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Definition, types, ecology, life cycles, structure.... More...
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Definition, types, ecology, life cycles, structure.
ALGAE DEFINED AND DELINEATED Thomas defines algae as: Plants belonging to the subphylum Algae of the phylum Thallophyta, the lowest division of the plant kingdom. They are nonparasitic plants without roots, stems, or leaves; they contain chlorophyll and vary in size from microscopic forms to massive seaweeds. They live in fresh or salt water or in moist places. Some serve as food or as sources of medicinal products (9:56-57). Alexander and Alexander (1) report that algae is one of the two distinct types of Thallophyta, or those plants without the specialized organs (i.e., leaves, stems, roots) that are characteristic in higher-order plants. There are several phyla
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Some serve as food or as sources of medicinal products (9:56-57). Gayles (2) adds that intermediate hues are also evident.Tait (8) further notes that the food is stored as a glycogenlikecarbohydrate. Tait (8) reports that there are certain species of blue-green algaethat use elemental nitrogen from the atmosphere, resultantly contributingusable nitrogen compounds to the soils of shallow water areas, such as ricepaddies. ALGAE DEFINED AND DELINEATED Thomas defines algae as: Plants belonging to the subphylum Algae of the phylum Thallophyta, the lowest division of the plant kingdom. There are certain blue-green algae thatare involved in the deposit of marl in lakes. Parsons, Takahashi, and Hargrave(5) report that Laminaria, or "Devil's Apron," may grow to over 1, feetin length. Arepresentative example of this phylum is Euglena, which has a singleflagellum for locomotion. Symbiosis in the oceans of the world. This is accomplished by the use of light rays thathave not been filtered out by surface water. Regarding reproduction, the basic methods ofreproduction in the plant kingdom evolved from the algae. Ecology of inland waters and estuaries, 2nd ed.New York: MacMillan Book Publishers; 198 .Renston, W. The haploid zoospores developinto diploid plant, which produces the haploid zoospores through meiosis.This represents an alternation of phases in reproduction. Biology as life. Reid and Wood(6) report that the Ulva involves two almost identical plant bodies, withone being haploid and one being diploid. London: Butterworths; 1981.Thomas, D.L. Although the cells contain nucleoproteins, and DNA is involved intheir heredity, there are no nuclei. Levine andRotman (3) report that these algae, which are primarily marine, are mostcommonly found along rocky seacoasts in the lower intertidal zone or indeeper water. Gayles (2) adds thatblue-green algae reproduces by means of (vegetative) cell division, with noevidence to date of a sexual or parasexual process being involved. The filamentis attached to the substrate by a modified basal cell, the holdfast. They range in size from the microscopic tothe monstrous kelps that are among the largest plants growing on the earth. In addition, cellulose cell wallsand whiplash flagella are or can be evident. Gayles (2) reports thatSpirogyra and Chlamydomonas have diplophases that are of minorsignificance, with most of their life cycles being passed during thehaplophase, which alone undergoes vegetative reproduction. PYRROPHYTA (FIRE ALGAE) Levine and Rotman (3: 328) report that there are approximately 1, known species of this form of algae. New York: Stewart, Tabori &Chang, Publishers; 1985.Levinton, J.S. The specie Oedogonium is afilamentous fresh water alga, which is similar in appearance to Ulothrix.The chloroplast consists of a cylindrical network with several paranoids(1). BROWN ALGAE The brown algae, or phylum Phaeophyta, are all multicellularorganisms, ranging from simple branched filaments lacking specialization togiant seaweeds. The cellulose cell wall is surrounded by a mucilaginouslayer, which is an economically important source of agar. New York: Pergammon Press; 1984.Reid, G. There are some red algae, however, that are fresh waterspecies occurring in cold swift-flowing streams. Red algae plantshave one or more elaborate filaments forming an axis, from which lateraland sometimes feathery filaments branch (1). Marine ecology. The cellulose cell wall issurrounded by a gelatinous layer containing alginates. The colors of hot springs are usually the result of the blue-green algae, some of which live and metabolize at temperatures as high as7 ?C. New York:MacMillan Book Publishers; 1981.Tait, R.V. Reid and Wood (6) as well note that the algae manifests the simplestform of sex organs, whereby a vegetative cell is converted into a cell thatforms one or more gametes. The gametes are flagellated. Blue-green algae are