Exercise 3 - World of Algae

• Eukaryotic algae encompass numerous and diverse organisms with the same intracellular organization in higher green plants such as presence of organelles
• Eukaryotic algae under class Rhodophyceae of division Rhodophyta, on one hand, exhibits bright pink or red pigmentation due to phycobiliproteins known as “phycoerythrin” and are known as “Red Algae”.
• Other pigmented algae belong to the following divisions: Pyrrophyta (Dinoflagellates), Chrysophyta (Diatoms), Phaeophyta (True Brown Algae), Euglenophyta and Chlorophyta (Green Algae). 
• Algae reproduces either vegetative (division of cells, fragmentation of colony), asexual by production of spores or sexual through union of gametes.
• Haplontic or Zygotic Life Cycle – Vegetative phase is predominant; haploid in nature; meiosis occurs during zygote germination.
• Diplontic or Gametic Life Cycle – characterized with single predominant vegetative diploid phase; meiosis leads to formation of haploid gametes
• Diplohaplontic Life Cycle- introduces alternation of generation between haploid gametophyte and diploid sporophyte phase
• A generalized cycle is seen in most members of Florideophycidae (e.g. Polysiphonia sp.) wherein it follows a diplohaplontic life cycle with predominance of the sporophyte phase.  
• Most red algae exhibit a triphasic life cycle: a gametophyte (n), carposporophyte (2n) and tetrasporophyte (2n).  
• The dinoflagellates are unicellular protists, so called due to the usual biflagellated nature of the vegetative cells
• Pyrrhophyta and two classes, i.e., Desmophyceae and Dinophyceae
• dinoflagellates may reproduce greatly, water appearing golden or red, hence “red tide”
• Marine life such as fishes and shellfish, clams, mussels, and oysters are affected because of the neurotoxins produced by dinoflagellates which also harms the consumers.  
• Representative Species: Pyrodinium bahamense, Prorocentrum, Ceratium
• The diatoms are classified under the division Chrysophyta and class Bacillariophyceae following the classification scheme of Bold and Wynne (1985).
• The term diatom is derived from the fact that their cell walls called frustules or shell. 
• they could have radial symmetry or bilateral symmetry that artificially group them into centric and pennate diatoms
• Auxospores that give rise to

  vegetative cells of maximum size for the species.
• auxospore formation is a sexual means of reproduction that involves the fusion of non-motile gametes either by isogamy, anisogamy or oogamy.
• Brown algae is the largest group of algae which grows in shallow waters and on rocky shores. They are characterized by its dominant pigment of xanthophylls – fucoxanthin. 
• Phaeophytes are the largest group among the chromists which were traditionally classified under Kingdom Plantae.
• Subclasses Isogeneratae and Heterogeneratae have diplohaplontic life cycles but the former has isomorphic alternation of generation while latter has heteromorphic alternation of generation.
• Subclass Cyclosporae has diplontic life cycle, possessing only diploid generation, hence, no alternation of generation.
• Fucus is a macro-algae, also called as rockweed commonly found on rocky seacoasts and salt marshes
• Sargassum is a widely distributed genus, especially in the tropic, which have the same type of life cycle as the above fucalean alga. 
• Ectocarpus with simplest habit as branched filament. The sporophyte (2n thallus) and the gametophyte (n) are morphologically alike, hence this alga exhibits isomorphic alternation of generation.
• Laminaria with one of most complex forms and true tissue organization of its thallus. It is an example of a kelp that grows to about 5 m or more in length and abounds on rocky coast of temperate or polar seas. This alga demonstrates heteromorphic alternation of generation.  
• Hydroclathrus is a net-like brown alga common in the tropic that exhibit the same type of alternation of generation as Laminaria except that it produces plurilocular sporangia along the margins of its blade.
• Green algae contain both chlorophylls a and b like higher plants. Also, they store starch inside double membraned plastids
• Chlorophyceae Species under this group are distinguished chiefly by clear green color, with chlorophyll being masked or altered little or not at all by other pigments (Simpson, 2010)
• Volvocales, Chaetophorales, & Chlorococcales - make up more than half of all chlorophyceans; have an offset flagellar arrangement (1 o'clock-7 o'clock).
• Chlorellales - have opposed flagellae (12 o'clock-6 o'clock), though some have only vestigial flagellae and so have not been definitively associated with this group.
• Oedogoniales - have complex multiflagellate crown on swimming spores; All are filamentous, oogamous, and have net-like chloroplasts. 
• Division Streptophyta - This division includes all embryophyte plants (land plants) and freshwater green algae:
• Charophyceae - Members of this group form macroscopic branching filaments with a long central axis punctuated by nodal cells
• Porphyra is known in Ilocano as ”gamet” or in Japanese as “nori” and sea laver in English that is a popular ingredient in preparing the Japanese dish called “sushi.
• Prostate System – creeping, basal part of thallus which is attached to the substratum
• Rhizoids – false roots attached to the Prostate system
• Attachment Disc – swollen distal ends of each rhizoids
• Erect System - vertical and profusely branch part of the thallus