Origin of Life Chapter 12.3 and 12.4

Defining Life What is life? Living things are made of cells. Living things obtain and use energy.  Living things grow and develop. Living things reproduce. Living things respond to their environment.  Living things adapt to their environment.

Early Life Likely formed around 3.5 – 3.8 billion years ago. Stromatolites were ancient microscopic organisms found in stacks of sediments. Have been dated to about this age Earth is about 4.5 billion years old Universe is about 15 billion years old

Early Thoughts Spontaneous Generation Popularized by Aristotle Was believed until the 1700s!!!! Redi was credited for performing the first experiments that refuted these ideas. Further confirmed by

Louis Pasteur Performed early experiments disproving the idea of spontaneous generation His experiments showed how heat could kill bacteria and prevent fermentation. Has been widely utilized to make foods more shelf-stable and last longer.

Sample 1: heat kill bacteria in sample, long neck of flask prevents air carrying bacteria into the solution. No growth Sample 2: heat kill bacteria in sample, long neck of flask is removed allowing air that carries bacteria to mix with solution. Growth occurs Sample 3: heat kill bacteria in sample, long neck of flask is tipped and exposed to the bacteria in the air. Growth occurs.

Oparin Said earth likely had a “reducing atmosphere” The Amazing Oparin Thinks Oparin is awesome Said earth likely had a “reducing atmosphere” He said earth has some basic chemicals in place, (H2, CO, NH3, H20) but no O2 Supported the claims of a “primordial soup”

Miller and Urey Using the ideas of Oparin they designed a simple experiment that showed the development of amino acids. (organic molecules) These amino acids could self-replicate and later form early life. Was a bit of an eureka moment.

Missing Oxygen Gas Geothermal energy aplenty Found Amino Acids

Margulis Said life likely became more complex from symbiotic mergers of bacteria. Really supports the idea that some of the earliest lifeforms were much like mitochondria and chloroplasts that were later adapted to work together with other larger lifeforms (Could also have been helped if we traveled from another place)

Endosymbiotic Theory Simple steps: Prokaryotic cells’ membranes start to fold inward making first eukaryote Simple aerobic bacteria fits inside of new cell Simple photosynthetic bacteria fits inside of new cell These bacteria become today’s mitochondria and chloroplasts

Evidence of Endosymbiosis There are many similarities between cyanobacteria and chloroplasts. They seem to share many parts and purposes. This supports the idea that modern day chloroplasts were likely directly descended from very old cyanobacteria. This support the idea of endosymbiotic theory.