Algae

From Palaeos

The term alga is used for any (usually aquatic) photosynthetic organism containing chlorophyll except land plants. As such, it is a polyphyletic group. However, the one bacterial group of algae, the Cyanobacteria (blue-green algae) is believed to be ancestral to the chloroplasts of all other algae via endosymbiosis. Aside from cyanobacteria, other major groups of algae include brown algae, yellow-brown algae, red algae and green algae. Multicellularity has evolved independently in each of these groups, probably multiple times in the case of green algae. There are also a wide range of unicellular algal groups, including (among others) dinoflagellates, coccolithophores, diatoms, golden algae and euglenoids. In palaeontology, the term "algae" is also used to refer to a number of sessile or unicellular organisms of uncertain relationships that may or may not be related to modern algal groups.

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