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					PROTISTA
  O2 ACCUMULATION
• Oxygenic photosynthesis arose in prokaryotes
  ~2.5 billion years ago
• The earth’s atmosphere was radically changed
  – O2 was toxic to cells
  – Energy-rich organic molecules no longer
    accumulated
  – Biotically produced organic molecules became the
    primary source of energy and carbon
   RAPID EVOLUTION
• Rapid evolutionary change typically follows
  major environmental changes
  – “Punctuated equilibrium”
  – A tolerance to O2 arose in many populations
  – The ability to use O2 metabolically quickly followed
    in many of these groups
  – New ways arose to acquire & use organic molecules
  – Various species interactions arose
     • Symbiosis, predation
  – Early eukaryotic cells arose
EARLY EUKARYOTES
• The earliest eukaryotes were protists
  – >2.1 billion years ago
• Significantly different from their prokaryotic
  ancestors
  – e.g., Membrane-bound nucleus containing DNA
    associated with histone proteins
  – e.g., Mitochondria and sometimes chloroplasts
  – e.g., Other internal membrane-bound organelles
  – e.g., Mitotic (and eventually meiotic) cell division
              PROTISTS
• Very diverse group
  – >60,000 known species
• Most are unicellular
  – Some are colonial
  – Some are multicellular
• Not “simple” at the cellular level
  – Remember, a unicellular organism must carry out all
    basic functions of life within a single cell
  – Cells within a multicellular organism can become
    specialized, and need not carry out all such functions
             NUTRITION
• Protists are the most nutritionally diverse
  eukaryotic group
  – Most are aerobic, and possess mitochondria
  – Some lack mitochondria and live in anaerobic
    environments
  – Some lack mitochondria, but possess mutualistic,
    respiring bacteria
             NUTRITION
• Protists are the most nutritionally diverse
  eukaryotic group
  – Some are photoautotrophs
  – Some are chemoheterotrophs
  – Some are both photoautotrophs and
    chemoheterotrophs
 KINGDOM PROTISTA
• The traditional Kingdom Protista does not
  represent a monophyletic group
  – Multiple monophyletic lineages are grouped
  – These groups should represent separate kingdoms
  – Exactly how to divide Kingdom Protista into
    multiple kingdoms is not entirely clear
MAJOR PROTISTAN GROUPS
       branch leading                                     branch leading      branch leading
          to plants                                          to fungi           to animals
                        charophytes


Stramenopiles                green algae          amoeboid                                     Alveolates
                                                  protozoans
       brown algae                         red
                                          algae                                         ciliates
  chrysophytes                                                                              sporozoans
      oomycotes
                                                      ?                                     dinoflagellates
                                            “crown” of eukaryotes
                     slime molds            (rapid divergences)
                                                                            euglenoids
                                  parabasalids                             kinetoplastids
                              (e.g., Trichomonas)
                         diplomonads
                        (e.g., Giardia)


                            Endosymbiotic origins
                              from prokaryotic
                                 ancestors
MAJOR PROTISTAN GROUPS
MONOPHYLETIC GROUPS
• We will discuss several monophyletic groups
  –   Ancient flagellates
  –   Flagellated protozoans
  –   Amoeboid protozoans
  –   Alveolates
  –   Stramenophiles
  –   Plant lineage
  –   Slime molds
ANCIENT FLAGELLATES
Parabasilids and Diplomonads
• Free-living predatory and parasitic cells
• Some possess both flagella and pseudopods
  – Evolutionary link with amoebae?
ANCIENT FLAGELLATES
Parabasilids
• e.g., Trichomonas vaginalis, a trichomonad
  – Sexually transmitted
  – A causative agent of vaginitis
     • Swelling, itching, burning
  – Can damage urinary and reproductive tracts
ANCIENT FLAGELLATES
Diplomonads
• e.g., Giardia lamblia
   – Internal parasite of various animals
      • e.g., humans, cattle, beavers, etc.
