4-classifications of algae

8/9/2019 4-Classifications of Algae

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CLASSIFICATIOCLASSIFICATIONSNS

OFOF

ALGAEALGAE


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Biologists classify algae into sixdivisions, based on color, food storage

substances, and the composition of cellwalls. Members of each division havedistinctive colors, depending on thephotosynthetic pigments of their cells.

These pigments absorb light. All algaecontain the pigment chlorophyll a. However,different divisions of algae also containother forms of chlorophyll, such as b, c, or d,

each of which absorbs a differentwavelength of light. Member of differentalgal divisions have different accessorypigments as well. Algae also vary in

methods of reproduction.


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CHLOROPHYTACHLOROPHYTA

Members of thedivisionChlorophyta, the

green algae, area diverse groupof organisms ofover 7,000species. Theycan beunicellular,colonial,filamentous, or


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Most green algae are aquaticalthough many inhibit moist terrestrial

environments such as soil, rocksurfaces, and tree trunks.

Three observations have ledbiologists to conclude that green algaeare ancestors of plants. First, bothgreen algae and plants have

chloroplasts the contain chlorophylls aand b. Second, both green algae andplants store food as starch. Finally,both green algae and plants have cell

wall made of cellulose.


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To understand some of the diversityin unicellular green algae:

ChlamydomonasIs common in soils

and in fresh ponds andstreams. It has a singlecup shapedchloroplasts. Each

chloroplast contains apyrenoid, where starchis made. Two anteriorenable the organism toswim. An eyespot, which

is an area sensitive tolight, enables alga tomove either toward oraway from the light.


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Desmids

are unusualunicellular algae thelive primarily in freshwater. In fact, the

presence of desmidsoften indicates degreeof water pollution.


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Unlike un icellular a lgae , colonial algae have som echaract er ist ics of m ult icellular organ ism s:

Oedogonium is another

common freshwaterfilamentous greenalga. Members ofthis genus have

netlike chloroplasts.


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Spirogyra is a

filamentousgreen alga with

unusual spiralchloroplasts thatstretch from oneend of the cell tothe other.


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Gonium is a small, motile, colonial

green alga consisting ofbiflagellate cells in a flat

plate. The cells use their pairof flagella to swim with arotating motion. Differentspecies may have 4, 8, 16, or32 cells that are ovoid orangular in shape. Each cellhas an eyespot, two

contractile vacuoles at thebase of the flagella, and alarge cup-shaped chloroplastwith at least one pyrenoid.Each cell is enclosed within amucilage sheath, which join

together to form the colony.Unlike the larger volvocaleancolonies such as Volvox orEudorina, the cells ofGoniumcolonies are identical andshow no evidence ofspecialization.


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Ulva has a leaf like ,

photosyntheticbody andcommonly growson rocks and

pilings. Its thalluscollapses duringlow tide to preventwater loss in the

intertidal zone, theare between highand low tides.


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PHAEOPHYTAPHAEOPHYTA

Members of thedivisionPhaeophyta,

the brownalgae, aremulticellularand usuallylarge. Most oftheapproximately

1,500 species


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The Rhodophyta (red algae) are adistinct eukaryotic lineage characterized bythe accessory photosynthetic pigments

phycoerythrin, phycocyanin andallophycocyanins arranged inphycobilisomes, and the absence of flagellaand centrioles. This is a large assemblage ofbetween 2500 and 6000 species in about670 largely marine genera that predominate

along the coastal and continental shelfareas of tropical, temperate and cold-waterregions. Red algae are ecologicallysignificant as primary producers, providersof structural habitat for other marine

organisms, and their important role in theprimary establishment and maintenance ofcoral reefs. Some red algae are economicallyimportant as providers of food and gels. Forthis reason, extensive farming and naturalharvest of red algae occurs in numerous

areas of the world.


