Algae - 3 1 General characters. INTRODUCTION TO ALGAL CHARACTERISTICS AND DIVERSITY PHYCOLOGY=STUDY...

Algae - 3Algae - 3

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General General characterscharacters

INTRODUCTION TO ALGAL INTRODUCTION TO ALGAL CHARACTERISTICS AND CHARACTERISTICS AND

DIVERSITYDIVERSITY

PHYCOLOGY=STUDY OF ALGAEPHYCOLOGY=STUDY OF ALGAEPhycology is the science (gr. logos) of Phycology is the science (gr. logos) of algae (gr. phycos). This discipline deals algae (gr. phycos). This discipline deals with the morphology, taxonomy, with the morphology, taxonomy, phylogeny, biology, and ecology of algae phylogeny, biology, and ecology of algae in all ecosystems in all ecosystems

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FOSSIL HISTORY OF FOSSIL HISTORY OF ALGAEALGAE

3.5 billion yrs ago3.5 billion yrs ago Cyanobacteria—first algaeCyanobacteria—first algae Prokaryotes—lack membrane bound Prokaryotes—lack membrane bound

organellesorganelles Later eukaryotes evolved—Later eukaryotes evolved—

mitochondria, chloroplasts, and mitochondria, chloroplasts, and chromosomes containing DNA.chromosomes containing DNA.

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Where do algae abound?Where do algae abound?

Kelp forest up to 50 m height Kelp forest up to 50 m height are the marine equivalent to are the marine equivalent to terrestrial forest; mainly built by terrestrial forest; mainly built by brown algae.brown algae.

Some algae encrustSome algae encrust with with carbonate, building reef-like carbonate, building reef-like structures; Cyanobacteria can structures; Cyanobacteria can from rock-like structures in from rock-like structures in warm tidal areas: stromatolites.warm tidal areas: stromatolites.

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Algae grow or are attached Algae grow or are attached to animals and serveto animals and serve as as camouflage for the animalcamouflage for the animal

Algae live as symbiontsAlgae live as symbionts in in animals such as Hydra, animals such as Hydra, corals, or the protozoan corals, or the protozoan ciliate Paramecium; in ciliate Paramecium; in corals they are referred to corals they are referred to as zooxanthellaeas zooxanthellae

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Small algae live on top of larger Small algae live on top of larger algae: epiphytonalgae: epiphyton

Algae in free water: Algae in free water: phytoplanktonphytoplankton

Terrestrial algaeTerrestrial algae Algae have adapted to life on Algae have adapted to life on

land and occur as land and occur as cryptobiotic crusts in desert cryptobiotic crusts in desert and grassland soils or and grassland soils or endocryptolithis algae in endocryptolithis algae in rocks rocks

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Algae live on the snow cover of glaciers Algae live on the snow cover of glaciers and in the brineand in the brine channels of sea ice. channels of sea ice.

A symbiosisA symbiosis of algae and fungi produced of algae and fungi produced the lichens, which are pioneer plants, help the lichens, which are pioneer plants, help convert rock into soil by excreting acids, convert rock into soil by excreting acids, stabilize desert soil, are sensitive to air stabilize desert soil, are sensitive to air pollutionpollution

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Algae can cover Algae can cover trees or buildings trees or buildings green or live in the green or live in the hollowhollow hairs of ice hairs of ice bearsbears

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Algal Blooms Algal Blooms Algae can be so dominant that they discolor the water Algae can be so dominant that they discolor the water Higher amounts of nutrients are usually the causeHigher amounts of nutrients are usually the cause Algal blooms can have harmful effects on life and ecosystem:Algal blooms can have harmful effects on life and ecosystem:

Reduced water clarity causes benthic communities to die offReduced water clarity causes benthic communities to die off Fish kills are common effectsFish kills are common effects 50% of algal blooms produce toxins harmful to other organisms, 50% of algal blooms produce toxins harmful to other organisms,

including humansincluding humans Algal blooms produce a shiftAlgal blooms produce a shift in food web structure and species in food web structure and species

compositioncomposition Algal blooms can mostly be linked to sewage input or agricultural Algal blooms can mostly be linked to sewage input or agricultural

activities, leading to nutrient pollution: Eutrophicationactivities, leading to nutrient pollution: Eutrophication

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SimilaritiesSimilarities

Presence of cell wall—mostly Presence of cell wall—mostly cellulosic.cellulosic.

