Biology: The Unity and Diversity of Life (14th Edition)

Published by Brooks/Cole Publishing Co.
ISBN 10: 1305073959
ISBN 13: 978-1-30507-395-1

Chapter 19 - Data Analysis Activities - Page 317: 2


Carbon dioxide levels now are much lower than they were when cells first arose. Oxygen levels are much higher.

Work Step by Step

The first cells arose 3.8 billion years ago. On the graph, it shows the carbon dioxide line much higher on the y-axis than modern day carbon because the line steadily decreases. Oxygen levels have been increasing since 3.8 billion years ago because the line was much lower on the y-axis 3.8 billion years ago than it is now.
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