widelydistributed, with these plants being found in damp soil and in both freshwater and sea water. Relative to size,there are some algae that are microscopic and, resultantly, are among thesmallest plants in existence. They are nonparasitic plants without roots, stems, or leaves; they contain chlorophyll and vary in size from microscopic forms to massive seaweeds. Life undersea. There are approximately 7, known species of green algae(3: 328). Some species grow in especially rigorousenvironments like hot springs, heavily mineralized waters, antarctic Pools,and other places where they (and often some bacteria) may be the only formsof life" (2: 328). These plants do not evidenceflagellated cells. New York: John Wiley & Sons; 1987.Levine, J. BLUE-GREEN ALGAE Levine and Rotman (3: 328) report that blue-green algae have 2, known species. Reid and Wood (6) further report that there are wide differencesamong algae with regard to pigment condition. Tait (8) reports that blue-green algae, or the phylumCyanophyta, are procaryotic, with the cell wall being similar to that ofbacteria. Tait (8) reports that many forms of blue-green algae are colonial,with individual generally unspecialized cells that are produced by asexualreproduction being held by the gelatinous sheath. To this, Gayles adds: "They also abound in lakes,streams, and the soil. The few algae that are capable of surviving with a low supplyof water must have a minimum amount to remain alive. There are other forms of this plant that form algal "blooms" thatmay give a disagreeable odor to drinking water and, occasionally, causefish lethality or human illness. GREEN ALGAE The phylum Chlorophyta (i.e., green algae) is a large groupconsisting of several species of unicellular and multicellular organisms.The green algae have chlorophylls a and b, with their reserve food beingstarch that is stored in chloroplasts. Alexander and Alexander (1) report that the green algae have lifecycles that include sexual and asexual reproduction, and that these plantsalternate between haploid and diploid generations. The red algae, or phylum Rhodophyta, consist of relatively smallplants ranging from a few inches in length to 2-3 feet. Renston further notes that: "Coral reefs are constructionalphysiographic features of tropical seas, and they primarily consist of arigid calcareous framework made of encrusted skeletons of reef-building(hermatypic) corals and crustose corraline red algae" (7:122). SUMMARY OF THE MAIN STRUCTURAL CHARACTERISTICS OF ALGAE Reid and Wood (6) report as to habitat that algae are primarilyaquatic organisms, although some are capable of living on land under dampconditions. Levine and Rotman (3) add that the Volvox is also among green algae,which is colonial in form, with individuals being structurally similar toChlamydomonas. Works CitedAlexander, G. The most characteristic form is afilament consisting of cells that are attached end to end. Taber's cyclopedic medical dictionary, 15th ed.Philadelphia: F.A. Gayles (2)notes that, specifically for Laminaria, the sporophyte has become moreconspicuous than is the gametophyte. The excess photosynthate is stored in the form oflipids and laminarin, or a soluble sugar. Biology. Forthis specie, each cell has a single chloroplast, with the latter shapedsimilarly to a broad transverse belt. That is, the blue-greenalgae are the only group in which the pigments are not organized intoplastids. Regarding nuclear condition, the blue-green algae present an unusualnuclear condition, whereby chromatin bodies function as a nucleus. The Dinoflagellate is a representative example of this type ofalgae. Gayles (2) reports that, while almost all algae are aquatic,others are not, by their growing in soil or inside or among the damp or wettissues of other plants. New York: MacMillan BookPublishers; 1985.Gayles, John. Among the specie of green algae is Ulothrix, which is a fresh wateralga consisting of an unbranched filament of cells in linear order. EUGLENOPHYTA (EUGLENOIDS) The phylum Euglenophyta consists of 45 known species (3: 328). This algae also has an eyespot, the presence ofchloroplasts, and manifests complex nutritional requirements. For all blue-green algae, the cell or the entire colony presents a mucilaginous outerwall. Davis Company; 1985.