1. Modern theory suggests that the early (pre-life) atmosphere on Earth was a reducing one. Why (for what reasons) is it believed that oxygen was not present when life formedon Earth?
2. What proposed energy sources existed on this early (pre-life) Earth?
3. In the 1950s, Stanley Miller performed a set of experiments to determine whether lifecould have evolved given the conditions stated in the answers to questions 1 and 2.
a. How was the experiment designed?
b. What were the necessary controls?
c. What was produced in the experiment?
d. What did the results imply about the possible origin of life on Earth?
e. There is a general agreement that life must have evolved in the oceans originally and only much later invaded land. What factors of the physical environment on the early and evolving Earth support these ideas? Changes in which of these factors were essential for life to survive on earth?
f. Most of us can't even imagine a world without oxygen. However, as you learned earlier, chemically oxygen is a powerful oxidizing compound. What effect(s) would the increase in oxygen levels of the atmosphere have on the organisms that existed at that time?