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Precambrian Time and Origin of Life on Earth

• Age of the Earth, U.S. Geological Survey. Short text summary of our current understanding of the earth's age based on the oldest rocks at the surface and data from meteorites.
• Age of the Earth. Talk. Origins Archive. Explanations of the age of the earth based on age dating the oldest rocks at the surface and meteorites (with data tables). Much of the site is devoted to providing scientific details as rebuttals to various creationists' counter theories (young-earth hypotheses), such as helium in the atmosphere, decay rate of the earth's magnetic field, accumulation rates of metals in the ocean, etc. There is also a discussion that addresses criticisms of age dating.
• Paleobiology--The Precambrian, Carleton University. Good , non-technical summary of theories concerning the origin of life on Earth. Explanations and pictures of prokaryote, eukaryote, stromatolite, and other Precambrian fossils. Includes learning objectives, key words, and review questions to make sure you understand the topic
• Origins of Life. University of California, Berkeley. Short discussions with pictures of how, where, and when life is interpreted to have evolved. Includes discussions: How did life originate? Looking for the oldest fossils; and Studying the origin of life.
• Proterozoic Era--Life, University of California, Berkeley. Short history of Precambrian (Proterozoic) fossil record with links to key words (stromatolite, eukaryote, etc.) and topics. Also, this section on Proterozoic life crosslinks with sections concerning Proterozoic stratigraphy, tectonics, and localities. At the time chart, you can select an important Precambrian topic to find out more information.
• Cyanobacteria: Fossil Record. University of California, Berkeley. Good, non-technical description of the oldest known fossils. Includes description of cyanobacteria mounds called stromatolites.
• Stromatolites: The Oldest Fossils . Virtual Museum, Tree of Life Project. Description (sometimes technical) of the geologic history of cyanobacteria and the stromatolites they form, including their contribution to oxygen in the atmosphere.
  
  Stromatolites. Hooper Virtual Museum, Carleton University. Provides three on-line slides that explain what stromatolites are and why they are important fossils. Several pictures of modern stromatolites from Shark Bay, Australia, as well as a nice diagram of how cyanobacteria build the stromatolite mound.
  
  Stromatolites: Our Mysterious Ancient Reefs . Jon Nelson. Great Lakes Stories. Short, general audience article with pictures about stromatolite fossils from the Gun Flint Chert along Lake Superior, which once were considered the world's oldest (1.9 billion years old) fossils.  Similar fossils of cyanobacteria are now known from rocks that are 3.5 billion years old. 
• Dawn of Ocean Life Exhibit, Dolex. Descriptions and pictures of fossils from the late Precambrian, Ediacara fauna. A window will pop up asking for Japanese text, which you can cancel to get to the Web site in English.
• The Ediacaran Assemblage, Peripatus. This page describes the geological and chronological settings of the Ediacaran fossils, the range of morphologies of the fossils (with pictures), and includes remarks about their relationships with other organisms. This site is a little bit more technical than the others on this list.
• Early Animal Evolution: Emerging Views from Comparative Biology and Geology , Andrew H. Knoll and Sean B. Carroll. Technical discussion of possible genetic and environmental catalysts to animal evolution using modern genetics in combination with paleontology.  Discusses paleontology and patterns of animal diversification (with a diagram of the diversification), the geneology and genetics of animal ancestors, and the environmental context of animal diversification.

 

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