Serial Endosymbiosis Flashcards
When did Eukaryotes arrive
1.5bya
What characteristics of cells enabled the serial endosymbiosis theory
-host cell was wall-less heterotroph
-flexible plasma membrane enabled phagocytosis of food particles
-breakdown of food particles within vesicles formed by plasma membrane
Origin of mitochondria and chloroplasts as bacterial endosymbiosis, ultimately transferring _____ DNA to the _____
Most
HOST
Internalization of a patch of plasma membrane with attracted DNA forms a ________
Primordial nucleus
Eukaryotes developed as a result of _________ ingesting _______
1 prokaryote
Another prokaryote
Precursor to chloroplast is digesting a ______
Cyanobacteria
Does endosymbiosis still occur?
Yes
Vorticella ingests chlorella
Serial Endosymbiosis theory
- Phagocytosis of a bacterium by an archaea
- Phagocytoses bacteria survive on nutrients from host prokaryotic cell
- Host and symbiotic bacterium reproduce co-independently
- Subsequent generations contain genes of the originally infested bacterium
Primary endosymbiosis
Free-living Cyanobacteria incorporated into phagotrophic eukaryotic cell ——> transformed into a chloroplast
3 groups emerged from primary endosymbiosis
Chlorophyta (green algae)
Glaucophyta
Rhodophyta (red algae)
Secondary endosymbiosis
A eukaryote that already acquired a chloroplast via primary endosymbiosis is engulfed by a second eukaryote
Outermost membrane if the chloroplast is interpreted as a remnant of the secondary host food vascular (phagosomal membrane)
Euglenids evolved by the ingestion of a…
How many plastid membranes?
Green algae
3
Heterokonts (brown algae, chrysophytes, and diatoms) developed from ingesting …..
How many plastid membranes?
Secondary endosymbiosis of a red algae
4
Most dinoflagellates have plastics of the ______ with ____ outer membranes
Red lineage
3
Tertiary endosymbiosis have how many membranes
3 membranes
Too many membranes may be functionally unstable
Primary endosymbiosis has how many membranes
2
Secondary endosymbiosis has how many membranes
3-4
Nucelomorph
Remnant algal nucleus
Gene transfer from plastic to engulfing cell (not all genetic material is transferred to host)
This genome lost in all algae, except chromalveolates and chlorarachiniophytes
Chlorarachniophytes and endosymbiosis
Marine amoebae with plastids obtained by secondary endosymbiosis of green algal cells
Retain remnant algal nucleus (nucleomorph) obtained through secondary endosymbiosis
Evidence of endosymbiosis
- Mitochondria and chloroplasts divide by binary fission (not manufactured by nuclear genes)
- Mitochondria and chloroplast have circular DNA
- Mitochondrial DNA does not encode all mitochondrial proteins (endosymbiotic gene transfer)
- Mitochondria and chloroplasts produce their own ribosomes (30s and 50s subunits instead of 40s and 60s subunits in eukaryotic cells)
- Antibiotics that kill or inhibit bacteria inhibit protein synthesis of mitochondria and chloroplasts
- Sequencing ribosomal RNA demonstrates that mitochondria and chloroplasts are related to bacteria
Conditions for engulfing food
Flexible cell membrane: sterols
Specialized cytoskeleton (microtubules) for capturing prey
Endocytosis to evaginate the plasmalemma
Sterols require ….
How did this help endosymbiosis
O2
Oxygen required for aerobic respiration
Oxygen in early atmosphere requires endosymbiosis association between ingested aerobic bacteria and anaerobic host prokaryotes
Protection from UV by ozone —-> 02 protects from UV
Appearance of eukaryotes depended on a build up of ____ in the atmosphere by ______
O2
Photosynthetic Cyanobacteria
