1. ORIGIN OF LIFE Theories Past and Present Nature of Early Cells Evolution of Cells RiverDell High School Biology Ms. C. Militano

2. I. Abiogenesis or Biogenesis ? Scientists Debate I. Abiogenesis or Biogenesis ? Scientists Debate A. Abiogenesis - life can arise from nonliving things B. Biogenesis – life can arise only from living things

3. C. Redi’s Experiment (1621-1697) 1. control – uncovered jars with meat 2. experimental group – jars with meat covered with netting 3. results – maggots only in control 4. conclusion – flies come from eggs laid by other flies

4. Redi’s Experiments

5. D. Spallanzani’s Experiment (1729-1799) 1. control – flask with boiled broth is left open 2. experimental group – flask with boiled broth is sealed immediately 3. results – open flask became cloudy closed flask remained clear 4. microrganisms came from the air

6. Spallanzani’s Experiment

7. E. Pasteur’s Experiment (1822-1895) 1. broth boiled in a flask with a curved neck 2. after one year the broth stayed clear 3. when the necks were broken the broth became cloudy 4. conclusion – the air is the source of microorganisms

8. Pasteur

9. II. Earth’s History A. Solar System begins to form 5 billion years ago B. Sun begins to form a few million years later C. Earth forms - 4.6 billion years ago D. Volcanoes form earth’s atmosphere E. 2.2 billion years ago earth like today

10. Formation of the Solar System Began 5 billion Years Ago

11. Planet Earth formed 4.6 billion years ago conditions were very different 2.2 billion years ago Earth was similar to the planet we live on today

12. III. Evolution of Life A. Origin of Organic Compounds 1. Early atmosphere – ammonia (NH 3 ) hydrogen gas (H 2 ), water vapor (H 2 O) and methane gas (CH 4 ) 2. High temperatures, frequent volcanoes, electrical storms, and comets 3. Maybe some organic compounds came to to earth from space

13. Early Earth

14. III. Evolution of Life A. Origin of Organic Compounds 4. Oparin and Haldane a. early gases and high temperatures formed simple organic compounds that collected in water and reacted to form macromolecules necessary for life

15. Conditions – Early Earth

16. III. Evolution of Life A. Origin of Organic Compounds 5. Urey and Miller (1953) a. experiment to test Oparin’s hypotheses b. chamber with early gases and electric sparks form several organic compounds c. similar experiments formed amino acids, ATP and nucleotides

17. Urey-Miller Experimental Apparatus

18. Urey-Miller Experiment

19. III. Evolution of Life A. Origin of Organic Compounds 6. Other Hypotheses a. early atmosphere composed of carbon dioxide, nitrogen, hydrogen water vapor b. early life may have formed in chemicals found in thermal vents found at the bottom of the ocean

20. Origin of Life - Thermal Vent Hypothesis

21. III. Evolution of Life B. Cell Like Structures Form 1. Solutions of organic compounds can form coacervates (collection of droplets of amino acids, sugars and lipids) 2. Microspheres – spherical forms surrounded by a protein membrane 3. Both do not have all properties of life

22. Sidney Fox and others researched structures which may have formed early cells Sidney Fox and others researched structures which may have formed early cells

23. Evolution of Life C. The First Cells 1. First cells were probably anaerobic heterotrophs 2. Similar to some prokaryotes 3. Eventually competition for organic molecules gave autotrophs an adaptive advantage

24. Evolution of Life C. The First Cells 4. Chemosynthetic organisms evolve a. get energy from oxidation of inorganic substances b. carbon dioxide used to make organic molecules that store energy

25. Evolution of Life C. The First Cells - The RNA World 5. Self-replicating RNA molecules may have evolved first 6. Ribozyme – RNA that can act as a catalyst – even for self-replication 7. Maybe first case of heredity and competition

26. Thomas Cech The Ribozyme

27. Evolution of the First Cells

28. D. Photosynthesis Evolves 1.About 3 billion years ago 2. Organisms similar to cyanobacteria 3. Oxygen is a product that might damage some types of cells 4. Ozone layer forms from the oxygen a. reduces ultraviolet light

