Chlorophyceae forms a major class of algae which is characterized by green plastids called chloroplast. This plastids called chloroplast. This plastid contains a starch storing region called pyrenoids. About 425 genera and 20000 species are known. In 1935 Fritsch divided chlorophyceae into nine orders: Volvocales, Chlorococcales, Ulotricales, Cladophorales, Chaetophorales, Oedogoniales, Conjugales, Siphonales and Charales.
- Fresh water or marine algae, with unicellular or multicellular body.
- Cells are eukaryotic, containing cellulose in the cell wall.
- Chief pigments include chlorophyll a and b, alpha, beta and gamma carotenes, lycopene, hexanthin, lentin, violaxanthin and astaxanthin.
- Reserve food includes starch and very rarely oils. Starch is elaborated in pyrenoids
- Sexual reproduction is isogamous, anisogamous or oogamous.
- Zoospore formation is common.
- Male gametes are flagellate and hence motile.
- Flagella are isokont (identical)
- Life cycle is mostly haplontic.