BIO 200 Lecture Notes - Lecture 13: Proteobacteria, Heterokont, Cellular Respiration
25 Oct 2018
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Lecture 13
Outline
● Origin of Euk
1. Earliest euk
2. Euk traits
3. Origin of organelles: membrane infolding + endosymbiosis
● Protists
1. Protists not monophyletic
2. Protist traits
3. Building bridge to multicellularity
● Types of Protists
1. Alveolates
2. Stramenopiles
3. Rhizarians
4. Excavates
5. Amoebozoans
6. Choanoflagellates
Earliest Euks
● Arose 1.7 bya as SPECIALIZED ARCHAEA: cell nucleus, internal membrane w
thicker walls, bigger than prok overall
Euk Traits
● Euk traits:
1. Multicellularity= diff of cell types into organs + tissues aka FLEXIBILITY
2. Sexual reprod: new gene combos thru recombination + faster adaptation rate aka
GENETIC DIVERSITY
3. Compartmentalizationleads to internal structure= ORGANELLES w indep
functions inside each cell
1. Cell wall lost: more flexibility to bring materials in and out
2. Infolding of cell membrane: UP SURFACE AREA for efficient gas + nutrient exchange
3. Cytoskeleton (microfilament/microtubules) more complex: support bigger cell size
4. ER forms: studded w ribosomes for translation
5. Regions of unfolded membrane enclose DNA: pre-nucleus
6. Microtubules form euk flagellum: can move!
7. Early digestive vacuoles evolve into lysosomes
8. Endosymbiosis into mitochondria: LATERAL TRANSFER
a. Anc euk cell engulfed proteobacterium
b. Bacteria detoxified O2 for euk; euk gave safe env
c. Breakdown of O2 eventually became cell respiration aka MITOCHONDRIAL JOB
9. Endosymbiosis into chloroplasts: LATERAL TRANSFER
a. See above but w Cyanobacteria instead
Document Summary
Origin of euk: earliest euk, euk traits, origin of organelles: membrane infolding + endosymbiosis. Protists: protists not monophyletic, protist traits, building bridge to multicellularity. Types of protists: alveolates, stramenopiles, rhizarians, excavates, amoebozoans, choanoflagellates. Arose 1. 7 bya as specialized archaea: cell nucleus, internal membrane w. Earliest euks thicker walls, bigger than prok overall. Euk traits: multicellularity= diff of cell types into organs + tissues aka flexibility, sexual reprod: new gene combos thru recombination + faster adaptation rate aka. Origin of euk begins w anc protist (protist= 1st euk) Protists are paraphyletic: microbial euk ; too diverse; includes all euk other than animals/plants/fungi. Variation in these traits= lack of unity: locomotion. Cilia: short protrusions that cause wave-like currents around protist. Pseudopodia: false feet aka steely protrusions stick to surface so it rolls: cell surfaces. Those w extracellular material deposited around it for protection. Those only surrounded w plasma membrane: nutrition: no photoautotrophs. Primary endosymbiosis: photosynthetic bc bac entered anc euk [red/green alga]
