Earliest Life: What Was the First Life on Earth Like? How We Study LUCA | GEO GIRL

Описание: This video is all about our guesses as to what metabolic pathway(s) the earliest life on Earth might have used! We start by going through the possibilities like photosynthesis vs chemosynthesis, then assuming a hydrothermal vent life origin, we moved on to discuss the possible chemotrophic pathways: chemoautotrophy (use inorganic carbon for metabolism) vs. chemoheterotrophy (use organic carbon for metabolism). We actually don't know for sure which one is first, but we assume a chemoautotrophic start for the rest of the discussion. We then discuss which chemolithoautotrophic pathways are most likely the earliest to evolve (both elemental sulfur reduction and sulfate reduction are possible, with the combination of Fe(III) reduction in some cases, and methane production by methanogenesis is the other main possible pathway). We further discuss the potential for these pathways to have evolved early by looking at the deepest-branching bacteria and archaea. Deep branching bacteria have the ability to reduce oxygen, nitrate, sulfur species, or iron using hydrogen (H2) as an electron donor. But we cannot pinpoint the first bacterial metabolism because lateral gene transfer (or horizontal gene transfer) prevents us from piecing together a perfect evolutionary tree. Deep branching archaea have the ability to either reduce elemental sulfur or reduce carbon dioxide to produce methane. However, sulfate reduction is present in both deep branching bacteria and some archaea, so was our last universal common ancestor (LUCA) a sulfate reducer? Again, lateral gene transfer prevents us from knowing for sure. Lastly, we discuss the first fermenting and respiring organisms. These chemoheterotrophs had to evolve to eat the organic carbon produced by the earlier chemoautotrophs.

References: Geomicrobiology: https://amzn.to/2WAloTR
Biology of Microorganisms: https://amzn.to/3kQqIuD

GEO GIRL Website: https://www.geogirlscience.com/ (visit my website to see all my courses, shop merch, learn more about me, and donate to support the channel if you'd like!)

0:00 what this video covers
0:53 life's origins
2:26 was phototrophy or chemotrophy first?
4:07 was autotrophy or heterotrophy first?
5:08 first metabolism on Earth
6:54 how we study LUCA
7:20 deepest branching bacteria
9:32 lateral gene transfer
10:29 deepest branching archaea
12:32 was LUCA a sulfate reducing microbe?
14:04 when did fermentation evolve?
14:50 when did respiration evolve?
16:31 evolution of macroorganisms
18:00 references & upcoming videos!
19:02 my cat ;)

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Non-textbook books I recommend:
Oxygen by D. Canfield: https://amzn.to/3gffbCL
Brief history of Earth by A. Knoll: https://amzn.to/3w3hC1I
Life on young planet by A. Knoll: https://amzn.to/2RBMpny
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Your inner fish by N. Shubin: https://amzn.to/3cpw3Wb
Oxygen by N. Lane: https://amzn.to/3z4FgwZ
Alien Oceans by K. Hand: https://amzn.to/3clMx1l
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