1. Evolution: Origins of Life

2. We know that there is a great variety of living organisms in our biosphere. All living organism also interact with one another as well as with abiotic factors. We are all composed of the 4 same biomolecules How did we get to be a planet with such rich biodiversity?

3. I. Theories on the Origins of Life A. People’s idea about where some living things come from have changed throughout history. B. Prior theories: – 1. Recipe for Bees (Aristotle) – 2. Spontaneous Generation (disproved by Francesco Redi) – 3. Pasteur’s Test Living things come from living things

5. II. Changing Theories A. Redi’s experiment: – 1. Controlled jars – open meat jars, maggots appeared – 2. Tested jars (covered in gauze) – maggots did not appear B. Redi’s experiment scientists understood that life could not rise from nonliving matter. (abiogenesis)

7. II. Changing Theories C. Pasteur’s Experiment: – 1. Boiled broth that was kept open to air through a round neck did not have any microorganisms living in it – 2. If the flask with broth was broken living things would begin to appear D. Pasteur’s experiment allowed scientists to begin to understand that living things only come from other living things. (biogenesis)

8. III. Conditions of Early Earth A. Some scientists still believe that spontaneous generation of life occurred once but was now impossible because the conditions found on early Earth have changed. B. Several scientists began experiments to replicate ancient Earth & gain support for the “primordial soup” theory. Oparin & Haldane proposed such theories.

9. C. Ancient Earth: – 1. Major volcanic eruptions – 2. Hundreds of meteor showers – 3. Constant lightning storms – 4. Atmosphere composed of carbon dioxide, nitrogen, hydrogen sulfide & sulfur dioxide – 5. NO OXYGEN!!

10. IV. Miller-Urey Experiment (1953) A. Mixture of water, hydrogen, methane, and ammonia was cycled through an apparatus that delivered electrical sparks to the mixture. B. At the end about 10% to 15% of the carbon in the system was now in the form of a mixture of organic compounds, including something similar to amino acids, which are the building blocks of proteins.

12. Life on Earth came from Mars

13. V. First Life A. All living things are composed of cells; the 1 st life form was an organism very similar to bacteria. B. First life forms were composed of prokaryotic cells – 1. Prokaryotic cells – cells with no nucleus

14. VI. Endosymbiosis A. Scientists theorize that eukaryotic cells originated through symbiosis between micro-organisms. – 1. In other words: organelles were taken inside another cell and became part of the cell B. Example: – 1. An animal cell’s mitochondria was originally a proteobacteria – 2. A plant cell’s chloroplasts was a cell taking up a cyanobacteria