Algae (Plant-like Protists)

• Protista Algae


  Autotrophs, some are mixotrophic
• Protista Algae


  • Most are motile, some are sessile
  • Undergo asexual reproduction through binary fission and sexual reproduction through conjugation
  • Can be classified by pigments, storage, and cell wall composition
• Protista Algae produce most of the O2 on earth
• Gametangia


  Gametes of Protista Algae
• Protista Algae


  • Mostly aquatic and have flagella
  • Store starch in pyrenoids
  • Contain chlorophyll
• Unicellular, multicellular, and colonial Protista Algae


  Unicellular means single cells<|>Multicellular means composed of different kinds of cells with different functions<|>Colonial means similar cells or generalized functions
• Protista Algae are simple eukaryotic photoautotrophs that lack tissue of a plant
• Divisions of Plant-like Protists


  • Division Chlorophyta (Green Algae)
  • Division Phaeophyta (Brown Algae)
  • Division Rhodophyta (Red Algae)
  • Division Pyrrophyta (Dinoflagellates)
  • Division Chrysophyta (Golden Algae-Diatoms)
  • Division Euglenophyta (Euglenoids)
• Euglenoids


  Differentiated cells with one or two flagella for locomotion
• Euglenoids


  • Mostly live in freshwater
  • Have a pellicle (supporting structure)
  • Have a light detector near the base of one of their flagella
  • Swim towards diffuse light, away from bright light
  • Have chlorophyll a and b
  • Some are not strictly photosynthetic, some are not at all
  • Have the ability to absorb organic molecules
  • Are mixotrophs
• The best example of an Euglenoid is the Euglena, which has chlorophyll a and b together with carotenoids
• Dinoflagellates


  Phytoplankton, unicellular and photosynthetic with over 3000 species
• Dinoflagellates


  • Their shape is determined by hard cellulose plates
  • Have two flagella that lie within two grooves (cingulum and sulcus)
  • Not all are photosynthetic, some are mixotrophic
  • Half are photosynthetic/mixotrophic, the other half are heterotrophic
  • Live symbiotically in marine animals as Zooxanthellae
  • Produce toxins like saxitoxin, causing paralytic shellfish poisoning
  • Optimal conditions for asexual reproduction can lead to toxin problems
  • Have chlorophylls a and c, carotenoids, and xanthophylls, with a yellowish-green to brown color
  • Some bioluminescent species include Noctiluca, Pyrodinium, and Gonyaulax
  • Gonyaulax has a cellulose theca and two distinct flagella
  • Ceratium species have unique shapes, are mixotrophic, and can encyst under adverse conditions
  • Gymnodinium catenatum is toxic, forms long cell chains, and causes paralytic shellfish poisoning
• Chrysophyta


  A diverse division with varied pigments, cell walls, and flagellated cells
• Major classes of Chrysophyta

  • Golden-brown algae
  • Yellow-green algae
  • Diatoms
• Chrysophyta


  • Major photosynthetic pigments: chlorophylls a, c1/c2, and fucoxanthin (gives golden-brown color)
  • Major carbohydrate reserve: chrysolaminarin
  • Some lack cell walls, others have intricate coverings like scales, walls, and plates
  • Typically have two anterior flagella of unequal length, though variations exist
  • Mostly unicellular or colonial
  • Reproduction is usually asexual, occasionally sexual
  • Primarily freshwater, though some marine forms exist
  • Blooms of some species can cause unpleasant odors and tastes in drinking water
• Best examples of Chrysophyta


  • Vaucheria
  • Diatoms
• Golden-Algae


  • 1,000 species, mostly planktonic in freshwater and marine environments
  • Cells have one large chloroplast and two unequal flagella emerging perpendicularly
  • Light detector and eyespot located at the base of the short flagellum
  • Some are mixotrophic, feeding on bacteria and organic matter by phagocytosis
  • Form dormant spores (statospores) encased in silica walls, germinating in spring
  • Synura forms swimming colonies with cells joined at posterior ends, each with two flagella
  • Synura cells have golden-brown chloroplasts with chlorophyll-c1 and fucoxanthin, and are covered in siliceous scales arranged in a spiral pattern
• Yellow-green Algae


  • Over 600 species, mostly in fresh water, some in ocean or damp soil
  • Important part of phytoplankton, especially in fresh water and salt marshes
  • Typically unicellular, but can form colonies, long filaments, or coenocytic masses with many nuclei
  • Most have two flagella: a tinsel flagellum with hairlike projections (pulls cell forward) and a whiplash flagellum (smooth, moves cell backward)
  • Reproduction is mainly asexual through filament fragmentation or spore formation; only two genera, including Vaucheria, reproduce sexually
  • Vaucheria: coenocytic filaments forming felt-like mats ("water felt"), common in various freshwater habitats, soil, estuarine mud, and saltmarshes
  • Filamentous and siphonous thallus with large central vacuole; chloroplasts parietal and aligned parallel to filament axis
  • Able to stream cytoplasm and nutrients along the filament, aiding survival in silt or partial desiccation
• Diatoms


