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Author Question: What evidence of life on Earth before stromatolites do we have? What will be an ideal ... (Read 51 times)

stephzh

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on: Jul 15, 2018
What evidence of life on Earth before stromatolites do we have? What will be an ideal response?

Question 2

What are stromatolites, and why are they important in Earth history? What will be an ideal response?


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Kdiggy

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Reply #1 on: Jul 15, 2018
Answer to Question 1

In Greenland, 3.8 billion-year-old rocks contain small carbon spheres that may be organic in origin,
but evidence is not conclusive. Archean and Early Paleoproterozoic rocks contain fossils of singlecelled
bacteria that lack a cell nucleus and reproduced asexually, called prokaryotic cells



Answer to Question 2

Stromatolites are blue-green algae that trap sediment. They are common in some Proterozoic rocks,
but the oldest are in 3.3 to 3.5 billion-year-old rocks. Stromatolites are important because the
atmosphere of the Paleoarchean had no free oxygen, but stromatolites release oxygen as a by-product
of photosynthesis. In the Archean and more so in the Proterozoic, they increased oxygen in Earth's
atmosphere.



stephzh

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Reply 2 on: Jul 15, 2018
YES! Correct, THANKS for helping me on my review

chereeb

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Reply 3 on: Yesterday
Excellent

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