      • >20% of human population infected at any given time
   – Fecal-oral infection route
      • Encysted cells shed in feces
      • Infection via feces-contaminated water
   – Often causes only mild intestinal upsets
   – Can cause severe gastroenteritis
      • “Girardiasis”
FLAGELLATED PROTOZOANS
Euglenoids & Kinetoplastids
• Possess one or more flagella
• All are heterotrophic
FLAGELLATED PROTOZOANS
Euglenoids
• >1,000 species
• Free-living, flagellated cells
• Most are photoautotrophs
   – Chloroplasts with chlorophylls a & b
      • (Just like plants)
   – Arose in parallel to chloroplasts in
     green algae
• Some are chemoheterotrophs
• Possess a pellicle
   – Flexible, protein-rich cell covering
             FLAGELLATED
             PROTOZOANS
Kinetoplastids
• e.g., Trypanosoma brucei
  – Causative agent of African sleeping sickness
     • Neurological disease
  – Transmission vector is tsetse fly
AMOEBOID PROTOZOANS
• “Sarcodina”
• Ancestors lost their permanent motile structures
• Move by pseudopod formation/cytoplasmic
  streaming
• Various groups
  – Rhizopods
     • Naked amoebas & foraminiferans
  – Actinopods
     • Radiolarans & heliozoans
AMOEBOID PROTOZOANS
Rhozopods: Naked Amoebas
• Found in damp soil, saltwater, fresh water
• Cytoskeletal elements change continually
• Most are free-living phagocytes
  – Engulf other protozoans & bacteria
• Some are opportunistic parasites
AMOEBOID PROTOZOANS
Rhizopods: Foraminiferans
• Most live on the seafloor
• Perforated external shell
  – Contains calcium carbonate
  – Mucus-covered pseudopods extend through
    perforations
• Most named species (99%) are extinct
• Fossilized remains mined for chalk, cement
           AMOEBOID
          PROTOZOANS
Actinopods: Radiolarans
• Numerous in fossil record
• Silica-hardened parts
• Components of plankton
  – Drifting aquatic communities
• Some species form colonies
AMOEBOID PROTOZOANS
Actinopods: Heliozoans
• Pseudopods radiate like sun’s rays
  – “Sun animals”
• Vacuoles impart buoyancy
         ALVEOLATES
• Possess tiny membrane-bound sacs (alveoli)
  beneath outer membrane
  – May stabilize cell surface
• Three groups
  – Ciliates
  – Sporozoans
  – Dinoflagellates
                 CILIATES
• e.g., Paramecium
• Many possess numerous cilia
    – Motile structures
    – Beat in synchronized fashion
•   Prey on bacteria, algae, each other
•   ~65% are free-living and motile
•   Others attach to some substrate
•   Some form colonies
•   ~30% are symbionts
               CILIATES
• Reproduce sexually and asexually
  – Similar to most protozoans in this regard
• Asexual process is “binary fission”
  – Not to be confused with prokaryotic fission
• Sexual process is “conjugation”
  – Not to be confused with bacterial conjugation
CONJUGATION
CONJUGATION
         SPOROZOANS
• Parasitic alveolates completing a portion of their
  life cycle within specific host cells
• Form motile infective cells (“sporozoites”)
• Many cause serious diseases
  – e.g., Cryptosporidium  cryptosporidiosis
  – e.g., Pneumocystis carinii  pneumonia
     • Common secondary infection in AIDS patients
  – e.g., Toxoplasma  toxoplasmosis
     • Cat  human
  – e.g., Plasmodium  malaria
               MALARIA
• Caused by 4 different species of Plasmodium
• Has infected > 100 million people
  – ~1 million die yearly in Africa alone
• Shaking, chills, fever, sweats
  – Symptoms subside, but can reoccur
• Transmitted to humans by mosquitoes
  – Females of genus Anopheles
                  MALARIA
•   Salivary gland  blood delivery of sporozoites
•   Sporozoites travel to liver
•   Asexual reproduction produces merozoites
•   Some merozoites divide mitotically in RBCs
•   Other merozoites develop into gametocytes
    – Male and female gametocytes develop into gametes
       • Occurs within mosquito, not human (too warm, O2 poor)
• Gametes fuse to form zygotes
• Zygotes divide to form sporozoites
PLASMODIUM LIFE CYCLE
PLASMODIUM LIFE CYCLE
                 MALARIA
• Malaria has been and still is prevalent in
  portions of Africa, Asia, and the Middle East
  – Malaria has infected > 100 million people
     • ~1 million die yearly in Africa alone
SICKLE-CELL ANEMIA
• The prevalence of sickle-cell anemia roughly
  parallels that of malaria
• Is there a connection?
