Origins of Life
Early Ideas I. Spontaneous Generation:(not rejected until the mid 1800s) -life arises from non living material -Francesco Redi, an Italian scientist, in 1668 tested the idea that flies arose spontaneously from rotting meat. (scientific community not all convinced)
Early Ideas Theory of Biogenesis: Living things can only produce living things Louis Pasteur designed an experiment to show that biogenesis was true even for microorganisms
Modern Ideas: Miller-Urey experiment Simple molecule formation: 1943 Stanley Miller and Harold Urey: Miller-Urey experiment Add the picture to your notes and list the steps in their experiment (watch video)Miller Urey Video
Modern Ideas: Miller-Urey experiment Purpose: demonstrate the formation of simple organic molecules from inorganic compounds Results: Experiment produced several amino acids- suggested that early earth had substances that could produce organic compounds and then living things.
Modern Ideas Once amino acids were formed, proteins are needed for life- scientists think clay particles could hold AA together to form proteins Early genetic material-RNA Scientists are working to Discover how organic molecules Became cells
Cellular evolution First cells were probably prokaryotic Archaea (modern prokaryotes) are probably the closest relatives of modern cells Cyanobacteria-primitive prokaryotes-autotrophs-produced oxygen to form ozone layer-alters conditions on earth for eukaryotic cells to survive
Endosymbiont Theory 1966, Lynn Margulis, ancestors of eukaryotic cells lived in association with prokaryotic cells-possibly inside-developed mutually beneficial symbiotic relationship Evidence: mitochondria and chloroplasts have their own DNA and ribosomes similar to prokaryotic ribosomes Mitochondria and chloroplasts reproduce by fission (like prokaryotic cells) View: Endosymbiont Theory-Concepts in Motion (online text)
Endosymbiont theory