Hypotheses on the origin of life
What is the evidence of early divergence in phospholipids?
Bacteria have phospholipids containing glycerol-3-phosphate Archaea have phospholipids containing glycerol-1-phosphate
Panspermia Hypothesis
the inoculation of Earth by life carried on meteorites. Life evolved elsewhere then was transferred here.
The RNA World Hypothesis
Suggests that short RNA molecules could have spontaneously formed and were capable of catalyzing their own continuing replication
The transformation of early Earth into how we recognize it today was mediated how?
by living organisms. Example: we can breathe in O2 thanks to other organisms living.
Emergent properties
complex forms deriving from simple elements Ex: Carbon-based molecules
Prebiotic ("Primordial") Soup Hypothesis
small organic molecules arise abiotically from simple reduced chemicals sparked by lightning. Produced complex macromolecules that eventually acquired apparatus for self-replication and membrane compartmentalization
Cyanobacterial hopanoids
steroid-like membrane molecules that are particularly durable
Miller and Urey were wrong about what in their experiment?
the atmospheric gases of early Earth. They used methane, ammonia, and hydrogen. Early Earth was probably more dominated by CO2 than methane.
Proterozoic era
2.5 bya - 500 mya Vast amounts of iron coming out of oceans, precipitated as O2 levels rose. Cambrian explosion of life forms (multicellular)
Archaean era
3.8-2.5 bya Begins with first stromatolites. Start to accumulate oxygen thanks to cyanobacteria
Hadean era
4.5-3.8 bya. Prior to evidence of life on earth.
What are the 3 fundamental conditions for life?
1. Essential elements 2. Continual source of energy 3. Temperature range permitting liquid H2O
Why was early Earth an inhospitable place? Name 3 reasons.
1. No oxygen 2. Molten surface 3. Cataclysmic collisions
Three common misconceptions on the origin of life
1. Theory vs. hypothesis 2. Mechanisms of evolution 3. Vast amounts of time
What are the enzymatic properties important for the beginning of life?
1. ability to self-duplicate and duplicate other RNA molecules 2. ability to catalyze simple chemical reactions which would enhance the creation of molecules which are building blocks of RNA molecules 3. ability to catalyze formation of peptide bonds
Name 5 predicted characteristics of LUCA
1. genetic code based on DNA 2. genetic code is expressed via RNA intermediates 3. genetic code is expressed into proteins 4. only 20 amino acids are used, only L-isomer form 5. ATP is used as energy intermediate
What are the two abilities of RNA that could support their role in early life?
1. store information 2. catalyze chemical reactions
Name the 3 different geological evidence for early life
1. stromatolites 2. microfossils 3. biosignatures
What are the biosignatures of early life?
C-13 isotope depletion and hopanoids
Stromatolites
Earliest recorded life on earth (3.8 byo). Fossilized photosynthetic microbial mat communities that form layered structures found in Precambrian sediments
What does LUCA stand for?
Last Universal Common Ancestor
Who came up with the Primordial Soup Hypothesis?
Miller and Urey
Deep Sea Vent Hypothesis
life may have begun at the interface where chemically rich fluids emerge from below the sea floor. Chemical energy is derived from the H2S and H coming out from the vent.