green algae

A large and diverse group of alga-like plants characterized by the photosynthetic pigments, chlorophylls a and b, which give them their green colour; typically storing food as starch in chloroplasts; found predominantly in fresh water; many have motile stages (zoospores) that swim using flagella. (Class: Chlorophyceae.)

The Green algae (singular: Green Alga) are the large group of algae from which the embryophytes (higher plants) emerged. The green algae include unicellular and colonial flagellates, usually but not always with two flagella per cell, as well as various colonial, coccoid, and filamentous forms. A number of cyanobacteria show similar pigmentation, but this appears to have arisen more than once, and the chloroplasts of green algae are no longer considered closely related to such forms. Instead, the green algae probably share a common origin with the red algae.

Green algae are often classified with their embryophyte descendants in the green plant clade Viridiplantae (or Chlorobionta). Viridiplantae, together with red algae and glaucophyte algae, form the supergroup Primoplantae, also known as Archaeplastida or Plantae sensu lato.

All green algae have mitochondria with flat cristae. In older systems the Chlorophyta may be taken to include all the green algae, but taken as above they appear to form a monophyletic group.

A few other organisms rely on green algae to conduct photosynthesis for them. Some species of green algae, particularly of genera Trebouxia or Pseudotrebouxia (Trebouxiophyceae), can be found in symbiotic associations with fungi to form lichens.