Volvox is a ball-shaped green alga that swims with a rolling motion. About 20 species (kinds) of Volvox have been identified. Volvox algae live in freshwater habitats around the world, from small puddles to ponds and lakes. Like plants, Volvox uses energy from light to combine water and carbon dioxide , making food. This process is called photosynthesis .
Volvox evolved (developed over time) from single-celled green algae. These algae formed colonies (groups) in which some cells specialized in reproductive functions.
Colonies may measure up to 3/25 inch (3 millimeters) in diameter. The number of cells in a colony varies among species, ranging from 500 to 50,000. All Volvox include two kinds of cells: somatic (body) cells and reproductive cells. The somatic cells move the organism using whiplike extensions called flagella . The reproductive cells divide and make new Volvox colonies, a type of asexual reproduction . When fully developed, the daughter colonies hatch out and live for a couple of days before hatching daughter colonies of their own. The remaining cells of the ruptured parent colony age and soon die.
In harsh conditions, Volvox may make use of sexual reproduction. The algae release sperm cells that are capable of moving on their own. These sperm cells then fuse with egg cells to form spores . When they reach suitable environments, the spores germinate and make new Volvox.
