General characteristics of algae

Brief account of algae is provided here.

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

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

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.

5. Fresh water algae Volvox Chlamydomonas

6. Stagnant water algae Oedogonium Chara

7. Running water algae Cladophora Ulothrix

8. Sea water algae Ectocarpus Porphyra

9. These are found free floating or freely swimming in water. Planktonic Algae Cyclotella Pinnularia

10. These are never attached to the substratum. Euplanktons Microcystis Cosmarium

11. Beginning they gets attached but later they get detached. Tychoplankton Cylindrospermum Rivularia

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 Phormidium species

14. Cryophytes(snow algae) Found on mountain peaks with snow. Haemococcus nivalis (red colour ) Chlamydomonas yellowstonensis (Green colour )

15. Thermophytes Hot springs, tolerate temperature upto 8 5c. Example: Haplosiphon lignosus

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

17. Lithophytes Found on moist rocks and rocky surfaces. Gleocapsa Rivularia

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

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 Endozoic Algae

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

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

23. Size of Algae 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. Unicellular 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. Colonial Volvox Pediastrum

27. Coenobial Algae It is a colony with fixed number of cells. Example:16 cells in Pandorina , 32 cells in Eudorina . P andorina 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 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. Reproduction Vegetative reproduction: Fragmentation Cell division Hormogone formation. Tubers Bulbils Akinetes

40. Asexual Reproduction 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 Chlamydomonas

43. 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

44. 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

45. 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

46. 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