Autotrophs/Primary producers—Autotrophs/Primary producers—carry out photosynthesiscarry out photosynthesis

Presence of chlorophyll aPresence of chlorophyll a

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DifferencesDifferences

Algae lack the roots, stems, leaves, and other Algae lack the roots, stems, leaves, and other structures typical of true plants. structures typical of true plants.

Algae do not have vascular tissues—non Algae do not have vascular tissues—non vascular plantsvascular plants

Algae do not form embryos within protective Algae do not form embryos within protective coverings—all cells are fertile.coverings—all cells are fertile.

Variations in pigments.Variations in pigments. Variations in cell structure—unicellular, colonial Variations in cell structure—unicellular, colonial

and multicellular forms.and multicellular forms.

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PROKARYOTIC VS PROKARYOTIC VS EUKARYOTIC ALGAEEUKARYOTIC ALGAE

ProkaryotesProkaryotes---No nuclear region and ---No nuclear region and

complex organelles—complex organelles—chloroplasts, mitochondria, chloroplasts, mitochondria, golgi bodies, and golgi bodies, and endoplasmic reticula.endoplasmic reticula.

-- -- Cyanobacteria. Chlorophylls Cyanobacteria. Chlorophylls are on internal membranes of are on internal membranes of flattened vesicles called flattened vesicles called thylakoids-contain thylakoids-contain photosynthetic pigments. photosynthetic pigments. Phycobiliproteins occur in Phycobiliproteins occur in granular structures called granular structures called phycobilisomes.phycobilisomes.

Prokaryote algal cellProkaryote algal cell

Source: http://www.botany.hawaii.edu/faculty/webb/BOT311/Cyanobacteria/Cyanobacteria.htm1212

Prokaryotic and Prokaryotic and Eukaryotic AlgaeEukaryotic Algae

EukaryotesEukaryotes

---Distinct chlorplast, nuclear ---Distinct chlorplast, nuclear region and complex organelles.region and complex organelles.

--- Thylakoids are grouped into --- Thylakoids are grouped into grana grana

pyrenoidspyrenoids are centers of are centers of carbon dioxide fixation within the within the chloroplasts of of algae and and hornworts. . Pyrenoids are not membrane-bound Pyrenoids are not membrane-bound organelles, but specialized areas of the organelles, but specialized areas of the plastid that contain high levels of ribulose-plastid that contain high levels of ribulose-1,5-bisphosphate carboxylase/oxygenase1,5-bisphosphate carboxylase/oxygenase

granum with aStack of thylakoids

pyrenoid

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Forms of AlgaeForms of Algae

Unicellular Multicellular

1. Colonies 2. Aggregations

•Palmelloid (Tetraspora)•Dendroid (Dinobryon)•Amoeboid (Chlororachnion)

3.Filaments4. Coenocytic / Vaucheria5.Parenkematus/ Ulva6. Psedoparenkematus / Batrachospermum7. Erect thallus / Chara

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BODY OF AN BODY OF AN ALGA=THALLUSALGA=THALLUS

DIVERSITY IN DIVERSITY IN MORPHOLOGYMORPHOLOGY

----MICROSCOPIC----MICROSCOPIC

Unicellular, Colonial Unicellular, Colonial and Filamentous and Filamentous forms.forms.

