Algae are a diverse group of aquatic organisms that have the ability to conduct photosynthesis. Certain algae are familiar to most people; for instance, seaweeds (such as kelp or phytoplankton), pond scum or the algal blooms in lakes.

1. ALGAE
Dr. RACHANA CHOUDHARY
Department of Microbiology
Shri Shankaracharya Mahavidyalaya Junwani, Bhilai

2. SYNOPSIS :-
•Introduction
•Contribution of Indian Phycologists
•General Characteristics features
•Habit & Habitat
•Organization of Thallus
•Form & Size of Algae
•Pigment Constitution of Algae
•Reproduction of Algae
•Classification of Algae
•Economic Importance of Algae
•Conclusion
•References

3. INTRODUCTION
Algae are a diverse group of aquatic organisms that
have the ability to conduct photosynthesis.
Certain algae are familiar to most people; for
instance, seaweeds (such as kelp or phytoplankton),
pond scum or the algal blooms in lakes.

4. Contribution of Indian Phycologists
•Ghose-1919-1932
•Prof. O. P. Iyenger 1920(Father of Algae in India)
•S. R. Narayan Rao 1941-49 –Indian Fossil Algae
•R. Subrahmanyam (1954)-Reproduction of Diatoms
•G.S. Venkataraman studied on Charophytes

5. General Characteristics features
•Algae are photosynthetic organisms
•They can be either unicellular or multicellular.
•Algae lack a well-defined body, so, structures like roots,
stems or leaves are absent
•Algae are found where there is adequate moisture.
•Reproduction in algae occurs in both asexual and sexual
forms.
• Asexual reproduction occurs by spore formation.
•Algae are free-living, although some can form a symbiotic
relationship.

6. Habit & Habitat
1. Aerial & Terrestrial
Algae
2. Aquatic Algae
Fresh Water
Marine Water
3.Algae of Unusual Habitats
1. Snow Algae
2. Thermal Algae
3. Halophytic Algae
4. Lithophytic Algae
5. Epiphytic Algae
6. Aero phytic Algae
7. Symbiotic Algae
8. Parasitic Algae
9. Epizoic Algae
10. Endozoic Algae

7. Organization of Thallus
1. Motile
2. Palmelloid
3. Dendroid
4. Coccoid
5. Filamentous
6. Heterotrichous
7. Siphonaceous.

8. Form & Size of Algae
•Algae have a great range of shapes and sizes, from
spherical cells with 0.5 μm diameter to 60 m long
multicellular thalli.
•There are about 72,500 validly described species
of algae; they live in the top 300 m of marine and
inland waters, and on land.

9. Pigment Constitution of Algae
1.Chlorophylls:
Chlorophyll a – present in all higher plants and algae
Chlorophyll b – present in all higher plants and green algae
Chlorophyll c – diatoms and brown algae
Chlorophyll d – red algae
2.a.Carotenes:
α-carotene – higher plants and most algae
β-carotene – most plants & some algae
b. Xanthophylls:
luteol, fucoxanthol and violaxanthol
3.Phycobillins
a. Phycocynin- Blue in Colour
b. Phycoerythrin- Red in Colour

10. Reproduction in Algae
(A) Vegetative Reproduction
(B) Asexual Reproduction
(C ) Sexual Reproduction

11. (A) Vegetative Reproduction
(i) Fragmentation
(ii) Fission
(iii) Tubers
(iv) Adventitious Branches
(v) Hormogonia
(vi) Budding

12. (i) Fragmentation
• The filamentous thallus breaks into
fragments, and each fragment is
capable of forming new thallus.
• The common examples are
Ulothrix, Spirogyra, Oedogoniwn,
Zygnema, Oscillatoria etc.

13. (ii) Fission
•Fission is common in desmids, diatoms and other
unicellular algae.
•The cell divides mitotically into two cells are
separated by septum formation.

14. (iii) Tubers
• Tubers are spherical or globular bodies formed on lower
nodes and rhizoids in Chara.
• They are formed due to storage of food.
• On detachment of Parent Plant these develop into new plant.

15. (iv) Adventitious Branches
• In some cases, certain adventitious branches are produced
which break off from the parent body and develop into new
plants.
• Common examples are Chara and Dictyota.

16. (v) Hormogonia
• In blue green algae like Nostoc, Cylindrospermum, the
main filament breaks into small fragments of varying length
called hormogonia.
• The hormogonia may be formed at the place of heterocyst in
the filaments.

