1. BIOLOGY WORKSHEET CHAPTER 17 HISTORY OF LIFE ON EARTH - NOVAK
Ws Ch17HistoryOfLife K1-12.doc

2. Chapter 12 Section 1
How Did Life Begin

3. How long ago did the Earth form? ___
FOUR POINT FIVE BILLION

4. What did the water vapor condense into? ___
OCEANS

5. Scientist think life has evolved over hundreds of ___ of years?
MILLIONS

6. Evidence of the age of the Earth can be found by measuring the age of ___.
ROCKS

8. ___ ___ is the estimation of the age of an object by measuring its content of certain radioactive isotopes.
RADIOMETRIC DATING

9. ___ are unstable isotopes that break down and give off energy in the form of charged particles called ___.
RADIOISOTOPES AND RADIATION

10. What is this breakdown called? ___
RADIOACTIVE DECAY

11. ___ ___ is the time it takes for one half of a given amount of a radioisotope to decay.
HALF LIFE

12. Half life from radioactive decay

13. By measuring the proportions of certain radioisotopes and their products of ___, scientists can compute how many half lives have passed since a rock was formed.
DECAY

14. The half life of uranium is 760 million years.
If the age of the earth is 4.2 billion years, then 4.2/.76 = about 6 doublings or about 64 times as much uranium existed on earth at creation as exists now.

15. Half life from radioactive decay

16. These chemical reactions produced many different simple ___ molecules.
ORGANIC

17. Energized by the ___ and ___ heat, these simple molecules formed more complex molecules that eventually became the building blocks of the first cells.
SUN & VOLCANIC

18. The hypothesis that many of the organic molecules necessary for life can be made from molecules of ___ matter has been tested and supported by results of lab experiments.
NONLIVING

19. In the 1920s A. I. Oparin and J. B. S
In the 1920s A. I. Oparin and J.B.S. Haldane suggest that the early ___ contained large amounts of organic molecules.
OCEANS

20. What did this hypothesis become known as? ___
PRIMORDIAL SOUP MODEL

21. They also hypothesized the molecules formed spontaneously in chemical reactions activated by ___ radiation, ___ eruptions, and ___.
SOLAR AND VOLCANIC AND LIGHTNING

22. The early Earth’s atmosphere lacked ___ making formation of organic molecules possible.
OXYGEN

23. Name four common compounds in Earth’s early atmosphere NOT including water. ___ ___ ___ ___ ___
NITROGEN GAS AND HYDROGEN GAS AND AMMONIA AND METHANE

24. In 1953, who tested the primordial soup model? ___
STANLEY MILLER AND HAROLD UREY

25. According to Figure 2, Miller-Urey heated ___ in a flask.
WATER

26. 29. According to Figure 2, Miller-Urey they then added water vapor and what other gases to the tubes? ___ ___ ___ ___ ___
NITROGEN GAS AND HYDROGEN GAS AND AMMONIA AND METHANE

27. According to Figure 2, Miller-Urey, after the spark and the vapors had been condensed, what did they find in the beaker below?
ORGANIC COMPOUNDS

28. These results support the hypothesis that some basic chemicals of ___ could have formed ___ under conditions like those in the experiment.
LIFE AND SPONTANEOUSLY

29. Recent discoveries have caused scientists to ___ the Miller-Urey experiment.
REEVALUATE

30. Four billion years ago, Earth did not have a protective layer of ___ gas.
OZONE

32. Without ozone, ___ radiation would have destroyed any ammonia or methane in the early atmosphere.
ULTRAVIOLET

34. 36. If these gases are absent from the Miller-Urey experiment, ___ biological molecules are NOT made.
KEY

35. If the chemicals needed to form life were not in the atmosphere some scientists argue that the chemicals ere produced within ocean ___ or ocean ___.
BUBBLES AND VENTS

36. In 1986, geophysicist Louis Lerman hypothesized the ___ model of chemical origins.
BUBBLE

37. The bubbles protected the methane and ammonia needed to make amino acids from ___ ___.
ULTRAVIOLET RADIATION

38. Next, the bubbles rose to the surface and burst, releasing simple ___ molecules into the air.
ORGANIC

39. Once in the wind, these simple organic molecules were exposed to ultraviolet radiation which provided ___ for further reactions
ENERGY

40. Scientists ___ about the details of the process that lead to the origin of life.
DISAGREE

41. However, short chains of ___ have been made to form on their own in water.
RNA

42. RNA is the nucleic acid that does what? _________
HELPS CARRY OUT DNA’S INSTRUCTIONS

43. In The 1980s, Thomas Cech hypothesized that ___ was the first self-replicating information-storage molecule.
RNA

44. Certain lipids, when combined with other molecules, can form a tiny droplet whose surface resembles a ___ ___.
CELL MEMBRANE

45. Short chains of amino acids can gather into tiny droplets called ___.
MICROSPHERES

46. Another type of droplet, called a ___ is composed of molecules of different types, including linked amino acids and sugars.
COACERVATES

47. Why do scientists think microspheres are important? _________
THEY MIGHT HAVE BEEN THE FIRST STEP TOWARD CELLULAR ORGANIZATION

48. Scientists disagree about the origin of ___.
HEREDITY

49. Many scientists agree that double-stranded DNA evolved after ___.
RNA

50. RNA “___” catalyzed the assembly of the earliest ___.
ENZYMES AND PROTEINS

51. But researchers do not yet understand how DNA, RNA and hereditary mechanisms first ___.
DEVELOPED

52. END of Chapter 12 Section 1