What Alga Is?

Chlorophyll bearing organisms with thylloid

(having no True roots., stems and

leaves ). Word Origination Algae has about 3000species &

2000 genera Algae has world wide distribution from

Europe - Pacific and Asia.( Arctic, Antarctic,North& South America).

Occurrence & Habitat

Been recorded from snow, hot springs, tide pools to

rocky coasts or floating as masses of filaments or water blooms.

See Weeds are mostly found in Rocky Coasts Euglena ,Diatoms & Anabaena found in River &

Ditches Polycystis & Dinoflagellates found in Moist

Places (Tree Trunks)

History

Early reference found in Chinese Literature mentioned as TsaO

Greeks & Roman literature used words like

Phycos & Fucus

Inhabitants of Hawaii used it as food known

as Limu.

Classification• Algae classification is based on following bases.

PigmentsReserve food productsFlagellationCell wall Cell Structure

Forms of Algae (W.h.Harvay)

• Red Algae

• Brown Algae

• Green algae

• Diatoms

Morphology

Algae are Eukaryotic except Blue Green Algae.

FlagellaFlagella are found in all except Cyanophyta &

Rhodophyta

Three important points Nature Number Position of Flagella in primary

Classification of Algae

•Cell Wall Made up of two materials

Inner Water Insoluble

Outer Pectic substances

Most common material of inner layer is

CelluloseIn cell wall of Phaephyta alaginic & Fucinic

acid are found whereas mucopeptide is

present in cell wall of Blue-Green Algae.In some algae, walls contain definite Pores for

Mucilage discharge & connections for

protoplasmic connections.

Plastids & Chromatophores

• Double membrane structures are of two types

Colored Chromatophores

Colorless LeucoplastsLeucoplasts

ChromatophoresChlorophyll a & b Chlorophyll b

Plastids

Pyrenoids

Protinaceous fibrils on or in the Chromatophore surface.

One in Chlamydomonas or many in Oedogonium

Store starch in green algaeFound in all except CyanophytaArise De Novo or by Division of pre-

existing cells.

Golgi Bodies Mitochondria ER

G-Complex here is known as Dictyosomes.

Situated near Chromatophores,Flagella, nucleus.

Exact function not defined so far.

Absent in Cyanophyta.

Are present

Number & size vary.

Exact function is Respiratory related.

Absent in Cyanophyta

Present in Most Algae

System of tubules.

Ribosomes on outer Surface

Absent in Cyanophyta.

Vacuoles Eye Spots (Stigma)

One or More Vacuoles.

Meant for Osmotic Relation & regulation of Solutes

Two Types1. Contractile2. Complex

Orange eye-spot located Consist of Lipid Droplets present irregularly.

They are light sensitive photoreceptors.

It helps in orientation of motile Flagella.

Ecology

• The various sorts of algae play significant roles in aquatic ecology

• Provide the food base for most marine food chains • In very high densities (so-called algal blooms)

discolor the water and out compete, asphyxiate other life forms

• Sea weeds have been recorded at depth of 300m.• Some are used as human food or harvested for

useful substances such as agar, carrageenan, or fertilizer

Nutrition Cell Chlorophyll Store light Energy CO2 + Water (Surrounding Environment) Sugars

Chemical equation6CO2+12H2O C6H12H6

+6O2+6H2O

PhotoautotrophicHolozoicParasiticHeterotrophic

Reproduction• Vegetative• Sexual • Asexual Vegetative

ReproductionUnicellular Cells Cell divisionFilamentous forms Fragments forms

FragmentationExample Blue Green Algae

Asexual Reproduction Special cells types Replication

of Organism

Asexual Reproduction results in development & maintenance of

stable population. Sexual ReproductionSexual reproduction involvesUnion of Cells(Plasmogamy)Union of Nuclei(Karyogamy)

Uses

Largest source of oxygen producer 83-87% of the total oxygen

Bio-diesel production .

There are also commercial uses of algae as

agar

Some Cosmetics can come from micro algae as well

chemical dyes and coloring agents

Seaweeds are used as fertilisers and

even food

Algae are used in wastewater treatment facilities

Algae and symbioses

lichens: A fungus is the host, usually with a green alga or a

cyanobacterium as its symbiont Corals: algae known as zooxanthellae are symbionts with

corals. Notable amongst these is the dinoflagellate Symbiodinium, found in many hard corals.

Sponges: green algae live close to the surface of some sponges, for example, breadcrumb sponge (Halichondria panacea). The alga is thus protected from predators; the sponge is provided with oxygen and sugars which can account

for 50 to 80% of sponge growth in some species.