17. (vi) Budding
In Protosiphon budding takes place due to proliferation
of vesicles. The buds detach to make new thalli.

18. (B) Asexual Reproduction
(i) Zoospores:
(ii) Aplanospores:
(iii) Akinetes
(iv) Hypnospores:
(v) Tetra spores:
(vi) Auto spores:

19. (i) Zoospores:
• The zoospores are flagellated formed
in reproductive body zoosporangium.
• Biflagellate e.g., Chlamydomonas
• Biflagellate and quadriflagellate e.g.,
Ulothrix, Cladophora.
• Multi-flagellate e.g., Oedogoniwn.
• Move in water before they germinate
to make new plants.
• Normally formed under favourable
conditions.
• In Vaucheria, a compound zoospore
called synzoospore is formed.

20. (ii) Aplanospores
• Aplanospores are formed under unfavourable conditions.
• They are non-motile structures, in which protoplasm gets
surrounded by thin cell wall.
• The aplanospores on release form new plants, e.g., Ulothrix.

21. (iii) Akinetes
• The akinetes are formed under unfavourable conditions as
method of perennation. The akinetes are thick walled, non-
motile structures like aplanospores.
• Akinetes, on release, form new thalli. e.g., Anabaena.

22. (iv) Hypnospores
• Hypnospores are thick walled structures, formed during
unfavorable conditions.
• Under prolonged unfavorable conditions, the protoplasm of
hypnospores divides to make cysts.
• The cysts are capable of forming new thallus.
• e.g., Chlamydomonas nivalis.

23. (v) Tetra spores:
•Tetra spores are non-motile spores formed in
some members of Rhodophyceae and
Phaeophyceae.
•In Polysiphonia, tetra spores are formed in
tetra sporangia by reduction division on special
tetrasporophytic plants.

24. (vi) Auto spores
• The auto spores are aplanospores like structures. These are
similar to the parent cell.
• In Chlorella, Scenedesmus, auto spores acquire all
characteristics of parent cells before their discharge from
sporangium.

25. (C ) Sexual Reproduction
(i) Isogamy
(ii) Anisogamy
(iii) Oogamy
a. Hologamy
b. Autogamy

26. (i) Isogamy
In isogamous reproduction the fusing gametes are
morphologically similar. These gametes are physiologically
different due to different hormones.
e.g., Chlamydomonas, Ulothrix, Spirogyra and Zygnema.

27. (ii) Anisogamy
• In anisogamy the fusing gametes are morphologically as
well as physiologically different. These are formed in
different gametangia.
• The microgametes/male gametes are smaller, active and
formed in large number.
• The macrogametes/female gametes are larger, less active
and formed in relatively smaller number
e.g., Chlamydomonas.

28. (iii) Oogamy
• It is the most advanced type of sexual reproduction.
• The male gametes or microgametes are formed in antheridia.
• The female gamete is large, usually one and formed in female
structure Oogonium.
• During fertilization the male gametes reach Oogonium to
fertilize egg and a diploid zygote is formed,
• e.g., Chlamydomonas.

29. Hologamy
the unicellular thallus of opposite strains (-) and (+) behaves
as gametes directly. The thalli fuse to make diploid zygote.
e.g., Chlamydomonas.
Autogamy
two gametes of same mother cell fuse to form diploid zygote.
Since both gametes are formed by same cell there is no
genetic recombination.
e.g., diatoms.

30. Classification of Algae
• Fritsch (1935, 1945) in his book “The Structure and
Reproduction of the Algae” proposed a system
of classification of algae.
• He treated algae giving rank of division and divided it into
11 classes.
• His classification of algae is mainly based upon characters
of pigments, flagella and reserve food material.

31. Class 1. Chlorophyceae (= Isokontae)
Class 2. Xanthophyceae (= Heterokontae)
Class 3. Chrysophyceae
Class 4. Bacillariophyceae (diatoms)
Class 5. Cryptophyceae
Class 6. Dinophyceae
Class 7. Chloromonadineae
Class 8. Eugleninae
Class 9. Phaeophyceae
Class 10. Rhodophyceae
Class 11. Myxophyceae (= Cyanophyceae)
Classification of Algae

32. Class 1. Chlorophyceae (= Isokontae)
• fresh water and chlorophyllous
thallophytes. Chlorophyll b &
carotenoides are present in
chloroplasts.
• Cell wall is made up of cellulose.
• food is synthesized in the form of
starch.
• Motile spores and cilia are found.
• The sexual reproduction is
isogamous, anisogamous and
oogamous types.
• Chlamydomonas, Volvox,
Chlorella, Ulothrix & Spirogyra

33. Class 2. Xanthophyceae (= Heterokontae)
• These are green-yellow in colour
due to the presence of xanthophyll.
The paranoids are absent
• food is in the form of fat.
• Chlorophyll e is found in place of
chlorophyll b.
• The sexual reproduction occurs by
fission of two gametes having cilia
of different length.
• Important genera are:
• Microspora, Vaucheria,
Protosiphon.

