This document provides an overview of algae. It describes that algae are thallophytes that contain chlorophyll as their primary photosynthetic pigment and lack a sterile cell covering around their reproductive cells. It classifies algae based on their habitat as aquatic, terrestrial, aerophytic, cryophytic, thermophytic, or of unusual habit. The document further discusses the structure of algal cells, types of algal thallus organization (unicellular, colonial, filamentous, dendroid), pigments, nutrition, reproduction (vegetative and sexual), examples of beneficial and harmful aspects, and references key characteristics of algae.

1. Keshav Narayan Pai
Msc I
Department of Botany

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

3. Habit and Habitat
They 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.

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

6. Stagnant water algae

7. Running water algae

9.  These are found free floating or freely
swimming in water.

10.  These are never attached to the substratum.

11.  Beginning they gets attached but later they
get detached.

12. Terrestrial Algae
 These are found on or beneath the soil
surface. Example: Trentifolia sp.

13. AEROPHYTES
 They are adopted to the aerial life,occur on
tree trunks, moist walls, flower pots,
rocks..etc

14. Cryophytes(snow algae)
 Found on mountain peaks with snow.

15. Thermophytes
 Hot springs, tolerate temperature upto 85c.

16. Halophytic Algae
 They are present in water containing high
percentage of salt.

17. Lithophytes
 Found on moist rocks and rocky
surfaces.

18. Epiphytic Algae
• The algaes grow on other plants.
Ceplaleuros algae on Chrysophyllun
leaf

19. Epizoic Algae
 These algaes are found on shells of
molluscans, turtles and fins of fishes.
 Example: Acrosiphonia.

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

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

22.  Many Cyanophycean members grow in
symbiotic association with other plants.
Association of
Nostoc within thalli
of Anthoceros.

23.  Their sizes varies from 0.5microns to 700 feet(
giant kelps) in length.

24. Thallus Organization
 Algae exhibit great diversity in organization of
plant body.
 Unicellular Motile
Non-motile
 Colonial
 Coenobial
 Filamentous Simple
Branched
 Dendroid

25.  They are single celled algae.
 They may be motile flagellated.
 example: Chlamydomonas.
 They may be non-motile coccoid.
 example: Chlorella

26.  The cells are grouped in aggregations called
Colonies.

27. It is a colony with fixed number of cells.
Example:16 cells in Pandorina, 32 cells in
Eudorina.

28. Filamentous
 Filamentous 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.

29.  Dendroid means tree like. These appear like
microscopic trees .example: Prasinocladus.

30. 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.

31. 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.

32. Algal Pigments
Colour 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.

33. CHLOROPHYLL
Algal 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.

34. 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.

35. Phycobilins
 Phycobilins include red
coloured
Phycoerythrins and
blue coloured
phycocyanins.
 They are present in
members of
Cyanophyceae and
Rhodophyceae.

36. Algal Flagella
 Flagella are extremely fine and
hyaline emergence of the
cytoplasm.
 Single anterior flagellum
 In pairs
 Many in number
 Isokont( equal in length)
 Heterokont(unequal in length)

37. 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.

38. 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.

39.  Vegetative reproduction:
 Fragmentation
 Cell division
 Hormogone formation.
 Tubers
 Bulbils
 Akinetes

40.  By aplanospores,
autospores, endospore
and auxospores and cyst
formation.
 Palmella stage occurs in
Chlamydomonas .

41. Sexual Reproduction
 By fusion of two
specialised cell
known as sex cells
or gametes.
 Isogamous- two
identical gametes
fuse to form
zygotes.
 Heterogamous-
dissimilar gametes
fuse

42. Sexual reproduction in Chlamydomona

46. Beneficial Aspects of Algae
 Food for humans
 Food for invertebrates and fishes in mariculture
 Animal feed
 Soil fertilizers and conditioners in agriculture
 Treatment of waste water
 Diatomaceous earth (= diatoms)
 Phycocolloids (agar, carrageenan from red algae;
alginates from brown algae)
 Drugs
 Model system for research

47.  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

48.  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.

49. 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