SICKLE-CELL ANEMIA
• Genetically determined
• Aberrant b-globin allele (HbS)
  – Glutamic acid (HbA)  valine (HbS)
• Cells sickle under low oxygen conditions
• Multiple
  deleterious
  effects
SICKLE-CELL ANEMIA
        SLAVE TRADE
• Many of the African slaves transported to the
  Americas came from regions where malaria and
  sickle-cell anemia were prevalent
• As a result, 0.25% of African-Americans have
  sickle-cell anemia
• 10% are carriers
  of the sickle-cell
  allele
SICKLE-CELL ANEMIA
• If the HbS allele is bad, why is its frequency so
  high in certain populations?
• Shouldn’t natural selection weed it out?
SICKLE-CELL ANEMIA
• Though having sickle-cell anemia is harmful,
  possession of a single HbS allele is beneficial
• Individuals possessing a single HbS allele
  possess an innate resistance to the malaria
  parasite
• Thus, natural selection preserves this allele in
  populations due to this beneficial effect
• How does this work?
      SSA & MALARIA
• HbS/HbS individuals have sickle-cell anemia
• HbA/HbS individuals are only mildly anemic
• HbA/HbA individuals are “normal”

• Who gets killed by sickle-cell anemia?
• Who gets killed by malaria?
    DINOFLAGELLATES
•   Pyrrhophyta, another branch of alveolates
•   > 1,200 species
•   Most are unicellular and photosynthetic
•   Some are symbionts with coral
•   Two flagella
    – One occupies groove around cell body
• Cellulose plates surround body
• Yellow-green, green, blue, brown, or red
    – Different pigments
  DINOFLAGELLATES
• Dinoflagellates periodically experience huge
  increases in population size
  –   “Algal blooms” cause “red tides”
  –   Toxins produced by dinoflagellates accumulate
  –   Toxins kill fish feeding on these phytoplankton
  –   Birds feeding on such fish can die
  –   Humans feeding on shellfish having eaten these
      dinoflagellates can experience “paralytic shellfish
      poisoning”
   STRAMENOPHILES
• Three groups
  – Oomycotes
  – Chrysophytes
  – Brown algae


• Possess two flagella
  – One has thin filaments projecting from it and
    resembles a feather
         OOMYCOTES
• Ancient stramenophiles
• Main groups
  – Water molds
  – Downy mildews & white rusts
          OOMYCOTES
Water Molds
• ~580 known species
• Non-photosynthetic
• Saprobic decomposers of aquatic habitats
• Some are parasites
  – e.g., Saprolegnia commonly attacks damaged tissue
    in aquarium fish
          OOMYCOTES
Downy Mildews
• Non-photosynthetic major pathogens
  – e.g., Plasmopara viticola molds grapevines & fruits
  – e.g., Phytophthora infestans caused the Irish potato
    blight
  – 1/3 of Irish population
    lost from 1845 – 1860
     • Starvation
     • Cholera
     • Emigration
         CHRYSOPHYTES
•   One photosynthetic group of stramenophiles
•   Possess chlorophylls a, c1, and c2
•   Most are free-living
•   Various groups
    –   Golden algae
    –   Yellow-green algae
    –   Diatoms
    –   Coccolithophores
       CHRYSOPHYTES
Golden Algae
• ~500 known species
• Covered by silica scales or
  other hard parts
• Possess accessory pigment
  fucoxanthin
   – Golden-brown pigment
• Can form colonies in
  phytoplankton
• Some species resemble true
  amoebas
   – (With chloroplasts)
     CHRYSOPHYTES
Yellow-green Algae
• ~600 known species
• Common components of aquatic phytoplankton
  – Can form colonies
• Lack fucoxanthin
  – Golden-brown carotenoid pigment
• Most are non-motile
  – All produce flagellated gametes
      CHRYSOPHYTES
Diatoms
• ~5,600 species currently exist
  – ~35,000 extinct species
• Possess a silica shell
  – Two parts overlap like a Petri plate
  – Very diverse shapes
• Finely crushed shells accumulate at the bottom
  of lakes and seas
  – Used as fine abrasives, filters, and insulation
       CHRYSOPHYTES
Coccolithophores
• ~500 species currently exist
• Most are unicellular marine
  organisms
• Protected by calcium carbonate
  plates
   – Accumulations of plates helped form
     marine sediments, chalk and limestone
     deposits
• Mucus around cells can clog fish
  gills during algal blooms
         BROWN ALGAE
•   Another group of photosynthetic stramenophiles
•   ~1,500 species currently exist
•   Most live in cool or temperate seawater
•   Possess chlorophylls a, c1, and c2
    – Possess fucoxanthin and/or other accessory pigments
    – Appear olive-green, golden,
      dark brown, etc.
