Protists

  • Protists are eukaryotes
  • Infolding of plasma membranes in bacteria resulted in the endoplasmic reticulum and nuclear envelop
  • Primary endosymbiosis:
  • Secondary endosymbiosis:
  • Primary endosymbiosis of aerobic bacteria formed the mitochondria
  • Primary endosymbiosis of photosynthetic cyanobacteria formed the chloroplasts
  • In brown algae there was likely secondary endosymbiosis of red algae
  • Main groups of protists
    • Excavata – euglenoids and diplomonads
    • SAR
    • Stramenopila - brown algae, diatoms
    • Alveolate - dinoflagellates, ciliates
    • Rhizaria – foraminifera
    • Archaeplastidia – red and green algae .
    • Amoebozoa – amoebas, slime molds.
    • Opisthoconta - choanflagellate
  • Excavata
    • Unicellular •
    • 2 or more flagellae •
    • Feeding groove (cava) •
    • May be mixotrophs, heterotrophs or parasitic •
    • Many have chloroplasts acquired through secondary endosymbiosis
    • Diplomonads
    • Lack mitochondira
    • Two haploid nuclei
    • Multiple flagellae
    • Have a hydrogenosome which is an organelle that produces anaerobic energy
    • Ex. Giardia
    • Parabasalids
    • Undulating membrane
    • Mitochondria that is semi-functional
    • One nucleus
    • May be symbiotic or parasitic
    • Ex. Trichomonas, Trichonympha
  • Euglenozoans:
    • Lacks a cell wall allowing their body to change shape
    • Have mitochondria
    • Euglenids:
    • Free living
    • One long flagella and one short one
    • Photosensitive eye spot
    • Chloroplasts likely from secondary endosymbiosis of green algae. Contains chlorophyll a and b and carotenoids
    • Asexual reproduction
    • Kinetoplastids:
    • All parasitic
    • Single large mitochonrion called a kinetoplastid.
    • Contains minicircles and maxicircles of DNA linked into chains
    • Causes human diseases: trypanosomiasis, leishmaniasis, chagas disease
  • SAR
    • Alveolata:
    • Outer membrane that secretes cellulose
    • Vesicles called alveoli form from inner membranes
    • Tricocysts or toxicysts (ejectable organelles) may be present
    • Can be photosynthetic, heterotrophic, or parasitic
    • Dinoflagellates:
      • Unicellular
      • Photosynthetic
      • Cellulose plates
      • Two flagella
      • Important autotroph of ocean littoral zone
      • Symbiotic in some animals
      • Can be bioluminescent
      • Cause of red tides
    • Apicomplexans
      • Endoparasites
      • Flagellated gametes are the only form of locomation
      • Apical complex that allows them to invade a host
      • Ex. Plasmodium, Toxoplasma and Cryptosporidium
    • Ciliates
      • Cilia that is either in rows or spirals around the cell
      • Micro and macronucleus
      • Form vacuoles to ingest food and maintain water balance
      • Sexual reproduction via conjugation
    • Stramenopila
    • Brown algae:
      • Photosynthetic
      • Large and multicellular
      • Mostly marine dwelling
      • Haplodiplontic life cycle, in some species the gametophyte and sporophyte are identical
      • Lack differentiated tissues
      • Edible
    • Diatoms:
      • Photosynthetic
      • Important in littoral marine ecosystem
      • Found in marine, fresh water, and soil
      • Unicellular
      • Unique silica test
      • Variety of shapes
      • Reproduction via fission
    • Oomycetes:
      • Water molds
      • often plant parasites
      • motile zoospores
      • Ex. Phytophthora, Ichthyophthitius
    • Rhizaria:
    • Move with thread like or needle like pseudopodia
    • Unicellular
    • Marine or soil dwelling
    • Tests may be silica or calcium carbonate
    • Radiolaria:
      • Common marine plankton
      • Glassy silica test
      • Pseudopodia has long spiky projections used to regulate buoyancy
      • Heterotrophic
      • May have symbiotic zooxanthellae
      • Abundant in the fossil record
    • Foraminifera:
      • abundant marine creatures
      • Most are benthic, some are planktonic
      • Tests made of calcium carbonate
      • Podia used for swimming, feeding, and gathering material for their tests
      • Abundant in limestone deposits
    • Cercozoa:
    • Primarily soil dwelling
    • Silica based test
    • Locomotion with pseudopodia or flagella
    • Mostly heterotrophic, some have endosymbiotic cyanobacteria
  • Archaeplastidia:
    • Rhodophyta (red algae)
    • Can be microscopic or multicellular
    • Red colour from the pigment phycoerythrin
    • Most are marine dwelling
    • Lack flagella
    • Coralline species secretes calcium carbonate
    • Edible (dulse, nori)
    • Chlorophyta (green algae):
    • Can be unicellular, filamentous, foliose, or colonial
    • Mostly fresh water but can be marine dwelling
    • In the fossil record dating back to the Proterozoic era
    • Sexual and asexual reproduction
    • Haplontic and haplodiplontic life cycles
    • In ideal environment can become sessile
    • Colonial forms have some specialized cells
      • Ex. Volvox
  • Charophytes
    • Closest living relative to land plants
    • Molecular evidence
    • Similar chloroplast structure
    • Plasmodesmata
    • Oogamy
    • Haplodiplontic life cycle
    • Haplontic or haplodiplontic life cycle
    • Freshwater and terrestrial
    • Often found in hard water
    • Tissue contains calcium hydroxide in their tissues
    • Not sure whether Coleochaetales or Charales are more closely related to land plants
  • Amoebozoa
    • Amoebas:
    • Locomotion using pseudopodia
    • Large nucleus and overall cell size
    • Heterotrophic
    • Free-living in fresh water and soil, or parasitic
    • Vacuoles for feeding and water balance
    • Ex. Amoeba proteus, Entamoeba histolytica, Acanthamoeba culbersoni
    • Plasmodial Slime Molds
    • Move as a plasmodium
    • Multinucleate
    • Terrestrial
    • Flow through porous materials
    • In poor conditions it will form spores
  • Opisthokonta
    • Includes fungi, animals, and choanoflagellates
    • Unicellular
    • Aquatic
    • Flagellum and collar for filter feeding
    • Colonial forms are similar to sponges
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