Q.1. There is a general agreement that life should have evolved in the oceans originally and only much later invaded land. What factors of physical environment on the early and evolving Earth support these ideas? Changes in which of these factors were essential for life to stay alive on earth?

2. Most of us can’t even imagine a world without oxygen. Though, as you learned earlier, chemically oxygen is a powerful oxidizing compound. What effect(s) would the increase in oxygen levels of atmosphere have on the organisms that existed at that time?