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  1. 1. The Theory of Evolution06/07/12 cott
  2. 2. Evolution • A process of change through time06/07/12 cott
  3. 3. (I) Heterotroph Hypothesis• Is one proposed explanation for how life arose and evolved on primitive earth• According to this hypothesis, the first life forms were heterotrophic and had to obtain their nutrients from the environment 06/07/12 cott
  4. 4. (A) Primitive Earth• Based on assumption2. Earth was very hot.3. consisted of inorganic substances4. Many sources of energy including heat, lightning, solar radiation(x-rays and U.V. rays),5. The atmosphere: water vapor, hydrogen, methane gas, and ammonia.6. As the earth cooled, water condensed in the atmosphere and rain fell forming seas described as “hot, thin soup” 06/07/12 cott
  5. 5. (B) Synthesis of Organic CompoundsIn the seas: – Chemical reactions formed inorganic substances – Inorganic substances bonded make organic substances: amino acids and sugar. 06/07/12 cott
  6. 6. (C) Nutrition• Some of the large, complex molecules formed groupings or clusters called aggregates. • Aggregates developed membranes • Aggregates absorbed organic molecules • Aggregates carry out first heterotrophic nutrition. 06/07/12 cott
  7. 7. (D) Reproduction1. In time, as these aggregates became more complex and highly organized, they developed the ability to reproduce2. At the point where the ability to reproduce had evolved, the aggregates were considered to be living cells 06/07/12 cott
  8. 8. (E) Heterotroph to Autotroph1. Early heterotrophs carry out fermentation.2. Fermentation adds carbon dioxide to the atmosphere3. Heterotrophs develop the capacity to use carbon dioxide from the atmosphere to form organic compounds (photosynthesis)4. These organisms were the first autotrophs. 06/07/12 cott
  9. 9. (F) Anaerobes to Aerobes1. Photosynthesis adds free oxygen to the atmosphere.2. Over time, the capacity to use oxygen in respiration (aerobic) evolved in both autotrophs and heterotrophs3. Present day organisms may be heterotrophic or autotrophic >>>>>> aerobic or anaerobic. 06/07/12 cott
  10. 10. II Theory of Evolution1. Suggests that existing forms of life on earth have evolved from earlier forms over long periods of time2. Evolution accounts – differences in structures – differences in function, and behavior – changes that occur in populations 06/07/12 cott
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  12. 12. Evidence of Evolution• Supports the theory of evolution• Geologic record• Comparative Cytology• Comparative Biochemistry• Comparative Anatomy• Comparative Embryology 06/07/12 cott
  13. 13. (A) Geologic Record• Earth’s age: 4.5 to 5 billion years old (age was determined by radioactive dating of rocks)• Fossils- are the remains of traces of organisms that no longer exist. Fossils have been preserved in ice, sedimentary rock, amber, and tar 06/07/12 cott
  14. 14. Tyrranosaurus rex06/07/12 cott
  15. 15. (B) Comparative Anatomy• Evidence supports that similarities of basic structures exist between different organisms• Homologous structures are anatomical parts found in different organisms in origin and structure• The presence of such homologous structures suggest that these organisms have evolved from a common ancestor cott 06/07/12
  16. 16. (B) Comparative Anatomy         Homo sapiens  Paranthropus boisei 06/07/12 cott
  17. 17. (C) Comparative Embryology• A comparison of the early stages of their embryonic development may show similarities that suggest a common ancestor 06/07/12 cott
  18. 18. (C) Comparative Embryology 06/07/12 cott
  19. 19. (D) Comparative Cytology1. All living things are made up of cells2. Cell organelles including the cell membrane, ribosomes, and mitochondria are structurally and functionally similar in most organisms 06/07/12 cott
  20. 20. Mitochondrion DNA and can replicate06/07/12 cott
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  22. 22. (E) Comparative Biochemistry• All living things contain similar biochemical compounds• Examples: structure and function of DNA, RNA, and proteins 06/07/12 cott
  23. 23. (III) Theories of Evolution• Attempts to explain the similarities and differences among species.• Adaptations- features which make a species better suited to live and reproduce in its environment. 06/07/12 cott
  24. 24. (C) Charles Darwin 06/07/12 cott
  25. 25. (C) Darwin’s Ship the HMS Beagle 06/07/12 cott
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  27. 27. (C) Darwin• Charles Darwin devised a theory of evolution based on variation and natural selection as seen in the Galapagos islands.• Included in hid theory were five main ideas: 1. Overpopulation 2. Competition 3. Survival of the Fittest 4. Reproduction 5. Speciation 06/07/12 cott
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  31. 31. Overpopulation • Within a population, there are more offspring produced in each generation than can possibly survive06/07/12 cott
  32. 32. Competition • Natural resources: food, water, and space available to a population is limited. • Many organisms with similar nutritional requirements, there must be competition between them for the resources needed to survive06/07/12 cott
  33. 33. Survival of the Fittest• Variations among members of a population make some of them better adapted to the environment than others• It is generally the best- adapted individuals that will survive• The environment is the agent of natural selection determining which species will survive 06/07/12 cott
  34. 34. Reproduction • Individuals that survive and then reproduce transmit these variations to their offspring06/07/12 cott
  35. 35. Speciation• The development of a new species occurs as variations or adaptations accumulate in a population over many generations • Ex: caveman  present man 06/07/12 cott
  36. 36. What mechanisms  led to this speciation? 06/07/12 cott
  37. 37. Explain the following:  Two islands with similar environments located in different oceans, are populated by organisms that resemble nearby mainland organisms more than they resemble each other. 06/07/12 cott
  38. 38. (IV) Modern Theories of Evolution • Includes both Darwin’s ideas of variation and natural selection and the current knowledge of the sources of variations. 06/07/12 cott
  39. 39. (A) Sources of Variations• Segregation and the recombination of genes during sexual reproduction• Gene mutation occurs spontaneously and at random 06/07/12 cott
  40. 40. (B) Natural Selection• Traits which are beneficial to the survival of an organism in a particular environment tend to be retained and passed on, and therefore, increase in frequency within a population. 06/07/12 cott
  41. 41. Ex: Insects resistant to insecticides1. Genetic make-up of some insects make them resistant to the effects of insecticides2. Before the widespread use of insecticides, this trait was of no particular survival value3. With the increased use of insecticides, this trait developed a very high survival value4. Therefore, insects with resistance to insecticides survived and reproduced much more successfully than those lacking the trait5. As a result, the frequency of insecticide resistance has increased greatly in insect populations 06/07/12 cott
  42. 42. (C) Geographic Isolation• Isolation of a population increases the chances for speciation (the development of a new species.)• Separates a small group of organisms from the main population with its large gene pool (inheritable traits).• Geographic isolation is caused by natural barriers like mountains, large bodies of water, and deserts. 06/07/12 cott
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  44. 44. (D) Reproductive Isolation• If the isolated population becomes so different from the main population that members of the two cannot interbreed and produce fertile offspring, then they have become two distinct species 06/07/12 cott
  45. 45. (V) Time Frame for Evolution• There are two different theories proposed by scientists to address the rate of evolution: 1. Gradualism- proposes that evolutionary change is slow, gradual, and continuous 2. Punctuated Equilibrium- proposes that species have long periods of stability (several million years) interrupted by geologically brief periods of significant change during which a new species may evolve 06/07/12 cott
  46. 46. Punctuated  Gradualism06/07/12 cott Equilibrium