17. Why would the fossil record tend to underestimate the proportions of jellyfish to clams living at any one time? How is this relevant to the issue of a shortage of Precambrian fossils?

18. What are pristane and phytane, and why is their presence considered as evidence for photosynthesis?

19. What is the oldest fossil evidence for bacterialike organisms? Where are these fossils found, and how old are they?

20. What is the oldest fossil evidence for eucaryotes? Where were they found, and how old is the deposit?

21. What are stromatolites? What organisms are believed to build them? How does the presence of stromatolites constitute evidence of a tentative sort for photosynthesis? How old are the oldest stromatolite formations?

22. What arguments led Stanley Miller to choose hydrogen, methane, ammonia, and water as components of his trial "primitive atmosphere"? What energy source was used to bring about chemical change? What natural phenomenon would this correspond to? What compounds were formed in the course of the reaction?

23. What is the Strecker synthesis, and how does it lead to the formation of amino acids? What determines the nature of the amino acid side chain, R-?

24. What are microspheres and coacervate drops, and what relevance do they have to the problem of the evolution of life? Why is a relative isolation from the surroundings advantageous to any living organism?

25. How did Oparin's experiments with coacervate drops mimic some of the metabolic activities of living organisms?

26. What advantage does water-decomposing photosynthesis have for the organism that possesses it, in comparison with H2S-using photosynthesis, if water is such a poor reducing agent compared with H2S?

27. What radical change in the environment of nonphotosynthetic organisms was brought about by water-decomposing photosynthetic organisms? How did this lead in time to a much more efficient means of extracting free energy from organic molecules?