Section14.2

Example #1 Observation: Every year in the spring, the Nile River flooded areas of Egypt along the river, leaving behind nutrient-rich mud that enabled the people to grow that year’s crop of food. However, along with the muddy soil, large numbers of frogs appeared that weren’t around in drier times

Example #1 Conclusion: It was perfectly obvious to people back then that muddy soil gave rise to the frogs

Example #2 Observation: In many parts of Europe, medieval farmers stored grain in barns with thatched roofs (like Shakespeare’s house). As a roof aged, it was not uncommon for it to start leaking. This could lead to spoiled or moldy grain, and of course there were lots of mice around.

Example #2 Conclusion: It was obvious to them that the mice came from the moldy grain.

Example #3 Observation: In the cities centuries ago, there were no sewers, no garbage trucks, no electricity, and no refrigeration. Sewage flowed down the streets, and chamber pots and left over food were thrown out into the streets each morning. Many cities also had major rat problems and a disease called Bubonic plague.

Example #3 Conclusion: Obviously, all the sewage and garbage turned into the rats.

Example #4 Observation: Since there were no refrigerators, the mandatory, daily trip to the butcher shop, especially in summer, meant battling the flies around the carcasses. Typically, carcasses were “hung by their heels,” and customers selected which chunk the butcher would carve off for them.

Example #4 Conclusion: Obviously, the rotting meat that had been hanging in the sun all day was the source of the flies.

I. Spontaneous Generation The idea that life can come from non-life F. Redi (Italian scientist) 1668 Disproved it with his experiment Flies and maggots did not magically appear from rotting meat Fig. 14.11 p. 401

II. Theory of Biogenesis Only living organisms can produce other living organisms Louis Pasteur Fig. 14.12 p. 402 How did Pasteur’s experiment support biogenesis? Microorganism only grow when they ____________________

III. Primordial Soup Hypothesis Oparin & Haldane (1920’s) Organic molecules could have been made from simple reactions, if Earth’s early atmosphere had a mix of certain gases Energy provided by the Sun and lightning

Urey & Miller (1953) 4. Built a glass apparatus to simulate Earth’s early conditions Fig. 14.13 p.403 5. What were the products of this experiment? Organic compounds, including amino acids

6. How did it support the primordial soup hypothesis? It explains how amino acids could have been created 7.Organic reactions could have began in deep sea hydrothermal volcanic vents

Amino Acids  Make Proteins Coding system for protein production IV. Required steps (p. 404) Amino Acids  Make Proteins Coding system for protein production RNA was probably the first coding system

V. First Cells Prokaryotes This means they ……… Archaea are closest relatives of Earth’s first cells Extreme environments Hot springs or deep sea volcanic vents Fig. 14.15 p. 405

Photosynthesizing prokaryotes Autotrophic This means they…… Do not need the Sun’s energy or oxygen Obtain energy from sulfur Photosynthesis gives off oxygen (waste) Oxygen levels increased Formed ozone layer Conditions became right for eukaryotic cells

Endosymbiont Theory Lynn Margulis (1966) The ancestors of eukaryotic cells lived closely with prokaryotic cells. Prokaryotes might have lived inside eukaryotes. Mutually beneficial relationship

5. Over millions of years: (Fig. 14.17) a) aerobic prokaryotes became mitochondria b) photosynthetic bacteria became chloroplasts c) Evidence → mitochondria and chloroplasts contain their own circular DNA and reproduce by fission just like prokaryotes

There are still a lot of unknowns about the origin of early life This is different than evolution We will be looking at evidence for evolution next week 