the organic beings which have ever lived on this earth have descended from some

The organic beings which have ever lived on this

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the organic beings which have ever lived on this earth have descended from some one primoridal form, into which life was first breathed” On the Origin of Species, p484
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Modern ‘tree of life’ starts with the Last Universal Common Ancestor. Lived 3.something billion years ago. All analyzed life forms share about 30 common genes that came from LUCA. Some studies identified over 350 LUCA genes, which suggest that it ‘ate’ Hydrogen and lived in hot springs on ocean floor. LUCA Phylogenetic Tree of Life (NSF)
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- Genome wide genetic similarity amongst humans 99.5% - Chimpanzees are 96%-98% similar - Cats = 90% - Cows = 80% - Mice = 75% - Fruit Fly = 60%
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So, how do species evolve? New species originate when the larger population is split up into sub-populations occupying different home ranges (ecological niches). Like Darwin’s finches on Galapagos Islands. Small, isolated populations evolve rapidly even if only a few members have unusual characteristics. New species favored. Genetic divergence of one group from the parent population could eventually lead to a different species no longer capable of interbreeding with the ancestral population.
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Where was the Primordial Soup kitchen?
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By 2.4 bln years life was abundant on Earth as evidenced by stable isotopic composition of sedimentary rocks Living things have cell membranes, self replication, and self-organized redox reactions. Metabolism first or genes first?
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? first cells 3.6 Ga
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Earliest Life on Earth Archean > 3.5 Bya to 2.5 BYA Single-cell Bacteria and Archaea doing chemosynthesis and photosynthesis. No nucleus and very small cells (1) Early sun 75% as bright (2) CO 2 Greenhouse, No/little free O 2 (3) Stronger tides, 18 hour day (4) Slowing impacts; larger each 100,000,000 years
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Prokaryotic cell Eukaryotic cell
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From the start of the Archaen on (~3.7 Bya to now) we have rocks
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Continental Rocks: our record of the past
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The Fossil Record BIG BIASES Hard parts Size Depositional environments Pull of the Recent
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Fossils
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Oldest Red Beds Photosynthesis? First multicellular fossils
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Proterozoic Time 2.5-0.6 Bya Archaen to early Proterozoic: Little Oxygen up to 3-2 Bya Find Pyrite (iron sulfide) and uranite (uranium oxide) in river sediments; require low oxygen levels. But photosynthesis is going on. Where is oxygen? Banded iron formations (3.5-2 Bya). Layers of chert and iron oxide. Low O 2 : iron soluble, chert deposits. High O 2 : forms rust deposits. Alternating waves of O 2 from stromatolites. Fluctuating mechanism? Photosynthesis by cyanobacteria: CO2 + H2O + light = (CH2O) + O2
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~2.9 – 1.8 Ga
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- As oxygen levels rose initially, Aerobic microbes developed while anaerobic microbes sought niches within reduced environments.
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Carbon Dioxide Sequestered in Carbonate Rocks
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