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CHRYSOPHYTACHRYSOPHYTA

Members of thedivisionChrysophytaare calledgolden brownalgae. Thereare over10,000 speciesof golden brown algae,the majority ofwhich arecommonly


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Chrysophytes, or golden algae,are common microscopic chromists in

fresh water. Some species arecolorless, but the vast majority arephotosynthetic. As such, they areparticularly important in lakes, wherethey may be the primary source of

food for zooplankton. They are notconsidered truly autotrophic by somebiologists because nearly allchrysophytes become facultativelyheterotrophic in the absence of

adequate light, or in the presence ofplentiful dissolved food. When thisoccurs, the chrysoplast atrophies andthe alga may turn predator, feedingon bacteria or diatoms.
http://www.ucmp.berkeley.edu/chromista/chromista.htmlhttp://www.ucmp.berkeley.edu/bacteria/bacteria.htmlhttp://www.ucmp.berkeley.edu/chromista/bacillariophyta.htmlhttp://www.ucmp.berkeley.edu/chromista/bacillariophyta.htmlhttp://www.ucmp.berkeley.edu/bacteria/bacteria.htmlhttp://www.ucmp.berkeley.edu/chromista/chromista.html


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There are more than a thousand

described species of golden algae, most ofthem free-swimming and unicellular, but thereare filamentous and colonial forms. Otherchrysophytes may spend part of their life asamoeboid cells. At the left and center of theabove illustration is Dinobryon, a freshwater

genus in which the individual cells aresurrounded by vase-shaped loricae, composedof chitin fibrils and other polysaccharides. Thecolonies grow as branched or unbranchedchains. A spherical colonial form, Synura, is onthe right; the surfaces of these cells are

covered by silica scales. Species whichproduce siliceous coverings may have bristlesor scales with quite complex structure. Someresearchers group the chrysophytes with silicascales in a separate taxon, the Synurophyceae.


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Some Pyrrophyta are photosyntheticspecies, however, whereas others are not.They come in a variety of shapes and sizes

and the photosynthetic species havegolden-brown or yellowish-greenchloroplasts. They can synthesize bothtypes of chlorophyll, type a and type c, andcontain high levels of carotenoids (yellow

pigments). Some Pyrrophyta, such asGymnodium and Gonyaulax aredinoflagellates responsible for red tides andsecrete neurotoxins that cause massive fishdeath. If these toxins are airborne in aclosed room, or if they get in contact with

the skin, they may contaminate humans andcause temporary or more severeneurological disorders. Some species suchas the Ceratium can deplete water fromoxygen, also leading to massive fish death,

a phenomenon known as black tide.


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EUGLENOPHYTAEUGLENOPHYTA

Approximately1,000 species ofthe division

Euglenophyta areunicellular algaethat have manyfeatures in

common withgreen algae.However, theyalso have many

characteristics


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Euglenophyta , small phylum (division)of the kingdom Protista , consisting of mostlyunicellular aquatic algae . Most live in

freshwater; many have flagella and aremotile. The outer part of the cell consists of afirm but flexible layer called a pellicle, orperiplast, which cannot properly beconsidered a cell wall. Some euglenoids

contain chloroplasts that contain thephotosynthetic pigments chlorophyll a and b,as in the phylum Chlorophyta ; others areheterotrophic and can ingest or absorb theirfood. Food is stored as a polysaccharide,paramylon. Reproduction occurs bylongitudinal cell division. The mostcharacteristic genus is Euglena, common inponds and pools, especially when the water

has been polluted by runoff from fields orlawns on which fertilizers have been used.
http://www.encyclopedia.com/doc/1E1-Protista.htmlhttp://www.encyclopedia.com/doc/1E1-algae.htmlhttp://www.encyclopedia.com/doc/1E1-chloropl.htmlhttp://www.encyclopedia.com/doc/1E1-Chloroph.htmlhttp://www.encyclopedia.com/doc/1E1-Chloroph.htmlhttp://www.encyclopedia.com/doc/1E1-chloropl.htmlhttp://www.encyclopedia.com/doc/1E1-algae.htmlhttp://www.encyclopedia.com/doc/1E1-Protista.html


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Euglena, themost familiar typeof euglenoid, ispropelled by a

long flagellum. Aneyspot guides thealga toward light.


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BACILLARIOPHYTBACILLARIOPHYT

AAThe

Bacillariophytaare the diatoms.

With theirexquisitelybeautiful silicashells, or

frustules such asthat ofOdontellashown above atright, diatoms

are among the


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They are also among the most importantaquatic microorganisms today: theyare extremely abundant both in theplankton and in sediments in marineand freshwater ecosystems, andbecause they are photosynthetic theyare an important food source formarine organisms. Some may even be

found in soils or on moist mosses. Diatoms have an extensive fossil record

going back to the Cretaceous; somerocks are formed almost entirely offossil diatoms, and are known as

diatomite or diatomaceous earth.These deposits are minedcommercially as abrasives andfiltering aids. Analysis of fossil diatomassemblages may also provide

important information on pasten ironmental conditions

4-classifications of algae

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