Source: http://images.google.com/images 1515


MACROALGAE

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MICRO ALGAE

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1.1. Unicells:Unicells: single cells, single cells, motile with flagellate motile with flagellate (like (like Chlamydomonas Chlamydomonas and Euglenaand Euglena) or ) or nonmotile (like nonmotile (like DiatomsDiatoms))

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2. 2. Multicellular formMulticellular form: the vegetation forms are in six forms:: the vegetation forms are in six forms:

a.a. ColoniesColonies: : Assemblage of individual cells with variable or constant Assemblage of individual cells with variable or constant

number of cells that remain constant throughout the colony number of cells that remain constant throughout the colony life in mucilaginous matrix (containing an extracellular matrix life in mucilaginous matrix (containing an extracellular matrix made of a gelatinous glycoprotein), these colonies may be made of a gelatinous glycoprotein), these colonies may be motile (like motile (like VolvoxVolvox and and PandorinaPandorina) or nonmotile (like ) or nonmotile (like Scendesmus Scendesmus andand Pediastrum Pediastrum).).

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CoenobiumCoenobium: :

Colony with constant number of cells, which cannot Colony with constant number of cells, which cannot survive alone; specific „tasks“ among groups of cells survive alone; specific „tasks“ among groups of cells is common (is a colony containing a fixed number of is common (is a colony containing a fixed number of cells, with little or no specialization)cells, with little or no specialization)

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b. b. AggregationsAggregations: is aggregation of cells that have : is aggregation of cells that have ability to simple division (so, its colony but ability to simple division (so, its colony but unconstant in form and size), the aggregations unconstant in form and size), the aggregations are in several types:are in several types:

• Palmelloid form:Palmelloid form: non-motile cells embedded in non-motile cells embedded in mucilage (like mucilage (like TetrasporaTetraspora).).

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•Dendroid form: resembling a tree in form or in pattern of growth (Dinobryon).

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•Amoeboid or Rhizopodial form such as Chlorarachnion.

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c. c. Filaments:Filaments: daughter cells remain attached after cell daughter cells remain attached after cell division and form a cell chain; adjacent cells share division and form a cell chain; adjacent cells share cell wall (distinguish them from linear colonies!); cell wall (distinguish them from linear colonies!); maybe unbranched (uniseriate such as maybe unbranched (uniseriate such as ZygnemaZygnema and and UlthrixUlthrix) or branched (regular mutiseriate such ) or branched (regular mutiseriate such as as Cladophora Cladophora or unreguler mutiseriate such as or unreguler mutiseriate such as PithophoraPithophora).).

Cladophora Pithophora2424

d. d. Coenocytic or siphonaceaous Coenocytic or siphonaceaous forms: one forms: one large, multinucleate cell without cross walls large, multinucleate cell without cross walls such as such as VaucheriaVaucheria

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e. e. ParenchymatousParenchymatous (such as (such as UlvaUlva ) and algae: mostly ) and algae: mostly macro-scopic algae with tissue of undifferentiated macro-scopic algae with tissue of undifferentiated cells and growth originating from a meristem with cell cells and growth originating from a meristem with cell division in three dimensionsdivision in three dimensions

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; pseudoparenchymatous (such as Batrachospermum) pseudoparenchymatous superficially resemble parenchyma but are composed of apprised filaments

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f. f. Erect thallus formsErect thallus forms: Thallus, from Latinized Greek : Thallus, from Latinized Greek (thallos), meaning a green shoot or twig, is an (thallos), meaning a green shoot or twig, is an undifferentiated vegetative tissue (leaves, roots, and undifferentiated vegetative tissue (leaves, roots, and stems) of some non-mobile organisms such as stems) of some non-mobile organisms such as CharaChara and and Nitella.Nitella.

Chara 2828

CELLULARCELLULAR ORGANIZATION ORGANIZATION

Flagella=organs of locomotion.Flagella=organs of locomotion. Chloroplast=site of Chloroplast=site of

photosynthesis. Thylakoids are photosynthesis. Thylakoids are present in the chloroplast. The present in the chloroplast. The pigments are present in the pigments are present in the thylakoids.thylakoids.

