• 1) Protists exhibit a remarkable variety of 'feeding' modes

  • a) autotrophic: photosynthesis in chloroplasts (phytoflagellates only)

  • b) heterotrophic:

    • phagocytosis (e.g., capture and ingestion by amoeba)
    • filtration (e.g., particle capture by sieving with microvilli of choanoflagellates or direct interception by cilia of ciliates)
    • engulfing (e.g., swallowing other protists whole by ciliates)

• 2) How does multicellularity differ from coloniality?

  • a) differentiation (identifiable cells perform specific functions)
  • b) interdependence (all cell types required for organism to work)
  • c) coordination (different cell types must work together)
  • d) multicellular organisms exhibit distinct cell layers

• 3) Examples of 'colonial' protists (some appear multicellular) include:

  • a) some choanoflagellates (clearly colonial)
  • b)Volvox (hollow spherical 'colonies' with different, interdependent cells)
  • c) swarming ciliates & sarcodines (slime molds) that alternate between isolated cells and complex stalked sporocarps
  • d) true multicellularity has evolved at least 5 times (green plants, red algae, brown algae, fungi , animals)

• 4) Taxa important to understanding the Tree of Life:

  • a) Phylum Metamonadida- amitochondrial, bilaterally symmetrical flagellated cell; possible sister group to mitochondrial eukaryotes
  • b) Phylum Ciliophora- a good monophyletic group of structurally complex protists; possess two nuclei: micro- & macronucleus
  • c) Phylum Choanoflagellata- a likely sister group to higher animals because they share two key characters with primitive Metazoa:

    • i) common cell type- single cilium (=monociliated) surrounded by a ring of microvilli (rules out ciliates as ancestor of Metazoa)
    • ii) diplosome- odd anchor structure to flagellum (2 basal bodies)

    • Also, a pelagic colonial form has skeletal matrix & amoebocytes

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