Lecture 1 - Lecture 1Ch 20 Earth was formed 4.6 bya...

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Lecture 1- Ch. 20 Earth was formed 4.6 bya: Chemical Evolution- The origin of life from non-living matter Atmosphere of early earth: CO2, H2O, CO, H2, N2. It may have contained: NH3 (Ammonia), H2S (Hydrogen Sulfide) and CH4 (Methane). [There was no O2] Four Requirements for the evolution of life- 1. Little or no free oxygen a. Because oxygen is quite reactive and would have oxidized the organic molecules that are necessary for the origins of life, life began only with the absence of oxygen b. The atmosphere was strongly reducing would have formed oxides (molecules with oxygen in them) 2. a source of energy a. Thunderstorms, volcanic activity, intense radiation (UV from the sun), bombardment of meteorites and extraterrestrial objects 3. the availability of chemical building blocks a. This included the presence of water, dissolved inorganic minerals, and the gases present in the early atmosphere 4. and time- a. For the molecules to accumulate and reach with one another. Concept of simple organic molecules (sugars and nucleotides, etc.) could spontaneously form from simpler raw materials. This concept was formed by Oparin and Haldane The idea that Abiotic synthesis of organic molecules (synthesis of molecules not produced by organisms)- This is the process tested by Miller and Urey: An electrical spark was produced in the upper right flask to simulate lightning. The gases present in the flask (similar to those of the early atmosphere) reacted together, forming a variety of simple organic compounds that accumulated. (Compounds such as amino acids and simple sugars formed which combined to form polymers) Iron Sulfur World- This proposed that the organic precursors formed at the cracks in the ocean’s floors. This is where hot water, carbon monoxide, and minerals such as iron and nickel spew forth… which is the iron-sulfur world hypothesis. (Places such as the hydrothermal vents would have been better protected than the earth’s surface and extraterrestrial) Or Prebiotic Soup Hypothesis-
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This basically states that the organic molecules, that are the building materials for organism, were formed near the earths surface. Protobionts- Assemblages of abiotically produced organic polymers. 1. Binary Fission- Divide in half 2. Homeostasis- Maintain an internal chemical environment different from the external environment 3. some show beginnings of metabolism Microspheres- type of protobiont formed by adding water to abiotically formed polypeptides 1. some produce on electric potential across the surface 2. absorb materials from their surroundings (selective permeability) 3. respond to changes in osmotic pressure Genetic information stored in DNA, transcribed in proteins. DNA and RNA can form spontaneously. They both appeared in the prebiotic world first.
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