Pyrenoid-structure associated Pyrenoid-structure associated with chloroplast. Contains with chloroplast. Contains ribulose-1,5-bisphosphate ribulose-1,5-bisphosphate Carboxylase, proteins and Carboxylase, proteins and carbohydrates.carbohydrates.

Eye-spot=part of chloroplast. Eye-spot=part of chloroplast. Directs the cell towards light.Directs the cell towards light.

Source: A Biology of the AlgaeBy Philip Sze, third edition, WCB MCGraw-Hill

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Variations in the pigment Variations in the pigment constitutionconstitution

Chlorophylls (green)Chlorophylls (green) Carotenoids (brown, yellow or red)Carotenoids (brown, yellow or red) Phycobilins (red pigment-phycoerythrinPhycobilins (red pigment-phycoerythrin

blue pigment –blue pigment –phycocyanin)phycocyanin)

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Growth in algaeGrowth in algae

1.1. Diffuse or generalized growth: (Diffuse or generalized growth: (UlvaUlva).).

2.2. Localized growth: Localized growth: a.a. Apical growth: (Apical growth: (Chara, CladophoraChara, Cladophora).).

b.b. Basal growth: Basal growth: (Bulbochaete)(Bulbochaete)..

c.c. Intercalary growth: (Intercalary growth: (Laminaria, OedogoniumLaminaria, Oedogonium).).

d.d. Trichothallic growth: (Trichothallic growth: (EctocarpusEctocarpus))

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Growth in algaeGrowth in algae

3232Tricothallic Apical and intercalary

Reproduction in algaeReproduction in algae The reproduction of algae can be discussed The reproduction of algae can be discussed

under two types, namely, asexual reproduction and under two types, namely, asexual reproduction and sexual reproduction. The former type refers to sexual reproduction. The former type refers to reproduction in which a new organism is generated reproduction in which a new organism is generated from a single parent. In case of sexual type, two from a single parent. In case of sexual type, two haploid sex cells are fused to form a diploid zygote haploid sex cells are fused to form a diploid zygote that develops into an organism. Let's discuss in that develops into an organism. Let's discuss in brief about the asexual and sexual reproduction in brief about the asexual and sexual reproduction in algae along with examples.algae along with examples.

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First: Asexual Reproduction includes:1. Vegetation reproduction:

a. In unicellular algae: simple cell division some time called binary fission (such as Gleocapsa).

b. In multicellular (colonies, filamentous, thallus, etc) by:

Fragmentation such as Microsystis. Hormogonia: A small, motile filament, formed by

some Cyanobacteria, that detaches and grows by cell division into a new filament such as Oscillatoria.

Propagules: a structure capable of producing a new individual such as Sphacelaria.

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Vegetative reproductionVegetative reproduction

Cell DivisionA cell could not keep growing bigger forever. Food molecules could not reach the inside of a large cell fast enough to keep it alive. So when a cell reached a certain size it had to divide into two smaller cells called daughters. The daughters grew and, when they reached that certain size, they too divided, this processes called binary fission.

But this caused a problem, Why?.


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Hormogonia in Oscillatoria

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Propagules

2. Another method of asexual reproduction in 2. Another method of asexual reproduction in algae is by formation of spores; the algal algae is by formation of spores; the algal species species UlothrixUlothrix, , ChlamydomonasChlamydomonas and and ChlorellaChlorella reproduce by this method. reproduce by this method. Depending upon the algal species, the Depending upon the algal species, the spores can be produced in normal spores can be produced in normal vegetative cells or specialized cells called vegetative cells or specialized cells called sporangia. They are either motile called zoo sporangia. They are either motile called zoo spores or non motile called akinete spores.spores or non motile called akinete spores.

