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Lecture 7

BIOLOGY 207 Lecture Notes - Lecture 7: Proteobacteria, Transitional Fossil, MotilityPremium

2 pages76 viewsSpring 2017

Department
Biology
Course Code
BIOLOGY 207
Professor
Manos
Lecture
7

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Bio 207 1/27/17
- A result of horizontal gene transfer (HGT): (54)
o Auxiliary gene trees will vary
o Metabolic diversity and other bits of foreign genomic sequences are passed
around
- Core gene trees, aka trees of genes involved in things like rDNA usually do not vary
o This model, however, has been challenged
- Slide 55 chimeric hypothesis for eukaryotic origin
o Hypothesis of a “fusion” event of archae and proteobacteria to form eukaryotes
o The archaean cell becomes the host cell, and the proteobacteria becomes the
mitochondria
Eukaryotes
- Eukaryotic diversity is mainly present in plants, animals and fungithe rest are in the
goup ‘protista’
- Nucleus development: zero evidence of any kind of transitional form; only see
prokaryotic form and then the completely compartmentalized nucleus
o Developed perhaps to compartmentalize transcription and translation
Protists
- Protistian scientists sort by mode of nutrition, phenotype, and locomotion
- No clear knowledge about how the protist supergroups fit togetherjust know it is like a
“star”, with lots of branching groups, but how and when they branch is unknown
Eukaryotic Innovations
- Larger single cells > multicellularity
o Just getting bigger, in general
- Genomic integration
- Sexuality
o Bidirectional contributions to make greater diversity
o In prokaryotes, any kind of diversity is made through unidirectional transfer like
HGT
- Motility
o Cilia, flagella
o All eukaryotes have cilia and flagella in a 9 + 2 arrangement of the microtubules,
a highly, highly conserved structure
o In the human, present in the lungs, intestines, sperm; have function both in
moving things as well as sensory perception
Amitochondriate eukaryotes
- Eukaryotes without mitochondria; where might these live
- These might be eukaryotes that are parasitesthese do not require their own energy
source, so eventually they lost their mitochondria
- Classic hypothesis: “archaezoans”
o Transitional eukaryotes
o Early-branching, with these being the first branches after nuclear development
that preceded mitochondria development
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