Exercise 3: Eukaryotic Algae

• Eukaryotic algae belong to Kingdom Protista, lack vascular tissues, and are not differentiated into roots, stems, or leaves
• Algae have chlorophyll as the main photosynthetic pigment and also possess accessory pigments similar to cyanobacteria
• Red algae under class Rhodophyceae exhibit bright pink or red pigmentation due to phycobiliproteins known as "phycoerythrin"
• Algae reproduce vegetatively (division of cells, fragmentation of colony), asexually (production of spores), or sexually (union of gametes)
• Algae life cycles can be haplontic (predominantly vegetative phase, haploid, meiosis during zygote germination), diplontic (single predominant vegetative diploid phase, meiosis leads to haploid gametes), or diplohaplontic (alternation of generation between haploid gametophyte and diploid sporophyte phase)
• Most red algae exhibit a triphasic life cycle: gametophyte (n), carposporophyte (2n), and tetrasporophyte (2n)
• Red algae are differentiated from pigmented algae by the absence of flagella and centrioles, lack of sexuality in some members, and the presence of unstacked thylakoids grouped into phycobilisomes
• Dinoflagellates are unicellular protists with biflagellated vegetative cells, enclosed by a cellulose covering, and reproduce asexually through binary fission
• Dinoflagellates may reproduce greatly in warm months, causing "red tide" due to neurotoxins harmful to marine life and consumers
• Diatoms, classified under Chrysophyta, have cell walls made of silica and are divided into centric and pennate diatoms based on valve face symmetry
• Diatoms reproduce by longitudinal division, forming auxospores that give rise to vegetative cells of maximum size for the species
• Radiolarians are a type of protist found in the ocean with a silica skeleton, important as a food source for other animals
• Auxospore formation in radiolarians is a sexual means of reproduction involving the fusion of non-motile gametes by isogamy, anisogamy, or oogamy
• Brown algae, the largest group of algae, grow in shallow waters and on rocky shores, characterized by dominant pigment of xanthophylls - fucoxanthin
• True brown algae do not have unicellular nor colonial forms, grouped in a single class, Phaeophyceae, and three subclasses based on alternation of generations
• Representative species under Phaeophyta include Fucus, Sargassum, Ectocarpus, Laminaria, Hydroclathrus, and Padina jamaicensis
• Green algae contain chlorophylls a and b, store starch inside double membraned plastids, and include Chlorophytes and Charophytes resembling higher plants
• Division Chlorophyta includes scaly green flagellates, Ulvophyceae, Chlorophyceae, and Trebouxiophyceae, most living in marine water
• Chlorophyceae species are distinguished by clear green color, with chlorophyll being masked or altered little by other pigments
• Division Streptophyta includes all embryophyte plants and freshwater green algae like Charophyceae, with macroscopic branching filaments and distinct orders
• Charophyceae members form macroscopic branching filaments with a long central axis punctuated by nodal cells, giving rise to secondary branches
• Red Algae:

  • Members of Bangiophycidae
  • Unicellular Red Algae
  • Make an original illustration of a colony of Porphyridium cruentum based on provided images
  • Close-up drawing of three cells in the colony, label the chromoplast, cell envelope, cell wall, cytoplasm, and nucleus
  • Filamentous Red Algae
  • Make an original illustration of a colony of Compsopogon caeruleus based on the provided image
  • Label the branching thallus, young branch, branched uniseriate/uniaxial filament
  • Label ensheathed filaments, cortical cells, note presence/absence of gaps between adjacent cells or pit connections, and the presence of different pigments and the color they exhibit
• Porphyra sp.

  • Make an original illustration of the habit and cells of Porphyra sp.
  • Label the parts (e.g. thallus, blade, etc.)
  • Draw a section of its thallus, label undifferentiated cells, reproductive cells, and vegetative cells
  • Note presence/absence of pit connections and cortication and the presence of different pigments and the color they exhibit
• Members of Florideophycidae

  • Make an original habit illustration of Eucheuma sp., Galaxaura sp., and Gracilaria sp.
  • Describe their form in terms of cellularity, presence/absence of pit connections, cortication, and presence of other pigments
  • Note differences in their structures e.g. thickness, form & texture of their thalli
  • Using the provided micrograph of Polysiphonia in a vegetative state, observe the gametophytic thallus and label various parts
• Reproductive Life Cycle in Red Algae

  • Based on micrographs of Polysiphonia sp. (antheridia & Carpogonium), create original illustrations and label various parts
  • Based on micrographs of Polysiphonia sp. cystocarp and tetraspores, draw and label various parts
• Dinoflagellates: Division Pyrrhophyta

  • Create original illustrations based on micrographs of Prorocentrum and Ceratium
  • Illustrate Pyrodinium bahamense var. compressa and label thecal plates, epitheca, hypotheca, cingulum, and sulcus
• Diatoms: Division Chrysophyta

  • Illustrate Cyclotella, Synedra, and Navicula sp. based on provided micrographs
  • Label visible parts on the diatoms: Striae, Pseudoraphe, True Raphe
• Ectocarpus exhibits an Isomorphic Alternation of Generation, needing culture studies to differentiate gametangia or sporangia
• Laminaria has parts like holdfast, stipe, blade for photosynthesis, and meiospores that germinate into male or female gametophytes
• Hydroclathrus has parts like sporophyte, holdfast, stipe, blade, air bladders, receptacles, and conceptacles
• Sargassum has parts like holdfast, cylindrical main axes, sterile leaf-like laterals, air bladders, conceptacles, and fertile branches
• Illustrations of Euglena, Chlamydomonas, Volvox, Spirogyra, Cladophora, and Caulerpa with labeled parts like nucleus, eyespot, pyrenoid, flagellum, and thallus
• Chara, resembling horsetail, has parts like antheridium, archaegonium, rhizoid, thallus, main axis, node, and internode
• Construct a dichotomous key per family of algal specimens and create a cladogram showing relationships between algal species and cyanobacteria