Although not all brown algae are structurally complex, those that are typically possess one or more characteristic parts.  While many carbonaceous fossils have been described from the Precambrian, they are typically preserved as flattened outlines or fragments measuring only millimeters long. The brown algae (singular: alga), comprising the class Phaeophyceae, are a large group of multicellular algae, including many seaweeds located in colder waters within the Northern Hemisphere. Cellulose and alginate biosynthesis pathways seem to have been acquired from other organisms through endosymbiotic and horizontal gene transfer respectively, while the suphated polysaccharides are of ancestral origin. A plantlike protist. The principal genera of kelp are the true kelps, found in most cool seas, and the giant kelps and bladder kelps, both of which are restricted to the northern Pacific. Giant kelps, classified in the genus Macrocystis, and bladder kelps, classified in the genus Nereocystis, belong to the family Lessoniaceae. Species of Sargassum also bear many blades and pneumatocysts, but both kinds of structures are attached separately to the stipe by short stalks. It may grow as a short structure near the base of the alga (as in Laminaria), or it may develop into a large, complex structure running throughout the algal body (as in Sargassum or Macrocystis). Brown algae include a number of edible seaweeds. Their morphological range includes filamentous, branched, feathered, and sheetlike thalli. Seaweeds, for example, are large multicellular organisms within the Protista kingdom. Other groups of brown algae grow to much larger sizes. In the order Fucales, sexual reproduction is oogamous, and the mature diploid is the only form for each generation. In low light conditions, may lose their chlorophyll and turn heterotrophic feeding on bacteria and/or diatoms.  And they can store a great amount of carbon dioxide in them which can help us in the fight against the climate change.  The Devonian megafossil Prototaxites, which consists of masses of filaments grouped into trunk-like axes, has been considered a possible brown alga. Most brown algae contain the pigment fucoxanthin, which is responsible for the distinctive greenish-brown color that gives them their name. The name lamina refers to that portion of a structurally differentiated alga that is flattened. For Questions 4â7, complete each statement by writing the correct word or words.  A large number of Phaeophyceae are intertidal or upper littoral, and they are predominantly cool and cold water organisms that benefit from nutrients in up welling cold water currents and inflows from land; Sargassum being a prominent exception to this generalisation. In species of Fucus, the pneumatocysts develop within the lamina itself, either as discrete spherical bladders or as elongated gas-filled regions that take the outline of the lamina in which they develop. It is eukaryotic, but it lack the specialized tissues of a plant. Most but not all stramenopiles are algae, the group includes diatoms, brown algae, synurophytes and other 'chrysophytes' single celled, colonial ... Protist Workshop 2008 Eukaryotes References Treehouses. Unlike a root system, the holdfast generally does not serve as the primary organ for water uptake, nor does it take in nutrients from the substrate. Kelp, common name for large, leafy brown algae, known as seaweed, that grow along colder coastlines. The true kelps belong to the family Laminariaceae and are classified in the genus Laminaria. In species like Egregia menziesii, this characteristic may change depending upon the turbulence of the waters in which it grows. In some brown algae, the pith region includes a core of elongated cells that resemble the phloem of vascular plants both in structure and function.  In other species, the surface of the blade is coated with slime to discourage the attachment of epiphytes or to deter herbivores. All algae can make their own food because they contain the pigment chlorophyll in their chloroplasts. First, members of the group possess a characteristic color that ranges from an olive green to various shades of brown. Green algae, members of the division Chlorophyta, comprising between 9,000 and 12,000 species. , Brown algae including kelp beds also fix a significant portion of the earth's carbon dioxide yearly through photosynthesis. Cambridge University Press, Cambridge. All brown algae contain alginic acid (alginate) in their cell walls, which is extracted commercially and used as an industrial thickening agent in food and for other uses. In contrast, the giant kelp Macrocystis pyrifera bears many blades along its stipe, with a pneumatocyst at the base of each blade where it attaches to the main stipe. Kingdom protista 1. They are found mainly in the tidal zones of temperate to polar