The Origin of Life

Last Class Got to know each other a little better Reviewed Lab Safety Introduced Biology Reviewed the Scientific Method

Objectives Determine the difference between spontaneous generation and biogenesis Look at the 3 experiments set out to determine how life comes to be Redi Spallanzani Pasteur Compare the “Electric Spark” theory and the “Panspermia” Theory

Where does life come from? Think (1m) Pair (1m) Share (3m)

The Theory of Spontaneous Generaton Dark Ages Hypothesis: Living Organisms could develop from non-living material Was this hypothesis proven, or disproven?

Redi’s Experiment Francesco Redi (17th C) Commonly held belief that flies were developed spontaneously from rotting meat. Hypothesis: Meat kept away from flies would remain free of maggots Experimental group: Covered jar containing meat Control group: Open jar containing meat

Redi’s Experiment Cont’d After a few days, maggots swarmed over the meat in the open jars, none in the covered jars Conclusion: Experiment showed that flies only come from eggs laid by other flies

Spallanzani’s Experiment Lazzaro Spallanzani Around the time of the invention of the microscope World introduced to microorganisms Believed to be generated from “Vital Force” in the air Hypothesis: Microorganisms are formed from other microorganisms, not the air. Experimental Group: Boiled clear, fresh broth until flask is filled with steam, sealed by melting neck closed. Control Group: Boiled broth, flask left open

Spallanzani’s Experiment Cont’d Observations: Broth in the sealed flask remained clear, while broth in open flask became clouded with microorganisms Conclusions: Boiled broth became contaminated only when microorganisms from the air enter the flask

But of course, there were critics… Opponents to Spallanzani claimed that he left the flask too hot, thereby boiling away all the life force in the air…

Enter Louis Pasteur 19th Century French Biologist Considered the Father of Microbiology Hypothesis: If he used a curved neck flask that allowed air inside the flask, but solid particles (such as microorganisms) not able to get in flask, then the broth would remain clear

Louis Pasteur’s Experiment Cont’d Broth boiled in experimental curved neck flask remained clear for up to a year! As soon as curved neck was broken, flasks became contaminated within a day! Conclusions: Pasteur reasoned that the contamination was due to microorganisms in the air, not a “life force”. Beginning of the principle of…

Biogenesis The theory that living organisms come only from other living organisms

In Your Journal Write out a journal/diary entry from the view point of one of these scientists What are your observations on that day? What are you expecting from these observations? Why are you undertaking this experiment?

But where did all of this life come from? Though there is no sure-fire way of knowing where all of life came from, there are several theories. We will focus on Electric Shock Panspermia

Electric Shock Start at the beginning of the formation of Earth (~4.5BYA) A condensed mass of orbiting debris consisting of an iron/nickel core, rock surface and an atmosphere consisting of Hydrogen- H2 Hydrogen Cyanide- HCN Methane- CH4 Water- H2O Ammonia- NH3

Electric Shock Earth cools off enough to a point where water can collect in hollow and low region of the Earth to form oceans Ocean water is salty due to leeching of earth materials into the water over a course of billions of years

Electric Shock While Oceans are forming, molecules of the atmosphere begin to react with one another Set forth by lightning, heat and radiation H2, HCN, CH4, H2O, NH3  React together to form organic subunits of life molecules Sugars (Glucose), Glycerine(fats), Amino Acids (proteins), Nucleotide Bases (RNA/DNA)

Electric Shock Miller and Urey (1950s) Designed an experiment using the early atmospheric molecules, and conditions similar to early earth, to see if these organic molecules could arise. Resulted in formation of the organic molecules responsible for life!

Electric Shock Organic Life molecules began reacting with one another E.g. amino acid+ amino acid= Proteins Sugar + Sugar= Polysaccharides These reactions lead to complex molecules known as nucleoproteins Like all life they were able to reproduce, mutate, evolve, and needed an energy supply (Nutrition)

Electric Shock Eventually these nucleoproteins became protocells Developed a mechanism to utilize the suns energy for nutrition- Rise of Photosynthesis (Became the autotrophic cells)

Electric Shock and the Oxygen Revolution Development of Photosynthesis meant that Oxygen was being expelled into the atmosphere as a waste product 1. Oxygen in atmosphere began reacting with each other in the upper atmosphere forming Ozone (O3)- protects life from radiaton 2. The Heteroptrophic cells were now able to utilize O2 in the atmosphere and get more energy  Aerobic Respiration

Recap Atmospheric Gases Simple Organic Compounds Complex Biological Molecules Hetero-trophic cells (Animals) Heterotrophic Protocells Nucleo-proteins Autotropic cells (Plants)

Panspermia Life exists throughout the universe, distributed by meteorites, asteroids, comets, planetoid and even space crafts. Tiny microorganisms from other worlds may be ejected on impact, and travel to other worlds, planting their “life seed” Some of the earliest microorganisms on our planet are able to survive the most extreme conditions of cold and radiation (similar to the conditions of outer space)

In your Journal What are your thoughts on the origin of life? Did you prefer the Electric Shock or Panspermia Hypothesis? Explain Do you have any other theories on how life may have come to be? Ch14 Review when finished For Interest, research other origin of life theories. Feel free to share with class next day