1. Arms, Camp. Chapter 17, "Evolution and Natural Selection," Chapter 21, "Origin of Life." Biology. Bonnie Boehme. Fourth Edition. The United States of America. Harcourt Brace College Publishers; 1995. Pages 352-372, 440-455 2. Curtis, Barnes. Chapter 46, " Evolution: Theory and Evidence," Chapter 48,"Natural Selection," Chapter 49 "On the Origin of Species." Biology. Sally Anderson. Fifth Edition. New York, USA; Worth; 1989: Pages 961-973, 991-1029 3. Roberts, M.B.V. Chapter 34, " Evolution in Evidence," Chapter 35,"The Mechanism of Evolution," Biology. Fourth Edition. Surrey, UK; Nelson; 1986: Pages 560-616 4. The World Book Encyclopedia. World Book, inc. London: v.6; Pages 406-413 "Evolution". 5. Encyclopedia Britannica. Encyclopedia Britannica, inc. Chicago: v.4; Page 623 "Evolution". 6. http://www.talkorigins.org/origins/faqs-evolution.html 7. http://www.wku.edu/~smithch/index1.htm 8. http://bioinfo.med.utoronto.ca/~lamoran/Evolution_home.shtml

on containing compounds. That might suggest that the combination of volcanic activity and a constant shower of meteorites released the gases that created the Earth’s atmosphere. Geologists believe that the earth’s early atmosphere contained water vapor, carbon monoxide, carbon dioxide, hydrogen, and nitrogen. It also may have contained ammonia and methane. It did not contain oxygen, which is the main reason why the Earth could not have supported life. As for oceans, they couldn’t have existed at first because the Earth’s surface was extremely hot. But about 3.8 billion years ago, the Earth’s surface cooled enough for water to remain a liquid on the ground. Thunderstorms wet the planet for many years and oceans began to fill. This is known because the earliest sedimentary rocks have been dated to that time period. Miller and Urey were two scientists who attempted to explain the origin of life on Earth without referring to any supernatural events. They performed an experiment that suggests how the Earth’s atmosphere might have formed. Miller mixed "atmospheric" gases (hydrogen, methane, ammonia, and water vapor) in a sterile glass container and charged them with energy by adding electric sparks to them. The electric sparks resembled lightning at the time of the Earth’s formation. After about a week, the mixture turned brown and was found to contain amino acids. This organic compound produced in this experiment was efficient in knowing how the Earth’s early atmosphere formed. That is because it was successful in producing some of the building blocks of nucleic acids under geologically relevant conditions. A question that puzzled scientists was how could all this have started in the first place. It is noted that amino acids and nucleic acids stick to the structures of clay crystals. By being held together in a regular pattern on clay crystals, these molecules combine to form proteins and polynucleotides. Other researchers not that some kinds of RNA can join amino acids into protein chains without help from protein enzymes. Some forms of RNA can copy themselves and can actually edit other RNAs by adding and deleting nucleotides. These experiments support another hypothesis that RNA, rather than DNA, functioned as life’s first information storage system. According to this hypothesis, life based on RNA have started when RNA fragments began to copy and edit themselves and assemble proteins. As time passed, these RNAs could have evolved to the point where they produced protein enzymes that took over the work of bringing about chemical reactions. Later, storing genetic information could have similarly been passed on to DNA. In this way, over thousands of years, RNA, DNA, and proteins could have evolved into the complex system that characterizes life today. Discovering that RNA can act as a catalyst, makes it easier to imagine how life began. According to Bruce M. Alberts, "One suspects that a crucial early event was the evolution of an RNA molecule that could catalyze it

Some topics in this essay:
DNA Eukaryotic, Earth Scientists, Evolution Evolution, Darwin’s Wallace’s, Revolution England, Miller Urey, Bruce Alberts, Jean Baptiste, Lynn Margulis, RNA DNA, natural selection, earth’s atmosphere, dark-colored moths, tree trunks, amino acids, common ancestor, nucleic acids, peppered moths, aerobic prokaryote, darwin’s theory, darwin’s theory natural, ancestors stretched necks, necks ancestors stretched, earth’s atmosphere formed, natural selection action,