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I. How Did Life Begin?

I. How Did Life Begin?. Prior to the 17 th century: 1. Spontaneous Generation : The belief that living things could come from non-living things. Francesco Redi (1668) Italian scientist. Attempted to discredit Spontaneous Generation. Experimented to prove that maggots came from flies.

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I. How Did Life Begin?

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  1. I. How Did Life Begin? Prior to the 17th century: 1. Spontaneous Generation: The belief that living things could come from non-living things.

  2. Francesco Redi (1668)Italian scientist • Attempted to discredit Spontaneous Generation. • Experimented to prove that maggots came from flies

  3. Redi’sExeriment 1668 – Experiment showing how maggots come from flies

  4. LazzaroSpallanzani (1700) Italian scientist Experimented with spontaneous generation of microorganisms. 1. Created meat broth 2. Boiled broth to kill microorganisms 3. Capped some flasks and left others open.

  5. Spallazani’s Experiment Opponents of his study claimed that he overheated the samples… Destroying the VITAL FORCE

  6. Louis Pasteur (1800’s)French scientist *The conclusions of Pasteur, brought about the theory of BIOGENESIS – Living things come from other living things

  7. B. Formation Of The Earth • About 5 billion years ago, the solar system was a mass of swirling gas and dust. • Possible result of a SUPERNOVA

  8. As millions of years passed, a large amount of material collapsed to the center and created the sun. Around 4.6 billion years ago, the earth and some of the other planets were formed.

  9. As earth cooled, water vapor in the air condensed to form water and the first oceans. 3.8 to 3.9 billion years ago.

  10. C. Measuring Earth’s Age Radiometric dating: Estimate the age of an object by measuring its content of radioactive isotopes. Radioactive isotopes: Unstable and “decay” over time. Half-life: The time that it takes for a radioactive isotope to decay by one half

  11. D. Life On The Earth The oldest evidence of life on the earth is found in rock estimated to be 3.5 billion years old. The evidence shows in the form of FOSSILS. The first fossils were referred to as MICROFOSSILS, ancient prokaryotic cells.

  12. A. Primordial Soup Model • Alexander Oparin (1923) • Soviet scientist • Gases of the primitive atmosphere came together and created simple organic compounds 1. Formation of Simple Organic Compounds

  13. When the atmosphere cooled and the rain fell, so did the compounds • Over time the compounds entered chemical reactions and proteins and other organic compounds resulted • * DID NOT run any experiments to support theory

  14. -In 1953, Americans, Stanley MillerandHarold Urey, set up an experiment that was based on Oparin’s theory.

  15. Ammonia and Methane were released from volcanoes into bubbles Bubbles rise to the surface and burst B. The Bubble Model

  16. 2. Formation of Complex Organic Compounds • Formation of protein occurred either by amino acids spontaneously combining… • Or they were heated in the absence of oxygen -Similar mechanisms may have led to the formation of carbohydrates,lipids, and nucleic acids

  17. 3. Concentration and Enclosure Proteins clump together to form microscopic droplets… • Coacervates- droplets of different types of irregularly shaped molecules . Includes Amino Acids and sugars

  18. B. Microspheres- • Round, usually from one type of molecule. • Separated from the environment by a membrane • Chemical reactions occur here more easily than in water • Can bud off

  19. 4. Evolution of Growth, Metabolism, and Reproduction Coacervatesand microspheres lack the complexity of living cells … -They can grow -They can bud • They lack the ability to respond to natural selection.

  20. 5. The Role of RNA RIBOZYME: A special type of RNA was discovered to be able to act like an enzyme They can replicate themselves Research indicates life may have started with RNA

  21. II. Evolution of Cellular Life • A. The First Prokaryotes Scientists hypothesize that the first cells were: • Anaerobic • Heterotrophic • Prokaryotic

  22. B. The First Eukaryotes • Some early Eukaryotes may have gone through a relationship known as SYMBIOSIS. Endosymbiosis Theory: • Prokaryotic intracellular parasites evolved into various cell organelles • Evidence in the mitochondria and chloroplasts

  23. ENDOSYMBIOSIS THEORY

  24. Life Invaded Land • Cyanobacteria: photosynthesizing organisms gave off oxygen as a waste product. (At about 2.8 billion years ago) • Oxygen had two effects on the environment: 1) Those organism that could bond oxygen to other compounds survived - beginning of aerobic respiration. 2) Ozone (O3) was created

  25. Lamarck’s Explanation • French scientist (1744-1829) • Similar species descended from common ancestors ACQUIRED TRAITS: explanation for species change. • Changes arise from experiences and behavior over a lifetime • Not determined by genes. EXAMPLES: web feet, giraffe neck, tails “USE and DISUSE”

  26. Charles Darwin • Went to medical school • Study become a minister • Interested wildlife and the environment • Took a voyage on a ship, the BEAGLE, as the boats naturalist

  27. Darwin proposed a mechanism for evolution Natural Selection: occurs because of ADAPTATIONS Published a book: “On the Origin of Species”1859, 1 year after Alfred Wallace (same basic ideas)

  28. Evolution by Natural Selection “Human populations are able to increase faster than the food supply can”– Thomas Malthus 1798 • Only a limited number of offspring survive to reproduce • Individuals with traits that best suit their environment are most likely to survive and reproduce

  29. Darwin’s Theories Descent with modification: Newer life forms appearing in the fossil record are modified versions of the old species Modification by Natural Selection: Mechanism for how evolution can occur.

  30. Why some organisms survive when others do not: The environment affects individuals differently Some traits provide an advantage Populations ADAPT as the proportion of favorable genes increases FITNESS: Single organisms genetic contribution to the next generation. Favorable traits provide an ADAPTIVE ADVANTAGE

  31. Adaptations: Inherited traits that have become popular due to a selective advantage

  32. Darwin’s Theory: Based on 4 major points…. • Inherited variation exists within the genes of every population 2. Some individuals are better suited for their environments

  33. Traits that provide an advantage are spread as individuals survive and have offspring • Fossils provide evidence that living species evolved from extinct species

  34. The Scopes Trial

  35. PBS VIDEO ON EVOLUTION

  36. Darwin and Evolution

  37. The Fossil Record: Fossils: Preserved or mineralized remains or imprints of an organism that lived long ago Evidence of Evolution

  38. Concerns with using fossils for source of evidence • The fossil record is NOT COMPLETE • Many times genetic information is not available from the fossils • Not all organisms are equally likely to be fossilized

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