Single Cells

The smallest collections of chemicals commonly considered to be alive. Most organisms are only a single cell. Each functions as a more or less autonomous unit, carrying out processes like reproduction, nutrition, and locomotion on their own or in small groups. In a few groups, colonies have developed to the point where different cells perform different tasks, and cease to be capable of the full range of behavior necessary to survive and reproduce without each other's cooperation. In those cases, it is the group which acts as the autonomous unit, called a MulticellularOrganism.