UNM Biology Undergraduate Labs

Protists

Useful Reading

Campbell, Biology 6th Ed - Chapter 28, pgs 545-574

Campbell, Biology 7th Ed - Chapter 28, pgs 549-572

Protists are a very large, diverse group of organisms, including the plant-like protists (algae), fungi-like protists, and the animal-like protists (protozoans). They are all eukaryotic, and most are unicellular. Traditional taxonomy of protists (Kingdom Protista) did not accurately represent evolutionary relationships, so the classification of this group is unsettled.  Modern taxonomy has rearranged the group formerly known as Kingdom Protista, separating the different types of organisms into their own candidate Kingdoms.

Protists vary in how they obtain energy (autotrophic or heterotrophic) and in their locomotion.

Locomotion

Movement is achieved by several different methods in the protists.

Cilia - Microscopic hair like projections extending from the surface of a cell or unicellular organism. Capable of rhythmical motion, they act in unison to bring about the movement of the cell or of the surrounding medium

 Paramecium

Flagella - A long, threadlike appendage, especially a whip like extension of certain cells or unicellular organisms, found singly or in pairs.

 Euglena

Pseudopodia - A temporary projection of the cytoplasm of certain cells, such as phagocytes, or of certain unicellular organisms, especially amoebas.

 Amoeba

Energy obtainment

Protists are classified by how they acquire energy.  Often a single method is specific to a single protist.  There are four grouping of how energy is obtained.

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Photosynthetic autotroph

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Chemosynthetic autotroph

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Heterotroph by ingestion

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Heterotroph by absorption

Photosynthetic autotrophs make their own food using energy from light to power complex chemical reactions to make glucose.  Chemosynthetic autotrophs do the same thing using energy obtained from the breakdown of chemicals.

Heterotrophs require food as they cannot make their own.  Heterotrophs by ingestion eat by consuming food; taking it into their bodies to be digested by enzymes.  Nutrients are then released from within the body.  Heterotrophs by absorption eat by secreting digestive enzymes outside of their bodies, then absorbing the nutrients into their bodies.

Excellent Protista Website!!

Excellent Algae Website!!

 

Diversity according to proposed Candidate Kingdoms

Candidate Kingdom Archaezoa
    Lack mitochondria, made up of several hundred species, most are parasitic
    Trichonomads, Diplomonads and Microsporidians

     -Order Trichomonadida
          Parasitic
          Example Trichomonas: note the anterior flagella

     -Order Diplomonadida
          Flagellates
          Example Giardia

Candidate Kingdom Euglenozoa
    All have anterior chamber from which 2 flagella emerge
    Euglenophyta and Zoomastigophora

     -Phylum Euglenophyta (Photosynthetic Flagellates)
        Photosynthetic
        Flexible pellicle for wall
        Motility by flagella
       ~ 800 species
        Example Euglena : flagella, pigment spot (or stigma), positive phototaxis

 

      - Phylum Zoomastigophora (Non-Photosynthetic Flagellates)
          Non-photosynthetic
          Motility by flagella
          Thousands of species
          Single Mitochondrion
          Concentration of extra-nuclear DNA
          Commonly called kinetoplastids 
          Variety of ecological associations: free-living, parasitic, mutualistic
          Example Trypanosoma : human parasite that causes African sleeping sickness, transmitted by tsetse flies

           Example Trichonympha : symbiont in termite gut, digests cellulose

Candidate Kingdom Alveolata
    All members of this group have small indentations in their cell membranes, called alveoli, beneath the material covering the outer surface
    Pyrrophyta, Ciliphora and Apicomplexa

     -Phylum Pyrrhophyta / Dinoflagellata
         
Most forms with cellulose "armored" plates (theca)
          Most marine (brown algae); large component of phytoplankton
          Two flagella in grooves
          Photosynthetic
          Reproduction mostly fission
          Some symbionts
          ~ 1,000 species
          Example Ceratium
         
Dinoflagellates : Source of red tides, can produce toxins, cause paralytic shellfish poisoning, cause many tropical fish poisonings

      - Phylum Ciliophora (Ciliates)
          Locomotion by cilia
          Multilayered pellicle
          Heterotrophic, many feeding modes
          Two types of nuclei: macronucleus and micronuclei
          ~ 8,000 species
          Reproduce sexually
          Examples Paramecium
(see above in locomotion section), Stentor (left) and Vorticella (right)

 

Candidate Kingdom Stramenopila
    All have unusual flagella with fine hair like projections
    Bacillariophyta, Oomycota, Phaeophyta and Chrysophyta

