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

Origins of Life Francesco Redi was first to disprove the theory of spontaneous generation in 1668 Experiments with rotting meat

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

Origins of Life Louis Pasteur Disproved the spontaneous generation of microorganisms Experiments with broth

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

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

How Did Life Begin On Earth? 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? 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? 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

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

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

The Endosymbiont Theory Lynn Margulis, in 1960’s Eukaryotes evolved from prokaryotes as a result of symbiotic relationship between prokaryotic bacteria