Biology 132 Mini Lecture 19: Protist Diversity

Overview

• Focus on understanding the six recognized supergroups of eukaryotes.
• Identify evolutionary relationships of plants, animals, and fungi within these supergroups.
• Define characteristics of protists within each supergroup.
• Flashcards recommended for memorization.

Supergroups and Key Characteristics

1. Archaeplastida

• Members: Red and green algae, plants.
• Key Features: Descendants of heterotrophic protists and cyanobacterium.
  • Alternation of generations (diploid sporophyte and haploid gametophyte stages).
  • Groups within:
    • Glaucophytes: Chloroplasts retaining cyanobacterium wall.
    • Red Algae: Used for agar (culture medium, ice cream).
    • Green Algae: Divided into charophytes (closest to land plants) and chlorophytes (e.g., Volvox).

2. Amoebozoa

• Members: Amoeba, slime molds.
• Key Features:
  • Slime molds: Plasmodial (multi-nucleate) and cellular types.
  • Can solve mazes, model networks.

3. Opisthokonta

• Members: Choanoflagellates (related to animals and fungi).
• Key Features: Single posterior flagellum.

4. Rhizaria

• Key Features:
  • Fine thread-like pseudopodia.
  • Shells (tests) crucial for carbon cycle, composed of silicon or other compounds.
  • Groups within:
    • Foraminifera: Porous tests, can host photosynthetic algae.
    • Radiolarians: Glassy silica shell.
    • Cercozoa: Photosynthetic, secondary endosymbiosis.

5. Chromalveolata

• Key Features: Phototrophs and heterotrophs.
  • Groups within:
    • Alveolata: Include dinoflagellates (cause red tide, bioluminescence), apicomplexans (e.g., malaria plasmodium).
    • Stramenopiles: Diatoms (silicon shells), brown algae (giant kelp), oomycetes (egg fungi, parasitic).

6. Excavata

• Key Features:
  • Asymmetrical with a feeding groove.
  • Groups within:
    • Diplomonads: Anaerobic, two haploid nuclei (e.g., Giardia).
    • Parabasalids: Trichomonas vaginalis, symbionts in termites.
    • Euglenozoa: Mixotrophs, parasites (e.g., Trypanosoma causing African sleeping sickness).

Key Concepts

• Alternation of Generations: Important in plant group discussions.
• Slime Molds: Useful in biological modeling and network mapping.
• Symbiotic Relationships: Various protists engage in symbiosis, contributing to ecological functions.
• Disease-Causing Protists: Some excavates cause significant diseases (e.g., Giardia, Trypanosoma).

Study Tips

• Utilize flashcards to memorize supergroups and key organisms.
• Review figure 23.9 for visual understanding of supergroups.
• Consider secondary endosymbiosis and its impact on protist diversity.

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Prepare these notes to help you understand and recall the diverse world of protists and their classifications. Use flashcards and visuals for effective learning.