Chapter 11 - Protozoan Groups

Notes for Chapter 11:
Protozoan Groups

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CSUF classes will resume Wednesday Sept. 12

Ch. 11: All; RQ-11: 1, 6, 8-11

Introduction: Emergence of Eukaryotes

source of image (©Lizzie Harper)
Featured Organism: Paramecium

Links: 1 - 2 - 3 - 4

Other Featured Protists: Giardia, dinoflagellates, Euglena, Volvox, Codosiga (choanoflagellate), Amoeba, forams, radiolarians, Toxoplasma, Plasmodium

0. "Protozoa" - Good example of paraphyletic group

a. It is a functional/nutritional grouping, not a clade (monophyletic)

• Includes common ancestor of eukaryotes and many descendants

Excludes those whose body is partitioned into cells

    (e.g., plants, fungi, metazoans)

Historically, "Protozoa" included only animal-like unicellular eukaryotes
    (e.g., microscopic life in pond water)

"Protozoologists" studied protozoans, especially parasitic forms

"Phycologists" studied plant-like unicellular eukaryotes (e.g., diatoms)

More recently, most use name "Protista" (protists) for all unicellular eukaryotes

Our text uses "Protozoa" as equivalent to most authors' "Protista" (see p. 214)

Our text only emphasizes the animal-like groups (see p. 236-237)

The multicellular red and brown algae are also included as protists by some
     (so then "protists" are not all unicellular)

Eukaryota is a clade (first organism with a nucleus and all its descendants)

Like "Protozoa," "Protista" is paraphyletic

We do not recognize it as a form taxon in this class ("Rule of Monophyly")

The authors (p. 236-237) use the outdated protozoologist names in this chapter
       • They admit most these groupings are invalid, composed of unrelated taxa
       • They are waiting for a newer "standardized" protozoan classification
       • Such a classification is available and is generally agreed upon
       • Exceptions usually involve where to put certain problematic taxa
       • One reason they classify "Protozoa" like this is that they are not cladists
       • Another is that the alternative is quite complicated
       • Here is a cladistic classification of Eukaryota (about 27+ clades)
       • Here is my attempt to sort out the classification in Hickman et al.
       • Links to current tree overviews of eukaryotes: 1 - 2 - 3 - 4 - 5
       • Link 4 above has the following relatively simple tree:

       • Notice that Metazoa (animals) is grouped with fungi and then green plants
       • Together these comprise a small portion of total eukaryotic diversity
       • Choandoflagellates are likely even closer to animals but are not included here

Classification of Eukaryotes based on the above tree (unranked indented):

Eukaryota
  diplomonads
  microsporidians
  clade 1 (with mitochondria)
    parabasalians
    clade 2
      clade 3
        kinetoplastids
        euglenoids
      clade 4
         cellular slime mold
        clade 5
          alveolates
            dinoflagellates
            ciliates
          clade 6 (eukaryotic "crown group")
            chrysophytes
            clade 7
              rhodophytes (red algae)
              clade 8
                chlorophytes (green algae and land plants)
                animal-fungi grouping
                   metazoans (animals)
                   fungi

b. The name "Protista" is more general, but still not a clade

c. Eukaryota is a clade, with taxon Metazoa nested inside it

I. Form and Function

Key Terms: nucleus, cytoplasm, locomotor organelles (pseudopodia, flagella, cilia), parts of flagellum (axoneme, basal body, centrioles), axopodia (Actinopoda), sliding microtubule hypothesis, division of labor among cells (only in some colonial forms), excretion vs. osmoregulation, contractile vacuoles, phagotrophs vs. osmotrophs, holozoic vs. saprozoic feeders, food vacuole (phagosome), cytostome, binary reprodction (binary fission)1, budding, multiple fission, schizogony, isogametes vs. anisogametes, syngamy vs. autogamy, conjugation

II. Representative types

Key Terms: chloroplasts (in "phytoflagellates" - see above), macro- vs. microgametes, "zooflagellates" - see above, test (e.g., Arcella and Difflugia), reticulapodia

Within Eukaryota, basal groups lack mitochondria (but have nucleus, mitosis)
    - example: Giardia
Mitochondria known to have arisen by endosymbiosis between early eukaryote and alpha-purple bacterium
Plastids have arisen at least once and possibly multiple times from cyanobacteria as eukaryote endosymbionts
   - example: chloroplasts
Endosymbiosis between 2 eukaryotes is also known –> combined organism
   - examples: euglenoplasts came from green algae, Mesodinium is a ciliate + cyptomonadwith plastids of two separate origins

Eukaryote "protist" Examples Emphasized:

Giardia
– basal eukaryote without mitochondria
– nasty parasite from drinking stream water

Euglena
– widely studied as typical flagellate
– freshwater habitat
– plastid came from green alga

Amoeba
– widely studied "naked" amoeboid
– uses pseudopodial locomotion

with lobopodia– other "sarcodina" have test

and axopodia
forams, radiolarians
"ooze" on sea floors

"flagellates" or "amoeboids" are each polyphyletic

Heterokonts
diatoms – unicellular phytoplankton
kelp - multicellular

Alveolates
dinoflagellates
– important "phytoflagellates"– free-living or symbiotic inside corals, anemones (zooxanthellae)
– includes "plants" & "predators"
ciliates (Paramecium)– highly diverse group
– usually large (10 µm to 3 mm)
– macro- and micronucleus
– conjugation – adults exchange haploid micronuclei, come away different (Fig. 11-27)
apicomplexans
– endoparasites lacking motility– have "apical complex"
– Toxoplasma is cat parasite that also infects AIDS patients
– Plasmodium causes malaria, transmitted by mosquitoes (see Fig. 11-20)

"Crown" eukaryotes:

Chlorophytes
– one or more cells
– green algae and land plants
– (+ red algae?)
– Volvox example of colony of cells

Fungi

Choanoflagellates (Codosiga)
– often colonial
– probably closest relative of animals (sister taxon)
– "collar" cells resemble feeding cells of sponges

Metazoa (multicellular animals)

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