34. Class 3. Chrysophyceae:
• Besides chlorophyll, yellow-green
pigments are present.
• Phycocyanin is the colouring
material.
• Plants are unicellular, multicellular
or colonial.
• The cell wall is present in the form
of two overlapping halves.
• Stored food is in the form of oil /
insoluble carbohydrates, leuosin.
• Example: Chrysosphaera.

35. Class 4. Bacillariophyceae (diatoms)
• These are yellow-green-brown or
olive green in colour.
• Diatomin is the colouring
material.
• Pyrenoids are also present.
• These are unicellular and non-
motile.
• Chlorophyll c is present in place
of chlorophyll b.
• Examples:
• Pinularia, Navicula, Fragilaria.

36. Class 5. Cryptophyceae
• These are red, green-blue,
olive-green or green coloured
algae.
• Each cell consists of two large
chloroplasts in which pyrenoids
are present.
• They occur in fresh water and
sea.
• Example: Cryptomonas.

37. Class 6. Dinophyceae:
• These are dark yellow or brown or red coloured algae.
• Stored food is oil or starch.
• Large nucleus and many discs like chromatophores are
present.
• Example:Peridinium.

38. Class 7. Chloromonadineae
• These algae are bright green or olive green colour.
• Xanthophyll is in abundance.
• Fatty compounds acts as food.
• Reproduction takes place by longitudinal division.
• Example: Vacuolaria.

39. Class 8. Eugleninae:
• They resemble microscopic animal due to presence of naked
ciliated reproductive organs.
• Chlorophyll is present.
• Example: Euglena.

40. Class 9. Phaeophyceae:
• These are yellow-brown coloured
marine algae.
• Fucoxanthin pigment is the main
colouring material.
• Storage food materials are
laminarian, mannitol .
• Zoospores are bi-ciliated and one
cilium is larger.
• There is no resting period in
zygote.
• Examples: Fucus, Sargassum.

41. Class 10. Rhodophyceae
• Red in colour due to phycoerythrin
pigment.
• Storage food is Floridian starch.
• Non- motile cells are found during
reproduction.
• These are commonly found in sea
water.
• Sexual reproduction is oogamous
type.
• Chlorophyll d is present in place of
chlorophyll b.
• Examples: Polysiphonia and
Batrachospermum.

42. Class 11. Myxophyceae (= Cyanophyceae)
• The nucleus is of prokaryotic type.
• The blue colour is due to the
presence of phycocyanin pigment.
• The chlorophylls are found in
thylakoids.
• Storage food is myxophycean
starch and protein granules.
• There is no motile stage in these
algae.
• Sexual reproduction is absent.
• Mainly these algae are unicellular
or filamentous.
• Examples:Nostoc, Oscillatoria,
Anabaena, Lyngbya, Plectonema.

43. ECONOMIC IMPORTANCE OF ALGAE
• Algae as Food
• Algae as fodder for cattle
• Utilization of Algae as Fertilizers
• Utilization of Algae in water Purification
• Utilization of Algae in Medicine & Antibiotic
• Use of Algae in Industries
• Algae in SewageDisposal
• Algae in Land Reclamation
• Algae In Biological Research

44. Conclusion
•According to some scientists, algae produce half of
the earth’s oxygen.
•They are a source of crude oil. These algal biofuels
could well be a replacement for the fossil fuels.
•Algae also play an effective role in keeping the
atmospheric carbon dioxide.
•The food industry also uses some algae. Agar is
obtained from Gelidium and Gracilaria and is
making ice-creams and jellies.The other food
supplements that are algae and which are widely
used are Chlorella and Spirulina.

45. REFERENCES
•Botany by Y.D. Tyagi
•Textbook of Microbiology by R. P. Singh
•Textbook of Microbiology by Dubey and Maheshwari
•Google Search

46. THANK YOU