πŸ”¬

Understanding Protists: Ciliates and Algae

Dec 6, 2024

Lecture Notes on Protists

Ciliates

  • Supergroup: "SAR" – alveolate clade
  • Movement and Feeding: Use cilia
  • Diversity: Very diverse group
  • Lifestyle: Mostly free-living (e.g., Paramecium sp.)
  • Nuclei: Multinucleate with macronucleus and micronucleus
  • Cilia Function: Operate synchronously
  • Osmoregulation: Contractile vacuole
  • Reproduction:
    • Asexual: Binary fission
    • Sexual: Conjugation
      • Micronuclei undergo meiosis
      • Exchange of nuclei with other paramecium
      • Fusion leads to new individuals

Fungi-like Protists

  • Characteristics: Fungi-like due to some shared traits
    • Spread by spores
    • Heterotrophic, many saprobic (decomposers)
  • Water Molds, White Rusts, and Downy Mildews:
    • Part of "SAR" Stramenopile clade (resemble fungi due to convergent evolution)
    • Habitat: Aquatic or on moist substrates
    • Ecology: Decomposers and some are parasitic
      • Example: Cottony growth on aquarium fish
    • Pathogens: Some attack plants (e.g., mildew on grapes)
    • Historical Impact: Irish potato famine (1845-1860) due to Phytophthora infestans
      • Economic and sociological significance
      • Led to mass emigration from Ireland
  • Slime Molds:
    • Fungi-like due to fruiting bodies producing spores
    • Types:
      • Cellular Slime Molds:
        • Supergroup Unikonta - Amoebozoa clade
        • Amoeboid single cells
        • Prey on bacteria and yeast
        • Aggregate into "slug" stage under nutrient scarcity
        • Form fruiting bodies and disperse spores
      • Plasmodial Slime Molds:
        • Bright yellow or orange, large multinucleated cell
        • Grow and use pseudopodia for feeding

Plant-like Protists = Algae

  • Classification:
    • Formerly part of Kingdom Protista
    • Includes single-celled (phytoplankton) and simple multicellular (seaweeds) photosynthetic organisms
  • Lineages:
    • Diatoms, brown algae (Stramenopile clade), dinoflagellates (Alveolate clade) in "SAR" supergroup
    • Green algae share common ancestry with land plants (Kingdom Plantae) in Supergroup Archaeplastida
  • Evolutionary Note:
    • Major algal lineages result from secondary symbiotic events
    • Originated through endosymbiosis, first producing mitochondria, then plastids
    • Secondary endosymbiotic events led to different algal plastids