Lecturer : Dr.Muhsin C. Abbas

1. lecturer : Dr.Muhsin C. Abbas Lecture of phycology Second year College of science / kufa university

2. The algae

3. Definition: - algae are non-vascular plants and consist of a thallus, a plant body with little or non tissue differentiation. They range from unicellular through multicellular but still microscopic cell filaments, to large and massive macroscopic plant (sea weeds) composed of millions of cells.

4. The occurrence and distribution of algae  Algae present in diverse habitats. They are aquatic and subaerial. Aquatic algae grow n waters of law salinity, called freshwater, and in marine water. Aquatic algae may be suspended (planktons) or attached and long on the bottom. Subaerial algae may be adaphic (growing in and on soil ) . algae also present in moist rocks ,woods, living trees and on the surface of moist soil. Algae occur in desert soil.

5. The form of the algal plant body The form of the plant body of algae (Fig.1) varies from the relative simplicity of a single cell to the more striking complexity exhibited by the giant kelps and rockweeds, While small eukaryotic algae like species of chlorella (2-8 m) are in the range of bacteria size,Kelps,some of which are the largest algae, may attain a length of 60m . Unicellular form example Chroococcus , Chlamydomonas . Colonial form example Microcystis , Volvo , Pandorina. Filamentous form example Nostoc , Spirogyra . Membrance form example Ulva. Tubular form example Caulerpa . Blade like form example Palmaria .

6. There are two types of colonial algae :- The aggregate is indefinite in cellular number continues to grow by cell division . The second type of colony called coenobium has a fixed number of cells at its origing .

8. Growth of multicellular algae Growth of multicellular algae may be diffuse or generalized or it may be localized. In generalized growth , all of the cells may undergo division , so that the organism undergoes an overall increase in size as in Ulva (the sea lettuce) . In localized growth, cell multiplication is restricted to certain parts of the organism Localized growth may be:- Apical growth is restricted to the tips of the organism for example Fucus . Basal growth is less common but may be observed in genus Bulbochaete . Intercalary growth is localized neither at the apex nor base but at one or several other loci , for example the green algae Oedogonium.

9. Algal Reproduction Both asexual and sexual reproduction are of widespread occurrence in algae, in some , however , sexual reproduction does not occur .

10. Asexual reproduction In some unicellular algae the organism reproduces by cell division to form new individual like the parent cell. This process is also sometime called binary fission. Non coenobic colonial, filamentous, and other types of multicellular algae reproduce by varies types of fragmentation, the fragment having the capacity through continuing growth of developing into new individuals. This is sometimes called vegetative reproduction. In the filamentous blue-green algae , the fragments which exhibit gliding motility , are called Hormogonia . In coenobic algae, the method of reproduction is auto colony formation .An auto colony is a miniature colony produced by a parental colony with repeated cellular bipartition. In addition to that, algae produce a variety of (usually) unicellular agents of asexual reproduction called spores.

11. There are many types of spores :- zoospores: flagellate agents of asexual reproduction and their motility is an animal-like trait. Aplanospores: zoospores may omit their motile phase and begin their development within the parent cell wall . autospores : non-motile spores are produced by various algae, they are superficially like aplanospores but differ in lacking the capacity for motility Akinetes : are of widespread occurrence in the blue-green and green algae .It is a vegetative (somatic)cell that has enlarged and formed an envelope external to its wall.

12. Sexual Reproduction Sexual reproduction at the cellular level is meant the union of cells , plasmogamy , the union of their nuclei, karyogamy , the association of their chromosomes and genes and meiosis. In certain unicellular algae (e.g. Chlamydomonas) the organism themselves may function as gametes.

13. * They are three types of gametes:- Isogametes : morphologically similar and the reproduction called isogamy reproduction. Anisogametes : are member of pair may be smaller then the other , the gamete , therefore , beging designated as anisogamous. Oogametes : the gametes may be extremely dimorphic, the larger , non-motile and called egg, and the smaller , motile by flagella called sperm , the reproduction is called Oogamous reproduction .

14. The gametes may arise from relatively unmodified vegetative cells that function as gametangia . The female gametangium inOogamous algae is the unicellular Oogonium . Flagellate male gametes are produced in special gametangia called antheridia .

15. Figure 1.3 methods of algal reproduction (diagrammatic). (a)-(c)binary fission.(d),(e) zoospores formation.(f) Aplanospores formation. (g),(h)Autospore formation. (i) Fragmenntation or hormogonium formation. (j) Autocolony formation. (k) Akinate formation. (l) isogamy. (m) anisogamy. (n) Oogamy

16. Biological and Economic Aspects of Algae The algae play both beneficial and detrimental roles in nature.A number of these are cited in the following :-

17. A- Beneficial Aspects of algae Algae are highly important as primary producers of organic matter in aquatic environmental because of their photosynthetic activities. When they disappear from aquatic environment , animal life would lack its source of food and energy. As food : many of marine algae ( red and brown ) have been used for food in oriental countries for example red algae Porphyra and Plamaria . To extract hydrocolloids which are used as stabilizers and thinking agent in ice cream. One of these extract is called carrageenan. In addition to carrageenan , agar is extracted from various red algae, Agar is important microbiology for solidifying culture media.

18. Algae as fodder for cattle and sheep (marine algae) in Chile and in Scottish island . Certain unicellular green algae have been used as supplements to the food of poultry and cattle. The role of many blue-green algae in nitrogen fixation is very important to improve the fertility of rice fields. Algae play a role to control pollution . The oxidation of sewage products is accomplished by bacteria whose activities are enhanced by oxygen ( O2 ) produced by photosynthesis of algae. Algae have been used as systems in biological research such as Chlorella in photosynthesis and Chlamydomonas in sexual reproduction at the cellular and molecular level.

19. B- Negative Aspects of Algae certain algae or their products are toxic to animals e.g. Microcystis algae (blue-green algae) are poisoning of livestock, fish, and shelfish and as a result human being. Activity of algae is forming water blooms which cause negative aesthetic effect. some algae when present in large concentrations impart unpleasant taste to drinking water .

20. End lecture