MORPHOLOGICAL CHARACTERS AND MODES OF REPRODUCTION OF ALGAE

1. Algae is a large group of eukaryotic microorganisms
2. They occupy a variety of aquatic habitat
3. The groups are Cyanophyceae, Chlorophyceae, Rhodophyceae and Phaeophyceae
4. The modes of reproduction are vegetative, asexual and sexual.
5. Chtomatophores are the pigment containing cells.

1. MORPHOLOGICAL CHARACTERS OF ALGAE Presented by, Ms. S. Vaishnavi M.Sc., DYMHH., M.Dip ., Assistant Professor, Department of Home Science- Nutrition & Dietetics

2. ALGAE Algae is a term that describes a large and incredibly diverse group of eukaryotic, photosynthetic lifeforms . These organisms do not share a common ancestor and hence are not related to each other(polyphyletic). They occupy a variety of aquatic habitat including freshwater and marine water. Size may vary from a few microns to several meters.

3. MORPHOLOGY Algal body is termed as thallus , i.e. The body is not differentiated into stem, root and leaves. The thallus is multicellular and complex and lacks vascular tissue. They can be unicellular- occuring as single cell( eg . Chlamydomonas ), colonial- occuring as groups ( eg . Volvox ). Filamentous- these undergo cell division and form filaments ( eg . Spirogyra ), Spiphonaceous - thallus is coenocytic and takes a tubular shape ( eg . Vaucheria ) or Parenchymatous ( Sargassum )

4. GROUPS Algae possess a diversity of pigments, which primarily belong to the major groups namely chlorophyll, carotenoids and phycobilins . Bases on the pigments, they are classified into: Cyanophyceae - Blue green algae contain phycocyanin pigment. Chlorophyceae - Green algae contain chlorophyll b pigment Phaeophyceae - Brown algae contain fucoxanthin pigment Rhodophyceae - Red algae contain phycoerythrin pigment.

5. Chromatophores are the pigment containing cells and such structures are called pyrenoids , which serve the function of synthesis and storage of starch. The food reserves that occur in algae includes: Cyanophyceae - Cyanophycean starch Chlorophyceae - Starch Rhodophyceae-Floridean starch Phaeophyceae - Laminarium , Manitol , Oil

6. REPRODUCTION Reproduction in algae occurs by Vegetative reproduction Asexual reproduction Sexual reproduction

7. VEGETATIVE REPRODUCTION In this method, the vegetative part of the plant develops into a new individual. It takes place by fission, fragmentation or budding. In fission, unicellular algae divides to two daughter cells. Eg . Chlamydomonas In fragmentation, the thallus of a multicellular alga breaks to form several fragment, which forms individuals . Eg . Spirogyra In budding, bud like structure separated by septum if formed, further it gets detached and results in a new plant.

8. ASEXUAL REPRODUCTION Asexual leads to production of offsprings without fusion of genetic material. It results in rejuvenation of the protoplasm. Asexual reproduction involves formation of spores, which may be motile(zoospores) or non-motile ( aplanospores ). The spores germinate into a new plant. There is no alteration of generation in asexual reproduction.

9. SEXUAL REPRODUCTION In sexual reproduction, gametes fuse to form zygote. It can be of following types: Autogamy - The fusing gametes belong to the same parent. Hologamy - It occurs in unicellular organism wherein the vegetative cell acts as a gamete. Isogamy - It occurs when the two gametes are morphologically and physiologically similar.

10. Anisogamy - In this, the two gametes are morphologically and physiologically dissimilar, the microgamete( male gamete) being small and more active and macrogamete (female gamete) being large and less active. Oogamy - In this, fertiliziation takes place between a female gamete which large and non-motile and the male gamete which is small and motile.

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