  • Found in fresh water, salt water, and moist vegetation; thrive in cool/cold regions
  • Major constituents of phytoplankton; essential food source for marine animals
  • Responsible for about one-quarter of Earth's photosynthesis
  • Over 5,600 identified species; potentially more than 100,000 species
  • Photosynthetic, with chlorophylls a and c, and carotenoids
  • Unique frustules (silica cell walls) with intricate patterns and pores; allow gliding movement
  • Frustules consist of two halves: larger epitheca and smaller hypotheca
  • Depend on dissolved silica for growth; store oil for buoyancy and food
  • Mainly reproduce asexually by mitosis; sexual reproduction occurs when cells reach a minimum size
  • Fossilized frustules form diatomaceous earth, used in various commercial products (detergents, polishes, fertilizers, filtering agents, insulation, soundproofing, paint additives)
• Chlorophyta (Green Algae)


  Varied division, mostly freshwater, some marine and terrestrial<|>Symbiotic relationships with other organisms (e.g., lichens)<|>Contain chlorophylls a and b, store starch in plastids<|>Diverse body forms: unicellular, colonial, filamentous, membranous, sheetlike, tubular<|>Some species have holdfasts for anchoring<|>Reproduction: both asexual and sexual
• Examples of Chlorophyta


  • Chlamydomonas (unicellular freshwater alga)
  • Acetabularia (found in warm tropical waters)
  • Motile colonial organism (example is Volvox)
  • Spirogyra (filamentous freshwater green algae)
  • Ulva (Sea Lettuce, multicellular seaweed with green blades)
  • Stoneworts (Chara, green algae in freshwater lakes and ponds)
• Chlamydomonas


  • Oval haploid cell, lacks cellulose, has glycoprotein
  • Two equal-length flagella at anterior end
  • Single large cup-shaped chloroplast, central nucleus, one or two pyrenoids, red eyespot near flagella base
  • Less than 25 micrometers in size, two small contractile vacuoles at flagella base
• Acetabularia


  • Found in warm tropical waters
  • Single, large cell shaped like a mushroom, up to several centimeters tall
  • Three parts: bottom rhizoid, middle stalk, top umbrella of branches
  • Single nucleus in rhizoid; can regenerate completely from rhizoid
  • Caps can be exchanged between Acetabularia, even different species
• Motile colonial organism (Volvox)


  • Hollow sphere with photosynthetic cells in single layer
  • Each cell has two flagella
  • Light detectors control flagella beating, colony movement toward light
  • Reproductive cells cluster inside, form daughter colonies
  • Reproduction can be sexual or asexual
• Spirogyra


  • Filamentous freshwater green algae
  • Unbranched filaments with cylindrical cells
  • Cell wall: outer layer cellulose, inner layer pectin
  • Each cell contains ribbon-shaped chloroplasts in spiral
  • Chloroplasts with pyrenoids for starch production
  • Asexual and sexual reproduction
• Ulva (Sea Lettuce)


  • Multicellular seaweed with green blades
  • Blades anchored by basal holdfast to rocks
  • Blades may be haploid or diploid
  • Found in tide pools and exposed areas at low tide
• Stoneworts (Chara)


  • Green algae in freshwater lakes and ponds
  • Some species precipitate calcium and magnesium carbonate
  • Complex thalli with whorls of branches, nodes, and internodes
  • Resemble small horsetail plants
  • Apical growth, tissues similar to vascular plants
  • Oogamous sexual reproduction with multicellular antheridia
• Phaeophyta (Brown Algae)


  Multicellular organisms predominantly found in the sea
• Phaeophyta (Brown Algae)


  • Majority grow in cold ocean waters, some in shallow areas
  • Notable genera include Macrocystis pyrifera (giant kelp) and Sargassum
  • Thallus structure: holdfast (rootlike), stipe (stemlike), blades (flattened, for photosynthesis)
  • Some thalli have gas-filled floats (pneumatocysts) at base of blades
  • Brown to olive green color due to fucoxanthin pigment
  • Cell walls composed of cellulose and alginic acid
  • Cells contain large vacuoles, plastids, and sometimes pyrenoids for laminarin storage
  • Motile cells have distinctive pair of flagella: longer one with projections points to anterior, shorter points to posterior
  • Algin extracted from cell walls used as thickener in food and nonfood products (e.g., ice cream, rubber tires)
• Rhodophyta (Red Algae)


  Predominantly found in warmer and deeper marine waters
• Rhodophyta (Red Algae)


  • Most are filamentous or multicellular, up to about 1 m long
  • Can be free-living, epiphytic, or parasitic
  • Store floridean starch as carbohydrate reserve
  • Red or pink color due to phycobilins (phycoerythrin and phycocyanin) and carotenoids
  • Phycobilins enable survival at depths up to 100 m by absorbing green, violet, and blue light
  • Cell walls have cellulose framework, rich in mucilages containing agars and carrageenans
  • Agar used in labs, medications, canned meats, ice cream; carrageenan stabilizes foods, cosmetics
  • Some red algae deposit calcium carbonate in cell walls, forming coralline algae crucial in coral reefs
  • Life cycle typically includes alternation of generations; no flagellated cells, even in sperm cells