Class notes (Protists)

The domain Eukarya consists mostly of protists
Each of the 7 major groups of Eukarya contain protists

  • Amoebozoa
  • Opisthokonta
  • Excavata
  • Plantae
  • Rhizaria
  • Aveolata
  • Stramenopila

Contractile vacuoles – expel water from the cell

Protist patterns of nutrition

  • Autotrophic (algae, plant-like) – capable of synthesizing own food
  • Heterotrophic – feeds from other organisms
    • ingestors (protozoa, animal-like)
    • absorbers (slime molds, fungus-like)
  • Mixotrophic – can be both photosynthetic and heterotrophic



  • Lack cell wall and feed by engulfing food
  • Move via amoeboid motion and produce large, lobe-like pseudopodia
    • Amoebae are abundant in freshwater habitats and wet soil
  • Some are also parasites of humans and other animals
  • Pseudopodia engulf food
  • They form a food vacuole following phagocytosis



  • Choanoflagellates
  • Many are colonial, ancestors of metazoans



  • Parabasalids, Diplomonads, and Euglenids
  • Includes free-living, mutualistic, and parasitic species
  • Are all single-celled
  • Most swim using their flagella



  • Green algae



  • Ciliates, Dinoflagellates, and Apicomplexans
  • Ciliates – named for the cilia that cover them and that they use for locomotion
  • All of the known 12,000 ciliate species live in freshwater habitats, marine environments, and wet soils
  • Large complex cells


Trichocysts – a type of extrusome; an organelle capable of ejection

Exocytosis – removal of waste


  • Have 2 flagella
  • Cell wall in made of interlocking plates, usually of cellulose
  • Important primary producers in ecosystems
  • Acquired chloroplasts via tertiary endosymbiosis
  • Zooanthellae are important dinoflagellates that are endosymbiotic in corals and other cnidarians, as well as other organisms


  • Radiolarians, Forminiferans
  • Foraminiferan skeletons are made of calcium carbonate
  • Radiolarian skeletons are made of silica

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