Bacteria and Life

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1. How abundant was oxygen in the early atmosphere?
2. What evidence do scientists have that the oxygen content of our atmosphere has increased since the earth’s origin?
3. Why is oxygen more abundant in the atmosphere today?
4. What are stromatolites?
5. What do scientists think is implied by the presence of stromatolites in Precambrian rock? 6. What is ozone and how is it produced?
7. Why is ozone important to life today?
8. What effect did increased levels of oxygen in the atmosphere have on early life forms? Banded Iron Formation (to the right of the Early Atmosphere exhibit) 1. What is banded iron?
2. When did these formations become common?
3. What is the significance of these formations?
The Oldest Rocks: Remnants of a Youthful Earth (by the mural) 1. How old are the oldest rocks on Earth?
2. What evidence of life do these ancient rocks contain?
3. Is this evidence great enough to allow scientists to conclude that life indeed existed during this period?
The Earliest Traces of Life
1. When do scientists think life originated on Earth?
2. What are the oldest fossils and how old are they?
The Precambrian
1. When did the first cells with nuclei appear?
2. Fossils of multicellular animals are from what time period? 3. In what era did all of these events take place?
Origin of Life
1. What six elements are most prevalent in living organisms? 2. Were these elements present in the infant solar system?
3. What circumstances may have fostered the development of chains of amino acids and nucleotides? 4. What are the characteristics of the ancestors of living cells, what could they “do”? 5. Why is water important to life?

6. What are the “true” hallmarks of life?
7. What molecular evidence do scientists have that all life is at least distantly related and has a common ancestor?
8. What conditions exist on the present day earth that make the spontaneous generation of life unlikely?
9. What conditions are thought to have existed on primitive earth...
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