q Review Notes General Characteristics Eukaryotic photoautotrophs/heterotrophs; body plans range from unicellular to multicellular thalli. Grouped into animal-like (protozoa), plant-like (algae), fungal-like (slime & water molds). Nutrition: heterotrophy, autotrophy, or mixotrophy; motility common (flagella, gliding) except some sessile forms. Key life-processes (circulation, respiration, excretion) largely by diffusion; reproduction asexual (fission, spores, fragmentation) or sexual (conjugation, gametes, alternation of generations). Taxonomic Framework (Domain Eukarya) Classic five-kingdom Protista splits into: Expanded eukaryote lineages relevant to algae: Division Euglenophyta (Euglenoids) Unicellular, flexible pellicle beneath plasma membrane; one or two anterior flagella. Pigments: chlorophyll a & b; storage product paramylon. Mixotrophic; stigma + light detector enables phototaxis. Osmoregulation via contractile vacuole; reproduction by longitudinal fission. Division Dinoflagellata (Dinoflagellates) Unicellular alveolates with cellulose plates; two flagella in transverse cingulum & longitudinal sulcus → spinning motion. Half are photo-/mixotrophs, rest heterotrophs; accessory pigments chlorophyll a & c, carotenoids. Many produce toxins (e.g., saxitoxin → paralytic shellfish poisoning); cause algal blooms “red tides”. Symbiotic zooxanthellae in corals; several bioluminescent genera. Division Chrysophyta Golden-brown & Yellow-green Algae Pigments: chlorophyll a & c plus fucoxanthin (golden color); reserve chrysolaminarin. Mostly freshwater plankton; two unequal flagella; form silica-walled statospores. Vaucheria: siphonous coenocytic filaments; both asexual & sexual (oogamy). Diatoms Frustule of silica (two thecae, epitheca & hypotheca); ornate pores. Major marine & freshwater phytoplankton, significant global photosynthesis. Asexual mitosis shrinks average cell size; size reset via sexual cycle. Fossil frustules accumulate as diatomaceous earth (filters, abrasives, insulation). Division Chlorophyta (Green Algae) Pigments chlorophyll a & b; starch in plastids; cellulose walls (most). Habitats: fresh, marine, terrestrial, symbiotic (lichens). Morphology spectrum: unicells (Chlamydomonas), colonies (Volvox), filaments (Spirogyra), sheets (Ulva), siphonous (Caulerpa), complex thalli (Chara). Reproduction diverse: isogamy, anisogamy, oogamy; many alternations of generations. Division Phaeophyta (Brown Algae) Multicellular marine seaweeds/kelps; pigments chlorophyll a & c + fucoxanthin. Thallus differentiated into holdfast, stipe, blades; pneumatocysts for buoyancy. Storage polysaccharide laminarin; cell wall alginic acid (source of food thickeners & industrial algin). Life cycle typically sporic with alternation of generations. Division Rhodophyta (Red Algae) Mostly multicellular marine; pigments phycoerythrin & phycocyanin mask chlorophyll → red coloration, adaptive to deep water. Reserve floridean starch; cell wall mucilages yield agar & carrageenan (food, pharma, industry). Some calcified coralline forms aid reef building. No flagellated stages; complex alternation of generations. Economic & Ecological Highlights Green algae: biomass for biofuels, wastewater remediation, model organisms (Chlamydomonas), food (Ulva). Brown algae: alginates (food stabilizers, cosmetics, textiles); giant kelp habitats. Red algae: agar (microbiology media), carrageenan (emulsifier), edible nori; coralline species reinforce reefs. Diatoms: diatomaceous earth (filters, abrasives); base of aquatic food webs. Dinoflagellates: primary producers, but also harmful algal blooms impacting fisheries. Key Terms for Review Pellicle, Paramylon, Mixotrophy, Statospore, Frustule, Pneumatocyst, Floridean starch, Algin, Agar, Carrageenan, Red tide. Knowt Play Call Kai