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Algae and Fungus-Like Protists

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					Algae and Fungus-Like
       Protists
      Chapter 27
      Characteristics of Algae
• photoautotrophic
• no tissue differentiation
  – no roots, stems, or leaves
• single cell gametangia
• most have flagella during life cycle
• pyrenoids – organelles used to synthesize
  starch
                       Algal Structure
•    Thallus = body type
    – 4 types of algae based on thallus
    1. unicellular
       –   aquatic, phytoplankton*, major producer of O2
       –   ex: Chlamydomonas
    2. Colonial
       –   division of labor [specialized within group]
       –   ex: Volvox
    3. Filamentous
       –   slender, rod-shaped thallus
       –   ex: Spirogyra
    4. Multicellular
       –   large, complex thallus – usually leaf-like
       –   ex: Ulva and Macrocystis
               Reproduction
• All algae have some form of asexual
  reproduction
• Most also utilize a form of sexual
  reproduction
• sexual reproduction in algae usually occurs
  in times of environmental stressors that
  warrant genetic diversity
• 4 examples of reproductive strategies in
  algae:
         Reproduction of Chlamydomonas
•    Asexual – occurs in nutrition rich environ.
    1.    absorbs flagellum
    2.    haploid organism divides by mitosis (2 to 3X)
    3.    mitotic division forms zoospores
    4.    zoospores mature into adults
–    Sexual – environmentally poor conditions
    1.    absorbs flagellum
    2.    mitotic division (2 to 3X) produces + and – gametes
    3.    + and – gametes fuse to form diploid zygote
    4.    zygote can form a zygospore – thick protective cell wall
    5.    favorable conditions return
    6.    organism undergoes meiosis producing haploid zoospores
    Reproduction of Oedogonium
• Oedogonium is a filamentous green algae
• Reproduce through self-fertilization
• The process:
  – male gametangia (antheridium) produce sperm above
    female gametangia (oogonium) that produce eggs
  – sperm are released from antheridium and swim to
    oogonium and fertilize egg
  – diploid zygote forms a resting spore which buds off
  – meiosis results in 4 haploid zoospores
  – each zoospore lands and divides
  – one of the cells becomes a holdfast (root-like structure)
  – the rest grow into an adult Oedogonium
         Conjugation in Spirogyra
•   Spirogyra is a filamentous green algae
•   Sexual reproduction through conjugation
•   The Process
    1. two Spirogyra line up
    2. form conjugation tube
    3. + gamete swims through tube and fuses with –
       gamete
    4. zygote forms thick wall and falls from parent
    5. zygote divides to become new Spirogyra
   Alternation of Generations in Ulva
• Ulva is leaf-like (seaweed)
• Alternation of generations means to alternate
  between a haploid form and a diploid form in an
  ongoing lifecycle
  – The Process:
     • Diploid phase = sporophyte
        – houses reproductive cells called sporangia
        – sporangia produce zoospores through meiosis
        – zoospores divide by mitosis, form motile spores which settle on
          rocks and divide to form mature, haploid gametophytes
     • Haploid phase = gametophyte
        – house gametangia
        – gametangia produce + and – gametes which fuse to form zygote
        – diploid zygote settles on rock and divides into sporophyte
         Phylum Chlorophyta
•   7,000 species of “green” algae
•   all thallus types
•   mostly aquatic, some terrestrial
•   chloroplasts with chlorophyll a and b
•   carotenoids
•   store food as starch
•   cell walls made of cellulose
•   ex: Caulerpa racemosa and Protococcus
            Phylum Phaeophyta
• 1,500 species of “brown” algae
• marine seaweeds and kelp (shallow to surface ocean)
• chlorophylls a and c
• fucoxanthin – brown pigment
• store food as laminarin
• multicellular stipe (stem-like) and blade (leaf-like)
• cell walls contain alginic acid – used to produce
  alginate which is used in production of cosmetics,
  drugs, stabilizer in ice cream
• ex: Macrocystis, Sargassum
             Phylum Rhodophyta
• 4,000 species of “red” algae
• mostly marine seaweeds (deeper than brown – 650
  feet deep)
• chlorophyll a and phycobilins
  – phycobilins is a pigment that absorbs wavelengths of light
    that penetrate deep beyond surface
• not all are red
• cell walls contain carageenan – polysaccharide used
  in cosmetics, gelatin capsules, cheeses
• agar is extracted from cell walls of red algae
• ex: Corallina
          Phylum Chrysophyta
• 850 species of “golden” algae
• mostly fresh water, some marine
• chlorophylls a and c and large amounts of
  carotenoids
• store food as oil – form petroleum deposits
• cells form cysts that allow them to survive
  frozen water
• two flagella of unequal length
            Phylum Bacillariophyta
• 11,500 species of diatoms
• aquatic
• cell walls form shells of two pieces called valves
   – made of SiO2
• 2 types of diatoms
   – pennate – rectangular shells, freshwater
   – centric – circular or triangular shells, marine
• component of phytoplankton
• dead diatoms form diatomaceous earth
   – used commercially to produce detergents, paint removers,
     fertilizers, insulators, toothpaste
           Phylum Dinoflagellata
• 1,100 species of dinoflagellates
• mostly unicellular and photosynthetic
• some are colorless and heterotrophic
• carotenoids, chlorophylls a and c
• 2 flagella of unequal length
• spins like a top
• cell walls made of cellulose plates
• some produce bioluminescence – light
• some produce toxins – eutriphication results in
  toxic red tides
• ex: Noctiluca
           Phylum Euglenophyta
• 1,000 species of euglenoids
• single flagella
• plant-like
  – photosynthetic, chlorophyll a and b
• animal-like as well
  – no cell wall, highly motile
• mostly freshwater, some terrestrial (moist)
• ex: Euglena – Fig. 27-10
  – usually photosynthetic (chloroplasts)
  – if raised in dark environment = heterotrophic
              Fungus-Like Protists
• Slime Molds
  – life cycle of 2 forms
     • amoeba feeding form
     • spore bearing, fruiting body form
  – 2 phyla
     • Acrasiomycota
        – 65 species of cellular slime molds
        – amoeba feeding in nutrient rich environ. come together in
          thousands to form psuedoplasmodium in harsh environ.
     • Myxomycota
        – 450 species of plasmodial slime molds
        – plasmodium is multinucleate mass of cytoplasm
        – form fruiting bodies when food is scarce
                          Water Molds
• a fungus-like organism
• aquatic [mostly freshwater]
• some terrestrial, some parasitic to plants
  – 2 phyla
     • Oomycota
        – pathogenic to plants
        – ex: Phytophthora infestans – causes blight in potatoes
            » Irish potato famine – late 1800’s
        – ex: Plasmopara viticola – causes blight in grapes
     • Chytridiomycota
        –   750 species of chytrids
        –   aquatic
        –   single flagellum
        –   unicellular
        –   some parasitic
        –   some saprophytic

				
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posted:5/11/2013
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