Lecture 2: Early Life Flashcards
What are the 3 domains of life?
- Bacteria
- Archaea
- Eukarya
Microbes are small and _____.
ubiquitous
Describe the bacterial cell structure.
What are the 7 bacterial cell shapes?
- Coccus
- Bacillus
- Coccobacillus
- Fusiform bacillus
- Vibrio
- Spirillum
- Spirochete
How do we categorize microbes?
- Metabolic lifestyle
- Genetic characterization
- Pigmentation
List different pigments.
- Carotenoids
- Melanin
- Chlorophylls
- Violacein
- Fucoxanthin
- Perinidin
- Pyocyanin
What are the 3 metabolic classifications of life?
- Carbon source
- Energy source
- Source of reducing power
How do we classify organisms by carbon source?
- Inorganic (autotroph)
- Organic (heterotroph)
- both (mixotroph)
How do we classify organisms by energy source?
- Phototroph (energy from light)
- Chemotroph (energy from chemicals)
How do we classify organisms by source of reducing power?
- Organotroph (reducing equivalents obtained from organic compounds)
- Lithotroph (reducing equivalents obtained from inorganic compounds)
What does the genome tell us?
- Pure culture vs. environment
- Lateral gene transfer can make this hard too
What were the hostile conditions on early Earth?
- Early bombardment by meteors
- Twice as much ocean as today
- Much higher temps
- No free oxygen
- High UV radiation
- High CO2, CH4, N2, NH3, H2O
- Traces of H2, H2S, FeS
How long have microbes been on Earth?
At least 3.8 billion years
Explain the chemical evolution model for the origin of life.
“Life arose from non-life”
- Oparin and Haldane (1920s): early conditions on Earth resulted in formation of organic compounds (need concentrated pools of prebiotic soup for evolution of life)
- Miller-Urey (1950s): experiments demonstrated that complex fatty acids and amino acids could form under these conditions
- They were wrong about conditions and there is no bridge between soup and life
What is the thermophilic origin of life based on?
The occurrence of thermophiles at root of tree of life
What is the evidence of the origin of life?
- Stable isotopic evidence of microbial life
- Fossil evidence
What is a microbial mat?
Multi-layered sheet of microbes
How were microbial mats involved in early fossilization?
Good at capturing corpses of other organisms
- Delaying decay
- Form impressions and replicas of vertebrates and invertebrates
Explain the RNA world hypothesis.
rRNA
1. Universally conserved
2. Functionally homologous
3. Alignable
4. Slowly evolving if looking at ancient divergence - multiple hits problem
Compare and contrast bacteria, archaea, and eukarya.
How did huge diversity arise?
- Long time periods
- Short generation time = fast evolutionary rate
- Prokaryotes have evolved into many different niches
- Huge metabolic/functional diversity allow organisms that coexist in the environment to differentiate themselves
What is the sequence of metabolic innovation?
What is Riftia and what is its symbiont?
- Riftia = giant tube worm, bottom or ocean near hydrothermal vents, no digestive system
- Symbiont: chemolithotrophic sulfur oxidizing gamma Proteobacteria
What are fossil stromatolites?
Ancient microbial mat communities
