1. In what sense has spontaneous creation been discredited as an explanation for the origin of life on Earth, and in what sense is it still the most acceptable theory?

2. If spontaneous creation is rejected as the origin of life, what other explanation could there be?

3. Why has the evolution of life at one moment on this planet made it unlikely that life ever will evolve independently on Earth again? What was wrong with the medieval picture of spontaneous generation?

4. What portion of the energy-extracting machinery of eucaryotes is a common heritage of all forms of life? Give an example of bacteria that depends solely on this type of energy production.

5. What types of respiration are encountered in bacteria, in addition to respiration with O2? Which type probably is related to O2 respiration, and which is quite different in evolutionary history?

6. There is no a priori reason why nearly all bacteria that do not make use of molecular O2 as an oxidant should be poisoned by the presence of O2, but this state of affairs is at least understandable in terms of how bacterial metabolism evolved. Why is it reasonable that the nonuse of O2 and the intolerance of its presence should go together?

7. How do bacterial and green-plant photosynthesis differ? Which more closely resembles the photosynthesis of blue-green algae?

8. What suggestions are there from bacterial metabolism that life evolved in an O2-free, reducing environment?

9. What geological evidence is there for a reducing atmosphere on the early Earth? Approximately when did the transition to oxidizing conditions occur, judging from the geological record?

10. What are chemoautotrophs, and why are they unlikely to be examples of a very primitive and ancient metabolism?

11. How does the presence of atmospheric O2 interfere with the spontaneous synthesis of organic molecules by the nonbiological process that must have occurred during the evolution of life?

12. How does the presence of atmospheric O2, make it improbable that organic molecules would evolve into living organisms a second time, if all life on Earth were to be quickly extinguished?

13. What is the main source of organic compounds on the Earth today?

14. How can organic compounds exist in an atmosphere of oxygen, if oxidation of all of these compounds is thermodynamically spontaneous?

15. What is "Haldane soup," and how is it relevant to the problem of the origin of life?

16. How is it now believed that the organic molecules of "Haldane soup" were formed?