Lecture 11 - Protists

Question 1

What are the three domains of life

Answer 1

• > bacteria
• > archaea
• > eukaryotes

Question 2

What was a mojor driver of eukaryotic evolution

Answer 2

Endosymbiosis

Question 3

Primary Endosymbiosis

Answer 3

• > gave rise to the first photosynthetic eukaryotes
• > eukaryotes ate prokaryotes and formed a symbiotic relationship
• > this event gave rise to Archaeplastida supergroup (red/green algae, plants)

Question 4

Secondary Endosymbiosis

Answer 4

• > eukaryote ate another eukaryote
• > this event gave rise to the members of the Excavata and SAR (Stramenopiles, Alveolates, Rhizarians) supergroups
• > spread photosynthesis throughout the major supergroups from the archaeplastida

Question 5

Evidence for secondary endosymbioses

Answer 5

• > some organisms have a nucleomorph (an additional nucleus in the chloroplast)
• > extra membranes around the chloroplast (3-4; extras from vacuole of previous organisms)

Question 6

Archaeplastida

Answer 6

• > a monophyletic group containing red algae, green algae, non vascular(mosses) and vascular (ferns and seed plants)
• > dominates fresh water and terrestrial environments

Question 7

Excavates

Answer 7

• > mostly are unicellular, heterotrophic (many Euglenozoans are photosynthetic)
• > many are parasites (diplomonads and parabasalids)

Question 8

Explain the three subclasses that make up Excavates

Answer 8

Diplomonads

• > reduced mitochondria called mitosomes

Parabasalids

• > reduced mitochondria called hydrogenosomes that release hydrogen

Euglenazoans

• > paraxonemal rods associated with flagella

Question 9

Why do diplomonads and parabasalids have reduced mitochondria

Answer 9

• > diplomonads have modified mitochondria that lack a functional ETC and cannot perform cellular respiration; they must get their energy from glycolysis
• > parabasalids are anaerobic and therefore don’t paricipate in oxidative phosphorylation; the hydrogenosomes developed from reduced mitochondria and are where anaerobic metabolism takes place

Question 10

SAR

Answer 10

• > very diverse supergroup
• > several unique endosymbiotic events that spread photosynthesis

Question 11

What are the three subclassification of the SAR supergroup

Answer 11

Stramenopiles

Alveolates

Rhizaria

Question 12

Stramenopiles

Answer 12

• > part of SAR
• > made up of many photosynthetic organisms
• > unicellular, colonial, and multicellular forms
• > common feature is two flagellas, one “smooth” and the other “hairy”(mastigonemes)

Question 13

Alveolates

Answer 13

• > sometimes photosynthetic, most not
• > mostly unicellular
• > originally defined by the presence of “alveoli” or sacs under plasma membrane but not all have them

Question 14

Rhizarians

Answer 14

• > mostly unicellular amoeboids, some flagellated
• > mostly heterotrophic, except for some cercozoans
• > forams have calcium carbonate shels that commonly fossilize on ocean floor

Question 15

Unikonts

Answer 15

• > have a single flagella
• > very diverse supergroup
• > made up of Amoebozoans and Opisthokonts

Question 16

Amoebozoans

Answer 16

• > mostly unicellular, some multicellular stages
• > slime molds common in most soils, rotting trees and leaf material
• > amoeba can be free-living or paracites

Question 17

Opisthokonts

Answer 17

• > most are not considered protists
• > all heterotrophic
• > rear flagella
• > united by molecular data, few shared morphological traits