• Microscopic to very
  macroscopic
• Diverse life cycles
    – Asexual and sexual phases
BROWN ALGAE
  • Giant kelps are largest, most complex
    protistans
  • Complex multicelled sporophytes
     –   Stipes (stemlike parts)
     –   Blades (leaflike parts)
     –   Holdfasts (anchoring structures)
     –   Buoyancy provided by hollow, gas-filled
         bladders
          • Why do you think this is important?
     – Tubelike arrays in blades carry sugars to
       rest of body
          • Evolved in parallel in vascular plants
       BROWN ALGAE
• Giant kelp beds function as productive
  ecosystems
  – Homes to diverse bacteria, protozoans, animals
• Some species commercially harvested
  – Food or fertilizer
  – Extracts are components of ice cream, pudding, jelly
    beans, salad dressings, etc.
  – Alginic acids from cell wall useful as a thickening
    agent
       PLANT LINEAGE
• The monophyletic group containing green algae
  and their closest relatives also contains plants
    – These groups are sometimes classified in the plant
      kingdom


•   Green algae (Chlorophyta)
•   Zygophyta
•   Charophyta
•   Plants
          GREEN ALGAE
• >7,000 known species
• Share many features with plants
  –   All are photosynthetic (oxygenic)
  –   Possess chlorophylls a & b
  –   Store carbohydrates as starch inside chloroplasts
  –   Some have cell walls composed of cellulose, pectins,
      and other polysaccharides
• Single-celled, sheetlike, tubular, or colonial
  – Most are microscopic
• Generally possess two anterior flagella
          GREEN ALGAE
• Most live in freshwater
• Some grow elsewhere
  –   Ocean surface
  –   Marine sediments
  –   Below soil surface
  –   On various substrates (rocks, snow, organisms, etc)
• Some are symbionts with fungi, protozoans, or
  marine animals
       GREEN ALGAE
• Diverse modes of reproduction
• e.g., Chlamydomonas sexual & asexual cycles
RED ALGAE (Rhodophyta)
• ~4,100 species
  – 95% saltwater / 5% freshwater
• Mucous material in cell wall imparts slippery
  texture
• Agar is made from cell wall extracts
  – Culture media, cosmetics, jellies, etc.
  – Nutritious food source
  – Wrapping for sushi
RED ALGAE (Rhodophyta)
• Most abundant in tropical seas & warm currents
• Some grow at great depths
  – Up to 265 meters in clear water
• Chlorophyll a plus accessory pigments
  – Typically appear red, green, purple, or black
  – Phycobilins are accessory pigments that absorb green
    and blue-green wavelengths that penetrate deep
    waters
RED ALGAE (Rhodophyta)
• Life cycles of most species include multicelled
  stages lacking
  tissues and organs
• Asexual and sexual
  phases in life cycle
CHLOROPLASTS
         SLIME MOLDS
• Free-living amoeba-like cells part of life cycle
• Two main types
  – Cellular slime molds (Acrasiomycota)
     • ~70 different species
  – Plasmodial slime molds (Myxomycota)
     • ~500 different species
• Predators
  – Eat organic compounds and microorganisms
• Asexual reproduction involves colonies
• Sexual reproduction also exists
SLIME MOLDS
      CELLULAR
SLIME MOLD LIFE CYCLE
     PLASMODIAL
SLIME MOLD LIFE CYCLE

				
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