Bio notes - 1. The Origin of Life 1. Universe is 13.7...

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1. The Origin of Life 1. Universe is 13.7 billion years old 1. According to the Hubble telescope 2. The earth is about 4.6 years old 3. Hadean Period : 4.6-3.8 billion years ago 1. No life, a few rocks and only a few mineral grains have been found from this period 1. Geologic subduction and bombardment by asteroids destroyed crust and left almost no rocks 4. Archean Period - 3.8 to 2.5 billion years ago 1. Bacteria first life 2. Evolution of first prokaryotes (3.5-3.8 bill. Years ago) 3. No large continents until late Archaen 4. The sun was 1/3 dimmer 5. Proterozoic Period - 2.5 billion to 540 million years ago 1. Period before abundant complex life 2. Characterized by buildup of O 2 3. A number of ice ages occurred 6. Around 2 billion years ago a new type of cell with nucleus appeared = eukaryotes 1. All life was single celled until around 1.2 billion yrs ago 2. Oldest fossils of multicellular are about 1.2 bill. yr old algae 1. Multicellularity evolved several diff. times 2. All Life 1. Composed of one or more cells 2. Growth and development 3. ATP based metabolism 4. Can reproduce 5. Has h o meostasis 1. = maintenance of stable internal environment 6. Has dna based heredity 1. Tells us how to build cells, materials and metabolize like parents 7. Sensitivity to stimuli 3. Early Earth 1. Most agree that there was lots of H 2 no O 2 1. This made it a reducing atmosphere which favored formation of organic molecules with carbon-carbon and carbon-hydrogen bonds 2. Lots of heat, lightning and radiation provided energy to make organic molecules 3. Problem: no O 2 meant no ozone layer and UV rays would cause organics to break down as soon as they’re made (ozone = O 3 ) 2. Some believe life may have evolved at deep sea vents 1. Right reactants and conditions exist there 2. Ancient bacteria live around deep sea vents 4. Early Life 1. First unequivocal fossils are 2.5 billion yrs old
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2. But there are 3.5 bill yr old fossil stromalolites 1. Formed by colonies of cyanobacteria 3. Believed that there is now no evolution of new life forms from the inanimate 1. New life would be out competed by existing forms 2. Today life evolves only from preexisting life 4. All life requires energy, and carbon and hydrogen sources 1. Some prokaryotes make own organic molecule = photosynthetic or chemoautotrophic 2. Some use existing molecules 3. The early photosynthetics split H 2 S and produced organic molecules plus S 2 4. Methanogens- use H 2 and CO 2 gasses and give off CH 4 1. Exist today in sewage, garbage, swamps and cow’s rumens 2. One type lives in 185 Fahrenheit water at deep sea vents with pressure 245 times greater than sea level 3. 5. Appearance of Aerobic Life 1. About 2.7 billion years ago a new cyanobacteria evolved from H 2 S splitters that could split H 2 O 1. Both types used sunlight to split 2. New type evolved a more powerful photosynthesis 1. Splitting H 2 O takes more energy than H
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Bio notes - 1. The Origin of Life 1. Universe is 13.7...

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