The Chlorophyceae are a large and important group of freshwater green algae. They include some of the most common species, as well as many members that are important both ecologically and scientifically.

There are approximately 350 genera and 2650 living species of chlorophyceans. They come in a wide variety of shapes and forms, including free-swimming unicellular species, colonies, non-flagellate unicells, filaments, and more. They also reproduce in a variety of ways, though all have a haploid life-cycle, in which only the zygote cell is diploid. The zygote will often serve as a resting spore, able to lie dormant though potentially damaging environmental changes such as dessication. Link

The Chlorophyceae are one of the classes of green algae, distinguished mainly on the basis of ultrastructural morphology. For example the chlorophycean CW clade, and chlorophycean DO clade, are defined by the arrangement of their flagella. Members of the CW clade have flagella that are displaced in a clockwise (CW, 1–7 o'clock) direction eg. Chlamydomonadales. Members of the DO clade have flagella that are directly opposed (DO, 12–6 o'clock) eg. Sphaeropleales. Link