Volvox is a freshwater green alga that proliferates by means of sexual and asexual reproduction. The cells that make up the rear portion of a volvox colony are generally involved in reproductive processes.
Volvox typically forms into mucilaginous spherical colonies that are hollow along the edges and consist of numerous cells. A colony, also known as a "coenobia," can be easily seen, and it is more or less the size of a pinhead. The two flagella that are attached to each cell provide the means of locomotion for the organism. Volvox colonies are predominant in tropical and subtropical regions.
Zoologists often classify volvox in the order volvocida while botanists place it in a category with green algae. Of the 20 species that have been identified, the volvox organism is said to be the most complex among the green algae family. Volvox colonies have evolved specialized cells, called "gonidia," which form daughter or even granddaughter colonies during asexual reproduction. These new colonies are produced within the original parent colony. When a daughter colony matures, it undergoes an inversion process where it creates the flagella. Once the granddaughter colony emerges, the parent colony breaks down. During sexual reproduction, gametes that were initially produced mature into eggs and spermatozoa. A fertilized egg results to the formation of a thick-walled embryo. New volvox colonies usually appear in the spring.