What is Brown algae?
{{Taxobox | fossil_range = Jurassic to present {{fossil range|earliest=200|150|0|ref=}} | image = Kelp-forest-Monterey.jpg | image_caption = Giant kelp (''[[Macrocystis pyrifera]]'') | domain = [[Eukaryota]] | regnum = [[Chromalveolata]] | divisio = [[Heterokont]]ophyta | classis = '''Phaeophyceae''' | classis_authority = [[Frans Reinhold Kjellman|Kjellman]], 1891<ref> {{cite book |last=Kjellman |first=F. R. |year=1891 |chapter=Phaeophyceae (Fucoideae) |editor1-last=Engler |editor1-first=A. |editor2-last=Prantl |editor2-first=K. |title=Die natürlichen Pflanzenfamilien |volume=1 |issue=2 |pages=176–192 |location=Leipzig |publisher=Wilhelm Engelmann }}</ref> | subdivision_ranks = [[Order (biology)|Order]]s | subdivision = ''see [[#Classification|Classification]]''. | synonyms = Fucophyceae<br /> Melanophyceae<br /> Phaeophyta }} '''Brown algae''' are a large group of [[multicellular]] [[algae]]. All the brown algae are multicellular. Most brown algae have [[fucoxanthin]], a chemical that gives them a brown color. They include many seaweeds in colder waters of the [[Northern Hemisphere]]. Most brown algae live in [[marine environment]]s, where they play an important role both as food and as a potential habitat. There are 2000 species of brown algae. Most species live in the [[ocean]]. They are important as food and as homes for many animals and marine life. Some brown algae are gathered by humans for food. The giant [[kelp]] ''Macrocystis'' is a brown alga that forms underwater forests, and it may grow to 60 meters. The [[Sargasso Sea]] gets its name from the ''[[Sargassum]]'' seaweed that floats on the surface. Many brown algae grow on rocks at the seashore. Brown algae are unique among heterokonts in developing into multicellular forms with differentiated tissues. But they reproduce by means of [[flagella]]ted [[spores]] and [[gametes]] that look like the cells of other heterokonts. Genetic studies show their closest relatives to be t