Origins of Life Notes (unit 1)

• Focus


  Students will be able to describe the scientific explanations for the origin of life on Earth, including chemical evolution and the endosymbiont theory through watching a video clip, reading a text, and completing a graphic organizer
• Intro video and questions

  How Life Began w/ Neil deGrasse Tyson NOVA Origins – YouTube
• Origin of the Atmosphere

  1. Sun's energy stripped away 1st atmosphere

  2. 2nd atmosphere formed from volcanic outgassing
• Primitive atmosphere


  • CO2
  • water vapor
  • lesser amounts of CO, N2, H2, HCl, and traces of NH3 and CH4 (3.5 bya)
  • Oxygen missing
• How Did Life Originate?

  • Spontaneous Generation? (old/incorrect theory)
  • Chemical Synthesis "Primordial Soup"
  • Panspermia (life from space)
• Chemical Synthesis


  1. Proteins

  2. DNA/RNA
• Chemical Synthesis- "Primordial Soup"


  Dr. Stanley Miller and Dr. Harold Urey-1953
• Used in the experiment

  • ammonia (NH3)
  • methane (CH4)
  • water (H2O)
  • hydrogen (H2)
• Chemical Synthesis- "Primordial Soup"

  1. Electricity was passed through the apparatus

  2. Amino Acids and hydrocarbons were synthesized
• If oxygen is present, these molecules are not formed
• For life to start, what must not be around? Free Oxygen
• Life probably did not begin on dry land
• Possibilities for where life began

  • Oceans near hydrothermal vents
  • Hot springs
  • Small pools of water (tidepools?)
  • Inside rocks
• the earth was formed

  4.6 BYA
• Macromolecules are formed


  Proteins & Nucleic Acids
• Simple life forms (anaerobic prokaryotes)


  Most likely Blue-green cyanobacteria, life existed only in the water, 3.5-4.0 BYA
• Free oxygen (O2) finally forms in the air and ozone (O3) is synthesized which shields the planet from harmful rays


  Aerobic life can now form
• Eukaryotes form by endosymbiosis (Protista)

  2 BYA
• Multicellular Eukaryotes form


  Plants/animals/fungi, most of the major phyla of animals appear in fossil record about 10–20 MYA
• Endosymbiosis


  Prokaryotes to Eukaryotes, Cells went inside the cells, the cells on the inside became chloroplasts and mitochondria
• Evidence: mitochondria/chloroplast are the size of a bacteria cell, have their own DNA, have an extra membrane, reproduce on their own
• Mass Extinctions


  At least 5 mass extinctions have occurred throughout history
• Possible causes


  • Dramatic climate changes occurring after meteorite collisions
  • Continents drift into new and different configurations
• It is argued we are in a new mass extinction right now