuoles for digestion.
Paramecia exhibit avoidance behavior by reversing their direction when encountering an obstacle or harmful substance.