Keshav Narayan PaiMsc IDepartment of Botany

General Characteristics of Algae

They are Thallophytes which have chlorophyll as their primary photosynthetic pigment and lack a sterile covering of cells around the reproductive cells.

Algae

Habit and HabitatThey may be free floating , free swimming or

attached to the bottom in the shallow water.According to habitat, algaes can be classified as

follows:

Aquatic algae: Example:- Chlamydomonas.Terrestrial algae : Example:- Fritschiella.Aerophytes : Example:- Scytonema.Cryophytes : Example:- Scotiella.Thermophytes : Example:- Oscillatoria brevis.Algae of unusual habit : Example:- Dunaliella.

Acquatic Algae

•Found from tiniest ditch to the mightiest river and ocean.

Fresh water algae

Volvox Chlamydomonas

Stagnant water algaeOedogoniu

mChara

Running water algaeCladophora Ulothrix

Sea water algae Ectocarpus Porphyra

These are found free floating or freely swimming in water.

Planktonic Algae

Cyclotella Pinnularia

These are never attached to the substratum.

Euplanktons

Microcystis Cosmarium

Beginning they gets attached but later they get detached.

Tychoplankton

Cylindrospermum Rivularia

Terrestrial Algae These are found on or beneath the soil

surface. Example: Trentifolia sp.

AEROPHYTES They are adopted to the aerial

life,occur on tree trunks, moist walls, flower pots, rocks..etc

Phormidium species

Cryophytes(snow algae)Found on mountain peaks with

snow.

Haemococcus nivalis

(red colour)

Chlamydomonas yellowstonensis(Green colour)

Thermophytes Hot springs, tolerate temperature upto

85c.

Example: Haplosiphon lignosus

Halophytic Algae They are present in water containing

high percentage of salt.

Haplosiphon salina

LithophytesFound on moist rocks and rocky

surfaces.

Gleocapsa Rivularia

Epiphytic Algae•The algaes grow on other plants.

Ceplaleuros algae on Chrysophyllun leaf

Audouinella on mosses

Epizoic AlgaeThese algaes are found on shells of

molluscans, turtles and fins of fishes.Example: Acrosiphonia.

These are found inside the body of aquatic animals.• Example: Zoochlorella

found inside the Hydra Viridis

Endozoic Algae

Eg: Cephaleuros virescens causes ‘ Red rust of tea’,by which a severe damage is caused.

Parasitic Algae

Many Cyanophycean members grow in symbiotic association with other plants.

Association of Nostoc within thalli of Anthoceros.

Symbiotic Algae

Size of Algae Their sizes varies from 0.5microns to

700 feet( giant kelps) in length.

Thallus Organization Algae exhibit great diversity in

organization of plant body. Unicellular Motile Non-motile Colonial Coenobial Filamentous Simple Branched Dendroid

Unicellular

They are single celled algae.

They may be motile flagellated.

example: Chlamydomonas.

They may be non-motile coccoid.

example: Chlorella

The cells are grouped in aggregations called Colonies.

Colonial

VolvoxPediastrum

Coenobial Algae

It is a colony with fixed number of cells.

Example:16 cells in Pandorina, 32 cells in Eudorina.

Pandorina Eudorina

FilamentousFilamentous types are

multicellular. They may be simple or

unbranched. Example: ulothrix, spirogyra. They may be branched. Branching is of 2 types:True branching. Ex:

Sytonema.False branching.

Ex:Cladophora.

DENDROID Dendroid means tree like. These appear

like microscopic trees .example: Prasinocladus.

Structure of the algal cell Prokaryotic cell They are found in the members of

Cyanophyta. Cell wall contains mucopeptide. DNA materials are concentrated in the

centre and nuclear membrane is absent.

Chloroplast, Mitochondria, Golgi bodies, Plastids and Endoplasmic reticulum is absent.

Ribosomes are present. Nuclear division doesnt take place by

mitosis.

Eukaryotic cell Eukaryotic cell has the

structure as in typical cell of higher plants.

Nucleus separated from Cytoplasm by distinct nuclear membrane.

It divides by mitosis. Cytoplasm contains

chloroplasts, mitochondria, golgi bodies and endoplasmic reticulum.

Algal PigmentsColour of algaes varies due to

presence of definite chemical compounds called as pigments.

Photosynthetic pigments in algae are of 3kinds,

Chlorophyll Carotenoids Phycobilins or biliproteins.

CHLOROPHYLLAlgal chlorophylls

is represented by greencolour.

They are fat soluble compounds.

Chlorophyll a is comman in all group of algaes.

Chlorophyll b, c, d and e have restricted distribution.

Carotenoids These are fat soluble

yellow coloured pigments.

They are sub divided into carotenes and xanthophylls.

There may be 20 xanthophylls so far known.

Carotenes are of 5types. α, β, γ, lycopene and ε carotene.

PhycobilinsPhycobilins include

red coloured Phycoerythrins and blue coloured phycocyanins.

They are present in members of Cyanophyceae and Rhodophyceae.

Algal FlagellaFlagella are extremely fine and

hyaline emergence of the cytoplasm.

Single anterior flagellum In pairsMany in number Isokont( equal in length)Heterokont(unequal in length)

Nutrition Algaes are Autotrophic.

All or most of the cells of thallus normally contain chlorophyll.

The cells can manufacture their own carbohydrate food from carbon dioxide and water through the agency of sunlight.

FOOD RESERVES Food accumulates in the form of

polysaccharides. Those are cyanophycean starch and

floridean starch(rhodophyta). Three important reserve food are

laminarin, paramylin and leucosin. Mannitol is also another reserve food

in red algae.

REPRODUCTION Vegetative

reproduction: Fragmentation Cell division Hormogone

formation. Tubers Bulbils Akinetes

Asexual Reproduction

By aplanospores, autospores, endospore and auxospores and cyst formation.

Palmella stage occurs in Chlamydomonas .

Sexual ReproductionBy fusion of two

specialised cell known as sex cells or gametes.

Isogamous- two identical gametes fuse to form zygotes.

Heterogamous- dissimilar gametes fuse

Sexual reproduction in Chlamydomonas

Beneficial Aspects of AlgaeFood for humansFood for invertebrates and fishes in maricultureAnimal feedSoil fertilizers and conditioners in agricultureTreatment of waste waterDiatomaceous earth (= diatoms)Phycocolloids (agar, carrageenan from red algae;

alginates from brown algae) DrugsModel system for research

Blooms of freshwater algae Red tides and marine blooms Toxins accumulated in food chains Damage to cave paintings, frescoes, and

other works of art Fouling of ships and other submerged

surfaces Fouling of the shells of commercially

important bivalves

HARMFUL EFFECTS of Algae

No other forms of organisms are so colourful as that of algae.

Various pigments can be found in the algae.

They are ubiquitous and the thallus organisation contains diversity.

CONCLUSION

References O.P.Sharma .1986. Textbook of Algae,

Tata Mcgraw-Hill Education:Pg.no.2-4. A.V.S.S.Sambamurty.2005. A Textbook of

Algae, I.K.International Pvt.Ltd:Pg.no.3-4.

http://www.algologists.yolasite.com