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Unformatted text preview: 6/12/2009 DRAFT Sequence of Events in Human Evolution Some essential elements in the sequence of events leading to homo sapiens . The Big Bang a. The first known event based on the red shift of light waves from stars b. 14.7 billion years ago c. All matter and energy that compose the universe came into existence. d. Matter/energy has been expanding outward and cooling forming nebula, galaxies, stars, plants and solar systems. e. The universe will continue to expand at increasing velocity driven by dark energy. . The Earth and our solar system began approximately 4.5 billion years ago . The earth at that time was not habitable . The earth was entirely molten rock and hot gasses . The earth has since cooled forming solid rock, water, and gasses . With the formation of the oceans self replicating molecules formed. The are the precursors of DNA. . Self replicating molecules collected and attached to other molecules . Collections of molecules that could self replicate combined with molecules that could extract energy from the sun and from the hydrogen in water. These were blue-green algae, the first form of life on earth. . The algae metabolized hydrogen from the water releasing oxygen into the thin gaseous atmosphere of the earth . Oxygen collected in the atmosphere forming the ozone layer that screened UV rays from the sun. Until the oxygen atmosphere was established and the UV rays were eliminated life as we know it could not have existed on the earth. . This was the origin of the Biosphere. All known life forms in the universe appear in the Biosphere which is stretches from the floor of the ocean to a few thousand feet above sea level. and is concentrated in the equatorial areas of the planet. . In the oceans single cell organisms appear and evolve many different means of movement and energy utilization. All reproduction is by cell division. Life and its metabolic processes are dependent on the medium of salt water. . Single cells begin to collect into colonies further diversifying movement and energy utilization. Division is by budding. . Individual cells within colonies begin specializing in function. Some obtain energy, some distribute energy, some move the organism. . Specialization of cells within an organism requires coordination which is accomplished by specialized cells that can communicate information among the cells. These cells were the precursors of the nervous systems and endocrine system . Reproduction also becomes the function of specialized cells . Sexual reproduction appears as individual organisms exchange genetic information in the process . Genetic errors result in changes in the characteristics of individuals. Almost all genetic errors are detrimental to the individual resulting in death. However, a few errors lead to characteristics that give the individual an advantage in competition with others. These individuals tend to out survive competitors and pass on the characteristics to offspring. 6/12/2009 DRAFT . There is great diversity in characteristics of living organisms. There is great diversity in characteristics of living organisms....
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- Spring '09