29. Present Day Ancient Cyanobacteria Cyanobacteria

30. Stromatolites Formed Carbon Deposits from by Cyanobacteria Ancient Cyanobacteria

31. Formation of the Ozone Layer Cyanobacteria release oxygen in the atmosphere O 2 is converted to O 3 (ozone) in the upper atmosphere Ozone layer blocks much of the UV light Allows life to move from the sea to land

32. Changes of O 3 Concentrations Between 1980 and 1991

33. Changes in Ozone Concentrations Between 1970 and 1998

34. E. Aerobic Respiration Evolves 1. More than one billion years before oxygen to reached current levels 2. Early function of aerobic respiration may have been to prevent oxygen from destroying essential organic compounds

35. F. Endosymbiosis Evolution of Eukaryote 1. 1.5 – 2.0 billion years ago 2. Aerobic prokaryote took residence inside a larger anaerobic prokaryote a. became the mitochondria 3. photosynthetic cyanobacteria may have evolved into chloroplasts

36. F. Endosymbiosis Evolution of Eukaryotes 4. Evidence of endosymbiosis a. both mitochondria and chloroplast 1) replicate independently from cell cycle 2) have their own genetic material 3) circular DNA like prokaryotes

37. Lynn Margulis – Theory of Endosymbiosis

38. Endosymbosis and Cell Evolution

39. Endosymbiosis and the Nucleus

40. Three Cell Organelles Formed by Endosymbiosis

41. Comparing Prokaryote and Eukaryote

42. Evolution From Prokaryotes to Eukaryotes The first cells were probably like Eubacteria or Archaebacteria (formely known as Monera) Unicellular eukaryotes came next Then multicellular eukaryotes evolved

43. Evolution of The Kingdoms

44. Cladogram of Evolutionary Relationships

45. IV. Radioactive Decay and Dating A. Isotope – atoms of the same element that differ in the number of neutrons B. Radioactive decay – process in which unstable nuclei release particles and/or energy until they are stable C. Half-life – the length of time it takes for ½ any amount of a radioactive isotope to decay

46. Half-lives 256 14 C atoms at time 0

47. Half-lives 128 14 C and 128 14 N atoms after 5,600 years or 1 half-life

48. Half-lives 64 14 C and 192 14 N atoms after 11,200 years or 2 half-lives

49. Half-lives 32 14 C and 224 14 N atoms after 16,800 years or 3 half-lives

50. Half-lives 16 14 C and 240 14 N atoms after 22,400 years or 4 half-lives

51. Half-lives 8 14 C and 248 14 N atoms after 28,000 years or 5 half-lives

52. Half-lives 4 14 C and 252 14 N atoms after 33,600 years or 6 half-lives

53. Half-lives 2 14 C and 254 14 N atoms after 39,200 years or 7 half-lives

54. The half-life of C-14 is 5,600 years and a sample today has 1,000 C-14 atoms, after 5,600 years  500 C-14 atoms will remain (1/2 original amount) After two half lives (11,200 years)  250 C-14 atoms will remain (1/4 original amount) Proportion of isotope left 1/4 1/8 1/16 1 1/2 30 452 Half-lives 1

55. IV. Radioactive Decay and Dating D. Hyphen notation of radioisotopes (element symbol and mass number) - examples (C-12, C-14, O-16, O-18) E. Carbon-14 dating – compare ratio of C-14 and C-12 and use the ratio to determine age

56. IV.Radioactive Decay and Dating ISOTOPE Carbon-14 Uranium-235 Potassium-40 Uranium-238 HALF LIFE (years) 5,730 704,000,000 1,250,000,000 4,500,000,000

57. A. Problem Solving 1. The half-life of thorium-230 is 75,000 years. If a scientist has 40.0g of thorium, how much will remain after 225,000 years?

58. B. Half Life Problem Solving 2. The half life of carbon-14 is 5,370 years. How long will it take for ½ of the sample to decay? 3. If a biologist has 64.0g of C-14, how long will it take until 8.0g remain un- decayed?