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.