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3939Ulotrix

There are a lot of types of akinete spores such There are a lot of types of akinete spores such as:as:

• Autospores: immobile spores that cannot Autospores: immobile spores that cannot develop flagella such as develop flagella such as Chlorella. Chlorella.

• Aplanospores: immobile spores that may Aplanospores: immobile spores that may nevertheless potentially grow flagella.nevertheless potentially grow flagella.

• Hypnospores: A thick-walled resting cyst.Hypnospores: A thick-walled resting cyst.• Tetraspores: spores produced by a Tetraspores: spores produced by a

tetrasporophyte, characteristic of red algae.tetrasporophyte, characteristic of red algae.• Statospores: spores that are not actively Statospores: spores that are not actively

discharged from the algal fruiting bodydischarged from the algal fruiting body• Auxospores: A spore in diatom algae that leads Auxospores: A spore in diatom algae that leads

to reformation of an enlarged vegetative cell.to reformation of an enlarged vegetative cell.4040

Second: Sexual Reproduction: Second: Sexual Reproduction:

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As already mentioned, sexual reproduction takes place by the union of male and female gametes. The gametes may be identical in shape and size called isogamy or different called heterogamy. Some of the simplest forms of algae like Spirogyra reproduce by the conjugation method of sexual reproduction. In the process of conjugation, two filamentous strands (or two organisms) of the same algae species exchange genetic material through the conjugation tube. Among two strands, one acts as a donor and another serves as a receiver. After exchanging the genetic material, two strands separate from each other. The receiver then give rise to a diploid organism.

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Second: Sexual Reproduction: Second: Sexual Reproduction:

Isogamy: is the form of sexual reproduction in which the gametes produced are identical in shape, size and motility. There is no structural distinction between "male" and "female" gametes. Pairs of isogametes align themselves with their flagellar poles touching and after several seconds, the motile gametes fuse to form a single, non-motile, diploid zygote.

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Second: Sexual Reproduction: Second: Sexual Reproduction: Isogametes, less commonly, may be non-motile structures. A specific example exhibiting non-motile isogametes is the reproductive process known as conjugation, in Figure below, the conjugating Spirogyra identify the four stages of the process as outlined.

Isogamy in Spirogyra sp.

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A. Resting filaments of alga cells.B. Formation of conjugation tubes between two adjacent filaments.C. Cytoplasmic contents of each cell form a compact mass, representing an isogamete. The isogametes from one filament migrate through the conjugation tubes into the adjacent filament.The two isogametes unite to form a zygote. Each zygote eventually undergoes meiosis to form four haploid cells. One haploid cell will form a new filament by mitosis, the other three degenerate.

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HeterogamyIn heterogamy, two different types of gametes are produced. The male gamete, the sperm cell, is typically very small, highly motile and is produced in very large numbers. The female gamete, the egg cell, is much larger and non-motile, called Oogamy. Fewer female gametes are produced but each is usually afforded some protection. Heterogametes are also produced by higher plants and animals.

Oedogonium sp. is a green alga that produces heterogametes. The figure bellow illustrates the life cycle of this alga. You can locate a mature egg cell and the small male filaments, which are the site of sperm production, the egg cells and male filaments are usually adjacent to one another on the same algal strand.

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Heterogamy in Oedogonium sp.

SEXUAL REPRODUCTIONSEXUAL REPRODUCTION ISOGAMYISOGAMY-Both gametes have flagella and similar in size and morphology.-Both gametes have flagella and similar in size and morphology.

ANISOGAMYANISOGAMY-Gametes have flagella but are dissimilar in shape and size. One -Gametes have flagella but are dissimilar in shape and size. One gamete is distinctly smaller than the other one.gamete is distinctly smaller than the other one.

OOGAMYOOGAMY-gamete with flagella (sperm) fuses with a larger, non flagellated -gamete with flagella (sperm) fuses with a larger, non flagellated gamete (egg).gamete (egg).

