ABSTRACT
Over 20,000 species of algae have been identified, and the global algal population is responsible for approximately 40–50% of global photosynthesis. Algae are primarily eukaryotes that typically, but not necessarily, live in aquatic environments. Most algae are autotrophic or photoautotrophic. However, certain species of algae are heterotrophic. The green lineage (Viridiplantae) includes the green algae and their descendants, the land plants. The evolution of green algae shows the early divergence of two clades: Chlorophyta and Streptophyta.
The macroalgae include the green algae with Chlorophyta and Charophyta, Rhodaphyta (red algae), and Phaephyceae (brown algae).
The microalgae include the Bacillariophyta (diatoms), the Cryptophyta, the Chrysophyta (golden algae), the Cyanobacteria (blue-green algae), the Dinophyta or Pyrrophyta (dinoflagellates), the Euglenophyta, and the Xanthophyta (yellow-green algae).
