Origin of Life Theories

Where does life come from? 2 ideas: 1. Spontaneous generation (abiogenesis) belief held before 1600s living things could arise from nonliving things (ex. maggots from meat)

disproved by the following experiments: - Francesco Redi (1668) – rotting meat experiment   http://www.sumanasinc.com/webcontent/animations/content/scientificmethod.html

- Lazzaro Spallanzani (1700s) – broth in closed flask

Louis Pasteur (mid 1800s) – broth in S-necked flask http://bcs.whfreeman.com/thelifewire/content/chp03/0302003.html

But, where did life ORIGINALLY come from? Theories: 2. Biogenesis currently accepted belief all living things come from other living things But, where did life ORIGINALLY come from? Theories: 1. divine origin/ intelligent design 2. meteorite  

3. PRIMORDIAL SOUP THEORY* proposed by Alexander Oparin in 1923 parts of the theory: a. early Earth was very hot; atmosphere contained inorganic molecules such as ammonia, hydrogen, water vapor, methane (very little oxygen)

b. high temperatures, UV light, and lightning converted inorganic molecules to simple organic molecules, then to more complex organic molecules such as amino acids c. when atmosphere cooled, organic molecules were washed into the oceans where life began

CRAZY?! – This theory was tested (and supported) in 1953 by Stanley Miller and Harold Urey. http://bcs.whfreeman.com/thelifewire/content/chp03/0302001.html

What kinds of organisms were formed first? Simple (prokaryotic – bacteria) Anaerobic (there was little or no oxygen!)

Where did eukaryotes come from Where did eukaryotes come from? – endosymbiosis theory States that eukaryotic cells formed from a relationship between two prokaryotic cells. Mitochondria evolved from aerobic bacteria; chloroplast evolved from photosynthetic bacteria http://highered.mcgraw-hill.com/sites/9834092339/student_view0/chapter4/animation_-_endosymbiosis.html

Where did oxygen and aerobic organisms come from? Heterotrophs were first; started to run out of food Organisms that had evolved to make food thrived; did photosynthesis Photosynthesis produced oxygen Oxygen allowed more ATP to be made; so organisms that use oxygen thrived