Keshav Narayan Pai Msc I Department of Botany General Characteristics of Algae
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