Z250 - Lec4 Outline- Protista I: Introduction (2011)

Zoology 250 (2011)

Kingdom PROTISTA I: Introduction

(protist study images)
click on tree to see full cladogram)

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1) Very heterogeneous group (35 phyla!). Includes important human parasites (malaria, sleeping sickness, beaver fever, dysentery) and some of the most structurally complex cells on the planet
2) Actual phylogenetic relations & classification hotly debated; four "groupings of convenience" based mainly on locomotion:
- a) "Flagellates" (approx. 6,900 spp.)- use 1 or more flagella and includes:
  - phytoflagellates (have chloroplasts; 13 phyla);
    EXAMPLES: dinoflagellates, Euglena, Volvox (colonial), diatoms
  - zooflagellates (lack chloroplasts; 6 phyla)
    EXAMPLES: choanoflagellates, Trypanosoma, Giardia
- b) "Sarcodines" (approx. 12,000 spp.; 14 phyla)- use pseudopodia (lobe- or spine-like outgrowths) of ectoplasm; some produce spectacular skeletons
  EXAMPLES: amoebas, slime molds, foraminifera, radiolarians
- c) "Sporozoans" (approx. 5,000 spp.; 4 phyla)- move in various ways (body flexion, flagella, pseudopods); all are parasitic & reproduce via spores
  EXAMPLES: Plasmodium (malarial parasite)
- d) "Ciliates" (approx. 8,000 spp.; 1 phylum: Ciliophora)- use cilia; includes the most structurally complex protists; come in a remarkable variety of forms
  EXAMPLES: Paramecium, Stentor
3) Defining characters: a) unicellular (some colonial); b) eukaryote (membrane-bound nucleus & 1 or more organelles, mitosis)
4) Other notable features: small size (0.001 - 5mm); symmetry (all types); some have rigid skeletal structures (make their own cellulose plates, carbonate or silicate shells, or attach bits); also:
- a) locomotory structures include: pseudopodia (temporary 'feet': rhizopodia= amoeboid lobes, or axopodia= rigid rods), cilia, flagella
  - cilia and flagella are ultrastructurally identical ("9 doublet +2 singlet" microtubule arrangement, basal body)
  - flagella: long, few per cell, continuous regular undulation
  - cilia: short, many per cell, separate power & recovery stroke
- b) may have a complex osmoregulatory structure: contractile vacuole

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