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Chap. 14 : Origin of Life ** Biogenesis – life coming from life as opposed to spontaneous generation (life coming from nonliving) I. Disproving Spontaneous Generation 1. Francesco Redi – flies, maggots, meat 2. Lazzaro Spallanzi – heated meat broth – no microorganisms – killed “vital force” 3. Louis Pasteur – heated broth, curved neck of flask - - no growth in broth. Broke off flask, growth in 1 day. Conclusion: did not kill “vital force” but rather air contains living things that we can not see II. Earth’s formation - 5 billion yrs. ago – solar system together in swirling mass of gas and dust. - Mass collapses inward forming sun - excess released to form planet 4.6 billion yrs. ago - volcanic eruptions formed atmosphere which lead to oceans - 2.2 billion yrs. ago Earth formed as we know it today III. Theories of Support 1. Radioactive dating – measure the rate of decay (breakdown) of radioactive isotopes – called half-life. Compare C12 (stable carbon) to C14 (radioactive carbon) in fossils. We know it takes 5,730 yrs. to be reduced by ½. Only accurate up to about 60,000 yrs. old. ---Can use U238 up to 4.5 billion yrs. ago. IV. Formation of Life 1. Alexander Oparin (1923) – said primative Earth’s atmosphere contained : NH3, H2, H2O, CH4 a. Add high heat (volcanic eruptions) to these chemicals and reactions occur to form simple organic compounds (amino acids) b. Earth cools, simple organic compounds collect in H2O c. Add lightning and UV radiation and these simple compounds join to make macromolecules such as proteins. 2. Miller and Urey (1953) – set up experiment to test Oparin’s hypothesis. 3. Fox – proteins joined together to form membraneous spheres called microspheres - linking together of microspheres creates coacervates (proteins + sugars ). Coacervates are considered nonliving because they do not contain nucleic acids but have some ingredients of nucleic acids. V. 1st life forms A. Conditions on Earth – lacking O2, therefore believed Archaebacteria were 1st cells (prokaryotes) to appear. Once the atmosphere began to thin, more sunlight penetrated Earth and photosynthetic bacteria evolved. About 3 billion years ago. • Released O2 into atmosphere over a billion yrs. – helped form ozone layer which was necessary for life to be protected from UV radiation. B. Eukaryote Cell Formation -- endosymbiosis – evidence suggests around 2 billion years ago a small aerobic prokaryote entered and lived inside a larger anaerobic prokaryote. Formed a mutualistic relationship together. • Over time these smaller aerobic prokaryotes evolved into mitochondria and/or chloroplast (make energy). Evidence is that both of these structures even today contain their own DNA inside them (not inside nucleus) and it is different from DNA inside the nucleus