Protists

• Monophyletic


  The group contains all the descendants of a particular ancestor
• Monophyletic


  Natural group = clade
• Paraphyletic


  The group does not contain all the descendants of a particular ancestor
• Protists


  • All eukaryotes that are not plants, fungi or animals
  • They are paraphyletic not monophyletic
  • Some are more closely related to plants, fungi or animals than to other protists
  • Some are motile, some are stationary
  • Photosynthetic, heterotrophic, mixotrophic
  • Most are unicellular, though some algae are multicellular and huge
  • Asexual or sexual
• Endosymbiosis in Eukaryote evolution


  1. Origins of protist diversity

  2. Mitochondria via endosymbiosis with aerobic prokaryote

  3. Plastids via endosymbiosis with photosynthetic cyanobacterium
• There are some lineages where red algae and green algae get swallowed by cells performing secondary endosymbiosis
• 5 "Supergroups" of eukaryotes


  • Excavata
  • Chromalveolata
  • Rhizaria
  • Archaeplastida
  • Unikonta
• Excavata - Diplomonads


  • Have modified mitochondria called mitosomes
  • Derive energy anaerobically by glycolysis
  • Have two equal sized nuclei and several flagellae
  • Are often parasites, for example Giardia intestinalis
• Excavata - Parabasalids


  • Have reduced mitochondria called hydrogenosomes that generate some energy anaerobically
  • Include Trichomonas vaginalis, the pathogen that causes some so called "yeast" infection
  • Have numerous flagellae, often arranged spirally
• Excavata - Euglenozoans


  • Kinetoplastid: Some parasitic forms causes diseases such as sleeping sickness
  • Euglena: Has two flagellae, can be heterotrophic or autotrophic, causes algal blooms
• Chromalveolata - Alveolata


  • All have cavities (alveoli) just below their plasma membranes
• Chromalveolata - Dinoflagellates


  • Unicellular, 2 flagella, very important primary photosynthetic producers
• Chromalveolata - Apicomplexans


  • Causes malaria
• Chromalveolata - Stramenopila
• Chromalveolata - Diatoms


  • Unicellular algae
  • Unique two part, glass-like wall of hydrated silica
  • Major photosynthetic producers in coastal waters and are also common in fresh waters
• Chromalveolata - Golden algae


  • Colour from carotene and xanthophyll pigments
  • Ingest food particles and photosynthesise
• Chromalveolata - Brown algae


  • All marine, most of our seaweeds
  • Obtain their colour from the carotenoid fucoxanthin, which is abundant in their chloroplasts
  • Some have gas filled cavities or bladders
• Chromalveolata - Oomycetes


  • Include water Molds and their relatives
  • Are decomposers, Downy mildews are parasites of plants
  • Have hyphae like fungi (convergent evolution)
  • Cellulose in cell wall whereas fungi have chitin
• Rhizaria - Chlorarachniophytes


  • Found in tropical oceans
  • Normally have form of small amoebae, with branching cytoplasmic extensions that capture prey and connect the cells together
  • Typically mixotrophic, ingesting bacteria and smaller protists as well as conducting photosynthesis
  • They may also form flagellate zoospores
  • They chloroplast were acquired by ingesting green algae (chlorophyl a and b)
  • They have 4 membranes, contain a small nucleomorph which is a remnant of the algas nucleus
• Rhizaria - Foraminiferans


  • Generally multichambered shells, called tests
  • Pseudopodia extend through the pores in the test
  • Foram tests in marine sediments form a large fossil record
• Rhizaria - Radiolarians


  • Marine protists with tests fused into one delicate piece, usually made of silica
  • Use their pseudopodia to engulf microorganisms, through phagocytosis
  • Pseudopodia radiate from the central body
• Archaeplastida - Red algae


  • Usually multicellular
  • They have chlorophyll a and b
  • They photosynthesis happily
  • Some incorporate caco3 into their cell walls and tissues (coralline alga)
• Archaeplastida - Green algae


  • They don't have clearly defined tissues, they have a thallus
  • Those algae that do have tissue structures are what land plants rose from
• Land plants
• Unikonta - Amoebozoans - Gymnamoebas


  • Common unicellular amoeboxoans in soil, fresh and marine water
  • Most are heterotrophic
  • Some are parasites - entamoebas
• Unikonta - Amoebozoans - Plasmodial slime Molds


  • Single mass of protoplasm without cell membranes
  • Cytoplasmic streaming aids distribution of nutrients and oxygen
  • Pseudopodia engulf decomposing material by phagocytosis
• Unikonta - Amoebozoans - Cellular slime molds
• The cilia suck food particles into the mouth to be processed
• Micronucleus are important for sexual reproduction