1. Does the advantage of oxygenic photoautotrophs have to do with the rate of autotrophic growth or with the range of environmental conditions permitted? describe.

2. Some researchers are trying to figure out when oxygenic photoautotrophs began by trying to pinpoint the origin of Rubisco.
a) What is Rubisco, and what does it do?

b) Does the presence of Rubisco mean that oxygenic photoautotrophs waswas occurring? describe, in one sentence. 

3. Oxygenic photoautotrophs may have been invented as long ago as 3.5 billion years ago (depending upon what evidence you trust). The atmosphere became oxidizing less than 2.4 billion years ago. Why the 900 million year discrepancy?