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Plants algae

  1. 1. KINGDOM PLANTAE Algae
  2. 2. PLANT KINGDOM • The earliest systems of classification were based on the gross morphological characters such as habitat, colour, number and shape of the leaves etc. • They were based mainly on vegetative structure (System given by Linnaeus). Such systems were Artificial Systems. They separated closely related species as they were based on a few characteristics only. • Moreover the Artificial system gave equal weightage to the vegetative and sexual characteristics which is not acceptable now. • The Natural Classification Systems on the other hand are based on natural affinities among the organisms and consider not only External features but also the Internal features, like the Ultra structure, Anatomy, Embryology and Phytochemistry. • Such a system of classification was given by George Bentham and Joseph Dalton Hooker. •According to the 5 Kingdom Classification, The Plant Kingdom includes: Algae, Bryophyta, Pteridophyta, Gymnospermae and Angiospermae.
  3. 3. • These days Taxonomists even use the other systems of classification too: • Phylogenetic Classification: It is based on the evolutionary relationships between various organisms which are acceptable. That means organisms belonging to the same Taxa have a common ancestor. • Numerical Taxonomy: It can be easily carried out using computers is based on all observable characteristics. Number and codes are assigned to all the characters and the data is then processed, so hundreds of characters can be considered for classification. • Cytotaxonomy: It is based on the cytological information like chromosome number, structure, behavior of the chromosomes. • Chemotaxonomy: It uses the chemical constituents of the plant to resolve confusions.
  4. 4. ALGAE General Characteristic features of Algae: • The term ‘Algae’ was coined by Carolus Linnaeus. • The study of algae is called Phycology. • Algae occur in both fresh water as well as marine water, on wet rocks, wet tree trunks etc. • They may be unicellular such as Chlamydomonas, Chlorella, Porphyra (red alga) etc. or they may be multi-cellular filamentous: e.g. Spirogyra, Ulothrix or Colonial e.g. Volvox. • The size may vary from simple microscopic to even several meters long as the Brown algae. e.g. Macrocystis. • The plant body is undifferentiated into root, stem or leaves, such an undifferentiated plant body is called Thallus. • They do not have any vascular tissues such as xylem and phloem. They do not need even mechanical tissues as they are supported by water. Their body is flexible and does not resist water. • They are photosynthetic.
  5. 5. • Plastids are present. The green plastids are called Chloroplasts and the coloured ones are called Chromatophores. • The photosynthetic pigments present in algae are – Chl-a, Chl- b, Chl – c, Carotenes (orange), Xanthophylls (yellow), Fucoxanthin (brown) Phycobillins usually red in colour. • The cell wall is cellulosic. • Their whole body is covered by a mucilage layer ( so that body does not get rotten). • The reserve food materials in algae is usually Floridean starch (red algae), Laminarin, Mannitol (brown algae). • They may have one or more Pyrenoid bodies for storing starch and protein. • Reproduction in algae may be of following types.
  6. 6. Reproduction in algae may be of following types. 1) Vegetative reproduction by fragmentation is very common. 2) Asexual reproduction takes place by different types of spores like – Zoospores, Aplanospores, Monospores, Tetraspores, Carpospores and so on. 3) Sexual reproduction may be: a) Isogamy i.e. fusion of similar gametes. b) Anisogamy i.e. the fusion of dissimilar gametes. c) Oogamy: Here the male gamete is small and motile while the female gamete is large and immotile. E.g. Volvox, Fucus.
  7. 7. Economic importance of Algae: 1) 50% of earth’s CO2 fixation is done by algae. 2) They also increase the amount of dissolved oxygen in water. 3) They are the primary producers of many aquatic eco- systems. 4) Some algae such as Laminaria, Sargassum are used as fodder. 5) Many algae are consumed as food by many aquatic animals. 6) Certain red and brown algae produce Hydrocolloids (water holding substances) e.g. Algin is produced by brown algae, Carragin is produced by red algae. Agar which are used as jellying agents in the cosmetic industry, for making ice- creams, medicines. Agar is one such material which is extensively used as a medium for the growth of microbes. Agar is obtained from Gelidium, Gracelaria (Red Algae).
  8. 8. 6) Spirullina is the richest source of protein used as food supplement by space travellers. 7) Many algae yield minerals like Iodine, Potash, Bromine etc. 8) Codium, Chlorella, Laminaria and many others have medicinal properties. 9) Several (brown algae) algae which grow several meters long get tangled with the hull of the ships and pose danger to them. 10) Aerobic algae are grown in the sewage tanks to provide Oxygen to the decomposer organisms. Algae are divided into 3 classes: 1. Chlorophyceae 2. Phaeophyceae and 3. Rhodophyceae.
  9. 9. Chlorophyceae: (Green Algae) • They may be unicellular such as Chlamydomonas, Chlorella, Multicellular: Filamentous – Spirogyra, Ulothrix, Colonial – Volvox. • They are mostly found in fresh waters, very few in salt waters. • The photosynthetic pigments are Chl – a and Chl – b. • The Chloroplast are of various shapes – disc like, cup shaped or ribbon like, reticulate etc. • They have one or more Pyrenoid bodies for storing starch and protein. • Vegetative Reproduction by Fragmentation or by formation of different types of spores. • Asexual reproduction by formation of Flagellated Zoospores produced in Zoosporangia. • Sexual reproduction shows variation in the type and formation of Gametes, which may Isogamous, Anisogamous or Oogamous.
