Green Algae: Chlorophyta and Streptophyta

Abstract

The green algae are a major group of photosynthetic eukaryotes. Together with the embryophytic land plants they form the Viridiplantae or the green plants. Green algae are ancient, and have played an important role in the global ecosystem for millions of years. Today, green algae display a wide variety of morphologies, ranging from unicellular algae to large, complex forms. Species abound from the tropics to the poles in diverse marine, freshwater and terrestrial environments. Several species form symbiotic associations with other eukaryotes. Some species are commercially important in aquaculture, other species can form nuisance blooms. Two main clades of Viridiplantae are recognized: Chlorophyta and Streptophyta. The Chlorophyta comprise several early diverging clades of unicellular planktonic algae, mainly from marine environments (collectively called the prasinophytes), and the core Chlorophyta, which include a wide diversity of forms, ranging from unicellular to large and complex multicellular algae found in marine, freshwater and terrestrial habitats. The Streptophyta include the charophyte green algae, which include unicellular, colonial and multicellular freshwater green algae, and the land plants.