- What role did cyanobacteria play in the evolution of life?
- Explain how changes in Earth's atmosphere affected the kinds and distribution of life forms.
- How is looking for primitive life forms in hot vents like a time capsule of Earth's history?
- Why do the samples from the geyser recall an "era when we humans could not have survived?"
- Are there any organisms today that are continuing to make profound changes upon Earth's atmosphere? (You might discuss how people are changing our climate.)