  10. 10. Chlamydomonas Chlorella Chara Spirogyra Ulothrix
  11. 11. Phaeophyceae: (Brown Algae): • The group includes multi-cellular forms of different sizes some of them are called giant – Kelps which reach the length of even 100 meters, such as Macrocystis (100 m approx), Nereocystis (60 m). • They are mostly marine. These algae are attached to the substratum with the help of an adhesive structure called Holdfast. The thallus even consists of a stalk called Stipe, which holds the photosynthetic lamina called Fronds. • A few species are free floating such as Fucus, Sargassum. • Some species are even epiphytic or endophytic such as Ectocarpus. • The Western part of North Atlantic Ocean is called Sargasso sea because of abundance of free floating Sargassum. • These Kelps pose danger to the ships by getting entangled at the bottom of the ships. • They have a cellulosic cell wall.
  12. 12. • There is a covering of Phycocollids such as Alginic acid and Fucoidin. They are responsible for: a) Protecting Brown Algae from drying or freezing on exposure to cold air. b) Protecting the Brown algae form damage when these algae beat against the rocks by the waves, otherwise the waves may cause mechanical damage to these algae. • The photosynthetic pigments are present in Phaeoplasts. • The photosynthetic pigments are Chl-a, Chl-c, Carotenes, Fucoxanthin [C40 H56O6]. • The reserve food materials are Laminarin, Mannitol. • Vegetative reproduction by fragmentation. • Asexual reproduction by different types of spores like Tetraspores, Monospores, Zoospores etc. • Sexual reproduction may be Isogamous, Anisogamous or Oogamous. E.g. Laminaria, Fucus, Ectocarpus, Sargassum, Dictyota, Macrocystis, Neoreocystis.
  13. 13. Macrocystis Nereocystis Sargassum
  14. 14. Laminaria Fucus Dictyota Ectocarpus
  15. 15. Rhodophyceae: (Red Algae): • They are mostly marine. • A few freshwater forms are such as Batrochospermum and Limnaea. • They have graceful, delicate, lace-like appearance, generally called sea weeds. • The only unicellular red alga is Porphyridium. • The freshwater forms are generally bluish green. The marine forms are generally red in the deep water forms. Near the shore, they change the colour to purple, pink or violet. • One or two members are even parasitic and colour less e.g. Harveyella, Riccardia. • The cell wall consists of cellulose and pectic compounds. • The Phycocolloids of red algae are usually made of Agar or Carragen, Funori. • The Chromatophores of red algae are called Rhodoplasts.
  16. 16. • The photosynthetic pigments of red algae are Chl-a, Chl-d and Phycobillins such as r-Phycoerythrin (red), r-Phycocyanin (blue) and Allophycocyanin. • The reserve e food in them is Floridian starch which is similar to Glycogen and Amylopectin. • Vegetative reproduction is very common and occurs by Fragmentation. • Asexual reproduction occurs by non-motile spores such as Monospores, Tetraspores, Carpospores, etc. • Sexual reproduction takes place by formation of non- motile gametes and it is usually of Oogamous type. E.g. of red algae: Polysiphonia, Porphyra, Gelidium, Gracelaria, Chondrus, etc.
  17. 17. Polysiphonia Chondrus Gelidium Porphyra Gracelaria
  18. 18. Note on Phycocolloids: i) The Phycocolloids of red algae are usually Agar and Carragenin, Funori. ii) Agar is one of the main products obtained from these algae. iii) The Agar producing red algae such as Gracelaria, Galidium, Gigatina, Chondrus etc. are together included in a group called Agarophyta. iv) The largest producer of Agar is China. v) Agar is used as a culture medium, as a stabilizer, as a thickener of many food items. vi) Agar has a property of forming a gel at room temperature. Therefore it is used in the preparation of Gelatin capsules as a laxative base for pills.
  19. 19. vii) It is also used as a base for cosmetics, for toothpaste, for making dental impressions and also as a jelling agent in the preparation of ice- creams. viii) Carragenin is obtained from Chondrus, Gigatina. ix) It is used as a cleaning agent in liquors, finishing leather. x) It is also used in the preparation of emulsions of ice-creams, chocolates, toothpastes and cosmetics. xi) Carragenin also has medicinal value, as it hastens blood coagulation.
  20. 20. Important Questions for Weekend Assignment: 1. Mention 5 distinguishing characteristic features of Division ‘Algae’. 2. Give one example of unicellular Green alga and Red alga. 3. What is the importance of Pyrenoid bodies in Chlorophyceae? 4. What are ‘Kelps’? Give two examples. 5. Why are Brown Algae named so, inspite of having Chlorophylls in them? 6. Name two parasitic Red algae. 7. Name two Red Algae used as a source of Agar. 8. What are Phycocolloids? How are they important for Brown Algae? 9. How are Hydrocolloids commercially useful? 10. State three differences between all the three groups of Algae, with reference to their: a) Photosynthetic pigments, b) Reserve food materials, c) Cell wall. 11. Give one example each of unicellular, filamentous and colonial Green Algae. 12. Mention any 5 points of ‘Economic Importance’ of Algae.
  21. 21. BIBLIOGRAPHY • Chapter:3 ‘Plant Kingdom’ (Algae): NCERT Text Book of Biology, Class XI. • Chapter:3 ‘Plant Kingdom’ (Algae): Rachna Sagar’s Together With Biology for Class XI. • Chapter:3 ‘Plant Kingdom’ (Algae): Dhanpat Rai’s Move Fast With Biology, Class XI. • Chapter:3 ‘Plant Kingdom’ (Algae): Modern’s abc Biology, Class XI. • Chapter: 3 from printed notes prepared by A. Jayashree, Biology Dept DPS Hyderabad. • Flow Charts & pictures from Google Chrome.

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