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Early Life on Earth

Early Life on Earth

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Early Life on Earth

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  1. Early Life on Earth

  2. Origin of Life • Even simple cyanobacteria perform extremely complicated processes (photosynthesis, stromatolite formation, reproduction, etc) that most probably evolved from a simpler ancestor

  3. Primordial Soup • Scientists reasoned that Earth’s early atmosphere consisted of hydrogen, ammonia, methane, etc(from outgassing) • With enough energy these molecules may react to form a primordial soup

  4. Miller-Urey Experiment / Reducing Atmosphere • Conducted in 1952 • Simulated conditions of the Archean • Reactants: water, methane, ammonia, carbon monoxide and hydrogen gas • Electrodes used to simulate lightning (energy source) • Products: Amino acids and sugars (but no DNA)

  5. BUT……..

  6. Other origins of life • Organic molecules were delivered to Earth from another place in space • Hydrothermal vents may have provided the conditions needed for life to develop (RE: extremophiles) • Something to keep in mind…Life may have started and restarted many times

  7. RNA World Hypothesis • Before the development of DNA>RNA>Protein, life may have relied exclusively on RNA • RNA is able to store genetic information (like DNA) and catalyze reactions (like proteins)

  8. Proterozoic Life • Fossil evidence suggests earth was dominated by unicellular organisms called PROKARYOTES. • One cell • No nucleus (DNA/RNA storage) • Organisms that have organelles are called EUKARYOTES

  9. Snowball Earth • A mass extinction event 750 mya caused the extinction of many of these unicellular eukaryotes • Evidence from glacial deposits suggest ice may have advanced all the way to the equator • Not everything died off

  10. The Rise of the Multicellular Organisms • After the ice retreated (630 mya), the climate warmed dramatically and the first multicellular organisms appeared. • In 1947, fossils dated to this time period were found in Australia's Ediacaran Hills (EDIACARAN BIOTA) • Impressions of large, soft bodied eukaryotes

  11. Ediacaran Biota • Answered why no fossils of ancestral complex life existed during the Cambrian • Thought to be representative of early jelly fish and other aquatic creatures but……

  12. Ediacaran Biota • Preservation Bias • The sudden vanishing of Ediacaran fossils at the Cambrian boundary could simply be because conditions no longer favoured the fossilisation of Ediacaran organisms, which may have continued to thrive unpreserved. • Some scientists suggest that this collection of fossils may not represent a relative, but rather another unique branch of the tree of life. • No mouth, anus, or gut

  13. Try This • Make a comic depicting the three hypotheses on how life may have begun. • You may use bit strips (you’ll need me to authorize you as a JFSS student) • Traditional pencil / paper • PREZI • Something else? • P. 637 Q: 3, 4, 5, 6