BIO 100 Life and Taxonomy PowerPoint.ppt - Origin ofOrigin of Life Life Three Possibilities 1 Special Creation not testable by science 2

BIO 100 Life and Taxonomy PowerPoint.ppt - Origin ofOrigin...

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Origin of Life Three Possibilities 1. Special Creation: not testable by science. 2. Extraterrestrial Origin: hypothesis called panspermia. Suggests that meteors or cosmic dust may have carried complex organic molecules necessary for life. 3. Abiogenesis (Spontaneous Origin): life evolved from non- living complex organic compounds formed from simpler substances present on the early Earth. Tentatively accepted. ***2 and 3 are scientifically testable. Origin of Origin of Life Life
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Origin of Origin of Life Life
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Earth is about 4.6 billion years old. First life on Earth: Oldest fossils of bacteria are ~3.5 billion years old. Likely that life is older, as early as 3.8 billion years, perhaps older. Carbon grains.
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Clock analogy for some key events in evolutionar y history, 5 billion years of Earth’s history presented on 12 hour clock.
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Early Atmosphere Consisted of many hot gases: Hydrogen, Nitrogen, Water, Carbon Monoxide, and Carbon Dioxide. No or little Oxygen.
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What was early Earth like? What was early Earth like? Earth was hot! Earth was hot! Little or no oxygen Gases in atmosphere: Gases in atmosphere: Hydrogen cyanide (poison to you!) Hydrogen cyanide (poison to you!) Hydrogen sulfide Hydrogen sulfide Carbon dioxide Carbon dioxide Carbon monoxide Carbon monoxide Nitrogen Nitrogen Water Water
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Some energy sources available on the early Earth: 1) Sun 2) Lightning 3) Geothermal a) Lava b) Hydrothermal vents
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The Origin of Life First cells may have originated by chemical evolution involving ~four steps: A. Abiotic (non-biological) synthesis of small organic molecules (monomers) C + H = organic molecule. B. Monomers joined together to form polymers (proteins, nucleic acids). C. Origin of self-replicating molecules (chemical inheritance and selection for stability) proteins and polynucleic acids. RNA World. D. Packaging of organic molecules into protobionts. Aggregates of abiotically produced molecules that maintain an internal chemical environment and exhibit some of the properties associated with life (i.e., metabolism, stability, replication).
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Synthesis of Organic Compounds Cells are made of four classes of organic compounds: proteins, carbohydrates, lipids, and nucleic acids. These organic compounds were thought to have spontaneously formed from simple substances present on early Earth with the input of energy from the sun, lightning, or heat from hydrothermal vents.
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Stanley Miller Experiment 1953 Conducted an experiment to see if organic molecules could spontaneously form under conditions on early Earth.
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