Volvox

Volvox is a polyphyletic genus of chlorophyte green algae in the family Volvocaceae. Volvox species form spherical colonies of up to 50,000 cells, and for this reason they are sometimes called globe algae. First reported by Antonie van Leeuwenhoek in 1700, it is distinctive and easily identified in the microscope. It occurs in a variety of freshwater habitats and has a widespread, cosmopolitan distribution. Volvox diverged from unicellular ancestors approximately 200 million years ago. Colonies of Volvox are differentiated into somatic and reproductive cells, and are capable of both sexual and asexual reproduction. Additionally, its close relatives are diverse in body plan and reproductive strategy, ranging from unicellular organisms such as Chlamydomonas to simple colonial organisms such as Pandorina and Eudorina. Because of this, Volvox and its relatives are used as model organisms in the classroom and laboratory to study biological processes such as cellular movement, sexual reproduction, and evolution of multicellularity.