Lectures: Excavates

Question 1

Is Protist a monophyletic group?

Answer 1

No, Protist is another “bad” term (like
prokaryote) because it does
not reflect evolutionary history

Question 2

Protist

Answer 2

term used for Eukarya that are
not land plants, fungi, or
animals

Question 3

Excavates:

Answer 3

• Unicellular
• Most have flagellum
• Many found only in the digestive tract of animals, including species that aid digestion of cellulose in insects
• Bodies typically supported by internal rod consisting of microtubules or strips of proteins under plasma membrane
• “excavated” feeding groove
• Many lack recognizable
  mitochondria
  a) but nuclear DNA contains genes
  typical in mitochondria
  b) cells contain vestigial
  mitochondria organelles

Question 4

Phagocytosis

Answer 4

The way Excavate consumes bacteria prey:

1. Prey is enveloped by the plasma membrane at the feeding groove
2. The membrane pitches off a food vesicle within the cytoplasm
3. Other vesicles deliver digestive enzymes to food vesicles; prey is digested for food

Question 5

What supports the hypothesis that
mitochondria were lost/reduced over time?

Answer 5

the fact that many Excavates lack recognizable mitochondria

Question 6

What are the 2 distinct Excavate types?

Answer 6

1. Giardia lamblia
   – Common intestinal parasite of mammals
   – Estimated 20,000 cases per year in US
2. Euglena species
   – One of best studied groups of Excavates
   – Mixotrophic

Question 7

Mixotrophic

Answer 7

organism that can obtain nutrition by autotrophic or heterotrophic means, usually facultatively

Question 8

What is the 1 derived trait of Excavates?

Answer 8

7: derived trait of Excavates:
- Excavated feeding groove