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Chapter 26 - Note that the following lectures include...

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Note that the following lectures include animations and PowerPoint effects such as fly ins and transitions that require you to be in PowerPoint's Slide Show mode (presentation mode).
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Life on Other Worlds Chapter 26
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This chapter is either unnecessary or critical, depending on our point of view. If we believe that astronomy is the study of the physical universe above the clouds, then this chapter does not belong here. But if we believe that astronomy is the study of our position in the universe, not only our physical position but also our role as living beings in the origin and evolution of the universe, then everything else in this book is just preparation for this chapter. Astronomy is the only science that truly acts as a mirror. In studying the universe up there, we learn what we are down here. Astronomy is not really about stars, galaxies, and planets; it is about us. Guidepost
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I. The Nature of Life A. The Physical Basis of Life B. Information Storage and Duplication C. Modifying the Information II. The Origin of Life A. The Origin of Life on Earth B. Geologic Time C. Life in Our Solar System D. Life in Other Planetary Systems III. Communication with Distant Civilizations A. Travel Between the Stars B. Radio Communication C. How Many Inhabited Worlds? Outline
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The Physical Basis of Life All life forms on Earth, from viruses to complex mammals (including humans) are based on carbon chemistry. Carbon-based DNA and RNA molecule strands are the basic carriers of genetic information in all life forms on Earth. The Tobacco Mosaic Virus contains a single strand of RNA, about 0.1 mm long This complex mammal contains about 30 AU of DNA.
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Information Storage and Duplication All information guiding all processes of life are stored in long spiral molecules of DNA (Deoxyribonucleic Acid) Basic building blocks are four Amino acids: Adenine, Cytosine, Guanine, and Thymine Information is encoded in the order in which those amino acids are integrated in the DNA molecule.
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Processes of Life in the Cell Information stored in the DNA in the nucleus is copied over to RNA (ribonucleic acid) strands, which acts as a messenger to govern the chemical processes in the cell.
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Duplication and Division In the course of cell division, the DNA strands in the nucleus ( chromosomes ) are duplicated by splitting the double-helix strand up and replacing the open bonds with the corresponding amino acids Process must be sufficiently accurate, but also capable of occasional minor mistakes to allow for evolution.
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The Origin of Life on Earth Life develops into more complex forms through gradual evolution, spanning many thousands of generations. Life began in the sea as single-celled creatures. Those as well as early multi-celled creatures had no hard parts to leave fossils.
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