City of Mesa, AZ

Arizona Through Time

Origins of Life
Life originated on earth nearly 4 billion years ago, yet multicellular life, organisms composed of more than one, differentiated cells, did not appear for over 3 billion years. Thus most of the history of life on this earth is little known.

Image of Journey onto Land

Journey onto Land
The emergence of vertebrates onto land, and the transition from fish to amphibian is well known. Less appreciated is the emergence onto land of plants and at least eleven other animal groups.


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