A Survey of the Kingdom Protista

  • to gain a broader appreciation for the diversity of the protists
  • to note similarities and differences between the various groups and how they attempt to solve the same basic problems of daily living
  • to note the unique relationships that sometimes exist within the groups
  • Introduction

    The Protista are probably the most diverse of the eukaryotic Kingdoms. Members are unicellular, filamentous, colonial or multicellular. All require some form of moisture, fresh or saltwater, to survive and reproduce. They are divided into three categories for ease of classification. The categories relate to the ways in which nutrition is obtained by organisms in each category. They may be subdivided as to the manner of locomotion in the case of the protozoans. Your Photographic Atlas for the Biology Laboratory, 4th Edition, contains pictures and drawing of the various protistan groups starting on page 29.

    In the absence of microscopes and slides we will observe the organisms by using the embedded links.

    1. Animal-like Protists (The Protozoans) - all are heterotrophic and are usually grouped by locomotion type and feeding means.

      1. Ameboid (Division Rhizopoda) - free-living (Amoeba proteus) and parasitic (Entamoeba histolytica) forms are present; some (Foraminiferans and Radiolarians)secrete shells, known as tests, around them. Move by extruding cytoplasm inside of membrane.

      2. Flagellate (Division Zoomastigophora) - free-living, symbiotic forms such as those found in termite intestines, and parasites such as Giardia lamblia (causative agent of Beaver Fever) and Trypanosoma gambiense (causative agent of African Sleeping Sickness) abound. Move by means of flagella - typical 9 + 2 microtubule arrangement.

      3. Ciliate (Division Ciliophora) - mostly solitary, free-living and fresh water groups; reproduce by conjugation. Have two nuclei - large macronucleus controls growth, small micronucleus controls conjugation. Move by means of cilia. Paramecium caudatum andStentor are examples.

      4. Sporozoans (Division Apicomplexa) - all members of group are parasitic with one or more intermediate hosts. All lack means of independent locomotion. Plasmodium is an example. This genus causes malaria. Four different species involved and vary with geography and time of onset of symptoms.

      typical amoebalabelled viewsAmeoba anatomy (drawing)animation
      Ameoba ingesting
      Ameoba with Chlorella
      Trypanosoma cruziGiardia lambliaTrypanosoma bruceiTermit gut
      parameciumparamecium trichocystsSelected species
      of Paramecium
      Paramecium labelled
      blue Stentors segmented nucleusStentor ingesting
      green algae
      blue Stentor
      Malarial VectorPlasmodium falciparumGuide to MalariaMalaria
      Life Cycle

    2. Plant-like Protists (The Algae) - all groups contain members that are photosynthetic and contain chlorophyll a. They are found in all water venues from the oceans to the rivers, lakes, streams and ponds. The single celled groups are called the phytoplankton and collectively all of the groups are known as the algae.

      1. Division Euglenophyta - contain light sensitive red pigment spot (called eyespot) and carry on photosynthesis when light is available and as heterotrophs otherwise. Lack cell wall and have pellicle made of protein strips inside of plasma membrane. Store their food as fats and paramylon (unique polysaccharide) and contain chlorophylls a & b and carotenoids. Chloroplasts are probably result of endosymbiosis. Euglena sp. is the common example.

      2. Division Chrysophyta - contains diatoms (Bacillariophyta) and golden and yellow green algae. Mostly photosynthetic and free-living some diatoms are symbiotic with foraminiferans. Groups contain chlorophylls a & c as well as a golden brown carotenoid called fucoxanthin. Food molecules produced through photosynthesis are stored as oils and chrysolaminarin (a polymer of glucose and mannitol). Cell wall contain silica not cellulose.

      3. Division Pyrrhophyta or Dinoflagellata - mostly photosynthetic and marine, pigmentation varies dependent in part on their endosymbiotic history. Pronounced “deeno” it refers to the twirling or whirlpool motion these organisms make. Some are bioluminescent and can be seen on the crest of waves coming in to shore at night. Algal blooms called red tides can poison animals including fish and humans as the result of toxin produced. They contain chlorophylls a & c and store their food as starch.

      4. Division Rhodophyta - mostly multicelled, and marine, living in clear tropical waters. Cell walls of some species contain calcium carbonate. these species are called the coralline algae and contribute to coral reef formation. Agar and carrageenan as well as cellulose are found in the cell walls of most. Some species such as Porphyra nereocystis are used as a wrapping for sushi and are known as nori. Chlorophylls a & perhaps d are found as are accessory pigments known as phycobilins which increase the portion of the spectrum that can be used for photosynthesis particularly in deep waters. Food is stored as Floridean starch similar to glycogen.

      5. Division Phaeophyta - known as the brown algae or kelp. Amongst the largest of the seaweeds. Contain chlorophylls a & c, carotenoids and fucoxanthin (also found in diatoms). Food stored as laminarin, a glucose-mannitol polymer. Food is translocated as mannitol and amino acids. Cell wall consist of cellulose and alginic acids which are converted to algin which is used as a stabilizer in paints and an emulsifier for foods. Sargassum, Fucus, Macrocystis, and Laminaria are the largest and best known.

      6. Division Chlorophyta - the green algae are the group from which the true plants developed. Extremely diverse in structure (single celled, colonial, filamentous, multicellular) and in types of reproduction. Contain chlorophylls a & b, and carotenoids; store food as starch grains inside chloroplasts; cell wall contains cellulose, pectins and other typical polysaccharides. Found in fresh water, salt water, bogs, sediments, on land and rocks, tree bark, and snow. Chlamydomonas and Chlorella are single-celled, Volvox and Pediastrum are colonial, Spirogyra and Ulothrix are filamentous, and Ulva and Codium are multicellular.

      EuglenophytaEuglena AnatomyEuglenaflagellaEuglena movies
      ChrysophytaDiatomsvarious shapesBasic formsBeautiful Diversity
      PyrrhophytaCeratiumGymnodiniumMultiple formsShellfish Toxins
      RhodophytaChondrusPorphyraCoralline AlgaeCorallina
      PhaeophytaFucusLaminariaMacrocystis infoKelp images
      ChlorophytaChlamydomonasSpirogyraVolvoxUlva at home

    3. Fungus-like Protists (The Slime and Water Molds)- all members resemble fungi and were originally classified as such. All groups differ from fungi by producing motile cells during their lifetime. Two major categories:

      1. Slime Molds (Divisions Acrasiomycota - the cellular slime molds and Myxomycota the plasmodial slime molds). Cellular slime molds behave like amebas while plasmodial slime molds stream along as a wallless cytoplasmic mass that resembles slime.

      2. Water Molds (Division Oomycota) may be free-living or parasitic such as Saprolegnia on fish or downy mildew on grapes or the parasite Phytophthora infestans which was responsible for potato blight and caused the emigration of many Irish in the late 1840’s.

    Additional Resources:

    Algae in Domestic Water Supplies

    The Odd Couple