Protists

Question 1

Tree of Life and the Three domains

Answer 1

• Bacteria
• Archaea
• Eukarya
• Protists span all four eukaryotic groups
• Endosymbiosis was a major driver of eukaryotic evolution

Question 2

Primary Endosymbiosis

Answer 2

• Gave rise to first photosynthetic eukaryotes
• Prokaryote - Eukaryote Endosymbiosis
• Gave rise to the Archaeplastida super group (red algae, green algae, plants)

Question 3

Secondary Endosymbiosis

Answer 3

• Eukaryote - Eukaryote endosymbiosis (engulfs result of primary endosymbiosis)
• Gave rise to the members of the Excavata and SAR (Stramenopiles, Alveolates, Rhixarians)
• Spread photosynthesis throughout the major supergroups from the Archaeplastida

Question 4

Evidence for secondary endosymbioses

Answer 4

• Extra membranes around the chloroplast (3-4)
• Some organisms have a nucleomorph (additional nucleus in chloroplast)
• Lots of molecular comparisons

Question 5

Archaeplastida

Answer 5

“ancient plasmids”
- Sometimes just called “Plantae”
- An monophyletic group containing red algae, green algae, non-vascular (mosses)
and vascular (ferns, seed plants)
- Dominate fresh water and terrestrial environments

Question 6

Excavates

Answer 6

many (not all) have an “excavated” feed groove

• Most are unicellular, heterotrophic (many Euglenozoans are phtosynthetic)
• Many parasites (Diplomonads and Parabasalids)
• Uncertain if this is a true monophyletic group. Taxonomic upheaval.

Question 7

Types of Excavates

Answer 7

• Diplomonads
• Parabasalids
• Euglenazoans

Question 8

Characteristic of Diplomonads

Answer 8

Contain reduced mitochondria called mitosomes

Question 9

Characteristic of Parasalids

Answer 9

Contained reduced mitochondria called Hydrogenosomes that release hydrogen

Question 10

Characteristic of Euglenazoans

Answer 10

Contain paraxonemal rods associated with flagella

Question 11

What is SAR?

Answer 11

Stramenopiles, Alveolates, Rhizaria

• Very diverse supergroup
• Several unique secondary endosymbiotic events that spread photosynthesis
• Ecologically dominant taxa

Question 12

Stramenopiles

Answer 12

Ex: Potato blight, Diatom, Brown Algae (kelp), Golden Algae
- Many photosynthetic , but not all
- Unicellular, Colonial and Multicellular forms
- Common feature is two different flagella:
> One smooth (no
hairs)
> One hairy
(mastigonemes)
- Sometimes called “heterokonts”

Question 13

Alveolates

Answer 13

Ex: Dinoflagellate, Apicomplexans, Parasitic Alveolates, Ciliate

• Some photosynthetic, most not
• Mostly Unicellular
• Originally defined by the presence of “Alveoli” or sacs under the plasma membrane Not all have them though

Question 14

Rhizarians

Answer 14

Ex: Foraminifera (Forams) with pseudopodes, Cercozoans, Radiolarians (with axopods)

• Mostly unicellular amoeboids, some flagellated
• Mostly heterotrophic, except for some Cercozoans
• Forams have calcium carbonate shells that commonly fossilize on ocean floor

Question 15

Unikonts

Answer 15

“single flagella” –> not a name generally agreed upon

• Very diverse supergroup
• United by molecular comparisons

Question 16

Amoebozoans

Answer 16

Ex: Slime moulds and Amoeba

• Mostly unicellular, some multicellular stages
• Slime moulds common in moist soils, rotting trees and leaf material
• Amoeba can be free-living parasites (dysentery)

Question 17

Opisthokons

Answer 17

Ex: Fungi, Choanoflagellates, Animals 
"rear flagella"
- Most are not considered "protists"
- all heterotrophic 
- united by molecular data, dew shared morphological traits