origins of life early idea: spontaneous generation –the idea that non-living material can produce...
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Origins of Life• Early Idea: Spontaneous
Generation– The idea that non-living
material can produce life—Life magically appears!
– Examples• Meat produces maggots• Mud produces fish
(mudskippers)• Grain produces mice
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Origins of Life
• Francesco Redi was first to disprove the theory of spontaneous generation in 1668– Experiments with rotting meat
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Origins of Life • Also during this time, scientists were
just beginning to use microscopes…
– They were able to see that microorganisms were EVERYWHERE!
– Even though Redi was able to disprove the theory of spontaneous generation, many scientists thought that microorganisms arose spontaneously from a “vital force” in the air
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Origins of Life
• Louis Pasteur– Disproved the spontaneous generation of
microorganisms – Experiments with broth
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Origins of Life
• Pasteur’s experiments showed that microorganisms do not arise from the broth alone even in the presence of air
• Biogenesis became the accepted theory about the origin of life– Biogenesis is the idea that living
organisms only come from other living organisms
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How Did Life Begin On Earth?
• Early Earth– Very Hot – Meteorite Collisions – Volcanoes– Very little oxygen
• Atmosphere made of H2O Vapor, CO2, N gas, CH4 & NH3
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• Ingredients for Life: Before life can occur, you need the molecules of life– 1st – Formation of simple organic molecules – 2nd – Organization into complex organic
molecules• Proteins / Carbohydrates / Nucleic Acids / Lipids
• So… How did this happen in such a harsh environment?
How Did Life Begin On Earth?
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• Miller & Urey (1953) – Tested theory by simulating
conditions on early Earth in a lab– Mixture of H20 vapor, NH3, CH4,
and H gasses was zapped with electrodes
– Cooled gasses condensed in flask
– After a week, several kinds of amino acids, sugars, and other small organic molecules were present in the flask
How Did Life Begin On Earth?
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• The next steps in the origin of life were the formation of complex organic molecules and cells
• Heat caused the amino acids to form proteins and also caused the production of ATP and nucleic acids
• Doing this formed “protocells” – or large ordered structures, enclosed by a membrane that carries out life functions
How Did Life Begin On Earth?
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The First True Cells
• First forms of life were prokaryotes that likely evolved from protocells– Anaerobic Heterotrophs
– Later, early prokaryotes evolved to be able to make their own food • These were similar to archaebacteria
and used chemosynthesis to produce their food
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The First Photosynthetic Prokaryotes
• Likely the next kind of organisms to have evolved– Were able to use sun to make
glucose
– Produced OXYGEN, which changed Earth’s atmosphere
– Lightening + Oxygen = Ozone Layer formation
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The Endosymbiont Theory
• Lynn Margulis, in 1960’s• Eukaryotes evolved from prokaryotes as a
result of symbiotic relationship between prokaryotic bacteria