🧬 EXCAVATA SUPERGROUP
🌍 Overview
Q: What defines the Excavata supergroup?
A: Protists with modified mitochondria or unique flagella; many live in anaerobic environments.
Q: What are the three main clades within Excavata?
A: Diplomonads, Parabasalids, and Euglenozoans.
🦠 Diplomonads
Q: What organelle do Diplomonads have instead of normal mitochondria?
A: Mitosomes — modified mitochondria used for anaerobic energy metabolism.
Q: How do Diplomonads obtain energy?
A: Through anaerobic biochemical pathways (no oxygen required).
Q: How many nuclei do Diplomonads have?
A: Two equal-sized nuclei.
Q: What illness is caused by the Diplomonad Giardia lamblia?
A: “Beaver Fever” — a diarrheal disease from contaminated water.
Q: How is Giardia lamblia treated?
A: With metronidazole (antibiotic/antiparasitic).
🧫 Parabasalids
Q: What organelles do Parabasalids possess for energy production?
A: Hydrogenosomes, which generate some energy anaerobically.
Q: What type of environments do Parabasalids live in?
A: Anaerobic environments (lacking oxygen).
Q: What human pathogen is a Parabasalid?
A: Trichomonas vaginalis — causes vaginitis in females.
Q: What structure helps Trichomonas vaginalis move?
A: Flagella and an undulating membrane.
🧬 Euglenozoans
Q: What unique structure do Euglenozoans share?
A: A spiral or crystalline rod inside their flagella (function unknown).
Q: What are the two main groups within Euglenozoans?
A: Kinetoplastids and Euglenids.
🧬 Kinetoplastids
Q: What defines Kinetoplastids?
A: They have a single mitochondrion with a large mass of DNA called a kinetoplast.
Q: What disease is caused by Trypanosoma (a kinetoplastid)?
A: African sleeping sickness, transmitted by the tsetse fly.
Q: How does Trypanosoma evade the immune system?
A: Uses antigenic variation — frequently changes surface proteins to avoid immune detection.
🌱 Euglenids
Q: How many flagella do Euglenids have?
A: One or two flagella emerging from a pocket at one end of the cell.
Q: What structure allows Euglenids to sense light?
A: An eyespot and light detector near the flagellum.
Q: What is “metaboly” in Euglenids?
A: A shape-changing movement used for crawling.
Q: Why are Euglenids considered mixotrophs?
A: They are photosynthetic in daylight but heterotrophic at night.
Q: What organelle helps Euglenids maintain water balance?
A: A contractile vacuole.
✨ Quick Concept Review
Q: Which Excavata groups lack plastids?
A: Diplomonads and Parabasalids.
Q: Which group contains photosynthetic members?
A: Euglenids (within Euglenozoans).
Q: Which groups are primarily parasitic?
A: Diplomonads, Parabasalids, and Kinetoplastids.