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Chapter 22

Notes from Textbook- Chapter 22- Evolution.docx

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Natural Science
NATS 1675
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Chapter 22 Evolution Notes from TextbookPages 510531Required ReadingChapter 22 Human Evolution Required readingsSections 222 Biological Evolution pp 520526 223 Humans are Primates pp 527529 225 Evolution of Humans pp 533536 first half ignore Fig 2218 and associated text Bioethical Focus p 538 Human Variation pp 539540221 Origin of Life Pg 510Biomolecules are the molecules of life and are organic molecules Life originated 35 4 billion years ago BYA from non living matter in a series of 4 stagesoStage 1 Small Organic Molecules Simple organic molecules called monomers evolved from inorganic compounds prior to the existence of cells Amino Acids the basis of protein and nucleotides the building blocks of DNARNA are examples of organic monomers oStage 2 Macromolecules Organic monomers were joined to form larger macromolecules polymers such as DNA RNA and proteins oStage 3 Protocells Organics polymers became enclosed in a membrane to form the first cell precursors called protocells or probionts oStage 4 Living cells Probionts acquired the ability to selfreplicate as well as other cellular properties Stages 13 involves the processes of chemical evolution and occurred before the origin of life Stage 4 is when life first evolved through the processes of biological evolution Small Organic Molecules Pg 510The first atmosphere was formed by gases escaping from volcanos Making the primitive atmosphere consist mostly of water vapor h20 Nitrogen N2 and carbon dioxide CO2 with only small amount o hydrogen H2 and carbon monoxide CO Primitive atmosphere has little if any free oxygen The primitive earth has many sources of energy such as volcanoes meteorites radioactive isotopes lightning and ultraviolet radiationInorganic chemicals may form organic molecules in the presence of a strong energy source even it oxygen is not present Fig 222 The Stanley Miller Experiment Gases thought to be present early in the Earths atmosphere were admitted to the apparatus circulated past an energy source electrical spark and cooled to produce a liquid that could be withdrawn Upon chemical analysis the liquid was found to contain various small organic molecules There are many hypotheses on how the first small organic monomers have evolved could have came from the bottom of earths oceans or from may not have originated on this planet
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