[1]The Origin and Evolutionary History of Life

[1]The Origin and Evolutionary History of Life - The Origin...

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The Origin and Evolutionary History of Life (Chapter 21) 1. Geologists believe that ancient earth provided the exact conditioned necessary for chemical evolution: What were those conditions? Why were they so important in the chemical reaction of life? geologist believes that ancient earth provided the exact conditions necessary for chemical evolution little or no free oxygen (reducing conditioned necessary to prevent oxidation of organic molecules, the building blocks of life) UV (sun) and energy (volcanic activity) to build biological molecules from simple inorganic chemicals Presence of chemical building blocks (water, minerals, and gases) time to allow resulting accumulation and interaction 2. If organic molecules were the building blocks of life, how might those precursors of life have originated 3. Describe the pre-biotic soup hypothesis and compare it to the Iron-Sulfur World hypothesis Prebiotic Soup hypothesis: organic molecules formed near earth’s surface in “sea of organic soup” or on rock o clay surfaces. Polymerization formed Iron-sulfur world hypothesis: Polymerization of organic molecules produced at hydrothermal vents in deep in the ocean’s floor What kinds of experiments could you do to support a thesis of chemical evolution on ancient earth? (Fig. 21-2) Miller and Urey’s Experiment: designed a closed apparatus that simulated conditions that presumably existed on early earth. They exposed an atmosphere rich in H 2 , CH 4 , H 2 O, and NH 3 to an electric discharge that simulated lightening. Their analysis of the chemicals produced in a week revealed that amino acids and other organic molecules had formed. gases in flask react; in one week a variety of simple organic compounds- amino acids etc accumulate first step in the origin of life Although there is no direct fossil evidence for the origin of life, experiments have demonstrated how they could have been formed. Could organic molecules form in a reducing atmosphere? The origin of cells macromolecules assembled from small organic molecules 4. What major steps are hypothesized to have occurred in the origin of cells? In other words, after the first polymers formed, could they have assembled spontaneously into more complex structures? 5. What are protobionts? Pharmaceutical companies use protobionts to deliver drugs – what qualifies do protobionts posses that tells us they could have been the precursors of simple cells? (Figure 21-3) protobionts -macromolecules assembled together -abiotically (not produced by organisms) formed from macromolecules -exhibited many functional and structural attributes of living cells; homeostasis, catalytic activity cells -cells arose from protobiont -enclosed the information necessary for self-replication Protobiont forms when water is added to abiotically formed polypeptide, selectively permeable, maintain homeostasis, electrical potential across surfaces.
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