----------------------- 1 & Rotman, J. This plant isa sheetlike thallus, which is two cells thick, with the cells beingelongated at right angles to the surface. There are several phyla of algae, consisting of the Cyanophyta,Chrsophyta, Pyrrophyta, Eublenophyta, Chlorophyta, Phaeophyta, andRhodophyta. & Hargrave, B. Biological oceanographicprocesses, 3rd ed. The food storage product isFloridean starch. Thisspecie is common between low and high tides on both coasts. The holdfast is formed byrhizoids from some of the lower cells. In fact, with further regard toaccessory pigments, they can function in part by transferring the lightenergy that they absorb to chlorophyll a, as is the case with phycocyaninand phycoerythrin, light absorbers during photosynthesis. The algae manifest diversity in reproduction, with some nothaving sporophytes. Thephotosynthetic cells contain cholorophylls a and c and the brown accessorypigment, fucoxanthin. They live in fresh or salt water or in moist places. The attributes of dinoflagellates include being red in color, whichis responsible for "red tide," and releasing toxin, which kills fishes. The characteristics of this phyluminclude fire algae being an important constituent of plankton, having greenand colorless forms, some being bioluminescent and the majority beingmotile. Alexander and Alexander (1) report that algae is one of the twodistinct types of Thallophyta, or those plants without the specializedorgans (i.e., leaves, stems, roots) that are characteristic in higher-orderplants. Thecharacteristics of this phylum include classification as both plants andanimals, green and colorless forms, and no known sexual reproduction. This diffuse condition would seem to be a simpler one than theplastid condition. These algae havebeen used as fertilizers, a source of iodine, and a source of alginates,which are used as food stabilizers in ice creams, salad dressings, andcandy bars, as well as components of underwater paints, some plastics, andwaterproof cloth, The brown algae are generally located on the ocean floorwithin intertidal regions and, with the exception of Sargassum, do notsurvive when suspended freely in water. This group of algae has numerous complex life cycles,with asexual and sexual reproduction and examples of either free-living orparasitic sporophyte and gametophyte stages. Theseplants contain chlorophyll as well as a blue pigment, or phycocyanin, andother pigments that may result in red, yellow, blue, or purple color aswell as green. There occurs with this plant simple differentiation, wherebythe holdfast is rootlike, the sipe is stemlike, and the blade is leaflike.For the rockweed (Fuchus), air bladders, or floats, present. Englewood Cliffs: Prentice-Hall, Inc.;1982.Parsons, T., Takahashi, M. In addition, this form of algaproduces two different gametophytes, consisting of a male and a female. The cell wall of this plant is surrounded by a gelatinous sheathand is absent of flagella. For theunicellular forms, the simple asexual reproduction proves sufficient forsurvival, while many multicellular forms reproduce via fragmentation.There are some forms that produce asexual zoospores, such as Chlamydomonasand other brown and red algae, in which haploid, motile cells give rise tohaploid plants. Alexander and Alexander (1) report that the brown algae phylum hasspecialized reproductive organs, with a variety of life cycles that includeasexual and sexual reproduction. The algaeEctocarpus, like the sea lettuce or Ulva, possesses a definite sporophyte,which allows it to evidence an evolutionary trend that is present in allplants; that is, a switch from the haplophase to the diplophase part of thecycle. & Wood, R. Further, various groups of algae are thought tohave arisen independently from protists, which is how some algae areclassified. While some blue-green algae are unicellular andsolitary, most of these plants consist of clumps or colonies of attachedcells, with little differentiation. As further example of pigment variations among algae,red algae have the accessory pigments red phycoerythrin, while Chrysophytahave yellow-green algae and diatoms. Renston notes that there are some species of this algae located incoral reefs and are believed to be important to the reef building process(7). The actionspectra that occurs in various algae demonstrate that phycocyanin andphycoerthrin have the ability to act as light absorbers during thephotosynthesis process. RED ALGAE Parsons et al. The broad ribbonlike thallus of the kelp (Laminaria) maybe in excess of 1 feet in length (1). While most species of greenalgae live in fresh water, some are marine and others are found on land inmoist habitats (1). Thespecie Ulva is a marine alga that is also referred to as sea lettuce. The chloroplast contains one or moresmall centers, or pyrenoids, which are surrounded by starch. & Alexander D. While cholorophyll a is theprimary photosynthetic pigment, accessory pigments, such as redphycoerythrin, enable red algae to live at greater ocean depths than otherphotosynthetic plants. (5) report that red algae consists of 2,5 knownspecies. Theremaining groups of algae have well-defined nuclei that compare with thoseof the higher-order plants. Elements of marine ecology. The individual cells are microscopicin size, but colonies are readily visible to the unassisted eye.
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