seas, but some exist in the deep ocean. The cell walls of the algae are made of a cellulose similar to that found in red algae; the outsides of the walls are covered by a gelatinous pectic compound called algin. It is a symmetrical protist that often grows in small clusters because of cell division. The occurrence of Phaeophyceae as fossils is rare due to their generally soft-bodied nature, and scientists continue to debate the identification of some finds. Brown algae was classified as kingdom protista because they are non- plant photoautotrophic eukaryotes. The stipe may be relatively flexible and elastic in species like Macrocystis pyrifera that grow in strong currents, or may be more rigid in species like Postelsia palmaeformis that are exposed to the atmosphere at low tide. Synedras are generally a golden brown color and lives naturally in freshwater and saltwater locations. The intertidal species are subject to desiccation and wave action and have evolved a The closest relatives of the brown algae include unicellular and filamentous species, but no unicellular species of brown algae are known. The taxonomy of the group is contentious, and organization of the The fertilized zygote settles onto a surface and then differentiates into a leafy thallus and a finger-like holdfast. Although some heterokont relatives of the brown algae lack plastids in their cells, scientists believe this is a result of evolutionary loss of that organelle in those groups rather than independent acquisition by the several photosynthetic members.  Specifically, the brown algal cell wall is consisted of several components with alginates and suphated fucan being its main ingredients, up to 40 % each of them. This pigment is not found in other algae or in plants such as red or green algae, and as a result, brown algae are in the kingdom Chromista. Red algae, (division Rhodophyta), any of about 6,000 species of predominantly marine algae, often found attached to other shore plants. Heterokontophyta have carotenoid secondary pigments that tend to mask the green of the primary chlorophyll pigment, giving them a golden or golden-brown appearance. The cell wall consists of two layers; the inner layer bears the strength, and consists of cellulose; the outer wall layer is mainly algin, and is gummy when wet but becomes hard and brittle when it dries out. They branch by getting wider at their tip, and then dividing the widening.. Kelps lack the complexity of plant cell and tissue structures that carry water and nutrients. Most brown algae live in marine environments, where they play an important role both as food and as a potential habitat. , The simplest browns are filamentousâthat is, their cells are elongate and have septa cutting across their width. Some have chlorophyll as seen in green algae, fucoxanthin found in brown algae and phycoerythrin found in red algae. Brown algae such as kelp are harvested for use as an emulsion stabilizer, an ingredient of ice cream; as a fertilizer; as a vitamin-containing food source; and for iodine. Characteristics of Algae: Plantlike members of the kingdom Protista ; Eukaryotes ; Most unicellular, but some multicellular; Autotrophic â contain chlorophyll & make food by photosynthesis Plankton = communities of organisms, mostly microscopic, that drift passively or swim weakly near the surface of oceans, ponds, and lakes; Produce oxygen that is returned to the atmosphere Many algae have a flattened portion that may resemble a leaf, and this is termed a blade, lamina, or frond. 2.  Between generations, the algae go through separate sporophyte (diploid) and gametophyte (haploid) phases. The female gametophyte produces an egg in the oogonium, and the male gametophyte releases motile sperm that fertilize the egg.  Second, all brown algae are multicellular. For instance, Macrocystis, a kelp of the order Laminariales, may reach 60 m (200 ft) in length and forms prominent underwater kelp forests. Fritsch, F. E. 1945. Choose from 500 different sets of and algae protists red brown green flashcards on Quizlet.  Likewise, the fossil Protosalvinia was once considered a possible brown alga, but is now thought to be an early land plant. For example, alginic acid enhances the immune system of rainbow trout. In form, the brown algae range from small crusts or cushions to leafy free-floating mats formed by species of Sargassum. Most brown algae live in marine environments, where they play an important role both as food and as a potential habitat. many red algae are important food sources in Orient v. brown algae have flagella (none in red algae) vi. Scientific classification: Kelp belongs to the order Laminariales. It's a protist, not a plant.  Other algal groups, such as the red algae and green algae, have a number of calcareous members. 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