     - Phylum Bacillariophyta (Diatoms)
          Photosynthetic
          Freshwater and marine; large component of phytoplankton
          Cell walls are two valves with silica; overlap at the girdle
          Abundant fossils (diatomaceous earth)
          ~ 11,500 species            
          Reproduction mostly by fission

 
  

      -Phylum Oomycota (water molds and parasitic fungi-like protists)
          Vegetative hyphae
          Sexual reproductive structures, oogonium and antheridium
          Zygote is called an oospore
          Asexual reproduction by biflagellated zoospores
          Cellulose cell walls
          Heterotrophic, decomposers and parasites
          ~ 500 species
          Example Saprolegnia

      -Phylum Phaeophyta (Brown Algae or Kelps)
          Marine tidal zone to 75 feet deep in temperate waters
          Sizes to 10O feet
          Color: brown to olive brown
          Pigments: Chlorophyll a and fucoxanthin
          All multicellular
          Many commercial uses
          Body Form has a Holdfast, Stipe, Lamina (Blade), and Air bladders
          Well defined alternation of diploid and haploid generations
          Sporophyte (diploid stage) dominant
          Reproductive cells flagellated
          Vegetative Reproduction by Fragmentation, Propagules, or Zoospores
          Examples Laminaria (left) and Nereocystis (right)

    

           Example Sargassum

      -Phylum Chrysophyta (Chrysophytes / Golden algae)

Candidate Kingdom Rhodophyta
    Commonly called coralline algae because of calcium carbonate in cellulosic cell walls
    None of the life cycle stages have flagellated cells
    Rhodophyta

     -Phylum Rhodophyta (Red Algae)
          97% marine
          ~ 4,000 species
          Size to 3 feet, depths to 300 feet
          Colors: red, purple, black
          Shapes: Unicells, Branching filaments, Sheetlike
          No flagellated cells
          Pigments: Phycobiliproteins (Phycocyanin, Phycoerythrin), Chlorophyll a
          Gametophyte forms gametes, gametes fuse to form Sporophyte
          Sporophyte may make many types of sporangia and spores
          Source of agar
          Examples Porphyra (left) and Rotalgen (right)

    

Candidate Kingdom Mycetozoa (Slime Molds)
    Myxomycota and Acrasiomycota

     -Phylum Myxomycota / Myxogastrida (Plasmodial slime molds)
          Naked protoplasm or multinucleate plasmodium stage
          Nuclei are generally diploid
          Heterotrophic (Phagotrophic)
          Produce sporangia for sexual reproduction

     -Phylum Acrasiomycota / Dictyostelida (Cellular slime molds)
          Alternate between amoeboid cells, flagellated cells and plasmodium
          Stage (called a slug) which is multicellular not multinucleate
          Nuclei are generally haploid
          Produce asexual fruiting bodies

Candidate Kingdom Chlorophyta (We will study with Non-flowering Plants)
    All have bright green choloroplasts
    Very close relationship with plants

     -Phylum Chlorophyta (Green Algae)
          ~ 7000 species
          Mostly freshwater
          Shapes: Unicellular, Colonial, Filaments, Sheet-like (thallus)
          Color: Mostly "grass-green"
          Cell walls have cellulose and pectin
          Food reserve is starch (stored in pyrenoids)
          Pigments: chlorophyll a and b, carotenoids -- like higher plants
          Reproduction: Vegetative - Fission, Fragmentation
          Reproduction: Sexual - Isogamy, Anisogamy, Oogamy, Conjugation

Sacrodina (Undetermined protist groups)
    Amoebas, Radiolarians and forams
    All move by pseudopod formation

     -Phylum Rhizopoda
          Heterotropic protozoans
          Lack permanent locomotive organelles like cilia or flagellae
          Move and catch prey with transient cellular extensions, pseudopods

         
Example Amoeba (see above in Locomotion)

 

     -Phylum Actinopoda (Radiolarians [left] and Heliozoans [right])

     - Phylum Foraminifera (Forams)
          Locomotion by pseudopodia
          Heterotrophic; feeding by phagocytosis
          Many secrete shells
          Examples Radiolaria (Silica) and Foraminifera (CaCO3)

 


Review Questions

-What protists are the major components of phytoplankton?

-What causes red tides?

-What are commercial uses of algae?

-What cell components are used by protists for locomotion?

-Why do some brown algae have air bladders?

-Which photosynthetic pigments are used by brown algae (Phaeophyta), red algae (Rhodophyta), and diatoms (Bacillariophyta)?

-Which protists are heterotrophic?

-What is positive phototaxis and why does Euglena demonstrate it?