Week 1 Unit 1 Main concepts
No description yet. This curated deck is ready for daily study.
Card preview (24)
Earth was formed how long ago? Was it hospitable at this time? Why/ why not
4.5 billion years ago Inhospitable - very hot, no oxygen, and water was only available as vapor
When did the first cellular life appear?
4 billion years ago (the end of the Hadean)
What are the 3 theories on how the first cell arose? Just list them
• Surface origin • subsurface origin • RNA world
Describe the surface origin theory on how the first cell arose
spontaneous arise of membrane-enclosed structure from primordial inorganic soup
Describe the sub-surface origin theory on how the first cell arose
interaction b/w alkaline hot water beneath the ocean and cold acidic ocean water - beneath the ocean, H2S & H2 were present as a constant energy source. @ sfc: iron present - interactions b/w iron and sulfides lead to formation of metal precipitates - metal precipitates catalyzed formation of amino acids & sugars = basis for formation of 1st macromolecules
Describe the RNA world theory on how the first cell arose
the first molecule that was entrapped in self-replicating systems were RNAs - RNA catalyzed the formation of first simple peptides that coated minerals (1st semipermeable membrane)
Put the following events in order according to the RNA world theory. - Synthesis of complex proteins via RNA catalysis - Formation of amino acids, nucleotides and sugars - RNA catalytic world and self-replicating RNA - LUCA appeared - DNA replaced RNA - Divergence of LUCA to Bacteria and Archaea - Lipid arise and entrapped proteins, RNA and DNA
1)Formation of amino acids, nucleotides and sugars 2) RNA catalytic world and self-replicating RNA 3) Synthesis of complex proteins via RNA catalysis 4)DNA replaced RNA 5) Lipid arise and entrapped proteins, RNA and DNA 6) LUCA appeared 7)Divergence of LUCA to Bacteria and Archaea
Explain evidence that bacteria and archaea branched from LUCA early
Evidence in the structure of their lipids • lipids in bacteria have ester bonds • lipids in archaea have ether bonds
When did cyanobacteria develop?
2.8 billion years ago: the end of Archaean
At the beginning of the Archaean, LUCA split into ______ and _____
bacteria and archaea
The Archean ended with the big _____ event that was led by cyanobacteria
oxygenation
After LUCA split into Bacteria & Archaea, both lineages evolved specific metabolisms to fit into the existing early-earth conditions. Explain the timeline of when each strategy developed
• First, methanogenesis developed in Archaea (3.9bya) • Next, anoxygenic photosynthetic organisms developed (purple & green bacteria- consumed H2S): 3.2bya • H2-oxidizing organisms developed along with the anoxygenic photosynthetic organisms • cyanobacteria developed 2.8bya
Cyanobacteria produced ___ which reacted with ____, making it insoluble in the ___ ____ formation
oxygen iron iron band formation
What kind of iron is present in the iron band formation?
ferric (Fe3+) (insoluble) O2 was trapped
What happened when all the iron was exhausted in early earth?
oxygen could no longer react with it, so atmospheric [O2] increased. Earth became oxic
At what point did evolution expand to the earth surface?
When an ozone layer formed (O3 UV shield). This was caused by O2 accumulation - UV was too damaging for life outside the water up until this point
Oxic earth was the base for the development of the _____ cell. Approx when was this?
eukaryotic 2bya
Describe the 2 theories on how eukaryotic cells appeared
• DNA accumulation led to the formation of nucleus and the 1st eukaryotic cell has a nucleus initially. Then the nuclear containing cell ingested chloroplasts & mitochondria • Early cell was archaeal & consumed O2. To ensure an energy source, the host ingested H2-producing bacteria
We know that eukaryotic cells is a chimera between bacterial & archaeal cell. What does this mean? Give 2 pieces of evidence
chimera= parts taken from multiple sources (it’s a mix of bacteria & archaea) • eukaryotes have types of lipids found in bacteria • eukaryotes have transcription and translational apparatuses more like archaea
Describe the theory of endosymbiosis
Chemoorganotrophic bacterium host ingested O2- consuming and ATP producing mitochondria - eventually, this host (facultative aerobic organism- chemoorganotroph) ingested chloroplast where O2 was made
Give 4 pieces of evidence supporting the endosymbiotic theory
• both mitochondria and chloroplasts contain ribosomes that are prokaryotic type 70S and they have 16S r RNA (same as prokaryotes) • same antibiotics that affect ribosomal function in bacteria inhibit ribosomal fxn in mitochondria and chloroplasts • mitochondria & chloroplasts contain their own DNA arranged in covalently closed circular form which is typical for bacteria • many signs of bacteria are present in eukaryotic organelles
** copy table on slide 9
stromatolites are evidence of early microbial life. What formed ancient stromatolites vs modern ones?
ancient= formed by phototrophic filamentous bacteria modern= formed by phototrophic O2- evolving cyanobacteria
To determine evolutionary history, we use DNA T/F • DNA is a record of future evolutionary events • DNA is used to determine phylogeny
• false: past evolutionary events • true - phylogeny= the evolutionary history of organisms