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REPRODUCTIONREPRODUCTION

VegetativeCell divisions/Fragmentation=part of the filamentbreaks off from the rest and forms a new one.

Asexual ReproductionZoospores after losing their flagella,form new filaments. No sexual fusion.

Sexual-Gametes

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a, b, and c are zoosporesd, e, and f are aplanosporesg, and h are hypnosporesK is autospores.L is Isogamous, m is Anisogamous, and n is Oogamous

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•Gametes look like vegetative cells or very different•Isogamy: both gametes look identical•Anisogamy: male and female gametes differ morphologically•Oogamy: One gamete is motile (male), one is nonmotile (female)•Monecious: both gametes produced by the same individual•Diecious: male and female gametes are produced by different individuals•Homothallic: gametes from one individual can fuse (self-fertile)•Heterothallic gametes from one individual cannot fuse (self-sterile)

The life cycles in algaeThe life cycles in algae

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•Three different types of life cycle, depending on when miosis occurs, the type of cells produced, and if there is more than one free-living stage present in the life-cycle.

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•Life-cycle I (haploid life cycle): major part of life-cycle (vegetative phase) in haploid state, with meiosis upon germination of the zygote (zygotic meiosis) also referred to

as haplontic life cycle, a single, predominant haploid phase

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•Life-cycle II (Diploid life cycle): vegetative phase is diploid, with meiosis upon formation of gametes (gametic

meiosis) also referred to as diplontic life cycle, a single,

predominant diploid phase

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The life cycles in algaeThe life cycles in algae•Life-cycle III (Diplobiontic life cycle): three multicellular phases, the gametophyte and one or more sporophyte(s)

Gametophyte: typically haploid, produces gametes by mitosis Sporophyte: typically diploid, produces spores by meiosis Isomorphic: sporophyte and gametophyte look alike Heteromorphic: sporo- and gametophyte look different

Basis of algal ClassificationBasis of algal Classification

the different groups of algae can be classified the different groups of algae can be classified on the basis of a number of characteristics.on the basis of a number of characteristics.

1. Color has been an important means of 1. Color has been an important means of classifying algae, and gives many groups their classifying algae, and gives many groups their names. However, other characteristics, such as names. However, other characteristics, such as type of photosynthetic food reserve, flagella type of photosynthetic food reserve, flagella type, cell wall structure and composition, and type, cell wall structure and composition, and life history, have been important in further life history, have been important in further distinguishing the algal divisions.distinguishing the algal divisions.

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FlagellaFlagellaLocomotion in algae is largely Locomotion in algae is largely

based on the action of flagella. based on the action of flagella. The figure below illustrates the The figure below illustrates the wide variety of flagella present wide variety of flagella present in the algae. The primary in the algae. The primary distinctions used for distinctions used for classification are the number classification are the number of flagella, their location on the of flagella, their location on the cell, and their morphology. cell, and their morphology. Two major types of flagella are Two major types of flagella are recognized: the smooth, or recognized: the smooth, or acronematic, and the hairy, or acronematic, and the hairy, or pleuronematic, types. The pleuronematic, types. The smooth flagella generally smooth flagella generally moves by whiplash motion and moves by whiplash motion and the hairy flagella moves by a the hairy flagella moves by a pulling motion.pulling motion.

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ECOLOGICAL DIVERSITYECOLOGICAL DIVERSITY

LAND---WATERLAND---WATER FRESH WATER---MARINE HABITATSFRESH WATER---MARINE HABITATS FLOATING (PLANKTONIC)—BENTHIC FLOATING (PLANKTONIC)—BENTHIC

(BOTTOM DWELLERS)(BOTTOM DWELLERS) EPIPHYTESEPIPHYTES

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Algae - 3 1 General characters. INTRODUCTION TO ALGAL CHARACTERISTICS AND DIVERSITY PHYCOLOGY=STUDY...

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