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What is the least complex organism? Why?

What is the least complex organism? Why?. confidential (adjective) (con fe ‘den shel ) - communicated in trust; secret; private “ I have something to tell you,” Malik said in a confidential tone. How did life on earth begin?. Early Earth.

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What is the least complex organism? Why?

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  1. What is the least complex organism? Why? • confidential (adjective) (con fe ‘den shel) - communicated in trust; secret; private • “I have something to tell you,” Malik said in a confidential tone.

  2. How did life on earth begin?

  3. Early Earth • Early Earth was formed about 4.6 billion years ago and was very different than earth today. • How do you think it might have been different?

  4. Early Earth • The atmosphere was very different than it is now, containing little or no oxygen. • Earth was too hot for liquid water. • Once the surface cooled enough for rocks to form, the surface was covered with volcanic activity.

  5. Early Earth • About 3.8 billion years ago the Earth cooled enough for liquid water to remain. • Thunderstorms drenched the planet and oceans covered most of the surface.

  6. Could organic molecules have evolved under these conditions? • In the 1950s Stanley Miller and Harold Urey tried to simulate the conditions of early Earth. • They showed how several amino acids could be created under those conditions.

  7. Miller and Urey • Took the molecules that were present in the early atmosphere and put them in a closed container • Methane, ammonia, hydrogen, and water • Electricity was continuously passed through the container • This electricity represented the lightening the atmosphere would have encountered from thunderstorms

  8. Miller and Urey

  9. What they found…. • They found that about 15% of the carbon in methane (CH4) turned into organic compounds • What is an organic compound? • Some of these compounds were amino acids (which we know make up proteins!!!)

  10. The Big Picture • Miller and Urey showed that the mixtures of organic compounds necessary for life could have arisen on primitive earth!

  11. After Miller and Urey …. • Many experiments followed the great discoveries of Miller and Urey • One experiment took the sample compounds found in early earth and discovered adenine was made • What is adenine found in? • It is possible for DNA to arise under these conditions!

  12. Hypothesis of the Origin of Life • The leap from a mixture of organic molecules to a living cell is large. • Tiny bubbles of organic molecules have characteristics of living systems • selectively permeable membranes and means of storing and releasing energy. • They may have become more and more like living cells over time.

  13. Origin of Life • Evidence indicates that about 200-300 million years after the accumulation of liquid water on Earth, cells similar to modern bacteria were common.

  14. Changing Earth • Photosynthetic bacteria became common and oxygen began to accumulate in the atmosphere and the ozone layer formed. • The rise in oxygen caused some life forms to go extinct, while others evolved ways to use oxygen for respiration.

  15. Hypothesis of Origin of Eukaryotic Cells • What is a eukaryotic cell? • Prokaryotic cells began to evolve internal cell membranes- this was the ancestor to eukaryotic cells. • Smaller prokaryotes began living inside this ancestor and over time it became an interdependent relationship. • ……organelles!

  16. Lynn Margulis • Studied cell biology in late 1960s • Noticed that mitochondria looked similar to bacteria • Suggested that mitochondria and chloroplasts arose from bacterial cells

  17. Endosymbiotic Theory • One group which entered the cell had the ability to use oxygen to generate ATP. These evolved into mitochondria. • Another group of prokaryotes which carried out photosynthesis evolved into chloroplasts.

  18. Endosymbiotic Theory • Mitochondria are the result of endocytosis of aerobic bacteria • Chloroplasts are the result of endocytosis of photosynthetic bacteria • Endocytosis: A substance gains entry into a cell without passing through the membrane

  19. Evolution of Mitochondria

  20. Evolution of Chloroplast

  21. Does the timing make sense? • Prokaryotes were present before eukaryotes

  22. Evidence for Endosymbiotic Theory • Mitochondria and chloroplasts have many characteristics of free living bacteria: 1- contain DNA similar to bacterial DNA 2- have ribosomes of similar size and structure to those of bacteria 3- reproduce by binary fission like bacteria

  23. How do we know how old fossils are?

  24. Relative Dating • Relative Dating is based on the layering of rocks • It can determine historical events in the correct order but CANNOT yield a numerical age

  25. Absolute Dating (Radiometric) • The properties of rocks can reveal their exact age! • This is determined based on the decay of naturally radioactive elements in the rocks • By determine how much of an element remains, we can determine its numerical age

  26. Absolute

  27. Why do we need both? • If we can determine the exact age through absolute why do we still need relative dating? • The problem is not all rocks can be numerically dated, so relative dating gives us a general idea of their age

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